MET-inhibitors meet MET mutations in lung cancer

Mesenchymal-to-epithelial transition (MET) exon 14 mutation in non-small cell lung cancer (NSCLC) has been recognized. However, clinical, molecular, and pathologic features have not been well understood. Awad et al. described NSCLC patients with MET exon 14 mutations precisely in the 'Journal of Clinical Oncology 2016; 34: 721-30'. Among 933 non-squamous NSCLC patients, they found 28 (3.0%) patients who represented a unique clinical and molecular subtype of NSCLC. Median age of the 28 patients was 72.5 years, 68% were women, 36% were never-smokers, 64% had stage IV, 100% were white, non-Hispanic, and 64% had adenocarcinoma and 14% had pleomorphic carcinoma. Genomic deletions and point mutations occurred in 17 and 11, respectively, occurred of the 28 patients. Although none of the 28 patients with MET exon 14 mutations had KRAS, epidermal growth factor receptor (EGFR), ERBB2, anaplastic lymphoma kinase (ALK), ROS1, or RET alterations, mutations of TP53, CDKN2A/B, BRAF600E, PIK3CA, PTEN, RB1, ATM, BRCA2, NF1, or ARID2 were co-existed. Amplification of MDM2 was observed in 13 (46%), and 6 (21%) and 8 (29%) had high-and low-level MET copy gain, respectively. To date, two MET inhibitors, onartuzumab or tivantinib, combination with erlotinib in previously treated NSCLC were investigated in phase III trials. However, neither showed prolonged overall survival (OS) compared with erlotinib alone in molecularly unselected patients. Several publications including the report of Awad et al. revealed that patients with MET exon 14 mutation were successfully treated with MET-tyrosine kinase inhibitors (TKIs) such as crizotinib. Prospective trials using MET-TKIs in MET exon 14 mutated NSCLC are ongoing. Concerning translational research, significance of co-existed other mutations or amplifications and mechanism of acquired resistance to MET-TKIs remain to be clarified. Finally, the therapeutic strategies against the MET-TKI resistance and intracranial metastasis in NSCLC with MET exon 14 mutation should be elucidated.