RENAL-CELL CARCINOMA DEVELOPMENT IN THE RAT INDEPENDENT OF ALTERATIONS AT THE VHL GENE LOCUS

Germline alterations of the human von Hippel-Lindau (VHL) tumor suppre ssor gene predispose to renal cell carcinoma and a constellation of ot her tumor types found in VHL disease. This gene is also mutated or del eted in a high proportion of sporadic nonpapillary renal cell carcinom as. In the Eker rat model, spontaneous renal cell carcinoma develops w ith a high frequency. We therefore investigated the role of this tumor suppressor gene in the development of these hereditary rat tumors. By using reverse transcriptase (RT)-polymerase chain reaction (PCR) anal ysis, the sequence of the rat VHL gene was determined over the portion of the gene homologous to regions where most mutations in the human V HL gene occur. The sequence homology was 90% and the amino-acid identi ty 99% between the rat and human genes. A developmental and tumor-spec ific pattern of expression for the VHL gene was found; a ubiquitous 3. 2-kb transcript was expressed in all rat tissues examined (neonatal ki dney, lung, liver, brain, heart, kidney, spleen, testis, and stomach), and an additional 4.5-kb transcript was expressed in neonatal kidney and cell lines derived from Eker rat renal cell carcinomas (ERC cell l ines). To determine whether mutations in the VHL gene were involved in tumor development in the Eker model, RT-PCR, single-strand conformati on polymorphism (SSCP) analysis, and direct sequencing were used to se arch for alterations in this gene in the ERC cell lines. Alterations i n the VHL gene were not detected by SSCP, and these data were confirme d by direct sequencing. Transformed rat kidney epithelial cell lines d erived from Fisher rats also expressed the VHL gene but like the ERC c ell lines did not contain mutations in the VHL gene. These data indica te that in the rat, transformation of kidney epithelial cells and the development of solid, nonpapillary renal cell carcinoma can occur via pathways that are independent of alterations at the VHL gene locus. (C ) 1996 Wiley-Liss, Inc.