MET amplification, protein expression, and mutations in pulmonary adenocarcinoma

Abstract

Objectives: MET amplification, protein expression, and splice mutations at exon 14 are known to cause dysregulation of the MET/HGF pathway. Our study aimed to confirm the relationship among MET amplification, protein expression, and mutations in pulmonary adenocarcinoma.

Materials and methods: MET protein expression by immunohistochemistry (IHC) and MET amplification by fluorescence in situ hybridization (FISH) were evaluated in 316 surgically resected lung adenocarcinomas. Patients were divided into 4 groups (IHC-negative/FISH-negative, IHC-negative/FISH-positive, IHC-positive/FISH-negative, and IHC-positive/FISH-positive), and 15-20 tumors in each group were randomly selected for mutation analyses to find splice mutations at exon 14.

Results: An IHC score of 0-3 was found in 168 (53.2%), 71 (22.5%), 59 (18.7%), and 18 (5.7%) tumors, respectively. The mean gene copy number (GCN) was 3.56; MET FISH positivity was detected in 123 (38.9%) samples, and 26 (8.2%) of them were gene amplifications. MET amplification were significantly associated with the IHC score (P<0.001, χ(2) test). Splice mutations were identified in only 2 (2.9%) of 70 cases. One had a MET IHC score of 2 and negative FISH without amplification; The other had a MET IHC score of 0 and positive FISH without amplification. MET IHC or FISH results were not prognostic indicators of overall survival in multivariate analysis.

Conclusion: There is a significant relationship between MET amplification and protein expression, and selection of tumors with amplification using IHC was effective. However, because of its rarity, a selection strategy for mutated tumors is implausible using IHC or FISH.

Keywords: Adenocarcinoma; Gene amplification; Gene expression; MET; Mutation; Non-small-cell lung carcinoma.