Phorbol 12-myristate 13-acetate (PMA) also commonly known as 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a phorbol ester that is commonly used to activate phospholipid-dependent protein kinase (protein kinase C). PMA/ TPA possesses potential antineoplastic effects and was studied in phase II clinical trials together with dexamethasone in patients with relapsed or refractory acute myeloid leukemia. In addition, PMA/ TPA participated in phase I trial for treating patients with hematologic cancer or bone marrow disorder that has not responded to previous treatment. Nevertheless, both clinical trials were terminated. Besides, PMA/ TPA was studied in patients with solid tumors, which had depressed white blood cell and neutrophil counts because of prior treatment with cytotoxic cancer chemotherapeutic drugs. It was shown, that the drug increased the low white blood cell and neutrophil counts toward the normal range.