A Study on the Association of Cytochrome-P450 1A1 Polymorphism and Breast Cancer Risk in North Indian Women

Metal exposure and breast cancer among Northern Mexican women: assessment of genetic susceptibility

This study aims to assess breast cancer (BC) association with metals and whether polymorphisms in CYP1A1, CYP1B1, GSTM1 and GSTT1 act as confounders or as modifiers of those relationships. We performed a secondary analysis of 499 histologically confirmed BC cases and the same number of age-matched population controls. We measured urinary concentrations of 18 metals with mass spectrometry. We determined the genetic variants of interest by allelic discrimination and multiplex PCR. After adjusting for covariates, we found BC negatively associated with arsenic, barium, cobalt, copper, magnesium, molybdenum and vanadium concentrations and positively with those of caesium, manganese, tin and thallium. Most associations remained after stratifying by the genetic variants. We identified that polymorphisms in CYP1B1, CYP1A1 and GSTM1 genes interacted with some metals on BC: interaction p-values CYP1B1 G119T × antimony= 0.036, CYP1B1 G119T × cobalt <0.001, CYP1B1 G119T × tin= 0.032, CYP1A1 A4889G × aluminium= 0.018, CYP1A1 A4889G × arsenic= 0.031, CYP1A1 A4889G × nickel= 0.036, CYP1A1 A4889G × vanadium= 0.031 and GSTM1 deletion × barium= 0.035. Exposure to various individual metals, along with genetic characteristics may contribute to BC development. Further studies are warranted to confirm our results.

Associations of CYP1A1 gene polymorphisms and risk of breast cancer in Indian women: a meta-analysis

Reported associations of CYP1A1 polymorphisms with breast cancer have been inconsistent. In this meta-analysis examining breast cancer associations of three CYP1A1 polymorphisms (M1, M2 and M4) among Indian women may yield information that may be of clinical and epidemiological use for this particular demography. We searched MEDLINE using PubMed and Embase for association studies. From seven published case-control studies, we estimated overall associations and applied subgroup analysis to explore differential effects. All three polymorphisms exhibited overall increased risk, significant in M1 (OR 1.61–1.65, p = 0.04) and M4 (OR 2.02–3.92, p = 0.02–0.04). Differential effects were observed only in the M1 polymorphism where M1 effects were significant in South Indians (OR 2.20–4.34, p < 0.0001) but not the North population, who were at reduced risk (OR 0.64–0.77, p = 0.03–0.55). These populations were not materially different in regard to M2 and M4 as did the women stratified by menopausal status. In this meta-analysis, M1 and M4 effects may render Indian women susceptible, but may be limited by heterogeneity of the studies. Differential effects of the M1 polymorphism in breast cancer render South Indians susceptible compared to those in the North.

Impact of xenobiotic-metabolizing gene polymorphisms on breast cancer risk in South Indian women

BACKGROUND

Functional variants of the xenobiotic-metabolizing genes (XMG) might modulate breast cancer (BC) risk by altering the rate of metabolism and clearance of myriad types of potent carcinogens from the breast tissue. Despite mounting evidence on the role of XMG variants on BC risk, the current knowledge regarding their influence on BC development is still fragmentary.

METHODS

The present study examined the candidate genetic variants in CYP1A1, NQO1, GST-T1, GST-M1, and GST-P1 in 1002 subjects (502 BC patients and 500 disease-free women). PCR-RFLP was employed to genotype the mono-nucleotide variation in CYP1A1, NQO1, and GST-P1, and allele-specific PCR was used to detect the deletion polymorphism in GST-T1 and GST-M1 genes.

RESULTS

Regarding CYP1A1-M1 polymorphism, the heterozygous TC and mutant CC genotype conferred 1.47-fold (95% CI 1.13-1.91, p = 0.004) and 1.84-fold (95% CI 1.17-2.91, p = 0.009) elevated risk of BC. GST-T1 null genotype was associated with increased BC risk (OR 1.47; 95% CI 1.02-2.11, p = 0.037). For the NQO1 C609T variant, the mutant T allele was associated with BC risk with an odds ratio of 1.22 (95% CI 1.02-1.48, p = 0.034). Combinatorial analysis indicated that the presence of NQO1*2 (CT), CYP1A1-M1 (CC), and GST-P1 rs1695 (AG) genotypes conferred 16.7-fold elevated risk of BC (95% CI 3.65-76.85; p < 0.001). Moreover, GST-M1 null genotype was associated with the development of larger primary breast tumors.

CONCLUSION

Xenobiotic-metabolizing gene polymorphisms may play a crucial role in mammary carcinogenesis in South Indian women.

Pleiotropic Functions of Cytochrome P450 Monooxygenase-Derived Eicosanoids in Cancer

Eicosanoids are a class of functionally bioactive lipid mediators derived from the metabolism of long-chain polyunsaturated fatty acids (PUFAs) mediated by multiple enzymes of three main branches, including cyclooxygenases (COXs), lipoxygenases (LOXs), and cytochrome P450s (CYPs). Recently, the role of eicosanoids derived by COXs and LOXs pathways in the control of physiological and pathological processes associated with cancer has been well documented. However, the role of CYPs-mediated eicosanoids, such as epoxyeicosatrienoic acids (EETs), epoxyoctadecenoic acids (EpOMEs), epoxyeicosatetraenoic acids (EpETEs), and epoxydocosapentaenoic acids (EDPs), as well as hydroxyeicosatetraenoic acids (HETEs), in tumorigenesis and cancer progression have not been fully elucidated yet. Here we summarized the association of polymorphisms of CYP monooxygenases with cancers and the pleiotropic functions of CYP monooxygenase-mediated eicosanoids (EETs, EpOMEs, EpETE, EDPs, and 20-HETE) in the tumorigenesis and metastasis of multiple cancers, including but not limited to colon, liver, kidney, breast and prostate cancers, which hopefully provides valuable insights into cancer therapeutics. We believe that manipulation of CYPs with or without supplement of ω-3 PUFAs to regulate eicosanoid profile is a promising strategy to prevent and/or treat cancers.

A meta-analysis and in silico analysis of polymorphic variants conferring breast cancer risk in the Indian subcontinent

Background: Genetic association studies on breast cancer on the Indian subcontinent have yielded conflicting results, and the precise effect of these variants on breast cancer pathogenesis is not known. Methods: Genomic variants, as obtained from selected studies from the Indian subcontinent, were subjected to random-effects and fixed-effect meta-analysis. Functional annotation of the relevant variants was done through a tried and tested in silico pipeline. Results: We found rs4646903/CYP1A1, rs1799814/CYP1A1, rs61886492/GCPII, del2/GSTM1, rs4680/COMT and rs1801394/MTRR to be associated with breast cancer. The del2/GSTM1 holds the association in premenopausal women. Conclusions: This is the first study of its kind from the Indian subcontinent analysing the extent of association of variants across populations followed by their functional annotation in the disease pathway.

Genetic Polymorphisms of the Human Cytochrome P450 1A1 (CYP1A1) and Cervical Cancer Susceptibility among Northeast Thai Women

Background:

CYP1A1 is an enzyme in phase I of the cytochrome P450 (CYP) superfamily, and plays a key role in detoxification of carcinogens. Host genetic predisposition in the CYP1A1 may be associated with an increased susceptibility to cervical cancer.The study aimed to evaluate four common polymorphisms of the CYP1A1 and cervical cancer susceptibility among Northeast Thai women.

Methods:

A case-control study was conducted involving 204 patients with squamous cell cervical cancer (SCCA) and 204 age-matched healthy controls. DNA was extracted from peripheral blood leucocytes. CYP1A1 m1, m3, and m4 genotypes were detected using PCR-RFLP, whereas the CYP1A1 m2 genotype was investigated using real-time PCR. Haplotype analysis was performed using PHASE algorithm version 2.1.1.

Results:

CYP1A1 m3 was monomorphic. Association between the common CYP1A1 polymorphisms, m1 and m2, and cervical cancer risk was not observed (p>0.05), nor was any association found between the m1–m2–m4 haplotype and cervical cancer risk (p>0.05). Interestingly, the CA genotype of CYP1A1 m4 was observed in 30.88% of the cervical cancer patients but was absent in healthy controls.

Conclusion:

Our results demonstrated a possible involvement of the CYP1A1 m4 polymorphism but no other common polymorphisms (viz., m1, m2, and m3) in the risk for cervical cancer.This finding may be useful when screening for risk of cervical cancer among Northeast Thai women.

Association of CYP1A1 M2 (A2455G) Polymorphism with Susceptibility to Breast Cancer in Mazandaran Province, Northern Iran: A Case-control Study

Background:

Breast cancer is one of the most frequent women malignancies in the world. The cytochrome P450 1A1 (CYP1A1) is a key enzyme in xenobiotics metabolism. Moreover, CYP1A1 plays a critical role in the etiology of breast cancer by involving in 2-hydroxylation of estrogen. Therefore, single-nucleotide polymorphisms (SNPs) of its coding gene have been verified to be important in cancer susceptibility. The aim of the study was to evaluate the association of CYP1A1 M2 (A2455G) includes rs1048943 of this SNP polymorphism with the risk of breast cancer in Mazandaran province.

Methods:

Ninety-six breast cancer patients with known clinicopathological characters and 110 healthy women as control were genotyped for CYP1A1 M2 polymorphisms by the restriction fragment length polymorphism technique.

Results:

The analysis of CYP1A1 gene (polymorphism M2) showed that the frequency of homozygous wild genotypes (AA), heterozygous (AG), and mutant genotype (GG) in the patient group, respectively, 78%, 22%, and 0%, and also the frequency of genotypes AA, AG, and GG in healthy included 82%, 16%, and 2%, respectively. Statistical analysis by Logistic regression model at P < 0.05 showed no significant correlation between polymorphisms in CYP1A1M2 and breast cancer risk (odds ratio = 0.84, confidence interval = 0.33–2.17).

Conclusions:

The results indicated that the M2 allelic genotypes were significantly associated neither with breast cancer risk nor with clinicopathological characteristics in Mazandaran province.

Association of Cytochrome CYP1A1 Gene Polymorphisms and Tobacco Smoking With the Risk of Breast Cancer in Women From Iraq

BACKGROUND

CYP1A1 gene polymorphisms and tobacco smoking are among several risk factors for various types of cancers, but their influence on breast cancer remains controversial. We analyzed the possible association of CYP1A1 gene polymorphisms and tobacco smoking-related breast cancer in women from Iraq.

MATERIALS AND METHODS

In this case-control study, gene polymorphism of CYP1A1 gene (CYP1A1m1, T6235C and CYP1A1m2, A4889G) of 199 histologically verified breast cancer patients' and 160 cancer-free control women's specimens were performed by using PCR-based restriction fragment length polymorphism.

RESULTS

Three genotype frequencies (TT, TC, and CC) of CYP1A1m1T/C appeared in 16.1, 29.6, and 54.3% of women with breast cancer, respectively, compared with 41.2, 40, and 18.8% in the control group, respectively. CYP1A1m1 CC genotype and C allele were significantly associated with increased risks for breast cancer in patients (54.3 and 69%, respectively) compared with controls (18.8 and 39%, respectively). While the three genotype frequencies (AA, AG, and GG) of CYP1A1m2A/G were detected in 20.1, 31.2, and 48.7% in patients compared with 46.3, 40.6, and 13.1% in controls, respectively. The frequency of GG genotypes and G allele was significantly higher in patients (48.7 and 64%, respectively) than in the controls (13.1 and 33%, respectively). Smoking women having either CC or GG genotypes showed a highly significant association with increased risk of breast cancer [odds ratio (OR) = 1.607, 95% confidence interval (CI) 0.91-1.64, p = 0.0001, and OR, 1.841, 95% CI, 0.88-1.67, p = 0.0001, respectively]. On the other hand, the T and A alleles of predominantly seen in healthy smoking women (83 and 85%, p = 0.0001, respectively).

CONCLUSION

These findings indicated that both C and G alleles of CYP1A1m1 and m2 were significantly associated with elevated risk of breast cancer in Iraqi women, while the T and A alleles were predominantly seen in healthy controls which may indicate their protective role. The C and G association with breast cancer incidence was more prevalent among tobacco smoking patients. These polymorphisms may be used as biomarkers of breast cancer in women from Iraq.

Impact of Cyp1A1 and Comt Genotypes on Breast Cancer Risk in Mexican Women: A Pilot Study

Background

Data suggest that estrogen-metabolizing genes may be involved in breast cancer carcinogenesis.

Objective

The aim of this study was to determine the association of CYP1A1 and COMT polymorphisms with this disease. Material and methods: A pilot case-control study was conducted with Mexican women. Ninety-one breast cancer patients and 94 healthy controls were selected. Epidemiological and clinical questionnaires were answered by all participants, and genotyping data were obtained. CYP1A1 3801 T>C (rs4646903), CYP1A1 4889 A>G (rs1048943) and COMT 1947 G>A (rs4680) polymorphisms were analyzed by PCR-RFLP.

Results

The results showed a high risk of breast cancer in women carrying the CYP1A1 (3801 T>C) m2/m2 genotype (OR=2.52; 95%CI=1.04–6.08). The risk was higher in postmenopausal women (OR=3.38; 95%CI=1.05–10.87). No association between COMT 1947 G>A (rs4680) or CYP1A1 4889 A>G (rs1048943) and breast cancer was found.

Conclusions

This study suggests that the CYP1A1 (3801 T>C) m2/m2 genotype may contribute to breast cancer susceptibility in Mexican women.

CYP1A1 and GSTP1 gene variations in breast cancer: a systematic review and case-control study

In first part of this study, a systematic review was designed to explore the involvement of CYP1A1 and GSTP1 genes in breast cancerogenesis. Based on systematic review, we designed a study to screen CYP1A1 and GSTP1 genes for mutation and their possible association with breast carcinogenesis. A total of 400 individuals were collected and analyzed by PCR-SSCP. After sequence analysis of coding region of CYP1A1 we identified eleven mutations in different exons of respective gene. Among these eleven mutations, ~3 folds increased breast cancer risk was found associated with Asp82Glu mutation (OR 2.99; 95% CI 1.26-7.09), with Ser83Thr mutation (OR 2.99; 95% CI 1.26-7.09) and with Glu86Ala mutation (OR 3.18; 95% CI 1.27-7.93) in cancer patients compared to controls. Furthermore, ~4 folds increase in breast cancer risk was found associated with Asp347Glu, Phe398Tyr and 5178delT mutations (OR 3.92; 95% CI 1.35-11.3) in patients compared to controls. The sequence analysis of GSTP1 resulted in identification of total five mutations. Among these five mutations, ~3 folds increase in breast cancer risk was observed associated with 1860G>A mutation, with 1861-1876delCAGCCCTCTGGAGTGG mutation (OR 2.70; 95% CI 1.10-6.62) and with 1861C>A mutation (OR 2.97; 95% CI 1.01-8.45) in cancer patients compared to controls. Furthermore, ~5 folds increase in breast cancer risk was associated with 1883G>T mutation (OR 4.75; 95% CI 1.46-15.3) and ~6 folds increase in breast cancer risk was found associated with Iso105Val mutation (OR 6.43; 95% CI 1.41-29.3) in cancer patients compared to controls. Our finding, based on systematic review and experimental data suggest that the polymorphic CYP1A1 and GSTP1 genes may contribute to risk of developing breast cancer.

Genotypes of CYP1A1, SULT1A1 and SULT1A2 and risk of squamous cell carcinoma of esophagus: outcome of a case-control study from Kashmir, India

Studies on associations of various polymorphism in xenobiotic metabolizing genes with different cancers including esophageal squamous cell carcinoma (ESCC) are mixed and inconclusive. To evaluate the association of CYP1A1*4, SULT1A1*2 and SULT1A2*2 genotypes with ESCC risk and their modifying effects on different risk factors of ESCC, we conducted a case-control study in Kashmir, India, an area with relative high incidence of ESCC. We recruited 404 histopathologically confirmed ESCC cases, and equal number of controls, individually matched for sex, age and district of residence to respective case. Information was obtained on various dietary, lifestyle and environmental factors in face-to-face interviews, using a structured questionnaire, from each subject. Genotypes were analyzed by polymerase chain reaction, restriction fragment length polymorphism and direct sequencing. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). A higher risk was observed in the subjects who harbored variant genotype of CYP1A1*4 (OR = 2.06; 95% CI: 1.28-3.32); and the risk was further enhanced in ever smokers (OR = 3.47; 95% CI: 1.62-7.42), adobe dwellers (OR = 6.71; 95% CI: 3.02-14.89), and biomass fuel users (OR = 5.11; 95% CI: 1.34-19.50). We did not find any significant differences in the polymorphic variants of SULT1A1*2 and SULT1A2*2 between cases and controls. The study indicates that, unlike SULT1A1*2 and SULT1A2*2, the polymorphism of CYP1A1*4 is associated with ESCC risk. However, replicative studies with larger sample size are needed to substantiate our findings.

Association of CYP1A1 A4889G and T6235C polymorphisms with the risk of sporadic breast cancer in Brazilian women

OBJECTIVES

We examined the influence of CYP1A1 A4889G and T6235C polymorphisms on the risk of sporadic breast cancer.

METHODS

DNA from 742 sporadic breast cancer patients and 742 controls was analyzed using the polymerase chain reaction, followed by the restriction fragment length polymorphism technique.

RESULTS

More patients had the CYP1A1 4889AG+GG genotype compared to controls (29.0% versus 23.2%, p=0.004). The G allele carriers had a 1.50-fold increased risk (95% CI: 1.14-1.97) of sporadic breast cancer compared to the other study participants. The frequency of the 4889AG+GG genotype among the Caucasian patients was higher than in the non-Caucasian patients (30.4% versus 20.2%, p=0.03) and controls (30.4% versus 23.2%, p=0.002). Caucasians and G allele carriers had a 1.61-fold increased risk (95% CI: 1.20-2.15) of sporadic breast cancer compared to other subjects. The CYP1A1 4889AG+GG genotype was more common among patients with a younger median age at first full-term pregnancy than among controls (33.8% versus 23.2%, p=0.001) and subjects whose first full-term pregnancies occurred at an older age (33.8% versus 26.1%, p=0.03). Women with the CYP1A1 4889AG+GG genotype and earlier first full-term pregnancies had a 1.87-fold (95% CI: 1.32-2.67) increased risk of sporadic breast cancer compared to the other study participants. Excess CYP1A1 4889AG+GG (39.8% versus27.1%, p=0.01) and 6235TC+CC (48.4% versus 35.9%, p=0.02) genotypes were also observed in patients with grade I and II tumors compared to patients with grade III tumors and controls (39.8% versus 23.2%, p=0.04; 48.4% versus 38.6%, p=0.04). The G and C allele carriers had a 2.44-fold (95% CI: 1.48-4.02) and 1.67-fold (95% CI: 1.03-2.69) increased risk, respectively, of developing grade I and II tumors compared to other subjects.

CONCLUSIONS

The CYP1A1 A4889G and T6235C polymorphisms may alter the risk of sporadic breast cancer in Brazilian women.

Cytochrome P4501A1 genotypes and smoking- and hypertension-related ischemic stroke risk

This study aimed to determine whether the coding (A4889G) and noncoding region (T6235C) polymorphisms of the gene coding for cytochrome P4501A1 (CYP1A1), a xenobiotic-metabolizing enzyme responsible for the metabolism of carcinogenic polycyclic aromatic hydrocarbons, are involved in the pathogenesis of ischemic stroke in Turkish population. Study group consisted of 226 ischemic stroke patients and 113 controls. Genotypes were attained by allele-specific polymerase chain reaction (PCR) for A4889G and PCR/restriction fragment length polymorphism analysis for T6235C. Frequency of 6235C allele was significantly lower in patients (0.151) compared with controls (0.226, P = 0.015). Prevalence of hypertension and hypertension-associated ischemic stroke risk was lower for 6235C allele carriers. This allele decreased ischemic stroke risk twofold (adjusted odds ratio = 0.48, P = 0.005). There was almost no difference in 4889G allele frequencies in patients (0.445) and controls (0.425). However, prevalence of hypertension was lower in 4889G allele carriers when compared with the wild-type genotypes. In addition, risk of ischemic stroke for smoker and hypertensive individuals was lower when they have at least one 4889G allele. The present study demonstrated that CYP1A1 genetic variants contribute to interindividual variability in smoking- and hypertension-induced ischemic stroke risk.

Polymorphisms of Metabolizing Enzymes and Susceptibility to Ethmoid Intestinal-type Adenocarcinoma in Professionally Exposed Patients

Intestinal-type adenocarcinoma (ITAC) of ethmoid is a rare tumor associated with occupational exposure to wood and leather dusts. Polymorphisms in xenobiotic metabolizing enzymes play an important role in gene-environment interactions and may contribute to a high degree of variance in individual susceptibility to cancer risk. The aim of this study was to investigate by polymerase chain reaction the role of polymorphisms at CYP1A1 and GSTM1 genes in 30 ethmoid ITAC patients and 79 healthy donors. The distribution of Thr/Asn genotype at CYP1A1 codon 461 was significantly overrepresented among the patients (23.3%; P = .0422), whereas the Ile/Val genotype at CYP1A1 codon 462 was not significantly different between cases and controls (P = .76). The GSTM1 null genotype was not significantly different between cases and control (P = 1), but we observed that the combined codon 461 Thr/Asn and GSTM1 null genotype was overrepresented in the patient group (P = .0019). The results reveal that patients with CYP1A1 codon 461 polymorphism may be at high genetic risk of ITAC and that the risk increases in the presence of combined polymorphism of CYP1A1 and GSTM1 null genotype. This strongly suggests that CYP1A1 codon 461 and GSTM1 null genotype may be useful in selecting exposed individuals at risk for ethmoid ITAC.

Polymorphism of xenobiotic-metabolizing genes and breast cancer susceptibility in North Indian women

NAD(P)H:quinone oxidoreductase 1 (NQO1) and cytochrome P450 1A2 (CYP1A2) are involved in the metabolism of estrogens. Genetic polymorphisms in these genes may lead to interindividual variation in breast cancer susceptibility. This study was undertaken to investigate the association of NQO1 exon 6 proline187serine (C609T) and CYP1A2 exon 2 phenylalanine21leucine (C63G) polymorphisms with breast cancer susceptibility in North Indian women. Polymorphisms were analyzed by polymerase chain reaction amplification of the desired segment of NQO1 and CYP1A2 genes followed by restriction fragment length polymorphism. NQO1 mRNA expression was analyzed by semiquantitative reverse transcription-polymerase chain reaction and its enzyme activity was estimated spectrofluorophotometrically. Odds ratios for NQO1 C609T heterozygous and homozygous variants were 0.66 (95% confidence interval: 0.39-1.13; p-value: 0.141) and 1.07 (95% confidence interval: 0.46-2.46; p-value: 0.976). All cases and controls were monomorphic for the CYP1A2 exon 2 phenylalanine21leucine (C63G) genotype. NQO1 mRNA expression and its catalytic activity among wild-type genotype, homozygous variant, and heterozygous variant were not significantly altered, except for catalytic activity of the NQO1 homozygous variant, which was observed extremely low. The results of the study suggest that NQO1 exon 6 proline187serine (C609T) and CYP1A2 exon 2 phenylalanine21leucine (C63G) polymorphisms do not play a significant role in breast cancer susceptibility in North Indian women.

Aromatic DNA adducts and polymorphisms in metabolic genes in healthy adults: findings from the EPIC-Spain cohort

Aromatic compounds such as polycyclic aromatic hydrocarbons, arylamines and heterocyclic amines require metabolic activation to form metabolites able to bind to DNA, a process mediated by polymorphic enzymes. We measured aromatic DNA adducts in white blood cells by the (32)P-post-labelling assay in a sample of 296 healthy adults (147 men and 149 women) from five regions of Spain. We also analyzed functional polymorphisms in the metabolic genes CYP1A1, CYP1A2, EPHX1, GSTM1, GSTT1, NAT2 and SULT1A1. A significant increased level of DNA aromatic adducts was found related to the fast oxidation-hydrolysis phenotype defined by the polymorphism I462V in CYP1A1, the allele A in IVS1-154C>A of CYP1A2 and the combination Tyrosine-Arginine for Y113H and H139R of EPHX1. Geometric means (adducts per 10(-9) normal nucleotides) were 2.17, 4.04 and 6.30 for slow, normal and fast phenotypes, respectively (P-trend = 0.01). Slow acetylation by NAT2 was associated with a significant decrease in adduct level; subjects with slow alleles *5A and *7A/B had in average 1.56 x 10(-9)adducts, as compared with 5.60 for those with normal NAT2 activity (P-value = 0.01). No association was seen with polymorphisms of other metabolic genes such as GSTM1, GSTT1 or SULT1A1. We concluded that the metabolic pathways of oxidation, hydrolysis and acetylation are relevant to the formation of bulky DNA adducts. This could suggest a potential involvement of aromatic compounds in the formation of such adducts; however, given lack of specificity of the post-labeling assay, a firm conclusion cannot be drawn.

Do single nucleotide polymorphisms in xenobiotic metabolizing genes determine breast cancer susceptibility and treatment outcomes?

SNPs in CYP1A1, CYP2A1, CYP2B6, CYP2C, CYP2D6, CYP3A, GSTM1, GSTT1, GSTP1, SULT1A1, SULT1A2, UGT, and MTHFR are associated with breast cancer susceptibility; however, lack of such associations are also reported in some populations. The contradictory findings are explained on the basis of ethnic variation among populations and due to lack of proper sample size, detailed genotype-phenotype combinations and validation of gene expression studies at protein level. In this review, SNPs in these genes that have tremendous potential in identification of susceptible individuals, development of preventive strategies, treatment outcomes and their limitations are discussed.

Interaction of cytochrome P4501A1 genotypes with other risk factors and susceptibility to lung cancer

Lung cancer is the most common cause of death throughout the world with cigarette smoking being established as the major etiological factor in lung cancer. Since not much information is available regarding the polymorphism in drug metabolizing enzymes and lung cancer risk in the Indian population, the present case-control study attempted to investigate the association of polymorphisms in cytochrome P450 1A1 (CYP1A1) and glutathione-S-transferase M1 (GSTM1) with risk to squamous cell carcinoma of lung malignancy. Patients suffering from lung cancer (n=200) and visiting OPD facility of Department of Radiotherapy, King George's Medical University, Lucknow, were included in the study. Equal number (n=200) of age and sex matched healthy individuals were also enrolled in the study. Our data revealed that the variant genotypes of CYP1A1*2A, CYP1A1*2C and CYP1A1*4 were found to be over represented in the lung cancer patients when compared to controls. CYP1A1*2A variant genotypes (combined heterozygous and mutant genotypes) revealed significant association towards the lung cancer risk (OR: 1.93, 95%CI: 1.28-2.89, p=0.002). Likewise, GSTM1 null genotypes were found to be over represented in patients when compared to controls. Haplotype analysis revealed that CYP1A1 haplotype, C-G-C increased the lung cancer risk (OR: 3.90, 95%CI: 1.00-15.04, p=0.025) in the patients. The lung cancer risk was increased several two-to fourfold in the patients carrying the genotype combinations of CYP1A1*2A and GSTM1 suggesting the role of gene-gene interaction in lung cancer. Cigarette smoking or tobacco chewing or alcohol consumption was also found to interact with CYP1A1 genotypes in increasing the risk to lung cancer further demonstrating the role of gene-environment interaction in development of lung cancer.

Differential effect of over-expressing UGT1A1 and CYP1A1 on xenobiotic assault in MCF-7 cells

Gene mutation has been considered as a major step of carcinogenesis. Some defective genes may induce spontaneous tumorigenesis, while others are required to interact with the environment to induce cancer. CYP1A1 and UGT1A1 are encoded for the respective phase I and II drug-metabolizing enzymes. Their expressions have been associated with breast cancer incidence in women, and some xenobiotics are substrates of these two enzymes. In the current study, cytochrome P450 (CYP) 1A1 and UDP-glucuronosyltransferase (UGT) 1A1 were over-expressed in the breast cancer MCF-7 cells, and potential interactions between these enzymes and estrogen or polycyclic aromatic hydrocarbon were evaluated. Compared with control cells (MCF-7(VEC)), reduced cell proliferation was seen in cells expressing UGT1A1 (MCF-7(UGT1A1)) under estradiol treatment. 7,12-Dimethylbenz[a]anthracene (DMBA) is an established breast cancer initiator in animal model. Over-expressing UGT1A1 reduced the binding of DMBA to DNA, and increased MCF-7(UGT1A1) intact cells under DMBA treatment was verified by comet assay. On the other hand, intensified DMBA binding and damages were observed in MCF-7(CYP1A1) cells. This study supported that UGT1A1 but not CYP1A1 expression could protect against xenobiotic assault.

Association of polymorphism in MDM-2 and p53 genes with breast cancer risk in Indian women

PURPOSE

Single nucleotide polymorphism (SNP) at position -309 (T309G) in MDM-2 promoter induces tumor formation in the individuals possessing inherited p53 mutations. The present study was undertaken to investigate the association of MDM-2 SNP309, p53 Arg72Pro, and p53 intron-6 G/A polymorphism with total, premenopausal, and postmenopausal breast cancer risks in Indian women.

METHODS

Genotyping of MDM-2 SNP309, p53 Arg72Pro, and p53 intron-6 G/A in 104 patients and 105 controls was performed either by ARMS-PCR or by polymerase chain reaction and direct sequencing.

RESULTS

The p53 Arg72Pro heterozygous variant and in combination with its homozygous variant exhibited a significant protective association with total (odds ratio [95% confidence interval]: 0.42 [0.22-0.81] and 0.46 [0.25-0.85], p value; 0.007 and 0.012) and postmenopausal breast cancer risk (odds ratio [95% confidence interval]: 0.25 [0.07-0.73] and 0.27 [0.08-0.77], p value; 0.009 and 0.013]. Neither combined nor homozygous/heterozygous MDM-2 SNP309G was associated with total, premenopausal, or postmenopausal breast cancer risk; however, MDM-2 SNP309G, along with p53 Arg72Pro heterozygous variant, showed a significant protective association with premenopausal breast cancer risk (odds ratio [95% confidence interval]: 0.18 [0.02-1.20], p value; 0.041 for homozygous + heterozygous MDM-2 SNP309G).

CONCLUSIONS

The results indicate protective associations of p53 Arg72Pro heterozygous variant with postmenopausal and MDM-2 SNP309G along with p53 Arg72Pro heterozygous variant with premenopausal breast cancer risk.

Cytochrome P450 1A1 (CYP1A1) T3801C and A2455G polymorphisms in breast cancer risk: a meta-analysis

The cytochrome P450 1A1 gene (CYP1A1), encoding Phase I metabolic enzymes, appeared to be a candidate gene for breast cancer risk. However, studies on the association between polymorphisms in this gene and breast cancer have yielded conflicting results. We performed a meta-analysis to investigate the association with breast cancer of the CYP1A1 polymorphisms T3801C (9,316 cases and 12,714 controls) and A2455G (9,552 cases and 9,320 controls). In the genotype contrast of A2455G, both additive [GG vs AA, P = 0.04, fixed-effects OR 0.72; 95% CI (0.53-0.99), P = 0.95 for heterogeneity] and recessive [GG vs (GA + AA), P = 0.04, fixed-effects OR 0.73; 95% CI (0.53-0.99), P = 0.97 for heterogeneity] models produced significant results in east-Asians. In pre-menopausal women in a worldwide population, significant association between A2455G and breast cancer was also found using both models [additive model: P = 0.02, fixed-effects OR 0.52; 95% CI (0.29-0.92), P = 0.39 for heterogeneity; recessive model: P = 0.02, fixed-effects OR 0.51; 95% CI (0.29-0.90), P = 0.38 for heterogeneity]. Our meta-analysis suggests that an A2455G G/G genotype is associated with a trend of reduced breast cancer risk, both in east-Asian women and in pre-menopausal women worldwide, while the T3801C C allele might not be a risk factor for breast cancer. Larger scale primary studies are required to further evaluate the interaction of CYP1A1 polymorphisms and breast cancer risk in specific populations.