Ethnic susceptibility to lung cancer: differences in CYP2E1, CYP1A1 and GSTM1 genetic polymorphisms between French Caucasian and Chilean populations

The role of phase I and II genetic polymorphisms, smoking, alcohol and cancer family history, in the risk of developing testicular cancer

BACKGROUND

Testicular cancer (TCa) is a malignant tumor with highest incidence and mortality rates in Chile. The genes coding for cytochrome P450, glutathione-S-transferases (GSTs), and UDP glucuronyl transferases (UGT) participate in the biotransformation and detoxification of xenobiotics. Mutations in these genes have been associated with a high incidence of various types of cancer and an increased risk of presenting adverse reactions to drugs.

OBJECTIVE

The aim of this study was to relate the presence of genetic polymorphisms in cytochrome P450 1A1 (CYP1A1), CYP3A4, GSTM1, GSTP1, GSTT1, and UGT1A1 genes and nongenetic factors with the risk of developing TCa.

METHODS

A total of 276 volunteers from the Chilean general population and 251 Chilean TCa patients were recruited for the study. Genotypic analyses were performed using qPCR and PCR-RFLP.

RESULTS

Variant alleles found to increase the risk of developing TCa were CYP1A1*2C (rs1048943), GSTP1 (rs1695), and GSTT1null, especially when in conjunction with a cancer family history and/or a smoking habit. The results of the multivariate analysis showed that the presence of variant alleles of GSTP1 (rs1695) together with a smoking habit and a family history of cancer accounted for a 15.9% risk of developing TCa in the Chilean population. CYP1A1*2C, GSTM1null, GSTT1null, and GSTP1 (rs1695) are statistically related to the risk of appearance of TCa, alone or associated with nongenetic factors.

CONCLUSION

Therefore, phase I and II variant alleles might be useful in evaluating susceptibility to TCa in the studied population.

Association Study Among Candidate Genetic Polymorphisms and Chemotherapy-Related Severe Toxicity in Testicular Cancer Patients

Testicular cancer is one of the most commonly occurring malignant tumors in young men with fourfold higher rate of incidence and threefold higher mortality rates in Chile than the average global rates. Surgery is the initial line of treatment for testicular cancers, and is generally followed by chemotherapy, usually with combinations of bleomycin, etoposide, and cisplatin (BEP). However, the adverse effects of chemotherapy vary significantly among individuals; therefore, the present study explored the association of functionally significant allelic variations in genes related to the pharmacokinetics/pharmacodynamics of BEP and DNA repair enzymes with chemotherapy-induced toxicity in BEP-treated testicular cancer patients. We prospectively recruited 119 patients diagnosed with testicular cancer from 2010 to 2017. Genetic polymorphisms were analyzed using PCR and/or qPCR with TaqMan^®probes. Toxicity was evaluated based on the Common Terminology Criteria for Adverse Events, v4.03. After univariate analyses to define more relevant genetic variants (p < 0.2) and clinical conditions in relation to severe (III–IV) adverse drug reactions (ADRs), stepwise forward multivariate logistic regression analyses were performed. As expected, the main severe ADRs associated with the non-genetic variables were hematological (neutropenia and leukopenia). Univariate statistical analyses revealed that patients with ERCC2 rs13181 T/G and/or CYP3A4 rs2740574 A/G genotypes are more likely to develop alopecia; patients with ERCC2 rs238406 C/C genotype may develop leukopenia, and patients with GSTT1-null genotype could develop lymphocytopenia (III–IV). Patients with ERCC2 rs1799793 A/A were at risk of developing severe anemia. The BLMH rs1050565 G/G genotype was found to be associated with pain, and the GSTP1 G/G genotype was linked infection (p < 0.05). Multivariate analysis showed an association between specific ERCC1/2 genotypes and cumulative dose of BEP drugs with the appearance of severe leukopenia and/or febrile neutropenia. Grades III–IV vomiting, nausea, and alopecia could be partly explained by the presence of specific ERCC1/2, MDR1, GSTP1, and BLMH genotypes (p < 0.05). Hence, we provide evidence for the usefulness of pharmacogenetics as a tool for predicting severe ADRs in testicular cancer patients treated with BEP chemotherapy.

Evidence that Genetic Variants of Metabolic Detoxication and Cell Cycle Control Are Not Related to Gallbladder Cancer Risk in Chilean Women

Background and aims

High consumption of red chili pepper has been shown to be a risk factor for gallbladder cancer (GBC) in Chilean women. However, genetic factors in addition to this and other environmental factors may also be associated with an increased risk of GBC. We aimed to examine the associations of cytochrome P450 1A1 (CYP1A1), glutathione S-transferase class mu (GSTM1), and tumor protein p53 (TP53) polymorphisms with the risk of GBC in Chilean women.

Methods

A hospital-based case-control study of 57 patients with GBC, 119 patients with gallstones, and 70 controls was conducted. The statuses of the polymorphisms CYP1A1 rs4646903, CYP1A1 rs1048943, and TP53 rs1042522 were assayed using Custom Taqman® SNP Genotyping Assays and TaqMan®SNP Genotyping Assay. GSTM1 deletion polymorphism was detected by allele-specific PCR analysis.

Results

No significant differences in the genotypic or allelic frequencies in the CYP1A1, GSTM1, and TP53 polymorphisms were found between the three groups.

Conclusion

These genetic variants were not related to an increased risk of GBC in Chilean women. Other polymorphisms, such as red-chili-pepper-related polymorphisms, may contribute to the development of GBC in Chilean women.

Association of CYP1A1, GSTM1 and GSTT1 gene polymorphisms with risk of non-small cell lung cancer in Andhra Pradesh region of South India

BACKGROUND

Lung cancer is one of the most preventable causes of death globally both in developed and developing countries. Although it is well established that smokers develop lung cancer, there are some smokers who are free from the disease risk. The predisposition to lung cancer is attributed to genetic polymorphisms in xenobiotic metabolizing genes. Reports on assessment of xenobiotic metabolizing genes like Cytochrome P 450 1A1 (CYP1A1), Glutathione -S -transferase M1 (GSTM1) and T1 (GSTT1) polymorphisms from India are meagre, and reports from Andhra Pradesh are lacking.

METHODS AND RESULTS

Assessment of polymorphisms in CYP1A1, GSTM1 and GSTT1 in NSCLC patients and healthy individuals specific to population of Andhra Pradesh, a South Indian state was attempted by multiplex PCR and RFLP, and this is the first study which tried to correlate oxidative stress with the polymorphisms in xenobiotic metabolizing genes. Results showed that CYP1A1 m1 'CC' genotype was significantly associated with lung cancer susceptibility with a 2.3-fold risk, CYP1A1 m2 'AG' gene polymorphisms with 8.8-fold risk and GSTT1 (-/-) genotype demonstrated a twofold risk of disease susceptibility.

CONCLUSIONS

A combined role of genetic polymorphisms and smoking status can be attributed for the cause of lung cancer. Further, the association between oxidative stress and genetic polymorphisms showed a correlation between GSTT1 and super oxide dismutase activity; CYP1A1 m1, m2 and GSTT1 with glutathione peroxidase activity; CYP1A1 m1 and GSTM1 with melondialdehyde levels; and CYP1A1 m1 and GSTT1 with 8-oxo-7,8-dihydro-2'-deoxyguanosine. A higher risk of lung cancer seems to be associated with combined gene polymorphisms of phase I and phase II enzymes than that ascribed to single gene polymorphism.

Genetic polymorphisms in GSTM1, GSTT1 and GSTP1 genes and risk of lung cancer in a North Indian population

BACKGROUND

A number of studies done so far in different populations have shown that polymorphisms within the GST genes play an important role in determining individual susceptibility to lung cancer; however, data obtained so far have been contradictory within the same or different populations. Few studies have focused on the combinatorial effect of the GST genes on susceptibility to lung cancer and also for different histological subtypes. Our aim is to investigate the roles of GSTM1, GSTT1, and GSTP1 polymorphisms as genetic modifiers of risk for lung cancer and histological subtypes using a larger sample size in a North Indian population.

METHODS

In total 540 subjects (270 lung cancer cases and 270 controls) were evaluated for the GST polymorphism. Genotyping for the GSTM1, GSTT1 and GSTP1 gene was done by using a multiplex PCR and PCR-RFLP method.

RESULTS

GSTM1 null genotype was found to be associated with lung cancer (OR=1.65, 95%CI: 116-2.3, P=0.005) and this risk was higher in cases of adenocarcinoma (ADCC). GSTT1 and GSTP1 did not show any significant association with lung cancer; however, when stratified for histological subtypes a significant association was observed for ADCC and small-cell lung cancer (SCLC) for both GSTT1 null and variant GSTP1 genotypes. The combined 'at risk' genotypes of null GSTM1 and GSTT1 genes were found to be associated with lung cancer risk, and this risk was higher in cases of ADCC (OR=4.09, 95%CI: 110-10.2, P=0.002). There is a twofold increased risk for lung cancer with the null GSTM1 and wild-type GSTP1 genotypes (P=0.0004); similarly, a fourfold increased risk was observed with the null GSTT1 and wild-type GSTP1 genotypes (P=0.0001).

CONCLUSIONS

The deficient GST genotypes seem thus to be important risk modifiers for lung cancer and related histological subtypes, especially in combination.

Association of PSMA4 polymorphisms with lung cancer susceptibility and response to cisplatin-based chemotherapy in a Chinese Han population

PURPOSE

Genetic factors play an important role in our predisposition to cancer. Genome-wide association studies have linked the chromosome 15q25.1 locus to lung cancer susceptibility and implicated proteasome subunit alpha type-4 (PSMA4) as a candidate gene. In this case-control study, pathologically confirmed lung cancer patients and controls from the Chinese Han population were investigated to determine the effect of variant genotypes within the PSMA4 locus on susceptibility to lung cancer and sensitivity to cisplatin-based chemotherapy.

METHODS

We identified validated tagged single nucleotide polymorphisms (tSNPs) with minor allele frequency >5 % in the HapMap Chinese Han Beijing population and genotyped seven SNPs within the PSMA4 locus. Their correlation with lung cancer risks and treatment response were examined using χ (2) test and haplotype analysis. Multivariate logistic regression analysis tested the association between the polymorphisms and chemotherapy response.

RESULTS

rs12901682 is associated with lung cancer risks (OR = 1.45, 95 % CI, 1.04-2.02; P = 0.029). Using SNPStats software, we found rs12901682 (OR = 6.30, 95 % CI, 1.31-30.26; P = 0.0073) associated with lung cancer risks in the recessive model. Haplotype analysis showed that "CAGAATC" conferred an increased risk of lung cancer (OR = 1.50, 95 % CI, 1.07-2.11; P = 0.019). After adjustment for age, this association was pronounced in the male gender (OR = 6.30, 95 % CI, 1.31-30.26; P = 0.0073). PSMA4 polymorphisms did not affect the tumor sensitivity to cisplatin combination chemotherapy.

CONCLUSIONS

Our study suggests a potential association between PSMA4 variants and lung cancer risk in Chinese Han population.

Impact of CYP1A1, GSTM1, and GSTT1 polymorphisms in overall and specific prostate cancer survival

OBJECTIVE

Prognostic biomarkers that distinguish between patients with good or poor outcome can be used to guide decisions of whom to treat and how aggressively. In this sense, several groups have proposed genetic polymorphisms as potential susceptibility and prognostic biomarkers; however, their validity has not been proven. Thus, the main goal of the present work was to investigate the potential role of single and combined CYP1A1, GSTM1, and GSTT1 genotypes as modifiers of cancer survival in Chilean patients with prostate cancer.

METHODS AND MATERIALS

A total of 260 histologically confirmed patients were recruited from a voluntary screening, and genomic DNA was obtained from their blood samples for genotyping analyses to detect the CYP1A1*2A polymorphism and GSTM1 and GSTT1 deletions. The progression of illness and mortality were estimated with a median follow-up of 8.82 years. Adjusted estimated genotype risks were evaluated by hazard ratio and 95% CI using the Cox proportional model. In addition, the Kaplan-Meier survival method and log-rank test were used to evaluate patient survival with regard to genotype.

RESULTS

The 9-year overall and specific survival rates were 67.6% and 36.6% in the GSTT1null group, 67.6% and 58.7% in the GSTM1non-null group, 69.0% and 51.6% in the *1A/*2A group, 63.9% and 61.5% in the *2A/*2A group vs. 76.2% and 62.3% in the GSTT1non-null group, 82.3% and 50% in the GSTM1null group, and 83.7% and 56.3% in the *1A/*1A group, respectively. The hazard ratios and the Kaplan-Meier curve results demonstrate that the GSTM1non-null, GSTT1null, and CYP1A1*2A genotypes are significantly associated with mortality. Our study has two main limitations: a relatively small sample size and a low global mortality percentage (25.4%); thus, we need to continue the follow-up to confirm these findings.

CONCLUSIONS

Our results suggest that the GSTM1non-null, GSTT1null, and CYP1A1*2A genotypes may be good prognosis markers, particularly in patients with high-risk tumors.

Polymorphisms in the human cytochrome P450 and arylamine N-acetyltransferase: susceptibility to head and neck cancers

The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes (CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes (CYP1A1, CYP1BA1, CYP2D6, and CYP2E1), and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.

Frequencies of 23 functionally significant variant alleles related with metabolism of antineoplastic drugs in the chilean population: comparison with caucasian and asian populations

Cancer is a leading cause of death worldwide. The cancer incidence rate in Chile is 133.7/100,000 inhabitants and it is the second cause of death, after cardiovascular diseases. Most of the antineoplastic drugs are metabolized to be detoxified, and some of them to be activated. Genetic polymorphisms of drug-metabolizing enzymes can induce deep changes in enzyme activity, leading to individual variability in drug efficacy and/or toxicity. The present research describes the presence of genetic polymorphisms in the Chilean population, which might be useful in public health programs for personalized treatment of cancer, and compares these frequencies with those reported for Asian and Caucasian populations, as a contribution to the evaluation of ethnic differences in the response to chemotherapy. We analyzed 23 polymorphisms in a group of 253 unrelated Chilean volunteers from the general population. The results showed that CYP2A6*2, CYP2A6*3, CYP2D6*3, CYP2C19*3, and CYP3A4*17 variant alleles are virtually absent in Chileans. CYP1A1*2A allele frequency (0.37) is similar to that of Caucasians and higher than that reported for Japanese people. Allele frequencies for CYP3A5*3(0.76) and CYP2C9*3(0.04) are similar to those observed in Japanese people. CYP1A1*2C(0.32), CYP1A2*1F(0.77), CYP3A4*1B(0.06), CYP2D6*2(0.41), and MTHFR T(0.52) allele frequencies are higher than the observed either in Caucasian or in Japanese populations. Conversely, CYP2C19*2 allelic frequency (0.12), and genotype frequencies for GSTT1 null (0.11) and GSTM1 null (0.36) are lower than those observed in both populations. Finally, allele frequencies for CYP2A6*4(0.04), CYP2C8*3(0.06), CYP2C9*2(0.06), CYP2D6*4(0.12), CYP2E1*5B(0.14), CYP2E1*6(0.19), and UGT2B7*2(0.40) are intermediate in relation to those described in Caucasian and in Japanese populations, as expected according to the ethnic origin of the Chilean population. In conclusion, our findings support the idea that ethnic variability must be considered in the pharmacogenomic assessment of cancer pharmacotherapy, especially in mixed populations and for drugs with a narrow safety range.

Polymorphism of glutathione S-transferase (GST) variants and its effect on distribution of urinary arsenic species in people exposed to low inorganic arsenic in tap water: an exploratory study

Glutathione S-tranferases (GST) are multigenic enzymes that have been associated with arsenic metabolism. The objective of this study was to evaluate the relationship between polymorphic variants of GST and urinary concentration of arsenic species in people exposed to low levels of arsenic. A cross-sectional study among 66 nonoccupationally exposed subjects, living in the city of Antofagasta, Chile. Polymorphic variants were analyzed by polymerase chain reaction (PCR) and arsenic species was determined by atomic absorption spectrometry. The effect of GST variants on arsenic concentration was evaluated using univariate and covariate-adjusted regressions. For both GSTT1 and GSTM1 there were no significant differences in detected arsenic relative species between carriers of the active and null polymorphic variants. There was nondefinitive evidence that polymorphic variants of GST play a role in arsenic metabolism in sample of the Chilean subjects studied.

Oral cancer susceptibility associated with the CYP1A1 and GSTM1 genotypes in Chilean individuals

Polycyclic aromatic hydrocarbons (PAHs) contained in tobacco smoke acquire carcinogenicity following their activation by xenobiotic-metabolizing enzymes to highly reactive metabolites. The cytochrome P4501A1 (CYP1A1) enzyme is central to the metabolic activation of these PAHs, and GSTM1 is the main enzyme responsible for its detoxification. CYP1A1 and GSTM1 polymorphisms were evaluated in 124 Chilean healthy controls and 48 oral cancer patients through PCR-based restriction fragment length polymorphism. In the healthy controls, frequencies of the CYP1A1 variant alleles for m1 (CYP1A1(*)2A) and the GSTM1null genotype were found to be 0.25 and 0.19, respectively. In the oral cancer patients, these frequencies were 0.33 and 0.50, respectively. Thus, the GSTM1 and m1 rare alleles were significantly more frequent in the oral cancer patients compared to the controls. The estimated relative risk for oral cancer associated with the single genotype CYP1A1 or GSTM1 was 2.08 for wt/m1, 1.04 for m1/m1 and 4.16 for the GSTM1null genotype. For smokers, the estimated relative risk (adjusted by age and gender) was higher in the individuals carrying the m1 allele of CYP1A1 [wt/m1: odds ratio (OR)=5.68, P=0.0080; m1/m1: OR=7.77, P=0.0420] or GSTM1null genotype (OR=20.81, P<0.0001). Combined genotypes CYP1A1 and GSTM1 increased the risk significantly (wt/m1/GSTM1null: OR=19.14, P=0.0030; m1/m1/GSTM1null: OR=21.39, P=0.0130). Taken together, these findings suggest that Chilean individuals carrying single or combined GSTM1 and CYP1A1 polymorphisms may be more susceptible to oral cancer induced by environmental tobacco smoking.

Polymorphism of the CYP1A1*2A gene and susceptibility to lung cancer in a Brazilian population

OBJECTIVE: To estimate and compare the frequency of CYP1A1*2A gene polymorphisms in a Brazilian population and determine the possible contribution of these genetic variations to lung cancer risk. METHODS: The study population included 200 patients with lung cancer, and the control group consisted of 264 blood donors. Genomic DNA was obtained from peripheral blood samples. The PCR-RFLP method was used for analysis of the CYP1A1*2A gene. RESULTS: There was no statistically significant difference between the lung cancer patients and the controls in terms of the distribution of CYP1A1*2A polymorphisms (p = 0.49). A multivariate logistic regression model analysis by ethnic group revealed that, within the lung cancer group, the CYP1A1*2A genotype CC plus TC was more common among the African-Brazilian patients than among the White patients (adjusted OR = 3.19; 95% CI: 1.53-6.65). CONCLUSIONS: The CYP1A1*2A gene cannot be linked with lung cancer risk in Brazilian patients at this time. Larger epidemiologic studies are needed in order to establish whether the CC plus TC polymorphism increases the risk of lung cancer in African-Brazilians.

Relevance of glutathione S-transferase M1 and cytochrome P450 1A1 genetic polymorphisms to the development of head and neck cancers

BACKGROUND

Cytochrome P450 (CYP) and glutathione S-transferase (GST) gene variants have been intensively investigated for their implication in the development of different neoplasms.

METHODS

In the present study, we analyzed genetic polymorphisms of CYP1A1, GSTM1, GSTP1, and GSTT1 in 127 head and neck cancer patients and 151 hospital controls.

RESULTS

No significant increase in risk in patients with the GSTM1 null genotype (OR=1.52, 95% CI: 0.93-2.49) or CYP1A1 462Val alleles (OR=1.60, 95% CI: 0.73-3.52) or GSTP1 105Val alleles (OR=0.97, 95% CI: 0.59-1.58) was observed. The GSTT1 null genotype was found in 30.5% of the controls and 21.3% of the head and neck cancer patients (p=0.15). The estimated head and neck cancer risk for the combination of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with either GSTP1 Ile105Val or Val105Val genotype (OR=2.89, 95% CI: 0.71-11.71) and for the combination of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with GSTT1 null genotype (OR=2.62, 95% CI: 0.64-10.85) suggested the absence of the modifying effect of combined variant alleles on head and neck cancer susceptibility. The joint effect of either CYP1A1 Ile462Val or CYP1A1 Val462Val genotype with GSTM1 null genotype significantly increased the risk of head and neck cancer (OR=7.15, 95% CI: 1.49-34.32).

CONCLUSIONS

Our findings corroborate metabolic genes interactions, especially for CYP1A1 462Val alleles and GSTM1 homozygous deletion, in the development of head and neck cancer in the investigated population groups in Poland.

Ethnogenetic layering (EL): an alternative to the traditional race model in human variation and health disparity studies

BACKGROUND

Traditionally, studies in human biodiversity, disease risk, and health disparities have defined populations in the context of typological racial models. However, such racial models are often imprecise generalizations that fail to capture important local patterns of human biodiversity.

AIM

More explicit, detailed, and integrated information on relevant geographic, environmental, cultural, genetic, historical, and demographic variables are needed to understand local group expressions of disease inequities. This paper details the methods used in ethnogenetic layering (EL), a non-typological alternative to the current reliance of the biological racial paradigm in public health, epidemiology, and biomedicine.

SUBJECTS AND METHODS

EL is focused on geographically identified microethnic groups or MEGs, a more nuanced and sensitive level of analysis than race. Using the MEG level of analysis, EL reveals clinical variations, details the causes of health disparities, and provides a foundation for bioculturally effective intervention strategies. EL relies on computational approaches by using GIS-facilitated maps to produce horizontally stratified geographical regional profiles which are then stacked and evaluated vertically. Each horizontal digital map details local geographic variation in the attributes of a particular database; usually this includes data on local historical demography, genetic diversity, cultural patterns, and specific chronic disease risks (e.g. dietary and toxicological exposures). Horizontal visual display of these layered maps permits vertical analysis at various geographic hot spots.

RESULTS AND CONCLUSIONS

From these analyses, geographical areas and their associated MEGs with highly correlated chronic disease risk factors can be identified and targeted for further study.

The role of GSTM1 gene polymorphisms in lung cancer development in Turkish population

Background

Glutathione S-transferase (GSTs) plays an important role in the detoxification of many xenobiotics involved in the etiology of cancer. In different ethnic groups, variations in null allele frequency have been observed. We have investigated GSTM1 gene polymorphisms in healthy subjects and lung cancer patients in the Turkish population and reviewed the control subjects of the studies performed in the Turkish population.

Methods

Following blood sampling from patients and controls, DNA samples were extracted from the whole blood and were amplified by using polymerase chain reaction (PCR) method in all of the 256 cases, consisting of 102 previously diagnosed with lung cancer and 154 healthy controls.

Results

The prevalence of GSTM1-null genotype in the lung cancer patients was 49%, compared to 52.6% in the control group (OR = 1.39, 95% CI = 0.70–1.90, p = 0.57). There were also no significant relationships in GSTM1 genotypes among histopathologic types of lung cancers (p > 0.05). The frequency of GSTM1 was found to be 41.2% (n = 1809) when the control subjects of the studies performed in Turkish population were reviewed.

Conclusion

We have observed that GSTM1 genotype is not an independent risk factor for lung cancer.

Cervical cancer and CYP2E1 polymorphisms: implications for molecular epidemiology

INTRODUCTION

Besides human papillomavirus (HPV) infection, several cofactors are considered important for the development of cervical cancer (CC). Among these, tobacco smoke, other sexually transmitted diseases, inflammation and nutritional factors have been intensively described. CYP2E1 polymorphisms have been associated with the metabolization of several carcinogens, some of them considered risk factors for CC development, such as tobacco smoke. The aim of this study was to evaluate the role of CYP2E1 polymorphisms in the susceptibility to cervical cancer in a Portuguese population.

PATIENTS AND METHODS

The genotypic analysis was performed with the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methodology, using peripheral blood samples of 454 individuals: 122 presented invasive squamous cell carcinoma (ICC), 59 presented squamous intraepithelial lesions (SIL), and the control population was composed of 274 healthy individuals.

RESULTS

Concerning the DraI polymorphism, we observed a decreased risk for the development of squamous cervical lesions in the presence of the C allele [odds ratio (OR)=0.600; 0.378<OR<0.952; p=0.029]. In the stratification of the analysis according to the mean age, we observed an increased risk for the development of SIL, for women older than 39 years of age, in the presence of the D allele (OR=0.087; 0.012<OR<0.651; p=0.003). Regarding the RsaI polymorphism, we did not find any significant differences.

CONCLUSION

The decreased risk observed for the development of SIL and not ICC in the presence of the D allele may indicate that CYP2E1 interferes with the initial steps of the carcinogenic process, probably due to its involvement in the action of immunological mediators, expressed during cervical inflammation. These aspects may help to define new therapeutic strategies for chemoprevention.

Concurrent expression of aryl hydrocarbon receptor and CYP1A1 but not CYP1A1 MspI polymorphism is correlated with gastric cancers raised in Dalian, China

The frequency of cancer-associated m2m2- (C-) genotype of CYP1A1 and the factors contributing to the increased CYP1A1 expression in gastric cancers (GCs) are largely unknown. To address theses issues, PCR-restriction fragment length polymorphism (PCR-RFLP) was performed to elucidate the MspI polymorphism in 60 GC cases and 57 normal donor samples. The frequencies of m1m1-, m1m2- and m2m2-genotype were 43.3, 45 and 11.7% among GC patients and 45.6, 49.1 and 5.3% among the normal donors respectively, demonstrating no significant difference of them between cancer and control groups (chi(2)=0.343, P=0.558). The correlation of Aryl hydrocarbon receptor (AhR) with the frequent CYP1A1 expression in stepwise gastrocarcinogenesis was determined by RT-PCR, immunohistochemical staining (IHC) and Western blotting, using GC samples as well as their pre-malignant and non-cancerous counterparts. RT-PCR revealed that the AhR detection rates were 100, 94.12 and 85.17% in GC, pre-malignant and non-cancerous mucosa (P>0.05) respectively but the level of AhR expression in GCs was much higher than that of non-cancerous tissues. IHC showed that the frequencies of AhR detection were 94.87% (37/39) in GCs, 94.12% (16/17) in pre-malignant lesions and 50% (3/6) in non-cancerous mucosa, revealing significant difference in frequencies of AhR detection and levels of AhR expression between GC or pre-malignant group and non-cancerous one (P<0.05). The frequency of AhR nucleus translocation was significantly high in GCs (94.87%; 37/39) than that in pre-malignant (70.59%; 12/17) and especially in non-cancerous group (16.67%; 1/6). Co-existence of AhR nuclear translocation and CYP1A1 expressions were found in 82.70% (43/52) of GCs (r(s)=0.437, P<0.01). Our results suggest (1) that CYP1A1 MspI polymorphism may not contribute to the high gastric cancer risk in Dalian region and (2) that enhanced AhR expression and especially its nuclear translocation may be a favorable factor for GC formation presumably via up-regulating CYP1A1 expression.

Possible risk modification by CYP1A1, GSTM1 and GSTT1 gene polymorphisms in lung cancer susceptibility in a South Indian population

Susceptibility to lung cancer has been shown to be modulated by inheritance of polymorphic genes encoding cytochrome P450 1A1 (CYP1A1) and glutathione S transferases (GSTM1 and GSTT1), which are involved in the bioactivation and detoxification of environmental toxins. As the incidence of lung cancer is known to differ according to ethnicity, we have conducted a case-control study of 146 South Indian lung cancer patients along with 146 healthy controls, to assess any association between CYP1A1, GSTM1 and GSTT1 polymorphisms, either separately or in combination, with the likelihood of development of lung cancer in our population. The current weight of evidence from our study indicated that the frequency of CYP1A1 MspI homozygous variant alleles was significantly higher in cases (OR = 3.178). We observed a considerable difference in the GSTT1 null deletion frequency in this population when compared with other populations (OR = 2.472, 95% CI: 1.191-5.094, P = 0.014). There was no relative risk in GSTM1 null genotype when analysed singly (P = 0.453). Considering genotype combinations, risk of lung cancer increased remarkably significantly in individuals having one variant allele of CYP1A1, GSTM1, or GSTT1, suggesting gene-gene interactions. Rare genotypic combinations (such as CYP1A1 wild GSTM1 or GSTT1 either null; CYP1A1 variant both GSTM1 and GSTT1 present; CYP1A1 variant GSTM1 or GSTT1 either null), were at higher risk compared to the reference group. Moreover, patients who had smoked <20 pack years and harboured the CYP1A1 variant allele or the GSTT1 null genotype also had a significant risk of lung cancer. Hence our study-the first to analyse a South Indian population-suggests the importance of combined CYP1A1, GSTM1 and GSTT1 polymorphisms in the development of smoking-induced lung cancer.

Smoking-gene interaction and disease development: relevance to pancreatic cancer and atherosclerosis

There is little doubt that cigarette smoking remains a major environmental health risk that humans are facing in the twenty-first century. Cigarette smokers are more likely to develop many forms of diseases than nonsmokers, including cancers and vascular diseases. With the availability of the human genome sequence, we become more aware of the genetic contributions to these common diseases, especially the interactive relations between environmental factors (e.g., smoking) and genes on disease susceptibility, development, and prognosis. Although smoking is responsible for up to 30% of pancreatic cancers and about 10% of cases are ascribed to genetic reasons, some genetic variants do not predispose carriers to disease development unless they are exposed to a specific adverse environment such as smoking. This smoke-gene interaction could potentially be responsible for most of the cases. Certain polymorphisms in genes such as CYP1A1 have been shown particularly sensitive to smoking-induced pathogenesis, including pancreatic cancer and atherosclerosis. We found that individuals with CYP1A1 CC genotype had a more than three fold increase in risk for severe coronary atherosclerosis when they smoked. Patients with endothelial nitric oxide synthase (eNOS) intron 4 27 repeat homozygotes were more likely to develop severe coronary stenosis when they smoked. On the other hand, DNA variants at the eNOS gene also dictate how smoking affects the expression of eNOS. We showed that GSTM1 deficiency was not involved in smoking-induced vascular diseases, but p53 polymorphisms tended to modify the disease severity in smokers. We are still at an early stage of defining the pairs and mechanisms of smoke-gene interaction, and this etiologic mechanism may hold great potential for risk assessment, treatment strategy, and prognostic predictions.

Relationship among metabolizing genes, smoking and alcohol used as modifier factors on prostate cancer risk: exploring some gene-gene and gene-environment interactions

BACKGROUND

Prostate cancer (PCa) is one of the most common male cancers, but the burden of this disease shows remarkable worldwide variation. The role of susceptibility low penetrance genes and environmental factors in the etiology of (PCa) is unclear, but may involve, in some cases, multiple alleles at multiple loci and environmental factors.

STUDY OBJECTIVES

To assess whether CYP1A1, GSTM1, GSTT1 susceptibility genotypes, smoking status and alcohol consumption factors contribute to PCa risk, gene-gene and gene-environment interactions were analyzed.

DESIGN AND PARTICIPANTS

We explored interactions on a multiplicative scale conducting a population-based case-control and a case-only study on 103 incident PCa patients and 132 unrelated controls.

MAIN RESULTS

The interaction odds ratios (IOR) for PCa risk were increased in men who had both susceptibility genotypes GST (M1; T1) null and CYP1A1-M1* in a case-control and case-only design (IOR(cc): 1.11; 95% CI: 0.12-10.02; IOR(cc): 6.23; 95%, CI: 0.51-75.89; IOR(co): 2.80; 95% CI: 0.44-17.45 and IORco: 2.65; 95%, CI: 0.30-25.40). No clear evidence for interaction on a multiplicative scale between smoking status, alcohol consumption and genetic polymorphisms in PCa risk was observed.

CONCLUSIONS

Our findings suggest that the interaction between genetic polymorphisms in GST (T1; M1) and CYP1A1-M1* would play a significant role as a modifying factor on PCa risk in Chilean people. However, these preliminary exploratory results should be confirmed in a larger study.

Chromosomal aberrations in workers exposed to low levels of benzene: association with genetic polymorphisms

Benzene and its metabolites damage human lymphocytes, resulting in chromosomal aberrations and aneuploidy. Polymorphisms in the genes for benzene-metabolizing enzymes have been implicated in benzene-associated haematotoxicity. In this study, we examined the specificity of benzene-induced aneuploidy and the influence of genetic polymorphisms (GSTM1, GSTT1, GSTP1, NAT2, NQO1 and CYP2E1) on chromosomal aberrations. In total, 82 benzene-exposed workers from a coke oven plant and 76 matched controls were examined. The benzene concentration in the work-place air ranged from 0.014-0.743 p.p.m. (geometric mean 0.557 p.p.m.). Benzene exposure was associated with significant increases in both monosomy and trisomy of chromosomes 8 and 21. Translocations between chromosomes 8 and 21 [t(8:21)] were eight-fold more frequent in the high-level exposure group compared to the control group. Multiple regression analysis indicated that the frequencies of chromosome aberrations were significantly associated with benzene exposure and polymorphisms in the metabolic enzyme genes. A particular subset of genotypes, which included the GSTM1-null and GSTT1-null genotypes, the slow acetylator type of NAT2, a variant of the NQO1 genotype and the CYP2E1 DraI and RsaI genotypes, were either separately, or in combination, associated with increased frequencies of aneuploidy among the benzene-exposed individuals after adjustments for age, alcohol consumption and smoking. These results suggest that polymorphisms in the genes for benzene-metabolizing enzymes influence the susceptibility of individuals to chromosomal aberrations in relation to benzene exposure.

Chromosome and DNA damage analysis in individuals occupationally exposed to pesticides with relation to genetic polymorphism for CYP 1A1gene in Ecuador

DNA damage was measured by using the alkaline comet assay and the chromosomal aberration (CA) test using peripheral blood samples from 45 pesticide sprayers from Cayambe, Ecuador. From a total of approximately 200 nuclei scored for each donor with the comet assay, a highly significant increase in DNA migration was observed when compared with a similar unexposed control population. Additionally, in the CA test, the exposed individuals were found to be significantly different when compared to the control population. Polymorphisms for the CYP 1A1 (Msp I and Ile/Val) in exposed individuals were analyzed by PCR-RFLP and allele-specific PCR techniques. No association was found between the polymorphisms and higher levels of DNA damage as assessed by the comet assay.

Occupational and environmental levels of mutagenic PAHs and respirable particulate matter associated with diesel exhaust in Santiago, Chile

This work studied the mutagenic potential and polycyclic aromatic hydrocarbon (PAH) levels onto PM10 collected in diesel revision plants, in an urban area as well as in a rural area in Santiago, Chile. The PM10 average levels in diesel emission plants during working hours (there is no occupational PM10 Chilean standard) were significantly higher than the atmospheric Chilean PM10 standard and highly mutagenic and with high PAHs levels. Additionally, we evaluated the contribution of CYP1A1 and GSTM1 polymorphisms on 1-OH-pyrene urinary levels. The diesel-exposed workers carrying the CYP1A1*2A allele showed significantly higher 1-OH-P levels than the subjects from the rural area with the same genotype. The higher levels of 1-OH-P were found in individuals carrying the combined CYP1A1*2A and GSTM1 null genotype. This kind of information might be relevant to establish prevention, protection, and mitigation actions to protect public health.

Strong association between the GSTM1-null genotype and lung cancer in a Turkish population

Glutathione S-transferases are possibly related to the detoxification of many xenobiotics involved in the etiology of cancer. To investigate the role of the glutathione S-transferase M1 deletion (GSTM1-null) in lung cancer, the polymerase chain reaction was used to determine the GSTM1 genotypes of lung cancer patients (n=101) and hospital (n=206) in a Turkish population. The prevalence of the GSTM1-null genotype in the case group was 48%, compared to 18% in the control group, giving an odds ratio (OR) of 4.14 (95% confidence interval [CI]=2.36-7.27). The analysis of patients by histologic type of lung cancer (10% adenocarcinoma, 43% squamous cell carcinoma, 26% small cell carcinoma, and 11% large cell carcinoma) showed no association between histopathologic type of lung cancer and GSTM1-null genotype. When the interaction between the GSTM1-null genotype and smoking status was analyzed, among the 67 smokers, the GSTM1-null genotype was found in 37 (55%) with an OR of 2.58 (95% CI=1.00-6.73) indicating a significant association. However, no association was found between smoking exposure (<30 and > or =30 packs/year) and GSTM1-null genotype. We conclude that, in this study the null GSTM1 genotype is an independent risk factor for the development of lung cancer for Turkish population.

Positive correlation between single or combined genotypes of CYP1A1 and GSTM1 in relation to prostate cancer in Chilean people

BACKGROUND

The prostate cancer is a slowly progressing disease that begins decades prior to diagnosis. It has been suggested that there might be differences in susceptibility due to genetic polymorphisms in biotransformation enzyme genes. In the present work, associations between CYP1A1(Msp1), GSTM1(-/-) polymorphisms, and prostate cancer were analyzed in a case-control study.

METHODS

Genomic DNA was isolated from peripheral blood samples, collected on EDTA. PCR-RFLP was used to determine simultaneously Msp1 and GSTM1(-/-) polymorphisms.

RESULTS

In cancer patients, frequency of m2 variant allele (0.377) and GSTM1(-/-) (0.362) showed statistically significant increases compared to the control group (0.262 and 0.227, respectively). The estimate relative risks (OR) were higher for individuals carrying combined CYP1A1 and GSTM1 rare genotypes, in relation to individuals carrying CYP1A1 or GSTM1 alone. Multivariate logistic regression analysis including confounding factors (age, digital examination, and PSA antigen) showed even higher risk for individuals carrying m2m2 genotype (OR = 3.99; 95% CI, 1.27-12.54), GST(-/-) genotype (OR = 2.75; 95% CI, 1.31-5.79), and m2m2/GST(-) genotype (OR = 16.63; 95% CI, 1.67-165.48).

CONCLUSIONS

Taken together, these findings suggest that Chilean people carrying single or combined GSTM1 and CYP1A1 polymorphisms are more susceptible to prostate cancer.

Genetic influence on cigarette-induced cardiovascular disease

Cigarette smoking as an addictive habit has accompanied human beings for more than 4 centuries. It is also one of the most potent and prevalent environmental health risks human beings are exposed to, and it is responsible for more than 1000 deaths each day in the United States. With recent research progress, it becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. These detrimental effects are not only present in active smokers who choose the risk, but also to innocent bystanders, as passive smokers, who are exposed to cigarettes not-by-choice. While the cigarette-induced harm to human health is indiscriminate and severe, the degree of damage also varies from individual to individual. This intersubject variability in cigarette-induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification process, eg, cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development. Through population studies, we have learned that certain CYP1A1 variants, such as Mspl polymorphism, may render the carriers more susceptible to cigarette-induced lung cancer or severe coronary atherosclerosis. The endothelial nitric oxide synthase intron 4 rare allele homozygotes are more likely to have myocardial infarction if they also smoke. In vitro experimental approach has further demonstrated that cigarettes may specifically regulate these genes in genotype-dependent fashion. While we still know little about genetic basis and molecular pathways for cigarette-induced pathological changes, understanding these mechanisms will be of great value in designing strategies to further reduce smoking in targeted populations, and to implement more effective measures in prevention and treatment of cigarette-induced diseases.

Dynamics of cytochrome P4502E1 activity in man: induction by ethanol and disappearance during withdrawal phase

BACKGROUND/AIMS

Chronic ethanol consumption results in the induction of hepatic cytochrome P4502E1 (CYP2E1) in man, which is believed to play an important role in the pathogenesis of alcoholic liver disease. However, the amount and duration of alcohol intake associated with CYP2E1 induction is not known but limited information is available on the disappearance of CYP2E1 following alcohol withdrawal.

METHODS

To study these questions, five healthy male volunteers received ethanol daily (40 g/day) over 4 weeks. CYP2E1 induction was monitored by using the chlorzoxazone test before and every week following the start of alcohol ingestion. In addition, CYP2E1 was also determined in five alcoholics 1, 3, 8 and 15 days following ethanol withdrawal and in five patients with non-alcoholic liver disease.

RESULTS

A significant CYP2E1 induction occurred 1 week following the ingestion of 40 g ethanol per day and increased further after 4 weeks. The disappearance of CYP2E1 was found to be significant 3 days following ethanol withdrawal and further decreased up to day 8. Thereafter, no significant change occurred and CYP2E1 activities were comparable with those in patients with non-alcoholic liver disease.

CONCLUSIONS

These data show a significant and quick induction of CYP2E1 activity, already at moderate alcohol consumption, which may be of importance in the pathogenesis of alcoholic liver disease, of ethanol, drug and vitamin A interactions and in alcohol associated carcinogenesis.

CYP1A1, CYP2E1 and GSTM1 genetic polymorphisms. The effect of single and combined genotypes on lung cancer susceptibility in Chilean people

CYP1A1, CYP2E1 and GSTM1 polymorphisms were evaluated in Chilean healthy controls and lung cancer patients. In the Chilean healthy group, frequencies of CYP1A1 variant alleles for MspI (m2 or CYP1A1*2A) and ile/val (val or CYP1A1*2B) polymorphisms were 0.25 and 0.33, respectively. Frequencies of variant alleles C (CYP2E1*6) and c2 (CYP2E1*5B) for CYP2E1 were 0.21 and 0.16, respectively and frequency for GSTM1(-) was 0.24. The presence of variant alleles for GSTM1, MspI and Ile/val polymorphisms was more frequent in cases than in controls. However, frequencies for the c2 and C alleles were not significantly different in controls and in cases. The estimated relative risk for lung cancer associated to a single mutated allele in CYP1A1, CYP2E1 or GSTM1 was 2.41 for m2, 1.69 for val, 1.16 for C, 0.71 for c2 and 2.46 for GSTM1(-). The estimated relative risk was higher for individuals carrying combined CYP1A1 and GSTM1 mutated alleles (m2/val, OR=6.28; m2/GSTM1(-), OR=3.56) and lower in individuals carrying CYP1A1 and CYP2E1 mutated alleles (m2/C, OR=1.39; m2/c2, OR=2.00; val/C, OR=1.45; val/c2, OR=0.48; not significant). The OR values considering smoking were 4.37 for m2, 4.05 for val, 3.47 for GSTM1(-), 7.38 for m2/val and 3.68 for m2/GSTM1(-), higher values than those observed without any stratification by smoking. Taken together, these findings suggest that Chilean people carrying single or combined GSTM1 and CYP1A1 polymorphisms could be more susceptible to lung cancer induced by environmental pollutants such as polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbon levels and mutagenicity of inhalable particulate matter in Santiago, Chile

The air in Santiago, Chile, is among the most highly polluted in the world. Due to the high levels of pollutants and the high incidence of respiratory diseases, especially in the most susceptible groups, Santiago has been declared a saturated zone for PM(10), O(3), and CO. The aim of this work was to investigate polycyclic aromatic hydrocarbon levels and mutagenic activity of Santiago s fine and coarse fractions of inhalable particles. The levels of 16 polycyclic aromatic hydrocarbons (PAHs) were determined by high-performance liquid chromatography in organic extracts from respirable particles (OERP). Respirable particulate matter (fine and coarse) contains high levels of PAHs including six mutagenic ones classified by the IARC as carcinogenic, which represented at least 45% of the total PAH concentration. A seasonal effect was observed, with higher values in months with lower temperatures. Although a significant decline of PAH levels in OERP was observed in the last years, the levels of carcinogenic PAHs are still higher than those reported in cities of the United States, Australia, and Europe. OERP were highly mutagenic and contained direct and indirect mutagens, which produced both frameshift and base substitution mutations in Salmonella typhimurium. In addition, organic extracts from total suspended particles were also highly mutagenic at the tk locus in h1A1v2 human lymphoblasts in culture. In spite of the important decrease in PAHs in the period 1991-1996, direct mutagenic response has not changed significantly, suggesting that the levels of direct mutagenic pollutants (e.g., nitroarenes) have not decreased considerably during the last years. These results suggest a risk for Santiago s inhabitants since pollutants adsorbed in inhalable particles are highly mutagenic and can damage DNA.

Association between GSTM1*0 and squamous dysplasia of the esophagus in the high risk region of Linxian, China

Individuals with specific phase I and phase II enzyme polymorphisms may be at increased risk for squamous cell carcinoma of the esophagus. However, to our knowledge there has been only one previous report that evaluates a potential role for these polymorphisms in increasing risk for preneoplastic squamous lesions of the esophagus. To explore this further, we examined polymorphisms in CYP1A1, CYP2E1, GSTM1 and GSTT1, both independently and in combination, for potential associations with the risk of biopsy-proven squamous dysplasia of the esophagus in asymptomatic adults from Linxian, a high risk region in China. Cases consisted of 56 individuals from an esophageal cancer screening study with an endoscopic biopsy diagnosis of mild or moderate squamous dysplasia. Each case was matched on age (+/- 1 year) and gender to a control. Controls were defined as screening study participants with an endoscopic biopsy diagnosis of normal mucosa or esophagitis. DNA was extracted from frozen cell samples obtained by cytologic balloon examination and genotyped using standard methods. Individuals who were GSTM1 null (homozygous for GSTM1*0) were found to have a tendency for an increased risk of esophageal squamous dysplasia (odds ratio=2.6, 95% CI, 0.9-7.4). No excess risks were observed for inheritance of other putative at risk genotypes CYP1A1*2B, CYP2E1*6 or GSTT1*0. The risk associated with the inheritance of combined genotypes was not significantly different than the risk estimates from the univariate analysis. These results are consistent with the notion that exposure to environmental carcinogens that are detoxified by GSTM1, such as polycyclic aromatic hydrocarbons, may contribute to the etiology of esophageal cancer in Linxian.