Phleomycin is an antibiotic produced by Streptomyces verticullus and is structurally related to Bleomycin. Used as a selective agent in transformation experiments with mammalian cells, plant cells and yeast. Its cytotoxic action results from its ability to cause fragmentation of DNA. In Vitro studies indicate that Phleomycin causes accumulation of cells in the G2 phase of the cell cycle.