Background: MET gene copy number gain (CNG) and protein overexpression have been reported in lung cancer, but the clinical implications in early stage adenocarcinoma remain unclear.
Methods: We investigated MET gene copy number and protein expression in 141 cases of surgically resected stage I pulmonary adenocarcinoma. MET gene CNG was determined by silver in situ hybridization, and MET protein expression was assessed by immunohistochemistry. The correlation between MET gene CNG/protein expression and clinicopathologic parameters and prognostic significance was analyzed.
Results: MET gene CNG was found in 24.1% (34 of 141) of the cases and was associated with larger tumor size, pleural invasion, and lymphatic vessel invasion. MET gene CNG was inversely correlated with the presence of lepidic subtype (r = -0.17, p = 0.045) and was not associated with EGFR, KRAS mutation, or ALK gene rearrangement. In addition, MET gene CNG was significantly associated with shorter disease-free survival (DFS) (49 vs. 75 months; p < 0.001) and shorter overall survival (OS) (65 vs. 78 months; p = 0.01). Multivariate analysis confirmed that MET gene CNG was significantly associated with poorer DFS [p < 0.001; hazard ratio (HR) 5.5; 95% confidence interval (CI) 2.2-13.9] but was not significantly associated with OS. MET overexpression was observed in 71.3% of cases (97 of 136), but it was not correlated with gene CNG.
Conclusions: MET gene CNG is an independent poor prognostic factor in patients with stage I lung adenocarcinoma. It is associated with aggressive pathologic features and is inversely correlated with the presence of lepidic subtype.