The role of yeasts in oral cancer by means of endogenous nitrosation.

Oral leukoplakias, particularly non-homogeneous types, are often invaded by yeasts, with Candida albicans being the dominant species. The more advanced precancerous leukoplakia lesions yield more rarely occurring biotypes of C. albicans, suggesting a causal role for these biotypes in the malignant transformation. N-nitroso-benzylmethylamine (NBMA) is a compound able to induce carcinoma of the esophagus and the oral cavity in the rat. The catalytic potential of yeasts, isolated from leukoplakia lesions and from normal mucosa, to produce NBMA from the precursors N-benzyl-methylamine and nitrite was assessed at pH 6.8. The yeast strains differed in nitrosation potential, ranking from 0 to 1.2 micrograms NBMA/10(6) cells. C. albicans strains of the more rarely occurring biotypes showed the highest nitrosation potential, whereas C. tropicalis, C. parapsilosis, and Torulopsis glabrata were ranked lower. Strains with high nitrosation potential were generally isolated from lesions with more advanced precancerous changes. Thus, further evidence is provided supporting the hypothesis that yeasts play a causal role in oral cancer by means of endogenous nitrosamine production.