Proteins involved in DNA damage response pathways and survival of stage I non-small-cell lung cancer patients

Biological complexity leads to significant variation in the survival of patients with stage I non-small-cell lung cancer (NSCLC). DNA damage response (DDR) pathways play a critical role in maintaining genomic stability and in the progression of NSCLC. Therefore, the development of a prognostic biomarker focusing on DDR pathways is an intriguing issue. Expression of several proteins (ATM, ATMpS1981, gamma H2AX, 53BP1, 53BP1pS25, Chk2, Chk2pT68, MDC1, MDC1pS964, BRCA1pS1423, and ERCC1) and overall survival were investigated in 889 pathological stage I NSCLC patients. Low expression of BRCA1pS1423 or ERCC1 was significantly associated with worse survival in the whole cohort of patients. Analysis performed based on histology revealed that low expression of gamma H2AX, Chk2pT68, or ERCC1 was a poor prognostic factor in squamous cell carcinoma patients [adjusted hazard ratio (aHR), Cox P: 1.544, 0.012 for gamma H2AX; 1.624, 0.010 for Chk2pT68; 1.569, 0.011 for ERCC1]. The analysis of the interaction between two proteins showed that this effect was more pronounced in squamous cell carcinoma patients. However, these effects were not detected in adenocarcinoma patients. The proteins involved in DDR pathways exhibited differential expression between squamous cell carcinoma and adenocarcinoma and were important determinants of survival in stage I squamous cell carcinoma patients.