An antibiotic isolated from the bacterium Streptomyces plicatus with antineoplastic activity. Plicamycin, also known as mithramycin, binds to the minor groove of DNA at GC-rich sites, resulting in inhibition of RNA synthesis; this agent also inhibits mRNA expression, resulting in a reduction in protein synthesis. In addition, plicamycin may inhibit bone resorption by down regulating transcription of c-src, an oncogene involved in bone metabolism and resorption.