Combined effect of smoking and inherited polymorphisms in arylamine N-acetyltransferase 2, glutathione S-transferases M1 and T1 on bladder cancer in a Tunisian population

Uncovering the epidemiology of bladder cancer in the Arab world: A review of risk factors, molecular mechanisms, and clinical features

Objective

Bladder cancer (BC) is a significant public health concern in the Middle East and North Africa, but the epidemiology and clinicopathology of the disease and contributors to high mortality in this region remain poorly understood. The aim of this systematic review was to investigate the epidemiological features of BC in the Arab world and compare them to those in Western countries in order to improve the management of this disease.

Methods

An extensive electronic search of the PubMed/PMC and Cochrane Library databases was conducted to identify all articles published until May 2022, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. A total of 95 articles were included in the final analysis after title, abstract, and full-text screening, with additional data obtained from the GLOBOCAN and WHO 2020 databases.

Results

Most of the included articles were case-control studies examining the risk factors and molecular mechanisms of BC. These studies originated from 10 different countries, with Egypt being the most active contributor. While BC in the Arab world shares some common risk factors with Western countries, such as smoking and occupational exposure, it also exhibits unique features related to schistosomiasis. The high mortality rates in this region are alarming and can be attributed to various factors, including the prevalence of smoking, the impact of schistosomiasis, a combination of genetic and socioeconomic factors, treatment shortages, and limited access to care or inadequate assessment of the quality of care.

Conclusion

Despite the relatively low incidence of BC in Arab countries, the mortality rates are among the highest worldwide. BC tends to be more aggressive in the Arab world, making it essential to implement strategies to address this burden.

N-acetyltransferase 2 polymorphism is associated with bladder cancer risk: An updated meta-analysis based on 54 case-control studies

OBJECTIVE

N-acetyltransferase 2 (NAT2) polymorphism could participate in the metabolism of carcinogens through regulating the activity of a series of critical enzymes. However, the effects of NAT2 polymorphism on bladder cancer (BCa) risk were still inconclusive. In order to illustrate whether NAT2 polymorphism may influence the susceptibility to BCa, we conducted this updated meta-analysis.

MATERIALS AND METHODS

Databases including PubMed, Medline, Embase, Web of Science, Cochrane Library, and China National Knowledge Infrastructure(CNKI) were systematically retrieved and we applied MetaGenyo to perform final meta-analysis. Odds ratios (ORs) as well as 95% confidence intervals (CIs) were calculated and Bonferroni method was applied to correct the P-value for multiple comparisons. The registration of this study protocol is at PROSPERO and ID is CRD42019133957.

RESULTS

Ultimately, 54 case-control studies were identified for final meta-analysis (13343 BCa cases and 18,586 controls). Overall analysis indicated that the slow genotype in NAT2 polymorphism was obviously associated with BCa risk (P_Bonferroni < 0.001). Subgroup analyses demonstrated that significant risk with the slow genotype was observed in Caucasians, Asians, smokers, non-exposed individuals, high grade bladder cancer (HGBC) patients and muscle-invasive bladder cancer (MIBC) patients. In addition, the intermediate NAT2 genotype was revealed to increase the BCa risk of Asians and transitional cell carcinoma (TCC) patients. However, no correlation was identified in Africans with the NAT2 polymorphism.

CONCLUSIONS

The slow NAT2 genotype was identified to be the risk genotype for BCa. The intermediate genotype could serve as the candidate risk genotype. The gene-smoking interaction with NAT2 polymorphism might accelerate the tumor progression.

Distribution and Role of N-acetyltransferase 2 Genetic Polymorphisms in Bladder Cancer Risk in a Lebanese Population

Background:

In Lebanon, bladder cancer (BC) has an unusually high prevalence. Individuals who are exposed to aromatic amines from smoking or certain occupations and carrying the slow N-acetyl transferase 2 (NAT2) acetylator’ phenotype may be at a higher risk.

Methods:

Data and DNA from 115 Lebanese BC cases and 306 controls were examined. Ten NAT2 single nucleotide polymorphisms were genotyped, seven of which were then included in haplotype and phenotype analysis.

Results:

BC patients were more likely to be males (87.8% vs. 54.9%) and current smokers (60.9% vs. 26.5%) when compared to controls. In both groups, most participants had the slow NAT2 acetylator phenotype (66.1% of BC cases vs 62.7% of controls; P=0.302) with the NAT2*5B and *6A haplotypes being the most common. The odds ratio (95%CI) of having BC among slow NAT2 acetylators was 1.157 (0.738-1.815) and remained non-significant after adjustment [1.097 (0.666-1.806)]. Sensitivity analysis with a subgroup of 113 cases and 84 controls for which occupational history was available revealed a statistically significant association between slow NAT2 acetylators and BC in females only. The sample size was however very small and the CI quite wide.

Conclusions:

This is the first study to evaluate the distribution of NAT2 haplotypes and their potential role in BC in a Lebanese population. The absence of any significant association may be due to the relatively small sample size, the unavailability of matching by gender, and the lack of evaluation of genetic interactions with extent of active and passive smoking, exposure to environmental pollutants, diet, and other genes. The potential association limited to females needs further evaluation.

Distribution of xenobiotic metabolising enzyme genotypes in different Tunisian populations

BACKGROUND

The N-acetyltransferase 2 (NAT2) and glutathione transferase enzymes play a crucial role in the metabolism of xenobiotics. Genetic polymorphisms affecting these enzymes can modify their activities with an effect on individual susceptibility for different pathologies. These metabolic phenotypes occur with varying prevalence in different populations.

AIM

This study sought to analyse the prevalence of important allelic variants of NAT2, GSTM1 and GSTT1 in different Tunisian populations and compare them to other previously reported data.

SUBJECTS AND METHODS

A total of 253 unrelated subjects from different Tunisian populations participated in this study. Subjects were examined with respect to the frequency of slow NAT2, GSTM1*0 and GSTT1*0 genotypes.

RESULTS

The frequency of 'slow' NAT2, GSTM1*0 and GSTT1*0 genotypes in the Tunisian population were, respectively, estimated at 23.3%, 53.75% and 29.24%. The frequency of slow NAT2 and GSTM1*0 genotypes were significantly different between the North, Centre and South of Tunisia. However, this study doesn't report any significant differences in the genotype distribution between Cosmopolitan, Arab and Berber populations.

CONCLUSIONS

In conclusion, these data indicate that the Tunisian population is highly heterogenic and, therefore, a strict definition of the populations involved in studies investigating the clinical effect of polymorphisms is required.

Polymorphisms in NAT2 (N-acetyltransferase 2) gene in patients with systemic lupus erythematosus

OBJECTIVE

To investigate potential associations of four substitutions in NAT2 gene and of acetylator phenotype of NAT2 with systemic lupus erythematosus (SLE) and clinical phenotypes.

METHODS

Molecular analysis of 481C>T, 590G>A, 857G>A, and 191G>A substitutions in the NAT2 gene was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, from DNA extracted from peripheral blood samples obtained from patients with SLE (n=91) and controls (n=97).

RESULTS AND CONCLUSIONS

The 857GA genotype was more prevalent among nonwhite SLE patients (OR=4.01, 95% CI=1.18-13.59). The 481T allele showed a positive association with hematological disorders that involve autoimmune mechanisms, specifically autoimmune hemolytic anemia or autoimmune thrombocytopenia (OR=1.97; 95% CI=1.01-3.81).

Involvement of genetic factors and lifestyle on the occurrence of colorectal and gastric cancer

Gastrointestinal cancers are diseases due to genetic and environmental factors. In this present work we are interested in the influence of environmental factors on the occurrence of gastrointestinal cancers in Tunisian population. We found that the MTHFR C677T polymorphism was associated with colorectal cancer (P<0.04) but not with gastric cancer. In addition, we have shown that alcohol is associated with an increased risk of colorectal cancer, but the consumption of cheese is protective. Furthermore, we studied tymidylate synthase gene involved in folate metabolism. Indeed, we observed that the 5'UTR repeat polymorphism, is associated with risk of colorectal cancer, and the LL genotype (3R/3R) was significantly frequent in patients with colorectal cancer compared to controls (p=0.002; OR=2.7, 95% CI=1.4-5.2). While we found that SL genotype (2R/3R) was associated with risk of gastric cancer (p=0.015; OR=4.46, 95% CI=1.08-19-64). This polymorphism was also shown to be a predictor of response to chemotherapy based 5'-fluorouracil. However, we are interested in studying the GPX -1 gene involved in phase I metabolism of xenobiotics. We therefore evaluated the risk of TT genotype in GPX-1 C599T polymorphism with the onset of gastric cancer (P=0.0001; OR=5.41, 95% CI 1.98 to 15.58) and colorectal cancer (P=0.00008; OR=4.40, 95% CI 1.93 to 10.27). To clarify the possible relationship between environmental factors and the occurrence of the disease, we studied the additive effect of risk genotype and behavior in order to highlight the interaction of gene-environment factors.

The relationship between GSTA1, GSTM1, GSTP1, and GSTT1 genetic polymorphisms and bladder cancer susceptibility: A meta-analysis

BACKGROUND

Previous studies have investigated the relationship between GSTA1, GSTM1, GSTP1, and GSTT1 polymorphisms and bladder cancer (BCa) susceptibility, respectively, but the results remain inconsistent. So, we conducted this meta-analysis including 79 case-control studies to explore such relationships.

METHODS

We searched PubMed, EMBASE, Cochrane library, Web of Science, and CNKI for relevant available studies. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were implemented to evaluate the intensity of associations. Publication bias was estimated using Begg funnel plots and Egger regression test. To assess the stability of the results, we used sensitivity analysis with the method of calculating the results again by omitting 1 single study each time. Between-study heterogeneity was tested using the I statistic.

RESULTS

No significant association between GSTA1 polymorphism and BCa susceptibility (OR = 1.05, 95% CI 0.83-1.33) was noted. Besides, meaningful association between individuals who carried the GSTM1 null genotype and increased BCa risk was detected (OR = 1.39, 95%CI 1.28-1.51). When stratified by ethnicity, significant difference was found in both Caucasian (OR = 1.39, 95% CI 1.23-1.58) and Asian populations (OR = 1.45, 95% CI 1.31-1.61). Moreover, in the subgroup analysis by source of controls (SOC), the results were significant in both hospital-based control groups (OR = 1.49, 95% CI 1.35-1.64) and population-based control groups (OR = 1.21, 95% CI = 1.07-1.37). Additionally, the analysis revealed no significant association between GSTP1 polymorphism and BCa risk (OR = 1.07, 95% CI 0.96-1.20). What is more, significant associations between GSTT1 polymorphism and BCa susceptibility were discovered (OR = 1.11, 95% CI 1.00-1.22). In the subgroup analysis by ethnicity, significant associations between GSTT1 null genotype and BCa risk were observed only in Caucasians (OR = 1.25, 95% CI 1.09-1.44). Furthermore, when stratified by SOC, no obvious relationship was found between the GSTT1 null genotype polymorphism with hospital-based population (OR = 1.11, 95% CI 0.97-1.28) or population-based population (OR = 1.10, 95% CI 0.96-1.27).

CONCLUSION

This study suggested that GSTM1 null genotype and GSTT1 null genotype might be related to higher BCa risk, respectively. However, no associations were observed between GSTA1 or GSTP1 polymorphisms and BCa susceptibility.

Inter-ethnic differences in genetic polymorphisms of xenobiotic-metabolizing enzymes (CYP1A1, CYP2D6, NAT1 and NAT2) in healthy populations: correlation with the functional in silico prediction

Several studies have shown that many polymorphisms of the xenobiotic-metabolizing enzymes (XME) affect either enzymatic functions or are associated with various aspects of human health. Owing to the presence of these single nucleotide variants (SNVs), differences in detoxification capacity have been observed between many ethnicities. The aim of this investigation was to study the prevalence of four polymorphisms in XME among various ethnic groups. Attention was focused on polymorphisms of CYP2D6 (rs1058172, G>A, p.Arg365His), CYP1A1 (rs4646421, c.-26-728C>T), NAT1 (rs4921880, c.-85-1014T>A) and NAT2 (rs1208, A>G, p.Arg268Lys). These polymorphisms were analyzed in 261 healthy Tunisians individuals in comparison with different ethnic backgrounds from hapmap database. In addition, in silico functional prediction was also performed to determine the loss of function variants. Our results demonstrated that population's origins widely affect the genetic variability of XME enzymes and Tunisians show a characteristic pattern. In silico predictions showed a deleterious effect for p.Arg268Lys substitution on CYP2D6 function, findings confirmed its key role played in cancer susceptibility. These data show that detoxification genes structures depend on the studied population. This suggests that ethnic differences impact on disease risk or response to drugs and therefore should be taken into consideration in genetic association studies focusing on XME enzymes. Our results provide the first report on these SNV in Tunisian population and could be useful for further epidemiological investigations including targeted therapy.

Do GSTT1 and GSTM1 polymorphisms influence intoxication events in individuals occupationally exposed to pesticides?

This study evaluated the variability of GSTM1 and GSTT1 polymorphisms in individuals occupationally exposed to pesticides in ten Goias municipalities that present intense agricultural activity. We evaluated blood samples of 235 individuals, which 120 were rural workers occupationally exposed to pesticides and 115 formed the control group, analyzing GST polymorphisms by quantitative polymerase chain reaction (qPCR).The exposed group consisted of 111 men and nine women only getting an average of 39 ± 9 years. These workers were from ten rural municipalities situated at Goias state. It was found that 18 % of the exposed individuals had the GSTT1 null genotype and 49 % had the GSTM1 null genotype, and 10 % had both null genotypes. Data as intoxication (42 %), use of Personal Protection Equipment (PPE; 52 %) and if the worker prepared the pesticide (7 %), or if just applied the pesticide (22 %) or if the worker prepared and applied (71 %) have all been correlated with genetic polymorphisms. There were no statistically significant differences between the GSTM1 and GSTT1 polymorphisms between control and exposed groups. Finally, we could not associate a null GSTT1 or null GSTM1 polymorphisms or both to intoxication events caused by pesticides, but instead we presented the importance to use PPE to prevent such harm, once we found a statistically significant association between the use of PPE and events of intoxication (p ≤ 0.001).

Association of CYP1A1 and CYP2D6 gene polymorphisms with head and neck cancer in Tunisian patients

The purpose of this study was to investigate the relationship between head and neck cancer (HNC) and environmental agents and polymorphisms in CYP1A1, CYP2D6, NAT1 and NAT2 metabolic enzymes genes. To the best of our knowledge, this is the first report on polymorphisms in CYP1A1 6310C>T, CYP2D6 Arg365His, NAT1 52936A>T and NAT2 Arg268Lys (NAT2*12A) genes and susceptibility to HNC in Tunisian population. We study the prevalence of these polymorphisms in 169 patients with HNC and 261 control subjects using polymerase chain reaction based methods in a Tunisian population. We detected an association between HNC and CYP1A1 6310C>T (TT) and CYP2D6 Arg365His (His/His) variant carriers (OR 1.75, P = 0.008 and OR 1.66, P = 0.016, respectively). No association was found between the polymorphisms genotypes of NAT1 52936T>A and NAT2 Arg268Lys and risk of HNC. An association between HNC and CYP1A1 (TT) genotype was found among patients with smoking (P = 0.011) and drinking habit (P = 0.009). The combinations of NAT1 (AT or AA) and NAT2 (AA) at-risk genotypes increased HNC risk (OR 4.23, P = 0.005 and OR 3.60, P = 0.048, respectively). However, the combinations of CYP1A1 (AA) and CYP2D6 (CC) genotypes decreased risk of HNC (OR 0.20; P = 0.006). Genetic polymorphisms in CYP1A1 and CYP2D6 may significantly associate with HNC in the Tunisian population. The results of this study suggest a possible gene-environment interaction for certain carcinogen metabolizing enzymes, but larger studies that fully evaluate the interaction are needed.

Association of NAT2 polymorphisms with type 2 diabetes in a population from Bosnia and Herzegovina

BACKGROUND AND AIMS

N-acetyltransferase 2 (NAT2) is a drug-metabolizing enzyme, which is genetically variable in human populations. Polymorphisms in the NAT2 gene have been associated with drug efficacy and toxicity as well as disease susceptibility. Recently, an association of NAT2 gene variation with risk of type 2 diabetes mellitus (T2DM) has been suggested. This is the first study performed in a population from Bosnia and Herzegovina (BH) in which the frequency of two common NAT2 polymorphisms, 341T>C (NAT2*5) and 590G>A (NAT2*6) was determined in diabetic patients.

METHODS

The frequency of the NAT2*5 (341T>C) and NAT2*6 (590G>A) polymorphisms was analyzed by employing TaqMan SNP Genotyping Assays (Applied Biosystems) in a group of 63 patients with T2DM and 79 nondiabetic subjects.

RESULTS

Our data demonstrated that the frequencies of NAT2*5 (341T>C) and NAT2*6 (590G>A) polymorphisms in BH population were in line with the Caucasians genotype data. The NAT2*5 and NAT2*6 alleles were in high linkage disequilibrium (D' = 0.969). Strinkingly, there was a significant difference in genotype frequencies for NAT2*5 (p <0.05) and NAT2*6 (p <0.001) polymorphisms between diabetic and nondiabetic subjects. NAT2*5 polymorphism was associated with 2.4-fold increased risk for developing T2DM (adjusted OR = 2.40, 95% CI = 1.10-5.25, p = 0.028). On the contrary, NAT2*6 variant significantly decreased by 5-fold susceptibility to the disease (adjusted OR = 0.20, 95% CI = 0.09-0.43, p <0.001).

CONCLUSIONS

Our data demonstrated that NAT2 genetic variation appeared to be an important risk factor in development of T2DM.

Possible association of NAT2 polymorphism with laryngeal cancer risk: an evidence-based meta-analysis

PURPOSE

N-acetyltransferase 2 (NAT2) plays an important role in the metabolism of various potential carcinogens, which can be subdivided into rapid and slow acetylation phenotype according to the different genotypes. A number of studies have been devoted to the association of NAT2 polymorphism with susceptibility to laryngeal carcinoma; however, the results were inconsistent and inconclusive. The aim of the present study was to conduct a meta-analysis assessing the possible association of NAT2 polymorphism with laryngeal cancer risk.

METHODS

The relevant studies were identified through a search of PubMed, Embase, ISI Web of Knowledge, and Chinese National Knowledge Infrastructure until February 2011 and selected on the basis of the established inclusion criteria for publications, and then a meta-analysis was performed to quantitatively summarize the association of NAT2 polymorphism with laryngeal cancer susceptibility.

RESULTS

Seven studies were included in the present meta-analysis, which described a total of 980 laryngeal cancer cases and 1,487 controls. The overall odds ratio (OR) for NAT2 slow and rapid acetylators was 0.99 (95% CI = 0.71-1.38) and 1.01 (95% CI = 0.72-1.40), respectively. When stratifying for race, the pooled ORs for NAT2 slow acetylator were 1.99 (95% CI = 1.10-3.63) in Asians and 0.85 (95% CI = 0.62-1.15) in Caucasians, and the pooled ORs for NAT2 rapid acetylator were 0.50 (95% CI = 0.28-0.91) in Asians and 1.18 (95% CI = 0.87-1.60) in Caucasians.

CONCLUSIONS

This meta-analysis suggested that there was overall lack of association between NAT2 polymorphism and laryngeal cancer risk; however, NAT2 slow acetylation may contribute to a risk factor for laryngeal cancer in Asians but not in Caucasians.

Glutathione S-transferase M1 polymorphism and bladder cancer risk: a meta-analysis involving 33 studies

Glutathione S-transferase M1 ( GSTM1) might be involved in inactivation of procarcinogens that contribute to the genesis and progression of cancers. GSTM1 null status has been extensively studied as a risk factor in bladder cancer susceptibility. The aim of this study is to evaluate the role of GSTM1 null genotype in bladder cancer risk. All available studies were considered in this meta-analysis, including 7301 cases and 9405 controls from 33 studies. Significantly increased risk was detected between GSTM1 deletion and bladder cancer susceptibility in all subjects (odds ratio [OR] = 1.409 [1.267–1.568], P < 0.001). The same patterns were observed in Caucasians (OR = 1.434 [1.212–1.697], P < 0.001) and Asians (OR = 1.485 [1.295–1.704], P < 0.001). When stratified with study design, a positive association was also found in hospital-based studies (OR = 1.552 [1.382–1.744], P < 0.001), but no association in population-based ones (OR = 1.088 [0.970–1.221], P = 0.151). In summary, our meta-analysis suggested that GSTM1 null status is associated with a high increase in the risk of bladder cancer, and further studies based on population design are necessary to confirm our conclusion.

Polymorphisms of glutathione S-transferase μ and θ, MDR1 and VEGF genes as risk factors of bladder cancer: a case-control study

OBJECTIVE

The present study was aimed at examining the local distribution of GSTM1, GSTT1, MDR1, and VEGF gene polymorphisms as possible risk factors contributing to the development of bladder cancer among the population from Canary Islands, Spain.

MATERIALS AND METHODS

The genotypes were determined by PCR-based methods in a hospital-based case-control study consisting of 119 cases and 110 controls. The socio-demographic and clinicopathologic data were collected, including the smoking habits of the population covered in the study.

RESULTS

The observed allelic frequencies were (%): GSTM1-GSTT1, (positive) 54 and (null) 46 in cases, and 65 and 35, respectively, in controls (P = 0.144); MDR1 C3435T, (C) 57 and (T) 43 in cases, and 54 and 46, respectively, in controls (P = 0.633); VEGF A2578C, (A) 40 and (C) 60 in cases, and 51 and 49, respectively, in controls (P = 0.221). Among Canary Islands subjects, GSTT1-null genotype appeared as a significant risk factor for bladder cancer (odds ratio (OR) 2.0; 95% confidence interval (CI), 1.0-3.7; P = 0.041), in multivariate analysis adjusted by age and smoking habits. No statistical changes in genotype distribution of GSTM1, MDR1 C3435T, and VEGF A2578C gene polymorphisms were observed between cases and controls. The distribution of the initial clinical stage, clinical grade, or recurrence status was not significantly different among the polymorphic variants in the case group (P = NS).

CONCLUSIONS

Subjects with the GSTT1-null genotype might be at an increased risk of bladder cancer in Canary Islands, Spain. However, extensive studies are required for accurate confirmation of these results.

NAT2 polymorphism and gastric cancer susceptibility: a meta-analysis

BACKGROUND AND AIMS

N-acetyltransferase 2 (NAT2) is a polymorphic enzyme that plays an important role in the metabolism of various potential carcinogens. NAT2 can be subdivided into rapid and slow acetylation phenotype according to the different genotypes. Studies investigating the association between NAT2 polymorphisms and gastric cancer risk in humans showed conflicting results. The aim of this study was to conduct a meta-analysis assessing the association of NAT2 acetylation phenotype with risk of gastric cancer.

METHODS

Relevant studies were identified through a search of Embase, ISI Web of Knowledge, Medline and Chinese Biomedicine Database until January 2010. A meta-analysis was conducted to quantitatively summarize association of NAT2 acetylation phenotype with GC susceptibility.

RESULTS

Thirteen studies were included in the present meta-analysis, which described a total of 2,391 gastric cancer cases and 3,237 controls. The combined ORs for NAT2 slow or rapid acetylator and gastric cancer risk were 1.05 (95% CI 0.810-1.35) and 0.96 (95% CI 0.74-1.23), respectively. When stratifying for race and Lauren's classification, results also showed no significant association in genotype distribution between gastric cancer and control.

CONCLUSIONS

No association is found between NAT2 acetylation status and gastric cancer risk in this meta-analysis.

GSTM1 null and NAT2 slow acetylation genotypes, smoking intensity and bladder cancer risk: results from the New England bladder cancer study and NAT2 meta-analysis

Associations between bladder cancer risk and NAT2 and GSTM1 polymorphisms have emerged as some of the most consistent findings in the genetic epidemiology of common metabolic polymorphisms and cancer, but their interaction with tobacco use, intensity and duration remain unclear. In a New England population-based case-control study of urothelial carcinoma, we collected mouthwash samples from 1088 of 1171 cases (92.9%) and 1282 of 1418 controls (91.2%) for genotype analysis of GSTM1, GSTT1 and NAT2 polymorphisms. Odds ratios and 95% confidence intervals of bladder cancer among New England Bladder Cancer Study subjects with one or two inactive GSTM1 alleles (i.e. the 'null' genotype) were 1.26 (0.85-1.88) and 1.54 (1.05-2.25), respectively (P-trend = 0.008), compared with those with two active copies. GSTT1 inactive alleles were not associated with risk. NAT2 slow acetylation status was not associated with risk among never (1.04; 0.71-1.51), former (0.95; 0.75-1.20) or current smokers (1.33; 0.91-1.95); however, a relationship emerged when smoking intensity was evaluated. Among slow acetylators who ever smoked at least 40 cigarettes/day, risk was elevated among ever (1.82; 1.14-2.91, P-interaction = 0.07) and current heavy smokers (3.16; 1.22-8.19, P-interaction = 0.03) compared with rapid acetylators in each category; but was not observed at lower intensities. In contrast, the effect of GSTM1-null genotype was not greater among smokers, regardless of intensity. Meta-analysis of the NAT2 associations with bladder cancer showed a highly significant relationship. Findings from this large USA population-based study provided evidence that the NAT2 slow acetylation genotype interacts with tobacco smoking as a function of exposure intensity.

Environmental factors and genetic susceptibility promote urinary bladder cancer

Cancer of the urinary bladder is the second most common malignancy of the genitourinary tract, currently accounting for up to 5% of all newly diagnosed tumours in the western world. Urinary bladder carcinogenesis seems to develop from the interaction of environmental exposure and genetic susceptibility. Smoking, specific industrial chemicals, dietary nitrates and arsenic represent the most important exogenous risk factors. Chromosomal abnormalities, silencing of certain genes by abnormal methylation of their promoter region, alterations in tumour suppressor genes and proto-oncogenes that induce uncontrolled cell proliferation and reduced apoptosis, are molecular mechanisms that have been reported in bladder carcinogenesis. In this article, we discuss the environmental risk factors of bladder cancer and we review the genetic and epigenetic alterations, including aberrant DNA methylation and deregulation of microRNAs expression. We also discuss the role of p53 and retinoblastoma suppressor genes in disease progression. Finally, we present recent reports on the use of molecular profiling to predict disease stage and grade and direct targeted therapy.