Genetic polymorphisms in CYP1B1, GSTA1, NQO1 and NAT2 and the risk of lung cancer

Synergistic polymorphic interactions of phase II metabolizing genes and their association toward lung cancer susceptibility in North Indians

Lung cancer is a multifactorial carcinoma with diverse heterogeneity. Genetic variations in drug-metabolizing enzymes may lead to defective detoxification and clearance of carcinogenic compounds. The high-order gene-gene interaction has been carried out between different genotypes of Phase II detoxification genes (NQO1, SULT1A1, NAT2, and EPHX1). Our results depict the genetic combination of SULT1A1 R213H with NAT2 × 5B L161L, SULT1A1 R213H with NAT2 × 5C K268R, EPHX1 H139R and NAT2 × 5B L161L exhibit a protective effect towards lung cancer risk. Further, the triple combinations of NQO1 P187S, EPHX1 Y113H, and EPHX1 H139R; NQO1 P187S, EPHX1 Y113H, and NAT2 × 6 R197Q; NQO1 P187S, EPHX1 Y113H, and NAT2 × 7 G286E; SULT1A1 R213H, EPHX1 H139R, and NAT2 × 7 G286E suggested a two-fold increased risk of lung cancer for subjects. Genetic polymorphisms of phase II detoxifying genes (NAT2, NQO1, EPHX1, SULT1A1) are prognostic markers for lung cancer.

Association of NAT-2 gene polymorphisms toward lung cancer susceptibility and prognosis in North Indian patients treated with platinum-based chemotherapy

Aim: The present study has been carried out to evaluate the association of the N-acetyl transferase 2 (NAT2) variants in North Indian lung cancer patients and healthy controls. Furthermore, we have also determined the effect of the polymorphic variants of the NAT2 gene on the clinical outcomes and overall survival among lung cancer (LC) subjects treated with platinum-based doublet chemotherapy. Methods: This case-control study comprised a total of 550 cases and 550 healthy controls. The genotyping was carried out using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and the statistical analysis was carried out using MedCalc. Results: There was a lack of any significant association for both 590G>A and 803A>G polymorphisms toward risk for LC, but 857G>A polymorphism exhibited a risk toward LC (p = 0.005). Whereas, variant alleles for the 481C>T polymorphism had a decreased risk for LC (p = 0.0003). Further, 857G>A polymorphism conferred a positive association between genotype and ADCC (p = 0.001) and 481C>T polymorphism had a decreased risk for SQCC (OR = 0.39, p = 0.0006) and SCLC (p = 0.001) subjects. The smokers carrying mutant genotype for the 481C>T polymorphism had a decreased risk toward LC (p < 0.0001) even in light (p = 0.002) as well as heavy smokers (p = 0.001). In case of females, 2.59-fold and 3.66-fold increased risk of LC development was observed in subjects with intermediate and slow acetylator for the 857G>A polymorphism. Whereas, in case of males this polymorphism depicts a reduced risk for LC. On the other hand, 803A>G depicted a 2.82-fold risk of LC in case of female subjects who were slow acetylators. Our study exhibits a significant difference in the overall haplotype distribution between cases and controls. In our study overall, (857G>A, 481C>T, 803A>G) was found to be best model, but was not significant using MDR. Considering the CART results 481C>T polymorphism came out to be the most significant factor in determining the LC risk. For the 803A>G polymorphism, a threefold odds of lymph node invasion were observed for mutant genotype, the recessive model exhibited an odd of 2.8. 590G>A appears to be a potential prognostic factor for OS of SCLC patients after irinotecan therapy as the survival time for such patients was better. Conclusion: These results suggest that NAT2 variant genotype for 590G>A and 803A>G was not found to modulate risk toward LC, but 857G>A polymorphism exhibited a risk toward LC and 481C>T polymorphism had a decreased risk for LC. NAT2 590G>A appears to be a potential prognostic factor for OS of SCLC patients after irinotecan therapy and 481C>T came out to be significant factor using CART.

Association Between NAT2 Polymorphism and Lung Cancer Risk: A Systematic Review and Meta-Analysis

Lung cancer is the leading cause of cancer-related death worldwide and has a high incidence rate. N-Acetyltransferase 2 (NAT2) is a polymorphic xenobiotic enzyme, which can catalyze N-acetylation and O-acetylation of various carcinogens such as aromatic, heterocyclic amines and hydrazines. At present, many studies have explored the effects of NAT2 polymorphism on lung cancer, but we found inconsistent results. We researched 18 published studies, involving 4,016 patients and 5,469 controls, to more accurately assess the effects of NAT2 polymorphism on lung cancer risk and to investigate whether smoking is associated. We used STATA software to analyze the extracted data and used STATA for subgroup analysis, sensitivity analysis, and to perform publication bias tests. To determine the correlation, we used the crude odds ratio (ORs) with 95% confidence interval (CIs). Our study was prospectively registered in PROSPERO (CRD42020159737). The odds ratio was 1.53 (95% CI: 1.21–1.95, I² = 45.2%, P=0.104) for the NAT2 slow + intermediate phenotype versus rapid phenotype. The results suggested that people with NAT2 non-rapid (slow + intermediate) phenotype have a significantly increased risk of lung cancer. In addition, NAT2 rapid phenotype was significantly associated with reduced risk of lung cancer, compared with slow phenotype or intermediate phenotype (slow phenotype vs. rapid phenotype: OR: 1.61, 95% CI: 1.07–2.42, I²= 50%, P= 0.075; intermediate phenotype vs. rapid phenotype: OR: 1.47, 95% CI: 1.15–1.88, I²= 40.3%, P= 0.137).

Relationship between CYP1B1 polymorphisms (c.142C > G, c.355G > T, c.1294C > G) and lung cancer risk in Polish smokers

AIM

To determine whether three of CYP1B1 single nucleotide polymorphisms, c.142C > G, c.355G > T and c.1294C > G are associated with a lung cancer risk.

PATIENTS & METHODS

 A total of 112 lung cancer patients and 100 controls were genotyped using the RFLP-PCR.

RESULTS

In the c.142C > G polymorphisms, G allele was more frequent in lung cancer patients than in controls (p < 0.001), while in the c.1294C > G polymorphisms, C allele was more frequent in lung cancer patients, than in controls (p = 0.012). In the c.355G > T polymorphism, the distribution of alleles in both analyzed groups was similar. The GTC haplotype turned out to be correlated with the increased lung cancer risk, compared with the most common CGG haplotype (OR: 2.38; p = 0.001).

CONCLUSION

CYP1B1 gene polymorphisms appear to influence lung cancer susceptibility.

Association Between NAT2 Polymorphisms and Lung Cancer Susceptibility

To further investigate the association between NAT2 polymorphisms and lung cancer susceptibility.In terms of phenotypes, we investigated the acetylator status of NAT2 polymorphisms associated with lung cancer risk. Additionally, in view of genotypes, we mainly analyzed 5 single nucleotide polymorphisms (SNPs) in NAT2 gene, namely C282T, A803G, C481T, G590A, and G857A. Twenty-six eligible studies were included in our meta-analysis by searching PubMed, Embase, and CNKI databases. We used odds ratios (ORs) with corresponding 95% confidence intervals (CIs) to evaluate the susceptibility to lung cancer associated with NAT2 polymorphisms.Overall, based on phenotypes, the pooled ORs showed no significant association between NAT2 polymorphisms and lung cancer susceptibility. In the subgroup analyses by ethnicity and source of control, there was still no significant association. In terms of genotypes, overall, no obvious relationship was observed between NAT2 polymorphisms and lung cancer risk. But increased risk of lung cancer was found in association with NAT2 C282T polymorphism (TT vs. CC + TC: OR = 1.58, 95% CI = 1.11-2.25).Our meta-analysis demonstrates that TT genotype in NAT2 C282T polymorphism may be a risk factor for lung cancer susceptibility. Additionally, the acetylator status of 5 SNPs in NAT2 gene may not be associated with lung cancer risk.

Association Between the CYP1B1 Polymorphisms and Lung Cancer Risk: A Meta-Analysis

The previously published data on the association between the cytochrome P450 1B1 Leu432Val, Asn453Ser, and Ala119Ser polymorphisms and lung cancer risk have remained controversial. Hence, we performed a meta-analysis to investigate the association between cytochrome P450 1B1 Leu432Val, Asn453Ser, and Ala119Ser polymorphisms and lung cancer risk under different inheritance models. A total of 22 studies were identified, including 2881 cases and 3653 controls for Leu432Val polymorphism (from 13 studies), 3009 cases and 3887 controls for Asn453Ser polymorphism (from 5 studies), and 1301 cases and 2045 controls for Ala119Ser polymorphism (from 4 studies). Overall, significant association was observed between cytochrome P450 1B1 Leu432Val polymorphism and lung cancer risk (dominant model: odds ratio = 1.29, 95% confidence interval = 1.08-1.53; recessive model: odds ratio = 1.21, 95% confidence interval = 1.05-1.39; additive model: odds ratio = 1.43, 95% confidence interval = 1.21-1.69) when all the eligible studies were pooled into the meta-analysis. In the further stratified and sensitivity analyses, significantly increased lung cancer risk was also observed in caucasians and smokers. No significant association was observed between cytochrome P450 1B1Asn453Ser and Ala119Ser polymorphisms and lung cancer risk in overall analysis. In summary, this meta-analysis suggests that cytochrome P450 1B1Leu432Val polymorphism is associated with increased lung cancer risk in caucasians and smokers.

Association of CYP1B1 Leu432Val polymorphism and lung cancer risk: an updated meta-analysis

BACKGROUND

Cytochrome P4501B1 (CYP1B1) a phase I enzyme, is involved in the activation of a broad spectrum of procarcinogens. Impacts on the catalytic activity of the CYP1B1 enzyme, as well as an association of the Leu432Val polymorphism with the risk of lung cancer, have been described; however, the results remain controversial.

METHODS

We conducted a meta-analysis of all available studies to clarify the effects of the Leu432Val polymorphism on lung cancer risks basing on 2,543 lung cancer cases and 3,304 controls from ten separate comparisons. We also performed subgroup analyses by ethnicity (categorized as Caucasian, Asian and African-American), gender, smoking status ,and histological type. A pooled odds ratio (OR) with 95% confidence interval (CI) was calculated to estimate the strength of the association.

RESULTS

A significantly increased risk was found in our meta-analysis in the overall population (Val/Val vs. Leu/Leu: OR = 1.371, 95% CI 1.137-1.652, P = 0.001). In subgroup analysis, significant associations with lung cancer susceptibility were also found in Caucasians (Val/Val vs. Leu/Leu: OR = 1.312, 95% CI 1.075-1.602, P = 0.008), females (Val/Val vs. Leu/Leu: OR = 1.472, 95% CI 1.097-1.976, P = 0.010), and smokers (dominant model Leu/Val + Val/Val vs. Leu/Leu: OR = 1.257, 95% CI 1.016-1.554, P = 0.035). Null results were noted in the subgroup analysis by histological type under different genetic models.

CONCLUSIONS

Our results suggest that the CYP1B1 Leu432Val polymorphism acts as a risk factor for the carcinogenesis of lung cancer.

The NQO1 polymorphism C609T (Pro187Ser) and cancer susceptibility: a comprehensive meta-analysis

Background:

Evidence is increasingly emerging about multiple roles for the NAD(P)H quinone oxidoreductase 1 enzyme in cancer. The C609T (rs1800566, Pro187Ser) null polymorphism of the NQO1 gene contributes significantly to the variation in enzymatic activity across different populations. NQO1 C609T polymorphism was thoroughly investigated with respect to cancer susceptibility. The results were inconsistent partly due to low sample sizes. The aim of the present work was to perform a meta-analysis to assess association for all common cancer sites separately and in combination.

Methods:

Our meta-analysis involved 92 studies including 21 178 cases and 25 157 controls. Statistical analysis involved individual cancer sites and the combined cancer risk. Association was tested under different genetic models.

Results:

We found a statistically significant association between the variant T allele and overall cancer risk in the worldwide population (for the TT vs CC model, OR=1.18 (1.07–1.31), P=0.002, I²=36%). Stratified analysis revealed that this association was largely attributed to the Caucasian ethnicity (for the TT vs CC model, OR=1.28 (1.12–1.46), P=0.0002, I²=1%). Stratification by tumour site showed significant association for bladder cancer in the worldwide population (for the TT vs CC model, OR=1.70 (1.17–2.46), P=0.005, I²=0%), and in the Asian population (for the TT vs CC model, 1.48 (1.14–1.93), P=0.003, I²=16%). Positive association was also found for gastric cancer in the worldwide population under the dominant model (OR=1.34 (1.09–1.65), P=0.006, I²=15%).

Conclusion:

Our results indicate that the C609T polymorphism of the NQO1 gene is an important genetic risk factor in cancer.

Polymorphisms of arylamine N-acetyltransferase2 and risk of lung and colorectal cancer

The arylamine N-acetyltransferase 2 (NAT2) enzymes detoxify a wide range of naturally occurring xenobiotics including carcinogens and drugs. Point mutations in the NAT2 gene result in the variant alleles M1 (NAT2 *5A), M2 (NAT2*6A), M3 (NAT2*7) and M4 (NAT2 *14A) from the wild-type WT (NAT2 *4) allele. The current study was aimed at screening genetic polymorphisms of NAT2 gene in 49 lung cancer patients, 54 colorectal cancer patients and 99 cancer-free controls, using PCR-RFLP. There were significant differences in allele frequencies between lung cancer patients and controls in the WT, M2 and M3 alleles (p < 0.05). However, only M2 and M3 allele frequencies were different between colorectal cancer patients and controls (p < 0.05). There was a marginal significant difference in the distribution of rapid and slow acetylator genotypes between lung cancer patients and controls (p = 0.06 and p = 0.05, respectively), but not between colorectal cancer patients and controls (p = 1.0 and p = 0.95, respectively). Risk of lung cancer development was found to be lower in slow acetylators [odds ratio (OR): 0.51, 95% confidence interval (95% CI): 0.25, 1.02, p-value = 0.07]. No effect was observed in case of colorectal cancer. Our results showed that NAT2 genotypes and phenotypes might be involved in lung cancer but not colorectal cancer susceptibility in Jordan.

Lack of association between NADPH quinone oxidoreductase 1 (NQO1) gene C609T polymorphism and lung cancer: a case-control study and a meta-analysis

Background

The association between NAD(P)H:quinone oxidoreductase 1 (NQO1) gene C609T polymorphism (rs1800566) and lung cancer has been widely evaluated, and a definitive answer so far is lacking. We first conducted a case-control study to assess this association in northeastern Han Chinese, and then performed a meta-analysis to further address this issue.

Methodology/Principal Findings

This case-control study involved 684 patients clinically diagnosed as lung cancer and 602 age-matched cancer-free controls from Harbin city, Heilongjiang province, China. Genotyping was conducted using the PCR-LDR (ligase detection reactions) method. Meta-analysis was managed by STATA software. Data and study quality were assessed in duplicate. Our case-control association study indicated no significant difference in the genotype and allele distributions of C609T polymorphism between lung cancer patients and controls, consistent with the results of the further meta-analysis involving 7286 patients and 9167 controls under both allelic (odds ratio (OR) = 0.99; 95% confidence interval (CI): 0.92–1.06; P = 0.692) and dominant (OR = 0.98; 95% CI: 0.89–1.08; P = 0.637) models. However, there was moderate evidence of between-study heterogeneity and low probability of publication bias. Further subgroup analyses by ethnicity, source of controls and sample size detected no positive associations in this meta-analysis.

Conclusions

Our study in northeastern Han Chinese, along with the meta-analysis, failed to confirm the association of NQO1 gene C609T polymorphism with lung cancer risk, even across different ethnic populations.

The effect of CYP1A1, GSTT1 and GSTM1 polymorphisms on the risk of lung cancer: a case-control study

Lung cancer, which is mainly affected by environmental factors, is a lethal malignancy. It is also important to investigate the effect of genetic factors on lung cancer aetiology. In this study, we aimed to investigate the distribution of CYP1A1*2C, GSTT1 and GSTM1 polymorphisms in Turkish lung cancer patients to determine whether any promoting effect of polymorphisms could cause development of lung cancer. For this purpose, genomic DNA samples obtained from peripheral blood of 128 patients with lung cancer and 122 healthy subjects were analyzed. Genotyping of polymorphic enzymes were carried out by polymerase chain reaction-restriction fragment length polymorphism methods. Although there were no significant differences between groups in terms of CYP1A1 polymorphism, the carriers of CYP1A1 Ile/Val genotype (odds ratio [OR] = 1.224, 95% confidence interval [CI]: 0.585-2.564) or CYP1A1 Val/Val genotype (OR = 3.058, 95% CI: 0.312-30.303) had an increased risk of lung cancer development. There was no statistical difference between groups in terms of both GSTT1 null genotype (OR = 1.114, 95% CI: 0.590-2.105) and GSTM1 null genotype (OR = 0.776, 95% CI: 0.466-1.290). This is the first case-control study investigating CYP1A1 Ile/Val, GSTT1 and GSTM1 polymorphisms in Turkish lung cancer patients. Although we suggest that other genes in addition to the proposed genes could play a role in lung cancer development, the results of our study will contribute to the possible associations between CYP1A1 Ile/Val, GSTT1 and GSTM1 gene polymorphism on the risk of lung cancer.

Relationship between CYP2A6 and CHRNA5-CHRNA3-CHRNB4 variation and smoking behaviors and lung cancer risk

Genetic variations in the CYP2A6 nicotine metabolic gene and the CHRNA5-CHRNA3-CHRNB4 (CHRNA5-A3-B4) nicotinic gene cluster have been independently associated with lung cancer. With genotype data from ever-smokers of European ancestry (417 lung cancer patients and 443 control subjects), we investigated the relative and combined associations of polymorphisms in these two genes with smoking behavior and lung cancer risk. Kruskal-Wallis tests were used to compare smoking variables among the different genotype groups, and odds ratios (ORs) for cancer risk were estimated using logistic regression analysis. All statistical tests were two-sided. Cigarette consumption (P < .001) and nicotine dependence (P = .036) were the highest in the combined CYP2A6 normal metabolizers and CHRNA5-A3-B4 AA (tag single-nucleotide polymorphism rs1051730 G>A) risk group. The combined risk group also exhibited the greatest lung cancer risk (OR = 2.03; 95% confidence interval [CI] = 1.21 to 3.40), which was even higher among those who smoked 20 or fewer cigarettes per day (OR = 3.03; 95% CI = 1.38 to 6.66). Variation in CYP2A6 and CHRNA5-A3-B4 was independently and additively associated with increased cigarette consumption, nicotine dependence, and lung cancer risk. CYP2A6 and CHRNA5-A3-B4 appear to be more strongly associated with smoking behaviors and lung cancer risk, respectively.

Current evidence on the relationship between CYP1B1 polymorphisms and lung cancer risk: a meta-analysis

The association between single-nucleotide polymorphisms (SNPs) of the CYP1B1 gene and lung cancer risk is still ambiguous. In this meta analysis, we assessed 10 case-control studies included 7,067 cases and 9,374 controls of the association between CYP1B1 SNPs of Leu432Val (rs1056836, 432C>G), Asn453Ser (rs1800440, 453A>G), Ala119Ser (rs1056827, 119G>T), Arg48Gly (rs10012, 48C>G) and the risk of lung cancer. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of association between the polymorphism and lung cancer risk under codominant model, dominant model and additive model respectively. Although there were limitations, this meta analysis indicated that individuals with 432GG genotype had a 39.7% higher risk of having lung cancer than those with the 432CC genotype, and individuals with the 432G allele had a 26.3% increased risk as well. An increased risk of lung cancer of 2.13 fold was observed in individuals with 119TT genotype. For Arg48Gly, individuals with 48GG genotype had a significantly increased risk of lung cancer compared with individuals with 48CC (OR 3.859; 95% CI 2.536-5.87). Elevated risk of lung cancer were observed in dominant model (OR 2.115; 95% CI 1.653-2.705) as well. The risk of lung cancer was elevated as the frequency of G allele increased in additive model (P = 0.000). For individuals with the polymorphism at codon 453, no evidence of such association was observed. Furthermore, a possible association between the CYP1B1 polymorphism at codon 432 and the lung cancer could be detected in individuals of Caucasian origin, while a negative association was suggested in Asians and African-Americans. An increased lung cancer risk was also found in women with polymorphism at codon 453. These results are supportive for the hypothesis that the CYP1B1 432GG, 119TT and 48GG genotypes are low-penetrance risk factors for developing lung cancer, and further studies are needed to validate these associations.

NAT2 polymorphism and lung cancer risk: a meta-analysis

N-acetyltransferase 2 (NAT2) gene encodes a key enzyme involved in the metabolism of xenobiotics and whose polymorphisms have been related to individual susceptibility to several malignancies. Although many epidemiological studies have explored the association between NAT2 genetic polymorphism and lung cancer risk, the results remain controversial. In order to assess the overall relationship between NAT2 polymorphism and lung cancer risk, we performed a meta-analysis including 3945 lung cancer cases and 6085 controls from 19 published studies which were selected from 29 articles identified by a search of PubMed up to 1st June 2010. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association. No significant association was found in overall analysis (OR=1.02, 95% CI=0.90-1.16, P=0.01 for heterogeneity) and in subgroup analyses by ethnicity, sex, histological type, smoking status and study design. In conclusion, this meta-analysis found little evidence of an association between the NAT2 polymorphism and the risk of lung cancer.

Pulmonary hypertension in women

Female predominance in pulmonary arterial hypertension (PAH) has been known for several decades and recent interest in the effects of sex hormones on the development of disease has substantially increased our understanding of this epidemiologic observation. Basic science data suggest a beneficial effect of estrogens in the pulmonary vasculature both acutely and chronically, which seems to contradict the known predilection in women. Recent human and rodent data have suggested that altered levels of estrogen, differential signaling and altered metabolism of estrogens in PAH may underlie the gender difference in this disease. Studies of the effects of sex hormones on the right ventricle in animal and human disease will further aid in understanding gender differences in PAH. This article focuses on the effects of sex hormones on the pulmonary vasculature and right ventricle on both a basic science and translational level.

NAD(P)H:quinone oxidoreductase 1 Pro187Ser polymorphism and the risk of lung cancer: A meta-analysis

BACKGROUND

NAD(P)H:quinine oxidoreductase 1 (NQO1) is a two-electron reductase that catalyzes quinine to hydroquinone. Variant genotypes of NQO1 Pro187Ser may be related to low enzyme activity and thus are suggested as affecting the risk of lung cancer. Our purpose was to study the NQO1 Pro187Ser polymorphism and the risk of lung cancer.

METHODS

We conducted a PubMed search and a China National Knowledge Infrastructure search using "NAD(P)H quinine reductase 1" ,"lung cancer", and " polymorphism" for articles published from January 1997 to March 2010. For each study, we calculated the crude odds ratios (OR) and 95% confidence intervals (CI) for lung cancer. Summary estimates for crude as well as adjusted OR were calculated with the statistical program stata.

RESULTS

The summary OR for carrying one variant allele and the homozygous variant genotype was 1.04 (95%CI, 0.97-1.13). In the Asian population, the summary OR for carrying one variant genotype was 1.09 (95%CI, 0.95-1.25).

CONCLUSIONS

Through our meta-analysis, we found that the Pro/Ser and Ser/Ser genotypes involving NQO1 were non-significantly associated with lung cancer. In the Asian population, the combined genotype was marginally associated with increased risk of lung cancer. When stratified on gender and smoking, the meta-analysis showed that there was no statistically significant difference between men and women, smokers and non-smokers, respectively.

Glutathione S-transferase T1 gene deletion polymorphism and lung cancer risk in Chinese population: a meta-analysis

Genetic variations in metabolic genes are considered to modulate metabolic process of carcinogens and are suggested to be related to cancer risk. However, epidemiological results are not always consistent. In this meta-analysis, we evaluated reported studies of association between polymorphism of glutathione S-transferase T1 gene (GSTT1) and the risk of lung cancer in Chinese population. We found an increased lung cancer risk among subjects carrying GSTT1 null genotype [odds ratio (OR)=1.36, 95 percent confidence interval (95% CI): 1.09-1.69], using 1625 cases and 2188 controls from 11 studies. We also observed an increased risk of lung cancer among null genotype carriers in squamous cell carcinoma and adenocarcinoma, and on the basis of population control in stratified analyses. The meta-analysis suggests that GSTT1 deletion polymorphisms may have an effect on the susceptibility of lung cancer in Chinese population, and a study with the larger sample size is needed to further evaluate gene-gene and gene-environment interaction on GSTT1 deletion polymorphisms and lung cancer risk in Chinese population.

Development of pulmonary arterial hypertension in women: interplay of sex hormones and pulmonary vascular disease

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature, ultimately resulting in right heart failure and death. This disease is strongly predominant in females, although little is known regarding how sex influences disease development. Recent developments highlighting the importance of estrogen metabolites in both animal models and human disease have substantially increased our understanding of PAH in women. This review will focus on general knowledge of PAH, translational and basic science data regarding sex hormones in the pulmonary vasculature and on clinical issues that are particular to women with PAH. Future directions for study include the influence of sex hormones on right ventricular responses, improving the understanding of the influence of estrogen exposure in human disease and the study of dehydroepiandrosterone in basic science and human disease.

Lifestyle, environmental, and genetic predictors of bulky DNA adducts in a study population nested within a prospective Danish cohort

Bulky DNA adducts are considered a potential biomarker of cancer risk. In this study, the association between various lifestyle, environmental, and genetic factors and the levels of bulky DNA adducts in peripheral leukocytes was examined in a study group nested within a population-based prospective Danish cohort. At enrollment, blood samples were collected and information on lifestyle, including dietary and smoking habits, obtained. Previously, bulky DNA adducts were measured in 245 individuals who developed lung cancer and 255 control members of the cohort. Of these 500 individuals, data on 375 individuals were included in this study, excluding 125 cases, which developed lung cancer within the first 3 yr after blood sampling. Bulky DNA adduct levels were measured by 32P-postlabeling technique and polymorphisms in carcinogen metabolism and DNA repair genes were determined. Potential predictors of bulky DNA adduct levels were analyzed by univariate and multivariate regression analyses. Women tended to have higher adduct levels than men. Living in central Copenhagen and surface darkness of fried meat and fish were associated with quantitative higher adduct levels. No significant associations were found between dietary factors or smoking and DNA adduct levels. Further, the results showed no prominent associations between any of 12 genetic polymorphisms and adduct levels. Overall, our study showed only few associations between dietary, environmental, and genetic factors and levels of bulky DNA adducts measured in peripheral leukocytes in a general Danish population.

Phase I metabolic genes and risk of lung cancer: multiple polymorphisms and mRNA expression

Polymorphisms in genes coding for enzymes that activate tobacco lung carcinogens may generate inter-individual differences in lung cancer risk. Previous studies had limited sample sizes, poor exposure characterization, and a few single nucleotide polymorphisms (SNPs) tested in candidate genes. We analyzed 25 SNPs (some previously untested) in 2101 primary lung cancer cases and 2120 population controls from the Environment And Genetics in Lung cancer Etiology (EAGLE) study from six phase I metabolic genes, including cytochrome P450s, microsomal epoxide hydrolase, and myeloperoxidase. We evaluated the main genotype effects and genotype-smoking interactions in lung cancer risk overall and in the major histology subtypes. We tested the combined effect of multiple SNPs on lung cancer risk and on gene expression. Findings were prioritized based on significance thresholds and consistency across different analyses, and accounted for multiple testing and prior knowledge. Two haplotypes in EPHX1 were significantly associated with lung cancer risk in the overall population. In addition, CYP1B1 and CYP2A6 polymorphisms were inversely associated with adenocarcinoma and squamous cell carcinoma risk, respectively. Moreover, the association between CYP1A1 rs2606345 genotype and lung cancer was significantly modified by intensity of cigarette smoking, suggesting an underling dose-response mechanism. Finally, increasing number of variants at CYP1A1/A2 genes revealed significant protection in never smokers and risk in ever smokers. Results were supported by differential gene expression in non-tumor lung tissue samples with down-regulation of CYP1A1 in never smokers and up-regulation in smokers from CYP1A1/A2 SNPs. The significant haplotype associations emphasize that the effect of multiple SNPs may be important despite null single SNP-associations, and warrants consideration in genome-wide association studies (GWAS). Our findings emphasize the necessity of post-GWAS fine mapping and SNP functional assessment to further elucidate cancer risk associations.

Alterations in oestrogen metabolism: implications for higher penetrance of familial pulmonary arterial hypertension in females

Mutations in bone morphogenetic protein receptor type 2 (BMPR2) cause familial pulmonary arterial hypertension (FPAH), but the penetrance is reduced and females are significantly overrepresented. In addition, gene expression data implicating the oestrogen-metabolising enzyme CYP1B1 suggests a detrimental role of oestrogens or oestrogen metabolites. We examined genetic and metabolic markers of altered oestrogen metabolism in subjects with a BMPR2 mutation. Genotypes for CYP1B1 Asn453Ser (N453S) were determined for 140 BMPR2 mutation carriers (86 females and 54 males). Nested from those subjects, a case-control study of urinary oestrogen metabolite levels (2-hydroxyoestrogen (2-OHE) and 16alpha-hydroxyoestrone (16alpha-OHE(1))) was conducted in females (five affected mutation carriers versus six unaffected mutation carriers). Among females, there was four-fold higher penetrance among subjects homozygous for the wild-type genotype (N/N) than those with N/S or S/S genotypes (p = 0.005). Consistent with this finding, the 2-OHE/16alpha-OHE(1) ratio was 2.3-fold lower in affected mutation carriers compared to unaffected mutation carriers (p = 0.006). Our findings suggest that variations in oestrogens and oestrogen metabolism modify FPAH risk. Further investigation of the role of oestrogens in this disease with profound sex bias may yield new insights and, perhaps, therapeutic interventions.

NAT2 fast acetylator genotypes are associated with an increased risk for lung cancer with wildtype epidermal growth factor receptors in Taiwan

Identifying the risk factors responsible for lung cancer especially for nonsmokers is critical for both its prevention and treatment. Studies have linked the polymorphisms in N-acetyltransferases (NAT2), a key enzyme for metabolism of hydrocarbons, with lung cancer in Asian female nonsmokers. Since a high percentage of lung adenocarcinoma in Asian female nonsmokers contains activating hotspot mutations in epidermal growth factor receptors (EGFR), we hypothesized that NAT2 polymorphisms might represent a risk factor in lung cancer with EGFR mutations. We studied NAT polymorphisms in 117 nonsmall cell lung cancer (NSCLC) patients and in 119 healthy controls and EGFR hotspot mutations in exons 18-21 in 100 of the 117 patients using polymerase chain reactions. NAT2 fast acetylator genotypes were significantly associated with patients with lung cancer (P = 0.04, odds ratio (OR): 1.90, 95% confidence interval (CI): 1.02-3.57). Further analyses revealed that NAT2 fast acetylator genotypes were significantly associated with NSCLC with wildtype EGFR (P = 0.008, OR: 3.16, 95% CI: 1.31-7.63), but not with those with EGFR mutations (P = 0.40). Therefore, NAT2 fast acetylator genotypes are a potential risk factor especially for lung cancer with wildtype EGFR.

Association of functionally important polymorphisms in cytochrome P4501B1 with lung cancer

In the present study, genotype and haplotype frequencies of four polymorphisms of cytochrome P450 1B1 (CYP1B1) that cause amino acid changes (Arg-Gly at codon 48, Ala-Ser at codon 119, Leu-Val at 432 and Asn-Ser at codon 453) were studied in 200 patients suffering from lung cancer and equal number of controls. A significant difference was observed for the distribution of variant genotypes of CYP1B1Arg48Gly and Ala119Ser polymorphisms (CYP1B1*2) in cases when compared to the controls. No significant difference was observed for the distribution of variant genotypes of CYP1B1Leu432Val (CYP1B1*3) and CYP1B1Asn453Ser (CYP1B1*4) polymorphism. When the four SNPs were analyzed using a haplotype approach, SNPs at codon 48 (Arg48Gly) and codon 119 (Ala119Ser) exhibited complete linkage disequilibrium (LD) in all the cases and controls. Significant differences in the distribution of the three haplotypes (G-T-C-A, G-T-G-A and G-T-C-G) were observed in the cases when compared to controls. Tobacco use in the form of smoking as well as chewing was found to significantly increase the risk of lung cancer in patients by interacting with CYP1B1Ala119Ser genotypes demonstrating the role of gene-environment interaction in lung cancer. Further, the risk of lung cancer increased several fold in the patients carrying the genotype combinations of CYP1B1Ala119Ser and CYP1B1Leu432Val with GSTM1, a phase II enzyme suggesting the importance of gene-gene interactions in enhancing the susceptibility to lung cancer.

Genetic polymorphisms in cytochrome P4501B1 and susceptibility to head and neck cancer

Cytochrome P4501B1 (CYP1B1), a polycyclic aromatic hydrocarbon (PAH) metabolizing CYP, is genetically polymorphic in humans and may be involved in the individual susceptibility to chemical-induced cancer. In the present study, genotype and haplotype frequencies of four single nucleotide polymorphisms (SNPs) in CYP1B1 that cause amino acid changes (Arg-Gly at codon 48, Ala-Ser at codon 119, Leu-Val at codon 432 and Asn-Ser at codon 453) were studied in 150 cases suffering from head and neck squamous cell carcinoma (HNSCC) and in an equal number of controls. A significant difference was observed for the distribution of variant genotypes of Arg48Gly (CYP1B1*2) and Ala119Ser (CYP1B1*2) polymorphisms of CYP1B1 in cases versus controls. No significant differences were observed for the distribution of variant genotypes-Leu432Val (CYP1B1*3) and Asn453Ser (CYP1B1*4), respectively. When the four SNPs were analyzed using a haplotype approach, SNPs at codon 48 (Arg48Gly) and codon 119 (Ala119Ser) exhibited complete linkage disequilibrium (LD) in all the cases and controls. Significant differences in the distribution of the two haplotypes (G-T-C-A and G-T-G-A) were observed both in the cases and in controls. Furthermore, our data indicates a several fold increase in risk in the cases who use tobacco (cigarette smoking or tobacco chewing) or alcohol with the variant genotypes of CYP1B1 (CYP1B1*2 and CYP1B1*3) suggesting the role of gene-environment interaction in the susceptibility to HNSCC.

Genetic susceptibility according to three metabolic pathways in cancers of the lung and bladder and in myeloid leukemias in nonsmokers

BACKGROUND

We chose a set of candidate single nucleotide polymorphisms (SNPs) to investigate gene-environment interactions in three types of cancer that have been related to air pollution (lung, bladder and myeloid leukemia).

PATIENTS AND METHODS

The study has been conducted as a nested case-control study within the European Prospective Investigation into Cancer and Nutrition cohort (409 cancer cases and 757 matched controls). We included never and ex-smokers. SNPs were in genes involved in oxidative stress, phase I metabolizing genes, phase II metabolizing genes and methylenetetrahydrofolate reductase (MTHFR).

RESULTS

The most notable findings are: GSTM1 deletion and bladder cancer risk [odds ratio (OR) = 1.60; 95% confidence interval 1.00-2.56]; CYP1A1 and leukemia (2.22, 1.33-3.70; heterozygotes); CYP1B1 and leukemia (0.47, 0.27-0.84; homozygotes); MnSOD and leukemia (1.91, 1.08-3.38; homozygotes) and NQO1 and lung cancer (8.03, 1.73-37.3; homozygotes). Other statistically significant associations were found in subgroups defined by smoking habits (never or ex-smokers), environmental tobacco smoke or gender, with no obvious pattern. When gene variants were organized according to the three main pathways, the emerging picture was of a strong involvement of combined phase I enzymes in leukemia, with an OR of 5 (1.63-15.4) for those having three or more variant alleles. The association was considerably stronger for leukemias arising before the age of 55.

Polymorphism of selected enzymes involved in detoxification and biotransformation in relation to lung cancer

Available data indicate that there are significant differences in individual susceptibility to lung cancer within the human population. It is believed to be underlie by inherited genetic predispositions related to the genetic polymorphism of several enzymes involved in the detoxification and xenobiotic metabolism. In this review, we collect and discuss the evidence reported up to date on the association between lung cancer and genetic polymorphism of cytochromes P450, N-acetyltransferase, glutathione S-transferases, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, myeloperoxidase and glutathione peroxidase. All these genes might appear to be candidates for lung cancer susceptibility genes, nevertheless, the present state of the art still offers only a limited explanation of the link between such polymorphisms and increased risk of lung cancer.

Risk of second cancer after chronic lymphocytic leukemia

Smoking is not considered a risk factor for chronic lymphocytic leukemia (CLL) yet increased lung cancer risk has been reported for these patients. Little data exist on the temporal variation in lung cancer risk after CLL, or its histological composition. We investigated the occurrence of second cancers in a large cohort of CLL patients with particular emphasis on lung cancer and its major subtypes. We followed all patients diagnosed with CLL in Denmark in the period 1943-2003 (n = 12,373) for the occurrence of second cancers. The relative risk was expressed as the standardized incidence ratio (SIR), i.e. the ratio of observed to expected number of cancers, based on incidence rates for the Danish population. During follow-up 1,105 cancers occurred among the CLL patients (SIR = 1.59 (95% CI 1.50-1.69)). SIR for all cancers combined remained elevated more than 10 years after CLL (SIR = 1.80 (1.56-2.08)). Lung cancer occurred in 141 patients (SIR = 1.61 (1.37-1.90)). The relative risk of lung cancer did not vary by gender, or time of follow-up, but was higher in younger (SIR(<60 years) = 2.22 (1.62-3.06)) than in older (SIR(70-79 years) = 1.21 (0.88-1.68)) age-groups. Elevated risks were observed for adenocarcinoma (SIR = 2.20 (1.57-3.08)) and squamous cell carcinoma (SIR = 1.52 (1.06-2.17)) of the lung. We speculate that shared genetic risk factors may explain the accumulation of lung and other cancers in CLL patients.

Combinations of cytochrome P-450 genotypes and risk of early-onset lung cancer in Caucasians and African Americans: a population-based study

Polymorphisms in CYP1A1 and CYP1B1 genes in humans are associated with reduction of enzymatic activity towards several substrates, including those found in tobacco smoke. To investigate the potential role these polymorphisms have as modulators of early-onset lung cancer risk, a population-based case-control study involving early-onset lung cancer cases was performed. Biological samples were available for 383 individuals diagnosed prior to 50 years of age identified from the metropolitan Detroit Surveillance, Epidemiology and End Results (SEER) program and 449 age, race and sex-matched controls ascertained through random digit dialing. Genotype frequencies varied significantly by race for CYP1A1 Ile(462)Val and CYP1B1 Leu(432)Val genotypes, so all analyses were stratified by race. No association was seen between lung cancer risk and polymorphisms in CYP1A1 Msp1 or CYP1B1 Leu(432)Val for Caucasians or African Americans, after adjusting for age at diagnosis, sex, pack years of smoking and family history of lung cancer. In Caucasians, those with the IIe/Val genotype at CYP1A1 Ile(462)Val locus were at decreased risk of having lung cancer compared to those with the lle/lle genotype, after adjusting for age at diagnosis, sex, pack years of smoking and family history of cancer (OR=0.41 95% Cl 0.19-0.90). These results were not replicated among the African American population, nor were they modified by amount of smoking.

NAD(P)H:quinone oxidoreductase 1 (NQO1) Pro187Ser polymorphism and the risk of lung, bladder, and colorectal cancers: a meta-analysis

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme that catalyzes the two-electron reduction of quinoid compounds into hydroquinones, their less toxic form. A sequence variant at position 609 (C --> T) in the NQO1 gene encodes an enzyme with reduced quinone reductase activity in vitro and thus was hypothesized to affect cancer susceptibility. We conducted meta-analyses focusing on three cancer sites (lung, bladder, and colorectum) to summarize the findings from the current literature and to explore sources of heterogeneity.

RESULTS

There is no clear association between the NQO1 Pro187Ser polymorphism and lung cancer risk in the three ethnic groups examined: odds ratio (OR(White)) C/T + T/T versus C/C = 1.04 [95% confidence interval (95% CI), 0.96-1.13], OR(Asian) = 0.99 (95% CI, 0.72-1.34), and OR(Blacks) = 0.95 (95% CI, 0.66-1.36). However, a modestly increased risk was suggested for the variant homozygotes in whites (OR T/T versus C/C, 1.19; 95% CI, 0.94-1.50). Analysis excluding one outlier study suggested the variant allele may be associated with reduced lung cancer risk in Asians. Meta-analyses for bladder and colorectal cancer suggested a statistically significant association with the variant genotypes in whites. In stratified analyses, the NQO1 Pro187Ser variant genotypes were associated with slightly increased lung cancer risk in white ever smokers but not in white never smokers and were mainly associated with a reduced risk of lung adenocarcinoma but not squamous cell carcinoma in Asians.

CONCLUSIONS

Results from our meta-analyses suggest that the variant NQO1 Pro187Ser genotype may affect individual susceptibility to lung, bladder, and colorectal cancer. Such effects of the NQO1 polymorphism seem to be modified by ethnicity and smoking status.

Arylamine N-acetyltransferase gene polymorphisms: markers for atopic asthma, serum IgE and blood eosinophil counts

INTRODUCTION

Polymorphisms in N-acetyltransferase 2 (NAT2), present on chromosome 8p22, are responsible for the N-acetylation variants, which segregate human populations into rapid, intermediate and slow acetylators and influence the susceptibility towards atopic disorders. We have undertaken a study of the North Indian population to screen for various NAT2 polymorphisms and to investigate their association with atopic asthma and related phenotypes.

METHODS

First, to establish linkage of the 8p22 region with asthma, 158 families were recruited from North India. Next, a total of 219 unrelated atopic asthmatics and 210 unrelated healthy controls were recruited for case-control disease association studies.

RESULTS

A suggestive linkage was observed with microsatellite marker D8S549, 2.6 MB upstream of NAT2. By sequencing the DNA of 40 individuals, the T111C, G191A, A434C and C759T single nucleotide polymorphisms (SNPs) in NAT2 were found to be nonpolymorphic in our population and a pattern of strong linkage disequilibrium was observed among the T341C, C481T and A803G polymorphisms. Thus, a total of 429 individuals were genotyped for the C481T and unlinked C282T polymorphisms. The C481T polymorphism was found to be significantly associated with asthma in our case-control studies at the genotype level (Armitage p = 0.00027). C481T also showed a marginal association with serum total IgE (TsIgE) (p = 0.022). Furthermore, percent blood eosinophil counts were found to be significantly higher in patients carrying the 481T allele (p = 0.0037). Significant association was also detected with respect to the C282T polymorphism and TsIgE (p = 0.008). Moreover, C_T was found to be an important risk (p = 0.001), while C_C was a major protective haplotype (p = 0.0005). The associations remained significant after Bonferroni correction for multiple testing.

CONCLUSION

In summary, the genetic variants of the NAT2 gene do not seem to affect asthma alone, but act as modulators of asthma-related traits, such as serum IgE and blood eosinophil counts, and therefore could serve as genetic markers.

Comparison of Polymorphisms in Genes Involved in Polycyclic Aromatic Hydrocarbon Metabolism with Urinary Phenanthrene Metabolite Ratios in Smokers

The hypothesis that interindividual differences among smokers in the metabolism of polycyclic aromatic hydrocarbons (PAH) are related to lung cancer risk has been extensively investigated in the literature. These studies have compared lung cancer risk in groups of smokers with or without polymorphisms in genes involved in PAH metabolism. We believe that carcinogen metabolite phenotyping, involving the actual measurement of PAH metabolites, would be a better way to investigate differences in lung cancer risk. With this goal in mind, we have developed methods for quantifying phenanthrene metabolites in urine. Phenanthrene is the simplest PAH with a bay region, a feature closely associated with carcinogenicity. The urinary metabolite r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT) is a measure of metabolic activation, whereas phenanthrols (HOPhe) are a measure of detoxification. In this study, we quantified urinary PheT/HOPhe ratios in 346 smokers who were also genotyped for 11 polymorphisms in genes involved in PAH metabolism: CYP1A1MspI, CYP1A1I462V, CYP1B1R48G, CYP1B1A119S, CYP1B1L432V, CYP1B1N453S, EPHX1Y113H, EPHX1H139R, GSTP1I105V, GSTP1A114V, and GSTM1 null. The geometric mean molar PheT/3-HOPhe ratio was 4.08 (95% confidence interval, 3.79-4.39). Ten percent of the smokers had PheT/3-HOPhe ratios of > or =9.90. We found a significant association between the presence of the CYP1A1I462V polymorphism and high PheT/3-HOPhe ratios (P = 0.02). This effect was particularly strong in females and in combination with the GSTM1 null polymorphism. In contrast, the CYP1B1R48G and CYP1B1A119S polymorphisms were associated with significantly lower PheT/3-HOPhe ratios, particularly in Blacks. There were no consistent significant effects of any of the other polymorphisms on PheT/3-HOPhe ratios. The highest 10% of PheT/3-HOPhe ratios could not be predicted by the presence of any of the 11 polymorphisms individually or by certain combinations. The effects of the CYP1A1I462 polymorphism observed here, particularly in combination with GSTM1 null, are quite consistent with reports in the literature. However, the results of this study indicate that genotyping is not an effective way to predict PAH metabolism at least as represented by PheT/HOPhe ratios.

Xenobiotic-metabolizing enzymes involved in activation and detoxification of carcinogenic polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental carcinogens and metabolized by a variety of xenobiotic-metabolizing enzymes such as cytochrome P450 (P450 or CYP), epoxide hydrolase, glutathione transferase, UDP-glucuronosyltransferase, sulfotransferase, NAD(P)H quinone oxidoreductase 1, and aldo-keto reductase. These enzymes mainly participate in the conversion of PAHs to more polar and water-soluble metabolites, and the resultant metabolites are readily excreted from the body. However, during the course of metabolism, a variety of unstable and reactive intermediates of PAHs are formed, and these metabolites attack DNA, causing cell toxicity and transformation. P450s and epoxide hydrolase convert PAHs to proximate carcinogenic metabolites, PAH-diols, and these products are further metabolized by P450s to ultimate carcinogenic metabolites, PAH diol-epoxides, or by aldo-keto reductase to reactive PAH o-quinones. PAHs are also activated by P450 and peroxidases to reactive radical cations that bind covalently to DNA. The oxygenated and reactive metabolites of PAHs are usually converted to more polar and detoxified products by phase II enzymes. Inter-individual differences exist in levels of expression and catalytic activities of a variety of enzymes that activate and/or detoxify PAHs in various organs of humans and these phenomena are thought to be critical in understanding the basis of individual differences in response to PAHs. Factors affecting such variations include induction and inhibition of enzymes by diverse chemicals and, more importantly, genetic polymorphisms of enzymes in humans.

N-acetyltransferase 2 (NAT2) gene polymorphisms in colon and lung cancer patients

BACKGROUND

N-acetyltransferase 2 (NAT2) metabolizes arylamines and hydrazines moeities found in many therapeutic drugs, chemicals and carcinogens. The gene encoding NAT2 is polymorphic, thus resulting in rapid or slow acetylator phenotypes. The acetylator status may, therefore, predispose drug-induced toxicities and cancer risks, such as bladder, colon and lung cancer. Indeed, some studies demonstrate a positive association between NAT2 rapid acetylator phenotype and colon cancer, but results are inconsistent. The role of NAT2 acetylation status in lung cancer is likewise unclear, in which both the rapid and slow acetylator genotypes have been associated with disease.

METHODS

We investigated three genetic variations, c.481C>T, c.590G>A (p.R197Q) and c.857G>A (p.G286E), of the NAT2 gene, which are known to result in a slow acetylator phenotype. Using validated PCR-RFLP assays, we genotyped 243 healthy unrelated Caucasian control subjects, 92 colon and 67 lung cancer patients for these genetic variations. As there is a recent meta-analysis of NAT2 studies on colon cancer (unlike in lung cancer), we have also undertaken a systematic review of NAT2 studies on lung cancer, and we incorporated our results in a meta-analysis consisting of 16 studies, 3,865 lung cancer patients and 6,077 control subjects.

RESULTS

We did not obtain statistically significant differences in NAT2 allele and genotype frequencies in colon cancer patients and control group. Certain genotypes, however, such as [c.590AA+c.857GA] and [c.590GA+c.857GA] were absent among the colon cancer patients. Similarly, allele frequencies in lung cancer patients and controls did not differ significantly. Nevertheless, there was a significant increase of genotypes [c.590GA] and [c.481CT+c.590GA], but absence of homozygous c.590AA and [c.590AA+c.857GA] in the lung cancer group. Meta-analysis of 16 NAT2 studies on lung cancer did not evidence an overall association of the rapid or slow acetylator status to lung cancer. Similarly, the summary odds ratios obtained with stratified meta-analysis based on ethnicity, and smoking status were not significant.

CONCLUSION

Our study failed to show an overall association of NAT2 genotypes to either colon or lung cancer risk.

CYP1A1 and CYP1B1 polymorphisms and risk of lung cancer among never smokers: a population-based study

The cytochrome P450 (CYP) superfamily of enzymes catalyse one of the first steps in the metabolism of carcinogens such as polycyclic aromatic hydrocarbons, nitroaromatics and arylamines. Polymorphisms within the CYP1A1 gene have been shown to be associated with lung cancer risk, predominantly among Asian populations. Despite functional evidence of a possible role of CYP1B1 in lung cancer susceptibility, only a few studies have evaluated polymorphisms in this gene in relation to lung cancer susceptibility. This population-based study evaluates polymorphisms in both of these CYP genes within never smokers, most of whom had environmental tobacco smoke (ETS) exposure. Cases (n = 160) were identified through the metropolitan Detroit Surveillance, Epidemiology and End Results program, and age, sex and race-matched population-based controls (n = 181) were identified using random digit dialing. Neither CYP1A1 MspI nor CYP1A1 Ile(462)Val was associated with lung cancer susceptibility among Caucasians or African-Americans. Among Caucasians, however, CYP1B1 Leu(432)Val was significantly associated with lung cancer susceptibility odds ratio (OR) for at least one valine allele = 2.87 [95% confidence interval (CI) 1.63-5.07]. Combinations of this Phase I enzyme polymorphism along with selected Phase II enzyme polymorphisms (GSTM1 null, GSTP1 Ile(105)Val and NQO1 C(609)T) were evaluated. The combination of CYP1B1 Leu(432)Val and NQO1 C(609)T appeared to be associated with the highest risk of lung cancer (OR = 4.14, 95% CI 1.60-10.74), although no combinations differed significantly from the risk associated with CYP1B1 Leu(432)Val alone. When individuals were stratified by household ETS exposure (yes/no), CYP1B1 Leu(432)Val alone and in combination with Phase II enzyme polymorphisms was more strongly associated with increased lung cancer susceptibility among those with at least some household ETS exposure. Additional studies will be required to further validate these findings among never smokers and to evaluate the effects of this polymorphism among smoking populations as well.