N-acetylation phenotype in bladder cancer

Risks on N-acetyltransferase 2 and bladder cancer: a meta-analysis

Background

It is known that bladder cancer disease is closely related to aromatic amine compounds, which could cause cancer by regulating of N-acetylation and N-acetyltransferase 1 and 2 (NAT1 and NAT2). The NAT2 slowed acetylation and would increase the risk of bladder cancer, with tobacco smoke being regarded as a risk factor for this increased risk. However, the relationship between NAT2 slow acetylation and bladder cancer is still debatable at present. This study aims to explore preliminarily correlation of NAT2 slow acetylation and the risk of bladder cancer.

Methods

The articles were searched from PubMed, Cochran, McGrane English databases, CBM, CNKI, and other databases. The extraction of bladder cancer patients and a control group related with the NAT2 gene were detected by the state, and the referenced articles and publications were also used for data retrieval. Using a random effects model, the model assumes that the studies included in the analysis cases belong to the overall population in the study of random sampling, and considering the variables within and between studies. Data were analyzed using STATA Version 6.0 software, using the META module. According to the inclusion and exclusion criteria of the literature study, 20 independent studies are included in this meta-analysis.

Results

The results showed that the individual differences of bladder cancer susceptibility might be part of the metabolism of carcinogens. Slow acetylation status of bladder cancer associated with the pooled odds ratio was 1.31 (95% confidence interval: 1.11–1.55).

Conclusion

The status of NAT2 slow N-acetylation is associated with bladder cancer risks, and may increase the risk of bladder cancer.

N-acetyltransferase 2 genetic polymorphism: effects of carcinogen and haplotype on urinary bladder cancer risk

A role for the N-acetyltransferase 2 (NAT2) genetic polymorphism in cancer risk has been the subject of numerous studies. Although comprehensive reviews of the NAT2 acetylation polymorphism have been published elsewhere, the objective of this paper is to briefly highlight some important features of the NAT2 acetylation polymorphism that are not universally accepted to better understand the role of NAT2 polymorphism in carcinogenic risk assessment. NAT2 slow acetylator phenotype(s) infer a consistent and robust increase in urinary bladder cancer risk following exposures to aromatic amine carcinogens. However, identification of specific carcinogens is important as the effect of NAT2 polymorphism on urinary bladder cancer differs dramatically between monoarylamines and diarylamines. Misclassifications of carcinogen exposure and NAT2 genotype/phenotype confound evidence for a real biological effect. Functional understanding of the effects of NAT2 genetic polymorphisms on metabolism and genotoxicity, tissue-specific expression and the elucidation of the molecular mechanisms responsible are critical for the interpretation of previous and future human molecular epidemiology investigations into the role of NAT2 polymorphism on cancer risk. Although associations have been reported for various cancers, this paper focuses on urinary bladder cancer, a cancer in which a role for NAT2 polymorphism was first proposed and for which evidence is accumulating that the effect is biologically significant with important public health implications.

Interaction effect in bladder cancer between N-acetyltransferase 2 genotype and alcohol drinking

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.

Bayesian synthesis of epidemiological evidence with different combinations of exposure groups: application to a gene–gene–environment interaction

Meta-analysis to investigate the joint effect of multiple factors in the aetiology of a disease is of increasing importance in epidemiology. This task is often challenging in practice, because studies typically concentrate on studying the effect of only one exposure, sometimes may report the interaction between two exposures, but rarely address more complex interactions that involve more than two exposures. In this paper, we develop a meta-analysis framework that combines estimates from studies of multiple exposures. A key development is an approach to combining results from studies that report information on any subset or combination of the full set of exposures. The model requires assumptions to be made about the prevalence of the specific exposures. We discuss several possible model specifications and prior distributions, including information internal and external to the meta-analysis data set, and using fixed-effect and random-effects meta-analysis assumptions. The methodology is implemented in an original meta-analysis of studies relating the risk of bladder cancer to two N-acetyltransferase genes, NAT1 and NAT2, and smoking status.

The enhanced bladder cancer susceptibility of NAT2 slow acetylators towards aromatic amines: a review considering ethnic differences

Human bladder cancer may be caused by exposure to aromatic amines. The polymorphic enzyme N-acetyltransferase 2 (NAT2) is involved in the metabolism of these compounds. Two classical studies on chemical workers in Europe, exposed in the past to aromatic amines like benzidine, unambiguously showed that the slow acetylator status is a genetic risk factor for arylamine-induced bladder cancer. In the former benzidine industry in Huddington, Great Britain, 22 of 23 exposed cases with bladder cancer, but only 57% of 95 local controls without bladder cancer were of the slow acetylator phenotype. In Leverkusen, Germany, 82% of 92 benzidine-exposed chemical workers with bladder cancer were of the slow acetylator phenotype, whereas only 48% of 331 chemical workers who had worked at that plant were of the slow acetylator phenotype. This is in line with several smaller studies, which also show an over-representation of the slow acetylator status in formerly arylamine-exposed subjects with bladder cancer. Some of these studies included also subjects that were exposed to aromatic amines by having applied dyes, paints and varnishes. These European findings are in contrast to a large study on Chinese workers occupationally exposed to aromatic amines. In this study, only five of 38 bladder cancer cases occupationally exposed to arylamines were of the slow acetylator genotype. This is much lower than the ratio of slow acetylators to the general population in China. This points to different mechanisms of susceptibility for bladder cancer upon exposure to aromatic amines between European (Caucasian) and Chinese populations.

N-acetyltransferase 2 and bladder cancer: an overview and consideration of the evidence for gene-environment interaction

Genetic polymorphism of the carcinogen metabolizing enzyme N-acetyl transferase 2 (NAT2) may influence susceptibility to bladder cancers related to smoking or to occupational exposure to arylamine carcinogens. This article reviews the results of 21 published case-control studies of NAT2 polymorphism and bladder-cancer risk, with a total of 2700 cases and 3426 controls. The published evidence suggests that NAT2 slow acetylator phenotype or genotype may be associated with a small increase in bladder cancer risk. However, given the possibility of selective publication of results from studies that found an excess risk, the current evidence is not sufficient to conclude that there is a real increase in risk. Only five of the 21 studies reported results separately for the effect of NAT2 on bladder cancer risk in smokers and non-smokers. Although the results suggest that the effect may be greater in smokers than in non-smokers, the possibility of publication bias makes these results difficult to interpret. There was insufficient evidence to assess the joint effect of NAT2 and occupational exposure to arylamines on bladder cancer risk. Even if estimates of the effect of NAT2 from published data are correct, studies with around 3000-5000 cases will be needed to confirm them.

Gender-specific effects of NAT2 and GSTM1 in bladder cancer

One approach for risk assessment of cancer is the evaluation of polymorphic enzymes involved in cancer using molecular tools. Phase II enzymes are involved in the detoxification of several drugs, environmental substances and carcinogenic compounds. Here, we analyzed enzymes for their putative relevance in urinary bladder cancer. The hereditable enzyme polymorphism of arylamine N-acetyltransferase 2 (NAT2) and glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) was studied in 157 hospital-based patients and in 223 control subjects. Slow acetylation was not observed to be a significant risk factor of developing bladder cancer (OR: 1.33; 95% CI 0.85-2.09). One genotype responsible for slow acetylation (NAT2*5B/*6A) was observed significantly more frequently in bladder cancer patients compared with control subjects (OR: 1.63; 95% CI 1.03-2.58). Gender-specific effects were observed when patients were divided into subgroups. In male patients, slow acetylators were identified as carrying a significant increased risk of developing bladder cancer, in particular when the genotype NAT2*5B/*6A was combined with the GSTM1 null genotype (OR: 4.39; 95% CI 1.98-9.74). By contrast, the same genotype combination significantly protected female patients from bladder cancer (OR: 0.21; 95% CI 0.06-0.80).

NAT2 slow acetylation and bladder cancer risk: a meta-analysis of 22 case-control studies conducted in the general population

The NAT2 gene is involved in phase II detoxification of aromatic monoamines, a class of known bladder carcinogens. Certain allelic combinations result in the slow acetylation phenotype, which is thought to increase bladder cancer risk. We conducted a meta-analysis of all identifiable published case-control studies conducted in the general population that had examined the relationship of acetylation status and bladder cancer risk (22 studies, 2496 cases, 3340 controls). Using meta-analysis techniques that employed weighting based on individual-study variation, slow acetylators had an approximately 40% increase in risk compared with rapid acetylators [odds ratio (OR) 1.4, 95% confidence interval (CI) 1.2-1.6]. Statistical tests indicated, however, that pooling of all studies, or of studies conducted in Caucasian populations, hid potentially important heterogeneity in the individual study results, and suggested that the relationship of NAT2 slow acetylation and bladder cancer risk might differ by geographical region. Studies conducted in Asia generated a summary OR of 2.1 (CI 1.2-3.8), in Europe, a summary OR of 1.4 (CI 1.2-1.6), and in the USA, a summary OR of 0.9 (CI 0.7-1.3). Among European studies, the relationship between NAT2 slow acetylation and bladder cancer risk did not differ by method used to assess acetylation status (older drug-based phenotyping methods: 10 studies, OR 1.5, CI 1.2-1.8; more recent NAT2 genotyping methods: four studies, OR 1.4, CI 1.1-1.7). Our results suggest that in most populations studied to date, NAT2 slow acetylation status is associated with a modest increase in bladder cancer risk.

N-acetyl transferase-2 and bladder cancer risk: a meta-analysis

Interindividual differences in bladder cancer susceptibility may be partly mediated through polymorphic variability in the metabolism of carcinogens. N-acetyl transferase-2 (NAT2) has been extensively studied as a risk factor in this context, but the results are inconsistent. In some studies the failure to demonstrate a relationship may be a consequence of a lack of statistical power. To overcome lack of power, data from 21 published case-control studies were pooled in a meta-analysis using a random-effects model. The pooled odds ratio of bladder cancer associated with slow acetylator status was 1.31 (95% CI: 1.11-1.55). The results suggest that NAT2 slow acetylator status is associated with a modest increase in risk of bladder cancer. There was, however, heterogeneity between studies. It is clear from this overview that greater attention should be paid to the design of these types of study.

Polymorphisms in xenobiotic conjugation and disease predisposition

Low activity of arylamine N-acetyltransferase 2 (slow NAT2) was consistently associated with urinary bladder cancer risk. The increased cancer risk attributable to slow NAT2 was more significant when taking gene-environment interactions and gene-gene interactions into account. In urinary bladder, slow NAT2 was no risk factor in subjects who never smoked but became increasingly relevant with increasing lifetime dose of tobacco smoke expressed by an odds ratio of 2.7 for slow NAT2 in extensive smokers. The functional impact of some arylamine N-acetyltransferase 1 variants is controversial. It was published that the NAT1 allele 10 was associated with high enzyme activity and that there was an overrepresentation of carriers of NAT1*10 in bladder and colon cancer, but we could only detect a moderately elevated activity of NAT1*10 and an underrepresentation of fast NAT1 alleles in bladder cancer. Recently, a C/A-polymorphism in intron 1 of cytochrome P450 1A2 was associated with high inducibility and persons with this high inducibility variant were overrepresented in bladder cancer, but only if they were smokers or if they had slow NAT2 genotypes. Numerous studies have shown that glutathione S-transferase M1 deficiency (GSTM1*0/0) increases the risk for lung and bladder cancer but the overall risk attributable to GSTM1*0/0 was only around 1.3 according to meta-analyses. The GSTM1*0/0 genotype appears to be the best established metabolic susceptibility factor. Several independent experimental approaches showed that GSTM1 decreases mutagenicity of reactive epoxides and it was shown that carriers of GSTM1*0/0 were at increased risk for several types of cancer and other diseases. There are also studies which showed no effects of GSTM1, a result which is compatible with the assumption that GSTM1*0/0 is a susceptibility factor of moderate strength. GSTM1*0/0 may, however, become a dominant risk factor in certain gene-gene combinations such as the combination with highly active CYP1A1 gene variants or in combination with specific types of exposure. Specific precautions have to be taken in the design of molecular epidemiological studies on risk factors with moderate strength; some requirements for high quality molecular epidemiological studies will be discussed in this article. Molecular epidemiology is an increasingly powerful approach to understand carcinogenesis and may be used in the future to individualize cancer prevention strategies.

N-Acetyltransferase 2 (NAT2) and Glutathione S-Transferase µ (GSTM1) in Bladder-cancer Patients in a Highly Industrialized Area

The study was designed to assess occupational and non-occupational risk factors in patients with urothelial carcinomas in an area of former coal, iron, and steel industries, with special regard to the impacts of polymorphic enzymes involved in the metabolism of aromatic amines (N-acetyltransferase 2, NAT2) and of polycyclic aromatic hydrocarbons (glutathione S-transferase µ, GSTM1). Inpatients with bladder cancer (n = 179) were interviewed for occupations ever engaged in for more than six months, and for bladder cancer risk factors in general. NAT2 was phenotyped by high-pressure liquid chromatography of caffeine metabolites in urine. The NAT2 status was additionally evaluated by genotyping 88 of these patients. Eighty-nine patients were genotyped for GSTM1. Of the 179 bladder-cancer patients, 115 (64%) were slow acetylators. In 70% of the subgroup of 89 patients, GSTM1 was negative, suggesting an impact of polycyclic aromatic hydrocarbons (PAHs) in bladder-cancer carcinogenesis in the general population in this area. Contrary to an ordinary distribution of the acetylator status in underground coal miners (18 slow acetylators out of 32), GSTM1 was negative in 16 of 19 of these coal miners. Five of six coke-oven workers were slow acetylators; GSTM1 was negative in all four genotyped coke-oven workers. Twelve of 17 patients formerly exposed to colorants were slow acetylators. Distributions of NAT2 (59% slow acetylators) and GSTM1 (54% GSTM1 negative) were normal in businessmen and administrative officers among the occupationally non-exposed bladder-cancer patients. The results are consistent with the view that a slow-acetylator status and lack of the GSTM1 gene are individual risk factors for bladder cancer in persons occupationally exposed to aromatic amines and PAHs. Aromatic amines may be connected with induction of bladder cancer in persons who have been in contact with azo dyes and in coke-oven workers. PAHs may also contribute to elevated bladder-cancer risks in coke-oven workers and in underground coal miners.

Genetic differences in drug disposition

Genetic polymorphisms of drug metabolizing enzymes are well recognized. This review presents molecular mechanisms, ontogeny and clinical implications of genetically determined intersubject variation in some of these enzymes. Included are the polymorphic enzymes N-acetyl transferase, cytochromes P4502D6 and 2C, which have been well described in humans. Information regarding other Phase I and Phase II polymorphic pathways, such as glutathione and methyl conjugation and alcohol and acetaldehyde oxidation continues to increase and are also discussed. Genetic factors effecting enzyme activity are frequently important determinants of the disposition of drugs and their efficacy and toxicity. In addition, associations between genetic differences in these enzymes and susceptibility to carcinogens and teratogens have been reported. Ultimately, the application of knowledge regarding these genetic factors of enzyme activity may guide medical therapy and minimize xenobiotic-induced disease.

Metabolic polymorphisms

Polymorphisms have been detected in a variety of xenobiotic-metabolizing enzymes at both the phenotypic and genotypic level. In the case of four enzymes, the cytochrome P450 CYP2D6, glutathione S-transferase mu, N-acetyltransferase 2 and serum cholinesterase, the majority of mutations which give rise to a defective phenotype have now been identified. Another group of enzymes show definite polymorphism at the phenotypic level but the exact genetic mechanisms responsible are not yet clear. These enzymes include the cytochromes P450 CYP1A1, CYP1A2 and a CYP2C form which metabolizes mephenytoin, a flavin-linked monooxygenase (fish-odour syndrome), paraoxonase, UDP-glucuronosyltransferase (Gilbert's syndrome) and thiopurine S-methyltransferase. In the case of a further group of enzymes, there is some evidence for polymorphism at either the phenotypic or genotypic level but this has not been unambiguously demonstrated. Examples of this class include the cytochrome P450 enzymes CYP2A6, CYP2E1, CYP2C9 and CYP3A4, xanthine oxidase, an S-oxidase which metabolizes carbocysteine, epoxide hydrolase, two forms of sulphotransferase and several methyltransferases. The nature of all these polymorphisms and possible polymorphisms is discussed in detail, with particular reference to the effects of this variation on drug metabolism and susceptibility to chemically-induced diseases.

Is environmental carcinogenesis modulated by host polymorphism?

It is now clear that tobacco smoking, alcohol consumption, dietary factors and occupation can all interact with genetic host factors to place one individual at a greater or lesser risk of a particular cancer than another. Phenotypes which confer significantly elevated risks arise from the human CYP1A1. CYP2D6, GST1 and NAT (N-acetyltransferase) genes. The last is the only one remaining to be cloned. It is envisaged that several of these genes may interact in a given circumstance cooperatively to increase susceptibility. For example CYP1A1, CYP2D6 and GST1 genotypes may have additive or multiplicative risks of bronchogenic carcinoma in cigarette smokers. CYP2D6 and NAT genotypes may interact in bladder cancer. The advent of molecular genetics brings us closer to the day when, for example, factory workers in potentially hazardous environments might be screened using PCR methodology on skin scrapings or buccal swabs for their innate susceptibility to combined workplace and lifestyle cancer risks.

Genetically determined N-acetylation and oxidation capacities in Japanese patients with non-occupational urinary bladder cancer

Genetically determined polymorphisms of N-acetylation and oxidative capacity have been studied using dapsone and metoprolol in 51 Japanese patients with spontaneous bladder cancer and 203 healthy control subjects. The results for N-acetylation pharmacogenetics were against the initial expectation that there would be a preponderance of slow acetylators in the cancer group, as 3 such patients (5.9%) were found as compared to 13 (6.4%) in the healthy group. There was no poor metabolizer (PM) of metoprolol in the cancer group, whereas in the healthy group one (0.5%) was a PM. There were no significant differences between the groups in the frequency of slow acetylator and poor oxidiser phenotypes, or in the frequency distribution profiles of acetylation (monoacetyldapsone/dapsone) and oxidative metabolic ratio (log metoprolol/alpha-hydroxymetoprolol). The results indicate that neither N-acetylation nor the debrisoquine/sparteine-type oxidative phenotype and/or capacity represent a genetic predisposition to spontaneous bladder carcinogenesis in Japanese patients. In the normal Japanese population there is a great predominance of rapid acetylators and extensive oxidisers.

Acetylator genotype and arylamine-induced carcinogenesis

A diverse array of arylamine chemicals derived from industry, diet, cigarette smoke and other environmental sources are carcinogenic. These chemicals require metabolic activation by host enzymes to chemically reactive electrophiles to initiate the carcinogenic response. Genetic regulation of activation and/or deactivation pathways are thought to account in large measure for corresponding differences in tumor incidence from these chemicals between tissues, between species, or between individuals within a species. Various acetyltransfer reactions are involved in arylamine metabolism and much has been learned regarding their enzymology, genetic regulation, and toxicological significance. The small amount of human data are supported by systematic investigations carried out in animal models characterized with respect to the acetylation polymorphism. Enzymological and genetic investigations suggest that common enzymes encoded by the acetyltransferase gene carry out a diverse set of acetyltransferase reactions. Thus, the acetylation polymorphism can influence both activation and deactivation pathways in arylamine metabolism. Of particular significance recently have been reports documenting the O-acetylation of N-hydroxyarylamine carcinogens and its genetic coregulation with the well-characterized arylamine N-acetylation polymorphism. The toxicological consequences of this polymorphic pathway have yet to be fully explored. Epidemiological investigations show associations between acetylator phenotype and the incidence and/or severity of tumors in the urinary bladder, colon and larynx. Associations between acetylator phenotype and breast cancer are more equivocal and require further study. The divergent influence of acetylator phenotype on the incidence of tumors in different organ sites suggests an important role for extrahepatic acetyltransferases, and further characterization of them in human and animal tissues is needed. The advent of newer methodologies to monitor chemical exposures and to measure acetylator phenotype (rapid, intermediate and slow) using less invasive and more standardized protocols should soon result in a much more definitive understanding regarding the role of acetylator status in arylamine-induced carcinogenesis.

N-Acetyltransferase phenotype of patients with bladder cancer

N-Acetyltransferase phenotype has been determined in 109 control subjects and in 23 patients with bladder cancer. Sixty-two per cent of control, and 39% of patients with bladder cancer were phenotypically slow acetylators. This difference was not significant. N-Acetyltransferase phenotype is unlikely to be a major determinant in the development of bladder cancer in the Turkish population.

Genetically determined variability in acetylation and oxidation. Therapeutic implications

The clinical significance of two separate genetic polymorphisms which alter drug metabolism, acetylation and oxidation is discussed, and methods of phenotyping for both acetylator and polymorphic oxidation status are reviewed. Particular reference is made to the dapsone method, which provides a simple means of distinguishing fast and slow - and possibly intermediate - acetylators, and to the sparteine method which allows a clear separation of oxidation phenotypes. Although acetylation polymorphism has been known for some time, definite indications for phenotyping are few. It is doubtful whether acetylator phenotype makes a significant difference to the outcome in most isoniazid treatment regimens, and peripheral neuropathy from isoniazid in slow acetylators is easily overcome by pyridoxine administration. However, in comparison with rapid acetylators, slow acetylators receiving isoniazid have an increased susceptibility to phenytoin toxicity, and perhaps also to carbamazepine toxicity. It is also possible that rapid acetylators receiving isoniazid attain higher serum fluoride concentrations from enflurane and similar anaesthetics than do similarly treated slow acetylators. Thus, when drug interactions of these types are suspected, phenotyping for acetylator status may be advisable. If routine monitoring of serum procainamide and N-acetylprocainamide concentrations is practised, phenotyping of subjects prior to therapy with these agents should not be necessary. Although acetylator phenotype influences serum concentrations of hydralazine, when this drug is given in combination with other drugs acetylator phenotype has not been shown to influence the therapeutic response. Slow acetylator phenotype along with female gender and the presence of HLA-DR antigens appear to be risk factors in the development of hydralazine-induced systemic lupus erythematosus (SLE). Determination of acetylator phenotype may therefore help determine susceptibility to this adverse reaction. In the case of sulphasalazine, adult slow acetylators require a lower daily dose of the drug than fast acetylators in order to maintain ulcerative colitis in remission without significant side effects. It is therefore advisable to determine acetylator phenotype prior to sulphasalazine therapy. Work on the association of acetylation polymorphism with various disease states is also reviewed. It is possible that a higher incidence of bladder cancer is associated with slow acetylation phenotype - especially in individuals exposed to high levels of arylamines. The question as to whether idiopathic SLE is more common in slow acetylators remains unresolved. There appears to be no difference between fa

Survey of the human acetylator polymorphism in spontaneous disorders

There is ample evidence that the human acetylator phenotypes are associated with drug induced phenomena. It is principally the slow acetylators who exhibit toxic adverse effects because of their relative inability to detoxify the original drug compounds. In rare instances, however, it is the rapid acetylators who are at a disadvantage. In the matter of association of spontaneous disease with either acetylator phenotype, there are two groups of disorders to consider. First, disorders in which carcinogenic amines are known to be an aetiological factor. This is because these amines are substrates for the polymorphic N-acetyltransferase activity and hence there is a possible rational basis for searching for an association. Secondly, other disorders where searches for associations are based more on hunches. In the first group there is a definite statistical association between cancer of the bladder and the slow acetylator phenotype. In prevalence studies the slow phenotype is 39% more associated with bladder cancer than is the rapid phenotype. On the basis of the evidence now available it is not possible to say whether this association is because slow acetylators develop the disease more frequently or whether they survive longer. In the second group the relevant studies show (1) a greatly increased prevalence of slow acetylators in Gilbert's disease; (2) a confirmed association between the rapid acetylator phenotype and diabetes; (3) a possible association between the rapid acetylator phenotype and breast cancer; (4) a possible association between the slow acetylator phenotype and leprosy in Chinese patients; (5) an earlier age of onset of thyrotoxicosis (Graves' disease) in slow acetylators than in rapid acetylators; (6) no evidence of an association between either phenotype and spontaneous systemic lupus erythematosus.

The association of the slow acetylator phenotype with bladder cancer

There is an association between exposure to aromatic amines and the development of bladder cancer. Aromatic amines such as are known to occur in tobacco smoke are polymorphically acetylated. One hundred bladder cancer patients have been acetylator phenotyped. Only three of them were non-smokers at the time of diagnosis. This new series, together with four previous series (each with its own control), have been statistically analysed together. The results show a significant association between the slow acetylator phenotype and bladder cancer. The slow acetylator phenotype is associated about 39% more with bladder cancer than is the rapid acetylator phenotype. This association can be interpreted in one of two ways: (1) rapid acetylators may be protected against developing bladder cancer because they are better able to render amines non-carcinogenic by acetylation, or (2) slow acetylators have greater survival with bladder cancer than rapid acetylators. Further evidence will be required to differentiate between these alternatives.