Interaction of genetic polymorphisms in cytochrome P450 2E1 and glutathione S-transferase M1 to breast cancer in Taiwanese woman without smoking and drinking habits

Association of CYP2E1, STK15 and XRCC1 Polymorphisms with Risk of Breast Cancer in Malaysian Women

BACKGROUND

Breast cancer is the most common type of cancer affecting Malaysian women. Recent statistics revealed that the cumulative probability of breast cancer and related deaths in Malaysia is higher than in most of the countries of Southeast Asia. Single nucleotide polymorphisms (SNPs) in CYP2E1 (rs6413432 and rs3813867), STK15 (rs2273535 and rs1047972) and XRCC1 (rs1799782 and rs25487) have been associated with breast cancer risk in a meta-analysis but any link in Southeast Asia, including Malaysia, remained to be determined. Hence, we investigated the relationship between these SNPs and breast cancer risk among Malaysian women in the present case-control study.

MATERIALS AND METHODS

Genomic DNA was isolated from peripheral blood of 71 breast cancer patients and 260 healthy controls and subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

Our study showed that the c1/c2 genotype or subjects with at least one c2 allele in CYP2E1 rs3813867 SNP had significantly increased almost 1.8-fold higher breast cancer risk in Malaysian women overall. In addition, the variant Phe allele in STK15 rs2273535 SNP appeared to protect against breast cancer in Malaysian Chinese. No significance association was found between XRCC1 SNPs and breast cancer risk in the population.

CONCLUSIONS

This study provides additional knowledge on CYP2E1, STK15 and XRCC1 SNP impact of risk of breast cancer, particularly in the Malaysian population. From our findings, we also recommend Malaysian women to perform breast cancer screening before 50 years of age.

Role of CYP2E1 polymorphisms in breast cancer: a systematic review and meta-analysis

BACKGROUND

CYP2E1 polymorphisms have been reported to influence individual's breast cancer susceptibility as a phase I enzyme, but the results of these previous studies remain controversial. We performed a comprehensive meta-analysis to assess their association.

METHODS

A comprehensive search of literature included in various databases (PubMed, Web of Science and Google scholar), published before August 2016, was performed. Odds ratios (ORs) with 95% confidence intervals (CIs) calculated in fixed or random-effects models were used to estimate the strength of the associations between three polymorphisms of CYP2E1 and breast cancer susceptibility. Subgroup analysis, sensitivity analysis and test for publication bias were also performed. A total of 11 separate comparisons involving 4311 cases and 4407 controls were included in the meta-analysis.

RESULTS

Our result showed that there was no significant association between the two common polymorphisms CYP2E1 rs2031920 C>T, CYP2E1*5 Rsa I/Rst I (c1/c2) and BC risk. For CYP2E1*6 Dra I (D/C) polymorphism, a significantly increased BC risk in the overall population was found in genetic model D/C vs. D/D (OR = 1.29, 95% CI = 1.04-1.61, P = 0.023) and C/C + D/C vs. D/D (OR = 1.25, 95% CI = 1.04-1.51, P = 0.019), together with subjects who have at least one C allele (C vs. D: OR = 1.46, 95% CI = 1.20-1.79, P < 0.001). Similar results were also found in subgroup analyses in Caucasians of these three comparison models.

CONCLUSIONS

The present meta-analysis suggests that CYP2E1*6 Dra I (D/C) variation significantly associated with the risk of BC. Individuals with D/C and C/C + D/C genotypes or carried at least one C allele of CYP2E1*6 Dra I (D/C) polymorphism had a significant higher susceptibility to develop BC.

Female breast cancer and alcohol consumption: a review of the literature

CONTEXT

Consumption of alcoholic beverages is one of the single most important known and modifiable risk factor for human cancer. Among women, breast cancer is the most common cancer worldwide and the leading cause of cancer-related mortality. Consumption of alcoholic beverages is causally associated with female breast cancer and the association shows a linear dose-response relationship. The role of heavy drinking has been long recognized and even a moderate intake is associated with an increased risk for breast cancer. The present review is an update of the current evidence on the association between alcohol consumption and breast cancer risk. The aim is to gain further insight into this association and to improve our current understanding of the effects of the major modifying factors.

EVIDENCE ACQUISITION

Epidemiologic and experimental studies published since the most recent International Agency for Research on Cancer (IARC) Monograph on alcoholic beverages were identified in PubMed using a combination of keywords such as alcohol, breast cancer, polymorphisms, menopausal status.

EVIDENCE SYNTHESIS

Cumulative lifetime consumption, drinking frequency, drinking patterns and timing of exposure each modulate the association between alcohol consumption and breast cancer. Hormonal status, genetic polymorphisms, and nutritional factors may interact with ethanol metabolism and further influence breast cancer risk.

CONCLUSIONS

Better standardization among experimental and epidemiologic designs in assessing alcohol intake and timing of exposure may improve our understanding of the heterogeneity observed across studies, possibly allowing the quantification of the effects of occasional heavy drinking and the identification of a window of higher susceptibility to breast cancer development.

Toxicogenetic profile and cancer risk in Lebanese

An increasing number of genetic polymorphisms in drug-metabolizing enzymes (DME) were identified among different ethnic groups. Some of these polymorphisms are associated with an increased cancer risk, while others remain equivocal. However, there is sufficient evidence that these associations become significant in populations overexposed to environmental carcinogens. Hence, genetic differences in expression activity of both Phase I and Phase II enzymes may affect cancer risk in exposed populations. In Lebanon, there has been a marked rise in reported cancer incidence since the 1990s. There are also indicators of exposure to unusually high levels of environmental pollutants and carcinogens in the country. This review considers this high cancer incidence by exploring a potential gene-environment model based on available DME polymorphism prevalence, and their impact on bladder, colorectal, prostate, breast, and lung cancer in the Lebanese population. The examined DME include glutathione S-transferases (GST), N-acetyltransferases (NAT), and cytochromes P-450 (CYP). Data suggest that these DME influence bladder cancer risk in the Lebanese population. Evidence indicates that identification of a gene-environment interaction model may help in defining future research priorities and preventive cancer control strategies in this country, particularly for breast and lung cancer.

Genetic polymorphisms of CYP2E1, GST, and NAT2 enzymes are not associated with risk of breast cancer in a sample of Lebanese women

Changes in the activity of drug metabolizing enzymes (DMEs) are potentially associated with cancer risk. This relationship is attributed to their involvement in the bioactivation of multiple procarcinogens or the metabolism of multiple substrates including an array of xenobiotics and environmental carcinogens. 326 Lebanese women of whom 99 were cancer free (controls) and 227 were diagnosed with breast cancer (cases) were included. Blood for DNA was collected and medical charts were reviewed. Three genotyping methods were employed including: (1) restriction fragment length polymorphism (RFLP) for CYP2E1*5B, CYP2E1*6, NAT2*5 and NAT2*6; (2) gel electrophoresis for GSTM1 and GSTT1; and (3) real-time PCR for GSTP1 Ile/Val polymorphism. We analyzed the relationship between genetic susceptibilities in selected xenobiotic metabolizing genes and breast cancer risk. Allele frequencies were fairly similar to previously reported values from neighboring populations with relevant migration routes. There were no statistically significant differences in the distribution of variant carcinogen metabolizing genes between cases and controls even after adjusting for age at diagnosis, menopausal status, smoking, and alcohol intake. Despite its limitations, this is the first study that assesses the role of genetic polymorphisms in DMEs with breast cancer in a sample of Lebanese women. Further studies are needed to determine the genetic predisposition and gene-environment interactions of breast cancer in this population.

Glutathione S-transferase M1 polymorphism and breast cancer susceptibility: a meta-analysis involving 46,281 subjects

Published data on the association between present/null polymorphism of glutathione S-transferase M1 (GSTM1) and breast cancer risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. Medline, PubMed, Embase, and Web of Science were searched. Crude ORs with 95% CIs were used to assess the strength of association between the GSTM1 present/null polymorphism and breast cancer risk. The pooled ORs were performed for null versus present genotype. A total of 59 studies including 20,993 cases and 25,288 controls were involved in this meta-analysis. Overall, significantly elevated breast cancer risk was associated with null genotype when all studies were pooled into the meta-analysis (OR = 1.10, 95% CI = 1.04-1.16). In the subgroup analysis by ethnicity, significantly increased risks were found for Caucasians (OR = 1.05, 95% CI = 1.00-1.10) and Asians (OR = 1.21, 95% CI = 1.08-1.35). When stratified by population-based studies or hospital-based studies, statistically significantly elevated risks were found among population-based studies (OR = 1.11, 95% CI = 1.03-1.20). In the subgroup analysis by menopausal status, statistically significantly increased risks were found among postmenopausal women (OR = 1.15, 95% CI = 1.04-1.28). In conclusion, this meta-analysis suggests that the GSTM1 null genotype is a low-penetrant risk factor for developing breast cancer.

Identifying hypothetical genetic influences on complex disease phenotypes

BACKGROUND

Statistical interactions between disease-associated loci of complex genetic diseases suggest that genes from these regions are involved in a common mechanism impacting, or impacted by, the disease. The computational problem we address is to discover relationships among genes from these interacting regions that may explain the observed statistical interaction and the role of these genes in the disease phenotype.

RESULTS

We describe a heuristic algorithm for generating hypothetical gene relationships from loci associated with a complex disease phenotype. This approach, called Prioritizing Disease Genes by Analysis of Common Elements (PDG-ACE), mines biomedical keywords from text descriptions of genes and uses them to relate genes close to disease-associated loci. A keyword common to, and significantly over-represented in, a pair of gene descriptions may represent a preliminary hypothesis about the biological relationship between the genes, and suggest the role the genes play in the disease phenotype.

CONCLUSION

Our experimentation shows that the approach finds previously published relationships, while failing to find relationships that don't exist. The results also indicate that the approach is robust to differences in keyword vocabulary. We outline a brief case study in which results from a recently published Type 2 Diabetes association study are used to identify potential hypotheses.

Glutathione S-transferase M1 and P1 polymorphisms and risk of breast cancer and fibrocystic breast conditions in Chinese women

Enzymes encoded by the glutathione S-tranferase mu 1 (GSTM1) and pi 1 (GSTP1) genes, which are expressed in breast tissue, catalyze the detoxification of endogenous and exogenous electrophiles. Reduced enzyme activity, due to carriage of the GSTM1 deletion or the GSTP1 Ile105Val Val allele, may therefore affect susceptibility to breast cancer and related conditions. In a case-control study of Chinese women, we examined whether these polymorphisms were associated with risk of breast cancer and fibrocystic breast conditions. Women diagnosed with breast cancer (n=615) or fibrocystic breast conditions (n=467) were compared to women without clinical breast disease (n=878). We also examined whether these associations differed by menopausal status or by presence of proliferation in the extra-tumoral epithelium among women with breast cancer and in lesions among women with fibrocystic conditions. No overall association of either GST polymorphism with risk of breast cancer or fibrocystic breast conditions was observed. There was some evidence of slightly elevated cancer risk associated with carriage of the GSTM1 null genotype and at least one GSTP1 105-Val allele (OR=1.33, 95% CI, 0.99-1.80), compared to carriage of the GSTM1 non-null and GSTP1 Ile/Ile genotypes. This relationship was stronger in women who had breast cancer with extra-tumoral tissue proliferation (OR=1.77, 95% CI, 1.03-3.04). Our results suggest that GSTM1 and GSTP1 genotypes do not individually influence susceptibility to breast cancer or fibrocystic breast conditions. The observed increased risk of breast cancer associated with joint carriage of the GSTM1 null genotype and GSTP1 105-Val allele needs confirmation in other studies.

Case-only study of interactions between metabolic enzymes and smoking in colorectal cancer

Background

Gene-gene and gene-environment interactions involved in the metabolism of carcinogens may increase the risk of cancer. Our objective was to measure the interactions between common polymorphisms of P450 (CYP1A2, CYP1B1, CYP2E1), GSTM1 and T1, SULT1A1 and cigarette smoking in colorectal cancer (CRC).

Methods

A case-only design was conducted in a Chinese population including 207 patients with sporadic CRC. Unconditional logistic regression analysis was performed adjusting for age, gender, alcohol consumption, and cigarette smoking.

Results

The interaction odds ratio (COR) for the gene-gene interaction between CYP1B1 1294G and SULT1A1 638A allele was 2.68 (95% CI: 1.16–6.26). The results of the gene-environment analyses revealed that an interaction existed between cigarette smoking and the CYP1B1 1294G allele for CRC (COR = 2.62, 95%CI: 1.01–6.72), the COR for the interaction of CYP1B1 1294G and smoking history > 35 pack-years was 3.47 (95%CI: 1.12–10.80). No other significant gene-gene and gene-environment interactions were observed.

Conclusion

Our results showed that the interaction between polymorphisms in CYP1B1 1294G and SULT1A1*2 may play a significant role on CRC in the Chinese population. Also, it is suggested that the association between cigarette smoking and CRC could be differentiated by the CYP1B1 1294G allele.