Abstract
Induction of apoptosis by nonsteroidal anti-inflammatory drugs, such as celecoxib, is involved in their antitumor activity. An endoplasmic reticulum chaperone, 150-kDa oxygen-regulated protein (ORP150) is essential for the maintenance of cellular viability under hypoxia and is reported to be overexpressed in clinically isolated tumors. We here found that ORP150 was up-regulated by celecoxib in human gastric carcinoma cells. In conjunction with the suppression of tumor growth, orally administered celecoxib up-regulated ORP150 in xenograft tumors. Both the ATF4 and ATF6 pathways were activated by celecoxib, and suppression of ATF4 and ATF6 mRNA expression by small interfering RNA (siRNA) inhibited the celecoxib-dependent up-regulation of ORP150. Celecoxib administration led to an increase in the intracellular concentration of Ca2+, whereas 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethyl ester, an intracellular Ca2+ chelator, inhibited the up-regulation of ORP150 and the activation of the ATF4 and ATF6 pathways. These results suggest that these Ca2+-activated pathways are involved in the celecoxib-mediated up-regulation of ORP150. Clones overexpressing ORP150 were less susceptible to celecoxib-induced, but not staurosporine-induced, apoptosis and displayed less up-regulation of C/EBP homologous transcription factor (CHOP), a transcription factor with apoptosis-inducing activity. In contrast, siRNA for ORP150 stimulated apoptosis and expression of CHOP in the presence of celecoxib but not staurosporine. These results suggest that up-regulation of ORP150 in cancer cells inhibits celecoxib-induced apoptosis, thereby decreasing the potential antitumor activity of celecoxib.
Footnotes
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We thank to Dr. K. Kawahara (Kumamoto University) for helpful suggestions. This work was supported by grants-in-aid for scientific research from the Ministry of Health, Labor, and Welfare of Japan as well as by the Suzuken Memorial Foundation, the Tokyo Biochemical Research Foundation, Kumamoto Technology and Industry Foundation, and the Japan Research Foundation for Clinical Pharmacology.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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doi:10.1124/mol.106.027698.
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ABBREVIATIONS: NSAID, nonsteroidal anti-inflammatory drug; COX, cyclooxygenase; PG, prostaglandin; AGS, apoptosis in human gastric carcinoma; ER, endoplasmic reticulum; IRE1, protein-kinase and site-specific endoribonuclease; PERK, eukaryotic translation initiation factor2 kinase; ATF, activating transcription factor; eIF2α, eukaryotic initiation factor-2α; CHOP, C/EBP homologous transcription factor; ORP150, 150-kDa oxygen-regulated protein; GRP, glucose-regulated protein; AM, acetoxymethyl ester; BAPTA, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; PARP, poly(ADP-ribose)polymerase; siRNA, small interfering RNA; PCR, polymerase chain reaction; FITC, fluorescein isothiocyanate; FACS, fluorescence activated cell sorting; PI, propidium iodide; PIPES, piperazine-N,N′-bis(2-ethanesulfonic acid); CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate; RT-PCR, reverse transcription-polymerase chain reaction; ERSE, endoplasmic reticulum stress response element; XBP-1, X box binding protein; ROSE, reactive oxygen species; VEGF, vascular endothelial growth factor.
- Received June 6, 2006.
- Accepted December 12, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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