ANK3, which codes for Ankyrin 3. This protein is involved in facilitating the propagation of action potentials by regulating the assembly of sodium gated ion channels. Since ANK3 influences the efficiency of transmission of neuronal impulses, allelic variation in this gene may have widespread cognitive effects. Preclinical data suggest that this may principally apply to sequential signal detection, a core process of sustained attention.Abnormalities in cognition have been reported in patients with Bipolar Disorder (BD) and their first degree relatives, suggesting that susceptibility genes for BD may impact on cognitive processes. Recent genome-wide genetic studies have reported a strong association with BD in a single nucleotide polymorphism (SNP) (rs10994336) within ANK3 rs10994336 polymorphism and received diagnostic interviews and comprehensive neurocognitive assessment of their general intellectual ability, memory, decision making, response inhibition and sustained attention. Participants comprised euthymic BD patients (n = 47), their unaffected first-degree relatives (n = 75) and healthy controls (n = 67). The risk allele T was associated with reduced sensitivity in target detection (p = 0.0004) and increased errors of commission (p = 0.0018) during sustained attention regardless of diagnosis. We found no effect of the ANK3 genotype on general intellectual ability, memory, decision making and response inhibition.One hundred and eighty-nine individuals of white British descent were genotyped for the ANK3 impacts cognitive processes associated with signal detection and this mechanism may relate to risk for BD. However, our results require independent replication and confirmation that ANK3 (rs10994336) is a direct functional variant.Our results suggest that allelic variation in  Within the nervous system, the protein coded by ANK3, known as Ankyrin3 or AnkyrinG, is localised in the initial axonal segment and the nodes of Ranvier Bipolar Disorder (BD) is a complex, highly heritable disease The focus on the potential relevance of ion channels for psychiatric disorders is relatively new; to date channelopathies were mostly considered in the context of cardiac In parallel to developments in genetic studies, the cognitive function of BD patients and their relatives has received much attention, particularly as cognition is considered more directly linked to genetic liability ANK3 for complex behaviour, either in health or in disease, is rudimentary. However, it has long been known that retinal ganglion cells are dependent on sodium channels for action potential generation ANK3 on visual sustained attention represents a logical first step in unravelling genotype-phenotype relationships.At present, our understanding of the functional significance of the allelic variation of ANK3 and undertook two analyses. A hypothesis led analysis on the effect of the ANK3 genotype and its interaction with diagnosis on target detection as assessed with the Degraded Symbol Continuous Performance task (DS-CPT) ANK3 on cognition is currently limited we also undertook a hypothesis generating analyses on the effect of allelic variation in ANK3 on other aspects of cognition.To this aim we evaluated cognitive function in patients with BD, their first degree relatives and healthy controls genotyped for We genotyped participants of the Vulnerability to Bipolar Disorder Study (n = 189) Healthy volunteers were recruited through advertisement in the local press and were enrolled if they were (a) aged 17–65 years and (b) had no personal or family history of any Axis I or II DSM-IV disorder. Healthy volunteers were selected so that they matched both patients and relatives in gender and level of education. Level of education was rated on a 5-point scale ranging from 1  to 5 .Exclusion criteria for the entire sample  included (a) head trauma resulting in loss of consciousness, (b) personal history of neurological or medical disorders, (c) family history of hereditary neurological disorders and (d) fulfilling DSM-IV criteria for lifetime drug or alcohol dependence and drug or alcohol abuse in the preceding six months.The study was approved by the Ethics Committee of the Institute of Psychiatry. Written informed consent was obtained from all participants and all clinical investigations were conducted according to the principles expressed in the Declaration of Helsinki.All participants were interviewed personally by trained psychiatrists, who were initially blind to diagnostic but not family status (BD family member or unrelated control), using the Structured Clinical Interview for DSM-IV (SCID) for Axis I (patient and non-patient version) All participants were assessed using the same battery administered in a single session by qualified psychologists. An estimate of current full-scale intelligence quotient (FSIQ) was obtained using the Wechsler Adult Intelligence Scale-Revised (WAIS-R) ANK3 on any aspect of cognition is not known; given the role of ANK3 in fundamental aspects of neuronal firing and neural connectivity we explored the possibility that its impact on cognition might be quite broad. Therefore we examined the effect of the genotype on all cognitive tests for which complete information was available for all participants. These were the Stroop Colour Word Test (SCWT) The effect of allelic variation in ANK3 T/C (rs10994336) genotype was determined by a ‘TaqMan’ allelic discrimination assay . End point analysis was performed using the Applied Biosystems 7900HT Fast Real-Time PCR System and genotypes were called with the SDS 2.3 software.DNA was obtained from buccal swabs using established procedures To compare demographic features, we conducted univariate analyses of variance (ANOVAs) for continuous variables with genotype and affection status  as fixed factors and chi-square tests for dichotomous variables. We used the same approach when comparing the effect of genotype on the clinical characteristics of BD patients.We examined the normality of distribution of the neurocognitive variables in the entire sample with goodness of fit Kolmogorov-Smirnov tests. For normally distributed variables we used univariate, multivariate or repeated measures analysis of covariance with total BPRS score as covariate to examine the main effects and interaction of genotype and affection status. Although YMRS and HAMD data on the entire sample were available these scales are not standardised for use in non-clinical populations. Therefore, the 24-item BPRS was chosen to allow meaningful comparisons between patient and non-patient groups as it can be used to rate both non-pathological (item ratings below 3) and pathological experiences (item ratings of 4–7).http://cran.r-project.org). We analyzed the data using the ANOVA and retained the test statistic . The random assignment of genotypes was repeated 100,000 times to derive a distribution of F-values. The latter analysis was conducted twice; once including only completely asymptomatic participants (BPRS score<27) and once including the entire sample while co-varying for BPRS score. Comparison of the observed F-values with the distribution from the simulation method produced empirical p-values which are robust to the non-normal distribution of the phenotype.For non-normally distributed variables we employed a simulation method, whereby we retained the phenotypic data (cognitive variables and affection status) and permuted the observed genotype among individuals using the R statistical package  assuming a minimum allele frequency 0.067 (hapmap.ncbi.nlm.nih.gov/cgi-perl/snp_details_B36?name=rs10994336&source=hapmap24_B36) and an additive model.As this is the first study to report on the effect of Ninety-two BD patients from an equal number of families were screened by telephone interview for eligibility by a trained psychiatrist. Families of 53 BD patients were enrolled in the study; these yielded 47 BD-I patients (6 patients were further excluded as they did not meet remission criteria throughout the study period) and 75 first-degree relatives. All participants were of self-reported British white ancestry. For the current analysis, 1 BD patient and 2 relatives were excluded due to failure in genotyping. Detailed flow chart of study sample recruitment is shown in www.hapmap.org), only one TT homozygote was identified and was analysed together with the heterozygotes. Genotype frequencies in unrelated participants were in Hardy-Weinberg equilibrium (p = 0.65). In total, 165 individuals  were C homozygotes and 21  carried the risk allele T. There were no affection status by genotype interactions for age at assessment , gender or educational status .Due to the rarity of the T allele  or duration of illness  or on the rates of psychosis . Although the carriers of the risk allele (T) had more depressive  and manic episodes .In the BD patient group, there was no genotype effect on age of onset , Response criterion  and reaction time . The effect size of the genotype was negligible for Hit Rate (Cohen's d = 0.08) and small for Response Criterion and reaction time (Cohen's d<0.25) so it is unlikely that these results reflect lack of power.6, 177 = 0.82, p = 0.55) and Sensitivity  were not significant. In contrast, the interaction between block and genotype was significant both for False Alarms  and Sensitivity . However polynomial linear within-subject contrasts revealed substantial 2 way interaction of genotype by block for False Alarms and Sensitivity (p = 0.014 and 0.038 respectively). In addition, the between subject effects of genotype was significant for both False Alarm  and Sensitivity .The within subjects main and interaction effects for False Alarm  was associated with poorer performance.ANK3 was negligible for FSIQ (Cohen's d = 0.14), WCST categories achieved and perseverative errors (Cohen's d = 0.05 for both) and IGT (Cohen's d = 0.02). For all WMS-III variables the effect of ANK3 ranged from negligible to small (Cohen's d range 0.03–0.17) with the exception of the composite index of working memory where a moderate effect size (Cohen's d = 0.35) was noted. Similarly a medium effect size of 0.44 was noted for the SCWT. The risk allele (T) was associated with poorer performance on all of these measures.There was no significant main effect of genotype or genotype by affection status interaction on test performance on the WAIS-R, SCWT, WCST, and WMS-III and IGT  . The effANK3 on cognition in BD patients, their relatives and healthy controls. We found that the ANK3 genotype may be specifically associated with visual sustained attention but not with measures of global intellectual function such as IQ. The effect of the ANK3 genotype was also explored in the domains of memory, response inhibition, decision making and executive function. With the exception of response inhibition the effect sizes observed in all other cognitive domains ranged from negligible to small and are therefore of doubtful biological significance This is first study to examine the effect of allelic variation in ANK3 in decreasing signal detection rather than lowering response criteria. The latter is often assumed to reflect increased “impulsivity” in responding ANK3 and reduced sensitivity in target detection is beyond the resolution of our methodology. However, the potential impact of ANK3 on sodium channel clustering and action potential propagation may impact on stimulus encoding and coupling of prefrontal and visual cortices The version of the CPT employed here depends on the effortful, sequential processing of multiple ambiguous visual targets but not on working memory processes that rely on representations of preceding stimuli ANK3 gene (rs10994336) is a direct functional variant or a tagging SNP, which may reflect the effect of another, as yet unknown, variant which has a direct functional effect on both risk of BD and visual sustained attention. Finally, decrements in sensitivity during the DS-CPT have been observed in other disorders notably schizophrenia where they seem to play a more important role than in BD There are several important methodological considerations. Firstly, there are several genes as well as behavioural, clinical and cognitive phenotypes for BD that could have been examined in this dataset. However, the simultaneous investigation of all possible combinations corrected for multiple comparisons would require very large datasets with the same or comparable measures on all participants. Although ideal, this is currently not feasible. At the same time, exploring the potential effect size of genetic polymorphisms in smaller, well characterised datasets has the potential of informing future collaborative approaches and reducing the number of target phenotypes. Secondly, the study sample comprised of individuals already in our database and was not specifically obtained for examining the effect of rs10994336. We fully appreciate that our sample size is moderate but we believe that to a large extent this is, at present, inevitable, as ANK3 is not a gene that was theoretically predicted as being of relevance to BD. Thirdly, the risk conferring allele is exceedingly rare and was therefore only identified in large samples pooled from different studies. Such pooled samples do not have detailed phenotypic information apart from diagnosis. Therefore we consider this paper as a first step in the process of unravelling the functional significance of the genes identified for BD. Fourthly, given the moderate size of our sample we were rigorous in the statistical approach employed to minimise the likelihood of spurious findings. Additionally, we have provided estimates of effect size for all our analyses that allows further inspection of the statistical properties of the dataset. Fifthly, since there is no information at present on whether the SNP in the ANK3 polymorphism on sensitivity to signal detection affecting individual's sustained attention and possibly contributing to the risk for BD. Further investigations are required to confirm the functional variant of ANK3 and to investigate the electrophysiological implications of genetic variability in this locus.In summary, we report a relatively selective effect of the Table S1Cognitive Task Performance(DOC)Click here for additional data file.


CYP450s), such as CYP1A1, CYP1B1, and CYP2D6, usually metabolize carcinogens to their inactive derivatives, but they occasionally convert the chemicals to more potent carcinogens. In addition, via CYP450 (CYP2E1) oxidase, alcohol is metabolized to acetaldehyde, a highly toxic compound, which plays an important role in carcinogenesis. Furthermore, two N-acetyltransferase isozymes (NATs), NAT1 and NAT2, are polymorphic and catalyze both N-acetylation and O-acetylation of aromatic and heterocyclic amine carcinogens. Genetic polymorphisms are associated with a number of enzymes involved in the metabolism of carcinogens important in the induction of HNC. It has been suggested that such polymorphisms may be linked to cancer susceptibility. In this paper, we select four cytochrome P450 enzymes , and two N-acetyltransferase isozymes (NAT1 and NAT2) in order to summarize and analyze findings from the literature related to HNC risk by focusing on (i) the interaction between these genes and the environment, (ii) the impact of genetic defect on protein activity and/or expression, and (iii) the eventual involvement of race in such associations.The occurrence of head and neck cancer (HNC) is associated with smoking and alcohol drinking. Tobacco smoking exposes smokers to a series of carcinogenic chemicals. Cytochrome P450 enzymes ( Head and neck squamous cell carcinoma (HNSCC) is the fifth most common cancer worldwide and is associated with low survival and high morbidity when diagnosed in advanced stage , 2. ThisCYP1A1, CYP1B1, CYP2D6, and CYP2E1) and N-acetyltransferase (NAT1 and NAT2) enzymes involved in the biotransformation of the carcinogenic constituents of tobacco have been shown to be the risk factors involved in HNSCC  is more frequent in the group of white HNSCC patients  than in white controls   and CYP1A1 m2    [Ile462Val (rs1048943)] in a total of 457 Cantonese nuclear families, consisting of 2134 members, has concluded that there is no absence of any statistical significance between m1 polymorphism and susceptibility to NPC. However, m2 polymorphism might be associated with NPC in the Cantonese nuclear families (P = 0.045) pyrene-7,8-diol metabolism pyrene and in healthy oral tissues from smokers and nonsmokers. They noticed that the interindividual variation in inducible CYP1B1 expression may account in part for variation in tobacco-related OSCC risk. Furthermore, Schwartz et al. [CYP1B1 expression in dibenz[a]pyrene-induced OSCC. Moreover, Kolokythas et al.   , 147. Acf CYP2E1 . In fact1 allele , 148. It2E1 gene .CYP2E1 polymorphism with the risk of lung cancer [CYP2E1 polymorphism and HNC have also been published, but those studies have yielded contradictory results. Four separate epidemiological studies showed no association between the c2 allelic variant (RasI−/PstI+) and the risk for UADT cancer in Brazilian [CYP2E1 PstI and HNC in Brazilian patients and oral cancer in South Indians. Moreover, Gajecka et al., [CYP2E1 RsaI polymorphism and the overall risk of larynx cancer in Polish and Chinese patients, respectively. In addition, other studies [RasI−/PstI+ variant allele was more frequent in controls (2.8%) than in larynx cancer group (1.6%), which may suggest that the mutated allele is rather “protective”. These results are in agreement with the Swedish study which reported that individuals with RasI−/PstI+ allele may be at lower risk for lung cancer [CYP2E1 RasI SNP was shown to be associated with increased risk of HNSCC, OSCC, and esophageal cancer [Over the last two decades, several studies have explored the association of the g cancer , gastricg cancer , 152, anrazilian  or Japanrazilian  subjectsrazilian  and Balarazilian  observed et al.,  Tai et a et al.,  did not  studies , 156 havg cancer . Howeverl cancer , 158–160CYP2E1 polymorphisms in the induction of HNC. A later study [RasI−/PstI+ variant allele was associated with an increased risk of suffering, specifically, from oral cancer. Furthermore, in another Brazilian study of HNC [CYP2E1*5A/*5B (c1/c2) genotype was more frequent in oral cavity tumors than in tumors from other anatomic sites (P = 0.003) and that the CYP2E1*5A/*5A (c1/c1) genotype was more frequently detected in white patients (P = 0.0031). A study including 289 Brazilian volunteers showed that the frequencies of the CYP2E1*6 alleles  are similar to those observed in Caucasians and African-Americans, but the frequency of the CYP2E1*5B allele is higher in Brazilians [Several Brazilian studies have explored the role of er study  on Braziy of HNC , it was azilians . Howeverazilians , 163.CYP2E1 (RsaI/PstI) and CYP2E1 (DraI) polymorphisms and HNC susceptibility has been widely investigated. However, results were inconsistent. Recently, Lu et al. [CYP2E1 (RsaI/PstI) polymorphism might be a risk factor for HNC in the Asian population as well as several carcinogenic processes that cpolymorphism might be a risk factorThe association between u et al.  and Tangu et al.  have assCYP2E1 (RsaI or DraI) polymorphisms and susceptibility to esophageal SCC . Therefore, it was suggested that c2 allele and DD genotype represent a risk factor for esophageal SCC. The frequencies of these two mutations in the Chinese population [CYP2E1 [RsaI and DraI polymorphisms for esophageal SCC in a population with high mutant frequencies.ould induce carcinogenesis. In contrast to these findings, studies conducted by Liu et al.  on a Chipulation  were all [CYP2E1 , 167. HeCYP2E1 (c2/c2) genotype was found to be associated with an increased NPC risk, an effect most pronounced in non-smokers. Recently, Jia et al. [CYP2E1 and NPC risk in the Cantonese population. They observed that individuals aged less than 46 years and who had a history of cigarette smoking present OR of specific genotypes ranging from 1.88 to 2.99 corresponding to SNPs rs9418990, rs1536826, rs3827688, and rs8192780 (P = 0.0001–0.0140). Furthermore, Liu et al. [CYP2E1*5B and CYP2E1*6 polymorphisms and gene-environment interactions in the risk of UADT cancers among Indians was conducted. Results showed absence of differences between groups for the two polymorphisms if analyzed separately. However, results for CYP2E1*6 polymorphisms showed significant interactions among tobacco smokers (>40 pack-years) and regular tobacco chewers. These results illustrate the interaction between genes and environment and provide an additional genetic risk factor, CYP2E1*6 polymorphisms, for UADT cancers in the Indian population [Tobacco and alcohol consumption represent the most important factors for HNC; hence, genes involved in tobacco carcinogen and alcohol metabolism should play a role in the HNC development. An association between the c2 allele and the increased oral cancer risk was previously demonstrated among nonbetel quid chewing males from Taiwan . In addia et al.  found rou et al.  comparedu et al. . A hospiu et al.  of CYP2Epulation .CYP2E1 metabolizes ethanol and generates reactive oxygen species, and it has been suggested that it is important for the development of alcoholic liver disease and cancer, including hepatoblastoma and HNC. Acetaldehyde dehydrogenases are a group of NAD-dependent enzymes, which catalyze the oxidation of acetaldehyde, being the second enzyme of the alcohol oxidation pathway  and alcohol consumption and were found to increase the risk of OSCC . In addition, in the study of Olivieri et al. [CYP2E1*5B variant allele was more frequently detected in HNC Brazilian patients than in control subjects . Overall, the data suggested that CYP2E1*5B is an independent biomarker of risk in alcohol-related HNC. Recently, Cury et al. [CYP2E1*6 and CYP2E1*5B polymorphisms investigated had no association with the development of HNC in Brazilian patients. Alcohol or tobacco consumptions were also found to interact with variant genotypes of CYP2E1 in significantly enhancing HNC risk [CYP2E1*5B polymorphism can be quite important in oral carcinogenesis in Brazilians [CYP2E1*5B polymorphism and lung cancer among patients from Rio de Janeiro has been previously observed [ pathway  [27, 173exposure , 175. Inexposure , the poli et al. , among ay et al.  confirmeHNC risk . In addiazilians  or can bazilians . Absenceobserved ; this coThe difference in the genetic background between different ethnicities associated to other genetic factors involved in the etiology of HNC might be behind the variability and the inconsistency of these results. It is well established the involvement of some genetic polymorphisms if combined with smoking and alcohol metabolism in the development of HNC. The risk is higher than the tobacco and alcohol consumption is immense. Regarding the genetic component, its effect is depending on the allele combination. Further population genetic studies focusing on metabolizing enzyme polymorphisms should be very helpful in clarifying the individual genetic susceptibility and hence offer the adequate and personalized management of the patient.NAT1 and NAT2 human isoforms are encoded by two genes with intronic less coding regions. The NAT genes are located on chromosome 8p21.3–23.1 and express two highly polymorphic isoenzymes (NAT1 and NAT2) with distinct functional roles. In humans, the products of these two genes appear to have distinct functional roles depending on their substrate, their expression in tissues, and the expression of the different genes during development. Although the two genes are organized in a single open-reading frame, their structure and control vary markedly  or N-hydroxy-aromatic and N-heterocyclic amines (O-acetylation). The substrate could be activated or deactivated by NAT1 and/or NAT2 if O-acetylated or N-acetylated, respectively [via O-acetylation [N-hydroxy heterocyclic amine carcinogens are catalyzed by human NAT2 than NAT1 [cinogens . Based ocinogens . The latectively . Becausetylation –187, thehan NAT1 , 187. ThNAT2 genetic variants have been identified in human. Among them, NAT2*4 is the most common allele reported to be associated with rapid acetylation [NAT2*11A, NAT2*12A-C, NAT2*13A, and NAT2*18 and the slow alleles such as NAT2*5, NAT2*6, and NAT2*7. For NAT1, the most common alleles are NAT1*3, NAT1*4, NAT1*10, and NAT1*11. NAT1*4 is the most common allele, while NAT1*10 is the putative rapid allele. Subjects having more than one rapid allele were designated by NAT1 rapid acetylation. For the others, they were classified under NAT1 slow acetylation [So far, 36 tylation . The othtylation .NAT1 and NAT2 genes are characterized by allelic heterogeneity, several haplotypes have been established. They were associated with either the rapid or the slow acetylator phenotype [NAT gene SNPs and their association with HNC  are significantly (P < 0.002) more prone to develop UADT cancer (0.37) as compared with controls (0.22) [NAT2*7 allele was correlated to a reduced UADT cancer risk [NAT2*7 genotype in HNC. NAT2*5 and NAT2*6 alleles seem to be associated with cancer risk [NAT2 haplotypes have shown an association between NAT2*4 and HNC [NAT2*4 combinations (NAT2*4/*6A) in larynx cancer predisposition  [NAT2*6/NAT2*6 were significantly higher in the group of nasopharyngeal carcinoma patients . Furthermore, in another Tunisian study [NAT2*5, rs1801280) in NAT2 gene . This finding is in accordance with the reported association between squamous cell carcinoma and T341C mutation [NAT2*5) in NAT2 gene [NAT2*6) mutation in NAT2 gene [NAT2 genotype and NPC was found in the Taiwanese population [Some studies have reported that alteration of NAT enzyme activity might be of risk for UADT cancer. It was previously shown that patients with s (0.22) . In a recer risk  as well cer risk , thus sucer risk . Studies and HNC . These r= 0.045) . In a Tu= 0.045)  observedan study , a signimutation . This isAT2 gene . HoweverAT2 gene . In addipulation .NAT2*4 allele and the increased oral cancer risk in a Brazilian population  [O-acetylation of nitrosamines by NAT2 could be more important as a negative metabolic pathway leading to oral carcinogenesis; therefore, slow acetylators would be protected. Chatzimichalis et al. [P = 0.0087). Furthermore, Buch et al. [NAT2*4) are more frequent in oral cancer patients (53.7%) than in controls .An association was found between the homozygous = 0.032) . Likewis= 0.032) , 196. Ats et al.  establiss et al.  concludeh et al.  found thNAT1 polymorphisms in the incidence of HNC. The first study [NAT1 gene. This study is still until now the only one that suggested a significant increased risk  associated with the NAT1*10 allele in the Japanese population [Several studies have explored the role of st study  was condpulation . Howeverpulation , 200.NAT2 associations. The strongest one was observed among persons without a CYP1A1 variant (*2C or *4) allele  [NAT2 acetylation as a risk factor for oral cancer in the American population (USA) [NAT1 and NAT2 gene combinations may influence the risk of developing HNC. A significant association was observed between the fast acetylator NAT2*4/NAT1*10 diplotype and risk of HNC [NAT1*11/NAT2*6A haplotypes was correlated to the risk of UADT cancer  [Gene-gene interaction testing has shown several cancer- = 0.03) . These ron (USA) . Moreoveon (USA)  and McKaon (USA)  found thk of HNC . Moreove = 0.03) .NAT gene presents a crucial role in the detoxification and activation reactions of numerous xenobiotics originating not only from tobacco-derived aromatic and heterocyclic amine carcinogens but also from drug metabolism. Its function is undergone through N- and O-acetylation pathways [via a ping-pong bi-bi mechanism. The initial step consists on acetylation of Cys68 by an acetyl-coenzyme A along with the release of the cofactor product coenzyme A. Secondly, the substrate is linked to the acetylated enzyme. Finally, the acetylated product is released [NAT genotypes. HNCs are strongly associated with smoking, and a few studies have explored the role of NAT1 polymorphisms in the risk of developing HNC in smokers [NAT1 [pathways , 202 viareleased . Since c smokers , 204. Hors [NAT1 , an incrrs [NAT1 , or a lars [NAT1 , 202.NAT1 and NAT2 acetylator polymorphisms in cancer risk from aromatic and heterocyclic amine carcinogens will become clearer with more precise determinations of both exposures and genotypes. Further studies of the haplotype combinations in different populations and with larger cohorts are warranted to determine the range of risks associated with the effect of genetic variation of the NAT genes with regard to HNC.The role of The present paper reviews studies that assessed association between genetic polymorphisms of genes encoding carcinogen-metabolizing enzymes and showed their possible involvement by significantly increasing the predisposition for HNC. This risk relies on many factors such as the level of carcinogen exposure , the ethnicity and/or racial groups, and so forth. Various polymorphisms in these genes are summarized in It is well known that there is a real logistical difficulty that consists in combating at least one of the potential biases listed above. However, careful attention should be given to all elements before conducting an association study in order to ensure accurate and significant results. If well designated, these studies would clarify the impact of xenobiotic-metabolizing enzymes in HNC development and help determine the value of potentially “high-risk” genotypes in HNC prevention strategies.


Observational studies suggest an association between tooth loss and risk of head and neck cancer. However, whether tooth loss is an independent risk factor for head and neck cancer still remains controversial. The aim of this study is to assess the association between tooth loss and head and neck cancer risk.Eligible studies were searched in PubMed and Embase databases from their inception to March 2013. A random-effects model or fixed-effects model was used to calculate the overall combined risk estimates.Eight case-control studies and one cross-sectional study involving 5,204 patients and 5,518 controls were included in the meta-analysis. The overall combined odds ratio for tooth loss and head and neck cancer was 2.00 . Similar results yielded both in the moderate and severe tooth loss group. Sensitivity analysis based on various exclusion criteria maintained this significance with respect to head and neck cancer individually. Little evidence of publication bias was observed.This meta-analysis suggests that tooth loss is associated with increased risk of head and neck cancer. This increase is probably independent of conventional head and neck cancer risk factors. Head and neck cancer includes cancer of oral cavity, pharynx, and larynx. It is estimated that one out of 99 people born in the United States today will experience head and neck cancer during their lifetime Periodontal disease is a chronic, destructive disease that affects approximately 35% dentate adults 30 to 90 years old in the United States periodontal disease, periodontitis, tooth loss, and head and neck cancer, filtered by Human, without language restrictions. Reference lists of reviews or studies identified in the literature search were hand searched for additional studies. If duplicated data were presented in several studies, only the most recent, largest or most complete study was included. Studies meeting the following criteria were included: (i) evaluating the association between tooth loss and head and neck cancer; (ii) with ≤5 lost teeth as the referent category; and (iii) providing the adjusted odds ratios (ORs) with the corresponding 95%CI or raw data to calculate the crude ORs and 95% confidence intervals (CIs).PubMed and Embase databases  were searched to identify relevant studies investigating the association between tooth loss and risk of head and neck cancer. The following search terms were used: Two reviewers (XYH and WJG) independently extracted data about the characteristics of selected studies using a standardized data extraction form. Data were recorded as follows: first author, year of publication, location, number of subjects (cases/controls), patient characteristics, assessment of tooth loss, cancer site, statistical adjustment for confounding factors, source of controls, study design, and outcome data. Disagreements were resolved by discussion and consensus with a third author (RSW).Q test (significance level at <0.10). The I2 statistics OR with 95% CI was used as a common measure of the association between tooth loss and risk of head and neck cancer across studies. For purposes of the present analysis, tooth loss was coded as a three-level indicator variable, with ≤5 lost teeth as the referent category, 6–15 lost teeth as the moderate tooth loss group, and >15 lost teeth as the severe tooth loss group, respectively. Statistical heterogeneity was evaluated using the Cochran P value less than 0.05 was judged as statistically significant, except where otherwise specified. Statistical analyses were carried out with STATA version 11.0 . All the P values were two-sided.Potential publication bias was assessed both by visually inspecting of the Begg funnel plot and statistically via Begg and Egger's unweighted regression tests Diagram S1.The search strategy identified 3,569 potential studies from PubMed and Embase databases. Of these, the majority were excluded after reviewing titles and abstracts, mainly because they were reviews, letter, comment, or not relevant to our analysis, leaving 18 for full-text review. In the review, 9 articles were excluded for the reasons as follows: three articles with unavailable data for analysis The characteristics of all included studies were presented in The assessment of tooth loss was from a variety of sources, including self-reported, and inspected by dentist or interviewer. The anatomical sites of head and neck cancer were various across studies, including oral cavity, pharynx, larynx, and unspecified cancer site. Three studies reported an association between tooth loss and three sites of head and neck cancer . Two studies did not adjust for confounder factors, whereas others controlled a group of conventional risk factors for head and neck cancer, including age, gender, smoking, and drinking.vs. ≤5: OR 2.00, 95%CI 1.28–3.14; P = 0.002). Substantial heterogeneity was observed  . Overall, tooth loss experienced a significant elevated risk for developing head and neck cancer , rather than in the moderate tooth loss group . To test the robustness of our findings, sensitivity analyses were performed. Sensitivity analyses yielded similar results, with substantial evidence of heterogeneity . However, no association was observed in tooth loss with oral cavity  or pharynx cancer .When studies were divided by anatomical sites of head and neck cancer, there was significant increase in larynx cancer  and Egger's funnel plot asymmetry test (regression method) in the meta-analysis indicated that there was no significant publication bias  An interesting clue on the topic may be useful for future research. Three case-control studies included in our meta-analysis were conducted to assess the association of tooth loss with the anatomical sites of head and neck cancer. Only two studies consistently suggest that tooth loss significantly increase the risk of larynx cancer rather than oral cavity and pharynx cancer. Thus, a new question arise, does tooth loss really increase the risk of different anatomical sites of head and neck cancer? However, overall risk estimates show that only the moderate tooth loss was associated with a 45% increase in the risk of larynx cancer. The results should be interpreted with caution. There might be several factors ascribing to these contradicting findings. Small numbers of study subjects and included studies were presented in this meta-analysis, which might lower the statistical power of the study by limiting the ability to estimate more precise association. Despite the imprecise estimate, we believe that these associations deserve attention and warrant additional study.A major strength of the present study is that there was no publication bias, suggesting that such an association is not an artifact of unpublished negative studies. Moreover, the association of tooth loss with risk of head and neck cancer persists and remains statistically significant in sensitivity analyses based on various exclusion criteria, which indicate that our main findings are robust and the association of tooth loss with head and neck cancer is independent of conventional risk factors of head and neck cancer. In addition, with the accumulating evidence and large sample size of included studies, we have great statistical power to provide precise and reliable risk estimates. Despite these advantages, several limitations might be acknowledged in this meta-analysis. First, substantial heterogeneity was observed among studies of tooth loss and head and neck cancer risk, which was not surprising given the differences in characteristics of populations, ascertainment of tooth loss, and adjustment for confounding factors. Despite sensitivity analyses were performed, we were unable to detect the major source of heterogeneity. Noteworthy, the pooled results still turned out to be significant. In addition, residual and unmeasured confounding, such as diabetes, diet changes, and socioeconomic factors, is of concern, which may confound the interpretation of the tooth loss-cancer association and potentially produce biases. Finally, although little evidence of publication bias was observed, the statistical power for these tests was limited due to a relatively small number of included studies.This meta-analysis suggests that tooth loss significantly increases the risk of head and neck cancer, and the increase is probably independent of conventional head and neck cancer risk factors. Future well-design study is warranted to confirm present findings using more specific measures of tooth loss status, and to examine this postulated association among never smokers. If epidemiologic study confirms the role of tooth loss in cancer etiology, additional studies will be needed to further elucidate the potential biological mechanisms involved.Diagram S1The flow diagram of this meta-analysis.(DOC)Click here for additional data file.


ABCG2, also known as BCRP, is a half ATP-binding cassette (ABC) transporter that localizes to plasma membranes. Recently, a number of studies have investigated the relationship between the C421A polymorphism in ABCG2 and cancer risk in multiple populations and various types of cancers; however, this relationship remains unclear. Therefore, we performed a meta-analysis to further explore this association.The meta-analysis incorporated 10 studies involving a total of 3593 cases and 5875 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated based on the date extracted from the studies to evaluate the strength of association. We also analyzed the heterogeneity and sensitivity of each report and the publication bias of the studies.Overall, our results showed that there appeared to be a significant association between the ABCG2 C421A polymorphism and decreased cancer susceptibility . Similarly, decreased cancer risk was also found after stratification of the SNP data by cancer type, ethnicity and source of controls in heterozygote model, dominant effects model and additive effects model.We found that the ABCG2 C421A polymorphism is a protective factor for developing cancer. The same relationship was found when the studies were stratified by cancer type, ethnicity and source of controls. Cancer is a multi-factorial disease, which results from complex interactions between environmental and genetic factors, has become one of the most challenging health issues today . In contABC transporters, or the family of adenosine triphosphate (ATP) binding cassette are a large superfamily of transmembrane glycoprotein and contain over 50 members which can mediate the transfer of a wide variety of substrates across cellular membranes . ATP-binIt has been recognized that single nucleotide polymorphisms (SNPs) are the most common inherited sequence variations in the human genome. These polymorphisms can change the expression and activity of the corresponding genes and their proteins and affect the susceptibility to different types of cancers -23. ReseTo date, numerous studies have investigated the association between the C421A polymorphism in ABCG2 and the cancer susceptibility. Unfortunately, however, the results of these studies have been inconsistent. Therefore, in order to gain insights into the association between polymorphism of ABCG2 C421A and cancer risk, we conducted a meta-analysis of eligible case–control and cohort studies.We conducted a systematic search in PubMed and Embase  using the terms "(ABCG2 or BCRP) and polymorphism "without any restriction in language and publication year. To identify other relevant studies, the articles cited by the retrieved studies were also searched. Each of the selected articles in our meta-analysis met all of the following criteria: 1) the article pertained to the ABCG2 C421A polymorphism and cancer risk; 2) the design was a human case–control or case-cohort study; and 3) the genotype frequencies in the cancer cases and controls were available. Studies were excluded if they did not include a control population, did not determine genotype frequency and or were duplicates of previous publications.The data were extracted from all eligible studies that met the selection criteria listed above. The data extraction was performed by two authors independently and any disagreements were resolved by discussion between the two authors. The data collected from each study were as follows: the first author's name, publication year, country of origin, ethnicity, cancer type, control groups source, number of cases and controls, and genotype frequencies for cases and controls. The deviation of the genotype frequencies in the control populations from Hardy-Weinberg Equilibrium (HWE) was calculated separately for each study. The control group sources were classified as population-based controls, hospital-based controls or mixed  controls. The population ethnicity was classified as Asian or Caucasian.We conducted all statistical analyses using STATA software . All P-values were two-sided and P < 0.05 was considered statistically significant. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association between the ABCG2 C421A polymorphism and the cancer risk. We also examined the overall association of the A allele of C421A with risk of cancers and compared cancer incidence in homozygote (AA versus CC) model and heterozygotes (AC versus CC) model, dominant (AC/AA versus CC) model and the recessive (AA versus CC/AC) model. The values for ORs and CIs of each individual were considered twice. Stratified analyses were conducted by cancer type, source of controls and ethnicity. The Hardy–Weinberg equilibrium was calculated for all the control groups of each study, and control groups of studies that were not in HWE (p < 0.05) were excluded. A chi-squared-based Q-statistic test was used to detect the heterogeneity among studies. When the P-value of the Q-test was > 0.05, which indicated a lack of heterogeneity among studies, a fixed-effects model (the Mantel–Haenszel method) was used . OtherwiSensitivity analyses to evaluate the possible biases of the results in our meta-analyses were also performed. In addition, we assessed the potential publication bias with funnel plots of the effect sizes versus the standard errors and identified the significant asymmetry by the Begg’s test. An asymmetric plot suggests possible publication bias. If the P value < 0.05, the publication bias was considered significantly.The meta-analysis included 8 eligible articles comprising 9 case–control studies and 1 case-cohort study, for a total of 3593 cases and 5875 controls. The study selection procedure is showed in Figure Overall, there was evidence for an association between decreased cancer risk and the variant genotypes in different genetic models and the results were listed in Table The same association was discovered in the subgroup analyses. In the subgroup analysis by cancer types, the ABCG2 C421A genotype significantly reduced the risk of leukemia and other cancers in additive model . Meanwhile, the variant heterozygote homozygote genotype AC was associated with significantly decreased colorectal cancer risk  compared with the wild-type homozygote genotype CC; When the studies were stratified by the source of controls, associations were observed in both studies with population-based controls  and those with hospital-based controls . In the dominant effects model and heterozygote model, this association was also present and the result was listed in Table There was significant heterogeneity among studies in the additive model, dominant effect model and heterozygote model  of the C421A polymorphism in ABCG2. However, in the other model comparisons , heterogeneity was not found .We assessed the potential publication biases of the included studies using the Begg’s funnel plot and Egger’s test Figure , the resCarcinogenesis is a complex process that involves both genetic and environmental factors and their interactions . Since tThe ABCG2 gene , located on chromosomal locus 4q22, encodes an ABC half-transporter protein that localizes to the plasma membrane. ABCG2 works as a multidrug efflux pump, influencing the metabolism of multiple substances including anticancer drugs and carcinogenic xenobiotics -13. The Generally speaking, our meta-analysis, which included 3593 cases and 5875 controls, revealed a significant association between the ABCG2 C421A allele and decreased cancer risk in different genetic model . This result provides convincing evidence that the C421A polymorphism in ABCG2 might protect against cancer development. Moreover, this effect persisted when the studies were stratified by ethnicity classification. When stratified by cancer, source of controls and ethnicity classification, the C421A polymorphism of ABCG2 was also an important protective factor against cancer development in the subgroups studied.However, the studies published by Hu and Korenaga ,34 were It is well known that four capital factors of genome-wide association studies (GWAS) consisting of models of the allelic architecture of common diseases, sample size, map density and sample-collection biases need to be taken into account in order to optimize the cost efficiency of identifying precise disease-susceptibility loci . To valiHeterogeneity is a potential problem which might influence the interpretation of the results. In our meta-analysis, significant heterogeneity between studies was present in additive model, heterozygote model and dominant model Table . The hetSome possible limitations of our meta-analysis should be acknowledged and taken into consideration. First, detailed information, such as the mean age and sex of the case and control populations, was not available in all of the selected studies, which limited further analyses. Second, the results may be influenced by the lack of observations regarding gene-gene and gene-environment interactions even different polymorphic loci of the same gene. Third, the conclusions had the possibility to be disturbed due to the existence of overlapping function of the other ABC transporters. Fourth, the numbers of published studies were not sufficiently enough for a comprehensive analysis on different types of cancer. For example, there were no published data for gastric cancer, nervous system neoplasm and lung cancer with association of ABCG2 C421A published up to now; we did not posses enough statistical power to detect the precise association. More studies are needed to explore the relationship between C421A polymorphism in ABCG2 and cancer risk. In spite of these potential limitations, our meta-analysis also has many advantages. Firstly, sufficient date was extracted form well-selected studies, providing good statistical power for this meta-analysis. Secondly, studies included in our meta-analysis contained available genotype frequency and the distribution of the genotypes in the control population of all the studies were consistent with Hardy-Weinberg equilibrium. Thirdly, no publication bias was detected among the pooled results.In conclusion, this meta-analysis demonstrates that the ABCG2 C421A polymorphism is associated with a decreased risk of cancer and is likely a protective factor against cancer development. However, further studies on the relationship between this polymorphism and cancer risk are warranted.Pin Chen and Lin Zhao are contributed equallyThe authors declare that there are no competing interests.PC participated in collection of data and manuscript preparation. LZ, PZ and HX performed the statistical analysis. PZ participated in study design and critically revised the manuscript. PZ and AL participated in study design and manuscript preparation All authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2407/12/383/prepub


Glutathione S-transferase M3 (GSTM3) is an important member of the GSTs that plays a critical role in the development of head and neck cancer (HNC). Several studies have investigated between the GSTM3 A/B polymorphism and risk of HNC, however, the results remain controversial. The aim of this meta-analysis is to evaluate the association between the GSTM3 A/B polymorphism and the risk of HNC.All eligible case-control studies published up to July 2013 were identified by searching PubMed and Web of Science. The HNC risk associated with the GSTM3 A/B polymorphism was estimated for each study by odds ratios (OR) together with its 95% confidence interval (CI), respectively.Fourteen studies from ten publications with 2110 patients and 2259 controls were included. Overall, the GSTM3 A/B polymorphism was associated with a decreased risk of HNC using the dominant model, homozygote comparison model and heterozygote comparison model ; besides, in stratification analyses by ethnicity, similar results were observed in Caucasian populations. Stratification by tumor site indicated that the GSTM3 polymorphism was associated with a decreased risk of laryngeal cancer under recessive model and homozygote comparison ; By stratifying source of control, decreased cancer risk was observed in hospital-based population under all genetic models .This meta-analysis suggests that the GSTM3 A/B polymorphism may be an important protective factor for HNC, especially of laryngeal cancer and Caucasian populations. Head and neck cancer (HNC), including cancers of the oral cavity, pharynx, and larynx, is the sixth most common cancer worldwide Glutathione S-transferases  are a large family of phase II isoenzymes that catalyze the detoxification of reactive electrophilic compounds, including many environmental carcinogens  The GST genes are highly polymorphic and frequently inducible. Among the numerous GST genes (comprising types M1 to M5), the GSTM3 gene is located on chromosome 1q13.3 and has 2 alleles identified so far: GSTM3 A and GSTM3 B, of which the latter has a 3 bp deletion in intron 6, known as a recognition motif for the YY1 transcription factor To date, GSTM3 A/B gene polymorphism has been extensively examined in association with risk of HNC A literature research was conducted using PubMed and Web of Science up to July 2013 without language restrictions. Relevant studies were identified using the terms: [‘Glutathione S-transferase M3 or GSTM3’] AND [‘genetic polymorphism or polymorphisms or variant or SNP’] AND [‘head and neck cancer or HNC or oral cancer or pharyngeal cancer or laryngeal cancer or hypopharyngeal cancer or oropharyngeal cancer or nasopharyngeal cancer’]. The search was restricted to humans. Additional studies were identified by a hand search of references of original or review articles on this topic. If more than one geographic or ethnic heterogeneous group was reported in one report, each was extracted separately.Studies were included if they met the following criteria: (1) studies that evaluated the association between the GSTM3 A/B polymorphism and HNC, (2) in a case-control study design, and (3) had detailed genotype frequency of cases and controls or could be calculated from the article text. While major exclusion criteria were: (1) case-only study, case reports, and review articles, (2) studies without the raw data of the GSTM3 A/B genotype, and (3) studies that compared the GSTM3 A/B variants in precancerous lesions and other cancers.Two investigators independently extracted data and reached consensus on all of the items. If they generated different results, they would check the data again and have a discussion to come to an agreement. If they could not reach an agreement, an expert was invited to the discussion. Data extracted from the selected articles included the first author's name, year of publication, country of origin, ethnicity, tumor site, genotyping methods, source of control, number of cases and controls. Tumor sites were categorized as oral, pharyngeal, laryngeal, and mixed HNC.vs. AA), the recessive model (BB vs. AB+AA), heterozygote comparison (AB vs. AA), and homozygote comparison (BB vs. AA). A χ2-test-based Q statistic test was performed to assess the between-study heterogeneity I2 test. When a significant Q test (P<0.05) or I2>50% indicated heterogeneity across studies, the random effects model was used 2 test. We performed stratification analyses on ethnicity, tumor site and source of control. Analysis of sensitivity was performed to evaluate the stability of the results. Finally, potential publication bias was investigated using Begg' funnel plot and Egger's regression test P<0.05 was regarded as statistically significant.Meta-analysis was performed using the Cochrane Collaboration RevMan 5.1 and STATA package version 12.0. The risk of HNC associated with the GSTM3 A/B polymorphism was estimated for each study by odds ratio (OR) and 95% confidence interval (95%CI). Four different ORs were calculated: the dominant model , but no significant association was observed under the recessive model ; while only one study focused on African-American, found that the GSTM3A/B polymorphism play an important role in risk for oral cancer .In the stratified analysis based on tumor site, significant associations were found in recessive and homozygote comparison model for laryngeal cancer ; However, no significant association was found for either oral cancer or pharyngeal or mixed HNC .Stratification based on the source of controls showed significant associations between the GSTM3 A/B polymorphism and risk of HNC in the hospital-based subgroup . However, no significant association was found in the population-based subgroup  .2 = 42%, Pheterogeneity = 0.05 for the dominant model; I2 = 0%, Pheterogeneity = 0.66 for the recessive model; I2 = 0%, Pheterogeneity = 0.54 for the homozygote comparison model; I2 = 35%, Pheterogeneity = 0.09 for the heterozygote comparison model). Therefore, we used the fixed-effects model that generated wider CIs. However, it's worth noting that there was moderate heterogeneity among overall studies under dominant model, so we conducted stratified analysis by ethnicity, tumor cites and the source of the controls to find the potential sources of heterogeneity and we found that heterogeneity still exists in Caucasian population , laryngeal cancer  and mixed HNC , however, heterogeneity significantly reduced or removed among oral , pharyngeal cancer , population-based population  and hospital-based populations . Then, sensitivity analysis, after removing one study at a time, was performed to evaluate the stability of the results. We found that the estimated pooled odd ratio changed quite little, indicating that our results were statistically robust.There were no inter-study heterogeneity among overall studies of the GSTM3 A/B polymorphism in all four genetic models .Begg's funnel plot and Egger's test were performed to assess the potential publication bias in the available literature. The shape of funnel plots did not reveal any evidence of funnel plot asymmetry . Egger'sTo our knowledge, this is the first meta-analysis which comprehensively assessed the associations between GSTM3 A/B polymorphism and HNC risk. In this study, we found significant associations in the overall comparison using dominant model, homozygote comparison model and heterozygote comparison model. Individuals with the AB/BB genotype could have a decreased risk of HNC. Moreover, in the stratified analyses by several variables, including ethnicity, tumor site, and source of the controls, significant associations were observed in the Caucasian population, laryngeal cancer and hospital-based population.GSTM3, a major member of the GSTs family, plays a role in metabolism of harmful agents, like polyaromatic hydrocarbons benzo(a)pyrene. The GSTM3 polymorphism could, therefore, confer different efficiencies in the metabolism of carcinogens and has been shown to modulate various cancers risk. Interestingly, it plays different roles in different cancers. Jain et al In this meta-analysis, we found that individuals with AB+BB genotype had a lower risk of developing HNC under dominant model, besides in the stratified analyses by ethnicity, tumor site, and source of control, we found that B allele carriers had a lower risk of HNC than A allele carriers in Caucasian population, laryngeal cancer and hospital-based population. The results may be explained that the B allele carriers could increase transcription of the GSTM3 gene and expression of GSTM3-related protein, then enhance detoxification activity. In addition, the pathways of carcinogen metabolism are complex, mediated by the activities of multiple genes  It would be hard to interpret results, if significant heterogeneity were present, in this meta-analysis, we did not find any obvious heterogeneity and publish bias across studies. While, it's worth noting that there was moderate heterogeneity among overall studies under dominant model, so stratified analysis by ethnicity, tumor cites and the source of the controls was performed and we found that moderate heterogeneity still exists in Caucasian population, laryngeal cancer and mixed HNC, however, heterogeneity significantly reduced or removed among oral, pharyngeal cancer, population-based population and hospital-based populations. The results above suggest that control selection and different tumor types may contribute to the moderate heterogeneity observed in the meta-analysis. Then sensitivity analyses were conducted by excluding one study successively, the estimated pooled OR changed quite little, strengthening the results from this meta-analysis.Although considerable effort was made to test for the possible association between the GSTM3 A/B polymorphism and risk of HNC, some limitations of this meta-analysis should also be addressed. First, due to limited detailed data presented in the published studies, the potential effect of important risk factors to HNC was not examined, such as smoking, alcohol consumption and HPV status. Second, all studies are focused on Caucasian populations, which may generate selective bias. Third, our results were based on unadjusted estimates, without adjustment for age, gender, family history and other risk factors, while lacking of the information for the date analysis may cause serious confounding bias. Fourth, GSTM3 may influence susceptibility to HNC independently or with other genes such as GSTM1 and GSTP1. However, due to lack of individual data in the present review, we did not perform more detailed analyses, such as analyses of joint effects with other risk factors or gene-gene or gene-environment interactions.In summary, this meta-analysis indicates that the GSTM3 A/B polymorphism may be an important protective factor for HNC, especially of laryngeal cancer and Caucasian populations. Further studies with standardized unbiased genotyping methods, homogeneous cancer patients, well-matched controls and multiethnic groups would be warranted.Checklist S1PRISMA Checklist for this study.(DOC)Click here for additional data file.Checklist S2MOOSE Checklist for this study.(DOC)Click here for additional data file.


The aim of this study was to estimate the magnitude of the risk for clinical outcomes associated with iceA.Although the iceA and clinical outcomes  were included.A literature search was performed using the PubMed and EMBASE databases for articles published through April 2011. Published case-control studies examining the relationship between iceA1-positive H. pylori increased the overall risk for peptic ulcer by 1.26-fold . However, the test for heterogeneity was significant among these studies. Sensitivity analysis showed that the presence of iceA1 was significantly associated with peptic ulcer . The presence of iceA2 was inversely associated with peptic ulcer . The presence of iceA was not associated with gastric cancer. Most studies examined the cagA status; however, only 15 studies examined the correlation and only 2 showed a positive correlation between the presence of cagA and iceA1.Fifty studies with a total of 5,357 patients were identified in the search. Infection with iceA for peptic ulcer, although the significance was marginal.Our meta-analysis confirmed the importance of the presence of  Helicobacter pylori infection is now accepted as the major cause of chronic gastritis. Several epidemiological studies have shown that H. pylori infection is also linked to severe gastritis-associated diseases, including peptic ulcer disease (PUD) and gastric cancer (GC) H. pylori infection as a group I carcinogen (definite carcinogen) H. pylori infection relates to differences in the virulence of H. pylori strains. Several H. pylori virulence factors have been reported to be associated with peptic ulcer and GC, including cagA, vacA, babA, and oipAdupA) for developing duodenal ulcer (DU) in a meta-analysis model iceA (induced by contact with epithelium) has 2 main allelic variants, iceA1 and iceA2iceA1 demonstrated sequence homology with a gene from Neisseria lactamica, nlaIIIR, which encodes a CTAG-specific restriction endonuclease iceA2 has no homology to known genes and the function of the iceA2 product remains unclear. van Doorn et al. reported that the iceA allelic type was independent of the cagA and vacA status, and there was a significant association between the presence of the iceA1 allele and PUD iceA1 was upregulated on contact between H. pylori and human epithelial cells, and the iceA1 genotype was linked with enhanced mucosal interleukin (IL)-8 expression and acute antral inflammation An initial series of studies showed that iceA was controversial subsequently since several studies were not able to reproduce the observation in other populations, including Japanese iceA allelic type and clinical outcomes could be explained by the genetic heterogeneity or differences in the geographic location, which were previously reported for other virulence genes iceA using meta-analysis. In this study, we aimed to perform a meta-analysis to examine the relationship between the iceA allelic type and clinical outcomes.However, the role of iceA, iceA1, or iceA2 and 2) pylori or Helicobacter. We did not include abstracts alone or unpublished articles.A literature search was performed using the PubMed and EMBASE databases for articles published through April 2011. The following text words were used: 1) iceA type and clinical outcomes  in adult populations: the presence of iceA (iceA1 or iceA2) was examined by polymerase chain reaction (PCR) and original articles were published in English. Studies were excluded if no raw data were presented. When it appeared that the same subjects were presented in multiple reports, the earliest article was selected. All potentially relevant articles were reviewed independently by 2 investigators (S.S and Y.Y) and disagreement was resolved by discussion.The following criteria were applied to select fully published case-control studies examining the relationship between the in vitro studies and studies conducted in child populations were also excluded.Studies were excluded if no raw data were presented or if no control groups were included. In addition, iceA, the number of subjects, and the iceA status according to clinical outcomes. Two studies examined the prevalence of iceA in several countries Data were extracted independently from each study by the investigators and entered into a computerized database. The information retrieved covered countries where the study was performed, characteristics of cases and controls, the method for detection of et alSummary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated from raw data. The Mantel-Haenszel method was used to test for statistical heterogeneity. When statistical heterogeneity was noted, the proportion of the total heterogeneity variance was calculated from each study using a fixed-effects model to guide the search for sources of methodologically and clinically important variables. To exclude any possible influence of a single study, we performed a sensitivity analysis to evaluate whether the exclusion of any single study substantially altered the magnitude or statistical result of the summary estimate. Publication bias was assessed by funnel plots and regression test by Egger in vitro studies. Therefore, 46 articles met the inclusion criteria  in PUD patients and 51.0%  in controls. The summary OR in the fixed-effects model was 1.26 . However, the test for heterogeneity was significant among these studies , suggesting the existence of either methodological or clinical heterogeneity. By exploring the sources of heterogeneity, we found that the studies by Peek et al.et al.iceA1 compared with other studies. They reported a quite low prevalence of iceA1 in controls  compared with PUD patients . In addition, the study by Yamaoka et al. in the United States showed a lower prevalence of iceA1, especially in PUD patients (0.0%) et al. showed 100% prevalence in controls The prevalence of iceA1 was 68.9%  in PUD patients and 58.1%  in controls in Asian countries. It was 43.5% (348 of 799) in PUD patients and 41.8%  in controls in Western countries. The summary OR was 1.19  in Asian countries and 1.28  in Western countries. Subgroup analysis was also performed according to the distribution of DU and GU. The prevalence of iceA1 in DU patients was examined in 32 studies. When 4 studies iceA1 was significantly associated with DU compared with controls     was also performed. The prevalence of 11–1.63) . This fi69–1.35) . The pre86–1.37) .iceA2 was examined in PUD patients from 41 studies (24 countries). The prevalence of iceA2 ranged from 0.0% to 91.7% in PUD patients and from 0.0% to 95.7% in controls. Among the 41 studies, a significantly lower prevalence of iceA2 in PUD patients compared with controls was found in 6 studies iceA2 was 30.1%  in PUD patients and 37.2%  in controls. The summary OR in the fixed-effects model was 0.76 . However, the test for heterogeneity was significant among these studies . The studies by Peek et al.et al.iceA2 compared with other studies. They reported a quiet high prevalence of iceA2 in controls  compared with PUD patients . In addition, the study by Yamaoka et al. in Korea showed a lower prevalence of iceA2, especially in gastritis patients (4.5%) et al. showed 0.0% prevalence in controls The prevalence of iceA2 was 23.4%  in PUD patients and 30.2%  in controls in Asian countries. It was 41.8% (280 of 669) in PUD patients and 47.7% (456 of 956) in controls in Western countries. The summary OR was 0.91  in Asian countries and 0.64  in Western countries. Subgroup analysis was performed according to the distribution of DU and GU. The prevalence of iceA2 in DU patients was examined in 27 studies. When 4 studies iceA2 was significantly associated with DU compared with controls     was also performed. The prevalence of 0- 0.92) . This fi69–1.46) . The pre64–1.11) . SubgrouiceA1 was 64.6%  in Asian countries and 42.1%  in Western countries. It was significantly higher in Asian countries than in Western countries (P<0.0001). On the other hand, the prevalence of iceA2 was 25.8%  in Asian countries and 45.1%  in Western countries. It was significantly higher in Western countries than in Asian countries (P<0.0001).The overall prevalence of cagA and iceA status. Only 1 study showed a significant positive association between iceA1 and the presence of cagAiceA2 and the presence of cagAiceA1 and cagA status Fifteen studies examined the correlation between the iceA1 was significantly associated with PUD. Although several studies failed to show a positive association between the iceA status and clinical outcomes, this meta-analysis supported the original report from 1998 Our present meta-analysis shows that the presence of iceA remains unclear. iceA1 demonstrated sequence homology with a gene from Neisseria lactamica, nlaIIIR, which encodes a CTAG-specific restriction endonuclease iceA locus indicated that a full-length nlaIIIR-like open reading frame has only been observed in 10 (20.4%) of 49 iceA1 H. pylori strains and only full-length iceA1 was a functional endonuclease gene iceA1 are common, resulting in protein products with poor or no endonuclease activity. It remains to be determined whether iceA1 plays a role other than encoding an nlaIII-like endonuclease or not.The mechanism of the development of PUD induced by iceA2 allele could be divided into 2 types according to the presence of repeated sequences of 105 nucleotides and the size of the PCR products (229 bp for iceA2-1 or 334 bp for iceA2-2) et al. reported that no association was observed between the size of the iceA2 amplicon and diseases et al. reported that the 334-bp iceA2 amplicon was more prevalent in strains from patients with PUD iceA2 remains unclear.Most isolates with an iceA1 and iceA2 was also different in each study. The strains of mixed infections were excluded in several studies et al. reported that 36.7% of strains were positive for both iceA1 and iceA2, and 53.8% of these strains also contained multiple vacA genotypes iceA1 and iceA2 positivity was significantly lower in the United States than in Korea, Japan, and Columbia  iceA1 and iceA2 genes in Genbank (data not shown). It may be speculated that more than 1 strain may be acquired in childhood, especially in countries with a high prevalence of H. pylori. Mixed infection by more than 1 strain in the same individual may reflect the capacity of H. pylori to evolve genetic variations during long-term colonization from childhood iceA-type strains may obscure any potential relationship between the allele and clinical outcomes.The prevalence of mixed infection by et al. indicated that in patients with H. pylori infection, those with DU have a higher degree of acute and chronic inflammation in the gastric antrum and higher H. pylori density than those with GU Fourteen studies combined DU with GU as PUD. However, DU and GU are linked to entirely different patterns of gastric inflammation, such that it would seem they should be examined separately iceA and cagA status remains unclear. Several virulence factors of H. pylori correlated with the presence of cagAiceA and cagA status. As a result, most of them showed no association, indicating that iceA1 might be a risk factor for PUD, independent of cagA. In addition, our recent meta-analysis showed that dupA, which induces DU and has a suppressive action on GC, was significantly associated with DU dupA and iceA has not been clarified yet; however, 1 study showed that there was no association iceA, it is better to perform a multivariate analysis adjusted for the cagA status and other risk factors for peptic ulcer. However, unfortunately, we could not obtain the raw data from each study. It is difficult to perform a multivariate analysis adjusted for these factors without the raw data. In addition, most studies did not consider other risk factors in their papers. Further study is necessary to examine which factors are true virulence factors and which are just confounding factors. However, it might be better to hypothesize that these factors interact synergistically with each other and induce serious diseases than to discuss which of these factors is the most virulent. A recent study showed that groupings by multi-locus sequence typing (MLST) using 7 housekeeping genes were associated with the prevalence of GC H. pylori according to the structure of the bacteria instead of each virulence factor.The association between the iceA1 was weakly, but significantly associated with PUD especially DU, whereas iceA2 was inversely associated with PUD. A relationship between iceA and GC and GU was not found in this meta-analysis. It is possible that iceA is a discriminating factor for PUD, independent of cagA.Figure S1Flow diagram of study selection.(TIF)Click here for additional data file.Figure S2iceA1-positive H. pylori infections.Results of the meta-analysis for the risk of duodenal ulcer in (TIF)Click here for additional data file.Figure S3iceA1-positive H. pylori infections.Results of the meta-analysis for the risk of gastric ulcer in (TIF)Click here for additional data file.Figure S4iceA1-positive H. pylori infections.Results of the meta-analysis for the risk of gastric cancer in (TIF)Click here for additional data file.Figure S5iceA2-positive H. pylori infections.Results of the meta-analysis for the risk of duodenal ulcer in (TIF)Click here for additional data file.Figure S6iceA2-positive H. pylori infections.Results of the meta-analysis for the risk of gastric ulcer in (TIF)Click here for additional data file.Figure S7iceA2-positive H. pylori infections.Results of the meta-analysis for the risk of gastric cancer in (TIF)Click here for additional data file.Table S1Characteristics of studies included in the meta-analysis.(XLS)Click here for additional data file.


Emerging evidence indicates that common functional polymorphisms in the estrogen receptor 1 (ESR1) gene may have an impact on an individual’s susceptibility to endometrial cancer, but individually published results are inconclusive. The aim of this meta-analysis is to derive a more precise estimation of the associations between eight polymorphisms in the ESR1 gene and endometrial cancer risk.st, 2012. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Statistical analyses were performed using the STATA 12.0 software.A literature search of PubMed, Embase, Web of Science and China Biology Medicine (CBM) databases was conducted on publications published before November 1Thirteen case-control studies were included with a total of 7,649 endometrial cancer cases and 16,855 healthy controls. When all the eligible studies were pooled into the meta-analysis, the results indicated that PvuII (C>T) polymorphism was associated with an increased risk of endometrial cancer, especially among Caucasian populations. There were also significant associations between rs3020314 (C>T) polymorphism and an increased risk of endometrial cancer. Furthermore, rs2234670 (S/L) polymorphism may decrease the risk of endometrial cancer. However, no statistically significant associations were found in XbaI (A>G), Codon 325 (C>G), Codon 243 (C>T), VNTR (S/L) and rs2046210 (G>A) polymorphisms.The current meta-analysis suggests that PvuII (C>T) and rs3020314 (C>T) polymorphisms may be risk factors for endometrial cancer, especially among Caucasian populations. Endometrial cancer is the seventh most common cancer among women worldwide. An estimated of 287,100 women were diagnosed with endometrial cancer in 2011 The ESR1 gene encoding the estrogen receptor 1 is a newly identified oncogene for endometrial cancer st, 2012 were identified through a search in Pubmed, Embase, Web of Science and China Biology Medicine (CBM) databases using the following terms: (“genetic polymorphism” or “polymorphism” or “SNP” or “single nucleotide polymorphism” or “gene mutation” or “genetic variants”) and  and . The references from the eligible articles or textbooks were also reviewed to find other potential sources. Disagreements were resolved through discussions between the authors.Relevant papers published before November 1Studies included in our meta-analysis have to meet the following criteria: (a) case-control studies or cohort studies focused on the associations between ESR1 gene polymorphisms and endometrial cancer risk; (b) all patients diagnosed with endometrial cancer should be confirmed by pathological or histological examinations; (c) published data about the frequencies of alleles or genotypes must be sufficient. Studies were excluded when they were: (a) not a case-control study or a cohort study; (b) duplicates of previous publications; (c) based on incomplete data; (d) meta-analyses, letters, reviews or editorial articles. If more than one study by the same author using the same case series was published, either the studies with the largest sample size or the most recently published study was included. The supporting PRISMA checklist is available as supporting information; see Supplement S1.Data from the published studies were extracted independently by two authors into a standardized form. For each study, the following characteristics and numbers were collected: the first author, year of publication, country, language, ethnicity, study design, numbers of subjects, source of cases and controls, pathological type, detecting sample, genotype method, allele and genotype frequencies, and evidence of Hardy-Weinberg equilibrium (HWE) in controls. In case of conflicting evaluations, disagreements were resolved through discussions between the authors.Two authors independently assessed the quality of included studies according to the modified STROBE quality score systems P-value <0.05 as statistically significant heterogeneity 2I test (ranges from 0 to 100%), which represents the proportion of inter-study variability that can be contributed to heterogeneity rather than to chance P<0.05 or 2I>50% indicated that heterogeneity among studies existed, the random effects model (DerSimonian Laird method) was conducted for the meta-analysis. Otherwise, the fixed effects model (Mantel-Haenszel method) was used. To explore sources of heterogeneity, we performed subgroup analysis by cancer types, ethnicity, country, source of controls and genotype methods. We tested whether genotype frequencies of controls were in HWE using the 2χ test. Sensitivity was performed through omitting each study in turn to assess the quality and consistency of the results. Begger’s funnel plots were used to detect publication biases. Egger’s linear regression test which measures funnel plot asymmetry using a natural logarithm scale of OR was also used to evaluate the publication biases P values were two-sided. All analyses were calculated using the STATA Version 12.0 software .Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association under five genetic models: the allele model, the dominant model, the recessive model, the homozygous model, and the heterozygous model. The statistical significance of the pooled ORs were examined using the Z test. Between-study variations and heterogeneities were estimated using Cochran’s Q-statistic with a P>0.05). All quality scores of included studies were higher than 20 . The characteristics of the included studies are summarized in In total, 116 articles relevant to the searched keywords were identified. Of these articles, 69 were excluded after reviewing their titles and key words; then, abstract and full text were reviewed, and another 34 papers were excluded. The details of the selection process were presented in a flow chart in P>0.05), so the fixed effects model was used. The meta-analysis results showed that the PvuII polymorphism may increase the risk of endometrial cancer under the allele and homozygous models  (P>0.05). Further subgroup analyses showed that there were significant associations between PvuII polymorphism and endometrial cancer risk in Caucasian populations, population-based and DNA sequencing subgroups (as shown in The association of PvuII (C>T) polymorphism with endometrial cancer risk is discussed in nine studies. The heterogeneity is not obvious (= 0.043) . HoweverP>0.05), which might result from the difference in ethnicity, country, source of controls and genotype methods, so the random effects model was used. Meta-analysis of these studies showed no significant associations between XbaI polymorphism and endometrial cancer risk under all five genetic models . Stratified analyses also indicated no significant associations between XbaI polymorphism and endometrial cancer risk in each subgroup (as shown in Seven studies referred to the association between XbaI (A>G) polymorphism and endometrial cancer risk. The heterogeneity was significantly observed under the allele, recessive and homozygous models .Two of thirteen studies  reported results on the association between rs3020314 (C>T) polymorphism and endometrial cancer risk. All these two studies were conducted in Caucasian populations and based on community populations. When all the eligible trials were pooled into the meta-analysis, the results indicated that rs3020314 polymorphism might be associated with increased risk of endometrial cancer , the random effects model was used. The meta-analysis results showed that there were no significant associations between Codon 325 polymorphism and endometrial cancer risk under all five genetic models . Subgroup analyses showed significant associations in hospital-based and PCR-RFLP subgroups , but these estimates from a single study were also unreliable.The Codon 325 (C>G) variation was investigated in four publications. Since heterogeneity was observed under the allele, recessive and heterozygous models . In the subgroup analysis by ethnicity, we also found no associations between Codon 243 polymorphism and endometrial cancer risk among both Caucasian and Asian populations .There were only three studies that referred to the associations between Codon 243 (C>T) polymorphism and endometrial cancer risk. All these studies were population-based, including two studies in Caucasian populations and one in Asian populations. We found no significant associations between Codon 243 (C>T) polymorphism and endometrial cancer risk under five genetic models , but these results were also extracted from a single study. However, there were also no significant associations of VNTR and rs2046210 (G>A) polymorphisms to the risk of endometrial cancer .Furthermore, we have evaluated the associations of VNTR, STR (S/L) and rs2046210 (G>A) polymorphisms with endometrial cancer risk. There were only two studies referring to VNTR, and each one study referring to rs2234670 (S/L), and rs2046210 (G>A). Our results showed that rs2234670 (S/L) polymorphism may decrease the risk of endometrial cancer under the allele, recessive and homozygous models  and XbaI (A>G) polymorphisms , indicatP  = 0.232; XbaI: t = −0.73, P  = 0.496).Publication biases within available research results might not be representative of all research results. Begger’s funnel plot and Egger’s linear regression test were performed to assess the publication biases of included studies. The shapes of the funnel plots did not reveal any evidence of obvious asymmetry under the dominant model of PvuII (C>T) and XbaI (A>G) polymorphisms . Egger’sESR1 gene is critical for hormone binding, DNA binding, and activation of transcription because it encodes an estrogen receptor that is key in the mediation of hormonal response in estrogen-sensitive tissues In this meta-analysis, 13 independent case-control studies were included with a total of 7,649 endometrial cancer cases and 16,855 healthy controls. When all the eligible studies were pooled into the meta-analysis, the results showed that PvuII (C>T) polymorphism was associated with increased risk of endometrial cancer, especially among Caucasian populations, while similar associations were not observed among Asian populations. Although the exact function of PvuII (C>T) polymorphism in the development of endometrial cancer among different populations is not yet clear, a possible reason could be that inherited mutations in ESR1 might be associated with changes in estrogen metabolism and thereby could possibly explain inter-individual differences in disease incidences of endometrial cancer Similar to other meta-analyses, our study also bears some limitations and shortages. First, the sample size is still relatively small and may not provide sufficient statistical power to estimate the correlations between ESR1 gene polymorphisms and endometrial cancer risk. Second, in this meta-analysis, potential sources of heterogeneity could include many other factors, such as age and sex structure, characteristics of healthy control, pre- and post-menopause, etc. Third, as a type of a retrospective study, a meta-analysis may encounter recall or selection bias, possibly influencing the reliability of our study results. Furthermore, in this meta-analysis, there is a significant difference in numbers between cancer cases and healthy controls, which may be one source of heterogeneity and may have some unfavorable effects on the reliability of our results. Finally, our lack of access to the original data from the studies limited further evaluation of potential interactions such as gene-environment and gene-gene interactions. In spite of these limitations, however, our present meta-analysis includes the largest number of eligible studies relevant to the relationship between ESR1 polymorphisms and endometrial cancer risk reported to date.In conclusion, our meta-analysis suggests that PvuII (C>T) and rs3020314 (C>T) polymorphisms may be risk factors in endometrial cancer development, especially among Caucasian populations. These relationships will promise us a functional profiling of ESR1 gene and an understanding of the biological processes associated with endometrial cancer development and progression. It may also be further utilized as a diagnostic tool, as well as, an accurate determination of endocrine therapeutic strategies in endometrial cancer. However, further studies are still needed in order to validate the associations between polymorphisms in ESR1 and endometrial cancer.Supplement S1PRISMA Checklist.(DOC)Click here for additional data file.Supplement S2The modified STROBE quality score systems.(DOC)Click here for additional data file.Supplement S3The genotype distributions of ESR1 polymorphism in case and control groups.(XLS)Click here for additional data file.Supplement S4Forest plot of ORs by random effects model for all eight polymorphisms of ESR1 gene and endometrial cancer risk under five genetic models: the allele model (A), the dominant model (B), the recessive model (C), the homozygous model (D), and the heterozygous model (E).(ZIP)Click here for additional data file.


In the subgroup analysis by ethnicity, miR-499 rs3746444 polymorphism was significantly associated with cancer risk in Asian population. In the subgroup analysis by cancer types, miR-499 rs3746444 polymorphism was significantly associated with breast cancer.A systematic search of the Pubmed, Excerpta Medica Database (Embase) and Chinese Biomedical Literature Database (CBM) databases was performed with the last search updated on May 6, 2012. The odds ratio (OR) and its 95% confidence interval (95%CI) were used to assess the strength of the association. A total of 15 independent studies including 7,188 cases and 8,548 controls were used in the meta-analysis. In the present meta-analysis, we found a significant association between miR-499 rs3746444 polymorphism and cancer risk. Large-scale and well-designed case-control studies are necessary to validate the risk identified in the present meta-analysis.This meta-analysis suggests a significant association between  Cancer remains a major cause of mortality worldwide MicroRNAs (miRNAs) are a subset of short, endogenous non-coding RNAs that regulate gene expression at the post-transcriptional level via either translational repression or mRNA degradation miR-499 with an A to G change (rs3746444) was identified. The miR-499 rs3746444 polymorphism involves an A>G nucleotide substitution which leads to a change from A:U pair to G:U mismatch in the stem structure of miR-499 precursor miR-499 rs3746444 polymorphism with cancer risk. Hence, we performed a meta-analysis to derive a more precise estimation of the association to help us better understand the relationship between this polymorphism and cancer risk.An important polymorphism in the miR-499 rs3746444 polymorphism and cancer risk, a systematic search of the US National Library of Medicine's Pubmed database, Excerpta Medica Database (Embase) and Chinese Biomedical Literature Database (CBM) was performed with the last search updated on May 6, 2012. Keywords used in searches included: “microRNA OR mir OR miRNA”, “cancer OR carcinoma OR tumor OR neoplasm”, “gene OR polymorphism OR allele OR variation”, and “499 OR rs3746444”. Searching was done without restriction on language or publication years.To examine the association between miR-499 rs3746444 polymorphism and cancers; 2) a case-control design; 3) sufficient published data for estimating an odds ratio (OR) with 95% confidence interval (CI); 4) only full-text manuscripts were included. Exclusion criteria included: 1) duplication of the previous publications; 2) abstract, comment, review and editorial. When there were multiple publications from the same population, only the largest study was included. When a study reported the results on different ethnicities, we treated them as separate studies. When a study included subjects of different countries, we extracted data separately.The inclusion criteria were: 1) evaluation of Information was carefully extracted from all eligible publications independently by two of the authors according to the inclusion criteria listed above. Disagreement was resolved by discussion between the two authors. If these two authors could not reach a consensus, then a third author was consulted to resolve the dispute. Articles identified for this meta-analysis included a case-control study and complete data, including the first author's name, the subjects' region/country, year of publication, cancer types, definition and numbers of cases and controls, allele as well as genotype frequencies in both case and control groups. Their reference lists were searched manually to identify additional eligible studies. If original genotype frequency data were unavailable in relevant articles, a request for additional data was sent to the corresponding author.P<0.05 was considered representative of departure from HWE. For the meta-analysis, OR and 95% CI were calculated to estimate the association between miR-499 rs3746444 polymorphism and cancer risk based on reported frequencies of alleles and genotypes in cases and controls. The pooled ORs were performed for allelic comparison (G versus A), dominant model (GG+AG versus AA), recessive model (GG versus AG+AA), homozygote comparison (GG versus AA) and heterozygote comparison (AG versus AA), respectively. The significance of the pooled OR was determined by the Z-test. Heterogeneity among studies was assessed by using the Chi-square test based Q-statistic, and, when not statistically significant (based on P>0.10), a fixed-effects model (using the Mantel-Haenszel method) was used for the meta-analysis I-squared statistic, 2I = 100%×(Q-df)/Q We used the PRISMA checklist as protocol of the meta-analysis and followed the guideline  [23]. Hat-test . The intercept a provides a measure of asymmetry, and the larger its deviation from zero the more pronounced the asymmetry.Funnel plots were created to graphically display evidence of publication bias, in which the standard error of logarithm for OR was plotted against its OR. An asymmetric plot suggested a possible publication bias. Funnel plot asymmetry was further assessed by the method of Egger's linear regression test http://www.cc-ims.net/RevMan/relnotes.htm/) and Stata version 10 . A P value less than 0.05 was considered statistically significant in the study, and all the P values were two sided.Analyses were performed using the software Review Manager 4.2 . The flow chart in miR-499 rs3746444 polymorphism and cancer susceptibility, stratified analyses by ethnicity and cancer types were performed. When the Q-test of heterogeneity was not significant, we conducted analyses using the fixed effect models. The random effect models were conducted when we detected significant between-study heterogeneity.The main results of this meta-analysis and the heterogeneity test are shown in miR-499 rs3746444 polymorphism and cancer risk in the allelic contrast, dominant model and heterozygote comparison .In the overall analysis, we found a significant association between Subgroup analysis was stratified by ethnicity. The meta-analysis included 11 studies  in Asian population and 4 studies  in Caucasian population.miR-499 rs3746444 polymorphism was significantly associated with an increased cancer risk in all genetic models except for recessive model . In Caucasian population, no significant association was observed between miR-499 rs3746444 polymorphism and cancer risk in any genetic model .In Asian population, Subgroup analysis was also stratified by cancer types. The meta-analysis included 4 studies  based on breast cancer and 3 studies (508 cases and 805 controls) based on liver cancer.miR-499 rs3746444 polymorphism was significantly associated with an increased risk of breast cancer in the allelic contrast and dominant model . No evidence of association was found in any genetic model between miR-499 rs3746444 polymorphism and the risk of liver cancer .In different types of cancer, Funnel plot and Egger's test were performed to assess the publication bias of included studies. The results of Egger's linear regression test are shown in miR-499 rs3746444 polymorphism and cancer risk. In the subgroup analysis of Asian population, miR-499 rs3746444 polymorphism was significantly associated with an increased cancer risk. Similarly in the subgroup analysis of breast cancer, our data also indicated that this polymorphism might be a risk factor.In the present meta-analysis with 7,188 cases and 8,548 controls, we found a significant association between miR-146a and miR-196a2 genes in the overall cancer risk miR-146a rs2910164 polymorphism, Xu et al. miR-196a2 C allele is a low-penetrant risk factor for cancer development, especially with breast cancer and in Asian populations miR-196a2 rs11614913 and miR-499 rs3746444) may be functional polymorphisms with potential value in cancer development.In recent few years, several meta-analyses have focused on genetic variants of pre-miR-146a sequence decreased the generation of pre- and mature miR-146a expression, led to less efficient inhibition of target genes, and contributed to the genetic predisposition to papillary thyroid carcinoma. Furthermore, it has been shown that aberrant expression of miRNA genes could influence the regulation of target genes and involved in tumorigenesis. Recent evidence showed that the cluster of miR-143 and miR-145 affected the risk of esophageal squamous cell carcinoma through regulating oncogenic Fascin Homolog 1 (FSCN1) miR-499 could discriminate breast cancer patients from healthy individuals in postmenopausal patients, which may represent novel biomarker. Based on the above reasons, it can be hypothesized that rs3746444 polymorphism in miR-499 precursor may alter miRNA processing, and ultimately change the mature miRNA level. Altered miRNA expression may influence cancer susceptibility. As a result, miR-499 rs3746444 polymorphism could contribute to cancer risk.The SNP variation within the miRNA sequence may either weaken or reinforce the binding between miRNA and its target. Therefore, this would probably lead to a corresponding regulation in the target mRNA translation miR-499 rs3746444 polymorphism and cancer risk, some limitations should be addressed. Firstly, the results should be interpreted with caution as a result of obvious heterogeneity in some comparisons. Secondly, the controls for several studies did not conform to Hardy-Weinberg equilibrium expectations, which may distort the results. However, when these studies that had evidence of departure from HWE were excluded from the analysis, a significant association can still be observed. Thirdly, publication bias existed in some comparisons, which may potentially influence the results of our meta-analysis. Fourthly, lacking sufficient eligible studies limited our further stratified analysis on more types of cancer, such as lung cancer, colorectal cancer and gastric cancer. Fifthly, for each selected case-control study, our results were based on unadjusted estimates, whereas a more precise analysis could be performed if individual data were available.In spite of the considerable efforts to explore the possible association between miR-499 rs3746444 polymorphism and cancer risk. In the future, large-scale and well-designed case-control studies are necessary to validate the risk identified in the present meta-analysis.In conclusion, our meta-analysis suggests a significant association between Table S1Checklist of items to include in this meta-analysis.(DOC)Click here for additional data file.