Mesenchymal-epithelial Transition Amplification Research Articles

Heterogeneous ERBB gene pathways, their targeted treatment and possible molecular mechanisms of resistance in metastatic gallbladder cancer

BackgroundERBB amplifications and mutations are known in metastatic gallbladder cancer (GBC). We conducted a prospective study on targeted therapy based on comprehensive genomic profiling (CGP). We report molecular pathways of ERBB gene and outcomes and explored the molecular mechanism of resistance. MethodsCGP was done for all consecutive GBC patients aged >18 years. Foundation medicines CDx and TarGT Absolute were used for analysis. Patients were enrolled from Jan 2017 till Dec 2022. Patient recruitment was done after ethics committee approval. Trastuzumab and/ or lapatinib were used as targeted therapy. ResultsTwenty-six patients out of 60 had ERBB1-4 gene alteration (amplification and/or mutation) that resulted in activation of PI3K/AKT/MTOR and RAS/RAF/MEK pathways. ERBB amplification (16%) was the most common genetic aberration. Mutations in TP53, RB1, CDKs, and cyclins lead to dysregulation of cell cycle and evasion of apoptosis. A total of 50% of ERBB2-positive patients carry CDK12 amplifications. The intrinsic resistance to anti-ERBB2 therapy was primarily due to downstream activation in ERBB pathway (PIK3CA) and its crosstalk with cell cycle pathway (TP53 and CDK12), JAK/STAT, VEGF, CTNNB1, and ARID1A that are known to drive MAPK/ERK signaling. Mesenchymal epithelial transition amplification or activating mutations is mechanism of resistance to anti-ERBB2 therapy. Kinase/Juxta membrane domain mutations in ERBB family proteins are also one of the potential mechanisms of resistance. ConclusionGBC is enriched with ERBB gene aberrations. Targeted therapy of ERBB pathway has shown encouraging responses. CDK12 gene amplification is a possible mechanism of resistance identified.

Targeting MET in Non-Small Cell Lung Cancer (NSCLC): A New Old Story?

In recent years, we have seen the development and approval for clinical use of an increasing number of therapeutic agents against actionable oncogenic drivers in metastatic non-small cell lung cancer (NSCLC). Among them, selective inhibitors, including tyrosine kinase inhibitors (TKIs) and monoclonal antibodies targeting the mesenchymal-epithelial transition (MET) receptor, have been studied in patients with advanced NSCLC with MET deregulation, primarily due to exon 14 skipping mutations or MET amplification. Some MET TKIs, including capmatinib and tepotinib, have proven to be highly effective in this molecularly defined subgroup of patients and are already approved for clinical use. Other similar agents are being tested in early-stage clinical trials with promising antitumor activity. The purpose of this review is to provide an overview of MET signaling pathways, MET oncogenic alterations primarily focusing on exon 14 skipping mutations, and the laboratory techniques used to detect MET alterations. Furthermore, we will summarize the currently available clinical data and ongoing studies on MET inhibitors, as well as the mechanisms of resistance to MET TKIs and new potential strategies, including combinatorial approaches, to improve the clinical outcomes of MET exon 14-altered NSCLC patients.

The Role of MET in Resistance to EGFR Inhibition in NSCLC: A Review of Mechanisms and Treatment Implications.

Utilizing targeted therapy against activating mutations has opened a new era of treatment paradigms for patients with advanced non-small cell lung cancer (NSCLC). For patients with epidermal growth factor (EGFR)-mutated cancers, EGFR inhibitors, including the third-generation tyrosine kinase inhibitor (TKI) osimertinib, significantly prolong progression-free survival and overall survival, and are the current standard of care. However, progression after EGFR inhibition invariably occurs, and further study has helped elucidate mechanisms of resistance. Abnormalities in the mesenchymal-epithelial transition (MET) oncogenic pathway have been implicated as common alterations after progression, with MET amplification as one of the most frequent mechanisms. Multiple drugs with inhibitory activity against MET, including TKIs, antibodies, and antibody-drug conjugates, have been developed and studied in advanced NSCLC. Combining MET and EGFR is a promising treatment strategy for patients found to have a MET-driven resistance mechanism. Combination TKI therapy and EGFR-MET bispecific antibodies have shown promising anti-tumor activity in early clinical trials. Future study including ongoing large-scale trials of combination EGFR-MET inhibition will help clarify if targeting this mechanism behind EGFR resistance will have meaningful clinical benefit for patients with advanced EGFR-mutated NSCLC.

Analysis of MET genetic aberrations in Chinese solid tumor patients.

e15031 Background: Mesenchymal-epithelial transition (MET) gene encodes a member of the receptor tyrosine kinase family of proteins and is a proto-oncogene. MET gene takes part in various signaling pathways such as PI3K/AKT, Ras/MAPK, and JAK/STAT which are associated with tumor development and progression. This study aimed to reveal MET aberrated characteristics in Chinese solid tumor patients and explore the occurrence of MET oncogenic variants in solid tumors. Methods: This study retrospectively analyzed MET alterations in 1856 solid tumor patients in China from laboratory of Simcere Diagnosis (Nanjing, China) during 2019-2021. Next-generation sequencing (NGS) was performed to detect gene mutations in tumor or blood samples of the patients. Results: We screened out 1856 patients with MET gene alterations from 45717 patients with solid tumor. The high frequency of MET gene alterations was lung cancer (72.8%), colorectal cancer (10.7%), gastric cancer (4.9%), and liver cancer (2.7%). MET gene variants included missense (61.7%), copy number variation (copy number≥5) (15.4%), truncation (7.9%), splicing site variant (7.2%),fusion (1.7%),and in-frame insertion/deletions (0.9%). Among them, MET amplification was detected in 285 patients, and 93 patients carried high-level MET amplification (copy number≥10). High-level MET amplification was most frequently detected in lung cancer (41, 44.1%), gastric cancer (17, 18.3%) and liver cancer (14, 15.1%). MET exon 14 skipping was detected in 287 solid tumor patients (15.5%), of which 277 patients were lung cancer, the remaining were liver cancer, colorectal cancer, gastric cancer, osteosarcoma, melanoma, bladder cancer and glioma. We analyzed MET exon 14 alterations and classified them into 4 subgroups according to the alteration types and locations. The most common alterations were at splice donor sites (215, 74.91%), followed by the splice acceptor sites (35, 12.20%), Y1003 site (5, 1.74%), and other types (32, 11.15%). Other types included insertion or deletion in MET intron 13 or 14, for example, c.3028+21_3028+65del, c.2888-20_2888-11del, c.2888-27_2888-9del, etc. 7 lung cancer patients carried MET exon 14 skipping and MET amplification simultaneously. 36 patients carried MET gene fusions, and mostly were lung cancer (22, 61.1%). The breakpoints often located in exon 2 of MET (4, 11.1%). Conclusions: We discovered MET alterations in multiple types of solid tumors in this study. We found classic MET exon 14 skipping and MET high-level amplification in solid tumors except for lung cancer. It suggested that the activation of MET-driven signaling pathway was ubiquitous in pan-cancer, which might benefit from MET inhibitors.

Mesenchymal Epithelial Transition (MET): A Key Player in Chemotherapy Resistance and an Emerging Target for Potentiating Cancer Immunotherapy

The MET protein is a cell surface receptor tyrosine kinase predominately expressed in epithelial cells. Upon binding of its only known ligand, hepatocyte growth factor (HGF), MET homodimerizes, phosphorylates, and stimulates intracellular signalling to drive cell proliferation. Amplification or hyperactivation of MET is frequently observed in various cancer types and it is associated with poor response to conventional and targeted chemotherapy. More recently, emerging evidence also suggests that MET/HGF signalling may play an immunosuppressive role and it could confer resistance to cancer immunotherapy. In this review, we summarized the preclinical and clinical evidence of MET's role in drug resistance to conventional chemotherapy, targeted therapy, and immunotherapy. Previous clinical trials investigating MET-targeted therapy in unselected or METoverexpressing cancers yielded mostly unfavourable results. More recent clinical studies focusing on MET exon 14 alterations and MET amplification have produced encouraging treatment responses to MET inhibitor therapy. The translational relevance of MET inhibitor therapy to overcome drug resistance in cancer patients is discussed.

MET-Targeted Therapies and Clinical Outcomes: A Systematic Literature Review.

IntroductionNumerous therapeutic agents specifically targeting the mesenchymal-epithelial transition (MET) oncogene are being developed.ObjectiveThe aim of the current review was to systematically identify and analyze clinical trials that have evaluated MET inhibitors in various cancer types and to provide an overview of their clinical outcomes.MethodsAn electronic literature search was carried out in the PubMed and Embase databases to identify published clinical trials related to MET inhibitors. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement was followed for the systematic appraisal of the literature. Data related to clinical outcomes, including progression-free survival, overall survival, objective response rate, and overall tumor response, were extracted.ResultsIn total, 49 publications were included. Among these, 51.02% were phase II studies, 14.28% were randomized controlled trials, three were phase III studies, two were prospective observational studies, and the remainder were either phase I or Ib studies. The majority (44.89%) of articles reported the clinical outcomes of MET inhibitors, including small molecules, monoclonal antibodies, and other agents, in patients with non-small-cell lung cancer (NSCLC) harboring MET alterations. MET amplification, overexpression, and MET exon 14 skipping mutations were the major MET alteration types reported across the included studies. Clinical responses/outcomes varied considerably.ConclusionThis systematic literature review provides an overview of the literature available in Embase and PubMed regarding MET-targeted therapies. MET-selective tyrosine kinase inhibitors (TKIs) (capmatinib, tepotinib, and savolitinib) may become a new standard of care in NSCLC, specifically with MET exon 14 skipping mutations. A combination of MET TKIs with epidermal growth factor receptor (EGFR) TKIs (osimertinib + savolitinib, tepotinib + gefitinib) may be a potential solution for MET-driven EGFR TKI resistance. Further, MET alteration (MET amplification/overexpression) may be an actionable target in gastric cancer and papillary renal cell carcinoma.

Effect of mesenchymal-epithelial transition amplification on immune microenvironment and efficacy of immune checkpoint inhibitors in patients with non-small cell lung cancer.

BackgroundImmune checkpoint inhibitors (ICIs) have brought clinical benefits to patients with various histological types of lung cancer. Previous studies have shown an association between mesenchymal-epithelial transition (MET) and the immunotherapy response in non-small cell lung cancer (NSCLC) but there is a lack of clinical data on the correlation of MET amplification with the ICI response in NSCLC.MethodsCopy number alteration (CNA), somatic mutation, and clinical data from two immunotherapy cohorts (Rizvi et al. cohort and our local cohort) were collected and pooled to further investigate the key role of MET amplification in patients with NSCLC receiving ICIs. The correlations between MET amplification and tumor immunogenicity and antitumor immunity were further investigated in The Cancer Genome Atlas (TCGA)-NSCLC [lung adenocarcinoma (LUAD)/lung squamous cell carcinoma (LUSC)] data-set.ResultsIn the immunotherapy cohorts, MET amplification was associated with longer progression-free survival (PFS) times in patients receiving ICI treatment (P=0.039; HR =0.37; 95% CI: 0.18–0.73). In the TCGA-NSCLC data-set, MET amplification was associated with high MET mRNA and protein levels, tumor mutation burden (TMB), neoantigen load (NAL), immune-activated cell patterns, immune-related gene expression levels, and the number of gene alterations in the DNA damage response and repair (DDR) pathway. Gene set enrichment analysis (GSEA) results indicated significant up-regulation of the immune response-related pathways in the MET-amplification group.ConclusionsOur results suggest that MET amplification may be a novel predictive marker for immunotherapy efficacy in NSCLC.

Capmatinib (Tabrecta™)

Capmatinib (Tabrecta™)

Targeted Therapy Approaches for MET Abnormalities in Non-Small Cell Lung Cancer.

The tyrosine kinase receptor mesenchymal epithelial transition (MET) is a proto-oncogene that, through the activation of the MET-hepatocyte growth factor (HGF) pathway, encodes a variety of biological processes, including cell development, proliferation, invasion, and migration. Abnormal activation of the MET pathway, occurring through MET protein overexpression, and gene amplification or mutation, can contribute to oncogenesis and has been implicated in non-small cell lung cancer (NSCLC). Though it is associated with poor clinical outcome in NSCLCs, MET overexpression and its role as a therapeutic target remains somewhat elusive due to discrepancies in its occurrence. Unlike MET overexpression, MET amplification has demonstrated a stronger potential as a biomarker for therapeutic treatment, with clinical data indicating a compelling connection between a high MET gene copy number and a high response rate to targeted therapies. However, MET exon 14 skipping mutations, occurring in 3%-4 % of lung adenocarcinomas, are of particular interest, as tumors harboring these mutations have shown a significant response to MET inhibitors. Following the discovery of MET as a potential therapeutic target, extensive clinical studies have proposed three approaches to targeting MET: (1) MET tyrosine kinase inhibitors (TKIs), including crizotinib, capmatinib, tepotinib, savolinitib, and cabozantinib; (2) MET or HGF monoclonal antibodies, including emibetuzumab and ficlatuzumab; and (3) MET or HGF antibody drug conjugates, including telisotuzumab. Herein, we discuss the relevant clinical trials, particularly focusing on the efficacy as well as the safety and tolerability of the treatment options, in the promising field of targeting MET in NSCLC.

Narrative review: mesenchymal-epithelial transition inhibitors-meeting their target.

Genetic alterations in mesenchymal-epithelial transition (MET) are commonly found in solid tumors, especially in non-small cell lung cancer (NSCLC). However, agents targeting MET have not progressed until recently. Advancements in our understanding of the role of various MET aberrations in carcinogenesis have allowed MET-directed therapy to find its way to clinic use. Of all MET alterations, MET exon 14 skipping (METex14 skip+ or MET∆14), stands out as a true oncogenic driver. Recently, MET tyrosine kinase inhibitors (TKI) targeting METex14 skipping were able to demonstrate significant improvement in clinical outcomes including response rate and progression free survival. Of these, capmatinib was granted accelerated approval by the FDA in May 2020 for patients with advanced NSCLC harboring METex14 skip alterations. Tepotinib, another TKI, has shown significant activity in a phase II trial and received breakthrough therapy designation from the FDA in September 2019. MET amplification (METAmp) and overexpression are usually a late phenomenon in tumorigenesis and aggravate malignant properties of transformed cells. Capmatinib and savolitinib have shown activity in patients with NSCLC with high levels of METAmp. Several other agents are being developed and under evaluation in clinical trials involving multiple tumor types. In addition to TKIs, MET overexpression is also an appealing target for development of antibody conjugated chemotherapy. Understanding the mechanisms of resistance to MET TKIs and alterations in anti-tumor immunity through MET inhibition are clinically relevant areas that need further exploration.

Molecular testing of metastatic non-small cell lung cancer in the Asia-Pacific region.

Molecular testing of metastatic non-small cell lung cancer in the Asia-Pacific region.

Abstract 1356: GENOCTC, a highly efficient system for enrichment of circulating tumor cells and its clinical application

Abstract Background: Liquid biopsy has been reported as a potential surrogate for detection of cancer biomarkers with minimally invasive procedures. Particularly, numerical, phenotypical and genetical information of circulating tumor cells (CTCs), one of critical liquid biopsy materials, is well known to have clinical significances predicting and monitoring of disease progression, drug response and metastasis. However, a number of technical challenges for isolating CTCs and appropriate downstream analysis are still to be addressed. Methods: Here we designed high-throughput CTC enrichment device, GenoCTC, which adopted microfluidic magnetophoresis and CTC isolation chip with optimized ferromagnetic wire patterned on it. CTCs were enriched either by Anti-human EpCAM beads, a marker for mesenchymal-epithelial transition (MET), or Anti-human Vimentin beads, a marker for epithelial-mesenchymal transition (EMT). After immuno-magnetic based separation for EpCAM positive or Vimentin positive cells, CTCs are characterized by immunocytochemistry with Cytokeratin 18 and CD45, and then enumerated. Furthermore, MET amplification was investigated with isolated CTCs by ddPCR. Results: GenoCTC performance was optimized using the EpCAM positive cancer cell line, MCF7; 63% of recovery, 88% of separation rate and 93% of purity in whole blood spiking test. Analyzing 16 clinical blood samples from 10 non-small cell lung cancer (NSCLC) patients receiving drug treatment, the number of CTCs ranged from 2 to 112 CTCs per 7.5 mL. In serial CTC assessment of 5 NSCLC patients, transient changes in CTC numbers were observed which was positively correlated with the clinical course of disease progression. Moreover, c-MET amplification was confirmed only in CTCs, but not in ctDNA or tissue biopsy, at the point of progressive disease (PD) status in NSCLC patient with stable disease (SD). We also investigated the different CTCs counts between EpCAM and Vimentin based isolation in breast cancer patients. Interestingly, in patient with triple negative breast cancer, we observed only 1 CTC in case of separation based on EpCAM, but when separated by Vimentin, 26 CTCs were found. This result suggests CTCs may show the MET or EMT status of cancer in each patient. Conclusion: A newly developed GenoCTC can isolate CTCs sensitively and precisely and enable to reveal the clinical significance of CTCs. We expect this novel microfluidic device may facilitate the use of CTCs on diagnostic and prognostic criteria. Citation Format: Miso Lee, Jiyeon Ryu, Hyeon Jin Kim, Dohyeong Kim, Mi Young Kim, Jin-Soo Kim, Seok-Woo Shin, Young Kee Shin, Seokbum Ko, Hun Seok Lee. GENOCTC, a highly efficient system for enrichment of circulating tumor cells and its clinical application [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 1356.

Identification of subsets of IDH-mutant glioblastomas with distinct epigenetic and copy number alterations and stratified clinical risks.

Background IDH-mutant glioblastoma is classified by the 2016 CNS WHO as a group with good prognosis. However, the actual number of cases examined in the literature is relatively small. We hypothesize that IDH-mutant glioblastoma is not a uniform group and should be further stratified.MethodsWe conducted methylation profiles and estimated copy number variations of 57 IDH-mutant glioblastomas.ResultsOur results showed that 59.6% and 40.4% of tumors belonged to glioma-CpG island methylator phenotype (G-CIMP)-high and G-CIMP-low methylation subgroups, respectively. G-CIMP-low subgroup was associated with significantly worse overall survival (OS) as compared to G-CIMP-high (P = .005). CDKN2A deletion (42.1%) was the most common gene copy number variation, and was significantly associated with G-CIMP-low subgroup (P = .004). Other frequent copy number changes included mesenchymal–epithelial transition (MET) (5.3%), CCND2 (19.3%), PDGFRA (14.0%), CDK4 (12.3%), and EGFR (12.3%) amplification. Both CDKN2A deletion (P = .036) and MET amplification (P < .001) were associated with poor OS in IDH-mutant glioblastomas. Combined epigenetic signature and gene copy number variations separated IDH-mutant glioblastomas into Group 1 (G-CIMP-high), Group 2 (G-CIMP-low without CDKN2A nor MET alteration), and Group 3 (G-CIMP-low with CDKN2A and/or MET alteration). Survival analysis revealed Groups 1 and 2 exhibited a favorable OS (median survival: 619 d [20.6 mo] and 655 d [21.8 mo], respectively). Group 3 exhibited a significant shorter OS (median survival: 252 d [8.4 mo]). Multivariable analysis confirmed the independent prognostic significance of our Groups.Conclusions IDH-mutant glioblastomas should be stratified for risk with combined epigenetic signature and CDKN2A/MET status and some cases have poor outcome.

Abstract 2723: MET exon 14 skipping mutations in advanced non-small cell lung cancer (NSCLC) are not associated with MET amplification and overexpression

Abstract Background: Activating alterations of the mesenchymal epithelial transition (MET) oncogene in NSCLC are potentially actionable with targeted MET inhibitors. MET exon 14 skipping mutations have been described in 3% of patients (p) in NSCLC,.Fluorescent in situ hybridization (FISH) and immunohistochemistry (IHC) are currently used for detecting MET amplification and overexpression, respectively, but are not useful to detect MET splicing variants. On the other hand, the reverse transcription-polymerase chain reaction (RT-PCR) technique has the potential to detect this actionable alteration. Methods: We designed and validated a custom set of 5´and 3´ primers to detect the MET exon 14 splicing variant by RT-PCR. RNA isolation from FFPE samples was performed with Roche High Pure FFPET RNA isolation kit and M-MLV Reverse Transcriptase enzyme was used in the RT-PCR. A panel of cell lines was initially employed to assess the performance of the technique. Subsequently, a total of 232 formalin-fixed paraffin-embedded (FFPE) samples from advanced NSCLC patients were analyzed. Of them, 15 were positive by RT-PCR (n=209) for the MET exon 14 variant. The bands corresponding to the splicing variant were submitted to Sanger sequencing. Results were compared with FISH (ZytoVision Dual Color probe Z-2087-200) and IHC (Ventana CONFIRM anti-Total c-MET (SP44)). Results: A total of 232 EGFR-wt advanced NSCLC p were analyzed by IHC and 42 (18.1%) were considered as positive (cut-off 3+≥ 50%). Regarding FISH, MET amplification was detected in 13 out of 58 p (22.4%) evaluable while the MET exon 14 skipping variant was detected in 15 (7.2%) out of 209 p . Unexpectedly, only three (21.4%) of the positive MET exon 14 skipping p by RT-PCR were positive for IHC. Finally, of the 15 MET exon 14 positive p, 5 were evaluable for FISH and none of them were positive for MET amplification. Conclusion: In our cohort of 232 EGFR-wt, advanced NSCLC p, the MET exon 14 skipping mutation had an incidence of 7.2% No correlation was found between the presence of the MET exon 14 variant by RT-PCR and MET overexpression or amplification. Detection of MET exon 14 alterations poses a challenge for diagnostic testing. Citation Format: Ana Gimenez-Capitan, Cristina Teixidó, Cristina Aguado, Sonia Rodríguez, Jordi Bertran-Alamillo, Josep Castellví, Zaira Yeste, Ana Pérez, Rafael Rosell, Miguel Angel Molina-Vila. MET exon 14 skipping mutations in advanced non-small cell lung cancer (NSCLC) are not associated with MET amplification and overexpression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2723. doi:10.1158/1538-7445.AM2017-2723

MET overexpression and gene amplification: prevalence, clinico-pathological characteristics and prognostic significance in a large cohort of patients with surgically resected NSCLC.

The prevalence of overexpression and amplification of the proto-oncogene mesenchymal epithelial transition (MET) in non-small cell lung cancer (NSCLC) varies greatly in the literature. Since MET is a potential treatment target, knowledge of its prevalence and prognostic importance is crucial. We investigated MET expression and gene status in 735 NSCLC cases using tissue microarrays. Prognostic significance as well as correlations with various clinico-pathological parameters were evaluated. The prevalence of MET overexpression was 17% and MET amplification was present in 2.4% of cases. MET overexpression was found more frequently in adenocarcinomas (and TTF1-positive tumors) and female patients and was also associated with expression of members of the epidermal growth factor receptor (EGFR) signaling cascade. MET amplified tumors tended to express MET more frequently and more intensively. MET expression or gene status did not prove to be relevant prognostic factors. MET may not be an unequivocal prognostic parameter; however, its expression is associated with certain clinico-pathological characteristics and with EGFR and downstream EGFR effectors. This could be an important point for future studies addressing targeted MET therapy and should be considered as a possible means of optimizing the benefit and minimizing undesirable effects.

Co-amplification of MET and PIK3CA in NSCLC and data on a PDX mouse model.

11591 Background: Amplification of the mesenchymal-epithelial transition ( MET) proto-oncogene or phosphatidylinositol3-kinase ( PI3K) is common in non-small-cell lung cancer (NSCLC) and represents a potential therapeutic target. NSCLC with coexisting driver mutations or amplifications is a cause of great concern. Methods: From 2013 until now, fluorescence in situ hybridization was used to screen for MET amplified NSCLC patients.The amplification of the MET was defined as centromere 7 ratio ≥ 2.0 and the criterion of Cappuzzi. The amplification of the PIK3CA was copy numbers ≥ 4.0. We established the patient-derived exnograft (PDX) mouse model from a dual MET/PIK3CA-amplified patient. Preclinical efficacy of single versus dual inhibition was evaluated in vivo. Six groups were allocated to receive the treatment of vehicle control, bozitinib,crizotinib, taselisib (PI3K inhibitor), bozitinib+taselisib, or crizotinib+taselisib, respectively. Results: Totally, 568 (568/2321, 24.47%) patients harbored positive MET amplification and 6 (6/568,1%) were comfirmed with dual MET/PI3K amplification. The two stageⅣ patients received MET inhibitor treatment.One trial (NCT02896231) patient was treated with bozitinib and achieved confirmed PR, but with 3 months PFS and 5 months OS. The best response was PR and PFS was 5.6 months for the other one receiving the study drug capmatinib (NCT02276027). In the PDX mouse model experiment, we found three single-anget inhibitors monotherapy to be active but only transiently effective in controlling the growth of PDX. The PDX models showed more sensitivity to taselisib among the three single-anget groups. In contrast, the combination of the two inhibitors caused a stronger and long-lasting growth inhibition in PDX models. The addition of taselisib to bozitinib or crizotinib monotherapy provided obvious enhanced activity. Regretfully, two mice died because of the toxicities in the crizotinib+taselisib group. Conclusions: Patients with dual MET/PIK3CA amplification represent a rare molecular subtype of NSCLC and have a relatively short duration of response to MET inhibitors.The combination of MET/PI3K inhibitors is synergistic preclinically.

MET and ALK in glioblastoma multiforme (GBM): Comparison of IHC and FISH.

2021 Background: GBM, the most common and lethal malignant primary brain tumor in adults, has an overall one-year life expectancy of 33.7%. Personalized medicine on the basis of predictive biomarkers remains elusive in GBM; however a recent case report showed clinical improvement after treatment with a mesenchymal-epithelial transition (MET) inhibitor. The authors of that report ascribe clinical response to the MET inhibitor, but the drug is also an inhibitor of anaplastic lymphoma kinase (ALK). We explored the co-expression, gain, or amplification of both MET and ALK by IHC and FISH in GBM. Methods: A convenience sample of 56 available tumors from gross-resected GBM cases within the Duke Brain Tumor tissue bank was stained for MET using clone 8F11 (Leica) and for ALK using clone 5A4 (Novocastra). FISH employed the LSI ALK (2p23) breakpoint-spanning dual-color DNA probe and the LSI D7S486 (MET)/CEP 7 dual color DNA probe (Vysis). Results: Of 56 GBM cases, MET was expressed in 69.6% and ALK in 17.9% by IHC. By FISH, gain or amplification was found in 100% of cases for MET and in 48.2% for ALK. Co-expression of MET and ALK by IHC was 14.3% and 48.2% by FISH. Co-expression by either IHC or FISH was also 48.2%. OS estimation for this cohort is premature, with 77% of patients still alive. Conclusions: MET and ALK are (co-)expressed in a significant proportion of GBM. IHC detection of MET and ALK did not correlate well with FISH results, suggesting that gene gain or amplification does not necessarily lead to abnormal MET and ALK protein expression or that IHC methods or antibodies used can be optimized. Prior studies reported MET amplification in GBM as low as 4%. Our study indicates that MET gain/amplification and protein expression may be much higher, having implications for MET-targeted therapy. Additionally, co-expression of ALK and MET has implications for dual inhibitors of these signaling pathways as well as resistance mechanisms. Our continued work will explore significance of MET and ALK as predictors of therapeutic response, with careful control for clinically relevant patient and disease characteristics. [Table: see text]