Aberrant promoter methylation profile and association with survival in patients with non-small cell lung cancer

The aim of this study was to investigate the prognostic value of hypermethylation of tumor suppressor genes in patients with non-small cell lung cancer (NSCLC).

We examined the methylation status of nine genes in 155 tumors from patients with NSCLC using quantitative methylation-specific PCR. We analyzed the associations between gene methylation status and overall patient survival.

The methylation index, defined as the ratio between the number of methylated genes and the number of genes tested, was significantly higher in adenocarcinomas (0.38 +/- 0.20) than in squamous cell carcinomas (0.30 +/- 0.22; P = 0.027), in tumors from older patients (0.37 +/- 0.20) than younger patients (0.30 +/- 0.22; P = 0.040), and in tumors from heavier smokers (0.39 +/- 0.21) than lighter smokers (0.29 +/- 0.20; P = 0.042). In the Cox proportional hazards model, p16 methylation was associated with significantly poorer survival [hazard ratio, 1.95; 95% confidence interval (95% CI), 1.21-3.39]. Kaplan-Meier survival curves showed that patients with hypermethylated p16 had significantly shorter survival (median = 21.7 months) than patients without p16 hypermethylation (median = 62.5 months; P = 0.0001, log-rank test). Hypermethylation of CDH1 or TIMP3 gene was associated with significantly better survival with hazard ratios of 0.51 (95% CI, 0.29-0.90) and 0.59 (95% CI, 0.36-0.97), respectively. Joint analysis of these three genes showed a significant trend for poorer survival as the number of unfavorable events increased (P = 0.0007).

Hypermethylation of multiple genes exhibited significant differential effect on NSCLC patient survival. Assessment of the effect of each methylated gene on survival is needed to provide optimal prognostic value.