Abstract
Excess relative risk of lung cancer among atomic-bomb survivors remains high even now, more than 60 years after the bombings. However, molecular mechanisms underlying the long-lasting effects of radiation exposure on lung cancer development remain unclear. To assess effects of radiation on lung carcinogenesis, we analyzed DNA methylation status of the p16 and RASSF1A genes in 20 atomic-radiation-exposed and 18 non-exposed non-small cell lung cancer (NSCLC) cases and examined association between methylation status and radiation exposure. Our analysis showed trends that RASSF1A methylation in the exposed NSCLC cases was less frequent compared with the non-exposed cases: 32% (6/19) vs. 56% (10/18), and that, among the exposed cases, methylation frequency of the gene in squamous cell carcinoma were less frequent than those in adenocarcinoma. These results suggest that frequencies of certain types of gene methylation might be associated with radiation exposure in a histologically dependent manner, although the association was not statistically significant. Further analysis with increased numbers of cases is required.
Methylation status of retrotransposone LINE1, a marker of global DNA methylation in genomic DNA, is under analysis. Results from this analysis also will be presented.
