The effects of sulindac on colorectal proliferation and apoptosis in familial adenomatous polyposis

Gastrointestinal Malignancy: Genetic Implications to Clinical Applications

Advances in molecular genetics have revolutionized our understanding of the pathogenesis, progression, and therapeutic options for treating gastrointestinal (GI) cancers. This chapter provides a comprehensive overview of the molecular landscape of GI cancers, focusing on key genetic alterations implicated in tumorigenesis across various anatomical sites including GIST, colon and rectum, and pancreas. Emphasis is placed on critical oncogenic pathways, such as mutations in tumor suppressor genes, oncogenes, chromosomal instability, microsatellite instability, and epigenetic modifications. The role of molecular biomarkers in predicting prognosis, guiding treatment decisions, and monitoring therapeutic response is discussed, highlighting the integration of genomic profiling into clinical practice. Finally, we address the evolving landscape of precision oncology in GI cancers, considering targeted therapies and immunotherapies.

Which Drugs are More Effective in Preventing Familial Adenomatous Polyposis Progression based on Network Meta-analysis?

BACKGROUND

Familial adenomatous polyposis (FAP) is an inherited disorder. At present, an increasing number of medications are being employed to treat FAP; however, only a few have been assessed for their efficacy and safety. Therefore, this study aimed to conduct a network meta-analysis to compare the therapeutic outcomes and adverse drug reactions of all FAP-associated medications.

METHODS

Six relevant databases were searched to identify pertinent randomized controlled trials (RCTs), and information on the dosage and frequency of various drugs was extracted. Additionally, data on changes in polyp counts and dimensions, as well as treatment-related adverse reactions for different medications were collected. The Bayesian method was employed to directly or indirectly compare the impact of different treatment regimens on changes in polyp numbers and diameters, and the safety of the drugs was investigated.

RESULTS

CXB at 16 mg/kg/day significantly reduced polyp numbers. Celecoxib at 8 mg/kg/day and sulindac (150 mg twice daily) plus erlotinib (75 mg/day) were effective for tolerant FAP patients. Additionally, EPAFFA 2 g daily and sulindac (150 mg twice daily) plus erlotinib (75 mg/day) emerged as the most effective for reducing polyp size.

CONCLUSION

The most effective treatment for reducing the number of colorectal polyps is celecoxib 16 mg/kg/day. On the other hand, a daily dosage of 2 g EPA-FFA demonstrates the best results in terms of decreasing colorectal polyp diameter.

Oxazole and thiazole analogs of sulindac for cancer prevention

Aim:

Experimental and epidemiological studies and clinical trials suggest that nonsteroidal anti-inflammatory drugs possess antitumor potential. Sulindac, a widely used nonsteroidal anti-inflammatory drug, can prevent adenomatous colorectal polyps and colon cancer, especially in patients with familial adenomatous polyposis. Sulindac sulfide amide (SSA) is an amide-linked sulindac sulfide analog that showed in vivo antitumor activity in a human colon tumor xenograft model.

Results/methodology:

A new analog series with heterocyclic rings such as oxazole or thiazole at the C-2 position of sulindac was prepared and screened against prostate, colon and breast cancer cell lines to probe the effect of these novel substitutions on the activity of sulindac analogs.

Conclusion:

In general, replacement of the amide function of SSA analogs had a negative impact on the cell lines tested. A small number of hits incorporating rigid oxazole or thiazole groups in the sulindac scaffold in place of the amide linkage show comparable activity to our lead agent SSA.

Amine Containing Analogs of Sulindac for Cancer Prevention

Background:

Sulindac belongs to the chemically diverse family of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) that effectively prevent adenomatous colorectal polyps and colon cancer, especially in patients with familial adenomatous polyposis. Sulindac sulfide amide (SSA), an amide analog of sulindac sulfide, shows insignificant COX-related activity and toxicity while enhancing anticancer activity in vitro and demonstrating in vivo xenograft activity.

Objective:

Develop structure-activity relationships in the sulindac amine series and identify analogs with promising anticancer activities.

Method:

A series of sulindac amine analogs were designed and synthesized and then further modified in a “libraries from libraries” approach to produce amide, sulfonamide and N,N-disubstituted sulindac amine sub-libraries. All analogs were screened against three cancer cell lines (prostate, colon and breast).

Results:

Several active compounds were identified viain vitro cancer cell line screening with the most potent compound (26) in the nanomolar range.

Conclusion:

Compound 26 and analogs showing the most potent inhibitory activity may be considered for further design and optimization efforts as anticancer hit scaffolds.

Pyrrolopyrimidine derivatives and purine analogs as novel activators of Multidrug Resistance-associated Protein 1 (MRP1, ABCC1)

Multidrug resistance (MDR) is the main cause of diminished success in cancer chemotherapy. ABC transport proteins are considered to be one important factor of MDR. Besides P-glycoprotein (P-gp, ABCB1) and Breast Cancer Resistance Protein (BCRP, ABCG2), Multidrug Resistance-associated Protein 1 (MRP1, ABCC1) is associated with non-response to chemotherapy in different cancers. While considerable effort was spent in overcoming MDR during the last two decades, almost nothing is known with respect to activators of transport proteins. In this work we present certain pyrrolo[3,2-d]pyrimidine derivatives with variations at positions 4 and 5 and purine analogs with variations at position 6 as novel activators of MRP1-mediated transport of the MRP1 substrate calcein AM and the anticancer drug daunorubicin in low nanomolar concentration range. Two different MRP1 overexpressing cell lines were used, the doxorubicin-selected human lung cancer cell line H69 AR and the transfected Madin-Darby Canine Kidney cell line MDCK II MRP1. No effect was observed in the sensitive counterparts H69 and MDCK II wild type (wt). Derivatives with higher molecular weight possessed also inhibitory properties at low micromolar concentrations, although most compounds were rather poor MRP1 inhibitors. Purine analogs derived from potent MRP1 inhibitors of the pyrrolopyrimidine class showed equal activating, but no inhibiting effects at all. All tested compounds were non-toxic and had only minor impact on P-gp or BCRP, showing no inhibition or activation.

Cyclooxygenase-2 (COX-2) inhibition for prostate cancer chemoprevention: double-blind randomised study of pre-prostatectomy celecoxib or placebo

OBJECTIVE

To evaluate the biological effects of selective cyclooxygenase-2 inhibition on prostate tissue in patients undergoing radical prostatectomy (RP).

PATIENTS AND METHODS

Patients with localised prostate cancer were randomised to receive either celecoxib 400 mg twice daily or placebo for 4 weeks before RP. Specimens were analysed for levels of apoptosis, prostaglandins, and androgen receptor (AR). Effects on serum prostate-specific antigen (PSA) and postoperative opioid use were also measured.

RESULTS

In all, 28 of 44 anticipated patients enrolled and completed treatment. One patient in the celecoxib arm had a myocardial infarction postoperatively. For this reason, and safety concerns in other studies, enrolment was halted. The apoptosis index (AI) in tumour cells was 0.29% [95% confidence interval (CI) 0.11-0.47%] vs 0.39% (95% CI 0.00-0.84%) in the celecoxib and placebo arms, respectively (P = 0.68). The AI in benign cells was 0.18% (95% CI 0.03-0.32%) vs 0.13% (95% CI 0.00-0.28%) in the celecoxib and placebo arms, respectively (P = 0.67). Prostaglandin E₂ and AR levels were similar in cancerous and benign tissues when comparing the two arms. The median baseline PSA level was 6.0 and 6.2 ng/mL for the celecoxib and placebo groups, respectively, and did not significantly change after celecoxib treatment. There was no difference in postoperative opiate usage between arms.

CONCLUSION

Celecoxib had no effect on apoptosis, prostaglandins or AR levels in cancerous or benign prostate tissues. These findings coupled with drug safety concerns should serve to limit interest in these selective drugs as chemopreventive agents.

Sulindac, 3,3'-diindolylmethane and curcumin reduce carcinogenesis in the Pirc rat, an Apc-driven model of colon carcinogenesis

Background

Recently, we showed that Sulindac (SU; 320 ppm) reduces precancerous lesions in the colon of Pirc rats, mutated in the Apc gene. Surprisingly, previous data in Apc-mutated mice showed that SU, with reported efficacy in Familial Adenomatous Polyposis (FAP), increases colon carcinogenesis. Therefore, we assessed the effect of SU 320 ppm in a long-term carcinogenesis experiment in Pirc rats. Moreover, since side effects of SU hamper its chronic use and a combination of drugs could be more effective and less toxic than single agents, we also studied whether two natural compounds, 3,3’-diindolylmethane (DIM; 250 ppm) and curcumin (CUR; 2000 ppm), with or without lower doses of SU could affect carcinogenesis

Methods

Pirc rats were fed an AIN76 diet containing SU, DIM and CUR and sacrificed at 8 months of age to measure intestinal tumours. Apoptosis and proliferation in the normal colon mucosa, as well as gene expression profile were studied

Results

Colon tumours were significantly reduced by SU 320 ppm (62 % reduction over Controls), by DIM and CUR without or with SU 80 and 160 ppm (50, 53 and 58 % reduction, respectively) but not by SU 80 ppm alone. Total tumours (colon and small intestine) were reduced by SU (80 and 320 ppm) and by DIM and CUR. Apoptosis in the normal mucosa was significantly increased by SU 320 ppm, and slightly increased by DIM and CUR with or without SU. A slight reduction in Survivin-Birc5 expression was observed with all the treatments compared to Controls. Proliferative activity was not varied

Conclusions

The results on SU reinforce the validity of Pirc rats to identify chemopreventive products. Moreover, the efficacy of the DIM and CUR combination to lower colon tumours, suggests an alternative strategy to be exploited in patients at risk.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1627-9) contains supplementary material, which is available to authorized users.

A review of the epidemiology of Barrett's oesophagus and oesophageal adenocarcinoma

While the incidence rates of many cancers have decreased in past decades, the incidence of oesophageal adenocarcinoma continues to increase. The only known precursor for oesophageal adenocarcinoma is Barrett's oesophagus. Studies conducted have identified white race, male sex, GORD, cigarette smoking, obesity, and the absence of Helicobacter pylori status as risk factors for oesophageal adenocarcinoma. Other potential associations include dietary factors and the absence of non-steroidal anti-inflammatory drug use. Many individual studies have been limited by sample size and several meta-analyses have pooled data from studies to address this limitation. In this review we present a synthesis of these studies and summarize current knowledge of risk factors for both oesophageal adenocarcinoma and Barrett's oesophagus.

Aspirin and nonsteroidal anti-inflammatory drug use and the risk of Barrett's esophagus

BACKGROUND

The use of aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) may decrease the risk of esophageal adenocarcinoma; however, it is unknown where these agents may act in the proposed pathway from normal mucosa to Barrett's esophagus to esophageal adenocarcinoma.

AIM

The aim of the study was to evaluate the association between aspirin and NSAID use and Barrett's esophagus in a case-control study within a large community-based population.

METHODS

We conducted a case-control study of aspirin/NSAID use and Barrett's esophagus within the Kaiser Permanente Northern California population. Cases had a new diagnosis of Barrett's esophagus between October 2002 and September 2005; controls were members without a diagnosis of Barrett's esophagus.

RESULTS

Persons with Barrett's esophagus were less likely to use aspirin than population controls [odds ratio (OR) 0.59, 95 % confidence interval (CI) 0.39-0.87]; a stronger association was found among cases and controls with reflux symptoms (OR 0.49, 95 % CI 0.32-0.75; p value interaction = 0.004). Similar associations were found with the use of either aspirin and/or non-aspirin NSAIDs (OR 0.53, 95 % CI 0.35-0.81), although NSAID use alone was not significantly associated with Barrett's esophagus (OR 0.74, 95 % CI 0.47-1.16). The strength of the association was highest among persons with at least moderate-to-high total medication intake.

CONCLUSIONS

Regular use of aspirin or NSAIDs was associated with a decreased risk of Barrett's esophagus, particularly among persons with gastroesophageal reflux disease symptoms. These findings have implications for chemoprevention, as some of the previously described protective association between aspirin/NSAIDs and esophageal adenocarcinoma may be explained by events that occur prior to the development of Barrett's esophagus.

Small-molecule modulation of Ras signaling

Despite intense efforts in pharmaceutical industry and academia, a therapeutic grip on oncogenic Ras proteins has remained elusive. Mutated Ras is associated with ~20-30% of all human cancers often not responsive to established therapies. In particular, K-Ras, the most frequently mutated Ras isoform, is considered one of the most important but 'undruggable' targets in cancer research. Recently, new cavities on Ras for small-molecule ligands were identified, and selective direct targeting of mutated K-Ras(G12C) has become possible for what is to our knowledge the first time. In addition, impairment of Ras spatial organization, in particular via targeting the prenyl-binding Ras chaperone PDEδ, has opened a fresh perspective in anticancer research. These recent advances fuel hopes for the development of new drugs targeting Ras.

COX-Independent Mechanisms of Cancer Chemoprevention by Anti-Inflammatory Drugs

Epidemiological and clinical studies suggest that non-steroidal anti-inflammatory drugs (NSAIDs), including cyclooxygenase (COX)-2 selective inhibitors, reduce the risk of developing cancer. Experimental studies in human cancer cell lines and rodent models of carcinogenesis support these observations by providing strong evidence for the antineoplastic properties of NSAIDs. The involvement of COX-2 in tumorigenesis and its overexpression in various cancer tissues suggest that inhibition of COX-2 is responsible for the chemopreventive efficacy of these agents. However, the precise mechanisms by which NSAIDs exert their antiproliferative effects are still a matter of debate. Numerous other studies have shown that NSAIDs can act through COX-independent mechanisms. This review provides a detailed description of the major COX-independent molecular targets of NSAIDs and discusses how these targets may be involved in their anticancer effects. Toxicities resulting from COX inhibition and the suppression of prostaglandin synthesis preclude the long-term use of NSAIDs for cancer chemoprevention. Furthermore, chemopreventive efficacy is incomplete and treatment often leads to the development of resistance. Identification of alternative NSAID targets and elucidation of the biochemical processes by which they inhibit tumor growth could lead to the development of safer and more efficacious drugs for cancer chemoprevention.

Cyclooxygenase-2 and Survivin in Superficial Urothelial Carcinoma of the Bladder and Correlation with Intratumoural Microvessel Density

This study was designed to investigate the protein levels of cyclooxyogenase-2 (COX-2) and survivin in superficial urothelial carcinoma (UC) and their correlation with microvessel density (MVD). High-grade UC was positive for both COX-2 and survivin protein, and the proportion of tumours positive for both proteins increased with increasing tumour grade. The presence of COX-2 protein was significantly correlated with the presence of survivin protein. Both COX-2 and survivin positivity were significantly correlated with MVD in all patients regardless of tumour grade, but there was no correlation between MVD and COX-2 and survivin positivity by individual tumour grade. Although there was no significant difference in the proportion of COX-2-positive tumours when patients were stratified by tumour stage, a significantly higher proportion of patients with pT1 stage tumours were survivin-positive compared with patients with pTa stage tumours. COX-2 and survivin positivity were significantly correlated in all patients regardless of tumour grade or stage. COX-2 and survivin were significantly correlated in patients with pTa, but there was no correlation in pT1 tumours. These findings demonstrate that together, COX-2, survivin and MVD may play an important role in UC.

Non-Steroidal Anti-Inflammatory Drugs in the Carcinogenesis of the Gastrointestinal Tract

It is estimated that underlying infections and inflammatory responses are linked to 15–20% of all deaths from cancer worldwide. Inflammation is a physiologic process in response to tissue damage resulting from microbial pathogen infection, chemical irritation, and/or wounding. Tissues injured throughout the recruitment of inflammatory cells such as macrophages and neutrophils, generate a great amount of growth factors, cytokines, and reactive oxygen and nitrogen species that may cause DNA damage that in turn predisposes to the transformation from chronic inflammation to neoplasia. Cyclooxygenase (COX), playing a key role in cell homeostasis, angiogenesis and tumourigenesis, may represent the link between inflammation and cancer. Currently COX is becoming a pharmacological target for cancer prevention and treatment.

Nine-year follow-up of a patient with attenuated familial adenomatous polyposis treated with cyclo-oxygenase-2 inhibitors

Familial adenomatous polyposis (FAP) is caused by germline mutations in the adenomatous polyposis coli (APC) gene with onset of florid polyposis in childhood and development of colorectal cancer by age 30. Colectomy is advised because of the high risk of developing colorectal cancer. Attenuated FAP (AFAP) is a variant of this condition with a later age of onset and milder clinical phenotype; however, colectomy is advised once polyposis develops and polyps cannot be managed endoscopically. We report a case of a patient with AFAP and previously resected colonic carcinoma that was treated with chemoprophylaxis with long-term cyclooxygenase-2 (COX-2) inhibitors after declining colectomy. Colonoscopic examination demonstrated regression of polyps by 18 months. After 9 years of follow-up, there was no evidence of colorectal cancer development or progression of polyposis. This is the first case report on long-term treatment with COX-2 inhibition in a patient with AFAP and previous colonic carcinoma.

NSAIDs downregulate Bcl-X(L) and dissociate BAX and Bcl-X(L) to induce apoptosis in colon cancer cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in preventing colorectal cancer. Apoptosis induction by NSAIDs plays a critical role in NSAID-mediated chemoprevention. Our previous study demonstrated that NSAIDs require the proapoptotic B-cell non-Hodgkin lymphoma-2 (Bcl-2) family member Bcl-2-associated x protein (BAX) to induce apoptosis and inhibit the expression of antiapoptotic basal cell lymphoma-extra large (Bcl-X(L)) in colon cancer cells. In this study, we further investigated how BAX and Bcl-X(L) mediate NSAID-induced apoptosis. We found that Bcl-X(L) is downregulated by NSAIDs in part through proteasome-mediated protein degradation. NSAIDs promote the dissociation of BAX and Bcl-X(L) and translocation of BAX to the mitochondria. Furthermore, we found that only wild-type BAX, but not a mutant BAX deficient in either protein-protein interaction or mitochondrial localization, was able to restore NSAID-induced apoptosis in the BAX-knockout colon cancer cells. These results suggest that NSAIDs induce apoptosis in colon cancer cells by dissociating BAX and Bcl-X(L), thereby promoting BAX mitochondrial translocation and multimerization.

Regulation of cell structure and function by actin-binding proteins: villin's perspective

Villin is a tissue-specific actin modifying protein that is associated with actin filaments in the microvilli and terminal web of epithelial cells. It belongs to a large family of actin-binding proteins which includes actin-capping, -nucleating and/or -severing proteins such as gelsolin, severin, fragmin, adseverin/scinderin and actin crosslinking proteins such as dematin and supervillin. Studies done in epithelial cell lines and villin knock-out mice have demonstrated the function of villin in regulating actin dynamics, cell morphology, epithelial-to-mesenchymal transition, cell migration and cell survival. In addition, the ligand-binding properties of villin (F-actin, G-actin, calcium, phospholipids and phospholipase C-gamma1) are mechanistically important for the crosstalk between signaling pathways and actin reorganization in epithelial cells.

Apoptosis in normal rectal mucosa, baseline adenoma characteristics, and risk of future adenomas

Low apoptosis in the normal rectal mucosa has been associated with colorectal adenomas in cross-sectional studies. It is unknown whether apoptosis can predict the occurrence of new adenomas. We evaluated whether apoptosis at baseline colonoscopy, as well as patient and adenoma characteristics, could predict future occurrence of adenomas. Study subjects were participants in the Diet and Health Study III, a cross-sectional study of adenoma risk factors between August 1998 and March 2000. At baseline, subjects underwent colonoscopy and provided normal rectal mucosal biopsies to evaluate apoptosis as well as information about diet and lifestyle. The present study includes 257 subjects who returned for follow-up colonoscopy between 2000 and 2005. Apoptosis, number of adenomas, size, and atypia at baseline colonoscopy were evaluated as predictors of new adenomas. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI). At baseline, low apoptosis was significantly associated with increased risk of adenomas (P = 0.0001). Compared with those in the lowest tertile, subjects with high apoptosis were less likely to have an adenoma at follow-up (crude OR, 0.25; 95% CI, 0.09-0.65; adjusted OR, 0.29; 95% CI, 0.08-1.06). Having three or more adenomas at baseline was associated with increased risk of new adenomas (crude OR, 2.46; 95% CI, 1.14-5.31; adjusted OR, 3.74; 95% CI, 1.01-13.83). This study suggests that lower apoptosis is associated with increased risk of future adenoma development. If confirmed in larger studies, apoptosis could potentially be used to identify patients at highest risk for developing new adenomas.

A novel role for villin in intestinal epithelial cell survival and homeostasis

Apoptosis is a key regulator for the normal turnover of the intestinal mucosa, and abnormalities associated with this function have been linked to inflammatory bowel disease and colorectal cancer. Despite this, little is known about the mechanism(s) mediating intestinal epithelial cell apoptosis. Villin is an actin regulatory protein that is expressed in every cell of the intestinal epithelium as well as in exocrine glands associated with the gastrointestinal tract. In this study we demonstrate for the first time that villin is an epithelial cell-specific anti-apoptotic protein. Absence of villin predisposes mice to dextran sodium sulfate-induced colitis by promoting apoptosis. To better understand the cellular and molecular mechanisms of the anti-apoptotic function of villin, we overexpressed villin in the Madin-Darby canine kidney Tet-Off epithelial cell line to demonstrate that expression of villin protects cells from apoptosis by maintaining mitochondrial integrity thus inhibiting the activation of caspase-9 and caspase-3. Furthermore, we report that the anti-apoptotic response of villin depends on activation of the pro-survival proteins, phosphatidylinositol 3-kinase and phosphorylated Akt. The results of our studies shed new light on the previously unrecognized function of villin in the regulation of apoptosis in the gastrointestinal epithelium.

Genetic polymorphisms in TP53, nonsteroidal anti-inflammatory drugs and the risk of colorectal cancer: evidence for gene-environment interaction?

OBJECTIVE

Substantial evidence indicates that nonsteroidal anti-inflammatory drugs protect against colorectal cancer by altering cell cycle progression and/or inducing apoptosis, whereas p53 protein is crucial to maintaining cell-cycle arrest and regulating DNA repair, differentiation, and apoptosis. Genetic variants in TP53 gene might therefore influence colorectal cancer risk and modify the effects of nonsteroidal anti-inflammatory drugs. We assessed the association of TP53 Arg72Pro and p53PIN3 polymorphisms with colorectal cancer risk and their possible interaction with nonsteroidal anti-inflammatory drug use.

METHODS

We included 467 cases and 563 controls from a population-based case-control study. Multivariate logistic regression analysis was used to estimate the association between genotypes, environmental exposures and colorectal cancer risk, adjusting for potential confounders.

RESULTS

Odds ratios of colorectal cancer were 0.75 (95% confidence interval, 0.57-0.99) for TP53 72Pro carriers compared with those homozygous for the TP53 72Arg allele and 0.78 (95% confidence interval, 0.58-1.05) for p53PIN3 A2 carriers compared with p53PIN3 A1A1. Risks differed by nonsteroidal anti-inflammatory drug use. For both investigated TP53 polymorphisms, we found that the colorectal cancer risk associated with regular nonsteroidal anti-inflammatory drug use was statistically significantly modified by the TP53 genotype (P values for interaction=0.049 and 0.034, respectively), whereby a substantial protective effect of nonsteroidal anti-inflammatory drug use was observed for homozygous carriers of the 72Arg allele and of the PIN3 A1 allele (odds ratio 0.44; 95% confidence interval, 0.30-0.65 and odds ratio, 0.45; 95% confidence interval, 0.31-0.65). The interaction between nonsteroidal anti-inflammatory drugs and TP53 genetic polymorphisms was confirmed by haplotype analysis.

CONCLUSIONS

These data suggest that the TP53 genotype may modify the influence of nonsteroidal anti-inflammatory drug use on the risk of colorectal cancer. A direct proof of functional analysis is warranted to confirm these findings.

Increased epithelial cell proliferation in the ileal pouch mucosa of patients with familial adenomatous polyposis

To eliminate the risk of colorectal cancer in patients with familial adenomatous polyposis (FAP), reconstructive proctocolectomy is performed. Although most colonic mucosa is resected during the ileal pouch anal anastomosis, adenomas and carcinomas may develop in the pouch. This may be caused by altered cell kinetics due to intraluminal changes in the pouch. In 32 patients with FAP, biopsy specimens from the mucosa of the pouch and also of the afferent ileal loop were taken. Tissue sections were immunohistochemically processed with the monoclonal antibodies M30 and MIB-1 to assess apoptotic and proliferative indices, respectively. Cell proliferation was also assessed by a modified sign test. There were no significant differences in apoptotic rates between the mucosa of the pouch and the mucosa of the afferent ileal loop. However, cell proliferation was significantly higher in the mucosa of the pouch vs afferent ileal loop, both by using the quantitative (68.3% vs 61.6%, p = 0.001) and semiquantitative methods (p < 0.05). Our newly developed semiquantitative approach outperformed previously described methods. The higher cell proliferation in the pouch as compared to the afferent ileal loop may contribute to the increased risk for adenomas and carcinomas in the pouch of patients with FAP and emphasizes the need for regular endoscopic surveillance.

Sulindac treatment in hereditary non-polyposis colorectal cancer

Non-steroidal anti-inflammatory drugs, e.g. sulindac have been extensively studied for chemoprevention in familial adenomatous polyposis, but not in hereditary non-polyposis colorectal cancer (HNPCC). We evaluated these effects in HNPCC using surrogate end-points for cancer risk. In a randomised double-blind cross-over study, 22 subjects (9 female; age 30-66 years, mean 44), all ascertained or probable mutation carriers for HNPCC, were included. Sulindac 150 mg b.i.d. and placebo were given for 4 weeks each, with 4 weeks in between, with biopsies taken from ascending, transverse and sigmoid colon and rectum by colonoscopy after both periods. Proliferation was determined by Ki-67 staining and apoptosis by staining of cytokeratin 18 cleavage products. Expression of cyclins B1, D3 and E and p21, p27, bax, bcl2 and cox-2 was studied immunohistochemically. Proliferation was higher during sulindac treatment than drug placebo treatment in ascending and transverse colon, but not in sigmoid and rectum. Apoptosis was not affected. Besides an increase in cyclin D3, no differences were found in expression of regulating proteins in the proximal colon.

CONCLUSION

Sulindac induces an increase in epithelial cell proliferation in the proximal colon of subjects with HNPCC. Since colorectal cancer predominantly arises in the proximal colon in HNPCC, these results cast doubts on the potential chemopreventive effects of sulindac in HNPCC.

Sulindac induces specific degradation of the HPV oncoprotein E7 and causes growth arrest and apoptosis in cervical carcinoma cells

Sulindac, a nonsteroidal anti-inflammatory drug (NSAID), induces growth arrest in HeLa cells and causes strong inhibition of the G1 to S transition of the cell cycle in a concentration-dependent manner. The G1 arrest is preceded by suppression of cyclin E and A, inactivation of cdk2, and the complete loss of the viral oncoprotein E7, despite ongoing HPV transcription. As shown by inhibitors specific for cyclooxygenase (COX) 1 and 2 loss of E7 is COX-independent. Moreover, inhibition of the proteasome activity with MG132 partially blocked the ability of sulindac to suppress E7 suggesting that sulindac induces degradation of E7 by the proteasomal pathway. In addition to inhibiting growth, sulindac strongly induces apoptosis, which can be abrogated by using the general caspase inhibitor zVAD-fmk. Unchanged expression of the pro-apoptotic protein Bax and suppression of the anti-apoptotic molecules Bcl-2 and Bcl-x(L) argues for the engagement of the mitochondrial apoptotic pathway. These results support the notion that sulindac is a potent growth inhibitor and inducer of apoptosis on cervical cancer cells in vitro and may offer new perspectives as a chemopreventive or supplementary anti-cervical cancer drug.

Cyclooxygenase-2 expression increases with the stage and grade in transitional cell carcinoma of the urinary bladder

OBJECTIVES

Experimental models of carcinogenesis show that non-steroidal anti-inflammatory drugs (NSAIDs) increase apoptosis, inhibit angiogenesis and reduce metastases. A linkage between the activity of prostaglandin synthase enzyme cyclooxygenase-2 (COX-2), a known mediator of inflammation, and cancer angiogenesis is implicated. We investigated the expression of COX-2 in bladder cancer tissue specimens using immunohistochemistry.

METHODS

The immunohistochemical expression of COX-2 in bladder cancer was evaluated by scoring the intensity of immunoreactivity from 0 to 3. Further, the degree of COX-2 expression was correlated with the tumor grade and depth of invasion (T stage).

RESULT

Fifty eight percent patients (n=22) had superficial bladder tumors, while 42% (n=16) were invasive bladder cancers. Overall, COX-2 immuno-positivity was seen in 84.2% (32/38) patients. COX-2 expression was positive in 76.4% (13/17) cases with pTa tumors, 100% (5/5) of pT1 tumors, 86.6% (13/15) of pT2 tumors and in 100% (1/1) of pT3 tumor. The higher stage tumors stained more intensely; this correlation was significant(p=0.01987; chi2=19.6977). With reference to the grade of tumors, a positive expression was seen in 81.25% (13/16) of the low-grade tumors and 89% (17/19) of the high-grade tumors. The differential COX-2 expression relative to the grade of tumor was found to be statistically significant (p=0.05; chi2=15.8612).

CONCLUSION

The degree of COX-2 expression is significantly increased with advancing grade and T stage of disease (p < 0.05).

Defective acute apoptotic response to genotoxic carcinogen in small intestine of APC(Min/+) mice is restored by sulindac

The effect of APC loss on azoxymethane (AOM)-induced apoptosis and cell proliferation, as well as their regulation by sulindac was examined in colon and small intestine in APC(Min/+) mice. APC(Min/+) mice showed increased epithelial proliferation in all regions, with significant impairment of apoptosis in small intestine, but not in colon. Sulindac administration restored defective apoptosis to normal. As the apoptotic defect occurred at the major site of intestinal tumor formation in APC(Min/+) mice and as it was restored to normal by a proven chemopreventive agent, this defect in apoptosis might be a key biological consequence of APC dysfunction contributing to tumor formation.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal-dominant colorectal cancer syndrome, caused by a germline mutation in the adenomatous polyposis coli (APC) gene, on chromosome 5q21. It is characterized by hundreds of adenomatous colorectal polyps, with an almost inevitable progression to colorectal cancer at an average age of 35 to 40 yr. Associated features include upper gastrointestinal tract polyps, congenital hypertrophy of the retinal pigment epithelium, desmoid tumors, and other extracolonic malignancies. Gardner syndrome is more of a historical subdivision of FAP, characterized by osteomas, dental anomalies, epidermal cysts, and soft tissue tumors. Other specified variants include Turcot syndrome (associated with central nervous system malignancies) and hereditary desmoid disease. Several genotype-phenotype correlations have been observed. Attenuated FAP is a phenotypically distinct entity, presenting with fewer than 100 adenomas. Multiple colorectal adenomas can also be caused by mutations in the human MutY homologue (MYH) gene, in an autosomal recessive condition referred to as MYH associated polyposis (MAP). Endoscopic screening of FAP probands and relatives is advocated as early as the ages of 10-12 yr, with the objective of reducing the occurrence of colorectal cancer. Colectomy remains the optimal prophylactic treatment, while the choice of procedure (subtotal vs proctocolectomy) is still controversial. Along with identifying better chemopreventive agents, optimizing screening of extracolonic cancers and applying new radiological and endoscopic technology to the diagnosis and management of extracolonic features are the major challenges for the future.

Non-steroidal anti-inflammatory drugs for cancer prevention: promise, perils and pharmacogenetics

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) show indisputable promise as chemopreventive agents. Possible targets include cancers of the colon, stomach, breast and lung. However, recent studies raise concern about potential cardiovascular toxicity associated with the use of NSAIDs that specifically target the enzyme cyclooxygenase 2. These findings, and others that show that inherited genetic characteristics might determine preventive success, argue for new strategies that are tailored to individual medical history and genetic make-up.

Sulindac inhibits beta-catenin expression in normal-appearing colon of hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis patients

Sulindac reduces colorectal cancer risk in genetically susceptible humans and animals. The molecular mechanisms underlying these effects are incompletely understood. Many studies suggest an important role for induction of apoptosis involving the mitochondrial pathway and the death receptor pathway. Alternatively, mechanisms involving the APC-beta-catenin-Wnt pathway have been suggested, possibly mediated by p21. We determined the effects of sulindac on apoptosis and expression of death receptor (DR)-4 and DR5, beta-catenin, and p21 in normal-appearing colorectal epithelium. Biopsies were obtained before and after sulindac treatment during two chemoprevention studies. Patients (n = 18) with hereditary nonpolyposis colorectal cancer (HNPCC) received 150 mg sulindac bd for 4 weeks in a placebo-controlled crossover design. Patients (n = 6) with familial adenomatous polyposis (FAP) received 150 mg sulindac bd for 6 months. Apoptosis was assessed by M30 staining and expression patterns of DR4, DR5, beta-catenin, and p21 were studied immunohistochemically. In HNPCC patients, apoptotic indices were similar following placebo and sulindac. Also in FAP patients, apoptotic indices were not different after sulindac compared with pretreatment values. Expression of DR4 and DR5 was observed in all samples with no consistent differences between placebo/baseline and sulindac. Intensity of membranous beta-catenin staining was lower in HNPCC samples following sulindac compared with placebo (P < 0.001). Similar results were obtained in FAP samples (P < 0.01). p21 expressions before and after sulindac treatment were similar in both patient groups. In conclusion, sulindac inhibits beta-catenin expression in normal colorectal epithelium from HNPCC and FAP patients without affecting apoptotic indices and DR4, DR5, and p21 expression.

Sulindac activates nuclear translocation of AIF, DFF40 and endonuclease G but not induces oligonucleosomal DNA fragmentation in HT-29 cells

Sulindac is one of the most widely studied nonsteroidal anti-inflammatory drugs in the prevention of colon cancer. Thus, from the viewpoint of colon cancer chemotherapy it is important to reveal the mechanism of sulindac-induced cell death. This study was undertaken to dissect the molecular mechanism underlying sulindac-induced apoptosis in human colon cancer cell line HT-29 (mutant p53), focusing on nuclear translocation of AIF, DFF and endonuclease G. On induction of apoptosis by sulindac, it was associated with decreased mitochondrial membrane potential, nuclear expression of active caspase-3, cleavage of poly(ADP-ribose) polymerase, translocation of mitochondrial proteins to the nucleus, and morphological evidence of nuclear condensation. However, sulindac led to only disintegration of nuclear DNA into high molecular weight DNA fragments of about 100-300 kbp as determined by a pulse-field gel electrophoresis, suggesting a predominantly AIF-mediated cell death process. In summary, our findings indicate that sulindac induces large-scale DNA fragmentation without oligonucleosomal DNA fragmentation. This result suggests that nuclear translocation of DFF and endonuclease G are not sufficient for the induction of oligonucleosomal DNA fragmentation in HT-29 cells.

Lack of guanylyl cyclase C, the receptor for Escherichia coli heat-stable enterotoxin, results in reduced polyp formation and increased apoptosis in the multiple intestinal neoplasia (Min) mouse model

Guanylyl cyclase C (GC-C), a transmembrane receptor for bacterial heat-stable enterotoxin and the mammalian peptides guanylin and uroguanylin, mediates intestinal ion secretion and affects intestinal cell growth via cyclic GMP signaling. In intestinal tumors, GC-C expression is maintained while guanylin and uroguanylin expression is lost, suggesting a role for GC-C activation in tumor formation or growth. We show by in situ hybridization that GC-C expression is retained in adenomas from multiple intestinal neoplasia (Apc(Min/+)) mice. In order to determine the in vivo role of GC-C in intestinal tumorigenesis, we generated Apc(Min/+) mice homozygous for a targeted deletion of the gene encoding GC-C and hypothesized that these mice would have increased tumor multiplicity and size compared to wild-type Apc(Min/+) mice on the same genetic background. In contrast, the absence of GC-C resulted in a reduction of median polyp number by 55%. There was no change in the median diameter of polyps, suggesting no effect on tumor growth. Somatic loss of the wild-type Apc allele, an initiating event in intestinal tumorigenesis, also occurred in polyps from GC-C-deficient Apc(Min/+) mice. We have found increased levels of apoptosis as well as increased caspase-3 and caspase-7 gene expression in the intestines of GC-C-deficient Apc(Min/+) mice compared with Apc(Min/+) mice. We propose that these alterations are a possible compensatory mechanism by which loss of GC-C signaling also affects tumorigenesis.

COX-2: a molecular target for colorectal cancer prevention

Cyclooxygenase (COX), a key enzyme in the prostanoid biosynthetic pathway, has received considerable attention due to its role in human cancers. Observational and randomized controlled studies in many different population cohorts and settings have demonstrated protective effects of nonsteroidal anti-inflammatory drugs (NSAIDs; the inhibitors of COX activity) for colorectal cancers (CRCs). COX-2, the inducible isoform of cyclooxygenase, is overexpressed in early and advanced CRC tissues, which portends a poor prognosis. Experimental studies have thus identified important mechanisms and pathways by which COX-2 plays an important role in carcinogenesis. Selective COX-2 inhibitors have been approved for use as adjunctive therapy for patients with familial polyposis. The role of COX-2 inhibitors is currently being evaluated for use in wider populations.

The role of prostaglandins and other eicosanoids in the gastrointestinal tract

Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally prescribed to ameliorate symptoms associated with acute pain and chronic inflammatory diseases such as arthritis. Recent epidemiologic studies and clinical trials indicate that use of NSAIDs and cyclooxygenase (COX)-2 selective inhibitors are associated with a reduced risk of certain malignancies, especially gastrointestinal cancer. The cyclooxygenase enzymes are the best known targets of NSAIDs; this diverse class of compounds blocks conversion of arachidonic acid to prostanoids. Prostaglandins and other eicosanoids derived from COX-1 and COX-2 are involved in a variety of physiologic and pathologic processes in the gastrointestinal tract. Recent efforts to identify the molecular mechanisms by which COX-2-derived prostanoids exert their proneoplastic effects have provided a rationale for the possible use of NSAIDs alone or in a combination with conventional or experimental anticancer agents for the treatment or prevention of gastrointestinal cancers.

Sulindac and its metabolites inhibit invasion of glioblastoma cells via down-regulation of Akt/PKB and MMP-2

Non-steroidal anti-inflammatory drug (NSAID), sulindac has chemopreventive and anti-tumorigenic properties, however, the molecular mechanism of this inhibitory action has not been clearly defined. The Akt/protein kinase B, serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. In the present study, we demonstrate that down-regulation of Akt is a major effect of anti-invasiveness property of sulindac and its metabolites in glioblastoma cells. Myristoylated Akt (MyrAkt) transfected U87MG glioblastoma cells showed increase invasiveness, whereas DN-Akt transfected cells showed decrease invasiveness indicating that Akt potently promoted glioblastoma cell invasion. MMP-2 promoter and enzyme activity were up-regulated in Akt kinase activity dependent manner. Sulindac and its metabolites down-regulated Akt phosphorylation, inhibited MMP-2 production, and significantly inhibited invasiveness of human glioblastoma cells. In addition, sulindac and LY294002, a selective inhibitor of phosphoinositide 3-kinase (PI3K), synergistically inhibited the invasion of glioblastoma cells. Furthermore, only celecoxib showed Akt phosphorylation reduction and an anti-invasivness in glioblastoma cells, whereas aspirin, ketoprofen, ketorolac, and naproxen did not. In conclusion, our results provide evidence that down-regulation of Akt pathway and MMP-2 may be one of the mechanisms by which sulindac and its metabolites inhibit glioblastoma cell invasion.

Sulindac corrects defective apoptosis and suppresses azoxymethane-induced colonic oncogenesis inp53 knockout mice

The acute apoptotic response to genotoxic carcinogens (AARGC) might be important for controlling the subsequent colonic mutational load and progression through oncogenesis. We have found previously that AARGC is p53-dependent with a gene-dosage effect, and that decreased AARGC in p53(+/-) and p53(-/-) mice is associated with increased susceptibility to carcinogen-induced oncogenesis. We tested the ability of sulindac to reverse these defects. The effect of sulindac on azoxymethane (AOM)-induced apoptosis was measured in colonic epithelium in wild-type, p53(+/-) and p53(-/-) mice, 8 hr after a single AOM injection. Sulindac supplementation (0.5 +/- 0.1 mg/day) restored defective AARGC in p53(+/-) but not in p53(-/-) mice. For effect on colon tumor development, sulindac treatment was started at age 4 weeks in wild-type, p53(+/-) and p53(-/-) mice; three weekly AOM injections were commenced at 6 weeks of age to induce tumors. Sulindac reduced significantly tumor incidence and multiplicity in wild-type mice (17% and 0.3 tumors/mouse compared to 36% and 0.8 respectively without drug), in p53(+/-)mice (38% and 0.8 compared to 64% and 1.63) and in p53(-/-) mice (63% and 1.0 compared to 90% and 1.74). Although loss of p53 function impairs the apoptotic response to AOM-induced DNA damage, sulindac is capable of partly restoring this defect. As sulindac also reverses the increased risk of oncogenesis due to p53 dysfunction, its enhancement of the apoptotic response to initiating mutations might act to reduce mutational load driving oncogenesis. Sulindac is an effective chemopreventive agent in the presence of p53 dysfunction.

Celecoxib, a Selective Cyclooxygenase-2 Inhibitor, Decreases Monocyte Chemoattractant Protein-1 Expression and Neointimal Hyperplasia in the Rabbit Atherosclerotic Balloon Injury Model

The inflammation in response to vascular injury is becoming increasingly recognized as a potential contributor to restenosis. Cyclooxygenase-2 (COX-2) is the inducible form of cyclooxygenase and has been shown to be involved in the proinflammatory response of vascular tissue. Bilateral femoral artery lesions were induced by air desiccation in New Zealand White rabbits followed by high cholesterol diet feeding for 28 days. Balloon injury and stent implantation were performed at the preinjured vessel segments. Immunostaining showed that uninjured vessel segments stained positive only for COX-1 but not for COX-2. Injured vessel segments showed, in addition to COX-1, significant positive staining for COX-2. In the efficacy study, celecoxib (75 mg/kg/d) was administered orally beginning 3 hours before balloon injury or stent implantation on day 28 and daily for 21 days. Monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-2 and -9 (MMPs) expression were quantified in arterial extracts 4 days after balloon injury by Western blot and gelatin zymography. Morphometric analysis and immunostaining for macrophages were performed 21 days after balloon injury. Celecoxib treatment significantly decreased MCP-1 expression (P < 0.01). Neointimal hyperplasia was significantly inhibited by celecoxib in both balloon injury and stent models (0.49 +/- 0.20 versus 0.70 +/- 0.35 mm2 from balloon injury model, P < 0.05, and 0.81 +/- 0.25 versus 1.69 +/- 0.43 mm2 from stent model, P < 0.05), accompanied by reduced macrophage infiltration. We conclude that celecoxib decreases the inflammatory response and intimal hyperplasia following vascular injury, possibly through inhibition of MCP-1 expression, implying a pivotal role of inflammation in the pathogenesis of restenosis.

Expression of cyclooxygenase-1 and -2 in canine nasal carcinomas

Cyclooxygenase-1 (COX-1) and cyclooxygenase -2 (COX-2) are known to play a role in the carcinogenesis of many human and animal primary epithelial tumours. However, expression of COX-1 and -2 has not been investigated in canine nasal epithelial carcinoma, a rare form of neoplasia. COX-1 immunolabelling was demonstrated in normal canine nasal mucosa and in a minority of neoplastic specimens. Cytoplasmic COX-2, however, was strongly expressed in the majority of canine nasal carcinomas. In addition, COX-2 expression was demonstrated in dysplastic epithelium and in a proportion of stromal cells. Co-expression of both enzyme isoforms was revealed by confocal laser scanning microscopy. The results indicate that COX-2 is overexpressed in a proportion of naturally occurring canine nasal carcinomas, suggesting its possible role in canine nasal tumorigenesis.

Cyclooxygenase Isozymes: The Biology of Prostaglandin Synthesis and Inhibition

Nonsteroidal anti-inflammatory drugs (NSAIDs) represent one of the most highly utilized classes of pharmaceutical agents in medicine. All NSAIDs act through inhibiting prostaglandin synthesis, a catalytic activity possessed by two distinct cyclooxygenase (COX) isozymes encoded by separate genes. The discovery of COX-2 launched a new era in NSAID pharmacology, resulting in the synthesis, marketing, and widespread use of COX-2 selective drugs. These pharmaceutical agents have quickly become established as important therapeutic medications with potentially fewer side effects than traditional NSAIDs. Additionally, characterization of the two COX isozymes is allowing the discrimination of the roles each play in physiological processes such as homeostatic maintenance of the gastrointestinal tract, renal function, blood clotting, embryonic implantation, parturition, pain, and fever. Of particular importance has been the investigation of COX-1 and -2 isozymic functions in cancer, dysregulation of inflammation, and Alzheimer's disease. More recently, additional heterogeneity in COX-related proteins has been described, with the finding of variants of COX-1 and COX-2 enzymes. These variants may function in tissue-specific physiological and pathophysiological processes and may represent important new targets for drug therapy.

Cell Proliferation and Apoptotic Indices Predict Adenoma Regression in a Placebo-Controlled Trial of Celecoxib in Familial Adenomatous Polyposis Patients

Background: Celecoxib was shown to regress colorectal adenomas in familial adenomatous polyposis (FAP) patients relative to placebo. To address the mechanism of polyp regression, we determined whether celecoxib can modulate cell proliferation, apoptosis, and prostaglandin E2 (PGE2) levels in colorectal epithelia from FAP trial participants and whether such alterations correlate with observed reductions in polyp number. Materials and Methods: Colorectal mucosal biopsies were obtained at baseline and on last day of celecoxib (100 or 400 mg twice daily) or placebo administration (6 months). Residual paraffin-embedded adenomas and normal mucosa from the same patients (n = 17) or normal tissue alone (n = 15) were analyzed. Immunoperoxidase staining for Ki-67 was performed and apoptotic cells were identified by their morphology. Ki-67 and apoptotic labeling indices and their ratios were calculated in superficials (s) and nonsuperficial (ns) regions of adenomas and normal mucosa, and baseline to 6-month differences were calculated. PGE2 levels were analyzed by mass spectroscopy (normal, n = 64; adenoma, n = 56). Biomarkers were analyzed by treatment arm and correlated with previously determined mean percentage reductions in colorectal polyp number. Results: In adenomas, a reduction in the superficial proliferative activity i.e., Ki-67s labeling index, accompanied polyp regression (r = −0.76, P = 0.006). An increase in the apoptotic ratio [i.e., superficial apoptotic index (AIs)/nonsuperficial apoptotic index (AIns)] was found to correlate with reduced polyp counts in that higher apoptotic ratios correlated with better response to celecoxib (r = 0.71, P = 0.004). Furthermore, the AIs/Ki-67s ratio (r = 0.58, P = 0.026) accompanied polyp regression. In normal mucosa, a trend toward increased AIs (r = 0.33, P = 0.053) and polyp regression was found. PGE2 levels did not significantly correlate with polyp regression. Changes in biomarker levels (baseline to 6 months) were correlated in adenomas and normal mucosa (AIs, r = 0.29, P = 0.024; AIns, r = 0.34, P = 0.009; PGE2, r = 0.50, P = 0.059) within individual patients. Conclusion: Suppression of cell proliferation and an increased apoptotic ratio, as well as the ratio of apoptosis to cell proliferation, accompany polyp regression in a chemoprevention trial in FAP patients. These findings suggest potential mechanisms for the efficacy of celecoxib and warrant further study of these biomarkers as intermediate endpoints in FAP patients.

Cyclooxygenase-2: a potential target in breast cancer

Use of nonsteroidal anti-inflammatory drugs has been shown to result in a 40% to 50% reduction in the relative risk of developing colorectal cancer. Cyclooxygenase-2 (COX-2) overexpression occurs in 43% of human invasive breast cancers and 63% of ductal carcinomas in situ. There is considerable in vitro, animal model, and epidemiologic evidence to suggest that COX-2 may play some role in breast tumor initiation and progression. PGE(2) is a major downstream mediator of COX-2 that promotes cellular proliferation and angiogenesis, makes cells resistant to apoptosis, enhances invasiveness, and modulates immunosuppression. COX-2 and COX-2-derived PGE(2) may be involved in mammary carcinogenesis. Therefore, COX-2 selective inhibitors may have a role in breast cancer prevention.

Sulindac targets nuclear beta-catenin accumulation and Wnt signalling in adenomas of patients with familial adenomatous polyposis and in human colorectal cancer cell lines

Nonsteroidal anti-inflammatory drugs (NSAIDs) have chemopreventive potential against colorectal carcinomas (CRCs). Inhibition of cyclooxygenase (COX)-2 underlies part of this effect, although COX-2-independent mechanisms may also exist. Nonsteroidal anti-inflammatory drugs appear to inhibit the initial stages of the adenoma-carcinoma sequence, suggesting a link to the APC/beta-catenin/TCF pathway (Wnt-signalling pathway). Therefore, the effect of the NSAID sulindac on nuclear (nonphosphorylated) beta-catenin and beta-catenin/TCF-mediated transcription was investigated. Nuclear beta-catenin expression was assessed in pretreatment colorectal adenomas and in adenomas after treatment with sulindac from five patients with familial adenomatous polyposis (FAP). Also, the effect of sulindac sulphide on beta-catenin/TCF-mediated transcription was studied. Adenomas of FAP patients collected after treatment with sulindac for up to 6 months showed less nuclear beta-catenin expression compared to pretreatment adenomas of the same patients. Sulindac sulphide abrogated beta-catenin/TCF-mediated transcription in the CRC cell lines DLD1 and SW480, and decreased the levels of nonphosphorylated beta-catenin. As a result, the protein levels of the positively regulated TCF targets Met and cyclin D1 were downregulated after sulindac treatment. This study provides in vivo and in vitro evidence that nuclear beta-catenin localisation and beta-catenin/TCF-regulated transcription of target genes can be inhibited by sulindac. The inhibition of Wnt-signalling provides an explanation for the COX-2-independent mechanism of chemoprevention by NSAIDs.

Microbial degradation products influence colon cancer risk: the butyrate controversy

All dietary fiber, by definition, escapes digestion in the small intestine and thus arrives relatively intact in the large intestine. Its fate in the large intestine depends upon the type of fiber and the colonic microflora. Highly fermentable fibers result in short chain fatty acids including butyrate, which is thought by some to be protective against colon cancer. However, not all studies support a chemopreventive effect for butyrate and the lack of agreement (particularly between in vivo and in vitro studies) on butyrate and colon cancer has been termed the "butyrate paradox." There are a number of reasons for this discrepant effect including differences between the in vitro and in vivo environments, the timing of butyrate administration, the amount of butyrate administered, the source of butyrate (usually dietary fiber) as a potential confounder, and an interaction with dietary fat. Collectively, the studies suggest that the chemopreventive benefits of butyrate depend in part on amount, time of exposure with respect to the tumorigenic process, and the type of fat in the diet.

Celecoxib: a potent cyclooxygenase-2 inhibitor in cancer prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used therapeutic agents in the treatment of pain, inflammation and fever. They may also have a role in the management of cancer prevention, Alzheimer's disease and prophylaxis against cardiovascular disease. These drugs act primarily by inhibiting cyclooxygenase enzyme, which has two isoforms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Selective COX-2 inhibitors provide potent anti-inflammatory and analgesic effects without the side effects of gastric and renal toxicity and inhibition of platelet function. Celecoxib is a potent COX-2 inhibitor being developed for the treatment of rheumatoid arthritis and osteoarthritis. Chemoprevention is the use of pharmacological or natural agents to prevent, suppress, interrupt or reverse the process of carcinogenesis. For this purpose, celecoxib is being used for different cancer types. The effects of NSAIDs on tumor growth remain unclear, but are most likely to be multifocal. In this article, we reviewed COX-2 selectivity, the pharmacological properties of celecoxib, the use of celecoxib for cancer prevention and the mechanisms of chemoprevention.

Colon cancer: prevalence, screening, gene expression and mutation, and risk factors and assessment

Colon cancer detection at an early stage and identifying susceptible individuals can result in reduced mortality from this prevalent cancer. Genetic events leading to the development of this cancer involve a multistage progression of adenoma polyps to invasive metastatic carcinomas. Currently, there is no satisfactory screening method that is highly specific, sensitive, or reliable. Dietary patterns associated with the greatest increase in colon cancer risk are the ones that typify a diet rich in fat and calories, and low in vegetable, fruits, and fibers. Genetic susceptibility to environmental carcinogenesis must be factored into the risk assessment for this cancer. Many genes have been shown to be associated with increased expression and mutations in colorectal cancer patients. These genes have been reviewed; it is hoped that by carefully selecting a number of them, a molecular approach that is suitable for arriving at a tumorigenic expression index is developed, which will reliably detect this cancer at an early stage (i.e., before it metastasizes), especially in exfoliated samples (e.g., stool and blood), so that appropriate intervention strategies can be implemented. Illustrated herein is the utility of employing real-time reverse transcriptase polymerase chain reaction (RT-PCR) to quantitatively measure gene expression, and develop an index that is specific for this cancer, which if perfected may result in a reliable and sensitive screening technique for colorectal cancer detection.

Calcium or resistant starch does not affect colonic epithelial cell proliferation throughout the colon in adenoma patients: a randomized controlled trial

Patients with a history of sporadic adenomas have increased epithelial cell proliferative activity, an intermediate risk marker for colorectal cancer. Reduction of proliferation by dietary intervention may reflect a decreased colorectal cancer risk. To evaluate whether calcium or resistant starch could reduce proliferative activity throughout the colon, we performed a randomized controlled trial in 111 sporadic adenoma patients. Patients received two placebos, 1 g of calcium + placebo, or 30 g of amylomaize (19 g of resistant starch) + placebo. After 2 mo, biopsies were collected from the cecum, transverse and sigmoid colon, and rectum during colonoscopy. Epithelial cell proliferation was determined by dividing the number of 5-bromo-2-deoxyuridine-labeled nuclei by the total number of nuclei x 100 (labeling index, LI). LI of luminal, mid, and basal compartments was determined. Twenty-five patients dropped out. In the remaining 86 patients (28 treated with placebo, 30 with calcium + placebo, and 28 with resistant starch + placebo), no difference was observed in total LI, the LI of the three compartments, or the crypt length in the four areas of the colorectum. Colonic epithelial cell proliferative activity throughout the colon of sporadic adenoma patients is not affected by supplementation with 1 g of calcium or 19 g of resistant starch.