Novel target for induction of apoptosis by cyclo-oxygenase-2 inhibitor SC-236 through a protein kinase C-beta(1)-dependent pathway.
Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of gastrointestinal cancers. Recently, a similar protective effect has been demonstrated by the specific cyclo-oxygenase-2 (COX-2) inhibitors. However, the exact mechanism that accounts for the anti-proliferative effect of specific COX-2 inhibitors is still not fully understood, and it is still controversial whether these protective effects are predominantly mediated through the inhibition of COX-2 activity and prostaglandin synthesis. Identification of molecular targets regulated by COX-2 inhibitors could lead to a better understanding of their pro-apoptotic and anti-neoplastic activities. In the present study, we investigated the effect and the possible molecular target of a COX-2-specific inhibitor SC-236 on gastric cancer. We showed that SC-236 induced apoptosis in gastric cancer cells. However, this effect was not dependent on COX-2 inhibition. SC-236 down-regulated the protein expression and kinase activity of PKC-beta(1), increased the expression of PKCdelta and PKCeta, but did not alter the expression of other PKC isoforms in AGS cells. Moreover, exogenous prostaglandins or PGE(2) receptor antagonists could not reverse the inhibition effect on PKCbeta(1) by SC-236, which suggested that this effect occurred through a mechanism independent of cyclo-oxygenase activity and prostaglandin synthesis. Overexpression of PKCbeta(1) attenuated the apoptotic response of AGS cells to SC-236 and was associated with overexpression of p21(waf1/cip1). Inhibition of PKCbeta(1)-mediated overexpression of p21(waf1/cip1) partially reduced the anti-apoptotic effect of PKCbeta(1). The down-regulation of PKCbeta(1) provides an explanation for COX-independent apoptotic effects of specific COX-2 inhibitor in cultured gastric cancer cells. We also suggest that PKCbeta(1) act as survival mediator in gastric cancer, and its down-regulation by COX-2 inhibitor SC-236 may provide new target for future treatment of gastric cancer.
Jiang
Xiao-Hua
XH
Department of Gastroenterology, Rui-jin Hospital, Shanghai, PR China.
Lam
Shiu-Kum
SK
Lin
Marie C M
MC
Jiang
Shi-Hu
SH
Kung
Hsiang-Fu
HF
Slosberg
Eric D
ED
Soh
Jae Won
JW
Weinstein
I Bernard
IB
Wong
Benjamin Chun-Yu
BC
D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D016373:DNA, Antisense / Q000494:pharmacology; D015536:Down-Regulation; D016259:Genes, myc / Q000502:physiology; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011453:Prostaglandins / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology*; D018078:Receptors, Prostaglandin E / Q000378:metabolism; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D013449:Sulfonamides / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D000096926:Benzenesulfonamides
D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins; D016861:Cyclooxygenase Inhibitors; D016373:DNA, Antisense; D007527:Isoenzymes; D011453:Prostaglandins; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011720:Pyrazoles; D018078:Receptors, Prostaglandin E; D013449:Sulfonamides; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; C119130:4-(5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl)benzenesulfonamide; D000096926:Benzenesulfonamides; C493956:CDKN1A protein, human