Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Male F344 rats were pretreated with various dietary compounds, and the effects of pretreatment on the in vitro alpha-hydroxylation of N-nitrosopyrrolidine or N'-nitrosonornicotine were determined in assays with liver microsomes or cultured esophagus, respectively. Dietary compounds included phenols, cinnamic acids, coumarins, indoles, and isothiocyanates. Pretreatments were carried out either by administering the compound by gavage 2 hr prior to sacrifice (acute protocol) or by adding the compound to the diet for 2 weeks (chronic protocol). Acute pretreatment with benzyl isothiocyanate, allyl isothiocyanate, phenethyl isothiocyanate, phenyl isocyanate, and benzyl thiocyanate but not sodium thiocyanate inhibited formation of alpha-hydroxylation products of both nitrosamines. When the chronic pretreatment protocol was used, only phenyl isothiocyanate and sodium thiocyanate inhibited formation of alpha-hydroxylation products of both nitrosamines. Pretreatments with butylated hydroxyanisole, p-methoxyphenol, or N-acetylcysteine had little, if any, effect on the alpha-hydroxylation of N-nitrosopyrrolidine or N'-nitrosonornicotine. Chronic pretreatment with p-hydroxycinnamic acid, 4-hydroxy-3- methoxycinnamic acid, coumarin, umbelliferone, limetine , indole, indole-3-carbinol, indole-3-acetonitrile, and L-tryptophan induced activity for the alpha-hydroxylation of N-nitrosopyrrolidine. The results of this study indicate that isothiocyanates are possible candidates for further study as potential inhibitors of carcinogenesis by N-nitrosopyrrolidine and N'-nitrosonornicotine.
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PMID:Effects of dietary compounds on alpha-hydroxylation of N-nitrosopyrrolidine and N'-nitrosonornicotine in rat target tissues. 672 18

The effects of two aromatic thiocyanates, benzyl thiocyanate (BTC) and benzyl isothiocyanate (BITC), on methylazoxymethanol (MAM) acetate-induced intestinal carcinogenesis were examined using female ACI/N rats. Starting at 5 weeks of age, animals were fed diets containing 100 or 400 p.p.m. BTC, 400 p.p.m. BITC or a control diet. At 6 weeks of age, all animals were treated with i.p. injections of MAM acetate (25 mg/kg body wt, once weekly for 3 weeks) or saline. Animals fed experimental diets were changed to the control diet from a week after the last carcinogen treatment. Three groups of animals fed the control diet were switched to 100 p.p.m. BTC, 400 p.p.m. BTC or 400 p.p.m. BITC diet from a week after carcinogen treatment. Animals given the high-dose BTC diet at the initiation and the post-initiation phase showed smaller incidence (5% and 17%) and multiplicity (0.05 +/- 0.21 and 0.17 +/- 0.37) of tumours in small intestine compared with those of rats exposed to the carcinogen alone (61% and 1.06 +/- 1.18). The incidence and multiplicity of tumors in small intestine (21% and 0.32 +/- 0.73) and the incidence of colon tumors of rats given BITC in the initiation phase (47%) were significantly lower than those of animals treated with carcinogen alone (61%, 1.06 +/- 1.18 and 83%). Bromodeoxyuridine labeling indices of the intestinal mucosal cells were measured. The labeling indices were reduced by BTC and BITC exposure at initiation phase in both small intestine and colon. The results of measurement of labeling indices correlated with the decreased tumor incidence and multiplicity in the intestine. These data suggest that BTC and BITC could be promising chemopreventive agents for human intestinal neoplasia.
Carcinogenesis 1994 Aug
PMID:Inhibitory effects of benzyl thiocyanate and benzyl isothiocyanate on methylazoxymethanol acetate-induced intestinal carcinogenesis in rats. 805 33

The effects of benzyl isothiocyanate (BITC) and benzyl thiocyanate (BTC) on two types of DNA synthesis were examined in hepatocyte primary cultures (HPC). Male F344 rats were fed BITC- or BTC-containing diets at a concentration of 400 p.p.m. Using hepatocytes isolated from these rats, DNA repair was measured by unscheduled DNA synthesis (UDS) for some genotoxic carcinogens, e.g. 2-acetylaminofluorene (AAF), methylazoxymethanol (MAM) acetate, 9,10-dimethyl-1,2-benzanthracene (DMBA) and diethylnitrosamine (DEN), and compared with that in the hepatocytes from rats without BITC or BTC treatment. Replicative DNA synthesis (RDS) was also evaluated in the hepatocytes of rats with or without thiocyanate treatment. Both BITC and BTC reduced UDS elicited by these carcinogens. The level of RDS in the hepatocytes of rats exposed to BITC or BTC was markedly lower than in the cells of rats without BITC or BTC exposure. These results indicate that in vivo exposure to BITC and BTC suppressed carcinogen-induced genotoxicity and cell proliferative activity and suggest that this assay may prove useful in detecting chemopreventive agents for cancer and in investigating the properties of carcinogenesis modifiers.
Carcinogenesis 1993 Feb
PMID:Modifying effects of benzyl isothiocyanate and benzyl thiocyanate on DNA synthesis in primary cultures of rat hepatocytes. 843 68

We observed that pretreatment of male F344 rats with benzyl selenocyanate, a versatile organoselenium chemopreventive agent in several animal model systems, decreases the levels of DNA and RNA modifications produced in the liver by the hepatocarcinogen 2-nitropropane. To clarify the mechanisms involved, we pretreated male F344 rats with either benzyl selenocyanate, its sulfur analog benzyl thiocyanate, phenobarbital or cobalt protoporphyrin IX; the latter is a depletor of P450. We then determined (1) the ability of liver microsomes to denitrify 2-nitropropane, (2) effects on 2-nitropropane-induced liver DNA and RNA modifications and (3) amount of nitrate excreted in rat urine following administration of the carcinogen. Pretreatment with benzyl selenocyanate or phenobarbital increased the denitrification activity of liver microsomes by 217 and 765%, respectively, increased liver P4502B1 by 31- and 435-fold, respectively, decreased the levels of 2-nitropropane-induced modifications in liver DNA (29-70% and 17-30%, respectively) and RNA (67-85% and 30-50%, respectively), and increased the 24-h urinary excretion of nitrate by 157 and 209%, respectively. Pretreatment with benzyl thiocyanate had no significant effect on any of these parameters. Pretreatment with cobalt protoporphyrin IX decreased liver P4502B 1 by 87%, decreased the denitrification activity of liver microsomes by 76%, decreased the 24 h urinary excretion of nitrate by 88.5%, but increased the extent of 2-nitropropane-induced liver nucleic acid modifications by 17-67%. These results indicate that the metabolic sequence from 2-nitropropane to the reactive species causing DNA and RNA modifications does not involve the removal of the nitro group. Moreover, they suggest that benzyl selenocyanate inhibits 2-NP-induced liver nucleic acid modifications in part by increasing its detoxication through induction of denitrification, although it is evident that other mechanisms must also be involved.
Carcinogenesis 1997 Sep
PMID:Inhibition of 2-nitropropane-induced rat liver DNA and RNA damage by benzyl selenocyanate. 932 79

The organoselenium compounds benzyl selenocyanate (BSC) and 1,4-phenylenebis(methylene)selenocyanate (p-XSC), as well as sodium selenite, are effective chemopreventive agents for various chemically induced tumors in animal models at both the initiation and postinitiation stages. The mechanisms involved at the postinitiation stage are not clear. Because several lines of evidence indicate that inhibition of excess DNA (cytosine-5)-methyltransferase (Mtase) may be a sufficient factor for the suppression or reversion of carcinogenesis, we examined the effects of sodium selenite, BSC, p-XSC and benzyl thiocyanate (BTC), the sulfur analog of BSC, on Mtase activity in nuclear extracts of human colon carcinomas, and of p-XSC on the Mtase activity of HCT116 human colon carcinoma cells in culture. For this purpose, we developed an improved Mtase assay, in which the incorporation of the methyl-[3H] group from S-adenosyl[methyl-3H]methionine into deoxycytidine of poly(dI-dC)-poly(dI-dC), is specifically determined by HPLC with radioflow detection after enzymatic hydrolysis, enhancing specificity and reliability. In a variation, using SssI methyltransferase and labeled S-adenosylmethionine, the overall methylation status of DNA in various tissues can also be compared. Selenite, BSC and p-XSC inhibited Mtase extracted from a human colon carcinoma with IC50s of 3.8, 8.1 and 5.2 microM, respectively; BTC had no effect. p-XSC also inhibited the Mtase activity and growth of human colon carcinoma HCT116 cells, with an IC50 of approximately 20 microM. The improved Mtase assay should prove to be a reliable method for screening potential Mtase inhibitors, especially using cells in culture. We suggest that inhibition of Mtase may be a major mechanism of chemoprevention by selenium compounds at the postinitiation stage of carcinogenesis.
Carcinogenesis 1998 Apr
PMID:Inhibition of DNA cytosine methyltransferase by chemopreventive selenium compounds, determined by an improved assay for DNA cytosine methyltransferase and DNA cytosine methylation. 960 Mar 43

Phenethyl isothiocyanate (PEITC)(1) and benzyl isothiocyanate (BITC), naturally occurring constituents of cruciferous vegetables, have been reported to exert inhibitory effects against development of tobacco-specific carcinogen-induced lung tumors and are regarded as promising chemopreventive agents for lung cancer. However, tumor promoting and carcinogenic activities in the rat urinary bladder have been detected in several animal models. The purpose of the present study was to investigate early changes in rat urinary bladder epithelium induced by PEITC and BITC and to explore promotion/carcinogenic mechanisms. In the first experiment, in order to assess acute toxic effects, PEITC or BITC at 0.1% each in the diet were administered to 6-week-old F344 rats for 1, 2, 3, and 7 days and sequential histopathological assessment and urinalysis were performed. In the second and third experiments, structure-activity relationships of PEITC, BITC and 8 other analogues, benzyl isocyanate and benzyl thiocyanate, and phenyl-, alpha-naphthyl-, tert-butyl-, butyl-, methyl-, and ethyl isothiocyanates (ITCs) were explored in a 14-day experiment. In the first experiment, the urinary pH was significantly lowered on day 1 by both PEITC and BITC. Striking features of toxicity, such as marked inflammatory changes characterized by cellular infiltration, apoptosis/single cell necrosis, cytoplasmic vacuolation, erosion, and hemorrhage in the urinary bladder were caused, with peaks apparent on days 2 or 3, respectively. Sequential change in 5-bromo-2'-deoxyuridine (BrdU) labeling indices was in line with the inflammatory response, but the thickness of the urinary bladder epithelium continued to gradually increase up to day 7. In the second and third experiments, simple and papillary or nodular (PN) hyperplasias were observed after 14-days treatment with PEITC, BITC, and phenyl- and butyl ITCs. These results suggest that continuous urinary epithelial cell proliferation due to cytotoxicity may play an important role in the early stage of rat urinary bladder carcinogenesis due to oral administration of ITCs. In addition, hydrophobic activity of ITCs, dependent on the alkyl carbon chain length, might strongly influence the induction of bladder lesions in rats.
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PMID:Involvement of toxicity as an early event in urinary bladder carcinogenesis induced by phenethyl isothiocyanate, benzyl isothiocyanate, and analogues in F344 rats. 1285 Nov 4

As early as 1550 B.C., Egyptians realized the benefits of garlic as a remedy for a variety of diseases. Many epidemiological studies support the protective role of garlic and related allium foods against the development of certain human cancers. Natural garlic and garlic cultivated with selenium fertilization have been shown in laboratory animals to have protective roles in cancer prevention. Certain organoselenium compounds and their sulfur analogs have been identified in plants. Organoselenium compounds synthesized in our laboratory were compared with their sulfur analogs for chemopreventive efficacy. Diallyl selenide was at least 300-fold more effective than diallyl sulfide in protecting against 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary adenocarcinomas in rats. In addition, benzyl selenocyanate inhibited the development of DMBA-induced mammary adenocarcinomas and azoxymethane-induced colon cancer in rats and benzo[a]pyrene-induced forestomach tumors in mice. The sulfur analog, benzyl thiocyanate, had no effect under the same experimental conditions. Furthermore, we showed that 1,4-phenylenebis(methylene)selenocyanate, but not its sulfur analog, significantly inhibited DMBA-DNA adduct formation and suppressed DMBA-induced mammary carcinogenesis. Collectively, these results indicate that structurally distinctive organoselenium compounds are superior to their corresponding sulfur analogs in cancer chemoprevention. Additionally, synthetic aromatic selenocyanates are more effective cancer chemopreventive agents than the naturally occurring selenoamino acids. Because plants are capable of utilizing selenium in a manner similar to that in sulfur assimilation pathways, future studies should aim at determining whether, under appropriate conditions, these potent cancer chemopreventive synthetic selenium compounds can be synthesized by garlic and related allium foods.
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PMID:Cancer chemoprevention by garlic and garlic-containing sulfur and selenium compounds. 1648 82