title: Protein kinase C-activating tumor promoters modulate the DNA damage response in UVC-irradiated TK6 cells.
abstract: 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a non-genotoxic tumor promoter that dysregulates the protein kinase C (PKC) pathway and causes variable cellular responses to DNA damage in different experimental models. In the present study, we pretreated human lymphoblastoid TK6 cells (wild-type p53) for 72 h with TPA, and five other PKC-activating tumor promoters, to determine how sustained exposure to these chemicals modulates key DNA damage response (DDR) endpoints induced by UVC-irradiation. Here we show that pre-treatment with PKC-activating tumor promoters augmented the sensitivity of TK6 cells to UVC-irradiation characterized by a synergistic increase in apoptosis compared to that induced by either stress alone. In addition, high residual levels of the DNA damage repair signal γH2AX was observed in tumor promoter treated cells indicating a delayed DDR recovery. NH32 (p53-null, isogenic to TK6) cells were resistant to the synergistic effects on apoptosis implicating p53 as a central mediator of the DDR modulating effects. In addition, analysis of p53 target genes in TPA-pre-treated TK6 cells revealed a significant modulation of UVC-induced gene expression that supported a shift toward a pro-apoptotic phenotype. Therefore, sustained exposure to tumor promoting agents modulates the UVC-induced DDR in TK6 cells, which may represent important synergistic interactions that occur during tumor promotion.
authors: DuPont Haskell Global Centers for Health & Environmental Sciences, P.O. Box 30, 1090 Elkton Road, Newark, DE, USA; University of the Sciences, Department of Biological Sciences, Cell and Molecular Biology Graduate Program, Philadelphia, PA, USA.
authors: Kyle P
authors: KP
authors: Glover
authors: DuPont Haskell Global Centers for Health & Environmental Sciences, P.O. Box 30, 1090 Elkton Road, Newark, DE, USA.
authors: Lauren K
authors: LK
authors: Markell
authors: DuPont Haskell Global Centers for Health & Environmental Sciences, P.O. Box 30, 1090 Elkton Road, Newark, DE, USA.
authors: E Maria
authors: EM
authors: Donner
authors: DuPont Haskell Global Centers for Health & Environmental Sciences, P.O. Box 30, 1090 Elkton Road, Newark, DE, USA. Electronic address: xing.han@dupont.com.
authors: Xing
authors: X
authors: Han
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D002273:Carcinogens / Q000378:metabolism* / Q000528:radiation effects / Q000633:toxicity; D002460:Cell Line; D045744:Cell Line, Tumor; D004249:DNA Damage; D004789:Enzyme Activation / Q000528:radiation effects; D016158:Genes, p53 / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation / Q000528:radiation effects; D011493:Protein Kinase C / Q000378:metabolism* / Q000528:radiation effects; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity; D014158:Transcription, Genetic / Q000235:genetics / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D017304:Annexin A5; D002273:Carcinogens; C468783:H2AX protein, human; D006657:Histones; D012313:RNA; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate
keywords: DNA damage response; TPA; Tumor promotion; p53