Phorbol-12-Myristate-13-Acetate (PMA) is a diester of phorbol and is a tumor promoting compound extracted from croton oil. PMA is a reversible, highly potent protein kinase C (PKC) activator in vitro and in vivo at nM concentrations. PMA′s effects on PKC are attributed to its similarity to diacylgylerol, a natural activator of PKC. PMA activates Ca2+-ATPase and potentiates forskolin-induced cAMP formation. PMA has been shown to inhibit apoptosis induced by the Fas antigen, but PMA induces apoptosis in HL-60 promyelocytic leukemia cells. PMA is also known as Phorbol-12-Myristate-13-Acetate, TPA, 12-O-Tetradecanoylphorbol-13-acetate, PKC Activator I, and tetradecanoic acid, (1aR,1bS,4aR,7aS,7bS,8R,9R,9aS)-9a-(acetyloxy)-1a,1b,4,4a,5,7a,7b,8,9,9a-decahydro-4a,7b-dihydroxy-3-(hydroxymethyl)-1,1,6,8-tetramethyl-5-oxo-1H-cyclopropa[3,4]benz[1,2-e]azulen-9-yl ester.