Studies on the biological activity of stubomycin.

Stubomycin showed direct cytotoxic activity on mammalian cells, yeast, and fungi, and rapid hemolytic activity on mouse erythrocytes. The rate and extent of the cytotoxic and hemolytic activities decreased at lower temperatures. Studies with radioactive precursors revealed that a marginal cytocidal concentration of the antibiotic inhibited synthesis of DNA, RNA, and protein of leukemic cells at almost the same rate. Stubomycin did not show any mutagenicity on mammalian cells and bacteria i.e. the induction of revertants on six bacterial strains, and chromosomal aberrations, sister chromatid exchanges, and the induction of cells resistant to 6-thioguanine on Chinese hamster cells (DON D-6). The antagonistic effect of various kinds of lipids including phospholipids, cholesterol, olive oil and squalene was studied. Significant antagonism of stubomycin against anti-Saccharomyces cerevisiae activity was observed with phospholipids except for egg lecithin and with cholesterol. The primary action of the antibiotic seems to be to change the cell surface and ultimately the lysis and death of the cells.