Interaction between celecoxib and docetaxel or cisplatin in human cell lines of ovarian cancer and colon cancer is independent of COX-2 expression levels

Celecoxib, an inhibitor of cyclooxygenase-2 (COX-2), is being investigated for enhancement of chemotherapy efficacy in cancer clinical trials. We determined whether continuous exposure to celecoxib would increase the antiproliferative effects of a 1-h treatment with docetaxel or cisplatin in four human ovarian cancer cell lines. COX-2 protein could not be detected in these cell lines, because of which three COX-2 positive human colon cancer cell lines were included. Multiple drug effect analysis demonstrated additive to borderline antagonistic effects of celecoxib combined with docetaxel. Combination indices with values of 1.4-2.5 in all cancer cell lines indicated antagonism between celecoxib and cisplatin regardless whether celecoxib preceded cisplatin for 3h, was added simultaneously or immediately after cisplatin. Apoptotic features measured in COX-2-negative H134 ovarian cancer cells and COX-2-positive WiDr colon cancer cells, such as the activation of caspase-3 and the number of cells in sub-G0 of the cell cycle, induced by docetaxel were increased in the presence of celecoxib, but were abrogated upon addition of celecoxib to cisplatin. Moreover, the G2/M accumulation in cisplatin-treated cells was less pronounced when celecoxib was present. Drugs did not affect p-Akt. Celecoxib upregulated p-ERK1/2 in H134 cells, but not in WiDr cells. Platinum-DNA adduct formation measured in WiDr cells, however, was reduced when celecoxib was combined with cisplatin. Taken together, our data demonstrate clear antagonistic effects when celecoxib is given concurrently with cisplatin, which is independent of COX-2 expression levels.     

Cyclooxygenase-2 (COX-2)-dependent and -independent anticarcinogenic effects of celecoxib in human colon carcinoma cells

Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, is the only non-steroidal anti-inflammatory drug so far which has been approved by the FDA for adjuvant treatment of patients with familial adenomatous polyposis. The molecular mechanism responsible for the anticarcinogenic effects of celecoxib is still not fully understood. To investigate the extent to which the anticarcinogenic effect of celecoxib depends on COX-2 expression, we transfected human colon carcinoma cells (Caco-2) with the human COX-2 cDNA, in both sense and in antisense orientation, to generate cells which either overexpress COX-2 (human COX-2-sense, hCOX-2-s), express no COX-2 (human COX-2-antisense, hCOX-2-as) or express only very small amounts of COX-2 (control cells). Treatment of these cells with celecoxib dose-dependently (0-100microM) reduced cell survival which was accompanied by an induction of a G(0)/G(1) phase block and apoptosis. The effect of celecoxib treatment on both, cell survival and induction of apoptosis in hCOX-2-as cells was less marked than in the COX-2-expressing cells. Apoptosis was accompanied by an activation of caspase-3 and caspase-9 and cytochrome c release. In contrast, we observed no difference in sensitivity with regard to the induction of a cell cycle block between the different cell clones. The G(0)/G(1) phase block caused by celecoxib correlated with a decrease in expression levels of cyclin A and cyclin B1 and an increase in the expression of the cell cycle inhibitory proteins p21(Waf1) and p27(Kip1) irrespective of the type of cell used. These data indicate that apoptosis-inducing effects of celecoxib partly depend on COX-2 expression of the cells, whereas induction of a cell cycle block occurred COX-2 independently. Thus, the anticarinogenic effects of celecoxib can be explained by both COX-2-dependent and -independent mechanisms.     

Celecoxib analogs that lack COX-2 inhibitory function: preclinical development of novel anticancer drugs

Celecoxib is an NSAID that was developed as a selective inhibitor of COX-2 and approved by the FDA for the treatment of various forms of arthritis and the management of acute or chronic pain. In addition, it was more recently approved as an oral adjunct to prevent colon cancer development in patients with familial adenomatous polyposis and is presently being investigated for its chemotherapeutic potential in the therapy of advanced cancers. However, in laboratory studies it was discovered that celecoxib was able to suppress tumor growth in the absence of any apparent involvement of COX-2, and additional pharmacologic activities associated with this drug were found. Intriguingly, the two pharmacologic effects, inhibition of COX-2 and suppression of tumor growth, were found to reside in different structural aspects of the celecoxib molecule and, therefore, could be separated. This dualism enabled the synthesis of close structural analogs of celecoxib that exhibited increased antitumor potency in the absence of COX-2 inhibition. In theory, such compounds should be superior to celecoxib for antitumor purposes because they might reduce gastrointestinal and cardiovascular risks and the life-threatening side effects that appear during the long-term use of selective COX-2 inhibitors. In this review, the authors present the status of preclinical development of anticancer analogs of celecoxib that are COX-2 inactive, with an emphasis on 2,5-dimethyl-celecoxib (DMC) and OSU-03012.     

Clinical pharmacology of celecoxib, a COX-2 selective inhibitor

NSAIDs are extensively used worldwide; nonetheless, they are associated with adverse gastrointestinal (GI) effects. COX-2 inhibitors (coxibs) have been developed to reduce pain and inflammation without associated GI and bleeding risks. Celecoxib was the first COX-2 inhibitor introduced on the market, and it still remains so, whereas rofecoxib and valdecoxib were withdrawn due to excess cardiovascular (CV) risk. There is consequently a concern that CV toxicity reflects a class effect of all COX-2 inhibitors. Celecoxib possesses anti-inflammatory and analgesic properties, and the evidence for CV risk is rather small and comparable to that of other traditional NSAIDs in short-term treatments (of < 4 weeks). It could be suggested that the use of low doses of celecoxib (100 mg b.i.d.) in short-treatment, especially in patients with previous experience of GI events and the recommendation of avoiding use of celecoxib in patients with CV history or risk, contribute in the decision-making process of prescribing COX-2 or NSAIDs.     

Thalidomide inhibits growth of tumors through COX-2 degradation independent of antiangiogenesis

Thalidomide is an antiangiogenic drug and is clinically useful in a number of cancers. However, the molecular mechanism by which thalidomide exerts its antitumor effects is poorly understood. This study was designed to clarify the relationship between antiangiogenesis and antitumor effects of thalidomide and to explore the molecular mechanism for its antitumor activity. We evaluated the effects of thalidomide on the growth of human tumor cells expressing (MCF-7 and HL-60) or not expressing (HeLa and K562) COX-2 in vitro. We also studied the effects of thalidomide on COX-1, COX-2 or bcl-2 expression, TNFalpha, VEGF, GSH and cytochrome c in these cells. Thalidomide could inhibit tumor growth in a concentration-dependent manner in MCF-7 and HL-60; its IC50s for them were 18.36+/-2.34 and 22.14+/-2.15 microM, respectively, while this effect was not observed in HeLa and K562. Thalidomide reduced COX-2 expression accompanied by a decrease of bcl-2 protein, TNFalpha, VEGF, GSH and an increased cytochrome c, but had no effect on that of COX-1, in MCF-7 and HL-60. Moreover, cells not expressing COX-2 were insensitive to the growth-inhibitory and effects on cytokines of thalidomide. In our mouse xenograft model of OVCAR-3 and HCT-8, we found that thalidomide could decrease intratumoral microvessel density in both tumors; it exerted antitumor effects only on OVCAR-3 expressing COX-2 but did not on HCT-8 not expressing COX-2. Effect of thalidomide on COX-1 and COX-2 in vivo was consistent with that of in vitro. These results demonstrated that thalidomide might inhibit growth of tumors through COX-2 degradation independent of antiangiogenesis.     

The anti-proliferative potency of celecoxib is not a class effect of coxibs

Celecoxib, a COX-2 (cyclooxygenase-2)-selective inhibitor (coxib), is the only NSAID (non-steroidal anti-inflammatory drug) that has been approved for adjuvant treatment of patients with familial adenomatous polyposis. To investigate if the anti-proliferative effect of celecoxib extends to other coxibs, we compared the anti-proliferative potency of all coxibs currently available (celecoxib, rofecoxib, etoricoxib, valdecoxib, lumiracoxib). Additionally, we used methylcelecoxib (DMC), a close structural analogue of celecoxib lacking COX-2-inhibitory activity. Due to the fact that COX-2 inhibition is the main characteristic of these substances (with exception of methylcelecoxib), we conducted all experiments in COX-2-overexpressing (HCA-7) and COX-2-negative (HCT-116) human colon cancer cells, in order to elucidate whether the observed effects after coxib treatment depend on COX-2 inhibition. Cell survival was assessed using the WST proliferation assay. Apoptosis and cell cycle arrest were determined using flow cytometric and Western blot analysis. The in vitro results were confirmed in vivo using the nude mouse model. Among all coxibs tested, only celecoxib and methylcelecoxib decreased cell survival by induction of cell cycle arrest and apoptosis and reduced the growth of tumor xenografts in nude mice. None of the other coxibs (rofecoxib, etoricoxib, valdecoxib, lumiracoxib) produced anti-proliferative effects, indicating the lack of a class effect and of a role for COX-2. Our data emphasize again the outstanding anti-proliferative activity of celecoxib and its close structural analogue methylcelecoxib in colon carcinoma models in vitro and in vivo.     

Anti-inflammatory and analgesic effect of LD-RT and some novel thiadiazole derivatives through COX-2 inhibition

Generally, highly selective COX-2 inhibitors cause cardiovascular side effects. Celecoxib is the highly marketed coxib, so there is still a need for the synthesis of COX-2 inhibitors with less adverse effects. Moreover, low-dose radiotherapy (LD-RT) is clinically used for the treatment of inflammatory diseases. The present study aimed to investigate the analgesic and anti-inflammatory activity of a novel series of 1,3,4-thiadiazole derivatives alone or combined with LD-RT with a single dose of 0.5 Gy. Initially, in vitro COX-1/COX-2 inhibition assays were performed, identifying the sulfonamide-containing compounds 5 – 10 as the most potent candidates, with IC₅₀ values in the range of 0.32–0.37 µM and the highest selectivity indices. These compounds and celecoxib were subjected to in vivo examination after their safety was assessed through the acute toxicity test. Treatment with compounds 5 – 10 inhibited carrageenan-induced edema by nearly 47–56%, which was nearly equivalent to celecoxib. Compounds 7 and 8 and celecoxib showed an analgesic activity of 64.15%, 49.05%, and 84.90%, respectively, whereas compounds 5 , 6 , 9 , and 10 did not show any analgesic activity unless combined with LD-RT. Ulcerogenic activity, histological paw examination, and docking studies were performed. Compounds 5 – 10 were nearly similar to celecoxib, showing normal histological features with no ulcerogenic activity.     

柚皮苷对人卵巢癌SKOV3细胞环氧化酶2mRNA及蛋白表达水平的影响

目的：研究中药柚皮苷对人卵巢癌SK—OV3细胞环氧化酶2（CoX-2）tuRNA及蛋白表达水平的影响。方法：常规培养人卵巢癌sK—OV3细胞,分为空白对照组、柚皮苷10umol／L组、柚皮苷20tzmol／L组、柚皮苷40umol／L组、阳性对照组（塞来昔布80tLmol／L）。MTT法测定柚皮苷对人卵巢癌SKOV3细胞增殖的影响,运用Real—timePCR和WesternBlot法测定培养48h后各组细胞中COX_2mRNA和蛋白表达水平的变化。结果：MTT检测法显示,柚皮苷各浓度处理组,时间依赖性和剂量依赖性地抑制人卵巢癌SKOV3细胞生长。经药物处理48h后,Real-timePCR结果显示,与空白对照组（1．094±0．053）比较,10、20umol／L柚皮苷即对SK—OV3细胞COX_2mRNA表达抑制作用（O．828±0．006,0．753±0．011,P〈0．05）,而40gmol／L柚皮苷则明显下调COX-2mRNA的表达（0．412±0．216,P〈0．01）,与塞来昔布组（0．321±0．017）的抑制程度相近。WesternBlot法检测结果显示,与空白对照组（1．7325±0．0826）相比,10umol／L柚皮苷组相对表达量（1．7925±0．0880）虽略有上调,但无统计学差异,20、40／umol／L柚皮苷组均可明显下调SKOV3细胞COX-2蛋白的表达（1．2225±0．0822,1．2725±0．0763,P〈0．05）,塞来昔布组也明显抑制CoX-2蛋白的表达。结论：柚皮苷可抑制人卵巢癌SKOV3细胞体外增殖并抑制COX-2mRNA和蛋白的表达。     

Compositions for treatment of cancer and inflammation

Celecoxib (Celebrex, Pfizer, NY, USA) is a worldwide top branded COX-2-specific inhibitor. It was shown to provide relief of arthritic pain and inflammation and has recently been under investigation for the prevention and treatment of cancer. However, recent studies showed that long term use of high doses of celecoxib is associated with an increased cardiovascular toxicity. We discovered that the addition of curcumin, a natural COX-2 inhibitor, to celecoxib synergistically (up to 1000%) augments the growth inhibitory effects of celecoxib in in-vitro and in-vivo models of arthritis and cancer, thus rendering effective action of the drug at up to tenfold lower dose. This may pave the way for a novel strategy to treat arthritis and cancer because its effect [1] can be achieved in the serum of patients receiving standard anti inflammatory or anti-neoplastic dosages of celecoxib, and [2] involves a regimen with a very low profile of side effects. Preliminary data suggest that the combination is not limited only to celecoxib and that addition of curcumin to other NSAIDs such as sulindac, synergistically augments neoplastic cell growth inhibition. Based on these finding we received an IRB approval to evaluate celecoxib+curcumin in patients with osteoarthritis, pancreatic cancer and metastatic CRC. We hope to complete these novel human clinical trials, in 12-18 months.     

塞来昔布对膀胱癌细胞T24 增殖的影响

目的观察塞来昔布对人膀胱癌细胞T24增殖的影响,并探讨其可能的作用机制。方法不同浓度塞来昔布（25、50、100和200μmoL·L^-1）分别作用于人膀胱癌细胞T24不同时间（24h、48h和72h）,MTT检测T24细胞增殖抑制率,半定量RT-PCR和Western-blot检测T24细胞中COX-2表达的变化。结果塞来昔布对膀胱癌T24细胞抑制作用存在剂量、时间依赖性,200μmoL·L^-1塞来昔布作用72h时抑制率达75.7±1.9%,明显高于其它各组（P〈0.05或0.01）;半定量RT-PCR和Western-blot方法显示塞来昔布可显著降低T24细胞中COX-2mRNA和蛋白水平（P〈0.05）,且呈时间依赖性。结论塞来昔布可通过减少COX-2的表达抑制人膀胱癌细胞T24的增殖,并呈时间和剂量依赖性。     

塞来昔布对肝癌HepG2 HepG3细胞的免疫增敏作用

目的探讨选择性环氧合酶-2（COX-2）抑制剂塞来昔布（Celecoxib）对人肝癌HepG2和HepG3细胞株对肿瘤坏死因子相关的凋亡诱导配体（TRAIL）的增敏作用及其可能机制。方法以人HepG2 HepG3肝癌细胞为研究对象,以塞来昔布和TRAIL作为干预手段,采用四甲基偶氮唑蓝（MTT）法检测塞来昔布对肝癌细胞株的增殖抑制作用,采用流式细胞术,检测塞来昔布联合TRAIL对HepG2,HepG3细胞的凋亡及DR4,DR5的表达。塞来昔布与不同效靶比的细胞因子诱导的杀伤细胞（CIK）联合作用于人肝癌细胞株,经LDH检测法检测其杀伤作用。结果塞来昔布及TRAIL对人肝癌HepG2和HepG3细胞株均有显著抑制作用,塞来昔布联合TRAIL可显著增敏TRAIL对HepG2和HepG3的杀伤,其差异具有统计学意义（P〈0.05）,经过塞来昔布预处理的肝癌细胞更易被CIK细胞杀伤。结论塞来昔布对人肝癌HepG2和HepG3细胞株具有明显细胞毒性,联合TRAIL及CIK可显著增敏后者对肝癌细胞的杀伤效应,其机制可能与塞来昔布上调DR4,DR5有关。     

Mathematical analysis of involvement ratio between central and peripheral COX-2 in rat pain models with two types of COX-2 inhibitors with different distribution, celecoxib and CIAA

The purpose of this study is to clarify involvement ratios between central and peripheral cyclooxygenase (COX)-2 in rat inflammatory pain models, by evaluating celecoxib and [6-chloro-2-(4-chlorobenzoyl)-1H-indol-3-yl]acetic acid (CIAA) on carrageenan-induced mechanical and thermal hyperalgesia. Celecoxib and CIAA exhibited ID(30) values with 1.5 and 7.7 mg/kg on mechanical hyperalgesia, respectively, and ID(25) values with 0.54 and 36 mg/kg on thermal hyperalgesia, respectively. By solving quadratic functional analysis with prostaglandin E(2) (PGE(2)) inhibitory activities, it was calculated that involvement ratios between central and peripheral COX-2 involvement were 0.47 and 0.53 on mechanical hyperalgesia, and 0.97 and 0.03 on thermal hyperalgesia, respectively. These data suggest that central and peripheral COX-2 are equally involved in mechanical hyperalgesia, while central COX-2 is predominantly involved in thermal hyperalgesia.     

Effects of the selective COX-2 inhibitors celecoxib and rofecoxib on human vascular cells

Rheumatoid arthritis (RA) is associated with a reduced life expectancy considered to be partly caused by cardiovascular events. A growing concern is that accelerated atherosclerosis is driven by inflammatory mechanisms similar to those responsible for RA. Therefore, selective COX-2 inhibitors, which are widely used for the symptomatic treatment of pain and inflammation in RA, may have an impact on atherosclerotic processes. Their anti-inflammatory properties might provoke anti-atherogenic effects but on the other hand, selective inhibition of anti-thrombotic prostacyclin and COX-2 independent effects might promote the risk of increased prothrombotic activity. In the current study, the effects of the presently marketed selective COX-2 inhibitors celecoxib and rofecoxib on vascular cells have been investigated. Celecoxib inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. At high concentrations, it induced apoptosis and the modulation of inhibitory cell cycle proteins. In contrast rofecoxib-even at high concentrations-had no effect on cell proliferation, apoptosis or cell cycle distribution indicating that celecoxib and rofecoxib do not affect the same signal transduction pathways in endothelial cells. Both drugs did not affect apoptosis induction or cell cycle proliferation in human vascular smooth muscle cells. The observed effects on endothelial cells appear to be COX-independent since both drugs selectively inhibited COX-2-activity and the applied concentrations lay beyond the IC(50) for inhibition of prostacyclin production. Regarding endothelial apoptosis as a relevant event in the initiation and progression of atherosclerosis the present data put forward the hypothesis that the presently marketed COX-2 inhibitors have a different impact on atherosclerotic processes.     

Pharmacological profile of celecoxib, a specific cyclooxygenase-2 inhibitor

The pharmacological profile of celecoxib (CAS 169590-42-5, SC-58635), a specific cyclooxygenase-2 (COX-2) inhibitor, was investigated. Celecoxib inhibited COX-2-mediated prostaglandin E2 (PGE2) production in human dermal fibroblasts (IC50 = 91 nmol/l), whereas it was a weak inhibitor of COX-1-mediated PGE2 production in human lymphoma cells (IC50 = 2800 nmol/l). In in vivo studies, the effects of celecoxib were compared with those of nonsteroidal anti-inflammatory drugs (NSAIDs) in acute rat models of hyperalgesia and pyrexia. Celecoxib abrogated carrageenan-induced hyperalgesia in the hind paw accompanied by a decrease in PGE2 content in paw exudates and cerebrospinal fluid in a dose-related manner, with an ED30 = 0.81 mg/kg. Its analgesic potency was comparable to those of NSAIDs. In lipopolysaccharide-induced pyrexia, the anti-pyretic potency of celecoxib was equal to that of NSAIDs. On the other hand, in a gastric toxicity study in rats, single oral administration of celecoxib had no effect on gastric mucosa or mucosal PGE2 content at doses up to 200 mg/kg. Additionally, celecoxib did not inhibit thromboxane B2 production of calcium ionophore-stimulated peripheral blood of rats or arachidonic acid-induced aggregation of human platelets. These findings suggest that celecoxib might be a safe and effective alternative to NSAIDs for clinical use.     

CDK2 and mTOR are direct molecular targets of isoangustone A in the suppression of human prostate cancer cell growth

Licorice extract which is used as a natural sweetener has been shown to possess inhibitory effects against prostate cancer, but the mechanisms responsible are poorly understood. Here, we report a compound, isoangustone A (IAA) in licorice that potently suppresses the growth of aggressive prostate cancer and sought to clarify its mechanism of action. We analyzed its inhibitory effects on the growth of PTEN-deleted human prostate cancer cells, in vitro and in vivo. Administration of IAA significantly attenuated the growth of prostate cancer cell cultures and xenograft tumors. These effects were found to be attributable to inhibition of the G1/S phase cell cycle transition and the accumulation of p27^kip1. The elevated p27^kip1 expression levels were concurrent with the decrease of its phosphorylation at threonine 187 through suppression of CDK2 kinase activity and the reduced phosphorylation of Akt at Serine 473 by diminishing the kinase activity of the mammalian target of rapamycin (mTOR). Further analysis using recombinant proteins and immunoprecipitated cell lysates determined that IAA exerts suppressive effects against CDK2 and mTOR kinase activity by direct binding with both proteins. These findings suggested that the licorice compound IAA is a potent molecular inhibitor of CDK2 and mTOR, with strong implications for the treatment of prostate cancer. Thus, licorice-derived extracts with high IAA content warrant further clinical investigation for nutritional sources for prostate cancer patients.     

COX-2 inhibitors block chemotherapeutic agent-induced apoptosis prior to commitment in hematopoietic cancer cells

Enzymatic inhibitors of pro-inflammatory cyclooxygenase-2 (COX-2) possess multiple anti-cancer effects, including chemosensitization. These effects are not always linked to the inhibition of the COX-2 enzyme. Here we analyze the effects of three COX-2 enzyme inhibitors (nimesulide, NS-398 and celecoxib) on apoptosis in different hematopoietic cancer models. Surprisingly, COX-2 inhibitors strongly prevent apoptosis induced by a panel of chemotherapeutic agents. We selected U937 cells as a model of sensitive cells for further studies. Here, we provide evidence that the protective effect is COX-independent. No suppression of the low basal prostaglandin (PG)E₂ production may be observed upon treatment by COX-2 inhibitors. Besides, the non-active celecoxib analog 2,5-dimethyl-celecoxib is able to protect from apoptosis as well. We demonstrate early prevention of the stress-induced apoptotic signaling, prior to Bax/Bak activation. This preventive effect fits with an impairment of the ability of chemotherapeutic agents to trigger apoptogenic stress. Accordingly, etoposide-induced DNA damage is strongly attenuated in the presence of COX-2 inhibitors. In contrast, COX-2 inhibitors do not exert any anti-apoptotic activity when cells are challenged with physiological stimuli (anti-Fas, TNFα or Trail) or with hydrogen peroxide, which do not require internalization and/or are not targeted by chemoresistance proteins. Altogether, our findings show a differential off-target anti-apoptotic effect of COX-2 inhibitors on intrinsic vs. extrinsic apoptosis at the very early steps of intracellular signaling, prior to commitment. The results imply that an exacerbation of the chemoresistance phenomena may be implicated.