Low incidence of point mutations in H-, K- and N-ras oncogenes and p53 tumor suppressor gene in renal cell carcinoma and peritoneal mesothelioma of Wistar rats induced by ferric nitrilotriacetate

An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces renal proximal tubular damage, a consequence of iron-catalyzed free radical reactions, that finally leads to a high incidence of renal cell carcinoma (RCC) in rodents. Previous studies have identified, within 24 h after administration of Fe-NTA, lipid peroxidation products, aldehyde-modified proteins and a variety of modified DNA bases such as 8-hydroxyguanine that may be mutagenic in vivo. In the present study, pathological features of the RCCs were studied, and, in an effort to correlate them with carcinogen-specific molecular events in Fe-NTA-induced carcinogenesis, the H-, K- and N-ras oncogenes and the p53 tumor suppressor gene were investigated for the presence of mutations. Fe-NTA-induced RCCs showed similarity to human RCCs in that they are often invasive, metastatic and fatal. None (0 of 12) of the tumors had mutation in codons 12, 13 and 61 of the H-, K- and N-ras genes by direct sequencing. Only one (1 of 12) tumor with high grade histology revealed a CGC-to-CTC (Arg to Leu) transversion in codon 246 of the p53 gene by the use of single strand conformation polymorphism (SSCP) analysis and direct sequencing. High expression of mutant p53 protein was confirmed by Western blotting and immunohistochemistry. Study of three peritoneal mesotheliomas induced by Fe-NTA revealed no mutation in ras and p53 genes. These results suggest that the ras and p53 genes are not the major targets of mutation in Fe-NTA-induced carcinogenesis of kidney and mesothelium. Instead, p53 mutation may work for potentiation of malignant character in Fe NTA-induced renal carcinogenesis.