Induction of cIAP-2 in human colon cancer cells through PKC delta/NF-kappa B.
Activation of protein kinase C (PKC) prevents apoptosis in certain cells; however, the mechanisms are largely unknown. Inhibitors of apoptosis (IAP) family members, including NAIP, cIAP-1, cIAP-2, XIAP/hILP, survivin, and BRUCE, block apoptosis by binding and potently inhibiting caspases. Activation of NF-kappa B contributes to cIAP-2 induction; however, the cellular mechanisms regulating cIAP-2 expression have not been entirely defined. In this study, we examined the role of the PKC and NF-kappa B pathways in the regulation of cIAP-2 in human colon cancers. We found that cIAP-2 mRNA levels were markedly increased in human colon cancer cells by treatment with the phorbol ester, phorbol-12-myristate-13-acetate (PMA), or bryostatin 1. Inhibitors of the Ca2+-independent, novel PKC isoforms, but not inhibitors of MAPK, PI3-kinase, or PKA, blocked PMA-stimulated cIAP-2 mRNA expression, suggesting a role of PKC in PMA-mediated cIAP-2 induction. Pretreatment with the PKC delta-selective inhibitor rottlerin or transfection with an antisense PKC delta oligonucleotide inhibited PMA-induced cIAP-2 expression, whereas cotransfection with a PKC delta plasmid induced cIAP-2 promoter activity, which, taken together, identifies a role for PKC delta in cIAP-2 induction. Treatment with the proteasome inhibitor, MG132 or inhibitors of NF-kappa B (e.g. PDTC and gliotoxin), decreased PMA-induced up-regulation of cIAP-2. PMA-induced NF-kappa B activation was blocked by either GF109203x, MG132, PDTC, or gliotoxin. Moreover, overexpression of PKC delta-induced cIAP-2 promoter activity and increased NF-kappa B transactivation, suggesting regulation of cIAP-2 expression by a PKC delta/NF-kappa B pathway. In conclusion, our findings demonstrate a role for a PKC/NF-kappa B-dependent pathway in the regulation of cIAP-2 expression in human colon cancer cells. These data suggest a novel mechanism for the anti-apoptotic function mediated by the PKC delta/NF-kappa B/cIAP-2 pathway in certain cancers.
Wang
Qingding
Q
Department of Surgery and the Sealy Center for Cancer Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
Wang
Xiaofu
X
Evers
B Mark
BM
D003110:Colonic Neoplasms / Q000473:pathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D011506:Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004791:Enzyme Inhibitors; D016328:NF-kappa B; D011506:Proteins; D012333:RNA, Messenger; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate