International comparison on ras gene mutations in latent prostate carcinoma.

Latent carcinomas of the prostate, discovered at autopsy in men with no prior treatment for prostatic disease, were studied for ras proto-oncogene mutations. Subjects included 21 Japanese, 15 U.S. whites, 15 U.S. blacks, 20 Hawaiian Japanese and 10 Colombians. PCR and sequence-specific oligonucleotide hybridization identified mutations in 5 Japanese, in 1 Hawaiian Japanese, in 1 U.S. black, in 1 U.S. white and in 3 Colombians. The 5 Japanese tumor samples contained 3 point mutations in codon 12 of K-ras and 2 mutations in codon 12 of N-ras respectively. One tumor in a Hawaiian Japanese man also showed a K-ras point mutation at codon 12. Two Colombians and one U.S. black man had tumors with mutations at codon 61 of H-ras, while 1 Colombian showed an N-ras mutation at this codon. The overall frequency of ras gene mutations was low, but point mutations in codon 12 were most common in latent tumors of Japanese, who experienced the lowest incidence and mortality from this tumor. Latent tumors in men from ethnic groups with high mortality and incidence rates showed fewer ras mutations than the Japanese, and these were more likely to involve codon 61. This finding is consistent with prior studies of more aggressive clinical cancers in Japanese men that indicated a higher frequency of mutations at codon 61.