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)

NO-donating aspirin (NO-ASA) is a potentially important chemopreventive agent against cancer. Since positional isomerism affects strongly its potency in inhibiting colon cancer cell growth, we studied the metabolic transformations of its ortho-, meta-, and para-isomers in rat liver and colon cytosolic, microsomal, and mitochondrial fractions as well as in intact HT-29 human colon cancer cells. NO-ASA and metabolites were determined by high-performance liquid chromatography and products identified by mass spectroscopy, as required. For all three isomers, the acetyl group on the ASA moiety was hydrolyzed rapidly. This was followed by hydrolysis of the ester bond linking the salicylate anion to the spacer. The ortho- and para-isomers produced salicylic acid and a putative intermediate consisting of the remainder of the molecule, which via a rapid step generated nitrate, (hydroxymethyl)phenol, and a conjugate of spacer with glutathione. The meta-isomer, in contrast, generated salicylic acid and (nitroxymethyl)phenol, the latter leading to (hydroxymethyl)phenol and the glutathione-spacer conjugate. This metabolic pathway takes place in its entirety only in the cytosolic fraction of the tissues tested and in intact human colon cancer cells, perhaps reflecting exposure to the cytosolic glutathione S-transferase, which catalyzes the formation of the spacer-glutathione conjugate. Thus, the three positional isomers of NO-ASA differ in their metabolism and these differences correlate with their differential effects on cancer cell growth, underscoring the importance of positional isomerism in modulating drug effects.
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PMID:In vitro metabolism of nitric oxide-donating aspirin: the effect of positional isomerism. 1552 52

NO-donating aspirin (NO-ASA), a novel pharmacological agent currently undergoing clinical testing, consists of ASA to which a nitrate group is covalently linked via a spacer molecule. We synthesized the three positional isomers of NO-ASA with respect to the -CH(2)ONO(2) group (ortho, meta, and para) and examined whether this isomerism affects the biological activity of NO-ASA on HT-29 human colon cancer cells. The ortho- and para-isomers showed similar IC(50) values (1-5 microM) for cell growth inhibition over 72 h, whereas the IC(50) of the meta-isomer was 200 to 500 microM. The ortho- and para-isomers inhibited cell proliferation more potently than the meta-isomer. All three induced apoptosis but the ortho- and para-isomers also induced atypical cells (they maintain their shape but have diminished or absent nuclear material). Treatment for 3 weeks of Min (Apc(min)(/+)) mice, a model of intestinal cancer, with equimolar amounts of meta- and para-NO-ASA decreased the number of tumors in the small intestine by 36 and 59% (P < 0.01), respectively, compared with vehicle-treated controls, thus confirming their in vitro differences in potency. A structure-activity study of the three isomers revealed that substituting an aliphatic for the aromatic spacer or removing the -ONO(2) group profoundly diminished NO-ASA's ability to inhibit cell growth, whereas removal of the acetyl group on the ASA moiety did not affect cell growth inhibition. Thus, positional isomerism is critical for the pharmacological properties of NO-ASA against colon cancer and it should be taken into consideration in rational drug design.
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PMID:Positional isomerism markedly affects the growth inhibition of colon cancer cells by nitric oxide-donating aspirin in vitro and in vivo. 1552 53

Inflammatory bowel disease (IBD) is classically subdivided into ulcerative colitis (UC) and Crohn's disease (CD). Patients with IBD have increased risk for colorectal cancer. Because the pathogenesis of colorectal carcinoma has not been entirely defined yet and there is no ideal treatment for colon cancer, cancer prevention has become increasingly important in patients with IBD. The two adopted methods to prevent the development of colon cancer in clinical practice include the prophylactic colectomy and colonoscopic surveillance. But patients and physicians seldom accept colectomy as a routine preventive method and most patients do not undergo appropriate colonoscopic surveillance. Chemoprevention refers to the use of natural or synthetic chemical agents to reverse, suppress, or to delay the process of carcinogenesis. Chemoprevention is a particularly useful method in the management of patients at high risk for the development of specific cancers based on inborn genetic susceptibility, the presence of cancer-associated disease, or other known risk factors. Prevention of colorectal cancer by administration of chemopreventive agents is one of the most promising options for IBD patients who are at increased risks of the disease. The chemopreventive efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) against intestinal tumors has been well established. But with reports that NSAIDs aggravated the symptoms of colitis, their sustained use for the purpose of cancer chemoprevention has been relatively contraindicated in IBD patients. Another hopeful candidate chemoprevention drug for IBD patients is 5-aminosalicylic acid (5-ASA), which is well tolerated by most patients and has limited systemic adverse effects, and no gastrointestinal toxicity. 5-ASA lacks the well-known side effects of long-term NSAIDs use. Retrospective correlative studies have suggested that the long-term use of 5-ASA in IBD patients may significantly reduce the risk of development of colorectal cancer. According to the literature, this agent might well satisfy clinical expectations with respect to a safe and effective chemopreventive agent.
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PMID:5-aminosalicylic acid is an attractive candidate agent for chemoprevention of colon cancer in patients with inflammatory bowel disease. 1563 33

Colorectal cancer is the second most deadly cancer in the United States. When diagnosed early, current treatments bring a limited success; however, once metastasis occurs, radiation and chemotherapy are generally ineffective. Structural changes in the ECM are necessary for cell migration during tissue remodeling. Matrix metalloproteinases (MMPs), VEGF, Ki-67 (proliferative protein), and constituents of ECM, such as fibronectin, play a critical role in angiogenesis and are thus crucial in neoplastic invasion and metastasis. Based on antitumor properties of certain nutrients, we investigated the effect of a diet containing lysine, proline, arginine, ascorbic acid, and green tea extract (NM) on the growth of tumors, induced by implanting human colon HCT 116 cancer cells in athymic nude mice, and the expression of MMPs, VEGF, Ki-67 and fibronectin in these tumors, as well as the production of mucin (by PAS staining). After one week of isolation, 5 to 6 week-old athymic male nude mice (n=12) were inoculated with 3x10(6) colon cancer HCT 116 cells. After injection, the mice were randomly divided into 2 groups; group A was fed a regular diet and group B was fed a regular diet supplemented with 0.5% NM. The mice were sacrificed 4 weeks later, and their tumors were excised, weighed, and processed for histology. Results showed that the nutrient mixture (NM) inhibited growth and reduced the size of tumors in nude mice. Furthermore, histological evaluation revealed increased mitotic index, MMP-9 and VEGF secretion and reduced basement membrane in the control group tissues. Nutrient supplementation strongly suppressed the growth of tumors without any adverse effects in nude mice, suggesting the nutrient combination has potential as an anticancer agent. Histological studies supported these findings by showing inhibition of MMP-9 and VEGF secretion and mitotic index, which are critical parameters for cancer control and prevention.
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PMID:In vivo antitumor effect of ascorbic acid, lysine, proline and green tea extract on human colon cancer cell HCT 116 xenografts in nude mice: evaluation of tumor growth and immunohistochemistry. 1570 10

Sulphasalazine (salicyl-azo-sulphapiridine, SAS) is a drug commonly used in the treatment of non-specific inflammatory bowel diseases, such as ulcerative colitis and Crohn disease. Chronic inflammatory states of the colon can lead to neoplastic changes of the intestinal mucosa. There are some suggestions in the literature that the intestinal bacterial azo-reductases are involved in biotransformation of SAS into 5-aminosalicylic acid (5-ASA) and sulphapyridine (SP). For this reason, it seemed worth of investigating whether transformation of SAS could be performed by the colon epithelial cells themselves. No enzymatic systems presumably exist in Caco-2, which could be responsible for SAS metabolism, because after 72 h-incubation of cell cultures with 1 mM SAS, its metabolites i.e., 5-ASA and SP were not detected in cells, neither in culture media. SAS metabolism, therefore, seems to depend on the presence of intestinal bacterial enzymatic systems. It was confirmed that 5-ASA is converted by Caco-2 cells to N-acetyl-5-aminosalicylic acid (Ac-5-ASA), which migrates to the culture medium. The other metabolite of SAS i.e., SP, was not transformed in the human colon cancer cells at all.
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PMID:Evaluation of biotransformation of sulphasalazine in the colon epithelial Caco-2 cells. 1590 23

The use of NSAIDs or COX-2 inhibitors for chemoprevention of colorectal cancer has been suggested for patients at high risk for this disease. However, the gastrointestinal side effects of traditional NSAIDs which consist of bleeding and ulceration, and the cardiovascular effects of COX-2 inhibitors may limit their usefulness. In preclinical studies, our laboratory has shown that the addition of phosphatidylcholine (PC) to the NSAIDs aspirin (ASA) or ibuprofen (IBU) results in a NSAID-PC with fewer GI side effects and also maintained or enhanced analgesic, anti-pyretic and anti-inflammatory efficacy over the unmodified NSAID. Because NSAID-PCs have not been tested for anti-cancer activity, in the present study, ASA-PC and IBU-PC were tested on the SW-480 human colon cancer cell line. SW-480 cells were incubated in media containing 1-5 mM NSAID or NSAID-PC for 2 days. Measurements were made of cell number, cell proliferation (DNA synthesis), and manner of cell death (necrosis and apoptosis). ASA and IBU reduced cell number in a dose-dependent manner with IBU showing a greater potency than ASA. The association of PC to the NSAID resulted in greater reductions of cell number for both NSAIDs. Furthermore, the NSAID-PC formulation had significantly greater efficacy and potency to inhibit cellular DNA synthesis than the unmodified NSAID. PC alone at the doses and times used had no effect on cell number in this cell line, but did have a small effect to reduce DNA synthesis. None of the drugs had a clear effect on cell death by necrosis. Only IBU and IBU-PC caused cell death by apoptosis in SW-480 cells. We conclude that NSAID-PCs have activity to impede the growth of colon cancer cells in vitro, which is due, in major part, to a marked reduction in DNA synthetic activity of these cells. This growth inhibitory effect appears to be independent of COX-2 activity, since it is known that SW-480 cells do not have this inducible COX isoform. Due to its greater efficacy in this model system, IBU-PC should be further evaluated as a chemopreventive agent that is safer for the GI tract than unmodified NSAID.
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PMID:Phosphatidylcholine-associated nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit DNA synthesis and the growth of colon cancer cells in vitro. 1603 31

Oxidative stress is a characteristic of cancerous colon tissue and inflammatory bowel diseases that increase colon cancer risk. Epidemiological evidence supports a protective effect of plant-derived compounds. Aspirin is also protective against colon cancer. The mechanism of action is unclear although salicylic acid, the main metabolite of aspirin, has been shown to decrease the synthesis of pro-inflammatory and potentially neo-plastic prostaglandins. Salicylic acid is found in significant quantities in a plant-based diet. However, in plants salicylic acid is also reported to modulate the expression of numerous enzymes with antioxidant activity. The aim of this study was to assess whether salicylic acid can modulate pro-cancerous biological pathways in the colon. Oxidative stress, prostaglandins and cytosolic glutathione peroxidase (cyGPX) were analysed in proximal, transverse and distal colon from a rat model of diet-induced oxidative stress. Elevated plasma pyruvate kinase activity (1293+/-206 U/ml) and increased indices of lipid peroxidation in colon (proximal 6.4+/-0.84 nM MDA/mg protein; transverse 6.9+/-0.97 nM MDA/mg protein; distal 5.2+/-0.62 nM MDA/mg protein) from rats fed a Vitamin E deficient diet were significantly decreased on supplementation with salicylic acid (plasma pyruvate 546+/-43 U/ml; salicylic acid proximal 3.6+/-0.39 nM MDA/mg protein; transverse 4.5+/-0.61 nM MDA/mg protein; distal 4.4+/-0.27 nM MDA/mg protein). Reductions in oxidative stress and prostaglandin production on supplementation with salicylic acid were associated with an elevation in glutathione peroxidase activity (Vitamin E deficient proximal 0.056+/-0.013 U/mg protein; transverse 0.073+/-0.008 U/mg protein; distal 0.088+/-0.010 U/mg protein; Vitamin E deficient with salicylic acid proximal 0.17+/-0.01 U/mg protein; transverse 0.23+/-0.016 U/mg protein; distal 0.16+/-0.020 U/mg protein). Gpx1 and Gpx2 gene transcripts were not elevated in association with increased activity of the soluble glutathione peroxidase activity. Glutathione peroxidases are key antioxidant enzymes, catalysing the decomposition of potentially toxic lipid peroxides. Gpx activity and regulation of Gpx gene transcription has been shown previously to be complex with activity not necessarily mirrored by a corresponding elevation in gene transcription. By supplementing the diet of Vitamin E deficient rats with salicylic acid (1 g/kg diet), this study assessed effects of salicylic acid on cytosolic glutathione peroxidase activity in the colon. The ability of salicylic acid to modulate antioxidant enzymes in colon tissue may be an important mechanism in inhibiting colon cancer development.
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PMID:Salicylic acid modulates oxidative stress and glutathione peroxidase activity in the rat colon. 1603 82

Nitric oxide-releasing aspirin (NO-ASA) is emerging as a potentially important chemopreventive agent against colon cancer. We examined in HT-29 human colon adenocarcinoma cells the effect of NO-ASA on the inducible form of nitric oxide synthase (NOS2), an enzyme implicated in colon carcinogenesis. NO-ASA inhibited in a time- and concentration-dependent manner the expression of NOS2 up to 70% compared to control (IC50 for this effect = 46 microM). NO-ASA also decreased the corresponding steady-state mRNA levels and this reduction preceded the reduction of protein levels by at least 6 h. NO-ASA also reduced the enzymatic activity of NOS2, as determined by a direct enzyme assay (maximal reduction = 80%) and by determining the accumulation of NO in the culture medium (IC50 for this effect = 36 microM). These effects of NO-ASA on NOS2 were paralleled by inhibition in cell growth (IC50 = 8.5 microM). These findings indicate that NO-ASA profoundly inhibits both the expression and enzymatic activity of NOS2 and suggest that these effects may represent an important mechanism for the colon cancer chemopreventive effect of NO-ASA.
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PMID:NO-donating aspirin inhibits both the expression and catalytic activity of inducible nitric oxide synthase in HT-29 human colon cancer cells. 1610 66

Nitric oxide donating aspirin (NO-ASA), consisting of a traditional ASA to which a NO-releasing moiety is covalently attached, is a promising chemopreventive agent against colon cancer. Its mechanism of action is not fully delineated. Here we examined its effect on the expression of the nuclear receptor PPARdelta, whose role in colon carcinogenesis remains highly controversial. We studied histochemically the effect of the meta and para positional isomers of NO-ASA on PPARdelta expression in Min (multiple intestinal neoplasia) and wild-type mice, and on cell proliferation and apoptosis. PPARdelta, minimally expressed in wild-type mice, was significantly expressed in Min mice. para NO-ASA inhibited intestinal tumor incidence (59%) and PPARdelta expression (55.3%) more than meta NO-ASA (38 and 41.5%, respectively). Neither isomer affected cell proliferation, but both induced apoptosis in Min mice (para 52.5% for normal mucosa and 70.3% for tumors; meta 31.4 and 21.9%, respectively). The changes in PPARdelta expression correlated significantly with changes in apoptosis. Furthermore, NO-ASA induced areas of necrosis in intestinal tumors are probably resulting from the induction of atypical apoptosis. Our data suggest that NO-ASA suppresses intestinal tumorigenesis possibly in part through its inhibitory effect on PPARdelta, the expression of which may contribute to intestinal carcinogenesis.
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PMID:NO-donating aspirin isomers downregulate peroxisome proliferator-activated receptor (PPAR)delta expression in APC(min/+) mice proportionally to their tumor inhibitory effect: Implications for the role of PPARdelta in carcinogenesis. 1614 Dec 40

We investigated therapeutic efficacy of rebamipide using dextran sulfate sodium (DSS) induced colitis model in rats. Three percent DSS solution was given to rats for 9 days. After that, we evaluated the drug efficacy on colitis sustained with continuous drinking of 1% DSS. Twice-daily treatment with 0.3% or 1% rebamipide for 14 days significantly ameliorated the stool abnormality in the colitis model, preferentially suppressed hematochezia. The colonic mucosal lesion, determined by Alcian blue staining on day 24, was significantly reduced by rebamipide enema in a dose-dependent manner. Either rebamipide or 5-aminosalycilic acid (5-ASA) enema treated once daily significantly ameliorated colitis. The minimum effective dose of rebamipide was 0.3% in once-daily treatment, and that of 5-ASA was 10%. In a mechanistic study, the epithelial cell sheet formation of the T84 colon cancer cell was measured as an increase in generation of trans-epithelial electrical resistance in vitro. Rebamipide accelerated the increase, while 5-ASA conversely suppressed it. These results suggest that rebamipide enema is effective for treatment of experimental ulcerative colitis (UC).
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PMID:Rebamipide enema is effective for treatment of experimental dextran sulfate sodium induced colitis in rats. 1618 15


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