MET overexpression and amplification define a distinct molecular subgroup for targeted therapies in gastric cancer

Research progress on the development of hepatocyte growth factor/c-Met signaling pathway in gastric cancer: A review

Hepatocyte growth factor (HGF) and its receptor, c-Met, play important roles in the occurrence, development, and treatment of gastric cancer (GC). This review explored the function of the HGF/c-Met signaling pathway in GC and its potential targeted therapeutic mechanisms. As one of the most common malignant tumors worldwide, GC has a complex pathogenesis and limited therapeutic options. Therefore, a thorough understanding of the molecular mechanism of GC is very important for the development of new therapeutic methods. The HGF/c-Met signaling pathway plays an important role in the proliferation, migration, and invasion of GC cells and has become a new therapeutic target. This review summarizes the current research progress on the role of HGF/c-Met in GC and discusses targeted therapeutic strategies targeting this signaling pathway, providing new ideas and directions for the treatment of GC.

Ferroptosis regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer

BACKGROUND

Gastric cancer is one of the most common malignant tumors in the world, and its occurrence and development involve complex biological processes. Iron death, as a new cell death mode, has attracted wide attention in recent years. However, the regulatory mechanism of iron death in gastric cancer and its effect on lipid peroxidation metabolism remain unclear.

AIM

To explore the role of iron death in the development of gastric cancer, reveal its relationship with lipid peroxidation, and provide a new theoretical basis for revealing the molecular mechanism of the occurrence and development of gastric cancer.

METHODS

The process of iron death in gastric cancer cells was simulated by cell culture model, and the occurrence of iron death was detected by fluorescence microscopy and flow cytometry. The changes of gene expression related to iron death and lipid peroxidation metabolism were analyzed by high-throughput sequencing technology. In addition, a mouse model of gastric cancer was established, and the role of iron death in vivo was studied by histology and immunohistochemistry, and the level of lipid peroxidation was detected. These methods comprehensively and deeply reveal the regulatory mechanism of iron death on lipid peroxidation metabolism in the occurrence and development of gastric cancer.

RESULTS

Iron death was significantly activated in gastric cancer cells, and at the same time, associated lipid peroxidation levels increased significantly. Through high-throughput sequencing analysis, it was found that iron death regulated the expression of several genes related to lipid metabolism. In vivo experiments demonstrated that increased iron death in gastric cancer mice was accompanied by a significant increase in lipid peroxidation.

CONCLUSION

This study confirmed the important role of iron death in regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer. The activation of iron death significantly increased lipid peroxidation levels, revealing its regulatory mechanism inside the cell.

Unraveling the Significance of MET Focal Amplification in Lung Cancer: Integrative NGS, FISH, and IHC Investigation

MET amplification (METamp) represents a promising therapeutic target in non-small cell lung cancer, but no consensus has been established to identify METamp-dependent tumors that could potentially benefit from MET inhibitors. In this study, an analysis of MET amplification/overexpression status was performed in a retrospectively recruited cohort comprising 231 patients with non-small cell lung cancer from Shanghai Chest Hospital (SCH cohort) using 3 methods: fluorescence in situ hybridization (FISH), hybrid capture-based next-generation sequencing, and immunohistochemistry for c-MET and phospho-MET. The SCH cohort included 130 cases known to be METamp positive by FISH and 101 negative controls. The clinical relevance of these approaches in predicting the efficacy of MET inhibitors was evaluated. Additionally, next-generation sequencing data from another 2 cohorts including 22,010 lung cancer cases were utilized to examine the biological characteristics of different METamp subtypes. Of the 231 cases, 145 showed MET amplification/overexpression using at least 1 method, whereas only half of them could be identified by all 3 methods. METamp can occur as focal amplification or polysomy. Our study revealed that the inconsistency between next-generation sequencing and FISH primarily occurred in the polysomy subtype. Further investigations indicated that compared with polysomy, focal amplification correlated with fewer co-occurring driver mutations, higher protein expressions of c-MET and phospho-MET, and higher incidence in acquired resistance than in de novo setting. Moreover, patients with focal amplification presented a more robust response to MET inhibitors compared with those with polysomy. Notably, a strong correlation was observed between focal amplification and programmed cell death ligand-1 expression, indicating potential therapeutic implications with combined MET inhibitor and immunotherapy for patients with both alterations. Our findings provide insights into the molecular complexity and clinical relevance of METamp in lung cancer, highlighting the role of MET focal amplification as an oncogenic driver and its feasibility as a primary biomarker to further investigate the clinical activity of MET inhibitors in future studies.

A Review on Anaplastic Lymphoma Kinase (ALK) Rearrangements and Mutations: Implications for Gastric Carcinogenesis and Target Therapy

Gastric adenocarcinoma is a complex disease with diverse genetic modifications, including Anaplastic Lymphoma Kinase (ALK) gene changes. The ALK gene is located on chromosome 2p23 and encodes a receptor tyrosine kinase that plays a crucial role in embryonic development and cellular differentiation. ALK alterations can result from gene fusion, mutation, amplification, or overexpression in gastric adenocarcinoma. Fusion occurs when the ALK gene fuses with another gene, resulting in a chimeric protein with constitutive kinase activity and promoting oncogenesis. ALK mutations are less common but can also result in the activation of ALK signaling pathways. Targeted therapies for ALK variations in gastric adenocarcinoma have been developed, including ALK inhibitors that have shown promising results in pre-clinical studies. Future studies are needed to elucidate the ALK role in gastric cancer and to identify predictive biomarkers to improve patient selection for targeted therapy. Overall, ALK alterations are a relevant biomarker for gastric adenocarcinoma treatment and targeted therapies for ALK may improve patients' overall survival.

Pulmonary lymphangitis carcinomatosis: A peculiar presentation clustering in MET-amplified gastric cancer

BACKGROUND

The clinicopathological features of MET-amplified gastric cancer (GC) and real-world data on the efficacy of MET-targeted therapies remain unknown. Pulmonary lymphangitis carcinomatosis (PLC) is a peculiar manifestation of GC, whose management has not been thoroughly described.

METHODS

This study analyzed patients diagnosed with MET-amplified GC or GC with PLC at any time point of the disease course from 2011 to 2021 in two centers. Clinicopathological features and survival outcomes of MET-amplified GC were analyzed. The clinical and molecular implications of GC with PLC were discussed.

RESULTS

Fifty-eight patients with MET-amplified GC and 20 patients with GC accompanied by PLC were finally enrolled for analysis (including 13 overlapped patients). GC with PLC was more common in female patients (p = 0.010), diagnosed at a younger age (p = 0.002), presented with a higher baseline ECOG PS (p = 0.016), and was more likely to develop lung metastasis (p < 0.001), and serous effusion (p = 0.026) than GC without PLC. Patients with primary MET-amplified GC had a worse prognosis than those with secondary MET-amplified GC (p = 0.005). The application of anti-MET therapy was associated with numerically prolonged survival, but the association was not statistically significant (p = 0.07). MET amplification was concentrated in patients with PLC, in which anti-MET therapies elicited a high response rate.

CONCLUSIONS

MET-targeted therapies are efficacious in real-world populations with MET-amplified GC. Patients with PLC have distinct clinical and molecular features and might benefit from MET-targeted therapies.

Transforming properties of MET receptor exon 14 skipping can be recapitulated by loss of the CBL ubiquitin ligase binding site

MET is a receptor tyrosine kinase that is activated in many cancers through various mechanisms. MET exon 14 (Ex14) skipping occurs in 3% of nonsmall cell lung tumors. However, the contribution of the regulatory sites lost upon this skipping, which include a phosphorylated serine (S985) and a binding site for the E3 ubiquitin ligase CBL (Y1003), remains elusive. Sequencing of 2808 lung tumors revealed 71 mutations leading to MET exon 14 skipping and three mutations affecting Y1003 or S985. In addition, MET exon 14 skipping and MET Y1003F induced similar transcriptional programs, increased the activation of downstream signaling pathways, and increased cell mobility. Therefore, the MET Y1003F mutation is able to fully recapitulate responses induced by MET exon 14 skipping, suggesting that loss of the CBL binding site is the main contributor of cell transformation induced by MET Ex14 mutations.

Kinase Inhibitor Screening Displayed ALK as a Possible Therapeutic Biomarker for Gastric Cancer

Despite advances in cancer chemotherapy, gastric cancer (GC) continues to have high recurrence rates and poor prognosis with limited treatment options. Understanding the etiology of GC and developing more effective, less harmful therapeutic approaches are vital and urgent. Therefore, this work describes a novel kinase target in malignant gastric cells as a potential therapeutic strategy. Our results demonstrate that among 147 kinase inhibitors (KI), only three molecules were significantly cytotoxic for the AGP-01 cell line. Hence, these three molecules were further characterized in their cellular mode of action. There was significant cell cycle impairment due to the expression modulation of genes such as TP53, CDKN1A, CDC25A, MYC, and CDK2 with subsequent induction of apoptosis. In fact, the Gene Ontology analysis revealed a significant enrichment of pathways related to cell cycle regulation (GO:1902749 and GO:1903047). Moreover, the three selected KIs significantly reduced cell migration and Vimentin mRNA expression after treatment. Surprisingly, the three KIs share the same target, ALK and INSR, but only the ALK gene was found to have a high expression level in the gastric cancer cell line. Additionally, lower survival rates were observed for patients with high ALK expression in TCGA-STAD analysis. In summary, we hypothesize that ALK gene overexpression can be a promising biomarker for prognosis and therapeutic management of gastric adenocarcinoma.

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.

Combination treatment with trastuzumab and crizotinib in metastatic gastric cancer harboring Her-2 amplification and c-MET amplification: A case report

RATIONALE

Metastatic gastric cancer patients with poor eastern cooperative oncology group performance status (PS) (≥3) were lack of effective anti-tumor strategies. They always lived with poor PS, severe and multiple symptoms, and usually resulted in extremely limited survival time. Herein, we reported a patient diagnosed with gastric cancer metastasized to multiple bones, along with lymphangitis carcinomatosa in lungs, harboring Her-2 and c-MET amplification with poor PS, positively responded to combinational therapy with trastuzumab and crizotinib.

PATIENT CONCERNS

The patient complained of persistent cough and fatigue for 2 months, otherwise, she denied smoking, alcohol history, or any other medical or family history.

DIAGNOSIS

With the biopsy results from gastroscopy, as well as computer tomography for chest and abdomen, the patient was diagnosed as gastric adenocarcinoma, with metastasis on lungs, left adrenal gland, retroperitoneal lymph nodes, and multiple bones.

INTERVENTIONS

Because of the poor PS (PS = 3), as well as Her-2 and c-MET amplification, the patient received combination treatment with trastuzumab and crizotinib as salvage strategy.

OUTCOMES

After 2 months' exposure of trastuzumab and crizotinib, symptoms including persistent cough, and chest distress were alleviated significantly. Simultaneously, chest computer tomography showed significant dissipation of lymphangitis carcinomatosa, as well as apparent reduction of pleural effusion. No adverse reactions including nausea, vomiting, diarrhea, or hypertension was observed during the following 2 months.

LESSONS

The present case suggested that combinational therapy with trastuzumab and crizotinib might be effective in metastatic gastric cancer patients harboring Her-2 and c-MET amplification, even with a poor PS. It was also implied that gene sequencing might be valuable, especially in patients with limited treatment strategies.

Advances in targeted therapy for esophageal cancer

Esophageal cancer (EC) is one of the most lethal cancers in the world, and its morbidity and mortality rates rank among the top ten in China. Currently, surgical resection, radiotherapy and chemotherapy are the primary clinical treatments for esophageal cancer. However, outcomes are still unsatisfactory due to the limited efficacy and severe adverse effects of conventional treatments. As a new type of approach, targeted therapies have been confirmed to play an important role in the treatment of esophageal cancer; these include cetuximab and bevacizumab, which target epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF), respectively. In addition, other drugs targeting surface antigens and signaling pathways or acting on immune checkpoints have been continuously developed. For example, trastuzumab, a monoclonal antibody targeting human epidermal growth factor receptor 2 (HER-2), has been approved by the Food and Drug Administration (FDA) as a first-line treatment of HER-2-positive cancer. Moreover, the PD-L1 inhibitor pembrolizumab has been approved as a highly efficient drug for patients with PD-L1-positive or advanced esophageal squamous cell carcinoma (ESCC). These novel drugs can be used alone or in combination with other treatment strategies to further improve the treatment efficacy and prognosis of cancer patients. Nevertheless, adverse events, optimal dosages and effective combinations still need further investigation. In this review, we expound an outline of the latest advances in targeted therapies of esophageal cancer and the mechanisms of relevant drugs, discuss their efficacy and safety, and provide a clinical rationale for precision medicine in esophageal cancer.

Characteristics and response to crizotinib in lung cancer patients with MET amplification detected by next-generation sequencing

OBJECTIVES

Mesenchymal-epithelial transition (MET) amplification is a rare gene alteration in lung cancer. The aim of this study was to investigate the clinical characteristics of MET amplification in lung cancer and the response to crizotinib by subsets of patients with MET amplification detected by next-generation sequencing (NGS).

PATIENTS AND METHODS

We collected NGS sequencing data for patients with MET amplification in our institution from January 2018 to April 2019. The efficacy of crizotinib in MET amplification was retrospectively analyzed.

RESULTS

A total of 2694 patients received NGS tests, 3.27 % (82/2507) of patients had primary MET amplification, and acquired MET amplification accounted for 16.04 % (30/187) of re-biopsy patients. Only 19 patients received monotherapy with crizotinib. In survival analysis, ten patients with copy number greater than 4 (CN > 4) had longer median PFS (mPFS) (4.76 months; 95 %CI: 1.67-7.85 months) compared with other nine patients (CN ≤ 4) (2.10 months; 95 %CI: 1.53-2.68 months; P = 0.063), but failed to get a statistical significance. No significant differences were observed between median PFS (mPFS) of the patients with primary and acquired MET amplification (4.04 months vs 2.76 months; P = 0.310).

CONCLUSIONS

Primary and acquired MET amplification were detected in 3.27 % and 16.04 % of lung cancer patients, respectively. Patients with CN > 4 seemed to have longer PFS after crizotinib treatment. No significant differences in PFS were observed between patients with primary and acquired MET amplification.

Analysis of the Effect of Increased α2,3-Sialylation on RTK Activation in MKN45 Gastric Cancer Spheroids Treated with Crizotinib

In the scenario of personalized medicine, targeted therapies are currently the focus of cancer drug development. These drugs can block the growth and spread of tumor cells by interfering with key molecules involved in malignancy, such as receptor tyrosine kinases (RTKs). MET and Recepteur d'Origine Nantais (RON), which are RTKs frequently overactivated in gastric cancer, are glycoprotein receptors whose activation have been shown to be modulated by the cellular glycosylation. In this work, we address the role of sialylation in gastric cancer therapy using an innovative 3D high-throughput cell culture methodology that mimics better the in vivo tumor features. We evaluate the response to targeted treatment of glycoengineered gastric cancer cell models overexpressing the sialyltransferases ST3GAL4 or ST3GAL6 by subjecting 3D spheroids to the tyrosine kinase inhibitor crizotinib. We show here that 3D spheroids of ST3GAL4 or ST3GAL6 overexpressing MKN45 gastric cancer cells are less affected by the inhibitor. In addition, we disclose a potential compensatory pathway via activation of the Insulin Receptor upon crizotinib treatment. Our results suggest that cell sialylation, in addition of being involved in tumor progression, could play a critical role in the response to tyrosine kinase inhibitors in gastric cancer.

Proteolytic cleavages of MET: the divide-and-conquer strategy of a receptor tyrosine kinase

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

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.

Off-label use of common predictive biomarkers in gastrointestinal malignancies: a critical appraisal

The use of immunohistochemistry (IHC) as a companion diagnostic is an increasingly important part of the case workup by pathologists and is often central to clinical decision making. New predictive molecular markers are constantly sought for to improve treatment stratification parallel to drug development. Unfortunately, official biomarker guidelines lag behind, and pathologists are often left hesitating when medical oncologists request off-labelled biomarker testing. We performed a literature review of five commonly requested off-label IHC predictive biomarkers in gastrointestinal tract (GIT) malignancies: HER2, mismatch repair (MMR), PD-L1, BRAF V600E and ROS1. We found that HER2 amplification is rare and poorly associated to IHC overexpression in extracolonic and extragastric GIT cancers; however in KRAS wild type colorectal cancers, which fail conventional treatment, HER2 IHC may be useful and should be considered. For MMR testing, more evidence is needed to recommend reflex testing in GIT cancers for treatment purposes. MMR testing should not be discouraged in patients considered for second line checkpoint inhibitor therapy. With the exception of gastric tumors, PD-L1 IHC is a weak predictor of checkpoint inhibitor response in the GIT and should be replaced by MMR in this context. BRAF inhibitors showed activity in BRAF V600E mutated cholangiocarcinomas and pancreatic carcinomas in non-first line settings. ROS1 translocation is extremely rare and poorly correlated to ROS1 IHC expression in the GIT; currently there is no role for ROS1 IHC testing in GIT cancers. Overall, the predictive biomarker literature has grown exponentially, and official guidelines need to be updated more regularly to support pathologists’ testing decisions.

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.

SwissMTB: establishing comprehensive molecular cancer diagnostics in Swiss clinics

Background

Molecular precision oncology is an emerging practice to improve cancer therapy by decreasing the risk of choosing treatments that lack efficacy or cause adverse events. However, the challenges of integrating molecular profiling into routine clinical care are manifold. From a computational perspective these include the importance of a short analysis turnaround time, the interpretation of complex drug-gene and gene-gene interactions, and the necessity of standardized high-quality workflows. In addition, difficulties faced when integrating molecular diagnostics into clinical practice are ethical concerns, legal requirements, and limited availability of treatment options beyond standard of care as well as the overall lack of awareness of their existence.

Methods

To the best of our knowledge, we are the first group in Switzerland that established a workflow for personalized diagnostics based on comprehensive high-throughput sequencing of tumors at the clinic. Our workflow, named SwissMTB (Swiss Molecular Tumor Board), links genetic tumor alterations and gene expression to therapeutic options and clinical trial opportunities. The resulting treatment recommendations are summarized in a clinical report and discussed in a molecular tumor board at the clinic to support therapy decisions.

Results

Here we present results from an observational pilot study including 22 late-stage cancer patients. In this study we were able to identify actionable variants and corresponding therapies for 19 patients. Half of the patients were analyzed retrospectively. In two patients we identified resistance-associated variants explaining lack of therapy response. For five out of eleven patients analyzed before treatment the SwissMTB diagnostic influenced treatment decision.

Conclusions

SwissMTB enables the analysis and clinical interpretation of large numbers of potentially actionable molecular targets. Thus, our workflow paves the way towards a more frequent use of comprehensive molecular diagnostics in Swiss hospitals.

Electronic supplementary material

The online version of this article (10.1186/s12911-018-0680-0) contains supplementary material, which is available to authorized users.

Optimization of Routine Testing for MET Exon 14 Splice Site Mutations in NSCLC Patients

INTRODUCTION

Genomic alterations affecting splice sites of MNNG HOS transforming gene (MET) exon 14 were recently identified in NSCLC patients. Objective responses to MET tyrosine kinase inhibitors have been reported in these patients. Thus, detection of MET exon 14 splice site mutations represents a major challenge. So far, most of these alterations were found by full-exome sequencing or large capture-based next-generation sequencing (NGS) panels, which are not suitable for routine diagnosis.

METHODS

Aiming to provide a molecular testing method applicable in routine practice, we first developed a fragment-length analysis for detecting deletions in introns flanking MET exon 14. Second, we designed an optimized targeted NGS panel called CLAPv1, covering the MET exon 14 and flanking regions in addition to the main molecular targets usually covered in genomic testing. In patients with MET exon 14 mutations, MET gene amplification, gene copy number and MET receptor expression were also determined.

RESULTS

Among 1514 formalin-fixed paraffin-embedded NSCLC samples, nonoptimized NGS allowed detection of MET exon 14 mutations in only 0.3% of the patients, and fragment length analysis detected deletions in 1.1% of the patients. Combined, the optimized CLAPv1 panel and fragment-length analysis implemented for routine molecular testing revealed MET exon 14 alterations in 2.2% of 365 additional NSCLC patients. MET gene amplification or high gene copy number was observed in 6 of 30 patients (20%) harboring MET exon 14 mutations.

CONCLUSIONS

These results show that optimized targeted NGS and fragment-length analysis improve detection of MET alterations in routine practice.

[MET exon 14 splicing sites mutations: A new therapeutic opportunity in lung cancer]

The mutations leading to MET exon 14 skipping represent a new class of molecular alterations described in various cancers. These alterations are observed in 2 to 3 % of cases of non-small cell lung cancer (NSCLC). Several cases of NSCLC carrying such alterations and achieving objective response to MET tyrosine kinase inhibitorshave recently been published. This review summarizes the molecular mechanisms responsible for MET exon 14 skipping as well as the consequences of the loss of this exon on receptor activity. We also describe the clinical characteristics of patients with METΔ14 mutations. Finally, we address the issues related to the detection of these mutations in lung cancer, and the need to anticipate resistance to MET inhibitors.

MET-overexpressing myxofibrosarcoma frequently exhibit polysomy of chromosome 7 but not MET amplification, especially in high-grade cases: clinical and pathological review of 30 myxofibrosarcoma cases

BACKGROUND

Myxofibrosarcoma (MFS) is one of the most common soft tissue sarcomas. Previous studies have shown that MET protein overexpressed in MFS patients and can serve as a prognostic factor. The reasons for MET protein overexpression include amplification of the MET gene, which is located on chromosome 7q. Triggered by an index case harboring chromosome 7 polysomy rather than MET gene amplification in myxofibrosarcoma, we investigated chromosome 7 polysomy in more cases.

METHODS

Immunohistochemistry and fluorescence in situ hybridization (FISH) were performed in 30 MFS cases (including 2 epithelioid variant) to detect the expression of MET protein and gene status.

RESULTS

MET was overexpressed in 14 cases out of 30, while thirteen cases were in higher FNCLCC grades (Grade 2-3). FISH showed that 11 cases having 3 signals on average of Met and more than 3 signals (Mean: 4.6) of centromere 7q (CEP7q). The MET/CEP7 ratio was about 0.65 on average, suggesting that chromosome 7 polysomy, rather than Met gene amplification, leading to the overexpression of MET protein in MFS. MET overexpression and chromosome 7 polysomy are positively correlated with higher Ki-67 index and higher grade and might have a high risk of local recurrence and metastasis.

CONCLUSIONS

It might reveals another explain of MET overexpression in myxofibrosarcoma, providing a clue for the therapy of MFS.

DUSP1 induces apatinib resistance by activating the MAPK pathway in gastric cancer

Dual-specificity phosphatase-1 (DUSP1) is an oncogene that is associated with cancer progression following drug resistance. In order to investigate the potential relationship between DUSP1 and apatinib resistance in gastric cancer cells, we preformed many assays to study this problem. DUSP1 gene was detected by RT-qPCR assay, proteins in MAPK pathway were quantified by western blot assay, and CCK-8 assay, flow cytometry and Hoechest 33342 stain were performed to detect the resistance of cells, cell cycles and apoptosis, respectively. Immunohistochemical staining was used to discover the expression of DUSP1 protein in patients' tumor or paratumor tissues. It was found that apatinib (Apa)-resistant gastric cancer (GC) cells showed increased expression of DUSP1, whereas the knockdown of DUSP1 in resistant cells resensitized these cells to Apa. The restored sensitivity to Apa was the result of inactivation of mitogen-activated protein kinase (MAPK) signaling and the induction of apoptosis. The in vitro use of Apa in combination with a DUSP1 inhibitor, triptolide, exerted significant effects on inhibiting the expression of DUSP1, growth inhibition, and apoptosis via the inactivation of MAPK signaling. In patients who did not undergo chemotherapy or targeted therapy, the expression of DUSP1 in adjacent tissues was higher when compared with that observed in tumor tissues. In addition, the expression of DUSP1 was higher in the early stages of GC than in the advanced stages. The expression of DUSP1 in tumor tissues was not associated with the survival rate of the patients. Therefore, increased expression of DUSP1 may be responsible for Apa resistance, and DUSP1 may serve as a biomarker for Apa efficacy. In conclusion, inducing the downregulation of DUSP1 may be a promising strategy to overcome Apa resistance.

Combination of histoculture drug response assay and qPCR as an effective method to screen biomarkers for personalized chemotherapy in esophageal cancer

Personalized chemotherapy with the use of biomarkers helps to maximize clinical efficiency. Therefore, the present study aimed to identify a potential method for identifying biomarkers in esophageal cancer. A total of 49 freshly resected tumor tissues and 72 paraffin-embedded specimens from patients with esophageal cancer were obtained. mRNA expression levels of ERCC1, BRCA1, TUBB3, FBW7, RRM1, MDM2, TS and TOP1 were measured quantitative reverse transcription polymerase chain reaction (RT-qPCR). In vitro chemosensitivity to cisplatin, docetaxel, gemcitabine, etoposide, fluorouracil and irinotecan were tested using histoculture drug response assay (HDRA). BRCA1 mRNA levels were positively correlated with resistance to cisplatin (P=0.027) and sensitivity to docetaxel (P=0.002). TS mRNA levels were inversely correlated with fluorouracil sensitivity (P=0.044), and TOP1 mRNA expression was positively correlated with irinotecan sensitivity (P=0.008). In addition, high BRCA1 mRNA levels correlated with decreased median overall survival (mOS; P<0.001) and response rate (RR; P=0.002) in cisplatin-fluorouracil chemotherapy group and also correlated with increased mOS (P<0.001) and RR (P=0.023) in docetaxel-fluorouracil chemotherapy group. Overall, these results suggested that HDRA combined with RT-qPCR may serve as an effective method for screening biomarkers in personalized chemotherapy for esophageal cancer.

The Therapeutic Potential of Targeting the HGF/cMET Axis in Ovarian Cancer

Survival rates for ovarian cancer have remained relatively stable for the past 2 decades despite advances in surgical techniques and cytotoxic chemotherapeutics, indicating a requirement for better therapies. One pathway currently proposed for targeting is the HGF/cMET pathway. Upregulated in a number of tumour types, cMET is a tyrosine kinase receptor expressed on epithelial cells. In ovarian cancer, it has been identified as highly expressed in the four major subtypes, with expression estimates ranging from 11 to 68 % of cases. HGF, the only known ligand for cMET, is found at high levels in both serum and ascites in women with ovarian cancer, and is proposed to induce both migration and metastasis. However, clinically validated biomarkers are not yet available for either HGF or cMET, preventing a clear understanding of the true rate of overexpression, or its correlation with prognosis. Despite this, a number of agents against HGF and cMET are currently being investigated in clinical trials for multiple tumour types, including ovarian. However, a lack of patient selection, biomarker usage, and post hoc analysis correlating response with expression has resulted in the majority of these trials showing little beneficial effect from these agents, indicating that additional research is required to determine their usefulness in patients with ovarian cancer.

MET-targeted therapy for gastric cancer: the importance of a biomarker-based strategy

The MET protooncogene encodes the receptor tyrosine kinase c-MET (MET). Aberrant activation of MET signaling occurs in a subset of advanced malignancies, including gastric cancer, and promotes tumor cell growth, survival, migration, and invasion as well as tumor angiogenesis, suggesting its potential importance as a therapeutic target. MET can be activated by two distinct pathways that are dependent on or independent of its ligand, hepatocyte growth factor (HGF), with the latter pathway having been attributed mostly to MET amplification in gastric cancer. Preclinical evidence has suggested that interruption of the HGF-MET axis either with antibodies to HGF or with MET tyrosine kinase inhibitors (TKIs) has antitumor effects in gastric cancer cells. Overexpression of MET occurs frequently in gastric cancer and has been proposed as a potential predictive biomarker for anti-MET therapy. However, several factors can trigger such MET upregulation in a manner independent of HGF, suggesting that gastric tumors with MET overexpression are not necessarily MET driven. On the other hand, gastric cancer cells with MET amplification are dependent on MET signaling for their survival and are thus vulnerable to MET TKI treatment. Given the low prevalence of MET amplification in gastric cancer (approximately 8 %), testing for this genetic change would substantially narrow the target population but it might constitute a better biomarker than MET overexpression for MET TKI therapy. We compare aberrant MET signaling dependent on the HGF-MET axis or on MET amplification as well as address clinical issues and challenges associated with the identification of appropriate biomarkers for MET-driven tumors.