Actinomycin D (dactinomycin) is a metabolite produced by Streptomyces parvullus (formerly S. antibioticus) that acts as an inhibitor of transcription, and it is able to block hypoxia-induced HIF-1 activity in the human hepatoma cell line Hep3B. The gene discussed is HIF1A; the disease is hepatocellular carcinoma.