No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Inhibition of Tumor Angiogenesis and Growth by a Small-Molecule Multi-FGF Receptor Blocker with Allosteric Properties
Abstract
Receptor tyrosine kinases (RTK) are targets for anticancer drug development. To date, only RTK inhibitors that block orthosteric binding of ligands and substrates have been developed. Here, we report the pharmacologic characterization of the chemical SSR128129E (SSR), which inhibits fibroblast growth factor receptor (FGFR) signaling by binding to the extracellular FGFR domain without affecting orthosteric FGF binding. SSR exhibits allosteric properties, including probe dependence, signaling bias, and ceiling effects. Inhibition by SSR is highly conserved throughout the animal kingdom. Oral delivery of SSR inhibits arthritis and tumors that are relatively refractory to anti-vascular endothelial growth factor receptor-2 antibodies. Thus, orally-active extracellularly acting small-molecule modulators of RTKs with allosteric properties can be developed and may offer opportunities to improve anticancer treatment.
... [22][23][24][25][26] Genetic deletion of Fgf2 decreases cardiac blood vessel density by about 25% 27 and impairs angiogenesis. [28][29][30] Moreover, FGF2 deficiency results in blood vessel degeneration. 27,28 FGFR1 is composed of an extracellular region with three immunoglobulin-like domains, a single hydrophobic trans-membrane region, and a cytoplasmic tyrosine kinase domain. ...
... In addition, FGFR1 is essential for the expression and function of VEGF-A and VEGFR2. [29][30][31][32][33] Despite the abundant expression and potent angiogenic activities of FGF2 and FGFR1, it is thus far not well understood how the potent angiogenic effect of the FGF2/FGFR1 pathway is finely controlled. ...
Although VEGF-B was discovered as a VEGF-A homolog a long time ago, the angiogenic effect of VEGF-B remains poorly understood with limited and diverse findings from different groups. Notwithstanding, drugs that inhibit VEGF-B together with other VEGF family members are being used to treat patients with various neovascular diseases. It is therefore critical to have a better understanding of the angiogenic effect of VEGF-B and the underlying mechanisms. Using comprehensive in vitro and in vivo methods and models, we reveal here for the first time an unexpected and surprising function of VEGF-B as an endogenous inhibitor of angiogenesis by inhibiting the FGF2/FGFR1 pathway when the latter is abundantly expressed. Mechanistically, we unveil that VEGF-B binds to FGFR1, induces FGFR1/VEGFR1 complex formation, and suppresses FGF2-induced Erk activation, and inhibits FGF2-driven angiogenesis and tumor growth. Our work uncovers a previously unrecognized novel function of VEGF-B in tethering the FGF2/FGFR1 pathway. Given the anti-angiogenic nature of VEGF-B under conditions of high FGF2/FGFR1 levels, caution is warranted when modulating VEGF-B activity to treat neovascular diseases.
... 15 A couple of years later, Bono et al reported the discovery of SSR128129E, a non-competitive inhibitor of FGFR receptor subtypes. 16 Strinkingly, the compound is much more potent in inhibiting FGF2-induced cellular responses (IC 50 in the 10-30 nM range) than inhibiting FGF2 binding in vitro (IC 50 ...
... The current study confirms the very few studies on extracellular inhibition by small molecular-weight compounds [15][16][18][19] of a very important target class (RTK) and demonstrates that RTK inhibition is not only achievable by intracellular kinase inhibitors or extracellular antibodies. Interestingly, a wide array of chemotypes were found among the newly discovered FLT3 inhibitors suggesting that this RTK exhibits either a single but permissive allosteric cavity in its extracellular domain or independent binding sites at different locations whose occupation allosterically prohibit the binding of the endogeneous cytokine and further receptor activation. ...
... AZD4547, BGJ398 and JNJ-42756493 are promising pan-FGFR inhibitors and are now undergoing clinical trials on patients who suffer from different FGFR1-dependent cancers [9,10]. A recently described small-molecule inhibitor, SSR128129E, is a rare example of a small-molecule drug binding to the extracellular domain of FGFR and allosterically preventing its activation [11,12]. ...
... FGF1 stimulation was inhibited by the addition of F8 and G10 peptide, as detected with the significant decrease in the amount of phosphorylated FGFR1. The effect was less pronounced when comparing the levels of downstream activation -(phospho-ERK1/2 kinase), but still comparable with the effect of SSR128129E small molecule inhibitor described before [11,12]. ...
Overexpression of fibroblast growth factor receptor 1 (FGFR1) is a common aberration in lung and breast cancers, which has necessitated the design of drugs targeting FGFR1‐dependent downstream signaling and FGFR1 ligand binding. To date, the major group of drugs being developed for treatment of FGFR1‐dependent cancers are small‐molecule tyrosine kinase inhibitors; however, the limited specificity of these drugs has led to increasing attempts to design molecules targeting the extracellular domain of FGFR1. Here, we used the phage display technique to select cyclic peptides F8 (ACSLNHTVNC) and G10 (ACSAKTTSAC) as binders of the FGF1‐FGFR1 interface. ELISA and in vitro cell assays were performed to reveal that cyclic peptide F8 is more effective in preventing the FGF1‐FGFR1 interaction, and also decreases FGF1‐induced proliferation of BA/F3 FGFR1c cells by over 40%. Such an effect was not observed for BA/F3 cells lacking FGFR1. Therefore, cyclic peptide F8 can act as a FGF1‐FGFR1 interaction antagonist, and may be suitable for further development for potential use in therapies against FGFR1‐expressing cancer cells.
... Only recently has a small molecule allosteric regulator that targets the extracellular domain (ECD) of an RTK been described (22,23). Allosteric or nonclassical small molecule inhibitors of RTKs offer significant therapeutic advantages (24,25). ...
... To our knowledge, there is only one other example of a small molecule allosterically targeting the ECD of an RTK (FGFR) (22,23). That compound inhibits signaling linked to receptor internalization in an allosteric manner without affecting orthosteric ligand binding. ...
Significance
To effectively prevent cancer spread from primary tumor sites, new treatments need to target tumor cells, the cells and extracellular matrix within the tumor environment, and communicating pathways between these sites simultaneously. The collagen receptor discoidin domain receptor 2 (DDR2) has been implicated as such a target. Here, we describe the identification and characterization of a small molecule inhibitor of DDR2 that uniquely acts in an allosteric manner via the extracellular domain to selectively inhibit the action of DDR2 in tumor cells and tumor stromal cancer-associated fibroblasts. In experimental mouse models of breast cancer, WRG-28 inhibits DDR2 signaling and tumor cell invasion.
... [9,27,30,39] In addition to FGFR-targeted therapies, another therapeutic strategy for targeting the extracellular domains of FGFRs has been developed, which creates more opportunities for different isoforms' selective inhibition of these receptors. [40][41][42][43] ...
Artificial intelligence talks about modeling intelligent behavior through a computer with the least human involvement. Drug repositioning techniques based on artificial intelligence accelerate the research process and decrease the cost of experimental studies. Dysregulation of fibroblast growth factor (FGF) receptors as the tyrosine kinase family of receptors plays a vital role in a wide range of malignancies. Because of their functional significance, they were considered promising drug targets for the therapy of various cancers. This review has summarized small molecules capable of inhibiting FGF receptors that progressed using artificial intelligence and repositioning drugs examined in clinical trials associated with cancer therapy. This review is based on a literature search in PubMed, Web of Science, Scopus EMBASE, and Google Scholar databases to gather the necessary information in each chapter by employing keywords like artificial intelligence, computational drug design, drug repositioning, and FGF receptor inhibitors. To achieve this goal, a spacious literature review of human studies in these fields—published over the last 20 decades—was performed. According to published reports, nonselective FGF receptor inhibitors can be used for cancer management, and multitarget kinase inhibitors are the first drug class approved due to more advanced clinical studies. For example, AZD4547 and BGJ398 are gradually entering the consumption cycle and are good options as combined treatments. Artificial intelligence and drug repositioning methods can help preselect suitable drug targets more successfully for future inhibition of carcinogenicity.
... These numerous accessory domains open the potential for selectivity to be designed into a kinase inhibitor. Here we provide two small-molecule examples: SSR128129E binds to the extracellular domain of FGFR1 and FGFR2 selectively over other receptor TKs [188], and WRG-28 selectively binds to the extracellular domain of DDR2 over DDR1 [189]. ...
There are over 500 human kinases ranging from very well-studied to almost completely ignored. Kinases are tractable and implicated in many diseases, making them ideal targets for medicinal chemistry campaigns, but is it possible to discover a drug for each individual kinase? For every human kinase, we gathered data on their citation count, availability of chemical probes, approved and investigational drugs, PDB structures, and biochemical and cellular assays. Analysis of these factors highlights which kinase groups have a wealth of information available, and which groups still have room for progress. The data suggest a disproportionate focus on the more well characterized kinases while much of the kinome remains comparatively understudied. It is noteworthy that tool compounds for understudied kinases have already been developed, and there is still untapped potential for further development in this chemical space. Finally, this review discusses many of the different strategies employed to generate selectivity between kinases. Given the large volume of information available and the progress made over the past 20 years when it comes to drugging kinases, we believe it is possible to develop a tool compound for every human kinase. We hope this review will prove to be both a useful resource as well as inspire the discovery of a tool for every kinase.
... The formation of cryptic pockets is also considered being adjusted by both mechanisms [339]: conformational selection based on the flexibility of the cryptic pockets first and then stabilised by ligand as induced fit [340]. MD simulations have been shown to be of great use in identifying cryptic binding pockets and distinguishing allosteric and orthosteric sites [341,342]. Mixed solvents MD simulation, which uses small molecules/fragments with water as probe, have been successfully applied to detect and characterise allosteric sites [343,344]. Zuzic et al. used molecular dynamics simulations with benzene probes to detect the cryptic pockets in the SARS-CoV-2 spike glycoprotein and successfully identified a potentially druggable cryptic [345]. ...
The drug discovery process is a rocky path that is full of challenges, with the result that very few candidates progress from hit compound to a commercially available product, often due to factors, such as poor binding affinity, off-target effects, or physicochemical properties, such as solubility or stability. This process is further complicated by high research and development costs and time requirements. It is thus important to optimise every step of the process in order to maximise the chances of success. As a result of the recent advancements in computer power and technology, computer-aided drug design (CADD) has become an integral part of modern drug discovery to guide and accelerate the process. In this review, we present an overview of the important CADD methods and applications, such as in silico structure prediction, refinement, modelling and target validation, that are commonly used in this area.
... Fibroblast growth factor (FGF) signaling is essential for embryonic organ development and the progression of tumors (Brewer et al., 2016) and increases proliferation, invasion, and epithelial-to-mesenchymal transformation of tumor cells. (Bono et al., 2013). In the majority of malignancies, numerous FGFs are increased, and different FGF receptor (FGFR) subtypes are activated on tumor and stromal cells. ...
Osteosarcoma (OS) is a common bone cancer in children and adolescents, and metastasis and recurrence are the major causes of poor treatment outcomes. A better understanding of the tumor microenvironment is required to develop an effective treatment for OS. In this paper, a single-cell RNA sequencing dataset was taken to a systematic genetic analysis, and potential signaling pathways linked with osteosarcoma development were explored. Our findings revealed 25 clusters across 11 osteosarcoma tissues, with 11 cell types including “Chondroblastic cells”, “Osteoblastic cells”, “Myeloid cells”, “Pericytes”, “Fibroblasts”, “Proliferating osteoblastic cells”, “Osteoclasts”, “TILs”, “Endothelial cells”, “Mesenchymal stem cells”, and “Myoblasts”. The results of Cell communication analysis showed 17 potential cellular communication networks including “COLLAGEN signaling pathway network”, “CD99 signaling pathway network”, “PTN signaling pathway network”, “MIF signaling pathway network”, “SPP1 signaling pathway network”, “FN1 signaling pathway network”, “LAMININ signaling pathway network”, “FGF signaling pathway network”, “VEGF signaling pathway network”, “GALECTIN signaling pathway network”, “PERIOSTIN signaling pathway network”, “VISFATIN signaling pathway network”, “ITGB2 signaling pathway network”, “NOTCH signaling pathway network”, “IGF signaling pathway network”, “VWF signaling pathway network”, “PDGF signaling pathway network”. This research may provide novel insights into the pathophysiology of OS’s molecular processes.
... Ader et al. [22] found that SSR improved radiotherapy efficiency by reducing the availability of FGFRs on the membrane in radiosensitive human glioblastoma. SSR has been reported to delay angiogenesis, growth, and metastasis in tumors [23][24][25], as well as hampers atherosclerosis [26]. Although SSR has been demonstrated as a novel and effective therapeutic agent for many diseases, its role in fat metabolism remains largely unknown. ...
Background
AS an allosteric inhibitor of fibroblast growth factor receptors (FGFRs), SSR128129E (SSR) extensively inhibits the fibroblast growth factor (FGF) signaling. Given the metabolic importance of FGFs and the global epidemic of obesity, we explored the effect of SSR on fat metabolism.
Methods and results
Three-week-old male mice were administered intragastrically with SSR (30 mg/kg/day) or PBS for 5 weeks. The effects of SSR on white and brown fat metabolism were investigated by respiratory metabolic monitoring, histological assessment and molecular analysis. Results indicated that SSR administration significantly reduced the body weight gain and the fat content of mice. SSR did not increase, but decreased the thermogenic capability of both brown and white fat. However, SSR markedly suppressed adipogenesis of adipose tissues. Further study demonstrated the involvement of ERK signaling in the action of SSR.
Conclusions
SSR may be a promising drug candidate for the prevention of obesity via suppressing adipogenesis. However, the influence of SSR on thermogenesis in humans should be further investigated before its clinical application.
... Although it is a normal and essential process in a healthy body, in cancer it provides vital nutrients and oxygen for the tumor as well as carrying away its wastes [125]. Tumor angiogenesis occurs under the influence of fibroblast growth factor (FGF), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), placental growth factor (PLGF),tumor necrosis factoralpha (TNFa), platelet-derived growth factor (PDGF) and angiogenin (Ang) [126,127]. However, today many Parchebafi et al. ...
Microbial infection and cancer are two leading causes of global mortality. Discovering and developing new therapeutics with better specificity having minimal side-effects and no drug resistance are of an immense need. In this regard, cationic antimicrobial peptides (AMP) with dual antimicrobial and anticancer activities are the ultimate choice. For better efficacy and improved stability, the AMPs available for treatment still required to be modified. There are several strategies in which AMPs can be enhanced through, for instance, nano-carrier application with high selectivity and specificity enables researchers to estimate the rate of drug delivery to a particular tissue. In this review we present the biology and modes of action of AMPs for both anticancer and antimicrobial activities as well as some modification strategies to improve the efficacy and selectivity of these AMPs.
Graphical Abstract
... The term 'allostery' was first used in enzymology studies in the early 1960s [53][54][55]. Subsequently, allosteric modulation has been identified for all receptor superfamilies, including GPCRs, nuclear hormone receptors [56,57], receptor tyrosine kinases [58,59], and ligand/voltage-gated ion channels [60][61][62][63][64]. The term "allosteric" began to be used increasingly in the literature, and a broad spectrum of allosteric modulators was described. ...
The therapeutic potential of targeting adenosine A2A receptors (A2ARs) is immense due to their broad expression in the body and central nervous system. The role of A2ARs in cardiovascular function, inflammation, sleep/wake behaviors, cognition, and other primary nervous system functions has been extensively studied. Numerous A2AR agonist and antagonist molecules are reported, many of which are currently in clinical trials or have already been approved for treatment. Allosteric modulators can selectively elicit a physiologic response only where and when the orthosteric ligand is released, which reduces the risk of an adverse effect resulting from A2AR activation. Thus, these allosteric modulators have a potential therapeutic advantage over classical agonist and antagonist molecules. This review focuses on the recent developments regarding allosteric A2AR modulation, which is a promising area for future pharmaceutical research because the list of existing allosteric A2AR modulators and their physiologic effects is still short.
... CC-BY-NC-ND 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made 66,67 , which bind to allosteric sites distal to the ATP-binding pocket. We have shown here that chemical proteomics offers a distinct way to discover allosteric inhibitors of kinases. ...
The JAK family of non-receptor tyrosine kinases includes four subtypes (JAK1, JAK2, JAK3, and TYK2) and is responsible for signal transduction downstream of diverse cytokine receptors. JAK inhibitors have emerged as important therapies for immuno(onc)ological disorders, but their use is limited by undesirable side effects presumed to arise from poor subtype selectivity, a common challenge for inhibitors targeting the ATP-binding pocket of kinases. Here, we describe the chemical proteomic discovery of a druggable allosteric cysteine present in the non-catalytic pseudokinase domain of JAK1 (C817) and TYK2 (C838), but absent from JAK2 or JAK3. Electrophilic compounds selectively engaging this site block JAK1-dependent transphosphorylation and cytokine signaling, while appearing to act largely as “silent” ligands for TYK2. Importantly, the allosteric JAK1 inhibitors do not impair JAK2-dependent cytokine signaling and are inactive in cells expressing a C817A JAK1 mutant. Our findings thus reveal an allosteric approach for inhibiting JAK1 with unprecedented subtype selectivity.
... Combined with the sensitivity of breast cancer to antiangiogenic therapy and related mouse studies, we selected 200mg/kg/day as the high-dose group, and 100mg/kg/day was the relatively low-dose control group. In addition, the optimal biotherapeutic dose of VEGFR2 mAb (DC101) remains controversial and fluctuates widely among mouse strains and tumor types, with a maximum of 50mg/kg, 3 times a week (22,23). Studies have found that the treatment efficiency is the highest at 6mg/kg dose of DC101, the highest at 13-16mg/kg dose, and then decreases with the increase of dose and duration (24). ...
Angiogenesis is an essential physiological process and hallmark of cancer. Currently, antiangiogenic therapy, mostly targeting the vascular endothelial growth factor (VEGF)/VEGFR2 signaling axis, is commonly used in the clinic for solid tumors. However, antiangiogenic therapies for breast cancer patients have produced limited survival benefits since cancer cells rapidly resistant to anti-VEGFR2 therapy. We applied the low-dose and high-dose VEGFR2 mAb or VEGFR2-tyrosine kinase inhibitor (TKI) agents in multiple breast cancer mouse models and found that low-dose VEGFR2 mAb or VEGFR2-TKI achieved good effects in controlling cancer progression, while high-dose treatment was not effective. To further investigate the mechanism involved in regulating the drug resistance, we found that high-dose anti-VEGFR2 treatment elicited IL17A expression in γδ T cells via VEGFR1-PI3K-AKT pathway activation and then promoted N2-like neutrophil polarization, thus inducing CD8 ⁺ T cell exhaustion to shape an immunosuppressive microenvironment. Combining anti-VEGFR2 therapy with immunotherapy such as IL17A, PD-1 or Ly-6G mAb therapy, which targeting the immunomodulatory axis of “γδT17 cells-N2 neutrophils” in vivo , showed promising therapeutic effects in breast cancer treatment. This study illustrates the potential mechanism of antiangiogenic therapy resistance in breast cancer and provides synergy treatment for cancer.
... Among these, AZD4547, BGJ398, and JNJ-42756493 are pan-FGFR inhibitors and may be used in patients who suffer from different types of cancer related to FGFR1 altered function [94]. In contrast, a molecule that binds at the extracellular domain of the RTK and allosterically inhibits its activation is SSR128129E [95,96]. Other FGFR inhibitors are TAS-120, ARQ-087, JNJ 42756493, DEBIO 1347, BAY-1163877, and FGF 401 [97][98][99]. ...
Receptor tyrosine kinases (RTKs) are membrane receptors that regulate many fundamental cellular processes. A tight regulation of RTK signaling is fundamental for development and survival, and an altered signaling by RTKs can cause cancer. RTKs are localized at the plasma membrane (PM) and the major regulatory mechanism of signaling of RTKs is their endocytosis and degradation. In fact, RTKs at the cell surface bind ligands with their extracellular domain, become active, and are rapidly internalized where the temporal extent of signaling, attenuation, and downregulation are modulated. However, other mechanisms of signal attenuation and termination are known. Indeed, inhibition of RTKs’ activity may occur through the modulation of the phosphorylation state of RTKs and the interaction with specific proteins, whereas antagonist ligands can inhibit the biological responses mediated by the receptor. Another mechanism concerns the expression of endogenous inactive receptor variants that are deficient in RTK activity and take part to inactive heterodimers or hetero-oligomers. The downregulation of RTK signals is fundamental for several cellular functions and the homeostasis of the cell. Here, we will review the mechanisms of signal attenuation and termination of RTKs, focusing on FGFRs.
... This compound binds to the extracellular portion of FGFR and prevents the internalisation of the FGF/FGFR complex, which negates intracellular signalling [124]. SSR128129E was able to reduce the growth of orthotopic PDAC tumours, pointing towards a therapeutic role for allosteric inhibition of FGFR [125]. With increasing interest in CAR-T cell therapy, FGFR may act as a potential target in at least a fraction of patients, in a manner similar to recently discovered targets such as CEACAM7 [126]. ...
Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis with a 5 year survival rate of less than 8%, and is predicted to become the second leading cause of cancer-related death by 2030. Alongside late detection, which impacts upon surgical treatment, PDAC tumours are challenging to treat due to their desmoplastic stroma and hypovascular nature, which limits the effectiveness of chemotherapy and radiotherapy. Pancreatic stellate cells (PSCs), which form a key part of this stroma, become activated in response to tumour development, entering into cross-talk with cancer cells to induce tumour cell proliferation and invasion, leading to metastatic spread. We and others have shown that Fibroblast Growth Factor Receptor (FGFR) signalling can play a critical role in the interactions between PDAC cells and the tumour microenvironment, but it is clear that the FGFR signalling pathway is not acting in isolation. Here we describe our current understanding of the mechanisms by which FGFR signalling contributes to PDAC progression, focusing on its interaction with other pathways in signalling networks and discussing the therapeutic approaches that are being developed to try and improve prognosis for this terrible disease.
... Particularly, excessive cytokine secretion has been implicated in severe inflammation as a major constituent leading to irAEs. For example, the overproduction of fibroblast growth factor 2 (FGF-2) [15][16][17][18] , granulocyte colonystimulating factor (G-CSF) 19 , granulocyte-macrophage colonystimulating factor (GM-CSF) 20 , and fractalkine (CX3CL1) 21 have been found to participate in immune-related inflammatory disease (e.g., rheumatoid arthritis, autoimmune gastritis, and Crohn's disease). These inflammatory cytokines have recently been reported to indicate irAEs for melanoma patients who underwent immune checkpoint therapy 9 . ...
The introduction of immune checkpoint inhibitors has demonstrated significant improvements in survival for subsets of cancer patients. However, they carry significant and sometimes life-threatening toxicities. Prompt prediction and monitoring of immune toxicities have the potential to maximise the benefits of immune checkpoint therapy. Herein, we develop a digital nanopillar SERS platform that achieves real-time single cytokine counting and enables dynamic tracking of immune toxicities in cancer patients receiving immune checkpoint inhibitor treatment - broader applications are anticipated in other disease indications. By analysing four prospective cytokine biomarkers that initiate inflammatory responses, the digital nanopillar SERS assay achieves both highly specific and highly sensitive cytokine detection down to attomolar level. Significantly, we report the capability of the assay to longitudinally monitor 10 melanoma patients during immune inhibitor blockade treatment. Here, we show that elevated cytokine concentrations predict for higher risk of developing severe immune toxicities in our pilot cohort of patients.
... Recently, we have identified the PTX3-derived small-molecule NSC12 as the first orally active pan-FGF trap able to inhibit FGFR activation and tumor growth in various FGF-dependent murine and human cancer models (20,21). Notably, extracellular FGF traps, including NSC12, appear to be devoid of the toxicities associated to TK FGFR inhibitors (21,22), thus representing a potential alternative to inhibit the FGF/FGFR system in multiple myeloma. ...
The human fibroblast growth factor/fibroblast growth factor-receptor (FGF/FGFR) axis deregulation is largely involved in supporting the pathogenesis of hematologic malignancies, including Waldenström's Macroglobulinemia (WM). WM is still an incurable disease, and patients succumb due to disease progression. Therefore, novel therapeutics designed to specifically target deregulated signaling pathways in WM are required. We aimed to investigate the role of FGF/FGFR system blockade in WM by using a pan-FGF trap molecule (NSC12). Wide-transcriptome profiling confirmed inhibition of FGFR-signaling in NSC12-treated WM cells; unveiling a significant inhibition of MYD88 also confirmed at protein level. Importantly, the NSC12-dependent silencing of MYD88 was functionally active, as it led to inhibition of MYD88-driven pathways, such as BTK and SYK, as well as the MYD88-downstream target HCK. Of note, both canonical and non-canonical NFkB cascades were down-regulated in WM cells upon NSC12 treatment. Functional sequelae exerted by NSC12 in WM cells were studied, demonstrating significant inhibition of WM cell growth, induction of WM cell apoptosis, halting MAPK, JAK/STAT3 and PI3K-Akt pathways. Importantly, NSC12 exerted an anti-WM effect even in the presence of bone marrow microenvironment, both in vitro and in vivo. Our studies provide the evidence for using NSC12 as a specific FGF/FGFR system inhibitor, thus representing a novel therapeutic strategy in WM.
... AG1296 was shown to differentially inhibit PDGFR autophosphorylation on different tyrosines. Another example is the negative allosteric modulator SSR128129E, a small molecule that binds to the extracellular region of all FGFRs and induces a structural change that decreases FGF ligand efficacy (101,102). SSR128129E was shown to inhibit tyrosine phosphorylation of an FGFR substrate (FRS2) but not another (PLCg). Other interesting examples are matuzumab and cetuximab, two EGFR inhibitory therapeutic antibodies with different binding sites in the EGFR extracellular region (103,104). ...
Ligand bias is the ability of ligands to differentially activate certain receptor signaling responses compared to others. It reflects differences in the responses of a receptor to specific ligands and has implications for the development of highly specific therapeutics. While ligand bias has been studied primarily for G protein-coupled receptors (GPCRs), there are also reports of ligand bias for receptor tyrosine kinases (RTKs). However, the understanding of RTK ligand bias is lagging behind the knowledge of GPCR ligand bias. In this review, we highlight how protocols that were developed to study GPCR signaling can be used to identify and quantify RTK ligand bias. We also introduce an operational model that can provide insights into the biophysical basis of RTK activation and ligand bias. Finally, we discuss possible mechanisms underpinning RTK ligand bias. Thus, this review serves as a primer for researchers interested in investigating ligand bias in RTK signaling.
... Other biological functions of the proteins are manifested in promoting injury repair (72), bone formation (73), and vascular and neural regeneration (74,75). FGFR overexpression has also been revealed to be associated with tumor and bone diseases, as well as arthritis (76)(77)(78). All of the aforementioned genes were subjected to AS analysis, and the results were validated by qPCR, which indicated consistency with RNA-seq except for the qPCR result for the PDGFB gene that was inconsistent with that of RNA-seq. ...
Double‑stranded RNA‑binding protein Staufen homolog 1 (STAU1) is a highly conserved multifunctional double‑stranded RNA‑binding protein, and is a key factor in neuronal differentiation. RNA sequencing was used to analyze the overall transcriptional levels of the upregulated cells by STAU1 and control cells, and select alternative splicing (AS). It was determined that the high expression of STAU1 led to changes in the expression levels of a variety of inflammatory and immune response genes, including IFIT2, IFIT3, OASL, and CCL2. Furthermore, STAU1 was revealed to exert a significant regulatory effect on the AS of genes related to the 'nerve growth factor receptor signaling pathway'. This is of significant importance for neuronal survival, differentiation, growth, post‑damage repair, and regeneration. In conclusion, overexpression of STAU1 was associated with immune response and regulated AS of pathways related to neuronal growth and repair. In the present study, the whole transcriptome of STAU1 expression was first analyzed, which laid a foundation for further understanding the key functions of STAU1.
... Several FGF2/FGFR inhibitors have shown promising anticancer and antiangiogenic efficacy in several in vitro assays and in vivo preclinical animal models. [50][51][52] Our data showed that TPs could significantly downregulate the expression of VEGF and bFGF in breast tumor tissue, consistent with previous studies of various cancer types in vivo and in vitro. [53][54][55][56] TIMP-2 is the natural specific inhibitor of MMP-2; however, TIMP-2 selectively inhibits the proliferation of endothelial cells through an MMP-independent mechanism. ...
Objective
To investigate the anti-angiogenic effect of tea polyphenols (TPS) on breast cancer and normal tissues in a mouse model.
Methods
Breast cancer was successfully implanted into 48 BALB/c mice, which were then randomly divided into a TP oral gavage group, a TP local injection group, a ginsenoside Rg3 group, and a model control group according to a random number table. The tumor inhibitory rates of each group were calculated, while microvessel density (MVD) and the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and tissue inhibitor of metalloproteinase (TIMP-2) were detected by immunohistochemistry.
Results
TPs could inhibit the growth of breast cancer xenografts in the mouse model. The tumor inhibition rates of the TP oral gavage and TP local injection groups were 37.43% and 40.94%, respectively. Compared with the model control group, MVD and VEGF and bFGF expression was downregulated (all P < .05), whereas TIMP-2 expression was elevated in the TP oral gavage and TP local injection groups (P = .015 and P = .032). TPs showed no significant effect on MVD and VEGF and TIMP-2 expression in the heart, brain, and kidney of the mouse model.
Conclusion
TPs can restrict the growth of breast cancer by specifically inhibiting the angiogenesis of breast tumor tissue while having little effect on the normal tissue of important organs including the heart, brain, and kidney.
... However, dasatinib may be less effective as a DDR-2 inhibitor because of its low specificity and high affinity, with its multitargeted design (in tight combination with other targets such as Src and Abl kinase), thereby lacking specificity for DDR-2 (57). Recently, a new kind of small molecule regulator that targets the extracellular domain of an RTK have been described (58). WRG-28 is a newly identified potent and selective allosteric inhibitor of DDR-2, which acts via the extracellular domain of DDR-2 and potentially disrupts receptor clustering without affecting DDR-1 (a homologous family member of DDR-2) and α1β1 integrin (an unrelated collagen receptor) (24). ...
Objective
This study was undertaken to uncover the pathophysiologic role of discoidin domain receptor 2 (DDR‐2), a putative fibrillar collagen receptor, in inflammation promotion and joint destruction in rheumatoid arthritis (RA).
Methods
In synovial tissue from patients with RA and from mice with collagen antibody–induced arthritis (CAIA) (using Ddr2−/− and DBA/1 mice), gene and protein expression levels of DDR‐2, interleukin‐15 (IL‐15), and Dkk‐1 were measured by quantitative reverse transcription–polymerase chain reaction, Western blotting, and immunohistochemistry. Gene knockdown of DDR2 in human RA fibroblast‐like synoviocytes (FLS) was conducted via small interfering RNA. Interaction between the long noncoding RNA H19 and microRNA 103a (miR‐103a) was assessed in RA FLS using RNA pulldown assays. Cellular localization of H19 was examined using fluorescence in situ hybridization assays. Chromatin immunoprecipitation and dual luciferase reporter assays were applied to verify H19 transcriptional and posttranscriptional regulation by miR‐103a.
Results
DDR2 messenger RNA (mRNA) expression was significantly associated with the levels of IL‐15 and Dkk‐1 mRNA in the synovial tissue of RA patients (r² = 0.2022–0.3293, all P < 0.05; n = 33) and with the serum levels of IL‐15 and Dkk‐1 in mice with CAIA (P < 0.05). In human RA FLS, activated DDR‐2 induced the expression of H19 through c‐Myc. Moreover, H19 directly interacted with and promoted the degradation of miR‐103a.
Conclusion
These results indicate a novel role for activated DDR‐2 in RA FLS, showing that DDR‐2 is responsible for regulating the expression of IL‐15 and Dkk‐1 in RA FLS and is involved in the promotion of inflammation and joint destruction during pathophysiologic development of RA. Moreover, DDR‐2 inhibition, acting through the H19–miR‐103a axis, leads to reductions in the inflammatory reaction and severity of joint destruction in mice with CAIA, suggesting that inhibition of DDR‐2 may be a potential therapeutic strategy for RA.
... FGF-targeted therapies in recent times reappraise as hopeful antiangiogenic and anti-tumor agents [102,103]. The FGF receptors (FGFRs) super family with its 18 ligands and four receptors has been involved in migration, proliferation and differentiation of endothelial cells. ...
... To the best of our knowledge, there are currently just two RTKs of which the ECD has been successfully allosterically targeted by small molecules: FGFR and DDR2 (34,59,60). The present study demonstrated that inhibition of DDR1, using an ECD neutralizing antibody, decreased breast cancer growth in vivo by recruiting CD4 + and CD8 + TILs. ...
Breast cancer is the second leading cause of cancer‑associated mortality among women worldwide. Triple‑negative breast cancer (TNBC) accounts for 15‑20% of all breast cancers and is defined by its aggressive nature and limited treatment options. Therefore, there is an urgent need to develop effective therapies for TNBC in order to improve breast cancer outcomes, as targeted therapies have done in other subtypes of breast cancer. Discoidin domain receptor tyrosine kinase 1 (DDR1) is activated by collagens, which are important components of the tumor stroma; therefore, DDR1 may serve a critical role in the communication between tumor cells and the tumor microenvironment. The aim of the present study was to determine how tumor DDR1 regulated tumor growth by affecting tumor infiltrated T cells. First, the DDR1 expression levels from a cohort of patients with breast cancer were analyzed. The results revealed that there were higher levels of DDR1 expression in tumor tissues compared with adjacent normal tissues. Overexpression of DDR1 in 4T1 cells promoted tumor growth in vivo, while knockout of DDR1 in EMT6 cells decreased tumor growth in vivo. In addition, it was revealed that DDR1 regulated tumor growth by modulating tumor infiltrating T cells, CD4+ and CD8+. Furthermore, inhibition of DDR1 by neutralizing antibodies decreased breast cancer growth in vivo. To the best of our knowledge, the results of the present study demonstrated for the first time that DDR1 expressed on the tumor cells promoted breast tumor growth by suppressing antitumor immunity. The present findings indicated that DDR1 may not only have a critical role in the progression of breast cancer, but may also serve as a potential therapeutic target for breast cancer, particularly TNBC.
... Recently, the PTX3-derived small molecule NSC12 has been identified as the first orally active pan-FGF trap able to inhibit FGFR activation and tumor growth in various FGF-dependent murine and human tumor models [20,21]. Notably, extracellular FGF traps, including NSC12, appear to be devoid of the toxicities associated with tyrosine kinase FGFR inhibitors [21,22], thus representing a potential alternative option to inhibit the FGF/FGFR system in cancer. On this basis, in this work we investigated the impact of a PTX3/NSC12-based, FGF trapping approach in the murine B16-LS9 melanoma model and on human UM cell lines. ...
Fibroblast growth factors (FGFs) play non-redundant autocrine/paracrine functions in various human cancers. The Cancer Genome Atlas (TCGA) data mining indicates that high levels of FGF and/or FGF receptor (FGFR) expression are associated with reduced overall survival, chromosome 3 monosomy and BAP1 mutation in human uveal melanoma (UM), pointing to the FGF/FGFR system as a target for UM treatment. Here, we investigated the impact of different FGF trapping approaches on the tumorigenic and liver metastatic activity of liver metastasis-derived murine melanoma B16-LS9 cells that, similar to human UM, are characterized by a distinctive hepatic tropism. In vitro and in vivo experiments demonstrated that the overexpression of the natural FGF trap inhibitor long-pentraxin 3 (PTX3) inhibits the oncogenic activity of B16-LS9 cells. In addition, B16-LS9 cells showed a reduced tumor growth and liver metastatic activity when grafted in PTX3-overexpressing transgenic mice. The efficacy of the FGF trapping approach was confirmed by the capacity of the PTX3-derived pan-FGF trap small molecule NSC12 to inhibit B16-LS9 cell growth in vitro, in a zebrafish embryo orthotopic tumor model and in an experimental model of liver metastasis. Possible translational implications for these observations were provided by the capacity of NSC12 to inhibit FGF signaling and cell proliferation in human UM Mel285, Mel270, 92.1, and OMM2.3 cells. In addition, NSC12 caused caspase-3 activation and PARP cleavage followed by apoptotic cell death as well as -catenin degradation and inhibition of UM cell migration. Together, our findings indicate that FGF trapping may represent a novel therapeutic strategy in UM.
... In addition, efforts have been made in the development of small molecule inhibitor targeting FGFR ectodomains. An inhibitor, SSR128129E, which allosterically binds to the ectodomain of FGFR in a non-FGF competitive manner, has been reported to inhibit FGF-induced signaling [99,100]. ...
Fibroblast growth factor receptors (FGFRs) are a family of receptor tyrosine kinases expressed on the cell membrane that play crucial roles in both developmental and adult cells. Dysregulation of FGFRs has been implicated in a wide variety of cancers, such as urothelial carcinoma, hepatocellular carcinoma, ovarian cancer and lung adenocarcinoma. Due to their functional importance, FGFRs have been considered as promising drug targets for the therapy of various cancers. Multiple small molecule inhibitors targeting this family of kinases have been developed, and some of them are in clinical trials. Furthermore, the pan-FGFR inhibitor erdafitinib (JNJ-42756493) has recently been approved by the U.S. Food and Drug Administration (FDA) for the treatment of metastatic or unresectable urothelial carcinoma (mUC). This review summarizes the structure of FGFR, especially its kinase domain, and the development of small molecule FGFR inhibitors.
... In the subset of pediatric and young adult samples in this cohort we found a negative association of FGFR1 expression and age; based on a small sample size these results must be validated by establishment of large scale TMAs. We next investigated the potential for cell migration in low and high grade pediatric gliomas as a prerequisite for disease progression and recurrence and, next, assessed the role of FGFR1 in cell migration and invasion for chemotherapeutic intervention (20)(21)(22)(23). This is a novel therapeutic approach, targeting a hallmark feature of brain tumor pathogenesis and has to our knowledge not been investigated in pediatric gliomas beyond genomic analyses. ...
The heterogeneous and invasive nature of pediatric gliomas poses significant treatment challenges, highlighting the importance of identifying novel chemotherapeutic targets. Recently, recurrent Fibroblast growth factor receptor 1 (FGFR1) mutations in pediatric gliomas have been reported. Here, we explored the clinical relevance of FGFR1 expression, cell migration in low and high grade pediatric gliomas and the role of FGFR1 in cell migration/invasion as a potential chemotherapeutic target. A high density tissue microarray (TMA) was used to investigate associations between FGFR1 and activated phosphorylated FGFR1 (pFGFR1) expression and various clinicopathologic parameters. Expression of FGFR1 and pFGFR1 were measured by immunofluorescence and by immunohistochemistry (IHC) in 3D spheroids in five rare patient-derived pediatric low-grade glioma (pLGG) and two established high-grade glioma (pHGG) cell lines. Two-dimensional (2D) and three-dimensional (3D) migration assays were performed for migration and inhibitor studies with three FGFR1 inhibitors. High FGFR1 expression was associated with age, malignancy, tumor location and tumor grade among astrocytomas. Membranous pFGFR1 was associated with malignancy and tumor grade. All glioma cell lines exhibited varying levels of FGFR1 and pFGFR1 expression and migratory phenotypes. There were significant anti-migratory effects on the pHGG cell lines with inhibitor treatment and anti-migratory or pro-migratory responses to FGFR1 inhibition in the pLGGs. Our findings support further research to target FGFR1 signaling in pediatric gliomas.
... For multidomain targets in which the kinase domain is functionally controlled by other domains, effective allosteric inhibitors could exert their effect by binding to sites outside the kinase domain. A precedent for such regulation is set by the small molecule SSR128129E, which binds to the extracellular domain of the fibroblast growth factor receptor (FGFR) and induces a conformational change that biases signalling 223,224 . Recent studies of RTK and cytokine receptor signalling have further demonstrated the remarkable communication between the conformation of receptor extracellular domains and downstream signalling kinetics and pathway bias 198,225,226 . ...
Pseudokinases are members of the protein kinase superfamily but signal primarily through noncatalytic mechanisms. Many pseudokinases contribute to the pathologies of human diseases, yet they remain largely unexplored as drug targets owing to challenges associated with modulation of their biological functions. Our understanding of the structure and physiological roles of pseudokinases has improved substantially over the past decade, revealing intriguing similarities between pseudokinases and their catalytically active counterparts. Pseudokinases often adopt conformations that are analogous to those seen in catalytically active kinases and, in some cases, can also bind metal cations and/or nucleotides. Several clinically approved kinase inhibitors have been shown to influence the noncatalytic functions of active kinases, providing hope that similar properties in pseudokinases could be pharmacologically regulated. In this Review, we discuss known roles of pseudokinases in disease, their unique structural features and the progress that has been made towards developing pseudokinase-directed therapeutics.
... This is best exemplified by the development of anti-FGFR2 and anti-FGFR3 monoclonal antibodies/ antibody-drug conjugates [120][121][122][123][124]. FP-1039, an FGF-ligand trap composed of an FGFR1 extracellular domain-IgG1 fusion which is able to inhibit tumour growth in xenograft models, has also been developed [125]. Furthermore, a novel small molecule inhibitor (SSR128129E) which binds to FGFR extracellular domains in a non-FGF competitive manner but induces selective, allosteric inhibition of receptor internalisation and ERK1/2 signalling has been described [107,126]. Lastly, there has also been exploration of the use of antisense therapy for targeting FGFR4 in obesity patients (Table 3) [127]. ...
The receptor tyrosine kinase family of fibroblast growth factor receptors (FGFRs) play crucial roles in embryonic development, metabolism, tissue homeostasis and wound repair via stimulation of intracellular signalling cascades. As a consequence of FGFRs’ influence on cell growth, proliferation and differentiation, FGFR signalling is frequently dysregulated in a host of human cancers, variously by means of overexpression, somatic point mutations and gene fusion events. Dysregulation of FGFRs is also the underlying cause of a number of developmental dysplasias such as hypochondroplasia and achondroplasia. Accordingly, FGFRs are attractive pharmaceutical targets, and multiple clinical trials are in progress for the treatment of various FGFR aberrations. To effectively target dysregulated receptors, a structural and mechanistic understanding of FGFR activation and regulation is required. Here, we review some of the key research findings from the last couple of decades and summarise the strategies being explored for therapeutic intervention.
Urothelial cancer, a common urinary system malignancy, often presents treatment challenges due to metastasis and chemotherapy side effects. Angiogenesis, crucial for tumor growth, has become a target for drug development. This study explores the expression, prognostic value, and clinical correlation of RHOJ in the TCGA BLCA, GSE31684, and GSE32894 datasets. We identify common differentially expressed genes across these databases and utilize g:Profiler and Cytoscape ClueGO for functional assessment. Further, we perform a gene set enrichment analysis (GSEA) using Hallmark gene sets and use the imsig package for immune cell infiltration analysis. Our analysis indicates that RHOJ expression levels significantly impact survival rates, tumor progression, and immune response in urothelial tumors. High RHOJ expression correlated with poor prognosis, advanced disease stages, and an increase in monocyte population within the tumor microenvironment. This aligns with current literature indicating a key role of immune infiltration in bladder cancer progression and treatment response. Moreover, the GSEA and imsig results further suggest a potential mech-anistic link between RHOJ expression and immune-related pathways. Considering the increasing emphasis on immunotherapeutic strategies in bladder cancer management, our findings on RHOJ's potential as a diagnostic biomarker and its association with immune response open new avenues for therapeutic interventions.
Cartilage development is a tightly regulated process that requires the interaction of epithelial and mesenchymal tissues layers to initiate the aggregation of mesenchyme in a condensation. Several signaling molecules have been implicated in cartilage formation including FGFs, WNTs, and members of the TGF-β super family. However, little is known about the earliest signals involved in these initial phases of development. Here we aimed to investigate whether direct intravitreal injection of pharmaceutical inhibitors for FGF and TGF-β signaling would perturb cranial cartilages in zebrafish. Via wholemount bone and cartilage staining, we found effects on multiple cranial cartilage elements. We found no effect on scleral cartilage development, however, the epiphyseal bar, basihyal, and basicapsular cartilages were disrupted. Interestingly, the epiphyseal bar arises from the same progenitor pool as the scleral cartilage, namely, the periocular ectomesenchyme. This study adds to the foundational knowledge about condensation induction of cranial cartilage development and provides insight into the timing and signaling involved in the early development of several craniofacial cartilage elements in zebrafish.
Overview
Angiogenesis, the growth of new capillary blood vessels, is central to cancer growth and metastasis and is recognized to be a potential therapeutic target for the treatment of cancer. Antiangiogenic agents have become part of the standard treatment armamentarium for many solid tumors, providing significant clinical benefits for some cancers (e.g., renal cell, colorectal) and modest or no benefit for others. This article is focused on principles of tumor angiogenesis that are intrinsic to the behavior of human cancer, and lessons that can be gleaned from the clinical testing and use of angiogenesis inhibitors alone and in combination with other agents to date.
Coarse-grained (CG) modeling with the Martini force field (FF) has come of age. By combining a variety of bead types and sizes with a new mapping approach, the newest version of the model is able to accurately simulate large biomolecular complexes at millisecond timescales. In this perspective, we discuss possible applications of the Martini 3 model in drug discovery and development pipelines and highlight areas for future development. Owing to its high simulation efficiency and extended chemical space, Martini 3 has great potential in the area of drug design and delivery. However, several aspects of the model should be improved before Martini 3 CG simulations can be routinely employed in academic and industrial settings. These include the development of automatic parameterization protocols for a variety of molecule types, the improvement of backmapping procedures, the description of protein flexibility, and the development of methodologies enabling efficient sampling. We illustrate our view with examples on key areas where Martini could give important contributions such as drugs targeting membrane proteins, cryptic pockets and protein-protein interactions, and the development of soft drug delivery systems.
Fibroblast growth factor 2 (FGF2) plays crucial roles in the growth and development of several tissues. However, its function in bone homeostasis remains controversial. Here, we found that exogenous FGF2 supplementation inhibited the mineralization of bone marrow stromal cells (BMSCs), at least partially, via up-regulating the gene expression of osteoclastogenesis. The FGF receptor (FGFR) allosteric antagonist SSR128129E modestly, whereas the FGFR tyrosine kinase inhibitor AZD4547 significantly antagonized the effects of FGF2. Mechanistically, FGF2 stimulated ERK phosphorylation, and the ERK signaling inhibitor PD325901 strongly blocked FGF2 enhancement of osteoclastogenesis. Moreover, the phosphorylation of CREB was also activated in response to FGF2, thereby potentiating the interaction of p-CREB with the promoter region of Rankl gene. Notably, FGF2-deficient BMSCs exhibited higher mineralization capability and lower osteoclastogenic gene expression. Correspondingly, FGF2-knockout mice showed increased bone mass and attenuated expression of osteoclast-related markers, which were associated with moderate inhibition of the ERK signaling. In conclusion, FGF2 positively regulates osteoclastogenesis via stimulating the ERK-CREB pathway. These findings establish the importance of FGF2 in bone homeostasis, hinting the potential use of FGF2/ERK/CREB specific inhibitors to fight against bone-related disorders, such as osteoporosis.
Targeted therapy is a groundbreaking innovation for cancer treatment. Among the receptor tyrosine kinases, the fibroblast growth factor receptors (FGFRs) garnered substantial attention as promising therapeutic targets due to their fundamental biological functions and frequently observed abnormality in tumors. In the past 2 decades, several generations of FGFR kinase inhibitors have been developed. This review starts by introducing the biological basis of FGF/FGFR signaling. It then gives a detailed description of different types of small-molecule FGFR inhibitors according to modes of action, followed by a systematic overview of small-molecule-based therapies of different modalities. It ends with our perspectives for the development of novel FGFR inhibitors.
Hand-foot skin reaction (HFSR) is the most debilitating and prevalent side effect caused by multikinase inhibitors (MKIs) that share vascular endothelial growth factor receptor (VEGFR) as the common inhibition target, such as sorafenib, regorafenib, axitinib, etc. Though not life threatening, HFSR can significantly deteriorate patients’ quality of life and jeopardize the continuity of cancer therapy. Despite years of efforts, there is no FDA approved treatments for HFSR and the understanding of precise pathogenic mechanism is still limited. In this study, we hypothesized that nitric oxide has the potential therapeutic effect to reverse the toxicity caused by MKI through upregulation of several VEGF/VEGFR downstream signaling pathways. We found that glyceryl trinitrate (GTN), a nitric oxide donor, could stimulate cell proliferation, migration, and protect cells from apoptosis induced by MKIs in vitro. Local application of GTN mitigated tissue damage in rat model, while not impacting the anti-tumor effect of the MKI in HepG2 tumor-bearing mice. Finally, GTN ointment alleviated cutaneous damages and improved quality of life in six HFSR patients. Our study proposed and validated the mechanism to counteract VEGFR inhibition, providing GTN as the potential treatment to MKI-induced HFSR, which may further improve the therapeutic window of various MKI based cancer therapies.
Receptor tyrosine kinases (RTKs) control cell growth, differentiation, survival, migration and metabolism. These single pass transmembrane receptors transduce biochemical signals via lateral dimerization or oligomerization in the plasma membrane. The lateral interactions bring the kinase domains together in close proximity, so they cross-phosphorylate and activate each other, triggering downstream signaling cascades. RTK dysregulation has been linked to many cancers and other pathologies. Here we discuss common inhibitors that target the RTKs, such as antibodies, aptamers, and ligand traps that perturb the ligand-mediated dimerization process and interfere with productive contacts between the kinases. We also discuss tyrosine kinase inhibitors, small molecules that bind to the active sites of the kinases and perturb their ability to effectively phosphorylate tyrosine substrates. There have been great successes in inhibitor design during the last two decades. We overview the recent progress while focusing on inhibitors used to target receptors from the FGFR, ErbB, VEGFR, Eph, Trk and IR families. However, further improvements are needed, as challenges remain with inhibitor specificity and with acquired resistance to the inhibitors. Inhibitor design remains an active area of research, with biased inhibitors and inhibitor cocktails holding great promise as new therapeutics.
Receptor tyrosine kinases (RTKs) are single-pass membrane proteins that regulate cell growth, differentiation, motility, and metabolism. Here, we review recent advancements in RTK structure determination and in the understanding of RTK activation. We argue that further progress in the field will necessitate new ways of thinking, and we introduce the concept that RTK dimers explore ensembles of microstates, each characterized by different kinase domain dimer conformations, but the same extracellular domain dimer structure. Many microstates are phosphorylation-competent and ensure the phosphorylation of one specific tyrosine. The prevalence of each microstate correlates with its stability. A switch in ligand will lead to a switch in the extracellular domain configuration and to a subsequent switch in the ensemble of microstates. This model can explain how different ligands produce specific phosphorylation patterns, how receptor overexpression leads to enhanced signaling even in the absence of activating ligands, and why RTK kinase domain structures have remained unresolved in cryogenic electron microscopy studies.
Background
To date, no targeted therapy has been approved for nasopharyngeal carcinoma (NPC), suggesting that comprehensive understanding of genomic changes turns out to be an urgent need to break through the calm of currently known therapies of NPC.
Methods
Whole exome sequencing (WES) was performed for 14 NPC patients, including 6 NPC-IIA cases, 8 NPC-IIB cases. The cancer chip expression data named GSE12452 was downloaded from the Gene Expression Omnibus (GEO) database, and differentially expressed genes (DEGs) of each subtype were obtained using the Lima R package. Then gene ontology (GO) function enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed. Protein-protein interaction (PPI) network and Gene Set Enrichment Analysis (GSEA) were performed. Finally 7 potentially subtype relevant genes (PSRGs)¹ were obtained.
Results
In total, 37 clinically relevant mutations (CRMs)² were obtained from WES. The 2 NPC subtypes exhibited different mutational landscapes, indicating that different NPC subtypes harbor different CRMs. Notably, we discovered that mutations of CCND1 and FGF family appeared simultaneously in 3 NPC-IIB cases, but 0 in NPC-IIA. In addition, 1395 DEGs were identified from GSE12452. PI3K-Akt signaling pathway showed significant enrichment in both the pathway distribution of CRMs and KEGG analysis of DEGs, suggesting that it is a key pathway in the development of NPC. Through PPI analysis of genes involved in the PI3K-Akt pathways and expression significance analysis of DEGs co-expressed by the 2 subtypes, 54 genes finally were screened for expression significance analysis. The GSEA analysis between patients with high and low expression of 11 candidate genes were performed. As a result, 7 PSRGs were selected, including COL4A1, ASB9, RDH10, TNFRSF21, BACE2, EVA1C and LHX2.
Conclusions
These results indicate that different NPC subtypes have different genetic changes, suggesting that they may be potential targets for the diagnosis and treatment of NPC, and ultimately point to new strategies for intelligence.
FGF19 signaling through the FGFR4/β-klotho receptor complex has been shown to be a key driver of growth and survival in a subset of hepatocellular carcinomas making selective FGFR4 inhibition an attractive treatment opportunity. A kinome-wide sequence alignment highlighted a poorly-conserved cysteine residue within the FGFR4 ATP-binding site at position 552, two positions beyond the gate-keeper residue. Several strategies for targeting this cysteine to identify FGFR4 selective inhibitor starting points are summarised which made use of both rationale and unbiased screening approaches. The optimisation of a 2-formylquinoline amide hit series is described in which the aldehyde makes a hemithioacetal reversible-covalent interaction with cysteine 552. Key challenges addressed during the optimisation are improving the FGFR4 potency, metabolic stability and solubility leading ultimately to the highly-selective first-in-class clinical candidate roblitinib.
Angiokinases, such as vascular endothelial-, fibroblast- and platelet-derived growth factor receptors (VEGFRs, FGFRs and PDGFRs) play crucial roles in tumor angiogenesis. Anti-angiogenesis therapy using multi-angiokinase inhibitor has achieved great success in recent years. In this study, we presented the design, synthesis, target identification, molecular mechanism, pharmacodynamics (PD) and pharmacokinetics (PK) research of a novel triple-angiokinase inhibitor WXFL-152. WXFL-152, identified from a series of 4-oxyquinoline derivatives based on a structure–activity relationship study, inhibited the proliferation of vascular endothelial cells (ECs) and pericytes by blocking the angiokinase signals VEGF/VEGFR2, FGF/FGFRs and PDGF/PDGFRβ simultaneously in vitro. Significant anticancer effects of WXFL-152 were confirmed in multiple preclinical tumor xenograft models, including a patient‐derived tumor xenograft (PDX) model. Pharmacokinetic studies of WXFL-152 demonstrated high favourable bioavailability with single-dose and continuous multi-dose by oral administration in rats and beagles. In conclusion, WXFL-152, which is currently in phase Ib clinical trials, is a novel and effective triple-angiokinase inhibitor with clear PD and PK in tumor therapy.
ConspectusThis Account highlights recent advances and discusses major challenges in investigations of cryptic (hidden) binding sites by molecular simulations. Cryptic binding sites are not visible in protein targets crystallized without a ligand and only become visible crystallographically upon binding events. These sites have been shown to be druggable and might provide a rare opportunity to target difficult proteins. However, due to their hidden nature, they are difficult to find through experimental screening. Computational methods based on atomistic molecular simulations remain one of the best approaches to identify and characterize cryptic binding sites. However, not all methods are equally efficient. Some are more apt at quickly probing protein dynamics but do not provide thermodynamic or druggability information, while others that are able to provide such data are demanding in terms of time and resources. Here, we review the recent contributions of mixed-solvent simulations, metadynamics, Markov state models, and other enhanced sampling methods to the field of cryptic site identification and characterization. We discuss how these methods were able to provide precious information on the nature of the site opening mechanisms, to predict previously unknown sites which were used to design new ligands, and to compute the free energy landscapes and kinetics associated with the opening of the sites and the binding of the ligands. We highlight the potential and the importance of such predictions in drug discovery, especially for difficult ("undruggable") targets. We also discuss the major challenges in the field and their possible solutions.
Multiple myeloma, the second most common hematologic malignancy, frequently relapses because of chemotherapeutic resistance. Fibroblast growth factors (FGF) act as proangiogenic and mitogenic cytokines in multiple myeloma. Here, we demonstrate that the autocrine FGF/FGFR axis is essential for multiple myeloma cell survival and progression by protecting multiple myeloma cells from oxidative stress–induced apoptosis. In keeping with the hypothesis that the intracellular redox status can be a target for cancer therapy, FGF/FGFR blockade by FGF trapping or tyrosine kinase inhibitor impaired the growth and dissemination of multiple myeloma cells by inducing mitochondrial oxidative stress, DNA damage, and apoptotic cell death that were prevented by the antioxidant vitamin E or mitochondrial catalase overexpression. In addition, mitochondrial oxidative stress occurred as a consequence of proteasomal degradation of the c-Myc oncoprotein that led to glutathione depletion. Accordingly, expression of a proteasome-nondegradable c-Myc protein mutant was sufficient to avoid glutathione depletion and rescue the proapoptotic effects due to FGF blockade. These findings were confirmed on bortezomib-resistant multiple myeloma cells as well as on bone marrow–derived primary multiple myeloma cells from newly diagnosed and relapsed/refractory patients, including plasma cells bearing the t(4;14) translocation obtained from patients with high-risk multiple myeloma. Altogether, these findings dissect the mechanism by which the FGF/FGFR system plays a nonredundant role in multiple myeloma cell survival and disease progression, and indicate that FGF targeting may represent a therapeutic approach for patients with multiple myeloma with poor prognosis and advanced disease stage.
Significance
This study provides new insights into the mechanisms by which FGF antagonists promote multiple myeloma cell death.
Over-expression and/or hyperactivation of signal transducer and activator of transcription 3 (STAT3) signaling are found in various human diseases, including cancer, autoimmune disorders, and inflammatory diseases. Therefore, STAT3 represents a highly promising therapeutic target for the treatment of these diseases. However, the traditional orthosteric inhibitors of STAT3 exhibit limited clinical efficacy, with low selectivity, numerous side effects, and emerging acquired resistance. Allosteric inhibitors targeting STAT3 or its upstream molecules have emerged as a promising approach to overcome these barriers. In this review, we summarize the recent advances in the development of these inhibitors as well as their applications.
Die allosterische Hemmung von Kinasesignalen ist vielversprechend für die gezielte Suche nach Therapeutika mit außergewöhnlicher Selektivität und der Fähigkeit, die erworbene Resistenz gegen die orthosterischen Hemmstoffe der ATP‐Bindestellen zu überwinden. Aktuelle Entwicklungen bei allosterischen Kinaseinhibitoren, die außerhalb der katalytischen Kinasedomäne binden, finden großes Interesse und bieten einzigartige Chancen auf diesem Forschungsgebiet.
Abstract
Wirkstoffe, die das Kinasesignal allosterisch hemmen, sind vielversprechend für die Suche nach hochselektiven Therapeutika. Die meisten allosterischen Kinasehemmer sind Typ‐III‐ oder Typ‐IV‐Inhibitoren, die gute Kinom‐Selektivität aufweisen, aber meist unselektiv für Subtypen innerhalb derselben Kinasefamilie sind. Kürzlich wurden allosterische Hemmstoffe entwickelt, die außerhalb der katalytischen Kinasedomäne hochselektiv für spezifische Kinasesubtypen binden. Wir stellen hier allosterische Hemmstoffe vor, die an die Pseudokinase‐Domäne von Pseudokinasen oder an die extrazelluläre Domäne von Rezeptortyrosin‐Kinasen binden. Daneben behandeln wir auch neue Entwicklungen auf dem Gebiet der allosterischen Kinaseinhibitoren, darunter Beispiele für PROTACs, beleuchten die Bindungsweisen bei jedem Inhibitortyp und diskutieren künftige Chancen in diesem Feld.
Drugs that function through allosteric inhibition of kinase signaling represent a promising approach for the targeted discovery of therapeutics. The majority of developed allosteric kinase inhibitors are characterized as type III and IV inhibitors that show good kinome selectivity but generally lack the subtype selectivity of same kinase family. Recently allosteric inhibitors have been developed that bind outside the catalytic kinase domain with high selectivity for specific kinase subtypes. Allosteric inhibitors that bind to the pseudokinase domain of pseudokinase or the extracellular domain of receptor tyrosine kinases are reviewed. We also review recent developments in the field of allosteric kinase inhibitors including examples of proteolysis targeting chimeras, and highlight the unique binding modes for each type of inhibitors and address future opportunities in this area.
Fibroblast growth factor receptor 1 (FGFR1) is frequently dysregulated in various human cancers, currently regarding as one of the attractive pharmaceutical targets for cancer therapy. The FGFR1 targeting antagonist peptides, especially of the short peptides harbouring only coding amino acid might highlights promising aspects for their higher affinity, specificity and lower adverse reactions. However, most of peptides inhibitors remain in preclinical research, likely associating with their instability and short half-life. In this study, we found a stable short peptide inhibitor P48 and speculated that the stability it exhibited might be related to its non-linear spatial structure. In addition, P48 could effectively block the particular signaling pathways of FGFR1 and lead to the inhibition of cancer proliferation, invasion in vitro and restraint of tumor growth in vivo. P48 promises to being explored for cancer therapeutic intervention and is interesting to scientists searching for FGFR1 targeted antagonist peptides.
Recently, fibroblast growth factors are identified to play a vital role in the development and progression of human pancreatic cancer. FGF pathway is critical involved in numerous cellular processes through regulation of its downstream targets, including proliferation, apoptosis, migration, invasion, angiogenesis and metastasis. In this review article, we describe recent advances of FGFR signalling pathway in pancreatic carcinogenesis and progression. Moreover, we highlight the available chemical inhibitors of FGFR pathway for potential treatment of pancreatic cancer. Furthermore, we discuss whether targeting FGFR pathway is a novel therapeutic strategy for pancreatic cancer clinical management.
FGFRs are receptor tyrosine kinases with a role in several biological processes, such as the regulation of development and tissue repair. However, alterations in FGFRs 1–4, such as amplifications, fusions and mutations, as well as aberrant epigenetic or transcriptional regulation and changes in tumour–stromal interactions in the tumour microenvironment, can lead to the development and/or progression of cancer. Similar to other kinase alterations, such alterations are targetable using small molecules or antibodies, and the benefits of FGFR inhibitors have been demonstrated in clinical trials involving subsets of patients with solid tumours harbouring FGFR alterations. However, the response rates in patients with FGFR alterations were relatively low, and responses in patients without detectable FGFR alterations were also observed. In this Review, the author describes the clinical experience with FGFR inhibitors to date, and highlights key aspects that might lead to improved response rates and/or the avoidance of acquired resistance, including the selection of patients who are most likely to benefit from treatment, and the use of FGFR inhibitors in combination regimens with other agents.
Nanosized drug delivery systems have offered promising approaches for cancer therapy. However, few was effective to selectively target cancer cells and release drug at desired tumor sites. Here, we report a “smart” polymeric nanoplatform which could actively accumulate at tumor sites and dissociate to release encapsulated cargos upon near infrared laser (NIR) irradiation. This nanoplatform composed of a novel amphiphilic block copolymer poly(propylene sulphide)-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PPS-P(NIPAM-co-DMAA)) formed spherical structures in aqueous solution and responded to both oxidants and elevated temperature. Upon laser irradiation at 808 nm, the doxorubicin (DOX) and indocyanine green (ICG) loaded micelles efficiently converted the NIR light to local heat for enhanced cell uptake and therapeutic efficacy. In vivo studies showed that the micelles effectively accumulated at the tumor sites guided by the application of NIR laser, exhibiting a 6-time higher and much faster targeting effect compared to the non-irradiation group. The tumor growth was effectively inhibited by the drug loaded micelles upon laser irradiation, demonstrating significant tumor inhibition without regrowth in 16 days. This micellar nanoplatform for precise NIR guided cancer targeting and combination therapy provides a novel and robust strategy for cancer therapy.
Biomolecular simulation is increasingly central to understanding and designing biological molecules and their interactions. Detailed, physics‐based simulation methods are demonstrating rapidly growing impact in areas as diverse as biocatalysis, drug delivery, biomaterials, biotechnology, and drug design. Simulations offer the potential of uniquely detailed, atomic‐level insight into mechanisms, dynamics, and processes, as well as increasingly accurate predictions of molecular properties. Simulations can now be used as computational assays of biological activity, for example, in predictions of drug resistance. Methodological and algorithmic developments, combined with advances in computational hardware, are transforming the scope and range of calculations. Different types of methods are required for different types of problem. Accurate methods and extensive simulations promise quantitative comparison with experiments across biochemistry. Atomistic simulations can now access experimentally relevant timescales for large systems, leading to a fertile interplay of experiment and theory and offering unprecedented opportunities for validating and developing models. Coarse‐grained methods allow studies on larger length‐ and timescales, and theoretical developments are bringing electronic structure calculations into new regimes. Multiscale methods are another key focus for development, combining different levels of theory to increase accuracy, aiming to connect chemical and molecular changes to macroscopic observables. In this review, we outline biomolecular simulation methods and highlight examples of its application to investigate questions in biology.
This article is categorized under:
• Molecular and Statistical Mechanics > Molecular Dynamics and Monte‐Carlo Methods
• Structure and Mechanism > Computational Biochemistry and Biophysics
• Molecular and Statistical Mechanics > Free Energy Methods
Protein kinases have emerged as the most important class of targets in oncology drug discovery because of their major roles in regulating cellular growth and survival. At least, 11 kinase inhibitors have received FDA approval to be used as cancer treatments, and there are continuous efforts to bring more candidates from laboratory benches to the clinic. Although many protein kinase inhibitors directly interact with the ATP binding site, other can alter the kinase conformation to prevent productive ATP binding. Herein we discuss the different mechanisms of action of kinase inhibitors and provide classification of the inhibitors according to their binding sites. Some of these are allosteric inhibitors, ATP competitive inhibitors, protein substrate competitive inhibitors, and covalent bond forming inhibitors. This review provides a broad overview of the relation between mechanism of action and the issues of target selectivity and resistance. Special attention was given to the kinase inhibitors currently in clinical trials.
VEGFs activate 3 receptor tyrosine kinases, VEGFR-1, VEGFR-2, and VEGFR-3, promoting angiogenic and lymphangiogenic signaling. The extracellular receptor domain (ECD) consists of 7 Ig-homology domains; domains 2 and 3 (D23) represent the ligand-binding domain, whereas the function of D4-7 is unclear. Ligand binding promotes receptor dimerization and instigates transmembrane signaling and receptor kinase activation. In the present study, isothermal titration calorimetry showed that the Gibbs free energy of VEGF-A, VEGF-C, or VEGF-E binding to D23 or the full-length ECD of VEGFR-2 is dominated by favorable entropic contribution with enthalpic penalty. The free energy of VEGF binding to the ECD is 1.0-1.7 kcal/mol less favorable than for binding to D23. A model of the VEGF-E/VEGFR-2 ECD complex derived from small-angle scattering data provided evidence for homotypic interactions in D4-7. We also solved the crystal structures of complexes between VEGF-A or VEGF-E with D23, which revealed comparable binding surfaces and similar interactions between the ligands and the receptor, but showed variation in D23 twist angles. The energetically unfavorable homotypic interactions in D4-7 may be required for re-orientation of receptor monomers, and this mechanism might prevent ligand-independent activation of VEGFR-2 to evade the deleterious consequences for blood and lymph vessel homeostasis arising from inappropriate receptor activation.
G protein-Coupled Receptors (GPCRs) use a complex series of intramolecular conformational changes to couple agonist binding to the binding and activation of cognate heterotrimeric G protein (Gαβγ). The mechanisms underlying this long-range activation have been identified using a variety of biochemical and structural approaches and have primarily used visual signal transduction via the GPCR rhodopsin and cognate heterotrimeric G protein transducin (G(t)) as a model system. In this chapter, we review the methods that have revealed allosteric signaling through rhodopsin and transducin. These methods can be applied to a variety of GPCR-mediated signaling pathways.
Antiangiogenic drugs targeting the VEGF pathway have slowed metastatic disease progression in some patients, leading to progression-free survival (PFS) and overall survival benefits compared with controls. However, the results are more modest than predicted by most preclinical testing and benefits in PFS are frequently not accompanied by overall survival improvements. Questions have emerged about the basis of drug resistance and the limitations of predictive preclinical models, and also about whether the nature of disease progression following antiangiogenic therapy is different to classic cytotoxic therapies—in particular whether therapy may lead to more invasive or metastatic behavior. In addition, because of recent clinical trial failures of antiangiogenic therapy in patients with early-stage disease, and the fact that there are hundreds of trials underway in perioperative neoadjuvant and adjuvant settings, there is now greater awareness about the lack of appropriate preclinical testing that preceded these studies. Improved preclinical assessment of all stages of metastatic disease should be a priority for future antiangiogenic drug discovery and development.
FGFs (fibroblast growth factors) and their receptors (FGFRs) play essential roles in tightly regulating cell proliferation, survival, migration and differentiation during development and adult life. Deregulation of FGFR signalling, on the other hand, has been associated with many developmental syndromes, and with human cancer. In cancer, FGFRs have been found to become overactivated by several mechanisms, including gene amplification, chromosomal translocation and mutations. FGFR alterations are detected in a variety of human cancers, such as breast, bladder, prostate, endometrial and lung cancers, as well as haematological malignancies. Accumulating evidence indicates that FGFs and FGFRs may act in an oncogenic fashion to promote multiple steps of cancer progression by inducing mitogenic and survival signals, as well as promoting epithelial-mesenchymal transition, invasion and tumour angiogenesis. Therapeutic strategies targeting FGFs and FGFRs in human cancer are therefore currently being explored. In the present review we will give an overview of FGF signalling, the main FGFR alterations found in human cancer to date, how they may contribute to specific cancer types and strategies for therapeutic intervention.
Angiogenesis inhibitors that block VEGF receptor (VEGFR) signaling slow the growth of many types of tumors, but eventually the disease progresses. Multiple strategies are being explored to improve efficacy by concurrent inhibition of other functionally relevant receptor tyrosine kinases (RTK). XL880 (foretinib, GSK1363089) and XL184 (cabozantinib) are small-molecule inhibitors that potently block multiple RTKs, including VEGFR and the receptor of hepatocyte growth factor c-Met, which can drive tumor invasion and metastasis. This study compared the cellular effects of XL880 and XL184 with those of an RTK inhibitor (XL999) that blocks VEGFR but not c-Met. Treatment of RIP-Tag2 mice with XL999 resulted in 43% reduction in vascularity of spontaneous pancreatic islet tumors over 7 days, but treatment with XL880 or XL184 eliminated approximately 80% of the tumor vasculature, reduced pericytes and empty basement membrane sleeves, caused widespread intratumoral hypoxia and tumor cell apoptosis, and slowed regrowth of the tumor vasculature after drug withdrawal. Importantly, XL880 and XL184 also decreased invasiveness of primary tumors and reduced metastasis. Overall, these findings indicate that inhibition of c-Met and functionally related kinases amplifies the effects of VEGFR blockade and leads to rapid, robust, and progressive regression of tumor vasculature, increased intratumoral hypoxia and apoptosis, and reduced tumor invasiveness and metastasis.
Antiangiogenic drugs targeting the VEGF pathway have slowed metastatic disease progression in some patients, leading to progression-free survival (PFS) and overall survival benefits compared with controls. However, the results are more modest than predicted by most preclinical testing and benefits in PFS are frequently not accompanied by overall survival improvements. Questions have emerged about the basis of drug resistance and the limitations of predictive preclinical models, and also about whether the nature of disease progression following antiangiogenic therapy is different to classic cytotoxic therapies-in particular whether therapy may lead to more invasive or metastatic behavior. In addition, because of recent clinical trial failures of antiangiogenic therapy in patients with early-stage disease, and the fact that there are hundreds of trials underway in perioperative neoadjuvant and adjuvant settings, there is now greater awareness about the lack of appropriate preclinical testing that preceded these studies. Improved preclinical assessment of all stages of metastatic disease should be a priority for future antiangiogenic drug discovery and development.
Antibodies that block vascular endothelial growth factor (VEGF) have become an integral part of antiangiogenic tumor therapy, and antibodies targeting other VEGFs and receptors (VEGFRs) are in clinical trials. Typically receptor-blocking antibodies are targeted to the VEGFR ligand-binding site. Here we describe a monoclonal antibody that inhibits VEGFR-3 homodimer and VEGFR-3/VEGFR-2 heterodimer formation, signal transduction, as well as ligand-induced migration and sprouting of microvascular endothelial cells. Importantly, we show that combined use of antibodies blocking ligand binding and receptor dimerization improves VEGFR inhibition and results in stronger inhibition of endothelial sprouting and vascular network formation in vivo. These results suggest that receptor dimerization inhibitors could be used to enhance antiangiogenic activity of antibodies blocking ligand binding in tumor therapy.
Fibroblast growth factors (FGFs) are a family of structurally related polypeptides that are essential for embryonic development
and that function postnatally as homoeostatic factors, in the response to injury, in the regulation of electrical excitability
of cells and as hormones that regulate metabolism. In humans, FGF signalling is involved in developmental, neoplastic, metabolic
and neurological diseases. Fgfs have been identified in metazoans but not in unicellular organisms. In vertebrates, FGFs can be classified as having intracrine,
paracrine and endocrine functions. Paracrine and endocrine FGFs act via cell-surface FGF receptors (FGFRs); while, intracrine
FGFs act independent of FGFRs. The evolutionary history of the Fgf family indicates that an intracrine Fgf is the likely ancestor of the Fgf family. During metazoan evolution, the Fgf family expanded in two phases, after the separation of protostomes and deuterostomes and in the evolution of early vertebrates.
These expansions enabled FGFs to acquire diverse actions and functions.
Hepatocyte growth factor (HGF) binds to its target receptor tyrosine kinase, Met, as a single-chain form (pro-HGF) or as a cleaved two-chain disulfide-linked α/β-heterodimer. However, only two-chain HGF stimulates Met signaling. Proteolytic cleavage of the Arg(494)-Val(495) peptide bond in the zymogen-like pro-HGF results in allosteric activation of the serine protease-like β-chain (HGF β), which binds Met to initiate signaling. We use insights from the canonical trypsin-like serine protease activation mechanism to show that isolated peptides corresponding to the first 7-10 residues of the cleaved N terminus of the β-chain stimulate Met phosphorylation by pro-HGF to levels that are ∼25% of those stimulated by two-chain HGF. Biolayer interferometry data demonstrate that peptide VVNGIPTR (peptide V8) allosterically enhances pro-HGF β binding to Met, resulting in a K(D)(app) of 1.6 μm, only 8-fold weaker than the Met/HGF β-chain affinity. Most notably, in vitro cell stimulation with peptide V8 in the presence of pro-HGF leads to Akt phosphorylation, enhances cell survival, and facilitates cell migration between 75 and 100% of that found with two-chain HGF, thus revealing a novel approach for activation of Met signaling that bypasses proteolytic processing of pro-HGF. Peptide V8 is unable to enhance Met binding or signaling with HGF proteins having a mutated activation pocket (D672N). Furthermore, Gly substitution of the N-terminal Val residue in peptide V8 results in loss of all activity. Overall, these findings identify the activation pocket of the serine protease-like β-chain as a "hot spot" for allosteric regulation of pro-HGF and have broad implications for developing selective allosteric activators of serine proteases and pseudoproteases.
Fibroblast growth factors (FGFs) and their receptors control a wide range of biological functions, regulating cellular proliferation, survival, migration and differentiation. Although targeting FGF signalling as a cancer therapeutic target has lagged behind that of other receptor tyrosine kinases, there is now substantial evidence for the importance of FGF signalling in the pathogenesis of diverse tumour types, and clinical reagents that specifically target the FGFs or FGF receptors are being developed. Although FGF signalling can drive tumorigenesis, in different contexts FGF signalling can mediate tumour protective functions; the identification of the mechanisms that underlie these differential effects will be important to understand how FGF signalling can be most appropriately therapeutically targeted.
Although the first fibroblast growth factor (FGF) was discovered as a mitogen on 3T3 fibroblasts [Gospodarowicz D: Localization of a fibroblast growth factor and its effect alone and with hydrocortisone on 3T3 cell growth. Nature 1974, 249:123-127], this name is functionally misleading. This group of secreted proteins consisting now of 22 members was composed based on common structural characteristics rather than on functional similarity. Thus, only a few members of the human FGF family promote growth and strictly act on fibroblasts. While the research in the last century firmly established FGFs as key players in development, morphogenesis, angiogenesis, hematopoiesis, and survival, this decade provided clues on FGF roles in metabolism. In particular, 'hormone-like' FGF19, FGF21, and FGF23, were shown to be involved in glucose, lipid, bile acid, phosphate, and vitamin D metabolism but the mechanisms underlying their functions as metabolic regulators are still being defined.
Angiogenesis and inflammation are closely integrated processes in a number of physiological and pathological conditions, including wound healing, psoriasis, diabetic retinopathy, rheumatoid arthritis, arteriosclerosis, and cancer. Fibroblast growth factor-2 (FGF2) belongs to the family of the heparin-binding FGF growth factors. FGF2 exerts its pro-angiogenic activity by interacting with various endothelial cell surface receptors, including tyrosine kinase receptors, heparan-sulfate proteoglycans, and integrins. Elevated levels of FGF2 have been implicated in the pathogenesis of several diseases characterized by a deregulated angiogenic/inflammatory response. FGF2 induces the expression of a wide repertoire of inflammation-related genes in endothelial cells, including pro-inflammatory cytokines/chemokines and their receptors, endothelial cell adhesion molecules, and components of the prostaglandin pathway. Consistent with this pro-inflammatory signature, in vivo evidence points to a non-redundant role for chemokines and infiltrating monocytes/macrophages in FGF2-driven neovascularization. This review will focus on the cross-talk between FGF2 and the inflammatory response in the modulation of blood vessel growth.
Overexpression of FGF receptor 3 (FGFR3) is implicated in the development of t(4;14)-positive multiple myeloma. While FGFR3 is frequently overexpressed and/or activated through mutations in bladder cancer, the functional importance of FGFR3 and its potential as a specific therapeutic target in this disease have not been elucidated in vivo. Here we report that inducible knockdown of FGFR3 in human bladder carcinoma cells arrested cell-cycle progression in culture and markedly attenuated tumor progression in xenografted mice. Further, we developed a unique antibody (R3Mab) that inhibited not only WT FGFR3, but also various mutants of the receptor, including disulfide-linked cysteine mutants. Biochemical analysis and 2.1-A resolution crystallography revealed that R3Mab bound to a specific FGFR3 epitope that simultaneously blocked ligand binding, prevented receptor dimerization, and induced substantial conformational changes in the receptor. R3Mab exerted potent antitumor activity against bladder carcinoma and t(4;14)-positive multiple myeloma xenografts in mice by antagonizing FGFR3 signaling and eliciting antibody-dependent cell-mediated cytotoxicity (ADCC). These studies provide in vivo evidence demonstrating an oncogenic role of FGFR3 in bladder cancer and support antibody-based targeting of FGFR3 in hematologic and epithelial cancers driven by WT or mutant FGFR3.
The family of fibroblast growth factors (FGFs) regulates a plethora of developmental processes, including brain patterning, branching morphogenesis and limb development. Several mitogenic, cytoprotective and angiogenic therapeutic applications of FGFs are already being explored, and the recent discovery of the crucial roles of the endocrine-acting FGF19 subfamily in bile acid, glucose and phosphate homeostasis has sparked renewed interest in the pharmacological potential of this family. This Review discusses traditional applications of recombinant FGFs and small-molecule FGF receptor kinase inhibitors in the treatment of cancer and cardiovascular disease and their emerging potential in the treatment of metabolic syndrome and hypophosphataemic diseases.
Despite G-protein-coupled receptors (GPCRs) being among the most fruitful targets for marketed drugs, intense discovery efforts for several GPCR subtypes have failed to deliver selective drug candidates. Historically, drug discovery programmes for GPCR ligands have been dominated by efforts to develop agonists and antagonists that act at orthosteric sites for endogenous ligands. However, in recent years, there have been tremendous advances in the discovery of novel ligands for GPCRs that act at allosteric sites to regulate receptor function. These compounds provide high selectivity, novel modes of efficacy and may lead to novel therapeutic agents for the treatment of multiple psychiatric and neurological human disorders.
Basic fibroblast growth factor or fibroblast growth factor-2 (FGF) has been shown to affect myeloid cell proliferation and hypothesized to stimulate primitive hematopoietic cells. We sought to evaluate the effect of FGF on hematopoietic stem cells and to determine if FGF mediated its effects on progenitor cells directly or through the induction of other cytokines. To address the direct effects of FGF, we investigated whether FGF induced production of interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, IL-6, granulocyte colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor by two types of accessory cells, bone marrow (BM) fibroblasts and macrophages. We further evaluated whether antibodies to FGF-induced cytokines affected colony formation. To determine if FGF was capable of stimulating multipotent progenitors, we assessed the output of different colony types after stimulation of BM mononuclear cells (BMMC) or CD34+ BMMC and compared the effects of FGF with the stem cell active cytokine, kit ligand (KL). In addition, a subset of CD34+ BMMC with characteristics of hematopoietic stem cells was isolated by functional selection and their response to FGF was evaluated using proliferation, colony-forming, and single-cell polymerase chain reaction (PCR) assays. We determined that FGF had a stimulatory effect on the production of a single cytokine, IL-6, but that the effects of FGF on colony formation were not attributable to that induction. FGF was more restricted in its in vitro effects on BM progenitors than KL was, having no effect on erythroid colony formation. FGF did not stimulate stem cells and FGF receptors were not detected on stem cells as evaluated by single-cell reverse transcription PCR. In contrast, FGF receptor gene expression was detected in myeloid progenitor populations. These data support a directly mediated effect for FGF that appears to be restricted to lineage-committed myeloid progenitor cells. FGF does not appear to modulate the human hematopoietic stem cell.
Vascular tone control is essential in blood pressure regulation, shock, ischemia-reperfusion, inflammation, vessel injury/repair, wound healing, temperature regulation, digestion, exercise physiology, and metabolism. Here we show that a well-known growth factor, FGF2, long thought to be involved in many developmental and homeostatic processes, including growth of the tissue layers of vessel walls, functions in vascular tone control. Fgf2 knockout mice are morphologically normal and display decreased vascular smooth muscle contractility, low blood pressure and thrombocytosis. Following intra-arterial mechanical injury, FGF2-deficient vessels undergo a normal hyperplastic response. These results force us to reconsider the function of FGF2 in vascular development and homeostasis in terms of vascular tone control.
We disrupted the fibroblast growth factor (FGF) receptor 2 (FGFR2) gene by introducing a neo cassette into the IIIc ligand binding exon and by deleting a genomic DNA fragment encoding its transmembrane domain and part of its kinase I domain. A recessive embryonic lethal mutation was obtained. Preimplantation development was normal until the blastocyst stage. Homozygous mutant embryos died a few hours after implantation at a random position in the uterine crypt, with collapsed yolk cavity. Mutant blastocysts hatched, adhered, and formed a layer of trophoblast giant cells in vitro, but after prolonged culture, the growth of the inner cell mass stopped, no visceral endoderm formed, and finally the egg cylinder disintegrated. It follows that FGFR2 is required for early postimplantation development between implantation and the formation of the egg cylinder. We suggest that FGFR2 contributes to the outgrowth, differentiation, and maintenance of the inner cell mass and raise the possibility that this activity is mediated by FGF4 signals transmitted by FGFR2. The role of early FGF signaling in pregastrulation development as a possible adaptation to mammalian (amniote) embryogenesis is discussed.
Vertebrate heart development is initiated from bilateral lateral plate mesoderm that expresses the Nkx2.5 and GATA4 transcription factors, but the extracellular signals specifying heart precursor gene expression are not known. We describe here that the secreted signaling factor Fgf8 is expressed in and required for development of the zebrafish heart precursors, particularly during initiation of cardiac gene expression. fgf8 is mutated in acerebellar (ace) mutants, and homozygous mutant embryos do not establish normal circulation, although vessel formation is only mildly affected. In contrast, heart development, in particular of the ventricle, is severely abnormal in acerebellar mutants. Several findings argue that Fgf8 has a direct function in development of cardiac precursor cells: fgf8 is expressed in cardiac precursors and later in the heart ventricle. Fgf8 is required for the earliest stages of nkx2.5 and gata4, but not gata6, expression in cardiac precursors. Cardiac gene expression is restored in acerebellar mutant embryos by injecting fgf8 RNA, or by implanting a Fgf8-coated bead into the heart primordium. Pharmacological inhibition of Fgf signalling during formation of the heart primordium phenocopies the acerebellar heart phenotype, confirming that Fgf signaling is required independently of earlier functions during gastrulation. These findings show that fgf8/acerebellar is required for induction and patterning of myocardial precursors.
Fibroblast growth factor 1 (FGF1) and FGF2, the prototypic members of the FGF family of growth factors, have been implicated in a variety of physiological and pathological processes. Unlike most other FGFs, FGF1 and FGF2 are ubiquitously expressed and are not efficiently secreted. Gene knockouts in mice have previously demonstrated a role for FGF2 in brain development, blood pressure regulation, and wound healing. The relatively mild phenotypic defects associated with FGF2 deletion led to the hypothesis that the continued expression of other FGFs partially compensated for the absence of FGF2 in these mice. We now report our generation of mice lacking FGF1 and their use, in combination with our previously described FGF2 null mice, to produce mice lacking both FGF1 and FGF2. FGF1-FGF2 double-knockout mice are viable and fertile and do not display any gross phenotypic defects. In the double-knockout mice we observed defects that were similar in extent to those previously described for the FGF2 null mice. Differences in the organization of neurons of the frontal motor cortex and in the rates of wound healing were observed. We also observed in FGF2(-/-) mice and in FGF1-FGF2 double-knockout mice novel impairments in hematopoiesis that were similar in severity. Essentially no abnormalities were found in mice lacking only FGF1. Our results suggest that the relatively mild defects in FGF2 knockout animals are not a consequence of compensation by FGF1 and suggest highly restricted roles for both factors under normal developmental and physiological conditions.
We investigated the pharmacology of three novel compounds, Org 27569 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)-ethyl]-amide), Org 27759 (3-ethyl-5-fluoro-1H-indole-2-carboxylic acid [2-94-dimethylamino-phenyl)-ethyl]-amide), and Org 29647 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid (1-benzyl-pyrrolidin-3-yl)-amide, 2-enedioic acid salt), at the cannabinoid CB1 receptor. In equilibrium binding assays, the Org compounds significantly increased the binding of the CB1 receptor agonist [3H]CP 55,940 [(1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl)cyclohexan-1-ol], indicative of a positively cooperative allosteric effect. The same compounds caused a significant, but incomplete, decrease in the specific binding of the CB1 receptor inverse agonist [3H]SR 141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride], indicative of a limited negative binding cooperativity. Analysis of the data according to an allosteric ternary complex model revealed that the estimated affinity of each Org compound was not significantly different when the radioligand was [3H]CP 55,940 or [3H]SR 141716A. However, the estimated cooperatively factor for the interaction between modulator and radioligand was greater than 1 when determined against [3H]CP 55,940 and less than 1 when determined against [3H]SR 141716A. [3H]CP 55,940 dissociation kinetic studies also validated the allosteric nature of the Org compounds, because they all significantly decreased radioligand dissociation. These data suggest that the Org compounds bind allosterically to the CB1 receptor and elicit a conformational change that increases agonist affinity for the orthosteric binding site. In contrast to the binding assays, however, the Org compounds behaved as insurmountable antagonists of receptor function; in the reporter gene assay, the guanosine 5'-O-(3-[35S]thio)triphosphate binding assay and the mouse vas deferens assay they elicited a significant reduction in the Emax value for CB1 receptor agonists. The data presented clearly demonstrate, for the first time, that the cannabinoid CB1 receptor contains an allosteric binding site that can be recognized by synthetic small molecule ligands.
Myocardial infarction and ischemic heart disease are the leading cause of death in the industrial world. Therapies employed for treating these diseases are aimed at promoting increased blood flow to cardiac tissue. Pharmacological induction of new coronary growth has recently been explored, however, clinical trials with known proangiogenic factors have been disappointing. To identify novel therapeutic targets, we have explored signaling pathways that govern embryonic coronary development. Using a combination of genetically engineered mice and an organ culture system, we identified novel roles for fibroblast growth factor (FGF) and Hedgehog (HH) signaling in coronary vascular development. We show that FGF signals promote coronary growth indirectly by signaling to the cardiomyoblast through redundant function of Fgfr1 and Fgfr2. Myocardial FGF signaling triggers a wave of HH activation that is essential for vascular endothelial growth factor (Vegf)-A, Vegf-B, Vegf-C, and angiopoietin-2 (Ang2) expression. We demonstrate that HH is necessary for coronary vascular development and activation of HH signaling is sufficient to promote coronary growth and to rescue coronary defects due to loss of FGF signaling. These studies implicate HH signaling as an essential regulator of coronary vascular development and as a potential therapeutic target for coronary neovascularization. Consistent with this, activation of HH signaling in the adult heart leads to an increase in coronary vessel density.
The concept of intrinsic efficacy has been enshrined in pharmacology for half of a century, yet recent data have revealed that many ligands can differentially activate signaling pathways mediated via a single G protein-coupled receptor in a manner that challenges the traditional definition of intrinsic efficacy. Some terms for this phenomenon include functional selectivity, agonist-directed trafficking, and biased agonism. At the extreme, functionally selective ligands may be both agonists and antagonists at different functions mediated by the same receptor. Data illustrating this phenomenon are presented from serotonin, opioid, dopamine, vasopressin, and adrenergic receptor systems. A variety of mechanisms may influence this apparently ubiquitous phenomenon. It may be initiated by differences in ligand-induced intermediate conformational states, as shown for the beta(2)-adrenergic receptor. Subsequent mechanisms that may play a role include diversity of G proteins, scaffolding and signaling partners, and receptor oligomers. Clearly, expanded research is needed to elucidate the proximal (e.g., how functionally selective ligands cause conformational changes that initiate differential signaling), intermediate (mechanisms that translate conformation changes into differential signaling), and distal mechanisms (differential effects on target tissue or organism). Besides the heuristically interesting nature of functional selectivity, there is a clear impact on drug discovery, because this mechanism raises the possibility of selecting or designing novel ligands that differentially activate only a subset of functions of a single receptor, thereby optimizing therapeutic action. It also may be timely to revise classic concepts in quantitative pharmacology and relevant pharmacological conventions to incorporate these new concepts.
Nature Medicine is the premier journal for biomedical research. Respected internationally for the quality of its papers on areas ranging from infectious disease to cancer and neurodegeneration, Nature Medicine aims to bridge the gap between basic research and medical advances and is consistently ranked the number one journal by the Institute of Scientific Investigation in the Medicine, Research and Experimental category.
The fibroblast growth factor (FGF)/fibroblast growth factor receptor (FGFR) signaling network plays an important role in cell growth, survival, differentiation, and angiogenesis. Deregulation of FGFR signaling can lead to cancer development. Here, we report an FGFR inhibitor, SSR128129E (SSR), that binds to the extracellular part of the receptor. SSR does not compete with FGF for binding to FGFR but inhibits FGF-induced signaling linked to FGFR internalization in an allosteric manner, as shown by crystallography studies, nuclear magnetic resonance, Fourier transform infrared spectroscopy, molecular dynamics simulations, free energy calculations, structure-activity relationship analysis, and FGFR mutagenesis. Overall, SSR is a small molecule allosteric inhibitor of FGF/FGFR signaling, acting via binding to the extracellular part of the FGFR.
We have identified two chemical series of compounds acting as selective positive allosteric modulators (enhancers) of native
and recombinant metabotropic glutamate 1 (mGlu1) receptors. These compounds did not directly activate mGlu1 receptors but
markedly potentiated agonist-stimulated responses, increasing potency and maximum efficacy. Binding of these compounds increased
the affinity of a radiolabeled glutamate-site agonist at its extracellular N-terminal binding site. Chimeric and mutated receptors
were used to localize amino acids in the receptor transmembrane region critical for these enhancing properties. Finally, the
compounds potentiated synaptically evoked mGlu1 receptor responses in rat brain slices. The discovery of selective positive
allosteric modulators of mGlu1 receptors opens up the possibility to develop a similar class of compounds for other family
3 G protein-coupled receptors.
The fibroblast growth factor (FGF) signaling pathway is implicated as a key driver of tumor progression and growth via the dysregulation of cell proliferation, differentiation, survival, and angiogenesis in multiple tumor types. In addition, it may serve as a mechanism of resistance to antivascular endothelial growth factor targeted therapy. As such this pathway has emerged as a relevant therapeutic target, and several agents that can inhibit or modulate its signaling are in various stages of development. This review will summarize the current clinical status of agents targeting FGF receptors. In addition, strategies to accelerate the clinical development of these targeted agents will be presented.
In this review, the evidence for a role of fibroblast growth factor receptor (FGFR) mediated signalling in carcinogenesis are considered and relevant underlying mechanisms highlighted. FGF signalling mediated by FGFR follows a classic receptor tyrosine kinase signalling pathway and its deregulation at various points of its cascade could result in malignancy. Here we review the accumulating reports that revealed the association of FGF/FGFRs to various types of cancer at a genetic level, along with in vitro and in vivo evidences available so far, which indicates the functional involvement of FGF signalling in tumour formation and progression. An increasing number of drugs against the FGF pathways is currently in clinical testing. We will discuss the strategies for future FGF research in cancer and translational approaches.
The formation of the vascular network is an intricate and complex process that is an obligate requirement during vertebrate development. The cardiovascular system is the first organ to develop and reach a functional state, which underscores the crucial role of the vasculature in the developing embryo. The development of the vasculature into highly branched conduits needs to occur in numerous sites and in precise patterns to supply oxygen and nutrients to the rapidly expanding tissue of the embryo. This process is mediated by the coordinated response of vascular endothelial and mural cells to the heterogeneous angiogenic cues provided by tissues and organs, whereas aberrant regulation and coordination of angiogenic signals during development result in lethality, impaired organ development, or disease states. This article reviews the essential signaling pathways required for establishment of the vertebrate vasculature with a major focus on a key regulatory factor, vascular endothelial growth factor (VEGF). We also discuss current knowledge of physiological angiogenic processes as well as their disruptions in pathological processes, particularly tumorigenesis.
Angiogenesis inhibitors targeting the vascular endothelial growth factor (VEGF) signalling pathways are affording demonstrable therapeutic efficacy in mouse models of cancer and in an increasing number of human cancers. However, in both preclinical and clinical settings, the benefits are at best transitory and are followed by a restoration of tumour growth and progression. Emerging data support a proposition that two modes of unconventional resistance underlie such results: evasive resistance, an adaptation to circumvent the specific angiogenic blockade; and intrinsic or pre-existing indifference. Multiple mechanisms can be invoked in different tumour contexts to manifest both evasive and intrinsic resistance, motivating assessment of their prevalence and importance and in turn the design of pharmacological strategies that confer enduring anti-angiogenic therapies.
Many members of the protein kinase family have emerged as key targets for pharmacological intervention, most notably in cancer. However, the high sequence and structural homology shared by the more than 500 human protein kinases renders it exceedingly difficult to develop selective inhibitors. Most, if not all, existing inhibitors target multiple protein kinases. Current paradigm suggests that an inhibitor that targets multiple kinases and displays polypharmacology is not only acceptable but also often desirable as a therapeutic agent. However, as we move toward personalized medicine the currently acceptable promiscuity is likely to pose significant hurdles in terms of their therapeutic index, especially for diseases that necessitate long-term drug administration. Moreover, selective inhibitors are the only pharmacologically relevant route toward reagents for the dissection of complex signal transduction pathways. This article provides an overview of recent developments in the design of kinase inhibitors that display increasing selectivity by targeting regions outside the highly conserved ATP-binding pocket. These new approaches may pave the way to potentially new avenues for drug discovery while providing valuable tools for studying signal transduction.
G protein-coupled receptor (GPCR)-based drug discovery has traditionally focused on targeting the orthosteric site for the endogenous agonist. However, many GPCRs possess allosteric sites that offer enormous potential for greater selectivity in drug action. The complex behaviors ascribed to allosteric ligands also present challenges to those interested in preclinical lead discovery. These challenges include the need to detect and quantify various phenomena when screening for allosteric ligands, such as saturability of effect, probe dependence, differential effects on orthosteric ligand affinity vs. efficacy, system-dependent allosteric agonism, stimulus-bias (functional selectivity), and the potential existence of bitopic (hybrid orthosteric/allosteric) ligands. These issues are also critical when interpreting structure-function studies of allosteric GPCR modulators because mutations in receptor structure, either engineered or naturally occurring, can differentially affect not only modulator affinity, but also the nature, magnitude and direction of the allosteric effect on orthosteric ligand function. The ever-expanding array of allosteric modulators arising from both academic and industrial research also highlights the need for the development of a uniform approach to nomenclature of such compounds.
Recent structural studies of receptor tyrosine kinases (RTKs) have revealed unexpected diversity in the mechanisms of their activation by growth factor ligands. Strategies for inducing dimerization by ligand binding are surprisingly diverse, as are mechanisms that couple this event to activation of the intracellular tyrosine kinase domains. As our understanding of these details becomes increasingly sophisticated, it provides an important context for therapeutically countering the effects of pathogenic RTK mutations in cancer and other diseases. Much remains to be learned, however, about the complex signaling networks downstream from RTKs and how alterations in these networks are translated into cellular responses.
A key function of blood vessels, to supply oxygen, is impaired in tumors because of abnormalities in their endothelial lining. PHD proteins serve as oxygen sensors and may regulate oxygen delivery. We therefore studied the role of endothelial PHD2 in vessel shaping by implanting tumors in PHD2(+/-) mice. Haplodeficiency of PHD2 did not affect tumor vessel density or lumen size, but normalized the endothelial lining and vessel maturation. This resulted in improved tumor perfusion and oxygenation and inhibited tumor cell invasion, intravasation, and metastasis. Haplodeficiency of PHD2 redirected the specification of endothelial tip cells to a more quiescent cell type, lacking filopodia and arrayed in a phalanx formation. This transition relied on HIF-driven upregulation of (soluble) VEGFR-1 and VE-cadherin. Thus, decreased activity of an oxygen sensor in hypoxic conditions prompts endothelial cells to readjust their shape and phenotype to restore oxygen supply. Inhibition of PHD2 may offer alternative therapeutic opportunities for anticancer therapy.
Inflammation in the tumor stroma greatly influences tumor development. In the present study, we investigated the roles of fibroblast growth factor (FGF)-2-induced chronic inflammation in the development of 4T1 murine mammary tumors. Administration of FGF-2 into the tumor inoculation site during the initial phase of tumor growth enhanced tumor growth and pulmonary metastasis as well as microvessel density in tumor tissues in normal but not in nude mice. Infiltration of T lymphocytes and macrophages, recruitment of pericytes/vascular mural cells in neovascular walls, and the expression levels of cyclooxygenase (COX)-2 and vascular endothelial growth factor A (VEGFA) were also enhanced in the FGF-2-activated host stroma of normal mice. In addition, FGF-2-induced tumor growth and metastasis was abrogated by administration of either an immunosuppressant, FK506, or a COX-2 inhibitor. FGF-2 enhanced prostaglandin E(2) secretion in cultured T lymphocytes. In addition, VEGFA secretion was increased in a co-culture of T lymphocytes and fibroblasts in vitro. These results indicate that the massive infiltration of T lymphocytes into FGF-2-activated host stroma during the initial phase of tumor growth enhances neovascular stability by regulating endogenous COX-2 and VEGFA levels because both compounds are known to play important roles in marked 4T1 mammary tumor development via FGF-2-induced inflammatory reactions.
Biological evidence suggests that interference with the function of the angiogenic growth factor receptor VEGFR2 (flk1/KDR) is a particularly promising strategy to inhibit tumor-induced angiogenesis. Proof of concept was established by developing a monoclonal rat anti-mouse VEGFR2 antibody (DC101) and showing that it potently blocked the binding of VEGF to its receptor, inhibited VEGF-induced signaling, and strongly blocked tumor growth in mice through an anti-angiogenic mechanism. Since DC101 does not cross-react with the human VEGFR2 KDR, anti-KDR monoclonal antibodies were generated by standard hybridoma technology and by using phage display library. High affinity antibodies (Kd = 4.9 × 1010−10 − 1.1 × 1010
9 M) were found with both approaches. The anti-KDR antibodies compete on an equimolar basis with VEGF for binding to KDR and inhibit with similar potency the VEGF-induced signaling and mitogenesis in human endothelial cells. Although these antibodies cannot be tested for in vivo efficacy in standard murine tumor models because of lack of species cross-reactivity, the similarity of their in vitro properties with those of DC101 suggests that they may be effective in blocking KDR function in vivo.
Metabotropic glutamate receptors (mGluRs) are a family of G protein-coupled receptors characterized by a large, extracellular N-terminal domain comprising the glutamate-binding site. In the current study, we examined the pharmacological profile and site of action of the non-amino-acid antagonist 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt). CPCCOEt selectively inhibited glutamate-induced increases in intracellular calcium at human mGluR1b (hmGluR1b) with an apparent IC50 of 6.5 microM while having no agonist or antagonist activity at hmGluR2, -4a, -5a, -7b, and -8a up to 100 microM. Schild analysis indicated that CPCCOEt acts in a noncompetitive manner by decreasing the efficacy of glutamate-stimulated phosphoinositide hydrolysis without affecting the EC50 value or Hill coefficient of glutamate. Similarly, CPCCOEt did not displace [3H]glutamate binding to membranes prepared from mGluR1a-expressing cells. To elucidate the site of action, we systematically exchanged segments and single amino acids between hmGluR1b and the related subtype, hmGluR5a. Substitution of Thr815 and Ala818, located at the extracellular surface of transmembrane segment VII, with the homologous amino acids of hmGluR5a eliminated CPCCOEt inhibition of hmGluR1b. In contrast, introduction of Thr815 and Ala818 at the homologous positions of hmGluR5a conferred complete inhibition by CPCCOEt (IC50 = 6.6 microM), i.e., a gain of function. These data suggest that CPCCOEt represents a novel class of G protein-coupled receptor antagonists inhibiting receptor signaling without affecting ligand binding. We propose that the interaction of CPCCOEt with Thr815 and Ala818 of mGluR1 disrupts receptor activation by inhibiting an intramolecular interaction between the agonist-bound extracellular domain and the transmembrane domain.
Epithelial-mesenchymal transformation (EMT) plays an important role in embryonic development and tumorigenesis and has been described in organ remodeling during fibrogenesis. In the kidney, EMT can be induced efficiently in cultured proximal tubular epithelium by coincubation of transforming growth factor (TGF)-beta1 and epidermal growth factor (EGF). Recently, we also have observed overexpression of basic fibroblast growth factor-2 (FGF-2) protein and mRNA in human kidneys with marked interstitial fibrosis. The aims of the present study were to compare the effects of FGF-2 as a facilitator of EMT in tubular epithelial cells with EGF and TGF-beta1. We analyzed the morphogenic effects of the three cytokines on four different aspects of EMT: cell motility, expression and regulation of cellular markers, synthesis and secretion of extracellular matrix (ECM) proteins as well as matrix degradation.
Cell motility was studied by a migration assay and cell differentiation markers were analyzed by immunofluorescence and immunoblots. In addition, regulation of the epithelial adhesion molecule E-cadherin and fibroblast-specific protein 1 (FSP1) were analyzed by luciferase reporter constructs and stable transfections. ELISAs for collagen types I and IV and fibronectin were used for ECM synthesis, and zymograms were utilized for analysis of matrix degradation.
FGF-2 induced cell motility across a tubular basement membrane in two tubular cell lines. All three cytokines induced the expression of vimentin and FSP1, but only FGF-2 and TGF-beta1 reduced cytokeratin expression by immunofluorescence. These effects were most demonstrable in the distal tubular epithelial cell line and were confirmed by immunoblot analyses. Expression of E-cadherin was reduced by 61.5 +/- 3.3% and expression of cytokeratin by 91 +/- 0.5% by TGF-beta1 plus FGF-2. Conversely, the mesenchymal markers alpha-smooth muscle actin (SMA) and FSP1 were induced with FGF-2 by 2.2 +/- 0.1-fold and 6.8 +/- 0.9-fold, respectively. Interestingly, de novo expression of the mesenchymal marker OB-cadherin was induced only by FGF-2 and EGF but not by TGF-beta1. All three cytokines stimulated FSP1 and decreased E-cadherin promoter activity. FGF-2 also induced intracellular fibronectin synthesis but not secretion, the latter of which was stimulated exclusively by TGF-beta1. Finally, zymographic analyses demonstrated that FGF-2 induced MMP-2 activity by 2.6 +/- 0.5-fold and MMP-9 activity by 2.4 +/- 0.1-fold, providing a mechanism for basement membrane disintegration and migratory access of transforming epithelium to the interstitium.
FGF-2 makes an important contribution to the mechanisms of EMT by stimulating microenvironmental proteases essential for disaggregation of organ-based epithelial units. Furthermore, the expression of epithelial and mesenchymal marker proteins seems to be affected at the promoter level.
G protein-coupled receptors (GPCRs) represent the largest family of cell-surface receptors. These receptors are natural allosteric proteins because agonist-mediated signaling by GPCRs requires a conformational change in the receptor protein transmitted between two topographically distinct binding sites, one for the agonist and another for the G protein. It is now becoming increasingly recognized, however, that the agonist-bound GPCR can also form ternary complexes with other ligands or "accessory" proteins and display altered binding and/or signaling properties in relation to the binary agonist-receptor complex. Allosteric sites on GPCRs represent novel drug targets because allosteric modulators possess a number of theoretical advantages over classic orthosteric ligands, such as a ceiling level to the allosteric effect and a potential for greater GPCR subtype-selectivity. Because of the noncompetitive nature of allosteric phenomena, the detection and quantification of such effects often relies on a combination of equilibrium binding, nonequilibrium kinetic, and functional signaling assays. This review discusses the development and properties of allosteric receptor models for GPCRs and the detection and quantification of allosteric effects. Moreover, we provide an overview of the current knowledge regarding the location of possible allosteric sites on GPCRs and candidate endogenous allosteric modulators. Finally, we discuss the potential for allosteric effects arising from the formation of GPCR oligomers or GPCRs complexed with accessory cellular proteins. It is proposed that the study of allosteric phenomena will become of progressively greater import to the drug discovery process due to the advent of newer and more sensitive GPCR screening technologies.
Cell-surface receptors are the targets for more than 60% of current drugs. Traditionally, optimizing the interaction of lead molecules with the binding site for the endogenous agonist (orthosteric site) has been viewed as the best means of achieving selectivity of action. However, recent developments have highlighted the fact that drugs can interact with binding sites on the receptor molecule that are distinct from the orthosteric site, known as allosteric sites. Allosteric modulators could offer several advantages over orthosteric ligands, including greater selectivity and saturability of their effect.
Increased local osteoclast (OC)-mediated bone resorption coincides with angiogenesis in normal bone development and fracture repair, as well as in pathological disorders such as tumor-associated osteolysis and inflammatory-related rheumatoid arthritis or periodontal disease. Angiogenic stimulation causes recruitment, activation, adhesion, transmigration, and differentiation of hematopoietic cells which may therefore enable greater numbers of pre-OC to emigrate from the circulation and develop into bone-resorptive OCs. A chick chorioallantoic membrane (CAM) model, involving coimplantation of a stimulus in an agarose plug directly adjacent to a bone chip was used to investigate if a potent angiogenic stimulator, basic fibroblast growth factor (bFGF), could promote OC recruitment, differentiation, and resorption in vivo. Angiogenesis elicited by bFGF on the CAM was accompanied by increased OC formation and bone pit resorption (both overall and on a per OC basis) on the bone implants in vivo. In complementary in vitro assays, bFGF did not directly stimulate avian OC development from bone marrow mononuclear cell precursors, consistent with their low mRNA expression of the four avian signaling FGF receptors (FGFR)-1, FGFR-2, FGFR-3, and FGFR-like embryonic kinase (FREK). In contrast, bFGF activated isolated avian OC bone pit resorption via mechanisms inhibited by a selective cyclo-oxygenase (COX)-2 prostaglandin inhibitor (NS-398) or p42/p44 MAPK activation inhibitor (PD98059), consistent with a relatively high expression of FGFR-1 by differentiated avian OCs. Thus, bFGF may sensitively regulate local bone resorption and remodeling through direct and indirect mechanisms that promote angiogenesis and OC recruitment, formation, differentiation, and activated bone pit resorption. The potential for bFGF to coinduce angiogenesis and OC bone remodeling may find clinical applications in reconstructive surgery, fracture repair, or the treatment of avascular necrosis. Alternatively, inhibiting such bFGF-dependent processes may aid in the treatment of inflammatory-related or metastatic bone loss.
(+/-)-1-(anti-3-Hydroxy-cyclopentyl)-3-(4-methoxy-phenyl)-7-phenylamino-3,4-dihydro-1H-pyrimido[4,5-d]pyrimidin-2-one (RO4383596) is a potent and selective inhibitor of the pro-angiogenic receptor tyrosine kinases KDR, FGFR, and PDGFR. This agent has an excellent pharmacokinetic profile and is highly efficacious in rodent models of angiogenesis upon oral administration.
Function-blocking antibodies to VEGF receptors R1 and R2 were used to probe their roles in controlling angiogenesis in a mouse model of pancreatic islet carcinogenesis. Inhibition of VEGFR2 but not VEGFR1 markedly disrupted angiogenic switching, persistent angiogenesis, and initial tumor growth. In late-stage tumors, phenotypic resistance to VEGFR2 blockade emerged, as tumors regrew during treatment after an initial period of growth suppression. This resistance to VEGF blockade involves reactivation of tumor angiogenesis, independent of VEGF and associated with hypoxia-mediated induction of other proangiogenic factors, including members of the FGF family. These other proangiogenic signals are functionally implicated in the revascularization and regrowth of tumors in the evasion phase, as FGF blockade impairs progression in the face of VEGF inhibition.
Vascular endothelial growth factor (VEGF) exerts crucial functions during pathological angiogenesis and normal physiology. We observed increased hematocrit (60-75%) after high-grade inhibition of VEGF by diverse methods, including adenoviral expression of soluble VEGF receptor (VEGFR) ectodomains, recombinant VEGF Trap protein and the VEGFR2-selective antibody DC101. Increased production of red blood cells (erythrocytosis) occurred in both mouse and primate models, and was associated with near-complete neutralization of VEGF corneal micropocket angiogenesis. High-grade inhibition of VEGF induced hepatic synthesis of erythropoietin (Epo, encoded by Epo) >40-fold through a HIF-1alpha-independent mechanism, in parallel with suppression of renal Epo mRNA. Studies using hepatocyte-specific deletion of the Vegfa gene and hepatocyte-endothelial cell cocultures indicated that blockade of VEGF induced hepatic Epo by interfering with homeostatic VEGFR2-dependent paracrine signaling involving interactions between hepatocytes and endothelial cells. These data indicate that VEGF is a previously unsuspected negative regulator of hepatic Epo synthesis and erythropoiesis and suggest that levels of Epo and erythrocytosis could represent noninvasive surrogate markers for stringent blockade of VEGF in vivo.
Adult rheumatoid arthritis (RA), a systemic autoimmune disorder of unknown etiology, is characterized by dysfunctional cellular and humoral immunity, enhanced migration and attachment of peripheral macrophages and pro-inflammatory leukocytes to the synovium and articular cartilage of diarthrodial joints. The progressive destruction of cartilage and bone in RA is a result of elevated pro-inflammatory cytokine gene expression, synovial neovascularization, proteinase-mediated dissolution of articular cartilage matrix and osteoclast-mediated subchondral bone resorption. Juvenile chronic arthritis (JCA) is disease with manifestations similar to adult RA that occurs in childhood. JCA usually causes precocious joint destruction and often also presents with evidence of growth plate anomalies and reduced stature. Three proteins play an integral role in both adult RA and JCA. These are somatotropin (also called pituitary growth hormone (GH)), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). GH is responsible for regulating long bone growth and skeletal maturation through its capacity to stimulate insulin-like growth factor-I (IGF-1) synthesis by hepatocytes. Mechanisms responsible for growth plate disturbances and short stature in children with JCA include deficient GH production, GH-insensitivity resulting from defects in the GH receptor, suppressed IGF-1 synthesis or neutralization of IGF-1 action by IGF-1 binding proteins (IGFBPs). In addition, GH has also been implicated in perpetuating inflammation and pain in adult RA. VEGF has been shown to be the critical angiogenesis factor responsible for vascular proliferation and blood vessel invasion of the synovial lining membrane in RA. Acidic FGF (FGF-1) and basic FGF (FGF-2) have also been implicated in aberrant synoviocyte proliferation (i.e. synovial hyperplasia) and apoptosis resistance in adult RA.