High incidence of allelic loss on chromosome 5 and inactivation of p15INK4B and p16INK4A tumor suppressor genes in oxystress-induced renal cell carcinoma of rats

Ferric nitrilotriacetate induces oxidative damage in renal proximal tubules, a consequence of Fenton-like reaction, that ultimately leads to a high incidence of renal cell carcinoma (RCC) in rats. In order to find common genetic alterations in this oxystress-induced carcinogenesis model, RCCs were produced in F1 hybrid rats between Wistar and Long-Evans strains and genomes were screened for loss of heterozygosity (LOH) with microsatellite polymorphic markers by PCR. Five consecutive markers on chromosome 5 (D5Mgh5, D5Mit9, D5Mgh6, D5Mit11 and D5Mit6) showed LOH in greater than or equal to 40% of the RCCs. As possible candidate tumor suppressor genes on chromosome 5, p15(INK4B) and p16(INK4A) were investigated for genetic alteration and aberrant methylation by Southern blot, PCR/SSCP/ sequencing and methylation-specific PCR. Genetic alteration (homozygous or hemizygous deletion with or without point mutation) or aberrant methylation were found in 30.7 and 53.8% of the RCC cases, respectively, which was proportionally associated with the histological nuclear grade and metastatic activity. Our data suggest that inactivation of p15 and p16 genes could be one of the major pathways responsible for oxystress-induced carcinogenesis.