The study aimed to assess the involvement of aberrant DNA methylation in lung carcinogenesis by measuring expressions of E-cadherin and p16 genes, and their DNA methylation status in the 5' upstream region in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). Six-week-old male Wistar rats were given 2000 ppm BHP in their drinking water for 12 wk, and maintained without further treatment until they were sacrificed at 25 wk. A total of nine lung adenocarcinomas were collected, and total RNA from each sample was extracted for assessment of gene expression by real-time reverse transcription (RT)-polymerase chain reaction (PCR). Expressions of E-cadherin and p16 genes were significantly reduced in lung adenocarcinomas (P < 0.05 and P < 0.005, respectively) compared with normal lung tissues. For methylation analysis, bisulfite sequencing was performed using two normal lung tissues and five tumors. The two normal lung tissues were all unmethylated in regions of E-cadherin and p16. In contrast, five adenocarcinomas were highly methylated, and these aberrant methylation patterns correlated with reduced expressions of E-cadherin and p16. These results suggest that aberrant DNA methylation of E-cadherin and p16 genes may play important roles in development of lung adenocarcinomas induced by BHP in rats.
Copyright 2005 Wiley-Liss, Inc.