PKCdelta-mediated regulation of FLIP expression in human colon cancer cells.
FLICE-like inhibitory protein (FLIP), a naturally occurring caspase-inhibitory protein that lacks the critical cysteine domain necessary for catalytic activity, is a negative regulator of Fas-induced apoptosis. Decreased FLIP levels sensitize tumor cells to Fas- and TRAIL-mediated apoptosis; however, the cellular mechanisms regulating FLIP expression have not been defined. Here, we examined the roles of the PKC and NF-kappaB pathway in the regulation of FLIP in human colon cancers. FLIP mRNA levels were increased in Caco-2 cells by treatment with PMA; actinomycin D completely inhibited the induction of FLIP by PMA, indicating transcriptional regulation. PKC inhibitors Gö6983 and Ro-31-8220 blocked PMA-stimulated FLIP expression. Pretreatment with the PKCdelta-selective inhibitor rottlerin or transfection with PKCdelta siRNA inhibited PMA-induced FLIP expression, which identifies a role for PKCdelta in FLIP induction. Treatment with the proteasome inhibitor, MG132, or the NF-kappaB inhibitor (e.g., PDTC and gliotoxin), or overexpression of the superrepressor of IkappaB-alpha inhibited PMA-induced upregulation of FLIP. Moreover, PMA-induced NF-kappaB transactivation was blocked by GF109203x. In conclusion, our results demonstrate a critical role for PKCdelta/NF-kappaB in the regulation of FLIP in human colon cancer cells.
Wang
Qingding
Q
Department of Surgery, University of Texas Medical Branch, Galveston, TX 77555, USA.
Wang
Xiaofu
X
Zhou
Yuning
Y
Evers
B Mark
BM
D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D018938:Caco-2 Cells; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000235:genetics*; D016328:NF-kappa B / Q000502:physiology; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000502:physiology*; D014158:Transcription, Genetic
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D051745:Protein Kinase C-delta