Mutations and Reduced Expression of the Transforming Growth Factor‐β Receptor II Gene in Rat Lung Adenocarcinomas Induced by N‐Nitrosobis‐(2‐hydroxypropyl)amine

Mutations and expression of the transforming growth factor‐β receptor type II (TGF‐βRII) gene were investigated in lung adenocarcinomas induced by N‐nitrosobis(2‐hydroxypropyl)amine (BHP) in rats. Males of the Wistar strain, 6 weeks old, were given 2000 ppm of BHP in their drinking water for 12 weeks and then maintained without further treatment until killed at week 25. Total RNA was extracted from 12 adenocarcinomas and mutations in TGF‐βRII were investigated by RT‐PCR‐restriction‐SSCP analysis followed by sequencing analysis. Two out of 12 adenocarcinomas showed band shifts, indicative of mutations (16.7%). One was a CTG‐to‐TTG (Leu to Leu) transition at codon 308 without amino acid alteration and the other a frameshift deletion of one of two guanines at nucleotides 1434 to 1435 (codon 477 to 478). Semi‐quantitative RT‐PCR analysis demonstrated significantly reduced TGF‐βRII expression in adenocarcinomas, as compared with normal lung tissue. These results suggest that TGF‐βRII alterations may play a role in the acquisition of growth advantage by lung adenocarcinomas induced by BHP in rats.