Activation of KRAS Mediates Resistance to Targeted Therapy in MET Exon 14-mutant Non-small Cell Lung Cancer

TWIST1 is a critical downstream target of the HGF/MET pathway and is required for MET driven acquired resistance in oncogene driven lung cancer

MET amplification/mutations are important targetable oncogenic drivers in NSCLC, however, acquired resistance is inevitable and the majority of patients with targetable MET alterations fail to respond to MET tyrosine kinase inhibitors (TKIs). Furthermore, MET amplification is among the most common mediators of TKI resistance. As such, novel therapies to target MET pathway and overcome MET TKI resistance are clearly needed. Here we show that the epithelial-mesenchymal transition (EMT) transcription factor, TWIST1 is a key downstream mediator of HGF/MET induced resistance through suppression of p27 and targeting TWIST1 can overcome resistance. We found that TWIST1 is overexpressed at the time of TKI resistance in multiple MET-dependent TKI acquired resistance PDX models. We have shown for the first time that MET directly stabilized the TWIST protein leading to TKI resistance and that TWIST1 was required for MET-driven lung tumorigenesis as well as could induce MET TKI resistance when overexpressed. TWIST1 mediated MET TKI resistance through suppression of p27 expression and genetic or pharmacologic inhibition of TWIST1 overcame TKI resistance in vitro and in vivo. Our findings suggest that targeting TWIST1 may be an effective therapeutic strategy to overcome resistance in MET-driven NSCLC as well as in other oncogene driven subtypes in which MET amplification is the resistance mechanism.

Unlocking c-MET: A comprehensive journey into targeted therapies for breast cancer

Breast cancer is the most common malignancy among women, posing a formidable health challenge worldwide. In this complex landscape, the c-MET (cellular-mesenchymal epithelial transition factor) receptor tyrosine kinase (RTK), also recognized as the hepatocyte growth factor (HGF) receptor (HGFR), emerges as a prominent protagonist, displaying overexpression in nearly 50% of breast cancer cases. Activation of c-MET by its ligand, HGF, secreted by neighboring mesenchymal cells, contributes to a cascade of tumorigenic processes, including cell proliferation, metastasis, angiogenesis, and immunosuppression. While c-MET inhibitors such as crizotinib, capmatinib, tepotinib and cabozantinib have garnered FDA approval for non-small cell lung cancer (NSCLC), their potential within breast cancer therapy is still undetermined. This comprehensive review embarks on a journey through structural biology, multifaceted functions, and intricate signaling pathways orchestrated by c-MET across cancer types. Furthermore, we highlight the pivotal role of c-MET-targeted therapies in breast cancer, offering a clinical perspective on this promising avenue of intervention. In this pursuit, we strive to unravel the potential of c-MET as a beacon of hope in the fight against breast cancer, unveiling new horizons for therapeutic innovation.

Recording and classifying MET receptor mutations in cancers

Tyrosine kinase inhibitors (TKI) directed against MET have been recently approved to treat advanced non-small cell lung cancer (NSCLC) harbouring activating MET mutations. This success is the consequence of a long characterization of MET mutations in cancers, which we propose to outline in this review. MET, a receptor tyrosine kinase (RTK), displays in a broad panel of cancers many deregulations liable to promote tumour progression. The first MET mutation was discovered in 1997, in hereditary papillary renal cancer (HPRC), providing the first direct link between MET mutations and cancer development. As in other RTKs, these mutations are located in the kinase domain, leading in most cases to ligand-independent MET activation. In 2014, novel MET mutations were identified in several advanced cancers, including lung cancers. These mutations alter splice sites of exon 14, causing in-frame exon 14 skipping and deletion of a regulatory domain. Because these mutations are not located in the kinase domain, they are original and their mode of action has yet to be fully elucidated. Less than five years after the discovery of such mutations, the efficacy of a MET TKI was evidenced in NSCLC patients displaying MET exon 14 skipping. Yet its use led to a resistance mechanism involving acquisition of novel and already characterized MET mutations. Furthermore, novel somatic MET mutations are constantly being discovered. The challenge is no longer to identify them but to characterize them in order to predict their transforming activity and their sensitivity or resistance to MET TKIs, in order to adapt treatment.

Targeting MEK in non-small cell lung cancer

The mitogen-activated protein kinase (MAPK or MEK) pathway modulates tumor cell survival and proliferation in non-small cell lung cancer (NSCLC). Unlike RAS or EGFR, activating mutations in MEK are exceedingly rare in NSCLC. Instead, enhanced activation of the MEK pathway is often linked to increased signaling by upstream oncogenic driver mutations. Thus far, MEK inhibitor monotherapy has shown little promise. However, treatment strategies involving MEK inhibition in combination with other targeted therapies in other oncogene-driven NSCLC has proven to be encouraging. For example, MEK inhibition - when combined with BRAF inhibition, - has shown strong anti-tumor activity in BRAF V600 mutated NSCLC. In this review, recent data on MEK inhibitor strategies in NSCLC are summarized. Furthermore, ongoing early phase trials investigating MEK inhibitor combination therapy with immunotherapy, chemotherapy and other oncogene drivers are highlighted. These and other studies could help inform future rational combination strategies of MEK-ERK inhibition in oncogene-driven NSCLC.

Prognostic and predictive biomarkers in non-small cell lung carcinoma

Lung cancer is the most common cause of cancer-related deaths globally, with the highest mortality rates among both men and women. Most lung cancers are diagnosed at late stages, necessitating systemic therapy. Modern clinical management of lung cancer relies heavily upon application of biomarkers, which guide the selection of systemic treatment. Here, we provide an overview of currently approved and emerging biomarkers of non-small cell lung cancer (NSCLC), including EGFR, ALK, ROS1, RET, NTRK1-3, KRAS, BRAF, MET, ERBB2/HER2, NRG1, PD-L1, TROP2, and CEACAM5. For practical purposes, we divide these biomarkers into genomic and protein markers, based on the tested substrate. We review the biology and epidemiology of the genomic and proteomic biomarkers, discuss optimal diagnostic assays for their detection, and highlight their contribution to the contemporary clinical management of NSCLC.

MET exon 14 skipping mutation drives cancer progression and recurrence via activation of SMAD2 signalling

BACKGROUND

c-Met encoded by the proto-oncogene MET, also known as hepatocyte growth factor (HGF) receptor, plays a crucial role in cellular processes. MET exon 14 skipping alteration (METΔ14EX) is a newly discovered MET mutation. SMAD2 is an important downstream transcription factor in TGF-β pathway. Unfortunately, the mechanisms by which METΔ14EX leads to oncogenic transformation are scarcely understood. The relationship between METΔ14EX and SMAD2 has not been studied yet.

METHODS

We generate METΔ14EX models by CRISPR-Cas9. In vitro transwell, wound-healing, soft-agar assay, in vivo metastasis and subcutaneous recurrence assay were used to study the role of METΔ14EX in tumour progression. RNA-seq, Western blotting, co-immunoprecipitation (CO-IP) and immunofluorescent were performed to explore the interaction between c-Met and SMAD2.

RESULTS

Our results demonstrated that METΔ14EX, independent of HGF, can prolong the constitutive activation of c-Met downstream signalling pathways by impeding c-Met degradation and facilitating tumour metastasis and recurrence. Meanwhile, METΔ14EX strengthens the interaction between c-Met and SMAD2, promoting SMAD2 phosphorylation. Therapeutically, MET inhibitor crizotinib impedes METΔ14EX-mediated tumour metastasis by decreasing SMAD2 phosphorylation.

CONCLUSIONS

These data elucidated the previously unrecognised role of METΔ14EX in cancer progression via activation of SMAD2 independent of TGF-β, which helps to develop more effective therapies for such patients. METΔ14EX alteration significantly triggers tumour progression via activation of SMAD2 signalling that are involved in activating tumour invasion, metastasis and recurrence. On the left, in the MET wild-type (METWT), the juxtamembrane (JM) domain is involved in the regulation of tyrosine kinase activity, receptor degradation, and caspase cleavage. On the right, the METΔ14EX mutation leads to the loss of the juxtamembrane domain, resulting in an abnormal MET protein lacking a CBL-binding site. This causes the accumulation of truncated MET receptors followed by constitutive activation of the MET signalling pathway. Thus, the METΔ14EX-mutated protein has strong binding and phosphorylation to SMAD2, which results in the phosphorylation of a large number of SMAD2/3 proteins that combine with SMAD4 to form a complex in the nucleus, activating downstream signalling pathways, such as EMT and ECM remodelling, resulting in tumour progression and recurrence. TF transcription factor.

The Efficacy and Safety of Treating Acquired MET Resistance Through Combinations of Parent and MET Tyrosine Kinase Inhibitors in Patients With Metastatic Oncogene-Driven NSCLC

Introduction

Acquired MET gene amplification, MET exon 14 skip mutations, or MET fusions can emerge as resistance mechanisms to tyrosine kinase inhibitors (TKIs) in patients with lung cancer. The efficacy and safety of combining MET TKIs (such as crizotinib, capmatinib, or tepotinib) with parent TKIs to target acquired MET resistance are not well characterized.

Methods

Multi-institutional retrospective chart review identified 83 patients with metastatic oncogene-driven NSCLC that were separated into the following two pairwise matched cohorts: (1) MET cohort (n = 41)-patients with acquired MET resistance continuing their parent TKI with a MET TKI added or (2) Chemotherapy cohort (n = 42)-patients without any actionable resistance continuing their parent TKI with a platinum-pemetrexed added. Clinicopathologic features, radiographic response (by means of Response Evaluation Criteria in Solid Tumors version 1.1), survival outcomes, adverse events (AEs) (by means of Common Terminology Criteria for Adverse Events version 5.0), and genomic data were collected. Survival outcomes were assessed using Kaplan-Meier methods. Multivariate modeling adjusted for lines of therapy, brain metastases, TP53 mutations, and oligometastatic disease.

Results

Within the MET cohort, median age was 56 years (range: 36-83 y). Most patients were never smokers (28 of 41, 68.3%). Baseline brain metastases were common (21 of 41, 51%). The most common oncogenes in the MET cohort were EGFR (30 of 41, 73.2%), ALK (seven of 41, 17.1%), and ROS1 (two of 41, 4.9%). Co-occurring TP53 mutations (32 of 41, 78%) were frequent. Acquired MET alterations included MET gene amplification (37 of 41, 90%), MET exon 14 mutations (two of 41, 5%), and MET gene fusions (two of 41, 5%). After multivariate adjustment, the objective response rate (ORR) was higher in the MET cohort versus the chemotherapy cohort (ORR: 69.2% versus 20%, p < 0.001). Within the MET cohort, MET gene copy number (≥10 versus 6-10) did not affect radiographic response (54.5% versus 68.4%, p = 0.698). There was no difference in ORR on the basis of MET TKI used (F [2, 36] = 0.021, p = 0.978). There was no difference in progression-free survival (5 versus 6 mo; hazard ratio = 0.64; 95% confidence interval: 0.34-1.23, p = 0.18) or overall survival (13 versus 11 mo; hazard ratio = 0.75; 95% confidence interval: 0.42-1.35, p = 0.34) between the MET and chemotherapy cohorts. In the MET cohort, dose reductions for MET TKI-related toxicities were common (17 of 41, 41.4%) but less frequent for parent TKIs (two of 41, 5%). Grade 3 AEs were not significant between crizotinib, capmatinib, and tepotinib (p = 0.3). The discontinuation rate of MET TKIs was 17% with no significant differences between MET TKIs (p = 0.315). Among pre- and post-treatment biopsies (n = 17) in the MET cohort, the most common next-generation sequencing findings were loss of MET gene amplification (15 of 17, 88.2%), MET on-target mutations (seven of 17, 41.2%), new Ras-Raf-MAPK alterations (three of 17, 17.6%), and EGFR gene amplification (two of 17, 11.7%).

Conclusions

The efficacy and safety of combining MET TKIs (crizotinib, capmatinib, or tepotinib) with parent TKIs for acquired MET resistance are efficacious. Radiographic response and AEs did not differ significantly on the basis of the underlying MET TKI used. Loss of MET gene amplification, development of MET on-target mutations, Ras-Raf-MAPK alterations, and EGFR gene amplification were molecular patterns found on progression with dual parent and MET TKI combinations.

The Treatment of a New Entity in Advanced Non-small Cell Lung Cancer: MET Exon 14 Skipping Mutation

BACKGROUND

MET (MET Proto-Oncogene, Receptor Tyrosine Kinase) exon 14 skipping mutation represents one of the most common MET alterations, accounting for approximately 1-3% of all mutations in advanced lung adenocarcinomas. While until 2020 no specific treatment was available for this subset of patients, as of today, three MET Tyrosine Kinase Inhibitors (TKIs) are currently approved in this setting, namely capmatinib, tepotinib and savolitinib.

OBJECTIVE

This article aims to provide an extensive overview of the current therapeutic standard of care for exon 14 skipped advanced Non-small Cell Lung Cancer (NSCLC) patients, alongside with mentions of the main future challenges and opportunities.

CONCLUSION

FDA-approved MET-TKIs currently represent the best option for treating exon 14 skipped advanced NSCLC patients, thanks to their excellent efficacy profile, alongside their manageable safety and tolerability. However, we currently lack specific agents to treat patients progressing on capmatinib or tepotinib, due to a limited understanding of the mechanisms underlying both on- and off-target resistance. In this respect, on-target mutations presently constitute the most explored ones from a mechanistic point of view, and type II MET-TKIs are currently under investigation as the most promising agents capable of overcoming the acquired resistance.

Advances and challenges in the treatment of lung cancer

Lung cancer accounts for a relatively high proportion of malignant tumors. As the most prevalent type of lung cancer, non-small cell lung cancer (NSCLC) is characterized by high morbidity and mortality. Presently, the arsenal of treatment strategies encompasses surgical resection, chemotherapy, targeted therapy and radiotherapy. However, despite these options, the prognosis remains distressingly poor with a low 5-year survival rate. Therefore, it is urgent to pursue a paradigm shift in treatment methodologies. In recent years, the advent of sophisticated biotechnologies and interdisciplinary integration has provided innovative approaches for the treatment of lung cancer. This article reviews the cutting-edge developments in the nano drug delivery system, molecular targeted treatment system, photothermal treatment strategy, and immunotherapy for lung cancer. Overall, by systematically summarizing and critically analyzing the latest progress and current challenges in these treatment strategies of lung cancer, we aim to provide a theoretical basis for the development of novel drugs for lung cancer treatment, and thus improve the therapeutic outcomes for lung cancer patients.

Overcoming Immune Checkpoint Therapy Resistance with SHP2 Inhibition in Cancer and Immune Cells: A Review of the Literature and Novel Combinatorial Approaches

SHP2 (Src Homology 2 Domain-Containing Phosphatase 2) is a protein tyrosine phosphatase widely expressed in various cell types. SHP2 plays a crucial role in different cellular processes, such as cell proliferation, differentiation, and survival. Aberrant activation of SHP2 has been implicated in multiple human cancers and is considered a promising therapeutic target for treating these malignancies. The PTPN11 gene and functions encode SHP2 as a critical signal transduction regulator that interacts with key signaling molecules in both the RAS/ERK and PD-1/PD-L1 pathways; SHP2 is also implicated in T-cell signaling. SHP2 may be inhibited by molecules that cause allosteric (bind to sites other than the active site and attenuate activation) or orthosteric (bind to the active site and stop activation) inhibition or via potent SHP2 degraders. These inhibitors have anti-proliferative effects in cancer cells and suppress tumor growth in preclinical models. In addition, several SHP2 inhibitors are currently in clinical trials for cancer treatment. This review aims to provide an overview of the current research on SHP2 inhibitors, including their mechanism of action, structure-activity relationships, and clinical development, focusing on immune modulation effects and novel therapeutic strategies in the immune-oncology field.

MET variants with activating N-lobe mutations identified in hereditary papillary renal cell carcinomas still require ligand stimulation

In hereditary papillary renal cell carcinoma (HPRCC), the MET receptor tyrosine kinase (RTK) mutations recorded to date are located in the kinase domain and lead to constitutive MET activation. This contrasts with MET mutations recently identified in non-small cell lung cancer (NSCLC), which lead to exon 14 skipping and deletion of a regulatory domain: in this latter case, the mutated receptor still requires ligand stimulation. Sequencing of MET in samples from 158 HPRCC and 2808 NSCLC patients revealed ten uncharacterized mutations. Four of these, all found in HPRCC and leading to amino acid substitutions in the N-lobe of the MET kinase, proved able to induce cell transformation, further enhanced by HGF stimulation: His1086Leu, Ile1102Thr, Leu1130Ser, and Cis1125Gly. Similar to the variant resulting in MET exon14 skipping, the two N-lobe MET variants His1086Leu, Ile1102Thr further characterized were found to require stimulation by HGF in order to strongly activate downstream signaling pathways and epithelial cell motility. The Ile1102Thr mutation displayed also transforming potential, promoting tumor growth in a xenograft model. In addition, the N-lobe-mutated MET variants were found to trigger a common HGF-stimulation-dependent transcriptional program, consistent with an observed increase in cell motility and invasion. Altogether, this functional characterization revealed that N-lobe variants still require ligand stimulation, in contrast to other RTK variants. This suggests that HGF expression in the tumor microenvironment is important for tumor growth. The sensitivity of these variants to MET TKIs opens the way for use of targeted therapies for patients harboring the corresponding mutations.

MET exon 14 skipping mutation is a hepatocyte growth factor (HGF)-dependent oncogenic driver in vitro and in humanised HGF knock-in mice

Exon skipping mutations of the MET receptor tyrosine kinase (METex14), increasingly reported in cancers, occur in 3-4% of non-small-cell lung cancer (NSCLC). Only 50% of patients have a beneficial response to treatment with MET-tyrosine kinase inhibitors (TKIs), underlying the need to understand the mechanism of METex14 oncogenicity and sensitivity to TKIs. Whether METex14 is a driver mutation and whether it requires hepatocyte growth factor (HGF) for its oncogenicity in a range of in vitro functions and in vivo has not been fully elucidated from previous preclinical models. Using CRISPR/Cas9, we developed a METex14/WT isogenic model in nontransformed human lung cells and report that the METex14 single alteration was sufficient to drive MET-dependent in vitro anchorage-independent survival and motility and in vivo tumorigenesis, sensitising tumours to MET-TKIs. However, we also show that human HGF (hHGF) is required, as demonstrated in vivo using a humanised HGF knock-in strain of mice and further detected in tumour cells of METex14 NSCLC patient samples. Our results also suggest that METex14 oncogenicity is not a consequence of an escape from degradation in our cell model. Thus, we developed a valuable model for preclinical studies and present results that have potential clinical implication.

MET in Non-Small-Cell Lung Cancer (NSCLC): Cross 'a Long and Winding Road' Looking for a Target

Non-Small-Cell Lung Cancer (NSCLC) can harbour different MET alterations, such as MET overexpression (MET OE), MET gene amplification (MET AMP), or MET gene mutations. Retrospective studies of surgical series of patients with MET-dysregulated NSCLC have shown worse clinical outcomes irrespective of the type of specific MET gene alteration. On the other hand, earlier attempts failed to identify the 'druggable' molecular gene driver until the discovery of MET exon 14 skipping mutations (METex14). METex14 are rare and amount to around 3% of all NSCLCs. Patients with METex14 NSCLC attain modest results when they are treated with immune checkpoint inhibitors (ICIs). New selective MET inhibitors (MET-Is) showed a long-lasting clinical benefit in patients with METex14 NSCLC and modest activity in patients with MET AMP NSCLC. Ongoing clinical trials are investigating new small molecule tyrosine kinase inhibitors, bispecific antibodies, or antibodies drug conjugate (ADCs). This review focuses on the prognostic role of MET, the summary of pivotal clinical trials of selective MET-Is with a focus on resistance mechanisms. The last section is addressed to future developments and challenges.

An Observatory for the MET Oncogene: A Guide for Targeted Therapies

The MET proto-oncogene encodes a pivotal tyrosine kinase receptor, binding the hepatocyte growth factor (HGF, also known as scatter factor, SF) and governing essential biological processes such as organogenesis, tissue repair, and angiogenesis. The pleiotropic physiological functions of MET explain its diverse role in cancer progression in a broad range of tumors; genetic/epigenetic alterations of MET drive tumor cell dissemination, metastasis, and acquired resistance to conventional and targeted therapies. Therefore, targeting MET emerged as a promising strategy, and many efforts were devoted to identifying the optimal way of hampering MET signaling. Despite encouraging results, however, the complexity of MET's functions in oncogenesis yields intriguing observations, fostering a humbler stance on our comprehension. This review explores recent discoveries concerning MET alterations in cancer, elucidating their biological repercussions, discussing therapeutic avenues, and outlining future directions. By contextualizing the research question and articulating the study's purpose, this work navigates MET biology's intricacies in cancer, offering a comprehensive perspective.

[Drug Resistance Mechanism and Therapeutic Strategy of Targeted Therapy of Non-small Cell Lung Cancer with MET Alterations]

Mesenchymal to epithelial transition factor (MET) gene alterations involve in the proliferation, invasion, and metastasis of non-small cell lung cancer. MET-tyrosine kinase inhibitors (TKIs) have been approved to treat non-small cell lung cancer with MET alterations, and resistance to these TKIs is inevitable. Molecular mechanisms of resistance to MET-TKIs are completely unclear. The review focused on potential mechanisms of MET-TKIs resistance and therapeutics strategies to delay and prevent resistance.
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Combination Therapy With MDM2 and MEK Inhibitors Is Effective in Patient-Derived Models of Lung Adenocarcinoma With Concurrent Oncogenic Drivers and MDM2 Amplification

INTRODUCTION

Although targeted therapies have revolutionized the therapeutic landscape of lung adenocarcinomas (LUADs), disease progression on single-agent targeted therapy against known oncogenic drivers is common, and therapeutic options after disease progression are limited. In patients with MDM2 amplification (MDM2amp) and a concurrent oncogenic driver alteration, we hypothesized that targeting of the tumor-suppressor pathway (by means of restoration of p53 using MDM2 inhibition) and simultaneous targeting of co-occurring MAPK oncogenic pathway might represent a more durably effective therapeutic strategy.

METHODS

We evaluated genomic next-generation sequencing data using the Memorial Sloan Kettering Cancer Center-Integrated Mutation Profiling of Actionable Cancer Targets platform to nominate potential targets for combination therapy in LUAD. We investigated the small molecule MDM2 inhibitor milademetan in cell lines and patient-derived xenografts of LUAD with a known driver alteration and MDM2amp.

RESULTS

Of 10,587 patient samples from 7121 patients with LUAD profiled by next-generation sequencing, 6% (410 of 7121) harbored MDM2amp. MDM2amp was significantly enriched among tumors with driver alterations in METex14 (36%, p < 0.001), EGFR (8%, p < 0.001), RET (12%, p < 0.01), and ALK (10%, p < 0.01). The combination of milademetan and the MEK inhibitor trametinib was synergistic in growth inhibition of ECLC5-GLx (TRIM33-RET/MDM2amp), LUAD12c (METex14/KRASG12S/MDM2amp), SW1573 (KRASG12C, TP53 wild type), and A549 (KRASG12S) cells and in increasing expression of proapoptotic proteins PUMA and BIM. Treatment of ECLC5-GLx and LUAD12c with single-agent milademetan increased ERK phosphorylation, consistent with previous data on ERK activation with MDM2 inhibition. This ERK activation was effectively suppressed by concomitant administration of trametinib. In contrast, ERK phosphorylation induced by milademetan was not suppressed by concurrent RET inhibition using selpercatinib (in ECLC5-GLx) or MET inhibition using capmatinib (in LUAD12c). In vivo, combination milademetan and trametinib was more effective than either agent alone in ECLC5-GLx, LX-285 (EGFRex19del/MDM2amp), L13BS1 (METex14/MDM2amp), and A549 (KRASG12S, TP53 wild type).

CONCLUSIONS

Combined MDM2/MEK inhibition was found to have efficacy across multiple patient-derived LUAD models harboring MDM2amp and concurrent oncogenic drivers. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions activating the MAPK pathway, has evident clinical implications and will be investigated as part of a planned phase 1/2 clinical trial.

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.

Targeting MET: Discovery of Small Molecule Inhibitors as Non-Small Cell Lung Cancer Therapy

MET has been considered as a promising drug target for the treatment of MET-dependent diseases, particularly non-small cell lung cancer (NSCLC). Small molecule MET inhibitors with mainly three types of binding modes (Ia/Ib, II, and III) have been developed. In this Review, we provide an overview of the structural features, activation mechanism, and dysregulation pathway of MET and summarize progress on the development and discovery strategies utilized for MET inhibitors as well as mechanisms of acquired resistance to current approved inhibitors. The insights will accelerate discovery of new generation MET inhibitors to overcome clinical acquired resistance.

SYK-mediated epithelial cell state is associated with response to c-Met inhibitors in c-Met-overexpressing lung cancer

Genomic MET amplification and exon 14 skipping are currently clinically recognized biomarkers for stratifying subsets of non-small cell lung cancer (NSCLC) patients according to the predicted response to c-Met inhibitors (c-Metis), yet the overall clinical benefit of this strategy is quite limited. Notably, c-Met protein overexpression, which occurs in approximately 20-25% of NSCLC patients, has not yet been clearly defined as a clinically useful biomarker. An optimized strategy for accurately classifying patients with c-Met overexpression for decision-making regarding c-Meti treatment is lacking. Herein, we found that SYK regulates the plasticity of cells in an epithelial state and is associated with their sensitivity to c-Metis both in vitro and in vivo in PDX models with c-Met overexpression regardless of MET gene status. Furthermore, TGF-β1 treatment resulted in SYK transcriptional downregulation, increased Sp1-mediated transcription of FRA1, and restored the mesenchymal state, which conferred resistance to c-Metis. Clinically, a subpopulation of NSCLC patients with c-Met overexpression coupled with SYK overexpression exhibited a high response rate of 73.3% and longer progression-free survival with c-Meti treatment than other patients. SYK negativity coupled with TGF-β1 positivity conferred de novo and acquired resistance. In summary, SYK regulates cell plasticity toward a therapy-sensitive epithelial cell state. Furthermore, our findings showed that SYK overexpression can aid in precisely stratifying NSCLC patients with c-Met overexpression regardless of MET alterations and expand the population predicted to benefit from c-Met-targeted therapy.

Regulation of VEGFR2 and AKT Signaling by Musashi-2 in Lung Cancer

Lung cancer is the most frequently diagnosed cancer type and the leading cause of cancer-related deaths worldwide. Non-small cell lung cancer (NSCLC) represents most of the diagnoses of lung cancer. Vascular endothelial growth factor receptor-2 (VEGFR2) is a member of the VEGF family of receptor tyrosine kinase proteins, which are expressed on both endothelial and tumor cells, are one of the key proteins contributing to cancer development, and are involved in drug resistance. We previously showed that Musashi-2 (MSI2) RNA-binding protein is associated with NSCLC progression by regulating several signaling pathways relevant to NSCLC. In this study, we performed Reverse Protein Phase Array (RPPA) analysis of murine lung cancer, which suggests that VEGFR2 protein is strongly positively regulated by MSI2. Next, we validated VEGFR2 protein regulation by MSI2 in several human lung adenocarcinoma cell line models. Additionally, we found that MSI2 affected AKT signaling via negative PTEN mRNA translation regulation. In silico prediction analysis suggested that both VEGFR2 and PTEN mRNAs have predicted binding sites for MSI2. We next performed RNA immunoprecipitation coupled with quantitative PCR, which confirmed that MSI2 directly binds to VEGFR2 and PTEN mRNAs, suggesting a direct regulation mechanism. Finally, MSI2 expression positively correlated with VEGFR2 and VEGF-A protein levels in human lung adenocarcinoma samples. We conclude that the MSI2/VEGFR2 axis contributes to lung adenocarcinoma progression and is worth further investigations and therapeutic targeting.

Regulation of VEGFR2 and AKT signaling by Musashi-2 in lung cancer

Lung cancer is the most frequently diagnosed cancer type and the leading cause of cancer-related deaths worldwide. Non-small cell lung cancer (NSCLC) represents most of the lung cancer. Vascular endothelial growth factor receptor-2 (VEGFR2) is a member of the VEGF family of receptor tyrosine kinase proteins, expressed on both endothelial and tumor cells which is one of the key proteins contributing to cancer development and involved in drug resistance. We previously showed that Musashi-2 (MSI2) RNA-binding protein is associated with NSCLC progression by regulating several signaling pathways relevant to NSCLC. In this study, we performed Reverse Protein Phase Array (RPPA) analysis of murine lung cancer which nominated VEGFR2 protein as strongly positively regulated by MSI2. Next, we validated VEGFR2 protein regulation by MSI2 in several human NSCLC cell line models. Additionally, we found that MSI2 affected AKT signaling via negative PTEN mRNA translation regulation. In silico prediction analysis suggested that both VEGFR2 and PTEN mRNAs have predicted binding sites for MSI2. We next performed RNA immunoprecipitation coupled with quantitative PCR which confirmed that MSI2 directly binds to VEGFR2 and PTEN mRNAs, suggesting direct regulation mechanism. Finally, MSI2 expression positively correlated with VEGFR2 and VEGF-A protein levels in human NSCLC samples. We conclude that MSI2/VEGFR2 axis contributes to NSCLC progression and is worth further investigations and therapeutic targeting.

Resistance to MET inhibition in MET-dependent NSCLC and therapeutic activity after switching from type I to type II MET inhibitors

OBJECTIVES

Resistance to MET inhibition occurs inevitably in MET-dependent non-small cell lung cancer and the underlying mechanisms are insufficiently understood. We describe resistance mechanisms in patients with MET exon 14 skipping mutation (METΔ^ex14), MET amplification, and MET fusion and report treatment outcomes after switching therapy from type I to type II MET inhibitors.

MATERIALS AND METHODS

Pre- and post-treatment biopsies were analysed by NGS (next generation sequencing), digital droplet PCR (polymerase chain reaction), and FISH (fluorescense in situ hybridization). A patient-derived xenograft model was generated in one case.

RESULTS

Of 26 patients with MET tyrosine kinase inhibitor treatment, eight had paired pre- and post-treatment biopsies (Three with MET amplification, three with METΔ^ex14, two with MET fusions (KIF5B-MET and PRKAR2B-MET).) In six patients, mechanisms of resistance were detected, whereas in two cases, the cause of resistance remained unclear. We found off-target resistance mechanisms in four cases with KRAS mutations and HER2 amplifications appearing. Two patients exhibited second-site MET mutations (p.D1246N and p. Y1248H). Three patients received type I and type II MET tyrosine kinase inhibitors sequentially. In two cases, further progressive disease was seen hereafter. The patient with KIF5B-MET fusion received three different MET inhibitors and showed long-lasting stable disease and a repeated response after switching therapy, respectively.

CONCLUSION

Resistance to MET inhibition is heterogeneous with on- and off-target mechanisms occurring regardless of the initial MET aberration. Switching therapy between different types of kinase inhibitors can lead to repeated responses in cases with second-site mutations. Controlled clinical trials in this setting with larger patient numbers are needed, as evidence to date is limited to preclinical data and case series.

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.

KRAS in NSCLC: State of the Art and Future Perspectives

In NSCLC, KRAS mutations occur in up to 30% of all cases, most frequently at codon 12 and 13. KRAS mutations have been linked to adenocarcinoma histology, positive smoking history, and Caucasian ethnicity, although differences have been described across KRAS mutational variants subtypes. KRAS mutations often concur with other molecular alterations, notably TP53, STK11, and KEAP1, which could play an important role in treatment efficacy and patient outcomes. For many years, KRAS mutations have been considered undruggable mainly due to a high toxicity profile and low specificity of compounds. Sotorasib and adagrasib are novel KRAS inhibitors that recently gained FDA approval for pre-treated KRAS mutant NSCLC patients, and other molecules such as GDC-6036 are currently being investigated with promising results. Despite their approval, the efficacy of these drugs is lower than expected and progression among responders has been reported. Mechanisms of acquired resistance to anti-KRAS molecules typically involves either on target secondary mutations (e.g., G12, G13, Q61H, R68S, H95, Y96C, V8L) or off-target alterations. Ongoing trials are currently evaluating strategies for implementing efficacy and overcoming acquired resistance to these compounds. Finally, the efficacy of immune-checkpoint inhibitors still needs to be completely assessed and responses to anti-PD-1/PD-L1 agents may strongly depend on concomitant mutations.

Circulating tumour DNA biomarkers in savolitinib-treated patients with non-small cell lung cancer harbouring MET exon 14 skipping alterations: a post hoc analysis of a pivotal phase 2 study

Background

Savolitinib, a selective MET inhibitor, showed efficacy in patients with non-small cell lung cancer (NSCLC), including pulmonary sarcomatoid carcinoma (PSC), harbouring MET exon 14 skipping alteration (METex14).

Objective

To analyse post hoc, the association between circulating tumour DNA (ctDNA) biomarkers and clinical outcomes, including resistance, with savolitinib.

Design

A multicentre, single-arm, open-label phase 2 study.

Methods

All enrolled patients with baseline plasma samples were included. Outcomes were objective response rate (ORR), progression-free survival (PFS) and overall survival (OS) by baseline METex14 and post-treatment clearance, coexisting gene alterations at baseline and disease progression.

Results

Among 66 patients with baseline ctDNA sequencing, 46 (70%) had detectable METex14. Frequent coexisting baseline gene alterations included TP53 and POT1 mutations. Patients with detectable baseline METex14 exhibited worse PFS [hazard ratio (HR), 1.77; 95% confidence interval (CI), 0.88-3.57; p = 0.108] and OS (HR, 3.26; 95% CI, 1.35-7.89; p = 0.006) than those without, despite showing a numerically higher ORR. Among 24 patients with baseline detectable METex14 and evaluable postbaseline samples, 13 achieved METex14 clearance post-treatment. Median time to first clearance was 1.3 months (range, 0.7-1.5). METex14 post-treatment clearance was associated with better ORR (92.3%; 95% CI, 64.0-99.8 versus 36.4%; 95% CI, 10.9-69.2; p = 0.0078), PFS (HR, 0.44; 95% CI, 0.2-1.3; p = 0.1225) and OS (HR, 0.31; 95% CI, 0.1-1.0; p = 0.0397) versus non-clearance. Among 22 patients with disease progression, 10 acquired pathway alterations (e.g. in RAS/RAF and PI3K/PTEN) alone or with secondary MET mutations (D1228H/N and Y1230C/H/S).

Conclusion

ctDNA biomarkers may allow for longitudinal monitoring of clinical outcomes with savolitinib in patients with METex14-positive PSC and other NSCLC subtypes. Specifically, undetectable baseline METex14 or post-treatment clearance may predict favourable clinical outcomes, while secondary MET mutations and other acquired gene alterations may explain resistance to savolitinib.

Registration

The trial was registered with ClinicalTrials.gov (NCT02897479) on 13 September 2016.

Biomarker-Targeted Therapies in Non-Small Cell Lung Cancer: Current Status and Perspectives

Non-small-cell lung cancer (NSCLC) is one of the most common malignancies and the leading causes of cancer-related death worldwide. Despite many therapeutic advances in the past decade, NSCLC remains an incurable disease for the majority of patients. Molecular targeted therapies and immunotherapies have significantly improved the prognosis of NSCLC. However, the vast majority of advanced NSCLC develop resistance to current therapies and eventually progress. In this review, we discuss current and potential therapies for NSCLC, focusing on targeted therapies and immunotherapies. We highlight the future role of metabolic therapies and combination therapies in NSCLC.

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.

Genomic landscape of lung adenocarcinomas in different races

Background

Lung adenocarcinoma is a molecularly heterogeneous disease. Several studies, including The Cancer Genome Atlas Research Network (TCGA) and Lung Cancer Mutation Consortium (LCMC), explored the genetic alterations among different ethnic groups. However, minority groups are often under-represented in these relevant studies and the genomic alterations among racial groups are not fully understood.

Methods

We analyze genomic characteristics among racial groups to understand the diversities and their impact on clinical outcomes.

Results

Native Americans had significantly higher rates of insertions and deletions than other races (P<0.001). Among patients with lung adenocarcinomas, EGFR and KRAS were the highest discrepancy genes in the different racial groups (P<0.001). The EGFR exon 21 L858R point mutation was three times higher in Asians than in all other races (P<0.001). Asians, Whites, and Blacks had 4.7%, 3.1%, and 1.8% ALK rearrangement, respectively (P<0.001). White patients had the highest rates of reported KRAS G12C (15.51%) than other races (P<0.001). Whites (17.2%), Blacks (15.1%), and Other (15.7%) had higher rates of STK11 mutation than Asians (3.94%) (P<0.001). RET rearrangement and ERBB2 amplification were more common in Asian patients than in Other racial groups. Apart from point mutations, structural variations, and fusion genes, we identified a significant amount of copy number alterations in each race.

Conclusions

The tumor genomic landscape is significantly distinct in different races. This data would shed light on the understanding of molecular alterations and their impacts on clinical management in different lung cancer patients.

Mutational Landscape and Expression of PD-L1 in Patients with Non-Small Cell Lung Cancer Harboring Genomic Alterations of the MET gene

Background

Mesenchymal-to-epithelial transition (MET) exon 14 skipping mutations and MET gene amplification occur in 3–5% of non-small cell lung cancer (NSCLC) patients. Tyrosine kinase inhibitors (TKIs) targeting MET alterations have shown promising results in these patients.

Objective

The aim of this study was to describe the genomic profile, PD-L1 expression and clinicopathological features of MET dysregulated NSCLC.

Patients and Methods

We identified 188 patients with advanced-stage NSCLC with data on MET expression by immunohistochemistry (IHC). IHC for PD-L1 expression was performed in 131 patient samples, and next-generation sequencing (NGS) analysis was performed in 109 patient samples.

Results

MET exon 14 skipping alterations were identified in 16 (14.7%) samples, MET amplifications with cut-off ≥4 copy number variations were identified in 11 (10.1%) samples, and an oncogenic MET mutation (MET p.D1228N) was identified in 1 (0.9%) sample. 12/15 tumors (80.0%) harboring MET exon 14 alterations and 7/11 (63.6%) MET-amplified tumors expressed PD-L1 in ≥1% of tumor cells. Tumors harboring MET exon 14 skipping alterations expressed PD-L1 more frequently than MET wild-type IHC-positive tumors (p = 0.045). Twenty-five percent of MET exon 14-altered cases and 33% of MET-amplified cases harbored potentially targetable oncogenic co-mutations in KRAS, BRAF, and EGFR. The most frequent co-occurring mutations in all MET-altered tumors were TP53, KRAS, BRAF, and CDK4.

Conclusions

We demonstrated that MET exon 14 skipping alterations and MET amplification are not mutually exclusive to other oncogenic co-mutations, and report the association of genomic MET alterations with PD-L1 expression. Since genomic MET alterations are emerging targets requiring upfront treatment, optimal understanding of the co-mutational landscape for this patient population is needed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11523-022-00918-6.

MET Exon 14 Splice-Site Mutations Preferentially Activate KRAS Signaling to Drive Tumourigenesis

Simple Summary

MET exon 14 splice-site mutations occur in ~3–4% of lung adenocarcinoma cases, defining a cohort of patients which might benefit from anti-MET targeted therapy. Such therapies have yielded mixed results, however, pointing to the need for better treatment design. Our study sought to aid this by characterizing key changes in mutant MET signaling behaviour. We first compared the transcriptional profiles of lung tumours with either METΔex14 or wild-type MET-amplification. METΔex14-mutant tumours exhibited increased activation of the Ras-MAPK pathway, consistent with our observations in an isogenic model system. Furthermore, sustained activity of this pathway is necessary for proliferation and maintenance of METΔex14 tumours, while forced reactivation of this pathway is sufficient to restore growth in the absence of MET activity. Our findings suggest that the MAPK pathway represents a main effector of METΔex14-driven cancer, lending credence to the possibility of combined MET-MAPK inhibition to improve therapeutic outcomes.

Abstract

Targeted therapies for MET exon 14-skipping (METΔex14)-driven lung cancers have generated some promising results but response rates remain below that seen for other kinase-driven cancers. One strategy for improving treatment outcomes is to employ rational combination therapies to enhance the suppression of tumour growth and delay or prevent the emergence of resistance. To this end, we profiled the transcriptomes of MET-addicted lung tumours and cell lines and identified the RAS-mitogen-activated protein kinase (MAPK) pathway as a critical effector required for METΔex14-dependent growth. Ectopic expression of MET in an isogenic cell line model showed that overexpression of the mutant MET receptor led to higher levels of MAPK phosphorylation and nuclear import, resulting in increased expression and phosphorylation of nuclear MAPK targets. In comparison, other known MET effectors were unaffected. Inhibition of this pathway by KRAS knockdown in MET-addicted cells in vitro led to decreased viability in only the METΔex14-mutant cells. Conversely, decoupling RAS-MAPK axis, but not other effector pathways, from MET activity via the introduction of constitutively active mutants conferred resistance to MET inhibitors in vitro. Our results suggest that aberrant hyperactivity of the MET receptor caused by the exon 14-skipping mutation does not uniformly upregulate all known downstream effectors, rather gaining a predilection for aberrantly activating and subsequently relying on the RAS-MAPK pathway. These findings provide a rationale for the co-targeting of the RAS-MAPK pathway alongside MET to prolong therapeutic response and circumvent resistance to improve patient survival.

KRAS and MET in non-small-cell lung cancer: two of the new kids on the 'drivers' block

Non-small-cell lung cancer (NSCLC) is a heterogeneous disease, and therapeutic management has advanced to identify various critical oncogenic mutations that promote lung cancer tumorigenesis. Subsequent studies have developed targeted therapies against these oncogenes in the hope of personalized treatment based on the tumor's molecular genomics. This review presents a comprehensive review of the biology, new therapeutic interventions, and resistance patterns of two well-defined subgroups, tumors with KRAS and MET alterations. We also discuss the status of molecular testing practices for these two key oncogenic drivers, considering the progressive introduction of next-generation sequencing (NGS) and RNA sequencing in regular clinical practice.

Targeting un-MET needs in advanced non-small cell lung cancer

Lung cancer classification has been radically transformed in recent years as genomic profiling has identified multiple novel therapeutic targets including MET exon 14 (METex14) alterations and MET amplification. Utilizing targeted therapies in patients with molecularly-defined NSCLC leads to remarkable objective response rates and improved progression-free survival. However, acquired resistance is inevitable. Several recent phase II trials have confirmed that METex14 NSCLC can be treated effectively with MET kinase inhibitors, such as crizotinib, capmatinib, tepotinib, and savolitinib. However, response rates for many MET TKIs are modest relative to the activity of targeted therapy in other oncogene-driven lung cancers, where ORRs are more consistently greater than 60%. In spite of significant gains in the field of MET inhibition in NSCLC, challenges remain: the landscape of resistance mechanisms to MET TKIs is not yet well characterized, and there may be intrinsic and acquired resistance mechanisms that require further characterization to enable increased MET TKI activity. In this review, we overview MET pathway dysregulation in lung cancer, methods of detection in the clinic, recent clinical trial data, and discuss current mechanisms of TKI resistance, exploring emerging strategies to overcome resistance.

Landscape and Clonal Dominance of Co-occurring Genomic Alterations in Non-Small-Cell Lung Cancer Harboring MET Exon 14 Skipping

MET exon 14 skipping alterations (METex14) comprise a diverse set of actionable oncogene drivers in non–small-cell lung cancer (NSCLC). Recent studies have established the efficacy of tyrosine kinase inhibitors for this patient population. The landscape of co-occurring genetic alterations in METex14 NSCLC and their potential impact to therapeutic sensitivities has not yet been fully described.

Targeted Treatment of Non-Small Cell Lung Cancer: Focus on Capmatinib with Companion Diagnostics

MET dysregulation promoting tumorigenesis in non-small cell lung cancer (NSCLC) is associated with worse outcomes following chemotherapy as compared to non-driver mutated NSCLC and occurs either through mutations causing MET exon 14 skipping (METex14) or gene amplification and overexpression that result in enhanced receptor signaling. Capmatinib is the first FDA-approved targeted therapy for NSCLC with METex14 skipping mutations, approved in 2020. FoundationOne^® CDx, a comprehensive genomic profiling test for solid tumors, was concurrently approved as a companion diagnostic for capmatinib use. The GEOMETRY mono-1 phase II trial of capmatinib monotherapy demonstrated an overall response rate (ORR) of 68% in treatment naïve (n=28) and 41% in pre-treated (n=69) METex14 skipping advanced NSCLC; in MET amplified advanced NSCLC (gene copy number ≥ 10) ORRs of 40% in treatment naïve and 29% in pre-treated disease was seen. This review outlines the clinical data supporting capmatinib approval in the treatment of NSCLC and FoundationOne^® CDx approval as a companion diagnostic. We detail the practical clinical administration of capmatinib, including dosing and toxicity management, compare capmatinib to other approved and investigational MET-targeted therapies, discuss limitations of capmatinib, and highlight ongoing trials of capmatinib in combinatorial approaches.

Concordance of acquired mutations between metastatic lesions and liquid biopsy in metastatic colorectal cancer

Aim:

To evaluate whether PCR-reverse sequence-specific oligonucleotide can examine the concordance between liquid biopsy and metastatic lesions with acquired resistance.

Materials & methods:

We examined acquired mutations in chemoresistant lesions and blood obtained from four patients with RAS wild-type metastatic colorectal cancer who underwent treatment with anti-epidermal growth factor receptor antibodies.

Results:

In one patient, metastatic lesions harbored diverse acquired mutations in KRAS in all seven metastases; the two acquired mutations were detectable in blood collected after the patient acquired resistance. None of the other patients exhibited liquid biopsy mutations, except one, with a BRAF mutation confirmed in primary tumor and peritoneal dissemination.

Conclusion:

Liquid biopsy based on PCR-reverse sequence-specific oligonucleotide is a successful procedure for capturing acquired mutations with precise information on the RAS mutational spectrum.

Beyond epidermal growth factor receptor: MET amplification as a general resistance driver to targeted therapy in oncogene-driven non-small-cell lung cancer

The rapidly changing treatment paradigm for patients with metastatic oncogene-driven lung cancer continues to evolve, and consequently our understanding of the landscape of resistance must also advance. MET amplification is an established and frequent driver of resistance in EGFR-mutant non-small-cell lung cancer (NSCLC). Recently, the combination of MET proto-oncogene (MET) and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has shown promise in overcoming this molecularly defined resistance in clinical trials, and this combination strategy is being pursued in ongoing trials. Emerging data also demonstrate MET amplification as a resistance driver to TKI-treated ALK-, RET-, and ROS-1-fusion NSCLC, consistently at the range of 15%, while the resistance profiling data are maturing for other molecular targets. In this review, we discuss MET amplification as a driver of acquired resistance in well-defined molecular subsets of NSCLC, explore the biology behind this mechanism of resistance, and summarize the recently published clinical data, including the proposed combination strategies in the clinic achieving success in overcoming acquired MET amplification-dependent resistance.

•

Understanding mechanisms of resistance in oncogene-driven lung cancer is crucial.

•

MET amplification is a recurrent driver of resistance, across molecularly defined subsets of NSCLC.

•

Overcoming this resistance in clinical trials, using combination strategies, is currently being pursued.

•

We explore the biology behind this mechanism of resistance and summarize recent successes in the clinic.

FARP1, ARHGEF39, and TIAM2 are essential receptor tyrosine kinase effectors for Rac1-dependent cell motility in human lung adenocarcinoma

Despite the undisputable role of the small GTPase Rac1 in the regulation of actin cytoskeleton reorganization, the Rac guanine-nucleotide exchange factors (Rac-GEFs) involved in Rac1-mediated motility and invasion in human lung adenocarcinoma cells remain largely unknown. Here, we identify FARP1, ARHGEF39, and TIAM2 as essential Rac-GEFs responsible for Rac1-mediated lung cancer cell migration upon EGFR and c-Met activation. Noteworthily, these Rac-GEFs operate in a non-redundant manner by controlling distinctive aspects of ruffle dynamics formation. Mechanistic analysis reveals a leading role of the AXL-Gab1-PI3K axis in conferring pro-motility traits downstream of EGFR. Along with the positive association between the overexpression of Rac-GEFs and poor lung adenocarcinoma patient survival, we show that FARP1 and ARHGEF39 are upregulated in EpCam⁺ cells sorted from primary human lung adenocarcinomas. Overall, our study reveals fundamental insights into the complex intricacies underlying Rac-GEF-mediated cancer cell motility signaling, hence underscoring promising targets for metastatic lung cancer therapy.

Integrative Profiling of T790M-Negative EGFR-Mutated NSCLC Reveals Pervasive Lineage Transition and Therapeutic Opportunities

PURPOSE

Despite the established role of EGFR tyrosine kinase inhibitors (TKIs) in EGFR-mutated NSCLC, drug resistance inevitably ensues, with a paucity of treatment options especially in EGFR ^T790M-negative resistance.

EXPERIMENTAL DESIGN

We performed whole-exome and transcriptome analysis of 59 patients with first- and second-generation EGFR TKI-resistant metastatic EGFR-mutated NSCLC to characterize and compare molecular alterations mediating resistance in T790M-positive (T790M⁺) and -negative (T790M^-) disease.

RESULTS

Transcriptomic analysis revealed ubiquitous loss of adenocarcinoma lineage gene expression in T790M^- tumors, orthogonally validated using multiplex IHC. There was enrichment of genomic features such as TP53 alterations, 3q chromosomal amplifications, whole-genome doubling and nonaging mutational signatures in T790M^- tumors. Almost half of resistant tumors were further classified as immune^hot, with clinical outcomes conditional on immune cell-infiltration state and T790M status. Finally, using a Bayesian statistical approach, we explored how T790M^- and T790M⁺ disease might be predicted using comprehensive genomic and transcriptomic profiles of treatment-naïve patients.

CONCLUSIONS

Our results illustrate the interplay between genetic alterations, cell lineage plasticity, and immune microenvironment in shaping divergent TKI resistance and outcome trajectories in EGFR-mutated NSCLC. Genomic and transcriptomic profiling may facilitate the design of bespoke therapeutic approaches tailored to a tumor's adaptive potential.

A Biparatopic Antibody-Drug Conjugate to Treat MET-Expressing Cancers, Including Those that Are Unresponsive to MET Pathway Blockade

Lung cancers harboring mesenchymal-to-epithelial transition factor (MET) genetic alterations, such as exon 14 skipping mutations or high-level gene amplification, respond well to MET-selective tyrosine kinase inhibitors (TKI). However, these agents benefit a relatively small group of patients (4%-5% of lung cancers), and acquired resistance limits response durability. An antibody-drug conjugate (ADC) targeting MET might enable effective treatment of MET-overexpressing tumors (approximately 25% of lung cancers) that do not respond to MET targeted therapies. Using a protease-cleavable linker, we conjugated a biparatopic METxMET antibody to a maytansinoid payload to generate a MET ADC (METxMET-M114). METxMET-M114 promotes substantial and durable tumor regression in xenografts with moderate to high MET expression, including models that exhibit innate or acquired resistance to MET blockers. Positron emission tomography (PET) studies show that tumor uptake of radiolabeled METxMET antibody correlates with MET expression levels and METxMET-M114 efficacy. In a cynomolgus monkey toxicology study, METxMET-M114 was well tolerated at a dose that provides circulating drug concentrations that are sufficient for maximal antitumor activity in mouse models. Our findings suggest that METxMET-M114, which takes advantage of the unique trafficking properties of our METxMET antibody, is a promising candidate for the treatment of MET-overexpressing tumors, with the potential to address some of the limitations faced by the MET function blockers currently in clinical use.

Intra-tumor and Inter-tumor Heterogeneity in MET Exon 14 Skipping Mutations and Co-mutations in Pulmonary Pleomorphic Carcinomas

BACKGROUND

MET exon 14 skipping mutation is a driver mutation in lung cancer and is highly enriched in pulmonary pleomorphic carcinomas (PPCs). Whether there is intratumor or intertumor heterogeneity in MET exon 14 skipping status or in co-occurring genetic alterations in lung cancers driven by MET exon 14 skipping is unknown.

METHODS

We analyzed tumor specimens obtained from 23 PPC patients (10 autopsied and 13 surgically resected). MET exon 14 skipping was detected by RT-PCR. For patients with MET exon 14 skipping mutation, further analyses were performed. Genomic DNA (gDNA) was extracted from various histological components for each patient who underwent surgical resection (to assess intratumor heterogeneity). In autopsied patients, gDNA and total RNA were extracted from all metastatic lesions (to assess intertumor heterogeneity).

RESULTS

MET exon 14 skipping mutation was detected in 4 patients (4/23, 17.4%): two surgically resected and two autopsied patients. We found no intratumor or intertumor heterogeneity in MET exon 14 skipping mutation status in these patients. We observed intratumor and intertumor heterogeneity in the copy number variations and/or mutational status of cancer-related genes; some of these differences may have an impact on MET tyrosine kinase inhibitor (TKI) efficacy.

CONCLUSION

In our exploratory analysis of four cases, we observed that MET exon 14 skipping mutations are distributed homogeneously throughout histological components and between metastatic lesions. Our results also suggest that there is marked intertumor and intratumor heterogeneity in co-occurring genetic alterations, and therapeutic implications of such heterogeneity should be evaluated in future studies.

Characterization of Non-Small-Cell Lung Cancers With MET Exon 14 Skipping Alterations Detected in Tissue or Liquid: Clinicogenomics and Real-World Treatment Patterns

PURPOSE

MET exon 14 (METex14) skipping alterations are oncogenic drivers in non–small-cell lung cancer (NSCLC). We present a comprehensive overview of METex14 samples from 1,592 patients with NSCLC, associated clinicogenomic characteristics, potential mechanisms of acquired resistance, treatment patterns, and outcomes to MET inhibitors.

METHODS

Hybrid capture–based comprehensive genomic profiling (CGP) was performed on samples from 69,219 patients with NSCLC. For treatment patterns and outcomes analysis, patients with advanced METex14-altered NSCLC were selected from the Flatiron Health-Foundation Medicine clinicogenomic database, a nationwide deidentified electronic health record–derived database linked to Foundation Medicine CGP for patients treated between January 2011 and March 2020.

RESULTS

A total of 1,592 patients with NSCLC (2.3%) were identified with 1,599 METex14 alterations spanning multiple functional sites (1,458 of 60,244 tissue samples and 134 of 8,975 liquid samples). Low tumor mutational burden and high programmed death ligand 1 expression were enriched in METex14-altered samples. MDM2, CDK4, and MET coamplifications and TP53 mutations were present in 34%, 19%, 11%, and 42% of tissue samples, respectively. Comparing tissue and liquid cohorts, coalteration frequency and acquired resistance mechanisms, including multiple MET mutations, EGFR, ERBB2, KRAS, and PI3K pathway alterations, were generally similar. Positive percent agreement with the tissue was 100% for METex14 pairs collected within 1 year (n = 7). Treatment patterns showed increasing adoption of MET inhibitors in METex14-altered NSCLC after receipt of CGP results; the real-world response rate to MET inhibitors was 45%, and time to treatment discontinuation was 4.4 months.

CONCLUSION

Diverse METex14 alterations were present in 2%-3% of NSCLC cases. Tissue and liquid comparisons showed high concordance and similar coalteration profiles. Characterizing common co-occurring alterations and immunotherapy biomarkers, including those present before or acquired after treatment, may be critical for predicting responses to MET inhibitors and informing rational combination strategies.

MET Mutation Is a Potential Therapeutic Target for Advanced Endometrial Cancer

Simple Summary

Endometrial cancer is the most common gynecological cancer in developed countries. At initial diagnosis, extra-uterine spread is observed in about 25% of patients. Chemotherapy is the suggested mode of treatment for patients with extra-uterine metastasis; however, the 5-year overall survival rate of these patients remains poor. The development of new therapeutic strategies to improve the poor clinical outcome of patients with advanced endometrial cancer is still in great demand. In this study, we aim to understand the genomic landscape of advanced endometrial cancer and identify new therapeutic targets. Integrated genomic, pathological, and clinical data are analyzed to identify the survival-associated genomic alterations. In addition, the impacts of the genomic alterations are examined in silico, in vitro, and in vivo. The results of this study may aid in developing biomarker-guided treatments for patients with advanced endometrial cancer.

Abstract

An optimal therapeutic regimen for endometrial cancer with extra-uterine metastasis is unavailable. This study aims to improve our understanding of the genomic landscape of advanced endometrial cancer and identify potential therapeutic targets. The clinical and genomic profiles of 81 patients with stage III or IV endometrial cancer were integrated. To identify genomic aberrations associated with clinical outcomes, Cox proportional hazard regression was used. The impacts of the genomic aberrations were validated in vitro and in vivo. The mutation status of MET, U2AF1, BCL9, PPP2R1A, IDH2, CBL, BTK, and CHEK2 were positively correlated with poor clinical outcomes. MET mutations occurred in 30% of the patients who presented with poor overall survival (hazard ratio, 2.606; 95% confidence interval, 1.167~5.819; adjusted p-value, 0.067). Concurrent MET and KRAS mutations presented with the worst outcomes. MET mutations in hepatocyte growth factor (HGF)-binding (58.1%) or kinase (16.2%) domains resulted in differential HGF-induced c-MET phosphorylation. Different types of MET mutations differentially affected tumor growth and displayed different sensitivities to cisplatin and tyrosine kinase inhibitors. MET N375S mutation is a germline variant that causes chemoresistance to cisplatin, with a high incidence in Eastern Asia. This study highlights the ethnic differences in the biology of the disease, which can influence treatment recommendations and the genome-guided clinical trials of advanced endometrial cancer.

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.

Kinase drug discovery 20 years after imatinib: progress and future directions

Protein kinases regulate nearly all aspects of cell life, and alterations in their expression, or mutations in their genes, cause cancer and other diseases. Here, we review the remarkable progress made over the past 20 years in improving the potency and specificity of small-molecule inhibitors of protein and lipid kinases, resulting in the approval of more than 70 new drugs since imatinib was approved in 2001. These compounds have had a significant impact on the way in which we now treat cancers and non-cancerous conditions. We discuss how the challenge of drug resistance to kinase inhibitors is being met and the future of kinase drug discovery.

Prognosis and Concurrent Genomic Alterations in Patients With Advanced NSCLC Harboring MET Amplification or MET Exon 14 Skipping Mutation Treated With MET Inhibitor: A Retrospective Study

Background

MET amplification or METex14 skipping mutations are uncommon oncogenic events in NSCLC patients. Clinicopathological characteristics, concurrent gene alterations, and prognosis of MET TKIs in these patients are yet to be elucidated.

Methods

We retrospectively analyzed the genomic profiles of 43 MET amplifications or 31 METex14 skipping mutations in NSCLC patients with no previous treatment with EGFR TKIs. Survival outcomes were analyzed in evaluable patients receiving MET TKI treatment: MET amplification cohort (n = 29) and METex14 skipping mutation cohort (n = 29).

Results

Among evaluable patients, a shorter PFS was observed in the MET amplification cohort than in the METex14 skipping mutation cohort (7.0 months vs. 11.0 months, P = 0.043). Concurrent mutations in both cohorts resulted in a statistically significant shorter PFS (MET amplification: 3.5 months versus 8.0 months, P = 0.038, METex14 skipping mutation: 7.0 versus NR months, P = 0.022). However, a statistically significant OS (17.0 months versus 20.0 months, P = 0.044) was only observed in the MET amplification cohort. TP53, the most common concurrent mutation in both cohorts, was associated with worse survival outcomes as compared to the wild type. The MET amplification cohort with a concurrent PIK3CA mutation exhibited primary resistance to MET TKIs and showed disease progression (80%).

Conclusion

MET TKIs could be a better treatment option for patients with METex14 skipping mutations. Concurrent mutations may deteriorate the PFS of MET TKIs in NSCLC patients with MET amplification or METex14 skipping mutations. PIK3CA mutations may confer primary resistance to MET TKIs in patients with MET amplification.

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

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

Has programmed cell death ligand-1 MET an accomplice in non-small cell lung cancer?-a narrative review

Recently approved and highly specific small-molecule inhibitors of c-MET exon 14 skipping mutations (e.g., capmatinib, tepotinib) are a new and important therapeutic option for the treatment of non-small cell lung cancer (NSCLC) patients harbouring c-MET alterations. Several experimental studies have provided compelling evidence that c-MET is involved in the regulation of the immune response by up-regulating inhibitory molecules (e.g., PD-L1) and down-regulating of immune stimulators (e.g., CD137, CD252, CD70, etc.). In addition, c-MET was found to be implicated in the regulation of the inflamed tumour microenvironment (TME) and thereby contributing to an increased immune escape of tumour cells from T cell killing. Moreover, it is a major resistance mechanism following treatment of epidermal growth factor receptor mutations (EGFRmut) with tyrosine kinase receptor inhibitors (TKIs). In line with these findings c-MET alterations have also been shown to be associated with a worse clinical outcome and a poorer prognosis in NSCLC patients. However, the underlying mechanisms for these experimental observations are neither fully evaluated nor conclusive, but clearly multifactorial and most likely tumour-specific. In this regard the clinical efficacy of checkpoint inhibitors (CPIs) and TKIs against EGFRmut in NSCLC patients harbouring c-MET alterations is also not yet established, and further research will certainly provide some guidance as to optimally utilise CPIs and c-MET inhibitors in the future.

When the MET receptor kicks in to resist targeted therapies

Although targeted therapies have increased the life expectancy of patients with druggable molecular alterations directly involved in tumor development, the efficacy of these therapies is limited by acquired resistances leading to treatment failure. Most targeted therapies, including ones exploiting therapeutic antibodies and kinase inhibitors, are directed against receptor tyrosine kinases (RTKs) or major signaling hubs. Resistances to these therapies arise when inhibition of these targets is bypassed through activation of alternative signaling pathways. In recent years, activation of the receptor tyrosine kinase MET has been shown to promote resistance to various targeted therapies. This casts MET as important actor in resistance. In this review, we describe how the MET receptor triggers resistance to targeted therapies against RTKs such as EGFR, VEGFR, and HER2 and against signaling hubs such as BRAF. We also describe how MET can be its own resistance factor, as illustrated by on-target resistance of lung tumors harboring activating mutations causing MET exon 14 skipping. Interestingly, investigation of all these situations reveals functional physiological relationships between MET and the target of the therapy to which the cancer becomes resistant, suggesting that resistance stems from preexisting mechanisms. Identification of MET as a resistance factor opens the way to co-treatment strategies that are being tested in current clinical trials.