Liver carcinogenesis in tropical Africa.

The geographical pathology of hepatocellular carcinoma (HCC) was essentially anecdotal until systematic cancer registration was introduced, but it is now clear that sub-Saharan Africa is a high-incidence area. The disease is multifactorial in etiology, the possible etiological agents including hepatitis B virus and a number of chemical carcinogens, among which the most important appear to be the aflatoxins and N-nitroso compounds. Medicinal plants and herbal teas used in the tropics also contain compounds such as furocoumarins that are mutagenic and/or carcinogenic. A modified form of the Ames Salmonella typhimurium assay was used to study the mutagenicity of aflatoxins B1 and M1 and palmotoxin B0, a co-metabolite of aflatoxin B1, and also of chamuvaritin and chamuvarin, two benzyldihydrochalcones derived from the roots of Uvaria chamae, which are used for medicinal purposes in West Africa. The mutagenicity of a number of furocoumarins isolated from Nigerian medicinal plants was studied by means of the same assay as well as with Chinese hamster V79 cells and C3H 10T1/2 cells; in the last two systems the studies were carried out both with and without photoactivation. The same compounds, and 8-methoxypsoralen, were also investigated by means of cell transformation studies.