Null Results in Brief No Apparent Association between NAT1 and NAT2 Genotypes and Risk of Stomach Cancer Qing Lan, 1 Nathaniel Rothman, Wong-Ho Chow, Jolanta Lissowska, Mark A. Doll, Gong H. Xiao, Witold Zatonski, and David W. Hein Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Department of Health and Human Services, Bethesda, Maryland 20892- 7240 [Q. L., N. R., W-H. C.]; Division of Cancer Epidemiology and Prevention, Cancer Center and M. Sklodowska-Curie Institute of Oncology, Warsaw, Poland [J. L., W. Z.]; and Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, Kentucky [M. A. D., G. H. X., D. W. H.] Introduction Intake of well-done meat, which contains heterocyclic amines, has been associated with stomach cancer in both experimental rodent and epidemiological studies (1–3). In addition, tobacco, which contains the heterocyclic amine (2-amino-1-methyl-6- phenylimidazo[4,5-b]pyridine), has been consistently associ- ated with increased risk of stomach cancer (4, 5). N-Acetyl- transferase 1 and 2 enzymes encoded by NAT1 and NAT2 (6) activate the N-hydroxylated forms of heterocyclic amines to DNA adducts (7), which has given rise to the hypothesis that genetic variants associated with rapid activity may be associ- ated with elevated risk of stomach cancer (8 –10). Both genes exhibit genetic polymorphisms in humans cor- responding to slow and rapid acetylator phenotypes (11). Two previous studies (8, 9) have provided support for an increased risk of stomach cancer associated with the NAT1*10 allele, and one (10) of three (8 –10) published papers found an association between NAT2 genotypes and stomach cancer risk. Here, we examined the relationship between NAT1 and NAT2 genotypes and stomach cancer. Materials and Methods Data were derived from a population-based case-control study of stomach cancer that was carried out in Warsaw, Poland, between 1994 and 1996, which has been described in detail (4). A 30-ml blood sample was collected from 304 cases and 433 controls. We have previously shown that demographic charac- teristics of this subgroup were similar to cases and controls without a blood sample (4). NAT2 genotype was determined using a comprehensive PCR-RFLP assay (12) designed to dis- tinguish among 25 NAT2 alleles. NAT1 genotype was deter- mined by sequencing two parts of the NAT1 gene (nucleotides 150 – 650 and 750-1150). Nucleotide sequence was determined after purification of the amplified PCR products with Qiaquick PCR Purification Kit (Qiagen, Valencia, CA) using the Big- Dye Terminator Cycle Sequencing Kit (Applied Biosystems, Foster City, CA). Electrophoresis and analysis of DNA se- quence reactions were performed with an ABI 310 Genetic Analyzer. Genotype data were not available for 4 –5% of sub- jects from whom a blood sample had been collected because of inadequate amount or quality of DNA. ORs 2 and 95% CIs, which were used to estimate the association between stomach cancer and NAT genotypes and other risk factors, were calculated via unconditional logistic regression using SAS 6.12 (SAS Institute, Inc.). Previous pa- pers from this study have shown associations between stomach cancer and cigarette smoking, a history of stomach cancer in a first-degree relative and GSTT1 null genotype (4, 13, 14). ORs were adjusted for age, sex, education, pack-years of cigarette smoking, family history of stomach cancer, GSTT1 genotype, years lived on a farm, and fruit intake. Gene-gene and gene- smoking multiplicative interactions were evaluated by the like- lihood ratio test. We carried out additional subgroup analyses to explore associations previously reported (8, 9), using the same reference group and adjusting for the same risk factors. Results Subjects with one copy of the NAT1*10 allele had a signifi- cantly decreased risk for stomach cancer, whereas the few subjects who were homozygous for this allele had a nonsignif- icant increased risk (Table 1A). There was no evidence of interaction with smoking and other risk factors, although there was low power to detect this (data not shown). To maximize the comparability of results from our study with the two previous reports (8, 9), we carried out analyses using the same reference group and combined subjects with one or two copies of NAT1*10. In contrast to the previous reports, we found no evidence of an increased risk and some support for a decreased risk (Table 1B). There was no association between stomach cancer risk and NAT2 genotype grouped into functional categories of slow, intermediate, and rapid activity (Table 1A) or with NAT2 gen- otypes associated with the slow phenotype compared with NAT2 combined rapid and intermediate activity genotypes (Ta- ble 1B). Also, there was no evidence of an interaction between NAT2 genotype with tobacco smoking, GSTT1 null genotype, or NAT1*10 (data not shown). Discussion We found evidence of a protective effect of the NAT1*10 allele among heterozygotes, but a gene-dosage effect was lacking in that risk was increased among the small numbers of subjects who were homozygotes for this allele. Boissy et al. (8) found a Received 12/4/02; accepted 1/21/03. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 To whom requests for reprints should be addressed, at Occupational Epidemi- ology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, MSC 7240, 6120 Executive Boulevard, EPS 8109, Bethesda, MD 20892-7240. Phone: (301) 435-4706; Fax: (301) 402-1819; E-mail: qingl@ mail.nih.gov. 2 The abbreviations used are: OR, odds ratio; CI, confidence interval. 384 Vol. 12, 384 –386, April 2003 Cancer Epidemiology, Biomarkers & Prevention Research. on November 12, 2021. © 2003 American Association for Cancer cebp.aacrjournals.org Downloaded from