Scatter factors and invasive growth

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Identification of prognostic genes in oral squamous cell carcinoma microenvironment

BACKGROUND

Numerous studies reveal the clinical significance of tumor microenvironment (TME) in multiple cancers. The association between TME in oral squamous cell carcinoma (OSCC) and clinical outcomes remains unsolved.

OBJECTIVE

This study aims to exhibit the TME of OSCC and identified the prognostic marker.

METHODS

Gene expression profile and clinical data OSCC patients were from the TCGA database. The validated stage data was from the Gene Expression Omnibus (GSE65858). Immune/stromal scores of each patient were calculated by ESTIMATE algorithm. Biological functional prediction was conducted. Prognostic genes identified by survival analysis. Nomogram and Receiver operating characteristic curves were employed to test the predicting power. TIMER database was applied to evaluated the immune infiltrates.

RESULTS

Lower immune scores were observed in male patients (P= 0.0107) and different primary tumor sites of oral cavity with different stromal scores (P= 0.0328). The Differentially expressed genes (DEGs) were involved in immune related pathways. HGF gene (hepatocyte growth factor) was prognostic related and with a better prognostic performance when combined with clinical features (AUC=TCGA 0.638, AUC=GEO 0.714). HGF was significantly related with B cell, CD4ï⁢¼⁢T cell, CD8+T cell, macrophage, neutrophils, and dendritic cell infiltration.

CONCLUSION

The current study analyzed the TME and presented immune related prognostic biomarkers for OSCC.

The Emerging Role of c-Met in Carcinogenesis and Clinical Implications as a Possible Therapeutic Target

Background

c-MET is a receptor tyrosine kinase receptor (RTK) for the hepatocyte growth factor (HGF). The binding of HGF to c-MET regulates several cellular functions: differentiation, proliferation, epithelial cell motility, angiogenesis, and epithelial-mesenchymal transition (EMT). Moreover, it is known to be involved in carcinogenesis. Comprehension of HGF-c-MET signaling pathway might have important clinical consequences allowing to predict prognosis, response to treatment, and survival rates based on its expression and dysregulation. Discussion. c-MET represents a useful molecular target for novel engineered drugs. Several clinical trials are underway for various solid tumors and the development of new specific monoclonal antibodies depends on the recent knowledge about the definite c-MET role in each different malignance. Recent clinical trials based on c-MET molecular targets result in good safety profile and represent a promising therapeutic strategy for solid cancers, in monotherapy or in combination with other target drugs.

Conclusion

The list of cell surface receptors crosslinking with the c-MET signaling is constantly growing, highlighting the importance of this pathway for personalized target therapy. Research on the combination of c-MET inhibitors with other drugs will hopefully lead to discovery of new effective treatment options.

Molecular Mechanisms of Antiproliferative and Apoptosis Activity by 1,5-Bis(4-Hydroxy-3-Methoxyphenyl)1,4-Pentadiene-3-one (MS13) on Human Non-Small Cell Lung Cancer Cells

Diarylpentanoid (DAP), an analog that was structurally modified from a naturally occurring curcumin, has shown to enhance anticancer efficacy compared to its parent compound in various cancers. This study aims to determine the cytotoxicity, antiproliferative, and apoptotic activity of diarylpentanoid MS13 on two subtypes of non-small cell lung cancer (NSCLC) cells: squamous cell carcinoma (NCI-H520) and adenocarcinoma (NCI-H23). Gene expression analysis was performed using Nanostring PanCancer Pathways Panel to determine significant signaling pathways and targeted genes in these treated cells. Cytotoxicity screening revealed that MS13 exhibited greater inhibitory effect in NCI-H520 and NCI-H23 cells compared to curcumin. MS13 induced anti-proliferative activity in both cells in a dose- and time-dependent manner. Morphological analysis revealed that a significant number of MS13-treated cells exhibited apoptosis. A significant increase in caspase-3 activity and decrease in Bcl-2 protein concentration was noted in both MS13-treated cells in a time- and dose-dependent manner. A total of 77 and 47 differential expressed genes (DEGs) were regulated in MS13 treated-NCI-H520 and NCI-H23 cells, respectively. Among the DEGs, 22 were mutually expressed in both NCI-H520 and NCI-H23 cells in response to MS13 treatment. The top DEGs modulated by MS13 in NCI-H520—DUSP4, CDKN1A, GADD45G, NGFR, and EPHA2—and NCI-H23 cells—HGF, MET, COL5A2, MCM7, and GNG4—were highly associated with PI3K, cell cycle-apoptosis, and MAPK signaling pathways. In conclusion, MS13 may induce antiproliferation and apoptosis activity in squamous cell carcinoma and adenocarcinoma of NSCLC cells by modulating DEGs associated with PI3K-AKT, cell cycle-apoptosis, and MAPK pathways. Therefore, our present findings could provide an insight into the anticancer activity of MS13 and merits further investigation as a potential anticancer agent for NSCLC cancer therapy.

Diospyros kaki leaves inhibit HGF/Met signaling-mediated EMT and stemness features in hepatocellular carcinoma

Persimmon (Diospyros kaki L.f.) trees are widely cultivated for their edible fruits in Asia. D. kaki leaves are abundant in phytochemicals that have numerous medicinal properties. Hepatocyte growth factor (HGF) and its receptor Met lead to poor prognosis via the promotion of metastasis and chemoresistance in hepatocellular carcinoma (HCC). Therefore, inhibitors targeting the HGF/Met pathway are regarded as promising drugs against HCC. Here, we investigated the effects of D. kaki leaves on HGF-induced epithelial-to-mesenchymal transition (EMT) and stemness traits in HCC. The ethanol extract of D. kaki leaves (EEDK) markedly suppressed HGF-mediated cell migration and invasion through upregulation of CDH1 and downregulation of SNAI1, VIM, MMP1, MMP2, and MMP9. Moreover, EEDK increased the cytotoxicity of sorafenib, which was reduced by HGF, and decreased the expression of the stemness markers KRT19 and CD44. Additionally, we found a clear correlation between stemness and EMT markers in HCC patients. Importantly, EEDK reduced Met activity and attenuated HGF-mediated activation of JNK/c-Jun. Our findings provide new evidence that EEDK can ameliorate HCC with poor prognosis and aggressive phenotype by blocking HGF/Met signaling.

Brain Metastases from Lung Cancer: Is MET an Actionable Target?

The process of metastatic dissemination begins when malignant cells start to migrate and leave the primary mass. It is now known that neoplastic progression is associated with a combination of genetic and epigenetic events. Cancer is a genetic disease and this pathogenic concept is the basis for a new classification of tumours, based precisely on the presence of definite genetic lesions to which the clones are addicted. Regarding the scatter factor receptors MET and Recepteur d'Origin Nantais (RON), it is recognised that MET is an oncogene necessary for a narrow subset of tumours (MET-addicted) while it works as an adjuvant metastogene for many others. This notion highlights that the anti-MET therapy can be effective as the first line of intervention in only a few MET-addicted cases, while it is certainly more relevant to block MET in cases of advanced neoplasia that exploit the activation of the invasive growth program to promote dissemination in other body parts. Few data are instead related to the role played by RON, a receptor homologous to MET. We have already demonstrated an implication of MET and RON genes in brain metastases from lung cancer. On this basis, the aim of this work is to recapitulate and dissect the molecular basis of metastatic brain dissemination from lung cancer. The latter is among the big killers and frequently gives rise to brain metastases, most often discovered at diagnosis. Molecular mechanisms leading to tumour spread to the brain are mostly unknown and in turn these tragic cases are still lacking effective therapies. Based on previously published data from our group, we aim to summarise and analyse the pathogenic mechanisms leading to activation of the scatter factor receptor in brain metastatic lesions of lung primaries, from the point of view of replacing the currently used empirical treatment with a more targeted approach.

First-in-human phase I dose escalation study of MK-8033 in patients with advanced solid tumors

Background C-Met, which is frequently activated in multiple cancers, has been implicated in tumor formation, progression, metastasis, angiogenesis, and resistance to multiple therapies. MK-8033 is a small-molecule inhibitor of c-Met that binds preferentially to the activated conformation, and has demonstrated anti-tumor activity in preclinical models. This first-in-human trial was performed to establish the safety and maximum tolerated dose (MTD), as well as preliminary pharmacokinetics (PK) and clinical activity. Methods Forty-seven patients were enrolled in three parts. The primary objective of Parts A and B was safety, whereas Part C evaluated the effect of proton-pump inhibitors on MK-8033 absorption. Dose escalation used an accelerated continual reassessment method, and dose-limiting toxicities (DLTs) were any treatment-related, first course non-hematologic grade ≥ 3 toxicity (except alopecia or inadequately treated nausea/vomiting/diarrhea), grade 4 hematologic toxicity (except grade 3 neutropenic fever and thrombocytopenia), or toxicity where treatment is held >3 weeks. Results Forty-six patients were treated across nine dose levels, and the MTD was 750 mg twice daily. DLTs were fatigue, nausea, vomiting, transaminitis, and hypokalemia. Most frequent toxicities were fatigue (28.3%), nausea (21.7%), and alopecia (19.6%), predominately grade ≤ 2. One patient with endometriod adenocarcinoma achieved a partial response and eight had stable disease. Median progression-free survival (PFS) was 57 days. Strikingly, the PFS for the one responder was 846 days. PK results showed that proton-pump inhibitors have no effect on MK-8033 absorption. Conclusion MK-8033 was well tolerated with no significant toxicity issues, albeit with limited clinical activity. Unfortunately, the company decided to discontinue further clinical development of MK-8033.

MET Activation and Physical Dynamics of the Metastatic Process: The Paradigm of Cancers of Unknown Primary Origin

The molecular and cellular mechanisms which drive metastatic spread are the topic of constant debate and scientific research due to the potential implications for cancer patients' prognosis. In addition to genetics and environmental factors, mechanics of single cells and physical interaction with the surrounding environment play relevant role in defining invasive phenotype. Reconstructing the physical properties of metastatic clones may help to clarify still open issues in disease progression as well as to lead to new diagnostic and therapeutic approaches. In this perspective cancer of unknown primary origin (CUP) identify the ideal model to study physical interactions and forces involved in the metastatic process. We have previously demonstrated that MET oncogene is mutated with unexpected high frequency in CUPs. We here analyze and discuss how the MET activation by somatic mutation may affect physical properties in giving rise to such a highly malignant syndrome, as that defined by CUP.

The Antitumor Effect of C-terminus of Hsp70-Interacting Protein via Degradation of c-Met in Small Cell Lung Cancer

Background

The mesenchymal-epithelial transition factor (MET) receptor can be overexpressed in solid tumors, including small cell lung cancer (SCLC). However, the molecular mechanism regulating MET stability and turnover in SCLC remains undefined. One potential mechanism of MET regulation involves the C-terminus of Hsp70-interacting protein (CHIP), which targets heat shock protein 90-interacting proteins for ubiquitination and proteasomal degradation. In the present study, we investigated the functional effects of CHIP expression on MET regulation and the control of SCLC cell apoptosis and invasion.

Methods

To evaluate the expression of CHIP and c-Met, which is a protein that in humans is encoded by the MET gene (the MET proto-oncogene), we examined the expression pattern of c-Met and CHIP in SCLC cell lines by western blotting. To investigate whether CHIP overexpression reduced cell proliferation and invasive activity in SCLC cell lines, we transfected cells with CHIP and performed a cell viability assay and cellular apoptosis assays.

Results

We found an inverse relationship between the expression of CHIP and MET in SCLC cell lines (n=5). CHIP destabilized the endogenous MET receptor in SCLC cell lines, indicating an essential role for CHIP in the regulation of MET degradation. In addition, CHIP inhibited MET-dependent pathways, and invasion, cell growth, and apoptosis were reduced by CHIP overexpression in SCLC cell lines.

Conclusion

CHIP is capable of regulating SCLC cell apoptosis and invasion by inhibiting MET-mediated cytoskeletal and cell survival pathways in NCI-H69 cells. CHIP suppresses MET-dependent signaling, and regulates MET-mediated SCLC motility.

89Zr-DFO-AMG102 Immuno-PET to Determine Local Hepatocyte Growth Factor Protein Levels in Tumors for Enhanced Patient Selection

The hepatocyte growth factor (HGF) binding antibody rilotumumab (AMG102) was modified for use as a ⁸⁹Zr-based immuno-PET imaging agent to noninvasively determine the local levels of HGF protein in tumors. Because recent clinical trials of HGF-targeting therapies have been largely unsuccessful in several different cancers (e.g., gastric, brain, lung), we have synthesized and validated ⁸⁹Zr-DFO-AMG102 as a companion diagnostic for improved identification and selection of patients having high local levels of HGF in tumors. To date, patient selection has not been performed using the local levels of HGF protein in tumors. Methods: The chelator p-SCN-Bn-DFO was conjugated to AMG102, radiolabeling with ⁸⁹Zr was performed in high radiochemical yields and purity (>99%), and binding affinity of the modified antibody was confirmed using an enzyme-linked immunosorbent assay (ELISA)-type binding assay. PET imaging, biodistribution, autoradiography and immunohistochemistry, and ex vivo HGF ELISA experiments were performed on murine xenografts of U87MG (HGF-positive, MET-positive) and MKN45 (HGF-negative, MET-positive) and 4 patient-derived xenografts (MET-positive, HGF unknown). Results: Tumor uptake of ⁸⁹Zr-DFO-AMG102 at 120 h after injection in U87MG xenografts (HGF-positive) was high (36.8 ± 7.8 percentage injected dose per gram [%ID/g]), whereas uptake in MKN45 xenografts (HGF-negative) was 5.0 ± 1.3 %ID/g and a control of nonspecific human IgG ⁸⁹Zr-DFO-IgG in U87MG tumors was 11.5 ± 3.3 %ID/g, demonstrating selective uptake in HGF-positive tumors. Similar experiments performed in 4 different gastric cancer patient-derived xenograft models showed low uptake of ⁸⁹Zr-DFO-AMG102 (∼4-7 %ID/g), which corresponded with low HGF levels in these tumors (ex vivo ELISA). Autoradiography, immunohistochemical staining, and HGF ELISA assays confirmed that elevated levels of HGF protein were present only in U87MG tumors and that ⁸⁹Zr-DFO-AMG102 uptake was closely correlated with HGF protein levels in tumors. Conclusion: The new immuno-PET imaging agent ⁸⁹Zr-DFO-AMG102 was successfully synthesized, radiolabeled, and validated in vitro and in vivo to selectively accumulate in tumors with high local levels of HGF protein. These results suggest that ⁸⁹Zr-DFO-AMG102 would be a valuable companion diagnostic tool for the noninvasive selection of patients with elevated local concentrations of HGF in tumors for planning any HGF-targeted therapy, with the potential to improve clinical outcomes.

An intramolecular G-quadruplex structure formed in the human MET promoter region and its biological relevance

Previous studies have shown that promoter regions of many proto-oncogenes can fold into G-quadruplexes, which are potentially involved in the regulation of genes. Bioinformatics analysis suggested that there was a G-rich sequence within -48 to -26 region of the human MET promoter (named Pu23WT). In this study, we proved that Pu23WT adopted an intramolecular parallel G-quadruplex structure under physiological conditions in vitro, and the cationic porphyrin TMPyP4 enhanced the stability of the Pu23WT G-quadruplex. To better understand the functions of Pu23WT in the MET expression, we performed a series of analysis on several cancer cells. Experimental data revealed that TMPyP4 treatment attenuated the expression of MET in HepG2, BGC823, and U87MG cells, resulting in the cellular proliferation inhibition, G1 phase cell cycle arrest and cell migration retardation. ChIP assay results indicated that TMPyP4 probably prohibited the Pu23WT G-quadruplex from binding to the activator Sp1, which could be one of the mechanisms that led to the transcription inhibition of MET gene. It is the first study on the G-quadruplex structure in the human MET promoter and its functions in cancer cells. We believe that this structure is a potential target for anticancer treatment.

MET genetic lesions in non-small-cell lung cancer: pharmacological and clinical implications

Lung cancer is the leading cause of death for solid tumors worldwide with an annual mortality of over one million. Lung carcinoma includes a series of different diseases which are roughly divided into two groups based on clinical and histo-pathological features: non-small cell lung cancer (NSCLC), accounting for almost 80% of lung cancer diagnosis and small cell lung cancer (SCLC) responsible for the remaining 20%. The NSCLC molecular profile has been deeply investigated; alterations in several oncogenes, tumor suppressor genes and transcription factors have been detected, mainly in adenocarcinomas. Dissection of such a complex scenario represents a still open challenge for both researchers and clinicians. MET, the receptor for Hepatocyte Growth Factor (HGF), has been recently identified as a novel promising target in several human malignancies, including NSCLC. Deregulation of the HGF/MET signaling pathway can occur via different mechanisms, including HGF and/or MET overexpression, MET gene amplification, mutations or rearrangements. While the role of MET mutations in NSCLC is not yet fully understood, MET amplification emerged as a critical event in driving cell survival, with preclinical data suggesting that MET-amplified cell lines are exquisitely sensitive to MET inhibition. True MET amplification, which has been associated with poor prognosis in different retrospective series, is a relatively uncommon event in NSCLC, occurring in 1-7% of unselected cases. Nevertheless, in highly selected cohorts of patients, such as those harboring somatic mutations of EGFR with acquired resistance to EGFR tyrosine kinase inhibitors, MET amplification can be observed in up to 20% of cases. Preclinical data suggested that a treatment approach including a combination of EGFR and MET tyrosine kinases could be an effective strategy in this setting and led to the clinical investigation of multiple MET inhibitors in combination with anti-EGFR agents. Results from ongoing and future trials will clarify the role of anti-MET molecules for the treatment of NSCLC and will provide insights into the most appropriate timing for their use. The present review recapitulates the current knowledge on the role of MET signaling in NSCLC mainly focusing on its implications in molecular diagnostic approach and on the novel targeted inhibitors.

Targeting the MET pathway for potential treatment of NSCLC

INTRODUCTION

The mesenchymal-epithelial transition (MET) protein is the only known receptor for hepatocyte growth factor and has recently been identified as a novel promising target in several human cancers, including NSCLC. Activation of the MET signaling pathway can occur via different mechanisms. A number of compounds targeting MET have been evaluated in clinical trials, and recent clinical data have begun to afford some insight into the tumor types and patient populations that might benefit from treatment with MET pathway inhibitors.

AREAS COVERED

We review recent publications and information disclosed at public conferences and summarize the epidemiology of dysregulation of MET signaling, and the associations thereof with other driver genes and therapeutic inhibitors useful to treat NSCLC.

EXPERT OPINION

The MET pathway is emerging as a target for advanced NSCLC that is either resistant to EGFR tyrosine kinase inhibitors or that arises de novo. MET inhibitors currently being evaluated in clinical trials have yielded compelling evidence of clinical activities when used to treat various solid tumors, especially NSCLC. Remaining challenges are the identification of patient populations who might benefit from the use of MET inhibitors, and the most effective diagnostic methods for such patients.

USP8 modulates ubiquitination of LRIG1 for Met degradation

The Met receptor tyrosine kinase is an attractive target for cancer therapy as it promotes invasive tumor growth. SAIT301 is a novel anti-Met antibody, which induces LRIG1-mediated Met degradation and inhibits tumor growth. However, detailed downstream mechanism by which LRIG1 mediates target protein down-regulation is unknown. In the present study, we discovered that SAIT301 induces ubiquitination of LRIG1, which in turn promotes recruitment of Met and LRIG1 complex to the lysosome through its interaction with Hrs, resulting in concomitant degradation of both LRIG1 and Met. We also identified USP8 as a LRIG1-specific deubiquitinating enzyme, reporting the interaction between USP8 and LRIG1 for the first time. SAIT301 triggers degradation of LRIG1 by inhibiting the interaction of LRIG1 and USP8, which regulates ubiquitin modification and stability of LRIG1. In summary, SAIT301 employs ubiquitination of LRIG1 for its highly effective Met degradation. This unique feature of SAIT301 enables it to function as a fully antagonistic antibody without Met activation. We found that USP8 is involved in deubiquitination of LRIG1, influencing the efficiency of Met degradation. The relation of Met, LRIG1 and USP8 strongly supports the potential clinical benefit of a combination treatment of a USP8 inhibitor and a Met inhibitor, such as SAIT301.

Mutant p53 cooperates with knockdown of endogenous wild-type p53 to disrupt tubulogenesis in Madin-Darby canine kidney cells

Mutation of the p53 gene is the most common genetic alteration in human malignances and associated clinically with tumor progression and metastasis. To determine the effect of mutant p53 on epithelial differentiation, we developed three-dimensional culture (3-D) of Madin-Darby canine kidney (MDCK) cells. We found that parental MDCK cells undergo a series of morphological changes and form polarized and growth-arrested cysts with hollow lumen, which resembles branching tubules in vitro. We also found that upon knockdown of endogenous wild-type p53 (p53-KD), MDCK cells still form normal cysts in 3-D culture, indicating that p53-KD alone is not sufficient to disrupt cysts formation. However, we found that ectopic expression of mutant R163H (human equivalent R175H) or R261H (human equivalent R273H) in MDCK cells leads to disruption of cyst polarity and formation of invasive aggregates, which is further compounded by knockdown of endogenous wild-type p53. Consistently, we found that expression of E-cadherin, β-catenin, and epithelial-to-mesenchymal transition (EMT) transcription factors (Snail-1, Slug and Twist) is altered by mutant p53, which is also compounded by knockdown of wild-type p53. Moreover, the expression level of c-Met, the hepatocyte growth factor receptor and a key regulator of kidney cell tubulogenesis, is enhanced by combined knockdown of endogenous wild-type p53 and ectopic expression of mutant R163H or R261H but not by each individually. Together, our data suggest that upon inactivating mutation of the p53 gene, mutant p53 acquires its gain of function by altering morphogenesis and promoting cell migration and invasion in part by upregulating EMT and c-Met.

The Molecular Crosstalk between the MET Receptor Tyrosine Kinase and the DNA Damage Response-Biological and Clinical Aspects

Radiation therapy remains an imperative treatment modality for numerous malignancies. Enduring significant technical achievements both on the levels of treatment planning and radiation delivery have led to improvements in local control of tumor growth and reduction in healthy tissue toxicity. Nevertheless, resistance mechanisms, which presumably also involve activation of DNA damage response signaling pathways that eventually may account for loco-regional relapse and consequent tumor progression, still remain a critical problem. Accumulating data suggest that signaling via growth factor receptor tyrosine kinases, which are aberrantly expressed in many tumors, may interfere with the cytotoxic impact of ionizing radiation via the direct activation of the DNA damage response, leading eventually to so-called tumor radioresistance. The aim of this review is to overview the current known data that support a molecular crosstalk between the hepatocyte growth factor receptor tyrosine kinase MET and the DNA damage response. Apart of extending well established concepts over MET biology beyond its function as a growth factor receptor, these observations directly relate to the role of its aberrant activity in resistance to DNA damaging agents, such as ionizing radiation, which are routinely used in cancer therapy and advocate tumor sensitization towards DNA damaging agents in combination with MET targeting.

3,3'-diindolylmethane rapidly and selectively inhibits hepatocyte growth factor/c-Met signaling in breast cancer cells

3,3'-Diindolylmethane (DIM), an indole derivative from vegetables of the Brassica genus, has antiproliferative activity in breast cancer cells. Part of this activity is thought to be due to DIM inhibition of Akt signaling, but an upstream mechanism of DIM-induced Akt inhibition has not been described. The goals of this study were to investigate the kinetics of inhibition of Akt by physiologically relevant concentrations of DIM and to identify an upstream factor that mediates this effect. Here we report that DIM (5-25 μM) inhibited Akt activation from 30 min to 24h in tumorigenic MDA-MB-231 cells but did not inhibit Akt activation in non-tumorigenic preneoplastic MCF10AT cells. DIM inhibited hepatocyte growth factor (HGF)-induced Akt activation by up to 46%, cell migration by 66% and cell proliferation by up to 54%, but did not inhibit induction of Akt by epidermal growth factor or insulin-like growth factor-1. DIM decreased phosphorylation of the HGF receptor, c-Met, at tyrosines 1234 and 1235, indicating decreased activation of the receptor. This decrease was reversed by pretreatment with inhibitors of p38 or calcineurin. Our results demonstrate the important role of HGF and c-Met in DIM's anti-proliferative effect on breast cancer cells and suggest that DIM could have preventive or clinical value as an inhibitor of c-Met signaling.

MicroRNA-449a is downregulated in non-small cell lung cancer and inhibits migration and invasion by targeting c-Met

MicroRNA-449a is expressed at a low level in several tumors and cancer cell lines, and induces G1 arrest, apoptosis, and senescence. To identify the function of miR-449a in non-small cell lung cancer (NSCLC), we discussed the potential relevance of miR-449a to clinicopathological characteristics and prognosis in NSCLC. We also investigated the impact of miR-449a on migration and invasion in NSCLC cells. The expression of miR-449a in NSCLC tissues and cell lines was detected using RT-qPCR. In vitro, gain-of-function, loss-of-function experiments, and fluorescence assays were performed to identify the potential target of miR-449a and the function of miR-449a in NSCLC cells. MiR-449a was downregulated in both NSCLC tissues and cell lines. Moreover, a low expression level of miR-449a appeared to be correlated with lymph node metastasis and poor survival. In vitro, miR-449 regulated cell migration and invasion in NSCLC cells as a potential tumor suppressor, at least in part by targeting c-Met. Furthermore, reciprocal expression of miR-449a and c-Met was shown in NSCLC tissue samples. This study indicates that miR-449a might be associated with NSCLC progression, and suggests a crucial role for miR-449a in NSCLC.

Prognostic value of MET, cyclin D1 and MET gene copy number in non-small cell lung cancer

The aim of this study was to analyze the correlation of the expression of MET and cyclin D1 and MET gene copy number in non-small cell lung cancer (NSCLC) tissues and patient clinicopathologic characteristics and survival. Sixty-one NSCLC tissue specimens were included in the study. The expression of MET and cyclin D1 was evaluated by immunohistochemistry and MET gene copy number was assessed by quantitative real-time polymerase chain reaction (Q-PCR). Positive expression of MET and cyclin D1 protein and increased MET gene copy number occurred in 59.0%, 59.0% and 18.0% of 61 NSCLC tissues, respectively. MET-positivity correlated with poor differentiation (P = 0.009). Increased MET gene copy number was significantly associated with lymph node metastasis (P = 0.004) and advanced tumor stage (P = 0.048), while the expression of cyclin D1 was not associated with any clinicopathologic parameters. There was a significant correlation between the expression of MET and MET gene copy number (P = 0.002). Additionally, the expression of cyclin D1 had a significant association with the expression of MET as well as MET gene copy number (P = 0.002 and P = 0.017, respectively). MET-positivity and increased MET gene copy number were significantly associated with poor overall survival (P = 0.003 and P < 0.001, respectively) in univariate analysis. Multivariate Cox proportional hazard analysis confirmed that the expression of MET and MET gene copy number were prognostic indicators of NSCLC (P = 0.003 and P = 0.001, respectively). The overexpression of MET and the increased MET gene copy number might be adverse prognostic factors for NSCLC patients. The activation of the MET/cyclin D1 signaling pathway may contribute to carcinogenesis and the development of NSCLC, and may represent a target for therapy.

Focus on the potential role of ficlatuzumab in the treatment of non-small cell lung cancer

Lung cancer treatment has rapidly changed in the last few years thanks to novel insights into cancer biology. Several biomarkers and signaling pathways have been recognized as conceivable targets for treatment, and among them is the mesenchymal–epithelial transition/hepatocyte growth factor (c-MET/HGF) axis. Alterations in the c-MET gene and aberrations of MET and HGF expression impact on lung cancer prognosis and are involved in resistance to epidermal growth factor receptor (EGFR) inhibitors in non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations. Several anti-MET and anti-HGF strategies are currently under investigation, including monoclonal antibodies. Ficlatuzumab is a monoclonal antibody directed against HGF that is currently under investigation in NSCLC. The aim of the present review is to critically review available data on HGF and ficlatuzumab in NSCLC.

Targeting the HGF-cMET Axis in Hepatocellular Carcinoma

Under normal physiological conditions, the hepatocyte growth factor (HGF) and its receptor, the MET transmembrane tyrosine kinase (cMET), are involved in embryogenesis, morphogenesis, and wound healing. The HGF-cMET axis promotes cell survival, proliferation, migration, and invasion via modulation of epithelial-mesenchymal interactions. Hepatocellular cancer (HCC) is the third most common cause of worldwide cancer-related mortality; advanced disease is associated with a paucity of therapeutic options and a five-year survival rate of only 10%. Dysregulation of the HGF-cMET pathway is implicated in HCC carcinogenesis and progression through activation of multiple signaling pathways; therefore, cMET inhibition is a promising therapeutic strategy for HCC treatment. The authors review HGF-cMET structure and function in normal tissue and in HCC, cMET inhibition in HCC, and future strategies for biomarker identification.

Structural basis of MET receptor dimerization by the bacterial invasion protein InlB and the HGF/SF splice variant NK1

The structural basis of ligand-induced dimerization of the receptor tyrosine kinase MET by its natural ligand hepatocyte growth factor/scatter factor (HGF/SF) is not well understood. However, interesting insight into the molecular mechanism of MET dimerization has emerged from crystal structures of MET in complex with a bacterial agonist, the invasion protein internalin B (InlB) from pathogenic Listeria monocytogenes. MET activation by InlB promotes uptake of bacteria into host cells. Structural and biophysical data suggest that InlB is monomeric on its own but dimerizes upon binding to the membrane-anchored MET receptor promoting the formation of a signaling active 2:2 complex. The dimerization interface is small and unusually located on the convex side of the curved InlB leucine-rich repeat (LRR) domain. As InlB does not dimerize in solution, the dimerization site could only be identified by studying packing contacts of InlB in various crystal forms and had to be proven by scrutinizing its biological relevance in cellular assays. InlB dimerization is thus an example of a low-affinity contact that appears irrelevant in solution but becomes physiologically significant in the context of 2-dimensional diffusion restricted to the membrane plane. The resulting 2:2 InlB:MET complex has an InlB dimer at its center with one MET molecule bound peripherally to each InlB. This model of ligand-mediated MET dimerization may serve as a blue-print to understand MET activation by NK1, a naturally occurring HGF/SF splice variant and MET agonist. Crystal structures of NK1 repeatedly show a NK1 dimer, in which residues implicated in MET-binding are located on the outside. Thus, MET dimerization by NK1 may also be ligand-mediated with a NK1 dimer at the center of the 2:2 complex with one MET molecule bound peripherally to each NK1. This article is part of a Special Issue entitled: Emerging recognition and activation mechanisms of receptor tyrosine kinases.

The Hepatocyte Growth Factor/c-Met Antagonist, Divalinal-Angiotensin IV, Blocks the Acquisition of Methamphetamine Dependent Conditioned Place Preference in Rats

The use of methamphetamine (MA) is increasing in the U.S. and elsewhere around the world. MA's capacity to cause addiction significantly exceeds other psychostimulant drugs, and its use negatively impacts learning and memory. Recently, attempts have been made to interfere with the presumed mechanism(s) underlying the establishment of drug-induced memory consolidation. The majority of these studies have employed matrix metalloproteinase (MMP) inhibitors to disrupt MMP-induced extracellular matrix molecule dependent synaptic reconfiguration, or GABA receptor agonists. The present investigation utilized an angiotensin IV (AngIV) analogue, Divalinal-AngIV (divalinal), to disrupt acquisition of MA-induced dependence in rats as measured using the conditioned place preference paradigm. Results indicate that both acute and chronic intracerebroventricular infusion of divalinal prior to each daily subcutaneous injection of MA prevented acquisition. However, divalinal was unable to prevent MA-induced reinstatement after prior acquisition followed by extinction trials. These results indicate that prevention of MA dependence can be accomplished by blockade of the brain AT4 receptor subtype. On the other hand, once MA-induced memory consolidation is in place divalinal appears to be ineffective. Mechanistic studies indicated that divalinal is a potent inhibitor of the hepatocyte growth factor (HGF)/c-Met receptor system, and thus it appears that a functional HGF/c-Met system is required for the acquisition of MA-mediated conditioned place preference.

Targeting the HGF/Met signaling pathway in cancer therapy

INTRODUCTION

Under normal conditions, hepatocyte growth factor (HGF)-induced activation of its cell surface receptor, the Met tyrosine kinase (TK), is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand-activated receptor internalization and degradation. Despite these controls, HGF/Met signaling contributes to oncogenesis and tumor progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumor metastasis.

AREA COVERED

The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programs. The authors review Met structure and function, the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development, as well as the latest clinical trial results.

EXPERT OPINION

Clinical trials with HGF/Met pathway antagonists show that as a class these agents are well tolerated. Although widespread efficacy was not seen in several completed Phase II studies, promising results have been reported in lung, gastric, prostate and papillary renal cancer patients treated with these agents. The main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment are optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of optimal therapy combinations. The wealth of basic information, analytical reagents, and model systems available concerning HGF/Met oncogenic signaling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.

MicroRNA-34a inhibits the proliferation and metastasis of osteosarcoma cells both in vitro and in vivo

Background

MicroRNAs (miRNAs) are a class of endogenously expressed, small noncoding RNAs, which suppress its target mRNAs at the post-transcriptional level. Studies have demonstrated that miR-34a, which is a direct target of the p53 tumor suppressor gene, functions as a tumor suppressor and is associated with the tumor growth and metastasis of various human malignances. However, the role of miR-34a in osteosarcoma has not been totally elucidated. In the present study, the effects of miR-34a on osteosarcoma and the possible mechanism by which miR-34a affected the tumor growth and metastasis of osteosarcoma were investigated.

Methodology/Principal Finding

Over-expression of miR-34a partially inhibited proliferation, migration and invasion of osteosarcoma cells in vitro, as well as the tumor growth and pulmonary metastasis of osteosarcoma cells in vivo. c-Met is a target of miR-34a, and regulates the migration and invasion of osteosarcoma cells. Osteosarcoma cells over-expressing miR-34a exhibited a significant decrease in the expression levels of c-Met mRNA and protein simultaneously. Finally, the results from bioinformatics analysis demonstrated that there were multiple putative targets of miR-34a that may be associated with the proliferation and metastasis of osteosarcoma, including factors in Wnt and Notch signaling pathways.

Conclusion/Significance

The results presented in this study demonstrated that over-expression of miR-34a could inhibit the tumor growth and metastasis of osteosarcoma probably through down regulating c-Met. And there are other putative miR-34a target genes beside c-Met which could potentially be key players in the development of osteosarcoma. Since pulmonary metastases are responsible for mortality of patient carrying osteosarcoma, miR-34a may prove to be a promising gene therapeutic agent. It will be interesting to further investigate the mechanism by which miR-34a functions as a tumor suppressor gene in osteosarcoma.

Down-regulation of survivin suppresses uro-plasminogen activator through transcription factor JunB

Survivin, a member of the inhibitors of apoptosis protein family, is expressed during development and in various human cancers. However, the clinical relevance of survivin in cancer is still a matter of debate. Genes induced by hepatocyte growth factor (HGF) were screened using cDNA microarray technology in the stomach cancer cell lines, NUGC3 and MKN28. The levels of JunB, survivin, and uro-plasminogen activator (uPA) were up-regulated in cells treated with HGF in a dose-dependent manner. HGF-induced up regulation of JunB, survivin, and uPA was inhibited by pre-treatment with a MEK inhibitor (PD 98059). HGF-induced up-regulation of uPA was repressed by survivin knockdown. HGF enhanced the binding activity of JunB to the survivin promoter in control cells, but not in the JunB-shRNA cells. Transfection with survivin- shRNA resulted in a decrement of cell proliferation, as determined with MTT assays. In an in vitro invasion assay, significantly fewer cells transfected with survivin shRNA than control cells were able to invade across a Matrigel membrane barrier. In conclusion, survivin appeared to play an important role in the up-regulation of uPA induced by HGF via JunB and might contribute to HGF-mediated tumor invasion and metastasis, which may serve as a promising target for gastric cancer therapy.

HGF-induced PKCζ activation increases functional CXCR4 expression in human breast cancer cells

The chemokine receptor CXCR4 and its ligand CXCL12 have been shown to mediate the metastasis of many malignant tumors including breast carcinoma. Interaction between hepatocyte growth factor (HGF) and the Met receptor tyrosine kinase mediates development and progression of cancers. HGF is able to induce CXCR4 expression and contributes to tumor cell invasiveness in breast carcinoma. However, the mechanism of the CXCR4 expression modulated by c-Met-HGF axis to enhance the metastatic behavior of breast cancer cells is still unclear. In this study, we found that HGF induced functional CXCR4 receptor expression in breast cancer cells. The effect of HGF was specifically mediated by PKCζ activity. After transfection with PKCζ-siRNA, the phosphorylation of PKCζ and CXCR4 was abrogated in breast cancer cells. Interference with the activation of Rac1, a downstream target of HGF, prevented the HGF-induced increase in PKCζ activity and CXCR4 levels. The HGF-induced, LY294002-sensitive translocation of PKCζ from cytosol to plasma membrane indicated that HGF was capable of activating PKCζ, probably via phosphoinositide (PI) 3-kinases. HGF treatment also increased MT1-MMP secretion. Inhibition of PKCζ, Rac-1 and phosphatidylinositol 3-kinase may attenuate MT1-MMP expression in cells exposed to HGF. Functional manifestation of the effects of HGF revealed an increased ability for migration, chemotaxis and metastasis in MDA-MB-436 cells in vitro and in vivo. Our findings thus provided evidence that the process of HGF-induced functional CXCR4 expression may involve PI 3-kinase and atypical PKCζ. Moreover, HGF may promote the invasiveness and metastasis of breast tumor xenografts in BALB/c-nu mice via the PKCζ-mediated pathway, while suppression of PKCζ by RNA interference may abrogate cancer cell spreading.

Downregulation of caspase-10 predicting poor survival after resection of stage II colorectal cancer

PURPOSE

The aim of this study was to evaluate the prevalence and clinical significance of caspase-10 mRNA expression in stage II colorectal cancer.

METHODS

Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze caspase-10 expression in cancer tissue and corresponding normal mucosa from 120 patients with stage II colorectal cancer. Variables were analyzed by Chi-square test or Fisher's exact test. Survival was evaluated with method of Kaplan-Meier. Multivariate analysis was performed with Cox's proportional hazards model.

RESULTS

The expression of caspase-10 mRNA was found to be downregulated in cancer tissue compared to normal mucosa (P = 0.001). Poorly differentiated cancer showed lower mRNA expression than cancer with greater differentiation (P = 0.031). Univariate survival curves, estimated using the method of Kaplan-Meier, defined a significant association between caspase-10 expression and both overall survival (P = 0.012) and disease-free survival (P = 0.021). A multivariate analysis, performed by Cox's proportional hazards regression model, confirmed that a low caspase-10 expression was the only significant factor to predict poor prognosis in patients with stage II colorectal cancer.

CONCLUSION

Our data indicate that caspase-10 expression, measured by quantitative real-time RT-PCR, is a possible prognostic factor in patients with stage II colorectal cancer.

Mimics of the dimerization domain of hepatocyte growth factor exhibit anti-Met and anticancer activity

The angiotensin IV analog norleual [Nle-Tyr-Leu-ψ-(CH(2)-NH(2))-Leu-His-Pro-Phe] has been shown recently to act as a hepatocyte growth factor (HGF)/Met antagonist capable of blocking the binding of HGF to the Met receptor, inhibiting HGF-dependent activation of Met, and attenuating HGF-dependent cellular activities. In addition, norleual exhibited marked anticancer activity. Homology between norleual and the dimerization domain (hinge region) of HGF led to the hypothesis that norleual acts by interfering with HGF dimerization/multimerization and functions as a dominant-negative hinge region mimic. To test this hypothesis we investigated the ability of norleual to bind to and inhibit the dimerization of HGF. To further evaluate the idea that norleual was acting as a hinge region mimic, we synthesized a hexapeptide representing the HGF hinge sequence and established its capacity to similarly block HGF-dependent activation of Met and HGF-dependent cellular functions. The hinge peptide not only bound with high affinity directly to HGF and blocked its dimerization but it also inhibited HGF-dependent Met activation, suppressed HGF-dependent cellular functions, and exhibited anticancer activity. The major implication of this study is that molecules targeting the dimerization domain of HGF may represent novel and viable anticancer therapeutic agents; the development of such molecules should be feasible using norleual and the hinge peptide as synthetic templates.

Reaction of plasma hepatocyte growth factor levels in non-small cell lung cancer patients treated with EGFR-TKIs

Hepatocyte growth factor induces resistance to epidermal growth factor receptor tyrosine kinase inhibitors. It has been hypothesized that epidermal growth factor receptor tyrosine kinase inhibitors administration may influence the levels of plasma hepatocyte growth factor. Patients with advanced non-small cell lung cancer and relapsed after chemotherapies were eligible. Plasma hepatocyte growth factor levels were analyzed on pretreatment and post-treatment day 15 and 30. We also investigated the correlation between plasma hepatocyte growth factor levels and sensitivity to epidermal growth factor receptor tyrosine kinase inhibitors, tissue immunoreactivity for hepatocyte growth factor and MET gene status. Thirty-one patients were enrolled. Plasma hepatocyte growth factor levels on post-treatment day 15 (630.1 ± 366.9 pg/ml) were significantly higher (p = 0.029) than the pretreatment plasma hepatocyte growth factor levels (485.9 ± 230.2 pg/ml). Plasma hepatocyte growth factor levels on the post-treatment day 30 (581.5 ± 298.1 pg/ml) tend to be higher than those before treatment (p = 0.057). Pretreatment plasma hepatocyte growth factor levels in patients with progressive disease (724.1 ± 216.4 pg/ml) were significantly higher than those in patients with stable disease (396.5 ± 148.3 pg/ml; p = 0.0008) and partial response (381.7 ± 179.0 pg/ml; p = 0.0039). The optimal pretreatment plasma hepatocyte growth factor cut-off value for diagnosis of responder was 553.5 pg/ml, and its sensitivity and specificity were 90% and 65%, respectively. Pretreatment plasma hepatocyte growth factor levels had no correlation with tissue immunoreactivities for hepatocyte growth factor, MET gene status and active EGFR mutations. Administration of epidermal growth factor receptor tyrosine kinase inhibitors significantly increased plasma hepatocyte growth factor levels. High levels of pretreatment plasma hepatocyte growth factor indicated intrinsic resistance to epidermal growth factor receptor tyrosine kinase inhibitors. Plasma hepatocyte growth factor can serve as a useful biomarker for the early diagnosis of tumor relapse treated with epidermal growth factor receptor tyrosine kinase inhibitors.

Novel agents in the treatment of metastatic colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer death in the United States. Research has led to an explosion of knowledge into the molecular basis of CRC in the past decades. Numerous receptors and intracellular proteins have been identified and implicated in the growth and progression of metastatic CRC, thus creating novel targets for drug development. Many agents are under development and have begun to enter early and even later-stage clinical trials. Results of these agents have demonstrated some encouraging activity but in a small number of patients. Research into predictive biomarkers aims to select the patients who may benefit from these novel agents. This review will address several of these promising new agents, their potential relevance to CRC, results from early clinical studies, and their incorporation into future and ongoing CRC clinical trials. Clearly, there is an urgent need for new agents in this disease, but as we learned from the experience with epidermal growth factor receptor-targeted antibodies, patient selection will be increasingly be required for individualized therapy to become a reality in CRC.

High MET gene copy number leads to shorter survival in patients with non-small cell lung cancer

INTRODUCTION

Activation of MET, either by increased gene copy number (GCN) or mutation, has been detected in various cancers. We investigate the clinicopathologic features of MET gene copy in nonsmall cell lung cancer (NSCLC).

METHODS

Tumor tissues were obtained from 180 resected NSCLCs, including 97 squamous cell carcinomas (SCCs) and 72 adenocarcinomas. No patient received epidermal growth factor receptor (EGFR)-targeted therapy. EGFR and MET GCNs were studied using fluorescence in situ hybridization (FISH) and were estimated according to the University of Colorado Cancer Center (UCCC) criteria. For MET, we also assessed GCNs using the Cappuzzo system.

RESULTS

FISH-positive MET was observed in 16.7% using the UCCC criteria; specifically, amplification was seen in 3.9% and high polysomy in 12.8%. FISH-positive MET status was significantly correlated with FISH-positive EGFR (p = 0.003). In the Cappuzzo system, high MET GCN (mean, >/=5 copies/cell) was found in 6.7% and also associated with FISH-positive EGFR (p = 0.031). MET gene copy status was not associated with gender, smoking history, histology, or stage. However, true MET amplification was more frequent in patients with SCC than in those with adenocarcinoma. FISH-positive MET status predicted worse survival in patients with NSCLC at advanced stages (p = 0.034) and in patients with SCC (p = 0.028). In multivariate analyses, increased MET GCN was significantly associated with shorter survival in patients with SCC, as analyzed using both the UCCC and Cappuzzo criteria (p = 0.019 and 0.008).

CONCLUSIONS

Our results suggest that increased MET GCN would be an independent poor prognostic factor in SCC of the lung.

Monocyte Derivatives Promote Angiogenesis and Myocyte Survival in a Model of Myocardial Infarction

In this study, we have investigated the hypothesis that previously reported beneficial effect of peripheral blood mononuclear cells cultured under angiogenic conditions on cardiovascular function following ischemia is not limited to EPCs but also to monocytes contained therein. We first purified and analyzed the phenotype and secretome of human and murine blood monocytes cultured under angiogenic conditions (named MDs for monocyte derivatives) and tested their effect in a mouse model of myocardial infarction (MI). FACS analysis of MDs shows that these cells express mature endothelial cell markers and that their proliferative capacity is virtually absent, consistent with their end-differentiated monocytic ontogeny. MDs secreted significant levels of HGF, IGF-1, MCP-1, and sTNFR-1 relative to their monocyte precursors. MDs were unable to form vascular networks in vitro when cultured on matrix coated flasks. Treatment of murine HL-1 cardiomyocyte cell line with MD-conditioned medium reduced their death induced by TNF-α, staurosporine, and oxidative stress, and this effect was dependent upon MD-derived sTNFR-1, HGF, and IGF-1. We further demonstrate that MD secretome promoted endothelial cell proliferation and capacity to form vessels in vitro and this was dependent upon MD-derived MCP-1, HGF, and IGF-1. Echocardiography analysis showed that MD myocardial implantation improved left ventricle fractional shortening of mouse hearts following MI and was associated with reduced myocardial fibrosis and enhancement of angiogenesis. Transplanted MDs and their secretome participate in preserving functional myocardium after ischemic insult and attenuate pathological remodeling.

Hepatocyte growth factor induced up-regulations of VEGF through Egr-1 in hepatocellular carcinoma cells

The potential role of hepatocyte growth factor (HGF) in the regulation of angiogenesis factors in hepatoma cells is not widely appreciated. We investigated the role of HGF-induced activation of a transcription factor, Egr-1, in the expression of pro-angiogenic factors. Genes associated with angiogenesis induced by HGF were screened by using cDNA microarray technology in hepatocellular carcinoma cell lines, HepG2 and Hep3B. Expression levels of Egr-1, vascular endothelial growth factor (VEGF), and interleukin (IL)-8 were further confirmed by real time RT-PCR and Western blot analysis. Roles of Egr-1 in the levels of HGF-induced up-regulations of VEGF and IL-8 were measured by knockdown of Egr-1 with Egr-1 shRNA and chromatin immunoprecipitation assay. The levels of Egr-1, VEGF and IL-8 were up-regulated in cells treated with HGF. HGF-induced up-regulations of Egr-1, VEGF, and IL-8 were inhibited by the pretreatment with an MEK inhibitor, PD098059. HGF-induced up-regulation of VEGF and IL-8 were repressed by Egr-1 knockdown. HGF enhanced the binding activity of Egr-1 to the VEGF promoter in control cells, but not in the Egr-1-shRNA cells. No constitutive and inducible Egr-1 binding activities to the IL-8 promoter were observed in control and Egr-1-shRNA cells. Egr-1 knockdown reduced the luciferase activities increased by HGF not in the IL-8 promoter, but in the VEGF promoter. Egr-1 might play an important role in the up-regulation of VEGF and IL-8 induced by HGF and contribute to HGF-mediated angiogenesis, which might be promising targets for hepatocellular carcinoma therapy.

Novel therapeutic inhibitors of the c-Met signaling pathway in cancer

A wide variety of human malignancies exhibit sustained c-Met stimulation, overexpression, or mutation, including carcinomas of the breast, liver, lung, ovary, kidney, and thyroid. Notably, activating mutations in c-Met have been positively identified in patients with a particular hereditary form of papillary renal cancer, directly implicating c-Met in human tumorigenesis. Aberrant signaling of the c-Met signaling pathway due to dysregulation of the c-Met receptor or overexpression of its ligand, hepatocyte growth factor (HGF), has been associated with an aggressive phenotype. Extensive evidence that c-Met signaling is involved in the progression and spread of several cancers and an enhanced understanding of its role in disease have generated considerable interest in c-Met and HGF as major targets in cancer drug development. This has led to the development of a variety of c-Met pathway antagonists with potential clinical applications. The three main approaches of pathway-selective anticancer drug development have included antagonism of ligand/receptor interaction, inhibition of the tyrosine kinase catalytic activity, and blockade of the receptor/effector interaction. Several c-Met antagonists are now under clinical investigation. Preliminary clinical results of several of these agents, including both monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have been encouraging. Several multitargeted therapies have also been under investigation in the clinic and have demonstrated promise, particularly with regard to tyrosine kinase inhibition.

MET as a target for treatment of chest tumors

The receptor tyrosine kinase MET has been studied of a large variety of human cancers, including lung and mesothelioma. The MET receptor and its ligand HGF (hepatocyte growth factor) play important roles in cell growth, survival and migration, and dysregulation of the HGF-MET pathway leads to oncogenic changes including tumor proliferation, angiogenesis and metastasis. In small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), and malignant pleural mesothelioma (MPM), MET is dysregulated via overexpression, constitutive activation, gene amplification, ligand-dependent activation, mutation or epigenetic mechanisms. New drugs targeted against MET and HGF are currently being investigated in vitro and in vivo, with promising results. These drugs function at a variety of steps within the HGF-MET pathway, including MET expression at the RNA or protein level, the ligand-receptor interaction, and tyrosine kinase function. This paper will review the structure, function, mechanisms of tumorigenesis, and potential for therapeutic inhibition of the MET receptor in lung cancer and mesothelioma.

Discovery of a novel and potent series of thieno[3,2-b]pyridine-based inhibitors of c-Met and VEGFR2 tyrosine kinases

A series of thieno[3,2-b]pyridine-based inhibitors of c-Met and VEGFR2 tyrosine kinases is described. The compounds demonstrated potency with IC(50) values in the low nanomolar range in vitro while the lead compound also showed in vivo activity against various human tumor xenograft models in mice. Further exploration of this class of compounds is underway.

c-Met ectodomain shedding rate correlates with malignant potential

PURPOSE

Many proteins are proteolytically released from the cell surface by a process known as ectodomain shedding. Shedding occurs under normal physiologic conditions and can be increased in certain pathologies. Among the many receptors for which ectodomain shedding has been shown is c-Met, the hepatocyte growth factor (HGF) receptor tyrosine kinase. HGF stimulates mitogenesis, motogenesis, and morphogenesis in a variety of cellular targets during development, homeostasis, and tissue regeneration. Inappropriate HGF signaling resulting in unregulated cell proliferation, motility, and invasion occurs in several human malignancies. This can occur through paracrine signaling, autocrine loop formation, receptor mutation, gene amplification, or gene rearrangement, accompanied frequently with overexpression of ligand and/or receptor proteins. We hypothesized that c-Met overexpression in cancer might result in increased ectodomain shedding, and that its measure could be a useful biomarker of tumor progression.

EXPERIMENTAL DESIGN

We developed a sensitive electrochemiluminescent immunoassay to quantitate c-Met protein in cell lysates, culture supernatants, and biological samples.

RESULTS

A survey of cultured cell models of oncogenic transformation revealed significant direct correlations (P < 0.001, t test or ANOVA) between malignant potential and the rate of c-Met ectodomain shedding that was independent of steady-state receptor expression level. Moreover, weekly plasma and urine samples from mice harboring s.c. human tumor xenografts (n = 4 per group) displayed soluble human c-Met levels that were measurable before tumors became palpable and that correlated directly with tumor volume (R2 > 0.92, linear regression).

CONCLUSIONS

For a variety of human cancers, c-Met ectodomain shedding may provide a reliable and practical indicator of malignant potential and overall tumor burden.

Membrane-type serine protease-1/matriptase induces interleukin-6 and -8 in endothelial cells by activation of protease-activated receptor-2: potential implications in atherosclerosis

OBJECTIVE

The serine protease MT-SP1/matriptase plays an important role in cell migration and matrix degradation. Hepatocyte growth factor (HGF), urokinase-type plasminogen activator (uPA), and protease-activated receptor 2 (PAR-2) have been identified as in vitro substrates of MT-SP1/matriptase. Because PAR-2 is expressed in endothelial cells and contributes to inflammatory processes, we sought to investigate the effects of MT-SP1/matriptase on endothelial cytokine expression and analyzed MT-SP1/matriptase expression in vascular cells and atherosclerotic lesions.

METHODS AND RESULTS

In endothelial cells, recombinant MT-SP1/matriptase dose-dependently induced interleukin (IL)-8 and IL-6 mRNA and protein expression dependent on its proteolytic activity. MT-SP1/matriptase time-dependently induced phosphorylation of p38 MAPK and p42/44 MAPK. Inhibitor experiments revealed that p38 MAPK and PKCalpha were necessary for IL-8 induction. PAR-2 downregulation abolished and PAR-2 overexpression augmented MT-SP1/matriptase-induced IL-8 expression as evidence for PAR-2 signaling. In human atherectomies, MT-SP1/matriptase was expressed in blood cells adherent to the endothelium. Concordantly, basal MT-SP1/matriptase expression was detected in isolated monocytes. Coincubation of monocytes and endothelial cells resulted in an increased IL-8 release, which was reduced after downregulation of endothelial PAR-2 and monocytic MT-SP1/matriptase.

CONCLUSION

MT-SP1/matriptase induces release of proinflammatory cytokines in endothelial cells through activation of PAR-2. MT-SP1/matriptase is expressed in monocytes, thus, interaction of monocytic MT-SP1/matriptase with endothelial PAR-2 may contribute to atherosclerosis.