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

Chromium(VI) and Cr(V) compounds increased the concentration of 8-hydroxydeoxyguanosine (oh8dG) in isolated DNA, whereas no such increase was seen with Cr(III). Furthermore, incubating DNA with H2O2 and Cr(VI) or Cr(V) potentiated the formation of oh8dG above levels observed with either chromium compound alone. In the presence of catalase, the increase in DNA oxidation observed with Cr(VI) was inhibited, the base oxidation observed being equivalent to background levels, and this indicated involvement of H2O2 in the mechanism. Glutathione did not enhance chromium-induced formation of this oxidized base. These results help to explain a mechanism of chromium-induced DNA oxidation involving H2O2 via a Fenton-type reaction.
Carcinogenesis 1992 Sep
PMID:Production of 8-hydroxydeoxyguanosine in isolated DNA by chromium(VI) and chromium(V). 132 73

Endogenous oxidative processes are shown to generate hydrogen peroxide and .OH radicals, which react in vivo to form a variety of products. Thymidine glycol (Tg) and 8-hydroxydeoxyguanosine (8-dRG-OH) are such products. They result from the excision repair of DNA and are excreted in urine. Both products can be used as biomarkers in the dosimetry of oxidative damage to DNA. Since oxidative processes and accumulation of their effects contribute to carcinogenesis, the proposed rate-of-damage hypothesis provides a rationale for using these biomarkers in early diagnostics and in the assessment of carcinogenic and anticarcinogenic properties of diets, foods, and food components, as well as certain exogenous toxicants and agents. Approaches for measurement of urinary biomarkers of DNA damage are reviewed.
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PMID:Urinary biomarkers and the rate of DNA damage in carcinogenesis and anticarcinogenesis. 137 30

Exposure to UV light contributes to the development of skin cancer. The importance of reactive oxygen species in UV-radiation carcinogenesis has been recognized for some time and several associated DNA base modifications have been identified. In particular, 8-hydroxydeoxyguanosine (8-OHdG) has been well studied as an indicator of oxidative damage to calf thymus DNA exposed to a variety of oxygen-generating systems, including UV light. However, to date, few studies of 8-OHdG have been conducted in cell or animal systems and those in vitro investigations that studied UV exposure have used UVC (< 290 nm), not the UVB (290-320 nm) or UVA (320-400 nm) ranges to which organisms are exposed through sunlight. The objective of this study was to measure 8-OHdG formation in the DNA of cultured mouse keratinocytes exposed to UVB. Using HPLC with electrochemical detection, background levels of 8-OHdG were approximately 6 fmol/micrograms DNA in DNA isolated and digested to the nucleoside level. UVB induced 8-OHdG up to 100% above that for mock-treated cells at a dose of 630 mJ/cm2 (dose-response range: 210-630 mJ/cm2). UVB exposure at 630 mJ/cm2 combined with 5 mM H2O2 elevated 8-OHdG formation up to 280% above that in control cells, whereas H2O2 alone had no effect. These results suggest that factors which increase the generation of reactive oxygen species by UV light may be potent cofactors of UV-radiation carcinogenesis.
Carcinogenesis 1992 Nov
PMID:Formation of 8-hydroxydeoxyguanosine within DNA of mouse keratinocytes exposed in culture to UVB and H2O2. 142 68

Oxidative DNA damage may be implicated in ageing, carcinogenesis and other degenerative diseases. Oxidative DNA damage can be assessed in humans in vivo from the urinary excretion of the DNA-repair product 8-hydroxydeoxyguanosine (8OHdG). We investigated factors influencing the excretion of 8OHdG in 24 h urine from 83 randomly selected healthy subjects (52 women) aged 40-64 years. For 2 weeks prior to urine collection the subjects kept a weighed diet record. 8OHdG was quantified by an automatic three-dimensional HPLC analysis with electrochemical detection. The 8OHdG excretion was 252 +/- 103 (mean +/- SD) pmol kg body weight/24 h with a range from 78 to 527. Multiple regression analysis identified three factors, smoking, body mass index (BMI) and gender, as significant predictors of the 8OHdG excretion. In 30 smokers the 8OHdG excretion was 320 +/- 99 pmol/kg/24 h opposed to 213 +/- 84 pmol/kg/24 h in 53 non-smokers. According to multiple regression analysis smokers excreted 50% (31-69%; 95% confidence interval) more 8OHdG than non-smokers. In 52 women the 8OHdG excretion was 240 +/- 106 pmol/kg/24 h opposed to 271 +/- 96 pmol/kg/24 h in 31 men. According to the multiple regression analysis men excreted 29% (10-48%) more 8OHdG than women. According to multiple regression analysis the 8OHdG excretion decreased with 4% (2-6%) per increment in BMI measured in kg/m2. The dietary distribution of energy demonstrated no important predictive value with respect to 8OHdG excretion. The intake of the antioxidant vitamins C and E and of vitamin A equivalents, including beta-carotene, was not associated with 8OHdG excretion. The results suggest that smoking increases oxidative DNA damage by approximately 50%. This effect implies potential serious health effects adding to the other well-known health hazards of smoking. The higher 8OHdG excretion in men and lean subjects may be related to a higher rate of metabolism with increased availability of reactive oxygen species. The apparent 7-fold individual variation in oxidative DNA damage carries implications regarding the rate of ageing and the risk of cancer and other degenerative diseases. The excretion of 8OHdG into urine offers a valuable tool for testing such hypotheses in humans.
Carcinogenesis 1992 Dec
PMID:Oxidative DNA damage estimated by 8-hydroxydeoxyguanosine excretion in humans: influence of smoking, gender and body mass index. 147 30

Fecapentaene-12 (fec-12), excreted in human faeces, is genotoxic to human cells and a known animal carcinogen. The mechanism of its genotoxicity is unknown but may involve direct alkylation and/or free-radical generation. The formation of reactive species during fec-12 aerobic degradation was thus investigated by electron paramagnetic resonance (EPR) and NMR spectroscopic techniques. Oxy- and alkyl-radicals were detected as the 5,5'-dimethyl-1-pyrroline-N-oxide spin-trap adducts at fec-12 concentrations of between 0.1 and 2.0 mM. Under anaerobic conditions no free-radical generation was observed. NMR spectroscopy indicated that fec-12 degraded at least initially into three unsaturated aldehydes. The co-formation of free-radicals and unsaturated aldehydes suggests that fec-12 decomposed aerobically via a process analogous to lipid peroxidation. As both types of species, thus formed, may subsequently interact with DNA to form adducts, fec-12-induced DNA damage was investigated by 32P-postlabelling techniques. Using procedures that detect alkyl-type adducts, a number of putative adducts were detected in fec-12-treated DNA; two of similar mobility were observed in fec-12-treated 2'-deoxyguanosine-3'-monophosphate. Adducts with similar mobility have been detected in acrolein-treated DNA. One adduct with similar mobility was also observed in DNA obtained from normal human fibroblasts treated with fec-12. Using a C-18 ODS column, these putative adducts were eluted in 60-85% methanol, whereas 8-hydroxydeoxyguanosine-3'-monophosphate (8OHdGp) was eluted with 1% acetonitrile. Also unlike these putative adducts, the detection of 8OHdGp required HPLC fractionation prior to 32P-postlabelling. The formation of adducts, possibly aldehyde-related, and free-radical damage suggests that fec-12 genotoxicity may be the result of several different mechanisms, the relative importance of each is as yet unknown. Hydroxyl radicals were also detected during the aerobic decomposition of deca-2,4,6,8-tetraenal, a possible degradation product of fec-12 and a less potent mutagen, suggesting that free-radical generation may have only a minor role in fec-12-induced genotoxicity.
Carcinogenesis 1992 Mar
PMID:Detection by 32P-postlabelling of DNA adducts induced by free radicals and unsaturated aldehydes formed during the aerobic decomposition of fecapentaene-12. 154 29

We investigated the accumulation of oxidative DNA damage during the aging process by using 8-hydroxydeoxyguanosine (8-OH-dG) as a marker. The 8-OH-dG is one of the oxidative DNA damage products and is supposed to be a critical factor in carcinogenesis involving oxygen radicals. The 8-OH-dG levels in the DNA of liver, kidney, brain, lung, and spleen were measured in male and female F344 rats 6- to 30-month-old. The 8-OH-dG levels in the liver and kidney DNA of male rats increased significantly with age, but did not change in brain, lung, and spleen. Similarly, the 8-OH-dG levels in the liver and kidney DNA of female rats significantly increased with age, while changes in the brain, lung, and spleen DNA were much smaller. These results indicate that the accumulation of oxidative DNA damage during the aging process varies among organs, with slight sex difference.
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PMID:Changes of 8-hydroxydeoxyguanosine levels in rat organ DNA during the aging process. 162 83

Reactive oxygen species can give rise to numerous modifications of DNA. We have investigated the formation of such modifications using the nuclease P1 digestion method of the 32P-postlabelling procedure for the detection of DNA damage. Analysis of DNA that had been treated with a Fenton-type system of copper (or iron) ions and H2O2 resulted in the detection of up to ten discrete 32P-labelled spots, displaying chromatographic characteristics similar to aromatic adducts, on PEI-cellulose TLC. Maximum total levels equivalent to 28 adducts/10(8) nucleotides were achieved after 15 min of treatment with Cu2+/H2O2. The formation of adducts was 1.5 times greater if single-stranded rather than double-stranded DNA was employed, suggesting an intrastrand effect. Experiments with 3'-deoxyribonucleotides demonstrated that the adducts detected did not represent base modifications such as 8-hydroxydeoxyguanosine or thymidine glycols. However, treatment of specific dinucleotides (dApdG and dApdA) was found to produce two major adducts that were chromatographically identical by TLC and HPLC to the two major adducts formed in DNA. It is proposed that these species with aromatic adduct-like characteristics are the result of the intrastrand linking of specific adjacent bases in DNA.
Carcinogenesis 1992 Jul
PMID:Detection and characterization by 32P-postlabelling of DNA adducts induced by a Fenton-type oxygen radical-generating system. 163 78

Effects of dietary iron deficiency on inductions of putative preneoplastic lesions and oxidative alterations in the livers of rats by a choline-deficient L-amino acid defined (CDAA) diet were examined. Male Fischer 344 rats, 4 weeks old, were used with a total experimental period of 16 weeks, consisting of 4-week pretreatment and 12-week treatment periods (periods A and B respectively). During period A, a choline-supplemented L-amino acid defined (CSAA) or an iron-deficient CSAA diet was administered, and the CDAA or an iron-deficient CDAA diet was fed in period B. Formation of 8-hydroxydeoxyguanosine (8OHdG), a DNA adduct generated by activated oxygen species, in DNA and lipid peroxidation in liver cell membranes were sequentially determined after the beginning of period B. At the end of the experiment, development of gamma-glutamyltransferase (GGT) and glutathione S-transferase placental form (GSTP) positive liver lesions were quantitatively analysed. In the animals fed the CDAA diet, formation of 8OHdG and lipid peroxidation increased with time, and GGT and GSTP positive liver lesions developed. Formation of 8OHdG, lipid peroxidation and the numbers of induced enzyme-altered liver lesions were all reduced in rats fed the iron-deficient CSAA diet in period A and/or the iron-deficient CDAA diet in period B. The present results indicate that iron plays an important role in induction of preneoplastic liver lesions in rats caused by exposure to the CDAA diet possibly in connection with its known catalytic role in generation of highly reactive activated oxygen species.
Carcinogenesis 1992 Jul
PMID:Inhibitory effect of dietary iron deficiency on inductions of putative preneoplastic lesions as well as 8-hydroxydeoxyguanosine in DNA and lipid peroxidation in the livers of rats caused by exposure to a choline-deficient L-amino acid defined diet. 163 91

Evidence for the involvement of free radicals in nitrosamine carcinogenesis comes mainly from increased lipid peroxidation as a result of nitrosamine treatment. More direct evidence for nitrosamine-induced oxidative DNA damage has been lacking. In this study we examined the levels of 8-oxodeoxyguanosine or 8-hydroxydeoxyguanosine (8-OH-dG) in tissue DNA of mice and rats treated with the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Multiple doses of NNK (0.25 or 0.50 mg/mouse, 3 times weekly for 3 weeks) administered by gavage resulted in a significant elevation of 8-OH-dG in lung DNA, from 2.1 to 3.8 adducts/10(5) dG for the lower dose or to 6.6 adducts/10(5) dG for the higher dose, 2 h after the last NNK administration. A single dose treatment of NNK by gavage (4 mg/mouse) also resulted in an increase of this lesion in the lung DNA, however, the increase was not statistically significant. In liver, however, the increase was only significant by multiple doses at the higher dose, from 2.3 to 3.4 adducts/10(5) dG. This lesion appeared to be repaired efficiently. At 4 and 24 h after NNK treatment, the 8-OH-dG levels declined to the basal levels in both liver and lung. A single dose of NNK (20 mg/rat) also caused a significant increase of 8-OH-dG from 3.0 to 5.1 adducts/10(5) dG in rat lung DNA. An increase of 8-OH-dG in liver DNA was also seen, however, it was not statistically significant. Unlike the liver and the lung, the 8-OH-dG levels in rat kidney, a non-target tissue, were inert to NNK treatment. These results provide for the first time direct evidence supporting the role of oxidative DNA damage in NNK lung tumorigenesis.
Carcinogenesis 1992 Jul
PMID:Increased 8-oxodeoxyguanosine levels in lung DNA of A/J mice and F344 rats treated with the tobacco-specific nitrosamine 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanone. 163 97

The DNA base adduct, 8-hydroxyguanine (8-OHGua), has been reported to be a key biomarker relevant to carcinogenesis and cellular oxidative stress important in tumor promotion. Although investigators often report artificially high levels of 8-OHGua in DNA samples that have been exposed to phenol solutions and/or air during processing, few quantitative results are available. We show that routine phenol-based DNA purification procedures can increase 8-hydroxydeoxyguanosine (8-OHdG) levels 20-fold in samples that are exposed to air after the phenol is removed from the solutions. Surprisingly, air exposure alone accounts for a significant portion of this increase (4-fold) when compared to dG or DNA samples that have been solubilized in buffers purged with nitrogen. Most importantly, phenol treatments of DNA are shown to sensitize DNA to 8-OHdG formation by subsequent exposures to air. The sensitization of DNA occurs even though extensive dialysis is used between phenol treatment and enzymatic DNA digestion. Alternate procedures, including chloroform:isoamyl-alcohol extractions, also yield air-sensitive DNA samples. Other artifacts of organic extraction prior to air exposure include alterations in DNA base ratios after nuclease digestions. Overall, these results strongly suggest that studies of 8-OHdG in carcinogenesis should avoid dry conditions, such as lyophilization followed by exposure to air, and that all four of the bases should be monitored before 8-OHdG concentrations are normalized by undamaged deoxynucleoside concentrations. Failure to heed these precautions can lead to 2- to 20-fold overestimates of 8-OHdG in target tissues or in vitro models.
Carcinogenesis 1992 Jul
PMID:Phenol sensitization of DNA to subsequent oxidative damage in 8-hydroxyguanine assays. 163 1


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