Produced by Streptomyces verticullus and part of the structurally related group of Bleomycin/Phleomycin type antibiotics. Used as a selective agent in transformation experiments with mammalian cells, plant cells and yeast. Cytotoxic action of this type antibiotic results from the ability to cause fragmentation of DNA. In Vitro studies indicate that Phleomycin causes accumulation of cells in the G2 phase of the cell cycle.