Thiostrepton is a natural antibiotic produced by bacteria of Streptomyces genus. Thiostrepton has been used in veterinary medicine in mastitis caused by gram-negative organisms and in dermatologic disorders. It is mostly used in complex ointments containing neomycin, nystatin, Thiostrepton and topical steroids. It is also active against gram-positive bacteria. It is notable that ointments for human usage contain neomycin, nystatin, and topical steroids, but no Thiostrepton. It can induce apoptotic cell death in human cancer cells. Thiostrepton was reported (in 2008) to exhibit activity against breast cancer cells through targeting the transcription factor forkhead box M1 (FOXM1). It has also been shown to circumvent acquired cisplatin resistance in breast cancer cells under in invitro conditions. Thiostrepton is used in molecular biology as a reagent for both positive and negative selection of genes involved in nucleotide metabolism. It is protein synthesis inhibitor.