No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Nanomedicines Eradicating Cancer Stem-Like Cells in Vivo by pH-Triggered Intracellular Cooperative Action of Loaded Drugs
Abstract
Nanomedicines capable of spatiotemporal control over drug functions have potential for developing resilient therapies, even against tumors harboring recalcitrant cancer stem cells (CSCs). By coordinating drug interactions within the confined inner compartment of core-shell nanomedicines, we conceived multicomponent nanomedicines directed to achieve synchronized and synergistic drug cooperation within tumor cells as a strategy for enhancing efficacy, overcoming drug resistance and eradicating CSCs. The approach was validated by using polymeric micellar nanomedicines co-incorporating the pan-kinase inhibitor staurosporine (STS), which was identified as the most potent CSC-inhibitor from a panel of signaling-pathway inhibitors, and the cytotoxic agent epirubicin (Epi), through rationally contriving the affinity between the drugs. The micelles released both drugs simultaneously, triggered by acidic endosomal pH, attaining concurrent intracellular delivery, with STS working as a companion for Epi, down-regulating efflux transporters and resistance mechanisms induced by Epi. These features prompted the nanomedicines to eradicate orthotopic xenografts of Epi-resistant mesothelioma bearing CSC sub-population.
... This was achieved by loading STS into our polymeric micelles encapsulating the anthracycline epirubicin (Epi), which are in phase I/II clinical trials in U.S.A. [15], indicating the potential of our approach for clinical translation. These nanomedicines load STS by interaction with the Epi molecules conjugated to the block copolymers forming the micelles [16,17]. Moreover, both STS and Epi are concomitantly released at endosomal pH to exert synergistic antitumor effects in vivo through STS-mediated blocking of drug-efflux transporters, and cytotoxic actions of Epi and STS for eradicating both bulk cancer cells and tumorigenic CSCs [16,17]. ...
... These nanomedicines load STS by interaction with the Epi molecules conjugated to the block copolymers forming the micelles [16,17]. Moreover, both STS and Epi are concomitantly released at endosomal pH to exert synergistic antitumor effects in vivo through STS-mediated blocking of drug-efflux transporters, and cytotoxic actions of Epi and STS for eradicating both bulk cancer cells and tumorigenic CSCs [16,17]. Our strategy was then evaluated in renal cell carcinoma (RCC), a form of genitourinary cancer with the highest mortality rate [18]. ...
... STS/Epi/m micelles were prepared as previously reported [16,17]. Briefly, the PEG-poly(aspartate-hydrazide-epirubicin) block copolymer (1 mg Epi/mL) was mixed with STS at 0.2 mg/mL in dimethylformamide (DMF). ...
Tumor resistance to tyrosine kinase inhibitors (TKIs) is an inexorable clinical event. The manipulation of adaptive changes in cancer cells while inhibiting the signaling pathways could be an effective strategy for overcoming TKI resistance toward reducing tumor relapse and prolonging survival. Here, we tested this approach by using polymeric nanomedicines delivering the pan-kinase inhibitor staurosporine (STS) to treat renal cell carcinoma (RCC) resistant to the multi-targeted TKI sunitinib. STS blocked the activity of TKI-resistant protein kinases and strongly inhibited adaptive dynamics in RCC cells promoted by MDR1 and GLUT1 to overcome sunitinib resistance. Co-delivery of STS and epirubicin directed to eliminate fast-proliferating cancer cells through the same nanomedicine platform enabled safe and potent in vivo efficacy in mouse models of RCC, overcoming sunitinib resistance and suppressing the development of metastasis. These results indicate our approach as a promising strategy for effectively managing TKI resistance.
... CSC-targeted treatment is, therefore, a promising strategy for improving the efficacy of breast cancer therapy [3,4]. Different approaches have been reported for the selective treatment of CSCs, by either inhibiting the CSC signal pathways [5], suppressing the protein kinases in CSCs [6,7], modulating the CSC-niches [8], reprogramming the metabolism of CSCs [9], or differentiating the CSCs [10]. The targeting of CSC biomarkers, such as CD44, has attracted much attention in CSC-specific drug delivery [11]. ...
... Then, the change in the CSC (or ALDH high cell) proportion in tumors was examined (Fig. 6E). Note that the ALDH high population in saline-treated tumors as control was similarly determined to be those reported in the previous studies [6,63,64]. The CSC (or ALDH high cell) proportion in the tumors treated with siPLK1-loaded Glu-NPs was significantly lower than that treated with saline, siCont-loaded Glu-NPs, and siPLK1-loaded MeO-NPs, probably due to the preferential accumulation of Glu-NPs in the CSCs and their RNAi-driven anticancer effect. ...
Cancer stem-like cells (CSCs) treatment is a plausible strategy for enhanced cancer therapy. Here we report a glucose-installed sub-50-nm nanocarrier for the targeted delivery of small interfering RNA (siRNA) to CSCs through selective recognition of the glucose ligand to the glucose transporter 1 (GLUT1) overexpressed on the CSC surface. The siRNA nanocarrier was constructed via a two-step assembling process. First, a glucose-installed poly(ethylene glycol)-block-poly(L-lysine) modified with lipoic acid (LA) at the ω-end (Glu-PEG-PLL-LA) was associated with a single siRNA to form a unimer polyion complex (uPIC). Second, a 20 nm gold nanoparticle (AuNP) was decorated with ~65 uPICs through Au–S bonding. The glucose-installed targeted nanoparticles (Glu-NPs) exhibited higher cellular uptake of siRNA payloads in a spheroid breast cancer (MBA-MB-231) cell culture compared with glucose-unconjugated control nanoparticles (MeO-NPs). Notably, the Glu-NPs became more efficiently internalized into the CSC fraction, which was defined by aldehyde dehydrogenase (ALDH) activity assay, than the other fractions, probably due to the higher GLUT1 expression level on the CSCs. The Glu-NPs elicited significantly enhanced gene silencing in a CSC-rich orthotopic MDA-MB-231 tumor tissue following systemic administration to tumor-bearing mice. Ultimately, the repeated administrations of polo-like kinase 1 (PLK1) siRNA-loaded Glu-NPs significantly suppressed the growth of orthotopic MDA-MB-231 tumors. These results demonstrate that Glu-NP is a promising nanocarrier design for CSC-targeted cancer treatment.
... Regarding the second approach, several systems have been considered, such as the co-delivery of small molecules and the combination of small molecules and nucleic acids. For instance, the co-delivery of cytotoxic epirubicin and staurosporine, which is a pan-kinase inhibitor, in pHsensitive polymeric micelles allowed overcoming epirubicin resistance and potentiating the efficacy against CSCs to treat epirubicin resistant breast tumors and eradicate intractable mesothelioma in mice after intravenous injection [85,93]. Co-delivering siRNA has been used for knocking down genes involved in drug resistance and enhancing efficacy. ...
... Thus, Guo et al. fabricated novel dual drug-loading polymeric nanoparticles using polyethylene glycol (PEG) and EPLYS that physically encapsulated lapatinib (LAP) and DOX (DMMA-P-DOX/LAP nanoparticles) [50][51][52][53][54][55][56][57]. In these polymer-drug conjugates, an acid-cleavable linker was inserted between the drug molecule and the polymer, accelerating the decomposition of the conjugate under intracellular pH conditions to accurately deliver and release drugs [58][59][60][61][62]. Therefore, DOX was conjugated to the hydrophilic PEG-EPLYS backbone through acid-labile imine bonds, and LAP was physically encapsulated into the nanoparticles; thus, after the cleavage of imine bond, the remaining hydrophobic chain was rendered insufficient, leading to rapid decomposition of nanoparticles. ...
The multi-dimensional challenge of drug resistance is one of the pivotal hindrances for cancer chemotherapy. A reductive approach to define and distinguish the main aspects of drug resistance, such as tumor growth kinetics about tumor micro-environment (tumor multifariousness), therapeutic pressure, physical barricades, irreversible genetic mutation, as well as role of the immune system, are the main causes of failure in cancer therapy are presented systematically. We are focusing on general approaches to reduce drug resistance: earlier diagnosis of tumors allowing for cancer halting; dynamic surveillance throughout treatment; the adding of new therapeutic strategies and improve pharmacodynamics precepts resulting in profound effects; and identification of cancerous cells repositories using high-throughput monitoring, as well as the interoperability of clinical- gene mapping statics are described in detail. These strategies could be potentially constructed for any tumor at any precise moment and used to guide therapy selection. Chemotherapeutic agents results in mild improved survival in clinical trials owing to several pathophysiologic obstacles, such as intra-tumoral dispersion, invasion & intra-cellular transportation. This review highlights recent advancements in developing new therapeutic innovations to combat drug resistance in cancer therapy by overcoming various barricades in the tumor microenvironment.
... pH-gradient offers an opportunity for release of therapeutic payloads from pH-sensitive polymeric nanocarriers upon a change in the pH of their microenvironment. Kataoka et al. developed pH-sensitive micellar nanocarriers from poly(ethylene glycol)-b-poly(aspartate) diblock copolymer for co-delivery of staurosporine, a cancer stem cell inhibitor, and the anticancer agent epirubicin [10]. Epirubicin was linked to the copolymer through acid-labile hydrazone bonds, which allowed it to be triggered and to have a coordinated release at endosomal pH. ...
We report the elaboration of redox-responsive functional micellar nanocarriers designed for triggered release of caffeic acid phenethyl ester (CAPE) in cancer therapy. Three-layered micelles, comprising a poly(ε-caprolactone) (PCL) core, a middle poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) layer and a PEO outer corona, were prepared by co-assembly of PEO113-b-PCL35-b-PEO113 and PAA13-b-PCL35-b-PAA13 amphiphilic triblock copolymers in aqueous media. The preformed micelles were loaded with CAPE via hydrophobic interactions between the drug molecules and PCL core, and subsequently crosslinked by reaction of carboxyl groups from PAA and a disulfide crosslinking agent. The reaction of crosslinking took place in the middle layer of the nanocarriers without changing the encapsulation efficiency (EE~90%) of the system. The crosslinked polymeric micelles (CPMs) exhibited superior structural stability and did not release CAPE in phosphate buffer (pH 7.4). However, in weak acidic media and in the presence of 10 mM reducing agent (dithiothreitol, DTT), the payload was released at a high rate from CPMs due to the breakup of disulfide linkages. The physicochemical properties of the nanocarriers were investigated by dynamic and electrophoretic light scattering (DLS and ELS) and atomic force microscopy (AFM). The rapid release of CAPE under intracellular-like conditions and the lack of premature drug release in media resembling the blood stream (neutral pH) make the developed CPMs a promising candidate for controllable drug release in the microenvironment of tumors.
... Some commonly used anticancer drugs, such as paclitaxel, cisplatin, and sunitinib, efficiently damage rapidly dividing cancer cells [1,8,9], but they are ineffective in eliminating CSCs; worse still, they may unexpectedly enrich the ratio of CSCs in tumors [9][10][11]. To date, only a few therapeutic agents have been used alone to directly eliminate CSCs or in combination with modulatory agents to sensitize them to standard therapies [1,[12][13][14][15][16][17][18][19]. However, cancer cells and CSCs are frequently embedded in the dense tumor stroma comprising versatile stromal cells and extracellular matrix networks, making them extremely difficult access [5,20,21]. ...
Cancer cells and cancer stem cells (CSCs) are the major players of cancer malignancy and metastasis, but they are extremely difficult to access. Inspired by the vital role of macrophages and microvesicle-mediated cell–cell communication in tumors, we herein designed M2 macrophage microvesicle-inspired nanovehicle of cabazitaxel (M-CFN) to promote accessibility to cancer cells and CSCs in tumors. In the 4T1 tumor model, M-CFN flexibly permeated the tumor mass, accessed cancer cells and CD90-positive cells, and significantly promoted their entry into CSC fractions in tumors. Moreover, M-CFN treatment profoundly eliminated aldehyde dehydrogenase (ALDH)-expressing CSCs in 4T1 and MCF-7 tumors, produced notable depression of tumor growth and caused 93.86% suppression of lung metastasis in 4T1 models. Therefore, the M2 macrophage microvesicle-inspired nanovehicle provides an encouraging strategy to penetrate the tumor tissues and access these insult cells in tumors for effective cancer therapy.
Graphical Abstract
... At present, chemotherapeutic drugs are mainly loaded in NDDSs in two forms: physical loading and chemical grafting. For example, Kinoh et al. [52] linked the epirubicin (Epi) to polyaspartic acid through a pH-sensitive hydrazide bond, and then loaded staurosporine via intermolecular interactions to obtain dual-drug-loaded copolymer micelles. Although nanomedicines have often shown greatly enhanced therapeutic efficacy in preclinical studies compared with traditional small molecule drugs, their efficacy in the clinical setting is suboptimal due to the heterogeneity of the EPR effect and the biological barriers of tumors hindering effective penetration of NPs [53]. ...
As one of the most important cancer treatment strategies, conventional chemotherapy has substantial side effects and leads easily to cancer treatment failure. Therefore, exploring and developing more efficient methods to enhance cancer chemotherapy is an urgently important problem that must be solved. With the development of nanotechnology, nanomedicine has showed a good application prospect in improving cancer chemotherapy. In this review, we aim to present a discussion on the significant research progress in nanomedicine for enhanced cancer chemotherapy. First, increased enrichment of drugs in tumor tissues relying on different targeting ligands and promoting tissue penetration are summarized. Second, specific subcellular organelle-targeted chemotherapy is discussed. Next, different combinational strategies to reverse multidrug resistance (MDR) and improve the effective intracellular concentration of therapeutics are discussed. Furthermore, the advantages of combination therapy for cancer treatment are emphasized. Finally, we discuss the major problems facing therapeutic nanomedicine for cancer chemotherapy, and propose possible future directions in this field.
... Many other research groups have also cultured mammospheres in the similar manner and used them to study the properties of CSCs. 25,42,43 Therefore, the mammospheres cultured and characterized by us depict the best in vitro model for CSCrelated studies. ...
Cancer stem-like cells (CSCs) have emerged as an important target for breast cancer therapy owing to their self-renewability, proliferation, and elevated chemoresistance properties. Here, we present a strategy of eliminating CSCs by differentiation therapy where "forced differentiation"reprograms CSCs so that they lose their intrinsic properties and become susceptible for conventional chemotherapeutic drugs. In this study, we report that a conventional chemotherapeutic paclitaxel enhances the stemness of CSCs, while a phytochemical forskolin being essentially nontoxic to CSCs possesses the intrinsic ability to reprogram them. To achieve simultaneous targeting of CSCs and bulk tumor cells, we used a co-delivery system where liquid crystal nanoparticles (LCN) were co-encapsulated with both paclitaxel and forskolin. LCN showed higher uptake, retention, and penetration potential in CSCs overcoming their high drug efflux property. Moreover, LCN improved the pharmacokinetic parameters of forskolin, which otherwise had very low retention and bioavailability. Forskolin-loaded LCN forced CSCs to exit from their mesenchymal state, which reduced their stemness and chemosensitized them while inhibiting E-cadherin-mediated survival and tumor-initiating potential as well as reversing paclitaxel-induced stemness. We further showed that upon administration of paclitaxel and forskolin co-loaded LCN to an orthotropic xenograft mouse model, the nanomedicine showed enhanced passive tumor targeting capability with very potent antitumor activity that eradicated small solid tumor in a single dose and showed no sign of tumor relapse or systemic toxicity over a long period. Overall, these findings give a proof of concept that co-delivery of forskolin and paclitaxel in a single nanoformulation can achieve overall tumor targeting where forskolin can efficiently reprogram/differentiate CSCs and paclitaxel can induce cytotoxicity in both differentiated CSCs and bulk tumor cells simultaneously. Hence, this study can provide a nanoformulation that can offer an efficient strategy for cancer therapy.
... Thus, Guo et al. fabricated novel dual drug-loading polymeric nanoparticles using polyethylene glycol (PEG) and EPLYS that physically encapsulated lapatinib (LAP) and DOX (DMMA-P-DOX/LAP nanoparticles) [50][51][52][53][54][55][56][57]. In these polymer-drug conjugates, an acid-cleavable linker was inserted between the drug molecule and the polymer, accelerating the decomposition of the conjugate under intracellular pH conditions to accurately deliver and release drugs [58][59][60][61][62]. Therefore, DOX was conjugated to the hydrophilic PEG-EPLYS backbone through acid-labile imine bonds, and LAP was physically encapsulated into the nanoparticles; thus, after the cleavage of imine bond, the remaining hydrophobic chain was rendered insufficient, leading to rapid decomposition of nanoparticles. ...
To overcome cancer, various chemotherapeutic studies are in progress; among these, studies on nano-formulated combinatorial drugs (NFCDs) are being actively pursued. NFCDs function via a fusion technology that includes a drug delivery system using nanoparticles as a carrier and a combinatorial drug therapy using two or more drugs. It not only includes the advantages of these two technologies, such as ensuring stability of drugs, selectively transporting drugs to cancer cells, and synergistic effects of two or more drugs, but also has the additional benefit of enabling the spatiotemporal and controlled release of drugs. This spatial and temporal drug release from NFCDs depends on the application of nanotechnology and the composition of the combination drug. In this review, recent advances and challenges in the control of spatiotemporal drug release from NFCDs are provided. To this end, the types of combinatorial drug release for various NFCDs are classified in terms of time and space, and the detailed programming techniques used for this are described. In addition, the advantages of the time and space differences in drug release in terms of anticancer efficacy are introduced in depth.
... Complex coacervation is an associative liquid-liquid phase separation phenomena that results from the electrostatic and entropic interactions between oppositely charged macro-ions. [21][22][23][24] Complex coacervation has a strong history of use as a method of encapsulation in the food and personal care industries, [25][26][27][28][29][30] and has gained recent attention for use in the fields of drug delivery [31][32][33][34][35] and gene therapy. [36][37][38] A number of reports have focused specifically on the incorporation of proteins into complex coacervates, with a goal of protecting proteins against degradation 39,40 and potentially enhancing protein thermal stability. ...
Widespread vaccine coverage for viral diseases could save the lives of millions of people each year. For viral vaccines to be effective, they must be transported and stored in a narrow temperature range of 2–8 °C. If temperatures are not maintained, the vaccine may lose its potency and would no longer be effective in fighting disease; this is called the cold storage problem. Finding a way to thermally stabilize a virus and end the need to transport and store vaccines at refrigeration temperatures will increase access to life-saving vaccines. We explore the use of polymer-rich complex coacervates to stabilize viruses. We have developed a method of encapsulating virus particles in liquid complex coacervates that relies on the electrostatic interaction of viruses with polypeptides. In particular, we tested the incorporation of two model viruses; a non-enveloped porcine parvovirus (PPV) and an enveloped bovine viral diarrhea virus (BVDV) into coacervates formed from poly(lysine) and poly(glutamate). We identified optimal conditions (i.e., the relative amount of the two polypeptides) for virus encapsulation, and trends in this composition matched differences in the isoelectric point of the two viruses. Furthermore, we were able to achieve a ∼103–104-fold concentration of virus into the coacervate phase, such that the level of virus remaining in the bulk solution approached our limit of detection. Lastly, we demonstrated a significant enhancement of the stability of non-enveloped PPV during an accelerated aging study at 60 °C over the course of a week. Our results suggest the potential for using coacervation to aid in the purification and formulation of both enveloped and non-enveloped viruses, and that coacervate-based formulations could help limit the need for cold storage throughout the transportation and storage of vaccines based on non-enveloped viruses.
... Given the miscellaneous agents needed to promote the advancement of the cancerimmune cycle in patients with solid tumors, a great deal of studies has further shifted to the invention of nanomedicines that amalgamate multiple immunotherapies (i.e., chemotherapy and immune-modulators; radiosensitizers, incorporating photothermal and photodynamic therapies and immune-modulators;RNA interference-based immune-modulators; RNA-based or other vaccines loaded with adjuvants)163 . As a matter of fact, some functions of nanomedicines (i.e., the control of release chemistry of drug-polymer joints, the conjugation of a drug or antibody on the surface, and coordination of drug interactions within the core of nanomedicines) indicate the possibilities of the synchronous administration of multiple drugs164 . In other words, multiple reagents (including nucleic acids) can be integrated into single nanomedicines. ...
Cancer immunotherapy has veered the paradigm of cancer treatment. Despite recent advances in immunotherapy for improved antitumor efficacy, the complicated tumor microenvironment (TME) is highly immunosuppressive, yielding both astounding and unsatisfactory clinical successes. In this regard, clinical outcomes of currently available immunotherapy are confined to the varied immune systems owing in large part to the lack of understanding of the complexity and diversity of the immune context of the TME. Various advanced designs of nanomedicines could still not fully surmount the delivery barriers of the TME. The immunosuppressive TME may even dampen the efficacy of antitumor immunity. Recently, some nanotechnology-related strategies have been inaugurated to modulate the immunosuppressive cells within the tumor immune microenvironment (TIME) for robust immunotherapeutic responses. In this review, we will highlight the current understanding of the immunosuppressive TIME and identify disparate subclasses of TIME that possess an impact on immunotherapy, especially those unique classes associated with the immunosuppressive effect. The immunoregulatory cell types inside the immunosuppressive TIME will be delineated along with the existing and potential approaches for immunosuppressive cell modulation. After introducing the various strategies, we will ultimately outline both the novel therapeutic targets and the potential issues that affect the efficacy of TIME-based nanomedicines.
... This can be accomplished by a stimuli-responsive release mechanism such as the lower pH in tumors and inflamed tissues. 10,11 One of the potential types of stimuli for this purpose is the usage of enzymes, which offer high selectivity toward their substrates. More importantly, the overexpression of disease-associated enzymes can be utilized to achieve selective release at the disease site. ...
Tuning the enzymatic degradation and disassembly rates of polymeric amphiphiles and their assemblies is crucial for designing enzyme-responsive nanocarriers for controlled drug delivery applications. The common methods to control the enzymatic degradation of amphiphilic polymers are to tune the molecular weights and ratios of the hydrophilic and hydrophobic blocks. In addition, to these approaches, the architecture of the hydrophilic block can also serve as a tool to tune enzymatic degradation and disassembly. To gain deeper understanding of the effect of the molecular architecture of the hydrophilic block we prepared two types of well-defined PEG-dendron amphiphiles bearing linear or V-shaped PEG chains as the hydrophilic blocks. The high molecular precision of these amphiphiles, which emerges from the utilization of dendrons as the hydrophobic blocks allowed us to study the self-assembly and enzymatic degradation and disassembly of the two types of amphiphiles with high resolution. Interestingly, the micelles of the V-shaped amphiphiles were significantly smaller and disassembled faster than those of the amphiphiles based on linear PEG. However, the complete enzymatic cleavage of the hydrophobic end-groups was significantly slower for the V-shaped amphiphiles. Our results show that the V-shape architecture can stabilize the unimer state and hence plays a double role in the enzymatic degradation and the induced disassembly and how it can be utilized to control the release of encapsulated or bound molecular cargo.
... Among the varieties of stimuli, pH-responsiveness are the most frequently used, as the pH value of endos/lysosomes (pH 5.0) in cancer cells is relatively lower than that of the extracellular microenvironment [10,32,33]. In this regard, pH responsive polymer-drug conjugates have been extensively explored by inserting an acid-cleavable linker between the drug molecule and the polymer backbone, the acid-cleavable linker may be hydrazone, imine, acetal/ketal, cis-acotinyl, substituted trityl, orthoester, or others [29,[34][35][36][37][38][39][40][41][42][43]. These polymer-drug conjugates are capable to self-assemble into three-dimensional (3D) structured polymeric nanoparticles which can be triggered to disassembly in the intracellular pH condition and release the payloads precisely as expected, thereby promoting the drug delivery efficacy. ...
Stimuli-responsive nanotechnology-mediated drug co-delivery system is a notable strategy to improve access of the systemically administered chemotherapeutics to the tumors. Herein, a tailor-made 2,3-dimethylmaleic-anhydride-poly(ethylene glycol)-ε-poly-l-lysine-doxorubicin /lapatinib polymeric nanoplatform (DMMA-P-DOX/LAP) for synergistically eliminating breast cancer is developed by encapsulating lapatinib into dual-pH responsive charge switchable biopolymer-doxorubicin conjugate nanoparticles. The physicochemical properties of polymeric nanoparticles are conducive to their stable circulation in the physiological condition, but reverse the surface charge from negative to positive ultrasensitively in slightly acidic tumor microenvironment, facilitating cell internalization and deep tumor penetration. Subsequently, DOX and LAP are synchronously released into the cytoplasm in response to the significantly increased acidity of intracellular environment. As a result, the combination therapy by DMMA-P-DOX/LAP nanoparticles compels the solid tumors to contract significantly or even vanish completely in the MCF-7 tumor model, moreover, the structural composition with amino acid and bioinert PEG ensures the favorable biosecurity of the co-delivery system in vivo. This dual-pH responsive nanotechnology-mediated drug co-delivery system provides great potentials for safe and effective cancer therapy.
... [123,124] By contrast, micelles allow for encapsulation of cargo in the coacervate core, while the presence of the neutral polymer corona prevents coalescence and can facilitate stealth properties for intravenous delivery applications. [47,64,67,68,125,126] While the general trends described thus far provide a useful guide to understanding of the phase behavior of coacervate-based materials, this intuition does not necessarily extend to cases where proteins are involved. In these cases, the more complex chemical nature of proteins can lead to seemingly incongruent results that require molecular-level inspection to understand. Figure 5. a,b) Plot of salt resistance versus charge fraction using poly(glutamate) with patterned cationic poly(lysine-co-glycine). c) Entropic gains as a function of charged block size determined using isothermal titration calorimetry. ...
Protein encapsulation is a growing area of interest, particularly in the fields of food science and medicine. The sequestration of protein cargoes is achieved using a variety of methods, each with benefits and drawbacks. One of the most significant challenges associated with protein encapsulation is achieving high loading while maintaining protein viability. This difficulty is exacerbated because many encapsulant systems require the use of organic solvents. By contrast, nature has optimized strategies to compartmentalize and protect proteins inside the cell—a purely aqueous environment. Although the mechanisms whereby aspects of the cytosol is able to stabilize proteins are unknown, the crowded nature of many newly discovered, liquid phase separated “membraneless organelles” that achieve protein compartmentalization suggests that the material environment surrounding the protein may be critical in determining stability. Here, encapsulation strategies based on liquid–liquid phase separation, and complex coacervation in particular, which has many of the key features of the cytoplasm as a material, are reviewed. The literature on protein encapsulation via coacervation is also reviewed and the parameters relevant to creating protein‐containing coacervate formulations are discussed. Additionally, potential opportunities associated with the creation of tailored materials to better facilitate protein encapsulation and stabilization are highlighted.
... The issues associated with conventional chemotherapy have prompted the development of a wide-range of nanocarriers for safer and more effective delivery of chemotherapeutics. These include inorganic (e.g., silica 6 and silver 7 ) and organic (e.g., polymers 8 and cellular membranes 9 ) nanoparticles (NPs). Among these NPs, block copolymer micelles, which are composed of a stealth hydrophilic shell surrounding a hydrophobic core encapsulating a variety of water insoluble drugs, have garnered considerable interest 10 . ...
The practical application of nanoparticles (NPs) as chemotherapeutic drug delivery systems is often hampered by issues such as poor circulation stability and targeting inefficiency. Here, we have utilized a simple approach to prepare biocompatible and biodegradable pH-responsive hybrid NPs that overcome these issues. The NPs consist of a drug-loaded polylactic-co-glycolic acid (PLGA) core covalently ‘wrapped’ with a crosslinked bovine serum albumin (BSA) shell designed to minimize interactions with serum proteins and macrophages that inhibit target recognition. The shell is functionalized with the acidity-triggered rational membrane (ATRAM) peptide to facilitate internalization specifically into cancer cells within the acidic tumor microenvironment. Following uptake, the unique intracellular conditions of cancer cells degrade the NPs, thereby releasing the chemotherapeutic cargo. The drug-loaded NPs showed potent anticancer activity in vitro and in vivo while exhibiting no toxicity to healthy tissue. Our results demonstrate that the ATRAM-BSA-PLGA NPs are a promising targeted cancer drug delivery platform. Palanikumar et al. prepare pH-responsive nanoparticles with drug-loaded PLGA core, cross-linked BSA corona to avoid opsonisation, and functionalised with ATRAM peptide that binds the cell membrane at low pH such as tumour microenvironment. The nanoparticles display both in vitro and in vivo efficacy while evading recognition by macrophages.
... In fact, several features of nanomedicines, such as coordinating drug interactions within the core of nanomedicines, controlling the release chemistry of a drug-polymer linker, and/or conjugating a drug or antibody on the surface of the nanomedicine, might enable the synchronous administration of multiple agents, including nucleic acids, into single nanomedicines. These features enable the control of pharmacokinetics, drug concentrations, drug ratios and release rates of bioactive payloads, thus enabling the optimization of synergistic effects 185,186 . For example, self-assembled micelles carrying oxaliplatin in the core and dihydroartemisinin in the shell are able to synergistically induce ICD and increase the efficacy of ICI in subcutaneously grown tumours 187 . ...
Multiple nanotherapeutics have been approved for patients with cancer, but their effects on survival have been modest and, in some examples, less than those of other approved therapies. At the same time, the clinical successes achieved with immunotherapy have revolutionized the treatment of multiple advanced-stage malignancies. However, the majority of patients do not benefit from the currently available immunotherapies and many develop immune-related adverse events. By contrast, nanomedicines can reduce — but do not eliminate — the risk of certain life-threatening toxicities. Thus, the combination of these therapeutic classes is of intense research interest. The tumour microenvironment (TME) is a major cause of the failure of both nanomedicines and immunotherapies that not only limits delivery, but also can compromise efficacy, even when agents accumulate in the TME. Coincidentally, the same TME features that impair nanomedicine delivery can also cause immunosuppression. In this Perspective, we describe TME normalization strategies that have the potential to simultaneously promote the delivery of nanomedicines and reduce immunosuppression in the TME. Then, we discuss the potential of a combined nanomedicine-based TME normalization and immunotherapeutic strategy designed to overcome each step of the cancer-immunity cycle and propose a broadly applicable ‘minimal combination’ of therapies designed to increase the number of patients with cancer who are able to benefit from immunotherapy.
... Nanoscale drug delivery and imaging systems have received tremendous interest in the past few decades [1][2][3][4][5][6][7][8][9][10][11][12]. They enjoy some intrinsic advantages over conventional drug delivery approaches. ...
Novel magnetite-ammonium bisphosphonate graft ionic copolymer nanocomplexes ( MGICs ) have been developed for potential drug delivery, magnetic resonance imaging, and hyperthermia applications. The complexes displayed relatively uniform sizes with narrow size distributions upon self-assembly in aqueous media, and their sizes were stable under simulated physiological conditions for at least 7 days. The anticancer drugs, cisplatin and carboplatin, were loaded into the complexes, and sustained release of both drugs was observed. The transverse NMR relaxivities ( r2 s) of the complexes were 244 s ⁻¹ (mM Fe) ⁻¹ which is fast compared to either the commercial T 2 -weighted MRI agent Feridex IV® or our previously reported magnetite-block ionomer complexes. Phantom MRI images of the complexes demonstrated excellent negative contrast effects of such complexes. Thus, the bisphosphonate-bearing MGICs could be promising candidates for dual drug delivery and magnetic resonance imaging. Moreover, the bisphosphonate MGICs generate heat under an alternating magnetic field of 30 kA·m ⁻¹ at 206 kHz. The temperature of the MGIC dispersion in deionized water increased from 37 to 41°C after exposure to the magnetic field for 10 minutes, corresponding to a specific absorption rate of 77.0 W·g ⁻¹ . This suggests their potential as hyperthermia treatment agents as well as the possibility of temperature-dependent drug release, making MGICs more versatile in potential drug delivery applications.
Chemotherapeutic drug delivery systems are commonly limited by their short half-lives, poor bioavailability, and unsuccessful targetability. Herein, pH-responsive hybrid NPs consist of benzimidazole-coated mesoporous silica nanoparticles (BZ-MSN) loaded with naturally occurring flavonoid quercetin (QUE-BZ-MSN). The NPs were further capped with beta-cyclodextrin (BCD) to obtain our desired BCD-QUE-BZMSN, with a zeta potential around 7.05 ± 2.37 mV and diameter about 115.2 ± 19.02 nm. The abundance of BZ onto the nanoparticles facilitates targeted quercetin chemotherapy against model lung and liver cancer cell lines. FTIR, EDX, and NMR analyses revealed evidence of possible surface functionalizations. Powder XRD analysis showed that our designed BCD-QUE-BZMSN formulation is amorphous in nature. The UV and SEM showed that our designed BCD-QUE-BZMSN has high drug entrapment efficiency and a nearly spherical morphology. In vitro, drug release assessments show controlled pH-dependent release profiles that could enhance the targeted chemotherapeutic response against mildly acidic regions in cancer cell lines. The obtained BCD-QUE-BZMSN nanovalve achieved significantly higher cytotoxic efficacy as compared to QUE alone, which was evaluated by in vitro cellular uptake against liver and lung cancer cell lines, and the cellular morphological ablation was further confirmed via inverted microscopy. The outcomes of the study imply that our designed BCD-QUE-BZMSN nanovalve is a potential carrier for cancer chemotherapeutics.
Currently, chemotherapy is one of the most practiced approaches for the treatment of cancers. However, existing chemotherapeutic drugs have poor aqueous solubility, poor selectivity, higher systematic toxicity, and poor target accumulation. In this study, we designed and synthesized a boronic acid/ester-based pH-responsive nano-valve that specifically targets the microenvironment in cancer cells. The nano-valve comprises phenylboronic acid-coated mesoporous silica nanoparticles (B-MSN) loaded with polyphenolic compound Rosmarinic acid (ROS-B-MSN). The nano-valve was further coated with lignin (LIG) to achieve our desired LIG-ROS-BMSN nano-valve for targeted chemotherapy against Hep-G2 and NCI-H460 cell lines. The structure and properties of NPs were characterized by Fourier-transformed infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) in combination with EDX, and Dynamic light scattering (DLS). The outcomes revealed that the designed LIG-ROS-BMSN were in nano range (144.1 ± 0.70 nm) had negative Zeta potential (-15.7 ± 0.46 mV) and nearly spherical morphology. In vitro, drug release investigations showed a controlled pH-dependent release profile under mild acidic conditions that could enhance the targeted chemotherapeutic response against mild acidic environments of cancer. The obtained LIG-ROS-BMSN nano valve achieved significantly lower IC50 values of (1.70 ± 0.01 μg/mL and 3.25 ± 0.14 μg/mL) against Hep-G2 and NCI-H460 cell lines as compared to ROS alone which was (14.0 ± 0.7 μg/mL and 29.10 ± 0.25 μg/mL) respectively. The cellular morphology before and after treatment was further confirmed via inverted microscopy. The outcomes of the current study implying that our designed LIG-ROS-BMSN nano valve is a potential carrier for cancer chemotherapeutics.
Nanotechnology has spread its wings in nearly all the spheres of our daily lives. This has become an integral part of pharmaceutical industry. Nanopharmaceuticals have gained a lot of importance. Current chapter focuses on nanopharmaceuticals and their development over the years. The chapter describes the regulatory requirements for the approval of nanopharmaceuticals, their therapeutic, as well as diagnostic applications, recent research going on in the area along with polymers, and carriers used in their formulation. What could be future challenges and trends are also written.
Polymeric micelles (PMs) have shown promising potential in multidrug codelivery and in the treatment of cancer. The potential of PMs has been further improved by fine-tuning their characteristics for precise targeting of tumors, controlled or sequential drug release, and enhanced cellular uptake. Although much has been done in the areas of drug targeting, their controlled release, and cellular uptake, more consideration is needed to improve synergistic therapeutic results and minimalize side effects. This chapter offers a comprehensive summary of numerous PMs used for the codelivery of drugs. These PMs possess potential to release the coloaded drugs either sequentially or simultaneously by using exclusive tumor microenvironment characteristics such as elevated local temperature, overexpressed enzyme, redox and acidic pH, and external environmental triggers. Limitations and future perspectives of these PMs for codelivery have also been discussed here.
Cancer stem cells (CSCs) are a small subpopulation of cells that reside inside the tumor and are believed to be causative for tumor initiation, metastasis, and relapse. Due to their specific intrinsic defense mechanisms, CSCs are resistant to conventional chemotherapy and radiotherapy, which leads to treatment failure in the clinic. Recent advances in nanotechnology and materials science have provided many opportunities for cancer therapy, especially nanoparticle-mediated ablation therapies (NMAT), such as photothermal therapy, magnetic hyperthermia therapy, and cryoablation therapy, that have shown promising outcomes in CSC eradication. The procedure of NMAT is minimally invasive and not restricted by resistance mechanism and could be potentially expanded to a broad spectrum of CSCs. Moreover, NMAT could effectively damage deep-tumor CSCs and interfere with the repair of treatment-induced DNA damage. Here, we review representative studies and summarize state-of-the-art NMAT strategies for ablating CSCs and discuss challenges and opportunities in this emerging field.
Advancements in the development of nanomaterials have led to the creation of a plethora of functional constructs as drug delivery vehicles to address many dire medical needs. The emerging prodrug strategy provides an alternative solution to create nanomedicines of extreme simplicity by directly using the therapeutic agents as molecular building blocks. This Review outlines different prodrug-based drug delivery systems, highlights the advantages of the prodrug strategy for therapeutic delivery, and demonstrates how combinations of different functionalities – such as stimuli responsiveness, targeting propensity, and multidrug conjugation – can be incorporated into designed prodrug delivery systems. Furthermore, we discuss the opportunities and challenges facing this rapidly growing field.
For its high mortality rate, cancer has posed a significant threat to human’s lives. Every year, more than 3.4 million people died for cancer all over the world. The main therapeutic methods for cancer include surgery, chemotherapy, and radiotherapy. However, surgery is only conducted for patients with early-stage cancers; chemotherapy and radiotherapy have obvious side effects. In addition, many researches have indicated that cancer stem cells play a crucial role in tumor recurrence and multidrug resistance. Compared with traditional drug carriers, nano drug delivery systems have many advantages in targeting delivery, combination therapy, etc. In recent years, more and more nano drug systems are applied in clinical practice, and various multifunctional nano drug systems are designed to kill cancer stem cells. Our review introduced the main problems in anticancer therapy for cancer stem cells, and the developments of several nano drug delivery systems.
There are various controlled delivery systems and several products have been developed which achieves a greater therapeutic effect of the drug. By altering the pharmacokinetic and pharmacodynamics characteristics of drug with the application of polymers results in better safety and efficacy. Several natural and synthetic polymers are utilised for the development of controlled drug delivery systems (CDDS). By using these natural and synthetic biopolymers in the drug delivery systems ensures the biocompatibility, biodegradation, mechanical strength and immunogenicity of the formulation. Therefore, the fabrication of CDDS with the biopolymers protects the drug from degradation in the gastrointestinal tract (GIT) and makes them deliver in other parts. And also, there are a lot of products developed based on drug delivery system are commercially available. The biopolymers are useful in controlling the release of bioactive from the formulation through a diffusion-controlled, degradation controlled or an environmental trigger controlled system. So, the biopolymers play a major role in the development of delivering the drugs by controlling the release of active components over the certain period of time and also helps in adjusting the release of hydrophilic/hydrophobic drugs.
Malignant peritoneal mesothelioma (MPeM) is an aggressive cancer affecting the peritoneal lining of the abdominal cavity and intra-abdominal organs, with a median survival of ~2.5 years. We constructed an ‘MPeM interactome’ with over 400 computationally predicted protein-protein interactions (PPIs) and over 4,700 known PPIs of 59 literature-curated genes whose activity affects MPeM. Known PPIs of the 59 MPeM-associated genes were derived from BioGRID and HPRD databases. Novel PPIs were predicted by applying the HiPPIP algorithm, which computes features of protein pairs such as cellular localization, molecular function, biological process membership, genomic location of the gene, and gene expression in microarray experiments, and classifies the pairwise features as interacting or non-interacting based on a random forest model. 75.6% of the interactome and 65% of the novel interactors in it were supported by transcriptomic evidence in rodent and human peritoneal mesothelioma/mesothelial cell lines and tumor specimens. 152 drugs targeted 427 proteins in the MPeM interactome. Comparative transcriptome analysis of peritoneal mesothelioma-associated versus drug-induced gene expression profiles revealed 39 repurposable drugs, out of which 29 were effective against peritoneal/pleural mesothelioma and/or peritoneal metastasis/primary peritoneal cancer in clinical trials, animal models or cell lines. Functional modules of chromosomal segregation, transcriptional deregulation, positive regulation of IL-6 production and hematopoiesis were identified from the interactome. Genes with tissue-specific expression in 2 sites of extramedullary hematopoiesis (spleen and thymus) and those correlated with unfavorable prognosis in liver, renal, pancreatic and lung cancers were noted. MPeM interactome showed extensive overlap with the malignant pleural mesothelioma (MPM) interactome and MPM cell line expression profiles. Our findings demonstrate the utility of the MPeM interactome in discovering systems-level functional links among MPeM genes and generating clinically translatable results such as repurposed drugs.
Recent years have seen increasing interests in the use of ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs) to prepare synthetic polypeptides, a class of biocompatible and versatile materials, for various biomedical applications. Because of their rich side-chain functionalities, diverse hydrophilicity/hydrophobicity profiles, and the capability of forming stable secondary structures, polypeptides can assemble into a variety of well-organized nano-structures that have unique advantages in drug delivery and controlled release. Herein, we review the design and use of polypeptide-based drug delivery system derived from NCA chemistry, and discuss the future perspectives of this exciting and important biomaterial area that may potentially change the landscape of next-generation therapeutics and diagnosis. Given the high significance of precise control over release for polypeptide-based systems, we specifically focus on the versatile designs of drug delivery systems capable of programmed release, through the changes in the chemical and physical properties controlled by the built-in molecular structures of polypeptides.
Nanoparticles used as drug carriers that have a prolonged circulation time, reduced early drug leakage, being stimulus triggered and having an improved drug release are a powerful tool for anticancer treatment. Herein, a new tailor-made polycarbonate-doxorubicin conjugate was prepared and characterized, in which the aliphatic polycarbonate was functionalized with tertiary amine groups, and an acid-sensitive benzoic imine bond was formed between doxorubicin (DOX) and the polycarbonate. The conjugate could self-assemble into nanoparticles (DOX-P1NPs) with a size of 49 nm and an initial negative surface charge. Furthermore, DOX-P1NPs possess a high drug-loading of 18.3% and exhibit pH-dependent drug-release behavior. As anticipated, DOX-P1NPs show good stability and can avoid early drug leakage during circulationin vivo. However, after endocytosis, the nanoparticle size expanded rapidly to 65 nm, allowing the maximized exposure of the benzoic imine bond and achieving fast intracellular drug release. In addition,in vitrocytotoxicity studies demonstrate a remarkable tumor inhibition of the DOX-P1NPs against 4T1 cells. Consequently, these intracellular pH-responsive expandable nanoparticles have great potential for safe and effective drug delivery. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021.
Effective inhibition of the protein derived from cellular myelocytomatosis oncogene (c-Myc) is one of the most sought-after goals in cancer therapy. While several c-Myc inhibitors have demonstrated therapeutic potential, inhibiting c-Myc has proven challenging, since c-Myc is essential for normal tissues and tumors may present heterogeneous c-Myc levels demanding contrasting therapeutic strategies. Herein, we developed tumor-targeted nanomedicines capable of treating both tumors with high and low c-Myc levels by adjusting their ability to spatiotemporally control drug action. These nanomedicines loaded homologues of the bromodomain and extraterminal (BET) motif inhibitor JQ1 as epigenetic c-Myc inhibitors through pH-cleavable bonds engineered for fast or slow drug release at intratumoral pH. In tumors with high c-Myc expression, the fast-releasing (FR) nanomedicines suppressed tumor growth more effectively than the slow-releasing (SR) ones, whereas, in the low c-Myc tumors, the efficacy of the nanomedicines was the opposite. By studying the tumor distribution and intratumoral activation of the nanomedicines, we found that, despite SR nanomedicines achieved higher accumulation than the FR counterparts in both c-Myc high and low tumors, the antitumor activity profiles corresponded with the availability of activated drugs inside the tumors. These results indicate the potential of engineered nanomedicines for c-Myc inhibition and spur the idea of precision pH-sensitive nanomedicine based on cancer biomarker levels.
The past few decades have witnessed an evolution of nanomedicine from biologically inert entities to more smart systems, aimed at advancing in vivo functionality. However, we should recognize that most systems still rely on reasonable explanation-including some over-explanation-rather than definitive evidence, which is a watershed radically determining the speed and extent of advancing nanomedicine. Probing nano-bio interactions and desirable functionality at the tissue, cellular, and molecular levels is most frequently overlooked. Progress toward answering these questions will provide instructive insight guiding more effective chemo-physical strategies. Thus, in the next generation, we argue that much effort should be made to provide definitive evidence for proof-of-mechanism, in lieu of creating many new and complicated systems for similar proof-of-concept.
Cancer stem cells (CSCs), which are resistant to the traditional therapies, have been considered to account for the development, metastasis, and relapse of various malignant tumors, and therefore, must be eliminated to cure cancer. However, they can reside in deep tumor regions away from the blood vessels, and are typically inaccessible owing to the low delivery efficiency and limited tumor penetrating ability of drug carriers. To overcome these problems, we designed a tumor-penetrating peptide (tLyP-1)-conjugated ZIF-90 nanosystem loaded with doxorubicin (DOX) and N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butyl ester (DAPT) to penetrate and eradicate differentiated cancer cells and CSCs simultaneously. The nanosystem exhibited beneficial biocompatibility, enhanced tissue penetration, high blood circulation stability, and pH-responsive drug release for favoring cancer therapy. It was found that the nanosystem could kill both cancer cells and CSCs in vitro. The in vivo results demonstrated that the ZIF-90 nanosystem can effectively accumulate in tumor tissues after long blood circulation and flexibly permeate throughout the tumor tissues. In the HCCLM3 xenograft model, the ZIF-90 nanosystem presented high-efficiency tumor suppression and drastically eradicated the CSCs in the tumor tissues with low systemic toxicity. Overall, the deep tumor-penetrating nanosystem exhibits outstanding potential for improving curative effect.
Nanomedicines (NMs) have emerged as promising agents for cancer treatment because of the enhanced permeability and retention (EPR) effect. Multiple biological barriers prevent NMs from efficiently accumulating at the tumor site and penetrating into the tumor tissue, leading to suboptimal therapeutic efficacy. To address this problem, we grafted tiny CuS nanocrystals (NCs) onto the surface of gelatin nanoparticles (GNPs, ~100 nm) to create transformable nanoparticles, denoted as [email protected], which can successively cross the biological barriers from intravenous injection to deep tumor zones via enzyme-induced multistage delivery. These transformable [email protected] possess an initial diameter of approximately 120 nm and significantly accumulated at the tumor site after intravenous administration. Upon accumulation at the tumor site, the over-expressed hydrolases in the tumor microenvironment trigger rapid dissociation of the scaffold (GNPs) of [email protected] and attendant release of the CuS NCs for deeper penetration into the tumor tissue. The spatiotemporal multistage delivery behavior of [email protected] within tumor tissue could be tracked in vivo by photoacoustic imaging in a real-time manner. Following the systemic administration of [email protected], near infrared laser irradiation was further employed and efficient photothermal ablation of tumors was realized in MDA-MB-231 tumor-bearing mice. Taken together, these results indicated that the as-fabricated transformable [email protected] could undergo enzyme-induced multistage delivery for enhanced accumulation at the tumor site and improved penetration into the inner tumor. Furthermore, the transformable [email protected] facilitated efficient photoacoustic imaging-guided photothermal ablation to inhibit tumor growth.
Multidrug resistance (MDR) of cancer stem cells (CSCs) is a major hurdle to chemotherapy, and it is very important to develop CSCs-specific targeted nanocarriers for the treatment of drug resistant CSCs. In this work, we developed CSCs-specific targeted mSiO2-dPG nanocarriers simultaneous delivery chemotherapy drug DOX along with the P-glycoprotein (P-gp) inhibitor tariquidar (Tar) for enhanced chemotherapy to overcome MDR in breast CSCs. The mSiO2-dPG nanocarriers possess a high loading capability, excellent pH stimuli-responsive performance, and good biocompatibility. With the help of CSCs-specific targeting and P-gp inhibitor Tar, the accumulation of DOX delivered by the mSiO2-dPG nanocarriers could be greatly increased in drug resistant three-dimensional mammosphere of breast CSCs, and the chemotherapeutic efficacy against breast CSCs was enhanced. Moreover, the expression of stemness-associated gene and tumorspheres' formation ability was also significantly suppressed, which indicates the excellent capability for overcoming MDR of breast CSCs. Taken together, we developed a CSCs-specific targeted mSiO2-dPG nanocarriers for co-delivery DOX and Tar, which provide a promising approach to effectively eliminate the CSCs and overcome the MDR of breast CSCs.
Cancer stem cells (CSCs) are a subpopulation of cancer cells with functions similar to those of normal stem cells. Although few in number, they are capable of self-renewal, unlimited proliferation, and multi-directional differentiation potential. In addition, CSCs have the ability to escape immune surveillance. Thus, they play an important role in the occurrence and development of tumors, and they are closely related to tumor invasion, metastasis, drug resistance, and recurrence after treatment. Therefore, specific targeting of CSCs may improve the efficiency of cancer therapy. A series of corresponding promising therapeutic strategies based on CSC targeting, such as the targeting of CSC niche, CSC signaling pathways, and CSC mitochondria, are currently under development. Given the rapid progression in this field and nanotechnology, drug delivery systems (DDSs) for CSC targeting are increasingly being developed. In this review, we summarize the advances in CSC-targeted DDSs. Furthermore, we highlight the latest developmental trends through the main line of CSC occurrence and development process; some considerations about the rationale, advantages, and limitations of different DDSs for CSC-targeted therapies were discussed.
Nanomedicines are emerging as effective approaches for developing new strategies against cancer. Nanomedicines can be designed for selectively delivering probes and anticancer agents to tumors for achieving improved diagnostic or therapeutic efficacy, while relieving potential side effects. In particular, the number of formulations based on self‐assembled nanostructures under clinical evaluation is increasing due to their unique advantages for elegant and facile preparation, working at the biointerface and spatiotemporally controlling the function of drugs. Here, the current status of clinically used self‐assembled nanomedicines is presented, and recent advances of candidates in clinical trials are reviewed. In addition, the challenges and future prospects of nanomedicines in the clinic are discussed.
Stimulus-responsive nanosystem is a powerful method to improve the bioavailability and reduce the side effects of anticancer agents. In the present study, a customized dual pH-responsive micellar nanoplatform (DOX+LAP-M) based on polycarbonate-doxorubicin conjugate micelles was prepared to co-deliver the chemotherapeutic agent lapatinib for inhibiting tumor growth and metastasis. DOX+LAP-M micelles with spherical morphology had a size of ~112 nm and had an initial negative surface charge, which are favorable characteristics for long-term circulation in the blood. Once the micelles accumulated in tumor tissues, the intrinsic tumor extracellular acidity triggered the charge switch of DOX+LAP-M micelles from -1 to 9 mV, thereby facilitating cell internalization and tumor penetration. Subsequently, the pH-sensitive micellar core accelerated the release of doxorubicin and lapatinib in the acidic intracellular environment. DOX+LAP-M micelles effectively inhibited the proliferation, migration, and invasion of 4T1 cells in vitro; furthermore, the administration of DOX+LAP-M micelles in 4T1 xenograft-bearing mice suppressed solid tumor growth with an inhibitory rate of 90.2% and significantly decreased pulmonary metastatic nodules, without significant systemic toxicity. This multifunctional micellar system has high potential for clinical cancer therapy.
Complex coacervation has become a prominent area of research in the fields of food science, personal care, drug stabilization, and more. However, little has been reported on the kinetics of assembly of coacervation itself. Here, we describe a simple, low-cost way of looking at the kinetics of coacervation by creating poorly mixed samples. In particular, we examine how polymer chain length, the patterning and symmetry of charges on the oppositely charged polyelectrolytes, and the presence of salt and a zwitterionic buffer affect the kinetics of complex coacervation. Our results suggested an interesting relationship between the time for equilibration and the order of addition of polymers with asymmetric patterns of charge. Furthermore, we demonstrated that increasing polymer chain length resulted in a non-monotonic trend in the sample equilibration times as a result of opposing factors such as excluded volume and diffusion. We also observed differences in the rate of sample equilibration based on the presence of a neutral, zwitterionic buffer, as well as the presence and identity of added salt, consistent with previous reports of salt-specific effects on the rheology of complex coacervates. While not a replacement for more advanced characterization strategies, this turbidity-based method could serve as a screening tool to identify interesting and unique phenomena for further study.
Polypeptides have attracted considerable attention in recent decades due to their inherent biodegradability and tunable cytocompatibility. Macromolecular design in conjunction with rational monomer composition can direct architecture, self-assembly and chemical behavior, ultimately guiding the choice of appropriate application within the biomedical field. This review focuses on the applications of polypeptides alongside the synthetic advances in the ring opening polymerization of α-amino acid N-carboxyanhydrides achieved in the past five years. Key architectures obtained through NCA ROP or in combination with other polymerization methods are reviewed, as these play an important role in the wide range of applications towards which polypeptides have been applied.
Medicine formulations at the nanoscale, referred to as nanomedicines, have managed to overcome key challenges encountered during the development of new medical treatments and entered clinical practice, but considerable improvement in terms of local efficacy and reduced toxicity still need to be achieved. Currently, the fourth-generation of nanomedicines is being developed, employing biocompatible nanocarriers that are targeted, multifunctional, and stimuli-responsive. Proteins and polypeptides can fit the standards of an efficient nanovector because of their biodegradability, intrinsic bioactivity, chemical reactivity, stimuli-responsiveness, and ability to participate in complex supramolecular assemblies. These biomacromolecules can be obtained from natural resources, produced in heterologous hosts, or chemically synthesized, allowing for different designs to access suitable carriers for a variety of drugs. To enhance targeting or therapeutic functionality, additional chemical modifications can be applied. This review demonstrates the potential of polypeptide and protein materials for the design of drug delivery nanocarriers with a special focus on their preclinical evaluation in vitro and in vivo.
Malignant pleural mesothelioma (MPM) is a highly aggressive form of cancer, with a median survival of less than 1 year. It is well known that the hyaluronan (HA) receptor CD44 is highly expressed by MPM cells and is reported to be correlated with a poor prognosis. We herein report on the development of a new type if drug delivery system against CD44 that involves the use of lipid nanoparticles (LNPs) equipped with a new type of HA derivative. In this study, we evaluated HA-lipid conjugation (HAL) via the end of the HA molecule through reductive amination, a process that allowed the carboxylate group to remain intact. As a result, the HAL-modified LNP appears to be a potent nanoparticle for dealing with MPM. Surprisingly, the use of a combination of a cationic lipid and HAL had a synergistic effect on cellular uptake in MPM and consequently permitted an anti-cancer drug such as cis-diamminedichloro-platinum(II) (CDDP). Intrapleural injection of CDDP-loaded HAL-LNP (1.5 mg/kg as CDDP) per week significantly suppressed the progression of this type of cancer in an MPM orthotopic model. These results suggest that HAL-modified LNP represents a potent delivery system for MPM cells that express high levels of CD44.
Polymeric micelles (PMs) play a vital role in multidrug co-delivery and cancer treatment. However, development of intelligent PMs further allows PMs to accurately target tumour, selectively release cargo multidrug and increase uptake. Therefore, targets, controlled release and uptake of intelligent PMs should be paid more attention to improvement of synergistic therapeutic outcomes and minimize side effects. In this review, tumour targeting of co-delivery intelligent PMs and its intracellular trafficking mechanisms were overviewed. And this review provides a comprehensive summarization of several intelligent co-delivery PMs. Such a system could control the multidrug to be released simultaneously or sequentially by special properties of tumour microenvironment (TME) (including acidic PH, redox, overexpressed enzyme, excessive temperature) and external environment trigger. Additionally, limitations, clinical translation and future perspectives of intelligent co-delivery PMs were also being discussed in this article.
Ligand-targeting specific liposomal probes are increasingly used as imaging and delivery vehicles for in vivo diagnosis. Thereinto, the ligand variety and density profoundly affect the binding behaviors towards the target. The synergetic effect of different ligands could be achieved only when the optimized molecular-recognition configuration occurred. In this study, we construct a dual-peptides-targeting liposomal probe named BTLS that could synergistically bind two different sites of the Prominin-1, a cancer stem cell marker. At the distance of 11Å between the two new peptides, ligands could insert into the hollow pocket of Prominin-1 and BTLS could achieve the appropriate spatial structure, showing the strong binding affinity in both cellular and in vivo level. It is indicated that the design of density-optimized peptide-targeted liposomes could be promising to maximize the multifunctional targeting effects on the cancer theranostics.
Sub-optimal intra-tumor accumulation and poorly controllable release of encapsulated drugs remain unresolved challenges hampering further advancement of nanomedicines on cancer therapy. Herein, we conceived near infrared (NIR) laser-triggered transformable BiS@HSA/DTX multiple nanorods (mNRs), which were made of small bundles of bismuth sulfide nanorods (BiS NRs) coated by docetaxel (DTX)-inlaid human serum albumin (HSA). The BiS@HSA/DTX mNRs had a lateral size of approximately 100 nm and efficiently accumulated in the tumor microenvironment upon systemic administration in tumor-bearing nude mice. NIR laser irradiation of the tumor area caused rapid disassembly of the BiS@HSA/DTX mNRs into individual HSA-coated BiS nanorods (BiS@HSA iNRs) and triggered the release of DTX from the HSA corona, due to the local temperature increase generated by BiS NRs via photothermal effect. The laser-induced transformation into BiS@HSA iNRs facilitated their penetration and increased the retention time in tumor. The spatiotemporal delivery behavior of the BiS@HSA/DTX mNRs could be monitored by photoacoustic/computed tomography dual-modal imaging in vivo. Furthermore, because of the excellent photothermal conversion properties of BiS NRs and laser-triggered DTX release from BiS@HSA/DTX mNRs, efficient tumor combinatorial therapy was achieved via concurrent hyperthermia and chemotherapy in mice treated with BiS@HSA/DTX mNRs upon NIR laser irradiation.
Cancer stem cells (CSCs) are proposed to account for the initiation of cancer metastasis, but their accessibility remains a great challenge. This study reports deep tumor‐penetrated biomimetic nanocages to augment the accessibility to CSCs fractions in tumor for anti‐metastasis therapy. The nanocages can load photothermal agent of 1,1‐dioctadecyl‐3,3,3,3‐tetramethylindotricarbocyanine iodide (DBN) and chemotherapeutic epirubicin (EBN) to eradicate CSCs for photothermal‐chemotherapy of breast cancer metastasis. In metastatic 4T1‐indcued tumor model, both DBN and EBN can efficiently accumulate in tumor sites and feasibly permeate throughout the tumor mass. These biomimetic nanosystems can be preferentially internalized by cancer cells and effectively accessed to CSCs fractions in tumor. The DBN+laser/EBN treatment produces considerable depression of primary tumor growth, drastically eradicates around 80% of CSCs fractions in primary tumor, and results in 95.2% inhibition of lung metastasis. Thus, the biomimetic nanocages can be a promising delivery nanovehicle with preferential CSCs‐accessibility for effective anti‐metastasis therapy. The access of drug to cancer stem cells (CSCs) remains a great challenge for anti‐metastasis therapy. Deep tumor‐penetrated biomimetic nanocages are reported. They can effectively ameliorate their accessibility to CSCs fractions in tumor, eradicate the CSCs fractions, and prevent the incidence of lung metastasis, thereby providing a promising delivery nanovehicle to access CSCs for anti‐metastasis therapy.
Sequentially-released codelivery system is an effective strategy to enhance anticancer efficacy. Here, we fabricate multicomponent-based liposomes (T/CM-L) loaded with sodium tanshinone IIA sulfonate (STS) and small-sized microemulsion of celastrol (CM), which shows synergistic anti-breast cancer activity through initial release of STS for modulation of tumor microenvironment and subsequent release of CM (and its payloads) for eradication of tumor tissues. In vitro studies exhibited that T/CM-L induced massive apoptosis toward MCF-7 cells, indicating coordinated cytotoxicity against cancer cells. Once liposomes accumulated at the tumor site, STS was released from T/CM-L in the first place to repair abnormal vessels as well as decrease fibroblasts. Owing to the retardarce by barriers of microemulsion and liposome, celastrol was then unloaded moderately to kill tumor cells, resulting in shrink of tumor size. Furthermore, T/CM-L displayed diminished systemic toxicity compared to celastrol used alone. Our work offers a novel strategy for combination anticancer treatment and holds promising potential not only in breast cancer treatment, but also in other solid tumors.
Malignant pleural mesothelioma (MPM) is a lethal cancer of the mesothelium with high chemotherapeutic resistance via unknown mechanisms. A prevailing hypothesis states that cancer stem cells (CSCs) persist in tumors causing relapse after chemotherapy, thus, rendering these cells as critical targets responsible for tumor resistance and recurrence. We selected candidate CSC markers based on expansion under hypoxic conditions, a hallmark for the selection of chemoresistant cells; and investigated the expression of CSC markers: CD133, Bmi-1, uPAR and ABCG2 in three MPM cell lines and normal mesothelial cells by quantitative RT-PCR. Furthermore, we evaluated the chemotherapeutic resistance associated with each CSC marker by determining the change in CSC marker-mRNA levels as an index of drug-resistance following treatment with either cisplatin or peme-trexed. We demonstrate the expression of CSC markers: CD133, Bmi-1, uPAR and ABCG2 in both normal and MPM cell lines. Bmi-1 + , uPAR + and ABCG2 + cells show a distinct role in conferring chemoresistance to cisplatin and pemetrexed in the malignant setting. By contrast, these markers have no apparent participation in chemoresistance to drug treatments in normal mesothelial cells. Intriguingly, CD133 revealed chemoresistant properties in both normal mesothelial and malignant pleural mesothelioma cells. This study provides evidence of putative CSCs conferring drug-resistance to cisplatin and pemetrexed in MPM cell lines. Specific targeting of these drug-resistant cells, while considering the functional heterogeneity of the MPM subtypes, may contribute to more focused and effective chemotherapeutic regimens for malignant pleural mesothelioma.
Purpose:
The hedgehog (HH) signaling pathway is a key regulator in tumorigenesis of pancreatic adenocarcinoma and is upregulated in pancreatic adenocarcinoma cancer stem cells (CSCs). GDC-0449 is an oral small-molecule inhibitor of the HH pathway. This study assessed the effect of GDC-0449-mediated HH inhibition in paired biopsies, followed by combined treatment with gemcitabine, in patients with metastatic pancreatic adenocarcinoma.
Experimental design:
Twenty-five patients were enrolled of which 23 underwent core biopsies at baseline and following 3 weeks of GDC-0449. On day 29, 23 patients started weekly gemcitabine while continuing GDC-0449. We evaluated GLI1 and PTCH1 inhibition, change in CSCs, Ki-67, fibrosis, and assessed tumor response, survival and toxicity.
Results:
On pretreatment biopsy, 75% of patients had elevated sonic hedgehog (SHH) expression. On posttreatment biopsy, GLI1 and PTCH1 decreased in 95.6% and 82.6% of 23 patients, fibrosis decreased in 45.4% of 22, and Ki-67 in 52.9% of 17 evaluable patients. No significant changes were detected in CSCs pre- and postbiopsy. The median progression-free and overall survival for all treated patients were 2.8 and 5.3 months. The response and disease control rate was 21.7% and 65.2%. No significant correlation was noted between CSCs, fibrosis, SHH, Ki-67, GLI1, PTCH1 (baseline values or relative change on posttreatment biopsy), and survival. Grade ≥ 3 adverse events were noted in 56% of patients.
Conclusion:
We show that GDC-0449 for 3 weeks leads to downmodulation of GLI1 and PTCH1, without significant changes in CSCs compared with baseline. GDC-0449 and gemcitabine were not superior to gemcitabine alone in the treatment of metastatic pancreatic cancer.
Patients with malignant mesothelioma have a poor prognosis and only 40% respond to first line treatment; a combination of pemetrexed and cisplatin or carboplatin. We used primary malignant mesothelioma cells and an ex vivo chemosensitivity assay with future purpose to predict best choice of treatment. The clinical outcome of these patients might be predicted by measuring drug sensitivity.
Pleural effusions containing primary malignant mesothelioma cells were received from the diagnostic routine. We characterized and tested the chemosensitivity of 18 malignant samples and four benign samples from 16 different patients with pleural effusions. Cells were seeded in a 384-well plate for a robotized ex vivo testing of drug sensitivity to 32 different drugs. The primary cells were further characterized by immunocytochemistry to evaluate the proportion of malignant cells and to study the RRM1 and ERCC1 reactivity, two proteins associated with drug resistance.
We observed great individual variability in the drug sensitivity. Primary cell isolates were affected by between one and ten drugs, and resistant to the remaining tested drugs. Actinomycin D and daunorubicin were the two drugs effective in most cases. Adjusting efficiency of individual drugs for varying proportion of tumor cells and to the average effect on benign cells correlated with effect of pemetrexed, cisplatin and survival time. General drug sensitivity, proportion of malignant cells and reactivity to RRM1 correlated to each other and to survival time of the patients.
The proportion of malignant cells and RRM1 reactivity in the pleural effusions correlate to drug sensitivity and survival time. The variability in response to the commonly used chemotherapies emphasizes the need for tests that indicate best individual choice of cytotoxic drugs. The efficiency of the obtained results should preferably be corrected for admixture of benign cells and effects of given drugs on benign cells.
Significance
In previous clinical testing, first-generation N -(2-hydroxypropyl)-methacrylamide (HPMA) copolymer-drug conjugates circumvented drug resistance and showed reduced side effects, although only minor improvement was seen in therapeutic efficacy. For effective clincial translation, second-generation high-molecular weight backbone-degradable HPMA copolymer carriers designed by our group sought to provide prolonged blood circulation and enhanced tumor accumulation to enable sufficient exposure of tumors to effective drug concentrations, and guarantee their biocompatibility by making polymer backbone degradable. The second-generation conjugates showed favorable pharmacokinetic profiles and controlled drug release, resulting in a dramatic improvement of therapeutic efficacy, as compared with first-generation conjugates and free drugs. For future industrial-scale manufacture, a new reversible addition-fragmentation chain transfer agent was developed that enables synthesis of conjugates in one step.
Background
Conventional chemotherapy in malignant pleural mesothelioma (MPM) has minimal impact on patient survival due to the supposed chemoresistance of cancer stem cells (CSCs). We sought to identify a sub-population of chemoresistant cells by using putative CSC markers, aldehyde dehydrogenase (ALDH) and CD44 in three MPM cell lines; H28, H2052 and Meso4.
Methods
The Aldefluor assay was used to measure ALDH activity and sort ALDHhigh and ALDHlow cells. Drug-resistance was evaluated by cell viability, anchorage-independent sphere formation, flow-cytometry and qRT-PCR analyses.
Results
The ALDHhigh - and ALDHlow -sorted fractions were able to demonstrate phenotypic heterogeneity and generate spheres, the latter being less efficient, and both showed an association with CD44. Cis- diamminedichloroplatinum (II) (cisplatin) treatment failed to reduce ALDH activity and conferred only a short-term inhibition of sphere generation in both ALDHhigh and ALDHlow fractions of the three MPM cell lines. Induction of drug sensitivity by an ALDH inhibitor, diethylaminobenzaldehyde (DEAB) resulted in significant reductions in cell viability but not a complete elimination of the sphere-forming cells, suggestive of the presence of a drug-resistant subpopulation. At the transcript level, the cisplatin + DEAB-resistant cells showed upregulated mRNA expression levels for ALDH1A2, ALDH1A3 isozymes and CD44 indicating the involvement of these markers in conferring chemoresistance in both ALDHhigh and ALDHlow fractions of the three MPM cell lines.
Conclusions
Our study shows that ALDHhigh CD44+ cells are implicated in conveying tolerance to cisplatin in the three MPM cell lines. The combined use of CD44 and ALDH widens the window for identification and targeting of a drug-resistant population which may improve the current treatment modalities in mesothelioma.
The goal of targeted therapy is to match a selective drug with a genetic lesion that predicts for drug sensitivity. In a diverse panel of cancer cell lines, we found that the cells most sensitive to focal adhesion kinase (FAK) inhibition lack expression of the neurofibromatosis type 2 (NF2) tumor suppressor gene product, Merlin. Merlin expression is often lost in malignant pleural mesothelioma (MPM), an asbestos-induced aggressive cancer with limited treatment options. Our data demonstrate that low Merlin expression predicts for increased sensitivity of MPM cells to a FAK inhibitor, VS-4718, in vitro and in tumor xenograft models. Disruption of MPM cell-cell or cell-extracellular matrix (ECM) contacts with blocking antibodies suggests that weak cell-cell adhesions in Merlin-negative MPM cells underlie their greater dependence on cell-ECM-induced FAK signaling. This provides one explanation of why Merlin-negative cells are vulnerable to FAK inhibitor treatment. Furthermore, we validated aldehyde dehydrogenase as a marker of cancer stem cells (CSCs) in MPM, a cell population thought to mediate tumor relapse after chemotherapy. Whereas pemetrexed and cisplatin, standard-of-care agents for MPM, enrich for CSCs, FAK inhibitor treatment preferentially eliminates these cells. These preclinical results provide the rationale for a clinical trial in MPM patients using a FAK inhibitor as a single agent after first-line chemotherapy. With this design, the FAK inhibitor could potentially induce a more durable clinical response through reduction of CSCs along with a strong antitumor effect. Furthermore, our data suggest that patients with Merlin-negative tumors may especially benefit from FAK inhibitor treatment.
To investigate the safety, dose-limiting toxicities, and pharmacokinetics of the smoothened inhibitor vismodegib in children with refractory or relapsed medulloblastoma.
Initially, vismodegib was administered daily at 85 mg/m2 and escalated to 170 mg/m2. The study was then revised to investigate a flat-dosing schedule of 150 mg for patients with small body surface area (BSA, 0.67-1.32 m2) or 300 mg for those who were larger (BSA, 1.33-2.20 m2). Pharmacokinetics were performed during the first course of therapy, and the right knees of all patients were imaged to monitor bone toxicity. Immunohistochemical analysis was done to identify patients with SHH-subtype medulloblastoma.
Thirteen eligible patients were enrolled on the initial study: 6 received 85 mg/m2 vismodegib, and 7 received 170 mg/m2. Twenty eligible patients were enrolled on the flat-dosing part of the study: 10 at each dosage level. Three dose-limiting toxicities were observed, but no drug-related bone toxicity was documented. The median (range) vismodegib penetration in the cerebrospinal fluid (CSF) was 0.53 (0.26-0.78), when expressed as a ratio of the concentration of vismodegib in the CSF to that of the unbound drug in plasma. Antitumor activity was seen in 1 of 3 patients with SHH-subtype disease whose tumors were evaluable and in none of the patients in the other subgroups.
Vismodegib was well tolerated in children with recurrent or refractory medulloblastoma; only 2 dose-limiting toxicities were observed with flat dosing. The recommended Phase-II study dose is 150 mg or 300 mg, depending on the patient's BSA.
Characterization of the molecular pathways that are required for the viability and maintenance of self-renewing tumor-initiating
cells may ultimately lead to improved therapies for cancer. In this study, we show that a CD133+/CD44+ population of cells enriched in prostate cancer progenitors (PCaPs) has tumor-initiating potential and that these progenitors
can be expanded under nonadherent, serum-free, sphere-forming conditions. Cells grown under these conditions have increased
in vitro clonogenic and in vivo tumorigenic potential. mRNA expression analysis of cells grown under sphere-forming conditions, compared with long-term monolayer
cultures, revealed preferential activation of the PI3K/AKT signaling pathway. PI3K p110α and β-protein levels were higher
in cells grown under sphere-forming conditions, and phosphatase and tensin homolog (PTEN) knockdown by shRNA led to an increase
in sphere formation as well as increased clonogenic and tumorigenic potential. Similarly, shRNA knockdown of FoxO3a led to
an increase in tumorigenic potential. Consistent with these results, inhibition of PI3K activity by the dual PI3K/mTOR inhibitor
NVP-BEZ235 led to growth inhibition of PCaPs. Taken together, our data strongly suggest that the PTEN/PI3K/Akt pathways are
critical for prostate cancer stem-like cell maintenance and that targeting PI3K signaling may be beneficial in prostate cancer
treatment by eliminating prostate cancer stem-like cells.
During the progression of malignant peritoneal mesothelioma (MPeM), tumor nodules propagate diffusely within the abdomen and tumors are characterized by distinct phenotypic sub-types. Recent studies in solid organ cancers have shown that cancer stem cells (CSCs) play a pivotal role in the initiation and progression of tumors. However, it is not known whether tumorigenic stem cells exist and whether they promote tumor growth in MPeM. In this study, we developed and characterized a CSC model for MPeM using stably expandable tumorigenic stem cells derived from patient tumors. We found morphologically distinct populations of CSCs that divide asymmetrically or symmetrically in MPeM in vitro cell culture. The MPeM stem cells (MPeMSCs) express stem cell markers c-MYC, NES and VEGFR2 and in the presence of matrix components cells form colony spheres. MPeMSCs are multipotent, differentiate into neuronal, vascular and adipose progeny upon defined induction and the differentiating cells express lineage-specific markers such as TUBB3, an early neuronal marker; vWF, VEGFA, VEGFC and IL-8, endothelial markers; and PPARγ and FABP4, adipose markers. Xenotransplantation experiments using MPeMSCs demonstrated early tumor growth compared with parental cells. Limiting dilution experiments using MPeMSCs and endothelial lineage-induced cells derived from a single MPeMSC resulted in early tumor growth in the latter group indicating that endothelial differentiation of MPeMSCs is important for MPeM tumor initiation. Our observation that the MPeM tumors contain stem cells with tumorigenic potential has important implications for understanding the cells of origin and tumor progression in MPeM and hence targeting CSCs may be a useful strategy to inhibit malignant progression.
From Wnt Signals to Telomerase Activity
Telomerase activity is associated with stem cell renewal and cancers, whereas a decrease in telomerase activity is seen during cell differentiation and senescence. Wnt/β-catenin signaling is also a critical regulator of stem cells, and deregulation of the pathway is associated with cancer. Now, Hoffmeyer et al. (p. 1549 ; see the Perspective by Greider ) have found a link between these two pathways. In embryonic stem cells, β-catenin was able to regulate telomerase expression and activity directly. Similar observations were obtained in adult stem cells, a model of intestinal tumors, and human cancer cells.
Alterations in hedgehog signaling are implicated in the pathogenesis of basal-cell carcinoma. Although most basal-cell carcinomas are treated surgically, no effective therapy exists for locally advanced or metastatic basal-cell carcinoma. A phase 1 study of vismodegib (GDC-0449), a first-in-class, small-molecule inhibitor of the hedgehog pathway, showed a 58% response rate among patients with advanced basal-cell carcinoma.
In this multicenter, international, two-cohort, nonrandomized study, we enrolled patients with metastatic basal-cell carcinoma and those with locally advanced basal-cell carcinoma who had inoperable disease or for whom surgery was inappropriate (because of multiple recurrences and a low likelihood of surgical cure, or substantial anticipated disfigurement). All patients received 150 mg of oral vismodegib daily. The primary end point was the independently assessed objective response rate; the primary hypotheses were that the response rate would be greater than 20% for patients with locally advanced basal-cell carcinoma and greater than 10% for those with metastatic basal-cell carcinoma.
In 33 patients with metastatic basal-cell carcinoma, the independently assessed response rate was 30% (95% confidence interval [CI], 16 to 48; P=0.001). In 63 patients with locally advanced basal-cell carcinoma, the independently assessed response rate was 43% (95% CI, 31 to 56; P<0.001), with complete responses in 13 patients (21%). The median duration of response was 7.6 months in both cohorts. Adverse events occurring in more than 30% of patients were muscle spasms, alopecia, dysgeusia (taste disturbance), weight loss, and fatigue. Serious adverse events were reported in 25% of patients; seven deaths due to adverse events were noted.
Vismodegib is associated with tumor responses in patients with locally advanced or metastatic basal-cell carcinoma. (Funded by Genentech; Erivance BCC ClinicalTrials.gov number, NCT00833417.).
Vismodegib (GDC-0449), an orally bioavailable small molecule inhibitor of Hedgehog signaling, was recently approved by the U.S. Food and Drug Administration for the treatment of basal cell carcinoma that is either metastatic or locally advanced in patients who are not candidates for surgical resection or radiation. Given the absence of previously defined effective drug therapy for this disease, approval was granted based primarily on outcome of a non-randomized parallel cohort phase II study of 99 patients with advanced basal cell carcinoma, with a primary endpoint of objective response rate. Response rates of 30.3 and 42.9 percent were observed in metastatic and locally advanced cohorts in this study, respectively, associated with median progression-free survival in both cohorts of 9.5 months. Ongoing clinical investigations include evaluation of the potential efficacy of vismodegib in a variety of disease contexts, and in combination with other agents. The mechanism of action, preclinical and clinical data, and potential utility in other disease contexts are reviewed.
Malignant pleural mesothelioma (MPM) is highly intractable and readily spreads throughout the surface of the pleural cavity, and these cells have been shown to express urokinase-type plasminogen activator receptor (uPAR). We here examined the potential of our new and powerful recombinant Sendai virus (rSeV), which shows uPAR-specific cell-to-cell fusion activity (rSeV/dMFct14 (uPA2), named "BioKnife"), for tumor cell killing in two independent orthotopic xenograft models of human. Multicycle treatment using BioKnife resulted in the efficient rescue of these models, in association with tumor-specific fusion and apoptosis. Such an effect was also seen on both MSTO-211H and H226 cells in vitro; however, we confirmed that the latter expressed uPAR but not uPA. Of interest, infection with BioKnife strongly facilitated the uPA release from H226 cells, and this effect was completely abolished by use of either pyrrolidine dithiocarbamate (PDTC) or BioKnife expressing the C-terminus-deleted dominant negative inhibitor for retinoic acid-inducible gene-I (RIG-IC), indicating that BioKnife-dependent expression of uPA was mediated by the RIG-I/nuclear factor-κB (NF-κB) axis, detecting RNA viral genome replication. Therefore, these results suggest a proof of concept that the tumor cell-killing mechanism via BioKnife may have significant potential to treat patients with MPM that is characterized by frequent uPAR expression in a clinical setting.
A major goal in cancer research is to develop carriers that can deliver drugs effectively and without side effects. Liposomal and particulate carriers with diameters of ∼100 nm have been widely used to improve the distribution and tumour accumulation of cancer drugs, but so far they have only been effective for treating highly permeable tumours. Here, we compare the accumulation and effectiveness of different sizes of long-circulating, drug-loaded polymeric micelles (with diameters of 30, 50, 70 and 100 nm) in both highly and poorly permeable tumours. All the polymer micelles penetrated highly permeable tumours in mice, but only the 30 nm micelles could penetrate poorly permeable pancreatic tumours to achieve an antitumour effect. We also showed that the penetration and efficacy of the larger micelles could be enhanced by using a transforming growth factor-β inhibitor to increase the permeability of the tumours.
DyeCycleViolet was used to set up the side population (SP) functional assay aimed at identifying subpopulations of malignant pleural mesothelioma (MPM) tumor cells with chemoresistance phenotype associated with ABCG2 transporter activity. Self-renewal, chemoresistance and tumorigenicity were tested for SP and non-side population (NSP) cells. Tumors were characterized by mesothelin, calretinin, N-cadherin, D2-40 and Wilms tumor 1 (WT1) immunohistochemistry. Surface expression of mesenchymal stem cell markers CD90, CD73 and CD105 was investigated in SP and NSP cells. We identified SP cells with self-renewal properties and increased chemoresistance in MPM cell lines and tumor-derived primary cell cultures. Compared with the non-SP fraction (NSP), the SP fraction led to the development of tumors including cells with mesothelium precursor phenotype characterized by mesenchymal morphology, being WT1 negative but cytoplasmic D2-40 positive and having a tendency of increased tumorigenicity. The same phenotypic shift was observed in patients with relapsing tumors after chemotherapy. Furthermore, the SP cells were enriched in CD105(-)(/low) expressing cells, which were small sized and had increased tumorigenicity compared with CD105(high) cells. Taken together, our results support the hypothesis that MPM CD105(-)(/low), chemoresistant small sized SP cells may constitute the cellular pool out of which recurrence develops. Further characterization of mechanisms of chemoresistance and self-renewal should lead to targets specific for this subpopulation in MPM patients.
Neuroblastoma (NB) is an often fatal pediatric tumor of neural crest origin. We previously isolated NB tumor-initiating cells (NB TIC) from bone marrow metastases that resemble cancer stem cells and form metastatic NB in immunodeficient animals with as few as ten cells. To identify signaling pathways important for the survival and self-renewal of NB TICs and potential therapeutic targets, we screened a small molecule library of 143 protein kinase inhibitors, including 33 in clinical trials. Cytostatic or cytotoxic drugs were identified that targeted PI3K (phosphoinositide 3-kinase)/Akt, PKC (protein kinase C), Aurora, ErbB2, Trk, and Polo-like kinase 1 (PLK1). Treatment with PLK1 siRNA or low nanomolar concentrations of BI 2536 or BI 6727, PLK1 inhibitors in clinical trials for adult malignancies, were cytotoxic to TICs whereas only micromolar concentrations of the inhibitors were cytotoxic for normal pediatric neural stem cells. Furthermore, BI 2536 significantly inhibited TIC tumor growth in a therapeutic xenograft model, both as a single agent and in combination with irinotecan, an active agent for relapsed NB. Our findings identify candidate kinases that regulate TIC growth and survival and suggest that PLK1 inhibitors are an attractive candidate therapy for metastatic NB.
Nanocarrier-mediated drug targeting is an emerging strategy for cancer therapy and is being used, for example, with chemotherapeutic agents for ovarian cancer. Nanocarriers are selectively accumulated in tumors as a result of their enhanced permeability and retention of macromolecules, thereby enhancing the antitumor activity of the nanocarrier-associated drugs. We investigated the real-time subcellular fate of polymeric micelles incorporating (1,2-diaminocyclohexane) platinum(II) (DACHPt/m), the parent complex of oxaliplatin, in tumor tissues by fluorescence-based assessment of their kinetic stability. These observations revealed that DACHPt/m was extravasated from blood vessels to the tumor tissue and dissociated inside each cell. Furthermore, DACHPt/m selectively dissociated within late endosomes, enhancing drug delivery to the nearby nucleus relative to free oxaliplatin, likely by circumvention of the cytoplasmic detoxification systems such as metallothionein and methionine synthase. Thus, these drug-loaded micelles exhibited higher antitumor activity than did oxaliplatin alone, even against oxaliplatin-resistant tumors. These findings suggest that nanocarriers targeting subcellular compartments may have considerable benefits in clinical applications.
Checkpoint kinase 1 (Chk1) is a checkpoint gene that is activated after DNA damage. It phosphorylates and inactivates the Cdc2 activating phosphatase Cdc25C. This in turn inactivates Cdc2, which leads to G2/M arrest. We report that blocking Chk1 expression by antisense or ribozymes in mammalian cells induces apoptosis and interferes with the G2/M arrest induced by adriamycin. The Chk1 inhibitor UCN-01 also blocks the G2 arrest after DNA damage and renders cells more susceptible to adriamycin. These results indicate that Chk1 is an essential gene for the checkpoint mechanism during normal cell proliferation as well as in the DNA damage response.
The survival of endothelial cells is dependent on interactions between the matrix and integrins mediated through focal adhesions. Focal adhesion kinase (FAK) is thought to play a key role in maintaining focal adhesion function and cell survival, whereas caspase-mediated FAK proteolysis is implicated in focal adhesion disassembly during apoptosis. We examined the relationship between changes in FAK phosphorylation and proteolysis during apoptosis of primary porcine aortic endothelial cells (PAEC) induced by staurosporine, a widely used apoptogenic agent in diverse cell types. Staurosporine-induced PAEC apoptosis was detected after 1 h and was preceded by disruption and loss of FAK localization to focal adhesions within a few minutes, whereas staurosporine-induced cleavage of FAK occurred only after 8-24h. Staurosporine induced a very rapid dephosphorylation of FAK at Tyr861 and Tyr397 and caused dissociation of phosphorylated FAK from focal adhesions as early as 30 s. The effect of staurosporine was very potent with striking inhibition of Tyr861 and Tyr397 phosphorylation and focal adhesion disruption occurring in the range 10-100 nM. Selective inhibition of a known target of staurosporine, protein kinase C, using GF109203X, and of phosphoinositide 3′-kinase using wortmannin, did not reduce FAK tyrosine phosphorylation at Tyr861 and Tyr397, or cause disruption of focal adhesions. Cycloheximide, the protein synthesis inhibitor, induced PAEC apoptosis more slowly than staurosporine, but did not induce FAK dephosphorylation or rapid focal adhesion disruption, and instead caused a slower loss of focal adhesions and a marked increase in FAK proteolysis. These studies show that FAK dephosphorylation and focal adhesion disassembly are very early events mediating the onset of staurosporine-induced endothelial cell apoptosis and are dissociated from FAK proteolysis. Cycloheximide induces apoptosis through a pathway involving FAK proteolysis without dephosphorylation.
Topoisomerase I (Top1), an abundant nuclear enzyme expressed throughout the cell cycle, relaxes DNA supercoiling by forming
transient covalent DNA cleavage complexes. We show here that staurosporine, a ubiquitous inducer of apoptosis in mammalian
cells, stabilizes cellular Top1 cleavage complexes. These complexes are formed indirectly as staurosporine cannot induce Top1
cleavage complexes in normal DNA with recombinant Top1 or nuclear extract from normal cells. In treated cells, staurosporine
produces oxidative DNA lesions and generates reactive oxygen species (ROS). Quenching of these ROS by the antioxidant N-acetyl-l-cysteine or inhibition of the mitochondrial dependent production of ROS by the caspase inhibitor benzyloxycarbonyl-VAD prevents
staurosporine-induced Top1 cleavage complexes. Down-regulation of Top1 by small interfering RNA decreases staurosporine-induced
apoptotic DNA fragmentation. We propose that Top1 cleavage complexes resulting from oxidative DNA lesions generated by ROS
in staurosporine-treated cells contribute to the full apoptotic response.
Protein kinase (PK)C theta is a critical regulator of mature T-cell activation and proliferation, being implicated in TCR-triggered nuclear factor (NF)-kappa B activation and providing important survival signals to leukemic T cells. We previously showed that overexpression of pT alpha/pre-TCR and constitutive activation of NF-kappa B characterize the T-cell leukemia/lymphoma developing in Notch3-IC transgenic mice. We report here that PKC theta is a downstream target of Notch3 signaling and that its activation and membrane translocation require a functional pre-TCR in order to trigger NF-kappa B activation in thymocytes and lymphoma cells of transgenic mice. Furthermore, deletion of PKC theta in Notch3-IC transgenic mice reduces the incidence of leukemia, correlating with decreased NF-kappa B activation. This paper therefore suggests that PKC theta mediates the activation of NF-kappa B by pre-TCR in immature thymocytes and contributes to the development of Notch3-dependent T-cell lymphoma.
Targeting tumors with long-circulating nano-scaled carriers is a promising strategy for systemic cancer treatment. Compared with free small therapeutic agents, nanocarriers can selectively accumulate in solid tumors through the enhanced permeability and retention (EPR) effect, which is characterized by leaky blood vessels and impaired lymphatic drainage in tumor tissues, and achieve superior therapeutic efficacy, while reducing side effects. In this way, drug-loaded polymeric micelles, i.e. self-assemblies of amphiphilic block copolymers consisting of a hydrophobic core as a drug reservoir and a poly(ethylene glycol) (PEG) hydrophilic shell, have demonstrated outstanding features as tumor-targeted nanocarriers with high translational potential, and several micelle formulations are currently under clinical evaluation. This review summarizes recent efforts in the development of these polymeric micelles and their performance in human studies, as well as our recent progress in polymeric micelles for the delivery of nucleic acids and imaging.
Block copolymer micelles have shown promise for the intracellular delivery of chemotherapeutic agents, proteins, and nucleic acids. Understanding the mechanism of their intracellular trafficking and fate, including the extracellular efflux of the polymers, will help improve their efficacy and minimize their safety risks. In this Leading Opinion paper, we discuss the molecular mechanism of block copolymer micelle trafficking, from intracellular uptake to extracellular efflux, on the basis of studies with HeLa cells. By using FRET (fluorescence resonance energy transfer) with confocal microscopy, we found that, following their intracellular transport via endocytosis, the micelles dissociated into their polymeric components in late endosomes and/or lysosomes. Furthermore, we confirmed that the intrinsic proteins NPC1 and ORP2 are involved in the intermembrane transfer of polymers from the endosome to the plasma membrane via the ER (endoplasmic reticulum) by using knockdown experiments with siRNAs. After the polymers were transported to the plasma membrane with the aid of ORP2, they were extruded into the cell medium via ABC transporter, ABCB1. Experiments with ABCB1-expressing vesicles indicated that the polymer itself, and not the fluorescent compounds, was recognized by the transporter. These findings, and the analysis of related mechanisms, provide valuable information that should help minimize the potential risks associated with the intracellular accumulation of block copolymer micelles and to improve their therapeutic efficacy.
The epithelial-mesenchymal transition program becomes activated during malignant progression and can enrich for cancer stem cells (CSCs). We report that inhibition of protein kinase C α (PKCα) specifically targets CSCs but has little effect on non-CSCs. The formation of CSCs from non-stem cells involves a shift from EGFR to PDGFR signaling and results in the PKCα-dependent activation of FRA1. We identified an AP-1 molecular switch in which c-FOS and FRA1 are preferentially utilized in non-CSCs and CSCs, respectively. PKCα and FRA1 expression is associated with the aggressive triple-negative breast cancers, and the depletion of FRA1 results in a mesenchymal-epithelial transition. Hence, identifying molecular features that shift between cell states can be exploited to target signaling components critical to CSCs.
Cancer stem cells (CSCs) have been proposed as the driving force of tumorigenesis and the seeds of metastases. However, their existence and role remain a topic of intense debate. Recently, the identification of CSCs in endogenously developing mouse tumours has provided further support for this concept. Here I discuss the challenges in identifying CSCs, their dependency on a supportive niche and their role in metastasis, and propose that stemness is a flexible — rather than fixed — quality of tumour cells that can be lost and gained.
Selective targeting of cancer stem cells (CSCs) offers promise for a new generation of therapeutics. However, assays for both human CSCs and normal stem cells that are amenable to robust biological screens are limited. Using a discovery platform that reveals differences between neoplastic and normal human pluripotent stem cells (hPSC), we identify small molecules from libraries of known compounds that induce differentiation to overcome neoplastic self-renewal. Surprisingly, thioridazine, an antipsychotic drug, selectively targets the neoplastic cells, and impairs human somatic CSCs capable of in vivo leukemic disease initiation while having no effect on normal blood SCs. The drug antagonizes dopamine receptors that are expressed on CSCs and on breast cancer cells as well. These results suggest that dopamine receptors may serve as a biomarker for diverse malignancies, demonstrate the utility of using neoplastic hPSCs for identifying CSC-targeting drugs, and provide support for the use of differentiation as a therapeutic strategy.
PaperClip
/cms/asset/bb2bbd9b-352a-417b-8ef7-0dbc5545940d/mmc4.mp3
Loading ...
(mp3, 3.29 MB)
Download audio
The differentiation of tumorigenic cancer stem cells into nontumorigenic cancer cells confers heterogeneity to some cancers beyond that explained by clonal evolution or environmental differences. In such cancers, functional differences between tumorigenic and nontumorigenic cells influence response to therapy and prognosis. However, it remains uncertain whether the model applies to many, or few, cancers due to questions about the robustness of cancer stem cell markers and the extent to which existing assays underestimate the frequency of tumorigenic cells. In cancers with rapid genetic change, reversible changes in cell states, or biological variability among patients, the stem cell model may not be readily testable.
Acquired resistance to targeted therapies threatens the value of these otherwise very promising agents. The recent description of resistance to the Hedgehog pathway inhibitor vismodegib (GDC-0449) in a medulloblastoma patient who had a dramatic initial response has spurred efforts to understand potential mechanisms of drug resistance. Elucidating these mechanisms will play a significant role in informing strategies to overcome this meaningful limitation. Cancer Res; 71(15); 5057-61. (c) 2011 AACR.
Tumor relapse and metastasis remain major obstacles for improving overall cancer survival, which may be due at least in part to the existence of cancer stem cells (CSCs). CSCs are characterized by tumorigenic properties and the ability to self-renew, form differentiated progeny, and develop resistance to therapy. CSCs use many of the same signaling pathways that are found in normal stem cells, such as Wnt, Notch, and Hedgehog (Hh). The origin of CSCs is not fully understood, but data suggest that they originate from normal stem or progenitor cells, or possibly other cancer cells. Therapeutic targeting of both CSCs and bulk tumor populations may provide a strategy to suppress tumor regrowth. Development of agents that target critical steps in the Wnt, Notch, and Hh pathways will be complicated by signaling cross-talk. The role that embryonic signaling pathways play in the function of CSCs, the development of new anti-CSC therapeutic agents, and the complexity of potential CSC signaling cross-talk are described in this Review.
Many human cancers are driven by cancer stem cells (CSCs) whose connection to metastatic spread remains incompletely understood. In this issue of Cell Stem Cell, Pang et al. (2010) isolate a subpopulation of human colorectal CSCs that uniquely possesses metastatic potential.
Screens for agents that specifically kill epithelial cancer stem cells (CSCs) have not been possible due to the rarity of these cells within tumor cell populations and their relative instability in culture. We describe here an approach to screening for agents with epithelial CSC-specific toxicity. We implemented this method in a chemical screen and discovered compounds showing selective toxicity for breast CSCs. One compound, salinomycin, reduces the proportion of CSCs by >100-fold relative to paclitaxel, a commonly used breast cancer chemotherapeutic drug. Treatment of mice with salinomycin inhibits mammary tumor growth in vivo and induces increased epithelial differentiation of tumor cells. In addition, global gene expression analyses show that salinomycin treatment results in the loss of expression of breast CSC genes previously identified by analyses of breast tissues isolated directly from patients. This study demonstrates the ability to identify agents with specific toxicity for epithelial CSCs.
Solid tumours are an enormous cancer burden and a major therapeutic challenge. The cancer stem cell (CSC) hypothesis provides an attractive cellular mechanism to account for the therapeutic refractoriness and dormant behaviour exhibited by many of these tumours. There is increasing evidence that diverse solid tumours are hierarchically organized and sustained by a distinct subpopulation of CSCs. Direct evidence for the CSC hypothesis has recently emerged from mouse models of epithelial tumorigenesis, although alternative models of heterogeneity also seem to apply. The clinical relevance of CSCs remains a fundamental issue but preliminary findings indicate that specific targeting may be possible.