mtDNA evidence: genetic background associated with related populations at high risk for esophageal cancer between Chaoshan and Taihang Mountain areas in China

There are three major geographic regions in China known for their high incidences of esophageal cancer (EC): the Taihang Mountain range of north-central China, the Minnan area of Fujian province, and the Chaoshan plain of Guangdong province. Historically, waves of great population migrations from north-central China through coastal Fujian to the Chaoshan plain were recorded. To study the genetic relationship among the related EC high-risk populations, we analyzed mitochondrial DNA (mtDNA) haplogroups based on 30 EC patients from Chaoshan and used control samples from the high-risk populations, including 48, 73, and 89 subjects from the Taihang, Fujian, and Chaoshan areas, respectively. The principal component of all haplogroups, correlation analysis of haplogroup frequency distributions between populations, and haplogroup D network analysis showed that compared with other Chinese populations, populations in the three studied areas are genetically related. The highest haplogroup frequency shared by all studied populations was haplogroup D, with much higher frequency in the Chaoshan area EC patients. The majority of haplogroup D individuals among the Chaoshan area EC patients belonged to subhaplogroups D4a and D5a, with the total frequency of these two haplogroups significantly higher than that in the high-risk population in the same area (chi(2)=9.017, p<0.01). In conclusion, EC high-risk populations in these three areas share a similar matrilineal genetic background, and D4a and D5a might be candidate genetic markers for screening populations susceptible to EC in the Chaoshan area. Ours is the first report to show the association between mtDNA haplogroups (D4a and D5a) and esophageal cancer.     

Genetic polymorphisms in the CYP1A1 and CYP1B1 genes and susceptibility to bladder cancer: a meta-analysis

The current meta-analysis of case–control studies was conducted to evaluated the relationships of genetic polymorphisms in the CYP1A1 and CYP1B1 genes with the susceptibility to bladder cancer, aiming at determine whether these polymorphisms may contribute to the pathogenesis of bladder cancer. Related articles were determined via searching the following electronic databases without any language restrictions: PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library, and CBM databases for relevant articles published before November 1st, 2013. STATA 12.0 software was also selected to deal with statistical data. The relationships were evaluated using the pooled odds ratios (ORs) and their 95 % confidence intervals (CI). Eleven case–control studies with a total of 2,609 bladder cancer patients and 2,634 healthy subjects met the inclusion criteria. The results of our meta-analysis demonstrated that CYP1A1 genetic polymorphisms were associated with increased risks of bladder cancer (allele model: RR = 1.18, 95 % CI 1.07–1.30, P = 0.001; dominant model: RR = 1.15, 95 % CI 1.05–1.27, P = 0.003; respectively), especially among 11599G>C, 2455A>G, 3810T>C, and 113T>C polymorphisms. A subgroup analysis by ethnicity was conducted to investigate its effect on susceptibility to bladder cancer. The subgroup analysis results revealed positive significant correlations between CYP1A1 genetic polymorphisms and bladder cancer risk among Asians (allele model: RR = 1.26, 95 % CI 1.10–1.44, P = 0.001; dominant model: RR = 1.22, 95 % CI 1.08–1.38, P = 0.001), but not among Caucasians (all P < 0.05). Nevertheless, we observed no significant correlations between CYP1B1 genetic polymorphisms and bladder cancer risk (all P > 0.05). Our meta-analysis indicates that CYP1A1 genetic polymorphisms may be involved in the pathogenesis of bladder cancer, especially among 11599G>C, 2455A>G, 3810T>C, and 113T>C polymorphisms. However, CYP1B1 genetic polymorphisms may not be important determinants of bladder cancer susceptibility.     

Polymorphisms in detoxification genes CYP1A1, CYP2E1, GSTT1 and GSTM1 in gastric cancer susceptibility

Cytochrome P450 (CYP) and glutathione S-transferase (GST) enzymes are involved in activation and detoxification of many potential carcinogens. Genetic polymorphisms in those enzymes have been found to influence the interindividual susceptibility to cancer. Some polymorphisms of those enzymes have been associated specifically with susceptibility to gastric cancer. We conducted a study in a Costa Rican population, where gastric cancer incidence and mortality rates are among the highest in the world. We investigated whether such variations affected the risk of developing gastric cancer. Subjects included 31 with gastric cancer, 58 controls with gastric injures others than cancer and 51 normal controls confirmed by X-rays (double-contrast) or endoscopic diagnostic. DNA from peripheral white blood cell was obtained from all subjects. Deletion of GSTT1 and GSTM1 was assessed by multiplex PCR and genotyping of CYP2E1 was performed using a PCR-based restriction fragment length polymorphism assay with the restriction enzyme PstI and the gene CYP1A1 using the restriction enzyme MspI The prevalence of CYP1A1 Msp1 polymorphism, GSTT1 and GSTM1 null genotype was similar in the three groups of individuals (p = 0.73, p = 0.88 y p = 0.89 respectively). Our findings suggest that the polymorphism CYP2E1 PstI could be associated with a reduced risk of having gastric cancer (OR = 0.09, IC95%:0.01 - 0.83).     

CYP1A1 *2B and *4 polymorphisms are associated with lung cancer susceptibility in Mexican patients

BACKGROUND: CYP1A1 is a gene involved in the high aryl hydrocarbon hydroxylase -inducible phenotype, which is a genetically-determined variation among individuals that has been associated with lung cancer risk. More specifically, CYP1A1 *2B and *4 polymorphisms have been associated with high susceptibility to lung cancer among cigarette smokers. MATERIALS AND METHODS: DNA was obtained from blood samples and we studied by PCR-RFLP the distribution of CYP1A1 *2B (n=248) and *4 (n=222) polymorphisms in healthy controls and 222 lung cancer patients from a Mexican population. RESULTS: Comparisons between groups showed an increased risk for lung cancer patients of *2B/*2B (18%; OR 7.6; 95% CI 3.0-19.2) and *4/ *4 genotypes (15%; OR 11.45; 95% CI 2.19-59.85) compared to the control group (1% for *2B/ *2B and 4.4% for *4/ *4). A significant association between lung cancer and homozygous *2B/ *2B passive smokers and *4/*4 ever (cigarettes) and passive smokers was also observed (p<0.05). Multivariate analysis revealed an increased risk for the *2B/*2B genotype (OR 6.83), as well as for *4/*4 (OR 28.8). CONCLUSION: The results of the study indicate a significant association between *2B/*2B and *4/*4 genotypes and the risk of developing lung cancer among Mexicans.     

Genetic polymorphism of the CYP1A1, CYP2E1, GSTM1 and GSTT1 genes and lung cancer susceptibility in a north Indian population

The present study investigates in a experimental system in vitro the relationship between the non-enzymatic (ascorbate-Fe2+) and enzymatic (NADPH) lipid peroxidation in rat liver microsomes and nuclei. Chemiluminescence was measured as cpm/mg protein during 180 min at 37 degrees C. Approximately 50-55% of the fatty acids located in rat liver microsomes and nuclei are polyunsaturated with a prevalence of C18:2 n6 and C20:4 n6. The values of total light emission during the non-enzymatic and enzymatic lipid peroxidation were highest in microsomes than in nuclei. A significant decrease of C20:4 n6 and C22:6 n3 in rat liver microsomes and nuclei was observed during the lipid ascorbate-Fe2+-dependent peroxidation, whereas a significant decrease of C20:4 n6 in rat liver microsomes was observed during enzymatic lipid peroxidation. Over the time course studies, analysis of chemiluminescence in microsomes and nuclei demonstrated that the lipid peroxidation in the presence of ascorbate-Fe2+ reach a maximum at 50 and 30 min, respectively, whereas in the presence of NADPH it reachs a maximum at 20 min in both organelles. In liver microsomes and nuclei the peroxidizability index (pi) which indicates the degree of vulnerability to degradation of a selected membrane showed statistically significant differences between control versus ascorbate-Fe2+ when microsomes or nuclei were compared. Our results indicate that non-enzymatic (ascorbate-Fe2+) and enzymatic (NADPH) lipid peroxidation are operative in rat liver microsomes and nuclei but the sensitivities of both organelles to lipid peroxidation evidenced by chemiluminescence was greater in the presence of ascorbate-Fe2+ when compared with NADPH.     

Meta-analysis of the association of CYP1A1 polymorphisms with gastric cancer susceptibility and interaction with tobacco smoking

The association of two cytochrome P4501A1 (CYP1A1) polymorphisms, m1 (T6235C transition) and m2 (A4889G transition), with gastric cancer risk is inconclusive. We conducted a meta-analysis of all available studies to evaluate the potential role of the polymorphisms and their interactions with tobacco smoking in gastric cancer susceptibility. Published literature from PubMed was retrieved by two investigators independently. Fourteen case-control studies with 2,032 gastric cancer cases and 5,099 controls were selected. A fixed effects model or a random-effects model was used to estimate the odds ratio (OR) for the CYP1A1 polymorphisms and the occurrence of gastric cancer. Significant associations between CYP1A1 m1 and m2 polymorphisms and gastric cancer susceptibility were not observed in all genetic models in the overall analyses. Subgroup analyses by ethnicity and source of controls did not reveal significant associations with gastric cancer risk. Stratification analysis by smoking status found that carriers of the heterozygous and homozygous m1 genotypes decreased the susceptibility of gastric cancer among ever-smokers (pooled OR = 0.56, 95 % CI 0.36-0.89, fixed effects). In contrast, the m2 genotypes (G/G and A/G) did not show any relevance to gastric cancer risk among the smoking population (pooled OR = 1.30, 95 % CI 0.84-2.00, fixed effects). Overall, we found that the CYP1A1 polymorphism itself, either m1 or m2, did not represent an independent genetic risk factor influencing gastric cancer. However, subgroup analyses suggest that carriers of the heterozygous and homozygous m1 genotype who are exposed to tobacco smoke have a significantly lower risk of developing gastric cancer. To explain the observed reduction of gastric cancer risk, we proposed a novel hypothesis of "observation bias". This hypothesis is also applicable to explain the combined effects of other genetic polymorphisms and environmental factors on the risk of developing cancers, and the rationality of the hypothesis needs to be further investigated.     

Associations between interleukin-10 polymorphisms and susceptibility to rheumatoid arthritis: a meta-analysis

The aim of this study was to determine whether the interleukin-10 (IL-10) polymorphisms confer susceptibility to rheumatoid arthritis (RA). A meta-analysis was conducted on the associations between the IL-10 −1082 G/A, −592 C/A, −892 C/T and IL-10.R polymorphisms and RA using; (1) allele contrast, (2) the recessive model, (3) the dominant model, and (4) the additive model. A total of 16 studies (19 comparisons) involving 2647 RA patients and 3383 controls were considered in the meta-analysis. Meta-analysis of the IL-10 −1082 G/A polymorphism showed no association with RA in the study subjects, or in European or Asian subjects. However, meta-analysis of the −1082 G allele in 4 studies in Hardy–Weinberg equilibrium showed a significant association with RA (OR = 1.217, 95% CI = 1.027–1.442, P = 0.0236). In contrast, meta-analysis of the C allele, the CC genotype, and of the CC versus the AA genotype of the IL-10 −592 C/A polymorphism showed significant associations with RA. The overall ORs of the associations between the C allele and RA were 0.684 and 0.758 (95% CI = 0.494–0.946, P = 0.022; 95% CI = 0.475–1.210, P = 0.045) in all study subjects and Asians. Meta-analysis of the CC + CT versus TT genotype and of the CC versus TT genotype of the IL-10 −892 C/T polymorphism revealed significant associations with RA. The overall OR of the association between the C allele carrier and RA was 0.552 (95% CI = 0.375–0.812, P = 0.003). No association was found between the IL10.R2 alleles and RA. This meta-analysis suggests that the IL-10 −592 C/A polymorphism confers susceptibility to RA in Asians and that the IL-10 −1082 G/A and −892 C/T polymorphisms are associated with RA susceptibility. These findings suggest the IL-10 genes confer susceptibility to RA.     

Association of CYP1A1 and CYP2D6 gene polymorphisms with head and neck cancer in Tunisian patients

The purpose of this study was to investigate the relationship between head and neck cancer (HNC) and environmental agents and polymorphisms in CYP1A1, CYP2D6, NAT1 and NAT2 metabolic enzymes genes. To the best of our knowledge, this is the first report on polymorphisms in CYP1A1 6310C>T, CYP2D6 Arg365His, NAT1 52936A>T and NAT2 Arg268Lys (NAT2*12A) genes and susceptibility to HNC in Tunisian population. We study the prevalence of these polymorphisms in 169 patients with HNC and 261 control subjects using polymerase chain reaction based methods in a Tunisian population. We detected an association between HNC and CYP1A1 6310C>T (TT) and CYP2D6 Arg365His (His/His) variant carriers (OR 1.75, P = 0.008 and OR 1.66, P = 0.016, respectively). No association was found between the polymorphisms genotypes of NAT1 52936T>A and NAT2 Arg268Lys and risk of HNC. An association between HNC and CYP1A1 (TT) genotype was found among patients with smoking (P = 0.011) and drinking habit (P = 0.009). The combinations of NAT1 (AT or AA) and NAT2 (AA) at-risk genotypes increased HNC risk (OR 4.23, P = 0.005 and OR 3.60, P = 0.048, respectively). However, the combinations of CYP1A1 (AA) and CYP2D6 (CC) genotypes decreased risk of HNC (OR 0.20; P = 0.006). Genetic polymorphisms in CYP1A1 and CYP2D6 may significantly associate with HNC in the Tunisian population. The results of this study suggest a possible gene–environment interaction for certain carcinogen metabolizing enzymes, but larger studies that fully evaluate the interaction are needed.     

CYP2E1 Rsa I/Pst I polymorphism contributes to oral cancer susceptibility: a meta-analysis

Previous data on association between CYP2E1 Rsa I/Pst I polymorphism and oral cancer risk were controversial. To investigate the association between CYP2E1 Rsa I/Pst I polymorphism and oral cancer risk. We performed a meta-analysis to assess the relationship between oral cancer and genotype with English language until June 2010. Twelve published case–control studies of 1259 patients with oral cancer and 2262 controls were acquired. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association in codominant and dominant models. Overall, the pooled ORs indicated a significant association between CYP2E1 Rsa I/Pst I polymorphism and oral cancer risk (for c1/c2 vs. c1/c1: OR = 1.30, 95% CI = 1.04–1.62, P_{heterogeneity} = 0.57; for (c1/c2 + c2/c2) vs. c1/c1: OR = 1.32, 95% CI = 1.07–1.64, P_{heterogeneity} = 0.57, respectively). In subgroup analysis by race, the same significant risks were found among Asian (for c1/c2 vs. c1/c1: OR = 1.41, 95% CI = 1.05–1.91, P_{heterogeneity} = 0.92; for (c1/c2 + c2/c2) vs. c1/c1: OR = 1.43, 95% CI = 1.08–1.88, P_{heterogeneity} = 0.97, respectively). In conclusion, this meta-analysis demonstrates that CYP2E1 Rsa I/Pst I c2 allele may be a biomarker for oral cancer, especially among Asian populations.     

CYP1A2 genetic polymorphisms and adenocarcinoma lung cancer risk in the Tunisian population

AimsIn this study, the effects of four single nucleotide polymorphisms (SNPs), ? 3860G > A, ? 2467delT, ? 739T > G and ? 163C > A, of CYP1A2 gene on lung cancer were evaluated in Tunisian population.Main methodsFour polymorphisms of CYP1A2 gene were analysed in 109 healthy smokers and in 101 lung cancer cases, including 63 with squamous cell carcinoma (SCC) and 41 with adenocarcinoma (AD). The genotyping for the SNPs ? 3860 G > A, ? 2467delT, ? 739T > G and ? 163C > A was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis.Key findingsThe results showed that smokers with CYP1A2 gene polymorphisms were associated with an increased risk for the development of lung AD. There was however no significant increased risk of developing lung SCC in smokers having CYP1A2 gene polymorphisms. An increased risk of developing AD was observed in smokers who are carriers of at least one copy of ? 3680A or ? 739G giving a significant odds ratio (OR) of 6.02 (CI = 2.91–12.9) and 3.01 (CI = 1.54–5.98), respectively.SignificanceThese genotyping data are consistent with the hypothesis that tobacco-specific-N-nitrosamines (TSN) such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are major contributors to the development of lung AD and that CYP1A2 gene product plays an important role in the metabolic activation of NNK. This study suggests that SNPs of CYP1A2 could be considered as promising biomarkers in the aetiology of lung AD in smokers.     

CYP1A1*2 and CYP1A1*3 polymorphisms cosegregate in the Indian population

Several ethnic groups have been genotyped for polymorphisms at the CYP1A1 gene locus that encodes the enzyme that catalyzes the initial step in the metabolism of polycyclic aromatic hydrocarbons. Two of the CYP1A1 polymorphisms, namely, CYP1A1*2 and CYP1A1*3 are reported to cosegregate among the Japanese and to a lesser extent in Caucasians, but not in people of African descent. In the absence of such information in the Indian population, the frequency of the CYP1A1*2 polymorphism was determined in this study, using DNA samples from 649 ethnic Indians who had been earlier genotyped for the CYP1A1*3 polymorphism. Analysis of the combined genotype data revealed that the two polymorphisms cosegregate in the Indian population.     

Associations between interleukin-23 receptor polymorphisms and susceptibility to rheumatoid arthritis: a meta-analysis

The aim of this study was to determine whether interleukin-23 receptor (IL-23R) polymorphisms confer susceptibility to rheumatoid arthritis (RA). A meta-analysis was conducted on the associations between the IL-23R rs1343151, rs10489629, rs7517847, rs11209026, rs1004819, and rs2201841 polymorphisms and RA using (1) allele contrast, (2) the recessive model, (3) the dominant model, and (4) the additive model. A total of 13 studies from eight articles involving 10,016 RA patients and 11,967 controls were considered in the meta-analysis. Meta-analysis identified a significant association between RA and the A allele of the rs1343151 polymorphism in the overall population (OR?=?1.110, 95?% CI?=?1.056–1.168, p?=?4.7?×?10^?6). Stratification by ethnicity identified a significant association between this polymorphism and RA in Europeans (OR?=?1.105, 95?% CI?=?1.049–1.163, p?=?1.4?×?10^?5). An association was also found between RA and the A allele carrier of the rs1343151 polymorphism in Europeans (OR?=?1.135, 95?% CI?=?1.058–1.217, p?=?4.0?×?10^?5). Meta-analysis revealed a significant association between RA and the A allele of the rs10489629 polymorphism in the overall population (OR?=?1.079, 95?% CI?=?1.029–1.131, p?=?0.002) and in Europeans (OR?=?1.092, 95?% CI?=?1.038–1.149, p?=?0.001). Meta-analyses of recessive, dominant, and additive models showed the same pattern as the meta-analysis of the A allele of the rs10489629 polymorphism, that is, a significant association with RA in Europeans. However, no association was found between the IL-23R rs7517847, rs11209026, rs1004819, and rs2201841 polymorphisms and RA susceptibility. This meta-analysis shows that the IL-23R rs1343151 and rs10489629 polymorphisms are associated with the development of RA in Europeans. These findings suggest that the IL-23R genes confer susceptibility to RA in the European population, but further study of this association is required in other ethnic groups.     

A comparison of substrate dynamics in human CYP2E1 and CYP2A6

Considering the dynamic nature of CYPs, methods that reveal information about substrate and enzyme dynamics are necessary to generate predictive models. To compare substrate dynamics in CYP2E1 and CYP2A6, intramolecular isotope effect experiments were conducted, using deuterium labeled substrates: o-xylene, m-xylene, p-xylene, 2,6-dimethylnaphthalene, and 4,4'-dimethylbiphenyl. Competitive intermolecular experiments were also conducted using d(0)- and d(6)-labeled p-xylene. Both CYP2E1 and CYP2A6 displayed full isotope effect expression for o-xylene oxidation and almost complete suppression for dimethylbiphenyl. Interestingly, (k(H)/k(D))(obs) for d(3)-p-xylene oxidation ((k(H)/k(D))(obs)=6.04 and (k(H)/k(D))(obs)=5.53 for CYP2E1 and CYP2A6, respectively) was only slightly higher than (k(H)/k(D))(obs) for d(3)-dimethylnaphthalene ((k(H)/k(D))(obs)=5.50 and (k(H)/k(D))(obs)=4.96, respectively). One explanation is that in some instances (k(H)/k(D))(obs) values are generated by the presence of two substrates-bound simultaneously to the CYP. Speculatively, if this explanation is valid, then intramolecular isotope effect experiments should be useful in the mechanistic investigation of P450 cooperativity.     

Mitochondrial targeting of intact CYP2B1 and CYP2E1 and N-terminal truncated CYP1A1 proteins in Saccharomyces cerevisiae--role of protein kinase A in the mitochondrial targeting of CYP2E1

Previously we showed that intact rat cytochrome P450 2E1, cytochrome P450 2B1 and truncated cytochrome P450 1A1 are targeted to mitochondria in rat tissues and COS cells. However, some reports suggest that truncated cytochrome P450 2E1 is targeted to mitochondria. In this study, we used a heterologous yeast system to ascertain the conservation of targeting mechanisms and the nature of mitochondria-targeted proteins. Mitochondrial integrity and purity were established using electron microscopy, and treatment with digitonin and protease. Full-length cytochrome P450 2E1 and cytochrome P450 2B1 were targeted both to microsomes and mitochondria, whereas truncated cytochrome P450 1A1 (+ 5 and + 33/cytochrome P450 1A1) were targeted to mitochondria. Inability to target intact cytochrome P450 1A1 was probably due to lack of cytosolic endoprotease activity in yeast cells. Mitochondrial targeting of cytochrome P450 2E1 was severely impaired in protein kinase A-deficient cells. Similarly, a phosphorylation site mutant cytochrome P450 2E1 (Ser129A) was poorly targeted to the mitochondria, thus confirming the importance of protein kinase A-mediated protein phosphorylation in mitochondrial targeting. Mitochondria-targeted proteins were localized in the matrix compartment peripherally associated with the inner membrane and their ethoxyresorufin O-dealkylation, erythromycin N-demethylase, benzoxyresorufin O-dealkylation and nitrosodimethylamine N-demethylase activities were fully supported by yeast mitochondrial ferredoxin and ferredoxin reductase.     

CYP2A6 gene deletion reduces susceptibility to lung cancer.

CYP2A6 is an enzyme with a high ability to activate a nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), to its potent and ultimate carcinogen. In the present study, we investigated the relationship between genetic polymorphism of CYP2A6 and lung cancer risk in a case-control study of Japanese subjects. Genotyping of the CYP2A6 gene in both healthy volunteers and lung cancer patients was conducted. The frequency with which the subjects carried homozygotes of the CYP2A6 gene deletion-type mutation (deletion), which causes lack of the enzyme activity, was lower in the lung cancer patients than in the healthy control subjects. The odds ratio (OR) of the group homozygous for the deletion was significantly lower and calculated to be 0.25 (95% CI; 0.08-0.83) when the OR for the population with homozygotes of the CYP2A6 wild-type gene was defined as 1.00. In the allelic-base analysis, there was also a significant decrease in the OR for the deletion allele. These data suggest that deficient CYP2A6 activity due to genetic polymorphism reduces lung cancer risk.     

Association between the CYP1A2-164 A/C polymorphism and colorectal cancer susceptibility: a meta-analysis

To date, epidemiological studies have assessed the association between CYP1A2-164 A/C polymorphism and colorectal cancer susceptibility. However, the results of these studies remained controversial. We aimed to examine the associations by conducting a meta-analysis of case–control studies. A total of 11 studies including 5,093 cases and 5,941 controls evaluated the association between the CYP1A2-164 A/C polymorphism and colorectal cancer susceptibility. No significantly associations were found in all genetic models (CC vs. AA: OR = 1.14, 95 % CI = 0.93–1.40; AC vs. AA: OR = 1.05, 95 % CI = 0.91–1.20; dominant model: OR = 1.08, 95 % CI = 0.95–1.24; recessive model: OR = 1.10, 95 % CI = 0.95–1.28). In the subgroup analysis by ethnicity or source of controls, there were still no significant associations detected in all genetic models. This meta-analysis suggested the CYP1A2-164 A/C polymorphism was not a risk factor for increasing colorectal cancer, further large and well-designed studies are needed to confirm these conclusions.