Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0009402 (colorectal cancer)
 53,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regular use of various nonsteroidal anti-inflammatory drugs (NSAIDs) was shown to decrease the incidence of colorectal cancer. This effect is thought to be caused predominantly by inhibition of cyclooxygenase-2 (COX-2) and, subsequently, prostaglandin synthesis. However, recent studies have suggested that COX-independent pathways may contribute considerably to these antiproliferative effects. To evaluate the involvement of COX-dependent and COX-independent mechanisms further, we assessed the effects of celecoxib (selective COX-2 inhibitor) and SC560 (selective COX-1 inhibitor) on cell survival, cell cycle distribution, and apoptosis in three colon cancer cell lines, which differ in their expression of COX-2. Both drugs induced a G0/G1 phase block and reduced cell survival independent of whether or not the cells expressed COX-2. Celecoxib was more potent than SC560. The G0/G1 block caused by celecoxib could be attributed to a decreased expression of cyclin A, cyclin B1, and cyclin-dependent kinase-1 and an increased expression of the cell cycle inhibitory proteins p21Waf1 and p27Kip1. In addition, celecoxib, but not SC560, induced apoptosis, which was also independent of the COX-2 expression of the cells. In vivo, celecoxib as well as SC560 reduced the proliferation of HCT-15 (COX-2 deficient) colon cancer xenografts in nude mice, but both substances had no significant effect on HT-29 tumors, which express COX-2 constitutively. Thus, our in vitro and in vivo data indicate that the antitumor effects of celecoxib probably are mediated through COX-2 independent mechanisms and are not restricted to COX-2 over-expressing tumors.
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PMID:COX-2 independent induction of cell cycle arrest and apoptosis in colon cancer cells by the selective COX-2 inhibitor celecoxib. 1160 77

Colorectal cancer is becoming increasingly common in Asian countries and still remains the second leading cause of cancer deaths in the United States. Efforts to prevent colon cancer have targeted early detection through screening and chemoprevention. For the last ten years our laboratory has utilized an in vivo screening assay for the testing of potential cancer preventives for colon cancer. We have conducted investigations on over 150 compounds including many with botanical or herbal origins. As part of our program on natural products we have examined a number of herbal and botanical products in the aberrant crypt foci (ACF) assay including Korean red ginseng powder, green tea catechins, curcumin from the Indian culinary spice, tumeric, compounds from garlic and onion, resveratrol from red grapes, among others. In the ginseng experiments groups of 10 F344 rats were fed ginseng powder at a dose of 0.5 g/kg or 2 mg/kg for 5 weeks. During weeks 2 and 3 rats were injected with 10 mg/kg azoxymethane to induce ACF. Controls (n=10) did not receive azoxymethane (AOM). Rats were killed by CO2 overdose and ACF counted in the rat colon. In 8 week post-initiation experiments ginseng powder inhibited the progression of established ACF, indicating a cytostatic effect. This may be due to an anti-inflammatory effect. There is a body of literature that suggests that compounds in wine, tumeric, and tea inhibit cyclooxygenases, thus reducing prostaglandin-mediated effects on the colon. As colon tumors have been shown to highly express COX-2 protein, and given, that many NSAID drugs also suppress COX-1, it is tempting to speculate that herbal products that inhibit one or both forms of the COX enzyme will be effective agents for the prevention of cancer in man.
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PMID:Colon cancer chemoprevention with ginseng and other botanicals. 1174 82

Eicosanoids play an important role in numerous physiologic and pathophysiologic processes in the gastrointestinal tract, including maintenance of mucosal integrity, stimulation of mucus and electrolyte secretion, and inflammation. A rapidly growing body of evidence implicates COX-2 in colorectal carcinogenesis. COX-2 has been shown to alter cellular adhesion, apoptosis, and angiogenesis, contributing to its neoplastic potential. NSAIDs appear to attenuate this potential by mechanisms that are COX-2 dependent and independent. Several advances have been made in understanding the details of COX-2 regulation. The downstream effect of COX-2-dependent metabolites varies with the enzymatic machinery present in a particular cell, the level of COX activity, differences in location and types of prostaglandin receptors, and differences in signal transduction pathways. Further studies are needed to understand better these complex interactions, which may provide insight into the role of COX-2 in pathologic conditions, such as intestinal inflammation and colorectal cancer.
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PMID:Role of cyclooxygenase inhibitors for the prevention of colorectal cancer. 1176 29

The cyclooxygenase-2 (COX-2) gene encodes an inducible enzyme that converts arachidonic acid to prostaglandins and is up-regulated in colorectal neoplasms. Evidence indicates that COX-2 may regulate apoptosis and can influence the malignant phenotype. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit COX enzymes and induce apoptosis in colorectal cancer cell lines, which may contribute to their antitumor effects. To determine whether forced COX-2 expression modulates susceptibility to drug-induced apoptosis, HCT-15 colon carcinoma cells were stably transfected with the COX-2 cDNA, and two clones overexpressing COX-2 were isolated. Selective COX-2 (NS398) and nonselective (sulindac sulfide) COX inhibitors, as well as 5-fluorouracil (5-FU), induced apoptosis (terminal deoxynucleotidyl transferase-mediated nick end labeling in a dosage-dependent manner. Forced COX-2 expression significantly attenuated induction of apoptosis by all three of the drugs compared with parental HCT-15 cells. NSAIDs and 5-FU induced the mitochondrial release of cytochrome c as well as caspase-3 and -9 activation, and to a much lesser extent, caspase-8. COX-2-overexpressing cells showed reduced cytochrome c and caspase activation, relative to parental cells. A specific inhibitor of caspase-3 restored cell survival after drug treatment. COX-2 transfectants were found to overexpress the antiapoptotic Bcl-2 mRNA and protein relative to parental cells. In conclusion, forced COX-2 expression significantly attenuates apoptosis induction by NSAIDs and 5-FU through predominant inhibition of the cytochrome c-dependent apoptotic pathway. COX-2-mediated up-regulation of Bcl-2 suggests a potential mechanism for reduced apoptotic susceptibility.
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PMID:Cyclooxygenase-2 overexpression reduces apoptotic susceptibility by inhibiting the cytochrome c-dependent apoptotic pathway in human colon cancer cells. 1241 64

Cyclooxygenase-2 (COX-2), the inducible cyclooxygenase isozyme involved in the conversion of arachidonic acid (AA) to biologically active prostanoids, has become the subject of intense interest during the last few years. The recent surge of interest stems from seminal studies that correlated elevated expression of COX-2 with tumor induction and progression, and epidemiological studies that correlated reduced risk of developing certain types of cancers with chronic use of non-steroidal anti-inflammatory agents (NSAIDs). Although these observations were first reported with colorectal cancer (CRC), similar findings have subsequently been made with other types of cancers. A wide spectrum of studies continue to be undertaken in both laboratory and clinical settings to elucidate the mechanisms underlying these anti-tumor effects of COX-2 for potential translation into cancer chemoprevention and therapy. The aim of this article is to present a review of COX genes, the prostaglandin-cyclooxygenase relationship, the role of COX-2 in carcinogenesis and the rationale for targeting COX-2 with NSAIDs for cancer chemoprevention. Special emphasis is given to the role of COX-2 expression in the genesis and progression of colorectal neoplasia, and its correlation with other pathological characteristics of CRC. Preliminary observations on COX-2 expression in inflammatory bowel disease (IBD)-related colorectal neoplasia are also presented.
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PMID:COX-2, NSAIDs and human neoplasia. Part I: Colorectal neoplasms. 1249 94

Non-steroidal anti-inflammatory drugs (NSAID) belong to the most commonly used drugs worldwide. NSAIDs can cause serious side effects to the gastrointestinal tract. During NSAIDs treatment 10-12% patients suffer from dyspepsia. Up to 1% patients develop severe gastrointestinal complications (ulcer, bleeding, perforation). Any part of gastrointestinal tract could be affected. In oesophagus, NSAIDs can cause oesophagitis of fibrous stricture. NSAID gastropathy can be detected in 40% patients chronically treated with NSAIDs. NSAIDs toxic injury to small and large bowel is frequent but only seldom properly recognised. Serious hepatic lesions are rare. There is no fully reliable and sure prophylaxis or treatment of NSAIDs impairment of to the gastrointestinal tract. Rate of side effects can be reduced by reasonable prescriptions and by primary and secondary prophylaxis. Low rate of side effects is associated with the use of pro-drugs (compound is metabolised to an active substance after absorption from the gastrointestinal tract). New promising drugs were developed with dual action (5-lipoxygenase- and COX-inhibition) and NSAID releasing NO (nitronaproxen, nitrophenac). Specific COX-2 inhibitors (coxibes) provide comparable anti-inflammatory and analgesic effect but the risk of serious side effects to the gastrointestinal tract is significantly lower (when compared with non-specific NSAIDs). Beside harmful effects, NSAIDs are powerful tool in chemoprevention of colorectal cancer.
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PMID:[Effects of nonsteroidal anti-inflammatory agents on the gastrointestinal tract]. 1256 74

The regular intake of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been associated with decreased incidence of certain types of cancer particularly those with an inflammatory component. The protective effects of these drugs in colorectal cancer are particularly marked, with a 40-50% reduction in risk. Research in this area has focussed on understanding and optimising these cytoprotective effects. NSAIDs are believed to operate by inhibiting COX-2, an enzyme that appears to be involved in a number of cancer promoting processes. This hypothesis is consistent with the observation that the COX-2 selective inhibitors dramatically decrease tumour formation in human and animal studies. Surprisingly aspirin, which is selective for COX-1 over COX-2, and sulindac, which is an equipotent inhibitor of the COX isoenzymes, appear to have a similar anticancer profile to the COX-2 selective NSAIDs. A number of mechanisms have been proposed to explain the anomalous effects of aspirin. The first of these relates to the unique mode of action of aspirin, which acetylates the COX-2 enzyme and generates the cancer-suppressing 15R-hydroxyeicosatetraenoic acid at the site of a potential tumour. The alternative rationale relates to the metabolism of aspirin to salicylic acid, which has a cyclooxygenase independent anti-inflammatory mechanism, preventing the inflammatory response at the gene transcription level. A new generation of drugs could evolve from approaches to improving the therapeutic index of aspirin or by modifications to known therapies such as sulindac and celecoxib.
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PMID:The medicinal chemistry implications of the anticancer effects of aspirin and other NSAIDs. 1276 97

Colorectal cancer (CRC) is the second leading cause of cancer death in the USA. Accumulation of beta-catenin protein is nearly ubiquitous in colon adenomas and cancers, presumably due to mutations in the APC or beta-catenin genes that inhibit proteasome-dependent degradation of beta-catenin protein. Substantial clinical, epidemiological, and animal evidence indicate that sulindac and other non-steroidal anti-inflammatory drugs (NSAIDs) prevent the development of CRC. The mechanisms by which sulindac exerts its potent growth inhibitory effects against colon tumor cells are incompletely understood, but down-regulation of beta-catenin has been suggested as one potential mechanism. The goal of this study was to determine the mechanism of beta-catenin protein down-regulation by sulindac metabolites. Treatment of human colon cancer cell lines with apoptotic concentrations of sulindac metabolites (sulindac sulfide, sulindac sulfone) induced a dose- and time-dependent inhibition of beta-catenin protein expression. Inhibition of proteasome activity with MG-132 partially blocked the ability of sulindac sulfide and sulindac sulfone to inhibit beta-catenin protein expression. Pretreatment with the caspase inhibitor z-VAD-fmk blocked morphological signs of apoptosis as well as caspase cleavage, and also partially prevented beta-catenin degradation by sulindac metabolites. These effects occurred in cells with bi-allelic APC mutation (SW480), with wild-type APC but mono-allelic beta-catenin mutation (HCT116) and in cells that lack expression of either COX-1 or -2 (HCT15). These results indicate that loss of beta-catenin protein induced by sulindac metabolites is COX independent and at least partially due to reactivation of beta-catenin proteasome degradation and partially a result of caspase activation during the process of apoptosis.
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PMID:Sulindac metabolites induce caspase- and proteasome-dependent degradation of beta-catenin protein in human colon cancer cells. 1455 7

Cyclooxygenase-2 (COX-2) is an inducible enzyme that regulates prostaglandin synthesis and is overexpressed at sites of inflammation and in several epithelial cancers. Recently, a causal link for COX-2 in epithelial tumorigenesis was shown in genetically-manipulated animal models of colon and breast carcinoma. Data indicate that COX-2 is involved in the regulation of apoptosis, angiogenesis, and tumor cell invasiveness, which appear to contribute to its effects on tumorigenesis. Multiple studies have shown that nonselective COX and selective COX-2 inhibitors effectively prevent experimental colon cancer. Furthermore, sulindac and the selective COX-2 inhibitor celecoxib were shown to regress colorectal polyps in patients with familial adenomatous polyposis. Although the exact anti-tumor mechanisms of these agents await further study, data indicate that both COX-dependent and COX-independent mechanisms may be important. In this review, the association between COX-2 and colorectal tumorigenesis and potential mechanisms of this effect are discussed. Additionally, evidence supporting the role of NSAIDs and selective COX-2 inhibitors for the prevention and treatment of human colorectal cancer is reviewed.
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PMID:Role of cyclooxygenase-2 in colorectal cancer. 1500 Jan 50

Two isoforms of cyclooxygenase, COX-1 and COX-2, have been identified and shown to be involved in tumorigenesis. Although, overexpression of COX-2 in human cancers has been repeatedly reported, no data have hitherto been available for Thai patients. To cast light on the role(s) of COX enzymes in the development and progression of colorectal cancers and to determine the incidence of COX-2 overexpression, the expression levels of COX-1 and COX-2 proteins using Western blot analysis in tumor tissues and adjacent normal tissues obtained from 44 Thai patients with colorectal cancer. Compared with paired normal tissues, COX-2 was overexpressed in 13 of 44 colorectal tumor tissues (29.5%). Overall, COX-2 levels in colorectal tumor specimens were significantly correlated with histological differentiation, in particular in the tumors with poor differentiation (p<0.05). In addition, overexpression of COX-2 was found more frequently in colorectal tumors with lymphatic invasion, regional lymph node metastasis and larger size, although without statistical significance. In contrast to the relatively consistent alteration in COX-2 expression, the level of COX-1 expression was quite varied in tumor tissues. Forty-eight percent of colorectal tumors exhibited a decreased level of COX-1 in comparison to normal tissues and overexpressed in 23%. Thus both isoforms may both play roles in promoting tumorigenesis. However, there was no significant relationship between the alteration of COX-1 protein levels and any pathological features of tumors.
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PMID:Expression of cyclooxygenase-1 and -2 and clinicopathologic features of colorectal cancer in northern Thailand. 1507 4


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