Reduced Expression of the Pcdh20 Gene and Its Aberrant DNA Methylation in Lung Adenocarcinomas Induced by N-nitrosobis(2-hydroxypropyl)amine in Rats

Abstract

Protocadherins are a major subfamily of the cadherin superfamily that play an important role in communication between adjacent cells. To clarify the involvement of Protocadherin 20 (Pcdh20) gene in rat lung carcinogenesis, we investigated the expression of Pcdh20 and its methylation status 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 weeks and were maintained without further treatment until they were sacrificed after 25 weeks. Total RNAs were extracted from 7 lung adenocarcinomas, one from each BHP-treated rat, and the expression levels of Pcdh20 were measured using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Four out of 7 tumors showed reduced expression of Pcdh20, compared with 3 normal lung tissues. For methylation analysis, bisulfite sequencing was performed. The 5' upstream region of Pcdh20 was methylated in 4 adenocarcinomas with reduced expression of Pcdh20, but was unmethylated in normal lung tissue. These results suggest that aberrant methylation of the Pcdh20 gene might be involved in the development of lung adenocarcinomas induced by BHP in rats.