UMLS:C0699790 - FACTA Search

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Query: UMLS:C0699790 (colon cancer)
28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutathione transferases (GSTs) have been shown to play an important role in multiple drug resistance in cancer chemotherapy. The inactivation of GST isoforms could lead to an enhanced activity of cytotoxic drugs. Thus, we have developed glutathione phosphono analogs [(S)-gamma-glutamyl-(2RS)-(+/-)-2-amino-(dialkoxyphosphinyl)-ac etylgl ycines], which were previously shown to be inhibitors of GSTP1-1. In the present study, the inhibition characteristics of these analogs, including isoenzyme specificities, type of inhibition, and determination of K(i) values, were determined. The inhibition of class alpha GSTs was competitive towards GSH. A mixed-type, non-competitive inhibition of class mu and pi GSTs was observed. The K(i) values varied between 880 +/- 210 and 0.45 +/- 0.1 microM. The inhibitors were most effective towards class mu GSTs. In order to investigate the potential use of these GST inhibitors in intact cellular systems, two additional approaches were examined. Firstly, the metabolic stability was tested with purified gamma-glutamyl transpeptidase and cell homogenates as well as during incubation of cell lines. No appreciable degradation was observed in any of the tested systems. Secondly, to facilitate cellular uptake, three derivatives were synthesized in which the glycine carboxylic group was esterified. Uptake and a possible intracellular cleavage to the corresponding free acids were monitored by HPLC analysis. The esters were effectively transported into HT29 (colon cancer) and EPG85-257P (gastric cancer) cells, respectively, and readily converted into the more active free acids. In conclusion, the tested inhibitors may be regarded as model compounds for the development of modulating agents in cancer chemotherapy.
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PMID:Phosphono analogs of glutathione: inhibition of glutathione transferases, metabolic stability, and uptake by cancer cells. 1069 62

Glutathione S-transferase mu-1 (GSTM1) is a polymorphic member of the mu class gene family of the glutathione S-transferases. Individuals who are GSTM1 null have increased susceptibility to lung and colon cancer. We hypothesized that: (a) GSTM1 null individuals might also be at increased risk for development of ovarian cancer; and (b) the GSTM1 genotype would influence response to chemotherapy. One hundred and forty-six individuals with invasive epithelial ovarian cancer were genotyped using a three-primer PCR reaction specific for the GSTM1 gene and an internal control glutathione S-transferase mu-4 (GSTM4). The products were analyzed on agarose gels. Healthy individuals without a family history of ovarian, breast, or colon cancer served as unmatched controls (n = 80). The results show that age at diagnosis, histological type, and stage of ovarian cancer were all independent of GSTM1 genotype. The frequency of the GSTM1 null genotype in the ovarian cancer cohort was similar to that in the control population, 51% versus 58%, P > 0.05. Likewise, median survival for individuals with advanced stage ovarian cancer was independent of GSTM1 genotype. We concluded that the GSTM1 null genotype does not increase ovarian cancer risk. These findings suggest that GSTM1 does not play a significant role in detoxifying environmental factors that influence ovarian carcinogenesis and does not play an important role in the resistance of ovarian cancer to chemotherapy.
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PMID:The glutathione S-transferase M1 genotype in ovarian cancer. 1086 93

Curcumin prevents colon cancer in rodent models. It inhibits lipid peroxidation and cyclooxygenase-2 (COX-2) expression and induces glutathione S-transferase (GST) enzymes. We tested the hypothesis that 14 days of dietary curcumin (2%) affects biomarkers relevant to cancer chemoprevention in the rat. Levels of inducible COX-2, as reflected by prostaglandin E(2) production by blood leukocytes, were measured ex vivo. Total GST activity and adducts of malondialdehyde with DNA (M(1)G), which reflect endogenous lipid peroxidation, were measured in colon mucosa, liver, and blood leukocytes. Curcumin and its metabolites were analyzed by high-performance liquid chromatography in plasma, and its pharmacokinetics were compared following a diet containing 2% curcumin versus intragastric (i.g.) administration of curcumin suspended in an amphiphilic solvent. The curcumin diet did not alter any of the markers in the blood but increased hepatic GST by 16% and decreased colon M(1)G levels by 36% when compared with controls. Administration of carbon tetrachloride during the treatment period increased colon M(1)G levels, and this increase was prevented by dietary curcumin. Dietary curcumin yielded low drug levels in the plasma, between 0 and 12 nM, whereas tissue concentrations of curcumin in liver and colon mucosa were 0.1--0.9 nmol/g and 0.2--1.8 micromol/g, respectively. In comparison with dietary administration, suspended curcumin given i.g. resulted in more curcumin in the plasma but much less in the colon mucosa. The results show that curcumin mixed with the diet achieves drug levels in the colon and liver sufficient to explain the pharmacological activities observed and suggest that this mode of administration may be preferable for the chemoprevention of colon cancer.
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PMID:Effects of dietary curcumin on glutathione S-transferase and malondialdehyde-DNA adducts in rat liver and colon mucosa: relationship with drug levels. 1135 Sep 17

Curcuma spp. extracts, particularly the dietary polyphenol curcumin, prevent colon cancer in rodents. In view of the sparse information on the pharmacodynamics and pharmacokinetics of curcumin in humans, a dose-escalation pilot study of a novel standardized Curcuma extract in proprietary capsule form was performed at doses between 440 and 2200 mg/day, containing 36-180 mg of curcumin. Fifteen patients with advanced colorectal cancer refractory to standard chemotherapies received Curcuma extract daily for up to 4 months. Activity of glutathione S-transferase and levels of a DNA adduct (M(1)G) formed by malondialdehyde, a product of lipid peroxidation and prostaglandin biosynthesis, were measured in patients' blood cells. Oral Curcuma extract was well tolerated, and dose-limiting toxicity was not observed. Neither curcumin nor its metabolites were detected in blood or urine, but curcumin was recovered from feces. Curcumin sulfate was identified in the feces of one patient. Ingestion of 440 mg of Curcuma extract for 29 days was accompanied by a 59% decrease in lymphocytic glutathione S-transferase activity. At higher dose levels, this effect was not observed. Leukocytic M(1)G levels were constant within each patient and unaffected by treatment. Radiologically stable disease was demonstrated in five patients for 2-4 months of treatment. The results suggest that (a) Curcuma extract can be administered safely to patients at doses of up to 2.2 g daily, equivalent to 180 mg of curcumin; (b) curcumin has low oral bioavailability in humans and may undergo intestinal metabolism; and (c) larger clinical trials of Curcuma extract are merited.
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PMID:Pharmacodynamic and pharmacokinetic study of oral Curcuma extract in patients with colorectal cancer. 1144 2

Cancers of the colon and breast are two of the most prevalent cancers in developed countries. The present experiments were conducted to determine the influence of several dietary doses of grape seed proanthocyanidins on 7,12-dimethylbenz[a]anthracene-induced mammary tumorigenesis and azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation in a dual-organ tumor model. In addition, the effects of the grape seed proanthocyanidins on liver cytochrome P-450 1A and 2E1 and glutathione S-transferase activities and on colonic ornithine decarboxylase activity were examined to determine possible mechanisms of action. Feeding female rats diets containing 0.1-1.0% grape seed proanthocyanidins was associated with a significant 72-88% inhibition of AOM-induced aberrant crypt foci formation and a 20-56% inhibition of ornithine decarboxylase activity in the distal third of the colon. Feeding the grape proanthocyanidins resulted in no significant effect on the activity of liver cytochrome P-450 2E1. There was no effect of feeding these doses of proanthocyanidins on 7,12-dimethylbenz[a]anthracene-induced rat mammary tumorigenesis. This lack of action on mammary tumorigenesis in part may be due to lack of effect of dietary proanthocyanidins on the liver carcinogen-metabolizing enzymes cytochrome P-450 1A and glutathione S-transferase. These results indicate that grape polyphenolics warrant further evaluation as potential colon cancer chemopreventive agents.
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PMID:Effect of grape seed proanthocyanidins on colon aberrant crypts and breast tumors in a rat dual-organ tumor model. 1175 89

Evidence for a protective role of the glutathione biotransformation system in carcinogenesis is growing. However, most data on this system in relation to colorectal cancer originate from animal studies. Here we review the human data. In humans, a significant association was found between glutathione S-transferase (GST) activity in the mucosa along the gastrointestinal tract and the corresponding tumour incidence. Low activity was correlated with high tumour incidence and vice versa. Also, in normal colonic mucosa, GST activity is lower in patients at risk of colon cancer than in healthy controls and therefore interventions which increase the glutathione detoxification capacity may reduce cancer incidence. Consumption of vegetables and fruit is associated with a lower risk of colorectal cancer. Human intervention studies showed that (components from) vegetables induced colonic glutathione detoxification capacity. Such an effect could contribute to a lower colon cancer risk, but further data are needed. The human GSTs consist of four main classes--alpha (A), mu (M), pi (P) and theta (T)--each of which is divided into one or more isoforms. Functional polymorphisms are known for the GST genes M1, P1 and T1 and they all lead to less active enzymes compared to the wild-type gene products. However, studies that compared these GST polymorphisms in relation to colon cancer risk were not conclusive with respect to an increased or decreased risk of a particular genotype. Diet or medication can also influence the expression levels of specific isoenzymes and the effect of such interventions on cancer risk deserves more attention.
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PMID:The glutathione biotransformation system and colorectal cancer risk in humans. 1176 64

Mirk/Dyrk1B is an arginine-directed serine/threonine protein kinase that is expressed at low levels in most normal tissues but at elevated levels in many tumor cell lines and in normal skeletal muscle. Colon carcinoma cell lines stably overexpressing Mirk proliferated in serum-free medium, but the mechanism of Mirk action is unknown. DCoHm (dimerization cofactor of hepatocyte nuclear factor 1alpha ( HNF1alpha) from muscle), a novel gene of the DCoH family with 78% amino acid identity to DCoH, was identified as a Mirk-binding protein by yeast two-hybrid analysis and cloned. Mirk co-immunoprecipitated with DCoHm and bound to DCoHm in glutathione S-transferase pull-down assays. DCoH stabilizes HNF1alpha as a dimer and enhances its transcriptional activity on the beta-fibrinogen promoter reporter, and DCoHm had similar activity. Mirk enhanced HNF1alpha transcriptional activity in a dose-dependent manner, whereas two kinase-inactive Mirk mutants and a Mirk N-terminal deletion mutant did not. Mirk, DCoHm, and HNF1alpha formed a complex. Mirk bound to a specific region within the CREB-binding protein-binding region of HNF1alpha and phosphorylated HNF1alpha at a site adjacent to the Mirk-binding region. Conversely, the HNF1alpha binding domain was located within the first five conserved kinase subdomains of Mirk. Mirk co-immunoprecipitated with the MAPK kinase MKK3, an upstream activator of p38. MKK3 enhanced Mirk kinase activity and the transcriptional activation of HNF1alpha by Mirk, suggesting that Mirk, like p38, is activated by certain environmental stress agents. The Mirk-binding protein DCoH has been shown to be selectively expressed in colon carcinomas but not in normal tissue. Mirk may function as an HNF1alpha transcriptional activator in response to an MKK3-mediated stress signal, and the selective expression of DCoH could restrict the Mirk response to carcinoma cells.
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PMID:Mirk protein kinase is activated by MKK3 and functions as a transcriptional activator of HNF1alpha. 1198 Sep 10

The coffee components kahweol and cafestol (K/C) have been reported to protect the colon and other organs of the rat against the formation of DNA adducts by 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) and aflatoxin B1. PhIP is a cooked-food mutagen to which significant human exposure and a role in colon cancer etiology are attributed, and, interestingly, such cancers appear to develop at a lower rate in consumers of coffees with high amounts of K/C. Earlier studies in rodent liver have shown that a key role in the chemopreventive effect of K/C is likely to be due to the potential of these compounds to induce the detoxification of xenobiotics by glutathione transferase (GST) and to enhance the synthesis of the corresponding co-factor glutathione. However, mutagens like PhIP may also be detoxified by UDP-glucuronosyl transferase (UDPGT) for which data are lacking regarding a potential effect of K/C. Therefore, in the present study, we investigated the effect of K/C on UDPGT and, concomitantly, we studied overall GST and the pattern of individual GST classes, particularly GST-theta;, which was not included in earlier experiments. In addition, we analyzed the organ-dependence of these potentially chemopreventive effects. K/C was fed to male F344 rats at 0.122% in the chow for 10 days. Enzyme activities in liver, kidney, lung, colon, salivary gland, pancreas, testis, heart and spleen were quantified using five characteristic substrates and the hepatic protein pattern of GST classes alpha, mu, and pi was studied with affinity chromatography/HPLC. Our study showed that K/C is not only capable of increasing overall GST and GST classes alpha, mu, and pi but also of enhancing UDGPT and GST-theta. All investigated K/C effects were strongest in liver and kidney, and some response was seen in lung and colon but none in the other organs. In summary, our results show that K/C treatment leads to a wide spectrum of increases in phase II detoxification enzymes. Notably, these effects occurred preferentially in the well perfused organs liver and kidney, which may thus not only contribute to local protection but also to anti-carcinogenesis in distant, less stimulated organs such as the colon.
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PMID:Enhancement of the chemoprotective enzymes glucuronosyl transferase and glutathione transferase in specific organs of the rat by the coffee components kahweol and cafestol. 1202 84

The protective effect of a curcumin analog [bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione] was investigated on hepatic lipid peroxidation (LPO) and antioxidant status during 1,2-dimethylhydrazine-induced colon carcinogenesis in male Wistar rats. The effects were compared with that of curcumin, a known antioxidant and anticarcinogen. Colon cancer was induced by sub-cutaneous injection of DMH at a dosage of 20mg/kg body weight (15 doses, at 1-week intervals). DMH administered rats developed gross tumours in the colon. Enhanced lipid peroxidation in the liver of colon tumour bearing rats was accompanied by a significant decrease in the activities of glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). Intragastric administration of curcumin (80mg/kg body weight) and curcumin analog (80mg/kg body weight) to DMH-injected rats significantly reduced the number and size of tumour in the colon, lowered lipid peroxidation and enhanced the activities of GPx, GST, SOD and CAT in the liver. We speculate that the curcumin analog used in the present study exerts chemoprevention against cancer development at extrahepatic sites by modulating hepatic biotransformation enzymes and antioxidant status. The effect is comparable with that of curcumin. This shows that the hydroxyl group in the aromatic ring is responsible for the protective effect rather than the methoxy group.
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PMID:Bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione (a curcumin analog) ameliorates DMH-induced hepatic oxidative stress during colon carcinogenesis. 1220 19

Several polymorphic cytochrome P-450 and glutathione S-transferase (GST) enzymes are involved in the activation and detoxification of many potential carcinogens and may therefore be important in susceptibility to cancer induction. CYP1A1 MspI, GSTM1, and GSTT1 are polymorphic enzymes and some alleles have been correlated with an increased risk of developing some cancers. In the present study, we examined possible associations between genetic polymorphisms of CYP1A1 MspI, GSTM1, and GSTT1 and colon cancer in a United Kingdom population. An excess of CYP1A1 MspI, and GSTM1 null genotypes was observed amongst colon cancer patients, although this did not reach the level of statistical significance. We found no significant increase in the risk of colon cancer for either CYP1A1 MspI (OR = 1.39; 95%CI: 0.46-4.21) or GSTM1 null (OR = 1.41; 95%CI: 0.76-3.01) genotypes. Individuals with GSTT1 null genotype had no association with colon cancer (OR = 0.42; 95%CI: 0.09-2.02). No significant association was observed in the site of colon cancer (proximal vs. distal). This study suggests that the polymorphisms of CYP1A1 MspI, GSTM1, and GSTT1 are not associated with a significant risk of developing colon cancer in a United Kingdom population.
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PMID:Genetic polymorphisms in the cytochrome P450 1A1, glutathione S-transferase M1 and T1, and susceptibility to colon cancer. 1221 May 2

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