Up-Regulation of 150-kDa Oxygen-Regulated Protein by Celecoxib in Human Gastric Carcinoma Cells

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 Ca 2ϩ , whereas 1,2-bis(2-aminophenoxy)ethane-N,N,NЈ,NЈ-tetraacetic acid-acetoxymethyl ester, an intracellular Ca 2ϩ chelator, inhibited the up-regulation of ORP150 and the activation of the ATF4 and ATF6 pathways. These results suggest that these Ca 2ϩ -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.

Oxygen-regulated protein-150 prevents calcium homeostasis deregulation and apoptosis induced by oxidized LDL in vascular cells

“…21,23 Furthermore, our data show that Ca 2 þ -mobilization early evoked by oxLDLs, and blocked by the calcium chelator BAPTA and by IP 3 channel inhibitors 2-APB and xestospongin C, is also involved in the expression of ORP150, in agreement with previous reports on celecoxib-induced ORP150 upregulation 26 (inhibited by BAPTA). The early Ca 2 þ mobilization evoked by oxLDLs has been reported in various cell types including macrophages, smooth muscle cells and platelets.…”

“…These data are consistent with the protective effect of ORP150 against calcium-mediated toxicity, reported in various in vitro and in vivo conditions, including ischemia/reperfusion, 21 glutamate toxicity 19 or treatment with Celecoxib. 26 Our data point out the ability of ORP150 to maintain calcium homeostasis as a crucial mechanism of its protective effect against oxLDL-induced apoptosis, since the apoptotic events (activation of calpain and of the mitochondrial apoptotic pathway) were completely blocked. Interestingly, this capacity to regulate calcium homeostasis is shared by other ER-resident chaperones, such as GRP78 (Bip) and GRP94, which may prevent hypoxia-induced apoptosis by inhibiting intracellular calcium rise, calpain and caspase activation.…”

“…This is consistent with the observation that neural, myocardial, macrophagic or tumoral cells expressing low level of ORP150, induced by specific antisense, siRNA or in heterozygous deficient cells (ORP150 þ /À), exhibited an increased vulnerability to hypoxia, ischemia-reperfusion, glutamate or celecoxib. 16,18,19,21,23,26,28 Conversely, the stable expression of ORP150 in ORP-HMEC enhanced significantly the cellular resistance to oxLDL-induced apoptosis. Interestingly, this is consistent with the protective effect of ORP150 against apoptosis induced by hypoxia in renal cells HEK16, cardiomyocytes 21 and neural cells.…”

Prevention of UVB Radiation-induced Epidermal Damage by Expression of Heat Shock Protein 70

“…Positive clones were maintained in the presence of 200 g/ml G418. Cell viability was determined by the MTT method as previously described (34), and the measurements of caspase-3-like activity and fluorescence-activated cell sorting analysis (for measurement of apoptotic cells in sub-G 1 ) were performed as described previously (34).…”

Untangling the unfolded protein response

“…Under hypoxic conditions the HIF1α (hypoxia-inducible factor 1α) isoform is stabilized promoting cell survival, [41][42][43] including upregulation of angiogenic factors, activation of NFκB, accumulation of p53 and upregulation of Grp170 (Orp150), a BiP-like protein that acts as a chaperone for VEGF, consequently promoting angiogenesis. 44 This adaptive response may prove to be an important mechanism which can be targeted by HSP90 inhibitors as the HIF1α-VEGF-angiogenic pathway is highly reliant on HSP90 and its inhibition results in oxygen-independent proteasomal degradation of HIF1α. 42,43,45,46 Alternate arms of the UPR pathway, which may also be targeted by HSP90 inhibitors, apart from HIF1α, include the activation of the IRE1α and PERK pathways, both of which are activated as a result of hypoxia.…”