title: S-Phase-specific activation of PKC alpha induces senescence in non-small cell lung cancer cells.
abstract: Protein kinase C (PKC) has been widely implicated in positive and negative control of cell proliferation. We have recently shown that treatment of non-small cell lung cancer (NSCLC) cells with phorbol 12-myristate 13-acetate (PMA) during G1 phase inhibits the progression into S phase, an effect mediated by PKC delta-induced up-regulation of the cell cycle inhibitor p21 Cip1. However, PMA treatment in asynchronously growing NSCLC cells leads to accumulation of cells in G2/M. Studies in post-G1 phases revealed that PMA induced an irreversible G2/M cell cycle arrest in NSCLC cells and conferred morphological and biochemical features of senescence, including elevated SA-beta-Gal activity and reduced telomerase activity. Remarkably, this effect was phase-specific, as it occurred only when PKC was activated in S, but not in G1, phase. Mechanistic analysis revealed a crucial role for the classical PKC alpha isozyme as mediator of the G2/M arrest and senescence, as well as for inducing p21(Cip1) an obligatory event for conferring the senescence phenotype. In addition to the unappreciated role of PKC isozymes, and specifically PKC alpha, in senescence, our data introduce the paradigm that discrete PKCs trigger distinctive responses when activated in different phases of the cell cycle via a common mechanism that involves p21 Cip1 up-regulation.
authors.affiliation: Department of Pharmacology and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA. jloliva@isciii.es
authors.forename: Jose L
authors.initials: JL
authors.lastname: Oliva
authors.forename: M Cecilia
authors.initials: MC
authors.lastname: Caino
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Senderowicz
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Kazanietz
mesh_terms: D002273:Carcinogens / Q000494:pharmacology; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000187:drug effects / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D002273:Carcinogens; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007527:Isoenzymes; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D019098:Telomerase; D001616:beta-Galactosidase; D013755:Tetradecanoylphorbol Acetate