Polymorphisms In Metabolism Genes Research Articles

Polymorphisms in folate metabolism genes are associated with susceptibility to presbycusis

AimPresbycusis or age related hearing loss is caused by several extrinsic and intrinsic factors that damage the auditory system. Gene polymorphisms in folate metabolism were found to play an important role in the etiology of presbycusis. The present study aimed to investigate the role of 5,10-methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and thymidylate synthase (TYMS) gene polymorphisms in the onset of presbycusis in a South Indian population. Main methodsA total of 220 subjects confirmed with presbycusis along with 270 age and sex matched healthy controls visiting MAA ENT Hospitals, Hyderabad, India were enrolled for the study. Genotyping of MTHFR C677T (rs180133) and A1298C (rs1801131), MTR A2756G (rs1805087), TSER (rs1801136) and TS1494indel6 bp (rs16430) was carried out using PCR & PCR-RFLP methods. Key findingsThe ‘TT’ genotype of MTHFR C677T and ′152 bp/152 bp′ genotype of TS1494indel6 bp showed statistically significant risk for presbycusis while CC genotype of MTHFR A1298C, ‘2R/2R’ genotype of TSER at 3′UTR and 6 bp ins/6 bp ins of TYMS at 5′UTR were found to be protective. The T-A-A haplotype combination of MTHFR C677T, MTHFR A1298C and MTR A2756G as well as 3R- 152 bp of TYMS at 5′UTR and 3′UTR were also found to contribute significant risk for the onset of presbycusis. Further, the combination of SNP loci TSER: TS1494indel6 bp exhibited moderate linkage in presbycusis. SignificanceThe present pilot study identified the significant association of gene variants of MTHFR and TYMS with presbycusis. These findings aid in early diagnosis of hearing loss in the elderly population.

Association between arsenic metabolism gene polymorphisms and arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China

Individuals in a given environment contaminated with arsenic have different susceptibilities to disease, which may be related to arsenic metabolism, age, gender, genetics and other factors. This study recruited 850 subjects, including 331 cases and 519 controls, from populations exposed to high levels of arsenic in drinking water in northwest China. Genotypes were determined using a custom-by-design 48-Plex SNPscanTM kit. The results indicated that subjects who carried at least one C allele for GSTO1 rs11191979 polymorphism, at least one A allele for GSTO1 rs2164624, at least one A allele for GSTO1 rs4925, the AG genotype for GSTO2 rs156697, the AG genotype or at least one G allele for GSTO2 rs2297235 or the GG genotype or at least one G allele for PNP rs3790064 had an increased risk of arsenic-related skin lesions. In addition, the haplotype CT between rs4925 and rs11191979 appeared to confer a high risk of arsenic-included skin lesions (OR = 1.377, 95% CI = 1.03–1.84), as did the haplotype GCG among rs156697, rs157077 and rs2297235 (OR = 2.197, 95% CI = 1.08–4.44). The results showed that the variants of GSTO1, GSTO2 and PNP render the susceptible toward developing arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China.

Multiplex Genotyping of Allelic Variants of Genes Involved in Metabolizing Antileukemic Drugs

A biochip, primer set, and genotyping protocol were developed to simultaneously address 16 single nucleotide polymorphisms in antileukemic drug metabolism genes, including TPMT, ITPA, MTHFR, SLCO1B1, SLC19A1, NR3C1, GRIA1, ASNS, MTRR, and ABCB1. The genotyping procedure included a one-round multiplex polymerase chain reaction (PCR) with simultaneous incorporation of a fluorescent label into the PCR product and subsequent hybridization on a biochip with immobilized probes. The method was used to test 65 DNA samples of leukemia patients. Fluorescence signal intensity ratios in pairs of wild-type and respective mutant sequence probes were analyzed for all polymorphic markers and demonstrated high accuracy of genotyping. The reliability of genotype determination using the biochip was confirmed by direct Sanger sequencing.

A review of the literature on the relationships between genetic polymorphisms and chemotherapy-induced nausea and vomiting

Despite current advances in antiemetic treatments, between 30% to and 60% of oncology patients experience chemotherapy-induced nausea (CIN) and 13% to 33% report chemotherapy-induced vomiting (CIV). Inter-individual differences are observed in the occurrence and severity of chemotherapy-induced nausea and vomiting (CINV). This review summarizes and critiques studies on associations between occurrence and severity of CINV and polymorphisms in serotonin receptor, drug metabolism, and drug transport pathway genes. Sixteen studies evaluated the associations between the occurrence and/or severity of CINV and single nucleotide polymorphisms (SNPs). Across these studies, three SNPs in 5-hydroxytryptamine receptor (5-HT3R) genes, two alleles of the cytochrome P450 family 2 subfamily D member 6 (CYP2D6) gene, and three SNPs in ATP binding cassette subfamily B member 1 (ABCB1) gene were associated with the occurrence and severity of CINV. Given the limited number of polymorphisms evaluated, additional research is warranted to identify new mechanisms to develop more targeted therapies.

Association Between Polymorphisms of Metabolic Enzyme Genes and Chromosomal Damage in Benzene-Exposed Workers in China.

To provide better understanding of genetic susceptibility for health risk among current benzene-exposed workers. Four hundred sixty one benzene-exposed workers and 88 matched controls were recruited, and their benzene exposure doses were monitored. Associations between genetic susceptibility for polymorphisms of metabolic enzymes CYP2E1 and NQO1, and expression of cytokinesis-block micronucleus (MN) were investigated. Mean MN frequency in the exposed workers was significantly higher than that in the control group (P < 0.01). Individuals with the NQO1 CC genotype showed significantly higher MN frequencies than those with the TT genotype (P < 0.05) in either single- or multiple-factor analyses. Age was an effect modifier for elevated MN frequency, while sex, smoking, and alcohol consumption had no relationship. Exposure to low dose of benzene among current workers can still cause health risk, especially among those with the NQO1 CC genotype.

Polymorphisms in Sex Hormone Metabolism Genes and Risk of Preeclampsia in Taiyuan, China

Objective: Aberrant synthesis and metabolism of sex hormone are likely to be associated with alterations in vascular function in preeclampsia (PE). The study aims to investigate whether single nucleotide polymorphisms (SNPs) in sex hormone-related genes are associated with PE. Method: We performed a nested case-control study including 436 pregnant women (203 PE and 233 healthy or normal pregnant women) to investigate associations between 96 SNPs in 28 sex hormone-related genes and risk of PE. Results:TXNRD2/COMT rs3788314 and SULT1A2/SULT1A1 rs4788073 were associated with an increased risk of PE overall (p_trend = 0.004 and 0.003, respectively), early-onset PE (p_trend = 0.007 and 0.009, respectively), and severe PE (p_trend = 0.002 and 0.005, respectively). Additionally, CYP17A1 rs4919690 and rs4919687 and LHCGR rs10180731 were associated with an increased risk of severe PE (p_trend = 0.005, 0.006, and 0.014, respectively), while GNRHR rs2630488 was associated with a decreased risk of severe PE (p_trend = 0.014). We also observed that HSD17B3 rs8190512 was associated with a decreased risk of early-onset PE (p_trend = 0.003). We observed strong linkage disequilibrium in SULF1 (rs10106958, rs7813987, and rs6990375). Conclusions: Our study suggested that genetic polymorphisms in TXNRD2/COMT, SULT1A2/SULT1A1, CYP17A1, HSD17B3, GNRHR, LHCGR, and SULF1 might play a role in PE, especially in early-onset PE and severe PE. Future studies are warranted to replicate the observed associations and their functional mechanisms.

Metabolic Phase I (CYPs) and Phase II (GSTs) Gene Polymorphisms and Their Interaction with Environmental Factors in Nasopharyngeal Cancer from the Ethnic Population of Northeast India.

Multiple genetic and environmental factors and their interaction are believed to contribute in the pathogenesis of Nasopharyngeal Cancer (NPC). We investigate the role of Metabolic Phase I (CYPs) and Phase II (GSTs) gene polymorphisms, gene-gene and gene-environmental interaction in modulating the susceptibility to NPC in Northeast India. To determine the association of metabolic gene polymorphisms and environmental habits, 123 cases and 189 controls blood/swab samples were used for PCR and confirmed by Sanger sequencing. Analysis for GSTM1 and GSTT1 gene polymorphism was done by multiplex PCR. The T3801C in the 3'- flanking region of CYP1A1 gene was detected by PCR-RFLP method. The Logistic regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). The GSTM1 null genotype alone (OR=2.76) was significantly associated with NPC risk (P<0.0001). The combinations of GSTM1 null and GSTT1 null genotypes also higher, 3.77 fold (P<0.0001), risk of NPC, while GSTM1 null genotype along with CYP1A1 T3801C TC+CC genotype had 3.22 (P=0.001) fold risk. The most remarkable risk was seen among individual carrying GSTM1 null, GSTT1 null genotypes and CYP1A1 T3801C TC+CC genotypes (OR=5.71, P=0.001). Further; analyses demonstrate an enhanced risk of NPC in smoked meat (OR=5.56, P<0.0001) and fermented fish consumers (OR=5.73, P<0.0001) carrying GSTM1 null genotype. An elevated risk of NPC was noted in smokers (OR=12.67, P<0.0001) and chewers (OR=5.68, P<0.0001) with GSTM1 null genotype. However, smokers had the highest risk of NPC among individuals carrying GSTT1 null genotype (OR=4.46, P=0.001) or CYP1A1 T3801C TC+CC genotype (OR=7.13, P<0.0001). The association of null genotypes and mutations of metabolic neutralizing genes along with the environmental habits (tobacco smokers and chewers, smoke meat, fermented fishes) can be used as a possible biomarker for early detection and preventive measure of NPC.

Interactions between genetic polymorphisms of glucose metabolizing genes and smoking and alcohol consumption in the risk of type 2 diabetes mellitus.

The impact of gene-environment interaction on diabetes remains largely unknown. We aimed to investigate if interaction between glucose metabolizing genes and lifestyle factors is associated with type 2 diabetes mellitus (T2DM). Interactions between genotypes of 4 glucose metabolizing genes (MTNR1B, KCNQ1, KLF14, and GCKR) and lifestyle factors were estimated in 722 T2DM patients and 759 controls, using multiple logistic regression. No significant associations with T2DM were detected for the single nucleotide polymorphisms of MTNR1B, KLF14 and GCKR. However, rs151290 (KCNQ1) polymorphisms were found to be associated with risk of T2DM. Compared with AA, the odds ratios (ORs) of AC or CC genotypes for developing T2DM were 1.545 (P = 0.0489) and 1.603 (P = 0.0383), respectively. In stratified analyses, the associations were stronger in smokers with CC than smokers with AA (OR = 3.668, P = 0.013); drinkers with AC (OR = 5.518, P = 0.036), CC (OR = 8.691, P = 0.0095), and AC+CC (OR = 6.764, P = 0.016) than drinkers with AA. Compared with nondrinkers with AA, drinkers who carry AC and CC had 12.072-fold (P = 0.0007) and 8.147-fold (P = 0.0052) higher risk of developing T2DM. In conclusions, rs151290 (KCNQ1) polymorphisms are associated with increased risk of T2DM, alone and especially in interaction with smoking and alcohol.

Blood lead levels, iron metabolism gene polymorphisms and homocysteine: a gene-environment interaction study

ObjectivesHomocysteine has been causally associated with various adverse health outcomes. Evidence supporting the relationship between lead and homocysteine levels has been accumulating, but most prior studies have not focused on...

Association mapping of starch chain length distribution and amylose content in pea (Pisum sativum L.) using carbohydrate metabolism candidate genes

BackgroundAlthough starch consists of large macromolecules composed of glucose units linked by α-1,4-glycosidic linkages with α-1,6-glycosidic branchpoints, variation in starch structural and functional properties is found both within and between species. Interest in starch genetics is based on the importance of starch in food and industrial processes, with the potential of genetics to provide novel starches. The starch metabolic pathway is complex but has been characterized in diverse plant species, including pea.ResultsTo understand how allelic variation in the pea starch metabolic pathway affects starch structure and percent amylose, partial sequences of 25 candidate genes were characterized for polymorphisms using a panel of 92 diverse pea lines. Variation in the percent amylose composition of extracted seed starch and (amylopectin) chain length distribution, one measure of starch structure, were characterized for these lines. Association mapping was undertaken to identify polymorphisms associated with the variation in starch chain length distribution and percent amylose, using a mixed linear model that incorporated population structure and kinship. Associations were found for polymorphisms in seven candidate genes plus Mendel’s r locus (which conditions the round versus wrinkled seed phenotype). The genes with associated polymorphisms are involved in the substrate supply, chain elongation and branching stages of the pea carbohydrate and starch metabolic pathways.ConclusionsThe association of polymorphisms in carbohydrate and starch metabolic genes with variation in amylopectin chain length distribution and percent amylose may help to guide manipulation of pea seed starch structural and functional properties through plant breeding.

Condition of sows during reproductive activity depending on lipid metabolism gene (DGAT1) polymorphism

Abstract Mutations at gene loci associated with body lipid metabolism may affect not only carcass and meat quality traits in young animals but also the production results of mother sows. The objective of the study was to determine the effect of mutations in the DGAT1 gene, found in Polish populations of maternal breeds, on condition of gilts and later on condition and reproductive performance of sows during three reproductive cycles. The study involved 118 gilts of maternal breeds (Polish Large White (PLW ) and Polish Landrace (PL)). Gilts and subsequently sows were monitored for body weight (BW) and P2 backfat thickness over three reproductive cycles and their litters were analysed for the number and body weight of the piglets. A total of 354 litters of pigs were evaluated. In the analysed pig populations, a single mutation (A/G) in the DGAT1 gene (rs45434075) had a significant effect on deposition of subcutaneous fat only in the PLW gilts (P2G, AA,AG&lt;GG P≤0.05 and P2F r=214 P≤0.01). As regards the G/A 3’UTR polymorphism of the DGAT1 gene (rs342152658), this mutation is negatively correlated only in the PL sows with fatness during their reproductive life and with BW of the piglets reared to 21 d of age. Sows of the DGAT1GG 3’UTR genotype had significantly lower P2F backfat thickness (P≤0.05) and, during a 21-d lactation, reared lighter piglets (P≤0.01) compared to sows of the same breed with the DGAT1AG 3’UTR genotype. The analysed traits were also affected by the interaction between mutations in the DGAT1 gene of the sows of maternal breeds (DGAT1/DGAT1 3’UTR). Sows of the DGAT1GG/GG genotype were characterised by the highest backfat thickness on selection day, and during three reproductive cycles they reared significantly more piglets compared to sows of the DGAT1AA/AG genotype. Heterozygous sows (AG/AG) reared significantly heavier piglets than sows of the AA/GG and AG/GG genotypes (P≤0.05).

Association between polymorphisms in folate metabolism genes and maternal risk for Down syndrome: A meta-analysis.

Previous studies have focused on the association between polymorphisms of the genes involved in folate metabolism and Down syndrome (DS); however, the results remain inconclusive. The present meta-analysis was conducted to assess the association between RFC-1 A80G/MTR A2756G/CBS 844ins68 polymorphisms and the maternal risk of DS. Published studies were retrieved from PubMed, Embase, China National Knowledge Infrastructure and Chinese Biomedicine databases. Pooled odds ratios (ORs) with 95% confidence interval (CIs) were calculated using the fixed- or random-effects model. Additionally, test of heterogeneity, cumulative meta-analysis, sensitivity analysis and assessment of bias were also performed. Finally, 11, 11 and 6 studies were deemed eligible for meta-analyses of RFC-1 A80G, MTR A2756G and CBS 844ins68, respectively. A significant association between RFC-1 A80G polymorphism and DS risk was observed for G vs. A (OR=1.19, 95% CI: 1.004–1.40, P=0.04) and the recessive model (OR=1.28, 95% CI: 1.05–1.56, P=0.01). In the stratified analysis by source of control or sample size, a significantly increased risk was observed among hospital-based studies and large-sample groups (>200 subjects), respectively. In addition, the cumulative meta-analysis of the RFC-1 A80G variant revealed a trend toward an association as the amount of data increased. However, for the MTR A2756G and CBS 844ins68 polymorphisms, no obvious association was found for all genetic models. In summary, the present meta-analysis demonstrated that RFC-1 A80G, but not MTR A2756G or CBS 844ins68, was considered as a maternal risk factor for DS in the offspring.

Association of prenatal passive smoking and metabolic gene polymorphisms with child growth from birth to 3 years of age in the Hokkaido Birth Cohort Study on Environment and Children's Health

Although the effects of prenatal passive smoking on birth weight have been reported, the effects of metabolic gene polymorphisms on passive smoking have not been studied. Therefore, we investigated the effects of maternal passive smoking and metabolic gene polymorphisms on child growth up to 3years of age using cotinine as a biomarker. We included 1356 Japanese participants in a prospective cohort between 2003 and 2007 (cotinine levels at the third trimester≤0.21ng/mL and 0.22 to 11.48ng/mL for non-passive and passive smokers, respectively), and measured child outcomes such as weight, length, head circumference, and Kaup index. Additionally, we analyzed cytochrome P450 1A1 (CYP1A1), epoxide hydrolase 1 (EPHX1), and two N-acetyltransferase 2 (NAT2) genotypes using real-time polymerase chain reaction methods. Associations were investigated using multiple regression models. Kaup index gain from birth up to 3years of age was significantly smaller in children born to passive smokers than in those born to non-passive smokers (−0.34kg/m2; 95% confidence interval: −0.67, −0.01). Maternal CYP1A1 genotype was not associated with prenatal passive smoking and Kaup index gain, but was significantly associated with prenatal passive smoking and head circumference gain from birth up to 3years of age (−0.75cm; 95% confidence interval: −1.39, −0.12). Thus, this study suggests that prenatal passive smoking may have potent effects on postnatal growth from birth up to 3years of age. Moreover, children with maternal CYP1A1 genotype may be more susceptible to the effects of prenatal passive smoking.

Polymorphisms in Renal Ammonia Metabolism Genes Correlate With 24-Hour Urine pH

IntroductionUrine pH is critical for net acid and solute excretion, but the genetic factors that contribute to its regulation are incompletely understood.MethodsWe tested the association of single nucleotide polymorphisms (SNPs) from 16 genes related to ammonia (NH3) metabolism (15 biological candidates selected a priori, 1 selected from a previous genome-wide association study analysis) to that of 24-hour urine pH in 2493 individuals of European descent across 2 different cohorts using linear regression, adjusting for age, sex, and body mass index.ResultsOf 2871 total SNPs in these genes, 13 SNPs in ATP6V0A4 (a4 subunit of hydrogen− adenosine triphosphatase), SLC9A3 (sodium/hydrogen exchanger, isoform 3), and RHCG (Rhesus C glycoprotein), and 12 SNPs from insulin-like growth factor binding protein 7 (IGFBP7) had a meta-analysis P value <0.01 in the joint analysis plus a consistent direction of effect and at a least suggestive association (P < 0.1) in both cohorts. The maximal effect size (in pH units) for each additional minor allele of the identified SNPs was −0.13 for IGFBP7, −0.08 for ATP6V0A4, 0.06 for RHCG, and −0.06 for SLC9A3; SNP rs34447434 in IGFBP7 had the lowest meta-analysis P value (P = 7.1 × 10−8). After adjusting for net alkali absorption, urine pH remained suggestively associated with multiple SNPs in IGFBP, 1 SNP in ATP6V0A4, and a new SNP in GLS (phosphate-dependent glutaminase).DiscussionOverall, these findings suggest that variants in common genes involved in ammonia metabolism may substantively contribute to basal urine pH regulation. These variations might influence the likelihood of developing disease conditions associated with altered urine pH, such as uric acid or calcium phosphate kidney stones.

Association of folate metabolism gene polymorphisms and haplotype combination with pulmonary embolism risk in Chinese Han population.

In this study, we aimed to investigate the association of four single nucleotide polymorphisms (SNPs) (MTHFR 677 C > T, MTHFR 1298 A > C, MTR 2756 A > G and MTRR 66 A > G), gene-gene interaction and haplotype combination with pulmonary embolism (PE) risk based on Chinese Han population. Logistic regression was performed to investigate association between four SNPs within folate metabolism gene and PE risk, and GMDR model was used to investigate the additional gene-gene interactions among the four SNPs. Logistic analysis showed that rs1801133 and rs1801131 in MTHFR gene were associated with increased PE risk in both additive and dominant models. The carriers with homozygous mutant of rs1801133 polymorphism and homozygous of rs1801131 were associated with increased PE risk, and ORs (95% CI) were 1.71(1.24-2.21) and 1.58 (1.24-2.01), respectively. We also found a significant gene-gene interaction between rs1801133 and rs1801131 on PE. Overall, the cross-validation consistency of this two-locus model was 10/10, and the testing accuracy was 60.72%, after adjusting for covariates. Haplotype containing the rs1801133- T and rs1801131- C alleles were associated with a statistically increased PE risk, OR (95% CI) = 2.68 (1.28-4.13), P < 0.001. We found that rs1801133 and rs1801131 within MTHFR gene, their interaction, and haplotype containing the rs1801133- T and rs1801131- C alleles were all associated with PE risk.

Clinical-pharmacogenetic models for personalized cancer treatment: application to malignant mesothelioma

Large interindividual differences in treatment outcome are observed in cancer patients undergoing chemotherapy. Our aim was to develop and validate clinical-pharmacogenetic prediction models of gemcitabine/cisplatin or pemetrexed/cisplatin treatment outcome and develop an algorithm for genotype-based treatment recommendations in malignant mesothelioma (MM). We genotyped 189 MM patients for polymorphisms in gemcitabine, pemetrexed and cisplatin metabolism, transport and drug target genes and DNA repair pathways. To build respective clinical-pharmacogenetic models, pharmacogenetic scores were assigned by rounding regression coefficients. Gemcitabine/cisplatin model was based on training group of 71 patients and included CRP, histological type, performance status, RRM1 rs1042927, ERCC2 rs13181, ERCC1 rs3212986, and XRCC1 rs25487. Patients with higher score had shorter progression-free (PFS) and overall survival (P < 0.001). This model’s sensitivity was 0.615 and specificity 0.812. In independent validation group of 66 patients the sensitivity and specificity were 0.667 and 0.641, respectively. Pemetrexed/cisplatin model was based on 57 patients and included CRP, MTHFD1 rs2236225, and ABCC2 rs2273697. Patients with higher score had worse response and shorter PFS (P < 0.001). This model’s sensitivity was 0.750 and specificity 0.607. In independent validation group of 20 patients the sensitivity and specificity were 0.889 and 0.500, respectively. The proposed algorithm based on these models could enable the choice of the most effective chemotherapy for 85.5% of patients and lead to improved treatment outcome in MM.

The Impacts of Cord Blood Cotinine and Glutathione-S-Transferase Gene Polymorphisms on Birth Outcome

This study aimed to investigate the association between cord blood cotinine levels and birth outcome, and to determine whether fetal metabolic gene polymorphisms of glutathione-S-transferase (GST) modulate the effect of environmental tobacco smoke exposure during pregnancy. This study included 328 maternal and neonatal pairs. Maternal and cord blood cotinine levels were measured using high performance liquid chromatography. The GST T1 (GSTT1) and GST M1 (GSTM1) polymorphisms were examined using the polymerase chain reaction method. The birth outcomes included birth weight, length, and head circumference, and the risks of having low birth weight and being small for gestational age (SGA). Cord cotinine level had a dose-dependent impact on the reduction of birth weight, length, and head circumference in newborns. Elevation of cord blood cotinine concentration increased the rate of SGA and low birth weight. The neonates who had GSTT1 or GSTM1 polymorphism were associated with an increased risk of being SGA. A combination of the GSTT1 and GSTM1 null genotype exacerbated the effect of maternal environmental tobacco smoke exposure on SGA more than the presence of either genotype alone (odds ratio=8.90, 95% confidence interval=1.00-79.5). Cord blood cotinine adversely affects birth outcomes. GSTT1 and GSTM1 null genotype may modify the effect of cord blood cotinine on birth outcomes.

Bulky DNA Adducts, Tobacco Smoking, Genetic Susceptibility, and Lung Cancer Risk.

The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a 32P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis. Polymorphisms of metabolic and DNA repair genes can increase the effects of environmental factors and confer greater likelihood of adduct formation. Nevertheless, the central question remains as to whether bulky adducts cause human cancer. If so, lowering them would reduce cancer incidence. Pooled and meta-analysis has shown that smokers with increased adducts have increased risk of lung cancer. Adduct excess in smokers, especially in prospective longitudinal studies, supports their use as biomarkers predictive of lung cancer.

Steroid metabolism gene polymorphisms and their implications on breast and ovarian cancer prognosis.

A role for estrogen in the etiology of breast and ovarian cancers has been suggested; therefore, genetic polymorphisms in steroid metabolism genes could be involved in the carcinogenesis of these tumors. We have aimed to investigate the role of GSTP1 and CYP17 polymorphisms and their correlation with MSI (microsatellite instability) and LOH (loss of heterozygosity) in AR, ERβ and CYP19 genes in women from Espírito Santo State, Brazil. The study population consisted of 107 female breast and 24 ovarian tumors. GSTP1 and CYP17 polymorphisms were detected by polymerase chain reaction (PCR) amplification followed by restriction fragment length polymorphism (RFLP) analysis while MSI and LOH were analyzed by PCR. GSTP1 and CYP17 polymorphisms alone were not associated with an increased risk for breast or ovarian tumors. However, when combined with MSI/LOH in AR, ERβ and CYP19 genes, we were able to detect significant associations with the GSTP1 wild-type genotype in PR (progesterone receptor) negative breast cancers or the CYP17 wild-type genotype in ER (estrogen receptor) and PR-negative breast tumors. No associations with ovarian tumors were detected. Our results suggest that wild-type GSTP1 or CYP17 genes when combined with LOH/MSI in steroid metabolism genes may play a role in ER and/or PR negative breast cancers. These data support the hypothesis that genes related to steroid metabolism are important in the characterization of breast cancer and that the analysis of single polymorphisms may not be sufficient.

Folate Deficiency and Gene Polymorphisms of MTHFR, MTR and MTRR Elevate the Hyperhomocysteinemia Risk.

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases (CVDs). We aimed to investigate the joint effect of homocysteine metabolism gene polymorphisms, as well as the folate deficiency on the risk of HHcy in a Chinese hypertensive population. This study enrolled 480 hypertensive patients aged 28 - 75 from six hospitals in different Chinese regions from 9/2005 - 12/2005. Known genotypes of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MTR) A2756G, and methionine synthase reductase (MTRR) A66G were detected by PCRRFLP methods. Serum Hcy was measured by high-performance liquid chromatography and serum folate was measured by chemiluminescent immunoassay. MTHFR C677T and MTR A2756G can independently elevate the risk of HHcy (TT vs. CC + CT, p < 0.001 and AG + GG vs. AA, p = 0.026, respectively), whereas MTHFR A1298C decreased HHcy risk (AC + CC vs. AA, p < 0.001) and showed a protective effect against HHcy risk. Importantly, the joint effect of these risk genotypes showed significantly higher odds of HHcy than non-risk genotypes, especially the patients with four risk genotypes. It is noteworthy that this deleterious effect was aggravated by folate deficiency. These findings were verified by generalized multifactor dimensionality reduction model (p = 0.001) and a cumulative effects model (p < 0.001). We have first demonstrated that the joint effect of homocysteine metabolism gene polymorphisms and folate deficiency lead to dramatic elevations in the HHcy risk.