Search

Tissue-type plasminogen activator (tPA) plays roles in the development and the plasticity of the nervous system. Here, we demonstrate in neurons, that by opposition to the single chain form (sc-tPA), the two-chains form of tPA (tc-tPA) activates the MET receptor, leading to the recruitment of N -Methyl-d-Aspartate receptors (NMDARs) and to the endocytosis and proteasome-dependent degradation of NMDARs containing the GluN2B subunit. Accordingly, tc-tPA down-regulated GluN2B-NMDAR-driven signalling, a process prevented by blockers of HGFR/MET and mimicked by its agonists, leading to a modulation of neuronal death. Thus, our present study unmasks a new mechanism of action of tPA, with its two-chains form mediating a crosstalk between MET and the GluN2B subunit of NMDARs to control neuronal survival.

Introduction and Objectives: It is well-known that signaling mediated by the hepatocyte growth factor (HGF) and its receptor c-Met in the liver is involved in the control of cellular redox status and oxidative stress, particularly through its ability to induce hepatoprotective gene expression by activating survival pathways in hepatocytes. It has been reported that HGF can regulate the expression of some members of the NADPH oxidase family in liver cells, particularly the catalytic subunits and p22 phox . In the present work we were focused to characterize the mechanism of regulation of p22 phox by HGF and its receptor c-Met in primary mouse hepatocytes as a key determinant for cellular redox regulation., Materials and Methods: Primary mouse hepatocytes were treated with HGF (50 ng/mL) at different times. cyba expression (gene encoding p22 phox ) or protein content were addressed by real time RT-PCR, Western blot or immunofluorescence. Protein interactions were explored by immunoprecipitation and FRET analysis., Results: Our results provided mechanistic information supporting the transcriptional repression of cyba induced by HGF in a mechanism dependent of NF-κB activity. We identified a post-translational regulation mechanism directed by p22 phox degradation by proteasome 26S, and a second mechanism mediated by p22 phox sequestration by c-Met in plasma membrane., Conclusion: Our data clearly show that HGF/c-Met exerts regulation of the NADPH oxidase by a wide-range of molecular mechanisms. NADPH oxidase-derived reactive oxygen species regulated by HGF/c-Met represents one of the main mechanisms of signal transduction elicited by this growth factor., (Copyright © 2021 AEDV. Published by Elsevier España, S.L.U. All rights reserved.)

Targeted therapy is a hallmark of cancer treatment that has changed the landscape of cancer management and enabled a personalized treatment approach. Nevertheless, the development of cancer resistance is a major challenge that is currently threatening the effective utilization of targeted therapies. The hepatocyte growth factor receptor, MET, is a receptor tyrosine kinase known for its oncogenic activity and tumorigenic potential. MET is a well-known driver of cancer resistance. A growing body of evidence revealed a major role of MET in mediating acquired resistance to several classes of targeted therapies. Deregulations of MET commonly associated with the development of cancer resistance include gene amplification, overexpression, autocrine activation, and crosstalk with other signaling pathways. Small-molecule tyrosine kinase inhibitors of MET are currently approved for the treatment of different solid cancers. This review summarizes the current evidence regarding MET-mediated cancer resistance toward targeted therapies. The molecular mechanisms associated with resistance are described along with findings from preclinical and clinical studies on using MET inhibitors to restore the anticancer activity of targeted therapies for the treatment of solid tumors., (© 2021. Springer Science+Business Media, LLC, part of Springer Nature.)

Rationale: Metastasis, the development of secondary malignant growth at a distance from a primary tumor, is the main cause of cancer-associated death. However, little is known about how metastatic cancer cells adapt to and colonize in the new organ environment. Here we sought to investigate the functional mechanism of cholesterol metabolic aberration in colorectal carcinoma (CRC) liver metastasis. Methods: The expression of cholesterol metabolism-related genes in primary colorectal tumors (PT) and paired liver metastases (LM) were examined by RT-PCR. The role of SREBP2-dependent cholesterol biosynthesis pathway in cell growth and CRC liver metastasis were determined by SREBP2 silencing in CRC cell lines and experimental metastasis models including, intra-splenic injection models and liver orthotropic injection model. Growth factors treatment and co-culture experiment were performed to reveal the mechanism underlying the up-regulation of SREBP2 in CRC liver metastases. The in vivo efficacy of inhibition of cholesterol biosynthesis pathway by betulin or simvastatin were evaluated in experimental metastasis models. Results: In the present study, we identify a colorectal cancer (CRC) liver metastasis-specific cholesterol metabolic pathway involving the activation of SREBP2-dependent cholesterol biosynthesis, which is required for the colonization and growth of metastatic CRC cells in the liver. Inhibiting this cholesterol biosynthesis pathway suppresses CRC liver metastasis. Mechanically, hepatocyte growth factor (HGF) from liver environment activates SREBP2-dependent cholesterol biosynthesis pathway by activating c-Met/PI3K/AKT/mTOR axis in CRC cells. Conclusion: Our findings support the notion that CRC liver metastases show a specific cholesterol metabolic aberration. Targeting this cholesterol biosynthesis pathway could be a promising treatment for CRC liver metastasis., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Radiofrequency ablation (RFA) is popularly used in the treatment of hepatocellular carcinoma (HCC). However, the accelerated malignant progression of residual HCC cells after RFA is the main obstacle for the application of this technology in HCC treatment. In the present study, HepG2 cells, an established human HCC cell line, experienced repeatedly with heat treatment, survived cells, HepG2-H cells, were used to simulate residual HCC cells after RFA. The abilities of proliferation, colony formation, and migration were compared between HepG2 and HepG2-H cells. Then, RNA sequencing was used to explore the difference in genes expression between two groups of cells. Subsequently, the level of c-Met, one of membranous receptors of MAPK signal pathway, was measured by RT-qPCR and western blot; the effect of c-Met inhibition on the malignant progression of HepG2-H cells was evaluated. The results showed that HepG2-H cells exhibited higher abilities in the proliferation, colony formation, and migration than that of HepG2 cells. Moreover, differentially expressed genes between two groups of cells were prominently enriched in MAPK signal pathway. The level of c-Met in HepG2-H cells was significantly higher than that in HepG2 cells, and the inhibition in the activity of c-Met could repress the malignant behaviors of HepG2-H cells. These results indicated that the accelerated malignant progression of residual HCC cells after RFA can be partly attributed to the overexpression of c-Met and the activation of MAPK signal pathway. Therefore, we proposed that RFA followed by c-Met inhibitor intake maybe is a better treatment protocol for HCC.

Aberrant DNA methylation is widely observed in various types of cancer, and expression of microRNAs (miRNAs/miRs) is suppressed by DNA methylation. The present study explored tumor suppressor miRNAs downregulated by DNA methylation in endometrial cancer cells, as the basis of a novel therapeutic approach for endometrial cancer. Among 821 candidate miRNAs, miR‑34b was identified as an upregulated miRNA after demethylation treatment in all four endometrial cancer cell lines (HEC‑108, SNG‑II, Ishikawa and HHUA) examined. miR‑34b expression with or without demethylation treatment in cancer cells was confirmed by TaqMan quantitative PCR. MYC and MET, the predicted target genes of miR‑34b, were downregulated at both the RNA and protein levels following miR‑34b overexpression. Following miR‑34b treatment, inhibition of cell growth and invasion, and cell cycle arrest were observed in HEC‑108 cells. Sensitivity to paclitaxel was increased in cancer cells with miR‑34b overexpression, compared with untreated cancer cells, but this difference was not identified for cisplatin or doxorubicin. In vivo, combination treatment with miR‑34b and paclitaxel markedly reduced tumor growth compared with treatment with negative control miRNA and paclitaxel. These data suggest that miR‑34b enhances paclitaxel sensitivity in endometrial cancer cells, and that miR‑34b and MET are key targets for treatment of endometrial cancer. The present results may contribute to the development of combination treatment with a demethylation agent, miR‑34b mimic or MET inhibitor and an anticancer drug.

Backgrounds and Aims: Hepatocyte Growth Factor (HGF)-MET signaling is known to promote biological functions such as cell survival, cell motility, and cell proliferation. However, it is unknown if HGF-MET alters the macrophage phenotype. In this study, we aimed to study the effects of HGF-MET signaling on the M1 macrophage phenotype. Methods and Materials: Bone marrow-derived macrophages (BMDMs) isolated from mice were either polarized to an M1 phenotype by IFN-γ and LPS treatment or to an M2 phenotype by IL-4 treatment. Changes in M1 or M2 markers induced by HGF-MET signaling were evaluated. Mechanisms responsible for alternations in the macrophage phenotype and intracellular metabolism were analyzed. Results: c-Met was expressed especially in M1 macrophages polarized by treatment with IFN-γ and LPS. In M1 macrophages, HGF-MET signaling induced the expression of Arg-1 mRNA and secretion of IL-10 and TGF-β1 and downregulated the mRNA expression of iNOS, TNF- α, and IL-6 . In addition, activation of the PI3K pathway and inactivation of NFκB were also observed in M1 macrophages treated with HGF. The increased Arg-1 expression and IL-10 secretion were abrogated by PI3K inhibition, whereas, no changes were observed in TNF-α and IL-6 expression. The inactivation of NFκB was found to be independent of the PI3K pathway. HGF-MET signaling shifted the M1 macrophages to an M2-like phenotype, mainly through PI3K-mediated induction of Arg-1 expression. Finally, HGF-MET signaling also shifted the M1 macrophage intracellular metabolism toward an M2 phenotype, especially with respect to fatty acid metabolism. Conclusion: Our results suggested that HGF treatment not only promotes regeneration in epithelial cells, but also leads to tissue repair by altering M1 macrophages to an M2-like phenotype., (Copyright © 2020 Nishikoba, Kumagai, Kanmura, Nakamura, Ono, Eguchi, Kamibayashiyama, Oda, Mawatari, Tanoue, Hashimoto, Tsubouchi and Ido.)

Control of cell death/survival balance is an important feature to maintain tissue homeostasis. Dependence receptors are able to induce either survival or cell death in presence or absence of their ligand, respectively. However, their precise mechanism of action and their physiological importance are still elusive for most of them including the MET receptor. We evidence that pro-apoptotic fragment generated by caspase cleavage of MET localizes to the mitochondria-associated membrane region. This fragment triggers a calcium transfer from endoplasmic reticulum to mitochondria, which is instrumental for the apoptotic action of the receptor. Knock-in mice bearing a mutation of MET caspase cleavage site highlighted that p40MET production is important for FAS-driven hepatocyte apoptosis, and demonstrate that MET acts as a dependence receptor in vivo. Our data shed light on new signaling mechanisms for dependence receptors' control of cell survival/death balance, which may offer new clues for the pathophysiology of epithelial structures., Competing Interests: LD, CL, AV, SP, JL, FV, SL, FG, RP, GB, LH, LP, AF, DT No competing interests declared, (© 2020, Duplaquet et al.)

Inactivating mutations of axis inhibition protein 1 (AXIN1), a negative regulator of the Wnt/β-Catenin cascade, are among the common genetic events in human hepatocellular carcinoma (HCC), affecting approximately 10% of cases. In the present manuscript, we sought to define the genetic crosstalk between Axin1 mutants and Wnt/β-catenin as well as Notch signaling cascades along hepatocarcinogenesis. We discovered that c-MET activation and AXIN1 mutations occur concomitantly in ~3%-5% of human HCC samples. Subsequently, we generated a murine HCC model by means of CRISPR/Cas9-based gene deletion of Axin1 (sgAxin1) in combination with transposon-based expression of c-Met in the mouse liver (c-Met/sgAxin1). Global gene expression analysis of mouse normal liver, HCCs induced by c-Met/sgAxin1, and HCCs induced by c-Met/∆N90-β-Catenin revealed activation of the Wnt/β-Catenin and Notch signaling in c-Met/sgAxin1 HCCs. However, only a few of the canonical Wnt/β-Catenin target genes were induced in c-Met/sgAxin1 HCC when compared with corresponding lesions from c-Met/∆N90-β-Catenin mice. To study whether endogenous β-Catenin is required for c-Met/sgAxin1-driven HCC development, we expressed c-Met/sgAxin1 in liver-specific Ctnnb1 null mice, which completely prevented HCC development. Consistently, in AXIN1 mutant or null human HCC cell lines, silencing of β-Catenin strongly inhibited cell proliferation. In striking contrast, blocking the Notch cascade through expression of either the dominant negative form of the recombinant signal-binding protein for immunoglobulin kappa J region (RBP-J) or the ablation of Notch2 did not significantly affect c-Met/sgAxin1-driven hepatocarcinogenesis. Conclusion: We demonstrated here that loss of Axin1 cooperates with c-Met to induce HCC in mice, in a β-Catenin signaling-dependent but Notch cascade-independent way., (© 2019 by the American Association for the Study of Liver Diseases.)

Melanoma is the leading cause of death due to cutaneous malignancy and its incidence is on the rise. Several signaling pathways, including receptor tyrosine kinases, have been recognized to have an etiopathogenetic role in the development and progression of precursor melanocytic lesions and malignant melanoma. Among those, the hepatocyte growth factor/MET (HGF/MET) axis is emerging as a critical player not only in the tumor itself but also in the immune microenvironment in which the tumor grows and advances in its development. Moreover, the activation of this pathway has emerged as a paradigm of tumor resistance to modern targeted therapies, and the assessment of its expression in patients' samples may be a valuable biomarker of tumor progression and response to targeted therapy. Here we summarize our current understanding of this important receptor tyrosine kinase in normal melanocyte proliferation/motility, in tumor progression and metastasis, its genetic alterations in certain subtype of melanocytic lesions, and how its pathway has been explored for the development of selective inhibitors., (Copyright © 2019 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

BACKGROUND Glioblastoma, the most common and malignant glial tumor, often has poor prognosis. Tivantinib has shown its potential in treating c-Met-high carcinoma. No studies have explored whether tivantinib inhibits the development of glioblastoma. MATERIAL AND METHODS The correlation between c-Met expression and clinicopathological characteristics of glioblastoma was investigated. U251 and T98MG glioblastoma cells treated with tivantinib, PI3K inhibitor (LY294002), PI3K activator (740 Y-P), and/or mammalian target of rapamycin (mTOR) inhibitor were subjected to MTT assay or colony formation assay to evaluate cell proliferation. The expression of mTOR signaling and caspase-3 in tivantinib-treated glioblastoma cells was differentially measured by western blotting. RESULTS In a group of Chinese patients, expression of c-Met was elevated with the size of glioblastoma, but not with the other clinicopathological characteristics, including gender, age, grade, IDH status, 1p/19q status, and Ki67 status. High dose of tivantinib (1 μmol/L) obviously repressed the proliferation and colony formation of U251 and T98MG glioblastoma cells, but low dose (0.1 μmol/L) of tivantinib failed to retard cell proliferation. Tivantinib blocked PI3K/Akt/mTOR signaling but did not change the expression of cleaved caspase-3. PI3K activator 740 Y-P (20 μmol/L) significantly rescued tivantinib-induced decrease of cell proliferation. Tivantinib (1 μmol/L) in combination with PI3K inhibitor LY294002 (0.5 μmol/L) and mTOR inhibitor rapamycin (0.1 nmol/L) largely inhibited the proliferation of glioblastoma cells. CONCLUSIONS c-MET inhibitor tivantinib blocks PIKE/Akt/mTOR signaling and hampers the proliferation of glioblastoma cells, which endows the drug a therapeutic effect.

Objective: Hepatocyte growth factor (HGF) and its receptor MET are expressed in the salivary glands during developmental stages and tumor formation; however, the function of HGF in injured salivary gland tissues remains unclear. The present study investigated the role of HGF in protecting the salivary glands against radiation-induced injury using an organotypic culture method., Materials and Methods: Acinar-like organoids were formed by means of a three-dimensional (3D) human parotid tissue-derived spheroids (hPTS) culture method. Radioprotective effects of HGF on irradiated hPTS and signaling pathways on radioprotection were investigated., Results: We detected MET expression in hPTS grown in a 3D culture. Treatment of irradiated hPTS with recombinant human HGF (rhHGF) restored salivary marker expression and secretory function of hPTS. Changes in the phosphorylation levels of apoptosis-related proteins through HGF-MET axis inhibited radiation-induced apoptosis. Treatment with PHA665752, a MET inhibitor, blocked MET-PI3K-AKT pathway, increased apoptosis, and suppressed the radioprotective effect of rhHGF against IR-induced damage of hPTS., Conclusions: These results suggest that HGF is a key effector of radioprotection and that HGF-MET-PI3K-AKT axis is involved in protecting the salivary glands from radiation-induced apoptosis., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Genetic aberrations in the hepatocyte growth factor receptor tyrosine kinase MET induce oncogenic addiction in various types of human cancers, advocating MET as a viable anticancer target. Here, we report that MET signaling plays an important role in conferring a unique metabolic phenotype to cellular models expressing MET-activating mutated variants that are either sensitive or resistant toward MET small molecule inhibitors. MET phosphorylation downregulated by the specific MET inhibitor tepotinib resulted in markedly decreased viability and increased apoptosis in tepotinib-sensitive cells. Moreover, prior to the induction of MET inhibition-dependent cell death, tepotinib also led to an altered metabolic signature, characterized by a prominent reduction of metabolite ions related to amino sugar metabolism, gluconeogenesis, glycine and serine metabolism, and of numerous TCA cycle-related metabolites such as succinate, malate, and citrate. Functionally, a decrease in oxygen consumption rate, a reduced citrate synthase activity, a drop in membrane potential, and an associated misbalanced mitochondrial function were observed exclusively in MET inhibitor-sensitive cells. These data imply that interference with metabolic state can be considered an early indicator of efficient MET inhibition and particular changes reported here could be explored in the future as markers of efficacy of anti-MET therapies., (© 2019 Federation of European Biochemical Societies.)

Membrane-anchored full-length MET stimulated by its ligand HGF/SF induces various biological responses, including survival, growth, and invasion. This panel of responses, referred to invasive growth, is required for embryogenesis and tissue regeneration in adults. On the contrary, MET deregulation is associated with tumorigenesis in many kinds of cancer. In addition to its well-documented ligand-stimulated downstream signaling, the receptor can be cleaved by proteases such as secretases, caspases, and calpains. These cleavages are involved either in MET receptor inactivation or, more interestingly, in generating active fragments that can modify cell fate. For instance, MET fragments can promote cell death or invasion. Given a large number of proteases capable of cleaving MET, this receptor appears as a prototype of proteolytic-cleavage-regulated receptor tyrosine kinase. In this review, we describe and discuss the mechanisms and consequences, both physiological and pathological, of MET proteolytic cleavages. [BMB Reports 2019; 52(4): 239-249].

Cardiovascular Disease (CVD) is one of the world-wide healthcare problem that involves the heart or blood vessels. CVD includes myocardial infarction and coronary artery diseases (CAD). Dysfunctional myocardial cells are leading causes of low cardiac output or ventricular dysfunction after cardiac arrest and may contribute to the progression of CVD which could not generate new cardiomyocytes in human adult heart. The mesenchymal stem cells (MSCs) which are present in adult marrow can self-renew and have the capacity of differentiation into multiple types of cells including cardiomyocytes. Recent biochemical analyses greatly revealed that several regulators of MSCs, such as HGF, PDGF, Wnt, and Notch-1 signaling pathways have been shown to be involved in the proliferation and differentiation into cardiomyocytes. Preclinical studies are paving the way for further applications of MSCs in the repair of myocardial infarction. In this study, we discuss and summarize the paracrine mechanisms involved in MSCs differentiation into cardiomyocytes., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background & Aims: Long noncoding RNAs (lncRNAs) play important roles in various biological processes, regulating gene expression by diverse mechanisms. However, how lncRNAs regulate liver repopulation is unknown. Herein, we aimed to identify lncRNAs that regulate liver repopulation and elucidate the signaling pathways involved., Methods: Herein, we performed 70% partial hepatectomy in wild-type and gene knockout mice. We then performed transcriptomic analyses to identify a divergent lncRNA termed lncHand2 that is highly expressed during liver regeneration., Results: LncHand2 is constitutively expressed in the nuclei of pericentral hepatocytes in mouse and human livers. LncHand2 knockout abrogates liver regeneration and repopulation capacity. Mechanistically, lncHand2 recruits the Ino80 remodeling complex to initiate expression of Nkx1-2 in trans, which triggers c-Met (Met) expression in hepatocytes. Finally, knockout of both Nkx1-2 and c-Met causes more severe liver injury and poorer repopulation ability. Thus, lncHand2 promotes liver repopulation via initiating Nkx1-2-induced c-Met signaling., Conclusions: Our findings reveal that lncHand2 acts as a critical mediator regulating liver repopulation. It does this by inducing Nkx1-2 expression, which in turn triggers c-Met signaling., Lay Summary: Long noncoding RNAs play important roles in various biological processes. While long noncoding RNAs do not directly code proteins, they can regulate gene expression by diverse mechanisms. We identified the long noncoding RNA, termed lncHand2 because of its proximity to the gene Hand2, to be an important determinant of liver regeneration through c-Met signaling., (Copyright © 2018 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Introduction: The prognostic value of the mesenchymal-epithelial transition (MET) in triple-negative breast cancers (TNBCs) remains controversial. A meta-analysis of the impact of MET in TNBCs was performed by searching published data., Methods: PubMed and Embase databases were searched for eligible literature. The principal outcome measures were hazard ratios (HRs) for recurrence-free survival or overall survival according to MET expression. Combined HRs were calculated using fixed- or random-effects models according to heterogeneity., Results: Six studies involving 785 patients met our selection criteria. The meta-analysis results showed that MET overexpression was associated with a 1.29-fold increased risk of recurrence (combined HR 1.29; 95% confidence interval, 1.04-1.60; P = .020) in the TNBCs. Three studies provided the related overall survival data (488 cases). The results showed that MET overexpression was associated with a 1.38-fold increased risk of mortality (HR, 1.38; 95% confidence interval, 1.08-1.76; P = .009)., Conclusion: MET is an adverse prognostic marker for TNBCs. The results strengthen the rationale for targeted therapy of TNBCs using MET inhibitors in future clinical trials., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Langerhans cells (LCs), the epidermal dendritic cell (DC) subset, express the transmembrane tyrosine kinase receptor Met also known as hepatocyte growth factor (HGF) receptor. HGF is the exclusive ligand of Met and upon binding executes mitogenic, morphogenic, and motogenic activities to various cells. HGF exerts anti-inflammatory activities via Met signaling and was found to regulate various functions of immune cells, including differentiation and maturation, cytokine production, cellular migration and adhesion, and T cell effector function. It has only recently become evident that a number of HGF-regulated functions in inflammatory processes and immune responses are imparted via DCs. However, the mechanisms by which Met signaling in DCs conveys its immunoregulatory effects have not yet been fully understood. In this review, we focus on the current knowledge of Met signaling in DCs with particular attention on the morphogenic and motogenic activities. Met signaling was shown to promote DC mobility by regulating matrix metalloproteinase activities and adhesion. This is a striking resemblance to the role of Met in regulating a cell fate program during embryonic development, wound healing, and in tumor invasion known as epithelial-mesenchymal transition (EMT). Hence, we propose the concept that an EMT program is executed by Met signaling in LCs.

The inhibitor of growth 5 (ING5), a novel member of the ING family, is involved in diverse biological processes such as cell growth, apoptosis and DNA repair. Recently, ING5 has been reported to be associated with cancer development. However, its specific role in thyroid cancer has yet to be elucidated. In this study, we found that the expression of ING5 was significantly down-regulated in human thyroid cancer tissues and cell lines. In addition, overexpression of ING5 markedly inhibited hepatocyte growth factor (HGF)-induced proliferation, invasion and epithelial-mesenchymal transition (EMT) of thyroid cancer cells as well as suppressed the tumor growth and metastasis in vivo. Furthermore, our data showed that the c-Met/PI3K/Akt signaling pathway was responsible for the inhibitory effect of ING5 on the thyroid cancer. Taken together, these findings provided an essential basis for the tumor-suppression role of ING5 in thyroid cancer., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Objectives: The hepatocyte growth factor (HGF)/mesenchymal-epithelial transition factor (c-MET) ligand/receptor axis has been implicated in pathogenesis of malignant diseases including squamous cell carcinoma of the head and neck (SCCHN). Overexpression of c-MET has been reported as a common molecular abnormality in SCCHN, although its prognostic and predictive value remains to be validated., Methods: We systematically searched literature for studies evaluating c-MET expression on immunohistochemistry in newly diagnosed, non-metastatic SCCHN. The c-MET expressing cases were classified into three categories according to predefined cut-off values for positivity. Our aim was to assess the prevalence of c-MET expression and its relationship with selected clinicopathological variables., Results: Twenty-eight studies with 2019 cases were included. Relative frequencies of c-MET expression above cut-off levels I, II, and III were 81.8%, 63.8%, and 46.2%, respectively. Differences between these three values were statistically significant (p<1.0×10 -6 ). Above cut-off level II, c-MET positivity was associated with worse overall survival (p=4.0×10 -6 ), positive nodal status (p=1.0×10 -4 ), higher disease stage (p=7.0×10 -4 ), older age (p=2.1×10 -3 ), disease recurrence (p=2.0×10 -2 ), and primary tumour localization in the oral cavity (p=2.3×10 -2 ). Above cut-off level III, c-MET positivity was associated with worse disease-free or progression-free survival (p=9.0×10 -6 ), p16 negativity (p=2.4×10 -4 ), worse overall survival (p=4.0×10 -4 ), positive epidermal growth factor receptor (EGFR) status (p=7.2×10 -4 ), and larger primary tumours (p=4.6×10 -3 )., Conclusion: In SCCHN, immunohistochemical overexpression of c-MET above cut-off levels III and particularly II was associated with inferior survival outcomes and advanced disease. Moreover, it represents a promising predictive biomarker for c-MET targeting, yet the optimal scoring method remains to be defined., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In alveolar rhabdomyosarcoma (ARMS) that is a highly malignant pediatric soft tissue tumor, MET, a receptor of hepatocyte growth factor (HGF), was reported to be downstream of the PAX3-FOXO1 fusion gene specific to ARMS, and a key mediator of metastatic behavior in RMS. So far, no studies have investigated the downstream signaling pathways of MET in ARMS, even though HGF and MET have been suggested to be deeply involved in the invasiveness of ARMS. In this study, we demonstrated the functions of MET signaling in ARMS in vitro by using three human ARMS cell lines and three human embryonal rhabdomyosarcoma (ERMS) cell lines. MET mRNA levels and MET protein expression in ARMS cell lines was higher than those in ERMS cell lines as detected by real-time quantitative PCR and western blotting, respectively. Based on cell growth and cell cycle analyses it was found that HGF stimulation did not enhance the proliferation of ERMS or ARMS cell lines. HGF-stimulated cell motility of ARMS cell lines was inhibited by U0126 (ERK1/2 inhibitor) but was only partially inhibited by PD98059 (ERK1 inhibitor) or rapamycin (mTOR inhibitor) as observed in wound-healing and migration assays. Western blotting revealed that ERK1/2 was dephosphorylated by U0126 to a higher extent than by PD98059 in the ARMS cells. HGF-stimulated cell motility of Rh30 cell line was inhibited not by ERK1 siRNA, but by ERK2 siRNA. Our data thus suggest that HGF/MET signaling promotes motility of ARMS cells mainly through ERK2 signaling. A specific inhibitor of ERK2 phosphorylation could therefore be a specific anticancer agent against invasiveness and metastasis in ARMS.

Receptor tyrosine kinases MET and epidermal growth factor receptor (EGFR) are critically involved in initiation of liver regeneration. Other cytokines and signaling molecules also participate in the early part of the process. Regeneration employs effective redundancy schemes to compensate for the missing signals. Elimination of any single extracellular signaling pathway only delays but does not abolish the process. Our present study, however, shows that combined systemic elimination of MET and EGFR signaling (MET knockout + EGFR-inhibited mice) abolishes liver regeneration, prevents restoration of liver mass, and leads to liver decompensation. MET knockout or simply EGFR-inhibited mice had distinct and signaling-specific alterations in Ser/Thr phosphorylation of mammalian target of rapamycin, AKT, extracellular signal-regulated kinases 1/2, phosphatase and tensin homolog, adenosine monophosphate-activated protein kinase α, etc. In the combined MET and EGFR signaling elimination of MET knockout + EGFR-inhibited mice, however, alterations dependent on either MET or EGFR combined to create shutdown of many programs vital to hepatocytes. These included decrease in expression of enzymes related to fatty acid metabolism, urea cycle, cell replication, and mitochondrial functions and increase in expression of glycolysis enzymes. There was, however, increased expression of genes of plasma proteins. Hepatocyte average volume decreased to 35% of control, with a proportional decrease in the dimensions of the hepatic lobules. Mice died at 15-18 days after hepatectomy with ascites, increased plasma ammonia, and very small livers., Conclusion: MET and EGFR separately control many nonoverlapping signaling endpoints, allowing for compensation when only one of the signals is blocked, though the combined elimination of the signals is not tolerated; the results provide critical new information on interactive MET and EGFR signaling and the contribution of their combined absence to regeneration arrest and liver decompensation. (Hepatology 2016;64:1711-1724)., (© 2016 by the American Association for the Study of Liver Diseases.)

Angiopoietin-like protein 1 (ANGPTL1) has been shown to act as a tumor suppressor by inhibiting angiogenesis, cancer invasion, and metastasis. However, little is known about the effects of ANGPTL1 on sorafenib resistance and cancer stem cell properties in hepatocellular carcinoma (HCC) and the mechanism underlying these effects. Here, we show that ANGPTL1 expression positively correlates with sorafenib sensitivity in HCC cells and human HCC tissues. ANGPTL1 significantly decreases epithelial-mesenchymal transition (EMT)-driven sorafenib resistance, cancer stemness, and tumor growth of HCC cells by repressing Slug expression. ANGPTL1 directly interacts with and inactivates MET receptor, which contributes to Slug suppression through inhibition of the extracellular receptor kinase/protein kinase B (ERK/AKT)-dependent early growth response protein 1 (Egr-1) pathway. ANGPTL1 expression inversely correlates with Slug expression, poor sorafenib responsiveness, and poor clinical outcomes in HCC patients., Conclusion: ANGPTL1 inhibits sorafenib resistance and cancer stemness in HCC cells by repressing EMT through inhibition of the MET receptor-AKT/ERK-Egr-1-Slug signaling cascade. ANGPTL1 may serve as a novel MET receptor inhibitor for advanced HCC therapy. (Hepatology 2016;64:1637-1651)., (© 2016 by the American Association for the Study of Liver Diseases.)

The abnormal stimulation of the multiple signal transduction pathways downstream of the receptor tyrosine kinase mesenchymal-epithelial transition factor (cMET) promotes cellular transformation, tumor motility, and invasion. Therefore, cMET has been the focus of prognostic and therapeutic studies in different tumor types, including non-small cell lung cancer. In particular, several cMET inhibitors have been developed as innovative therapeutic candidates and are currently under investigation in clinical trials. However, one of the challenges in establishing effective targeted treatments against cMET remains the accurate identification of biomarkers for the selection of responsive subsets of patients. Recently, splice site mutations have been discovered in cMET that lead to the skipping of exon 14, impairing the breakdown of the receptor. Patients with NSCLC who are carrying this splice variant typically overexpress the cMET receptor and show a response to small molecule inhibitors of cMET. Here, we review the main differences at the structural level between the wild-type and the splice variants of cMET and their influence on cMET signaling. We clarify the reason why this variant responds to small molecule inhibitors and their prognostic/predictive role., (Copyright © 2016 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Metastasis-associated in colon cancer-1 (MACC1) is an oncogene that was first identified in colon cancer. The upstream and downstream of MACC1 form a delicate regulatory network that supports its tumorigenic role in cancers. Multiple functions of MACC1 have been discovered in many cancers. In gastric cancer (GC), MACC1 has been shown to be involved in oncogenesis and tumor progression. MACC1 overexpression adversely affects the clinical outcomes of GC patients. Regarding the mechanism of action of MACC1 in GC, studies have shown that it promotes the epithelial-to-mesenchymal transition and accelerates cancer metastasis. MACC1 is involved in many hallmarks of GC in addition to metastasis. MACC1 promotes vasculogenic mimicry (VM) via TWIST1/2, and VM increases the tumor blood supply, which is necessary for tumor progression. MACC1 also facilitates GC lymphangiogenesis by upregulating extracellular secretion of VEGF-C/D, indicating that MACC1 may be an important player in GC lymphatic dissemination. Additionally, MACC1 supports GC growth under metabolic stress by enhancing the Warburg effect. In conclusion, MACC1 participates in multiple biological processes inside and outside of GC cells, making it an important mediator of the tumor microenvironment.

The deregulation of HGF/c-Met signaling is implicated in epithelial-mesenchymal transition (EMT) and progress of hepatocellular carcinoma (HCC). However, the epigenetic mechanisms that HGF/c-Met regulates EMT and metastasis of HCC cells are less explored. In this study, we demonstrated that HCC cells express a high level of SUMO/sentrin-specific protease 1 (Senp1) which is induced by HGF/c-Met signals. Lentivirus-mediated small hairpin RNA (shRNA) transduction results in Senp1 silence in HCC cells. Senp1 silence reduces the HGF-induced proliferation and migration of HCC cells. Senp1 inhibition also induces HCC cell apoptosis and growth arrest. Furthermore, Senp1 knockdown inhibits epithelial-to-mesenchymal transition, with increase of E-cadherin and ZO-1 expression, decrease of fibronectin and N-cadherin expression. The EMT-related transcription factor Zeb1 was SUMO-modified and decreased in Senp1-silenced HCC cells. These results delineate that senp1 might play an important role in the regulation of HGF-induced invasion and migration of HCC cells.

Malignant mesothelioma is an asbestos-related cancer that occurs most commonly in the pleural space and is incurable. Increasing evidence suggests that aberrant receptor tyrosine kinase (RTK)-directed signalling plays a key role in the pathogenesis of this cancer. In the majority of mesotheliomas, up-regulated expression or signalling by Met, the receptor for hepatocyte growth factor (HGF) can be demonstrated. Following binding of ligand, Met relays signals that promote cell survival, proliferation, movement, invasiveness, branching morphogenesis and angiogenesis. Here we describe the HGF/Met axis and review the mechanisms that lead to the aberrant activation of this signalling system in mesothelioma. We also describe the cross-talk that occurs between HGF/Met and a number of other receptors, ligands and co-receptor systems. The prevalent occurrence of HGF/Met dysregulation in patients with mesothelioma sets the scene for the investigation of pharmaceutical inhibitors of this axis. In light of the inter-relationship between HGF/Met and other ligand receptor, combinatorial targeting strategies may provide opportunities for therapeutic advancement in this challenging tumour., (© 2016 Authors; published by Portland Press Limited.)

The biological behaviors of hepatocellular carcinoma (HCC) are complex mainly due to heterogeneity of progressive genetic and epigenetic mutations as well as tumor environment. Hepatocyte growth factor (HGF)/c-Met signaling pathway is regarded to be a prototypical example for stromal-epithelial interactions during developmental morphogenesis, wound healing, organ regeneration and cancer progression. And p53 plays as an important regulator of Met-dependent cell motility and invasion. Present study showed that 2 HCC cell lines, Hep3B and HepG2, displayed different invasive capacity when treated with HGF which was secreted by hepatic stellate cells (HSCs). We found that HGF promoted Hep3B cells invasion and migration as well as epithelial-mesenchymal transition (EMT) occurrence because Hep3B was p53 deficient, which leaded to the c-Met over-expression. Then we found that HGF/c-Met promoted Hep3B cells invasion and migration by upregulating Snail expression. In conclusion, HGF/c-Met signaling is enhanced by loss of p53 expression, resulting in increased ability of invasion and migration by upregulating the expression of Snail.

Adrenocortical carcinoma is a rare malignancy with poor prognosis and limited response to chemotherapy. Hepatocyte growth factor (HGF) and its receptor cMET augment cancer growth and resistance to chemotherapy, but their role in adrenocortical carcinoma has not been examined. In this study, we investigated the association between HGF/cMET expression and cancer hallmarks of adrenocortical carcinoma. Transcriptomic and immunohistochemical analyses indicated that increased HGF/cMET expression in human adrenocortical carcinoma samples was positively associated with cancer-related biologic processes, including proliferation and angiogenesis, and negatively correlated with apoptosis. Accordingly, treatment of adrenocortical carcinoma cells with exogenous HGF resulted in increased cell proliferation in vitro and in vivo while short hairpin RNA-mediated knockdown or pharmacologic inhibition of cMET suppressed cell proliferation and tumor growth. Moreover, exposure of cells to mitotane, cisplatin, or radiation rapidly induced pro-cMET expression and was associated with an enrichment of genes (e.g., CYP450 family) related to therapy resistance, further implicating cMET in the anticancer drug response. Together, these data suggest an important role for HGF/cMET signaling in adrenocortical carcinoma growth and resistance to commonly used treatments. Targeting cMET, alone or in combination with other drugs, could provide a breakthrough in the management of this aggressive cancer., (©2015 American Association for Cancer Research.)

We have previously reported that an adaptor protein CRK, including CRK-I and CRK-II, plays essential roles in the malignant potential of various aggressive human cancers, suggesting the validity of targeting CRK in molecular targeted therapy of a wide range of cancers. Nevertheless, the role of CRK in human bladder cancer with marked invasion, characterized by distant metastasis and poor prognosis, remains obscure. In the present study, immunohistochemistry indicated a striking enhancement of CRK-I/-II, but not CRK-like, in human bladder cancer tissues compared to normal urothelium. We established CRK-knockdown bladder cancer cells using 5637 and UM-UC-3, which showed a significant decline in cell migration, invasion, and proliferation. It is noteworthy that an elimination of CRK conferred suppressed phosphorylation of c-Met and the downstream scaffold protein Gab1 in a hepatocyte growth factor-dependent and -independent manner. In epithelial-mesenchymal transition-related molecules, E-cadherin was upregulated by CRK elimination, whereas N-cadherin, vimentin, and Zeb1 were downregulated. A similar effect was observed following treatment with c-Met inhibitor SU11274. Depletion of CRK significantly decreased cell proliferation of 5637 and UM-UC-3, consistent with reduced activity of ERK. An orthotopic xenograft model with bioluminescent imaging revealed that CRK knockdown significantly attenuated not only tumor volume but also the number of circulating tumor cells, resulted in a complete abrogation of metastasis. Taken together, this evidence uncovered essential roles of CRK in invasive bladder cancer through the hepatocyte growth factor/c-Met/CRK feedback loop for epithelial-mesenchymal transition induction. Thus, CRK might be a potent molecular target in bladder cancer, particularly for preventing metastasis, leading to the resolution of clinically longstanding critical issues., (© 2015 The Authors. Cancer Science published by Wiley Publishing Asia Pty Ltd on behalf of Japanese Cancer Association.)

The receptor tyrosine kinase c-Met is overexpressed in renal cancer cells and can play major role in the growth and survival of tumor. We investigated how the c-Met-mediated signaling through binding to its ligand hepatocyte growth factor (HGF) can modulate the apoptosis and immune escape mechanism(s) of renal cancer cells by the regulations of novel molecules heme oxygenase-1 (HO-1) and programmed death-1 ligand 1 (PD-L1). We found that HGF/c-Met-mediated signaling activated the Ras/Raf pathway and down-regulated cancer cell apoptosis; and it was associated with the overexpression of cytoprotective HO-1 and anti-apoptotic Bcl-2/Bcl-xL. c-Met-induced HO-1 overexpression was regulated at the transcriptional level. Next, we observed that c-Met induction markedly up-regulated the expression of the negative co-stimulatory molecule PD-L1, and this can be prevented following treatment of the cells with pharmacological inhibitors of c-Met. Interestingly, HGF/c-Met-mediated signaling could not induce PD-L1 at the optimum level when either Ras or HO-1 was knocked down. To study the functional significance of c-Met-induced PD-L1 expression, we performed a co-culture assay using mouse splenocytes (expressing PD-L1 receptor PD-1) and murine renal cancer cells (RENCA, expressing high PD-L1). We observed that the splenocyte-mediated apoptosis of cancer cells during co-culture was markedly increased in the presence of either c-Met inhibitor or PD-L1 neutralizing antibody. Finally, we found that both c-Met and PD-L1 are significantly up-regulated and co-localized in human renal cancer tissues. Together, our study suggests a novel mechanism(s) by which c-Met can promote increased survival of renal cancer cells through the regulation of HO-1 and PD-L1., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Background/aim: The epidermal growth factor family (EGF) has been suggested to influence the sensitivity to anti-epidermal growth factor receptor therapy. We examined the correlation between circulating levels of the epidermal growth factors amphiregulin and transforming growth factor-α (TGF-α) and the MET ligand hepatocyte growth factor and sensitivity to the anti-epidermal growth factor receptor antibody in colorectal cancer (CRC) patients., Materials and Methods: Plasma levels of each ligand were measured by enzyme-linked immunosorbent assay in 51 patients with wild-type KRAS CRC., Results: Patients with high hepatocyte growth factor (HGF) levels had a significantly lower disease control rate (DCR) and shorter median progression-free survival (PFS) and overall survival (OS) than those with low expression levels. Amphiregulin was correlated with objective response rate (ORR) but not with PFS or OS. Cetuximab response and survival were not associated with TGF-α., Conclusion: Circulating HGF may help identify CRC patients most likely to benefit from anti-epidermal growth factor receptor antibody therapy., (Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Melanoma is a therapy-resistant skin cancer due to numerous mechanisms supporting cell survival. Although components of melanoma cytoprotective mechanisms are overexpressed in many types of tumors, some of their regulators are characteristic for melanoma. Several genes mediating pro-survival functions have been identified as direct targets of microphthalmia-associated transcription factor (MITF), a melanocyte-specific modulator also recognized as a lineage addiction oncogene in melanoma. BRAF(V600E) and other proteins deregulated in melanoma influence MITF expression and activity, or they are the partners of MITF in melanoma response to radiotherapy and chemotherapeutics. In this review, the pro-survival activity of MITF is discussed.

The MET receptor tyrosine kinase (RTK), implicated in risk for autism spectrum disorder (ASD) and in functional and structural circuit integrity in humans, is a temporally and spatially regulated receptor enriched in dorsal pallial-derived structures during mouse forebrain development. Here we report that loss or gain of function of MET in vitro or in vivo leads to changes, opposite in nature, in dendritic complexity, spine morphogenesis, and the timing of glutamatergic synapse maturation onto hippocampus CA1 neurons. Consistent with the morphological and biochemical changes, deletion of Met in mutant mice results in precocious maturation of excitatory synapse, as indicated by a reduction of the proportion of silent synapses, a faster GluN2A subunit switch, and an enhanced acquisition of AMPA receptors at synaptic sites. Thus, MET-mediated signaling appears to serve as a mechanism for controlling the timing of neuronal growth and functional maturation. These studies suggest that mistimed maturation of glutamatergic synapses leads to the aberrant neural circuits that may be associated with ASD risk., (Copyright © 2014 the authors 0270-6474/14/3416166-14$15.00/0.)

Background and Aim: The hepatocyte growth factor (HGF)/c-Met pathway has attracted attention in the formation of malignant tumors, as HGF secreted from the microcirculatory components as well as residing macrophages has been suggested to act on the c-Met receptors of cancer cells to decrease apoptosis and increase proliferation, invasion, and metastasis. The present study was undertaken to elucidate the interaction of the gastric, hepatic, and pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma induced by Helicobacter heilmannii infection with c-Met and HGF., Methods: C57BL/6 female mice, infected with H. heilmannii for 3 months were used. The localization of the HGF, c-Met, and HGF activator immunoreactivities was observed by the indirect immunohistochemical methods. In addition, the effect of c-Met antibody and c-Met inhibitor, PHA-665752, was also investigated., Results: c-Met immunoreactivity was found in the lymphocytes composing the MALT lymphoma, and HGF immunoreactivity was recognized mostly in the endothelial cells and macrophages in the MALT lymphoma. HGFA was localized on mesenchymal cells other than the lymphocytes. The administration of the antibody against c-Met or the c-Met inhibitor to the infected mice induced the significant suppression of hepatic and pulmonary MALT lymphoma, while the gastric MALT lymphoma showed only a tendency to decrease in size, while the active caspase 3 positive cells markedly decreased in the gastric, hepatic, and pulmonary MALT lymphoma after the treatment with the c-Met antibody or the c-Met antagonist., Conclusions: HGF and c-Met pathway were suggested to contribute to the lymphomagenesis in the MALT lymphoma after H. heilmannii infection., (© 2014 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.)

Cell-based drug screenings indicate that tumors displaying c-MET gene amplification are "addicted" to MET signaling and therefore are very sensitive to MET-targeted agents. However, these screenings were conducted in the absence of the MET ligand, hepatocyte growth factor (HGF), which is abundant in the tumor microenvironment. Sensitivity of six MET-addicted human tumor cells to three MET kinase inhibitors (JNJ-38877605, PHA-665752, crizotinib) and one antagonistic anti-MET antibody (DN30 Fab) was analyzed in the absence or presence of HGF, in a stroma-tumor coculture system, and by combining anti-MET drugs with an HGF neutralizing antibody (ficlatuzumab) in human HGF knock-in mice bearing c-MET-amplified tumors. In all models examined, HGF promoted resistance to MET-targeted agents, affecting both their potency and efficacy. HGF-induced resistance was due to restoration of physiologic GAB1-mediated PI3K activation that compensated for loss of aberrant HER3-dependent PI3K signaling. Ficlatuzumab restored sensitivity to MET-targeted agents in coculture systems and overcame resistance to JNJ-38877605, crizotinib, and DN30 Fab in human HGF knock-in mice. These data suggest that c-MET-amplified tumor cells-which normally exhibit ligand-independent, constitutive MET activation-become dependent on HGF for survival upon pharmacologic MET inhibition. Because HGF is frequently overexpressed in human cancer, this mechanism may represent a major cause of resistance to anti-MET therapies. The ability of ficlatuzumab to overcome HGF-mediated resistance generates proof of principle that vertical inhibition of both a tyrosine kinase receptor and its ligand can be therapeutically beneficial and opens new perspectives for the treatment of MET-dependent tumors., (©2014 American Association for Cancer Research.)

In 1984, the Met receptor and its ligand, the HGF/SF, were discovered thanks to their ability to induce cell transformation and proliferation. Thirty years of research highlighted their crucial role in the development and homeostasis of various structures, including many epithelial organs. This period also allowed unraveling the structural basis of their interaction and their complex signaling network. In parallel, Met was shown to be deregulated and associated with a poor prognosis in many cancers. Met involvement in resistance to current therapies is also being deciphered. Based on these data, pharmaceutical companies developed a variety of Met inhibitors, some of which are evaluated in phase III clinical trials. In this review, we trace the exemplary track record of research on Met receptor, which allowed moving from bench to bedside through the development of therapies targeting its activity. Many questions still remain unanswered such as the involvement of Met in several processes of development, the mechanisms involving Met in resistance to current therapies or the likely emergence of resistances to Met-targeted therapies., (© 2014 médecine/sciences – Inserm.)

The HGF/MET signaling pathway is critical in mediating a wide range of normal physiological functions including embryological development, wound healing, and tissue regeneration. Aberrant activation of the pathway has frequently been found in human cancers via protein overexpression, mutation, gene amplification, and also paracrine or autocrine up-regulation. In addition, the activation of HGF/MET signaling confers resistance to the effects of cancer treatments. Therefore, inhibition of the HGF/MET signaling pathway has great potential for therapeutic intervention in cancer. Currently, there are three approaches toward modulating HGF/MET signaling in human clinical studies of cancer: anti-HGF monoclonal antibodies, MET monoclonal antibodies, and small molecule MET inhibitors. Preliminary clinical benefit from inhibition of HGF or MET has been reported. This Perspective will provide an overview of the HGF/MET signaling pathway in cancer and then will review the development of small molecule MET inhibitors and their progress in clinical applications.

MicroRNAs (miRNAs) are a class of small non-coding RNAs that bind protein-coding mRNAs and negatively regulate protein expression by translation repression or mRNA cleavage. Accumulating evidence suggests that miRNAs are involved in cancer development and progression, acting as either tumor suppressors or oncogenes. It has been shown that miR-199a-3p was significantly down-regulated in several types of cancers. However, its role and relevance in renal cell carcinoma (RCC) are still largely unknown. Here, we show that miR-199a-3p is significantly down-regulated in human RCC primary tumors and cell lines compared to their non-tumor counterparts. Moreover, the down-regulation of miR-199a-3p is correlated with the histological grade and TNM (tumor-lymph node-metastasis) stage of RCC. Reintroducing miR-199a-3p in RCC cell lines 769-P and Caki-1 inhibited cell proliferation and caused G1 phase arrest. We found that c-Met was up-regulated in RCC cell lines and its expression could be repressed by miR-199a-3p. Moreover, c-Met was up-regulated in RCC primary tumors and reversely correlated with miR-199a-3p expression in the same paired RCC tissues. Reintroducing miR-199a-3p inhibited c-Met expression and led to attenuated activation of c-Met downstream signaling pathways including STAT3, mTOR and ERK1/2. We found that the concentrations of serum hepatocyte growth factor (HGF), the ligand of c-Met receptor, were significantly elevated in RCC patients compared to healthy persons. In addition, HGF treatment could promote proliferation of RCC cells, and the increased cell proliferation was abrogated by miR-199a-3p. Our findings indicated that miR-199a-3p target HGF/c-Met signaling pathway which is crucial for RCC development and suggest that miR-199a-3p may serve as a potential target miRNA for RCC therapy.

The Met receptor tyrosine kinase (RTK) is an attractive oncology therapeutic target. Met and its ligand, HGF, play a central role in signaling pathways that are exploited during the oncogenic process, including regulation of cell proliferation, invasion, angiogenesis, and cancer stem cell regulation. Elevated Met and HGF as well as numerous Met genetic alterations have been reported in human cancers and correlate with poor outcome. Alterations of pathways that regulate Met, such as the ubiquitin ligase c-Cbl are also likely to activate Met in the oncogenic setting. Moreover, interactive crosstalk between Met and other receptors such as EGFR, HER2 and VEGFR, underlies a key role for Met in resistance to other RTK-targeted therapies. A large body of preclinical and clinical data exists that supports the use of either antibodies or small molecule inhibitors that target Met or HGF as oncology therapeutics. The prognostic potential of Met expression has been suggested from studies in numerous cancers including lung, renal, liver, head and neck, stomach, and breast. Clinical trials using Met inhibitors indicate that the level of Met expression is a determinant of trial outcome, a finding that is actively under investigation in multiple clinical scenarios. Research in Met prognostics and predictors of drug response is now shifting toward more sophisticated methodologies suitable for development as validated and effective biomarkers that can be partnered with therapeutics to improve patient survival., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Aim: We aimed to investigate the possibility of an association between a stem-like hallmark and radiotherapeutic sensitivity in human cervical carcinoma cells., Material and Methods: Side-population (SP) cells and non-SP (NSP) cells in HeLa cells were isolated using flow cytometry and Hoechst 33342 efflux. We performed Western blot analysis to evaluate the expression of stem cell markers (CXCR4, Oct3/4, CD133, and SOX2) and apoptosis markers after irradiation. In addition, SP and NSP cells were injected into nude mice and we assessed subcutaneous tumor formation. To examine tolerance of irradiation, colony formation and apoptosis change were confirmed in the SP and NSP cells., Results: SP cells showed a higher expression of CXCR4, Oct3/4, CD133, and SOX2 than NSP cells. The colony size of SP cells cultured on non-coated dishes was larger than that of NSP cells, and NSP cells were easily induced to undergo apoptosis. SP cells tended to form spheroids and showed a higher level of tumorigenicity compared with NSP cells. In addition, nude mice inoculated with SP cells showed greater tumor growth compared with NSP cells. SP cells showed a higher tumorigenicity and lower apoptotic potential, leading to enhanced radiotolerance., Conclusion: Tumor SP cells showed higher-level stem-cell-like characters and radioresistance than NSP cells. SP cells may be useful for new therapeutic approaches for radiation-resistant cervical cancer., (© 2014 The Authors. Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology.)

Unlabelled: Met, the transmembrane tyrosine kinase receptor for hepatocyte growth factor (HGF), is known to function as a potent antiapoptotic mediator in normal and neoplastic cells. Herein we report that the intracellular cytoplasmic tail of Met has evolved to harbor a tandem pair of caspase-3 cleavage sites, which bait, trap, and disable the active site of caspase-3, thereby blocking the execution of apoptosis. We call this caspase-3 cleavage motif the Death Defying Domain (DDD). This site consists of the following sequence: DNAD-DEVD-T (where the hyphens denote caspase cleavage sites). Through functional and mechanistic studies, we show that upon DDD cleavage by caspase-3 the resulting DEVD-T peptide acts as a competitive inhibitor and entraps the active site of caspase-3 akin to DEVD-CHO, which is a potent, synthetic inhibitor of caspase-3 activity. By gain- and loss-of-function studies using restoration of DDD expression in DDD-deficient hepatocytic cells, we found that both caspase-3 sites in DDD are necessary for inhibition of caspase-3 and promotion of cell survival. Employing mutagenesis studies, we show that DDD could operate independently of Met's enzymatic activity as determined by using kinase-dead human Met mutant constructs. Studies of both human liver cancer tissues and cell lines uncovered that DDD cleavage and entrapment of caspase-3 by DDD occur in vivo, further proving that this site has physiological and pathophysiological relevance., Conclusion: Met can directly inhibit caspase-3 by way of a novel mechanism and promote hepatocyte survival. The results presented here will further our understanding of the mechanisms that control not only normal tissue homeostasis but also abnormal tissue growth such as cancer and degenerative diseases in which apoptotic caspases are at play., (© 2014 by the American Association for the Study of Liver Diseases.)

Malignant mesothelioma is a highly aggressive, asbestos-related cancer frequently marked by mutations of both NF2 and CDKN2A. We demonstrate that germline knockout of one allele of each of these genes causes accelerated onset and progression of asbestos-induced malignant mesothelioma compared with asbestos-exposed Nf2(+/-) or wild-type mice. Ascites from some Nf2(+/-);Cdkn2a(+/-) mice exhibited large tumor spheroids, and tail vein injections of malignant mesothelioma cells established from these mice, but not from Nf2(+/-) or wild-type mice, produced numerous tumors in the lung, suggesting increased metastatic potential of tumor cells from Nf2(+/-);Cdkn2a(+/-) mice. Intraperitoneal injections of malignant mesothelioma cells derived from Nf2(+/-);Cdkn2a(+/-) mice into severe combined immunodeficient mice produced tumors that penetrated the diaphragm and pleural cavity and harbored increased cancer stem cells (CSC). Malignant mesothelioma cells from Nf2(+/-);Cdkn2a(+/-) mice stained positively for CSC markers and formed CSC spheroids in vitro more efficiently than counterparts from wild-type mice. Moreover, tumor cells from Nf2(+/-);Cdkn2a(+/-) mice showed elevated c-Met expression/activation, which was partly dependent on p53-mediated regulation of miR-34a and required for tumor migration/invasiveness and maintenance of the CSC population. Collectively, these studies demonstrate in vivo that inactivation of Nf2 and Cdkn2a cooperate to drive the development of highly aggressive malignant mesotheliomas characterized by enhanced tumor spreading capability and the presence of a CSC population associated with p53/miR-34a-dependent activation of c-Met. These findings suggest that cooperativity between losses of Nf2 and Cdkn2a plays a fundamental role in driving the highly aggressive tumorigenic phenotype considered to be a hallmark of malignant mesothelioma., (©2013 AACR.)

Neuropilin 1 (NRP1) is a transmembrane glycoprotein that acts as a co-receptor for a number of extracellular ligands including class III/IV semaphorins, certain isoforms of vascular endothelial growth factor and transforming growth factor beta. An exact understanding of the role of NRP1 in the immune system has been obscured by the differences in NRP1 expression observed between mice and humans. In mice, NRP1 is selectively expressed on thymic-derived Tregs and greatly enhances immunosuppressive function. In humans, NRP1 is expressed on plasmacytoid dendritic cells (pDCs) where it aids in priming immune responses and on a subset of T regulatory cells (Tregs) isolated from secondary lymph nodes. Preliminary studies that show NRP1 expression on T cells confers enhanced immunosuppressive activity. However, the mechanism by which this activity is mediated remains unclear. NRP1 expression has also been identified on activated T cells and Tregs isolated from inflammatory microenvironments, suggesting NRP1 might represent a novel T cell activation marker. Of clinical interest, NRP1 may enhance Treg tumour infiltration and a decrease in NRP1+ Tregs correlates with successful chemotherapy, suggesting a specific role for NRP1 in cancer pathology. As a therapeutic target, NRP1 allows simultaneous targeting of NRP1-expressing tumour vasculature, NRP1+ Tregs and pDCs. With the development of anti-NRP1 monoclonal antibodies and cell-penetrating peptides, NRP1 represents a promising new target for cancer therapies. This paper reviews current knowledge on the role and function of NRP1 in Tregs and pDCs, both in physiological and cancer settings, as well as its potential as a therapeutic target in cancer.

The proto-oncogene MET is aberrantly activated via overexpression or mutation in numerous cancers, making it a prime anticancer molecular target. However, the clinical success of MET-directed tyrosine kinase inhibitors (TKI) has been limited due, in part, to mutations in the MET kinase domain that confer therapeutic resistance. Circumventing this problem remains a key challenge to improving durable responses in patients receiving MET-targeted therapy. MET is an HSP90-dependent kinase, and in this report we show that HSP90 preferentially interacts with and stabilizes activated MET, regardless of whether the activation is ligand-dependent or is a consequence of kinase domain mutation. In contrast, many MET-TKI show a preference for the inactive form of the kinase, and activating mutations in MET can confer resistance. Combining the HSP90 inhibitor ganetespib with the MET-TKI crizotinib achieves synergistic inhibition of MET, its downstream signaling pathways, and tumor growth in both TKI-sensitive and -resistant MET-driven tumor models. These data suggest that inclusion of an HSP90 inhibitor can partially restore TKI sensitivity to previously resistant MET mutants, and they provide the foundation for clinical evaluation of this therapeutic combination in patients with MET-driven cancers.

Hepatocyte growth factor is a pleiotrophic protein that promotes injury repair and regeneration in multiple organs. Here, we show that after acute kidney injury (AKI), the HGF receptor, c-met, was induced predominantly in renal tubular epithelium. To investigate the role of tubule-specific induction of c-met in AKI, we generated conditional knockout mice, in which the c-met gene was specifically disrupted in renal tubules. These Ksp-met-/- mice were phenotypically normal and had no appreciable defect in kidney morphology and function. However, in AKI induced by cisplatin or ischemia/reperfusion injury, the loss of tubular c-met substantially aggravated renal injury. Compared with controls, Ksp-met-/- mice displayed higher serum creatinine, more severe morphologic lesions, and increased apoptosis, which was accompanied by an increased expression of Bax and Fas ligand and decreased phosphorylation/activation of Akt. In addition, ablation of c-met in renal tubules promoted chemokine expression and renal inflammation after AKI. Consistently, ectopic expression of hepatocyte growth factor in vivo protected the kidneys against AKI in control mice, but not in Ksp-met-/- counterparts. Thus, our results suggest that tubule-specific c-met signaling is crucial in conferring renal protection after AKI, primarily by its anti-apoptotic and anti-inflammatory mechanisms.

Since its discovery more than 25 years ago, numerous studies have established that the MET receptor is unique among tyrosine kinases. Signaling through MET is necessary for normal development and for the progression of a wide range of human cancers. MET activation has been shown to drive numerous signaling pathways; however, it is not clear how MET signaling mediates diverse cellular responses such as motility, invasion, growth, and angiogenesis. Great strides have been made in understanding the pleotropic aspects of MET signaling using three-dimensional molecular structures, cell culture systems, human tumors, and animal models. These combined approaches have driven the development of MET-targeted therapeutics that have shown promising results in the clinic. Here we examine the unique features of MET and hepatocyte growth factor/scatter factor (HGF/SF) structure and signaling, mutational activation, genetic mouse models of MET and HGF/SF, and MET-targeted therapeutics.

Background: Colon cancer is one of the major malignancies worldwide and it still remains resistant to much of the currently available chemotherapy. Downregulation of HGF/c-Met signaling pathway is an emerging therapy for cancer treatment., Methods: In this study, the inhibitory effects of c-Met phosphorylation were observed with SU11274 on different colon cancer cell lines in vitro., Results: The results revealed the significant inhibitory effects of SU11274 on cell proliferation and cell survival, in a time and dose-dependent manner. Furthermore, the inhibitory effects of SU11274 on different subgroups of colon cancer cells via the HGF/c-Met signaling pathway were implicated in this study., Conclusion: The results suggested the possible selective therapeutic effects of c-Met inhibitor on colon cancer.

Our laboratory has previously shown that some gefitinib-insensitive head and neck squamous cell carcinoma (HNSCC) cell lines exhibit dominant autocrine fibroblast growth factor receptor (FGFR) signaling. Herein, we deployed a whole-genome loss-of-function screen to identify genes whose knockdown potentiated the inhibitory effect of the FGFR inhibitor, AZ8010, in HNSCC cell lines. Three HNSCC cell lines expressing a genome-wide small hairpin RNA (shRNA) library were treated with AZ8010 and the abundance of shRNA sequences was assessed by deep sequencing. Under-represented shRNAs in treated cells are expected to target genes important for survival with AZ8010 treatment. Synthetic lethal hits were validated with specific inhibitors and independent shRNAs. We found that multiple alternate receptors provided protection from FGFR inhibition, including receptor tyrosine kinases (RTKs), v-erb-b2 erythroblastic leukemia viral oncogene homolog 2 (ERBB2), and hepatocyte growth factor receptor (MET). We showed that specific knockdown of either ERBB2 or MET in combination with FGFR inhibition led to increased inhibition of growth relative to FGFR tyrosine kinase inhibitor (TKI) treatment alone. These results were confirmed using specific small molecule inhibitors of either ERBB family members or MET. Moreover, the triple combination of FGFR, MET, and ERBB family inhibitors showed the largest inhibition of growth and induction of apoptosis compared with the double combinations. These results reveal a role for alternate RTKs in maintaining progrowth and survival signaling in HNSCC cells in the setting of FGFR inhibition. Thus, improved therapies for HNSCC patients could involve rationally designed combinations of TKIs targeting FGFR, ERBB family members, and MET.