Immunochemical and genetic analysis of the p53 gene in liver preneoplastic nodules from aflatoxin-induced rats in one year.

Mutations of the p53 tumour-suppressor gene in human hepatocellular carcinomas from certain geographic areas appear to be associated with high dietary exposure to aflatoxin B1 (AFB1). In this study, the effects of AFB1 on p53 locus at the preneoplastic stage of rat liver oncogenesis were assessed. Male Wistar rats were treated with a single dose of 1.5 mg AFB1/kg body weight by a gastric tube. Liver biopsies over a period of one year were examined for aberrations of the p53 gene together with the expression of placental glutathione-S transferase (GST-P), a marker for preneoplasia. Immunohistochemistry, Western blot, polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing techniques were used. AFB1 induction resulted in GST-P overexpression, forming GST-P-positive multi-foci and nodules of hepatocytes, but no aberrations in the p53 expression and the microstructure of exons 5-8 of the p53 gene. These results suggested that p53 mutation(s) might not occur at this early stage of AFB1-induced hepatocarcinogenesis.