Frequent amplification of the c-met gene in scirrhous type stomach cancer

c-MET pathway in human malignancies and its targeting by natural compounds for cancer therapy

BACKGROUND

c-MET is a receptor tyrosine kinase which is classically activated by HGF to activate its downstream signaling cascades such as MAPK, PI3K/Akt/mTOR, and STAT3. The c-MET modulates cell proliferation, epithelial-mesenchymal transition (EMT), immune response, morphogenesis, apoptosis, and angiogenesis. The c-MET has been shown to serve a prominent role in embryogenesis and early development. The c-MET pathway is deregulated in a broad range of malignancies, due to overexpression of ligands or receptors, genomic amplification, and MET mutations. The link between the deregulation of c-MET signaling and tumor progression has been well-documented. Overexpression or overactivation of c-MET is associated with dismal clinical outcomes and acquired resistance to targeted therapies. Since c-MET activation results in the triggering of oncogenic pathways, abrogating the c-MET pathway is considered to be a pivotal strategy in cancer therapeutics. Herein, an analysis of role of the c-MET pathway in human cancers and its relevance in bone metastasis and therapeutic resistance has been undertaken. Also, an attempt has been made to summarize the inhibitory activity of selected natural compounds towards c-MET signaling in cancers.

METHODS

The publications related to c-MET pathway in malignancies and its natural compound modulators were obtained from databases such as PubMed, Scopus, and Google Scholar and summarized based on PRISMA guidelines. Some of the keywords used for extracting relevant literature are c-MET, natural compound inhibitors of c-MET, c-MET in liver cancer, c-MET in breast cancer, c-MET in lung cancer, c-MET in pancreatic cancer, c-MET in head and neck cancer, c-MET in bone metastasis, c-MET in therapeutic resistance, and combination of c-MET inhibitors and chemotherapeutic agents. The chemical structure of natural compounds was verified in PubChem database.

RESULTS

The search yielded 3935 publications, of which 195 reference publications were used for our analysis. Clinical trials were referenced using ClinicalTrials.gov identifier. The c-MET pathway has been recognized as a prominent target to combat the growth, metastasis, and chemotherapeutic resistance in cancers. The key role of the c-MET in bone metastasis as well as therapeutic resistance has been elaborated. Also, suppressive effect of selected natural compounds on the c-MET pathway in clinical/preclinical studies has been discussed.

The MET Oncogene: Thirty Years of Insights into Molecular Mechanisms Driving Malignancy

The discovery and subsequent research on the MET oncogene's role in cancer onset and progression have illuminated crucial insights into the molecular mechanisms driving malignancy. The identification of MET as the hepatocyte growth factor (HGF) receptor has paved the path for characterizing the MET tyrosine kinase activation mechanism and its downstream signaling cascade. Over the past thirty years, research has established the importance of HGF/MET signaling in normal cellular processes, such as cell dissociation, migration, proliferation, and cell survival. Notably, genetic alterations that lead to the continuous activation of MET, known as constitutive activation, have been identified as oncogenic drivers in various cancers. The genetic lesions affecting MET, such as exon skipping, gene amplification, and gene rearrangements, provide valuable targets for therapeutic intervention. Moreover, the implications of MET as a resistance mechanism to targeted therapies emphasize the need for combination treatments that include MET inhibitors. The intriguing "flare effect" phenomenon, wherein MET inhibition can lead to post-treatment increases in cancer cell proliferation, underscores the dynamic nature of cancer therapeutics. In human tumors, increased protein expression often occurs without gene amplification. Various mechanisms may cause an overexpression: transcriptional upregulation induced by other oncogenes; environmental factors (such as hypoxia or radiation); or substances produced by the reactive stroma, such as inflammatory cytokines, pro-angiogenic factors, and even HGF itself. In conclusion, the journey to understanding MET's involvement in cancer onset and progression over the past three decades has not only deepened our knowledge, but has also paved the way for innovative therapeutic strategies. Selective pharmacological inactivation of MET stands as a promising avenue for achieving cancer remission, particularly in cases where MET alterations are the primary drivers of malignancy.

An Observatory for the MET Oncogene: A Guide for Targeted Therapies

The MET proto-oncogene encodes a pivotal tyrosine kinase receptor, binding the hepatocyte growth factor (HGF, also known as scatter factor, SF) and governing essential biological processes such as organogenesis, tissue repair, and angiogenesis. The pleiotropic physiological functions of MET explain its diverse role in cancer progression in a broad range of tumors; genetic/epigenetic alterations of MET drive tumor cell dissemination, metastasis, and acquired resistance to conventional and targeted therapies. Therefore, targeting MET emerged as a promising strategy, and many efforts were devoted to identifying the optimal way of hampering MET signaling. Despite encouraging results, however, the complexity of MET's functions in oncogenesis yields intriguing observations, fostering a humbler stance on our comprehension. This review explores recent discoveries concerning MET alterations in cancer, elucidating their biological repercussions, discussing therapeutic avenues, and outlining future directions. By contextualizing the research question and articulating the study's purpose, this work navigates MET biology's intricacies in cancer, offering a comprehensive perspective.

A consolidated working classification of gastric cancer for histopathologists (Review)

Gastric cancer (GC) remains a disease with poor prognosis despite increasing availability of more effective targeted treatment. This may be in part due to the difficulty in selecting patients for appropriate treatment. Conventional taxonomic classifications of GC are ill-suited to make full use of recent advances in personalised therapy. In the past decade a number of molecular classifications have been proposed to address this; however, to date, there has been little implementation in the diagnostic routine. The lack of harmonisation between these classifications, the complexity and unavailability of some of the tests required plus the demands on time and resources, all contribute to poor uptake in the diagnostic routine. In the present study, these classifications were reviewed and an inclusive working classification that includes their main points, focuses on prognosis and treatment options and can be delivered using four on-slide tests (in situ hybridization for Epstein-Barr encoding region and immunohistochemistry for mismatch repair, E-cadherin and p53) is proposed. These tests can be performed on paraffin-embedded tissue and could be available in the majority of histopathology laboratories. The proposed classification also includes reflex testing for specific biomarkers relevant to treatment selection.

The Role of cMET in Gastric Cancer—A Review of the Literature

Gastric cancer (GC) is an important cause of cancer worldwide with over one million new cases yearly. The vast majority of cases present in stage IV disease, and it still bears a poor prognosis. However, since 2010, progress has been made with the introduction of targeted therapies against HER2 and with checkpoint inhibitors (PDL1). More agents interfering with other targets (FGFR2B, CLDN18.2) are being investigated. cMET is a less frequent molecular target that has been studied for gastric cancer. It is a proto-oncogene that leads to activation of the MAPK pathway and the PI3K pathway, which is responsible for activating the MTOR pathway. The prevalence of cMET is strongly debated as different techniques are being used to detect MET-driven tumors. Because of the difference in diagnostic assays, selecting patients who benefit from cMET inhibitors is difficult. In this review, we discuss the pathway of cMET, its clinical significance and the different diagnostic assays that are currently used, such as immunohistochemy (IHC), fluorescence in situ hybridization (FISH), the H-score and next-generation sequencing (NGS). Next, we discuss all the current data on cMET inhibitors in gastric cancer. Since the data on cMET inhibitors are very heterogenous, it is difficult to provide a general consensus on the outcome, as inclusion criteria differ between trials. Diagnosing cMET-driven gastric tumors is difficult, and potentially the only accurate determination of cMET overexpression/amplification may be next-generation sequencing (NGS).

Advances in targeted therapy for gastric cancer based on tumor driver genes

As the understanding of the pathogenic mechanisms of gastric cancer deepens and the identification of gastric cancer driver genes advances, drugs targeting gastric cancer driver genes have been applied in clinical practice. Among them, trastuzumab, as the first targeted drug for gastric cancer, effectively inhibits the proliferation and metastasis of tumor cells by targeting overexpressed human epidermal growth factor receptor 2 (HER2). Trastuzumab has become the standard treatment for HER2-positive gastric cancer patients. Ramucirumab, on the other hand, inhibits tumor angiogenesis by targeting vascular endothelial growth factor receptor 2 (VEGFR2) and has been used as second-line therapy for advanced gastric cancer patients. In addition, bemarituzumab targets overexpressed fibroblast growth factor receptor 2 (FGFR2), while zolbetuximab targets overexpressed claudin 18.2 (CLDN18.2), significantly extending progression-free survival and overall survival in patients with gastric cancer in clinical trials. This article reviews the roles of tumor driver genes in the progression of gastric cancer, and the treatment strategies for gastric cancer primarily based on targeting HER2, VEGF, FGFR2, CLDN18.2 and MET. This provides a reference for clinical application of targeted therapy for gastric cancer.

Short Telomere Lesions with Dysplastic Metaplasia Histology May Represent Precancerous Lesions of Helicobacter pylori-Positive Gastric Mucosa

Gastric cancers are strongly associated with Helicobacter pylori infection, with intestinal metaplasia characterizing the background mucosa in most cases. However, only a subset of intestinal metaplasia cases proceed to carcinogenesis, and the characteristics of high-risk intestinal metaplasia that link it with gastric cancer are still unclear. We examined telomere reduction in five gastrectomy specimens using fluorescence in situ hybridization, and identified areas with localized telomere loss (outside of cancerous lesions), which were designated as short telomere lesions (STLs). Histological analyses indicated that STLs were characteristic of intestinal metaplasia accompanied by nuclear enlargement but lacking structural atypia, which we termed dysplastic metaplasia (DM). A review of gastric biopsy specimens from 587 H. pylori-positive patients revealed 32 cases of DM, 13 of which were classified as high-grade based on the degree of nuclear enlargement. All high-grade DM cases exhibited a telomere volume reduced to less than 60% of that of lymphocytes, increased stemness, and telomerase reverse transcriptase (TERT) expression. Two patients (15%) exhibited low levels of p53 nuclear retention. After a 10-year follow-up, 7 (54%) of the high-grade DM cases had progressed to gastric cancer. These results suggest that DM is characterized by telomere shortening, TERT expression, and stem cell proliferation, and high-grade DM is a high-grade intestinal metaplasia that likely represents a precancerous lesion of gastric cancer. High-grade DM is expected to effectively prevent progression to gastric cancer in H. pylori-positive patients.

Receptor Tyrosine Kinases Amplified in Diffuse-Type Gastric Carcinoma: Potential Targeted Therapies and Novel Downstream Effectors

Simple Summary

Diffuse-type gastric carcinoma (DGC) is an aggressive subtype of gastric carcinoma with an extremely poor prognosis due to frequent peritoneal metastasis and high probability of recurrence. Its pathogenesis is poorly understood, and consequently, no effective molecular targeted therapy is available. The importance of oncogenic receptor tyrosine kinase (RTK) signaling has been recently demonstrated in the malignant progression of DGC. In particular, RTK gene amplification appears to accelerate peritoneal metastasis. In this review, we provide an overview of RTK gene amplification in DGC and the potential of related targeted therapies.

Abstract

Gastric cancer (GC) is a major cause of cancer-related death worldwide. Patients with an aggressive subtype of GC, known as diffuse-type gastric carcinoma (DGC), have extremely poor prognoses. DGC is characterized by rapid infiltrative growth, massive desmoplastic stroma, frequent peritoneal metastasis, and high probability of recurrence. These clinical features and progression patterns of DGC substantially differ from those of other GC subtypes, suggesting the existence of specific oncogenic signals. The importance of gene amplification and the resulting aberrant activation of receptor tyrosine kinase (RTK) signaling in the malignant progression of DGC is becoming apparent. Here, we review the characteristics of RTK gene amplification in DGC and its importance in peritoneal metastasis. These insights may potentially lead to new targeted therapeutics.

Transferrin receptor 1 promotes the fibroblast growth factor receptor-mediated oncogenic potential of diffused-type gastric cancer

Diffuse-type gastric cancer (DGC) is a highly invasive subtype of gastric adenocarcinoma that frequently exhibits scattered peritoneal metastasis. Previous studies have shown that the genes of receptor tyrosine kinases (RTKs), such as fibroblast growth factor receptor 2 (FGFR2) or Met, are amplified in some DGC cell lines, leading to the constitutive activation of corresponding RTKs. In these cell lines, the survival of cancer cells appears to be dependent on the activation of RTKs. To gain novel insights into the downstream signaling pathways of RTKs specific to DGC, phosphotyrosine-containing proteins associated with activated FGFR2 were purified through two sequential rounds of immunoprecipitation from the lysates of two DGC cell lines. As a result, transferrin receptor 1 (TfR1) was identified as the binding partner of FGFR2. Biochemical analysis confirmed that TfR1 protein binds to FGFR2 and is phosphorylated at tyrosine 20 (Tyr20) in an FGFR2 kinase activity-dependent manner. The knockdown of TfR1 and treatment with an inhibitor of FGFR2 caused significant impairment in iron uptake and suppression of cellular proliferation in vitro. Moreover, the suppression of expression levels of TfR1 in the DGC cells significantly reduced their tumorigenicity and potency of peritoneal dissemination. It was indicated that TfR1, when phosphorylated by the binding partner FGFR2 in DGC cells, promotes proliferation and tumorigenicity of these cancer cells. These results suggest that the control of TfR1 function may serve as a therapeutic target in DGC with activated FGFR2.

The dawn of precision medicine in diffuse-type gastric cancer

Gastric cancer (GC) is one of the most common malignancies worldwide. The histology- and morphology-based Lauren classification of GC has been widely used for over 50 years in clinical practice. The Lauren classification divides GC into intestinal and diffuse types, which have distinct etiology, molecular profiles, and clinicopathological features. Diffuse-type GC (DGC) accounts for approximately 30% of GCs. Tumor cells lack adhesion and infiltrate the stroma as single cells or small subgroups, leading to easy dissemination in the abdominal cavity. Clinically, DGC has aggressive traits with a high risk of recurrence and metastasis, which results in unfavorable prognosis. Although systemic chemotherapy is the main therapeutic approach for recurrent or metastatic GC patients, clinical benefits are limited for patients with DGC. Therefore, it is urgent to develop effective therapeutic strategies for DGC patients. Considerable research studies have characterized the molecular and genomic landscape of DGC, of which tight junction protein claudin-18 isoform 2 (CLDN18.2) and fibroblast growing factors receptor-2 isoform IIIb (FGFR2-IIIb) are the most attractive targets because of their close association with DGC. Recently, the impressive results of two phase II FAST and FIGHT trials demonstrate proof-of-concept, suggesting that anti-CLDN18.2 antibody (zolbetuximab) and FGFR2-IIIb antibody (bemarituzumab) are promising approaches for patients with CLDN18.2-positive and FGFR2-IIIb-positive GC, respectively. In this review, we summarize the clinicopathological features and molecular profiles of DGC and highlight a potential therapeutic target based on the findings of pivotal clinical trials.

Roles of MET in human cancer

The MET proto-oncogene was first identified in osteosarcoma cells exposed to carcinogens. Although expressed in many normal cells, MET is overexpressed in many human cancers. MET is involved in the initiation and development of various human cancers and mediates proliferation, migration and invasion. Accordingly, MET has been successfully used as a biomarker for diagnosis and prognosis, survival, post-operative recurrence, risk assessment and pathologic grading, as well as a therapeutic target. In addition, recent work indicates that inhibition of MET expression and function has potential clinical benefit. This review summarizes the role, mechanism, and clinical significance of MET in the formation and development of human cancer.

c-Met-Specific Chimeric Antigen Receptor T Cells Demonstrate Anti-Tumor Effect in c-Met Positive Gastric Cancer

Simple Summary

c-Met is known to be overexpressed in gastric cancers. Here, we developed anti-c-Met CAR T cell and measured its anti-tumor efficacy in vitro and in vivo. Our anti c-Met CAR T cells have shown selective killing of c-Met overexpressed gastric cancer cells. Based on our results, we suggest that anti-c-Met CAR T cell therapy could be effective for gastric cancer patients.

Abstract

Chimeric antigen receptor (CAR) technology has been highlighted in recent years as a new therapeutic approach for cancer treatment. Although the impressive efficacy of CAR-based T cell adoptive immunotherapy has been observed in hematologic cancers, limited effect has been reported on solid tumors. Approximately 20% of gastric cancer (GC) patients exhibit a high expression of c-Met. We have generated an anti c-Met CAR construct that is composed of a single-chain variable fragment (scFv) of c-Met antibody and signaling domains consisting of CD28 and CD3ζ. To test the CAR construct, we used two cell lines: the Jurkat and KHYG-1 cell lines. These are convenient cell lines, compared to primary T cells, to culture and to test CAR constructs. We transduced CAR constructs into Jurkat cells by electroporation. c-Met CAR Jurkat cells secreted interleukin-2 (IL-2) only when incubated with c-Met positive GC cells. To confirm the lytic function of CAR, the CAR construct was transduced into KHYG-1, a NK/T cell line, using lentiviral particles. c-Met CAR KHYG-1 showed cytotoxic effect on c-Met positive GC cells, while c-Met negative GC cell lines were not eradicated by c-Met CAR KHYG-1. Based on these data, we created c-Met CAR T cells from primary T cells, which showed high IL-2 and IFN-γ secretion when incubated with the c-Met positive cancer cell line. In an in vivo xenograft assay with NSG bearing MKN-45, a c-Met positive GC cell line, c-Met CAR T cells effectively inhibited the tumor growth of MKN-45. Our results show that the c-Met CAR T cell therapy can be effective on GC.

SHP2 as a Potential Therapeutic Target in Diffuse-Type Gastric Carcinoma Addicted to Receptor Tyrosine Kinase Signaling

Simple Summary

Diffuse-type gastric carcinoma (DGC) is characterized by rapid infiltrative growth associated with massive stroma and frequent peritoneal dissemination, which leads to poor patient outcomes. In this study, we found that the oncogenic tyrosine phosphatase SHP2 is tyrosine-phosphorylated downstream of the amplified receptor tyrosine kinases (RTKs) Met and fibroblast growth factor receptor 2 (FGFR2) in DGC cell lines. SHP2 knockdown or pharmacological inhibition selectively suppressed the growth of DGC addicted to amplified Met and FGFR2. Moreover, targeting SHP2 abrogated malignant phenotypes, including peritoneal dissemination, of Met-addicted DGC and could overcome acquired resistance to Met inhibitors. Our findings suggest that SHP2 is a potential target for the treatment of DGC addicted to amplified RTK signaling.

Abstract

Diffuse-type gastric carcinoma (DGC) exhibits aggressive progression associated with rapid infiltrative growth, massive fibrosis, and peritoneal dissemination. Gene amplification of Met and fibroblast growth factor receptor 2 (FGFR2) receptor tyrosine kinases (RTKs) has been observed in DGC. However, the signaling pathways that promote DGC progression downstream of these RTKs remain to be fully elucidated. We previously identified an oncogenic tyrosine phosphatase, SHP2, using phospho-proteomic analysis of DGC cells with Met gene amplification. In this study, we characterized SHP2 in the progression of DGC and assessed the therapeutic potential of targeting SHP2. Although SHP2 was expressed in all gastric carcinoma cell lines examined, its tyrosine phosphorylation preferentially occurred in several DGC cell lines with Met or FGFR2 gene amplification. Met or FGFR inhibitor treatment or knockdown markedly reduced SHP2 tyrosine phosphorylation. Knockdown or pharmacological inhibition of SHP2 selectively suppressed the growth of DGC cells addicted to Met or FGFR2, even when they acquired resistance to Met inhibitors. Moreover, SHP2 knockdown or pharmacological inhibition blocked the migration and invasion of Met-addicted DGC cells in vitro and their peritoneal dissemination in a mouse xenograft model. These results indicate that SHP2 is a critical regulator of the malignant progression of RTK-addicted DGC and may be a therapeutic target.

PLEKHA5 regulates the survival and peritoneal dissemination of diffuse-type gastric carcinoma cells with Met gene amplification

Met gene amplification has been found in a subset of malignant carcinomas, including diffuse-type gastric carcinoma (DGC), which has a poor prognosis owing to rapid infiltrative invasion and frequent peritoneal dissemination. Met is considered a promising therapeutic target for DGC. However, DGC cells with Met gene amplification eventually acquire resistance to Met inhibitors. Therefore, identification of alternate targets that mediate Met signaling and confer malignant phenotypes is critical. In this study, we conducted a phosphoproteomic analysis of DGC cells possessing Met gene amplification and identified Pleckstrin Homology Domain Containing A5 (PLEKHA5) as a protein that is tyrosine-phosphorylated downstream of Met. Knockdown of PLEKHA5 selectively suppressed the growth of DGC cells with Met gene amplification by inducing apoptosis, even though they had acquired resistance to Met inhibitors. Moreover, PLEKHA5 silencing abrogated the malignant phenotypes of Met-addicted DGC cells, including peritoneal dissemination in vivo. Mechanistically, PLEKHA5 knockdown dysregulates glycolytic metabolism, leading to activation of the JNK pathway that promotes apoptosis. These results indicate that PLEKHA5 is a novel downstream effector of amplified Met and is required for the malignant progression of Met-addicted DGC.

Lidocaine suppresses the malignant behavior of gastric cancer cells via the c-Met/c-Src pathway

The present study was designed to investigate the role and mechanism of action behind the action of lidocaine in gastric cancer cells. Lidocaine was tested for its potential role in affecting the viability of cells using Cell Counting Kit-8 (CCK-8) assays. It was found that there was a decreased MKN45 cell viability upon lidocaine treatment in a dose-dependent manner. Phosphorylated c-Met, phosphorylated c-Src, c-Met and c-Src levels were detected using western blotting following lidocaine or hepatocyte growth factor (HGF) intervention. It was found that the phosphorylation levels of c-Met and c-Src were markedly reduced by lidocaine treatment, with this effect being further relieved by the addition of HGF. Subsequently, whether lidocaine repressed the malignant biological properties of gastric cancer cells through the c-Met/c-Src axis was further investigated through the detection of epithelial-mesenchymal transition markers (N-caderin and vimentin), wound healing and transwell assay analysis. In addition, cell apoptosis and the levels of apoptosis-related proteins were determined using TUNEL and western blot assays, respectively. The results demonstrated that the malignant behavior of cells were notably repressed upon lidocaine treatment, but the addition of HGF markedly reversed these effects, indicating that the effects of lidocaine on supressing the malignant behaviour of cells could be mediated through the c-Met/c-Src axis. Subsequently, whether lidocaine affected the sensitivity of cells to cisplatin or 5-FU was analyzed using a CCK-8 assay. Enhanced sensitivity of cells to cisplatin or 5-FU was observed when treated in combination with lidocaine. The present study concluded that the involvement of the c-Met/c-Src pathway in the biological behaviour of MKN45 cells was mediated by lidocaine. Therefore, lidocaine may have the potential to suppress the malignant behaviour and proliferation of gastric cancer cells.

The Effects of Capsaicin on Gastrointestinal Cancers

Gastrointestinal (GI) cancers are a group of diseases with very high positions in the ranking of cancer incidence and mortality. While they show common features regarding the molecular mechanisms involved in cancer development, organ-specific pathophysiological processes may trigger distinct signaling pathways and intricate interactions with inflammatory cells from the tumoral milieu and mediators involved in tumorigenesis. The treatment of GI cancers is a topic of increasing interest due to the severity of these diseases, their impact on the patients' survivability and quality of life, and the burden they set on the healthcare system. As the efficiency of existing drugs is hindered by chemoresistance and adverse reactions when administered in high doses, new therapies are sought, and emerging drugs, formulations, and substance synergies are the focus of a growing number of studies. A class of chemicals with great potential through anti-inflammatory, anti-oxidant, and anti-tumoral effects is phytochemicals, and capsaicin in particular is the subject of intensive research looking to validate its position in complementing cancer treatment. Our paper thoroughly reviews the available scientific evidence concerning the effects of capsaicin on major GI cancers and its interactions with the molecular pathways involved in the course of these diseases.

Foretinib Inhibits Cancer Stemness and Gastric Cancer Cell Proliferation by Decreasing CD44 and c-MET Signaling

Purpose

CD44 isoforms are highly expressed in cancer stem cells, initiating tumor growth and sustaining tumor self-renewal. Among these isoforms, CD44 variant 9 (CD44v9) is overexpressed in chronic inflammation-induced cancer. CD44 and the mesenchymal-to-epithelial transition (MET) receptor tyrosine kinase are coactivated in some gastric cancers (GCs). In this study, we characterized MET and CD44 expression and signaling in human GC cell lines and analyzed differences in the susceptibility of these lines to foretinib.

Patients and Methods

We analyzed cell viability and the rate of apoptotic cells using MTS assays and flow cytometry, respectively. Gene and protein expression were assessed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunoblotting, respectively.

Results

Foretinib treatment resulted in dose-dependent inhibition of growth in c-MET-amplified MKN45 and SNU620 cells with concomitant induction of apoptosis, but not in c-MET-reduced MKN28 and AGS cells. Foretinib treatment also significantly reduced phosphor-c-MET, phosphor-AKT, beta-catenin, and COX-2 protein expression in MKN45 and SNU620 cells. Interestingly, foretinib significantly reduced CD44, CD44v9, COX-2, OCT3/4, CCND1, c-MYC, VEGFA, and HIF-1a gene expression in CD44 and MET coactivated MKN45 cells and increased CD44s gene expression; in contrast, these drugs were only slightly active against SNU620 cells.

Conclusion

The results of this study indicate that foretinib could be a therapeutic agent for the prevention or treatment of GCs positive for CD44v9 and c-MET.

Role of Metastasis-Related Genes in Cisplatin Chemoresistance in Gastric Cancer

The role of metastasis-related genes in cisplatin (CDDP) chemoresistance in gastric cancer is poorly understood. Here, we examined the expression of four metastasis-related genes (namely, c-met, HMGB1, RegIV, PCDHB9) in 39 cases of gastric cancer treated with neoadjuvant therapy with CDDP or CDDP+5-fluorouracil and evaluated its association with CDDP responsiveness. Comparison of CDDP-sensitive cases with CDDP-resistant cases, the expression of c-met, HMGB1, and PCDHB9 was correlated with CDDP resistance. Among them, the expression of HMGB1 showed the most significant correlation with CDDP resistance in multivariate analysis. Treatment of TMK-1 and MKN74 human gastric cancer cell lines with ethyl pyruvate (EP) or tanshinone IIA (TAN), which are reported to inhibit HMGB1 signaling, showed a 4–5-fold increase in inhibition by CDDP. Treatment with EP or TAN also suppressed the expression of TLR4 and MyD88 in the HMGB1 signal transduction pathway and suppressed the activity of NFκB in both cell lines. These results suggest that the expression of these cancer metastasis-related genes is also related to anticancer drug resistance and that suppression of HMGB1 may be particularly useful for CDDP sensitization.

Identification of candidates for driver oncogenes in scirrhous-type gastric cancer cell lines

Scirrhous‐type gastric cancer (SGC) is one of the most intractable cancer subtypes in humans, and its therapeutic targets have been rarely identified to date. Exploration of somatic mutations in the SGC genome with the next‐generation sequencers has been hampered by markedly increased fibrous tissues. Thus, SGC cell lines may be useful resources for searching for novel oncogenes. Here we have conducted whole exome sequencing and RNA sequencing on 2 SGC cell lines, OCUM‐8 and OCUM‐9. Interestingly, most of the mutations thus identified have not been reported. In OCUM‐8 cells, a novel CD44‐IGF1R fusion gene is discovered, the protein product of which ligates the amino‐terminus of CD44 to the transmembrane and tyrosine‐kinase domains of IGF1R. Furthermore, both CD44 and IGF1R are markedly amplified in the OCUM‐8 genome and abundantly expressed. CD44‐IGF1R has a transforming ability, and the suppression of its kinase activity leads to rapid cell death of OCUM‐8. To the best of our knowledge, this is the first report describing the transforming activity of IGF1R fusion genes. However, OCUM‐9 seems to possess multiple oncogenic events in its genome. In particular, a novel BORCS5‐ETV6 fusion gene is identified in the OCUM‐9 genome. BORCS5‐ETV6 possesses oncogenic activity, and suppression of its message partially inhibits cell growth. Prevalence of these novel fusion genes among SGC awaits further investigation, but we validate the significance of cell lines as appropriate reagents for detailed genomic analyses of SGC.

Phase I Study of AMG 337, a Highly Selective Small-molecule MET Inhibitor, in Patients with Advanced Solid Tumors

PURPOSE

This first-in-human, open-label phase I study evaluated AMG 337, an oral, highly selective small-molecule inhibitor of MET in advanced solid tumors.Patients and Methods: Patients enrolled into dose-escalation cohorts received AMG 337 up to 400 mg once daily or up to 250 mg twice daily, following a modified 3+3+3 design. Dose expansion was conducted in MET-amplified patients at the maximum tolerated dose (MTD). Primary endpoints included assessment of adverse events (AEs), establishment of the MTD, and pharmacokinetics; clinical response was a secondary endpoint.

RESULTS

The safety analysis set included 111 patients who received ≥1 dose of AMG 337. Thirteen patients had ≥1 AE qualifying as dose-limiting toxicity. The MTD was determined to be 300 mg once daily; the MTD for twice-daily dosing was not reached. Most frequent treatment-related AEs were headache (63%) and nausea (31%). Grade ≥3 treatment-related AEs occurred in 23 patients (21%), most commonly headache (n = 6) and fatigue (n = 5). Maximum plasma concentration occurred at 3.0 hours following 300-mg once-daily dosing, indicating AMG 337 absorption soon after treatment. Objective response rate was 9.9% (11/111; 95% CI, 5.1%-17.0%) in all patients and 29.6% (8/27; 95% CI, 13.8%-50.2%) in MET-amplified patients; median (range) duration of response was 202 (51-1,430+) days in all patients and 197 (64-1,430+) days in MET-amplified patients.

CONCLUSIONS

Oral AMG 337 was tolerated with manageable toxicities, with an MTD and recommended phase II dose of 300 mg once daily. The promising response rate observed in patients with heavily pretreated MET-amplified tumors warrants further investigation.See related commentary by Ma, p. 2375.

INC280 inhibits Wnt/β-catenin and EMT signaling pathways and its induce apoptosis in diffuse gastric cancer positive for c-MET amplification

OBJECTIVE

Gastric cancer is more open related to genetic predisposition. In our RNA sequencing study on gastric cancer patients, Runt-related transcription factor-3 (RUNX3) expression was significantly down-regulated in gastric cancer. We showed that decreased levels of RUNX3 are significantly associated with c-MET (r = - 0.4216, P = 0.0130). In addition, c-MET expression is a candidate for targeted therapy in gastric cancer. Therefore, in the present study, the anti-cancer effects of the c-MET inhibitor on gastric cancer cells from positive or negative for c-MET amplification were evaluated.

RESULTS

INC280 treatment inhibits growth of a c-MET-amplified MKN45 (RUNX3-positive) and SNU620 (RUNX3-negative) diffuse type cells. Then, INC280 showed the highest inhibition and apoptotic rates with the lowest IC₅₀s in MKN45 cells but not in c-MET-reduced MKN28 (intestinal type) cells. We also showed that INC280 inhibits the WNT signaling pathway and SNAIL expression in MKN45 cells. The data indicate that INC280 could be used as therapeutic agents for the prevention or treatment of diffuse gastric cancer positive for c-MET amplification.

The Oncogenic Activity of miR-29b-1-5p Induces the Epithelial-Mesenchymal Transition in Oral Squamous Cell Carcinoma

Background: The relationship between miR-29b-1-5p and c-Met proto-oncogene in oral squamous cell carcinoma (OSCC) remains to be investigated. This study aimed to reveal the role of miR-29b-1-5p in the pathogenesis of OSCC using molecular and biological analyses. Methods: We investigated the expression of miR-29b-1-5p, c-Met, and markers of the epithelial-mesenchymal transition (EMT) in the tissues of 49 patients with OSCC and in human OSCC cells with different tumorigenicity. Further, we determined the effects of miR-29b-1-5p on the phenotypes of OSCC cell lines. Results: The expression levels of miR-29b-1-5p in most patients with OSCC were higher than those of the normal oral epithelium. In OSCC, upregulation of miR-29b-1-5p significantly correlated with histological grade, the EMT, and the immunohistochemical grade, indicated by c-Met expression. The prognosis was poor for patients with miR-29b-1-5p expression and coexpression of miR-29b-1-5p and c-Met. In OSCC cells exhibiting the EMT phenotype, knockdown of miR-29b-1-5p suppressed the EMT, which was recovered by enforced expression of c-Met. Further, the mRNA encoding cadherin 1 (CDH1) was a direct target of miR-29b-1-5p. Conclusions: Our results suggest that miR-29b-1-5p acts as an oncogenic miRNA that synergizes with c-Met to induce the EMT of OSCC cells.

3D-QSAR-aided design of potent c-Met inhibitors using molecular dynamics simulation and binding free energy calculation

Mesenchymal-epithelial transition factor (c-Met) is a member of receptor tyrosine kinase. It involves in various cellular signaling pathways which includes proliferation, motility, migration, and invasion. Over-expression of c-Met has been reported in various cancers. Hence, it is an ideal therapeutic target for cancer. The main objective of the study is to identify crucial residues involved in the inhibition of c-Met kinase and to design a series of potent imidazo [4,5-b] pyrazine derivatives as c-Met inhibitors. Docking was used to identify important active site residues involved in the inhibition of c-Met kinase which was further validated by 100 ns of molecular dynamics simulation and free energy calculation using molecular mechanics generalized born surface area. Furthermore, binding energy decomposition identified that residues Tyr1230, Met1211, Asp1222, Tyr1159, Met1160, Val1092, Ala1108, and Leu1157 contributed favorably to the binding stability of compound 32. Receptor-guided Comparative Molecular Field Analysis (CoMFA) (q² = 0.751, NOC = 6, r² = 0.933) and Comparative Molecular Similarity Indices Analysis (COMSIA) (q² = 0.744, NOC = 6, r² = 0.950) models were generated based on the docked conformation of the most active compound 32. The robustness of these models was tested using various validation techniques and found to be predictive. The results of CoMFA and CoMSIA contour maps exposed the regions favorable to enhance the activity. Based on this information, 27 novel c-Met inhibitors were designed. These designed compounds exhibited potent activity than the most active compound of the existing dataset. Communicated by Ramaswamy H. Sarma.

A Multicenter Phase II Study of AMG 337 in Patients with MET-Amplified Gastric/Gastroesophageal Junction/Esophageal Adenocarcinoma and Other MET-Amplified Solid Tumors

PURPOSE

MET gene amplification is associated with poor prognosis in gastric/gastroesophageal junction/esophageal (G/GEJ/E) cancers. We determined antitumor activity, safety, and pharmacokinetics of the small-molecule MET inhibitor AMG 337 in MET-amplified G/GEJ/E adenocarcinoma or other solid tumors.Patients and Methods: In this phase II, single-arm study, adults with MET-amplified G/GEJ/E adenocarcinoma (cohort 1) or other MET-amplified solid tumors (cohort 2) received AMG 337 300 mg/day orally in 28-day cycles. The primary endpoint was objective response rate (ORR; cohort 1). Secondary endpoints included ORR (cohort 2), progression-free survival (PFS), overall survival (OS), and safety.

RESULTS

Of 2101 patients screened for MET amplification, 132 were MET-amplified and 60 were enrolled: 45 in cohort 1, and 15 in cohort 2. Fifty-six patients (97%) had metastatic disease; 57 had prior lines of therapy (1 prior line, 29%; ≥2 prior lines, 69%). A protocol-permitted review showed efficacy that was lower-than-expected based on preliminary data from a first-in-human study, and enrollment was stopped. Fifty-eight patients received ≥1 AMG 337 dose. ORR in cohort 1 was 18% (8 partial responses). No responses were observed in cohort 2. Of 54 evaluable patients, median (95% CI) PFS and OS were 3.4 (2.2-5.0) and 7.9 (4.8-10.9) months, respectively. The most frequent adverse events (AEs) were headache (60%), nausea (38%), vomiting (38%), and abdominal pain, decreased appetite, and peripheral edema (33% each); 71% had grade ≥3 AEs and 59% had serious AEs.

CONCLUSIONS

AMG 337 showed antitumor activity in MET-amplified G/GEJ/E adenocarcinoma but not in MET-amplified non-small-cell lung cancer.See related commentary by Ma, p. 2375.

The significance of scirrhous gastric cancer cell lines: the molecular characterization using cell lines and mouse models

Scirrhous gastric cancer (SGC) exhibits aggressiveness of the rapid infiltrating tumor cells with abundant fibroblasts. Experimental studies using SGC cell lines have obtained useful information about this cancer. Our literature search divulged a total of 18 SGC cell lines; two cell lines were established from primary SGC and the other lines were established from a metastatic lesion of SGC. Fibroblast growth factor receptor 2 (FGFR2) and transforming growth factor-beta receptor (TβR) are linked to the rapid development of SGC. Cross-talk between the cancer cells and cancer-associated fibroblasts (CAFs) has been shown to contribute to the progression of SGC. Chemokine (C-X-C motif) receptor 1 (CXCR1) from SGC cells might be associated with the abundant CAFs in cancer microenvironments. The in vivo models established using SGC cell lines are expected to serve as a useful tool for the development of drugs such as FGFR2 inhibitors, TβR inhibitors, and CXCR1 inhibitors, which might be promising as SGC treatments. However, the number of available SGC cell lines is insufficient for the clarification of the entire biologic behavior of SGC. Since the mechanisms responsible for the characteristic aggressiveness of SGC are not fully elucidated, the establishment of new SGC cell lines could help clarify the biological behavior of SGC and contribute to its treatment.

Effects of trastuzumab and afatinib on kinase activity in gastric cancer cell lines

The molecular mechanism of action of the HER2‐targeted antibody trastuzumab is only partially understood, and the direct effects of trastuzumab on the gastric cancer signaling network are unknown. In this study, we compared the molecular effect of trastuzumab and the HER kinase inhibitor afatinib on the receptor tyrosine kinase (RTK) network and the downstream‐acting intracellular kinases in gastric cancer cell lines. The molecular effects of trastuzumab and afatinib on the phosphorylation of 49 RTKs and 43 intracellular kinase phosphorylation sites were investigated in three gastric cancer cell lines (NCI‐N87, MKN1, and MKN7) using proteome profiling. To evaluate these effects, data were analyzed using mixed models and clustering. Moreover, proliferation assays were performed. Our comprehensive quantitative analysis of kinase activity in gastric cancer cell lines indicates that trastuzumab and afatinib selectively influenced the HER family RTKs. The effects of trastuzumab differed between cell lines, depending on the presence of activated HER2. The effects of trastuzumab monotherapy were not transduced to the intracellular kinase network. Afatinib alone or in combination with trastuzumab influenced HER kinases in all cell lines; that is, the effects of monotherapy and combination therapy were transduced to the intracellular kinase network. These results were confirmed by proliferation analysis. Additionally, the MET‐amplified cell line Hs746T was identified as afatinib nonresponder. The dependence of the effect of trastuzumab on the presence of activated HER2 might explain the clinical nonresponse of some patients who are routinely tested for HER2 expression and gene amplification in the clinic but not for HER2 activation. The consistent effects of afatinib on HER RTKs and downstream kinase activation suggest that afatinib might be an effective candidate in the future treatment of patients with gastric cancer irrespective of the presence of activated HER2. However, MET amplification should be taken into account as potential resistance factor.

Gelsolin-mediated activation of PI3K/Akt pathway is crucial for hepatocyte growth factor-induced cell scattering in gastric carcinoma

In gastric cancer (GC), the main subtypes (diffuse and intestinal types) differ in pathological characteristics, with diffuse GC exhibiting early disseminative and invasive behaviour. A distinctive feature of diffuse GC is loss of intercellular adhesion. Although widely attributed to mutations in the CDH1 gene encoding E-cadherin, a significant percentage of diffuse GC do not harbor CDH1 mutations. We found that the expression of the actin-modulating cytoskeletal protein, gelsolin, is significantly higher in diffuse-type compared to intestinal-type GCs, using immunohistochemical and microarray analysis. Furthermore, in GCs with wild-type CDH1, gelsolin expression correlated inversely with CDH1 gene expression. Downregulating gelsolin using siRNA in GC cells enhanced intercellular adhesion and E-cadherin expression, and reduced invasive capacity. Interestingly, hepatocyte growth factor (HGF) induced increased gelsolin expression, and gelsolin was essential for HGF-medicated cell scattering and E-cadherin transcriptional repression through Snail, Twist and Zeb2. The HGF-dependent effect on E-cadherin was found to be mediated by interactions between gelsolin and PI3K-Akt signaling. This study reveals for the first time a function of gelsolin in the HGF/cMet oncogenic pathway, which leads to E-cadherin repression and cell scattering in gastric cancer. Our study highlights gelsolin as an important pro-disseminative factor contributing to the aggressive phenotype of diffuse GC.

The Prognostic Significance of c-MET and EGFR Overexpression in Resected Gastric Adenocarcinomas

OBJECTIVES

Epidermal growth factor receptor (EGFR) and c-MET are tyrosine kinase growth factor receptors implicated in gastric cancer (GC), and their pathways appear to be interdependent. The aim of this study was to investigate the prognostic value of EGFR and c-MET protein overexpression by immunohistochemistry in Canadian patients with resected GC and correlate it with clinicopathologic characteristics and overall survival (OS).

MATERIALS AND METHODS

Tissue microarray blocks were constructed from 120 resected GCs stained with EGFR and c-MET and scored semiquantitatively (0 to 3+). Each receptor's expression was compared with clinicopathologic characteristics and survival. Descriptive statistics, Kaplan-Meyer, and Cox regression were used for statistical analyses.

RESULTS

Of the 113 interpretable cases, overexpression of EGFR and c-MET was noted in 17 (15%) and 65 (57%), respectively; coexpression of EGFR and c-MET was observed in 12 (10%) of GC. EGFR and c-MET overexpression correlated with poor OS: median 13 versus 30 months in EGFR positive versus negative GC (hazard ratio [HR]=1.67, P=0.11); 27 versus 49 months in c-MET positive versus negative GC (HR=1.17, P=0.49), respectively. GC coexpressing EGFR and c-MET was significantly correlated with poor survival: 12 versus 29 months in double-positive versus rest of tumors both in univariate (HR=2.62, P=0.003) and multivariate analyses (HR=2.58, P=0.01).

CONCLUSIONS

This study describes the prevalence and prognostic value of EGFR and c-MET in a Canadian population of patients undergoing curative intent resection for GC. Both c-MET and EGFR overexpression trended toward poor OS, but only the group with EGFR+/c-MET+ GC reached statistical significance on multivariate analysis.

A Phase II Study of the c-Met Inhibitor Tivantinib in Combination with FOLFOX for the Treatment of Patients with Previously Untreated Metastatic Adenocarcinoma of the Distal Esophagus, Gastroesophageal Junction, or Stomach

BACKGROUND

This phase I/II study was designed to determine the maximum tolerated dose of tivantinib in combination with standard dose FOLFOX for the treatment of patients with advanced solid tumors and to evaluate the safety and efficacy of this combination for patients with previously untreated metastatic adenocarcinoma of the distal esophagus, gastroesophageal (GE) junction, or stomach.

METHODS

Patients with advanced solid tumors for which FOLFOX would be appropriate chemotherapy received escalating doses of tivantinib BID (days 1-14) in a standard 3 + 3 design in phase I. In phase II, patients with advanced GE cancer received standard FOLFOX day 1 and tivantinib (360 mg PO BID) days 1-14 of each 2-week cycle. Restaging occurred every four cycles. The primary phase II endpoint was response rate (RR).

RESULTS

Forty-nine patients were enrolled (15 on phase I and 34 on phase II). The expansion dose was established as tivantinib 360 mg BID in combination with FOLFOX. Thirty-two phase II patients were treated for a median of eight cycles (range, 1-38), with an overall RR of 38%. Treatment-related toxicities included neutropenia, fatigue, diarrhea, nausea, and peripheral neuropathy. Median progression-free survival (PFS) was 6.1 hmonths with a median time to progression of 7.0 months. Median overall survival was 9.6 months. Two patients remain on study at the time of this analysis.

CONCLUSIONS

The combination treatment of tivantinib plus FOLFOX in patients with advanced GE cancer showed a response and PFS in the range of historical controls for first-line FOLFOX therapy. However, two patients had extended time on study treatment (36 and 45 cycles) at the time of data cutoff.

Personalized and precision medicine: integrating genomics into treatment decisions in gastrointestinal malignancies

The advent of next generation sequencing (NGS) technologies has advanced our understanding of the intrinsic biology of different gastrointestinal (GI) tumor types. The use of novel, more efficient sequencing platforms has improved turnaround times of sequencing results. This is providing real time opportunities to put precision medicine to the test. A number of early phase clinical trials are testing targeted therapies in unique molecularly characterized subsets of patients (baskets). While basket studies are gaining momentum, treatment failures serve to remind us that shifting from a histology-driven to a histology-agnostic approach is unlikely to be a failure-free strategy for a number of tumor types as recently learnt from vemurafenib failure in BRAF mutated metastatic colorectal cancer (mCRC). GI malignancies are clinically and molecularly heterogeneous. Unfortunately, development of biomarkers of response to therapy as well as targeted therapies for GI adenocarcinomas has fallen behind compared to other malignancies. Trastuzumab is the only FDA approved targeted therapy for GI adenocarcinomas for which a biomarker of response (HER2 amplifications) is available. In addition, RAS mutations are known to predict lack of response to epidermal growth factor receptor (EGFR) inhibitors in advanced colorectal cancer (CRC) patients. However, NGS has recently revealed that a number of actionable genetic aberrations are present at low prevalence across different GI malignancies. Prospective randomized clinical trials will determine whether matching actionable aberration with targeted therapy will contribute to improve survival in patients with GI malignancies. Here, we review current evidence for targeted therapies in GI malignancies, as well as application and pitfalls of NGS including tissue testing and liquid biopsies.

The gene copy number of c-MET has a significant impact on progression-free survival in Korean patients with ovarian carcinoma

The aim of this study was to compare the protein overexpression and gene copy number (GCN) of c-MET in ovarian carcinoma and to assess their prognostic roles in Korean women. MET protein expression and GCN status were determined using immunohistochemistry (IHC) and silver in situ hybridization, respectively, in 105 ovarian carcinomas comprising 63 serous, 12 mucinous, 20 clear cell, and 10 endometrioid carcinomas. All cases had been treated and followed up at a single institute in Seoul, Korea. MET protein overexpression was observed in 35 of 105 (33.3%) ovarian carcinomas, with IHC 2+ in 27 and IHC 3+ in 8. The overexpression rates of serous, mucinous, clear cell, and endometrioid carcinomas were 14.3%, 83.3%, 65.0%, and 30.0%, respectively. MET protein overexpression was significant in mucinous carcinoma (P < .001) and was correlated with better progression-free survival (PFS) (P = .028). High polysomy (HP) of chromosome 7 and gene amplification (GA) were found in 10 (9.5%) and 2 (1.9%) of the 105 ovarian carcinomas, respectively. Eleven of 12 cases were high-grade serous carcinomas. The remaining case was clear cell carcinoma. HP and GA were associated with a poor PFS (P = .001). There was no significant correlation between a high level of protein expression and increased GCN of MET (r = -0.127, P = .197). In Korean women, HP and GA of MET were significantly correlated with a poor PFS. MET GCN may serve as a biomarker for poor prognosis in patients with ovarian carcinoma.

Molecular heterogeneity in the novel fusion gene APIP-FGFR2: Diversity of genomic breakpoints in gastric cancer with high-level amplifications at 11p13 and 10q26

Several novel fusion transcripts were identified by next-generation sequencing in gastric cancer; however, the breakpoint junctions have yet to be characterized. The present study characterized a plethora of APIP-FGFR2 genomic breakpoints in the SNU-16 gastric cancer cell line, which harbored homogeneously staining regions (hsrs) and double minute chromosomes. Oligonucleotide microarrays revealed high-level amplifications at chromosomes 8q24.1 (0.8 Mb region), 10q26 (1.1 Mb) and 11p13 (1.1 Mb). These amplicons contained MYC and PVT1 at chromosome 8q24.1, BRWD2, FGFR2 and ATE1 at chromosome 10q26, and 24 genes, including APIP, CD44, RAG1 and RAG2, at chromosome 11p13. Based on these findings, reverse transcription-polymerase chain reaction (PCR) was performed using various candidate gene primers to detect possible fusion transcripts, and several products using primer sets for the APIP and FGFR2 genes were detected. Eventually, three in-frame and two out-of-frame fusion transcripts were detected. Notably, PCR analysis of the entire genomic DNA detected three distinct genomic junctions. The breakpoints were within intron 5 of APIP, which contained three distinct breakpoints, and introns 5, 7 and 9 of FGFR2. Fluorescence in situ hybridization showed several fusion signals within hsrs using two short probes (~10-kb segments of a bacterial artificial chromosome clone) containing exons 2–5 of APIP or exons 11–13 of FGFR2. Although, for any given fusion, a multiplicity of transcripts is thought to be created by alternative splicing of one rearranged allele, the results of the present study suggested that genomic fusions of APIP and FGFR2 are generated in hsrs with a diversity of breakpoints that are then faithfully transcribed.

Biomarker development in MET-targeted therapy

Activation of the MET receptor tyrosine kinase by its ligand, hepatocyte growth factor (HGF), has been implicated in a variety of cellular processes, including cell proliferation, survival, migration, motility and invasion, all of which may be enhanced in human cancers. Aberrantly activated MET/HGF signaling correlates with tumorigenesis and metastasis, and is regarded as a robust target for the development of novel anti-cancer treatments. Various clinical trials were conducted to evaluate the safety and efficacy of selective HGF/MET inhibitors in cancer patients. There is currently no optimal or standardized method for accurate and reliable assessment of MET levels, or other biomarkers that are predictive of the patient response to MET-targeted therapeutics. In this review, we discuss the importance of accurate HGF/MET signal detection as a predictive biomarker to guide patient selection for clinical trials of MET-targeted therapies in human cancers.

Establishment of clival chordoma cell line MUG-CC1 and lymphoblastoid cells as a model for potential new treatment strategies

Chordomas are rare malignant tumors that develop from embryonic remnants of the notochord and arise only in the midline from the clivus to the sacrum. Surgery followed by radiotherapy is the standard treatment. As chordomas are resistant to standard chemotherapy, further treatment options are urgently needed. We describe the establishment of a clivus chordoma cell line, MUG-CC1. The cell line is characterized according to its morphology, immunohistochemistry, and growth kinetics. During establishment, cell culture supernatants were collected, and the growth factors HGF, SDF-1, FGF2, and PDGF analyzed using xMAP^® technology. A spontaneous lymphoblastoid EBV-positive cell line was also developed and characterized. MUG-CC1 is strongly positive for brachyury, cytokeratin, and S100. The cell line showed gains of the entire chromosomes 7, 8, 12, 13, 16, 18, and 20, and high level gains on chromosomes 1q21–1q24 and 17q21–17q25. During cultivation, there was significant expression of HGF and SDF-1 compared to continuous chordoma cell lines. A new, well-characterized clival chordoma cell line, as well as a non-tumorigenic lymphoblastoid cell line should serve as an in vitro model for the development of potential new treatment strategies for patients suffering from this disease.

Understanding and Targeting MET Signaling in Solid Tumors - Are We There Yet?

The MET signaling pathway plays an important role in normal physiology and its deregulation has proved critical for development of numerous solid tumors. Different technologies have been used to investigate the genomic and proteomic status of MET in cancer patients and its association with disease prognosis. Moreover, with the development of targeted therapeutic drugs, there is an urgent need to identify potential biomarkers for selection of patients who are more likely to derive benefit from these agents. Unfortunately, the variety of technical platforms and analysis criteria for diagnosis has brought confusion to the field and a lack of agreement in the evaluation of MET status as a prognostic or predictive marker for targeted therapy agents. We review the molecular mechanisms involved in the deregulation of the MET signaling pathway in solid tumors, the different technologies used for diagnosis, and the main factors that affect the outcome, emphasizing the urge for completing analytical and clinical validation of these tests. We also review the current clinical studies with MET targeted agents, which mostly focus on lung cancer.

Ephedrae herba stimulates hepatocyte growth factor-induced MET endocytosis and downregulation via early/late endocytic pathways in gefitinib-resistant human lung cancer cells

The MET tyrosine kinase receptor and its ligand, hepatocyte growth factor (HGF), are known to be overexpressed in a variety of malignant tumor cells, and are implicated in the development of gefitinib-resistance in human non-small cell lung cancer (NSCLC) cells. Ephedrae herba was previously reported to prevent HGF-induced cancer cell motility by directly suppressing HGF/MET signaling through the inhibition of MET tyrosine kinase, and treatment with its extract also considerably reduced MET protein levels. To further investigate the mechanism underlying the Ephedrae herba-induced inhibition of MET phosphorylation as well as its degradation and subsequent disappearance, we examined the effect of Ephedrae herba on HGF-stimulated MET endocytosis and downregulation via early/late endocytic pathways in an NSCLC cell line. Using immunofluorescence microscopy, we found that pretreatment of cells with Ephedrae herba extract dramatically changed the intracellular distribution of plasma membrane-associated MET, and that the resultant MET staining was distributed throughout the cytoplasm. Pretreatment of the cells with Ephedrae herba extract also led to the rapid loss of MET and phosphorylated (p)-MET in HGF-stimulated cells. In contrast, inefficient endocytic delivery of MET and p-MET from early to late endosomes was observed in the absence of Ephedrae herba extract, since considerable amounts of the internalized MET accumulated in the early endosomes and were not delivered to lysosomes up to 1 h after HGF-stimulation. Furthermore, large amounts of MET and p-MET that had accumulated in late endosomes of Ephedrae herba-pretreated cells after HGF stimulation were observed along with bafilomycin A1. Therefore, we inferred that degradation of MET occurred in the late endosome/lysosome pathway. Moreover, western blot analysis revealed the accelerated degradation of MET and p-MET proceeds in cells pretreated with Ephedrae herba extract. Collectively, our results suggest that some components of Ephedrae herba have a novel role in promoting HGF-stimulated MET and p-MET endocytosis followed by its downregulation, likely mediated by the early/late endocytic pathways.

Anti-c-Met monoclonal antibody ABT-700 breaks oncogene addiction in tumors with MET amplification

Background

c-Met is the receptor tyrosine kinase for hepatocyte growth factor (HGF) encoded by the MET proto-oncogene. Aberrant activation of c-Met resulting from MET amplification and c-Met overexpression is associated with poor clinical outcome in multiple malignancies underscoring the importance of c-Met signaling in cancer progression. Several c-Met inhibitors have advanced to the clinic; however, the development of inhibitory c-Met-directed therapeutic antibodies has been hampered by inherent agonistic activity.

Method

We generated and tested a bivalent anti-c-Met monoclonal antibody ABT-700 in vitro for binding potency and antagonistic activity and in vivo for antitumor efficacy in human tumor xenografts. Human cancer cell lines and gastric cancer tissue microarrays were examined for MET amplification by fluorescence in situ hybridization (FISH).

Results

ABT-700 exhibits a distinctive ability to block both HGF-independent constitutive c-Met signaling and HGF-dependent activation of c-Met. Cancer cells addicted to the constitutively activated c-Met signaling driven by MET amplification undergo apoptosis upon exposure to ABT-700. ABT-700 induces tumor regression and tumor growth delay in preclinical tumor models of gastric and lung cancers harboring amplified MET. ABT-700 in combination with chemotherapeutics also shows additive antitumor effect. Amplification of MET in human cancer tissues can be identified by FISH.

Conclusions

The preclinical attributes of ABT-700 in blocking c-Met signaling, inducing apoptosis and suppressing tumor growth in cancers with amplified MET provide rationale for examining its potential clinical utility for the treatment of cancers harboring MET amplification.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2138-z) contains supplementary material, which is available to authorized users.

Targeting the MET Pathway in Gastric and Oesophageal Cancers: Refining the Optimal Approach

Gastric and oesophageal cancers are a major cause of global cancer-related morbidity and mortality. Improvements in treatment for locoregional and metastatic gastric and oesophageal cancer have been incremental and the overall prognosis remains poor. Increasingly, molecular classification has identified recurrent, therapeutically relevant, somatic alterations in gastroesophageal malignancies. However, other than ERBB2 amplification, molecularly directed therapies have not translated to improved survival. Amplification of the receptor tyrosine kinase MET is found in about 5% of gastroesophageal cancers and represents an oncogenic driver and therapeutic target. Small series have shown activity of MET-directed tyrosine kinase inhibitors, but the clinical benefit of anti-MET antibodies has been disappointing. Here we discuss the MET pathway in gastroesophageal cancers, the clinical data for MET small molecule tyrosine kinase inhibitors, anti-MET antibodies and future clinical directions for targeting MET in gastric and oesophageal cancers. To our knowledge, this is the most comprehensive review of the clinical experience with MET-directed therapies in gastric and oesophageal cancers.

Novel c-Met inhibitor suppresses the growth of c-Met-addicted gastric cancer cells

BACKGROUND

c-Met signaling has been implicated in oncogenesis especially in cells with c-met gene amplification. Since 20 % of gastric cancer patients show high level of c-Met expression, c-Met has been identified as a good candidate for targeted therapy in gastric cancer. Herein, we report our newly synthesized c-Met inhibitor by showing its efficacy both in vitro and in vivo.

METHODS

Compounds with both triazolopyrazine and pyridoxazine scaffolds were synthesized and tested using HTRF c-Met kinase assay. We performed cytotoxic assay, cellular phosphorylation assay, and cell cycle assay to investigate the cellular inhibitory mechanism of our compounds. We also conducted mouse xenograft assay to see efficacy in vivo.

RESULTS

KRC-00509 and KRC-00715 were selected as excellent c-Met inhibitors through biochemical assay, and exhibited to be exclusively selective to c-Met by kinase panel assay. Cytotoxic assays using 18 gastric cancer cell lines showed our c-Met inhibitors suppressed specifically the growth of c-Met overexpressed cell lines, not that of c-Met low expressed cell lines, by inducing G1/S arrest. In c-met amplified cell lines, c-Met inhibitors reduced the downstream signals including Akt and Erk as well as c-Met activity. In vivo Hs746T xenograft assay showed KRC-00715 reduced the tumor size significantly.

CONCLUSIONS

Our in vitro and in vivo data suggest KRC-00715 is a potent and highly selective c-Met inhibitor which may have therapeutic potential in gastric tumor with c-Met overexpression.

Resistance to the c-Met inhibitor KRC-108 induces the epithelial transition of gastric cancer cells

Investigation of the mechanisms of resistance to targeted therapies is essential as resistance acquired during treatment may lead to relapse or refractoriness to the therapy. Our previous study identified the small molecule KRC-108 as a result of efforts to find an anticancer agent with c-Met-inhibitory activity. In the present study, the changes accompanying resistance to KRC-108 were investigated in the gastric cancer cell line MKN-45 and its KRC-108-resistant clones by western blot and immunofluorescence analyses. Increased expression of the c-Met protein was observed in KRC-108-resistant cells compared with that of the parental cells, and the phosphorylation of c-Met also increased in cell lines resistant to KRC-108. Resistance to the c-Met inhibitor was associated with cell morphological changes: MKN-45 parental cells, which had a round and poorly differentiated morphology, were altered to exhibit an epithelial cell-like phenotype in KRC-108-resistant clones. Consistent with the transition to an epithelial morphology, the expression of E-cadherin was increased in resistant cells. Using immunoprecipitation, an interaction between E-cadherin and the c-Met protein was observed in the KRC-108-resistant cells. Immunohistochemical analysis of human gastric carcinoma tissues revealed the co-expression of E-cadherin and c-Met. These results suggest that the epithelial transition in KRC-108-resistant cells is mediated by recruiting E-cadherin to c-Met protein. Thus, the present study identified a mechanism used by cancer cells to confer resistance to anticancer agents.

Emerging kinase inhibitors of the treatment of gastric cancer

INTRODUCTION

Gastric cancer (GC) is the fifth most common malignancy in the world. In the last years, for the first time in literature, the addition of a targeted therapy to standard chemotherapy has proved to prolong median overall survival. In this scenario, kinase inhibitors (KIs), smaller intracellular agents, could be an interesting and novel type of targeted treatment of metastatic GC both in first and further lines of therapy.

AREAS COVERED

Several KI have been evaluated in the preclinical setting. This review will underline the most relevant targeted pathways involved in GC tumorigenesis and disease progression including EGFR, VEGFR, c-MET, mTOR, fibroblast growth factor receptor, Src and Aurora kinases.

EXPERT OPINION

Despite the good results of TOGA, RAINBOW and REGARD trials about the addition of monoclonal antibodies to standard of care in GC, the addition of KI seems not to achieve comparable interesting results in management of GC. However, an improved patient selection before and during treatment according to molecular characteristics, as well as combination studies evaluating the synergistic effect of combination schedules of different KIs and standard chemotherapy, or KI plus KI or KI plus antibodies-based therapy may reveal interesting results and lead to understand mechanisms of multi-drug resistance.