Molecular Diagnostic Assays and Clinicopathologic Implications of MET Exon 14 Skipping Mutation in Non-small-cell Lung Cancer

MET alterations in advanced non-small cell lung cancer

Precision medicine has helped identify several tumor molecular aberrations to be treated with targeted therapies. These therapies showed substantial improvement in efficacy without excessive toxicity in patients with specific oncogenic drivers with advanced cancers. In metastatic lung cancers, the implementation of broad platforms for molecular tumor sequencing has helped oncology providers identify oncogenic drivers linked with better outcomes when treated upfront with targeted therapies. Mesenchymal-epithelial transition factor (MET) alterations are present in up to 60% of non-small cell lung cancer and are associated with a poor prognosis. Capmatinib and tepotinib are currently the only two approved targeted therapies by the U.S. Food and Drug Administration (FDA) for patients with MET exon 14 skipping mutation. Several agents are being developed to tackle an unmet need in patients with MET alterations. Some of these agents are being used in combination with EGFR targeted therapy to mitigate resistance to EGFR inhibitor. These agents are poised to provide new hope for these patients.

Chinese expert consensus on clinical practice of MET detection in non-small cell lung cancer

Mesenchymal epithelial transition (MET) factor alteration in non-small cell lung cancer (NSCLC) includes MET exon 14 skipping alteration (METex14 skipping), MET gene amplification, MET gene mutation (mainly kinase domain mutation), MET gene fusion, and MET protein overexpression. The incidence of METex14 skipping in patients with NSCLC is 0.9-4.0%. At present, drugs targeting METex14 skipping have been approved in China and other countries like Japan and USA. Patients with advanced NSCLC should undergo testing, including METex14 skipping, to screen the population with benefit from targeted therapy with MET inhibitors. The incidence of de novo MET gene amplification in NSCLC patients is 1-5%, the incidence of acquired MET gene amplification in epidermal growth factor receptor tyrosine kinase inhibitor (TKI)-resistant patients is 5-50%, and the incidence in anaplastic lymphoma kinase (ALK) TKI-resistant patients is about 13%; the incidence of MET protein overexpression in NSCLC patients is 13.7-63.7%. Several clinical trials on MET gene amplification and MET protein overexpression are ongoing, which have demonstrated their important guiding significance as biomarkers in the clinical treatment with MET inhibitors. Accurate detection of MET alterations is a prerequisite for MET inhibitor therapy. Since there are many types of MET alterations and related testing methods, as well as many problems and challenges during clinical testing, further sorting and standardization are required. Combined with clinical practice experience, literature review, and expert discussion, the writing group developed this consensus on the three main types of MET alterations (METex14 skipping, MET gene amplification, and MET protein overexpression) in order to guide the practical applications of clinical MET testing.

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.

An Italian Multicenter Perspective Harmonization Trial for the Assessment of MET Exon 14 Skipping Mutations in Standard Reference Samples

Lung cancer remains the leading cause of cancer deaths worldwide. International societies have promoted the molecular analysis of MET proto-oncogene, receptor tyrosine kinase (MET) exon 14 skipping for the clinical stratification of non-small cell lung cancer (NSCLC) patients. Different technical approaches are available to detect MET exon 14 skipping in routine practice. Here, the technical performance and reproducibility of testing strategies for MET exon 14 skipping carried out in various centers were evaluated. In this retrospective study, each institution received a set (n = 10) of a customized artificial formalin-fixed paraffin-embedded (FFPE) cell line (Custom METex14 skipping FFPE block) that harbored the MET exon 14 skipping mutation (Seracare Life Sciences, Milford, MA, USA), which was previously validated by the Predictive Molecular Pathology Laboratory at the University of Naples Federico II. Each participating institution managed the reference slides according to their internal routine workflow. MET exon 14 skipping was successfully detected by all participating institutions. Molecular analysis highlighted a median Cq cut off of 29.3 (ranging from 27.1 to 30.7) and 2514 (ranging from 160 to 7526) read counts for real-time polymerase chain reaction (RT-PCR) and NGS-based analyses, respectively. Artificial reference slides were a valid tool to harmonize technical workflows in the evaluation of MET exon 14 skipping molecular alterations in routine practice.

Optimized Detection of Unknown MET Exon 14 Skipping Mutations in Routine Testing for Patients With Non-Small-Cell Lung Cancer

PURPOSE

MET exon 14 (METex14) skipping is an actionable biomarker in non-small-cell lung cancer. However, MET variants are highly complex and diverse, and not all variants lead to exon 14 skipping. Assessing the skipping effect of unknown variants is still a key issue in molecular diagnosis.

MATERIALS AND METHODS

We retrospectively collected MET variants around exon 14 from 4,233 patients with non-small-cell lung cancer who underwent next-generation sequencing testing using DNA, as well as two published data sets.

RESULTS

Among the 4,233 patients, 44 unique variants including 29 novel variants (65.9%) were discovered from 53 patients. Notably, 31 samples (58.5%) failed RNA verification. Using RNA verification, nine novel skipping variants and five nonskipping variants were confirmed. We further used SpliceAI with the delta score cutoff of 0.315 to aid the classification of novel variants (sensitivity = 98.88% and specificity = 100%). When applied to the reported variants, we also found three wrongly classified nonskipping variants. Finally, an optimized knowledge-based interpretation procedure for clinical routine was built according to the mutation type and location, and five more skipping mutations from the 13 unknown variants were determined, which improved the population determination rate to 0.92%.

CONCLUSION

This study discovered more METex14 skipping variants and optimized an innovative approach that could be adapted for the interpretation of infrequent or novel METex14 variants timely without experimental validation.

[Research Progresses in the Treatment of NSCLC with MET Gene Variants: A Riview]

Mesenchymal-epithelial transition factor (MET) has long been considered as the most crucial and promising driver gene in the occurrence and development of non-small cell lung cancer (NSCLC), except for epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), and c-ROS oncogene 1 receptor tyrosine kinase (ROS1). In recent years, therapeutic drugs targeting MET have been continuously developed and applied in clinical practice. First, the curative effect of NSCLC patients with MET exon 14 skipping mutations has been further improved. In addition, when MET amplification occurs after resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs) in patients with advanced EGFR-mutant NSCLC, the combination of MET-TKIs and EGFR-TKIs has brought significant survival benefits and many other advances. This article reviews the treatment progress of NSCLC patients with different types of MET variants under different circumstances, which provides reference for the selection of clinical treatment strategies.
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MET Signaling Pathways, Resistance Mechanisms, and Opportunities for Target Therapies

The MET gene, known as MET proto-oncogene receptor tyrosine kinase, was first identified to induce tumor cell migration, invasion, and proliferation/survival through canonical RAS-CDC42-PAK-Rho kinase, RAS-MAPK, PI3K-AKT-mTOR, and β-catenin signaling pathways, and its driver mutations, such as MET gene amplification (METamp) and the exon 14 skipping alterations (METex14), activate cell transformation, cancer progression, and worse patient prognosis, principally in lung cancer through the overactivation of their own oncogenic and MET parallel signaling pathways. Because of this, MET driver alterations have become of interest in lung adenocarcinomas since the FDA approval of target therapies for METamp and METex14 in 2020. However, after using MET target therapies, tumor cells develop adaptative changes, favoring tumor resistance to drugs, the main current challenge to precision medicine. Here, we review a link between the resistance mechanism and MET signaling pathways, which is not only limited to MET. The resistance impacts MET parallel tyrosine kinase receptors and signals shared hubs. Therefore, this information could be relevant in the patient's mutational profile evaluation before the first target therapy prescription and follow-up to reduce the risk of drug resistance. However, to develop a resistance mechanism to a MET inhibitor, patients must have access to the drugs. For instance, none of the FDA approved MET inhibitors are registered as such in Chile and other developing countries. Constant cross-feeding between basic and clinical research will thus be required to meet future challenges imposed by the acquired resistance to targeted therapies.

Meeting an un-MET need: Targeting MET in non-small cell lung cancer

The MET pathway can be activated by MET exon 14 skipping mutations, gene amplification, or overexpression. Mutations within this pathway carry a poor prognosis for patients with non-small cell lung cancer (NSCLC). MET exon 14 skipping mutations occur in 3-4% of patients with NSCLC, while MET amplifications are found in 1-6% of patients. The most effective method for detection of MET amplification is fluorescent in situ hybridization (FISH) and of MET exon 14 skipping mutations is RNA-based next generation sequencing (NGS). Immunohistochemistry (IHC) is an alternative method of diagnosis but is not as reliable. Early studies of MET tyrosine kinase inhibitors (TKIs) demonstrated limited clinical benefit. However, newer selective MET TKIs, such as capmatinib and tepotinib, have improved efficacy. Both drugs have an acceptable safety profile with the most common treatment-related adverse event being peripheral edema. One of the most frequent resistance mechanisms to EGFR inhibition with osimertinib is MET amplification. There is interest in combining EGFR inhibition plus MET inhibition in an attempt to target this resistance mechanism. Additional ways of targeting MET alterations are currently under investigation, including the bi-specific antibody amivantamab. Additional research is needed to further understand resistance mechanisms to MET inhibition. There is limited research into the efficacy of immune checkpoint inhibition for MET-altered NSCLC, though some data suggests decreased efficacy compared with wild-type patients and increased toxicity associated with the combination of immunotherapy and MET TKIs. Future directions for research will include combination clinical trials and understanding rational combinations for MET alterations.

MET alterations in NSCLC—Current Perspectives and Future Challenges

Targeted therapies have revolutionized the treatment and improved the outcome for oncogene-driven NSCLC and an increasing number of oncogenic driver therapies have become available. For MET-dysregulated NSCLC (especially MET exon 14 skipping mutations and MET-amplifications, which is one of the most common bypass mechanisms of resistance in oncogene-addicted NSCLC), several anti-MET-targeted therapies have been approved recently (MET exon 14 skipping mutation) and multiple others are in development. In this narrative review, we summarize the role of MET as an oncogenic driver in NSCLC, discuss the different testing methods for exon 14 skipping mutations, gene amplification, and protein overexpression, and review the existing data and ongoing clinical trials regarding targeted therapies in MET-altered NSCLC. As immunotherapy with or without chemotherapy has become the standard of care for advanced NSCLC, immunotherapy data for MET-dysregulated NSCLC are put into perspective. Finally, we discuss future challenges in this rapidly evolving landscape.

Characterization of MET Exon 14 Skipping Alterations (in NSCLC) and Identification of Potential Therapeutic Targets Using Whole Transcriptome Sequencing

Introduction

Genomic alterations in the juxtamembrane exon 14 splice sites in NSCLC lead to increased MET stability and oncogenesis. We present the largest cohort study of MET Exon 14 (METex14) using whole transcriptome sequencing.

Methods

A total of 21,582 NSCLC tumor samples underwent complete genomic profiling with next-generation sequencing of DNA (592 Gene Panel, NextSeq, whole exome sequencing, NovaSeq) and RNA (NovaSeq, whole transcriptome sequencing). Clinicopathologic information including programmed death-ligand 1 and tumor mutational burden were collected and RNA expression for mutation subtypes and MET amplification were quantified. Immunogenic signatures and potential pathways of invasion were characterized using single-sample gene set enrichment analysis and mRNA gene signatures.

Results

A total of 533tumors (2.47%) with METex14 were identified. The most common alterations were point mutations (49.5%) at donor splice sites. Most alterations translated to increased MET expression, with MET co-amplification resulting in synergistic increase in expression (q < 0.05). Common coalterations were amplifications of MDM2 (19.0% versus 1.8% wild-type [WT]), HMGA2 (13.2% versus 0.98% WT), and CDK4 (10.0% versus 1.5% WT) (q < 0.05). High programmed death-ligand 1 > 50% (52.5% versus 27.3% WT, q < 0.0001) and lower proportion of high tumor mutational burden (>10 mutations per megabase, 8.3% versus 36.7% WT, p < 0.0001) were associated with METex14, which were also enriched in both immunogenic signatures and immunosuppressive checkpoints. Pathways associated with METex14 included angiogenesis and apical junction pathways (q < 0.05).

Conclusions

METex14 splicing alterations and MET co-amplification translated to higher and synergistic MET expression at the transcriptomic level. High frequencies of MDM2 and CDK4 co-amplifications and association with multiple immunosuppressive checkpoints and angiogenic pathways provide insight into potential actionable targets for combination strategies in METex14 NSCLC.

Spotlight on Tepotinib and Capmatinib for Non-Small Cell Lung Cancer with MET Exon 14 Skipping Mutation

Mesenchymal-epithelial transition (MET) receptor tyrosine kinase is overexpressed, amplified, or mutated in 1–20% of NSCLC. MET dysregulation is associated with a poor prognosis. Recently, development of targeted therapies against MET exon 14 mutations has demonstrated efficacy and tolerability in early trials. Here we focus on tepotinib and capmatinib in regards to molecular characteristics, early preclinical and clinical data, and the emerging role in future studies and clinical practice.

The Clinically Actionable Molecular Profile of Early versus Late-Stage Non-Small Cell Lung Cancer, an Individual Age and Sex Propensity-Matched Pair Analysis

Background: Despite meticulous surgery for non-small cell lung cancer (NSCLC), relapse is as high as 70% at 5 years. Many institutions do not conduct reflexive molecular testing on early stage specimens, although targeted gene therapy may extend life by years in the event of recurrence. This ultimately delays definitive treatment with additional biopsy risking suboptimal tissue acquisition and quality for molecular testing. Objective: To compare molecular profiles of genetic alterations in early and late NSCLC to provide evidence that reflexive molecular testing provides clinically valuable information. Methods: A single-center propensity matched retrospective analysis was conducted using prospectively collected data. Adults with early and late-stage NSCLC had tissue subject to targeted panel-based NGS. Frequencies of putative drivers were compared, with 1:3 matching on the propensity score; p < 0.05 deemed statistically significant. Results: In total, 635 NSCLC patients underwent NGS (59 early, 576 late); 276 (43.5%) females; age 70.9 (±10.2) years; never smokers 140 (22.0%); 527 (83.0%) adenocarcinomas. Unadjusted frequencies of EGFR mutations were higher in the early cohort (30% vs. 18%). Following adjustment for sex and smoking status, similar frequencies for both early and late NSCLC were observed for variants in EGFR, KRAS, ALK, MET, and ROS1. Conclusion: The frequency of clinically actionable variants in early and late-stage NSCLC was found to be similar, providing evidence that molecular profiling should be performed on surgical specimens. This pre-determined profile is essential to avoid treatment delay for patients who will derive clinical benefit from targeted systemic therapy, in the high likelihood of subsequent relapse.

Met inhibitors in the treatment of lung cancer: the evidence to date

INTRODUCTION

: The hepatocyte growth factor (HGF) receptor MET is an oncogenic driver in a subpopulation of Non-small Lung Cancer Cells (NSCLC) at the primary tumor stage or in acquired resistance to treatment with tumor-targeting tyrosine kinase inhibitors (TKIs).

AREAS COVERED

This article summarizes the mechanisms leading to overexpression and activation of MET by amplification and mutations including exon 14 aberrations. Furthermore, the methods to detect and categorize MET as a tumor driver and the selective TKIs for patient treatment are discussed.

EXPERT OPINION

: Activating mutations and rearrangements of kinases in NSCLC are the target of successful therapeutic intervention. However, MET activation involves a number of complex alterations including gene amplification, prevention of degradation by METex14 exon skipping and a host of gene mutations. A high-level of MET expression is the precondition for tumor responses to TKIs and the confirmation of MET-dependent tumor progression is difficult in primary lesions and in tumors exhibiting resistance to mutated EGFR-directed therapy in absence of standardized and concordant assays of MET amplification.

Roles of MET in human cancer

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

Pulmonary sarcomatoid carcinoma mimicking pleural mesothelioma: A case report

INTRODUCTION

Pulmonary sarcomatoid carcinoma (PSC) is an extremely rare biphasic tumor characterized by a mixture of malignant epithelial and mesenchymal cells. Owing to the rarity, as well as the lack of typical manifestations and imaging signs, the rate of misdiagnosis is high. Herein, we present a case of PSC misdiagnosed as pleural mesothelioma in a 59-year-old man.

PATIENT CONCERNS

A 59-year-old man presented with recurrent coughing, fever, and chest pain.

DIAGNOSIS

Chest computed tomography showed 2 large and dense masses involving the inferior lobes of right lung, along with slight irregular pleural thickening and a small amount of effusion.

INTERVENTIONS

Chest computed tomography-guided tumor biopsy was performed. PSC was confirmed based on histopathology and immunohistochemistry. The patient refused treatment due to economic reasons.

OUTCOMES

The patient developed adrenal, multiple lung and brain metastasis. The overall survival time was 11 months.

CONCLUSIONS

PSC, despite its rarity, should be considered in the differential diagnosis of lung cancer. Besides, biopsy, histopathology, and specific immunohistochemical staining of larger tissue specimens can be contributing to the accurate diagnosis of PSC.

Canadian Consensus Recommendations on the Management of MET-Altered NSCLC

In Canada, the therapeutic management of patients with advanced non-small cell lung cancer (NSCLC) with rare actionable mutations differs between provinces, territories, and individual centres based on access to molecular testing and funded treatments. These variations, together with the emergence of several novel mesenchymal-epithelial transition (MET) factor-targeted therapies for the treatment of NSCLC, warrant the development of evidence-based consensus recommendations for the use of these agents. A Canadian expert panel was convened to define key clinical questions, review evidence, discuss practice recommendations and reach consensus on the treatment of advanced MET-altered NSCLC. Questions addressed by the panel include: 1. How should the patients most likely to benefit from MET-targeted therapies be identified? 2. What are the preferred first-line and subsequent therapies for patients with MET exon 14 skipping mutations? 3. What are the preferred first-line and subsequent therapies for advanced NSCLC patients with de novo MET amplification? 4. What is the preferred therapy for patients with advanced epidermal growth factor receptor (EGFR)-mutated NSCLC with acquired MET amplification progressing on EGFR inhibitors? 5. What are the potential strategies for overcoming resistance to MET inhibitors? Answers to these questions, along with the consensus recommendations herein, will help streamline the management of MET-altered NSCLC in routine practice, assist clinicians in therapeutic decision-making, and help ensure optimal outcomes for NSCLC patients with MET alterations.

Mesenchymal-Epithelial Transition Exon 14 Skipping Mutation and Amplification in 5,008 Patients With Lung Cancer

Background

Lung cancer is a major health concern worldwide because of its increasing incidence and mortality. This study aimed to clarify the association between mesenchymal-epithelial transition (MET) genomic alterations and clinical characteristics of lung cancer.

Method

We collected data from 5,008 patients with lung cancer diagnosed and treated between January 2017 and July 2021 at the Affiliated Hospital of Qingdao University. Genomic alterations in the MET gene, including the exon 14 skipping mutation and amplification, were detected using amplification refractory mutation system-polymerase chain reaction (2,057 cases) and next-generation sequencing (2,951 cases). Clinical characteristics such as age, sex, tumor location, tumor stage, smoking, pleural invasion, and histology were statistically analyzed for MET exon 14 skipping mutation and amplification. The DNA splicing sites causing the MET exon 14 skipping mutation at the mRNA level were also investigated.

Results

The incidence of the MET exon 14 skipping mutation was 0.90% (41/4,564) in adenocarcinoma, 1.02% (3/294) in squamous cell carcinoma, and 8.33% (1/12) in sarcomatoid carcinoma specimens. It was more frequently observed in patients over 60 years of age than the MET exon 14 skipping mutation wildtype. The MET exon 14 skipping mutation co-occurred with epidermal growth factor receptor (EGFR) L858R, EGFR 19-Del, and BRAF V600E mutations. At the DNA level, single nucleotide mutation and small fragment deletion (1-38 base pairs) upstream and downstream of MET exon 14 led to MET exon 14 skipping mutation at the mRNA level. MET amplification occurred in 0.78% (21/2,676) adenocarcinoma and 1.07% (2/187) squamous cell carcinoma specimens and was significantly associated with advanced tumor stages (III + IV) compared to the MET amplification wildtype. MET amplification primarily co-occurred with the EGFR mutation.

Conclusions

Our study found that MET genomic alterations were statistically related to age and tumor stage and co-existed with mutations of other oncogenic driver genes, such as EGFR and BRAF. Moreover, various splicing site changes at the DNA level led to the exon 14 skipping mutation at the mRNA level. Further studies are required to clarify the association between MET genomic alterations and prognosis.

Robust home brew fragment sizing assay for detection of MET exon 14 skipping mutation in non-small cell lung cancer patients in resource constrained community hospitals

BACKGROUND

A mutation/deletion involving donor or acceptor sites for exon 14 results in splicing out of exon 14 of the mesenchymal epithelial transition (MET) gene and is known as "MET exon 14 skipping" (ΔMET14). The two recent approvals with substantial objective responses and improved progression-free survival to MET inhibitors namely capmatinib and tepotinib necessitate the identification of this alteration upfront. We herein describe our experience of ΔMET14 detection by an mRNA-based assay using polymerase chain reaction followed by fragment sizing.

METHODS

This is a home brew assay which was developed with the concept that the transcripts from true ΔMET14 will be shorter by ~140 bases than their wild type counterparts. The cases which were called MET exon 14 skipping positive on next-generation sequencing (NGS) were subjected to this assay, along with 13 healthy controls in order to establish the validity for true negatives.

RESULTS

Thirteen cases of ΔMET14 mutation were detected on NGS using RNA-based sequencing. Considering NGS as a gold standard, the sizing assay using both gel and capillary electrophoresis that showed 100% specificity for both with concordance rates of 84.6% and 88.2% with NGS, respectively, were obtained.

CONCLUSIONS

Owing to the cost-effective nature and easy to use procedures, this assay will prove beneficial for small- and medium-sized laboratories where skilled technical personnel and NGS platforms are unavailable.

Therapeutic strategies in METex14 skipping mutated non-small cell lung cancer

METex14 skipping mutations occur in about 3–4% of lung adenocarcinoma patients and 1–2% of patients with other lung cancer histology. The MET receptor tyrosine kinase and its ligand hepatocyte growth factor (HGF) are established oncogenic drivers of NSCLC. A mutation that results in loss of exon 14 in the MET gene leads to dysregulation and inappropriate signaling that is associated with increased responsiveness to MET TKIs. Results from GEOMETRY mono-1 and VISION Phase I/II clinical trials demonstrated significant clinical activity in patients treated with the MET Exon 14 skipping mutation inhibitors capmatinib and tepotinib with tolerable toxicity profile. In the GEOMETRY mono-1 trial, capmatinib was especially active in treatment-naïve patients supporting the upfront testing of this oncogenic driver. Tepotinib demonstrated superior activity in the pretreated patients in the VISION trial. Savolitinib is another MET TKI that has shown efficacy in the first- and second-line settings, including patients with aggressive pulmonary sarcomatoid carcinoma. These studies have demonstrated that these TKIs can cross the blood brain barrier and demonstrated some activity toward CNS metastases. MET Exon 14 skipping mutation is detected by NGS-based testing of liquid or tissue biopsies, with preference for RNA-based NGS. The activity of capmatinib and tepotinib is limited by the development of acquired resistance. Current research is focused on strategies to overcome resistance and improve the effectiveness of these agents. Our aim is to review the current status of MET Exon 14 skipping mutation as it pertains NSCLC.

Detection of MET exon 14 skipping mutations in non-small cell lung cancer: overview and community perspective

Introduction: Non-small cell lung cancer (NSCLC), which accounts for the majority of lung cancer diagnoses in the United States, has many known driver mutations, including MET exon 14 skipping mutation (METex14). The detection of oncogenic driver mutations in NSCLC and the development of drugs to target these alterations, including METex14, has created the need for accurate and reliable testing, of which next-generation sequencing (NGS) is the gold standard. However, detection of METex14 in patients with NSCLC can be challenging due to the complex biology of METex14 and the abilities of different NGS platforms to detect METex14.Areas covered: This review provides an overview of METex14 biology, discusses the optimal platforms for the detection of METex14 in NSCLC, and provides an overview of the use of NGS in the community setting.Expert opinion: Broad molecular testing is crucial for identifying actionable oncogenic drivers in NSCLC. METex14 is a complex oncogenic driver mutation requiring carefully optimized platforms for proper detection. To identify patients eligible for targeted therapies - including therapies targeting novel oncogenic drivers, such as MET inhibitors - community oncologists need to be aware of both the use of NGS platforms and the differences in their capabilities to detect certain oncogenic drivers.

Lung Cancer with MET exon 14 Skipping Mutation: Genetic Feature, Current Treatments, and Future Challenges

MET exon 14 skipping mutation (MET∆ex14) is present about 3% of non-small cell lung cancers (NSCLCs). NSCLC patients with MET∆ex14 are characterized by an average age of over 70 years at diagnosis, a smoking history and a higher frequency in pleomorphic carcinoma and adenosquamous cell carcinoma than in adenocarcinoma. It has also been reported that NSCLCs with MET∆ex14 often have codriver alterations such as EGFR amplification (6–28%), FGFR1 alterations (5–17%), KRAS alterations (~8%), BRAF alterations (~21%), or PIK3CA mutation/amplification (~14%). In 2020, the approval of two MET-tyrosine kinase inhibitors (TKIs), capmatinib and tepotinib, for NSCLCs carrying MET∆ex14 dawned a new era for MET-targeted therapy. These drugs yielded progression-free survival of 5.4−12.4 months in clinical trials; however, it has also been reported that one-third to half of patients show inherent resistance to MET-TKIs. In addition, the emergence of acquired resistance to MET-TKIs is inevitable. In this review, we summarize the clinical and molecular characteristics of NSCLCs with MET∆ex14, the efficacy and safety of capmatinib and tepotinib, the inherent and acquired resistance mechanisms to MET-TKIs, and new treatment strategies for NSCLCs with MET∆ex14 in the near future.

Biology of the mRNA Splicing Machinery and Its Dysregulation in Cancer Providing Therapeutic Opportunities

Dysregulation of messenger RNA (mRNA) processing—in particular mRNA splicing—is a hallmark of cancer. Compared to normal cells, cancer cells frequently present aberrant mRNA splicing, which promotes cancer progression and treatment resistance. This hallmark provides opportunities for developing new targeted cancer treatments. Splicing of precursor mRNA into mature mRNA is executed by a dynamic complex of proteins and small RNAs called the spliceosome. Spliceosomes are part of the supraspliceosome, a macromolecular structure where all co-transcriptional mRNA processing activities in the cell nucleus are coordinated. Here we review the biology of the mRNA splicing machinery in the context of other mRNA processing activities in the supraspliceosome and present current knowledge of its dysregulation in lung cancer. In addition, we review investigations to discover therapeutic targets in the spliceosome and give an overview of inhibitors and modulators of the mRNA splicing process identified so far. Together, this provides insight into the value of targeting the spliceosome as a possible new treatment for lung cancer.

Novel MET exon 14 skipping analogs characterized in non-small cell lung cancer patients: A case study

MET exon 14 skipping (METex14) is a validated oncogenic driver in lung cancer and MET tyrosine kinase inhibitors are now available as effective clinical treatments. The majority of known METex14 alterations are typical donor/acceptor splicing or ubiquitination site mutations. Herein, two new METex14 variants were detected in two patients with lung adenocarcinoma by targeted next generation sequencing (NGS). Reverse transcription (RT)-based analysis confirmed that these mutations led to MET exon 14 skipping. Our analysis provided evidence for possible targeted therapy options for patients carrying these MET mutations or similar METex14 analogs.

Novel Therapies for Metastatic Non-Small Cell Lung Cancer with MET Exon 14 Alterations: A Spotlight on Capmatinib

MET exon 14 (METex14) alterations are now an established therapeutically tractable target in non-small cell lung cancer (NSCLC). Recently reported trials of several MET tyrosine kinase inhibitors (TKI) in this patient population have demonstrated promising efficacy data in both the treatment naïve and pre-treated settings and have led to regulatory approvals. This review will focus on practical diagnostic considerations for METex14 alterations, the trial evidence for capmatinib in this molecular subset including dosing and toxicity management, and the future therapeutic landscape of METex14 altered NSCLC.

Long-term efficacy of immune checkpoint inhibitors in non-small cell lung cancer patients harboring MET exon 14 skipping mutations

INTRODUCTION

MET exon 14 skipping mutation, observed in 3-4% of non-small cell lung cancer (NSCLC), is emerging as a targetable alteration. In recent years, immune checkpoint inhibitors (ICI) have been effective in treating several NSCLCs. Our research aimed to investigate the characteristics of patients with NSCLCs harboring MET exon 14 mutations and their response to ICI in Japan.

METHODS

Among the 1954 consecutive NSCLCs diagnosed at Saitama Cancer Center between 2010 and 2019, MET exon 14 skipping mutations were detected in 68 (3.5%) NSCLCs. We evaluated their characteristics such as programmed cell death ligand 1 (PD-L1) expression.

RESULTS

Median age of patients with NSCLCs harboring MET exon 14 skipping mutations was 73 years. PD-L1 was highly expressed in 17 (70.8%) of the 24 patients examined. Seven patients received ICI monotherapy, and three out of seven had a remarkable treatment response, resulted in objective response rate (ORR) of 42.9% and progression-free survival of 24.7 months. Three patients with donor splice-site mutations showed a long-term treatment response, despite the fact that two with acceptor splice-site mutations demonstrated no response and experienced early disease progression with ICI monotherapy.

CONCLUSION

Our results indicated that patients with NSCLCs harboring MET exon 14 mutations presented with a high rate of positive PD-L1 expression. ICI treatment showed a high ORR and long-term efficacy for NSCLCs harboring MET exon 14 mutations. Variants of MET exon 14 splice-site mutations may be associated with ICI response.

Capmatinib for patients with non-small cell lung cancer with MET exon 14 skipping mutations: A review of preclinical and clinical studies

The mesenchymal-epithelial transition (MET) receptor tyrosine kinase binds the hepatocyte growth factor to activate downstream cell signaling pathways involved in cell proliferation, survival, and migration. Several genetic mechanisms can result in an aberrant activation of this receptor in cancer cells. One such activating mechanism involves the acquisition of gene mutations that cause MET exon 14 skipping (METex14) during mRNA splicing. Mutations leading to METex14 are found in approximately 3-4% of patients with non-small cell lung cancer (NSCLC). Accumulating evidence suggests that METex14 is a true, independent oncogenic driver in NSCLC, as well as being an independent prognostic factor for poorer survival in patients with NSCLC. The successes of target therapies have relied on improved understanding of the genetic alterations that lead to the dysregulation of the molecular pathways and more advanced molecular diagnostics. Multiple efforts have been made to target the MET pathway in cancer; however, real clinical progress has only occurred since the emergence of METex14 as a valid biomarker for MET inhibition. Capmatinib is a highly potent and selective type Ib inhibitor of MET. Following preclinical demonstration of activity against MET-dependent cancer cell line growth and MET-driven tumor growth in xenograft models, data from a phase 1 clinical trial showed an acceptable safety profile of capmatinib and preliminary evidence of efficacy in patients with MET-dysregulated NSCLC. The multicohort GEOMETRY mono-1 phase 2 trial reported objective response rates of 68% and 41% in treatment-naïve and in pre-treated patients with METex14 advanced NSCLC, respectively. These results have supported the approval of capmatinib by the US Food and Drug Administration for patients with metastatic NSCLC harboring METex14.

A narrative review of MET inhibitors in non-small cell lung cancer with MET exon 14 skipping mutations

Treatment of advanced non-small cell lung cancer (NSCLC) has radically improved in the last years due to development and clinical approval of highly effective agents including immune checkpoint inhibitors (ICIs) and oncogene-directed therapies. Molecular profiling of lung cancer samples for activated oncogenes, including epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), c-ros oncogene 1 (ROS1) and BRAF, is routinely performed to select the most appropriate up-front treatment. However, the identification of new therapeutic targets remains a high priority. Recently, MET exon 14 skipping mutations have emerged as novel actionable oncogenic alterations in NSCLC, sensitive to MET inhibition. In this review we discuss: (I) MET gene and MET receptor structure and signaling pathway; (II) MET exon 14 alterations; (III) current data on MET inhibitors, mainly focusing on selective MET tyrosine kinase inhibitors (TKIs), in the treatment of NSCLC with MET exon 14 skipping mutations. We identified the references for this review through a literature search of papers about MET, MET exon 14 skipping mutations, and MET inhibitors, published up to September 2020, by using PubMed, Scopus and Web of Science databases. We also searched on websites of main international cancer congresses (ASCO, ESMO, IASLC) for ongoing studies presented as abstracts. MET exon 14 skipping mutations have been associated with clinical activity of selective MET inhibitors, including capmatinib, that has recently received approval by FDA for clinical use in this subgroup of NSCLC patients. A large number of trials are testing MET inhibitors, also in combinatorial therapeutic strategies, in MET exon 14-altered NSCLC. Results from these trials are eagerly awaited to definitively establish the role and setting for use of these agents in NSCLC patients.

Characteristics and Clinical Outcomes of Non-small Cell Lung Cancer Patients in Korea With MET Exon 14 Skipping

BACKGROUND/AIM

MET exon 14 skipping occurs in 3-4% of patients with lung adenocarcinomas. In this study, we performed a comprehensive analysis of clinical data from Korean non-small cell lung cancer (NSCLC) patients with MET exon 14 skipping.

PATIENTS AND METHODS

Overall, 1,020 patients diagnosed with NSCLC between January 2015 and July 2017 were analyzed by next-generation sequencing.

RESULTS

MET exon 14 skipping was identified in 20 NSCLC patients (1.9%). The median age was 69 years (range=39-86 years), 60.0% were male, and most (55.0%) were ever-smokers. For first-line chemotherapy, the median overall survival was 9.5 months and progression-free survival was 4.0 months, respectively. Twelve patients received pemetrexed-based chemotherapy and the overall response rate was 33.3% (4/12). Among four crizotinib-treated patients, one continued therapy for 8 months with the best response being disease stability.

CONCLUSION

Given the poor clinical outcome and response to therapy for NSCLC, and the availability of promising anti-tumor MET inhibitors, screening for the MET exon 14 skip mutation should be incorporated into clinical practice.

Responses to crizotinib and cabozantinib in patient with lung adenocarcinoma harboring mesenchymal-epithelial transition factor exon 14 skipping mutation: A case report

RATIONALE

Lung cancer is a leading cause of cancer-related mortality worldwide. Currently, targeted therapy has proved highly efficient in the treatment of advanced non-small cell lung cancer (NSCLC). Mesenchymal-epithelial transition factor (MET) is considered a validated molecular target in NSCLC. Given the low incidence of MET exon 14 skipping mutation, the planning of precision treatment for patients is a clinical problem that needs to be solved. In this report, we present a MET-positive case that benefited from crizotinib and cabozantinib treatment.

PATIENT CONCERNS

A 77-year-old patient was diagnosed with lung adenocarcinoma in our hospital. Positron emission tomography-computed tomography (PET-CT) showed a right upper lobe mass (58 × 56 mm, SUVmax 15.6), right hilar enlarged lymph nodes, and multiple bone and left adrenal metastases (c-T3N1M1c).

DIAGNOSES

MET exon 14 mutation (exon14, c.2888-1G>C) was examined using the lung puncture sample by next generation sequencing. Therefore, the patient was diagnosed with late-stage lung adenocarcinoma with MET exon14 skipping gene mutation.

INTERVENTIONS

Crizotinib was given as the first-line treatment from August 2019. Considering the resistance of crizotinib, cabozantinib was given for second-line treatment.

OUTCOMES

Crizotinib was administered (250 mg bid) for 8 months, and her disease achieved partial regression (PR) and progression-free survival (PFS), which lasted for 8 months. The patient also reached PR after the second-line treatment with cabozantinib, and is currently under follow-up, with an overall survival (OS) of >12 months.

LESSONS

As MET exon 14 skipping mutation is rare in clinical practices, MET-TKIs (tyrosine kinase inhibitors) treatment can boost curative effects and improve prognosis of patients with advanced lung adenocarcinoma. This case report supports a rationale for the treatment of lung adenocarcinoma patients with a MET exon 14 skipping mutation and provides alternative treatment options for these types of NSCLC patients.

Combination of HGF/MET-targeting agents and other therapeutic strategies in cancer

MET receptor has emerged as a druggable target across several human cancers. Agents targeting MET and its ligand hepatocyte growth factor (HGF) including small molecules such as crizotinib, tivantinib and cabozantinib or antibodies including rilotumumab and onartuzumab have proven their values in different tumors. Recently, capmatinib was approved for treatment of metastatic lung cancer with MET exon 14 skipping. In this review, we critically examine the current evidence on how HGF/MET combination therapies may take advantage of synergistic effects, overcome primary or acquired drug resistance, target tumor microenvironment, modulate drug metabolism or tackle pharmacokinetic issues. Preclinical and clinical studies on the combination of HGF/MET-targeted agents with conventional chemotherapeutics or molecularly targeted treatments (including EGFR, VEGFR, HER2, RAF/MEK, and PI3K/Akt targeting agents) and also the value of biomarkers are examined. Our deeper understanding of molecular mechanisms underlying successful pharmacological combinations is crucial to find the best personalized treatment regimens for cancer patients.

Detection of MET Exon 14 Skipping Alterations in Lung Cancer Clinical Samples Using a PCR-Based Approach

The receptor tyrosine kinase (RTK) c-MET plays important roles in cancer, yet despite being frequently overexpressed, clinical responses to targeting this receptor have been limited in the clinical setting. A singular significant challenge has been the accurate identification of biomarkers for the selection of responsive patients. However, recently mutations which result in the loss of exon 14 (called METex14 skipping) have emerged as novel biomarkers in non-small cell lung carcinomas (NSCLC) to predict for responsiveness to targeted therapy with c-MET inhibitors. Currently, the diverse genomic alterations responsible for METex14 skipping pose a challenge for routine clinical diagnostic testing. Next generation sequencing (NGS) is the current gold standard for identifying the diverse mutations associated with METex14, but the cost for such a procedure remains to some degree prohibitive as often NGS is requested on a case-by-case basis, and many hospitals may not even have the capacity or resources to conduct NGS.However, PCR-based approaches to detect METex14 have been developed which can be conducted in most routine hospital laboratories and may therefore allow a cost-effective approach to pre-screen patients that may respond to c-MET inhibitors prior to conducting NGS, or until all patients will have NGS conducted as routine practise. In this chapter, we describe one such PCR-based approach for screening samples for the detection of METex14 in NSCLC.

The investigation of the healing effect of active ingredients in traditional medicinal plants on lung cancer

The healing effect of herbal active compounds on lung cancer has been recently investigated. Lung cancer is one of the leading types of cancer. The causes and prevention of lung cancer diagnosis have an important role as the inhibition of proteins in the initial treatment of the disease. The docking score was used to investigate the effect of some active compounds in traditional medicinal plants. The use of widespread medicinal plants and determination of active substances reveal the importance of docking studies in choosing the right active substance in a short time. The inhibition of essentially active compounds on lung cancer has been an important condition as the traditional medicinal plants that are rich in active substance and direct the experimental studies. In this study, the effects of the active ingredients in traditional food supplements used in many countries on the lung cancer were calculated based on the drugs used as standard. It will be hope that these active substances with high healing effects will be tested in the clinical field and turned into drugs.

Beyond EGFR, ALK and ROS1: Current evidence and future perspectives on newly targetable oncogenic drivers in lung adenocarcinoma

Lung cancer is the leading cause of cancer death worldwide. In the past decade EGFR, ALK and ROS1 TKIs lead to an unprecedented survival improvement of oncogene-addicted NSCLC patients, with better toxicity profile compared to chemotherapy. In recent years the implementation of high-throughput sequencing platforms led to the identification of uncommon molecular alterations in oncogenic drivers, such as BRAF, MET, RET, HER2 and NTRK. Moreover, newly developed drugs have been found to be active against hard to target drivers, such as KRAS. Specific TKIs targeting these genomic alterations are currently in clinical development and showed impressive activity and survival improvement, leading to FDA-accelerated approval for some of them. However, virtually all patients develop resistance to TKIs by on-target or off-target mechanisms. Here we review the clinicopathological features, the emerging targeted therapies and mechanisms of resistance and strategies to overcome them of KRAS, BRAF, MET, RET, HER2 and NTRK-addicted advanced NSCLCs.

Emerging MET tyrosine kinase inhibitors for the treatment of non-small cell lung cancer

Introduction MET aberrations, including MET exon 14 skipping mutation and amplification, are present in ~5% of non-small cell lung cancer (NSCLC) cases, and these levels are comparable to the frequency of ALK fusion. MET amplification also occurs as an acquired resistance mechanism in EGFR-mutated NSCLC after EGFR tyrosine kinase inhibitors (TKI) treatment failure. Therefore, the development of therapies for activated MET is urgently needed. Areas covered This review summarizes (1) the mechanisms and frequencies of MET aberrations in NSCLC, (2) the efficacies and toxicities of MET-TKIs under clinical development and (3) the mechanisms of inherent and acquired resistance to MET-TKIs. Expert opinion Type Ia, Ib and II MET-TKIs are currently under clinical development, and phase I/II studies have shown the potent activities of tepotinib, capmatinib and savolitinib; in fact, tepotinib and capmatinib were approved for use by health authorities. However, inherent and acquired resistance through on- and off-target mechanisms has been detected, and strategies to overcome this resistance are being developed.

Molecular Pathology of Primary Non-small Cell Lung Cancer

Lung carcinoma is one of the most common human cancers and is estimated to have an incidence of approximately 2 million new cases per year worldwide with a 20% mortality rate. Lung cancer represents one of the leading causes of cancer related death in the world. Of all cancer types to affect the pulmonary system, non-small cell lung carcinoma comprises approximately 80-85% of all tumors. In the past few decades cytogenetic and advanced molecular techniques have helped define the genomic landscape of lung cancer, and in the process, revolutionized the clinical management and treatment of patients with advanced non-small cell lung cancer. The discovery of specific, recurrent genetic abnormalities has led to the development of targeted therapies that have extended the life expectancy of patients who develop carcinoma of the lungs. Patients are now routinely treated with targeted therapies based on identifiable molecular alterations or other predictive biomarkers which has led to a revolution in the field of pulmonary pathology and oncology. Numerous different testing modalities, with various strengths and limitations now exist which complicate diagnostic algorithms, however recently emerging consensus guidelines and recommendations have begun to standardize the way to approach diagnostic testing of lung carcinoma. Herein we provide an overview of the molecular genetic landscape of non-small cell lung carcinoma, with attention to those clinically relevant alterations which drive management, as well as review current recommendations for molecular testing.

Targeting MET Dysregulation in Cancer

Aberrant MET signaling can drive tumorigenesis in several cancer types through a variety of molecular mechanisms including MET gene amplification, mutation, rearrangement, and overexpression. Improvements in biomarker discovery and testing have more recently enabled the selection of patients with MET-dependent cancers for treatment with potent, specific, and novel MET-targeting therapies. We review the known oncologic processes that activate MET, discuss therapeutic strategies for MET-dependent malignancies, and highlight emerging challenges in acquired drug resistance in these cancers. SIGNIFICANCE: Increasing evidence supports the use of MET-targeting therapies in biomarker-selected cancers that harbor molecular alterations in MET. Diverse mechanisms of resistance to MET inhibitors will require the development of novel strategies to delay and overcome drug resistance.

Frequency of MET exon 14 skipping mutations in non-small cell lung cancer according to technical approach in routine diagnosis: results from a real-life cohort of 2,369 patients

Background

Mesenchymal epithelial transition receptor (MET) alterations, including MET exon 14 skipping mutation, are oncogenic in non-small cell lung cancer (NSCLC) and may confer sensitivity to targeted therapy. Given the rarity and the diversity of exon 14 skipping mutations, diagnosis may be challenging on small-biopsy specimens.

Methods

Between March 2014 and May 2018, tissue samples from patients with metastatic NSCLC were analysed for MET exon 14 skipping mutation as part of routine practice in the Pathology Department of the Hospices Civils de Lyon, France. Over the study period, Sanger sequencing and/or two different DNA-based next generation sequencing (NGS) assays were used.

Results

Genomic alterations of MET exon 14 were detected in 2.6% (62/2,369) samples of NSCLC analysed for MET exon 14 mutations. Patients were mainly women (38/62, 61%) without smoking history (22/39, 56%) and the median age was 75 years. MET exon 14 skipping mutations were diagnosed by NGS in 50 cases and by classical Sanger sequencing in 12 cases. The frequency of MET mutations was 15.4% when Sanger sequencing was performed at the request of the clinician and 4.1% when the DNA-based NGS assay coverage included the 3' and 5' parts of the MET exon 14 and performed systematically.

Conclusions

The frequency of genomic alterations is highly dependent on patient selection and the technical approach.

Gene rearrangement detection by next-generation sequencing in patients with non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is the leading cause of cancer-related deaths worldwide. Various molecular markers in NSCLC patients have been developed, including gene rearrangements, currently used in therapeutic strategies. With increasing number of these molecular biomarkers of NSCLC, there is a demand for highly efficient methods for detecting mutations and translocations in treatable targets. Those currently available U.S. Food and Drug Administration (FDA) approved approaches, for example imunohistochemisty (IHC) and fluorescence in situ hybridization (FISH), are inadequate, due to sufficient quantity of material and long time duration. Next-generation massive parallel sequencing (NGS), with the ability to perform and capture data from millions of sequencing reactions simultaneously could resolve the problem. Thanks to gradual NGS introduction into clinical laboratories, screening time should be considerably shorter, which is very important for patients with advanced NSCLC. Moreover, only a minimum sample input is needed for achieving adequate results. NGS was compared to the current detection methods of ALK, ROS1, c-RET and c-MET rearrangements in NSCLC and a significant match, between IHC, FISH and NGS results, was found. Recent available researches have been carried out on a small numbers of patients. Verifying these results on larger patients cohort is important. This review sumarizes the literature on this subject and compares current possibilities of predictive gene rearrangements detection in patients with NSCLC.

Antibody-drug conjugates for lung cancer in the era of personalized oncology

With 9.6 million deaths in 2018, cancer represents one of the most common causes of death, both in men and women. Despite recent advances in the understanding of molecular mechanisms involved in cancer development and progression, treatment options are still limited. Limitations of traditional chemotherapy include the lack of selectivity and the unfavorable safety profile. The efficacy of targeted therapies (e.g., tyrosine kinase inhibitors) is also limited by their cytostatic action, which inhibits tumor cell proliferation without inducing tumor cell death, and by the risk of acquired resistance. Antibody-drug conjugates (ADCs), a newly developed class of engineered anticancer drugs, consist of recombinant monoclonal antibodies against tumor-specific antigens that are covalently bound to cytotoxic agents. They have been designed to overcome the limitations of traditional chemotherapy and targeted therapies by combining the target selectivity of monoclonal antibodies with the high potency of cytotoxic drugs. Currently, ADCs that have received regulatory approval include brentuximab vedotin for CD30-positive Hodgkin lymphoma and trastuzumab emtansine for human epidermal growth factor receptor 2-positive breast cancer. However, over 80 novel ADCs are actively being investigated in preclinical studies and early-phase clinical trials. In this review, we will provide a comprehensive overview of the biological rational, efficacy and safety of ADCs as therapeutic agents against non-small cell lung cancer and small cell lung cancer.

Approaches to Tumor Classification in Pulmonary Sarcomatoid Carcinoma

Pulmonary sarcomatoid carcinoma (PSC) is a heterogeneous category of primary lung cancer accounting from 0.3% to 3% of all primary lung malignancies. According to the most recent 2015 World Health Organization (WHO) classification, PSC includes several different variants of malignant epithelial tumors (carcinomas) histologically mimicking sarcomas showing or entirely lacking a conventional component of non-small cell lung cancer (NSCLC). Thus, this rare subheading of lung neoplasms includes pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, pulmonary blastoma, and carcinosarcoma. A diagnosis of PSC may be suspected on small biopsy or cytology, but commonly requires a surgical resection to reach a conclusive definition. The majority of patients with PSC consists of elderly, smoking men with a large, peripheral mass characterized by well-defined margins. However, presentation with a central, polypoid endobronchial lesion is well-documented, particularly in pleomorphic carcinoma and carcinosarcoma showing a squamous cell carcinoma component. As expected, PSC may pose diagnostic problems and immunohistochemistry is largely used when pathologists deal these tumors in routine practice. Indeed, PSC tends to overexpress molecules associated with the epithelial-to-mesenchymal transition, such as vimentin, but the panel of immunostains also includes epithelial markers (cytokeratins, EMA), TTF-1, p40 and negative markers (e.g., melanocytic, mesothelial and sarcoma-related primary antibodies). Although rare, PSC has increased their interest among oncologist community for different reasons: a. identification of the epithelial-to-mesenchymal phenomenon as a major mechanism of secondary resistance to tyrosine kinase inhibitors; b. over-expression of PD-L1 and effective treatment with immunotherapy; c. identification of c-MET exon 14 skipping mutation representing an effective target to crizotinib and other specific inhibitors. In this review, the feasibility of the diagnosis of PSC, its differential diagnosis and novel molecular findings characterizing this group of lung tumor are discussed.

Benefit of Targeted DNA Sequencing in Advanced Non-Small-Cell Lung Cancer Patients Without EGFR and ALK Alterations on Conventional Tests

BACKGROUND

Genetic sequencing testing has become widely used to inform treatment decisions for advanced non-small-cell lung cancer (NSCLC) patients. We analyzed benefits of genetic sequencing testing in real practice.

PATIENTS AND METHODS

We retrospectively reviewed 209 NSCLC patients who had no EGFR and ALK alterations on routine molecular tests and underwent next-generation targeted DNA sequencing of 380 cancer-related genes between November 2013 and October 2016. Median patient age was 59 years. A total of 96 patients (46%) were never smokers, and 195 patients (93%) had adenocarcinoma.

RESULTS

Among 209 total patients, 64 (31%) demonstrated actionable genetic alterations; 20 had EGFR mutations (6 L858R, 8 exon 19 deletions, 1 L861Q, 1 G719S, 4 exon 20 duplications), 4 ALK fusions, 9 ROS1 fusions, 6 BRAF V600E mutations, 15 RET fusions, 1 MET high-level amplification, 6 MET exon 14 skipping mutations, and 3 ERBB2 exon 20 insertion mutations. Of the 64 patients harboring actionable alterations, 28 patients received therapy targeted to their own actionable alterations (15 EGFR, 3 ALK, 1 ROS1, 8 RET, 1 BRAF). There were significant differences in overall survival between individuals with no actionable alterations, those with actionable alterations but no targeted therapy, and those with actionable alterations and targeted therapy (20.1 vs. 17.1 vs. 66.2 months, P < .001).

CONCLUSION

The results of targeted DNA sequencing testing could provide improved treatment options for some NSCLC patients and result in a survival benefit to NSCLC patients with no EGFR and ALK alterations on routine tests who are treated with targeted therapy.

Highly accurate DNA-based detection and treatment results of MET exon 14 skipping mutations in lung cancer

OBJECTIVES

The oncogenic MET exon 14 skipping mutation (METex14del) is described to drive 1.3 %-5.7 % of non-small-cell lung cancer (NSCLC) and multiple studies with cMET inhibitors show promising clinical responses. RNA-based analysis seems most optimal for METex14del detection, however, acquiring sufficient RNA material is often problematic. An alternative is DNA-based analysis, but commercially available DNA-based panels only detect up to 63 % of known METex14del alterations. The goal of this study is to describe an optimized DNA-based diagnostic test for METex14del in NSCLC, including clinical features and follow-up of patients treated with cMET-targeted therapy and consequent resistance mechanisms.

MATERIAL AND METHODS

Routinely processed diagnostic pathology non-squamous NSCLC specimens were investigated by a custom-made DNA-based targeted amplicon-based next generation sequencing (NGS) panel, which includes 4 amplicons for METex14del detection. Retrospectively, histopathological characteristics and clinical follow up were investigated for advanced non-squamous NSCLC with METex14del.

RESULTS

In silico analysis showed that our NGS panel is able to detect 96 % of reported METex14 alterations. METex14del was found in 2 % of patients with non-squamous NSCLC tested for therapeutic purposes. In total, from May 2015 - Sep 2018, METex14del was found in 46 patients. Thirty-six of these patients had advanced non-squamous NSCLC, they were predominantly elderly (76.5 years [53-90]), male (25/36) and (ex)-smokers (23/36). Five patients received treatment with crizotinib (Pfizer Oncology), in a named patient based program, disease control was achieved for 4/5 patients (3 partial responses, 1 stable disease) and one patient had a mixed response. Two patients developed a MET D1228N mutation during crizotinib treatment, inducing a resistance mechanism to crizotinib.

CONCLUSIONS

This study shows that METex14del can be reliably detected by routine DNA NGS analysis. Although a small cohort, patients responded well to targeted treatment, underlining the need for routine testing of METex14del in advanced non-squamous NSCLC to guarantee optimal personalized treatment.

HGF/MET pathway aberrations as diagnostic, prognostic, and predictive biomarkers in human cancers

Cancer is a major cause of death worldwide. MET tyrosine kinase receptor [MET, c-MET, hepatocyte growth factor (HGF) receptor] pathway activation is associated with the appearance of several hallmarks of cancer. The HGF/MET pathway has emerged as an important actionable target across many solid tumors; therefore, biomarker discovery becomes essential in order to guide clinical intervention and patient stratification with the aim of moving towards personalized medicine. The focus of this review is on how the aberrant activation of the HGF/MET pathway in tumor tissue or the circulation can provide diagnostic and prognostic biomarkers and predictive biomarkers of drug response. Many meta-analyses have shown that aberrant activation of the MET pathway in tumor tissue, including MET gene overexpression, gene amplification, exon 14 skipping and other activating mutations, is almost invariably associated with shorter survival and poor prognosis. Most meta-analyses have been performed in non-small cell lung cancer (NSCLC), breast, head and neck cancers as well as colorectal, gastric, pancreatic and other gastrointestinal cancers. Furthermore, several studies have shown the predictive value of MET biomarkers in the identification of patients who gain the most benefit from HGF/MET targeted therapies administered as single or combination therapies. The highest predictive values have been observed for response to foretinib and savolitinib in renal cancer, as well as tivantinib in NSCLC and colorectal cancer. However, some studies, especially those based on MET expression, have failed to show much value in these stratifications. This may be rooted in lack of standardization of methodologies, in particular in scoring systems applied in immunohistochemistry determinations or absence of oncogenic addiction of cancer cells to the MET pathway, despite detection of overexpression. Measurements of amplification and mutation aberrations are less likely to suffer from these pitfalls. Increased levels of MET soluble ectodomain (sMET) in circulation have also been associated with poor prognosis; however, the evidence is not as strong as it is with tissue-based biomarkers. As a diagnostic biomarker, sMET has shown its value in distinguishing cancer patients from healthy individuals in prostate and bladder cancers and in melanoma. On the other hand, increased circulating HGF has also been presented as a valuable prognostic and diagnostic biomarker in many cancers; however, there is controversy on the predictive value of HGF as a biomarker. Other biomarkers such as circulating tumor DNA (ctDNA) and tumor HGF levels have also been briefly covered. In conclusion, HGF/MET aberrations can provide valuable diagnostic, prognostic and predictive biomarkers and represent vital assets for personalized cancer therapy.

Response and acquired resistance to savolitinib in a patient with pulmonary sarcomatoid carcinoma harboring MET exon 14 skipping mutation: a case report

Background

Pulmonary sarcomatoid carcinoma (PSC) is a rare and poorly differentiated type of non-small cell lung cancer (NSCLC) with specific characteristics, which usually presents a challenge in clinical practice. Mesenchymal–epithelial transition (MET) gene has been identified as a promising target for treatments in the past few years. Here, we report a case of a patient with PSC harboring MET exon 14 mutation, who responded to a novel MET inhibitor – savolitinib.

Case presentation

A 75-year-old male patient with symptoms of cough, dyspnea and intermittent chest pain was diagnosed with sarcomatoid carcinoma. The tumor involved the right lung, the right hilum and multiple lesions in the right pleura, indicating a clinical disease stage IV. Next-generation sequencing of lung biopsy specimen indicated a MET exon 14 skipping mutation (NM_000245:c.3028+3A>G), with a variant allele frequency of 73.9%. The patient achieved a rapid and durable partial response with the initiation of savolitinib administration (600 mg, orally, once daily). The progression-free survival in this patient was 36 weeks. There were no ≥grade 3 adverse events reported and there was no dose reduction during treatment. Following savolitinib treatment, the allele frequency of MET exon 14 mutation in plasma circulating tumor DNA decreased with the reduction in tumor size. At the time of disease progression, fibroblast growth factor receptor 1 (FGFR1), EGFR and KRAS gene amplification were newly identified in tumor biopsy sample.

Conclusion

This patient with PSC harboring MET exon 14 skipping mutation achieved significant clinical benefit with savolitinib treatment. Emergence of FGFR1, EGFR and KRAS gene amplification at the time of disease progression was likely responsible for the resistance to savolitinib in this case.

PCR-based identification of point mutation mediating acetolactate synthase-inhibiting herbicide resistance in weed wild mustard (Sinapis arvensis)

Acetolactate synthase (ALS)-inhibiting herbicides have been widely used for effective management and control of wild mustard (Sinapis arvensis) biotypes in Iran. The resistance of the ALS inhibitor to weeds is attributed to either target site alteration or enhanced herbicide degradation. Molecular and genetic characterization of the resistance mechanism is relevant to the evolution and management of herbicide resistance. The aims of this research were (a) to characterize the mechanism molecular suspected to Granstar (tribenuron methyl) and Atlantis (Mesosulfuron + Iodosulfuron) resistance in S. arvensis biotypes in the greenhouse and laboratory (b) to investigate the organization of the target-site loci in field selected S. arvensis populations and (c) instantly recognize the mutations that cause resistance to ALS inhibitors. Eighty resistant populations of S. arvensis were carefully collected from fields repeatedly treated with Granstar and Atlantis. The resistance level and pattern of the population were determined through a greenhouse dose-response experiment by applying the above-mentioned herbicides. Extraction of genomic DNA was carried out for PCR and ALS gene analysis. Our results showed that by greenhouse experiment across 80 biotypes suspected to resistance collected in the fields of whole Kermanshah Province, 30 biotypes (37.5%) conferred S. arvensis resistance species reported in the farm. Among 30 biotypes screened in a greenhouse experiment, six biotypes (20%), No. 9, 14, 17, 19, 23 and 28 revealed a mutation in the ALS gene that was detected by PCR-based method. Biotype No. 9 in the position 376 (Asp376-Gly, GAC to GGC), biotypes 14 and 19 in the position 197 (Pro197-Ala, CCT to GCT), biotypes 17, 23 and 28 in the position 574 (Trp574-Leu, TGG to TTG) and biotype No. 23 in the position 122 (Thr-122-Ala, ACA to GCA) showed herbicide resistance. The specific mutation in the position of 122 of the ALS gene in S. arvensis is the first report. Other biotypes showed resistance in the greenhouse but didn't indicate any mutation by PCR-based method. Most of the resistance to Granstar and Atlantis are genetic and are induced by mutations in the ALS gene. The resistance to herbicides may contain a non-mutagenic and non-genetic origin. The reason of herbicide resistance as non-target-site in some of the biotypes may relate to the activity of the herbicide-metabolizing enzyme(s) or transporter proteins that will naturally lead to an increase in herbicide degradation or compartmentation away from its active site.

Cost-Efficient and Easy to Perform PCR-Based Assay to Identify Met Exon 14 Skipping in Formalin-Fixed Paraffin-Embedded (FFPE) Non-Small Cell Lung Cancer (NSCLC) Samples

MET is a receptor tyrosine kinase (RTK) that plays important roles in carcinogenesis. Despite being frequently overexpressed in cancer, clinical responses to targeting this receptor have been limited. Recently novel splicing mutations involving the loss of exon 14 (called METex14 skipping) have emerged as potential biomarkers to predict for responsiveness to targeted therapies with Met inhibitors in non-small cell lung cancer (NSCLC). Currently, the diverse genomic alterations responsible for METex14 skipping pose a challenge for routine clinical diagnostic testing. In this report, we examine three different methodologies to detect METex14 and assess their potential utility for use as a diagnostic assay for both the identification of METex14 and intra-tumoural distribution in NSCLC.