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

Alcoholic beverage consumption is classified as a known human carcinogen, causally related to an increased risk of cancer of the upper gastrointestinal tract. The formation of acetaldehyde from ethanol metabolism seems to be the major mechanism underlying this effect. Acetaldehyde is carcinogenic in rodents and causes sister chromatid exchanges and chromosomal aberrations in human cells. The best-studied DNA adduct from acetaldehyde is N(2)-ethyl-2'-deoxyguanosine, which is increased in liver DNA obtained from ethanol-treated rodents and in white blood cells obtained from human alcohol abusers. However, the carcinogenic relevance of this adduct is unclear in view of the lack of evidence that it is mutagenic in mammalian cells. A different DNA adduct, 1,N(2)-propano-2'-deoxyguanosine (PdG), can also be formed from acetaldehyde in the presence of histones and other basic molecules. PdG has been shown to be responsible for the genotoxic and mutagenic effects of crotonaldehyde. The PdG adduct can exist in either of two forms: a ring-closed form or a ring-opened aldehyde form. Whereas the ring-closed form is mutagenic, the aldehyde form can participate in the formation of secondary lesions, including DNA-protein cross-links and DNA interstrand cross-links. The formation of these types of complex secondary DNA lesions resulting from PdG may explain many of the observed genotoxic effects of acetaldehyde described above. Repair of PdG and its associated adducts is complex, involving multiple pathways. Inherited variation in the genes encoding the proteins involved in the repair of PdG and its secondary adducts may contribute to susceptibility to alcoholic beverage-related carcinogenesis.
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PMID:DNA adducts from acetaldehyde: implications for alcohol-related carcinogenesis. 1605 80

Breast cancer is the most common cancer in women in the United States, and it is second among cancer deaths in women. Results of most epidemiologic studies, as well as of most experimental studies in animals, have shown that alcohol intake is associated with increased breast cancer risk. Alcohol consumption may cause breast cancer through different mechanisms, including through mutagenesis by acetaldehyde, through perturbation of estrogen metabolism and response, and by inducing oxidative damage and/or by affecting folate and one-carbon metabolism pathways. Alcohol-metabolizing enzymes are present in human breast tissue. Acetaldehyde is a known, although weak, mutagen. However, results of some studies with human subjects implicate this agent in the context of genetic susceptibilities to increased ethanol metabolism. Reactive oxygen species, resulting from ethanol metabolism, may be involved in breast carcinogenesis by causing damage, as well as by generating DNA and protein adducts. Alcohol interferes with estrogen pathways in multiple ways, influencing hormone levels and effects on the estrogen receptors. With regard to one-carbon metabolism, alcohol can negatively affect folate levels, and the folate perturbation affects DNA methylation and DNA synthesis, which is important in carcinogenesis. Some study results indicate that genetic variants of one-carbon metabolism genes might increase alcohol-related breast cancer risk. For all these pathways, genetic polymorphisms might play a role in increasing further a woman's risk for breast cancer. Additional studies are needed to determine the relative importance of these pathways, as well as the modifying influence by genetic variation.
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PMID:The etiology of alcohol-induced breast cancer. 1605 83

Acrolein is a highly reactive alpha,beta-unsaturated aldehyde and is known to react with DNA forming exocyclic acrolein-deoxyguanosine adducts (Acro-dG). These aldehyde-DNA lesions may play a role in mutagenesis, carcinogenesis, and neurodegenerative diseases. In the present work, we described the development and evaluation of a highly sensitive and selective capillary liquid chromatography nanoelectrospray isotope dilution tandem mass spectrometry method for quantitatively analyzing Acro-dG in DNA hydrolysates. This was achieved by applying a stable isotope-labeled analogue Acro-dG-13C10,15N5 as an internal standard to the DNA to be analyzed and then hydrolyzing the DNA enzymatically to nucleosides. The acrolein-modified nucleosides were separated from normal nucleosides by capillary liquid chromatography and quantified by a high-capacity ion trap mass spectrometer in the MS/MS mode. The developed method achieved attomole-level sensitivity (limit of detection was 10 fg, 31 amol on column) for detection of pure Acro-dG adduct standards. The limit of quantification of Acro-dG adducts obtained in 10 mug of DNA hydrolysates was 1.5 fmol, which corresponded to 50 adducts/10(9) normal nucleosides. Application of this method to the analysis of Acro-dG adducts in acrolein (10-fold)-treated calf thymus DNA showed approximately 830 lesion/10(6) DNA nucleosides using as low as 50 ng of DNA. Application of this method to DNA samples (1-2 mug) isolated from brain tissues from Alzheimer's disease subjects and age-matched controls demonstrated 2800-5100 Acro-dG adducts/10(9) DNA nucleosides. Statistically significant differences (P < 0.05) in levels of Acro-dG between AD subjects and controls were observed in DNA isolated from the hippocampus/parahippocampal gyrus.
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PMID:Development of a method for quantification of acrolein-deoxyguanosine adducts in DNA using isotope dilution-capillary LC/MS/MS and its application to human brain tissue. 1615 31

A causal association has been established between alcohol consumption and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colon, rectum, and, in women, breast; an association is suspected for cancers of the pancreas and lung. Evidence suggests that the effect of alcohol is modulated by polymorphisms in genes encoding enzymes for ethanol metabolism (eg, alcohol dehydrogenases, aldehyde dehydrogenases, and cytochrome P450 2E1), folate metabolism, and DNA repair. The mechanisms by which alcohol consumption exerts its carcinogenic effect have not been defined fully, although plausible events include: a genotoxic effect of acetaldehyde, the main metabolite of ethanol; increased oestrogen concentration, which is important for breast carcinogenesis; a role as solvent for tobacco carcinogens; production of reactive oxygen species and nitrogen species; and changes in folate metabolism. Alcohol consumption is increasing in many countries and is an important cause of cancer worldwide.
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PMID:Alcohol and cancer. 1645 79

Acetaldehyde, an ubiquitous mutagen and carcinogen, could be involved in human cancer etiology. Because DNA adducts are important in carcinogenesis, we have used liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) to explore the presence in human liver DNA of the major acetaldehyde DNA adduct, N2-ethylidenedeoxyguanosine (1). DNA was isolated and enzymatically hydrolyzed in the presence of NaBH3CN, which quantitatively converts adduct 1 to N2-ethyldeoxyguanosine (N2-ethyl-dGuo, 2). [15N5]N2-Ethyl-dGuo was synthesized and used as an internal standard. Adduct 2 was enriched from the hydrolysate by solid phase extraction and analyzed by LC-ESI-MS/MS. Clear peaks were observed for adduct 2 in analyses of human liver DNA, calf thymus DNA, and rat liver DNA. These peaks were not observed, or were much smaller, when the NaBH3CN step was omitted. When the DNA was subjected to neutral thermal hydrolysis prior to NaBH3CN treatment, adduct 2 was not observed. Control experiments using [13C2]acetaldehyde demonstrated that adducts 1 and 2 were not formed as artifacts during DNA isolation and analysis. These results strongly indicate that adduct 1 is present in human liver DNA and demonstrate that it can be quantified as adduct 2. Levels of adduct 2 measured in 12 human liver samples were 534 +/- 245 fmol/micromol dGuo (mean +/- SD). The results of this study establish the presence of an acetaldehyde adduct in human liver DNA and suggest that it is a commonly occurring endogenous DNA adduct.
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PMID:Identification of an acetaldehyde adduct in human liver DNA and quantitation as N2-ethyldeoxyguanosine. 1648 9

Furan is a toxic and carcinogenic compound used in industry and commonly found in the environment. The mechanism of furan's carcinogenesis is not well-understood and may involve both genotoxic and nongenotoxic pathways. Furan undergoes oxidation by cytochrome P450 to cis-2-butene-1,4-dial, which is thought to mediate furan's toxic effects. Consistently, cis-2-butene-1,4-dial readily reacts with glutathione, amino acids, and nucleosides. To determine the importance of DNA alkylation in furan-induced carcinogenesis, we developed an assay for the detection of cis-2-butene-1,4-dial-derived DNA adducts. DNA samples were treated with O-benzyl-hydroxylamine, which reacts with the aldehyde functionality of the DNA adducts. Enzyme hydrolysates of these samples were then analyzed by capillary electrospray tandem mass spectrometry with selected reaction monitoring. The dCyd and dAdo adducts were detected in digests of DNA treated with nanomolar concentrations of cis-2-butene-1,4-dial. In addition, these adducts were present in DNA isolated from Ames assay strain TA104 treated with mutagenic concentrations of cis-2-butene-1,4-dial. These data support the hypothesis that cis-butene-1,4-dial is a genotoxic metabolite of furan. This method will allow us to explore the role of these adducts in furan-induced carcinogenesis.
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PMID:Detection of DNA adducts derived from the reactive metabolite of furan, cis-2-butene-1,4-dial. 1654 46

Chronic exposure to 2-butoxyethanol increased liver hemangiosarcomas in male mice. The mechanism for the selective induction of hemangiosarcomas by 2-butoxyethanol is unknown but has been suggested to occur through non-DNA-reactive mechanisms. The occurrence of liver hemangiosarcomas in male mice has been linked to oxidative damage subsequent to RBC hemolysis and iron deposition and activation of macrophages (Kupffer cells) in the liver, events that exhibit a threshold in both animals and humans. 2-Butoxyethanol is metabolized to 2-butoxyacetaldehyde and 2-butoxyacetic acid, and although the aldehyde metabolite is short lived, the potential exists for this metabolite to cause DNA damage. The present study examined whether 2-butoxyethanol and its metabolites, 2-butoxyacetaldehyde and 2-butoxyacetic acid, damaged mouse endothelial cell DNA using the comet assay. No increase in DNA damage was observed following 2-butoxyethanol (1-10mM), 2-butoxyacetaldehyde (0.1-1.0mM), or 2-butoxyacetic acid (1-10mM) in endothelial cells after 2, 4, or 24 h of exposure. Additional studies examined the involvement of hemolysis and macrophage activation in 2-butoxyethanol carcinogenesis. DNA damage was produced by hemolyzed RBCs (10 x 10(6), 4 h), ferrous sulfate (0.1-1.0 microM; 2-24 h), and hydrogen peroxide (50-100 microM; 1-4 h) in endothelial cells. Hemolyzed RBCs also activated macrophages, as evidenced by increased tumor necrosis factor (TNF) alpha, while neither 2-butoxyethanol nor butoxyacetic acid increased TNF-alpha from macrophages. The effect of activated macrophages on endothelial cell DNA damage and DNA synthesis was also studied. Coculture of endothelial cells with activated macrophages increased endothelial cell DNA damage after 4 or 24 h and increased endothelial cell DNA synthesis after 24 h. These data demonstrate that 2-butoxyethanol and related metabolites do not directly cause DNA damage. Supportive evidence also demonstrated that damaged RBCs, iron, and/or products from macrophage activation (possibly reactive oxygen species) produce DNA damage in endothelial cells and that activated macrophages stimulate endothelial cell proliferation. These events coupled together provide the events necessary for the induction of hemangiosarcomas by 2-butoxyethanol.
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PMID:Mechanisms of 2-butoxyethanol-induced hemangiosarcomas. 1667 16

Aldehydes are ubiquitous contaminants in the human environment. Intracellular aldehydes are mainly derived from the metabolism of polyunsaturated fatty acids and from lipid peroxidation, which is significantly elevated under oxidative stress conditions. Oxidative stress has long been suspected to be involved in many disease processes, including carcinogenesis, neurodegeneration and aging, but its mechanisms are largely unknown. Aldehydes are reactive not only toward nucleic acids but also to many amino acids, and these aldehyde-protein interactions have been suspected of affecting many cellular functions, including DNA repair. To test this possibility we determined the effect of malondialdehyde (MDA), one of the most abundant intracellular aldehyde, on ultraviolet (UV) light- and benzo(a)pyrene diol epoxide (BPDE)-induced cytotoxicity and mutagenesis in human cells. We found that MDA treatment greatly sensitized cells to both UV- and BPDE-induced cell killing and that, MDA pre-treatment significantly enhanced UV-induced mutagenesis. Using in vitro DNA repair synthesis and host cell reactivation assays we found that MDA treatment of cells greatly inhibited nucleotide excision repair for both and UV light- and BPDE-induced DNA damage. Further experiments raise the possibility that the inhibitory effect on nucleotide excision repair is mainly caused by the direct interaction of MDA with cellular repair proteins. Together these results strongly suggest that intracellular aldehydes play an important role in oxidative stress-related mutagenesis and carcinogenesis through their inhibitory effect on DNA repair mechanisms as well as on induction of DNA damage.
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PMID:Malondialdehyde, a major endogenous lipid peroxidation product, sensitizes human cells to UV- and BPDE-induced killing and mutagenesis through inhibition of nucleotide excision repair. 1687 41

Alcohol consumption is a strong risk factor for squamous cell carcinoma of the head and neck (SCCHN). The genetic polymorphisms aldehyde dehydrogenase2 (ALDH2) Glu487Lys and alcohol dehydrogenase 2 (ADH2) His47Arg, which have a strong impact on alcohol metabolism, are common in the Japanese population. To clarify the significance of these polymorphisms in SCCHN carcinogenesis, we conducted a matched case-control study with 239 incident SCCHN subjects and 716 non-cancer controls. Both ADH2 Arg/Arg and ALDH2 Glu/Lys were found to be independently associated with increased risk, with odds ratios (OR) of 2.67 (95% confidence interval [CI] 1.51-4.57) and 1.66 (95% CI 1.20-2.31), respectively. Further, compared with subjects having both ADH2 His/His and ALDH2 Glu/Glu, the adjusted OR and its 95% CI for those with both ADH2 Arg/Arg and ALDH2 Glu/Lys was 5.00 (2.32-10.71) in all subjects. This combination effect was evident in heavy drinkers (OR 11.3, 95% CI 2.97-43.3) but not in moderate or non-drinkers. Statistically significant gene-environment interactions between the two polymorphisms and drinking level were seen (ADH2 P = 0.035, ALDH2, P = 0.013). Furthermore, we also found a statistically significant gene-gene interaction between the two polymorphisms (P = 0.042). In conclusion, this case-control study showed a significantly increased risk of SCCHN in subjects with the ADH2 Arg/Arg and ALDH2 Glu/Lys polymorphisms in a Japanese population. In addition, our results also demonstrated that this risk was associated with significant gene-gene interactions between ADH2 and ALDH2 polymorphisms, as well as gene-environment interactions between these polymorphisms and alcohol drinking.
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PMID:Gene-gene and gene-environment interactions between alcohol drinking habit and polymorphisms in alcohol-metabolizing enzyme genes and the risk of head and neck cancer in Japan. 1748 85

Acetaldehyde has been classified as a carcinogen in experimental animal research. Acetaldehyde is highly toxic, mutagenic and carcinogenic. Acetaldehyde causes point mutations, sister chromatid exchanges and gross chromosomal aberrations. In the liver, acetaldehyde binds to DNA and the formation of stable adducts represents one mechanism by which acetaldehyde could trigger the occurrence of replication errors and/or mutations in oncogenes or tumour suppressor genes. In experimental colorectal carcinogenesis the inhibition of acetaldehyde dehydrogenase with elevated acetaldehyde levels results in an acceleration of cancer development. The production of acetaldehyde is reduced when germ-free animals are studied, emphasizing the role of bacteria in the generation of colorectal acetaldehyde. Acetaldehyde levels in the colorectum correlate with crypt cell production rate and result in hyper-regeneration, a precancerous condition. Genetic linkage studies give further evidence for acetaldehyde as a carcinogen. Individuals who accumulate acetaldehyde due to polymorphism and/or mutations in the genes coding for enzymes responsible for acetaldehyde generation and detoxification have an increased cancer risk. This is true for Asians with low acetaldehyde dehydrogenase 2 and for Caucasians with alcohol dehydrogenase 1C*1/1. In conclusion, there is an enormous body of evidence from in vitro studies, animal experiments and genetic linkage studies, that acetaldehyde is the major factor responsible for tumour development in alcohol-associated carcinogenesis of the gastrointestinal tract.
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PMID:The role of acetaldehyde in alcohol-associated cancer of the gastrointestinal tract. 1759 Sep 90


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