Haplotype of N-acetyltransferase 1 and 2 and risk of pancreatic cancer.

We examined the association between N-acetyltransferase 1 and 2 (NAT1 and NAT2) haplotype and risk of pancreatic cancer by genotyping eight NAT1 and seven NAT2 single nucleotide polymorphisms in 532 patients and in 581 healthy controls (all non-Hispanic white) who were recruited at M. D. Anderson Cancer Center from January 2000 to December 2006. Haplotypes were reconstructed by using an expectation-maximization algorithm. Odds ratios and 95% confidence intervals were estimated by using unconditional logistic regression models. Covariates included age (continuous variable), sex, pack-year of smoking (categorical), and history of diabetes when appropriate. NAT1 and NAT2 genotype was mutually adjusted. The prevalence of haplotype NAT1*10-NAT2*6A was 4.3% versus 2.7% (P=0.06) and NAT1*11-NAT2*6A was 1.2% versus 0.4% (P=0.05) in patients and controls, respectively. The diplotype NAT1*10/*10 or NAT1*10/*11 and NAT2*6A/any slow allele was associated with a higher risk of pancreatic cancer compared with other diplotypes (multivariate odds ratio, 4.15; 95% confidence interval, 1.15-15.00; P=0.03). NAT2 slow genotype were associated with increased risk of pancreatic cancer among heavy smokers and among individuals with a history of diabetes. We for the first time found that rare NAT1*10 or NAT1*11-NAT2*6A diplotype may be an "at-risk" genetic variant for pancreatic cancer. The NAT2*6A/any slow acetylation genotype may be a predisposing factor for pancreatic cancer among diabetics with smoking exposure. Our observations must be confirmed in larger independent studies.     

NAT2*7 allele is a potential risk factor for adult brain tumors in Taiwanese population.

Arylamine N-acetyltransferase-2 (NAT2) displays extensive genetic polymorphisms that affect the rates of acetylation of drugs and toxic compounds such as amine carcinogens. The association of NAT2 polymorphisms with adult brain tumors has been unclear. To investigate whether the NAT2 genotype is a risk factor of brain tumors, we determined the frequencies of three common polymorphisms in the NAT2 gene, NAT2*5 (T341C), NAT2*6 (G590A), and NAT2*7(G857A), in brain tumor patients and in age- and gender-matched control subjects (n = 27 in each group). Genotyping was carried out using PCR-RFLP and subjects were phenotyped as a fast or slow acetylator based on the genotypes. The odds ratio of NAT2*7 allele frequency was significantly higher in patients with brain tumor than in controls (odds ratio, 6.786; 95% confidence interval, 2.06-22.37; P = 0.003); in the mean time, NAT2*4/*7 genotype was significantly more common in the patient group than in controls (odds ratio, 6.19; 95% confidence interval, 1.68-22.79; P = 0.0039). The tumors in the patients with NAT2*7 allele tended to be high-grade astrocytoma or glioblastoma multiforme (P = 0.016). In conclusion, these data suggest that the presence of NAT2*7 allele might be a potential risk factor for the development of brain tumors in Taiwan.     

Genetic polymorphisms of glutathione S-transferases as modulators of lung cancer susceptibility

Some of the glutathione S-transferases (GSTs) are polymorphic and may play a role in lung cancer susceptibility. Our previous study in a French Caucasian study population suggested GSTM1 null genotype as a moderate risk factor for lung cancer. Here we extended the study to investigate the potential role of GSTT1 and GSTP1 polymorphisms in susceptibility to lung cancer, either separately or in combination. The study population consisted of 268 controls and 251 cases. Nineteen percent of the controls and 15% of the cases had GSTT1 null genotype. The distribution of GSTP1*A/*A, *A/*B and *B/*B genotypes were 46.9, 45.5 and 7.6% in controls, and 47.8, 40.2 and 12.0% in cases, respectively. No statistically significant effects in the lung cancer risk were observed for the GSTT1 genotypes, but the GSTP1*B/*B genotype posed a 2-fold risk [odds ratio (OR) = 2.0, 95% confidence interval (CI) 1.0-4.1] of this malignancy compared with the GSTP1*A allele containing genotypes; this association was mainly attributable to small cell lung cancer (OR = 3.6, 95% CI 1.3-9.8). The most remarkable risk was seen for the small cell carcinoma among subjects with the GSTP1*B/*B genotype and concurrent lack of the GSTM1 gene (OR = 6.9, 95% CI 1.6-30.2). The deficient genotypes for GSTM1 and GSTP1 seem thus to be important risk modifiers for lung cancer, especially in combination.     

Increased frequency of wild-type arylamine-N-acetyltransferase allele NAT2*4 homozygotes in Portuguese patients with colorectal cancer

Here we report that colorectal cancer patients show a markedly higher frequency (3-fold) of wild-type NAT2*4 allele homozygotes than the control population. However, a marked difference in NAT2*4/NAT2*4 genotype frequency associated with the patients gender was observed pointing to a male-specific effect of this genotype as a risk factor in colon cancer. The arylamine-N-acetyltransferase (E.C. 2.3.1.5.) NAT2, a phase II detoxification enzyme, has been implicated in procarcinogen activation, namely from food contained arylamines, cigarette smoking, as well as environmental amines of various types. NAT2 is encoded by a polymorphic gene presenting several allelic variants encoding partially inactive enzymes expressed in human liver and colon. Epidemiological studies based on phenotype determination have long indicated the importance of the NAT2 active phenotype as a susceptibility factor in colorectal cancer. In the present study we investigated the NAT2 allelic frequencies and genotype distribution in a group of 114 unrelated colorectal cancer patients, in parallel with 201 healthy Portuguese subjects. We first demonstrate that the frequency of the wild-type NAT2*4 allele in the Portuguese sample population (23.4%) does not significantly differ from the values described for other Europeans. Besides the 3-fold higher frequency of NAT2*4 homozygotes found in colorectal cancer subjects, the NAT2*4/NAT2*5A compound genotype, known to determine a faster acetylator phenotype than other heterozygotic combinations, also increased by the same order of magnitude. These two genotypes represent 32% of the patients population versus 11% of the healthy controls. Taken together, our results strongly indicate that NAT2 genotype, particularly NAT2*4 allele zygosity, constitutes an individual susceptibility trait associated with sporadic colorectal cancer development, probably due to the local dietary habits in Portugal.      

Aromatic DNA adducts and polymorphisms of CYP1A1, NAT2, and GSTM1 in breast cancer

Previous studies by us and others have shown a significantly higher level of aromatic DNA adducts in normal adjacent breast tissue samples obtained from breast cancer patients than in those obtained from non-cancerous controls. The increased amount of DNA damage could be related to excess environmental carcinogen exposure and/or genetic susceptibility to such exposure. In the current study, we investigated the relationship between the levels of aromatic DNA adducts in breast tissues and polymorphisms of the drug-metabolizing genes cytochrome P4501A1 (CYP1A1), N-acetyltransferase-2 (NAT2), and glutathione S-transferase M1 (GSTM1), in 166 women having breast cancer. DNA adducts were measured using (32)P-postlabeling and information on smoking status was obtained from medical records. When pooled data of smokers and non-smokers were analyzed by multiple regression analyses, no significant correlation was found between the level of total DNA adducts and age, race, or polymorphisms of CYP1A1, GSTM1, and NAT2. The only significant predictor of the level of DNA adducts in breast tissues was smoking (P = 0.008). When data were analyzed separately in smokers and non-smokers, however, a significant gene-environment interaction was observed. Smokers with CYP1A1*1/*2 or *2/*2 genotypes had a significantly higher level of DNA adducts than those with the CYP1A1*1/*1 genotype. This effect was not seen among non-smokers. There was also a gene-gene interaction, as smokers with combined CYP1A1*1/*2 or CYP1A1*2/*2 genotypes and GSTM1 null had a much higher level of adducts than those with either CYP1A1 or GSTM1 polymorphism. Genetic polymorphisms of CYP1A1 and NAT2 were also significantly correlated with the frequency of certain types of DNA adducts. For example, a bulky benzo[a]pyrene (B[a]P)-like adduct was detected in 26% of the samples, the presence of which was not related to age, race, smoking status, or GSTM1 and NAT2 genotype. However, a significantly higher frequency of the B[a[P-like adduct was found in individuals having CYP1A1*1/*2 or *2/*2 genotypes than in those having the *1/*1 genotype (P = 0.04). In addition, individuals having slow NAT2 alleles had a significantly higher frequency of the typical smoking-related DNA adduct pattern, i.e. a diagonal radioactive zone (DRZ), than others did (P = 0.008). These findings suggest that polymorphisms of CYP1A1, GSTM1, and NAT2 significantly affect either the frequency or the level of DNA adducts in normal breast tissues of women having breast cancer, especially in smokers. Further large-scale studies are required to determine the exact role of these polymorphisms and types of DNA damage in breast cancer susceptibility.     

Association between genetic polymorphisms of CYP1A2, arylamine N-acetyltransferase 1 and 2 and susceptibility to cholangiocarcinoma.

Human CYP1A2 and arylamine N-acetyltransferases, which are encoded by the polymorphic CYP1A2 and NAT genes respectively, have been shown to have wide interindividual variations in metabolic capacity and may be potential modifiers of an individual's susceptibility to certain types of cancers. The present study aimed to evaluate the relationship between CYP1A2, NAT1 and NAT2 polymorphisms and cholangiocarcinoma (CCA), the most prevalent cancer in the north-east of Thailand. A total of 216 CCA patients and 233 control subjects were genotyped by polymerase chain reaction with restriction fragment length polymorphism based assays. Two CYP1A2 alleles (CYP1A2*1A wild-type and *1F), six NAT1 alleles (NAT1*4 wild-type, *3, *10, *11, *14A and *14B) and seven NAT2 alleles (NAT2*4 wild-type, *5, *6A, *6B, *7A, *7B and *13), which are the major alleles found in most populations, were analysed. Although CYP1A2*1A allele, NAT1*10 allele, and the NAT2 slow acetylator alleles were not associated with CCA risk, among the male subjects, the genotype CYP1A2*1A/*1A conferred a decreased risk of the cancer (adjusted odds ratio (OR) 0.28, 95% confidence interval (CI) 0.08-0.94) compared with CYP1A2*1F/1*F. Frequency distributions of rapid NAT2*13 and two slow alleles (*6B and *7A), but not the other major alleles, were associated with lower CCA risk. Adjusted OR of the genotypes consisting of at least one of these alleles significantly decreased the cancer risk compared with none of them (OR 0.26, 95% CI 0.15-0.44). This study suggests that the NAT2 polymorphism may be a modifier of individual risk to CCA.     

Inherited polymorphism in the N-acetyltransferase 1 (NAT1) and 2 (NAT2) genes and susceptibility to gastric and colorectal adenocarcinoma

The polymorphic arylamine N-acetyltransferases (NAT1 and NAT2) have been implicated in increased susceptibility to certain malignancies. We analyzed genetic polymorphisms in both the NAT1 and NAT2 genes among 140 gastric adenocarcinoma patients, 103 colorectal adenocarcinoma patients and 122 healthy controls from Japan. The frequency of the specific genotype NAT1*10 allele, which contains a variant polyadenylation signal, was higher among all gastric adenocarcinoma cases, but this increase did not reach statistical significance. After grouping according to tumor differentiation of gastric adenocarcinoma patients, NAT1 polymorphism was a risk factor among the well-differentiated type of tumors (OR = 3.03, 95% CI 1. 08-8.46). Stratifying by smoking status, we found that the OR for heavy smokers with the NAT1*10 allele was 2.97 (95% CI 1.23-7.14). When the combined risk of NAT1*10 allele from smoking and tumor differentiation was calculated, we found that the risk of the NAT1*10 allele with heavy smoking was increased among the well - differentiated type of gastric adenocarcinoma (OR = 4.24, 95% CI 0. 87-20.6). The NAT1*10 genotype was not a significant risk factor in colorectal adenocarcinoma. No statistically significant differences were observed in the frequency of NAT2 rapid acetylation genotype in gastric (91.4%) or colorectal (95.2%) adenocarcinoma patients when compared with the control population (94.3%). Our results suggest the NAT1*10 allele may be an important genetic determinant of the well-differentiated type of gastric adenocarcinoma, which may be induced by smoking.     

NAT2 slow acetylation and bladder cancer in workers exposed to benzidine

This study expands a previous study of NAT2 polymorphisms and bladder cancer in male subjects occupationally exposed only to benzidine. The combined analysis of 68 cases and 107 controls from a cohort of production workers in China exposed to benzidine included 30 new cases and 67 controls not previously studied. NAT2 enzymatic activity phenotype was characterized by measuring urinary caffeine metabolite ratios. PCR-based methods identified genotypes for NAT2, NAT1 and GSTM1. NAT2 phenotype and genotype data were consistent. A protective association was observed for the slow NAT2 genotype (bladder cancer OR = 0.3; 95% CI = 0.1 = 1.0) after adjustment for cumulative benzidine exposure and lifetime smoking. Individuals carrying NAT1wt/*10 and NAT1*10/*10 showed higher relative risks of bladder cancer (OR = 2.8, 95% CI = 0.8-10.1 and OR = 2.2, 95% CI = 0.6-8.3, respectively). No association was found between GSTM1 null and bladder cancer. A metaanalysis risk estimate of case-control studies of NAT2 acetylation and bladder cancer in Asian populations without occupational arylamine exposures showed an increased risk for slow acetylators. The lower limit of the confidence interval (OR = 1.4; 95% CI = 1.0-2.0) approximated the upper confidence interval for the estimate obtained in our analysis. These results support the earlier finding of a protective association between slow acetylation and bladder cancer in benzidine-exposed workers, in contrast to its established link as a risk factor for bladder cancer in people exposed to 2-naphthylamine and 4-aminobiphenyl. Study findings suggest the existence of key differences in the metabolism of mono- and diarylamines.     

N-acetyltransferase (NAT1, NAT2) and glutathione S-transferase (GSTM1, GSTT1) polymorphisms in breast cancer

To evaluate the potential association between NAT1/NAT2 polymorphisms and breast cancer, a case-control study was conducted in Korean women (254 cases, 301 controls). NAT1 *4/*10 genotype (42%) was the most common NAT1 genotype in this Korean population. The frequencies of slow, intermediate and rapid NAT2 acetylator genotype were 16, 39 and 44% in cases and 16, 42 and 42% in controls. Neither NAT1 rapid (homozygous or heterozygous NAT1 *10) (OR=1.2, 95% CI=0.8-1.9) nor NAT2 rapid acetylator genotype (OR=1.2, 95% CI=0.8-1.7) showed significant association with breast cancer risk. Although the risk of NAT2 rapid acetylator genotype in postmenopausal women (OR=1.4, 95% CI=0.7-2.8) was higher than that in premenopausal women (OR=1.1, 95% CI=0.7-1.7), those were not statistically significant. However, combinations of NAT1, GSTM1 and GSTT1 genotypes showed a significant linear gene-dosage relationship with breast cancer (p for trend=0.04) and those women with NAT2 rapid acetylator and both GSTM1 and GSTT1 null genotypes were at the elevated risk (OR=3.1, 95% CI=1.0-9.1). These results suggest that genetic polymorphisms of NAT1 and NAT2 have no independent effect on breast cancer risk, but they modulate breast cancer risk in the presence of GSTM1 and GSTT1 null genotypes.     

2-Amino-3,8-dimethylimidazo-[4,5-f]quinoxaline-induced DNA adduct formation and mutagenesis in DNA repair-deficient Chinese hamster ovary cells expressing human cytochrome P4501A1 and rapid or slow acetylator N-acetyltransferase 2.

2-Amino-3,8-dimethylimidazo-[4,5-f]quinoxaline (MeIQx) is one of the most potent and abundant mutagens in the western diet. Bioactivation includes N-hydroxylation catalyzed by cytochrome P450s followed by O-acetylation catalyzed by N-acetyltransferase 2 (NAT2). In humans, NAT2*4 allele is associated with rapid acetylator phenotype, whereas NAT2*5B allele is associated with slow acetylator phenotype. We hypothesized that rapid acetylator phenotype predisposes humans to DNA damage and mutagenesis from MeIQx. Nucleotide excision repair-deficient Chinese hamster ovary cells were constructed by stable transfection of human cytochrome P4501A1 (CYP1A1) and a single copy of either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles. CYP1A1 and NAT2 catalytic activities were undetectable in untransfected Chinese hamster ovary cell lines. CYP1A1 activity did not differ significantly (P > 0.05) among the CYP1A1-transfected cell lines. Cells transfected with NAT2*4 had 20-fold significantly higher levels of sulfamethazine N-acetyltransferase (P = 0.0001) and 6-fold higher levels of N-hydroxy-MeIQx O-acetyltransferase (P = 0.0093) catalytic activity than cells transfected with NAT2*5B. Only cells transfected with both CYP1A1 and NAT2*4 showed concentration-dependent cytotoxicity and hypoxanthine phosphoribosyl transferase mutagenesis following MeIQx treatment. Deoxyguanosine-C8-MeIQx was the primary DNA adduct formed and levels were dose dependent in each cell line and in the following order: untransfected < transfected with CYP1A1 < transfected with CYP1A1 and NAT2*5B < transfected with CYP1A1 and NAT2*4. MeIQx DNA adduct levels were significantly higher (P < 0.001) in CYP1A1/NAT2*4 than CYP1A1/NAT2*5B cells at all concentrations of MeIQx tested. MeIQx-induced DNA adduct levels correlated very highly (r2 = 0.88) with MeIQx-induced mutants. These results strongly support extrahepatic activation of MeIQx by CYP1A1 and a robust effect of human NAT2 genetic polymorphism on MeIQx-induced DNA adducts and mutagenesis. The results provide laboratory-based support for epidemiologic studies reporting higher frequency of heterocyclic amine-related cancers in rapid NAT2 acetylators.     

Human glutathion S-transferase A1 polymorphism and susceptibility to urothelial cancer in the Japanese population

GSTA1 has been reported to be most efficient in detoxifying N-acetoxy PhIP. In this study, 341 Japanese urothelial cancer patients and 457 healthy controls were compared for frequencies of GSTA1 genotype. We present the first evidence of an association between GSTA1*B (-567G, -69T, -52A) and urothelial cancer among never smokers. The frequency of GSTA1 *A/*B or *B/*B genotype was 24.3% in urothelial cancer cases, compared with 21.2% in the control groups (OR=1.22; 95%CI 0.87-1.72) after adjustment for age, gender and smoking status. But among never smokers, the GSTA1 *A/*B or *B/*B genotype was significantly higher in urothelial cancer cases (31.2%) compared with the controls (19.9%) (OR=1.73; 95%CI 1.01-2.97). This study suggests that exposure to food-derived PhIP could be one of the risk factors in the incidence of urothelial cancer in never smokers.     

Oral squamous cell cancer risk in relation to alcohol consumption and alcohol dehydrogenase-3 genotypes.

Heavy alcohol consumption, particularly in combination with cigarette smoking, increases the risk of oral squamous cell carcinoma (OSCC). Alcohol dehydrogenase 3 (ADH3) converts ethanol to acetaldehyde, which is a suspected oral carcinogen. The ADH3*1 allele is associated with increased conversion of ethanol to acetaldehyde, but whether the risk of OSCC is increased among ADH3*1 carriers, or whether the risk of OSCC attributable to alcohol consumption is modified by ADH3 genotype is unclear from previous studies. We examined the association between ADH3 genotypes, alcohol consumption, and OSCC risk in a population-based study of 333 cases and 541 controls from the state of Washington. The distribution of ADH3 genotypes was similar among cases and controls: ADH3*1/*1: 32.7% cases, 36.5% controls; ADH3*1/*2: 49.0% cases, 43.1% controls: ADH3*2/*2: 18.3% cases, 20.3% controls. The age-, sex-, and race-adjusted odds ratios (OR), relative to ADH3*2/*2 carriers, were as follows: ADH*1/*1: OR, 1.0 [95% confidence interval (CI) = 0.7, 1.5]; and ADH3*1/*2: OR, 1.3 (95% CI = 1.0, 1.8). We modeled the risk of OSCC associated with alcohol consumption as modified by ADH3 genotype adjusting for age, sex, race, and cigarette smoking. Among ADH3*2 homozygotes, the risk of OSCC increased 5.3% (2.1-8.5%) with each additional alcoholic drink/week, compared with 2.5% (1.5-2.6%) and 1.2% (0.0-2.4%) among persons carrying the ADH3*1/*2 and ADH3*1/*1 genotypes, respectively. These data suggest that the ADH3*2 allele confers increased susceptibility to the effect of alcohol on OSCC risk in our population.     

Association between a glutathione S-transferase A1 promoter polymorphism and survival after breast cancer treatment

Glutathione S-transferase (GST) enzymes detoxify chemotherapeutic drugs, and several studies have reported differences in survival for cancer patients who have variant genotypes for GSTP1, GSTM1 or GSTT1 enzymes. A recently described polymorphism alters hepatic expression of GSTA1, a GST with high activity in glutathione conjugation of metabolites of cyclophosphamide (CP). To consider the possible influence of the reduced-expression GSTA1*B allele on cancer patient survival, we have conducted a pilot study of breast cancer patients treated with CP-containing combination chemotherapy. GSTA1 genotype was determined by polymerase chain reaction and restriction fragment length polymorphism. Kaplan-Meier methods and Cox proportional hazards models were used to evaluate survival in relation to genotype. Among 245 subjects, 35% were GSTA1*A/*A, 49% GSTA1*A/*B and 16% GSTA1*B/*B; the genotype distribution did not differ by ethnic group, age or stage at diagnosis. Among patients who had 0 or 1 GSTA1*B allele, the proportion surviving at 5 years was 0.66 (95% CI = 0.59-0.72), whereas for GSTA1*B/*B subjects the proportion was higher, 0.86 (95% CI = 0.67-0.95). Significantly reduced hazard of death was observed for GSTA1*B/*B subjects during the first 5 years after diagnosis, hazard ratio (HR) = 0.3, 95% CI = 0.1-0.8. The association varied with time, with no survival difference observed for subjects who survived beyond 5 years. These results, although based on a small study population, describe an apparent difference in survival after treatment for breast cancer according to GSTA1 genotype. Further studies should consider the possible association between the novel GSTA1*B variant and outcomes of cancer therapy.     

Glutathione-S-transferase gene polymorphisms in colorectal cancer patients: interaction between GSTM1 and GSTM3 allele variants as a risk-modulating factor.

The distribution of polymorphisms in the glutathione S-transferase (GST) family genes has been studied in 355 healthy controls and 206 cancer (59 proximal and 147 distal) patients. All controls were subjected to flexible sigmoidoscopy. Odds ratios (OR) after stratification by age, gender and smoking were slightly higher in the cancer group as a whole for GSTM1-null (*0/*0), GSTT1-null (*0/*0) and GSTM3 *A/*B or *B/*B when compared with the control group, but the differences did not reach statistical significance. GSTP1 variants had no effect. Separate analysis of patients with proximal and distal tumours has shown stronger associations for the distal cancers, the GSTM3*B allele presence being significantly more frequent in these patients [OR = 1.77; 95% confidence interval (CI) = 1.15-2.74]. Taking into account strong linkage between the GSTM1*A and GSTM3*B alleles, a separate analysis of the GSTM1-nulled individuals was undertaken. The combination of GSTM1-null genotype with GSTM3*B allele presence (*A/*B or *B/*B) was significantly overrepresented among patients with proximal and distal tumours taken together (OR = 2.12; 95% CI = 1.24-3.63), and especially in distal cancer patients (OR = 2.75; 95% CI = 1.56-4.84). Male individuals displayed a stronger association between the presence of the GSTM1-null in combination with GSTM3 *A/*B or *B/*B and distal tumours with a higher odds ratio (OR = 3.57; 95% CI = 1.73-7.36). In contrast, the frequency of GSTM1 *B/*0 or *B/*B combined with GSTM3 *A/*A was significantly lower in patients with distal colorectal cancer, especially in males (OR = 0.37; 95% CI = 0.15-0.92). Neither of these combinations was associated with proximal tumours. Our findings suggest that interactions of polymorphic genotypes within the GSTM gene cluster affect individual susceptibility to colorectal carcinogenesis, the GSTM3*B variant presence being a risk factor especially in combination with the GSTM1-null genotype.     

Genetic polymorphisms of N-acetyltransferases 1 and 2 and gene-gene interaction in the susceptibility to childhood acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. In utero and postnatal exposures to various carcinogens may play a role in the etiology of this disease. N-acetyltransferases, encoded by the NAT1 and NAT2 genes are involved in the biotransformation of aromatic amines present in tobacco smoke, environment, and diet. Their rapid and slow acetylation activity alleles have been shown to modify the risk to a variety of solid tumors in adults. To investigate the role of NAT1 and NAT2 variants as risk-modifying factors in leukemogenesis, we conducted a case-control study on 176 ALL patients and 306 healthy controls of French-Canadian origin. Slow NAT2 acetylation genotype was found to be a significant risk determinant of ALL (odds ratio, 1.5; 95% confidence interval, 1.0-2.2) because of overrepresentation of the alleles NAT2*5C and *7B and underrepresentation of NAT2*4. Besides a slight increase in NAT1*4 allele frequency among cases, no independent association of NAT1 acetylation genotypes and ALL risk was observed. However, the risk associated with NAT2 slow acetylators was more apparent among homozygous individuals for NAT1*4 (odds ratio, 1.9; 95% confidence interval, 1.1-3.4). When NAT2 slow acetylators were considered together with the other risk-elevating genotypes, GSTM1 null and CYP1A1*2A, the risk of ALL increased further, which showed that the combination of these genotypes is more predictive of risk then either of them independently. These findings suggest that leukemogenesis in children is associated with carcinogen metabolism and consequently related to environmental exposures.     

Association of NAT1 and NAT2 polymorphisms to urinary bladder cancer: significantly reduced risk in subjects with NAT1*10.

The role of hereditary polymorphisms of the arylamine N-acetyltransferase 1 (NAT1) gene in the etiology of urinary bladder cancer is controversial. NAT1 is expressed in the urothelium and may O-acetylate hydroxyl amines, particularly in subjects with low NAT2 activity. Thus, NAT1 polymorphisms may affect the individual bladder cancer risk by interacting with environmental factors (smoking and occupational risks) and by interacting with the NAT2 gene. We studied the frequencies of the NAT1 haplotypes *3, *4, *10, *11, *14, *15, *17, and *22 in 425 German bladder cancer patients and 343 controls by PCR-RFLP. NAT1*10 allelic frequency was lower in bladder cancer patients (15.1%) compared with controls (20.4%; P = 0.012). Genotypes that included NAT1*10 were significantly less frequent among the cases (odds ratio adjusted for age, gender, and smoking, 0.65; 95% confidence interval, 0.46-0.91; P = 0.013). Two subtypes of NAT1*11 were detected: *11A (-344T, -40T, 445A, 459A, 640G, and 1095A) and *11C (-344T, -40T, 459A, 640G, and 1095A). The allele frequency of NAT1*11 was 4.3% in the cases versus 3.9% in the controls. The rare low-active NAT1*14A was overrepresented in the cases (P = 0.026). With regard to the NAT2 genotype, our data showed: (a) a partial linkage of NAT1*10 to NAT2*4; (b) a clear underrepresentation of NAT1*10 genotypes among rapid NAT2 genotypes in the cases studied (odds ratio, 0.39; 95% confidence interval, 0.22-0.68; P = 0.001), and (c) a gene-gene-environment interaction. NAT2*slow/NAT1*4 genotype combinations with a history of occupational exposure were 5.96 (2.96-12.0) times more frequent in cancer cases than in controls without risk occupation (P < 0.0001). Hence, our data suggest that individuals provided with NAT2*4 and NAT1*10 are at a significantly lower risk for bladder cancer, particularly when exposed to environmental risk factors.     

Combined effects of well-done red meat, smoking, and rapid N-acetyltransferase 2 and CYP1A2 phenotypes in increasing colorectal cancer risk.

Heterocyclic amines (HAAs) are suspected carcinogens that are formed in meat when it is cooked at high temperature for long durations. These compounds require metabolic activation by CYP1A2 and N-acetyltransferase (NAT) 2 or NAT1 before they can bind to DNA. It has been hypothesized that well-done meat increases the risk of colorectal cancer (CRC), especially in individuals with the rapid phenotype for CYP1A2 and NAT2. This association may be particularly strong in smokers because smoking is known to induce CYP1A2. We conducted a population-based case-control study on Oahu, Hawaii to specifically test this hypothesis. An in-person interview assessed the diet and preference for well-done red meat of 349 patients with CRC and 467 population controls. A urine collection after caffeine challenge and a blood collection were used to assess phenotype for CYP1A2 and NAT2 and genotype for NAT2 and NAT1, respectively. No statistically significant main effect association with CRC was found for red meat intake, preference for well-done red meat, the NAT2 rapid genotype, the CYP1A2 rapid phenotype or the NAT1*10 allele. However, in ever-smokers, preference for well-done red meat was associated with an 8.8-fold increased risk of CRC (95% confidence interval, 1.7-44.9) among subjects with the NAT2 and CYP1A2 rapid phenotypes, compared with smokers with low NAT2 and CYP1A2 activities who preferred their red meat rare or medium. No similar association was found in never-smokers, and there was no increased risk for well-done meat among smokers with a rapid phenotype for only one of these enzymes or for smokers with both rapid phenotypes who did not prefer their red meat well-done. These data provide additional support to the hypothesis that exposure to carcinogens (presumably HAAs) through consumption of well-done meat increases the risk of CRC, particularly in individuals who are genetically susceptible (as determined by a rapid phenotype for both NAT2 and CYP1A2) and suggest that smoking, by inducing CYP1A2, facilitates this effect.     

N-acetyltransferase 2 phenotype but not NAT1*10 genotype affects aminobiphenyl-hemoglobin adduct levels.

Aminobiphenyls (ABPs) in tobacco have been implicated in bladder cancer etiology in smokers. N-Acetylation of ABPs in the liver, predominantly by the N-acetyltransferase 2 (NAT2) isozyme, represents a detoxification pathway, whereas O-acetylation of N-hydroxy-ABPs in the bladder, predominantly by the N-acetyltransferase 1 (NAT1) isozyme, represents a bioactivation pathway. We and others have demonstrated that NAT2 phenotype affects 3- and 4-ABP-hemoglobin adduct levels (higher levels in slow acetylators), which are considered valid biomarkers of the internal dose of ABP to the bladder. We have also shown that NAT1 genotype (NAT1*10 allele) is associated with increased DNA adduct levels in urothelial tissue and higher risk of bladder cancer among smokers. It is not known whether NAT1*10 genotype influences ABP-hemoglobin adduct levels. Therefore, we assessed 403 primarily non-Hispanic white residents of Los Angeles County for their NAT2 acetylator phenotype, NAT1*10 acetylator genotype, and 3- and 4-ABP-hemoglobin adduct levels. Eighty-two subjects were current tobacco smokers of varying intensities. Tobacco smokers had significantly higher mean 3- and 4-ABP-hemoglobin adduct levels relative to nonsmokers. The levels increased with increased amounts smoked per day (two-sided, P < 0.0001 in all cases). With adjustment for NAT1 genotype and race, the smoking-adjusted geometric mean level of 3-ABP-hemoglobin adducts in NAT2 slow acetylators was 47% higher than that in NAT2 rapid acetylators (P = 0.01). The comparable value for 4-ABP-hemoglobin adducts was 17% (P = 0.02). In contrast, no association between NAT1*10 genotype and 3- or 4 ABP-hemoglobin adduct levels was observed after adjustment for NAT2 phenotype, smoking, and race. The present study suggests that the impact of the NAT1*10 genotype on 3- and 4-ABP-hemoglobin adducts is noninformative on the possible association between NAT1 activity and bladder cancer risk.     

ADH1B and ALDH2 polymorphisms and their associations with increased risk of squamous cell carcinoma of the head and neck in the Korean population

Alcohol consumption is a major risk factor for squamous cell carcinoma of the head and neck (SCCHN). Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are key enzymes in ethanol metabolism. The objective of this study was to investigate the relationships of ADH and ALDH single nucleotide polymorphisms (SNPs) with the risk of developing SCCHN in a Korean sample. We genotyped ADH1B +3170A>G (rs1229984) and ALDH2 +1951G>A (rs671) SNPs in 225 Korean SCCHN patients and 301 healthy controls by single base extension and TaqMan assay. The frequencies of the ADH1B +3170A>G (*2*2/*2*1/*1*1) genotypes were 48.0%/38.7%/13.3% in SCCHN patients, and 57.8%/37.2%/5.0% in controls, respectively. The odds ratio (OR) and 95% confidence interval of the ADH1B*1*1 genotype was 1.89 (1.23-2.92) relative to the *2*2 genotype. The frequencies of the ALDH2 +1951G>A (*1*1/*1*2/*2*2) genotypes were 67.6%/31.6%/0.9% in SCCHN patients, and 67.8%/29.6%/2.7% in controls, respectively. In subgroup analyses according to smoking and alcohol drinking status, the OR of the ADH1B*1*1 genotype was increased in the heavy drinker group [8.85 (1.095-40.0)] and in the heavy smoker group [4.7 (1.54-14.29)]. We conclude that the ADH1B*1*1 genotype is associated with an increased risk of SCCHN, especially in heavy drinkers and heavy smokers. This genotype could be a useful biomarker for identifying Koreans with a greater risk of SCCHN.