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)

Arylamine N-acetyltransferases (NATs) play an important role in the detoxification and metabolic activation of a variety of aromatic xenobiotics, including numerous carcinogens. Both of the human isoforms, NAT1 and NAT2, display interindividual variations, and associations between NAT genotypes and cancer risk have been established. Contrary to NAT2, NAT1 has a ubiquitous tissue distribution and has been shown to be expressed in cancer cells. Given that the activity of NAT1 depends on a reactive cysteine that can be a target for oxidants, we studied whether peroxynitrite, a highly reactive nitrogen species involved in human carcinogenesis, could inhibit the activity of endogenous NAT1 in MCF7 breast cancer cells. We show here that exposure of MCF7 cells to physiological concentrations of peroxynitrite and to a peroxynitrite generator (3-morpholinosydnonimine N-ethylcarbamide, or SIN1) leads to the irreversible inactivation of NAT1 in cells. Further kinetic and mechanistic analyses using recombinant NAT1 showed that the enzyme is rapidly (k(inact) = 5 x 10(4) m(-1).s(-1)) and irreversibly inactivated by peroxynitrite. This inactivation is due to oxidative modification of the catalytic cysteine. We conclude that the reducing cellular environment of MCF7 cells does not sufficiently protect NAT1 from peroxynitrite-dependent inactivation and that only high concentrations of reduced glutathione could significantly protect NAT1. Thus, cellular generation of peroxynitrite may contribute to carcinogenesis and tumor progression by weakening key cellular defense enzymes such as NAT1.
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PMID:Peroxynitrite irreversibly inactivates the human xenobiotic-metabolizing enzyme arylamine N-acetyltransferase 1 (NAT1) in human breast cancer cells: a cellular and mechanistic study. 1467 57

2-Amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and some metabolites were investigated for mutagenicity in mammalian cell lines and bacterial strains engineered for the expression of human enzymes. MeAalphaC induced gene mutations (studied at the hprt locus) in Chinese hamster V79-derived cells co-expressing cytochrome (CYP) 1A2 and sulphotransferase (SULT) 1A1 even at a concentration of 30 nM, but was inactive in cells co-expressing CYP1A2 and N-acetyltransferase (NAT) 1 or 2. MeAalphaC, tested in the presence of rat liver post-mitochondrial fraction, showed strongly enhanced mutagenicity in a Salmonella typhimurium strain expressing human SULT1A1 compared with the control (recipient) strain TA1538/1,8-DNP (deficient in endogenous acetyltransferase). Mutagenicity was also enhanced, although to a lesser extent, when NAT2 was expressed in the latter strain. The metabolite, 2-hydroxylamino-3-methyl-9H-pyrido[2,3-b]indole (N-OH-MeAalphaC) was a direct mutagen to strains TA1538 and TA1538/ 1,8-DNP. This mutagenicity was strongly enhanced in corresponding strains expressing SULT1A1. A moderate enhancement was observed when SULT1A2, SULT1B1, SULT1C2 or NAT2 were expressed in strain TA1538. The remaining enzymes studied (SULT1A3, 1C1, 1E1, 2A1, 2B1a, 2B1b, 4A1 and NAT1) did not indicate any activation of N-OH-MeAalphaC. Preliminary mutagenicity experiments in SULT-expressing S.typhimurium strains were conducted with other hydroxylated metabolites of MeAalphaC. The phenols, 6- and 7-hydroxy-MeAalphaC, were inactive under the conditions studied. The benzylic alcohol, 2-amino-3-hydroxymethyl-9H-pyrido[2,3-b]indole, was mutagenic in a strain expressing SULT1A1, but its activity was much weaker than that of N-OH-MeAalphaC. Thus, N-hydroxylation (e.g. mediated by CYP1A2) and sulpho conjugation (primarily mediated by SULT1A1) was the dominating activation pathway of MeAalphaC in model systems engineered for human enzymes. Some other SULT forms as well as NAT2 were also capable of activating N-OH-MeAalphaC, although with much lower efficiency than SULT1A1. Another minor activation pathway involved benzylic hydroxylation followed by sulpho conjugation by SULT1A1.
Carcinogenesis 2004 May
PMID:Bioactivation of the heterocyclic aromatic amine 2-amino-3-methyl-9H-pyrido [2,3-b]indole (MeAalphaC) in recombinant test systems expressing human xenobiotic-metabolizing enzymes. 1472 82

Nitrofen had been used as a herbicide, until its carcinogenic and teratogenic activity in rodents was detected. A food contamination occurring in 2002 in Germany led to the initiation of new studies in order to better understand the potential risk for humans. Nitrofen is a nitroarene and as such might be activated to a mutagen via reduction to the corresponding hydroxylamine and subsequent formation of a reactive acetic or sulfuric acid ester. Therefore, we have investigated the mutagenicity of nitrofen in Salmonella typhimurium strains engineered for the expression of all human xenobiotic-metabolizing sulfotransferases (SULTs) and acetyltransferases (NATs) identified. Nitrofen was inactive in the parental strains TA1538, TA98 and TA100, but was mutagenic even at low doses when human sulfotransferase SULT1A1 (the major broad-spectrum phenol SULT) was expressed in these strains, but not when it was expressed in a TA1538-derived strain deficient in an endogenous nitroreductase. Several other human SULTs (in particular 1A3 and 1C1) as well as human NAT2 (unlike NAT1) also activated nitrofen, but were markedly less efficient than SULT1A1. Likewise, expression of rat and mouse SULT1A1 led to weaker mutagenic activity of nitrofen than expression of the corresponding human enzyme. An endogenous acetyltransferase only activated nitrofen to a mutagen when it was strongly over-expressed in the TA98-derived strain YG1024. Thus, humans might be more susceptible to the carcinogenic effects of nitrofen than mice and rats, which have been used in long-term studies. The fact that several SULTs show particular high expression in fetal tissues suggests that this activation pathway may also play a role in the teratogenic effects observed.
Carcinogenesis 2004 May
PMID:Use of genetically manipulated Salmonella typhimurium strains to evaluate the role of sulfotransferases and acetyltransferases in nitrofen mutagenicity. 1475 74

Lack of functional telomeres can cause chromosomal aberrations. This type of genetic instability may promote tumorigenesis. We have investigated the association between mean telomere length in buccal cells (assessed with quantitative real-time PCR) and bladder cancer risk in a case-control study. Patients with bladder cancer displayed significantly shorter telomeres than control subjects (P = 0.001). Median telomere length ratio was 0.95 (range 0.53-3.2) for cases and 1.1 (0.51-2.4) for controls. Moreover, the adjusted odds ratio (OR) for bladder cancer was significantly increased in the quartile with the shortest telomere length OR = 4.5 [95% confidence interval (CI) 1.7-12]. It is known that oxidative stress, alkylation or UV radiation increases shortening of telomeres. Therefore, we also analyzed whether environmental and genetic factors associated with DNA damage, i.e. smoking and polymorphisms in the genes involved in the metabolism of genotoxic carcinogens (EPHX1, GSTA1, GSTM1, GSTP1, GSTT1, NAT1, NAT2 and NQO1) or DNA repair (APE1, NBS1, XPC, XPD, XRCC1, XRCC3 and XRCC4), could modify the association between telomere length and cancer risk. A clear effect of smoking and telomere length could be observed. Current smokers with short telomeres had more than six times as higher risk as non-smokers/former smokers with long telomeres (OR = 6.3, 95% CI 1.7-23). Lack of the biotransformation gene GSTM1 and short telomeres were associated with OR = 6.5 (95% CI 2.4-18), whereas homozygous carriers of 312Asn in the DNA repair gene XPD, with short telomeres, displayed an OR of 17 (95% CI 1.9-150). However, no significant interaction for cancer risk could be proven for telomere length, smoking and susceptibility genotypes of metabolizing and DNA-repairing genes.
Carcinogenesis 2005 Jul
PMID:Constitutional short telomeres are strong genetic susceptibility markers for bladder cancer. 1574 60

Dietary factors appear to be involved in the high incidence of prostate cancer in "Westernized" countries, implicating dietary carcinogens such as heterocyclic amines (HAs) in the initiation of prostate carcinogenesis. We examined 24 human prostate samples with respect to their potential for activation and detoxification of HAs and the presence of DNA adducts formed in vivo. Cytochromes P450 1B1, 3A4 and 3A5 were expressed at low levels (<0.1-6.2 pmol/mg microsomal protein). N-Acetyltransferase (NAT) activities, using p-aminobenzoic acid (NAT1) and sulfamethazine (NAT2) as substrates, were <5-5,500 and <5-43 pmol/min/mg cytosolic protein, respectively. Glutathione S-transferases (GSTs) P1, M2 and M3 were expressed at 0.038-1.284, 0.005-0.126 and 0.010-0.270 microg/mg cytosolic protein, respectively; GSTM1 was expressed in all GSTM1-positive samples (0.012-0.291 microg/mg cytosolic protein); and GSTA1 was expressed at low levels (<0.01-0.11 microg/mg cytosolic protein). Binding of N-hydroxy-PhIP to DNA in vitro occurred primarily by an AcCoA-dependent process (<1-54 pmol/mg/DNA), PAPS- and ATP-dependent binding being <1-7 pmol/mg DNA. In vivo, putative PhIP- or 4-aminobiphenyl-DNA adducts were found in 4 samples (0.4-0.8 adducts/10(8) bases); putative hydrophobic adducts were found in 6 samples (8-64 adducts/10(8) bases). Thus, the prostate appears to have low potential for N-hydroxylation of HAs but greater potential for activation of N-hydroxy HAs to genotoxic N-acetoxy esters. The prostate has potential for GSTP1-dependent detoxification of ATP-activated N-hydroxy-PhIP but little potential for detoxification of N-acetoxy-PhIP by GSTA1. However, there were no significant correlations between expression/activities and DNA adducts formed in vitro or in vivo, DNA adducts in vivo possibly reflecting carcinogen exposure.
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PMID:Expression of cytochromes P450 and glutathione S-transferases in human prostate, and the potential for activation of heterocyclic amine carcinogens via acetyl-coA-, PAPS- and ATP-dependent pathways. 1588 May 31

To test the hypothesis that genetic variation in the metabolism of tobacco carcinogens, such as aromatic amines (AA) and heterocyclic amines (HCA), contributes to pancreatic cancer, we have examined genetic polymorphisms of three key enzymes, i.e. cytochrome P450 1A2 (CYP1A2) and N-acetyltransferase 1 and 2 (NAT1 and NAT2), in a hospital-based case-control study of 365 patients with pancreatic adenocarcinoma and 379 frequency-matched healthy controls. Genotypes were determined using PCR-restriction fragment length polymorphism (RFLP) and Taqman methods. Smoking information was collected by personal interview. Adjusted odds ratio (AOR) and 95% confidence interval (CI) was estimated by unconditional multivariate logistic regression analysis. We found that the NAT1 'rapid' alleles were associated with a 1.5-fold increased risk of pancreatic cancer (95% CI: 1.0-2.1) with adjustment of potential confounders. This effect was more prominent among never smokers (AOR: 2.4, 95% CI: 1.4-4.3) and females (AOR: 1.8, 95% CI: 1.0-3.1). Some genotypes were significantly associated with increased risk for pancreatic cancer among smokers, especially heavy smokers (<20 pack years). For example, heavy smokers with the CYP1A2*1D (T-2467delT) delT, CYP1A2*1F(A-163C) C allele, NAT1 'rapid' or NAT2 'slow' alleles had an AOR (95% CI) of 1.4 (0.7-2.3), 1.9 (1.1-3.4), 3.0 (1.6-5.4) and 1.5 (0.8-2.6), respectively, compared with never smokers carrying the non-at-risk alleles. These effects were more prominent in females than in males. The corresponding AOR (95% CI) was 3.1 (1.0-8.0), 3.8 (1.5-10.1), 4.5 (1.6-12.7) and 2.0 (0.8-5.1) for females versus 1.0 (0.4-1.9), 1.1 (0.5-2.4), 2.1 (1.0-4.6) and 1.1 (0.5-2.6) for males. A significant synergistic effect of CYP1A2*1F C allele and NAT1"rapid" alleles on the risk for pancreatic cancer was also detected among never smokers (AOR: 2.9, 95% CI: 1.2-6.9) and among females (AOR: 2.5, 95% CI: 1.1-5.7). These data suggest that polymorphisms of the CYP1A2 and NAT1 genes modify the risk of pancreatic cancer.
Carcinogenesis 2006 Jan
PMID:Polymorphisms of cytochrome P4501A2 and N-acetyltransferase genes, smoking, and risk of pancreatic cancer. 1598 14

NAT2 as phase II enzyme is involved in the detoxification/activation of various drugs, environmental substances and carcinogenic compounds. A genotyping approach has been used to investigate NAT2 genotype with putative relevance in lung cancer in population of 110 Slovak-Caucasians patients and 167 non-malignant individuals from the same region. Slow acetylation was not observed to be a significant risk factor of lung cancer development (OR=1.19; 95% CI: 0.71-1.99). However, one genotype responsible for slow acetylation (NAT2*5B/*6) was observed significantly more frequently in lung cancer patients with squamous cell carcinoma compared with control subjects (OR=2.24; 95% CI: 1.14-4.34). Stratified analysis showed an increasing impact of the specific allelic combination NAT2*5B/*6 in non-smokers (OR=6.5; 95% CI: 1.25-15.08). In the case of squamous lung carcinoma an analysis revealed a tendency to adversely affect cancer risk in the individuals with the mentioned genotype in younger than 60 years (OR=3.14; 95% CI: 0.98-9.72) non-smokers (OR=10.40; 95% CI: 1.35-118.89) and in females (OR=4.25; 1.08-16.25). Additional studies are needed to confirm the results we observed and to assess the impact of other effects (specific allelic combinations, sex differences and histological subtype of lung cancer) on NAT2 susceptibility in lung carcinogenesis.
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PMID:A pilot study testing the genetic polymorphism of N-acetyltransferase 2 as a risk factor in lung cancer. 1615 80

Cigarette smoking, aromatic amines and ionizing radiation are known carcinogens of bladder cancer. NAT2 genotype might play a role in bladder cancer carcinogenesis. This hospital-based, case-control study was conducted in Kaohsiung, Taiwan, which neighbors the high incidence region of bladder cancer in the black-foot disease area. A total of 103 cases with diagnosed bladder cancer were collected. For each case, 1 control was selected from the same hospital. A structured questionnaire was applied for all cases and controls. DNA was extracted from peripheral blood cell. The ASO-PCR/RFLP technique was used to determine the NAT2 genotype. For bladder cancer, the significantly excessive risks were observed in regular drinkers (OR = 2.74, 95% CI = 1.28-5.87) and residents of the black-foot disease endemic area (OR = 7.53, 95% CI = 2.16-26.33), and interaction of regular drinking and slow type of NAT2 (OR = 18.04, 95% CI = 2.28-142.80). We suggested that NAT2 genotype might play a role of effect modifier in bladder cancer carcinogenesis.
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PMID:Interaction effect in bladder cancer between N-acetyltransferase 2 genotype and alcohol drinking. 1632 7

Benzidine (Bz) is a known human carcinogen. Several azo dyes have been synthesized with Bz. Bz can be metabolically released from azo dyes. In a group of Indian workers producing Bz and azo dyes the presence of hemoglobin (Hb) adducts was investigated. The following Hb adducts were identified and quantified by GC-MS: Bz, N-acetylbenzidine (AcBz), 4-aminobiphenyl (4ABP), aniline. 4ABP and aniline were quantitatively the major adducts. In the exposed workers (n = 33) all correlations between 4ABP, Bz and AcBz were r = 0.89 (P < 0.01) or greater. The group of workers exposed to Bz (Bz workers, n = 15) had 10-17-fold higher adduct levels than the workers exposed to dyes (dye workers, n = 18). 4ABP can be metabolically released from Bz and azo dyes. Aniline can be metabolically released from azo dyes. Therefore, the presence of 4ABP and aniline as Hb adducts is a consequence of exposure to the parent compounds or to the exposure of Bz and azo dyes and a consequent metabolical release of the arylamine moiety. The mean adduct ratios of 4ABP/(AcBz + Bz) varied up to 4-fold across all seven factories. Therefore, it is possible that 4ABP may have derived from general contamination in the work environment or endogenous metabolism, or a combination of the two. Since 4ABP is also a known human carcinogen, tumors observed in workers exposed to Bz or Bz dyes might be caused by both compounds. Further, these results suggest that understanding the role that genetic variants in NAT1 and NAT2 play in modifying the impact of Bz on bladder cancer risk may be complicated, as N-acetylation detoxifies 4ABP and activates Bz.
Carcinogenesis 2006 Aug
PMID:Hemoglobin adducts in workers exposed to benzidine and azo dyes. 1649 5

Exposures such as cigarette smoke and meat contain a variety of procarcinogens, which are thought to play a role in elevation of risk for colorectal polyps and/or cancer. These procarcinogens (including heterocyclic amines and polycyclic aromatic hydrocarbons) are metabolized by a variety of polymorphic enzymes including N-acetyltransferases, sulfotransferases, cytochrome P450 enzymes and epoxide hydrolase. We hypothesized that genetic variation in the encoding genes NAT1, NAT2, SULT1A1, SULT1A2, CYP1A1 or EPHX1 is associated with risk of colorectal polyps and interacts with cigarette use or meat intake to modify risk of colorectal polyps. We examined the role of these genes in a clinic-based study of 651 Caucasian cases with hyperplastic polyps, adenomatous polyps or both types of polyps and 556 polyp-free controls. We found evidence for interaction between NAT acetylator status and SULT1A1 genotype in risk of hyperplastic polyps: individuals with SULT1A1 638AA genotype and NAT1 and NAT2 intermediate/fast phenotypes had 3.5-fold increased risk (95% CI 1.2-10.3) compared with individuals with SULT1A1 638GG genotype and NAT1 and NAT2 slow phenotypes. Data were also consistent with interactions between smoking and variation in SULT1A1, CYP1A1 and EPHX1 and between meat intake and variation in CYP1A1 and EPHX1. No interactions were statistically significant. Although results should be interpreted with caution considering sample size and the number of hypotheses examined, our study suggests future avenues of investigation in larger investigations of genetic and lifestyle factors in the pathway to colorectal cancer.
Carcinogenesis 2007 Feb
PMID:Inherited variation in carcinogen-metabolizing enzymes and risk of colorectal polyps. 1692 76


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