EARLY DETECTION OF KNUDSON 2-HITS IN PRENEOPLASTIC RENAL-CELLS OF THEEKER RAT MODEL BY THE LASER MICRODISSECTION PROCEDURE

Hereditary renal cell carcinomas invariably develop by the age of 1 ye ar in Eker rats. At the histological level, renal cell carcinomas deve lop through multiple stages from early preneoplastic lesions (e.g., ph enotypically altered tubules) to adenomas. We previously reported that ionizing radiation induces additional tumors (large adenomas and carc inomas) in a linear dose-response relationship and that loss of hetero zygosity (LOH) at chromosome 10, where the predisposing tuberous scler osis (Tsc2) gene is localized, was found in the renal cell carcinomas which developed from hybrid F1 rats carrying the Eker mutation, indica ting that in heterozygotes two events (one inherited, one somatic) are necessary to produce at least large adenomas and carcinomas, This stu dy was designed to examine LOH in the earliest preneoplastic lesions, using a laser microdissection procedure, We could accurately dissect s ingle altered renal tubules out of freeze-dried sections and clearly d etected LOH in 4 of 19 altered tubules (21%). This is the first demons tration of LOH in single renal tubules, Our present results support th e theory of a second, somatic mutation (second hit) as rate-limiting s tep of renal carcinogenesis in the Eker rat model of dominantly inheri ted cancer and the tumor suppressor nature of the Tsc2 gene function.