FRAMESHIFT MUTATION IN CODON-176 OF THE P53 GENE IN RAT ESOPHAGEAL EPITHELIAL-CELLS TRANSFORMED BY BENZO[A]PYRENE DIHYDRODIOL

Mutations in the p53 tumor suppressor gene have been associated with e xposure to environmental chemical carcinogens. Cultured rat esophageal epithelial cells were transformed in vitro by treatment with benzo[a] pyrene dihydrodiol (BP-DHD). A BP-DHD-transformed cell line and contr ol cell lines were analyzed for mutations in the p53 gene and in the H a-ras gene by single-strand conformation polymorphism analysis of poly merase chain reaction-amplified products and direct DNA sequencing. Th e deletion of one cytosine in codons 174-176 (TGCCCCCAC --> TGCCCCAC) of the p53 gene was found only in the BP-DHD-transformed cell line. Th e BP-DHD-transformed cells were highly invasive and tumorigenic when t ransplanted into syngeneic rats, whereas control lines either were non tumorigenic or formed epithelial cysts. BP-DHD-transformed cells and c ontrol lines were negative for mutations in the Ha-ras gene. Our resul ts suggest that the tumorigenic potential of the BP-DHD-transformed ce ll line is associated with a frameshift mutation in codon 176 of the p 53 gene but not with mutations in the Ha-ras gene. The CIC-rich codons 174-176 in the rat p53 gene may be specific targets for BP-DHD. (C) 1 995 Wiley-Liss, Inc.