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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using rat liver microsomal preparations and peroxidase enzymes, we have investigated the formation of DNA adducts by the antiestrogen compound tamoxifen (TAM) and its metabolite 4-hydroxy-tamoxifen (4-OH-TAM). When reduced nicotinamide-adenine dinucleotide phosphate (NADPH) was used as a cofactor in microsomal activation of either 4-OH-TAM or TAM, one DNA adduct and relative DNA adduct levels of 4.6 and 3.1 x 10(-8), respectively were detected by 32P-postlabeling. The DNA adduct produced by microsomal activation of 4-OH-TAM and TAM was the same. With cumene hydroperoxide (CuOOH) as the cofactor for the microsomal activation of either 4-OH-TAM or TAM, three to six DNA adducts were produced; the relative adduct levels were 8.0 and 20.6 x 10(-8), respectively. Comparison of the DNA adduct patterns produced by 4-OH-TAM and TAM showed that they were distinct. However one of the DNA adducts (a) produced by microsomal activation of 4-OH-TAM using CuOOH was the same as adduct a produced by microsomal activation of 4-OH-TAM with NADPH. Activation of 4-OH-TAM with horseradish peroxidase resulted in the formation of a single DNA adduct and a relative adduct level of 20.7 x 10(-8). Rechromatography analysis of this DNA adduct showed that it was identical to that produced by microsomal activation of 4-OH-TAM with NADPH and one of the adducts produced using CuOOH as the cofactor. Ten DNA adducts and a relative adduct level of 15.3 x 10(-8) were detected in the liver of female Sprague-Dawley rats treated daily with 20 mg/kg of TAM for 7 days. The DNA adduct pattern in the liver of the treated animals was similar to that produced by microsomal activation of TAM using CuOOH as the co-factor. The principal DNA adduct (no. 6) formed in the livers of rats treated with TAM was the same as the principal DNA adduct formed following microsomal activation of TAM using CuOOH as a cofactor. The DNA adduct formed following microsomal activation of either TAM or 4-OH-TAM using NADPH was also present as one of the adducts (1) formed in vivo following TAM treatment. These studies demonstrate that 4-OH-TAM can be activated to form DNA adducts and that it contributes to the formation of DNA adducts in the liver of rats treated with TAM.
Carcinogenesis 1995 Jan
PMID:Microsomal and peroxidase activation of 4-hydroxy-tamoxifen to form DNA adducts: comparison with DNA adducts formed in Sprague-Dawley rats treated with tamoxifen. 783 94

Precancerous lesions and early invasive carcinomas were produced in the tongues of rats by oral administration of 0.001% 4-nitroquinoline 1-oxide in drinking water. The distribution and densities of S-phase cells were then studied in an attempt to clarify the mechanism of carcinogenesis from the viewpoint of cell cycle. Bromodeoxyuridine (BrdU)-labeled S-phase cells were demonstrated by an indirect peroxidase method, using anti-BrdU monoclonal antibody, and their percentage was determined as the labeling index (LI). The average BrdU LI was significantly higher in the precancerous lesions than in the normal epithelium. There was a wide range of LI found in cells showing such changes as hyperplasia, hyperparakeratosis, dysplasia and papilloma, but the differences among them were not significant. These findings also showed that there could be considerable differences in proliferative activity among lesions of the same grade, while the difference in histology did not mean a difference in proliferative activity. Additionally, many BrdU-labeled cells were seen in a few layers over the basement membranes of non-cancerous lesions immediately adjacent to early invasive carcinoma, suggesting that these layers had a higher possibility for advancing to early invasive carcinoma.
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PMID:Assessment of bromodeoxyuridine-labeled S-phase cells in experimentally induced precancerous lesions in the rat's tongue. 808 Jun 35

Glutathione (GSH)-driven lipid peroxidation (LPO) in vitro was catalyzed by gamma-glutamyltranspeptidase (GGT; EC 2.3.2.2.). The reaction required iron, iron chelators and oxygen, was accelerated by glycylglycine (gly)2, a GGT enhancer, and was inhibited by the GGT inhibitors serine--borate and acivicin. LPO occurred at rat plasma concentrations of GSH and transferrin, and in the presence of putative physiological chelators such as citrate and ADP. GSH-driven LPO was inhibited by butylated hydroxytoluene, but not by catalase, peroxidase or superoxide dismutase. These results suggest that metabolism of GSH initiated by GGT may lead to oxidative damage. Such oxidative damage may be induced in vivo by GSH in proximity to GGT-rich preneoplastic foci in rat liver.
Carcinogenesis 1993 Feb
PMID:Glutathione metabolism by gamma-glutamyltranspeptidase leads to lipid peroxidation: characterization of the system and relevance to hepatocarcinogenesis. 809 45

We tested whether a concentration of unleaded gasoline (UG) vapor that was selectively hepatocarcinogenic in female mice in a chronic bioassay is antiestrogenic and whether liver tumor promotion by UG is secondary to antiestrogenicity. Twelve-day-old female C57BL/6 x C3H F1 mice (hereafter called B6C3F1) received i.p. injections of N-nitrosodiethylamine (5 mg/kg) or vehicle. Beginning at 5-7 weeks of age, mice were exposed to 0, 292, or 2056 ppm of PS-6 blend UG vapor for 6 h/day, 5 days/week for 16 weeks, 1 ppm ethinyl estradiol (EE2) in the diet, or 2056 ppm UG vapor and 1 ppm EE2 in the diet. Treatment with 2026 ppm UG but not 292 ppm UG increased relative liver weight, the number of macroscopic hepatic neoplasms, and the size and volume fraction of altered hepatic foci in N-nitrosodiethylamine-initiated mice. Treatment with 2056 ppm UG reduced relative uterus, ovary, and pituitary weights but did not change serum 17 beta-estradiol levels, uterine peroxidase activity, or uterine cytosolic estrogen receptor levels. EE2 treatment reduced the number and size of altered hepatic foci in N-nitrosodiethylamine-initiated mice, caused weight loss, anestrus, vaginal keratinization, decreased uterine peroxidase activity, and decreased uterine cytosolic estrogen receptor levels. UG/EE2 co-treatment attenuated the weight loss, anestrus, and vaginal keratinization caused by EE2 treatment alone but dramatically increased the number of macroscopic hepatic neoplasms and the size and volume fraction of altered hepatic foci as compared to UG treatment alone. Thus, in this two-stage model of carcinogenesis (a) 2056 ppm UG had antiestrogenic effects, particularly with respect to pharmacological actions of EE2; (b) 2056 ppm UG but not 292 ppm UG acted as a liver tumor promoter; (c) EE2 inhibited liver tumor promotion; and (d) EE2 strongly potentiated liver tumor promotion by UG. These data demonstrate significant individual and interactive effects of UG vapor and estrogens in liver tumor promotion in female mice.
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PMID:Interactive effects of unleaded gasoline and estrogen on liver tumor promotion in female B6C3F1 mice. 811 6

Using microsomal preparations from rat and human liver, we investigated the activation of the anti-estrogen compound tamoxifen (TMX) to form DNA adducts. Pretreatment of rats with phenobarbital increased DNA adduct formation by microsomal activation of TMX 3- to 6-fold, depending on the cofactors used. When reduced nicotinamide-adenine dinucleotide phosphate (NADPH) was used as a cofactor in human and rat microsomal activation systems, the relative DNA adduct levels were 2.9 and 5.2 x 10(-8) respectively and 1-3 TMX-DNA adducts were detected by 32P-postlabeling; DNA adduct 1 was the same in both microsomal systems. When cumene hydroperoxide (CuOOH) was used as a cofactor, activation of TMX produced four major DNA adducts and several minor DNA adducts in both rat and human liver microsomes; the relative adduct levels were 11.1 and 23.1 x 10(-8) respectively. TMX-DNA adducts 1, 4, 5 and 6 were similar in both human and rat microsomal systems with CuOOH as the cofactor. The TMX-DNA adducts formed with NADPH as the cofactor were clearly different from those formed with CuOOH as the cofactor, which implies that the metabolites leading to the individual DNA adducts were different. Addition of a P450 inhibitor, either n-octylamine or alpha-naphthylisothiocyanate, to the activation system reduced adduct formation by 70-93%. We propose that the TMX-DNA adducts formed with NADPH as the cofactor result from P450 acting as a mono-oxygenase, whereas the adducts formed with CuOOH as the cofactor result from P450 acting as a peroxidase. Our findings suggest that further studies may be required to establish the safety of TMX treatment of women for purposes other than chemotherapy.
Carcinogenesis 1994 Mar
PMID:DNA adduct formation by tamoxifen with rat and human liver microsomal activation systems. 811 38

Metabolism of benzene results in the formation of multiple metabolites, including hydroquinone (HQ). HQ is a reducing co-substrate for peroxidase enzymes, and the resultant semiquinone and para-benzoquinone (p-BQ) may bind to DNA. The role of peroxidase activation in the formation of DNA adducts by benzene metabolites has not been established. In this study we investigated the role of peroxidase activation in the formation of DNA adducts by HQ and p-BQ in HL-60 cells, human bone marrow (HBM) cells, mouse bone marrow macrophages (MBMM) and the U-937 and Raji leukemia cell lines. Adduct formation was measured by P1-enhanced 32P-postlabeling; peroxidase activity was measured with a spectrophotometric assay. Treatment with p-BQ resulted in the formation of two DNA adducts in all of the cell lines. The DNA adducts were identical in all of the cells, however, the adduct level varied by 80-fold. Treatment with HQ produced one DNA adduct in HL-60 cells, HBM and MBMM; no adducts were detected in U-937 or Raji cells. The HQ-DNA adducts in the three cell lines were identical. The adduct level was highest in the HL-60 cells, followed by HBM and MBMM. There was a statistically significant correlation between peroxidase activity and the formation of HQ-DNA adducts. These results suggest that peroxidase-mediated metabolism is involved in the activation of HQ to form DNA adducts in mouse bone marrow and HBM.
Carcinogenesis 1993 Nov
PMID:Peroxidase activation of hydroquinone results in the formation of DNA adducts in HL-60 cells, mouse bone marrow macrophages and human bone marrow. 824 63

Diethylstilbestrol (DES), an estrogen analogue, was converted into a free radical in alkaline dimethyl sulfoxide as well as in an H2O2/peroxidase system. The presence of the hydroxyl group of the DES molecule was essential to free radical formation. Indenestrol A (IA), a microsomal metabolite of DES, showed a paramagnetic property without enzymatic activation. The electron spin resonance spectrum of IA seemingly corresponded to that of the enzymatically formed DES radical. In an NADH/peroxidase system, DES induced concomitant production of active oxygen species, which were also produced by IA. Related compounds of IA were also examined to compare with DES and IA. The significance of the free radical is discussed in relation to the process of carcinogenesis by DES.
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PMID:Formation of free radicals and active oxygen species from diethylstilbestrol and its derivatives. 839 75

Benzoquinones (BQ) are genotoxic species that stem from metabolism of phenolic compounds. We have developed a method for measuring adducts of 1,2- and 1,4-benzoquinone (1,2-BQ and 1,4-BQ) with cysteine residues of hemoglobin (Hb) and albumin (Alb). The method employs a reductive catalyst (Raney nickel) to selectively cleave sulfur-bound adducts so that they may be extracted with an organic solvent, derivatized with heptafluorobutyrylimidazole and measured by GC-ECD or GC-MS. Reactions of 1,4-BQ (0-300 microM) with whole blood of both F344 rats and humans resulted in linear formation of adducts with Hb and Alb. Adducts of 1,2-BQ with human Alb were formed by activation of catechol (0-300 microM) in situ with horseradish peroxidase. The mean half lives in vitro of 1,4-BQ in blood from humans and rats were 3.5 and 0.68 h, respectively. Second-order rate constants for reaction of 1,4-BQ with Hb and Alb in whole blood were estimated to be 18 and 76 l/mol/h for humans and 180 and 74 l/mol/h for rats respectively. Interestingly, the following high background levels of 1,2-BQ and 1,4-BQ adducts were observed in the proteins: 1,2-BQ-human Hb = 1.5 nmol/g, rat Hb = 25.1 nmol/g; human Alb = 8.0 nmol/g; 1,4-BQ-human Hb = 27.2 nmol/g, rat Hb = 11.5 nmol/g; human Alb = 20.5 nmol/g. These large background levels of BQ adducts suggest that significant exposure to BQ precursors occurs from dietary and/or endogenous sources. Given current evidence regarding the genotoxicity of BQ, such exposures and their health consequences should be investigated.
Carcinogenesis 1993 Sep
PMID:Measurement of adducts of benzoquinone with hemoglobin and albumin. 840 20

The C-hydroxyderivatives of the carcinogenic dye Sudan I, 1-phenylazo-2,6-dihydroxynaphthalene and 1-(4-hydroxyphenylazo)-2-hydroxynaphthalene, which are considered to be detoxication products of this dye bind to DNA or tRNA after oxidation into active metabolites by peroxidase and H2O2 in vitro. The 32P-postlabeling analysis of DNA modified by active metabolites of both Sudan I derivatives provides evidence that the covalent binding to DNA is the principal type of DNA modification. Since the urinary bladder is rich in peroxidases, the participation of these enzymes in activation of detoxicating products of Sudan I may be involved in the initiation of Sudan I-carcinogenesis in this organ.
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PMID:Detoxication products of the carcinogenic azodye Sudan I (solvent yellow 14) bind to nucleic acids after activation by peroxidase. 842 48

Inbred strains of mice with differential response to known tumor promoters were compared with respect to their susceptibility to modulation of hepatic antioxidant enzymes by long-term treatment with high fat diet (HF) and phenobarbital (PB). Mice of the C57BL/6J (C57), C3H/HeOuJ (C3H) and DBA/2J (DBA) strains were fed diets containing low (5%) or high (15%) amounts of fat (sunflower oil) for 26 weeks from the age of 6 weeks onwards. Groups of mice on the 5% fat diet received 0.05% PB in their drinking water from 12 to 22 weeks of age. Mice of the C57 strain are known to be refractory to promotion of hepatocarcinogenesis, the C3H strain has a high incidence of spontaneous tumors and is sensitive to promotion by HF and PB, and the DBA strain is especially sensitive to promotion by PB. Within all strains of mice, and in both dietary groups, the degree of oxidative stress in the liver was found to increase with age, as was indicated by the increased amounts of TBA reactive material (lipid peroxidation) and decreased glutathione (GSH) and phospholipid contents of the tissue. HF elevated the amount of TBA reactive material in the liver of C57 and C3H mice, induced GSH-peroxidase and Mn-superoxide dismutase activities in the C3H strain, and depressed the hexose monophosphate shunt activity within all mouse strains. PB drastically decreased the amount of TBA reactive material in the liver in all mouse strains, increased catalase activity in all strains and the activity of GSH-peroxidase in the C3H and DBA strains. The above strain differences in responses of hepatic antioxidant functions to HF and PB parallel the differential responsiveness of these mouse strains to promotion of hepatocarcinogenesis by these agents, and the increased antioxidant capacity was proportional to susceptibility to tumor promotion.
Carcinogenesis 1993 Jun
PMID:Dietary fat- and phenobarbital-induced alterations in hepatic antioxidant functions of mice. 850 10


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