Analysis of ras gene mutations in hepatocellular carcinoma in southern African blacks.

Paired samples of hepatocellular carcinoma and non-tumorous liver tissue from 12 southern African blacks were examined for mutations in codons 12, 13, and 61 of the three ras proto-oncogenes (H-, K-, and N-ras). Deoxyribonucleic acid was isolated from carcinoma and non-tumorous tissues and amplified with the polymerase chain reaction. Using the single-stranded conformational polymorphisms method, products of the polymerase chain reaction amplification of codons 12, 13, and 61 of H-, K-, and N-ras were analysed for mutations. Mobility shifts were not detected except in one tumour in the region of codon 61 of K-ras. By sequencing the relevant polymerase chain reaction products, this sequence of deoxyribonucleic acid was proved to be normal, indicating that the single-stranded conformational polymorphisms result was an artifact of the polymerase chain reaction. Thus, no mutations were detected in the regions of interest in any of the tumours studied. These results indicate that activation of ras proto-oncogenes by mutations in codons 12, 13, and 61 does not play an important role in hepatocellular carcinogenesis in southern African Blacks despite the fact that dietary exposure to aflatoxin B1 is a risk factor in this population.