title: Variable expression of protein kinase C epsilon in human melanoma cells regulates sensitivity to TRAIL-induced apoptosis.
abstract: Protein kinase C (PKC) activation is believed to protect against apoptosis induced by death receptors. We have found however that the effect of activation of PKC on tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis of melanoma differs between cell lines. Pretreatment with phorbol 12-myristate 13-acetate (PMA) led to inhibition of apoptosis in the majority of the melanoma cell lines, but those with relatively low PKC epsilon expression were sensitized to TRAIL-induced apoptosis. Introduction of PKC epsilon into PKC epsilon-low cell lines reversed sensitization of the cells to TRAIL-induced apoptosis by PMA. In contrast, a dominant-negative form of PKC epsilon caused an increase in sensitivity. The changes in sensitivity to TRAIL-induced apoptosis were reflected in similar changes in conformation of Bax and its relocation from the cytosol to mitochondria. Similarly, there were concordant increases or decreases in mitochondrial release of second mitochondria-derived activator of caspase/DIABLO, activation of caspase-3, and processing of its substrates. Activation of PKC seemed to mediate its effects upstream of mitochondria but downstream of caspase-8 and Bid in that pretreatment with PMA did not cause significant changes in the expression levels of TRAIL death receptors, alterations in the levels of caspase-8 activation, or cleavage of Bid. PKC activated the anti-apoptotic extracellular signal-regulated kinase 1/2 pathway, but inhibitors of this pathway only partially reversed the protective effect of PKC against TRAIL-induced apoptosis. These results provide further insights into the variable responses of melanoma to TRAIL-induced apoptosis and may help define responsive phenotypes to treatment of melanoma with TRAIL.
authors.affiliation: Immunology and Oncology Unit, Newcastle Mater Hospital, Room 443, David Maddison Clinical Sciences Building, Corner King & Watt Streets, Newcastle, New South Wales 2300, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Gillespie
authors.forename: Xu Dong
authors.initials: XD
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Hersey
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors; D006801:Humans; D008545:Melanoma / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D011493:Protein Kinase C / Q000096:biosynthesis*; D051744:Protein Kinase C-epsilon; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D053221:TNF-Related Apoptosis-Inducing Ligand; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases; D013755:Tetradecanoylphorbol Acetate