MET in gastric carcinomas: comparison between protein expression and gene copy number and impact on clinical outcome

Urolithins' interaction with hepatocyte growth factor receptor: a mechanistic basis for anticancer activity in gastric adenocarcinoma cells

Gastric adenocarcinoma (GAC) ranks among the most common cancers worldwide. Hepatocyte growth factor receptor, also known as MET, plays crucial roles in GAC progression. Present study aimed to investigate whether urolithin A (UA), urolithin B (UB) and methyl UA (mUA) could induce anticancer effects on GAC cells via targeting MET. For computational analysis, potential molecular targets of urolithins and pathogenic targets of GAC were identified, PPI network was constructed, enrichment analyses were carried out and the expression of MET was assessed in MKN-45 cells. Additionally, pharmacokinetic and druglikeness of urolithins were evaluated, and molecular docking and dynamics simulations were performed. For in vitro analysis, urolithins were synthesized and viability of MKN-45, MG-63 and HFF-3 cells was investigated by alamarBlue assay, followed by apoptosis detection. MET was identified as one of the seven top hub genes for GAC and urolithins, and GO and KEGG enrichment analyses confirmed its involvement in several biological processes and pathways. Volcano plot revealed MET overexpression in MKN-45 cells. Web-based analyses revealed favorable lipophilicity, reasonable water solubility, intestinal absorption, moderate distribution and no significant toxicity concerns for urolithins. Viability assay indicated dose- and cell type-dependent cytotoxicity of urolithins, as the lowest IC50 values belonged to MKN-45 cells, which was confirmed by flow cytometry analysis. Molecular docking demonstrated favorable interactions between UA and UB within the active site of MET. Additionally, molecular dynamics simulations indicated both conformational flexibility and binding stability of UA-MET complex. Our comprehensive study suggests a potential mechanism for anticancer effects of urolithins through interaction with MET in GAC cells.

Helicobacter pylori reduces METTL14-mediated VAMP3 m6A modification and promotes the development of gastric cancer by regulating LC3C-mediated c-Met recycling

Helicobacter pylori (H. pylori) plays an important role in the malignant transformation of the gastric mucosa from chronic inflammation to cancer. However, the mechanisms underlying the epigenetic regulation of gastric carcinogenesis mediated by H. pylori remain unclear. Here, we uncover that H. pylori inhibits METTL14 by upregulating ATF3. METTL14 inhibits gastric cancer (GC) cell proliferation and metastasis in vitro and in vivo. Downregulation of METTL14 inhibits Vesicle-associated membrane protein-3 (VAMP3) by reducing the m6A modification level of VAMP3 mRNA and the stability of IGF2BP2-dependent mRNA. H. pylori also accelerates the malignant progression of GC by regulating VAMP3/LC3C-mediated c-Met recycling. Moreover, the expression of METTL14 and VAMP3 in Hp+ chronic gastritis tissues is much lower than that in Hp- chronic gastritis tissues. METTL14 and VAMP3 expression levels are downregulated notably in cancerous tissues of patients with GC. Therefore, our results show a novel METTL14-VAMP3-LC3C-c-Met signalling axis in the GC development mediated by H. pylori infection, which reveals a novel m6A epigenetic modification mechanism for GC and provides potential prognostic biomarkers for GC progression.

Claudin 1, 4, 6 and 18 isoform 2 as targets for the treatment of cancer (Review)

The 24 claudin (CLDN) genes in the human genome encode 26 representative CLDN family proteins. CLDNs are tetraspan‑transmembrane proteins at tight junctions. Because several CLDN isoforms, such as CLDN6 and CLDN18.2, are specifically upregulated in human cancer, CLDN‑targeting monoclonal antibodies (mAbs), antibody‑drug conjugates (ADCs), bispecific antibodies (bsAbs) and chimeric antigen receptor (CAR) T cells have been developed. In the present review, CLDN1‑, 4‑, 6‑ and 18.2‑targeting investigational drugs in clinical trials are discussed. CLDN18.2‑directed therapy for patients with gastric and other types of cancer is the most advanced area in this field. The mouse/human chimeric anti‑CLDN18.2 mAb zolbetuximab has a single‑agent objective response rate (ORR) of 9%, and increases progression‑free and overall survival in combination with chemotherapy. The human/humanized anti‑CLDN18.2 mAb osemitamab, and ADCs AZD0901, IBI343 and LM‑302, with single‑agent ORRs of 28‑60%, have been tested in phase III clinical trials. In addition, bsAbs, CAR T cells and their derivatives targeting CLDN4, 6 or 18.2 are in phase I and/or II clinical trials. AZD0901, IBI343, zolbetuximab and the anti‑CLDN1 mAb ALE.C04 have been granted fast track designation or priority review designation by the US Food and Drug Administration.

Progress of antibody-drug conjugates (ADCs) targeting c-Met in cancer therapy; insights from clinical and preclinical studies

The cell-surface receptor tyrosine kinase c-mesenchymal-epithelial transition factor (c-Met) is overexpressed in a wide range of solid tumors, making it an appropriate target antigen for the development of anticancer therapeutics. Various antitumor c-Met-targeting therapies (including monoclonal antibodies [mAbs] and tyrosine kinases) have been developed for the treatment of c-Met-overexpressing tumors, most of which have so far failed to enter the clinic because of their efficacy and complications. Antibody-drug conjugates (ADCs), a new emerging class of cancer therapeutic agents that harness the target specificity of mAbs to deliver highly potent small molecules to the tumor with the minimal damage to normal cells, could be an attractive therapeutic approach to circumvent these limitations in patients with c-Met-overexpressing tumors. Of great note, there are currently nine c-Met-targeting ADCs being examined in different phases of clinical studies as well as eight preclinical studies for treating various solid tumors. The purpose of this study is to present a broad overview of clinical- and preclinical-stage c-Met-targeting ADCs.

Targeting the MET gene: unveiling therapeutic opportunities in immunotherapy within the tumor immune microenvironment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC) represents the most prevalent histological subtype of lung cancer. Within this disease, the MET gene emerges as a critical therapeutic target, exhibiting various forms of dysregulation. Although MET tyrosine kinase inhibitors, HGF/c-MET targeting antibodies, and antibody-drug conjugates constitute the primary treatment modalities for patients with MET-altered NSCLC, numerous questions remain regarding their optimal application. The advent of immunotherapy holds promise for enhancing therapeutic outcomes in patients with MET-altered NSCLC. MET mutations can reshape the tumor immune microenvironment of NSCLC by reducing tumor immunogenicity, inducing exhaustion in immune-activated cells, and promoting immune evasion, which are crucial for modulating treatment responses. Furthermore, we emphasize the promising synergy of immunotherapy with emerging treatments and the challenges and opportunities in refining these approaches to improve patient outcomes.

A phase II study of cabozantinib and pembrolizumab in advanced gastric/gastroesophageal adenocarcinomas resistant or refractory to immune checkpoint inhibitors

BACKGROUND

Most patients with metastatic gastroesophageal adenocarcinoma (mGEA) progress on immune checkpoint inhibitors (ICIs). Novel approaches to overcome resistance to ICI in mGEA are needed. Cabozantinib is a multi-tyrosine kinase inhibitor thought to enhance the immunomodulatory effects of ICI. This study evaluated the combination of cabozantinib and pembrolizumab in ICI refractory or resistant mGEA.

METHODS

Investigator-initiated, single-arm, single institution, and phase II study in patients with mGEA. Patients had progressed on ICI and/or had PD-L1 CPS score ≤10%. Cabozantinib dose was 40 mg p.o. daily on days 1-21 of a 21-day cycle, with pembrolizumab 200 mg i.v. on day 1. The primary endpoint was progression-free survival at 6 months (PFS-6).

RESULTS

Twenty-seven patients were enrolled. Median age 58 years (24-87), female (n = 14), ECOG 0/1 = 13/14, GC/GEJ = 16/11, and non-Hispanic White/Hispanic/Asian = 12/8/7. The primary endpoint was met. After a median follow-up of 31.4 months (range 3.3-42.5), PFS-6 was 22.2% (95% CI 9.0-39.0). The median PFS and OS are 2.3 months (95% CI 1.7-4.1) and 5.5 months (3.1-14.0), respectively. The most common mutations were TP53 (78.3%) and CDH1/PIK3CA/CTNNB1 (17.4% each). The most common grade (G) treatment-related adverse events (TRAE) were diarrhea (25.9%), fatigue (18.5%), hypertension, and muscle cramps (14.8% each). G3-4 TRAE were seen in n = 3 patients (hypertension, thromboembolic event, esophageal perforation; each n = 1). No G5 was observed.

CONCLUSIONS

The addition of cabozantinib to pembrolizumab shows clinical benefit in ICI-resistant or refractory mGEA with a tolerable safety profile. (ClinicalTrials.gov Identifier: NCT04164979. IRB Approved: UCI 18-124, University of California Irvine IRB#20195426.).

Advances in MET tyrosine kinase inhibitors in gastric cancer

Gastric cancer is among the most frequently occurring cancers and a leading cause of cancer-related deaths globally. Because gastric cancer is highly heterogenous and comprised of different subtypes with distinct molecular and clinical characteristics, the management of gastric cancer calls for better-defined, biomarker-guided, molecular-based treatment strategies. MET is a receptor tyrosine kinase mediating important physiologic processes, such as embryogenesis, tissue regeneration, and wound healing. However, mounting evidence suggests that aberrant MET pathway activation contributes to tumour proliferation and metastasis in multiple cancer types, including gastric cancer, and is associated with poor patient outcomes. As such, MET-targeting therapies are being actively developed and promising progress has been demonstrated, especially with MET tyrosine kinase inhibitors. This review aims to briefly introduce the role of MET alterations in gastric cancer and summarize in detail the current progress of MET tyrosine kinase inhibitors in this disease area with a focus on savolitinib, tepotinib, capmatinib, and crizotinib. Building on current knowledge, this review further discusses existing challenges in MET alterations testing, possible resistance mechanisms to MET inhibitors, and future directions of MET-targeting therapies.

MET alterations detection platforms and clinical implications in solid tumors: a comprehensive review of literature

MET alterations, including MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion, play pivotal roles in primary tumorigenesis and acquired resistance to targeted therapies, especially EGFR tyrosine kinase inhibitors. They represent important diagnostic, prognostic, and predictive biomarkers in many solid tumor types. However, the detection of MET alterations is challenging due to the complexity of MET alterations and the diversity of platform technologies. Therefore, techniques with high sensitivity, specificity, and reliable molecular detection accuracy are needed to overcome such hindrances and aid in biomarker-guided therapies. The current review emphasizes the role of MET alterations as oncogenic drivers in a variety of cancers and their involvement in the development of resistance to targeted therapies. Moreover, our review provides an overview of and recommendations on the selection of various cross-platform technologies for the detection of MET exon 14 skipping variants, MET amplification, MET overexpression, and MET fusion. Furthermore, challenges and hurdles underlying these common detection platforms are discussed.

Early-onset gasrtric cancer (review)

Objective. Early-onset gastric cancer (EOGC) constitutes a serious medical and social problem. Early-onset gastric cancer accounts for approximately 6% of all malignant epithelial neoplasms.

Material and Methods. We reviewed retrospective and prospective randomized trials using Medline and Elibrary databases.

Results. The applied significance of the molecular genetic classifications consist in the formation of groups for evaluating prognosis of the disease using multifactorial analysis. This classification indicates that EOGC diagnosed at a locally advanced stage and primary dissemination is most often caused by GS (TCGA) and MSS/EMT(ACRG) subtypes and is characterized by mutations in CDH1, RhoA, CLDN18-ARHGAP genes. These changes are accompanied by the prevalence of diffuse histological type of gastric cancer according to the Lauren classification and ulcerated or infiltrative type according to the Borrmann classification (type III and IV) with the presence of high-grade adenocarcinoma with a signet ring cell component.

Conclusion. Considering the aggressiveness of gastric cancer in young patients, who more frequently present with locally advanced and metastatic disease at the time of diagnosis, there is a need for increased cancer alertness among physicians of other specialties, early endoscopic controls to detect cancer at early stages and benefit from both surgical and multimodal treatment.

Targeted therapy for multiple gene mutations in multiple metastases of advanced gastric cancer: a case report

In China, gastric cancer is the second most common cause of cancer-related death, after lung cancer. At present, the morbidity and mortality rates of gastric cancer are increasing, and targeted therapy for gastric cancer has become a research hotspot. Herein, we report a patient with multiple metastases from advanced gastric cancer. After identifying MET gene amplification, initial treatment induced regression of the tumor. However, in later stages, due to the overexpression or mutation of HER-2, KRAS, TP53, and other genes, the targeted drug therapy became ineffective, and the disease progressed rapidly, leading to the death of the patient.

Nanoparticles targeting Sialyl-Tn for efficient tyrosine kinase inhibitor delivery in gastric cancer

Gastric cancer (GC) is the fourth leading cause of cancer-related deaths worldwide and, therefore, it is urgent to develop new and more efficient therapeutic approaches. Foretinib (FRT) is an oral multikinase inhibitor targeting MET (hepatocyte growth factor receptor) and RON (recepteur d'origine nantais) receptor tyrosine kinases (RTKs) that has been used in clinical trials for several solid tumors. Targeted uptake of therapeutic polymeric nanoparticles (NPs) represents a powerful approach in cancer cell drug delivery. Previously, a nanodelivery system composed of polymeric NPs functionalized with B72.3 antibody, which targets the tumor-associated antigen Sialyl-Tn (STn), has been developed. Herein, these NPs were loaded with FRT to evaluate its capacity in delivering the drug to multicellular tumors spheroids (MCTS) and mouse models. The data indicated that B72.3 functionalized FRT-loaded PLGA-PEG-COOH NPs (NFB72.3) specifically target gastric MCTS expressing the STn glycan (MKN45 SimpleCell (SC) cells), leading to a decrease in phospho-RTKs activation and reduced cell viability. In vivo evaluation using MKN45 SC xenograft mice revealed that NFB72.3 were able to decrease tumor growth, reduce cell proliferation and tumor necrosis. NFB72.3-treated tumors also showed inactivation of phospho-MET and phospho-RON. This study demonstrates the value of using NPs targeting STn for FRT delivery, highlighting its potential as a therapeutic application in GC. STATEMENT OF SIGNIFICANCE: Despite the advances in gastric cancer therapeutics, it remains one of the diseases with the highest incidence and mortality in the world. Combining targeted therapies with a controlled drug release is an attractive strategy to reduce drug cytotoxic effects and improve specific drug delivery efficiency to the cancer cells. Thus, we developed nanoparticles loaded with a tyrosine kinase inhibitor and targeting a specific tumor glycan exclusive of cancer cells. In in vivo gastric cancer xenograft mice models, these nanoparticles efficiently reduced tumor growth, cell proliferation and tumor necrosis area and inactivated phosphorylation of targeting receptors. This approach represents an innovative therapeutic strategy with high impact in gastric cancer.

An Overview of Current Biomarkers, the Therapeutic Implications, and the Emerging Role of hERG1 Expression in Gastric Cancer: A Literature Review

Gastric cancer remains one of the most commonly diagnosed cancers in the world. It carries a high mortality rate, with cases being more prevalent in the developing world, and has been linked to diet and Helicobacter pylori infection. It is a highly heterogeneous disease, with most cases being of a sporadic nature. Most patients present at an advanced stage due to the asymptomatic nature of the early stages of the disease. A multidisciplinary approach is often best implemented to help decide how to best manage individual cases. However, the overall clinical outcome and survival of patients with advanced gastric cancer remain poor. Recent therapeutic advancements focus on the identification of molecular biomarkers associated with gastric cancer that have predictive, diagnostic, and prognostic implications. This enables the development of specific targeted therapies that have shown efficacy in numerous trials, either as monotherapy or in combination with standard chemotherapy. Despite this, tumour heterogeneity and treatment resistance are still issues leading to poor survival outcomes. An emerging approach is focusing efforts on the bidirectional crosstalk between tumour cells and the microenvironment through targeting ion channels. A key player in this is human ether-á-go-go-related gene 1 (hERG1). This voltage-gated potassium ion channel has been shown to have predictive, diagnostic, and prognostic significance, enabling the stratification of high-risk individuals. In addition, targeting hERG1 in combination with chemotherapy has been shown to potentiate tumour regression. This comprehensive literature review will aim to consolidate our understanding of current biomarkers in gastric cancer. The relevance of hERG1 in gastric cancer as a useful novel biomarker and the potential therapeutic implications as targeted therapy will be explored. This offers a new and personalised approach to helping to manage patients with gastric cancer.

α-Fetoprotein contributes to the malignant biological properties of AFP-producing gastric cancer

This study aimed to investigate whether α-fetoprotein (AFP) could affect the malignant behavior of AFP-producing gastric cancer (AFP-GC) and to explore the relationship between AFP and mesenchymal-epithelial transition factor (c-Met) in AFP-GC. In this study, 23 patients with AFP-GC (AFP[+]) and 18 patients with common gastric cancer (AFP[-]) were evaluated for the c-Met expression using immunohistochemical analysis. The AFP-GC cell line, GCIY, was used. The AFP endoribonuclease-prepared small interfering RNA (siRNA) and eukaryotic AFP overexpression vector were used to increase/knockdown the expression of AFP. Afterward, the c-Met expression was evaluated by polymerase chain reaction and western blot. The proliferation, migration, and invasion of GCIY cells were estimated before and after the AFP overexpression/knockdown. The c-Met expression in both groups was the same (p > 0.05), and AFP[+] group had a higher positive incidence of the c-Met expression than the AFP[-] group (p < 0.01). Furthermore, the c-Met expression frequency was decreased by AFP knockdown and increased by AFP overexpression (p < 0.01). The cell counting kit-8 cell proliferation assay, cell invasion, and migration assays confirmed that the AFP could affect the malignant biological behavior of AFP-GC. These findings suggest that AFP contributes to the malignant biological properties of AFP-GC and the high expression of c-Met in AFP-GC.

Molecular characterization of MET fusions from a large real-world Chinese population: A multicenter study

PURPOSE

MET is a notable driver gene in the diversity of aberrations with clinical relevance, including exon 14 skipping, copy number gain, point mutations, and gene fusions. Compared with the former two, MET fusions are severely under-reported, leaving a series of unanswered questions. In this study, we addressed this gap by characterizing MET fusions in a large, real-world Chinese cancer population.

METHODS

We retrospectively included patients with solid tumors who had DNA-based genome profiles acquired through targeted sequencing from August 2015 to May 2021. MET fusion-positive (MET+) patients were subsequently selected for clinical and molecular characterization.

RESULTS

We screened 79,803 patients across 27 tumor types and detected 155 putative MET fusions from 122 patients, resulting in an overall prevalence of 0.15%. Lung cancer comprised the majority of MET+ patients (92, 75.4%). Prevalence was markedly higher in liver cancer, biliary tract cancer, and renal cancer (range 0.52%-0.60%). It was lower in ovarian cancer (0.06%). A substantial proportion (48/58, 82.8%) of unique partners were reported for the first time. High heterogeneity was observed for partners, with ST7, HLA-DRB1, and KIF5B as the three most common partners. Mutational landscape analysis of lung adenocarcinoma (n = 32) revealed a high prevalence of TP53 in MET+ alterations, EGFR L858R, EGFR L861Q, and MET amplification.

CONCLUSION

To our knowledge, this is currently the largest study in characterizing MET fusions. Our findings warrant that further clinical validation and mechanistic study may translate into therapeutic avenues for MET+ cancer patients.

Overview of Molecular Detection Technologies for MET in Lung Cancer

MET tyrosine kinase receptor pathway activation has become an important actionable target in solid tumors. Aberrations in the MET proto-oncogene, including MET overexpression, the activation of MET mutations, MET mutations that lead to MET exon 14 skipping, MET gene amplifications, and MET fusions, are known to be primary and secondary oncogenic drivers in cancer; these aberrations have evolved as predictive biomarkers in clinical diagnostics. Thus, the detection of all known MET aberrations in daily clinical care is essential. In this review, current molecular technologies for the detection of the different MET aberrations are highlighted, including the benefits and drawbacks. In the future, another focus will be on the standardization of detection technologies for the delivery of reliable, quick, and affordable tests in clinical molecular diagnostics.

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).

Crizotinib-based proteolysis targeting chimera suppresses gastric cancer by promoting MET degradation

As one of the common malignant cancer types, gastric cancer (GC) is known for late-stage diagnosis and poor prognosis. Overexpression of the receptor tyrosine kinase MET is associated with poor prognosis among patients with advanced stage GC. However, no MET inhibitor has been used for GC treatment. Like other tyrosine kinase inhibitors that fit the "occupancy-driven" model, current MET inhibitors are prone to acquired resistance. The emerging proteolysis targeting chimera (PROTAC) strategy could overcome such limitations through direct degradation of the target proteins. In this study, we successfully transformed the MET-targeted inhibitor crizotinib into a series of PROTACs, recruiting cereblon/cullin 4A E3 ubiquitin ligase to degrade the MET proteins. The optimized lead PROTAC (PRO-6 E) effectively eliminated MET proteins in vitro and in vivo, inhibiting proliferation and motility of MET-positive GC cells. In the MKN-45 xenograft model, PRO-6 E showed pronounced antitumor efficacy with a well-tolerated dosage regimen. These results validated PRO-6 E as the first oral PROTAC for MET-dependent GC.

MET Amplification as a Resistance Driver to TKI Therapies in Lung Cancer: Clinical Challenges and Opportunities

Targeted therapy has emerged as an important pillar for the standard of care in oncogene-driven non-small cell lung cancer (NSCLC), which significantly improved outcomes of patients whose tumors harbor oncogenic driver mutations. However, tumors eventually develop resistance to targeted drugs, and mechanisms of resistance can be diverse. MET amplification has been proven to be a driver of resistance to tyrosine kinase inhibitor (TKI)-treated advanced NSCLC with its activation of EGFR, ALK, RET, and ROS-1 alterations. The combined therapy of MET-TKIs and EGFR-TKIs has shown outstanding clinical efficacy in EGFR-mutated NSCLC with secondary MET amplification-mediated resistance in a series of clinical trials. In this review, we aimed to clarify the underlying mechanisms of MET amplification-mediated resistance to tyrosine kinase inhibitors, discuss the ways and challenges in the detection and diagnosis of MET amplifications in patients with metastatic NSCLC, and summarize the recently published clinical data as well as ongoing trials of new combination strategies to overcome MET amplification-mediated TKI resistance.

MET gene alterations predict poor survival following chemotherapy in patients with advanced cancer

Background: To aid in oncology drug development, we investigated MET proto-oncogene receptor tyrosine kinase gene aberrations in 2,239 oncology patients who underwent next-generation sequencing (NGS) in clinical practice. Materials and methods: From November 2019 to January 2021, 2,239 patientswith advanced solid tumors who visited oncology clinics underwent NGS. The NGS panel included >500 comprehensive NGS tests using archival tissue specimens. Programmed death-ligand 1(PD-L1) 22C3 assay results and clinical records regarding initial chemotherapy were available for 1,137 (50.8%) and 1,761 (78.7%) patients, respectively for overall survival (OS) analysis. Results: The 2,239 patients represented 37 types of cancer. The NGS panel included >500 genes, microsatellite instability status, tumor mutational burden, and fusions. The most common cancer types were colorectal (N = 702), gastric (N = 481), and sarcoma (N = 180). MET aberrations were detected in 212 patients. All MET-amplified tumors had microsatellite stable status, and 8 had a high tumor mutational burden. Of 46 patients with MET-amplified cancers, 8 had MET-positive protein expression by immunohistochemistry (2+ and 3+). MET fusion was detected in 10 patients. Partner genes of MET fusion included ST7, TFEC, LRRD1, CFTR, CAV1, PCM1, HLA-DRB1, and CAPZA2. In survival analysis, patients with amplification of MET gene fusion had shorter OS and progression-free survival (PFS) than those without. Thus, MET aberration was determined to be a factor of response to chemotherapy. Conclusion: Approximately 2.1% and 0.4% of patients with advanced solid tumors demonstrated MET gene amplification and fusion, respectively, and displayed a worse response to chemotherapy and significantly shorter OS and PFS than those without MET gene amplification or fusion.

Bioinformatically Expanded Next-Generation Sequencing Analysis Optimizes Identification of Therapeutically Relevant MET Copy Number Alterations in >50,000 Tumors

PURPOSE

Clinical relevance thresholds and laboratory methods are poorly defined for MET amplification, a targetable biomarker across malignancies.

EXPERIMENTAL DESIGN

The utility of next-generation sequencing (NGS) in assessing MET copy number alterations was determined in >50,000 solid tumors. Using fluorescence in situ hybridization as reference, we validated and optimized NGS analysis.

RESULTS

Incorporating read-depth and focality analyses achieved 91% concordance, 97% sensitivity, and 89% specificity. Tumor heterogeneity, neoplastic cell proportions, and genomic focality affected MET amplification assessment. NGS methodology showed superiority in capturing overall amplification status in heterogeneous tumors and defining amplification focality among other genomic alterations. MET copy gains and amplifications were found in 408 samples across 23 malignancies. Total MET copy number inversely correlated with amplified segment size. High-level/focal amplification was enriched in certain genomic subgroups and associated with targeted therapy response.

CONCLUSIONS

Leveraging our integrated bioinformatic approach, targeted therapy benefit was observed across diverse MET amplification contexts.

[Research Progress of Acquired Resistance Mediated by MET Amplification in Advanced Non-small Cell Lung Cancer]

Mesenchymal-epithelial transition factor (MET) amplification is an important driver of resistance in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC), and the combination of MET proto-oncogene (MET) and EGFR-tyrosine kinase inhibitors (TKIs) has shown promise in overcoming this molecularly defined acquired resistance. Emerging data also demonstrate MET amplification as a resistance driver to TKIs-treated anaplastic lymphoma kinase (ALK)-, RET-, and ROS1-fusion NSCLC. Here, we review the literature on recent research progress of MET amplification as a resistance driver to targeted therapy in oncogene-driven NSCLC and summarize the progress of clinical strategies to overcome the resistance mechanism.
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Targeting MET amplification in Gastro-oesophageal (GO) malignancies and overcoming MET inhibitor resistance: challenges and opportunities

INTRODUCTION

MET, the hepatocyte growth factor receptor is amplified in 8% of gastroesophageal (GO) malignancies and associated with poor prognosis. Therapeutic targeting of MET amplification and MET mutations has the potential to improve outcomes for patients with GO cancers (GOC).

AREAS COVERED

The efficacy of MET inhibition (METi) in preclinical studies has yet to translate into meaningful improvements in the treatment paradigm for unselected GOC. MET amplification has been proposed as a superior modality for patient selection; however even if confirmed, frequency and duration of response to METi are limited by rapid activation of primary and secondary resistance pathways. These observations illustrate the challenges inherent in the application of precision oncology predicated on the theory of oncogenic addiction.

EXPERT OPINION

A standardized definition of MET positivity is critical to enhance patient selection. Early successes targeting the METex14 skipping mutation demonstrate the potent therapeutic effects of METi in a clearly molecularly defined cohort. There is robust preclinical rationale and early-phase data supporting exploitation of immune system interaction with MET. Pragmatic investigation of rational therapeutic combinations based on molecular profiling of both primary and metastatic disease sites with sequential circulating tumor DNA analysis can inform successful clinical development of METi agents in GOC.

Case Report: Prompt Response to Savolitinib in a Case of Advanced Gastric Cancer With Bone Marrow Invasion and MET Abnormalities

Gastric cancer is one of the most common malignant tumors and patients show a short survival, those combined with bone marrow invasion have a median survival of only 37 days. Here we reported the treatment of a 47-year-old male with advanced gastric cancer and complicated with bone marrow invasion and extensive metastases, who did not tolerate chemotherapy, under monotherapy with savolitinib, a MET receptor tyrosine kinase inhibitor. Before treatment, the patient was in severe pain and presented with thrombocytopenia and hemorrhagic anemia. Savolitinib was given based on amplification and rearrangement of the MET gene in his tumor. After savolitinib treatment, the patient’s condition promptly improved, efficacy evaluation indicated partial remission, and the patient was alive and remained progression-free at 15 weeks at the time of reporting. No obvious adverse reactions occurred. Besides, another case of a female gastric cancer patient with MET amplification who received savolitinib monotherapy as a third-line treatment that remained progression-free at 12 weeks was also reported. This report provides a new reference for understanding MET abnormalities in gastric cancer and offers a possibility for future application of MET tyrosine kinase inhibitors in the therapy of gastric cancer with MET abnormalities. Also, it suggests that sequencing of MET can be considered a routine target in advanced gastric cancer patients.

Gastric Cancer: Mechanisms, Biomarkers, and Therapeutic Approaches

Gastric cancer (GC) remains one of the most common deadly malignancies worldwide. Recently, several targeted therapeutics for treating unresectable or metastatic GC have been developed. Comprehensive characterization of the molecular profile and of the tumor immune microenvironment of GC has allowed researchers to explore promising biomarkers for GC treatment and has enabled a new paradigm in precision-targeted immunotherapy. In this article, we review established and promising new biomarkers relevant in GC, with a focus on their clinical implications, diagnostic methods, and the efficacy of targeted agents.

Alpha-fetoprotein can promote gastric cancer progression via upregulation of metastasis-associated colon cancer 1

High serum alpha-fetoprotein (AFP) level is a predictor of poor prognosis in patients with gastric cancer (GC). AFP-producing GC (AFP-GC) is an aggressive subtype of GC characterized by a high incidence of liver metastasis and high c-Met expression. High expression of metastasis-associated colon cancer 1 (MACC1), which is the transcription activator of c-Met, also predicts a poor prognosis of GC. c-Met is known to be involved in tumor progression into malignant invasive phenotypes. Considering that high c-Met expression is simultaneously positively correlated with high AFP and MACC1 expression levels and that high expression of AFP or MACC1 predicts poor prognosis in GC, we hypothesized that an interaction may exist between AFP and MACC1. In the present study, GC cell lines with AFP-overexpression, MACC1-downregulation and the combination of both transfections were used as experimental models. The relative mRNA and protein expression of c-Met, AFP and MACC1 were analyzed using reverse transcription quantitative PCR and western blotting, respectively. Cell viability was evaluated using Cell Counting Kit-8 assay. Cell invasion and cell migration were examined using Transwell migration assay with and without Matrigel, respectively. The results demonstrated that, compared with the control group, the mRNA and protein expression of MACC1was significantly elevated in the AFP-overexpressed group and in the group with AFP overexpressed and MACC1 downregulated. Furthermore, a significantly enhanced cell viability, migration and invasion were observed in the AFP-overexpressing group, whereas opposite effects were found in the MACC1-downregulating group. In summary, the results from this study indicated that AFP may promote GC progression by stimulating MACC1. This finding may help illustrating the aggressive behaviors of GC in patients with high AFP serum level and AFP-GC.

RhoA, Claudin 18, and c-MET in Gastric Cancer: Clinicopathological Characteristics and Prognostic Significance in Curative Resected Patients

Background: Recently, markers related to molecular classification were suggested as promising therapeutic targets for treatment and prediction of prognosis in gastric cancer (GC), including c-MET, RhoA, and Claudin-18 (CLDN18). This study aimed to investigate their expression in GC and its correlation with clinicopathological characteristics and survival. Methods: We retrospectively evaluated GC patients who underwent curative gastrectomy. c-MET, RhoA, and CLDN18 were analyzed through immunohistochemistry (IHC), and groups for analysis were determined according to the median values obtained for each marker. Results: Among the 349 GC evaluated, 180 (51.6%), 59 (16.9%), and 61 (17.5%) patients were completely negative for c-MET, RhoA, and CLDN18, respectively. Total gastrectomy, D1 lymphadenectomy, poorly differentiated histology, and greater inflammatory infiltrate were more frequent in the c-MET-negative group. Diffuse type, greater inflammatory infiltrate, and advanced pT and pTNM stage were associated with low-RhoA GC. The venous invasion was more frequent in the low-CLDN18 group. Furthermore, c-MET was positively correlated with RhoA and negatively with CLDN18. HER2 expression was associated with c-MET-positive and high-CLDN18 GC; and loss of E-cadherin expression in c-MET-negative and low-RhoA GC. c-MET-negative and Low-RhoA were significantly associated with worse disease-free survival. Conclusions: c-MET, RhoA, and CLD18 expression occurred frequently in GC. RhoA GC had distinct clinicopathological characteristics related to prognosis. c-MET and RhoA were associated with survival but were not independent predictors of prognosis.

Emerging biological drugs for the treatment of gastroesophageal adenocarcinoma

INTRODUCTION

Gastric cancer (GC) and gastroesophageal junction cancer (GOJC) patients have a poor prognosis with a 5-year relative survival rate of 6% in the metastatic setting. Despite the well-characterized molecular features, patients have been historically considered for treatment with universal and undistinguishing chemotherapies and targeted agents, except for the HER2-positive population and some immunological approaches.

AREAS COVERED

In this review, we discuss the intrinsic characteristics of GC/GOJC from an epidemiological, molecular, and clinical perspective with an exhaustive evaluation of the reported and ongoing phase II/III clinical trials with targeted therapies.

EXPERT OPINION

The absence of robust biomarkers, the difficulties in measuring it due to the well-recognized molecular heterogeneity, and in part nonoptimistic clinical trial designs have been a major cause of frequent failure. Current efforts should focus on proper recognition of the distinctive molecular and clinical features of each GC/GOJC patient. Sequencing both tumor tissue DNA and ctDNA could identify targetable alterations, including rare alterations, thus allowing GC/GOJC patients for a precision medicine benefit.

Molecular Targets for Gastric Cancer Treatment and Future Perspectives from a Clinical and Translational Point of View

Gastric cancer is a leading cause of cancer death worldwide. Systemic treatment comprising chemotherapy and targeted therapy is the standard of care in advanced/metastatic gastric cancer. Comprehensive molecular characterization of gastric adenocarcinomas by the TCGA Consortium and ACRG has resulted in the definition of distinct molecular subtypes. These efforts have in parallel built a basis for the development of novel molecularly stratified treatment approaches. Based on this molecular characterization, an increasing number of specific genomic alterations can potentially serve as treatment targets. Consequently, the development of promising compounds is ongoing. In this review, key molecular alterations in gastric and gastroesophageal junction cancers will be addressed. Finally, the current status of the translation of targeted therapy towards clinical applications will be reviewed.

The Significance of MET Expression and Strategies of Targeting MET Treatment in Advanced Gastric Cancer

Background

Accurate assessment of predictive biomarker expression is critical in patient selection in clinical trials or clinical practice. However, changes in biomarker expression may occur after treatment. The aim of the present study was to evaluate the effects of chemotherapy on MET expression in gastric cancer (GC).

Methods

MET expression was examined immunohistochemically before and after treatment in 122 patients with unresectable or recurrent GC, and was evaluated according to H-score or the scoring criteria used in the MetMAb trial. MET gene amplification was assessed by chromogenic in situ hybridization (CISH). The antitumor effect of MET targeted therapy was investigated in human gastric cancer cells in vitro and in vivo, and the underlying molecular mechanisms were analyzed by western blot.

Results

MET expression was associated with Lauren classification as well as tumor differentiation by either scoring system. MET amplification was not associated with clinical characteristics. Of the 71 patients who had paired pre- and post-treatment tumor tissues, 28 patients (39%) were initially positive for MET expression, and 43 (61%) were negative. Twenty-five patients (35%) showed significant changes in MET expression after treatment (P=0.007). Additionally, there was a concomitant overexpression of MET and HER2 in a subset of GC patients. MET inhibitor volitinib could significantly inhibit cell proliferation and xenograft growth in vitro and in vivo in MKN45 cells with MET and phosphorylated MET (pMET) high expressions via suppressing downstream PI3K/Akt and MAPK signaling pathways. Furthermore, combination therapy targeting both MET and HER2 demonstrated a synergistic antitumor activity.

Conclusions

MET expression is altered post chemotherapy and MET status should be evaluated in real-time. Both MET and pMET expressions might need to be considered for patients suitable for volitinib treatment.

ATM Expression as a Prognostic Marker in Patients With Advanced Biliary Tract Cancer Treated With First-line Gemcitabine and Platinum Chemotherapy

BACKGROUND/AIM

Biliary tract cancer (BTC) has a poor prognosis due to its highly invasive and metastatic potential. Ataxia-telangiectasia mutated (ATM) is a key regulator of DNA damage response and an emerging therapeutic target; however, the association between the expression of ATM and the prognosis in advanced BTC is unknown. We aimed to identify the relationship between ATM expression, clinicopathological characteristics, and survival outcomes in patients with advanced BTC.

PATIENTS AND METHODS

We analyzed 113 patients with advanced BTC who received first-line gemcitabine and platinum.

RESULTS

The tumor location was intrahepatic cholangiocarcinoma (IH-CCC) in 43 patients, extrahepatic cholangiocarcinoma (EH-CCC) in 49, and gallbladder (GB) cancer in 21 patients. Fifty-four patients (47.8%) exhibited loss of ATM protein expression. The overall response rate (ORR) of ATM loss and intact ATM was 13.3% and 19.6%, respectively. In a subgroup analysis, EH-CCC patients with ATM loss tended to have improved PFS after platinum-based chemotherapy compared to those with intact ATM (7.9 vs. 6.2 months, respectively; p=0.050).

CONCLUSION

We demonstrated that ATM loss could be a prognostic marker after platinum-based chemotherapy in patients with advanced EH-CCC.

MET alterations and their impact on the future of non-small cell lung cancer (NSCLC) targeted therapies

Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.

C1GALT1 in health and disease

O-linked glycosylation (O-glycosylation) and N-linked glycosylation (N-glycosylation) are the two most important forms of protein glycosylation, which is an important post-translational modification. The regulation of protein function involves numerous mechanisms, among which protein glycosylation is one of the most important. Core 1 synthase glycoprotein-N-acetylgalactosamine 3-β-galactosyltransferase 1 (C1GALT1) serves an important role in the regulation of O-glycosylation and is an essential enzyme for synthesizing the core 1 structure of mucin-type O-glycans. Furthermore, C1GALT1 serves a vital role in a number of biological functions, such as angiogenesis, platelet production and kidney development. Impaired C1GALT1 expression activity has been associated with different types of human diseases, including inflammatory or immune-mediated diseases, and cancer. O-glycosylation exists in normal tissues, as well as in tumor tissues. Previous studies have revealed that changes in the level of glycosyltransferase in different types of cancer may be used as potential therapeutic targets. Currently, numerous studies have reported the dual role of C1GALT1 in tumors (carcinogenesis and cancer suppression). The present review reports the role of C1GALT1 in normal development and human diseases. Since the mechanism and regulation of C1GALT1 and O-glycosylation remain elusive, further studies are required to elucidate their effects on development and disease.

The Prognostic Significance of c-Met and p53 Immunohistochemical Expression in Gastric and Colorectal Carcinomas

BACKGROUND: Colorectal and gastric carcinomas are the most common and deadly gastrointestinal (GIT) malignancies. AIM: This study aimed to evaluate the expression of c-Met and p53 in gastric and colorectal carcinomas (CRCs) as well as colorectal adenomas using immunohistochemistry. MATERIALS AND METHODS: c-Met and p53 immunohistochemical expression was conducted on 66 cases of gastric adenocarcinomas and total of 60 colonic cases (36 CRCs and 24 colorectal adenomas). RESULTS: In this study, c-Met was positively expressed in 54.5% of gastric carcinomas and 50% of CRCs. In addition, p53 was positively expressed in 56.1% of gastric carcinomas and 72.2% of CRCs. Moreover, higher expression of both c-Met (p = 0.001) and p53 expression (p < 0.001) was reported in CRCs compared to colorectal adenomas. In the same context, c-Met and p53 expressions were positively correlated with intestinal type gastric adenocarcinoma (p < 0.001 and p = 0.03, respectively). Moreover, c-Met was correlated with non-mucinous adenocarcinomas (p = 0.008) and lower grades (p < 0.001) of gastric carcinomas. As regard survival analysis in gastric carcinomas, median overall survival (OS) was better in p53 positive patients (p = 0.05), patients with negative lymph node metastasis (p = 0.03), and patients with better response to neoadjuvant chemotherapy (p = 0.04). In contrast, c-Met did not exhibit significant correlation with OS (p > 0.05). Both c-Met and p53 did not reveal significant correlation with tumor stage and site in both CRCs and gastric carcinomas (p > 0.05). CONCLUSION: We concluded that c-Met and p53 are expressed in the most common GIT malignancies addressing them as potential biomarkers. In addition, c- Met and p53 may have a potential role in colorectal cancer development as they showed higher positivity in CRCs compared to adenomas.

Phase 1 study of telisotuzumab vedotin in Japanese patients with advanced solid tumors

Telisotuzumab vedotin (formerly ABBV‐399) is an antibody‐drug conjugate targeting c‐Met–overexpressing tumor cells, irrespective of MET gene amplification status. Safety, pharmacokinetics, and preliminary efficacy of telisotuzumab vedotin were evaluated outside of Japan. This phase 1 open‐label study evaluated the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of telisotuzumab vedotin in Japanese patients with advanced solid tumors. Telisotuzumab vedotin was administered intravenously at either 2.4 mg/kg (n = 3) or 2.7 mg/kg (n = 6) every 3 weeks, following a 3 + 3 design. Maximum tolerated dose was not reached on the basis of the study design; no dose‐limiting toxicity events were observed. The most common treatment‐emergent adverse events related to telisotuzumab vedotin were peripheral sensory neuropathy (44%), and nausea, decreased appetite, and decreased white blood cell count (33% each). Most frequent grade ≥3 treatment‐emergent adverse events, irrespective of relationship to telisotuzumab vedotin, were decreased neutrophil count and hypoalbuminemia, reported in two patients (22%) each. Systemic exposure of telisotuzumab vedotin at both dose levels was approximately dose proportional. Pharmacokinetic profile in Japanese patients was similar to that previously reported in non‐Japanese patients. Two (22%) patients achieved a partial response, six (67%) had stable disease, one (11%) had progressive disease. Overall disease control rate was 89% (eight of nine patients; 95% confidence interval: 51.8%–99.7%]). Median progression‐free survival was 7.1 months (95% confidence interval: 1.2–10.4). In conclusion, telisotuzumab vedotin demonstrated a manageable safety profile, with antitumor activity in Japanese patients with advanced solid tumors; the recommended phase 2 dose was confirmed as 2.7 mg/kg every 3 weeks.

ClinicalTrials.gov registration number: NCT03311477.

MET deletion is a frequent event in gastric/gastroesophageal junction/esophageal cancer: a cross-sectional analysis of gene status and signal distribution in 1,580 patients

BACKGROUND

MET gene aberrations are found in several human cancers including gastric, ovarian and lung. In a large multinational cohort of patients with gastric/gastroesophageal junction/esophageal (G/GEJ/E) adenocarcinoma we assessed the MET status with respect to amplification and deletion and correlate the results with the phenotypical gene signal distribution pattern.

METHODS

Tissue specimens from 1,580 patients were analyzed using a novel fluorescence in situ hybridization (FISH) assay employing a MET/CEN-7 IQFISH Probe Mix. MET amplification and deletions were defined as a MET/CEN-7 ratio ≥2.0 and a MET/CEN-7 ratio <0.8, respectively. Furthermore, the link between the MET gene status and the phenotypical signal distribution was investigated.

RESULTS

The prevalence of MET amplification and deletions was found to be 7.2% and 8.7%, respectively. Significant differences were observed with regard to geographic regions and sex. The Asian population had the highest percentage of MET amplification (9.4%) and the lowest percentage of deletions (3.2%). MET deletions was found more frequently among males (10.1%) compared to females (5.3%) and in esophagus (17.6%) compared to the stomach (5.7%). More than 50% of the patients who harbored MET gene amplification had a heterogeneous distribution of the FISH signals. Patients with a focal signal distribution were solely to be found among the MET amplified population. MET deletion were mainly observed in the group of patients with a homogenous signal distribution.

CONCLUSIONS

The screening data from this cross-sectional study showed that MET deletion and amplification are frequent events in G/GEJ/E cancer, which are linked to different phenotypical signal distribution patterns. The role of MET deletion in relation to tumor development is not fully understood but it is likely to play a role in the oncogenic transformation of the cells.

[Intratumoral heterogeneity of gastric cancer-impact on biomarker evaluation]

BACKGROUND

Gastric carcinomas often measure more than 5 cm at primary diagnosis. Predictive biomarker testing is usually carried out on tissue biopsies, which do not represent the entire tumor biology and intratumoral heterogeneity.

OBJECTIVES

The aim of this study was to explore gastric cancer's intratumoral heterogeneity and its impact on the evaluation of predictive and prognostic biomarkers.

MATERIALS AND METHODS

The study cohort consisted of approximately 500 patients with therapy-naive adenocarcinomas of the stomach or the esophagogastric junction. The following biomarkers were determined: HER2, MET, Ki67, PD-L1/PD‑1, VISTA, EBV-status, and PIK3CA.

RESULTS

All examined biomarkers were influenced by gastric cancer's intratumoral heterogeneity. Tissue biopsies might carry the risk of sampling errors, which may significantly hamper adequate tumor classification in a clinical setting.

CONCLUSIONS

Our findings unravel issues of tumor heterogeneity in gastric cancer. Biomarker diagnostics on tissue biopsies should be carried out on at least five biopsies of different tumor areas. If possible, biomarker diagnostics should be repeated on resection specimens. Tissue microarrays should no longer be used for research studies of gastric cancer.

SATB1-Mediated Upregulation of the Oncogenic Receptor Tyrosine Kinase HER3 Antagonizes MET Inhibition in Gastric Cancer Cells

MET-amplified gastric cancer cells are extremely sensitive to MET inhibition in vitro, whereas clinical efficacy of MET inhibitors is disappointing. The compensatory activation of other oncogenic growth factor receptors may serve as an underlying mechanism of resistance. In this study, we analyzed the role of HER receptors, in particular HER3 and its ligand heregulin, in this respect. This also included the chromatin-organizer protein SATB1, as an established regulator of HER expression in other tumor entities. In a panel of MET-amplified gastric carcinoma cell lines, cell growth under anchorage-dependent and independent conditions was studied upon inhibitor treatment or siRNA-mediated knockdown. Expression analyses were performed using RT-qPCR, FACS, and immunoblots. Signal transduction was monitored via antibody arrays and immunoblots. As expected, MET inhibition led to a growth arrest and inhibition of MAPK signaling. Strikingly, however, this was accompanied by a rapid and profound upregulation of the oncogenic receptor HER3. This finding was determined as functionally relevant, since HER3 activation by HRG led to partial MET inhibitor resistance, and MAPK/Akt signaling was even found enhanced upon HRG+MET inhibitor treatment compared to HRG alone. SATB1 was identified as mediator of HER3 upregulation. Concomitantly, SATB1 knockdown prevented upregulation of HER3, thus abrogating the HRG-promoted rescue from MET inhibition. Taken together, our results introduce the combined HER3/MET inhibition as strategy to overcome resistance towards MET inhibitors.

MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

Cellular mesenchymal epithelial transition (C-MET) gene copy number variation in gastric adenocarcinoma: A pilot search for new marker for targeted therapy in HER-2/neu resistance

Increasing HER-2/neu resistance in gastric carcinoma has encouraged search for new biomarkers for targeted therapy. Cellular mesenchymal epithelial transition (C-MET) is one such tyrosine kinase inhibitor proposed for personalized salvage treatment. We determined frequency of C-MET gene copy number variation (CNV) by Fluorescent in-situ hybridization (FISH) in gastric adenocarcinoma (GAC) and sought its correlation with conventional clinicopathologic parameters. Dual-coloured FISH was done on 32 GAC cases. C-MET gene and centromere 7 signals were counted under fluorescent microscope and ratio was calculated for each case. Correlation between C-MET CNV and conventional clinic-pathologic parameters was done by Fischer exact test. CNV was identified in the form of amplification and polysomy (3.1% each) and associated with poorer prognostic parameters. Our pilot study highlights limited subset of patients that may benefit from anti-C-MET-targeted therapy and thus could be a novel biomarker for targeted intervention in GAC.

Harnessing Omics Approaches on Advanced Preclinical Models to Discovery Novel Therapeutic Targets for the Treatment of Metastatic Colorectal Cancer

Metastatic colorectal cancer (mCRC) remains challenging because of the emergence of resistance mechanisms to anti-epidermal growth factor receptor (EGFR) therapeutics, so more effective strategies to improve the patients’ outcome are needed. During the last decade, the application of a multi-omics approach has contributed to a deeper understanding of the complex molecular landscape of human CRC, identifying a plethora of drug targets for precision medicine. Target validation relies on the use of experimental models that would retain the molecular and clinical features of human colorectal cancer, thus mirroring the clinical characteristics of patients. In particular, organoids and patient-derived-xenografts (PDXs), as well as genetically engineered mouse models (GEMMs) and patient-derived orthotopic xenografts (PDOXs), should be considered for translational purposes. Overall, omics and advanced mouse models of cancer represent a portfolio of sophisticated biological tools that, if optimized for use in concert with accurate data analysis, could accelerate the anticancer discovery process and provide new weapons against cancer. In this review, we highlight success reached following the integration of omics and experimental models; moreover, results produced by our group in the field of mCRC are also presented.

MET-dependent solid tumours - molecular diagnosis and targeted therapy

Attempts to develop MET-targeted therapies have historically focused on MET-expressing cancers, with limited success. Thus, MET expression in the absence of a genomic marker of MET dependence is a poor predictor of benefit from MET-targeted therapy. However, owing to the development of more sensitive methods of detecting genomic alterations, high-level MET amplification and activating MET mutations or fusions are all now known to be drivers of oncogenesis. MET mutations include those affecting the kinase or extracellular domains and those that result in exon 14 skipping. The activity of MET tyrosine kinase inhibitors varies by MET alteration category. The likelihood of benefit from MET-targeted therapies increases with increasing levels of MET amplification, although no consensus exists on the optimal diagnostic cut-off point for MET copy number gains identified using fluorescence in situ hybridization and, in particular, next-generation sequencing. Several agents targeting exon 14 skipping alterations are currently in clinical development, with promising data available from early-phase trials. By contrast, the therapeutic implications of MET fusions remain underexplored. Here we summarize and evaluate the utility of various diagnostic techniques and the roles of different classes of MET-targeted therapies in cancers with MET amplification, mutation and fusion, and MET overexpression.

Genomics and Targeted Therapies in Gastroesophageal Adenocarcinoma

Gastroesophageal adenocarcinomas (GEA) are devastating diseases with stark global presence. Over the past 10 years, there have been minimal improvements in treatment approach despite numerous clinical trials. Here, we review recent progress toward understanding the molecular features of these cancers and the diagnostic and therapeutic challenges posed by their intrinsic genomic instability and heterogeneity. We highlight the potential of genomic heterogeneity to influence clinical trial outcomes for targeted therapies and emphasize the need for comprehensive molecular profiling to guide treatment selection and adapt treatment to resistance and genomic evolution. Revising our clinical approach to GEA by leveraging genomic advances will be integral to the success of current and future treatments, especially as novel targets become therapeutically tractable. SIGNIFICANCE: GEAs are deadly cancers with few treatment options. Characterization of the genomic landscape of these cancers has revealed considerable genetic diversity and spatial heterogeneity. Understanding these fundamental properties of GEA will be critical for overcoming barriers to the development of novel, more effective therapeutic strategies.

Precision medicine in gastric cancer

Gastric cancer (GC) is a complex disease linked to a series of environmental factors and unhealthy lifestyle habits, and especially to genetic alterations. GC represents the second leading cause of cancer-related deaths worldwide. Its onset is subtle, and the majority of patients are diagnosed once the cancer is already advanced. In recent years, there have been innovations in the management of advanced GC including the introduction of new classifications based on its molecular characteristics. Thanks to new technologies such as next-generation sequencing and microarray, the Cancer Genome Atlas and Asian Cancer Research Group classifications have also paved the way for precision medicine in GC, making it possible to integrate diagnostic and therapeutic methods. Among the objectives of the subdivision of GC into subtypes is to select patients in whom molecular targeted drugs can achieve the best results; many lines of research have been initiated to this end. After phase III clinical trials, trastuzumab, anti-Erb-B2 receptor tyrosine kinase 2 (commonly known as ERBB2) and ramucirumab, anti-vascular endothelial growth factor receptor 2 (commonly known as VEGFR2) monoclonal antibodies, were approved and introduced into first- and second-line therapies for patients with advanced/metastatic GC. However, the heterogeneity of this neoplasia makes the practical application of such approaches difficult. Unfortunately, scientific progress has not been matched by progress in clinical practice in terms of significant improvements in prognosis. Survival continues to be low in contrast to the reduction in deaths from many common cancers such as colorectal, lung, breast, and prostate cancers. Although several target molecules have been identified on which targeted drugs can act and novel products have been introduced into experimental therapeutic protocols, the overall approach to treating advanced stage GC has not substantially changed. Currently, surgical resection with adjuvant or neoadjuvant radiotherapy and chemotherapy are the most effective treatments for this disease. Future research should not underestimate the heterogeneity of GC when developing diagnostic and therapeutic strategies aimed toward improving patient survival.

Clinical significance of MET gene amplification in metastatic or locally advanced gastric cancer treated with first-line fluoropyrimidine and platinum combination chemotherapy

Objective

To investigate the clinical significance of MET gene amplification in patients with gastric cancer in the palliative setting.

Methods

MET amplification was assessed using fluorescence in situ hybridization (FISH) in 50 patients and quantitative polymerase chain reaction (qPCR) in 326 patients; 259 patients treated with first-line fluoropyrimidine and platinum were included for survival analysis.

Results

The results of FISH and qPCR indicated that the c-MET/CEP7 ratio was correlated with gene copy number. The optimal cutoff value for the copy number using qPCR to detect MET gene amplification with FISH was 5 (κ=0.778, P<0.001). Twenty-one out of 326 patients (6.4%) were identified asMET amplification with a copy number of >5 detected by qPCR. MET-amplified gastric cancer was associated with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of ≥2 (33.3% vs. 10.5% P=0.007), peritoneal metastasis (76.2% vs. 46.2%, P=0.008), and elevated bilirubin levels (28.6% vs. 7.3%, P=0.006). The median overall survival (OS) and progression-free survival (PFS) were 11.9 and 5.6 months, respectively. MET-amplified gastric cancer was not associated with survival outcomes [hazard ratio (HR)=0.68, 95% confidence interval (95% CI): 0.35−1.32, P=0.254 for PFS; HR=0.68, 95% CI: 0.35−1.32, P=0.251 for OS].

Conclusions

qPCR can be used to detect MET gene amplification. MET amplification was not a predictor of poor prognosis in patients with metastatic or unresectable gastric cancer.

Volumetric parameters on 18F-FDG PET/CT predict the survival of patients with gastric cancer associated with their expression status of c-MET

Background

This study aimed to investigate the prognostic value of volumetric parameters on ¹⁸F- fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in gastric-cancer patients, according to the expression status of c-MET (MET proto-oncogene, receptor tyrosine kinase), which was previously unclear.

Methods

The study included 61 patients with advanced gastric cancer. Data on the baseline ¹⁸F-FDG PET/CT, clinical-pathological information, progression-free survival (PFS), and overall survival (OS) were collected. The maximum standardized uptake value (SUV_max), peak SUV (SUV_peak), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of gastric tumors in situ were measured on PET/CT. The expression status of c-MET was recorded based on immunohistochemical staining. Associations between the parameters on PET/CT and patients’ survival outcomes were analyzed in relation to expression status of c-MET.

Results

Patients with positive c-MET expression had significantly shorter PFS (11.5 vs. 17.6 months, P = 0.039) and OS (17.0 vs. 24.3 months, P = 0.043), and had gastric tumors with a larger MTV (70.8 ± 53.11 vs. 41.1 ± 52.32, P = 0.034) and TLG (428.39 ± 442.95 vs. 205.7 ± 354.40, P = 0.039), compared with those with negative c-MET expression. However, SUV_max (9.6 ± 7.40 vs. 8.0 ± 4.91, P = 0.335) and SUV_peak (7.7 ± 5.99 vs. 6.62 ± 4.08, P = 0.438) were similar between these two patient groups. In patients with c-MET-positive tumors, MTV and TLG were independent factors in predicting patient OS after correction by distant metastasis (hazards ratio = 1.014 and 1.002, respectively; P = 0.024 and 0.027, respectively), while these associations were not significant in patients with c-MET-negative tumors.

Conclusions

Patients with c-MET-positive gastric cancer had higher MTV and TLG values compared to those with c-MET-negative gastric cancer. In patients with c-MET-positive gastric cancer, volumetric parameters on ¹⁸F-FDG PET/CT have prognostic value for patient overall survival.

Evaluation of Intratumoral and Intertumoral Heterogeneity of MET Protein Expression in Gastric Cancer

Tumor heterogeneity of a target molecule could contribute to failure of the targeted therapy. We investigated the heterogeneity of MET expression within same primary gastric cancer (GC) and between primary and corresponding secondary GC lesions using immunohistochemistry (IHC). Intratumoral heterogeneity was defined as discordant MET status among 3 tissue microarray cores (3 different areas of same tumor). IHC 3+ was considered positive for MET overexpression. MET overexpression was observed in 2.7% (50/1869) of all examined cores and 5.3% (33/623) of primary GCs. When we compared MET IHC results between 3 cores from each tumor, intratumoral heterogeneity was identified (65.0% in total 623 cases; 84.4% in 480 cases with any staining intensity; 84.9% in 251 cases with moderate to strong intensity; 90.9% in 33 cases with strong intensity). Of 33 MET-overexpressed GCs, the average proportion of strongly stained area was 19.6% in the whole sections. Of 269 cases with primary GC and regional lymph node metastasis, 17 (6.3%) showed MET positivity in which 9 (52.9%) were discordant (negative conversion). In 123 cases with primary and corresponding local recurrent/distant metastatic GC, 3 (2.4%) showed MET positivity in which 2 (66.7%) were discordant (positive conversion). In the survival analysis, MET IHC 3+ in lymph node metastases was an independent negative prognostic factor for overall survival. We found that MET overexpression is uncommon and highly heterogeneous in GC. This severe heterogeneity of MET status should be considered in tissue sampling and development of biomarkers for anti-MET therapy.

Crizotinib-resistant MET mutations in gastric cancer patients are sensitive to type II tyrosine kinase inhibitors

Aim: Crizotinib has been used to counter MET amplification in different human malignancies. However, transient responses were observed in some patients with rapid acquisition of resistant mutations in MET. Materials & methods: MET mutations stably expressed Ba/F3 cell lines were used for IC₅₀ detection. Signaling pathway analysis was done using 293T cell line. Results: Four MET mutations conferred resistance to crizotinib with sustained activation of downstream signaling pathways of MET. On the other hand, the four MET mutations displayed different response to type II tyrosine kinase inhibitors with variable deterioration of the downstream signals. Conclusion: This study suggested that patients carrying MET V1092L, D1228G or Y1230H mutations could benefit from type II tyrosine kinase inhibitor treatment, but not patients with G1163R or D1228Y/N mutations.

Increased MET gene copy number negatively affects the survival of esophageal squamous cell carcinoma patients

BACKGROUNDS

Since Mesenchymal epithelial transition (MET) amplification has been regarded as a potential treatment target, the knowledge of its prevalence and prognostic importance is crucial. However, its clinical pathologic characteristics are not well known in esophageal squamous cell carcinoma (ESCC).

METHODS

We investigated MET gene status with fluorescence in situ hybridization (FISH) assay in 495 ESCC cases using tissue microarrays. Prognostic significance as well as correlations with various clinicopathological parameters was evaluated.

RESULTS

Among 495 patients, 28 (5.7%) cases were MET FISH positive, including 5 cases (1%) with true gene amplification. There were no statistically significant associations between MET FISH-positivity and clinicopathologic characteristics. A significantly poorer prognosis was observed in 28 patients with MET FISH-positivity (disease free survival/DFS, P < 0.001 and overall survival/OS, P = 0.001). Multivariate analysis revealed MET FISH-positivity was an independent prognostic factor for DFS (hazard ratio/HR, 1.953; 95% confidence interval/CI, 1.271-2.999; P = 0.002) and OS (HR, 1.926; 95% CI, 1.243-2.983; P = 0.003). MET FISH-positivity was associated with DFS (P = 0.022 and 0.020) and OS (P = 0.046 and 0.024) both in stage I-II ESCC and in stage III-IVa ESCC. No statistical significance (DFS, P = 0.492 and OS, P = 0.344) was detected between stage I-II ESCC with MET FISH-positivity and stage III-IVa ESCC with FISH-negativity.

CONCLUSIONS

Increased MET gene copy number is an independent prognostic factor in ESCC, and ESCC might have potentially been up-staged by increased MET gene copy number. The results indicate that increased MET gene copy number is a very promising parameter, in clinical therapy and follow-up plans.