The association of the slow acetylator phenotype with bladder cancer

Determination of isoniazid acetylation patterns in tuberculosis patients receiving DOT therapy under the Revised National tuberculosis Control Program (RNTCP) in India

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Monitoring of liver function tests is very important in patient receiving DOT therapy.

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There was no significance difference reported in the differential leucocytes count.

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We define mechanisms underlying the adverse drug reactions observed following DOTS.

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The plasma INH concentration was reported to be high in slow acetylation.

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Plasma INH concentration greater than the antimode are slow acetylator.

Isoniazid is the most commonly used drug for treatment of tuberculosis, and is administered individually or in combination with other drugs as standard first line therapy. Offsetting its efficacy, severe adverse effects, especially peripheral neuropathy and hepatotoxicity, are associated with isoniazid therapy, limiting its use in tuberculosis. Isoniazid is acetylated in vivo producing hydrazine and acetyl hydrazine, which are responsible for hepatotoxicity. Marked pharmacogenetic differences in acetylation have been reported among different population across the globe. This study evaluates isoniazid acetylation patterns in tuberculosis patients receiving DOT therapy under the Revised National Tuberculosis Control Program (RNTCP) in a specialized tuberculosis hospital in north India. Of 351 patients from whom samples were taken for biochemical analysis of adverse events, 36 were assessed for acetylation patterns. Blood samples were taken 1 h after administration of a 600 mg dose of isoniazid, and plasma concentrations of isoniazid were determined using a validated HPLC method. Of these 36 patients, 20 (55.56%) were slow acetylators and 16 (44.44%) were fast acetylators. Our results are consistent with those of an earlier study conducted in a different region of India. Most biochemical changes produced during long-term isoniazid therapy resolve after therapy is terminated.

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.

Environmental procarcinogen hypothesis of bladder cancer in humans: Dapsone hydroxylation as a susceptibility risk factor for aggressive bladder cancer

The dapsone recovery ratio (DPRR), which is determined after single oral dose administration of dapsone by measuring the parent drug and hydroxylated metabolite, provides an in vivo measure of the efficiency of the drug metabolizing enzymes responsible for this metabolic route, putatively CYP3A4. This affords the potential to evaluate the hypothesis that this drug metabolizing enzyme system is involved in the pathogenesis of human bladder cancer. The present study is a matched case-control comparison of DPRR in patients with nonaggressive bladder cancer (grades I and II or Ta, T1 and T2, n = 43), patients with aggressive bladder cancer without invasion (grade III or Ta, T1 and T2, n = 32), patients with aggressive bladder cancer and invasion (grade III or T3 and T4, n = 32), and age- and gender-matched subjects with no urologic tumor on cystoscopy from an urban U.K. community (n = 85). Demographic variables associated with aggressive bladder cancer (Gill or T3, T4, Tis) included pack-years of smoking, alcohol intake, and occupational exposure; for nonaggressive bladder cancer variables included smoking and occupational exposure. DPRR exhibited an unimodal distribution in all subjects: activity was significantly reduced in both noninvasive and invasive aggressive bladder cancer, and was a significant risk factor for cancer after adjustment for other significant risk factors. Combining the two aggressive groups, the lowest tertile of DPRR activity was associated with a sixfold increase in risk (p < 0.02) compared with the upper tertile. We conclude that a low dapsone recovery ratio is an independent risk factor for aggressive bladder cancer irrespective of its stage of invasion and suggest that the enzymes involved in its metabolism are detoxifying enzymes for unknown environmental factors to which an urban community is exposed.

Effects of ethanol and phenobarbital on hemoglobin adducts formation in rats exposed to benzidine and Direct Black 38

The objective of this study was to evaluate the effects of pretreatment of ethanol (EtOH) and phenobarbital (PB), which are known to affect the metabolism of xenobiotics, in the formation of hemoglobin adducts in rats administered with benzidine (BZ) and Direct Black 38 (DB38). The experimental rats were divided into BZ and DB38 groups; each group was subdivided into control, EtOH, and PB groups. Blood samples were separated into hemoglobin and plasma immediately after obtaining and basic hydrolysis was done to convert the adducts into aromatic amines. Hydrolyzed BZ, monoacetylbenzidine (MABZ), and 4-aminobiphenyl (4ABP) were separated by reversed-phase liquid chromatography without derivatization. Then, quantitative analyses were performed using a high performance liquid chromatograph equipped with an electrochemical detector. The amount of metabolites was expressed in the hemoglobin binding index (HBI). As a result, the formations of hemoglobin in BZ-, MABZ-, and 4ABP-HBI of BZ-EtOH and BZ-PB groups were increased compared with those of BZ-control group. In DB38 group, all of HBIs except for BZ-HBI were increased more than those of DB38-control group regardless of the pretreatment. These results are attributable to the fact that EtOH and PB induced N-hydroxylation is related to the formation of hemoglobin adducts. They indicate that EtOH not only increases the adduct formation by inducing N-hydroxylation but also induces N-acetylation. PB induced N-hydroxylation and increased the adduct formation in BZ group, but decreased the adduct formation in DB38 group due to decreasing azo reduction. These results suggest that the effects of EtOH or PB should be considered in biochemical monitoring of BZ and DB38 for the assessment of intermittent exposure to BZ and DB38.

Genetic polymorphism in N-Acetyltransferase (NAT): Population distribution of NAT1 and NAT2 activity

N-Acetyltransferases (NAT) are key enzymes in the conjugation of certain drugs and other xenobiotics with an arylamine structure. Polymorphisms in NAT2 have long been recognized to modulate toxicity produced by the anti-tubercular drug isoniazid, with molecular epidemiologic studies suggesting a link between acetylator phenotype and increased risk for bladder cancer. Recent evidence indicates that the other major NAT isozyme, NAT1, is also polymorphic. The current analysis characterizes the main polymorphisms in both NAT2 and NAT1 in terms of their effect on enzyme activity and frequency in the population. Multiple NAT2 alleles (NAT2*5, *6, *7, and *14) have substantially decreased acetylation activity and are common in Caucasians and populations of African descent. In these groups, most individuals carry at least one copy of a slow acetylator allele, and less than 10% are homozygous for the wild type (fast acetylator) trait. Incorporation of these data into a Monte Carlo modeling framework led to a population distribution of NAT2 activity that was bimodal and associated with considerable variability in each population assessed. The ratio of the median to the first percentile of NAT2 activity ranged from 7 in Caucasians to 18 in the Chinese population. This variability indicates the need for more quantitative approaches (e.g., physiologically based pharmacokinetic [PBPK] modeling) to assess the full distribution of internal dose and adverse responses to aromatic amines and other NAT2 substrates. Polymorphisms in NAT1 are generally associated with relatively minor effects on acetylation function, with Monte Carlo analysis indicating less interindividual variability than seen in NAT2 analysis.

Epidemiology of carcinogen metabolism genes and risk of squamous cell carcinoma of the head and neck

The risk association between tobacco and alcohol use with squamous cell carcinoma of the head and neck (SCCHN) is well recognized. However, clearly not all individuals who smoke or drink develop SCCHN. Individual genetic susceptibility differences in carcinogen-metabolizing enzyme function, mutagen sensitivity, apoptosis, and chromosomal aberrations either alone or in combination have been theorized to modify the risk of SCCHN. Nearly all carcinogens and procarcinogens require activation by metabolizing enzymes. Similarly, detoxifying enzymes exist and deactivate carcinogens as well as their intermediate by-products. Together these enzymes are termed xenobiotic-metabolizing enzymes; genetic polymorphisms of these enzymes can modify an individual's response to carcinogens and hence the carcinogenic potential of such exposures. In this review, we explore the available evidence in recent literature regarding the risk association between SCCHN and various xenobiotic-metabolizing enzymes, including cytochrome P450s, glutathione S-transferases, N-acetyltransferases, NAD(P)H:quinone oxidoreductase 1, alcohol dehydrogenase, and aldehyde dehydrogenase.

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.

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.

Incorporating pharmacokinetic differences between children and adults in assessing children's risks to environmental toxicants

Children's risks from environmental toxicant exposure can be affected by pharmacokinetic factors that affect the internal dose of parent chemical or active metabolite. There are numerous physiologic differences between neonates and adults that affect pharmacokinetics including size of lipid, and tissue compartments, organ blood flows, protein binding capacity, and immature function of renal and hepatic systems. These factors combine to decrease the clearance of many therapeutic drugs, which can also be expected to occur with environmental toxicants in neonates. The net effect may be greater or lesser internal dose of active toxicant depending upon how the agent is distributed, metabolized, and eliminated. Child/adult pharmacokinetic differences decrease with increasing postnatal age, but these factors should still be considered in any children's age group, birth through adolescence, for which there is toxicant exposure. Physiologically based pharmacokinetic (PBPK) models can simulate the absorption, distribution, metabolism, and excretion of xenobiotics in both children and adults, allowing for a direct comparison of internal dose and risk across age groups. This review provides special focus on the development of hepatic cytochrome P-450 enzymes (CYPs) in early life and how this information, along with many factors unique to children, can be applied to PBPK models for this receptor population. This review describes a case study involving the development of neonatal PBPK models for the CYP1A2 substrates caffeine and theophylline. These models were calibrated with pharmacokinetic data in neonates and used to help understand key metabolic differences between neonates and adults across these two drugs.

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.

Genetic polymorphism of N-acetyltransferase 2 in patients with esophageal cancer

OBJECTIVE

N-Acetylation polymorphism is a representative genetic trait related to an individual's susceptibility to several cancers. However, there remains a controversy and no consensus concerning whether there is a true association between esophageal cancer and N-acetylation polymorphism.

METHODS

To analyze the distribution of N-acetyltransferase 2 polymorphism in Japanese patients with esophageal squamous cell cancer, a molecular genotyping method using a polymerase chain reaction-based restriction fragment length polymorphism was used.

RESULTS

Based on an analysis of 71 Japanese patients with esophageal squamous cell cancer and 329 healthy control subjects, the distribution of the slow acetylator phenotype was significantly higher in esophageal cancer patients than in the controls (19.7% and 9.4%, respectively, p = 0.040). The odds ratio of esophageal cancer for the slow phenotype was 2.55 (95% CI = 1.15-5.65, p = 0.023) compared with the rapid type. Furthermore, a significant difference between the distribution of acetylator phenotype and the incidence of lymph node metastasis and lymphatic involvement was found based on the clinicopathological features of these cancers. Esophageal cancer patients with a higher smoking exposure history tended to have the rapid acetylator phenotype.

CONCLUSION

These results suggest that N-acetylation polymorphism may be implicated as a genetic trait affecting an individual's susceptibility and biological behavior of esophageal squamous cell cancer.

Association analysis of drug metabolizing enzyme gene polymorphisms in HIV-positive patients with co-trimoxazole hypersensitivity

The use of co-trimoxazole in HIV-positive patients has been associated with a high frequency (40-80%) of hypersensitivity reactions. This has been attributed to the bioactivation of the sulphonamide component, sulphamethoxazole (SMX), to its toxic hydroxylamine and nitroso metabolites. The aim of this study was to determine whether functionally significant polymorphisms in the genes coding for enzymes involved in SMX metabolism influence susceptibility to SMX hypersensitivity. HIV-positive patients with (n = 56) and without (n = 89) SMX hypersensitivity were genotyped for allelic variants in CYP2C9, GSTM1, GSTT1, GSTP1 and NAT2 using polymerase chain reaction (PCR) and/or PCR-restriction fragment length polymorphism analysis. The CYP2C9*2/*3 genotype and CYP2C9*3 allele frequencies were nine- and 2.5-fold higher in the hypersensitive group compared to non-sensitive patients, respectively, although they were not statistically significant when corrected for multiple testing. There were no differences in the frequencies of the GSTM1 and GSTT1 null genotypes, and the slow acetylator genotype, between hypersensitive and non-sensitive patients, while GSTP1 frequency was lower (although non-significant) in the hypersensitive group [21% versus 32%, odds ratio (OR) = 0.5, Pc = 0.24]. Comparison of the genotype frequencies in HIV-positive and -negative patients showed that the NAT2 slow acetylator genotype frequency in the HIV-positive patients (74%) was significantly (Pc = 0.0003, OR = 2.3) higher than in control subjects (56%). Our results show that genetic polymorphisms in drug metabolizing enzymes are unlikely to be major predisposing factors in determining individual susceptibility to co-trimoxazole hypersensitivity in HIV-positive patients.

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.

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.

Drug metabolism polymorphisms as modulators of cancer susceptibility

Recently, several molecular genetic bases of polymorphic enzyme activities involved in drug activation and detoxification have been elucidated. Many molecular epidemiology studies based on these premises have sought to gather information on the association of genetically determined metabolic variants with different risks of environmentally induced cancer. While rare alterations of tumor suppressor genes dramatically raise cancer risk for the single affected subjects, far more common and less dramatic differences in genes encoding for drug metabolism enzymes can be responsible for a relatively small, but rather frequent increase of cancer risk at the population level. This increase could be especially important in specific cases of occupational, pharmacological or environmental exposure. Examination of the current literature reveals that the most extensively investigated metabolic polymorphisms are those of P450 1A1 and P450 2D6 cytochromes, glutathione S-transferases (GSTs; M1 and, to a lesser extent, M3, P1 and T1) and N-acetyltransferases (NATs; NAT1 and NAT2). Making reference to these enzymes, we have assayed the current knowledge on the relations among polymorphisms of human xenobiotic-metabolizing enzymes and cancer susceptibilities. We have found intriguing models of susceptibility toward different types of cancer. We have reviewed and commented these models on light of the complex balance among different enzyme activities that, in each individual, determines the degree of each cancer susceptibility. Moreover, we have found techniques of molecular genetic analysis, more suitable than previous ones on phenotypic expression, now allowing better means to detect individuals at risk of cancer. According to the models presently available, a systematic screening of individuals at risk seems to make sense only in situations of well defined carcinogenic exposures and when performed by the polymorphism analysis of coordinated enzyme activities concurring to the metabolism of the carcinogen(s) in question. Genetic polymorphism analysis can allow for the detection of patients more prone to some types of specific cancers, or to the adverse effects of specific pharmaceutical agents. Considering the increasingly confirmed double-edged sword nature of metabolism polymorphism (both wild-type and variant alleles can predispose to cancer, albeit in different situations of exposure), individual susceptibility to cancer should be monitored as a function of the nature, and mechanism of action, of the carcinogen(s) to which the individual under study is known to be exposed, and with reference to the main target organ of the considered type of exposure.

Polymorphisms of xenobiotic-metabolizing enzymes and susceptibility to cancer

The variation in individual responses to exogenous agents is exceptionally wide. It is because of this large diversity of responsiveness that risk factors to environmentally induced diseases have been difficult to pinpoint, particularly at low exposure levels. Opportunities now exist for studies of host factors in cancer or other diseases in which an environmental component can be presumed. Many of the studies have shown an elevated disease proneness for individuals carrying the potential at-risk alleles of metabolic genes, but a number of controversial results have also been reported. This article is an overview of the data published to date on metabolic genotypes related to individual susceptibility to cancer.

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.

Genotyping of the polymorphic N-acetyltransferase (NAT2) and loss of heterozygosity in bladder cancer patients

Acetylation is one of the major routes in metabolism and detoxification of a large number of drugs, chemicals and carcinogens. Slow acetylators are said to be more susceptible to developing bladder cancer and because of investigations about tumor risk based on phenotyping procedures, it was our aim to study the distribution of allelic constellations of the N-acetyltransferase (NAT2) by genotyping patients with bladder cancer. We analysed NAT2 gene of blood and tumor DNA from 60 patients with primary bladder cancer and DNA of blood samples from 154 healthy individuals. Using ASO-PCR/RFLP techniques we identified 70% of patients with bladder cancer (n = 42) to be slow acetylators while genotyping of controls resulted in 61% with slow acetylators (n = 94). In addition, dividing bladder cancer patients in males and females the genotype NAT2*5B/NAT2*6A occured with much higher frequencies in males (OR = 4, 95%); CI = 1.8-8.9). Furthermore, investigating bladder cancer tissues we could detect loss of heterozygosity (LOH) in slow and rapid acetylator genotypes. In eleven out of 60 tumor samples (18.3%) we observed allelic loss at the NAT2 locus while in control DNA of blood from the same patients both alleles were still detectable.

4-Aminobiphenyl-DNA adducts and p53 mutations in bladder cancer

Epidemiologic studies have suggested that smokers of air-cured tobacco (rich in arylamines) are at higher risk of bladder cancer than smokers of flue-cured tobacco. The risk has been shown to be modulated by the N-acetyltransferase genotype. We analyzed the biopsies of 45 patients with bladder cancer. p53 mutations were sought by direct sequencing, and 4-aminobiphenyl-DNA adducts were measured by negative ion gas chromatography-mass spectrometry. 4-Aminobiphenyl-DNA adducts were higher in smokers of air-cured tobacco and in current smokers, but no relationship with the number of cigarettes smoked was found. Adducts were higher in more advanced histologic grades of tumors. No pattern was evident for p53 mutations. Seven of 9 mutations occurred in grade 3 tumors. No association was found between 4-ABP adducts and GSTM1 or NAT2 genetic polymorphisms.

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.

Biomonitoring of urinary aromatic amines and arylamine hemoglobin adducts in exposed workers and nonexposed control persons

The renal excretion of arylamines in occupationally exposed and nonexposed subjects was measured by a gas chromatography-electron capture detector method. Additionally, in the occupationally exposed persons hemoglobin adduct levels of arylamines were determined by a liquid chromatography-electrochemical detector method, together with the individual acetylator status. The aromatic amines aniline, p-toluidine, 2-naphthylamine, and 4-chloro-o-toluidine were detected in the urine of nonsmoking subjects who were not occupationally exposed to arylamines. Significantly higher concentrations of aniline, o-toluidine, m-toluidine, 2-naphthylamine, and 4-methyl-1,3-phenylenediamine could be observed in the urine of smoking control persons in comparison to nonsmokers. Comparison of smokers and nonsmokers in a group of workers primarily exposed to aniline and 4-chloroaniline revealed significant differences (P < 0.05) in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 2-naphthylamine. The slow acetylators in this group produced significantly more hemoglobin adducts of aniline and 4-chloroaniline than did the fast acetylators. In slow acetylators among the smoking workers there was a significant increase in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 4-chloroaniline and m-toluidine. The results indicate that there are influences of smoking habits and acetylator status on the levels of arylamine hemoglobin adducts as well as urinary arylamine concentrations. Hemoglobin adducts seem to be good parameters for monitoring aniline and 4-chloroaniline exposure at the workplace, especially if the acetylator polymorphism can be taken into account. 4-Aminodiphenyl hemoglobin adducts might be good parameters for monitoring individual smoking habits. The determination of urinary arylamine concentrations provides additional information concerning acute exposures to aromatic amines.

N-acetyltransferase activity in the urine in Japanese subjects: comparison in healthy persons and bladder cancer patients

The activity of urinary N-acetylamino-transferase was determined by high-performance liquid chromatographic assay of acetylisoniazid and isoniazid after administration of isoniazid to healthy Japanese male and bladder cancer patients in Japan. The healthy subjects were 47 college students and 44 company employees ranging from 18 to 64 years old (mean +/- SC = 34.5 +/- 13.7). The bladder cancer group consisted of 58 male and 13 female patients, ranging from 28 to 82 years old (mean +/- SD = 60.8 +/- 11.6), who were being treated at several hospitals. The slow phenotype, defined as an acetylation ratio (acetylisoniazid/isoniazid) of less than 2.0, was observed in 13 (14.3%) of the 91 healthy subjects, and in 20 (28.2%) of the 71 bladder cancer patients; the difference between the two groups is significant (p < 0.05). A histogram of the acetylation ratio values showed an overall leftward shift of the patient group, indicating low values of acetylation ratio in this group as a whole (p < 0.01).

Xenogenetics in multifactorial disease susceptibility

Susceptibility to multifactorial disease includes both genetic and environmental components. These two aspects of susceptibility are interlinked through genetic control of an individual's response to the environment. As a first step in identifying disease susceptibility genes that influence the response of an individual to foreign compounds (xenobiotics), it is necessary to study disorders in which there is an identified environmental trigger. Establishing a DNA resource from individuals with known environmental exposure ('a xenogenetic register') for diseases with an established environmental aetiology is an essential step in beginning to understand how environmental factors contribute to the susceptibility to polygenic diseases. A complementary approach to identification of environmental factors is suggested using a comparison of genetically homogeneous subdivisions of individuals with polygenic diseases where there is no clue to the environmental trigger.

Modeling human interindividual variability in metabolism and risk: the example of 4-aminobiphenyl

We investigate, through modeling, the impact of interindividual heterogeneity in the metabolism of 4-aminobiphenyl (ABP) and in physiological factors on human cancer risk: A physiological pharmacokinetic model was used to quantify the time course of the formation of the proximate carcinogen, N-hydroxy-4-ABP and the DNA-binding of the active species in the bladder. The metabolic and physiologic model parameters were randomly varied, via Monte Carlo simulations, to reproduce interindividual variability. The sampling means for most parameters were scaled from values developed by Kadlubar et al. (Cancer Res., 51: 4371, 1991) for dogs; variances were obtained primarily from published human data (e.g., measurements of ABP N-oxidation, and arylamine N-acetylation in human liver tissue). In 500 simulations, theoretically representing 500 humans, DNA-adduct levels in the bladder of the most susceptible individuals are ten thousand times higher than for the least susceptible, and the 5th and 95th percentiles differ by a factor of 160. DNA binding for the most susceptible individual (with low urine pH, low N-acetylation and high N-oxidation activities) is theoretically one million-fold higher than for the least susceptible (with high urine pH, high N-acetylation and low N-oxidation activities). The simulations also suggest that the four factors contributing most significantly to interindividual differences in DNA-binding of ABP in human bladder are urine pH, ABP N-oxidation, ABP N-acetylation and urination frequency.

Molecular genotyping for N-acetylation polymorphism in Japanese patients with colorectal cancer

BACKGROUND

N-acetylation polymorphism has been documented as a representative pharmacogenetic trait, and also has been implicated ecogenetically in an individual's susceptibility to cancer. However, there still remains controversy concerning the association between colorectal cancer and N-acetylation polymorphism.

METHODS

A newly established molecular genotyping method using polymerase chain reaction-based restriction fragment length polymorphism to analyze the distribution of polymorphism in a large group of Japanese patients with colorectal cancer was used.

RESULTS

Based on an analysis of 234 Japanese patient with colorectal cancer and 329 healthy control subjects, no significant difference was observed in either the distribution of acetylator phenotypes or of allele frequencies between the two groups. In addition, no significant difference in their distribution was found based on the age at which cancer was first detected, the location of tumors, or the histopathologic features.

CONCLUSIONS

N-acetylation polymorphism does not appear to be implicated crucially as a genetic trait affecting an individual's susceptibility to colorectal cancer.

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.

Biomarkers and molecular epidemiology of occupationally related cancer

Effective prevention of cancer requires sensitive early warning systems to identify groups, and ultimately individuals, who are at high risk of developing cancer and to accurately estimate the magnitude of their risk. Incorporated with molecular epidemiologic studies, biologic markers have the potential to provide quantitative human data on the biologically effective dose of carcinogens, resultant molecular effects, and genetic/acquired factors that modulate these effects. Clearly, this information is directly relevant to risk identification and to risk quantification.

The effects of high dietary concentrations of saccharin on in vitro metabolism of xenobiotics in rats

The effects of feeding male rats a diet containing 7.5% sodium saccharin on drug metabolism in vitro were studied using both one- and two-generation protocols. Saccharin administration did not affect the hepatic concentrations of total cytochrome P-450, cytochrome b5, cytochrome P-450 reductase, aryl hydrocarbon hydroxylase activity or glutathione content but caused a statistically significant increase in dimethylnitrosamine-N-demethylase activity. This increase was detectable in neonatal animals treated using a two-generation protocol. Administration of the sodium, potassium or calcium salts of saccharin or its acid form at 5% in the diet to male rats for 8 wk each caused a significant increase in dimethylnitrosamine-N-demethylase activity. Fasting control and saccharin-treated male rats for 24 hr before the dimethylnitrosamine-N-demethylase assay increased the activity of this enzyme in both groups slightly. The observed increase in dimethylnitrosamine-N-demethylase activity recorded in both male and female rats fed diets containing saccharin after 8 to 12 wk of treatment was reversed when the animals were given control diet for 4 wk.

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.

An arylamine acetyltransferase (AT-I) from Syrian golden hamster liver: cloning, complete nucleotide sequence, and expression in mammalian cells

A cDNA clone (designated hamAT101) encoding an arylamine acetyltransferase, AT-1, was isolated from a hamster liver lambda gt11 cDNA library using a specific polyclonal antibody raised against AT-1. The cloned cDNA insert consisted of 1181 nucleotides, including an open reading frame of 870 nucleotides encoding 290 amino acid (Mr 33,503). The isolated cDNA displayed high sequence similarity to those of chicken, rabbit, and human acetyltransferases. In Northern blots, the hamAT101 cDNA probe hybridized to an RNA band of 18S in the livers of both slow and rapid acetylator phenotypes. To confirm that hamAT101 cDNA encodes the monomorphic but not the polymorphic protein, the isolated cDNA was expressed in monkey kidney cells (COS-1 cells) using the vector p91023(B). A protein with a molecular weight similar to that of AT-1 was detected upon Western blotting in the 9000 x g supernatant from the transfected cells. The activity toward four different substrates of the 9000 x g supernatant was also examined. In agreement with the results of purified AT-1, the cDNA-expressed protein exhibited a high capacity for N-acetylation of 4-aminoazobenzene and 2-aminofluorene, and O-acetylation of 2-hydroxyamino-6-methyldipyrido [1,2-a:3',2'-d] imidazole, whereas no activity was found for the N-acetylation of p-aminobenzoic acid. These results, in addition to the RNA blot hybridization, indicate that hamAT101 encodes the hamster acetyltransferase AT-1.

Interspecies comparisons in toxicology: the utility and futility of plasma concentrations of the test substance

A classical dilemma in toxicology is how the dose administered relates to the dose delivered to the target site. Plasma concentrations of the test substance may be misleading since the concentration of any given substance in the plasma may not be representative of its concentration in tissues. Furthermore, a given tissue concentration of a xenobiotic can evoke responses which are highly species-dependent. While evaluating toxicity data within one species, plasma concentrations reflect the effects of route of administration, bioavailability, dose level, multiple dosing, age, gender, etc. However, when toxicity data is compared across species, the relevance of plasma concentrations depends on the nature of the toxicity. Reversible, pharmacodynamic effects often correlate with plasma concentrations, although there may be marked interspecies differences in dose-response relationships. Irreversible effects, if pharmacodynamic in origin, often correlate better with the intensity/duration of the pharmacodynamic response, rather than with plasma concentration. On the other hand, irreversible effects, if chemically mediated, may not correlate at all with plasma concentration, the lesions being caused by reactive metabolites of fleeting existence, which rarely survive long enough to leave their site of synthesis. They cannot be measured in the plasma nor predicted from plasma concentrations of the parent xenobiotic. The limitations of plasma concentrations in interpreting the toxicology of substances which are tissue-sequestered, which are subject to pharmacogenetic factors, or which show plasma concentrations that are not proportional to dose are also discussed. Mention is made of possible alternatives to plasma concentrations in assessing exposure in toxicology studies.

N-acetylation in healthy and diseased children

Acetylation capacity was examined in three groups of Czech children by measuring the plasma and urine concentrations of sulphamethazine and its acetylated metabolite 6 h after an oral test dose of 20 mg/kg sulphamethazine. Amongst 82 healthy children aged 4-15 y there were 32 (39%) fast acetylators; there was no significant difference between the number of boys and girls, or between children over or less than 6 years of age. In 41 patients aged 3-15 y with phenylketonuria, the acetylation indices showed a significantly higher proportion of fast acetylators - 24 (58.5%) using plasma measurements and 29 (70.7%) using urine data. In them the ratio between slow and fast acetylators was inverted compared to normal children. The preponderance of fast acetylators was greater in boys than in girls and in children over 6 years of age. An increased acetylation capacity in patients with phenylketonuria was apparent even in individuals classified as slow acetylators, because in them the plasma concentration of the acetylated metabolite was higher than in control acetylators. Amongst 48 young patients (5-15 y) with insulin-dependent diabetes there were 19 (39.6%) fast and 29 (60.4%) slow acetylators, which corresponded well to the phenotype distribution in control children. This did not support the suggested association between the fast acetylator phenotype and Type I diabetes.

Familial cancer syndromes and clusters

Familial aggregation has been reported for virtually every form of cancer in humans. In general, close relatives of a cancer patient appear to have a twofold to threefold increase in risk for that tumor. Among cancer families, however, the level of excess risk is heterogeneous and ranges up to 1000-fold. Familial clusters of cancer are often due to inherited susceptibility, but environmental influences and chance association also must be considered. The effect of chance is large, due to the 50% lifetime risk of developing cancer that is present in the general U.S. population. Thus, a family history of cancer is the rule rather than the exception, and special studies are needed to distinguish predisposition from chance. An inherited susceptibility to cancer often becomes apparent through the occurrence of the same neoplasm among multiple blood relatives. These neoplasms tend to occur at earlier ages than usual, to appear bilaterally in paired organs, and to develop in multiple primary foci within the predisposed organ. Hereditary cancers can also develop as multiple primary tumors in organs that share the same embryological origins, as in the multiple endocrine neoplasia (MEN) syndromes. In addition, neoplasia occurs as a feature of diverse inherited diseases, such as neurofibromatosis types 1 and 2, which predispose to tumors of the peripheral nerves and brain. Recent advances in molecular biology have greatly enhanced the importance of studying cancer families. Newly developed molecular probes have been applied to map the loci of several human cancer genes. The studies have also revealed a new class of human oncogenes, the tumor suppressor genes. These genes normally function by suppressing the tumor phenotype. When inactivated or deleted in germinal cells, they can be transmitted to subsequent generations and predispose to cancer among carriers in the family. At the molecular level, these carriers have inherited a structural abnormality in one allele of a recessive oncogene, and loss of the second allele at the locus results in tumor development. The first tumor suppressor that has been isolated is the retinoblastoma gene on chromosome 13q14. Studies indicate that this gene is involved in the development of many more human cancers than had been appreciated previously on the basis of clinical observations. Presently, the identification of cancer families can be applied to genetic counseling, the in-utero diagnosis of carriers, and early disease detection. In familial cancers that are triggered by environmental carcinogens, patient education regarding the avoidance of harmful exposures can help prevent or delay the onset of neoplasia.

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.

Plasma trehalase activity and diabetes mellitus

Trehalase is an enzyme which hydrolyzes the disaccharide trehalose, yielding glucose. It is widespread in nature and found in various human tissues as well as in human plasma. The synthesis and degradation of its substrate trehalose have been considered as being implicated in carbohydrate transport mechanisms. Trehalase activity has been examined in both normal subjects and diabetic patients. In the normal subjects, the frequency histogram of the enzyme activity is bimodal, indicating the existence of genetic polymorphism. The proposed model of a single autosomal locus with two alleles has been verified, with 27% of the population tested belonging to the "low-activity" phenotype and 73% being of the "high-activity" phenotype. Males have higher mean plasma trehalase activity than females. Apparently, the reverse appears to be the case in the diabetic subjects. The mean value for all nondiabetics and that of diabetics were computed and the difference was found to be statistically significant (F = 7.02, N1 = 3, N2 = 56, P less than 0.01). An experiment showed that neither the abnormally high concentration of glucose in diabetics nor any other constituent of the diabetic plasma caused an increase in plasma trehalase activity (t = 0.0724, P greater than 0.10). A Woolf and Haldane test to determine association of diabetes mellitus and plasma trehalase phenotype indicated a highly significant association with the high-activity phenotype (chi 2 = 18.5350, P less than 0.01). Thus the inference is that people with high plasma trehalase activity are more prone to develop diabetes mellitus than people with low enzyme activity.

Acetylation phenotype in abstinent alcoholics

No association between acetylation phenotype and alcoholism was discovered. Fifty-four percent of both the alcoholic patients and healthy volunteers were rapid acetylators. Acetylation phenotyping is not helpful to the investigation of the genetics of alcoholism.

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.

Genetic factors in toxicology: implications for toxicological screening

Methods of assessing the toxicity of xenobiotics have improved substantially during the last decade. However, as compounds become generally safer, the problem of individual variation in response assumes increasing relative importance. Environmental factors such as age, health and nutritional status, and interactions with other xenobiotics account for some of this variation, but genetic differences between individuals and races have important implications. In a few cases, Mendelian loci which control drug susceptibility (e.g., to isoniazid) have been described. However, in most cases the exact mode of inheritance has not yet been determined due to the problems of carrying out genetic studies in man. It is well established that many loci that are polymorphic in man are also so in laboratory animals, so much of this genetic variation should be picked up in preclinical screening, and could be used to more accurately predict potential variation in toxicity in man. Unfortunately, most toxicologists use only a single stock of laboratory animals, which does not show whether the response to a given xenobiotic is under genetic control. The design of animal tests would be improved by using more than one strain of genetically defined animals, and by paying more attention to genetic variation in responses to xenobiotics, both in animals and man.

Risk of second malignancy after cancers of the renal parenchyma, renal pelvis, and ureter

Risk of second primary malignancy was assessed in a population-based survey of persons who developed cancers of the renal parenchyma, renal pelvis, or ureter in Connecticut during the period 1935-1982. Among 4176 patients with a first primary tumor of the renal parenchyma, a second cancer was reported in 219 (5%), yielding a small but significantly elevated relative risk (RR) of 1.2, which reflects excesses for cancers of the bladder, kidney, and lymphatic-hematopoietic system. Among 939 patients with a first primary tumor of the renal pelvis or ureter, a second cancer was reported in 155 (17%), associated with a significantly elevated RR of 2.7. This resulted mainly from a 21-fold increase in risk for bladder cancer, although significant excesses were also found for lung and prostate cancers, and metachronous cancers of the renal pelvis and ureter. These associations seem to reflect the multicentric behavior of tumors arising in the urinary tract, the role of cigarette smoking, and host factors yet to be defined, and some degree of heightened medical surveillance and detection of tumors, especially in the same organ system.

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.

Susceptibility in urinary bladder cancer: acetyltransferase phenotypes and related risk factors

The excess proportion of slow acetylator phenotypes has previously been found among bladder tumour patients. Among 228 bladder tumour patients in the present study, the slow acetylator phenotype was significantly associated to the unskilled worker and T3-T4 tumour, and to a certain extent to tobacco smoking. It is suggested that slow acetylator subjects are more susceptible to bladder tumour development when exposed to arylamines.