Nonsteroidal anti-inflammatory drugs as anticancer agents: mechanistic, pharmacologic, and clinical issues

Potentiation of tumor response to radiation or chemoradiation by selective cyclooxygenase-2 enzyme inhibitors

Cyclooxygenase-2 (COX-2) is an enzyme expressed primarily in pathologic states, such as inflammatory disorders and cancer, where it mediates prostaglandin production. Its overexpression is associated with more aggressive biologic tumor behavior and adverse patient outcome. Increasing evidence shows that agents that selectively inhibit COX-2 enhance tumor response to radiation or chemotherapeutic agents. This article gives an overview of some of this evidence. In addition, we describe new results showing that celecoxib, a selective COX-2 inhibitor, enhanced response of A431 human tumor xenografts in nude mice to radiation by an enhancement factor (EF) of 1.43 and to the chemotherapeutic agent docetaxel by an EF of 2.07. Celecoxib also enhanced tumor response when added to the combined docetaxel plus radiation treatment (EF = 2.13). Further experiments showed that selective COX-2 inhibitors enhanced tumor cell sensitivity to ionizing radiation, involving inhibition of cellular repair from radiation damage and cell cycle redistribution as mechanisms for some cell types. The results show that selective COX-2 inhibitors have the potential to improve tumor radiotherapy or radiochemotherapy, and this therapeutic strategy is currently under clinical testing.

Piroxicam selectively inhibits the growth of premalignant and malignant human oral cell lines by limiting their progression through the S phase and reducing the levels of cyclins and AP-1

Studies have shown that nonsteroidal antiinflammatory drugs (NSAIDs) reduce the risk of and mortality from a variety of cancers. Although cyclooxygenase (COX)-dependent and -independent pathways may be involved, the mechanisms responsible for these effects remain unknown. In our study, we found that piroxicam inhibited cell growth in premalignant and malignant, but not normal, human oral epithelial cell lines in a concentration- and time-dependent manner. After 6 days of exposure, the concentration that inhibited growth by 50% was 181 and 211 microM for premalignant and malignant cells, respectively. Piroxicam did not induce apoptosis. The growth inhibitory effect was COX and PGE2 independent. Adding PGE2 or infecting cells with a COX-1 transgene did not abrogate piroxicam-induced growth inhibition. After treatment of the premalignant and malignant cell lines with piroxicam, cells accumulated in the S phase of the cell cycle. Upon removal of piroxicam, cells entered the G2 phase. The S phase block was accompanied by a reduction in the protein levels of cyclin A, cyclin B1, cyclin D1, cdc2, PCNA and the c-jun AP-1 component. Therefore, piroxicam may exert its growth inhibitory effects selectively on the premalignant and malignant human oral epithelial cells lines via signaling pathways regulating the progression of cells through the S phase of the cell cycle.

Aspirin and the Risk of Hodgkin's Lymphoma in a Population-Based Case-Control Study

BACKGROUND

Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with decreased risk of several malignancies. NSAIDs may prevent cancer development by blocking the cyclooxygenase-catalyzed synthesis of proinflammatory prostaglandins. Aspirin may also protect against Hodgkin's lymphoma by inhibiting transcription factor nuclear factor kappaB (NF-kappaB), which is necessary for immune function and the survival of Hodgkin's lymphoma cells. We examined the association between regular analgesic use and the risk of Hodgkin's lymphoma.

METHODS

A population-based case-control study of 565 case patients with Hodgkin's lymphoma and 679 control subjects was conducted in the metropolitan area of Boston, Massachusetts, and in the state of Connecticut. Participants reported their average use of aspirin, non-aspirin NSAIDs, and acetaminophen over the previous 5 years. Regular analgesic use was defined as consumption of at least two tablets per week on average over the preceding 5 years; non-regular use was defined as consumption of fewer than two tablets per week.

RESULTS

The risk of Hodgkin's lymphoma associated with regular aspirin use was statistically significantly lower (odds ratio [OR] = 0.60, 95% confidence interval [CI] = 0.42 to 0.85) than that associated with non-regular aspirin use. The risk was not associated with use of other non-aspirin NSAIDs (OR = 0.97, 95% CI = 0.73 to 1.30). However, the risk associated with regular acetaminophen use was statistically significantly higher (OR = 1.72, 95% CI = 1.29 to 2.31) than that associated with non-regular use.

CONCLUSION

The inverse association between aspirin, but not other NSAIDs, and Hodgkin's lymphoma suggests that NF-kappaB signaling may play a key role in Hodgkin's lymphoma pathogenesis.

NO-donating aspirin inhibits intestinal carcinogenesis in Min (APC(Min/+)) mice

The chemopreventive effect of nitric oxide-releasing aspirin (NO-ASA) against gastrointestinal tumorigenesis was evaluated in Min (APC(Min/+)) mice. NO-ASA consists of a traditional ASA that bears covalently attached to it an NO-releasing moiety. Four groups (N=10) of six-week-old female C57BL/6J APC(Min/+) and the corresponding C57BL/6J(+/+) wild type mice were treated either with vehicle or NO-ASA 100 mg/kg/day intrarectally for 21 days. There were no signs of overt toxicity including gastrointestinal toxicity from NO-ASA. Vehicle treated Min mice had 24.7 +/- 3.8 tumors (mean +/- SEM) and NO-ASA treated Min mice had 10.1 +/- 1.4 tumors (59% reduction; P<0.001). Wild type mice showed no tumors. NO-ASA did not affect cell proliferation in small intestinal mucosa, determined by immunohistochemical staining for PCNA. Our findings establish the strong inhibitory effect of NO-ASA in intestinal carcinogenesis in the Min mouse and suggest that this agent merits further evaluation as a chemopreventive agent against colon cancer.

Cyclooxygenase-2 and Microsomal Prostaglandin E Synthase-1 Are Overexpressed in Squamous Cell Carcinoma of the Penis

PURPOSE

Prostaglandin E2 (PGE2) promotes malignant growth. Cyclooxygenase (COX) catalyzes the synthesis of PGH2, which is converted, in turn, by microsomal prostaglandin E synthase (mPGES-1) to PGE2. One strategy for inhibiting carcinogenesis is to prevent PGE2 production in premalignant and malignant tissues. It is important, therefore, to determine whether enzymes involved in PGE2 biosynthesis are deregulated in neoplasia. The main purpose of this study was to determine whether amounts of COX-2 or mPGES-1 were increased in intraepithelial neoplasia or squamous cell carcinoma (SCC) of the penis. Because human papillomavirus (HPV) has been linked to the development of penile SCC, a secondary objective was to determine whether COX-2 was overexpressed in SCC arising in an HPV16 transgenic mouse.

EXPERIMENTAL DESIGN

Immunohistochemistry and immunoblotting were used to evaluate the expression of COX-2 and mPGES-1 in benign and malignant lesions including metastases to lymph nodes. Amounts of intratumoral PGE2 were quantified by enzyme immunoassay. Reverse transcription-PCR was used to determine the expression of each of the four known receptors (EP(1-4)) for PGE2.

RESULTS

Immunohistochemistry demonstrated increased expression of COX-2 and mPGES-1 in dysplasia, carcinoma in situ, invasive SCC, and metastases to lymph nodes. Immunoblot analysis confirmed that COX-2 and mPGES-1 were consistently overexpressed in SCC. PGE2 and all four of the PGE2 receptor subtypes were detected in each of the tumor samples. Elevated levels of COX-2 were also detected in SCC arising in an HPV16 transgenic mouse.

CONCLUSIONS

Increased amounts of COX-2 and mPGES-1 were detected in penile intraepithelial neoplasia and carcinoma. These findings provide the basis for evaluating whether inhibiting COX-2 will be useful in the prevention or treatment of penile SCC.

Prostate Cancer Chemoprevention Agent Development: The National Cancer Institute, Division of Cancer Prevention Portfolio

PURPOSE

We describe the current National Cancer Institute chemoprevention agent development program and provide a summary of the intermediate end points used.

MATERIALS AND METHODS

The National Cancer Institute is currently sponsoring a wide range of studies of promising chemoprevention agents in a variety of informative cohorts, eg high grade prostatic intraepithelial neoplasia, positive family history of cancer, increased prostate specific antigen with negative biopsies, prostate cancer followed expectantly, prostate cancer awaiting definitive therapy and the general population. The rationale for each agent under investigation is derived from epidemiological observations, prostate cancer treatment trials, secondary analyses of large cancer prevention studies, an understanding of cancer biology and prostate carcinogenesis, and/or experimental animal models.

RESULTS

Carcinogenesis is a multistep process occurring over decades which is characterized by disruption of the normal regulatory pathways controlling cellular proliferation, programmed cell death and differentiation. Administration of agents to reverse, inhibit or slow this process of malignant transformation is known as chemoprevention.

CONCLUSIONS

Chemoprevention represents a promising approach to reducing the morbidity and mortality of prostate cancer. A variety of agents are currently being studied in phase 2 clinical trials, some of which may warrant subsequent evaluation in phase 3 trials with definitive cancer end points. Two large phase 3 trials, the Prostate Cancer Prevention Trial and the Selenium and Vitamin E Cancer Prevention Trial, which are ongoing, are also sponsored by the National Cancer Institute.

A prospective study of aspirin use and the risk of pancreatic cancer in women

BACKGROUND

In vitro experiments and limited animal studies suggest that aspirin and nonsteroidal anti-inflammatory drugs may inhibit pancreatic carcinogenesis. Because few studies have examined the association between aspirin use and pancreatic cancer in humans and the results have been inconsistent, we examined the relationship between aspirin use and the development of pancreatic cancer in the Nurses' Health Study.

METHODS

Among 88 378 women without cancer at baseline, we documented 161 cases of pancreatic cancer during 18 years of follow-up. Aspirin use was first assessed at baseline in 1980 and updated biennially thereafter. All statistical tests were two-sided.

RESULTS

Participants were classified according to history of aspirin use. In a multivariable analysis, the risk of pancreatic cancer was not associated with current regular aspirin use (defined as two or more standard tablets per week; relative risk [RR] = 1.20, 95% confidence interval [CI] = 0.87 to 1.65), compared with use of fewer than two tablets per week. Increasing duration of regular aspirin use, compared with non-use, was associated with a statistically significant increase in risk: Women who reported more than 20 years of regular aspirin use had an increased risk of pancreatic cancer (RR = 1.58, 95% CI = 1.03 to 2.43; P(trend) =.01). Among women who reported aspirin use on at least two of three consecutive biennial questionnaires compared with consistent non-users of aspirin, the risk increased with dose (one to three tablets per week: RR = 1.11, 95% CI = 0.70 to 1.76; four to six tablets per week: RR = 1.29, 95% CI = 0.70 to 2.40; seven to 13 tablets per week: RR = 1.41, 95% CI = 0.76 to 2.61; and > or = 14 tablets per week: RR = 1.86, 95% CI = 1.03 to 3.35) (P(trend) =.02).

CONCLUSION

Extended periods of regular aspirin use appear to be associated with a statistically significantly increased risk of pancreatic cancer among women.

Effects of Dexamethasone or Celecoxib on Biliary Toxicity after Hepatic Arterial Infusion of 5-Fluorodeoxyuridine in a Canine Model

Previous work has shown that in humans the dose-limiting toxicity for fluorodeoxyuridine [2-fluoro-5'-deoxyuridine (FdUrd)] when administered by hepatic arterial infusion is biliary sclerosis. The current study was undertaken to attempt to modify this toxicity in a canine model that has been demonstrated to closely mimic the clinical situation. Unlike previous studies using this model, in which animals were sacrificed after extensive fibrosis had already occurred, the current experiments were designed so that observations of pathology were made at an earlier time, when the initial inflammatory injury underlying the fibrotic process was still taking place. Implantable pumps were used to deliver FdUrd into the hepatic artery of animals at a rate of 0.3 mg/kg/day in the presence or absence of 10 mg/week dexamethasone or 100 mg/day of celecoxib for 35 days, at which time the animals were beginning to show signs of toxicity. After evaluation for radiological evidence of biliary obstruction, the animals were sacrificed and portions of their livers were processed for examination of microscopic pathology and 2-bromo-5'deoxyuridine labeling index. Dexamethasone treatment protected the animals from biliary sclerosis determined radiologically, further validating this model as being representative of the response in humans. Similarly the Cox-2 inhibitor, celecoxib, appeared to provide protection against radiological changes of biliary stricture, although possibly to a lesser degree than the resultant from dexamethasone. In addition, FdUrd treatment caused elevation of the DNA 2-bromo-5'deoxyuridine labeling index above control levels in biliary epithelial cells. Dexamethasone and celecoxib each significantly attenuated the FdUrd-induced elevation of DNA labeling index in biliary epithelium. These findings demonstrate the usefulness of this canine model for studying the mechanisms of drug-induced biliary sclerosis and reinforce the hypothesis that blocking inflammation may retard the progression of injury that eventually leads to fibrosis. This study suggests that clinical testing of celecoxib as a preventive for hepatic arterial-FdUrd induced biliary damage could prove valuable.

Celecoxib simulates respiratory burst through pertussis toxin-sensitive G-protein, a possible signal for β2-integrin expression on human neutrophils

The superoxide anion-generating effect of celecoxib (4-[5-(4-methylpheny)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide); SC58633), a selective cyclooxygenase-2 inhibitor, on human neutrophils was evaluated in this study. Celecoxib induced superoxide anion generation in a concentration-dependent manner in human neutrophils. The EC50 value of celecoxib on superoxide anion generation was 15.5+/-2.5 microM. A NADPH oxidase inhibitor, diphenyliodonium (20 microM), and superoxide dismutase (150 U/ml) completely inhibited the free radical generation caused by celecoxib, indicating that the respiratory burst was activated by celecoxib. 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) (BAPTA/AM;10 microM) and staurosporine (200 nM) completely inhibited the superoxide anion release caused by celecoxib, respectively. These data indicated that celecoxib increased superoxide anion release by increasing intracellular calcium and protein kinase C activation. Moreover, 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-C)-carbazole (Go-6976; 1 microM) and 3-[1-[3-(amidinothio)propyl-1H-indol-3-yl]-3-(1-methyl-1H-indol-3-yl)maleimide, methane sulfate (Ro-31-8220; 0.5 microM), specific inhibitors of conventional protein kinase C isotypes (alpha, beta(I) and beta(II)), significantly inhibited superoxide anion release caused by celecoxib. Rottlerin (5 microM), a protein kinase C delta inhibitor, did not affect the free radical generation caused by celecoxib. Celecoxib caused translocation of protein kinase C alpha, beta(I) and beta(II) from the cytosol to the cellular membrane. 2-[2-amino-3-methoxyphenyl]-4H-1-benzopyran-4-one (PD98059; 20 microM) and wortmannin (100 nM) did not decrease the superoxide anion generation caused by celecoxib, indicating that Mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase (PI3 kinase) were not involved in the respiratory burst induced by celecoxib. Pertussis toxin (2 microg/ml), a Gi-protein sensitive inhibitor, significantly inhibited superoxide anion release. Moreover, pertussis toxin significantly inhibited intracellular calcium mobilization and protein kinase C alpha, beta(I) and beta(II) translocation from the cytosol to the membrane. Celecoxib increased beta(2)-integrin expression on human neutrophils and this effect was inhibited by BAPTA/AM (10 microM), superoxide dismutase (150 U/ml), genistein (25 microM) and PD98059 (20 microM). This information indicated that intracellular calcium, superoxide anion, tyrosine kinase and MAP kinase are involved in beta(2)-integrin expression. Furthermore, BAPTA/AM, superoxide dismutase and genistein inhibited celecoxib-increased MAP kinase activity, indicating that MAP kinase is a downstream signal for beta(2)-integrin expression. In conclusion, celecoxib stimulates superoxide anion release from human neutrophils by activating pertussis toxin sensitive G-protein. An increase in intracellular calcium and protein kinase C alpha, beta(I) and beta(II) is involved in this process. Celecoxib also regulates beta(2)-integrin expression through superoxide anion release, tyrosine kinase and p42/p44 MAP kinase on human neutrophils.

Green tea constituent epigallocatechin-3-gallate selectively inhibits COX-2 without affecting COX-1 expression in human prostate carcinoma cells

Overexpression of cyclooxygenase (COX)-2 has been implicated in many pathologic conditions, including cancer. One practical inference of this finding is that sustained inhibition of COX-2 could serve as a promising target for prevention or therapy of cancer. Conventional nonsteroidal antiinflammatory drugs (NSAIDs) and recently developed COX-2-specific inhibitors have shown considerable promise in prevention of some forms of human cancer; however, its application is limited due to severe toxic side effects on normal cells. Therefore, there is a need to define novel, nontoxic dietary constituents with proven chemopreventive effects through other pathways that also possess COX-2 but not COX-1 inhibitory activity. Recent studies on green tea and its major polyphenolic constituent (-)epigallocatechin-3-gallate (EGCG) have established its remarkable cancer preventive and some cancer therapeutic effects. Here, we show that EGCG inhibits COX-2 without affecting COX-1 expression at both the mRNA and protein levels, in androgen-sensitive LNCaP and androgen-insensitive PC-3 human prostate carcinoma cells. Based on our study, it is tempting to suggest that a combination of EGCG with chemotherapeutic drugs could be an improved strategy for prevention and treatment of prostate cancer.

Effect of Aspirin and Indomethacin on Prostaglandin E2 Synthesis in C6 Glioma Cells

Prostaglandin E2 (PGE2) plays an important role in immunosuppression and tumor growth. PGE2 inhibitors such as aspirin and indomethacin suppress experimental tumor growth. Little is known of the relationship between PGE2 synthesis in brain tumors and the dose of aspirin or indomethacin. The present study was undertaken to evaluate the effect of different doses of aspirin and indomethacin on PGE2 synthesis in C6 glioma cells. C6 glioma cells were incubated with different concentrations (2, 4, and 8 microM) of aspirin and indomethacin for 1, 2, 4, 6, 8, 12, and 24 hours. Intracellular PGE2 concentration was measured by enzyme immunoassay. Each concentration of aspirin and indomethacin effectively inhibited PGE2 synthesis. Concentrations of 2, 4, and 8 microM of aspirin significantly inhibited PGE2 production at 6, 4, and 1 hour, respectively, and the inhibition persisted for more than 24 hours (p < 0.05). Concentrations of 2 and 4 microM of indomethacin were effective at 4 and 2 hours (p < 0.05), respectively. However, inhibition was not observed beyond 12 hours (p > 0.05). Indomethacin 8 microM was effective at 1 hour and the inhibition persisted beyond 24 hours (p < 0.05). Our study demonstrates that aspirin and indomethacin inhibit PGE2 synthesis in C6 glioma cells and that low-dose aspirin is as effective as high-dose aspirin. This study may encourage future clinical use of low-dose aspirin in the prevention or treatment of brain tumors.

Celecoxib derivatives induce apoptosisvia the disruption of mitochondrial membrane potential and activation of caspase 9

Celecoxib is a potent nonsteroid antiinflammatory drug (NSAID) that has shown great promise in cancer chemoprevention and treatment. The tumor suppression activity of celecoxib and other NSAIDs have been related to the induction of apoptosis in many cancer cell lines and animal models. While celecoxib is a specific inhibitor of cyclooxygenase (COX)-2, recent data indicate that its apoptotic properties may also be mediated through COX-independent pathways. In our study, we evaluated second generation celecoxib derivatives, lacking COX-2 inhibitory activity, in a premalignant and malignant human oral cell culture model to determine their potential anticancer effect and mechanisms responsible for the COX-independent apoptotic activity. Celecoxib and its derivatives delayed the progression of cells through the G(2)/M phase and induced apoptosis. The derivatives with apolar substituents at the terminal phenyl moiety of celecoxib greatly enhanced apoptosis and cell cycle delay. Apoptosis and cell cycle arrest appeared to be independent of derivative induced inhibition of PDK1 and phosphorylation of Akt and Erk1/2. Derivatives induced apoptosis was mediated by the cleavage and activation of caspase-9 and caspase-3, but not caspase 8, implicating the mitochondrial pathway for apoptosis induction. Inhibitors of caspase-3 and caspase-9 and cyclosporin A, a mitochondrial membrane potential stabilizer, attenuated derivative induced apoptosis. Inhibition of caspase-3 prevented the activation of caspase 8, while the inhibition of caspase-9 inhibitor blocked activation of both caspase 3 and 8 by the derivatives. Apoptosis was independent of Bcl-2. These results indicate that the second generation celecoxib derivatives induce apoptosis in human oral cancer lines by the disruption of mitochondrial membrane potential activating caspase 9 and downstream caspase 3 and 8. This suggests that the modification of the celecoxib structure can lead to highly effective COX-independent growth inhibitory and apoptotic agents in chemoprevention and therapy.

Cyclooxygenase-2 and gastric carcinogenesis

Epidemiological studies have shown that the use of nonsteroid anti-inflammatory drugs (NSAIDs) is associated with reduced risk of gastric cancer. The best-known target of NSAIDs is the cyclooxygenase (Cox) enzyme. Two Cox genes have been cloned, of which Cox-2 has been connected with gastric carcinogenesis. Expression of Cox-2 is elevated in gastric adenocarcinomas, which correlates with several clinicopathological parameters, including depth of invasion and lymph node metastasis. This suggests that Cox-2-derived prostanoids promote aggressive behavior of adenocarcinomas of the stomach. Cox-2 expression is especially prominent in intestinal-type gastric carcinoma and it is already present in dysplastic precursor lesions of this disease, which suggests that Cox-2 contributes to gastric carcinogenesis already at the preinvasive stage. Our most recent data show that Cox-2 is expressed in gastric adenomas of trefoil factor 1 deficient mice. Treatment of these mice with a Cox-2 selective inhibitor, celecoxib, reduced the size of the adenomas. Taken together these data support efforts to initiate clinical studies to investigate the effect of Cox-2 inhibitors as chemotherapeutic agents and as adjuvant treatment modalities against gastric neoplasias.

Cyclooxygenase-2 and 5-lipoxygenase converging functions on cell proliferation and tumor angiogenesis: implications for cancer therapy

Cyclooxygenase (COX) and lipoxygenase (LO) metabolic pathways are emerging as key regulators of cell proliferation and neo-angiogenesis. COX and LO inhibitors are being investigated as potential anticancer drugs and results from clinical trials seem to be encouraging. In this article we will review evidence of COX-2 and 5-LO involvement in cancer pathobiology, propose a model of integrated control of cell proliferation by these enzymes, and discuss the pharmacologic implications of this model.

Potential cost-effectiveness of colorectal cancer chemoprevention with nonsteroidal anti-inflammatory drugs

Colorectal cancer is the second leading cause of cancer-related death in the Western world. Screening for colorectal neoplasia, including the removal of adenomas, is highly effective and cost-effective in reducing colorectal cancer incidence and mortality. However, only a minority of the population is currently screened. Based on data from animal models, observational studies and randomized trials in humans, nonsteroidal anti-inflammatory drugs appear to have great promise as chemopreventive agents against colorectal cancer. The critical factors that will determine the roles of aspirin, other nonselective nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors in colorectal cancer chemoprevention include the magnitude of their protective effect, their risks, their costs, the treated population's characteristics, treatment adherence rates and how chemoprevention compares with established screening strategies.

Transcriptional profiling of the transition from normal intestinal epithelia to adenomas and carcinomas in the APCMin/+ mouse

Mutations in the adenomatous polyposis coli (APC) gene that result in excessive beta-catenin-induced cell signaling are implicated in the risk of colon cancer. Although the mechanism of APC-mediated tumorigenesis is known, the pathways that translate beta-catenin signaling into tumor growth in vivo are undefined. To address this, gene expression profiles of normal intestinal epithelial cells were compared with those from adenomas and carcinomas from APC(Min/+) mice, a model of APC-related colorectal cancer. The gene expression profiles of adenomas and carcinomas were very similar, which is consistent with the theory that carcinomas progress from adenomas in this model system. Tumors had altered transcript abundance for members of several pathways that influence cell growth and proliferation including growth factors/receptors, molecules involved in apoptosis, and protein processing and catabolism enzymes. Comparison of gene expression between adenomas and carcinomas revealed nine differentially expressed transcripts. These included members of three growth-regulating pathways, and the results are consistent with the increased growth potential of carcinomas. SRY-box containing gene 17 (Sox 17), a negative regulator of beta-catenin signaling, and calbindin-D9K, a factor that enhances calcium transport, were more highly expressed in adenomas than carcinomas (approximately 4-fold and 15- to 22-fold, respectively). Transcript abundance for insulin-like growth factor binding protein 5, which mediates insulin-like growth factor function, was 2.6-fold greater in carcinomas. Because the changes in gene expression observed in this study are directly associated with a deficiency in APC, the data provide new insights into how loss of this important tumor suppressor translates into benign and malignant tumor growth.

Arachidonic acid cascade inhibitors modulate phorbol ester-induced oxidative stress in female ICR mouse skin: differential roles of 5-lipoxygenase and cyclooxygenase-2 in leukocyte infiltration and activation

We recently developed a short-term assay for skin H2O2 generation induced by double 12-O-tetradecanoylphorbol-13-acetate (TPA) applications for mechanistic study on skin epidermal carcinogenesis. In the present study, we investigated the individual roles of arachidonic acid metabolism in H2O2 generation in mouse skin inflammation. The experiments using inhibitors of arachidonic acid (AA) metabolism showed that corticosteroid and a lipoxygenase (LO) inhibitor expectedly suppressed double TPA application-induced H2O2 generation through the interference of chemotactic action but not by direct decomposition or scavenging. We also demonstrated that the treatment of AA (1 mumol) and 5-LO metabolites including leukotriene B4 (LTB4) partly mimicked, though soybean LO-derived lipid hydroperoxide and prostaglandins did not, the priming effect evaluated by edema formation and leukocyte infiltration. We also confirmed that inflammatory leukocytes accumulated by LTB4 generated a significant amount of H2O2 by TPA stimulation. These results suggested that 5-LO metabolites of AA are the potential key molecules in the TPA-induced priming event. Interestingly, the cyclooxygenase (COX-) 2-selective inhibitor nimesulide (NS) and celecoxib (CXB) showed different responses than those of other inhibitors. These agents showed no specific potential to inhibit the priming event but significantly suppressed H2O2 generation, lipid peroxidation, and hyperplasia in mouse skin. From the results based on an in vitro leukocyte differentiation model, we speculated that the antioxidant effect of the COX-2 inhibitors might be partly associated with both counteraction of proinflammatory cytokine-enhanced ROS generation and inhibition of CD11b, an important molecule for cell adhesion, expression. Indeed, the topical application of NS attenuated the number of infiltrated leukocytes induced by TPA in mouse skin. Thus, these gathered data indicated the differential roles of 5-LO and COX-2 in leukocyte adhesion, infiltration, and H2O2 generation.

Effects of non-steroidal anti-inflammatory drugs on cancer sites other than the colon and rectum: a meta-analysis

Background

Observational studies have consistently shown that aspirin and non-steroidal anti-inflammatory drug (NSAID) use is associated with a close to 50% reduced risk of colorectal cancer. Studies assessing the effects of NSAIDs on other cancers have shown conflicting results. Therefore, we conducted a meta-analysis to evaluate the relationship between NSAID use and cancer other than colorectal.

Methods

We performed a search in Medline (from 1966 to 2002) and identified a total of 47 articles (13 cohort and 34 case-control studies). Overall estimates of the relative risk (RR) were calculated for each cancer site using random effects models.

Results

Aspirin use was associated with a reduced risk of cancer of the esophagus and the stomach (RR, 0.51; 95%CI (0.38–0.69), and 0.73; 95%CI (0.63–0.84)). Use of NSAIDs was similarly associated with a lower risk of esophageal and gastric cancers (RR,0.65; 95% CI(0.46–0.92) and RR,0.54; 95%CI (0.39–0.75)). Among other cancers, only the results obtained for breast cancer were fairly consistent in showing a slight reduced risk among NSAID and aspirin users (RR, 0.77; 95%CI (0.66–0.88), and RR, 0.77; 95%CI (0.69–0.86) respectively)).

Conclusions

The results of this meta-analysis show that the potential chemopreventive role of NSAIDs in colorectal cancer might be extended to other gastrointestinal cancers such as esophagus and stomach. Further research is required to evaluate the role of NSAIDs at other cancers sites.

Chapter 4: Genital tract infections, cervical inflammation, and antioxidant nutrients--assessing their roles as human papillomavirus cofactors

Cervical infections by approximately 15 human papillomavirus (HPV) types are the necessary cause of cervical cancer and its immediate precursor lesions. However, oncogenic HPV infections are usually benign and usually resolve within 1-2 years. A few of these infections persist and progress to cervical precancer and cancer. A number of cervical factors, such as infection by sexually transmitted pathogens other than HPV, cervical inflammation, and antioxidant nutrients, may influence the natural history of HPV infection along the pathways of persistence and progression or resolution. We examine the possible roles of these HPV cofactors in cervical carcinogenesis and discuss new methodologies that may enable researchers to measure relevant markers of the cervical microenvironment in which these cofactors may be active.

Inhibitors of cyclo-oxygenase 2: a new class of anticancer agents?

Experimental studies have shown that cyclo-oxygenase 2 (COX2) is involved in tumour development and progression. Selective inhibitors of COX2 (coxibs) block tumour growth through many mechanisms, especially by antiangiogenic and proapoptotic effects. In experimental models, coxibs potentiate the activity of cytotoxic agents, hormones, and radiotherapy. Large clinical studies have shown chemopreventive activity of coxibs in colorectal cancer. The findings of preclinical studies coupled with the overexpression of COX2 observed in advanced human tumours are the basis for new therapeutic anticancer strategies based on combinations of coxibs with other anticancer treatment modalities. Early clinical studies have documented the feasibility, good tolerability, and promising activity of coxibs combined with chemotherapy in patients with advanced colorectal and non-small-cell lung cancers. Here, we describe the recent findings on the antitumour effects of coxibs with particular focus on the opportunities that have emerged for treatment of cancer.

Should Aspirin be Used to Counteract ‘Salicylate Deficiency’?

Aspirin (acetylsalicylate) is an inexpensive drug that is used extensively to reduce cardiovascular disease risk. Emerging evidence suggests that aspirin reduces the risk of other chronic diseases such as certain forms of cancer. Salicylate may contribute to the disease reduction effects. It is present naturally in fruits and vegetables and individuals with a low intake of these foods may be 'salicylate deficient'. This deleterious state may constitute a significant public health threat. Interventions to prevent deficiency, such as low-dose aspirin programmes, could have substantial beneficial health impacts around the world.

The oncogene Nup98-HOXA9 induces gene transcription in myeloid cells

The nucleoporin Nup98 gene is frequently rearranged in acute myelogenous leukemia (AML). In most cases this results in fusion of the N terminus of Nup98 to the DNA binding domain of a homeodomain transcription factor. The prototype of these fusions, Nup98-HOXA9, is associated with human AML and induces AML in mouse models. To understand the mechanisms by which Nup98-HOXA9 causes AML, we expressed it in myeloid cells and identified its target genes using high density oligonucleotide microarrays. The analysis was performed in triplicate and was confirmed by quantitative real time PCR. Of the 102 Nup98-HOXA9 target genes identified, 92 were up-regulated, and only 10 were down-regulated, suggesting a transcriptional activation function. A similar analysis of wild-type HOXA9 revealed 13 target genes, 12 of which were up-regulated, and 1 was down-regulated. In contrast, wild-type Nup98 had no effect on gene expression, demonstrating that the HOXA9 DNA binding domain is required for gene regulation. Co-transfection experiments using a luciferase reporter linked to the promoter of one of the Nup98-HOXA9 target genes confirmed up-regulation at the transcriptional level by Nup98-HOXA9 but not by either HOXA9 or Nup98. These data indicate that Nup98-HOXA9 is an aberrant transcription factor whose activity depends on the HOXA9 DNA binding domain but has a stronger and wider transcriptional effect than HOXA9. Several of the genes regulated by Nup98-HOXA9 are associated with increased cell proliferation and survival as well as drug metabolism, providing insights into the pathogenesis and epidemiology of Nup98-HOXA9-induced AML.

Cyclo-oxygenase-2 over-expression in sporadic colorectal carcinoma without lymph node involvement

BACKGROUND

Cyclo-oxygenase-2 over-expression has been reported in most advanced human colorectal cancers.

AIMS

To assess the prevalence of cyclo-oxygenase-2 over-expression in non-advanced colorectal cancers, to investigate the correlation between cyclo-oxygenase-2 status and tumour clinicopathological features and molecular phenotype, and to determine the impact of cyclo-oxygenase-2 status on long-term clinical outcome.

METHODS

Sixty-one patients who had undergone surgery for colorectal cancer without lymph node involvement were evaluated retrospectively. Cyclo-oxygenase-2 expression was determined by immunohistochemistry. The tumour replication error phenotype was assessed by amplification of the two microsatellites, BAT-25 and BAT-26.

RESULTS

Thirty-six tumours were classified as cyclo-oxygenase-2 positive and 25 as cyclo-oxygenase-2 negative. No correlation was found between cyclo-oxygenase-2 over-expression and clinicopathological features or molecular phenotype. Cyclo-oxygenase-2 over-expression was an independent predictor of a poor prognosis. Indeed, the relative risk of tumour recurrence or death for patients with cyclo-oxygenase-2-positive tumours was 2.13 times that of patients with cyclo-oxygenase-2-negative tumours (P=0.008; 95% confidence interval, 1.22-3.73). This difference remained significant when post-operative deaths were censored in the multivariate analysis (P=0.014).

CONCLUSION

Cyclo-oxygenase-2 over-expression is not associated with tumour phenotype, but is indicative of a poorer clinical outcome in patients with non-advanced colorectal carcinoma.

Inhibitory effects of selective cyclooxygenase-2 inhibitors, nimesulide and etodolac, on the development of squamous cell dysplasias and carcinomas of the tongue in rats initiated with 4-nitroquinoline 1-oxide

The present study was conducted to examine the effects of selective cyclooxygenase (COX)-2 inhibitors, nimesulide and etodolac, on early stages of tongue carcinogenesis due to 4-nitroquinoline 1-oxide(4-NQO). Fischer 344 rats, 6 weeks old, were given 15 ppm of 4-NQO in their drinking water for 8 weeks followed by diet containing either nimesulide or etodolac at the doses of 150 and 300 ppm for 16 weeks. Rats were sacrificed at 24 weeks and tongue lesions were histologically examined. Nimesulide dose-dependently reduced the incidence and multiplicity of squamous cell dysplasias and carcinomas (SCCs), with significance at the 300 ppm dose. This suppression was associated with an increased incidence and multiplicity of hyperplasias. Etodolac exhibited similar but less extensive suppressive effects. The results suggest that COX-2 is involved in the progression of hyperplasia to dysplasia and from dysplasia to SCCs.

Association of aspirin and other non-steroidal anti-inflammatory drug use with incidence of non-Hodgkin lymphoma

Non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, seem to have chemopreventive properties against several types of cancer, particularly colon cancer. Persons with rheumatoid arthritis, an autoimmune disease for which NSAIDs are used commonly, have been reported to be at lower risk of colon cancer but at elevated risk of non-Hodgkin lymphoma (NHL), raising the possibility that NSAIDs may be a risk factor for NHL. We evaluated the association of use of NSAIDs, arthritis history, and risk of NHL in a prospective cohort of 27,290 postmenopausal women from the state of Iowa. The frequency of use of aspirin and of other NSAIDs excluding aspirin (e.g., ibuprofen), as well as a physician diagnosis of rheumatoid arthritis (RA) or osteoarthritis (OA), were self-reported on a questionnaire mailed in 1992. The incidence of NHL was ascertained through annual linkages to the Iowa SEER Cancer Registry. Relative risks (RR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards regression. Through 7 years of follow-up, 131 cases of NHL were identified. Compared to women who did not use either aspirin or other non-aspirin NSAIDs, women using aspirin exclusively (RR = 1.71; 95% CI = 0.94-3.13), non-aspirin NSAIDs exclusively (RR = 2.39; 95% CI = 1.18-4.83), or both types of drugs (RR = 1.97; 95% CI = 1.06-3.68) were at increased risk of NHL. A diagnosis of RA (RR = 1.75; 95% CI = 1.09-2.79), but not OA (RR = 1.06; 95% CI = 0.67-1.68), was associated with risk of NHL, but the positive association of use of aspirin and other NSAIDs with NHL was independent of RA history. Multivariate adjustment for other NHL risk factors only attenuated slightly these associations, whereas exclusion of cases occurring during the first 2 years of follow-up strengthened the associations. These data suggest that use of NSAIDs, either aspirin or other non-aspirin NSAIDs, are associated positively with risk of NHL, and that this association is independent of RA history.

Cyclooxygenase-2 (COX-2) inhibitors sensitize tumor cells specifically to death receptor-induced apoptosis independently of COX-2 inhibition

Cyclooxygenase-2 (COX-2) is involved in diverse processes such as inflammation, carcinogenesis and apoptosis. As COX-2 inhibitors interfere with these processes, inhibition of COX-2 has been suggested as a promising anticancer treatment. However, the role of COX-2 in modulation of apoptosis as well as the death pathways affected by COX-2 inhibitors are poorly characterized. Here we demonstrate that the selective COX-2 inhibitors NS-398 and nimesulide increased TNF sensitivity of TNF-resistant HeLa H21 and TNF-sensitive HeLa D98 cells, although this cytokine induced significant COX-2 activity, as judged by prostaglandin E(2) (PGE(2)) production, only in H21 cells. TNF did also not induce PGE(2) production in MCF-7/casp-3 cells stably expressing COX-2; however, nimesulide strongly enhanced TNF-induced apoptosis in these cells. Furthermore, COX-2 activity in HeLa H21 cells could be inhibited by NS-398 concentrations that were 10 000-fold lower compared to those required for the induction of cell death. Most intriguingly, sensibilization to apoptosis was specifically observed in response to activation of death receptors. Not only TNF-induced cell death but also apoptosis triggered by the CD95 and TRAIL receptors was enhanced by nimesulide. In contrast, apoptosis induced by the anticancer drugs doxorubicine and etoposide that target the mitochondrial death pathway remained unaffected. Together, our data suggest that COX-2 inhibitors overcome apoptosis resistance and selectively sensitize tumor cells to the extrinsic death receptor-induced apoptotic pathway independently of COX-2.

Chemoprevention of gastrointestinal malignancies

BACKGROUND

There has been considerable interest in the use of chemical or dietary agents to suppress or inhibit the development of tumours in the early stages of carcinogenesis. This concept is known as chemoprevention and although the potential for such agents is tremendous, evaluating their clinical benefit is beset with difficulties.

AIMS

Using selected agents, such as curcumin and indole-3-carbinol, as examples, the present review will discuss the possible mechanisms of chemoprevention and the problems encountered in developing these agents into clinical drugs.

METHODS

A review of the published literature from 1985 to the present day was performed using Medline and Web of Science search engines. Key words used were 'gastrointestinal cancer' and 'chemoprevention'.

CONCLUSION

A huge number of agents with possible chemopreventive action has been identified. Pilot trials using molecular signatures of cancer activity can be used to select which agents should be included in large-scale phase III clinical trials. Publications concerning chemoprevention are concentrated in the scientific and oncological literature but surgeons with their greater exposure to premalignant gastrointestinal disease need to be aware of current concepts in this rapidly expanding field. This knowledge would allow collaboration between oncologists and surgeons in clinical trials to further evaluate chemopreventive compounds and ascertain their clinical impact.

Cyclooxygenase-2 promotes hepatocellular carcinoma cell growth through Akt activation: evidence for Akt inhibition in celecoxib-induced apoptosis

Cyclooxygenase-2 (COX-2)-controlled prostaglandin (PG) metabolism recently has been implicated in the pathogenesis of hepatocellular carcinoma (HCC). However, the biologic role and molecular mechanism of COX-2-mediated PGs in the control of liver cancer growth have not been established. This study was designed to examine the direct effect of COX-2 and its inhibitor celecoxib on the growth control of liver cancer cells. Human HCC cell lines Hep3B and HepG2 transfected with COX-2 expression vector showed increased cell growth and enhanced phosphorylation of serine/threonine protein kinase B (Akt). The level of COX-2 expression and Akt phosphorylation is correlated positively in cultured HCC cells and human liver cancer tissues. Inhibition of Akt activation by phosphatidylinositol 3-kinase (PI3-kinase) inhibitor LY294002 significantly decreased the viability of Hep3B and HepG2 cells (P <.01). These results reveal a novel role of Akt activation in COX-2-induced HCC cell survival. Furthermore, HCC cells treated with the COX-2 inhibitor celecoxib showed significant reduction of Akt phosphorylation and marked morphologic and biochemical characteristics of apoptosis. Overexpression of COX-2 or addition of exogenous PGE(2) partially prevented celecoxib-induced apoptosis (P <.01). In conclusion, our results suggest the involvement of COX-2-dependent and -independent mechanisms in celecoxib-mediated HCC cell apoptosis.

Dosage, duration and timing of nonsteroidal antiinflammatory drug use and risk of prostate cancer

Experimental studies suggest that NSAIDs could reduce prostate cancer risk. Results of observational studies on the relation between NSAIDs and prostate cancer risk have, however, been inconsistent. Moreover, none has addressed the issues of dosage, duration and timing of exposure. In a population-based, age-matched case-control study, we measured the association between prostate cancer risk and NSAIDs defined in terms of mean daily dose, cumulative duration and timing of exposure. Eight-year drug exposure history was obtained from the Quebec health insurance system database. Parallel analyses were performed for aspirin and NSAIDs other than aspirin. We controlled for detection bias and assessed the potential impact of protopathic bias. Analyses were performed with conditional logistic regression. Among the 2,221 cases and 11,105 controls, there was a negative trend between cumulative duration of aspirin use and prostate cancer risk (p = 0.0009). Also, exposure to a mean daily dose of aspirin of at least 80 mg, maintained throughout the entire 8 years of follow-up, was associated with an 18% reduction in prostate cancer risk (OR = 0.82, 95% CI 0.71-0.95). In more recent users of such a dose, the risk reduction was 7%. However, 1 year after the end of a 7-year regular aspirin exposure, no residual protective effect persisted. No association was observed between prostate cancer risk and exposure to NSAIDs other than aspirin. The results suggest that long-term and regular use of aspirin, at a dosage beneath that usually recommended for an anti-inflammatory effect, may prevent prostate cancer.

An immunohistochemical study of cyclooxygenase-2 expression in various feline neoplasms

Cyclooxygenase (COX) enzymes catalyze the synthesis of prostaglandins and exist as two isoforms, COX-1 and COX-2. COX-2 is a potent inducible mediator of inflammation. COX-2 is also upregulated in several human tumors and in canine squamous cell, renal cell, and transitional cell carcinomas, prostatic adenocarcinoma, and intestinal neoplasia. The purpose of this study was to determine whether COX-2 is expressed in various feline tumors. Results of this study may help determine whether COX-2 is a potential target for therapeutic and preventive strategies in cats. Immunohistochemical studies were performed on paraffin-embedded tissues using the amplified streptavidin-biotin-horseradish peroxidase system. COX-2 was found in 7 of 19 (37%) feline transitional cell carcinomas and in 2 of 21 (9%) feline oral squamous cell carcinomas. No COX-2 immunoreactivity was detected in cutaneous squamous cell carcinomas (6), adenocarcinomas (nine mammary, eight pulmonary, seven intestinal), lymphomas (six nasal, six intestinal), or 10 vaccine-associated sarcomas. The widespread absence of COX-2 expression in most feline neoplasms might suggest that COX-2 inhibitors would have a low potential as anticancer agents.

Cyclo-oxygenase 2 inhibition in colorectal cancer therapy

BACKGROUND

Cyclo-oxygenase inhibition for the treatment of colorectal neoplasia has been studied with renewed interest since the discovery of cyclo-oxygenase (Cox) 2 and the introduction of specific Cox-2 inhibitors. These drugs have implications for both the prevention of colorectal carcinoma and the potential treatment of the disease.

METHODS AND RESULTS

A Medline database search was performed for articles using the keywords "colonic, colon or rectal and neoplasia or cancer" and "cyclo-oxygenase or Cox-2." Cross-references of relevant historical papers were also included. There is substantial evidence that Cox-2 plays a role in the development and progression of colorectal cancer. The specific inhibition of this enzyme has been shown to inhibit cancer growth in in vitro and in vivo models. The mechanisms of action for these effects are poorly understood and potential clinical applications at present remain under investigation.

CONCLUSION

Cox-2 inhibitors have great promise as useful additions to current cancer treatments. There is a need for randomized clinical trials to define a role for these drugs in chemoprevention, recurrence prophylaxis, and adjuvant therapy for colorectal and other solid tumours.

Evidence that nonsteroidal anti-inflammatory drugs decrease amyloid beta 42 production by direct modulation of gamma-secretase activity

Chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a lower risk of developing Alzheimer's disease. Recent evidence indicates that some NSAIDs specifically inhibit secretion of the amyloidogenic A beta 42 peptide in cultured cells and mouse models of Alzheimer's disease. The reduction of A beta 42 peptides is not mediated by inhibition of cyclooxygenases (COX) but the molecular mechanism underlying this novel activity of NSAIDs has not been further defined. We now demonstrate that NSAIDs efficiently reduce the intracellular pool of A beta 42 in cell-based studies and selectively decrease A beta 42 production in a cell-free assay of gamma-secretase activity. Moreover, we find that presenilin-1 (PS1) mutations, which affect gamma-secretase activity, differentially modulate the cellular A beta 42 response to NSAID treatment. Overexpression of the PS1-M146L mutation enhances the cellular drug response to A beta 42 lowering NSAIDs as compared with cells expressing wild-type PS1. In contrast, expression of the PS1-Delta Exon9 mutation strongly diminishes the A beta 42 response, showing that PS1 mutations can modulate the cellular drug response to NSAID treatment both positively and negatively. Enhancement of the NSAID drug response was also observed with overexpression of the APP V717F mutation but not with Swedish mutant APP, which affects beta-secretase cleavage. In sum, these results strongly suggest that NSAIDs represent a founding group of compounds that lower A beta 42 production by direct modulation of gamma-secretase activity or its substrate.

Expression profiling of CC531 colon carcinoma cells reveals similar regulation of beta-catenin target genes by both butyrate and aspirin

The CC531 cell line has been widely used to study different aspects of tumor growth and metastasis and provides an excellent experimental platform to develop novel antitumor strategies. To characterize the CC531 model at the molecular level, we screened for mutations in genes covering important signal-transduction pathways that are known to play major roles during colon carcinogenesis, the wnt and the ki-ras signaling pathways. We found both a prototypic beta-catenin (Ctnnb1) mutation (Thr(41)Ile) and a ki-ras (G12D) mutation, providing unambiguous evidence for the constitutive activation of these pathways in CC531 cells. We further established comprehensive gene expression profiles of CC531 cells and investigated the molecular response to 2 antitumor drugs, butyrate and aspirin. Using oligonucleotide microarrays, we screened the expression levels of 7,700 genes and identified a total of 398 genes whose expression was significantly changed upon treatment with butyrate. When using aspirin, 121 genes were significantly altered. Interestingly, 36 genes were regulated by both butyrate and aspirin and 35 of them were regulated in the same direction. We found 7 differentially expressed genes, cyclin D1, cyclin E, c-myc, Fosl1, c-fos, Cd44 and follistatin, which are known targets of the beta-catenin and/or the ras pathway. In all cases, butyrate and aspirin reversed the changes in expression normally found in response to active signaling of these oncogenic pathways. The microarray data are available (http://ncbi.nlm.nih.gov/geo/).

Molecular mechanisms involved in the antiproliferative effect of two COX-2 inhibitors, nimesulide and NS-398, on colorectal cancer cell lines

BACKGROUND

Cyclooxygenase (COX)-2 is up-regulated in most colorectal cancers. Chronic use of non-steroidal anti-inflammatory drugs, which target cyclooxygenases, have been shown to reduce the risk of these cancers. However, the mechanisms underlying this protective effect remain unclear.

AIMS

The aim of our study was to characterize the effects of two COX-2 selective inhibitors, NS-398 and nimesulide, on colorectal cancer cell proliferation, and to describe the molecular mechanisms involved.

MATERIALS AND METHODS

HT-29 and SW-1116 cell lines were cultured with either NS-398 or nimesulide. Cell proliferation was assessed by staining DNA with crystal violet. Cell cycle repartition and apoptosis were analysed by flow cytometry. The expression of COX-1 and COX-2. and of two cyclin dependent kinase inhibitors, p21Cip1 and p27Kip1, was analysed by Western blotting and RT-PCR.

RESULTS

Both drugs dose-dependently inhibited cell proliferation and induced G1 cell cycle blockade. HT-29 cells were more sensitive to both drugs than SW-1116 cells. p21Cip1 and p27Kip1 were induced on both cell lines. Concomitant induction of p21Cip1 mRNA indicates transcriptional modulation, whereas induction of p27Kip1 only at the protein level suggests post-translational modulation.

CONCLUSION

NS-398 and nimesulide inhibit colorectal cell proliferation through induction of p21Cip1 and p27Kip1.

Inhibition of apoptosis in normal and transformed intestinal epithelial cells by cAMP through induction of inhibitor of apoptosis protein (IAP)-2

Cyclooxygenase (COX)-2, a rate-limiting enzyme of prostaglandin (PG) production, is overexpressed in colorectal adenomas and adenocarcinomas, and its inhibition by nonsteroidal antiinflammatory drugs protects against colorectal cancer. Mechanisms of cancer promotion by COX-2 are not fully understood, but signaling through prostaglandin (PG)E2 receptors is a contributing factor. The major PGE2 receptors on epithelial cells, EP2 and EP4, increase cAMP production, which promotes growth and inhibits apoptosis in some cell types. Here, we show that cAMP agonists, including PGE2, cholera toxin, and a membrane-permeant cAMP analog, protect normal and transformed intestinal epithelial cells from apoptosis induced by diverse stimuli. This protection is associated with cAMP-mediated, rapid induction of cellular inhibitor of apoptosis protein (c-IAP)-2 and delayed induction of LIVIN, but not of six other members of the IAP family. Concurrently and characteristic of IAP functions, the activity, but not generation, of the cleaved form of the central executioner caspase 3 is inhibited. Induction of c-IAP2 expression by cAMP agonists is accompanied by phosphorylation of cAMP response element binding protein and cAMP response element-dependent activation of transcriptional reporters. Furthermore, inhibition of COX-2 in cells overexpressing the enzyme decreases c-IAP2 expression and promotes apoptosis, both of which are reversible by PGE2 addition, suggesting that COX-2-promoted antiapoptosis is mediated by release of PGE2 and subsequent cAMP-dependent c-IAP2 induction. These results help to explain the cancer chemoprotective effects of nonsteroidal antiinflammatory drugs by defining a mechanism through which cAMP signaling can promote the development of colorectal and possibly other epithelial cancers by means of disruption of normal apoptotic processes.

Non-steroidal anti-inflammatory drugs and molecular carcinogenesis of colorectal carcinomas

CONTEXT

Colorectal cancer is the second most common cause of cancer-related mortality in the west. The high incidence and mortality make effective prevention an important public-health and economic issue. Non-steroidal anti-inflammatory drugs (NSAIDs) can inhibit colorectal carcinogenesis and are among the few agents known to be chemopreventive. Randomised trials have shown that sulindac and celecoxib suppress the development of adenomatous polyps and cause regression of existing polyps in patients with familial adenomatous polyposis (FAP), who have a high risk for developing colorectal cancer. The mechanisms by which NSAIDs inhibit neoplastic growth are not fully known.

STARTING POINT

Two recently reported randomised placebo-controlled trials show a chemopreventive effect of aspirin in populations other than those with FAP (Robert Sandler and colleagues, N Engl J Med 2003; 348: 883-90; John Baron and colleagues, N Engl J Med 2003; 348: 891-99). In the Sandler study 635 patients with colorectal cancer were randomised to receive 325 mg aspirin or placebo daily. After a follow-up of around 31 months, the mean number of adenomas was lower in the aspirin group than in the placebo group, corresponding to a relative risk of any recurrent adenoma in the aspirin group of 0.65. In the Baron study 1121 patients with colorectal adenomas were assigned to receive 81 or 325 mg aspirin or placebo daily. Follow-up colonoscopy, 32 months after the index endoscopy, showed an incidence of one or more adenomas of 38% in the 81 mg aspirin group, 45% in the 325 mg aspirin group, and 47% in the placebo group. Together, these studies indicate a moderate chemopreventive effect of aspirin in populations with an intermediate risk of developing colorectal cancer. WHERE NEXT? The anticancer properties of NSAIDs have been demonstrated in vitro and in animal studies, epidemiological reports, and intervention studies. Several mechanisms through which NSAIDs alter colonic carcinogenesis have been elucidated, including the induction of apoptosis in neoplastic cells, via mechanisms dependent and independent of cyclo-oxygenase. Some studies have suggested an important role for the cell-cycle regulating protein p21 in mediating the chemopreventive effect of sulindac. A decrease in p21 expression may be one of the main oncogenic events in the development of colorectal cancer. Thus p21 could be the molecular link in the chemopreventive effects of NSAIDs.

The enteric nervous system III: a target for pharmacological treatment

The past decade has seen major advances in the pharmacological understanding of the nervous system of the gastrointestinal tract, the enteric nervous system, and its importance for gut functions in several states of disease. Indeed, the enteric nervous system has become a promising target in the treatment of many gastrointestinal symptoms and disorders. Some of these new therapeutic concepts, such as botulinum toxin for achalasia and serotonergic drugs for functional bowel diseases, are already in clinical use. This paper is part 3 of three Minireviews in Pharmacology & Toxicology, and presents the neurogastrointestinal pharmacological therapeutic options in gastrointestinal pain, functional gastrointestinal disorders, inflammatory bowel diseases, cancer and related conditions with focus on future drug targets. The diagnosis of gastrointestinal neuropathy, the role of serotonin and related neuroendocrine transmitters, serotonergic drugs, and neurotrophic factors in neurogastrointestinal pharmacology will be addressed in this context.

Molecular prognostication in bladder cancer--a current perspective

The optimal management of bladder cancer depends on the accurate assessment of the tumour's biological potential. Advances in molecular biology and cytogenetics have spurred intense research in identifying and characterising prognostic markers for patients with transitional cell carcinoma (TCC) of the bladder. The molecular changes that occur can be categorised into (1) chromosomal alterations leading to carcinogenesis, (2) cellular proliferation as a result of dysregulation of cell cycle control, and (3) growth control processes such as angiogenesis leading to metastasis. The accumulation of these changes ultimately determines a tumour's clinical behaviour and response to therapy. As the understanding of bladder cancer evolves, novel molecular markers for prognostication will make their way from the research laboratory to the clinical setting with the promise to improve patient care and outcomes.

Preventing cancer: dietary lifestyle or clinical intervention?

In Australia, colorectal, prostate and breast cancers are the most frequently occurring cancers in our society, a pattern that is quite different from that of underdeveloped countries. While diet is largely responsible for these differences, technological advances mean that the solutions can be viewed as systematic, financial, lifestyle or technological. They range from those that require self-discipline and care for personal well-being through to those that are seemingly a quick technological fix that will work in spite of an unhealthy lifestyle. There are three main approaches available for prevention of these cancers: dietary lifestyle, chemoprevention and screening. It has been estimated that the potential for prevention by a healthy dietary lifestyle is excellent and might reduce the burden of breast, prostate and colorectal cancer by 33-55%, 10-20% and 66-75%, respectively. This should be safe and inexpensive and have collateral benefit such as reduced cardiovascular disease and osteoporosis. But, population compliance with more plant-based, less calorie dense foods is uncertain, the most healthy are likely to be the most compliant and evidence for effectiveness when interventional programs are undertaken is disappointing. It is not clear how dependable the dietary approach would be where inherited genetic factors determine risk for one of these cancers. Chemoprevention, the administration of natural or synthetic agents that delay, slow down or inhibit the process of tumorigenesis, are still under development and study. Hormone receptor modulators for breast and derivatives of non-steroidal anti-inflammatory drugs for colorectal cancers seem to have most promise and may reduce tumour incidence or death by as much as 50%. These agents are simpler to comply with than changing dietary lifestyle and they are more potent, hence they may be of particular value in high-risk settings. But they are likely to be more costly and run the risk of adverse effects with few collateral benefits. Screening, or the testing of an individual for a disease when that individual does not have any symptoms or signs suggesting that the disease is present, aims to prevent or delay the development of the cancer. Screening impacts on mortality more so than on incidence, reducing colorectal cancer mortality in the range 15-60% and breast cancer mortality by 23-37%. Screening has the advantage of being effective in high-risk as well as average-risk groups and is an 'easy' solution for the person who elects not to follow a healthy dietary lifestyle. Nonetheless, it is expensive, demanding on resources, provides no collateral benefits and does not have the same potential to reduce incidence of disease as does the dietary approach. With these Western cancers, we are fortunate that there are options for prevention. At least choices are available and some will suite certain circumstances and personalities more than others.

Pronounced reduction in adenoma recurrence associated with aspirin use and a polymorphism in the ornithine decarboxylase gene

Most sporadic colon adenomas acquire mutations in the adenomatous polyposis coli gene (APC) and show defects in APC-dependent signaling. APC influences the expression of several genes, including the c-myc oncogene and its antagonist Mad1. Ornithine decarboxylase (ODC), the first enzyme in polyamine synthesis, is a transcriptional target of c-myc and a modifier of APC-dependent tumorigenesis. A single-nucleotide polymorphism exists in intron 1 of the human ODC gene, which lies between two myc-binding domains. This region is known to affect ODC transcription, but no data exist on the relationship of this polymorphism to risk of colorectal neoplasia in humans. We show that individuals homozygous for the minor ODC A-allele who reported using aspirin are approximately 0.10 times as likely to have an adenoma recurrence as non-aspirin users homozygous for the major G-allele. Mad1 selectively suppressed the activity of the ODC promoter containing the A-allele, but not the G-allele, in a human colon cancer-derived cell line (HT29). Aspirin (>or=10 microM) did not affect ODC allele-specific promoter activity but did activate polyamine catabolism and lower polyamine content in HT29 cells. We propose that the ODC polymorphism and aspirin act independently to reduce the risk of adenoma recurrence by suppressing synthesis and activating catabolism, respectively, of colonic mucosal polyamines. These findings confirm the hypothesis that the ODC polymorphism is a genetic marker for colon cancer risk, and support the use of ODC inhibitors and aspirin, or other nonsteroidal antiinflammatory drugs (NSAIDs), in combination as a strategy for colon cancer prevention.

A quantitative illustration of the public health potential of aspirin

Aspirin is showing potential in reducing the risk of several diseases of public health importance. These include cardiovascular disease, cancer and Alzheimer's disease. In this paper, a fictional scenario is considered in which 50 year old individuals are encouraged to take aspirin. Using crude assumptions and simple calculations, a Kaplan-Meier survival curve of aspirin users is presented. The main finding of this exercise is the possibility that the long-term use of low dose aspirin may double the chances of individuals living a healthy life into their 90's. Further research is needed.

Cyclooxygenase-2 inhibitors and nonsteroidal anti-inflammatory drugs in the management of arthritis

The management of arthritis pain should be individualized to the needs and characteristics of the patient. The decision to use nonsteroidal anti-inflammatory drugs (NSAIDs), and in particular the cyclooxygenase-2 (COX-2) inhibitors, is multidimensional. The challenge is to achieve optimal pain relief at the minimum dose to minimize adverse effects. Whenever possible, NSAIDs should be given as monotherapies or in combinations at the lowest effective doses. The COX-2 inhibitors are a safe choice for most patients who are at low risk for a cardiovascular event. Individuals who are at risk for thromboses should not receive unopposed COX-2 inhibitors; COX-2 should be given in combination with low-dose aspirin which is expected to be cardioprotective in high-risk patients.

Cooperative effects of matrix metalloproteinase and cyclooxygenase-2 inhibition on intestinal adenoma reduction

Matrix metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2) are expressed in both sporadic and familial adenomatous colonic polyps and tumours and have been independently shown to play causal roles in intestinal tumour formation in mouse models of colon cancer. The apparent roles of these enzymes in intestinal tumorigenesis led us to examine, in the Min mouse model of colon cancer, if selective COX-2 and MMP inhibitors provide additive or synergistic therapeutic benefits in intestinal tumour prevention. The broad-spectrum MMP inhibitor (A-177430; MMPI) and the selective COX-2 inhibitor (A-285969; COX-2I) both showed dose-dependent inhibition of the number of adenomas in Min mice. Using suboptimal doses, the MMPI reduced tumour multiplicity by 32%, the COX-2I by 48% and, both agents in combination resulted in a 67% decrease compared to control demonstrating a cooperative effect on intestinal tumorigenesis. Apoptosis, proliferation, and angiogenesis were assayed in tumors from each treatment group. These agents in combination allowed for a lowered dosage to be administered to achieve significant biological effects. Clinically, this could potentially reduce side effects associated with currently used MMP and COX-2 inhibitors. Together, these compounds could represent an easily tolerated chemopreventive approach.

Combinatorial effects of nonsteroidal anti-inflammatory drugs and food constituents on production of prostaglandin E2 and tumor necrosis factor-alpha in RAW264.7 murine macrophages

Combinatorial chemopreventive strategies, in contrast to those with individual agents, show potential in terms of potentially lower toxicity and higher efficacy. In this study, we combined several agents and examined their suppressive effects on the combined lipopolysaccharide (LPS)- and interferon(IFN)-gamma-induced formation of proinflammatory mediators, including prostaglandin (PG) E2 and tumor necrosis factor (TNF)-alpha, in RAW264.7 murine macrophages. The combinatorial effects of indomethacin/genistein (GEN) and aspirin/GEN were found to be synergistic for PGE2 suppression, while the nimesulide/GEN combination was antagonistic. Further, while (-)-epigallocatechin gallate (EGCG) alone increased LPS/IFM-gamma-induced production of PGE2 and TNF-alpha as well as cyclooxygenase-2 expression, the EGCG/GEN combination markedly suppressed these parameters. Our results suggest that certain chemopreventive agents act complexly and that, when used in combination, they affect the intracellular signaling pathways of the paired agents to exert additive, synergistic, or antagonistic effects.

NO-NSAIDs and cancer: promising novel agents

Three potential applications of NO-donating NSAIDs in human cancer include their use: as chemopreventive agents; against already developed cancers (chemotherapy); and for the control of cancer symptoms, notably cancer pain. The evidence to date of greater safety and enhanced efficacy of NO-donating NSAIDs underscores their potential to prevent colon cancer and overcome the limitations of traditional NSAIDs. NO-donating NSAIDs affect several pathways critical to colon carcinogenesis and this may explain in part their greater efficacy in colon cancer prevention as assessed in preclinical models.