The MET Oncogene: Thirty Years of Insights into Molecular Mechanisms Driving Malignancy

The discovery and subsequent research on the MET oncogene's role in cancer onset and progression have illuminated crucial insights into the molecular mechanisms driving malignancy. The identification of MET as the hepatocyte growth factor (HGF) receptor has paved the path for characterizing the MET tyrosine kinase activation mechanism and its downstream signaling cascade. Over the past thirty years, research has established the importance of HGF/MET signaling in normal cellular processes, such as cell dissociation, migration, proliferation, and cell survival. Notably, genetic alterations that lead to the continuous activation of MET, known as constitutive activation, have been identified as oncogenic drivers in various cancers. The genetic lesions affecting MET, such as exon skipping, gene amplification, and gene rearrangements, provide valuable targets for therapeutic intervention. Moreover, the implications of MET as a resistance mechanism to targeted therapies emphasize the need for combination treatments that include MET inhibitors. The intriguing "flare effect" phenomenon, wherein MET inhibition can lead to post-treatment increases in cancer cell proliferation, underscores the dynamic nature of cancer therapeutics. In human tumors, increased protein expression often occurs without gene amplification. Various mechanisms may cause an overexpression: transcriptional upregulation induced by other oncogenes; environmental factors (such as hypoxia or radiation); or substances produced by the reactive stroma, such as inflammatory cytokines, pro-angiogenic factors, and even HGF itself. In conclusion, the journey to understanding MET's involvement in cancer onset and progression over the past three decades has not only deepened our knowledge, but has also paved the way for innovative therapeutic strategies. Selective pharmacological inactivation of MET stands as a promising avenue for achieving cancer remission, particularly in cases where MET alterations are the primary drivers of malignancy.

Aberrant MET Receptor Tyrosine Kinase Signaling in Glioblastoma: Targeted Therapy and Future Directions

Brain tumors represent a heterogeneous group of neoplasms characterized by a high degree of aggressiveness and a poor prognosis. Despite recent therapeutic advances, the treatment of brain tumors, including glioblastoma (GBM), an aggressive primary brain tumor associated with poor prognosis and resistance to therapy, remains a significant challenge. Receptor tyrosine kinases (RTKs) are critical during development and in adulthood. Dysregulation of RTKs through activating mutations and gene amplification contributes to many human cancers and provides attractive therapeutic targets for treatment. Under physiological conditions, the Met RTK, the hepatocyte growth factor/scatter factor (HGF/SF) receptor, promotes fundamental signaling cascades that modulate epithelial-to-mesenchymal transition (EMT) involved in tissue repair and embryogenesis. In cancer, increased Met activity promotes tumor growth and metastasis by providing signals for proliferation, survival, and migration/invasion. Recent clinical genomic studies have unveiled multiple mechanisms by which MET is genetically altered in GBM, including focal amplification, chromosomal rearrangements generating gene fusions, and a splicing variant mutation (exon 14 skipping, METex14del). Notably, MET overexpression contributes to chemotherapy resistance in GBM by promoting the survival of cancer stem-like cells. This is linked to distinctive Met-induced pathways, such as the upregulation of DNA repair mechanisms, which can protect tumor cells from the cytotoxic effects of chemotherapy. The development of MET-targeted therapies represents a major step forward in the treatment of brain tumours. Preclinical studies have shown that MET-targeted therapies (monoclonal antibodies or small molecule inhibitors) can suppress growth and invasion, enhancing the efficacy of conventional therapies. Early-phase clinical trials have demonstrated promising results with MET-targeted therapies in improving overall survival for patients with recurrent GBM. However, challenges remain, including the need for patient stratification, the optimization of treatment regimens, and the identification of mechanisms of resistance. This review aims to highlight the current understanding of mechanisms underlying MET dysregulation in GBM. In addition, it will focus on the ongoing preclinical and clinical assessment of therapies targeting MET dysregulation in GBM.

Tyrosine Kinase Inhibitors for Glioblastoma Multiforme: Challenges and Opportunities for Drug Delivery

Glioblastoma multiforme (GBM) is an aggressive brain tumor with high mortality rates. Due to its invasiveness, heterogeneity, and incomplete resection, the treatment is very challenging. Targeted therapies such as tyrosine kinase inhibitors (TKIs) have great potential for GBM treatment, however, their efficacy is primarily limited by poor brain distribution due to the presence of the blood-brain barrier (BBB). This review focuses on the potential of TKIs in GBM therapy and provides an insight into the reasons behind unsuccessful clinical trials of TKIs in GBM despite the success in treating other cancer types. The main section is dedicated to the use of promising drug delivery strategies for targeted delivery to brain tumors. Use of brain targeted delivery strategies can help enhance the efficacy of TKIs in GBM. Among various drug delivery approaches used to bypass or cross BBB, utilizing nanocarriers is a promising strategy to augment the pharmacokinetic properties of TKIs and overcome their limitations. This is because of their advantages such as the ability to cross BBB, chemical stabilization of drug in circulation, passive or active targeting of tumor, modulation of drug release from the carrier, and the possibility to be delivered via non-invasive intranasal route.

hOA-DN30: a highly effective humanized single-arm MET antibody inducing remission of ‘MET-addicted’ cancers

Background

The tyrosine kinase receptor encoded by the MET oncogene is a major player in cancer. When MET is responsible for the onset and progression of the transformed phenotype (MET-addicted cancers), an efficient block of its oncogenic activation results in potent tumor growth inhibition.

Methods

Here we describe a molecular engineered MET antibody (hOA-DN30) and validate its pharmacological activity in MET-addicted cancer models in vitro and in vivo. Pharmacokinetics and safety profile in non-human primates have also been assessed.

Results

hOA-DN30 efficiently impaired MET activation and the intracellular signalling cascade by dose and time dependent removal of the receptor from the cell surface (shedding). In vitro, the antibody suppressed cell growth by blocking cell proliferation and by concomitantly inducing cell death in multiple MET-addicted human tumor cell lines. In mice xenografts, hOA-DN30 induced an impressive reduction of tumor masses, with a wide therapeutic window. Moreover, the antibody showed high therapeutic efficacy against patient-derived xenografts generated from MET-addicted gastric tumors, leading to complete tumor regression and long-lasting effects after treatment discontinuation. Finally, hOA-DN30 showed a highly favorable pharmacokinetic profile and substantial tolerability in Cynomolgus monkeys.

Conclusions

hOA-DN30 unique ability to simultaneously erase cell surface MET and release the ‘decoy’ receptor extracellular region results in a paramount MET blocking action. Its remarkable efficacy in a large number of pre-clinical models, as well as its pharmacological features and safety profile in non-human primates, strongly envisage a successful clinical application of this novel single-arm MET therapeutic antibody for the therapy of MET-addicted cancers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02320-6.

Safety and Efficacy of Crizotinib in Combination with Temozolomide and Radiotherapy in Patients with Newly Diagnosed Glioblastoma: Phase Ib GEINO 1402 Trial

Simple Summary

Most patients with glioblastoma, the most frequent primary brain tumor in adults, develop resistance to standard first-line treatment combining temozolomide and radiotherapy. Signaling through the hepatocyte growth factor receptor (c-MET) and the midkine (ALK ligand) promotes gliomagenesis and glioma stem cell maintenance, contributing to the resistance of glioma cells to anticancer therapies. This trial reports for the first time that the addition of crizotinib, an ALK, ROS1, and c-MET inhibitor, to standard RT and TMZ is safe and resulted in a promising efficacy for newly diagnosed patients with glioblastoma.

Abstract

Background: MET-signaling and midkine (ALK ligand) promote glioma cell maintenance and resistance against anticancer therapies. ALK and c-MET inhibition with crizotinib have a preclinical therapeutic rationale to be tested in newly diagnosed GBM. Methods: Eligible patients received crizotinib with standard radiotherapy (RT)/temozolomide (TMZ) followed by maintenance with crizotinib. The primary objective was to determine the recommended phase 2 dose (RP2D) in a 3 + 3 dose escalation (DE) strategy and safety evaluation in the expansion cohort (EC). Secondary objectives included progression-free (PFS) and overall survival (OS) and exploratory biomarker analysis. Results: The study enrolled 38 patients. The median age was 52 years (33–76), 44% were male, 44% were MGMT methylated, and three patients had IDH1/2 mutation. In DE, DLTs were reported in 1/6 in the second cohort (250 mg/QD), declaring 250 mg/QD of crizotinib as the RP2D for the EC. In the EC, 9/25 patients (32%) presented grade ≥3 adverse events. The median follow up was 18.7 months (m) and the median PFS was 10.7 m (95% CI, 7.7–13.8), with a 6 m PFS and 12 m PFS of 71.5% and 38.8%, respectively. At the time of this analysis, 1 died without progression and 24 had progressed. The median OS was 22.6 m (95% CI, 14.1–31.1) with a 24 m OS of 44.5%. Molecular biomarkers showed no correlation with efficacy. Conclusions: The addition of crizotinib to standard RT and TMZ for newly diagnosed GBM was safe and the efficacy was encouraging, warranting prospective validation in an adequately powered, randomized controlled study.

Molecular Mechanisms of Treatment Resistance in Glioblastoma

Glioblastoma is the most common malignant primary brain tumor in adults and is almost invariably fatal. Despite our growing understanding of the various mechanisms underlying treatment failure, the standard-of-care therapy has not changed over the last two decades, signifying a great unmet need. The challenges of treating glioblastoma are many and include inadequate drug or agent delivery across the blood-brain barrier, abundant intra- and intertumoral heterogeneity, redundant signaling pathways, and an immunosuppressive microenvironment. Here, we review the innate and adaptive molecular mechanisms underlying glioblastoma's treatment resistance, emphasizing the intrinsic challenges therapeutic interventions must overcome-namely, the blood-brain barrier, tumoral heterogeneity, and microenvironment-and the mechanisms of resistance to conventional treatments, targeted therapy, and immunotherapy.

Advances in Targeted Therapies for Pediatric Brain Tumors

Purpose of Review

Over the last years, our understanding of the molecular biology of pediatric brain tumors has vastly improved. This has led to more narrowly defined subgroups of these tumors and has created new potential targets for molecularly driven therapies. This review presents an overview of the latest advances and challenges of implementing targeted therapies into the clinical management of pediatric brain tumors, with a focus on gliomas, craniopharyngiomas, and medulloblastomas.

Recent Findings

Pediatric low-grade gliomas (pLGG) show generally a low mutational burden with the mitogen-activated protein kinase (MAPK) signaling presenting a key driver for these tumors. Direct inhibition of this pathway through BRAF and/or MEK inhibitors has proven to be a clinically relevant strategy. More recently, MEK and IL-6 receptor inhibitors have started to be evaluated in the treatment for craniopharyngiomas. Aside these low-grade tumors, pediatric high-grade gliomas (pHGG) and medulloblastomas exhibit substantially greater molecular heterogeneity with various and sometimes unknown tumor driver alterations. The clinical benefit of different targeted therapy approaches to interfere with altered signaling pathways and restore epigenetic dysregulation is undergoing active clinical testing. For these multiple pathway-driven tumors, combination strategies will most likely be required to achieve clinical benefit.

Summary

The field of pediatric neuro-oncology made tremendous progress with regard to improved diagnosis setting the stage for precision medicine approaches over the last decades. The potential of targeted therapies has been clearly demonstrated for a subset of pediatric brain tumors. However, despite clear response rates, questions of sufficient blood-brain barrier penetration, optimal dosing, treatment duration as well as mechanisms of resistance and how these can be overcome with potential combination strategies need to be addressed in future investigations. Along this line, it is critical for future trials to define appropriate endpoints to assess therapy responses as well as short and long-term toxicities in the growing and developing child.

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

OBJECTIVES

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Potential roads for reaching the summit: an overview on target therapies for high-grade gliomas

Background:

The tailored targeting of specific oncogenes represents a new frontier in the treatment of high-grade glioma in the pursuit of innovative and personalized approaches. The present study consists in a wide-ranging overview of the target therapies and related translational challenges in neuro-oncology.

Methods:

A review of the literature on PubMed/MEDLINE on recent advances concerning the target therapies for treatment of central nervous system malignancies was carried out. In the Medical Subject Headings, the terms “Target Therapy”, “Target drug” and “Tailored Therapy” were combined with the terms “High-grade gliomas”, “Malignant brain tumor” and “Glioblastoma”. Articles published in the last five years were further sorted, based on the best match and relevance. The ClinicalTrials.gov website was used as a source of the main trials, where the search terms were “Central Nervous System Tumor”, “Malignant Brain Tumor”, “Brain Cancer”, “Brain Neoplasms” and “High-grade gliomas”.

Results:

A total of 137 relevant articles and 79 trials were selected. Target therapies entailed inhibitors of tyrosine kinases, PI3K/AKT/mTOR pathway, farnesyl transferase enzymes, p53 and pRB proteins, isocitrate dehydrogenases, histone deacetylases, integrins and proteasome complexes. The clinical trials mostly involved combined approaches. They were phase I, II, I/II and III in 33%, 42%, 16%, and 9% of the cases, respectively.

Conclusion:

Tyrosine kinase and angiogenesis inhibitors, in combination with standard of care, have shown most evidence of the effectiveness in glioblastoma. Resistance remains an issue. A deeper understanding of the molecular pathways involved in gliomagenesis is the key aspect on which the translational research is focusing, in order to optimize the target therapies of newly diagnosed and recurrent brain gliomas. (www.actabiomedica.it)

Glioblastoma multiforme: novel therapeutic targets

INTRODUCTION

The increasingly detailed genetic characterization of glioblastoma (GBM) has failed to translate into meaningful breakthroughs in treatment. This is likely to be attributed to molecular heterogeneity of GBM. However, the understanding of the tumor microenvironment in GBM has become more refined and has revealed a wealth of therapeutic targets that may enable the disruption of angiogenesis or immunosuppression.

AREAS COVERED

This review discusses the selective targeting of tumor-intrinsic pathways, therapies that target the GBM tumor microenvironment and relevant preclinical studies and their limitations. Relevant literature was derived from a PubMed search encompassing studies from 1989 to 2020.

EXPERT OPINION

Despite appropriate target engagement, attempts to directly inhibit oncogenic pathways in GBM have yielded little success. This is likely attributed to the molecular heterogeneity of GBM and the presence of redundant signaling that allow for accumulation of adaptive mutations and development of drug resistance. Subsequently, there has been a shift toward therapies modulating the pro-angiogenic, immunosuppressive tumor microenvironment in GBM. The non-transformed cells in the microenvironment which includes endothelial cells, myeloid cells, and T cells, are presumably genetically stable, less susceptible to heterogeneity, and easier to target. This approach offers the highest potential for a therapeutic breakthrough in GBM.

Dose-escalation trial of the ALK, MET & ROS1 inhibitor, crizotinib, in patients with advanced cancer

Aim: This first-in-human, dose-finding study evaluated safety, pharmacokinetics and pharmacodynamics of crizotinib and established a recommended Phase II dose (RP2D) among patients with advanced solid malignancies. Patients & methods: Patients received oral crizotinib in a 3 + 3 dose escalation design. Results: Thirty-six patients received crizotinib (50 mg once daily-300 mg twice daily); maximum tolerated dose (and RP2D) was 250 mg twice daily. Most patients (89%) experienced ≥1 treatment-related adverse event. Three patients had grade 3 dose-limiting toxicities: alanine aminotransferase increased (n = 1) and fatigue (n = 2). Generally, an increase in soluble MET was found with increasing crizotinib concentrations. Conclusion: Crizotinib demonstrated a favorable safety profile. The observed pharmacodynamic effect on soluble MET provide evidence for targeted MET inhibition by crizotinib. Clinicaltrials. gov identifier: NCT00585195.

Icotinib-resistant HCC827 cells produce exosomes with mRNA MET oncogenes and mediate the migration and invasion of NSCLC

Background

Icotinib has been widely used in patients with non-small cell lung cancer (NSCLC), and have significantly enhanced the overall survival rate of NSCLC patients. However, acquired drug resistance limits its clinical efficacy. Tumor cell-derived exosomes have been reported to participate in various biological processes, including tumor invasion, metastasis and drug resistance.

Materials and methods

In the present study, drug resistance was measured by MTT assay. Exosomes were extracted from the cell supernatant using ultracentrifugation and identified by exosomal marker. HCC827 cells were treated with exosomes derived from icotinib-resistant (IR) HCC827 to observe the invasion and migration of parent cells. The expression of exo-mRNA was analyzed by reverse transcription-quantitative polymerase chain reaction (RT-PCR). In addition, 10 exo-mRNAs detecting from the plasma and bronchoalveolar lavage fluid (BALF) of NSCLC patients with icotinib treatment were used to establish a new drug resistant-warning formula.

Results

The oncogene MET into exosomes was identified from icotinib-resistant lung cancer cells, and this was also presented in exosomes in NSCLC patients diagnosed with cancer metastasis after icotinib treatment. The knockdown of MET in exosomes significantly decreased the ability of invasion and migration in HCC827 cells.

Conclusion

It was suggested that MET might be specifically package and transferred by exosomes to modify the invasion and migration ability of the surrounding icotinib-sensitive cells.

Molecular targeted therapy of glioblastoma

Glioblastomas are intrinsic brain tumors thought to originate from neuroglial stem or progenitor cells. More than 90% of glioblastomas are isocitrate dehydrogenase (IDH)-wildtype tumors. Incidence increases with age, males are more often affected. Beyond rare instances of genetic predisposition and irradiation exposure, there are no known glioblastoma risk factors. Surgery as safely feasible followed by involved-field radiotherapy plus concomitant and maintenance temozolomide chemotherapy define the standard of care since 2005. Except for prolonged progression-free, but not overall survival afforded by the vascular endothelial growth factor antibody, bevacizumab, no pharmacological intervention has been demonstrated to alter the course of disease. Specifically, targeting cellular pathways frequently altered in glioblastoma, such as the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), the p53 and the retinoblastoma (RB) pathways, or epidermal growth factor receptor (EGFR) gene amplification or mutation, have failed to improve outcome, likely because of redundant compensatory mechanisms, insufficient target coverage related in part to the blood brain barrier, or poor tolerability and safety. Yet, uncommon glioblastoma subsets may exhibit specific vulnerabilities amenable to targeted interventions, including, but not limited to: high tumor mutational burden, BRAF mutation, neurotrophic tryrosine receptor kinase (NTRK) or fibroblast growth factor receptor (FGFR) gene fusions, and MET gene amplification or fusions. There is increasing interest in targeting not only the tumor cells, but also the microenvironment, including blood vessels, the monocyte/macrophage/microglia compartment, or T cells. Improved clinical trial designs using pharmacodynamic endpoints in enriched patient populations will be required to develop better treatments for glioblastoma.

Met inhibition revokes IFNγ-induction of PD-1 ligands in MET-amplified tumours

BACKGROUND

Interferon-induced expression of programmed cell death ligands (PD-L1/PD-L2) may sustain tumour immune-evasion. Patients featuring MET amplification, a genetic lesion driving transformation, may benefit from anti-MET treatment. We explored if MET-targeted therapy interferes with Interferon-γ modulation of PD-L1/PD-L2 in MET-amplified tumours.

METHODS

PD-L1/PD-L2 expression and signalling pathways downstream of MET or Interferon-γ were analysed in MET-amplified tumour cell lines and in patient-derived tumour organoids, in basal condition, upon Interferon-γ stimulation, and after anti-MET therapy.

RESULTS

PD-L1 and PD-L2 were upregulated in MET-amplified tumour cells upon Interferon-γ treatment. This induction was impaired by JNJ-605, a selective inhibitor of MET kinase activity, and MvDN30, an antibody inducing MET proteolytic cleavage. We found that activation of JAKs/ STAT1, signal transducers downstream of the Interferon-γ receptor, was neutralised by MET inhibitors. Moreover, JAK2 and MET associated in the same signalling complex depending on MET phosphorylation. Results were confirmed in MET-amplified organoids derived from human colorectal tumours, where JNJ-605 treatment revoked Interferon-γ induced PD-L1 expression.

CONCLUSIONS

These data show that in MET-amplified cancers, treatment with MET inhibitors counteracts the induction of PD-1 ligands by Interferon-γ. Thus, therapeutic use of anti-MET drugs may provide additional clinical benefit over and above the intended inhibition of the target oncogene.

Targeted Therapies in Non-small-Cell Lung Cancer

The treatment landscape for non-small-cell lung cancer (NSCLC) has dramatically shifted over the past two decades. Targeted or precision medicine has primarily been responsible for this shift. Older paradigms of treating metastatic NSCLC with cytotoxic chemotherapy, while still important, have given way to evaluating tumor tissues for specific driver mutations that can be treated with targeted agents. Patients treated with targeted agents frequently have improved progression-free survival and overall survival compared to patients without a targetable driver mutation, highlighting the clinical benefit of precision medicine. In this chapter, we explore the historic landmark trials, the current state of the field, and potential future targets under investigation, in this exciting, rapidly evolving discipline of precision medicine in lung cancer.

Using genomics to guide treatment for glioblastoma

Glioblastoma has been shown to have many different genetic mutations found both within and between tumor samples. Molecular testing and genomic sequencing has helped to classify diagnoses and clarify difficult to interpret histopathological specimens. Genomic information also plays a critical role in prognostication for patients, with IDH mutations and MGMT methylation having significant impact of the response to chemotherapy and overall survival of patients. Unfortunately, personalized medicine and targeted therapy against specific mutations have not been shown to improve patient outcomes. As technology continues to improve, exome and RNA sequencing will play a role in the design of clinical trials, classification of patient subgroups and identification of rare mutations that can be targeted by small-molecule inhibitors and biologic agents.

Phase 1 trial, pharmacokinetics, and pharmacodynamics of dasatinib combined with crizotinib in children with recurrent or progressive high-grade and diffuse intrinsic pontine glioma

BACKGROUND

Progressive/recurrent high-grade and diffuse intrinsic pontine gliomas (DIPGs) are fatal. Treatments targeting molecular pathways critical for these cancers are needed.

METHODS

We conducted a phase 1 study (rolling-six design) to establish the safety and maximum tolerated dose (MTD) of dasatinib, an oral platelet-derived growth factor receptor A (PDGFRA) inhibitor, and crizotinib, an oral c-Met inhibitor, in such patients. Pharmacokinetics of both agents were performed. Biomarkers of cellular pathway activation in peripheral-blood mononuclear cells (PBMC) were evaluated before and after administration of dasatinib. PDGFRA and MET amplification, and PDGFRA mutations were studied in tumor samples.

RESULTS

Twenty-five patients were enrolled in this study (median age: 11.9 years). Eleven patients had DIPG. Glioblastoma accounted for 40% of cases. Dasatinib at 50 mg/m² and crizotinib at 130 mg/m² or 100 mg/m² were poorly tolerated when administered twice daily. Drug administration was then switched to once daily. Dasatinib administered at 50 mg/m² and crizotinib at 215 mg/m² once daily was the MTD. Dose-limiting toxicities consisted of diarrhea, fatigue, proteinuria, hyponatremia, rash, and grade 4 neutropenia. Only two patients received therapy for at least 6 months. No objective radiologic responses were observed. Pharmacokinetics of dasatinib and crizotinib were comparable to previous studies. A statistically significant decrease in the ratio of p-AKT/total AKT in PBMC occurred after dasatinib administration. PDGFRA and MET amplification were found in four and two cases, respectively. Only one of 10 tumors harbored a PDGFRA mutation.

CONCLUSIONS

This drug combination was poorly tolerated and its activity was minimal. We do not recommend further testing of this combination in children.

Known and novel roles of the MET oncogene in cancer: a coherent approach to targeted therapy

The MET oncogene encodes an unconventional receptor tyrosine kinase with pleiotropic functions: it initiates and sustains neoplastic transformation when genetically altered ('oncogene addiction') and fosters cancer cell survival and tumour dissemination when transcriptionally activated in the context of an adaptive response to adverse microenvironmental conditions ('oncogene expedience'). Moreover, MET is an intrinsic modulator of the self-renewal and clonogenic ability of cancer stem cells ('oncogene inherence'). Here, we provide the latest findings on MET function in cancer by focusing on newly identified genetic abnormalities in tumour cells and recently described non-mutational MET activities in stromal cells and cancer stem cells. We discuss how MET drives cancer clonal evolution and progression towards metastasis, both ab initio and under therapeutic pressure. We then elaborate on the use of MET inhibitors in the clinic with a critical appraisal of failures and successes. Ultimately, we advocate a rationale to improve the outcome of anti-MET therapies on the basis of thorough consideration of the entire spectrum of MET-mediated biological responses, which implicates adequate patient stratification, meaningful biomarkers and appropriate clinical end points.

The dual blockade of MET and VEGFR2 signaling demonstrates pronounced inhibition on tumor growth and metastasis of hepatocellular carcinoma

BACKGROUND

The application of VEGF signaling inhibitors have been associated with more invasive or metastatic behavior of cancers including hepatocellular carcinoma (HCC). We explored the contribution of MET pathway to the enhanced HCC invasion and metastasis by VEGF signaling inhibition, and investigated the antitumor effects of NZ001, a novel dual inhibitor of MET and VEGFR2, in HCC.

METHODS

Immunocompetent orthotopic mice model of hepal-6 was established to investigate the effects of either VEGF antibody alone or in combination with the selective MET inhibitor on tumor aggressiveness. The antitumor effects of NZ001 were examined in cultured HCC cells as well as in vivo models. MET gene amplification was determined by SNP 6.0 assay. MET/P-MET expression was detected by IHC.

RESULTS

Selective VEGF signaling inhibition by VEGF antibody significantly reduced in vivo tumor growth of the orthotopic mice models, simultaneously also enhanced tumor invasion and metastasis, but inhibiting MET signaling attenuated this side-effect. Further study revealed that hypoxia caused by VEGF signaling inhibition induced HIF-1α nuclear accumulation, subsequently leading to elevated total-MET expression, and synergized with HGF in inducing invasion. NZ001, a novel dual inhibitor of MET and VEGFR2, markedly inhibited both tumor growth and metastasis of HCC, which showed obvious advantages over sorafenib in not inducing more invasive and metastatic behaviors. This effect is more pronounced in HCC with MET amplification and overexpression.

CONCLUSIONS

The activation of MET is responsible for the metastasis-promoting effects induced by VEGF inhibition. MET and VEGFR2 dual blockade, NZ001, has advantages over sorafenib in not inducing more invasive and metastatic behaviors; MET amplification and overexpression can be used to identify the subgroup of patients most likely to get the optimal benefit from NZ001 treatment.

Discordant inheritance of chromosomal and extrachromosomal DNA elements contributes to dynamic disease evolution in glioblastoma

To understand how genomic heterogeneity of glioblastoma contributes to the poor response to therapy characteristic of this disease, we performed DNA and RNA sequencing on GBM tumor samples and the neurospheres and orthotopic xenograft models derived from them. We used the resulting data set to show that somatic driver alterations including single nucleotide variants, focal DNA alterations, and oncogene amplification on extrachromosomal DNA (ecDNA) elements were in majority propagated from tumor to model systems. In several instances, ecDNAs and chromosomal alterations demonstrated divergent inheritance patterns and clonal selection dynamics during cell culture and xenografting. We infer that ecDNA inherited unevenly between offspring cells, a characteristic that affects the oncogenic potential of cells with more or fewer ecDNAs. Longitudinal patient tumor profiling found that oncogenic ecDNAs are frequently retained throughout the course of disease. Our analysis shows that extrachromosomal elements allow rapid increase of genomic heterogeneity during glioblastoma evolution, independent of chromosomal DNA alterations.

LRIG proteins in glioma: Functional roles, molecular mechanisms, and potential clinical implications

Gliomas are the most common intracranial tumors of the nervous system. These tumors are characterized by unlimited cell proliferation and excessive invasiveness. Despite the advances in diagnostic imaging, microneurosurgical techniques, radiation therapy, and chemotherapy, significant increases in the progression free survival of glioma patients have not been achieved. Improvements in our understanding of the molecular subtypes of gliomas and the underlying alterations in specific signaling pathways may impact both the diagnosis and the treatment strategies for patients with gliomas. Growth factors and their corresponding receptor tyrosine kinases are associated with oncogenesis and development of tumors in numerous human cancer types, including glioma. Leucine-rich repeats and immunoglobulin-like domains (LRIG) are integral membrane proteins which contain three vertebrate members including LRIG1, LRIG2 and LRIG3. They mainly function as regulators of growth factor signaling. Specifically, LRIG1 has been identified as a tumor suppressor in human cancers. In contrast, LRIG2 appears to function as a tumor promoter, while LRIG3 appears to have a function similar to that of LRIG1. In the present review, we summarize the functional roles, molecular mechanisms, and clinical perspectives of LRIG proteins in gliomas and propose that these proteins may be useful in the future as targets for treatment and prognostication in glioma patients.

Molecular-Based Recursive Partitioning Analysis Model for Glioblastoma in the Temozolomide Era: A Correlative Analysis Based on NRG Oncology RTOG 0525

Importance

There is a need for a more refined, molecularly based classification model for glioblastoma (GBM) in the temozolomide era.

Objective

To refine the existing clinically based recursive partitioning analysis (RPA) model by incorporating molecular variables.

Design, Setting, and Participants

NRG Oncology RTOG 0525 specimens (n = 452) were analyzed for protein biomarkers representing key pathways in GBM by a quantitative molecular microscopy-based approach with semiquantitative immunohistochemical validation. Prognostic significance of each protein was examined by single-marker and multimarker Cox regression analyses. To reclassify the prognostic risk groups, significant protein biomarkers on single-marker analysis were incorporated into an RPA model consisting of the same clinical variables (age, Karnofsky Performance Status, extent of resection, and neurologic function) as the existing RTOG RPA. The new RPA model (NRG-GBM-RPA) was confirmed using traditional immunohistochemistry in an independent data set (n = 176).

Main Outcomes and Measures

Overall survival (OS).

Results

In 452 specimens, MGMT (hazard ratio [HR], 1.81; 95% CI, 1.37-2.39; P < .001), survivin (HR, 1.36; 95% CI, 1.04-1.76; P = .02), c-Met (HR, 1.53; 95% CI, 1.06-2.23; P = .02), pmTOR (HR, 0.76; 95% CI, 0.60-0.97; P = .03), and Ki-67 (HR, 1.40; 95% CI, 1.10-1.78; P = .007) protein levels were found to be significant on single-marker multivariate analysis of OS. To refine the existing RPA, significant protein biomarkers together with clinical variables (age, Karnofsky Performance Status, extent of resection, and neurological function) were incorporated into a new model. Of 166 patients used for the new NRG-GBM-RPA model, 97 (58.4%) were male (mean [SD] age, 55.7 [12.0] years). Higher MGMT protein level was significantly associated with decreased MGMT promoter methylation and vice versa (1425.1 for methylated vs 1828.0 for unmethylated; P < .001). Furthermore, MGMT protein expression (HR, 1.84; 95% CI, 1.38-2.43; P < .001) had greater prognostic value for OS compared with MGMT promoter methylation (HR, 1.77; 95% CI, 1.28-2.44; P < .001). The refined NRG-GBM-RPA consisting of MGMT protein, c-Met protein, and age revealed greater separation of OS prognostic classes compared with the existing clinically based RPA model and MGMT promoter methylation in NRG Oncology RTOG 0525. The prognostic significance of the NRG-GBM-RPA was subsequently confirmed in an independent data set (n = 176).

Conclusions and Relevance

This new NRG-GBM-RPA model improves outcome stratification over both the current RTOG RPA model and MGMT promoter methylation, respectively, for patients with GBM treated with radiation and temozolomide and was biologically validated in an independent data set. The revised RPA has the potential to contribute to improving the accurate assessment of prognostic groups in patients with GBM treated with radiation and temozolomide and to influence clinical decision making.

Trial Registration

clinicaltrials.gov Identifier: NCT00304031.

Tracking MET de-addiction in lung cancer: A road towards the oncogenic target

The discovery of druggable oncogenic drivers (i.e. EGFR and ALK), along with the introduction of comprehensive tumor genotyping techniques into the daily clinical practice define non-small-cell lung cancer (NSCLC) asa group of heterogeneous diseases, requiring a context-personalized clinico-therapeutical approach. Among the most investigated biomarkers, the MET proto-oncogene has been extensively demonstrated to play a crucial role throughout the lung oncogenesis, unbalancing the proliferation/apoptosis signaling and influencing the epithelial-mesenchymal transition and the invasive phenotype. Nevertheless, although different mechanisms eliciting the aberrant MET-associated oncogenic stimulus have been detected in lung cancer (such as gene amplification, increased gene copy number, mutations and MET/HGF overexpression), to date no clinically impactful results have been achieved with anti-MET tyrosine kinase inhibitors and monoclonal antibodies in the context of an unselected or MET enriched population. Recently, MET exon 14 splicing abnormalities have been identified asa potential oncogenic target in lung cancer, able to drive the activity of MET inhibitors in molecularly selected patients. In this paper, the major advancement and drawbacks of MET history in lung cancer are reviewed, underlying the renewed scientific euphoria related to the recent identification of MET exon 14 splicing variants asan actionable oncogenic target.

Role and Therapeutic Targeting of the HGF/MET Pathway in Glioblastoma

Glioblastoma (GBM) is a lethal brain tumor with dismal prognosis. Current therapeutic options, consisting of surgery, chemotherapy and radiation, have only served to marginally increase patient survival. Receptor tyrosine kinases (RTKs) are dysregulated in approximately 90% of GBM; attributed to this, research has focused on inhibiting RTKs as a novel and effective therapy for GBM. Overexpression of RTK mesenchymal epithelial transition (MET), and its ligand, hepatocyte growth factor (HGF), in GBM highlights a promising new therapeutic target. This review will discuss the role of MET in cell cycle regulation, cell proliferation, evasion of apoptosis, cell migration and invasion, angiogenesis and therapeutic resistance in GBM. It will also discuss the modes of deregulation of HGF/MET and their regulation by microRNAs. As the HGF/MET pathway is a vital regulator of multiple pro-survival pathways, efforts and strategies for its exploitation for GBM therapy are also described.

Glioblastoma targeted therapy: updated approaches from recent biological insights

Glioblastoma (WHO grade IV astrocytoma) is the most frequent primary brain tumor in adults, representing a highly heterogeneous group of neoplasms that are among the most aggressive and challenging cancers to treat. An improved understanding of the molecular pathways that drive malignancy in glioblastoma has led to the development of various biomarkers and the evaluation of several agents specifically targeting tumor cells and the tumor microenvironment. A number of rational approaches are being investigated, including therapies targeting tumor growth factor receptors and downstream pathways, cell cycle and epigenetic regulation, angiogenesis and antitumor immune response. Moreover, recent identification and validation of prognostic and predictive biomarkers have allowed implementation of modern trial designs based on matching molecular features of tumors to targeted therapeutics. However, while occasional targeted therapy responses have been documented in patients, to date no targeted therapy has been formally validated as effective in clinical trials. The lack of knowledge about relevant molecular drivers in vivo combined with a lack of highly bioactive and brain penetrant-targeted therapies remain significant challenges. In this article, we review the most promising biological insights that have opened the way for the development of targeted therapies in glioblastoma, and examine recent data from clinical trials evaluating targeted therapies and immunotherapies. We discuss challenges and opportunities for the development of these agents in glioblastoma.

Targeting Epigenetic Pathways in the Treatment of Pediatric Diffuse (High Grade) Gliomas

Progress in the treatment of adult high-grade gliomas (HGG), including chemoradiation with concurrent and adjuvant temozolomide for glioblastoma, has not translated into significant therapeutic advances for pediatric HGG, where overall survival has plateaued at 15% to 20%, especially when considering specialized pediatric treatment in tertiary care centers, maximal safe neurosurgical resection, optimized delivery of involved field radiation, and improvements in supportive care. However, recent advances in our understanding of pediatric HGG, including the application of next-generation sequencing and DNA methylation profiling, have identified mutations in the histone variant H3.3 and canonical H3.1 genes, respectively. These mutations are relatively specific to neuroanatomic compartments (cortex, midline structures, thalamus, brainstem) and are often associated with other mutations, especially in specific growth factor receptor tyrosine kinases. Targeting epigenetic pathways affected by these histone mutations, alone or in combination with small molecule inhibitors of growth factor receptor signaling pathways, will inform new treatment strategies for pediatric HGG and should be incorporated into novel cooperative group clinical trial designs.

Efficiency of Crizotinib on an ALK-Positive Inflammatory Myofibroblastic Tumor of the Central Nervous System: A Case Report

Inflammatory myofibroblastic tumors (IMT) of the central nervous system (CNS) are rare entities that have a predilection for local recurrences. Approximately half of the inflammatory myofibroblastic tumors contain translocations that result in the over-expression of the anaplastic lymphoma kinase (ALK) gene. We hereby present the case of a patient diagnosed with a left parieto-occipital IMT that recurred after multiple surgeries and radiotherapy. Immuno-histochemical examination of the tumor demonstrated ALK overexpression and the presence of an ALK rearrangement observed in lung cancers. The patient was subsequently started on an ALK inhibitor. A response evaluation criteria in solid tumors (RECIST) partial response was observed by the seventh month of ALK inhibition and the tumor remained in control for 14 months. The current case reiterates the activity of ALK inhibitors within the CNS and suggests that radiotherapy may potentiate the permeability of ALK inhibitors in CNS tumors addicted to ALK signalling.

High-Throughput Genomic Profiling of Adult Solid Tumors Reveals Novel Insights into Cancer Pathogenesis

Genomic profiling is widely predicted to become a standard of care in clinical oncology, but more effective data sharing to accelerate progress in precision medicine will be required. Here, we describe cancer-associated genomic profiles from 18,004 unique adult cancers. The dataset was composed of 162 tumor subtypes including multiple rare and uncommon tumors. Comparison of alteration frequencies to The Cancer Genome Atlas identified some differences and suggested an enrichment of treatment-refractory samples in breast and lung cancer cohorts. To illustrate novelty within the dataset, we surveyed the genomic landscape of rare diseases and identified an increased frequency of NOTCH1 alterations in adenoid cystic carcinomas compared with previous studies. Analysis of tumor suppressor gene patterns revealed disease specificity for certain genes but broad inactivation of others. We identified multiple potentially druggable, novel and known kinase fusions in diseases beyond those in which they are currently recognized. Analysis of variants of unknown significance identified an enrichment of SMAD4 alterations in colon cancer and other rare alterations predicted to have functional impact. Analysis of established, clinically relevant alterations highlighted the spectrum of molecular changes for which testing is currently recommended, as well as opportunities for expansion of indications for use of approved targeted therapies. Overall, this dataset presents a new resource with which to investigate rare alterations and diseases, validate clinical relevance, and identify novel therapeutic targets. Cancer Res; 77(9); 2464-75. ©2017 AACR.

Development of crizotinib, a rationally designed tyrosine kinase inhibitor for non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the number one cause of global mortality. Despite aggressive treatment, the prognosis is dismal. Patients with advanced NSCLC have a median survival of 4 months from the time of diagnosis. Fortunately, molecularly based approaches to drug discovery have yielded a tyrosine kinase inhibitor, crizotinib, which significantly prolongs median progression-free survival in a subset of patients. Although initial clinical trial results demonstrate crizotinib has a promising role to play in NSCLC treatment, development of resistance leaves much to be elucidated about how to effectively combat this deadly disease. In this review, we follow the discovery and development of crizotinib from bench to bedside and provide an example of successful bottom-up drug design. Then, we explore the clinical trial results that fast-tracked its eventual use as a frontline therapy for sensitive NSCLC patients and the development of resistance. Lastly, we discuss the potential for future uses of crizotinib both within and beyond NSCLC.

Anaplastic lymphoma kinase expression and gene alterations in glioblastoma: correlations with clinical outcome

Aims

To study anaplastic lymphoma kinase (ALK) protein expression and possible underlying gene alterations in glioblastoma (GBM), correlating them with clinical outcome.

Methods

We studied ALK immunohistochemical expression and fluorescent in situ hybridisation (FISH)-detected ALK gene alterations in 51 GBMs (46 isocitrate dehydrogenase-1 (IDH1)R132H-negative and 5 IDH-mutant (IDH1R132H-positive)). We compared two anti-ALK antibodies and immunohistochemical detection systems (5Α4/Nichirei Biosciences, D5F3/Ventana). The results were correlated with tumour cell proliferation and clinical outcome.

Results

Intense granular cytoplasmic ALK immunostaining was observed in 10/51 (19.61%) GBM and correlated with high Ki67 proliferation index; only 1 in 10 ALK-positive cases displayed multiple alk gene signals by FISH. Moderate ALK immunostaining was observed in 21 (41.17%), weak immunostaining in 5 (9.80%) while 15 (29.42%) cases were negative. p53 was expressed in 26/51 GBM (50.9%) (10% cut-off). IDH1R132H-negative GBM showed higher ALK expression compared with IDH-mutant GBM (65.2% vs 20%). ALK overexpression was more common in older patients but did not correlate with other clinicopathological variables or patient overall survival.

Conclusions

ALK overexpression can be identified in up to 70% of GBMs and does not correlate with underlying alk gene amplification. Despite being more common in rapidly growing, clinically aggressive GBM, ALK overexpression did not show correlation with prognosis in this study.

Recurrent MET fusion genes represent a drug target in pediatric glioblastoma

Pediatric glioblastoma is one of the most common and most deadly brain tumors in childhood. Using an integrative genetic analysis of 53 pediatric glioblastomas and five in vitro model systems, we identified previously unidentified gene fusions involving the MET oncogene in ∼10% of cases. These MET fusions activated mitogen-activated protein kinase (MAPK) signaling and, in cooperation with lesions compromising cell cycle regulation, induced aggressive glial tumors in vivo. MET inhibitors suppressed MET tumor growth in xenograft models. Finally, we treated a pediatric patient bearing a MET-fusion-expressing glioblastoma with the targeted inhibitor crizotinib. This therapy led to substantial tumor shrinkage and associated relief of symptoms, but new treatment-resistant lesions appeared, indicating that combination therapies are likely necessary to achieve a durable clinical response.

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

BACKGROUND

Currently, only trastuzumab, ramucirumab, and apatinib effectively treat gastric cancer. Thus, additional novel targets are required for this disease.

METHODS

We investigated the immunohistochemical and fluorescence in situ hybridization expression of MET, ROS1, and ALK in four gastric cell lines and a cohort of 98 gastric cancer patients. Crizotinib response was studied in vitro and in vivo.

RESULTS

Crizotinib potently inhibited in vitro cell growth in only one cell line, which also showed MET amplification. A positive correlation between crizotinib sensitivity and MET overexpression was observed (P = 0.045) in the histoculture drug response assay. Meanwhile, patient-derived tumor xenograft mouse models transplanted with tissues with higher MET protein expression displayed a highly selective sensitivity to crizotinib. In the 98 patients, MET overexpression was found in 42 (42.9 %) and MET was amplified in 4 (4.1 %). ROS1 and ALK overexpression were found in 25 (25.5 %) and 0 patients, respectively. However, none of the patients screened harbored ALK or ROS1 rearrangements. No significant association was found between overall survival and MET or ROS1 status. We also observed a stage IV gastric cancer patient with MET amplification who experienced tumor shrinkage and clinical benefit after 3 weeks of crizotinib as fourth-line treatment.

CONCLUSIONS

Crizotinib may induce clinically relevant anticancer effects in MET-overexpressed or MET-amplified gastric cancer patients.

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

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

cMET Exon 14 Skipping: From the Structure to the Clinic

The abnormal stimulation of the multiple signal transduction pathways downstream of the receptor tyrosine kinase mesenchymal-epithelial transition factor (cMET) promotes cellular transformation, tumor motility, and invasion. Therefore, cMET has been the focus of prognostic and therapeutic studies in different tumor types, including non-small cell lung cancer. In particular, several cMET inhibitors have been developed as innovative therapeutic candidates and are currently under investigation in clinical trials. However, one of the challenges in establishing effective targeted treatments against cMET remains the accurate identification of biomarkers for the selection of responsive subsets of patients. Recently, splice site mutations have been discovered in cMET that lead to the skipping of exon 14, impairing the breakdown of the receptor. Patients with NSCLC who are carrying this splice variant typically overexpress the cMET receptor and show a response to small molecule inhibitors of cMET. Here, we review the main differences at the structural level between the wild-type and the splice variants of cMET and their influence on cMET signaling. We clarify the reason why this variant responds to small molecule inhibitors and their prognostic/predictive role.

In Vitro and In Vivo Activity of AMG 337, a Potent and Selective MET Kinase Inhibitor, in MET-Dependent Cancer Models

The MET receptor tyrosine kinase is involved in cell growth, survival, and invasion. Clinical studies with small molecule MET inhibitors have shown the role of biomarkers in identifying patients most likely to benefit from MET-targeted therapy. AMG 337 is an oral, small molecule, ATP-competitive, highly selective inhibitor of the MET receptor. Herein, we describe AMG 337 preclinical activity and mechanism of action in MET-dependent tumor models. These studies suggest MET is the only therapeutic target for AMG 337. In an unbiased tumor cell line proliferation screen (260 cell lines), a closely related analogue of AMG 337, Compound 5, exhibited activity in 2 of 260 cell lines; both were MET-amplified. Additional studies examining the effects of AMG 337 on the proliferation of a limited panel of cell lines with varying MET copy numbers revealed that high-level focal MET amplification (>12 copies) was required to confer MET oncogene addiction and AMG 337 sensitivity. One MET-amplified cell line, H1573 (>12 copies), was AMG 337 insensitive, possibly because of a downstream G12A KRAS mutation. Mechanism-of-action studies in sensitive MET-amplified cell lines demonstrated that AMG 337 inhibited MET and adaptor protein Gab-1 phosphorylation, subsequently blocking the downstream PI3K and MAPK pathways. AMG 337 exhibited potency in pharmacodynamic assays evaluating MET signaling in tumor xenograft models; >90% inhibition of Gab-1 phosphorylation was observed at 0.75 mg/kg. These findings describe the preclinical activity and mechanism of action of AMG 337 in MET-dependent tumor models and indicate its potential as a novel therapeutic for the treatment of MET-dependent tumors. Mol Cancer Ther; 15(7); 1568-79. ©2016 AACR.

MET immunolabelling is a useful predictive tool for MET gene amplification in glioblastoma

AIMS

MET gene amplification is rare in glioblastoma (GBM) and represents a potential target for MET inhibitors. An immunohistochemical screening may be useful to identify MET amplification. The aim of our study was to establish how MET immunolabelling correlates with MET amplification.

METHODS

Three cohorts including 108 GBM (cohort 1, prospective), 104 GBM (cohort 2, retrospective) and 52 GBM (cohort 3, prospective) were investigated for MET expression by immunohistochemistry. MET amplification was assessed by comparative genomic hybridization on microarray (CGH-array) in all cohorts and by fluorescent in situ hybridization (FISH) in cohorts 2 and 3. Active form of MET was assessed using p-MET (Y1349) immunohistochemistry.

RESULTS

Diffuse MET amplification detectable by CGH-array was associated with diffuse, strong MET immunolabelling (four cases in cohort 1 and one case in cohort 2). Focal MET amplification detectable only by FISH was observed in small foci of strongly immunopositive cells in two GBM (cohort 2). In both cohorts, MET amplification was never detected in GBM devoid of strongly immunopositive cells. MET overexpression, observed in 23% of unamplified GBM, was associated with a predominant weak-to-moderate staining intensity and with necrosis (P < 0.005). p-MET was detected in all MET-amplified GBM and in perinecrotic areas of nonamplified GBM. A strong MET immunostaining intensity, at least focal and distant from necrosis, showed 100% sensitivity and 84% specificity for predicting MET amplification in cohort 3.

CONCLUSIONS

MET amplification is characterized by strongly immunopositive cells. Only GBM showing strong MET immunostaining is appropriate for the assessment of MET amplification.

Systemic therapies in the treatment of non-small-cell lung cancer brain metastases

Non-small-cell lung cancer (NSCLC) brain metastases are common. Even though there are various subsets of NSCLC with molecular alterations, there is a common theme of brain metastases. Current treatment modalities are suboptimal. Systemic therapies for the treatment of NSCLC brain metastases have been explored and recent advances may pave the way for their successful employment in this patient population. While no specific agents have been associated with a marked benefit, stability of disease as well as radiographic responses have been noted in some patients. Biological activity of systemic therapies in some patients with NSCLC brain metastases raises hope for future advances and supports further investigation for this patient population with limited treatment options.

Dual Constant Domain-Fab: A novel strategy to improve half-life and potency of a Met therapeutic antibody

The kinase receptor encoded by the Met oncogene is a sensible target for cancer therapy. The chimeric monovalent Fab fragment of the DN30 monoclonal antibody (MvDN30) has an odd mechanism of action, based on cell surface removal of Met via activation of specific plasma membrane proteases. However, the short half-life of the Fab, due to its low molecular weight, is a severe limitation for the deployment in therapy. This issue was addressed by increasing the Fab molecular weight above the glomerular filtration threshold through the duplication of the constant domains, in tandem (DCD-1) or reciprocally swapped (DCD-2). The two newly engineered molecules showed biochemical properties comparable to the original MvDN30 in vitro, acting as full Met antagonists, impairing Met phosphorylation and activation of downstream signaling pathways. As a consequence, Met-mediated biological responses were inhibited, including anchorage-dependent and -independent cell growth. In vivo DCD-1 and DCD-2 showed a pharmacokinetic profile significantly improved over the original MvDN30, doubling the circulating half-life and reducing the clearance. In pre-clinical models of cancer, generated by injection of tumor cells or implant of patient-derived samples, systemic administration of the engineered molecules inhibited the growth of Met-addicted tumors.

Clinical Development of c-MET Inhibition in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death. In patients with advanced or unresectable HCC, there are few treatment options. Conventional chemotherapy has limited benefits. Sorafenib, a multi-kinase inhibitor, improves survival, but options for patients intolerant of or progressing on sorafenib are limited. There has been much interest in recent years in molecular therapeutic targets and drug development for HCC. One of the more promising molecular targets in HCC is the cellular-mesenchymal-epithelial transition (c-MET) factor receptor. Encouraging phase II data on two c-MET inhibitors, tivantinib and cabozantinib, has led to phase III trials. This review describes the c-MET/hepatocyte growth factor (HGF) signalling pathway and its relevance to HCC, and discusses the preclinical and clinical trial data for inhibitors of this pathway in HCC.

Patterns of response to crizotinib in recurrent glioblastoma according to ALK and MET molecular profile in two patients

Two patients with an unmethylated MGMT promoter and IDH1 (R132H) wild-type recurrent glioblastoma were treated with crizotinib. Prolonged stabilization of the disease (17 months) was achieved in the first case. Interestingly, anaplastic lymphoma kinase (ALK) expression and c-MET protein overexpression was observed. Conversely, no response to crizotinib was obtained in the second case with MET protein overexpression and c-MET amplification but no ALK expression or ALK gene amplification. These case studies suggest that novel targeted ALK inhibitors may provide relevant clinical benefit in selected cases in which driver mutations are demonstrable.

Inhibition of ligand-independent constitutive activation of the Met oncogenic receptor by the engineered chemically-modified antibody DN30

An awesome number of experimental and clinical evidences indicate that constitutive activation of the Met oncogenic receptor plays a critical role in the progression of cancer toward metastasis and/or resistance to targeted therapies. While mutations are rare, the common mechanism of Met activation is overexpression, either by gene amplification ('addiction') or transcriptional activation ('expedience'). In the first instance ligand-independent kinase activation plays a major role in sustaining the transformed phenotype. Anti-Met antibodies directed against the receptor binding site behave essentially as ligand (Hepatocyte Growth Factor, HGF) antagonists and are ineffective to counteract ligand-independent activation. The monovalent chimeric MvDN30 antibody fragment, PEGylated to extend its half-life, binds the fourth IPT domain and induces 'shedding' of the Met extracellular domain, dramatically reducing both the number of receptors on the surface and their phosphorylation. Downstream signaling is thus inhibited, both in the absence or in the presence of the ligand. In vitro, MvDN30 is a strong inhibitor not only of ligand-dependent invasive growth, sustained by both paracrine and autocrine HGF, but notably, also of ligand-independent growth of 'Met-addicted' cells. In immunocompromised mice, lacking expression of Hepatocyte Growth Factor cross-reacting with the human receptor - thus providing, by definition, a model of 'ligand-independent' Met activation - PEGylated MvDN30 impairs growth of Met 'addicted' human gastric carcinoma cells. In a Met-amplified patient-derived colo-rectal tumor (xenopatient) MvDN30-PEG overcomes the resistance to EGFR targeted therapy (Cetuximab). The PEGylated MvDN30 is thus a strong candidate for targeting tumors sustained by ligand-independent Met oncogenic activation.

Input of molecular analysis in medical management of primary brain tumor patients

Primary brain tumors comprise a large group of malignant and non-malignant tumors including heterogeneous entities with various biological and clinical behaviors. Up till recently, diagnosis of brain cancers, that drives treatment decision-making, was based on integration of clinical, radiological and pathological features of patients and tumors. Over the last years, practical neuro-oncology has entered an era of molecular-based personalized medicine. Indeed, molecular features of tumors provide critical information to physicians for daily clinical management of patients and for design of relevant clinical research. Sporadic gliomas or glial tumors are the most common primary brain tumors in adults. Recently, their medical management has been revolutionized by molecular data. Indeed, optimal therapeutic management of grade III glioma patients now requires assessment of chromosome arms 1p/19q copy number and IDH mutational statuses as predictive and prognostic biomarkers. Indeed, two large phase III clinical trials have demonstrated that early chemotherapy plus radiotherapy, versus radiotherapy alone, doubles median overall survival of patients suffering from 1p/19q co-deleted and/or IDH mutated anaplastic oligodendroglial tumor. Interestingly, both biomarkers have been identified in a large proportion of WHO grade II gliomas. Their clinical value, in this population, is under investigation through multiple phase III clinical trials. In sporadic WHO grade I gliomas, and specifically in pilocytic astrocytomas, MAPK signaling pathway activation is a frequent event, mainly due to genetic alterations involving BRAF gene. This characteristic opens new therapeutic perspectives using MAPK signaling pathway inhibitors. Finally, in the most aggressive gliomas, WHO grade IV gliomas, two critical biomarkers have been identified: (i) MGMT promoter methylation associated with longer survival and better response to chemotherapy and (ii) IDH mutations predicting better prognosis. Although, further studies are needed, MGMT promoter methylation will undoubtedly be transferred soon to clinical practice. Molecular characteristics are beginning to be valuable and indispensable in neuro-oncology for better management of brain tumors patients. The near future will be marked by identification of novel molecular biomarkers and their validation for clinical practice.

Activation of MET via diverse exon 14 splicing alterations occurs in multiple tumor types and confers clinical sensitivity to MET inhibitors

Focal amplification and activating point mutation of the MET gene are well-characterized oncogenic drivers that confer susceptibility to targeted MET inhibitors. Recurrent somatic splice site alterations at MET exon 14 (METex14) that result in exon skipping and MET activation have been characterized, but their full diversity and prevalence across tumor types are unknown. Here, we report analysis of tumor genomic profiles from 38,028 patients to identify 221 cases with METex14 mutations (0.6%), including 126 distinct sequence variants. METex14 mutations are detected most frequently in lung adenocarcinoma (3%), but also frequently in other lung neoplasms (2.3%), brain glioma (0.4%), and tumors of unknown primary origin (0.4%). Further in vitro studies demonstrate sensitivity to MET inhibitors in cells harboring METex14 alterations. We also report three new patient cases with METex14 alterations in lung or histiocytic sarcoma tumors that showed durable response to two different MET-targeted therapies. The diversity of METex14 mutations indicates that diagnostic testing via comprehensive genomic profiling is necessary for detection in a clinical setting.

SIGNIFICANCE

Here we report the identification of diverse exon 14 splice site alterations in MET that result in constitutive activity of this receptor and oncogenic transformation in vitro. Patients whose tumors harbored these alterations derived meaningful clinical benefit from MET inhibitors. Collectively, these data support the role of METex14 alterations as drivers of tumorigenesis, and identify a unique subset of patients likely to derive benefit from MET inhibitors.

Glioblastoma multiforme: Pathogenesis and treatment

Each year, about 5-6 cases out of 100,000 people are diagnosed with primary malignant brain tumors, of which about 80% are malignant gliomas (MGs). Glioblastoma multiforme (GBM) accounts for more than half of MG cases. They are associated with high morbidity and mortality. Despite current multimodality treatment efforts including maximal surgical resection if feasible, followed by a combination of radiotherapy and/or chemotherapy, the median survival is short: only about 15months. A deeper understanding of the pathogenesis of these tumors has presented opportunities for newer therapies to evolve and an expectation of better control of this disease. Lately, efforts have been made to investigate tumor resistance, which results from complex alternate signaling pathways, the existence of glioma stem-cells, the influence of the blood-brain barrier as well as the expression of 0(6)-methylguanine-DNA methyltransferase. In this paper, we review up-to-date information on MGs treatment including current approaches, novel drug-delivering strategies, molecular targeted agents and immunomodulative treatments, and discuss future treatment perspectives.