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

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