Suppression of intestinal polyp development by nimesulide, a selective cyclooxygenase-2 inhibitor, in Min mice

Potential utility of COX-2 inhibitors in chemoprevention and chemotherapy

Increased prostaglandin (PG) production is associated with many inflammatory pathophysiological conditions; it is derived from arachidonic acid by either of two enzymes: cyclooxygenase-1 or -2 (COX-1 or COX-2). In addition to its role in inflammation, recent work suggests COX-2 derived prostaglandins may play a pivotal part in the maintenance of tumour viability, growth and metastasis. In this review, we summarise the non-steroidal anti-inflammatory drug (NSAID) epidemiological evidence, studies demonstrating overexpression of COX-2 in multiple human tumours and the pharmacological evidence in animal models which also support this hypothesis. We also discuss the potential functional roles of COX-2 activity during tumourigenesis, and speculate on the mechanism by which COX-2 inhibitors may exert their anticancer effects.

The clinical potential of cyclooxygenase-2-specific inhibitors

Emerging evidence suggests that cyclooxygenase-2 (COX-2) has diverse physiologic and pathophysiologic functions. It is expressed constitutively in the developing kidney and brain, playing a role in their proper maturation and function. Further, COX-2 expression may be up-regulated at certain sites: in the kidney during sodium restriction; in the microglia of cognitive centers within the hippocampus and cortex in Alzheimer's disease; and in intestinal adenomas and colon tumors. On the basis of COX-2 expression in Alzheimer's disease and colon cancer, COX-2-specific inhibitors may find clinical utility in the prevention or treatment of these conditions. Despite this apparently optimistic outlook for future uses of COX-2 inhibitors, most of the findings supporting this perspective are based on in vitro and in vivo models and must be rigorously corroborated in human studies, some of which are already planned.

Chemopreventive effect of N-(2-cyclohexyloxy-4-nitrophenyl)methane sulfonamide (NS-398), a selective cyclooxygenase-2 inhibitor, in rat colon carcinogenesis induced by azoxymethane

Non-steroidal anti-inflammatory drugs (NSAIDs) such as sulindac and indomethacin inhibit colon carcinogenesis, and selective cyclooxygenase (COX)-2 inhibitors are considered to be potential chemopreventive agents without the side effects of usual NSAIDs. We reported that NS-398, N-(2-cyclohexyloxy-4-nitrophenyl)methane sulfonamide, suppressed the formation of preneoplastic lesions, aberrant crypt foci (ACF), induced by azoxymethane (AOM) in a short-term assay of rat colon carcinogenesis. In this study, we examined the effects of long-term NS-398 administration on rat colon carcinogenesis. After three AOM treatments at weekly intervals, a dose of 10 mg/kg of NS-398 in 5% Arabic gum solution was administered by gavage three times per week in group 2 until the termination of the experiment. Rats in group 1 were fed in a basal diet and given 5% Arabic gum solution alone after AOM treatment. At 40 weeks after the first AOM treatment, all rats were killed and the whole intestines including colon were examined. While the incidences of whole intestinal and colon neoplasms in group 1 were 84.6% and 80.8%, respectively, those in group 2 (given NS-398) were 51.9% and 44.4% respectively (P=0.0177 and P=0.0103 by Fisher's exact test, respectively). The multiplicities in group 2 (0.67+/-0.78 and 0.48+/-0.58) were also decreased significantly compared with those (1.39+/-1.10 and 1.08+/-0.74) in group 1 (P<0.01 by Welch's method and P<0.002 by Student's t test, respectively). In immunohistochemistry for proliferative cell nuclear antigen (PCNA), the PCNA-stained cell index (7.40+/-0.5) in group 2 was significantly decreased from that in group 1 (14.03+/-0.82) (P<0.001 by Welch's method). The results suggest that NS-398, a selective COX inhibitor, has a chemopreventive activity against colon carcinogenesis without side-effects such as gastric ulceration.

Inhibitory effects of nabumetone, a cyclooxygenase-2 inhibitor, and esculetin, a lipoxygenase inhibitor, on N-methyl-N-nitrosourea-induced mammary carcinogenesis in rats

We investigated the modifying effects of nabumetone, a relatively selective cyclooxygenase-2 inhibitor, and esculetin, a lipoxygenase inhibitor, on N-methyl-N-nitrosourea(MNU)-induced mammary carcinogenesis in female Sprague-Dawley rats. A total of 124 rats, 6 weeks old, were divided into 6 groups. At 50 days of age, groups 1, 2, and 3 were treated with MNU (50 mg/kg body weight) by subcutaneous injection. From the age of 8 weeks, groups 2 and 4 were given 0.03% nabumetone in the diet and groups 3 and 5 were given 0.03% esculetin in the diet. All rats were necropsied at the termination (25 weeks after the start of experiment). The incidence and multiplicity of neoplasms in group 2 were significantly smaller than those in group 1 (P < 0.005 and P < 0.001, respectively). The incidence of neoplasms in group 3 was also significantly smaller than that in group 1 (P < 0.05). These results indicate that the intake of nabumetone or esculetin during the time corresponding to the post initiation phase has a chemopreventive effect on MNU-induced mammary carcinogenesis in rats.