Transformation of kidney epithelial cells by a quinol thioether via inactivation of the tuberous sclerosis-2 tumor suppressor gene

Although hydroquinone (HQ) is a rodent carcinogen, because of its lack of m utagenicity in standard bacterial mutagenicity assays it is generally consi dered a nongenotoxic carcinogen. 2,3,5-Tris-(glutathion-S-yl)HQ (TGHQ) is a potent nephrotoxic metabolite of HQ that may play an important role in HQ- mediated nephrocarcinogenicity. TGHQ mediates cell injury by generating rea ctive oxygen species and covalently binding to tissue macromolecules. We de termined the ability of HQ and TGHQ to induce cell transformation in primar y renal epithelial cells derived from the Eker rat. Eker rats possess a ger mline inactivation of one allele of the tuberous sclerosis-2 (Tsc-2) tumor suppressor gene that predisposes the animals to renal cell carcinoma. Treat ment of primary Eker rat renal epithelial cells with HQ (25 and 50 muM) or TGHQ (100 and 300 muM) induced 2- to 4-fold and 6- to 20-fold increases in cell transformation, respectively. Subsequently, three cell lines (The QT-R RE 1, 2, and 3) were established from TGHQ-induced transformed colonies. Th e QT-RRE cell lines exhibited a broad range of numerical cytogenetic altera tions, loss of heterozygosity at the Tsc-2 gene locus, and loss of expressi on of tuberin, the protein encoded by the Tsc-2 gene. Only heterozygous (Ts c-2(EK/+)) kidney epithelial cells were susceptible to transformation by HQ and TGHQ, as wild-type cells (Tsc-2(+/+)) showed no increase in transforma tion frequency over background levels following chemical exposure. These da ta indicate that. TGHQ and HQ are capable of directly transforming rat rena l epithelial cells and that the Tsc-2 tumor suppressor gene is an important target of TGHQ-mediated renal epithelial cell transformation. (C) 2001 Wil ey-Liss, Inc.