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)

Computer-driven scanning and image processing methodology has demonstrated that genetic inheritance of risk for colorectal cancer in familial polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC) families is associated with highly pleiotropic effects on patterns of gene expression in the flat colonic mucosa. The mitochondrial (mt) gene encoding subunit 3 of cytochrome oxidase (COXIII) is one of a panel of cloned sequences which characterize genetic risk. Expression of COXIII decreased in progression of, and risk for, colonic tumors in vivo. Further, metabolizable, unbranched, short-chain fatty acids (SCFAs) elevated expression of mtCOXIII, as well as mtCOXI, in HT29 cells and also elevated mtCOX enzymatic activity. However, expression of nuclear encoded COX subunits were unaffected. These changes may be related to documented alterations in mitochondria structure and function in transformed colonic epithelial cells. SCFAs produced when colonic microflora causes fermentation of fiber are the principle energy source for normal colonic epithelial cells; SCFAs also induce a more differentiated phenotype both in vitro and in vivo. Therefore, a mechanistic link may exist between molecular events in inherited risk and a dietary factor (fiber) which may modulate such risk. In a preliminary intervention trial in collaboration with M. Lipkin, high risk HNPCC patients received daily supplements of 1500 mg CaCO3 per day, which may be protective for development of colorectal tumors. Elevations in COXIII expression were seen in 7 of 12 patients within the first 7 months, followed by complex changes in expression of this sequence.
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PMID:Modulation of gene expression as a biomarker in colon. 133 98

A considerable amount of evidence collected from several different experimental systems indicates that cyclooxygenase-2 (COX-2) may play a role in colorectal tumorigenesis. Large epidemiologic studies have shown a 40-50% reduction in mortality from colorectal cancer in persons taking aspirin or other nonsteroidal antiinflammatory drugs on a regular basis. One property shared by all of these drugs is their ability to inhibit COX, a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX have been characterized, COX-1 and COX-2. COX-2 is expressed at high levels in intestinal tumors in humans and rodents. In this study, we selected two transformed human colon cancer cell lines for studies on the role of COX-2 in intestinal tumorigenesis. We evaluated HCA-7 cells which express high levels of COX-2 protein constitutively and HCT-116 cells which lack COX-2 protein. Treatment of nude mice implanted with HCA-7 cells with a selective COX-2 inhibitor (SC-58125), reduced tumor formation by 85-90%. SC-58125 also inhibited colony formation of cultured HCA-7 cells. Conversely, SC-58125 had no effect on HCT-116 implants in nude mice or colony formation in culture. Here we provide evidence that there may be a direct link between inhibition of intestinal cancer growth and selective inhibition of the COX-2 pathway.
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PMID:Inhibition of human colon cancer cell growth by selective inhibition of cyclooxygenase-2. 915 99

Continuous use of nonsteroidal anti-inflammatory drugs (NSAIDs) lowers the relative risk of colorectal cancer in humans and decreases tumor yield in rodents treated with carcinogens. One well documented target for NSAIDs is prostaglandin endoperoxide synthase (cyclooxygenase) and two isoforms of this enzyme have been identified, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). COX enzymes produce eicosanoid products, some of which have recently been shown to activate transcription mediated by the nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARgamma), whose expression is largely restricted to adipose tissue. The present study was undertaken to determine if PPARgamma was expressed in colonic tumors. PPARgamma messenger RNA (mRNA) and protein levels were assayed in colonic tumors and normal adjacent mucosa, as well as in a variety of human colon cancer cell lines. There was a marked increase in PPARgamma RNA levels in four out of four of the colonic tumors compared to paired normal mucosa, where little expression of PPARgamma was detected. Western blotting analysis showed that PPARgamma protein was expressed in four out of five colonic tumor samples. PPARgamma was also expressed in a subset of polyps, and in certain human colon cancer cell lines as well. Additionally, we were able to demonstrate that an eicosanoid, 15 deoxy-delta12,14 PGJ2, transactivated transcription of a PPRE-driven promoter in CaCo-2 cells. Thus, we have shown that PPARgamma gene and protein expression is elevated in rodent colon tumors, in selected human colon cancer cell lines and that the PPARgamma receptor is functional in CaCo-2 cells. Since PPARgamma is a ligand-modulated transcription factor, it may provide a novel target for chemopreventive strategies for colorectal cancer.
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PMID:The nuclear eicosanoid receptor, PPARgamma, is aberrantly expressed in colonic cancers. 947 92

Epidemiologic studies indicate strongly that aspirin use reduces the risk of colorectal cancer and adenoma by approximately 40 to 50%. Perhaps up to ten years of use may be required before a benefit is apparent in colorectal cancer. The chemo-preventive actions of aspirin and other non-steroidal anti-inflammatory agents (NSAIDs) in colorectal carcinogenesis are also supported by animal studies, and by intervention studies that demonstrate that the anti-inflammatory agent sulindac causes regression of adenomas in familial adenomatous polyposis. Despite this evidence, the clinical implications are not clear because of increased gastro-intestinal irritation and bleeding episodes related to chronic aspirin use. Emerging evidence suggests that the anti-tumor properties of NSAIDs may be related primarily to the inhibition of cyclooxygenase-2 (COX-2), one of the two isoenzymes of the COX enzyme family. If confirmed, a new generation of selective COX-2 inhibitors may retain some of the chemo-preventive properties of NSAIDs with fewer side-effects. Firm recommendations regarding the use of aspirin or other NSAIDs to prevent colorectal cancer must await further research. For now, the decision must lie with the patient, in consultation with his or her healthcare provider, after a careful weighing of all potential risks and benefits.
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PMID:The prevention of colorectal cancer by aspirin use. 1047 28

Cyclooxygenase-2 (COX-2) gene overexpression is suggested to play important roles in colorectal tumorigenesis. Epidemiological studies revealed that nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and sulindac, which inhibit COX activity, reduce colorectal cancer mortality. Current investigations have focused on delineating the molecular mechanisms that regulate COX-2 gene expression and the roles of NSAIDs in cancer chemoprevention. COX-2 catalyzes the production of prostaglandins (PGs) from arachidonic acid (AA), generated by phospholipases A2 (PLA2s), a family of acyl esterases that cause the release of AA from cellular phospholipids. Pancreatic secretory PLA2 (sPLA2), via its receptor (sPLA2R), transcriptionally activates COX-2 gene expression in several cell types, although a specific transcription factor mediating COX-2 expression has not yet been identified. Here, we report that a transcription factor, CCAAT/enhancer-binding protein beta(C/EBPbeta), plays a critical role in sPLA2IB-induced, receptor-mediated COX-2 gene expression in MC3T3E1 and NIH3T3 cells. Furthermore, treatment of these cells with NSAIDs in the presence of sPLA2IB appears to potentiate the stimulatory effects on COX-2 mRNA and COX-2 protein expression and a concomitant elevation in PG production. Most significantly, NSAID treatment appears to drastically suppress the production of cytosolic PLA2 (cPLA2) mRNA. The lack of sPLA2IB, sPLA2IIA, and sPLA2V mRNA expression in both NIH3T3 and MC3T3E1 cells suggests that cPLA2 is the most likely enzyme that catalyzes the release of AA, the rate-limiting substrate of COX for the production of PGs. Our results suggest that: (a) sPLA2IB receptor-mediated COX-2 expression is mediated via C/EBPbeta; (b) NSAIDs in the presence of sPLA2IB potentiate the stimulatory effects of sPLA2IB on COX-2 mRNA expression; and (c) despite the apparent stimulation of COX-2 expression by NSAIDs, they strikingly deprive COX-2 of its substrate, AA, by suppressing cPLA2 mRNA expression. Both AA and PGs regulate many vital biological functions (e.g., motility and invasiveness) that are dysregulated in most cancer cells, and they have profound effects on cellular differentiation. Our results raise the possibility that deprivation of COX-2 of its substrate by the suppression of cPLA2 mRNA expression is an additional mechanism used by NSAIDs to inhibit tumorigenesis.
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PMID:Transcriptional regulation of cyclooxygenase-2 gene expression: novel effects of nonsteroidal anti-inflammatory drugs. 1070 28

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation and induce apoptosis in human colorectal cancer cells in vitro. It remains unclear whether individual NSAIDs act by cyclooxygenase-2 (COX-2) inhibition and how NSAIDs exert their anti-proliferative effects. We investigated the effects of NS-398 (a selective COX-2 inhibitor), indomethacin (a non-selective COX inhibitor) and aspirin on four human colorectal cancer cell lines (HT29.Fu, HCA-7, SW480 and HCT116). NS-398 completely inhibited proliferation, induced G1 arrest and promoted apoptosis in COX-2-expressing cells (HT29.Fu and HCA-7). However, indomethacin had similar effects on all cells, regardless of COX-2 expression. NS-398 also had anti-proliferative activity on COX-2-negative cell lines (SW480 and HCT116). Aspirin inhibited proliferation of all cell lines but did not induce apoptosis. Indomethacin decreased beta-catenin protein expression in all cells (unlike NS-398 or aspirin). NSAIDs act on human colorectal cancer cells via different mechanisms. Decreased beta-catenin protein expression may mediate the anti-proliferative effects of indomethacin.
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PMID:The effect of non-steroidal anti-inflammatory drugs on human colorectal cancer cells: evidence of different mechanisms of action. 1073 33

Inhibitors of the inducible cyclooxygenase (COX-2) have emerged as a promising new class of drugs that may be useful for the prevention of colorectal cancer. Experimental evidence to support such a claim has come from both clinical and laboratory findings that show that both selective and nonselective COX inhibitors effectively block tumor growth. Although the precise mechanism(s) by which these drugs modulate tumor growth is not known, there is evidence from colon carcinoma cell culture studies that COX-2 activity may play an important role in regulating angiogenesis and apoptosis. Recent data obtained in animal studies suggest that COX-2 inhibitors may also be useful in the treatment of established colorectal tumors. Treatment of COX-2 expressing tumor cells with selective COX-2 inhibitors appears to reset the balance between cell proliferation and cell death such that there is no increase in tumor volume.
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PMID:Translational studies on Cox-2 inhibitors in the prevention and treatment of colon cancer. 1091 14

There is evidence from both genetic and pharmacologic studies to suggest that the cyclooxygenase-2 (COX-2) enzyme plays a causal role in the development of colorectal cancer. However, little is known about the identity or role of the eicosanoid receptor pathways activated by COX-derived prostaglandins (PG). We previously have reported that COX-2-derived prostacyclin promotes embryo implantation in the mouse uterus via activation of the nuclear hormone receptor peroxisome proliferator-activated receptor (PPAR) delta. In light of the recent finding that PPARdelta is a target of beta-catenin transactivation, it is important to determine whether this signaling pathway is operative during the development of colorectal cancer. Analysis of PPARdelta mRNA in matched normal and tumor samples revealed that expression of PPARdelta, similar to COX-2, is up-regulated in colorectal carcinomas. In situ hybridization studies demonstrate that PPARdelta is expressed in normal colon and localized to the epithelial cells at the very tips of the mucosal glands. In contrast, expression of PPARdelta mRNA in colorectal tumors was more widespread with increased levels in transformed epithelial cells. Analysis of PPARdelta and COX-2 mRNA in serial sections suggested they were colocalized to the same region within a tumor. Finally, transient transfection assays established that endogenously synthesized prostacyclin (PGI(2)) could serve as a ligand for PPARdelta. In addition, the stable PGI(2) analog, carbaprostacyclin, and a synthetic PPARdelta agonist induced transactivation of endogenous PPARdelta in human colon carcinoma cells. We conclude from these observations that PPARdelta, similar to COX-2, is aberrantly expressed in colorectal tumors and that endogenous PPARdelta is transcriptionally responsive to PGI(2). However, the functional consequence of PPARdelta activation in colon carcinogenesis still needs to be determined.
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PMID:Prostacyclin-mediated activation of peroxisome proliferator-activated receptor delta in colorectal cancer. 1108 69

DISTINCT EFFECTS: Since the discovery of the two isoforms of COX, the therapeutic effects of nonsteroidal antiinflammatory drugs (NSAID) can be distinguished from their adverse effects linked to the inhibition of the constitutional form via selective inhibition of the inducible form. Non-selective NSAID that inhibit both COX isoforms are difficult to use for long-term regimens. NSAID AND CANCER PREVENTION: Epidemiology studies and animal and in vitro studies have demonstrated that regular use of NSAID reduced the incidence of colorectal cancer and certain precancer lesions. PROMISING PERSPECTIVES: COX-2 specific inhibitors, for example cerecoxib or rofecoxib, are potentially interesting for human therapy for chemoprevention of epithelial cancer or as medical treatment, alone or in combination with other anticancer treatments.
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PMID:[Cyclooxygenase inhibitors]. 1130 98

We have investigated the possible functional relationships between cellular invasion pathways induced by trefoil factors (TFFs), src, and the cyclooxygenases COX-1 and COX-2. Pharmacological inhibitors of the Rho small GTPase (C3 exoenzyme), phospholipase C (U-73122), cyclooxygenases (SC-560, NS-398), and the thromboxane A2 receptor (TXA2-R) antagonist SQ-295 completely abolished invasion induced by intestinal trefoil factor, pS2, and src in kidney and colonic epithelial cells MDCKts.src and PCmsrc. In contrast, invasion was induced by the TXA2-R mimetic U-46619, constitutively activated forms of the heterotrimeric G-proteins Galphaq (AGalphaq), Galpha12, Galpha13 (AGalpha12/13), which are signaling elements downstream of TXA2-R. Ectopic overexpression of pS2 cDNA and protein in MDCKts.src-pS2 cells and human colorectal cancer cells HCT8/S11-pS2 initiate distinct invasion signals that are Rho independent and COX and TXA2-R dependent. We detected a marked induction of COX-2 protein and accumulation of the stable PGH2/TXA2 metabolite TXB2 in the conditioned medium from cells transformed by src. This led to activation of the TXA2-R-dependent invasion pathway, which is monitored via a Rho- and Galpha12/Galpha13-independent mechanism using the Galphaq/PKC signaling cascade. These findings identify a new intracrine/paracrine loop that can be monitored by TFFs and src in inflammatory diseases and progression of colorectal cancers.
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PMID:Activation of cellular invasion by trefoil peptides and src is mediated by cyclooxygenase- and thromboxane A2 receptor-dependent signaling pathways. 1142 83


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