[Show abstract][Hide abstract] ABSTRACT: Triple negative breast cancers (TNBCs) account for 15% of all breast cancers, and represent one of the most aggressive forms of the disease, exhibiting short relapse-free survival. In contrast to other breast cancer subtypes, the absence of knowledge about the etiopathogenic alterations that cause TNBCs force the use of chemotherapeutics to treat these tumors. Because of this, efforts have been devoted with the aim of incorporating novel therapies into the clinical setting. Kinases play important roles in the pathophysiology of several tumors, including TNBC. Since expression of the MAP kinase ERK5 has been linked to patient outcome in breast cancer, we analyzed the potential value of its targeting in TNBC. ERK5 was frequently overexpressed and active in samples from patients with TNBC, as well as in explants from mice carrying genetically-defined TNBC tumors. Moreover, expression of ERK5 was linked to a worse prognosis in TNBC patients. Knockdown experiments demonstrated that ERK5 supported proliferation of TNBC cells. Pharmacological inhibition of ERK5 with TG02, a clinical stage inhibitor which targets ERK5 and other kinases, inhibited cell proliferation by blocking passage of cells through G1 and G2, and also triggered apoptosis in certain TNBC cell lines. TG02 had significant antitumor activity in a TNBC xenograft model in vivo, and also augmented the activity of chemotherapeutic agents commonly used to treat TNBC. Together, these data indicate that ERK5 targeting may represent a valid strategy against TNBC, and support the development of trials aimed at evaluating the clinical effectiveness of drugs that block this kinase.
[Show abstract][Hide abstract] ABSTRACT: Objective: The Extracellular Signal-Regulated kinase 5 (ERK5 or BMK1) is involved in tumour development. The ERK5 gene may be amplified in hepatocellular carcinoma (HCC) but its biological role has not been clarified. In this study we explored the role of ERK5 expression and activity in HCC in vitro and in vivo.
Design: ERK5 expression was evaluated in human liver tissue. Cultured HepG2 and Huh-7 were studied after ERK5 knockdown by siRNA or in the presence of the specific pharmacologic inhibitor, XMD8-92. The role of ERK5 in vivo was assessed using mouse Huh-7 xenografts.
Results: In tissue specimens from patients with HCC, a higher percentage of cells with nuclear ERK5 expression was found both in HCC and in the surrounding cirrhotic tissue, compared to normal liver tissue. Inhibition of ERK5 decreased HCC cell proliferation, and increased the proportion of cells in G0/G1 phase. These effects were associated with increased expression of p27 and p15 and decreased CCND1. Treatment with XMD8-92 or ERK5 silencing prevented cell migration induced by EGF or hypoxia, and caused cytoskeletal remodelling. In mouse xenografts, the rate of tumour appearance and the size of tumours were significantly lower when Huh-7 were silenced for ERK5. Moreover, systemic treatment with XMD8-92 of mice with established HCC xenografts markedly reduced tumour growth and decreased the expression of the proto-oncogene c-Rel.
Conclusions: ERK5 regulates the biology of HCC cells and modulates tumour development and growth in vivo. This pathway should be investigated as a possible therapeutic target in HCC.
[Show abstract][Hide abstract] ABSTRACT: Extracellular signal-regulated kinase 5 (ERK5), also known as big mitogen-activated protein kinase (MAPK) 1, is implicated in a wide range of biologic processes, which include proliferation or vascularization. Here, we show that ERK5 is degraded through the ubiquitin-proteasome system, in a process mediated by the tumor suppressor von Hippel-Lindau (VHL) gene, through a prolyl hydroxylation-dependent mechanism. Our conclusions derive from transient transfection assays in Cos7 cells, as well as the study of endogenous ERK5 in different experimental systems such as MCF7, HMEC, or Caki-2 cell lines. In fact, the specific knockdown of ERK5 in pVHL-negative cell lines promotes a decrease in proliferation and migration, supporting the role of this MAPK in cellular transformation. Furthermore, in a short series of fresh samples from human clear cell renal cell carcinoma, high levels of ERK5 correlate with more aggressive and metastatic stages of the disease. Therefore, our results provide new biochemical data suggesting that ERK5 is a novel target of the tumor suppressor VHL, opening a new field of research on the role of ERK5 in renal carcinomas.
Full-text · Article · Jun 2013 · Neoplasia (New York, N.Y.)
[Show abstract][Hide abstract] ABSTRACT: Glioblastoma (GBM) is associated with infiltration of peritumoral parenchyma by isolated tumor cells that leads to tumor regrowth. Recently, GBM stem-like or initiating cells (GICs) have been identified in the peritumoral (PT) area, but whether these GICs have enhanced migratory and invasive capabilities compared with GICs from the tumor mass (TM) is presently unknown. We isolated GICs from the infiltrated PT tissue and the TM of three patients and found that PT cells have an advantage over TM cells in 2D and 3D migration and invasion assays. Interestingly, PT cells display a high plasticity in protrusion formation and cell shape and their migration is insensitive to substrate stiffness, which represent advantages to infiltrate microenvironments of different rigidity. Furthermore, mouse and chicken embryo xenografts revealed that only PT cells showed a dispersed distribution pattern, closely associated to blood vessels. Consistent with cellular plasticity, simultaneous Rac and RhoA activation is required for the enhanced invasive capacity of PT cells. Moreover, Rho GTPase signaling modulators αVβ3 and p27 play key roles in GIC invasiveness. Of note, p27 is upregulated in TM cells and inhibits RhoA activity. Gene silencing of p27 increased the invasive capacity of TM GICs. Additionally, β3 integrin is upregulated in PT cells. Blockade of dimeric integrin αVβ3, a Rac activator, reduced the invasive capacity of PT GICs in vitro and abrogated the spreading of PT cells into chicken embryos. Thus, our results describe the invasive features acquired by a unique subpopulation of GICs that infiltrate neighbouring tissue.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To analyze the antimyeloma potential of TG02, an ERK5/CDK inhibitory drug.
Utilizing different multiple myeloma cell lines we determined the effect of TG02 over viability by MTT assays. The apoptotic effect over multiple myeloma patient samples was studied ex vivo by cytometry. The mechanism of action of TG02 was analyzed in the cell line MM1S, studying its effect on the cell cycle, the induction of apoptosis, and the loss of mitochondrial membrane potential by cytometry and Western blot. Two models of multiple myeloma xenograft were utilized to study the in vivo action of TG02.
TG02 potently inhibited proliferation and survival of multiple myeloma cell lines, even under protective bone marrow niche conditions, and selectively induced apoptosis of primary patient-derived malignant plasma cells. TG02 displayed significant single-agent activity in two multiple myeloma xenograft models, and enhanced the in vivo activity of bortezomib and lenalidomide. Signaling analyses revealed that the drug simultaneously blocked the activity of CDKs 1, 2, and 9 as well as the MAP kinase ERK5 in MM1S cells, leading to cell-cycle arrest and rapid commitment to apoptosis. TG02 induced robust activation of both the intrinsic and extrinsic pathways of apoptosis, and depletion of XIAP and the key multiple myeloma survival protein Mcl-1.
TG02 is a promising new antimyeloma agent that is currently in phase I clinical trials in leukemia and multiple myeloma patients.
Full-text · Article · Mar 2013 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer. Despite response to chemotherapy, relapses are frequent and resistance to available treatments is often seen in the metastatic setting. Therefore, identification of new therapeutic targets is required. With this aim, we have profiled the activation status of 44 receptor tyrosine kinases (RTKs) and their major signaling pathways in patient-derived TNBC tumors. Frequent co-activation of several RTKs as well as the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) and mammalian target of rapamycin (mTOR) routes was found. Pharmacologic targeting of the activated kinases indicated that agents that attack the mTOR route are more potent and efficient antitumoral treatments than agents targeting RTKs. mTOR signals through two multiprotein complexes, mTORC1 and mTORC2. We used a genetic approach to explore the contribution of each of the two mTOR branches to the regulation of cell number of TNBC cells. RNA interference experiments indicated that mTORC1 predominated over mTORC2 in the control of TNBC cell proliferation. Moreover, RNA interference of mTOR had a superior antiproliferative action than separately acting on mTORC1 or mTORC2. To analyze the relevance of mTOR targeting in vivo, we used mice with TNBC. Treatment of these mice with BEZ235, a drug that targets mTOR, slowed tumor growth. Mechanistically, BEZ235 delayed cell cycle progression without affecting cell viability. Our results show that TNBCs are particularly sensitive to inhibition of the mTOR pathway, and indicate that mTOR targeting may be a more efficient anti-TNBC therapy than exclusively acting on the mTORC1 branch of the pathway. This is relevant as most mTOR inhibitors used in the clinic act on mTORC1. Collectively with the fact that BEZ235 synergized with drugs commonly used in the treatment of TNBC, our data support the clinical development of agents that act on mTOR as a therapy for this disease.
[Show abstract][Hide abstract] ABSTRACT: Resistance to Imatinib Mesylate (IM) is a major problem in Chronic Myelogenous Leukaemia management. Most of the studies about resistance have focused on point mutations on BCR/ABL. However, other types of resistance that do not imply mutations in BCR/ABL have been also described. In the present report we aim to study the role of several MAPK in IM resistance not associate to BCR/ABL mutations. Therefore we used an experimental system of resistant cell lines generated by co-culturing with IM (K562, Lama 84) as well as primary material from resistant and responder patient without BCR/ABL mutations. Here we demonstrate that Erk5 and p38MAPK signaling pathways are not implicated in the acquired resistance phenotype. However, Erk2, but not Erk1, is critical for the acquired resistance to IM. In fact, Bcr/Abl activates preferentially Erk2 in transient transfection in a dose dependent fashion through the c-Abl part of the chimeric protein. Finally, we present evidences demonstrating how constitutive activation of Erk2 is a de novo mechanism of resistance to IM. In summary our data support the use of therapeutic approaches based on Erk2 inhibition, which could be added to the therapeutic armamentarium to fight CML, especially when IM resistance develops secondary to Erk2 activation.
[Show abstract][Hide abstract] ABSTRACT: Breast cancer is the most common neoplasia in women. Even though advances in its treatment have improved disease outcome, some patients relapse. Therefore, attempts to better define the molecular determinants that drive breast cancer cell proliferation may help in defining potential therapeutic targets. Mitogen-activated protein kinases (MAPK) play important roles in tumorigenesis. One of them, Erk5, has been linked to the proliferation of breast cancer cells in vitro. Here we have investigated the expression and prognostic value of Erk5 in human breast cancer.
Animal and cellular models were used to study Erk5 expression and function in breast cancer. In 84 human breast tumours the expression of Erk5 was analyzed by immunohistochemistry. Active Erk5 (pErk5) was studied by Western blotting. Correlation of Erk5 with clinicopathological parameters and with disease-free survival in early stage breast cancer patients was analyzed. Expression of Erk5 was detected in most patients, and overexpression was found in 20%. Active Erk5 was present in a substantial number of samples, as well as in tumours from an animal breast cancer model. Overexpression of Erk5 was associated with a decrease in disease-free survival time, which was independent of other clinicopathological parameters of prognosis. Transient transfection of a short hairpin RNA (shRNA) targeting Erk5, and a stable cell line expressing a dominant negative form of Erk5 (Erk5(AEF)), were used to investigate the influence of Erk5 on drugs used in the clinic to treat breast tumours. We found that inhibition of Erk5 decreased cancer cell proliferation and also sensitized these cells to the action of anti-HER2 therapies.
Overexpression of Erk5 is an independent predictor of disease-free survival in breast cancer, and may represent a future therapeutic target.
[Show abstract][Hide abstract] ABSTRACT: Receptor tyrosine kinases play an important role in breast cancer. One of them, the type I insulin-like growth factor, has been linked to resistance to trastuzumab (Herceptin), an agent that targets human epidermal growth factor receptor 2. Here, we show that the insulin-like growth factor-I receptor (IGF-IR) antagonist NVP-AEW541 inhibits proliferation of breast cancer cells and synergizes with trastuzumab.
Patient samples and breast cancer cell lines were evaluated for IGF-IR expression or activation by western blotting. 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT) uptake assays and Annexin V staining were used for the analyses of cell proliferation/apoptosis. Biochemical and genomic studies were carried out to gain insights into the mechanism of action of NVP-AEW541.
The IGF-IR was expressed above normal levels in a number of breast cancer samples. Activation of this receptor was inhibited by NVP-AEW541 that also decreased cell proliferation and increased apoptosis. NVP-AEW541 decreased the amount of pAkt and increased the level of p27. Combination studies with several drugs used in the breast cancer clinic showed that NVP-AEW541 synergistically increased the action of trastuzumab.
Our results show the anti-breast cancer action of NVP-AEW541 and support the clinical development of anti-IGF-IR agents, especially in combination with trastuzumab.
Full-text · Article · Nov 2008 · Annals of Oncology
[Show abstract][Hide abstract] ABSTRACT: Mesangial activation occurs in many forms of renal disease that progress to renal failure. Mitogen-activated protein kinases (MAPKs) are important mediators involved in the intracellular network of interacting proteins that transduce extracellular stimuli to intracellular responses. The extracellular signal-regulated kinases 5 (Erk5) MAPK pathway has been involved in regulating several cellular responses. Thus, we examined the expression of Erk5 in human renal tissue and the function of Erk5 in cultured human mesangial cells.
Erk5 was visualized in human renal tissue by immunohistochemistry and in mesangial cells by immunofluorescence microscopy using the anti-Erk5 C-terminus antibody. Erk5 expression and activation, and collagen I expression were determined by western blot. To generate a dominant-negative form of the Erk5 in human mesangial cells, an EcoRI fragment from wild-type pCEFL-HA-Erk5 was subcloned into the EcoRI site of pCDNA3. Cell proliferation was analysed by an MTT-based assay. Cell contraction was analysed by studying the changes in the planar cell surface area.
Erk5 was expressed in the kidney, mainly localized at the glomerular mesangium. In cultured human mesangial cells, Erk5 was activated by foetal calf serum (FCS), high glucose, endothelin-1, platelet-activating factor (PAF), epidermal growth factor (EGF) and transforming growth factor beta-1 (TGF-beta1). The expression of a dominant-negative form of Erk5 in human mesangial cells resulted in a significant decrease in proliferation, EGF-induced cell contraction and TGF-beta1-induced collagen I expression.
These results suggest that Erk5 is involved in agonist-induced mesangial cell contraction, proliferation and ECM accumulation and point to a multifunctional role of Erk5 in the pathophysiology of glomerular mesangial cells.
[Show abstract][Hide abstract] ABSTRACT: The neuregulins represent the largest subclass of polypeptide factors of the epidermal growth factor family of ligands. These molecules are synthesized as membrane-bound, biologically active growth factors that act by binding to the HER/ErbB receptor tyrosine kinases. Preclinical data have indicated that increased expression and function of neuregulins may provoke cancer. Furthermore, neuregulin expression has been detected in several neoplasias, and their presence may correlate with response to treatments that target the HER receptors such as trastuzumab. In addition, the neuregulins have also been implicated in resistance to anti-HER therapies. Therefore, targeting of the neuregulins may be helpful in neoplastic diseases in which these polypeptide factors contribute to tumor generation and/or maintenance.
Preview · Article · Jun 2008 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: Nucleocytoplasmic shuttling of multiple signalling proteins is critical in the control of processes such as cell proliferation, differentiation, or apoptosis. One group of proteins whose activity depends on this nucleocytoplasmic traffic includes the mitogen-activated protein kinases. Usually, these kinases reside in the cytoplasm and move to the nucleus upon dual phosphorylation. One of these kinases, Erk5, has been found to reside in the nucleus of breast cancer cells that overexpress the ErbB2 receptor. This raises questions with respect to the mechanisms implicated in Erk5 nuclear location in these cells, as well as the biological consequences of this nuclear residency. In breast cancer cells overexpressing ErbB2, Erk5 dual phosphorylation required ErbB2 tyrosine kinase activity; however, Erk5 nuclear residency did not require ErbB2 activity. Furthermore, translocation of Erk5 from the cytosol to the nucleus occurred in the absence of dual phosphorylation. Nuclear residency of Erk5 in these cells depended on the integrity of a nuclear localization signal present in the unique C-terminus of Erk5. The Erk5 form expressed by these breast cancer cells included the N- and C-terminal cytoplasmic targeting signals, yet Erk5 was nuclear, and remained at this location throughout the interphase without being tightly bound to DNA. Biological studies using a mutant Erk5 that accumulates in the nucleus indicate that nuclear Erk5 favours MEF2-dependent transcriptional activity, and inhibits TRAIL-induced cell death.
No preview · Article · Aug 2007 · Cellular Signalling
[Show abstract][Hide abstract] ABSTRACT: Human epidermal growth factor receptor 2 (HER-2) overexpression has been associated with the genesis and progression of a subset of breast cancers. The function of HER-2 may be upregulated by overexpression or by the availability of neuregulins (NRGs), a group of transmembrane growth factors. Transmembrane NRGs strongly activated HER-2 and cell proliferation in breast cancer cells that did not overexpress HER-2, and treatment with trastuzumab prevented the proliferative action of transmembrane NRG. This raised the relevant clinical question of whether patients considered as HER-2 negative, but expressing transmembrane NRG, may benefit from treatment with trastuzumab.
MCF7 cells expressing transmembrane NRG (MCF7-NRG2c) were injected into mice, and their sensitivity to trastuzumab was assessed. A retrospective study of 124 patients with early-stage or metastatic breast cancer was conducted. Expression of transmembrane NRG was evaluated by immunohistochemistry. In 11 patients, Western blot for NRGs was also carried out. Statistics were performed to analyze possible correlations between NRG expression and response to trastuzumab-based therapies, event-free survival, and overall survival (OS).
Trastuzumab inhibited tumor growth in mice injected with MCF7-NRG2c cells. Transmembrane NRG was frequently expressed in breast cancer patients. Overexpression of transmembrane NRG significantly correlated with a longer event-free survival and OS in patients with low or normal HER-2 expression who were treated with trastuzumab-based therapies but not in patients with HER-2 overexpression.
We suggest that the spectrum of patients who may benefit from trastuzumab-based therapies may be widened to include patients with metastatic breast cancer without HER-2 amplification but who express transmembrane NRGs.
No preview · Article · Aug 2007 · Journal of Clinical Oncology
[Show abstract][Hide abstract] ABSTRACT: The neuregulins (NRGs) play important roles in animal physiology, and their disregulation has been linked to diseases such as cancer or schizophrenia. The NRGs may be produced as transmembrane proteins (proNRGs), even though they lack an N-terminal signal sequence. This raises the question of how NRGs are sorted to the plasma membrane. It is also unclear whether in their transmembrane state, the NRGs are biologically active. During studies aimed at solving these questions, we found that deletion of the extracellular juxtamembrane region termed the linker, decreased cell surface exposure of the mutant proNRG(DeltaLinker), and caused its entrapment at the cis-Golgi. We also found that cell surface-exposed transmembrane NRG forms retain biological activity. Thus, a mutant whose cleavage is impaired but is correctly sorted to the plasma membrane activated ErbB receptors in trans and also stimulated proliferation. Because the linker is implicated in surface sorting and the regulation of the cleavage of transmembrane NRGs, our data indicate that this region exerts multiple important roles in the physiology of NRGs.
Full-text · Article · Mar 2007 · Molecular Biology of the Cell
[Show abstract][Hide abstract] ABSTRACT: The ligands of the epidermal growth factor family and their receptors, the ErbB proteins, have been linked to the development of different types of cancer. Particular attention has focused on ErbB2, whose activation may occur by receptor overexpression or by ligand-induced oligomerization with other ErbB receptors. Whether these two modes of ErbB2 activation cause the same biological responses is unknown. Here, we uncovered important differences in the signaling, proliferation rates, and the response to anti-ErbB2 antibodies when comparing MCF7 cells expressing the ligand neuregulin, to MCF7 cells overexpressing ErbB2. Expression of neuregulin caused higher proliferation than ErbB2 overexpression. Transmembrane neuregulin expression was accompanied by constitutive activation of ErbB2, ErbB3, and ErbB4 receptors. ErbB2 overexpression caused tyrosine phosphorylation of ErbB2, whereas ErbB3 and ErbB4 were only slightly tyrosine phosphorylated. Autocrine transmembrane neuregulin also caused constitutive activation of several signaling pathways, such as the Erk1/2, Erk5, and Akt routes, which have been linked to breast cancer cell proliferation. Interestingly, expression of neuregulin increased p21 levels and this was required for the proliferation of MCF7 cells. Treatment with the anti-ErbB2 receptor antibody Herceptin had an inhibitory effect on proliferation only in cells expressing neuregulin but not on cells overexpressing ErbB2, and its inhibitory activity was accompanied by a decrease in p21. These results suggest that Herceptin may also be of help in the treatment of tumors in which neuregulin feeds the tumoral tissue.