Molecular heterogeneity and co-altered genes in MET-amplified ALK-positive lung cancer: Implications for MET targeted therapy

Objectives MET amplification is a common mechanism of resistance to second- and third-generation anaplastic lymphoma kinase (ALK) inhibitors. In case series of MET-amplified ALK-rearranged (ALK + ) lung cancer, durability of responses to combinations targeting ALK and MET is variable, suggesting heterogeneity across tumors. However, little is known about the molecular composition of this subset of ALK-rearranged (ALK + ) NSCLC. Materials and methods We queried tissue and plasma databases to compile a group of > 50 specimens with ALK rearrangements and concurrent MET amplification. Fluorescence in-situ hybridization (FISH) and next-generation sequencing (NGS) were utilized to quantify the range of MET copies and describe the global molecular landscape of co-altered genes. Results By FISH, high-level amplification (overall MET/centromere 7 probe ratio ≥ 5) was detected in 75 % of MET-amplified ALK + NSCLC tissue specimens. Intralesional heterogeneity of MET copies was observed, with high-level amplification identified even in cells from tumors with overall low-level MET amplification. Analysis of 48 MET-amplified ALK + NSCLC plasma specimens suggested that high-level amplification is rarely (17 %) detected in plasma. In both tissue and plasma, EML4-ALK variant 1 was the predominant variant (51 %) identified in MET-amplified specimens. ALK kinase domain mutations were only present in a minority of MET-amplified ALK + NSCLCs. MET-amplified ALK + NSCLC plasma specimens were enriched for TP53 mutations (81 % vs 45 %, p = 0.002), EGFR amplification (17 % vs 4 %, p < 0.001), and MYC amplification (21 % vs 3 %, p < 0.001) compared to ALK + NSCLC specimens lacking MET amplification. Conclusions MET-amplified, ALK + NSCLC often presents with high-level and heterogeneous amplification in tissue, seldom overlaps with ALK mutations, and frequently co-occurs with alterations associated with aggressive tumor biology.