title: Induction of senescence in diterpene ester-treated melanoma cells via protein kinase C-dependent hyperactivation of the mitogen-activated protein kinase pathway.
abstract: The diterpene ester PEP005 is a novel anticancer agent that activates protein kinase C (PKC) and induces cell death in melanoma at high doses. We now describe the in vitro cytostatic effects of PEP005 and the diterpene ester phorbol 12-myristate 13-acetate, observed in 20% of human melanoma cell lines. Primary cultures of normal human neonatal fibroblasts were resistant to growth arrest, indicating a potential for tumor selectivity. Sensitive cell lines were induced to senesce and exhibited a G(1) and G(2)-M arrest. There was sustained expression of p21(WAF1/CIP1), irreversible dephosphorylation of the retinoblastoma protein, and transcriptional silencing of E2F-responsive genes in sensitive cell lines. Activation of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) 1/2 by PKC was required for diterpene ester-induced senescence. Expression profiling revealed that the MAP kinase inhibitor HREV107 was expressed at a higher transcript level in resistant compared with sensitive cell lines. We propose that activation of PKC overstimulates the RAS/RAF/MEK/ERK pathway, resulting in molecular changes leading to the senescent phenotype.
authors.affiliation: Melanoma Genomics Group, Queensland Institute of Medical Research, Brisbane, Queensland, Australia.
authors.forename: Sarah-Jane
authors.initials: SJ
authors.lastname: Cozzi
authors.forename: Peter G
authors.initials: PG
authors.lastname: Parsons
authors.forename: Steven M
authors.initials: SM
authors.lastname: Ogbourne
authors.forename: Julie
authors.initials: J
authors.lastname: Pedley
authors.forename: Glen M
authors.initials: GM
authors.lastname: Boyle
mesh_terms: D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000187:drug effects; D004224:Diterpenes / Q000494:pharmacology*; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004952:Esters / Q000494:pharmacology*; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008545:Melanoma / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: C486592:3-ingenyl angelate; D004224:Diterpenes; D050687:E2F1 Transcription Factor; D004952:Esters; D007527:Isoenzymes; D016160:Retinoblastoma Protein; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate