Selective effect of fractions of a yeast extract (PCO) on normal and malignant cells

The selective action of two fractions of PCO (a yeast extract) on normal and malignant cells was demonstrated. In vivo, the mitotic activity of malignant cells was inhibited by the methanol-insoluble fraction of PCO, whereas the methanol-soluble fraction caused no inhibition. The in vitro studies, however, showed inhibition of mitoses with both fractions. The malignant cells employed in vitro and in vivo were the Krebs-2 and Ehrlich carcinomas. The nonneoplastic cells tested in vitro were established cultures of epithelial-like cells from murine bone marrow and thymus, and corneal epithelium and peripheral blood in vivo.