Association of Methylation of the RAR-β Gene with Cigarette Smoking in Non-Small Cell Lung Cancer with Southern-central Chinese Population

Pathogenesis of lung cancer is a complicated biological process including multiple genetic and epigeneticchanges. Since cigarette smoking is confirmed as the most main risk factor of non-small cell lung cancer (NSCLC),the aim of this study was to determine whether tobacco exposure plays a role in gene methylation. Methylationof the RAR-β gene were detected using methylation-specific polymerase chain reaction in DNA from 167 newlydiagnosed cases with NSCLC and corresponding 105 controls. A significant statistical association was found inthe detection rate of the promoter methylation of RAR-β gene between NSCLC and controls (x2=166.01; p<0.01),and hypermethylation of the RAR-β gene was significantly associated with smoking status (p=0.038, p<0.05). Norelationship was found between RAR-β gene methylation and pathologic staging including clinical stage, celltype, gender and drinking (p>0.05), and the methylation of RAR-β gene rate of NSCLC was slightly higher instages Ⅲ+Ⅳ (80.0%) than in Ⅰ+Ⅱ (70.8%). Similar results were obtained for methylation of the RAR-β genebetween squamous cell carcinoma (77.9%) and other cell type lung cancer (73.9%). These results showed thatthe frequency of methylation increased gradually with the development of clinical stage in smoking-associatedlung cancer patients, and tobacco smoke may be play a potential role in RAR-β gene methylation in the earlypathogenesis and process in lung cancer, particularly squamous cell carcinoma. Aberrant promoter methylationis considered to be a promising marker of previous carcinogen exposure and cancer risk.