Phorbol ester-induced apoptosis in prostate cancer cells via autocrine activation of the extrinsic apoptotic cascade: a key role for protein kinase C delta.
It is well established that activation of protein kinase C (PKC) by phorbol esters promotes apoptosis in androgen-dependent prostate cancer cells. However, there is limited information regarding the cellular mechanisms involved in this effect. In this report we identified a novel autocrine pro-apoptotic loop triggered by PKCdelta activation in prostate cancer cells that is mediated by death receptor ligands. The apoptotic effect of phorbol 12-myristate 13-acetate in LNCaP cells was impaired by inhibition or depletion of tumor necrosis factor alpha-converting enzyme, the enzyme responsible for tumor necrosis factor alpha (TNFalpha) shedding. Moreover, the apoptogenic effect of conditioned medium collected after phorbol 12-myristate 13-acetate treatment could be inhibited by blocking antibodies against TNFalpha and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), but not FasL, as well as by RNA interference depletion of TNFalpha and TRAIL receptors. Moreover, depletion or inhibition of death receptor downstream effectors, including caspase-8, FADD, p38 MAPK, and JNK, significantly reduced the apoptogenic effect of the conditioned medium. PKCdelta played a major role in this autocrine loop, both in the secretion of autocrine factors as well as a downstream effector. Taken together, our results demonstrate that activation of PKCdelta in prostate cancer cells causes apoptosis via the release of death receptor ligands and the activation of the extrinsic apoptotic cascade.
Gonzalez-Guerrico
Anatilde M
AM
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA.
Kazanietz
Marcelo G
MG
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D001483:Base Sequence; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051745:Protein Kinase C-delta / Q000378:metabolism*; D034622:RNA Interference; D012334:RNA, Neoplasm / Q000235:genetics; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000037:antagonists & inhibitors / Q000235:genetics; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000037:antagonists & inhibitors / Q000235:genetics; D053221:TNF-Related Apoptosis-Inducing Ligand; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D000911:Antibodies, Monoclonal; D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D012334:RNA, Neoplasm; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate