Actinomycin D is a polypeptide antibiotic produced from Streptomyces; it exhibits anticancer chemotherapeutic activity but does not display antibacterial benefit. Actinomycin D is clinically used to treat various cancers and is one component of the VAC chemotherapy regimen. Actinomycin D binds DNA, preventing chain elongation and inhibiting RNA polymerase and topoisomerase activity. In cellular and animal models of chronic lymphocytic leukemia (CLL), this compound downregulates expression of Bcl-2 and Mcl-1, induces apoptosis, inhibits cellular proliferation, and decreases tumor burden.