SOMATIC MUTATION OF THE TUBEROUS SCLEROSIS (TSC2) TUMOR-SUPPRESSOR GENE IN CHEMICALLY-INDUCED RAT RENAL-CARCINOMA CELL

Purpose: von Hippel-Lindau (VHL) gene mutations are detected in noninh erited, sporadic human renal cell carcinomas (RCs) at a high frequency . We recently identified a germline mutation in the rat homologue of t he human tuberous sclerosis (TSC) predisposing RC gene in the Eker rat model, and in this study we searched for mutations of the Tsc2 gene i n chemically induced non-Eker rat RCs. Materials and Methods: Chemical ly [N-ethyl-N-hydroxyethylnitrosamine (EHEN)]-induced non-Eker rat RC lines (designated as BP13 and BP36B) were subjected to PCR-single stra nd conformation polymorphism (PCR-SSCP) analysis using specific primer s covering entire exons of Tsc2 gene (41 coding exons and one non-codi ng exon). We simultaneously searched for mutations of Vhl gene, a rat homologue of von Hippel-Lindau disease gene (VHL) as well as Tsc2 gene . Results: BP36B showed an abnormal mobility shift from the normal tis sue of the same rat in exon 35 on analysis by PCR-SSCP. This mutation was confirmed by direct sequencing and found to be a T-to-C transition at the second position of codon 1470, resulting in an amino acid chan ge from leucine to proline (missense mutation). Conclusions: This is t he first demonstration of Tsc2 gene somatic mutation in non-Eker rat R Cs. Our present findings call attention to further investigation of th e role of Tsc2 gene mutations in rat renal carcinogenesis and possible Tsc2 gene mutations in human RCs, especially of the non-clear cell ty pe, which are not related to the VHL gene.