Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are extensively used as anti-inflammatory and analgesic agents in the elderly, as well as for their anti-thrombotic properties. In the future, NSAIDs may be more widely used in this sector of the population for the prevention of colon cancer. However, the elderly demonstrate a particularly high incidence of adverse reactions to this class of compounds. The factors responsible for this differential toxicity involve age-related pharmacokinetic, pharmacodynamic and physiological factors, as well as coincident disease states and polypharmacy. Selective inhibitors of cyclooxygenase-2 form a novel class of anti-inflammatory drugs that, in animal studies, exhibit significantly fewer adverse effects on the gastrointestinal tract than standard NSAIDs. If this proves to be the case in humans, these novel agents may be useful for the treatment of inflammation and pain as well as in colorectal cancer prevention, but they will not have utility as antithrombotic agents.
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PMID:Selective inhibitors of cyclooxygenase-2. Potential in elderly patients. 897 41

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

The recent development of mouse strains with cancer-related genes overexpressed or inactivated has provided investigators with new models for testing chemoprevention strategies to offset specific genetic susceptibilities to cancer. This review focuses on the three genetically altered mouse models that have been the most widely used in chemoprevention studies: Min mice, which carry a mutation in the adenomatous polyposis coli (APC) gene; APC-knockout mice; and p53-knockout mice. Studies with the Min and APC-knockout mice provide the strongest evidence to date that the enzyme cyclooxygenase-2 plays a major role in colon carcinogenesis, and that nonsteroidal anti-inflammatory drugs that target cyclooxygenase-2 have great potential as colon cancer chemopreventive agents. In addition, chemoprevention studies in mice deficient of the p53 tumor-suppressor gene, the most commonly altered gene in human cancer, suggest that the increased susceptibility to cancer resulting from the loss of p53 function may be offset by preventive approaches. Other recently developed transgenic and knockout models of potential interest for chemoprevention studies will also be discussed.
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PMID:Experimental models of gene-environment interaction for cancer chemoprevention studies. 932 28

The synovial fluid or group II secretory phospholipase A2 (sPLA2) has been implicated in various inflammatory processes and has been shown to release arachidonic acid for prostaglandin biosynthesis. In human colorectal cancer, both arachidonic acid and eicosanoid levels are elevated. Recently, sPLA2 has been identified as a candidate gene that modifies the Apc gene in the Min mouse, a murine model for familial adenomatous polyposis (FAP). Loss of sPLA2 gene function results in susceptibility to the Min phenotype and the formation of multiple intestinal polyps, whereas mice expressing an active sPLA2 gene are resistant to polyp formation. Therefore, there are two potentially contrasting roles for sPLA2 in colon cancer; one is protection against polyp formation, and the other, the release of arachidonic acid for prostaglandin production and subsequent tumor promotion. To investigate these contrasting dual roles of sPLA2, we have examined the expression and sequence of the sPLA2 mRNA in normal mucosa and duodenal and colorectal polyps from FAP patients. In 11 of 14 patients, there was a significant increase in sPLA2 mRNA levels in the adenoma over the normal tissue. In some cases, there was over 100-fold increase in mRNA levels in the adenoma compared with normal tissue. Analysis of multiple adenomatous polyps from individual patients revealed that not all polyps contained elevated levels of sPLA2 mRNA. Immunoblot analysis also showed that sPLA2 protein expression was elevated in adenoma over normal tissue in five of six FAP patients analyzed. Furthermore, sequence analysis of sPLA2 mRNA present in these samples did not reveal mutations in the coding region. The implications of the up-regulation of sPLA2 in FAP is not clear, but unlike the Min mouse model, it does not seem to have a significant effect on polyp formation. In contrast, the high level of sPLA2 expression is more likely contributing to the elevated levels of arachidonic acid found in colorectal cancer and, in conjunction with the elevated expression of cyclooxygenase-2, could be another factor in tumor formation.
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PMID:Overexpression of the nonpancreatic secretory group II PLA2 messenger RNA and protein in colorectal adenomas from familial adenomatous polyposis patients. 945 96

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

Many of aspirin's therapeutic effects arise from its acetylation of cyclooxygenase-2 (COX-2), whereas its antithrombotic and ulcerogenic effects result from its acetylation of COX-1. Here, aspirin-like molecules were designed that preferentially acetylate and irreversibly inactivate COX-2. The most potent of these compounds was o-(acetoxyphenyl)hept-2-ynyl sulfide (APHS). Relative to aspirin, APHS was 60 times as reactive against COX-2 and 100 times as selective for its inhibition; it also inhibited COX-2 in cultured macrophages and colon cancer cells and in the rat air pouch in vivo. Such compounds may lead to the development of aspirin-like drugs for the treatment or prevention of immunological and proliferative diseases without gastrointestinal or hematologic side effects.
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PMID:Aspirin-like molecules that covalently inactivate cyclooxygenase-2. 963 99

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to cause apoptosis in several cell lines including transformed chicken embryo fibroblasts and human colon cancer cells. We herein report the apoptotic effect of NSAIDs in a non-transformed cell line derived from the rat gastric mucosa, RGMI (rat gastric mucosa cell first). 1-[p-Chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid (indomethacin) and sodium 2-(2,6-dichloroanilino)phenylacetate (sodium diclofenac), potent and non-selective inhibitors of cyclooxygenase, were found to induce DNA fragmentation in RGM1 cells in a time- and concentration-dependent manner. The expression of mRNA for cyclooxygenase-2 was hardly detected in the intact cells but was clearly enhanced when the cells were incubated with the two NSAIDs. In contrast, the expression of mRNA for cyclooxygenase-1 was constitutive and was never affected by NSAIDs. The effect of [3,4-di(4-methoxyphenyl)-5-isoxazolyl] acetic acid (mofezolac), a potent and highly preferential inhibitor of cyclooxygenase-1, and N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulphonamide (NS-398), a selective inhibitor of cyclooxygenase-2, on DNA fragmentation and cyclooxygenase-2 mRNA expression was weak compared to the effect of indomethacin or sodium diclofenac. The DNA fragmentation induced by sodium diclofenac was hardly affected by the exogenous addition of 16,16-dimethyl prostaglandin E2 but was inhibited by caspase inhibitors such as Ac-YVAD-CHO and Ac-DEVD-CHO. The present data provide the first evidence that NSAIDs, such as indomethacin and sodium diclofenac, cause apoptotic DNA fragmentation in cultured gastric mucosal cells, and also indicate the involvement of caspases rather than the inhibition of cellular prostaglandin synthesis in the apoptotic process.
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PMID:Induction of apoptotic DNA fragmentation by nonsteroidal anti-inflammatory drugs in cultured rat gastric mucosal cells. 985 95

Cyclooxygenase-2 has been reported to play an important role in colorectal carcinogenesis. The effects of meloxicam (a COX-2 inhibitor) on the growth of two colon cancer cell lines that express COX-2 (HCA-7 and Moser-S) and a COX-2 negative cell line (HCT-116) were evaluated. The growth rate of these cells was measured following treatment with meloxicam. HCA-7 and Moser-S colony size were significantly reduced following treatment with meloxicam; however, there was no significant change in HCT-116 colony size with treatment. In vivo studies were performed to evaluate the effect of meloxicam on the growth of HCA-7 cells when xenografted into nude mice. We observed a 51% reduction in tumor size after 4 weeks of treatment. Analysis of COX-1 and COX-2 protein levels in HCA-7 tumor lysates revealed a slight decrease in COX-2 expression levels in tumors taken from mice treated with meloxicam and no detectable COX-1 expression. Here we report that meloxicam significantly inhibited HCA-7 colony and tumor growth but had no effect on the growth of the COX-2 negative HCT-116 cells.
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PMID:Meloxicam inhibits the growth of colorectal cancer cells. 988 78

Inducible nitric oxide synthase (iNOS) is overexpressed in colonic tumors of humans and also in rats treated with a colon carcinogen. iNOS appear to regulate cyclooxygenase-2 (COX-2) expression and production of proinflammatory prostaglandins, which are known to play a key role in colon tumor development. Experiments were designed to study the inhibitory effects of S,S'-1,4-phenylene-bis(1,2-ethanediyl)bis-isothiourea (PBIT) a selective iNOS-specific inhibitor, measured against formation of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF). Beginning at 5 weeks of age, male F344 rats were fed experimental diets containing 0 or 50 p.p.m. of PBIT, or 2000 p.p.m. of curcumin (non-specific iNOS inhibitor). One week later, rats were injected s.c. with AOM (15 mg/kg body wt, once weekly for 2 weeks). At 17 weeks of age, all rats were killed, colons were evaluated for ACF formation and colonic mucosa was assayed for isoforms of COX and NOS activities. Both COX and iNOS activities in colonic mucosa of the AOM-treated rats were significantly induced. Importantly, 50 p.p.m. PBIT suppressed AOM-induced colonic ACF formation to 58% (P < 0.0001) and crypt multiplicity containing four or more crypts per focus to 78% (P < 0.0001); it also suppressed AOM-induced iNOS activity. Curcumin inhibited colonic ACF formation by 45% (P < 0.001). These observations suggest that iNOS may play a key regulatory role in colon carcinogenesis. Developing iNOS-specific inhibitors may provide a selective and safe chemopreventive strategy for colon cancer treatment.
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PMID:Chemoprevention of colonic aberrant crypt foci by an inducible nitric oxide synthase-selective inhibitor. 1022 93

Emerging evidence suggests that cyclooxygenase-2 (COX-2) has diverse physiologic and pathophysiologic functions. It is expressed constitutively in the developing kidney and brain, playing a role in their proper maturation and function. Further, COX-2 expression may be up-regulated at certain sites: in the kidney during sodium restriction; in the microglia of cognitive centers within the hippocampus and cortex in Alzheimer's disease; and in intestinal adenomas and colon tumors. On the basis of COX-2 expression in Alzheimer's disease and colon cancer, COX-2-specific inhibitors may find clinical utility in the prevention or treatment of these conditions. Despite this apparently optimistic outlook for future uses of COX-2 inhibitors, most of the findings supporting this perspective are based on in vitro and in vivo models and must be rigorously corroborated in human studies, some of which are already planned.
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PMID:The clinical potential of cyclooxygenase-2-specific inhibitors. 1039 Jan 28


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