Immunopotentiation of anticancer chemotherapy byCandida albicans, other yeasts and insoluble glucan in an experimental lymphoma model

Several yeast species in the genera Candida, Saccharomyces and Cryptococcus showed powerful immunoadjuvant, chemotherapy-synergic effects against a histocompatible, virus-induced murine lymphoma. Sensitizing and booster intraperitoneal injections of 2 x 10(7) yeast cells on days -14 and +1 (with respect to tumor challenge on day 0) followed by treatment with antiblastic drugs (on day +5) were required to elicit optimum activity. The antitumor effect was not markedly influenced by the morphological growth form of merthiolate-inactivated C. albicans nor by the nature of the carbon source in the growth medium, except for C. albicans cells grown in a medium containing stearic acid, which were not effective. These cells had a higher ratio of soluble to insoluble cell wall components, as compared to glucose-grown cells, but this finding alone could hardly explain the lack of antitumor effects. Previous observations, suggesting that the alkali-acid insoluble beta-glucan (in the form of cell wall ghosts) is the only component of yeast cell walls endowed with antitumor activity comparable to that of whole cells, were confirmed and extended; the soluble mannan and glucan-protein fractions were unable to replace whole cells and glucan ghosts even as sensitizers or as boosting agents.