Infrequent mutation of the ras genes in skin tumors of xeroderma pigmentosum patients in Japan.

By using PCR amplification and oligonucleotide mismatch hybridization, base-substitution mutations of the ras genes in 26 skin tumors of Japanese xeroderma pigmentosum (XP) patients were studied. Thin sections of tumor tissues which were fixed and embedded in paraffin blocks were used in this study. After analyzing codons 12, 13 and 61 of the H-, K- and N-ras genes by using 66 oligomer probes, we detected only one mutation of the K-ras gene at codon 61 in one tumor sample. All the other tumors were therefore considered not to have a mutation in the ras genes. These results suggest that mutations of the ras genes are not particularly associated with skin tumors of Japanese XP patients.