title: Ingenol 3-angelate induces dual modes of cell death and differentially regulates tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in melanoma cells.
abstract: Ingenol 3-angelate (PEP005), one of the active ingredients in an extract from Euphorbia peplus, was shown in preclinical studies to have activity against human melanoma xenografts in nude mice. In the present study, we have tested its ability to induce the apoptosis of melanoma cells in vitro in the absence or presence of tumor necrosis factor-related apoptosis inducing ligand (TRAIL). The results showed that at relatively high concentrations (100 microg/mL), PEP005 killed melanoma cells mainly by induction of necrosis. In 20% of cell lines, evidence of apoptosis was observed. Apoptosis was caspase-dependent and associated with changes in mitochondrial membrane potential that were not inhibitable by overexpression of Bcl-2 or inhibition of caspases but were blocked by inhibition of protein kinase C (PKC). Low concentrations (1 or 10 microg/mL) of PEP005 either increased or decreased TRAIL-induced apoptosis in a cell line-dependent manner. These changes in TRAIL-induced apoptosis seemed to be due to activation of PKC and varying levels of PKC isoenzymes in different melanoma cell lines. PEP005-mediated enhancement of apoptosis seemed to be associated with low expression of the PKCepsilon isoform. These results indicate that PEP005 may enhance or inhibit sensitivity of melanoma to treatments associated with TRAIL-induced apoptosis depending on the PKC isoform content of melanoma cells.
authors.affiliation: Oncology & Immunology Unit, Royal Newcastle Hospital, Newcastle, New South Wales, Australia.
authors.forename: Susan K
authors.initials: SK
authors.lastname: Gillespie
authors.forename: Xu Dong
authors.initials: XD
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Hersey
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D020169:Caspases / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004952:Esters / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008545:Melanoma / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051744:Protein Kinase C-epsilon; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012878:Skin Neoplasms / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology
chemical_list: C486592:3-ingenyl angelate; D051017:Apoptosis Regulatory Proteins; D004224:Diterpenes; D004952:Esters; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D020169:Caspases