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

Carcinogenicity of phenacetin was tested using Sprague-Dawley rats. Two groups of animals containing 50 males and 50 females per group were fed respectively with 2.5% and 1.25% phenacetin diet for 18 months and fed thereafter with basal diet for 6 months. Control animals containing 65 males and 65 females were fed with basal diet for 24 months. Animals surviving more than 24 months were regarded as effective animals and killed. Rats that died of tumor development within 24 months were also regarded effective animals. Every organ from the killed and dead animals was fixed in 10% formaldehyde solution and examined histopathologically. Effective number of rats was 27 males and 27 females in 2.5% phenacetin feeding group, and 22 males and 25 females in 1.25% phenacetin feeding group. In control group, 19 males and 25 females were effective. Neoplasms including spontaneous tumors were detected in 26 out of 27 males (96.3%) and 21 out of 27 females (77.8%) of 2.5% phenacetin feeding group, and in 20 out of 22 males (90.9%) and 19 out of 25 females (76.0%) of 1.25% phenacetin feeding group. In control group, 1 out of 19 males (5.3%) and 6 out of 25 females (24.0%) showed spontaneous tumor development. Histopathologically, carcinomas of the nasal cavity, such as adenocarcinoma, squamous cell carcinoma, and transitional cell carcinoma, and the urinary passage, as renal cell carcinoma of the kidney pelvis, and transitional cell carcinoma of the urinary bladder, were most conspicuous, suggesting the target organs of phenacetin carcinogenesis. Males showed higher tumor incidence compared to females. The higher the concentration of phenacetin given, higher incidence of tumors was observed.
 ...
PMID:Tumors of Sprague-Dawley rats induced by long-term feeding of phenacetin. 44 75

In vivo administration to rats of the mixed-function oxidase modifiers 3-methylcholanthrene (MC), pregnenolone-16 alpha-carbonitrile (PCN) or beta-naphthoflavnoe (beta-f) inhibits the hepatic microsome-catalyzed in vitro binding of dimethylnitrosamine (DMN) to DNA. This parallels their effect on DMN-demethylase I, regarded to be the sole activating step in DMN carcinogenesis and fails to account for the previously observed anomaly that MC and PCN inhibit, while beta-NF enhances, the hepatocarcinogenic activity of DMN. The in vitro binding of DMN is clearly dependent on microsomes and NADPH, and is strongly enhanced by soluble cytoplasmic proteins; the presence of the latter has no effect. however, on the relative response to pretreatment by the modifiers. In mice beta-NF enhances and PCN inhibits DMN-demethylase I; beta-NF has no effect on either the cytochrome P-450 level or on the LD50, while PCN strongly increases the cytochrome P-450 level but without influencing the LD50. Neither of the two modifiers has any effect in mice on the host-mediated mutagenicity of DMN in a dose-response study, except for the highest dose of DMN (200 mg/kg) where PCN pretreatment significantly enhanced mutagenicity. To account for the anomalous observations, other potential pathways of DMN metabolism have been explored. Whole rat liver nuclei or isolated nuclear membrane fractions contain no DMN-demethylase or diethylnitrosamine-deethylase activity. In a microsomal mixed-function amine-oxidase assay system neither purified enzyme preparations nor whole microsomes catalyze NADPH oxidation in the presence of DMN as substrate. In addition, the purified enzyme does not catalyze formaldehyde production in the DMN-demethylase assay system. Benzylamine, a typical inhibitor of mitochondrial monoamine oxidase (MAO), is a potent inhibitor of DMN-demethylase activity, but microsomes are devoid of MAO activity. Furthermore, purified MAO has no DMN-demethylase activity. The differential effect of modifiers on the carcinogenicity of DMN probably involves pathways other than DMN metabolism.
 ...
PMID:Role of dimethylnitrosamine-demethylase in the metabolic activation of dimethylinitrosamine. 49 63

Tetrakis(hydroxymethyl)phosphonium chloride (THPC) and Pyroset TKP, which is the mixed acetate/phosphate of the same phosphonium base, are widely used in flame-retardant cotton fabrics, particularly in children's sleepwear. THPC degrades thermally and under certain chemical conditions to yield hydrochloric acid and formaldehyde (CH2O). In solution, the latter two compounds are in equilibrium with the known potent carcinogen bis(chloromethyl)ether (BCME). A sample of commercial THPC contained from 4% (at pH 0.4) to 14% (at pH greater than 4.5) free CH2O. The material, as supplied by the manufacter, showed pH 0.4. Gas chromatographic analysis of aqueous commercial THPC did not reveal any peak chracteristic of BCME under conditions where 0.1 ppm of the material can be detected. Application to mouse skin of THPC ( 2 mg in 0.1 ml DMSO) and of Pryset TKP (7 mg in 0.1 ml DMSO), three times per week for 400 days with 20 female ICR/Ha Swiss mice per group, gave one squamous carcinoma in the THPC-treated group. THPC was inactive as an initiating agent in two-stage mouse skin carcinogenesis with phorbol myristate acetate as promoter. Both agents were active as tumor promoters, using a single application of 7,12-dimethylbenz[a]anthracene (20 microng in 0.1 ml acetone) as initiator. With THPC as promoter (2 mg in 0.1 ml DMSO, thrice weekly) 3 of 20 mice bore papillomas which progressed to squamous carcinoma. With Pyroset TKP as promoter (7 mg in 0.1 ml DMSO) 7 of 20 mice bore papillomas of which two progressed to squamous carcinoma.
 ...
PMID:Evaluation of chemical flame retardants for carcinogenic potential. 84 2

Activation of the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) produced methylating species and two aldehydes: formaldehyde and 4-oxo-4-(3-pyridyl)-butanal (OPB). We investigated the modulation by glutathione of single-strand breaks (SSB) generated by N-methyl-N-nitrosourea (MNU) and the two aldehydes. Hepatocytes were simultaneously exposed to 0.2 mM MNU and to 0-2.00 mM formaldehyde or OPB for 4 h. Both aldehydes induced SSB in a dose-dependent manner. Formaldehyde and OPB exerted a synergistic effect on the formation of DNA SSB by MNU. It is postulated that both aldehydes interfere with DNA repair processes and thus increase the genotoxic effect of DNA methylating species. We investigated whether glutathione (GSH) could protect DNA from NNK-derived intermediates. Formaldehyde (2 mM) and OPB (2 mM) decreased intracellular GSH contents to 60 and 86% of control respectively. DL-Buthionine-[S,R]-sulfoximine (BSO) treatment reduced the GSH contents of hepatocytes to 19% of control but did not reduce the content of cytochrome P450 nor the metabolism of NNK. The frequency of DNA SSB induced by NNK, formaldehyde or OPB was significantly higher in GSH-depleted hepatocytes. GSH repletion with GSH monoethyl ester returned NNK-induced SSB to its initial frequency. OPB but not NNK nor formaldehyde induced double-strand breaks. We conclude that OPB and formaldehyde inhibit the repair of DNA damage induced by methylating species and that GSH reduces the level of DNA damage induced by NNK-derived reactive metabolites.
Carcinogenesis 1992 Aug
PMID:Modulation by glutathione of DNA strand breaks induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and its aldehyde metabolites in rat hepatocytes. 149 96

Addition of potassium chloride to sodium dodecyl sulfate (SDS) resulted in the formation of an insoluble precipitate that was easily recovered by low-speed centrifugation. Since SDS tightly binds to proteins but not DNA, all proteins and detergent-resistant DNA--protein complexes were also effectively co-precipitated in the presence of potassium--SDS leaving free DNA in the supernatant. The amount of SDS-precipitable DNA represented a measure of DNA--protein crosslinks. We have adapted this method for determining DNA--protein crosslinks formed in cells following their exposure in culture or in vivo to crosslinking agents such as chromate, cis-Pt(II) diammine dichloride and formaldehyde. The critical parameters for application of the K--SDS assay to cells were rigorously reproducible shearing of chromosomal DNA and effective washing steps. We have found that freeze-thawing SDS lysed cells followed by vortexing and repeated resuspensions of the precipitate by pipeting resulted in a low background and high reproducibility of the assay. The method detected in a dose-dependent manner DNA--protein crosslinks induced in CHO cells by chromate, cis-platinum and formaldehyde, with sensitivity similar to the alkaline elution procedure. The K--SDS assay was also successfully utilized to determine DNA--protein crosslinks in rat and mouse white blood cells exposed in vivo to chromate. Its sensitivity and simplicity in sample handling and DNA--protein complex isolation potential allows wide application of the assay to measure formation of DNA--protein crosslinks. The ease of recovery of DNA--protein complexes allows for a more thorough investigation of this lesion.
Carcinogenesis 1992 Aug
PMID:A simple, sensitive assay to detect DNA-protein crosslinks in intact cells and in vivo. 149 1

A mixture of 100 mM creatinine and 100 mM L-phenylalanine was heated at 60 or 37 degrees C in the presence of sugar or aldehyde. A mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) formed in the model system was determined by reversed-phase HPLC. Any sugars tested induced the formation of PhIP when heated at 60 degrees C, though PhIP was not detected in a mixture without sugar. Among the sugars tested, D-erythrose and D-glyceraldehyde were more productive than pentose (D-arabinose and D-ribose) and hexose (D-glucose and D-galactose) in the yield of PhIP. Moreover, PhIP was formed even when a mixture of creatinine, L-phenylalanine and D-glucose or D-ribose was incubated at 37 degrees C for a long time. Both formaldehyde and acetaldehyde also induced the formation of PhIP, though PhIP was not detected in a mixture without sugar or aldehyde even when heated at 100 degrees C. These results indicate that PhIP can be formed at low-temperature heating and that either sugar or aldehyde is essential for PhIP formation in the model system. Our data also suggest that aldehydes may be a key reactant in the formation of PhIP in aqueous heating of the mixture of creatinine and L-phenylalanine.
Carcinogenesis 1992 May
PMID:Formation of PhIP in a mixture of creatinine, phenylalanine and sugar or aldehyde by aqueous heating. 158 94

Hereditary nonpolyposis colorectal carcinoma (HNPCC) is the most common form of hereditary colon cancer. Autosomal dominant inheritance is evident from pedigrees but the genetic basis of the disorder is otherwise unknown. Recently, two genes in 5q21 involved in colon carcinogenesis, APC and MCC, were identified, and APC was shown to be the gene predisposing to familial adenomatous polyposis. To determine if these genes also confer susceptibility to HNPCC we performed linkage analyses in nine affected families. The MCC-APC region could be formally excluded as the locus for HNPCC in seven families. In one family the results were suggestive of exclusion, although they were not conclusive. The remaining family was uninformative. We used two alternative definitions of affected status. Based on haplotypes for MCC and APC the added pairwise logarithm-of-odds score for all nine families was -22.57 at the recombination fraction of 0.00 using more stringent criteria for the HNPCC phenotype and -22.67 for less stringent criteria. In addition to blood DNA samples from living family members, DNA from formaldehyde-fixed archival pathology specimens from decreased individuals contributed to these linkage results.
 ...
PMID:Evidence that the MCC-APC gene region in 5q21 is not the site for susceptibility to hereditary nonpolyposis colorectal carcinoma. 164 45

It has been suggested that formaldehyde hydrazone, a condensation product of hydrazine with formaldehyde, plays an important role in hydrazine-promoted DNA methylation in vivo. The present study demonstrated by spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide and tert-nitrosobutane that catalase-mediated oxidation of formaldehyde hydrazone generates methyl radicals. Both the use of two spin-traps and parallel studies of oxygen consumption were important for excluding possible artefacts of spin-trapping experiments with tert-nitrosobutane. Hydrazine was also oxidized by catalase but only hydroxyl radicals were detected. Metabolic activation of formaldehyde hydrazone to methyl radicals may be of importance in regard to hydrazine-mediated toxicity and carcinogenicity.
Carcinogenesis 1991 Jul
PMID:Formation of methyl radicals during the catalase-mediated oxidation of formaldehyde hydrazone. 164 16

Several previous studies have suggested that cytochrome P450IIB1 is involved in the bioactivation of the tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in rats as well as in mouse lung microsomes. The present investigation was undertaken to study the metabolism of NNK by purified cytochrome P450IIB1 in a reconstituted system. The metabolites 4-hydroxy-4-(3-pyridyl) butyric acid (hydroxy acid), 4-oxo-4-(3-pyridyl) butyric acid (keto acid), 4-oxo-4-(3-pyridyl) butanol (keto aldehyde), 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone (NNK-N-oxide) and 4-oxo-4-(3-pyridyl)-1-butanol (keto alcohol) were quantitated by HPLC. The results showed that, in addition to alpha-hydroxylations, cytochrome P450IIB1 also catalyzed the formation of NNK-N-oxide efficiently, and to a certain extent, the conversion of NNK primary hydroxylation metabolites (keto aldehyde and keto alcohol) to secondary metabolites (keto acid and hydroxy acid). Cytochrome b5 at a ratio of 1:1 or 2:1 to P450IIB1 had no significant effect on the metabolic activities and profiles of NNK. The apparent Km values for the formation of keto aldehyde, NNK-N-oxide and keto alcohol were respectively 191.2, 131.4 and 318.0 microM with corresponding apparent Vmax values of 89.7, 295.5 and 333.3 pmol/min/nmol P450, indicating that hydroxylation at the alpha-methyl position is preferred over the alpha-methylene position. Measurement of formaldehyde, a product derived from the alpha-methyl hydroxylation, was developed as a convenient method to study NNK metabolism. Thiourea activated cytochrome P450IIB1-catalyzed NNK metabolism significantly. Phenethyl isothiocyanate, an inhibitor of NNK-induced lung carcinogenesis, inhibited P450IIB1-catalyzed NNK demethylation in a concentration-dependent manner. This work demonstrates that purified P450IIB1 can catalyze the conversion of NNK to most of its oxidative metabolites.
Carcinogenesis 1991 Dec
PMID:Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by cytochrome P450IIB1 in a reconstituted system. 174 27

The metabolism of azoxymethane (AOM), methylazoxymethanol (MAM) and N-nitrosodimethylamine (NDMA) by liver microsomes from acetone-induced rats as well as by a reconstituted system containing purified cytochrome P450IIE1 was examined. The products consisted of MAM from AOM; methanol and formic acid from MAM; and methylamine, formaldehyde, methanol, methylphosphate and formic acid from NDMA. Compared to liver microsomes from untreated rats, the metabolic activity of acetone-induced microsomes was approximately 4 times higher for all three carcinogens. Using the reconstituted system, the enzyme activities (nmol substrate metabolized/nmol P450/min) for AOM, MAM and NDMA were 2.88 +/- 1.14, 2.87 +/- 0.59 and 9.47 +/- 2.24 respectively. Incubations carried out in the presence of a monoclonal antibody to cytochrome P450IIE1 resulted in a 85-90% inhibition of all three reactions in this system. These results provide conclusive evidence that AOM, MAM and NDMA are metabolized by the same form of rat liver cytochrome P450. In addition, the stoichiometry of NDMA products formed in these reactions indicates that denitrosation, a presumed detoxication process, and alpha-hydroxylation, an activation reaction, are also catalyzed by the same cytochrome P450 isozyme.
Carcinogenesis 1991 Jan
PMID:Metabolism of azoxymethane, methylazoxymethanol and N-nitrosodimethylamine by cytochrome P450IIE1. 198 72


1 2 3 4 5 6 7 8 9 10 Next >>