Effect Of Selective Cyclooxygenase-2 Inhibitor Research Articles

Differential involvement of cyclooxygenase isoforms in neutrophil migration in vivo and in vitro

Pretreatment using celecoxib, a cyclooxygenase (COX) 2 inhibitor, or indomethacin, a nonselective COX inhibitor, reduced lypopolyssaccharide (LPS)-induced leukocyte migration to the rat peritoneal cavity. The effect of celecoxib (12 mg/kg) or indomethacin (2 mg/kg) on neutrophil chemotaxis induced by formyl-methionyl-leucyl-phenylalanine (FMLP) in an in vitro chemotactic assay (Boyden chamber) was investigated. Celecoxib and indomethacin inhibited chemotaxis induced by FMLP (Control = 26.6 ± 1.45, Celecoxib = 12.8 ± 3.04, Indomethacin = 6.26 ± 2.19 cells/field). When observed under intravital microscopy, a mouse cremaster preparation was used to assess the microvasculature to further investigate which step of cell recruitment was affected by these drugs. Celecoxib and indomethacin inhibited leukocyte migration induced by 0.05 μg/kg LPS injected into the cremaster muscle. However, the effect of celecoxib was associated with reduced cell rolling and adhesion, whereas indomethacin was only effective at inhibiting cell adhesion. Furthermore, SC560 pretreatment (a COX-1 selective inhibitor) of normal or LPS-challenged tissues did not alter leukocyte migration or cell adhesion, but it did enhance leukocyte rolling activity in both cases. Taken together, these results indicate that: 1) COX-1 activity is mainly related to leukocyte traffic under physiological conditions, and 2) COX-2 activity is mainly related to cell traffic under inflammatory conditions in vascular beds, suggesting a possible effect of selective COX-2 inhibitors on the expression of adhesion molecules.

Effects of a non‐selective COX inhibitor and selective COX‐2 inhibitors on contractility of human and porcine ureters in vitro and in vivo

Anti-inflammatory drugs are used in the treatment of acute renal colic. The aim of this study was to investigate the effects of selective COX-2 inhibitors and the non-selective COX inhibitor diclofenac on contractility of human and porcine ureters in vitro and in vivo, respectively. COX-1 and COX-2 receptors were identified in human ureter and kidney. Human ureter samples were used alongside an in vivo pig model with or without partial ureteral obstruction. COX-1 and COX-2 receptors were located in human ureters by immunohistochemistry. Diclofenac and valdecoxib significantly decreased the amplitude of electrically-stimulated contractions in human ureters in vitro, the maximal effect (Vmax) being 120 and 14%, respectively. Valdecoxib was more potent in proximal specimens of human ureter (EC50=7.3 x 10(-11) M) than in distal specimens (EC50=7.4 x 10(-10) M), and the Vmax was more marked in distal specimens (22.5%) than in proximal specimens (8.0%) in vitro. In the in vivo pig model, parecoxib, when compared to the effect of its solvent, significantly decreased the maximal amplitude of contractions (Amax) in non-obstructed ureters but not in obstructed ureters. Diclofenac had no effect on spontaneous contractions of porcine ureter in vivo. COX-1 and COX-2 receptors were found to be expressed in proximal and distal human ureter and in tubulus epithelia of the kidney. Selective COX-2 inhibitors decrease the contractility of non-obstructed, but not obstructed, ureters of the pig in vivo, but have a minimal effect on electrically-induced contractions of human ureters in vitro.

Effects of nimesulide, a cyclooxygenase-2 selective inhibitor, on colitis induced tumors

Cyclooxygenase-2 (COX-2) is known to suppress sporadic colorectal cancer, but effect of selective COX-2 inhibitor in UC-associated neoplasia is still unknown. This study investigated effect of a selective COX-2 inhibitor on colorectal carcinogenesis in experimental murine UC. Chronic colitis was induced in mice by four cycles of administration of dextran sulfate sodium (DSS) (i. e., 5 % DSS for 7 days and distilled water for the following 14 days), and the mice were sacrificed 120 days after the end of the fourth cycle. The mice were divided into the following five groups: Group A, served as a disease control; Group B, received a diet mixed with 400 ppm of nimesulide (NIM), a selective COX-2 inhibitor, during the whole period; Group C, received NIM during the four cycles of DSS administration; Group D, received NIM for 120 days from the end of the fourth cycle; Group E, served as a normal control. In Group D, NIM significantly suppressed the occurrence of dysplasia and/or cancer. The results show that NIM inhibited both dysplasia and cancer in DSS-treated mice, thus showing that NIM has preventive effects on the remission phase of carcinogenesis.

Differential effects of selective cyclooxygenase-2 inhibitors in inhibiting proliferation and induction of apoptosis in oral squamous cell carcinoma

Cyclooxygenase-2 (COX-2), an enzyme that catalyzes the synthesis of prostaglandins, is made inducible by various stimuli such as inflammation. Although COX-2 is commonly overexpressed in a variety of premalignant and malignant conditions including oral leukoplakia and squamous cell carcinoma, relatively little research has compared the effects of various COX-2 inhibitors (celecoxib, NS-398, nimesulide and meloxicam). Therefore, we investigated the effects of four different selective COX-2 inhibitors on the growth of KB cells, derived from oral squamous cell carcinoma (OSCC) and its mechanisms. Celecoxib and NS-398 strongly suppressed the proliferation of KB cells at 10-100 microM, whereas nimesulide and meloxicam are less potent proliferation inhibitors. Only celecoxib induced apoptosis of the KB cells, as detected on the basis of DNA fragmentation, caspase-3/7 activation and cleaved poly(ADP-ribose) polymerase (PARP) fragmentation. All four COX-2 inhibitors increased COX-2 protein expression but suppressed prostaglandin (PG) E2 production in the KB cells, suggesting that the pro-apoptotic effect of celecoxib was unrelated to the inhibition of COX-2. Mechanistically, a high level of p53 protein and a low level of multidrug-resistant protein 1 (MRP1) and breast cancer resistant protein (BCRP) mRNA in KB cells with celecoxib may explain the differential effect of these selective COX-2 inhibitors in KB cells. Taken together, celecoxib is a good therapeutic candidate for treating OSCC through the suppression of cell proliferation and the induction of apoptosis in a COX-2 independent manner.

Use of Nonsteroidal Antiinflammatory Drugs

Clinical trial data have prompted questions about the degree to which patients and their physicians should consider an increased risk of cardiovascular or cerebrovascular events when selecting medications for pain relief. Since the 2005 publication of a Science Advisory on the use of nonsteroidal antiinflammatory drugs (NSAIDs) by the American Heart Association,1 several important events have occurred that have served as the catalyst for this update for clinicians. (1) Additional data from randomized controlled trials of cyclooxygenase (COX)-2–selective agents have been reported and summarized in meta-analyses, which has reinforced the concern about cardiovascular events with COX-2 inhibitors (coxibs; Figure 1). (2) Several reports have appeared that have identified an increased risk of cardiovascular events even with the nonselective NSAIDs, which has raised concern about the use of those agents as well (Table). (3) Regulatory authorities in several regions of the world have introduced warning statements and advisories to both healthcare professionals and the lay public about the use of various NSAIDs (Figures 2 and 3⇓). Figure 1. Comparison of effects of different selective COX-2 inhibitors vs placebo on myocardial infarction. Event numbers and person-years of exposure, with corresponding mean annual event rates in parentheses, are presented for patients allocated to selective COX-2 inhibitor or placebo. Event rate ratios for pooled data with 95% CIs are indicated by a diamond; rate ratios for individual selective COX-2 inhibitors, with 99% CIs, are indicated by a square and horizontal line. Diamonds to the right of the solid line indicate hazard with a selective COX-2 inhibitor compared with placebo. As noted, there was a significant increase in the rate ratio for myocardial infarction with COX-2 inhibitors compared with placebo. Similar analyses (data not shown) include rate ratios of 1.42 (1.13 to 1.78; P =0.003) for vascular events, 1.02 (0.71 to 1.47; P …

Thromboembolic Cardiovascular Risk Among Arthritis Patients Using Cyclooxygenase-2-Selective Inhibitor or Nonselective Cyclooxygenase Inhibitor Nonsteroidal Anti-inflammatory Drugs

Selective cyclooxygenase (COX)-2 inhibitors have been associated with an increased risk of thromboembolic cardiovascular (CV) events. Prior studies have found that rofecoxib has a destabilizing effect on blood pressure; however, whether this translates to an increased risk of thromboembolic CV events is unknown. The objective of this study was to evaluate risk of thromboembolic CV events among hypertensive and nonhypertensive patients treated with rofecoxib or celecoxib, nonselective nonsteroidal anti-inflammatory drugs (ns-NSAIDs), or no NSAIDs (nonusers). This was a retrospective cohort study of 31,743 adult arthritis patients enrolled in a Blue Cross/Blue Shield health insurance plan in the northeastern United States. The main outcome measure was incident acute myocardial infarction and stroke. A clinically significant channeling effect was observed where selective COX-2 inhibitor users had a more severe CV risk profile. Among normotensive patients, the hazard ratio (HR) of CV events for ns-NSAIDs, rofecoxib, or celecoxib versus nonusers was 0.91 (95% confidence interval, 0.68-1.21), 1.05 (0.61-1.80), and 1.19 (0.86-1.66), respectively. Among hypertensive patients, the risk of CV events for ns-NSAIDs users was not significantly different versus nonusers (HR=1.21; 0.88-1.67). However, rofecoxib was associated with a significant 2-fold increase in CV risk versus nonusers of NSAIDs (HR=2.16; 1.51-3.09), whereas celecoxib was not (HR=1.18; 0.89-1.57). These data support the hypothesis that elevated CV risk is not a drug class effect of selective COX-2 inhibitors. That this effect was specific to hypertensive patients indicates that blood pressure destabilization is likely an important contributing mechanism.

Cyclooxygenase II:A Molecular Target for Colorectal Cancer Prevention and Treatment?

PGE2 plays a key role in colon carcinogenesis. Evidence continues to accumulate that cyclooxygenase-2 (COX-2), an inducible COX isoform, represents a potential pharmacological target for the prevention and treatment of cancer, including tumors affecting the large bowels. Several mechanisms of COX-2 related tumor promotion have been identified. Some are dependent on PGE2 production (such as induction of cell proliferation, angiogenesis or local immunosuppression, inhibition of apoptosis, increase in cell motility). COX-2 expression has been demonstrated in epithelial cells of colorectal cancers and adenomas. Studies in experimental models of colon carcinogenesis show that selective COX-1 or COX-2 inhibitors reduce tumor formation and growth. Clinical studies have been initiated to determine the chemoprotective effects of selective COX-2 inhibitors in patients with familial adenomatous polyposis or sporadic adenoma. Possible cardiovascular effects will need to be taken into account in an assessment of the potential ability of any of these drugs to prevent neoplasia in the large bowel and other organs. Based on the fact that PGE2 is involved in almost all events concerning carcinogenesis, further examinations concerning mPGES-1, EP receptors, and 15-PGDH, should be promoted as a target for colon cancer prevention and therapeutics. Hence, detailed analyses are needed to clarify PGE2 related carcinogenesis.

COX-2 and the Kidney

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of pain and inflammation. Nonselective NSAIDs inhibit both cyclooxygenase (COX)-1 and COX-2. Nephrotoxicity of nonselective NSAIDs has been well documented. The effects of selective COX-2 inhibitors on renal function and blood pressure are attracting increasing attention. In the kidney, COX-2 is constitutively expressed and is highly regulated in response to alterations in intravascular volume. COX-2 metabolites have been implicated in the mediation of renin release, regulation of sodium excretion, and maintenance of renal blood flow. Similar to nonselective NSAIDs, inhibition of COX-2 may cause edema and modest elevations in blood pressure in a minority of subjects. COX-2 inhibitors may also exacerbate preexisting hypertension or interfere with other antihypertensive drugs. Occasional acute renal failure has also been reported. Caution should be taken when COX-2 inhibitors are prescribed, especially in high-risk patients (including elderly patients and patients with volume depletion).

Endogenous opioids mediate the hypoalgesia induced by selective inhibitors of cyclo-oxygenase 2 in rat paws treated with carrageenan

Mechanical hyperalgesia induced in rat paws by carrageenan (250 μg) was modified by pre-treatment with three selective inhibitors of cyclo-oxygenase-2 (COX-2); celecoxib, rofecoxib and SC236. These inhibitors raised the nociceptive threshold above the normal, non-inflamed, level, inducing a state of hypoalgesia. Such hypoalgesia was observed in different strains of rat (Holtzman, Wistar and Sprague–Dawley) and after different modes of administration of the COX-2 inhibitor (locally, in the paw, or systemically). A selective inhibitor of COX-1 (SC 560; 1–10 mg kg −1) decreased hyperalgesia but did not induce hypoalgesia. Pre-treatment with naltrexone (3 mg kg −1), an opioid receptor antagonist, did not affect carrageenan-induced hyperalgesia but abolished the hypoalgesic effects of COX-2 inhibitors, without diminishing the anti-hyperalgesic effect of indomethacin. In rats made tolerant to the anti-nociceptive effects of morphine, all anti-nociceptive effects of SC236 were abolished but the anti-hyperalgesic effects of indomethacin or SC 560 were unaffected. We conclude that, in our model of inflammatory hyperalgesia, the anti-nociceptive effect of selective COX-2 inhibitors involved the participation of endogenous opioids.

Effects of Selective Cyclooxygenase-2 Inhibitor and Omega-3 Fatty Acid on Serum Interleukin-1β, Osteocalcin, and C-Reactive Protein Levels in Rats.

The aim of this study was to evaluate the effects of selective cyclooxygenase-2 inhibitor, celecoxib, and omega-3 fatty acid on serum levels of interleukin 1-beta (IL-1β), osteocalcin (OC), and C-reactive protein (CRP) in experimental periodontitis. Experimental periodontitis in rats was induced by repeated injection of purified lipopolysaccharide (LPS) derived from Escherichia coli endotoxin. Forty-seven adult male Sprague-Dawley rats were divided into five study groups as follows: saline control, LPS, LPS + celecoxib, LPS + omega-3 fatty acid, and LPS + celecoxib + omega-3 fatty acid. Celecoxib and omega-3 fatty acid were given alone or in combination during 14 days of the experimental study period. At the end of the 2-week protocol, serum samples were obtained, and the rats were sacrificed. Serum samples were analyzed for IL-1β, OC, and CRP concentrations by enzyme-linked immunosorbent assay. Defleshed jaws were analyzed morphometrically for alveolar bone loss. Data were evaluated statistically by non-parametric tests. According to the morphometric measurements, the LPS and drug treatment groups showed significantly higher bone loss than the saline control group (P <0.05). Omega-3 fatty acid, both alone and in combination with celecoxib, revealed significantly higher IL-1β levels than LPS and celecoxib groups (P <0.05). Individual and combined administration of celecoxib and omega-3 fatty acid significantly increased OC levels compared to the LPS group (P <0.05). There were no significant differences in serum CRP levels. Celecoxib and/or omega-3 fatty acid administration does not significantly influence circulating levels of CRP. The significantly increased serum OC level observed after individual and combination administration suggests that celecoxib and omega-3 fatty acid may influence bone remodeling and thereby inhibit the progression of alveolar bone resorption. However, the failure to observe any significant inhibition of bone loss in celecoxib- and/or omega-3 fatty acid-treated rats compared to the LPS group suggests that their therapeutic effect may be reduced by other factors, such as increases in serum IL-1β promoting osteoclast activity.

The Effect of Cyclooxygenase-2 Inhibitor on the Gene Expression Profile of N-butyl-N-(4-hydroxybutyl) nitrosamine-induced Rat Urinary Bladder Cancer

Purpose: Cyclooxygenase (COX)-2 plays an important role in promoting cancer cell proliferation and angiogenesis in human bladder cancer. In this study, we investigated the antitumor or antiangiogenic effects of selective COX-2 inhibitor on N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced rat bladder tumorigenesis. Materials and Methods: Forty male Fischer 344 rats (control) were given only 0.05% BBN, while 40 rats (experimental) were administered 1,500mg/ kg celecoxib once daily and this treatment started from 1 week before their BBN treatment. Ten rats from the control groups and the experimental groups were then sacrificed at 4, 12, 16 and 24 weeks after BBN treatment. We observed all the bladders macroscopically as well as microscopically, and we measured the COX-2 expression in the bladder tissues. Utilizing a cDNA microarray, we analyzed the significant differences of gene expression between the 12 week-control group and the 12 weekexperimental group. Results: The incidence of tumor was lower in the experimental group than in the control group from week 12 to week 24. The COX-2 expressions were more significantly decreased via the BBN induction (p<0.05) in the experimental groups than in the control groups after 4 weeks. For the 12 weekexperimental group, there were 15 genes altered by the administration of selective COX-2 inhibitor, and the selective COX-2 inhibitor especially regulated transgelin, membrane metallo endopeptidase and apolipoprotein E of these 15 genes to prevent the incidence of bladder tumor. Conclusions: Selective COX-2 inhibitor has an inhibitory effect on BBNinduced rat bladder tumorigenesis. In the pre-neoplastic phase, selective COX-2 inhibitor regulates transgelin, membrane metallo endopeptidase and apolipoprotein E to prevent the incidence of bladder tumor. (Korean J Urol 2006;47:310-315)

Cyclooxygenases in hepatocellular carcinoma

Many epidemiological studies demonstrate that treatment with non-steroidal anti-inflammatory drugs (NSAIDs) reduce the incidence and mortality of certain malignancies, especially gastrointestinal cancer. The cyclooxygenase (COX) enzymes are well-known targets of NSAIDs. However, conventional NSAIDs non-selectively inhibit both the constitutive form COX-1, and the inducible form COX-2. Recent evidence indicates that COX-2 is an important molecular target for anticancer therapies. Its expression is undetectable in most normal tissues, and is highly induced by pro-inflammatory cytokines, mitogens, tumor promoters and growth factors. It is now well-established that COX-2 is chronically overexpressed in many premalignant, malignant, and metastastic cancers, including hepatocellular carcinoma (HCC). Overexpression of COX-2 in patients with HCC is generally higher in well-differentiated HCCs compared with less-differentiated HCCs or histologically normal liver, suggesting that COX-2 may be involved in the early stages of hepatocarcinogenesis, and increased expression of COX-2 in noncancerous liver tissue has been significantly associated with shorter disease-free survival in patients with HCC. In tumors, overexpression of COX-2 leads to an increase in prostaglandin (PG) levels, which affect many mechanisms involved in carcinogenesis, such as angiogenesis, inhibition of apoptosis, stimulation of cell growth as well as the invasiveness and metastatic potential of tumor cells. The availability of novel agents that selectively inhibit COX-2 (COXIB), has contributed to shedding light on the role of this molecule. Experimental studies on animal models of liver cancer have shown that NSAIDs, including both selective and non-selective COX-2 inhibitors, exert chemopreventive as well as therapeutic effects. However, the key mechanism by which COX-2 inhibitors affect HCC cell growth is as yet not fully understood. Increasing evidence suggests the involvement of molecular targets other than COX-2 in the anti-proliferative effects of COX-2 selective inhibitors. Therefore, COX-inhibitors may use both COX-2-dependent and COX-2-independent mechanisms to mediate their antitumor properties, although their relative contributions toward the in vivo effects remain less clear. Here we review the features of COX enzymes, the role of the expression of COX isoforms in hepatocarcinogenesis and the mechanisms by which they may contribute to HCC growth, the pharmacological properties of COX-2 selective inhibitors, the antitumor effects of COX inhibitors, and the rationale and feasibility of COX-2 inhibitors for the treatment of HCC.

The Effects of Selective Cyclooxygenase-2 Inhibitor and Prostaglandin E2Receptor Agonists on the Endothelin Axis of Prostate Cancer Cells

Purpose: The enhanced expression of the cyclooxygenase-2 (COX-2), prostaglandin E2 receptor (EPs) and endothelin-1 (ET-1) axis is known to play a significant role in the development and progression of several malignancies. To date, little work has been done to investigate the relationships between the COX-2, EPs and ET-1 axis in prostate cancer (PC) cells. The aim of this study is to investigate the expression of preproET-1 (PPET-1), ET-1 receptor A (ETAR), and endothelin converting enzyme-1 (ECE-1) in the PC cell lines and to evaluate the effects of COX-2 and EPs on the expression of PPET-1, ETAR, and ECE-1. Materials and Methods: Two PC cell lines, PC-3 and DU-145 cells were used for this study. By performing reverse transcription polymerase chain reaction (RT-PCR), the mRNA expressions of PPET-1, ETAR and ECE-1 were detected, and then the mRNA expressions of PPET-1, ETAR and ECE-1 were detected after being treating the cells with selective COX-2 inhibitor (NS-398), or EP2 (butaprost) and EP4 (misoprostol), which are both agonist of 10, 10 and 10M. Results: PPET-1, ETAR and ECE-1 mRNA were expressed in both cell lines. After NS-398 treatment, only the PPET-1 mRNA expression was decreased at 4, 8 and 12 hours in the PC-3 cells. EP2 and EP4 agonist induced an increase for the PPET-1, ETAR and ECE-1 mRNA expressions, compared with the NS-398 treated group (control), in the PC-3 cells. Conclusions: ET-1/ETAR and ECE-1, whose expressions are increased by EP2 and EP4, may play key roles in the development and progression of PC via COX-2. A combination treatment with selective inhibitors for COX-2, EPs and ETAR would be novel approach to prostate cancer therapy. (Korean J Urol 2006;47:195-200)

More pronounced inhibition of cyclooxygenase 2, increase in blood pressure, and reduction of heart rate by treatment with diclofenac compared with celecoxib and rofecoxib

Recent findings suggest that permanent blockade of cyclooxygenase 2 (COX-2) is one factor contributing to the cardiovascular side effects of selective COX-2 inhibitors (coxibs) and nonsteroidal antiinflammatory drugs (NSAIDs). The present study compared the extent and time course of COX-2 inhibition and the effects on cardiovascular parameters (changes in blood pressure and heart rate) between various antirheumatic doses of diclofenac, celecoxib, and rofecoxib in healthy elderly volunteers. A randomized, parallel-group study was conducted in volunteers receiving 75 mg diclofenac twice daily, 200 mg celecoxib twice daily, or 25 mg rofecoxib once daily for 8 days. Blood samples were obtained predose and at specified time points postdose, on days 1 and 8, for assay of drug plasma concentrations and COX-2 inhibition. Lipopolysaccharide-induced prostaglandin E(2) synthesis was measured ex vivo as an index of COX-2 activity in human whole blood. COX-2 inhibition was significantly less pronounced after treatment with celecoxib and rofecoxib than with diclofenac. Maximal inhibitions after a single dose and at steady state, respectively, were as follows: 99% and 99% with diclofenac, 70% and 81% with celecoxib, and 56% and 72% with rofecoxib. At steady state, only diclofenac caused virtually complete COX-2 inhibition over the whole dose interval, and this corresponded to the highest increase in systolic blood pressure and greatest reduction in heart rate. Diclofenac elicited the most pronounced COX-2 inhibition, blood pressure elevation, and suppression of heart rate. It is assumed that the extent and time course of intravascular COX-2 inhibition may determine the differential profile of cardiovascular side effects associated with NSAIDs and coxibs, but this has to be proven in future studies.

Cutting Edge: Yin-Yang: Balancing Act of Prostaglandins with Opposing Functions to Regulate Inflammation

For many years, cyclooxygenase-2 (COX-2), a critical enzyme for PG production, has been the favorite target for anti-inflammatory drug development. However, recent revelations regarding the adverse effects of selective COX-2 inhibitors have stimulated intense debate. Interestingly, in the early phase of inflammation, COX-2 facilitates inflammatory PG production while in the late phase it has anti-inflammatory effects. Moreover, although some PGs are proinflammatory, others have anti-inflammatory effects. Thus, it is likely that PGs with opposing effects maintain homeostasis, although the molecular mechanism(s) remains unclear. We report here that an inflammatory PG, PGD2, via its receptor, mediates the activation of NF-kappaB stimulating COX-2 gene expression. Most interestingly, an anti-inflammatory PG (PGA1) suppresses NF-kappaB activation and inhibits COX-2 gene expression. We propose that while pro- and anti-inflammatory PGs counteract each other to maintain homeostasis, selective COX-2 inhibitors may disrupt this balance, thereby resulting in reported adverse effects.

Cyclooxygenase-2 inhibitors suppress angiogenesis and growth of gastric cancer xenografts

Many researches have confirmed the tumor-prophylactic effects of cyclooxygenase-2 (COX-2) inhibitors. We previously observed their anti-cancer effects in vivo in nude mice and found that sulindac, a traditional non-steroidal anti-inflammatory drug (NSAID), and celecoxib, a selective COX-2 inhibitor, depressed the growth of SGC7901 xenografts via altering cell kinetics. Then we deeply studied the relationship between the two drugs and angiogenesis in gastric cancer. The results showed both sulindac and celecoxib decreased the micro-vessel density (MVD), which was labeled by either CD34 or VWF staining, within xenografts. Expression of both vascular endothelial growth factor (VEGF) and FGF-1 was suppressed. In addition, a positive correlation between MVD and the volume of SGC7901 xenografts was found. The effect of selective COX-2 inhibitor was stronger than non-special one despite of the insignificant difference. These results demonstrate that COX-2 plays an important role in angiogenesis of cancer. Apart from interfering cell kinetics, decreasing the expression of angiogenic factors and then inhibiting tumor angiogenesis could also be one of the mechanisms that COX-2 inhibitors suppress the growth of gastric cancer. These findings offer another theory basis for the future clinical application of NSAIDs against cancer.

To the Heart of the Matter

When cyclooxygenase (COX)-2–selective inhibitors (coxibs) first entered the market about 5 years ago, the major concern with regard to cardiovascular side effects related to their potential to increase blood pressure and cause salt and water retention, in a manner similar to conventional (nonselective) nonsteroidal antiinflammatory drugs (NSAIDs). In the short time since, wariness about these side effects has grown into widespread alarm about putative prothrombotic actions and generation of excess major cardiovascular events with these agents. See p 1024 In September 2004, safety findings of the Adenomatous Polyp Prevention on Vioxx (APPROVe) study indicated an increase in risk for myocardial infarction and stroke among subjects randomized to rofecoxib compared with those randomized to placebo. This study had been designed to examine recurrent colonic polyps rather than cardiovascular disease end points and therefore could only be considered hypothesis generating. Subsequent data from a number of observational studies further implicated the drug’s association with arterial thromboembolic disease. As with APPROVe, no single study generated sufficiently robust attestation by itself, but they provided concordant signals, and the accumulating evidence eventually reached a critical mass. As the data on rofecoxib emerged, concerns about other COX-2–selective agents on the market also grew. This was based on the assumption of a “class effect” for an increase in risk of cardiovascular disease related to preferential inhibition of prostacyclin over thromboxane and thus a tendency toward prothrombosis. The results presented by McAdam and colleagues in this issue of Circulation 1 challenge our view with regard to this prostanoid hypothesis and raise new questions about the mechanisms underlying the potential cardiovascular side effects of coxibs and traditional NSAIDs. The authors hypothesized that the enhanced systemic biosynthesis of prostacyclin in smokers was dependent on COX-2 activity. They also sought to determine the functional importance of COX2–derived prostacyclin (PGI2) in limiting platelet activation in smokers in vivo. Contrary to the conventional wisdom of an expected increase in the biosynthesis of TxA2 (related to increased platelet activation via COX-1), the authors demonstrated the opposite finding—ie, that COX-2 contributed to, and a COX-2 inhibitor reduced, TxA2 biosynthesis in smokers.

The effect of a selective cyclooxygenase-2 (COX-2) inhibitor on the proliferation rate of retinoblastoma cell lines

To examine the effect of nepafenac, a selective cyclooxygenase-2 (COX-2) inhibitor, on the proliferation rate of two human retinoblastoma (Rb)cell lines. Two human Rb cell lines (WERI-RB and Y79) were cultured. COX-2 expression in these cell lines was verified by immunocytochemical analysis of cytospin sections and Western blotting. An MTT-based proliferation assay was used to compare Rb cell growth with and without amfenac, the active metabolite of nepafenac. The averaged results per condition were recorded. The Student's t-test was used to compare results from the cells cultured with and without amfenac. The Y79 cell line showed a higher proliferative rate than the WERI-RB cell line. Both cell lines were negative for COX-2 expression by immunocytochemical analysis; however, both cell lines were positive for COX-2 expression by Western blot. When amfenac was added to both of the cell lines, a statistically significant reduction in proliferation was observed in both cell lines. The two Rb cell lines were positive for COX-2 only in the Western blot, indicating that they probably express low levels of COX-2, which was undetectable by immunocytochemical analysis. The selective, anti-COX-2 molecule amfenac inhibited proliferation of both tested Rb cell lines. Further trials should be undertaken to study the effect of selective COX-2 inhibitors on Rb.

Effect of Selective Cyclooxygenase-2 Inhibitors on Heart Rate in Healthy Young Men

During an investigation of the possible pharmacokinetic interactions of cyclooxygenase-2 (COX-2) inhibitors with metoprolol, we observed that rofecoxib caused a significant reduction in heart rate in young healthy volunteers. The effect of valdecoxib did not reach significance. When these drugs were given together with metoprolol, the effect was continued. The latter effect could not be related to pharmacokinetic interactions. In the light of experimental results claiming a cardioprotective effect of possibly COX-2-derived prostaglandins and clinical observations hinting at an increased risk of sudden cardiovascular death in conjunction with the long-term use of selective cyclooxygenase inhibitors, our results may help to increase awareness and to suggest investigation of the impact of coxibs on heart function.

Celecoxib Inhibits Prostate Cancer Growth: Evidence of a Cyclooxygenase-2-Independent Mechanism

Selective cyclooxygenase-2 (COX-2) inhibitors may suppress carcinogenesis by both COX-2-dependent and COX-2-independent mechanisms. The primary purpose of this study was to evaluate whether celecoxib or rofecoxib, two widely used selective COX-2 inhibitors, possess COX-2-independent antitumor activity. PC3 and LNCaP human prostate cancer cell lines were used to investigate the growth inhibitory effects of selective COX-2 inhibitors in vitro. To complement these studies, we evaluated the effect of celecoxib on the growth of PC3 xenografts. COX-1 but not COX-2 was detected in PC3 and LNCaP cells. Clinically achievable concentrations (2.5-5.0 micromol/L) of celecoxib inhibited the growth of both cell lines in vitro, whereas rofecoxib had no effect over the same concentration range. Celecoxib inhibited cell growth by inducing a G(1) cell cycle block and reducing DNA synthesis. Treatment with celecoxib also led to dose-dependent inhibition of PC3 xenograft growth without causing a reduction in intratumor prostaglandin E(2). Inhibition of tumor growth occurred at concentrations (2.37-5.70 micromol/L) of celecoxib in plasma that were comparable with the concentrations required to inhibit cell growth in vitro. The highest dose of celecoxib led to a 52% reduction in tumor volume and an approximately 50% decrease in both cell proliferation and microvessel density. Treatment with celecoxib caused a marked decrease in amounts of cyclin D1 both in vitro and in vivo. Two clinically available selective COX-2 inhibitors possess different COX-2-independent anticancer properties. The anticancer activity of celecoxib may reflect COX-2-independent in addition to COX-2-dependent effects.