MET Protein Expression Research Articles

MACC1 and MET as markers associated with progression and metastasis in cutaneous melanoma.

Cutaneous melanoma is the most common lethal malignancy among skin cancers and has a high propensity for metastasis. Understanding the mechanisms governing tumorigenesis, progression and metastasis as well as identifying biomarkers guiding risk stratification and management of the disease is essential. MACC1 has been found to play key roles in cancer cell migration, invasion, epithelial-to-mesenchymal transition, and metastasis in various types of cancer, through activation of MET signaling. In this study, we examined the extent of MACC1 and MET protein expression by immunohistochemical staining in a tissue microarray constructed from twenty-three melanomas and ten melanocytic nevi. We observed significantly higher levels of MACC1 expression on average in metastatic melanomas, comparing to primary melanomas and nevi. MET expression in metastatic melanomas was also significantly higher than in nevi. MACC1 expression does not appear to correlate with MET expression in nevi and primary melanomas. However, this correlation appears stronger in metastatic melanomas, where seven (78%) of nine cases show intermediate to high expression of both MACC1 and MET. The expressions of MACC1 and MET do not show significant differences based on other clinicopathologic factors including patient age, gender, histologic subtypes, depth of invasion, and staging. Our study suggests that high expression of MACC1 or both MACC1 and MET is associated with metastasis of cutaneous melanoma.

MET Exon 14-altered Lung Cancers and MET Inhibitor Resistance.

MET tyrosine kinase inhibitors (TKIs) can achieve modest clinical outcomes in MET exon 14-altered lung cancers, likely secondary to primary resistance. Mechanisms of primary resistance remain poorly characterized and comprehensive proteomic analyses have not previously been performed. We performed hybrid capture-based DNA sequencing, targeted RNA sequencing, cell-free DNA sequencing, selected reaction monitoring mass spectrometry (SRM-MS), and immunohistochemistry on patient samples of MET exon 14-altered lung cancers treated with a MET TKI. Associations between overall response rate (ORR), progression-free survival (PFS), and putative genomic alterations and MET protein expression were evaluated. Seventy-five of 168 MET exon 14-altered lung cancers received a MET TKI. Previously undescribed (zygosity, clonality, whole-genome duplication) and known (copy-number focality, tumor mutational burden, mutation region/type) genomic factors were not associated with ORR/PFS (P > 0.05). In contrast, MET expression was associated with MET TKI benefit. Only cases with detectable MET expression by SRM-MS (N = 15) or immunochemistry (N = 22) responded to MET TKI therapy, and cancers with H-score ≥ 200 had a higher PFS than cancers below this cutoff (10.4 vs. 5.5 months, respectively; HR, 3.87; P = 0.02). In MET exon 14-altered cancers treated with a MET TKI, a comprehensive analysis of previously unknown and known genomic factors did not identify a genomic mechanism of primary resistance. Instead, MET expression correlated with benefit, suggesting the potential role of interrogating the proteome in addition to the genome in confirmatory prospective trials.

The relationship between PD-L1 expression and tumor driver gene mutations and survival in non small cell lung carcinoma.

To explore the relationship between PD-L1 expression and gene mutations and survival. PD L1, ALK and MET protein expression were detected by immunohistochemistry, and EGFR gene mutation by RT-PCR in 209 cases of NSCLC. The correlations between PD-L1 expression and gene mutations, clinicopathological features and survival was analyzed. PD-L1 was expressed in 99/209 cases (47.4%) of NSCLC, including score 1 (≥ 1% to < 5%) 23 cases (11%), score 2 (≥ 5% to 50%) 40 cases (19.1%). There were 89 cases (42.6%) of EGFR mutation, 12 (5.7%) of ALK and 90 (43.1%) of MET protein positive. PD-L1 positive expression occurred more frequently in men and non-adenocarcinoma, and was negatively correlated with EGFR mutation and histological differentiation of NSCLC. PD-L1 expression was concordant in primary and metastatic cancers. There was no any effect of PD-L1 expression on overall survival of patients with NSCLC. These results suggested that PD-L1 expression is not an independent risk factor for survival of patients with NSCLC. Because of mutual complementarities of PD-L1 expression and EGFR mutation in NSCLC, both should be simultaneously detected for the patients to achieve eligible treatments.

MET canonical transcript expression is a predictive biomarker for chemo-sensitivity to MET-inhibitors in hepatocellular carcinoma cell lines.

Long interspersed nuclear element 1 (LINE-1 or L1) is a dominant non-long terminal repeat (non-LTR) retrotransposon in the human genome that has been implicated in the overexpression of MET. Both the canonical MET and L1-MET transcripts are considered to play a role in hepatocellular carcinoma (HCC) development. The aim of this study was to assess the utility of canonical MET, L1-MET, and MET protein expressions as predictive biomarkers for chemo-sensitivity to MET-inhibitors in HCC cell lines in vitro. Additionally, we assessed their expression in tumour tissues from Egyptian HCC patients. MET and L1-MET expressions were assessed by qRT-PCR in six liver cancer cell lines (SNU-387, SNU-475, SK-HEP-1, PLC/PRF/5, SNU-449 and SNU-423) and 47 HCC tumour tissues. MET protein expression was measured by western blot in cell lines and immunohistochemistry in the tumours. Cell proliferation assay was used to assess the effect of crizotinib and tivantinib on the six liver cancer cell lines in correlation with the expression of MET, L1-MET and MET. The antitumor effect of crizotinib and tivantinib correlated with MET gene expression but not with L1-MET transcript or MET protein expressions. No significant difference was observed between HCC tumours and non-tumour samples in MET and L1-MET transcripts expression. There were no significant correlations between the 2-year overall survival rate and the MET, L1-MET transcripts and the MET protein expression. MET RNA expression could be useful biomarker for tivantinib and crizotinib targeted therapy in HCC. The value of assessment of MET protein expression is limited.

Circ-DB participates in the progression of gastric cancer by competitively binding microRNA-34a to regulate the expression of MET.

To figure out the possible role and mechanism of circ-DB in the pathogenesis of gastric cancer (GCa). 32 cases of postoperative GCa tissue samples and adjacent ones were collected and divided into groups of ≥ 5 cm and < 5 cm according to tumor diameter. Circ-DB, microRNA-34a, and MET expressions were detected by real time-quantitative PCR (RT-qPCR) in GCa tissues and adjacent tissues. To determine the main mode of action of circ-DB, the subcellular localization of circ-DB was examined by dividing the cells into the nucleus and cytoplasmic fractions. The binding of microRNA-34a to circ-DB was demonstrated by a Dual-Luciferase reporter gene assay. The expression of circ-DB in HGC-27 and AGS cells was overexpressed and knocked down to evaluate the migration function of the cells by transwell. The protein expression of MET, as well as the target gene of microRNA-34a, was detected by Western blot. The expression of circ-DB and MET in GCa tissues was significantly higher than that in the corresponding adjacent tissues. Circ-DB was positively correlated with MET expression, while microRNA-34a expression was negatively correlated with circ-DB and MET expression. Circ-DB was mainly located in the cytoplasm, and the Dual-Luciferase reporter gene demonstrated that microRNA-34a can bind to circ-DB. The down-regulation of circ-DB expression inhibited the migration of HGC-27 and AGS cells. In vitro cell experiments showed that low expression of circ-DB inhibited cell migration, which could be recovered by the co-transfection with microRNA-34a inhibitor. Circ-DB may regulate MET level through microRNA-34a and affect the proliferative ability and migration of GCa cells.

Prevalence and Clinicopathological Significance of MET Overexpression and Gene Amplification in Patients with Gallbladder Carcinoma.

PurposeMesenchymal epithelial transition (MET) is a proto-oncogene that encodes a heterodimeric transmembrane receptor tyrosine kinase for the hepatocyte growth factor. Aberrant MET signaling has been described in several solid tumors—especially non-small cell lung cancer— and is associated with tumor progression and adverse prognosis. As MET is a potential therapeutic target, information regarding its prevalence and clinicopathological relevance is crucial.Materials and MethodsWe investigated MET expression and gene amplification in 113 gallbladder cancers using tissue microarray. Immunohistochemistry was used to evaluate MET overexpression, and silver/fluorescence in situ hybridization (ISH) was used to assess gene copy number.ResultsMET overexpression was found in 37 cases of gallbladder carcinoma (39.8%), and gene amplification was present in 17 cases (18.3%). MET protein expression did not correlate with MET amplification. MET amplification was significantly associated with aggressive clinicopathological features, including high histological grade, advanced pT category, lymph node metastasis, and advanced American Joint Committee on Cancer stage. There was no significant correlation between any clinicopathological factors and MET overexpression. No difference in survival was found with respect to MET overexpression and amplification status.ConclusionOur data suggested that MET might be a potential therapeutic target for targeted therapy in gallbladder cancer, because MET amplification was found in a subset of tumors associated with adverse prognostic factors. Detection of MET amplification by ISH might be a useful predictive biomarker test for anti-MET therapy.

Abstract 214: Preclinical evaluation of a novel MET antibody-drug conjugate in uveal melanoma models

Abstract Uveal melanoma is the most common primary intraocular malignant tumor in adults. These tumors are characterized by mutations in G-proteins (GNAQ and GNA11) and high expression of MET, a receptor tyrosine kinase. While inhibition of MET signaling delays the development of uveal melanoma metastases in preclinical models (possibly by inhibiting cell migration), primary tumor growth is not inhibited, indicating a lack of dependence on the MET pathway. Thus, treatment of established metastatic uveal melanoma with MET signal blockers is unlikely to be effective. However, the high expression of MET protein in metastatic uveal melanoma presents an opportunity to directly kill tumor cells with a MET-targeted antibody drug conjugate (ADC). METxMET-ADC is a novel bispecific antibody that binds to two distinct epitopes on MET and is conjugated to a maytansinoid payload via a cleavable linker. The METxMET-ADC potently induces receptor internalization and mitotic arrest of cancer cells. Our in vitro studies show that the METxMET-ADC significantly and specifically decreases the viability of MET expressing uveal melanoma cell lines in a dose-dependent manner with an IC50 of less than 1 nM. A longer 7-day cell viability assay shows significantly enhanced inhibition of proliferation of several MET expressing cell lines (Mel270, Mel202, OMM1.3 and MP65) but not of OCM3 cells which express low levels of MET. Apoptosis is also induced up to 40% in the MET-expressing cell lines when treated with 10 nM of the METxMET-ADC for 48 hours. Cell cycle analysis shows a significant increase of OMM1.3 and Mel202 cells in mitosis after 6-24 hours of treatment and appearance of a sub-G1 population after 24-48 hours. Western blots confirm a decrease of MET protein levels, presumably due to receptor internalization and trafficking to lysosomes. Finally, treatment with the METxMET ADC is associated with induction of PARP cleavage and phosphorylation of histone H3 after 24 hours in OMM1.3 and Mel202 cells, but not in OCM3 cells. In summary, conjugation of a METxMET bispecific antibody with a cytotoxic payload allows for potent and selective killing of MET-expressing uveal melanoma cells. The METxMET-ADC demonstrates promising therapeutic potential for the treatment of uveal melanoma. Citation Format: Oliver Surriga, John DaSilva, Gary K. Schwartz. Preclinical evaluation of a novel MET antibody-drug conjugate in uveal melanoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 214.

Measuring phospho-MET by multiplex immunofluorescence to aid in selection of patients with MET activation in tumors.

3131 Background: Currently, patient selection criteria for clinical testing of MET inhibitors are limited. Robust studies selecting patients based on MET protein expression, MET gene amplification, or mutations have not met their efficacy goals. Development of microscopy-based assays to quantify levels of phospho-MET (pMET) in tumors has been hampered by poor antibody specificity. Here, we present the development and validation of a robust, highly specific multiplex immunofluorescence assay (IFA) that measures pY1235-MET and total MET in tumor tissue. Methods: This assay utilizes antibodies to pY1235-MET (NCI-23111), total MET (D1C2), and plasma membrane (PM) marker Na+/K+-ATPase, each conjugated to a different Alexa Fluor dye. We used tumor tissue from crizotinib-treated SNU5 xenograft models to demonstrate pY1235-MET assay fitness-for-purpose and cross-platform assay concordance with our validated pMET ELISA. In addition, this IFA was validated by phospho-peptide competition using custom tissue microarrays (TMA) derived from patients with colorectal carcinoma (CRC). Finally, we developed quantitative algorithms to assess pY1235 MET levels in the plasma membrane and nucleus using PM and DAPI masks, respectively. Patient-derived xenograft models (PDX) were obtained from NCI’s Patient-Derived Models Repository (www.pdmr.cancer.gov). Results: The prevalence of high pY1235-MET expression in CRC patient specimens was greater than expected; of the 64 TMA cores evaluated, 29 (45%) and 19 (29%) had high pY1235-MET and total MET levels, respectively, as defined by mean marker area of ≥ 30 μm2/cell. To address the potential utility of pY1235-MET as a diagnostic biomarker, we examined 15 CRC PDX models by pMET ELISA and IFA. Two CRC tumor models were positive for pY1235-MET expression in both assays. The pY1235-MET IFA results and gene expression data were used to select PDX models for ongoing preclinical trials of potent MET inhibitors. Conclusions: This novel pY1235-MET IFA will enable clinicians to address the utility of activated MET as a biomarker for patient selection and/or prediction of response in clinical trials of MET inhibitors. Funded by NCI Contract No. HHSN261200800001E.

P1.13-20 MET Protein Expression and Activation During Targeted Therapy in EGFR Mutated Lung Adenocarcinoma

P1.13-20 MET Protein Expression and Activation During Targeted Therapy in EGFR Mutated Lung Adenocarcinoma

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

BackgroundMyxofibrosarcoma (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.MethodsImmunohistochemistry 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.ResultsMET 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.ConclusionsIt might reveals another explain of MET overexpression in myxofibrosarcoma, providing a clue for the therapy of MFS.

Met is involved in TIGAR-regulated metastasis of non-small-cell lung cancer.

TIGAR is a p53 target gene that is known to protect cells from ROS-induced apoptosis by promoting the pentose phosphate pathway. The role of TIGAR in tumor cell invasion and metastasis remains elusive. Here we found that downregulation of TIGAR reduced the invasion and metastasis of NSCLC cells in vitro and in vivo. Immunohistochemical analysis of 72 NSCLC patients showed that TIGAR and Met protein expression was positively correlated with late stages of lung cancer. Besides, patients with high co-expression of TIGAR and Met presented a significantly worse survival. In addition, we found that Met signaling pathway is involved in TIGAR-induced invasion and metastasis. Our study indicates that TIGAR/Met pathway may be a novel target for NSCLC therapy. It is necessary to evaluate the expression of TIGAR before Met inhibitors are used for NSCLC treatment.

Keratin 19 Expression in Hepatocellular Carcinoma Is Regulated by Fibroblast-Derived HGF via a MET-ERK1/2-AP1 and SP1 Axis.

Keratin (KRT) 19 is a poor prognostic marker for hepatocellular carcinoma (HCC); however, regulatory mechanisms underlying its expression remain unclear. We have previously reported the presence of fibrous tumor stroma in KRT19-positive HCC, suggesting that cross-talk between cancer-associated fibroblasts (CAF) and tumor epithelial cells could regulate KRT19 expression. This was investigated in this study using an in vitro model of paracrine interaction between HCC cell lines (HepG2, SNU423) and hepatic stellate cells (HSC), a major source of hepatic myofibroblasts. HSCs upregulated transcription and translation of KRT19 in HCC cells via paracrine interactions. Mechanistically, hepatocyte growth factor (HGF) from HSCs activated c-MET and the MEK-ERK1/2 pathway, which upregulated KRT19 expression in HCC cells. Furthermore, AP1 (JUN/FOSL1) and SP1, downstream transcriptional activators of ERK1/2, activated KRT19 expression in HCC cells. In clinical specimens of human HCC (n = 339), HGF and KRT19 protein expression correlated with CAF levels. In addition, HGF or MET protein expression was associated with FOSL1 and KRT19 expression and was found to be a poor prognostic factor. Analysis of data from The Cancer Genome Atlas also revealed KRT19 expression was closely associated with CAF and MET-mediated signaling activities. These results provide insights into the molecular background of KRT19-positive HCC that display an aggressive phenotype.Significance: These findings reveal KRT19 expression in hepatocellular carcinoma is regulated by cross-talk between cancer-associated fibroblasts and HCC cells, illuminating new therapeutic targets for this aggressive disease. Cancer Res; 78(7); 1619-31. ©2018 AACR.

The impact of MET, IGF-1, IGF1R expression and EGFR mutations on survival of patients with non-small-cell lung cancer.

IntroductionTo compare the efficacy of silver in situ hybridization (SISH) and immunohistochemistry (IHC) in detecting MET and IGF1R alterations and to investigate their prevalence and prognostic significance. A possible correlation between MET receptor expression, MET gene alterations and the two most frequent occurring EGFR gene mutations was also investigated.Materials and methodsStage I to IIIA tumors from 326 patients with NSCLC were immunohistochemically tested for protein expression of MET and IGF-1. Their cytoplasmic expression was compared with the gene copy number of the MET and IGF1Rgenes by SISH in paraffin-embedded, formalin-fixed material. Correlations were made with the immunohistochemical expression of two frequent EGFR mutations and clinicopathological variables. Univariate and multivariate survival analyses was used to evaluate the prognostic efficacy of the tested markers.ResultsIn univariate analyses, high cytoplasmic MET expression showed a significant negative prognostic effect in adenocarcinoma patients (p = 0.026). MET gene to chromosome 7 ratio was a significant positive prognostic marker (p = 0.005), probably only due to the highly negative prognostic significance of chromosome 7 polysomy (p = 0.002). High IGF1R gene copy number was a negative prognostic marker for all NSCLC patients (p = 0.037). In the multivariate analysis, polysomy of chromosome 7 in tumor cells correlated significantly and independently with a poor prognosis (p = 0.011). In patients with adenocarcinoma, a high cytoplasmic MET expression was an independent negative prognostic marker (p = 0.013). In males a high IGF1R gene copy number to chromosome 15 count ratio was significantly and independently correlated to a poor prognosis (p = 0.018).ConclusionMET protein expression provides superior prognostic information compared with SISH. Polysomy of chromosome 7 is an independent negative prognostic factor in NSCLC patients. This finding has an important implication while examining genes located on chromosome 7 by means of SISH. High IGF1R gene copy number to chromosome 15 count ratio is an independent predictor of inferior survival in male patients with primary NSCLC.

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

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

P2.03b-078 MET Gene Amplification and Overexpression in Chinese NSCLC Patients without EGFR Mutations: Topic: Biomarkers

The prevalence and clinic pathologic characteristics of MET amplification and overexpression in Chinese patients with non-small cell lung cancer (NSCLC) remain unknown. In this multicenter study, we focus on revealing the frequency and clinic pathological characteristics of MET amplification and explore the predictive value of MET amplification and overexpression status to survival in Chinese NSCLC patients. MET amplification was detected by fluorescence in-situ hybridization (FISH) in 791 patients with EGFR wild-type samples. MET protein expression was detected by immunohistochemistry. In total, 8 patients were identified as harboring MET amplification from 791 NSCLC patients with EGFR wild-type. Among these 8 patients, one was with histology of adeno-squamous carcinoma and 7 of adenocarcinoma. There was no statistically significant difference among age, gender, smoking status and histologic type between patients with and without MET amplification. MET amplification was more frequent in advanced stage and solid predominant subtype of adenocarcinoma. MET protein expression was performed in 395 patients and 138 were positive. Patients with MET protein expression positive had an inferior overall survival compared to those without MET protein expression (45.0 months vs 65.8 months; P=0.001). Multivariate analysis revealed that MET expression was independent prognostic factor for poor overall survival (HR=1.497, P=0.017), while the MET amplification shows weak relevance for overall survival (HR=1.974, P=0.251). MET amplification was rare in Chinese NSCLC without EGFR mutation, with a prevalence of about 1%. MET expression but not amplification could be an independent prognostic factor for shorter OS among those EGFR wild-type NSCLC patients.

MET tyrosine kinase receptor expression and amplification as prognostic biomarkers of survival in gastroesophageal adenocarcinoma.

BACKGROUND MET gene amplification and Met protein overexpression may be associated with a poor prognosis. The MET/Met status is typically determined with fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), respectively. Targeted proteomics uses mass spectrometry–based selected reaction monitoring (SRM) to accurately quantitate Met expression. FISH, IHC, and SRM analyses were compared to characterize the prognostic value of MET/Met in gastroesophageal adenocarcinoma (GEC).METHODSSamples from 447 GEC patients were analyzed for MET gene amplification (FISH) and Met protein expression (IHC and SRM). Cox proportional hazards models and Kaplan‐Meier estimates were applied to explore relations between Met, overall survival (OS), and clinical/pathological characteristics. Spearman's rank coefficient was used to assess the correlation between parameters.RESULTSPatients with MET‐amplified tumors had worse OS when: the MET/centromere enumeration probe for chromosome 7 FISH ratio was ≥ 2 (hazard ratio [HR], 3.13; 95% confidence interval [CI], 1.84‐5.33), the MET gene copy number was ≥5 (HR, 2.51; 95% CI, 1.45‐4.34), or ≥ 10% of the cells had ≥15 copies (HR, 4.28; 95% CI, 2.18‐8.39). Similar observations were made with Met protein overexpression by IHC (≥1 + intensity in ≥ 25% of the tumor cell membrane: HR, 1.39; 95% CI, 1.04‐1.86) or SRM (≥400 amol/μg: HR, 1.76; 95% CI, 1.06‐2.90). A significant correlation was observed between MET FISH/Met IHC, MET FISH/Met SRM, and Met IHC/Met SRM; only MET FISH and Met SRM were independent negative prognostic biomarkers in multivariate analyses.CONCLUSIONS MET amplification and overexpression, assessed by multiple methods, were associated with a worse prognosis in univariate analyses. However, only MET amplification by FISH and Met expression by SRM were independent prognostic biomarkers. Compared with IHC, SRM may provide an added benefit for informed decisions about Met‐targeted therapy. Cancer 2017;123:1061–70. © 2016 American Cancer Society.

MET/ERK2 pathway regulates the motility of human alveolar rhabdomyosarcoma cells.

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

MET Gene Amplification and Overexpression in Chinese Non–Small-Cell Lung Cancer Patients Without EGFR Mutations

BackgroundThe prevalence and clinical pathologic characteristics of MET amplification and overexpression in Chinese patients with non–small-cell lung cancer (NSCLC) remain unknown. In this multicenter study, we sought to reveal the frequency and clinical pathologic characteristics of MET amplification and to explore the predictive value of MET amplification and overexpression status in relation to survival in Chinese NSCLC patients. Patients and MethodsMET amplification was detected by fluorescence in-situ hybridization in 791 patients with EGFR wild-type samples. MET protein expression was detected by immunohistochemistry. ResultsIn total, 8 of 791 NSCLC patients with EGFR wild type patients were identified as harboring MET amplification. Among these 8 patients, 1 had adenosquamous carcinoma histology and 7 adenocarcinoma. There was no statistically significant difference among age, sex, smoking status, and histologic type between patients with and without MET amplification. MET amplification was more frequent in advanced-stage disease and in the solid predominant subtype of adenocarcinoma. MET protein expression was performed in 395 patients, and 138 were positive. Patients positive for MET protein expression had worse overall survival (OS) compared to those without MET protein expression (45.0 vs. 65.8 months; P = .001). Multivariate analysis revealed that MET expression was an independent prognostic factor for poor OS (R = 1.497, P = .017), while MET amplification had weak relevance for OS (hazard ratio = 1.974, P = .251). ConclusionMET amplification was rare in Chinese NSCLC patients without EGFR mutation, with a prevalence of about 1%. MET expression but not amplification could be an independent prognostic factor for shorter OS among these EGFR wild-type NSCLC patients.

MET expression during prostate cancer progression.

Tyrosine-kinase inhibitors of the hepatocyte growth factor receptor MET are under investigation for the treatment of hormone-refractory prostate cancer (HRPC) metastasis. Analysis of MET protein expression and genetic alterations might contribute to therapeutic stratification of prostate cancer patients. Our objective was to investigate MET on protein, DNA and RNA level in clinical prostate cancer at various stages of progression.Expression of MET was analyzed in hormone-naive primary prostate cancers (N=481), lymph node (N=40) and bone (N=8) metastases, as well as HRPC (N=54) and bone metastases (N=15). MET protein expression was analyzed by immunohistochemistry (D1C2 C-terminal antibody). MET mRNA levels and MET DNA copy numbers were determined by in situ hybridization.None of the hormone-naive primary prostate cancer or lymph node metastases demonstrated MET protein or mRNA expression. In contrast, MET protein was expressed in 12/52 (23%) evaluable HRPC resections. RNA in situ demonstrated cytoplasmic signals in 14/54 (26%) of the HRPC patients, and was associated with MET protein expression (p=0.025, χ2), in absence of MET amplification or polysomy. MET protein expression was present in 7/8 (88%) hormone-naive and 10/15 (67%) HRPC bone metastases, without association of HRPC (p=0.37; χ2), with MET polysomy in 8/13 (61%) evaluable cases.In conclusion, MET was almost exclusively expressed in HRPC and prostate cancer bone metastasis, but was not related to MET amplification or polysomy. Evaluation of MET status could be relevant for therapeutic stratification of late stage prostate cancer.

The autism-associated MET receptor tyrosine kinase engages early neuronal growth mechanism and controls glutamatergic circuits development in the forebrain.

The human MET gene imparts a replicated risk for autism spectrum disorder (ASD), and is implicated in the structural and functional integrity of brain. MET encodes a receptor tyrosine kinase, MET, which plays a pleiotropic role in embryogenesis and modifies a large number of neurodevelopmental events. Very little is known, however, on how MET signaling engages distinct cellular events to collectively affect brain development in ASD-relevant disease domains. Here, we show that MET protein expression is dynamically regulated and compartmentalized in developing neurons. MET is heavily expressed in neuronal growth cones at early developmental stages and its activation engages small GTPase Cdc42 to promote neuronal growth, dendritic arborization, and spine formation. Genetic ablation of MET signaling in mouse dorsal pallium leads to altered neuronal morphology indicative of early functional maturation. In contrast, prolonged activation of MET represses the formation and functional maturation of glutamatergic synapses. Moreover, manipulating MET signaling levels in vivo in the developing prefrontal projection neurons disrupts the local circuit connectivity made onto these neurons. Therefore, normal time-delimited MET signaling is critical in regulating the timing of neuronal growth, glutamatergic synapse maturation and cortical circuit function. Dysregulated MET signaling may lead to pathological changes in forebrain maturation and connectivity, and thus contribute to the emergence of neurological symptoms associated with ASD.