Promoter hypermethylation of the p16 and Wif-1 genes as an independent prognostic marker in stage IA non-small cell lung cancers

Hypermethylation of promoter CpG islands is a major inactivation mechanism of tumor suppressor genes, some of which are thought to be related to the prognosis of patients with non-small cell lung cancer (NSCLC). Therefore, hypermethylation of the specific genes may be expected to serve as a prognostic biomarker for NSCLC. In this study, the methylation status of 14 genes was analyzed in 44 stage IA NSCLC cases using methylation-specific PCR. Hypermethylation was detected in PTGER2 (70% of cases), DRM/Gremlin (66%), sFRP-2 (57%), IL-12Rβ2 (48%), Reprimo (41%), APC (39%), CXCL12 (39%), HPP1 (30%), SPARC (30%), sFRP-5 (30%), p16 (25%), RUNX3 (20%), sFRP-1 (20%) and Wif-1 (16%). Patients with p16, sFRP-5, Wif-1 or CXCL12 methylation had a significantly shorter duration of relapse-free survival than their counterparts with an unmethylated gene (p16, P=0.011; sFRP-5, P=0.030, Wif-1, P=0.036; CXCL12, P=0.026). Also, those with methylated HPP1, p16 or Wif-1 had a significantly shorter duration of overall survival (HPP1, P=0.031; p16, P=0.026; Wif-1, P=0.008). Multivariate analysis revealed that p16 methylation in relapse-free survival and Wif-1 methylation in overall survival were the strongest independent prognostic factors (p16, P=0.036; Wif-1, P=0.035). In conclusion, the hypermethylation of the p16 and Wif-1 genes has potential as biomarkers that may be used to predict the prognosis of stage IA NSCLC.