PTGS2) variants  on the development of HCC, but the conclusions are inconsistent. We conducted a meta-analysis in this work. Data from 7 case–control studies were combined to assess the association between PTGS2 variants and HCC. The risk of HCC (OR and 95% CI) was estimated using either the fixed- or the random-effects model according to the Q test. No significant association was identified for −765G/C and +8473T/C. However, we identified a significantly decreased risk in relation to the GG genotype of −1195A/G . We also observed a similar decrease  in Caucasian samples. Variant −1195A/G in the promoter PTGS2 may protect against the malignant progression of HCC. This significant association suggests that −1195A/G could be used as a biomarker of HCC.Hepatocellular carcinoma (HCC) is a heterogeneous disease with substantial genetic constitution. Previous work has evaluated the effect of prostaglandin-endoperoxide synthase 2 ( It works only among sustained responders by repressing replication of hepatitis virus.8 There is wide difference in individual susceptibility toward HCC among hepatitis virus-infected populations,10 suggesting the possible role of genetic variation in the disease pathogenesis.Hepatitis virus infection, hepatitis B virus and hepatitis C virus in particular, is a known cause of hepatocellular carcinoma (HCC), an end-stage complication of fibrotic and chronic inflammatory liver disease.PTGS2) is a pro-inflammatory enzyme induced by prostaglandins involved in cell proliferation, tumorigenesis, progression, and metastasis.11 The inducible enzyme enables the transformation of arachidonic acid into prostaglandins. The PTGS2 gene, also known as cyclooxygenase-2 (COX-2), is situated at human chromosome 1q25.2-q25.3. It is suggested that increased serum PTGS2 levels lead to upregulation of the prostaglandin EP1 receptor, which in turn decreases PTGS2 levels through certain pathways.12 The levels significantly increase in cancerous tissues and this increase may constitute a mechanism that facilitates carcinogenesis.13 In addition, cyclooxygenase inhibitors could downregulate serum concentrations of potent angiogenic factors, thus suppressing angiogenesis and precluding tumor growth.14 Therefore, the PTGS2 gene may contribute to the progression of human cancer.Prostaglandin-endoperoxide synthase 2  in control populations using the X19 and the random-effect model described by DerSimonian and Laird20 were properly used to estimate the risk of HCC . The former model was performed when the Chi-square based Q statistic test and I2 statistic indicated no notable heterogeneity between studies (PQ-test > 0.05 and I2 < 50%);21 otherwise, the latter model was used. Subgroup analyses were performed according to ethnicity for PTGS2 −1195A/G. Sensitivity analyses were used to check if the single studies had significant influence on the combined risk estimates. Publication bias was determined using the funnel plots and the Egger liner regression test.23 All 2-sided P values less than 0.05 were considered significant. Statistical analyses were done using the Stata software package  and the meta package for R .The fixed-effect model proposed by Mantel and Haensze25 1 did not provide sufficient genetic data and no reply was received after contacting the authors.17 The pooling dataset therefore comprised 7 studies.30 Of these, 5 studies analyzed −765G/C, 6 investigated −1195A/G, and 3 studied +8473T/C. For −765G/C, 2 studies were conducted in Caucasians and 3 in Asians, with Akkiz et al deviating from HWE. With respect to −1195A/G, there were 4 Asian studies and 2 Caucasian studies, and no HWE deviation was detected. In terms of +8473T/C, 2 studies employed Asians and 1 Caucasians. Two types of methods were used in determining the genotypes of PTGS2 variants, including PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and PCR-TaqMan. Genotype frequencies between cases and controls and quality status are presented in Table A total of 39 records were initially identified, as shown in Figure As shown in Table 30 In addition, analysis restrained to high-quality studies showed no significant association in Asian (data not shown).Meta-analysis of −1195A/G and HCC susceptibility was performed among 1807 patients and 2089 control subjects. We found 30% decreased susceptibility of HCC in relation to the GG genotype using the GG versus AA model . The ORs calculated using other genetic models indicated the same results. No analyses showed evidence of significant heterogeneity Table .P > 0.05). However, the Egger test demonstrated evidence of high possibility of publication bias in the GC versus GG model of −765G/C .We assessed the publication bias for −765G/C and −1195A/G. Symmetrical distribution was observed in all funnel plots  and HCC susceptibility by the use of meta-analysis. A total of 7 case–control studies were incorporated. Of the PTGS2 variants studied, only one, corresponding to −1195A/G, was found to be associated with HCC. We noted that the presence of a GG genotype may reduce the risk to develop HCC, especially in Caucasians. Although the statistical power is relatively stronger compared to the previously published studies, some findings should be interpreted with caution due to the large heterogeneity and significant publication bias.This study, for the first time to our knowledge, has examined the association between PTGS2 gene and HCC. The first case–control study was published by Xu et al in 2008.15 In this analysis, 270 HCC patients and 540 controls subjects of Chinese race were analyzed to evaluate the effects conferred by −765G/C and −1195A/G, which were reported to be associated with significantly increased risk of HCC . In the independent studies following Xu et al, some replicated the significant association, while others did not. For example, Liu and Lin29 investigated the variant −1195A/G only and found 1.38-fold increased risk among 420 Chinese samples (210 cases and 210 controls) with the −1195A allele. In contrast, Fan et al30 showed no evidence supporting that −1195A/G is a risk factor for HCC, even though they identified 50% decreased risk associated with +8473T/C among 780 cases and 780 controls of Chinese ancestry. Such controversial results were also indicated in Caucasian samples.28 The wide disparity in the reported results may result from certain aspects, including methodological errors , different ethnic groups, and limited sample size. Other plausible factors, such as poor study design, may also contribute to the inconsistency.Several groups have investigated the hypothesis of a relationship between the variants in the PTGS2 promoter variants being investigated, with the possible exception of −1195A/G, were not associated with the risk of developing HCC. Our findings were in agreement with most published papers, including a recent meta-analysis by Bu et al.31 This meta-analysis evaluated the effects of −1195A/G only and identified a statistically significant increase in the risk of HCC (OR ranged from 1.26 to 1.45). We identified a new Caucasian study and found significant effects in these populations. In addition, we assessed the association for −765G/C and +8473T/C, showing no evidence of a major effect.In our study, we demonstrated that the 16 reported that −765CC genotype downregulates the expression of PTGS2; it is the decreased promoter activity that may represent an important mechanism to explain the significant reduction in the risk of HCC. It is suggested that aberrant expression of the PTGS2 gene induced by the genetic variations in its promoter region would result in chronic immune activation and inflammation, uncontrolled cell growth, suppressed apoptosis, precancerous lesions, and subsequent tumor formation.33 Therefore, the PTGS2 genetic variants are likely to modulate HCC predisposition through up- or downregulating the expression of the gene they are mapped on.The results of the present analysis seem to contradict the previous experimental studies. Akkiz et alPTGS2 variants and HCC susceptibility. We included all available data for the commonly studied variants to provide compelling evidence for the associations that remain elusive. The second strength is that we identified no genetic contributions for −765G/C and +8473T/C, which was not reported in the early meta-analysis. Nevertheless, there was some evidence of notable between-study heterogeneity, and publication bias possibly caused by the failure to include pertinent unpublished reports. Some of our findings may be affected. This is the first limitation that should be taken into consideration when interpreting the present results. Second, the sample size is too low for some variant sites and subgroups, leading to less definite conclusions for some findings. Third, as none of the included studies stated adjusted ORs, the genetic association of interest was evaluated using unadjusted ORs. Finally, both environmental and inherited genetic risk factors are involved in the etiology of HCC. Nonetheless, the effect of gene–environment interactions was not assessed and this may finally influence the findings we demonstrated in the present study. These limitations emphasize the need for continued clinical and basic research to provide new evidence for the molecular mechanisms underlying HCC incidence.There are several strengths in the meta-analysis. The first strength refers to the comprehensive evaluation of the association between PTGS2 variant −1195A/G, but not −765G/C or +8473T/C. A larger study which takes gene–environment interactions and role of confounding factors into account is expected to validate our findings and to determine the role of these variants in HCC pathogenesis.In summary, our meta-analysis suggests that the development of HCC may be associated with


It is widely acknowledged that suicidal behavior (SB) has a genetic influence. As a consequence, molecular genetic studies have been mostly conducted on serotonergic genes. One of the most promising candidate genes of this system is tryptophan hydroxylase (TPH). Although there have been several positive studies associating TPH genes and SB, the evidence is not entirely consistent. Therefore, we performed a meta-analysis to gain a better understanding into this issue.The meta-analysis was conducted with 37 articles of genetic association studies of TPH-1 (A218C and A779C) and TPH2  genes. To analyze the association of these variants with SB we used the following models: allelic, additive, dominant and recessive. In addition, we performed a sub-group analysis by Caucasian and Asian populations using the same four models.TPH-1 gene variants showed a positive significant association with SB, but only in the fixed effects models. With regard to TPH-2 gene variants we could not find an association with SB.The study provides evidence that A218C/A779C TPH-1 variants may be a risk factor to manifest SB at the clinical level, which is in agreement with previously reported meta-analyses. With regard to G-703 T/A-473 T/G19918A TPH-2 variants, our up-to-date meta-analysis could not detect any significant association between those genetic variants and SB. However, these results should be interpreted with caution since further studies need to be undertaken using larger sample sizes in different ethnic populations to confirm our findings. Suicidal behavior (SB) is a leading cause of injury and death worldwide; it accounts for almost one million deaths annually and is the leading cause of death among individuals between 15 and 44 years of age . SuicideA genetic influence in SB is now widely acknowledged and has received convincing support from familial, twin and adoption studies ,8, togetWith regard to the TPH enzyme there are two genes encoding it, both lie on intron seven: TPH-1, located on the human chromosome 11p15.3-14, has an approximate length of 29 kb and contains at least 11 exons and TPH-2 on chromosome 12q 21.1 covers a region of about 97 kb and comprises also 11 exons . The firAlthough there have been several positive studies associating TPH genes and SB the evidence is inconsistent. These inconclusive results are probably due to small sample sizes, different polymorphic markers used in the analysis, as well as variations in sampling strategies, mainly in the control groups, and the different ethnic populations assessed . AlthougIn population with suicidal behavior, what is the influence of TPH-1 and TPH2 genes variants in manifesting a clinical expression of suicidal behavior when compared to healthy subjects?The research protocol of this analysis is available upon request. The meta-analysis and systematic review were performed by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria ,27.Data were obtained by searching in EBSCO and PubMed databases from May to Jun 2013. Relevant publications were identified using the following search terms: “TPH1 and suicidal behavior” , “TPH2 and suicidal behavior” , “TPH1 and suicide” , “TPH2 and suicide” , “Tryptophan hydroxylase and suicidal behavior” . These words were combined to retrieve the summaries. The search also implicated the review of the bibliography cited at the end of the various research articles. To be selected, the publications had to meet the following criteria: (1) to be published in peer-reviewed journals, (2) to contain independent data, (3) to be case–control association studies in which the frequencies of three genotypes were clearly stated or could be calculated, (4) diagnosis of suicidal behavior of the patients in the study , and (5) the use of healthy individuals as controls. A final requirement was that the articles were written in English. The following polymorphisms were studied: A779C (rs1799913) and A218C (rs1800532) of the TPH-1 gene, and rs4570625 (G-703 T), rs11178997 (A-473 T), and rs1386494 (G19918A) of the TPH-2 gene.Two researchers (González-Castro and Juárez-Rojop) working independently screened each of the titles, abstracts, and full texts to determine inclusion. When the researchers were in disagreement a third researcher (Tovilla-Zárate) was consulted.The same authors mentioned above carefully extracted the information from all the included publications. They worked in an independent manner and in accordance with the inclusion criteria listed above. The following data were obtained from each of the studies: authors, year of publication, region, number of cases and controls, age, gender, psychiatric diagnosis, number of males in the groups and ethnical origin of the participants. These data were not always available for all the studies. In the cases of missing data, we contacted the respective authors to ask for the allele frequencies not included in the main text of the papers. One of the studies did not include a control group , but we Figure http://www.sergas.es/MostrarContidos_N3_T01.aspx?IdPaxina=62715). This software is freely available for epidemiologic analysis of tabulated data. Data were analyzed with the random-effects and fixed effects models following the reports in the literature [2) analysis was used to calculate the Hardy-Weinberg equilibrium to evaluate genotype distribution. Studies deemed for inclusion in the systematic review were scored for methodological quality using the Newcastle-Ottawa Assessment Scale (NOS). A score of six or more was taken as the cut-off point to distinguish high from low quality studies [For the meta-analysis procedures we used the EPIDAT 3.1 program (terature -65. Samp studies  (see AddWe measured the Hardy-Weinberg equilibrium (HWE) in both groups (cases and controls) for all the samples of TPH genes; we also explored all populations in a combined way. Results are shown in Tables Firstly, an analysis of the variant A218C rs1800532) of the TPH-1 gene was performed. In this study we evaluated the role of this variant in several models: allelic, additive, dominant and recessive. Also, we considered the Caucasian and Asian populations separately, using the same four models. And as in a previous meta-analysis -25, we f2 of the With this variant we conducted the same analyses than in the previous variant gene (A218C). We observed a significant association with suicidal behavior, using the fixed effects model. This analysis was extended to Caucasian and Asian populations treated separately. Table The first variant analyzed was the G-703 T rs4570625) polymorphism. Initially, we explored the association of the G allele and patients with SB; we did not find significant differences  =0.99). We observed heterogeneity in all studies . The Egger's test provided no evidence of publication bias   polymorphism in association with SB and we found the same negative results with heterogeneity  =0.98; Q test = 18.81 df = 5; p = 0.002). No evidence of publication bias was found . Next, we eliminated heterogeneity by excluding the study by Zhou et al.  in a Cau97 polymoFinally, the G19918A rs1386494) polymorphism was the last variant studied in association with SB. When we analyzed allele G vs allele A, we could not find any significant differences in the analysis without heterogeneity  =0.98; Figure 94 polymoIn this study, we explored the association of THP-1 and TPH-2 gene polymorphisms with suicidal behavioral. We found an association between A218C/ATT9C polymorphism of TPH1 and suicidal behavior. However, we could not find an association between TPH2 gene variants and this behavior. To our knowledge, this is the first study evaluating TPH2 gene variants and suicidal behavior.Suicide has become a serious problem around the world. Various published studies show the search for possible genetic markers that could help in the early detection and prevention of suicidal behavior ,67,68. OOn the other hand, to explore the association of SB with TPH-2 gene, we chose rs4570625 (G-703 T), rs11178997 (A-473 T) and rs1386494 (G19918A) variants, given their functionality and the extensive amount of studies evaluating these polymorphisms in association with SB. We performed the analysis with the same four models used for the TPH1-gene: allelic, additive, dominant, and recessive. We also conducted a sub-group analysis in the Caucasian and Asian populations utilizing the same previously mentioned models. In the present study we could not find any association in any of the models, but we found a slight protective effect concerning polymorphism A-473 T toward suicidal behavior in the recessive model  =0.80; Q test = 4.54; df = 4; p = 0.33); no evidence of publication bias was encountered .There are several explanations for the present outcomes concerning the lack of association of TPH-2 variants with SB. First, the criteria used in the selection of the control groups differ among studies. Second, although the subjects were patients with SB, there were differences in the diagnoses . For example, Souery et al.  work witThis study has some limitations. First, we performed the present meta-analysis based only on published studies. We considered that by selecting only published results, we ensured that our meta-analysis excluded poorly designed studies. Second, although the present analysis involves a large number of studies and genetic variants, it is relatively small in comparison with other meta-analysis on different diseases. Also, we could not perform an analysis including suicide ideation, suicide attempt, or completed suicide. Other limitation is that we did not stratify the analysis by gender because it was not always possible to obtain all the data from the reports or directly from the authors. Also, we did not perform the analysis of all the variants of the TPH-2 gene in the Asian population because there were not enough studies. Sixth, we did not evaluate SB endophenotypes or psychopathologies which could increase the risk for suicidal behavior. One last comment: is that although there are previous meta-analyses evaluating the association of the TPH-1 gene (A218C and A779C variants) and SB, our study contains more recent data and the use of various types of models to perform the analysis.In summary, we performed a meta-analysis to assess the association of A779C (rs1799913) and A218C (rs1800532) variants of the TPH-1 gene, and rs4570625 (G-703 T), rs11178997 (A-473 T), and rs1386494 (G19918A) of the TPH-2 gene with SB. Our analysis of TPH-1 provided evidence that A218C/A779C TPH-1 variants may be risk factors to present SB, which is in agreement with previously reported meta-analyses -25. WithThe authors declare that they have no competing interests.TZC and GCTB conceived the study, participated in its design and helped to draft the manuscript. TZC, JRI, and LNML helped to perform the statistical analysis and to draft the manuscript. All authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-244X/14/196/prepubTable S2. Methodological quality of TPH1 gene variants studies association included based on the Newcastle-Ottawa scale.Summary finding of studies association between TPH1 gene variants and suicidal behavior. Click here for file


Aims. Genetic association studies have reported the E23K variant of KCNJ11 gene to be associated with Type 2 diabetes. In Arab populations, only four studies have investigated the role of this variant. We aimed to replicate and validate the association between the E23K variant and Type 2 diabetes in Tunisian and Arab populations. Methods. We have performed a case-control association study including 250 Tunisian patients with Type 2 diabetes and 267 controls. Allelic association has also been evaluated by 2 meta-analyses including all population-based studies among Tunisians and Arabs . Results. A significant association between the E23K variant and Type 2 diabetes was found . Furthermore, our meta-analysis has confirmed the significant role of the E23K variant in susceptibility of Type 2 diabetes in Tunisian and Arab populations . Conclusion. Both case-control and meta-analyses results revealed the significant association between the E23K variant of KCNJ11 and Type 2 diabetes among Tunisians and Arabs. Type 2 diabetes is a polygenic disorder characterized by defects in insulin secretion and peripheral insulin resistance . TunisiaKCNJ11) gene located at chromosome 11p15.1 is involved in insulin secretion in humans and that mutations in this KCNJ11 gene can cause congenital hyperinsulinism [ KCNJ11 has been so far investigated as T2DM candidate gene.It is well established that the potassium inwardly rectifying channel, subfamily J, member 11 (sulinism  and perm KCNJ11 gene encodes a pore-forming subunit of the inwardly rectifying ATP-sensitive K+ channel (Kir6.2), which is one component of the ATP-sensitive potassium (KATP) channels in pancreatic β-cells. KATP channels regulate insulin secretion by coupling the metabolic state of the cell to membrane potential. Elevation of blood glucose level leads to an increase in the ATP to ADP ratio and a decrease in KATP channel permeability that in turn leads to membrane depolarization, activation of voltage-dependent calcium channels, Ca2+ influx into the cell, and finally insulin exocytosis [In 2003, the E23K variant was shown to be a robustly associating T2DM susceptibility variant  and, in ocytosis . ABCC8 gene (rs757110) was found in complete linkage disequilibrium with the E23K variant [However, the reported functional studies are not yet categorical and the full mutational mechanism(s) is still incomplete  due to t variant .The E23K variant has been reported to be associated with T2DM in various ethnic populations, including European-descent populations , 9, 10 a KCNJ11 gene in the development of T2DM in the Tunisian population.Thus, we proposed in this study to investigate the role of the E23K variant ofDetails of genotyping data for each subject are given in The study population consisted of 250 unrelated Tunisian patients with T2DM  and 267 control subjects  .Subjects with T2DM were diagnosed according to the World Health Organization (WHO) criteria  and recrPopulation control subjects were chosen (1) older than 40 years, age described as significantly related to diabetes in Tunisian population , (2) wit KCNJ11 with T2DM in four North African populations . In the present work, we have evaluated the association of the E23K variant in 250 T2DM patients and 250 controls from Tunisian population.This study is a part of an international cooperative project, NEPAD/NABNet_T2D_NA , which aims to assess the involvement of the E23K variant ofPeripheral blood was drawn from T2DM patients and controls in ethylenediaminetetraacetic acid (EDTA) anticoagulated tubes. DNA was extracted from the blood using salting-out protocol .μL, according to the manufacturer's instructions and using commercially available primers and probes. A random sample set of 10% was retested with the same method to confirm genotype accuracy. The genotyping success rate was 97.13% for cases and controls and the concordance rates were 100% in duplicate samples.Genotyping of E23K variant was carried out using a TaqMan allelic discrimination assay. The assay was carried out using an ABI Prism 7500 Sequence Detection System  in a reaction volume of 20 R using SNP-HWE program [t-test. For qualitative traits we used chi-square test. We tested E23K variant allelic and genotypic association with T2DM risk using multivariate logistic regression to adjust for age, gender, and body mass index (BMI). Odd ratios (ORs) with 95% confidence interval (95% CI) were assessed for the risk allele. For the genotyping data we tested various genetic models including additive, dominant, and recessive models. Allelic exact test was computed on R using allelic package. Analysis of variance (ANOVA) or the unpaired two-tailed Student's t-test was performed to compare clinical data. Multivariate linear regression was used to test the association of the E23K variant with quantitative traits. A t-stat of greater than 1.96 with significance less than 0.05 indicates that the independent variable is a significant predictor of the dependent variable. Statistical analyses were performed using Stata 11 software . A P value < 0.05 was considered statistically significant. Power calculations were performed using PS ) [P < 0.05.Hardy-Weinberg equilibrium (HWE) analyses were performed on  program . Comparion 3.0)) . Based o KCNJ11 gene in Arab populations by searching PubMed using key words: KCNJ11, Arab, E23K, and Diabetes. Four studies were identified after literature search. Three reports were combined to our study data as the last report by Mtiraoui et al. [Q test and quantified using I-squared test. The fixed-effects method of Mantel-Haenszel was used when Pheterogeneity > 0.10 or I2 < 50%. Otherwise, a random-effects model of DerSimonian and Laird was used. The conservative Egger's regression analysis was used to evaluate publication bias between the considered 3 studies. Begg's test was used when just two studies are pooled. All statistical analyses were conducted by using STATA software version 11.0.We further collected data from the literature for E23K variant in thei et al.  was a rei et al.  by increP = 0.32 in T2DM patients and P = 0.69 in controls (P < 10−4) than that observed among controls (53.7 ± 11.76). Systolic blood pressure, fasting glucose, and triglycerides means were significantly higher in T2DM patients than in controls (P < 10−4). The high density lipoprotein-cholesterol (HDL-C) distribution was significantly higher in controls than in T2DM patients (P < 10−4). Sex ratio did not significantly differ between the two groups (P = 0.65).Genotypic distribution of E23K did not show any deviation from Hardy-Weinberg equilibrium, controls . The obsP = 0.015). The K allele is significantly associated with susceptibility to T2DM   .P = 0.007) (P = 0.016), in the dominant model , and in the recessive model   . The E23= 0.028) .P = 0.04 and P = 0.03, respectively ) among T2DM group, control group, and the overall sample, fasting plasma glucose values were found to differ significantly across the E23K genotypes in T2DM and in the pooled sample, ectively . Fasting KCNJ11 gene was found to be independently related to fasting plasma glucose levels under a dominant model: fasting plasma glucose explained 65% (P = 0.031) of the E23K variability of E23K , the age, the gender, and the BMI to fasting plasma glucose. E23K genotype of the of E23K .P < 10−3, Pheterogeneity = 0.427, and I2 = 0.0% (fixed effects) (P = 0.317).We first pooled overall effects of the E23K variant and T2DM risk of 1720 Tunisian patients and 1105 control subjects from the current study with the one from Central East Tunisia of Mtiraoui et al. [effects) . Begg's We extended the analysis to Arab populations and performed a meta-analysis of the E23K variant on 3156 T2DM patients and 2493 controls. For this purpose, we have added results from a Saudi study realized in 2007 , the LebP = 0.001, Pheterogeneity = 0.03, and I2 = 62.7% (random effects) (P = 0.228).The pooled OR for allelic frequency comparison suggested that the E23K variant is significantly associated with an increased T2DM risk: OR = 1.33, 95% CI = 1.13–1.56, effects) . Egger's KCNJ11 gene identified in the aforementioned studies [β-cells KATP channels overactivity and insulin secretion inhibition [In the present study, we sought to replicate the association of the E23K variant in studies , 20–22 whibition  have alsWe also found that the KK genotype confers a 3.62 times higher risk for T2DM compared to the EE genotype. Our findings were in contrast with several studies on Caucasians , 10 and Interestingly, all these data showed that allelic distribution in our sample is closer to Saudi and Mauritanian populations than to the East-Central Tunisians. These findings reveal the genetic heterogeneity of the Tunisian population which is made of a mosaic of communities from different ethnic background . This population stratification was additionally maintained by a high prevalence of endogamous unions . The obsOn the other hand, findings from Mtiraoui et al.  showed tP < 10−3). We have also performed allelic meta-analysis in Arab population given the fact that several meta-analyses have reported the association of E23K with an increased T2DM risk in Caucasians and Asians [P = 0.00022) and additive model , respectively. Likewise, two East Asian meta-analyses conducted by Zhou et al. [P = 3 × 10−9) and an OR of 1.168 (P < 10−3), respectively. More recently, a global meta-analysis based on 49 case-control studies [P < 10−5). Significant results were found in only East Asians and Caucasians after ethnic stratification. Unfortunately, in the former study, the association in Arab populations has not been tested according to their ethnicity.When performing a “Tunisian” meta-analysis , the E23d Asians , 13, 29.u et al.  grouping studies  reported KCNJ11 E23K variant is significantly associated with the susceptibility to T2DM in the Tunisian population. Further genetic and functional studies are required to identify the relevant variant(s) at this locus and to investigate their effect(s) on T2DM susceptibility. To our knowledge, this study represents the first meta-analysis of E23K variant in KCNJ11 gene in association with T2DM in Arab populations and complement previous meta-analyses in Asians and Caucasians. Nevertheless, due to our small sample size, further larger investigations and meta-analysis are needed to confirm the role of the E23K variant in genetic predisposition to T2DM in Arab populations.In conclusion, our case-control study confirmed that the


A meta-analysis based on 57 eligible studies was carried out to clarify the role of MTHFR gene polymorphisms in breast cancer.The MTHFR polymorphisms and breast cancer risk. The pooled ORs were performed with additive model, dominant model and recessive model, respectively. Subgroup analysis was also performed by ethnicity. The statistical heterogeneity across studies was examined with χ2-based Q-test. A meta-analysis was performed using the Stata 12.0 software. Overall, the 677 C allele was significantly associated with breast cancer risk  when compared with the 677 T allele in the additive model, and the same results were also revealed under other genetic models. Simultaneously, the 1298 A allele was not associated with the breast cancer susceptibility when compared with the 1298 C allele . Furthermore, analyses under the dominant, recessive and the allele contrast model yielded similar results.Eligible articles were identified by searching databases including PubMed, Web of Science, EMBASE, CNKI and CBM for the period up to August 2012. Finally, a total of 57 studies were included in this meta-analysis. Crude ORs with 95% CIs were used to assess the association between the 677 C>T polymorphism in the MTHFR gene may contribute to breast cancer development. However, the 1298 A>C polymorphism is not significantly associated with increased risks of breast cancer.The results of this meta-analysis suggest that  MTHFR) gene. The MTHFR gene produces a key enzyme for intracellular folate homeostasis and metabolism, which catalyzes the conversion of 5,10-methylenetetrahydrofolate  to 5-methyltetrahydrofolate (5-methylene-THF). The latter is the predominant circulating form of folate in plasma and provides the methyl group for de novo methionine synthesis through homocysteine remethylation Breast cancer is currently the most common cancer among women and one of the leading causes of cancer-related death in the world MTHFR enzyme activity may increase the cancer risk through impaired DNA repair synthesis and disruption of DNA methylation. In addition, it has been suggested that breast carcinogenesis could be associated with alteration of oestrogen receptor gene methylation patterns Folates play an integral role in maintaining DNA stability by regulating DNA biosynthesis, DNA repair and DNA methylation. Low intake of folate may increase the risk of several cancers, including breast cancer MTHFR is polymorphic located at 1p36.3 MTHFR gene, 677 C>T (rs1801133) and 1298 A>C (rs1801131), are both associated with reduced enzyme activity MTHFR 677 TT (homozygote) genotype results in 30% enzyme activity in vitro compared with the CC wild-type, whereas the MTHFR 1298 CC genotype has been found to result in 60% enzyme activity in vitro compared with the AA wild-type MTHFR gene and breast cancer susceptibility, but provided inconclusive results. Some studies found MTHFR 677 TT genotype is significantly associated with an increased risk of breast cancer 1298 A>C polymorphism, C allele was associated with increased risk in the studies of Ergul et al. A/C vs C/C) by Chou et al.MTHFR 677 C>T and 1298 A>C polymorphisms and the risk of breast cancer.The gene encoding MTHFR”, “MTHFR C677 T”, “MTHFR Ala222Val”, “MTHFR A1298 C”, “MTHFR Glu222Val”, “folate”, “one-carbon metabolism”, “rs1801133”, “rs1801131”, “polymorphism”, “genotype”, “variant”, “breast cancer”, and “breast neoplasm”. We did not define any minimum number of subjects for the studies included in this meta-analysis. No language restrictions were imposed. The reference lists of reviewed articles, clinical trials, and meta-analyses, were also hand-searched for collecting other relevant studies. Two authors conducted all searches independently. When the same patient population was included in several publications, only the most recent or complete study was used in this meta-analysis.A computerized literature search was conducted for the relevant available studies published in English in PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure database (CNKI) and Chinese Biomedical Literature database (CBM). The literature search was updated on August 1, 2012. The search strategy identified all possible studies using combinations of the following keywords: “methylenetetrahydrofolate reductase”, “MTHFR 677 C>T and 1298 A>C polymorphisms and beast cancer risk; (5) clearly described the source of cases and controls; (6) provided sample sizes, and sufficient genotyping data to calculate odds ratios (ORs) and their 95% confidence intervals (CIs).The studies included in this meta-analysis had to meet the following criteria: (1) utilized platinum-based regimens for patients with pathologically proven breast cancer; (2) controls were matched with normal persons; (3) only cohort studies and case-control studies were included in this meta-analysis; (4) evaluation of the Accordingly, the exclusion criteria were: (1) not designed as case-control or cohort studies; (2) reviews; (3) not offering the source of cases and controls and other essential information; (4) control population including malignant tumor patients; (5) duplicated publications.Quality of the studies was assessed using the Newcastle–Ottawa Quality Assessment Scale for cohort studies CC, CT and TT genotypes, and the AA, AC and CC genotypes, respectively. Different ethnicity descents were categorized as Caucasian, Asian and Mixed population. When studies included subjects of more than one ethnicity, data were extracted separately for each ethnic group.Information was independently extracted from all eligible publications by two authors according to the inclusion and exclusion criteria listed above. Disagreement was resolved by discussion between the two authors. The following data were collected from each study: first author’s surname, year of publication, ethnicity, the numbers of cases and controls with the frequencies of MTHFR 677 C>T and 1298 A>C polymorphisms and breast cancer risk. For the two polymorphisms, the meta-analysis examined their associations for the allele model C vs T; homozygote (CC vs TT), recessive model (CC vs CT+TT) and dominant model (CC+CT vs TT). Subgroup analyses were stratified by ethnicity. Both fixed-effects model using the Mantel–Haenszel method and random-effects model using the DerSimonian and Laird method were used to pool the results.Crude ORs with 95% CIs were used to assess the strength of association between the P-value greater than 0.10 for the Q-test indicates a lack of heterogeneity among studies, so the pooled OR estimate of the included studies was calculated by the fixed-effects model. Otherwise, the random-effects model was used. The significance of the pooled OR was determined by the Z-test, and P<0.05 was considered as statistically significant. One-way sensitivity analyses were performed to assess the stability of the results, namely, a single study in the meta-analysis was deleted each time to reflect the influence of the individual dataset on the pooled OR. An estimate of potential publication bias was carried out by the funnel plot, in which the standard error of log (OR) of each study was plotted against its log (OR). An asymmetric plot suggests a possible publication bias. Funnel plot asymmetry was assessed by the method of Egger’s linear regression test, a linear regression approach to measure funnel plot asymmetry on the natural logarithm scale of the OR. The significance of the intercept was determined by the t-test suggested by Egger  P-value <0.05 was considered significant. All of the calculations were performed using STATA , using two-sided P-values.Heterogeneity assumption was checked by the Chi-square-based Q-test MTHFR 677 C>T and 1298 A>C polymorphisms  and breast cancer risk were ultimately analyzed (MTHFR 677 C>T (rs1801133) and 1298 A>C (rs1801131) polymorphisms and breast cancer were identified. After screening the duplicated articles, 28 publications were excluded. And then titles and abstracts were screened, 134 articles were excluded and 79 full-test studies were left for further evaluating. Furthermore, 25 publications were excluded because they were 7 review articles, 17 non-case control studies, 2 other meta-analysis, and 3 studies lack of sufficient data. Last, 3 studies were included in this work through manual search of the reference list of retrieved reviews. Hence, 57 publications including 57 studies for MTHFR 677 C>T (rs1801133) and 29 studies for MTHFR 1298 A>C (rs1801131) were included in this meta-analysis MTHFR 677 C>T (rs1801133) polymorphism and breast cancer susceptibility, included 28 groups of Caucasians, 20 groups of Asians, and 9 Mixed populations. While 29 studies for MTHFR 1298 A>C (rs1801131) polymorphism and breast cancer susceptibility, included 13 groups of Caucasians, 9 groups of Asians, and 7 Mixed populations. The distribution of genotypes in the controls of all studies was in agreement with Hardy–Weinberg equilibrium.Studies relevant to the searching words were retrieved originally. 57 eligible publications addressing the association between analyzed Figure 1Table S1. The association between the 677 C>T polymorphism and breast cancer risk was investigated under the additive model . Substantial heterogeneity among the studies  was found. The overall OR under a random-effects model was 0.942 (95%CI = 0.898 to 0.988), suggesting a significant association  . However, compared with homozygotes of the CC allele, significant association of the AC genotype with breast cancer risk was not found and the overall OR was 0.983 (95%CI = 0.962 to 1.006). Analyses under different genetic models were shown in 29 studies were included in the meta-analysis to describe the association between o 1.009) Figure 31298A allele in Caucasian population had significant effect on the risk of breast cancer , whereas this effect was reversed in Asian  and Mixed population  .According to study characteristics, subgroup analysis and sensitivity analysis were performed. The results showed that the o 1.107) Table 2In order to compare the difference and evaluate the sensitivity of the meta-analyses, we conducted one-way sensitivity analysis to evaluate the stability of the results. The statistical significance of the results was not altered when any single study was omitted (data not shown), confirming the stability of the results.P = 0.322 for C allele vs T allele, P = 0.066 for A allele vs C allele, Begg’s funnel plot and Egger’s test were performed to assess the publication bias. The shapes of the funnel plots did not reveal significant evidence of obvious asymmetry in all comparison models . Furthermore, Egger’s test was used to provide statistical evidence for funnel plot symmetry. The results still did not suggest any evidence of publication bias Click here for additional data file.Table S2The main characteristics of these studies included in this meta-analysis and the distribution of MTHFR gene 1298A>C genotypes and alleles among cases and controls.(DOCX)Click here for additional data file.Checklist S1PRISMA Checklist.(DOC)Click here for additional data file.


The associations between toll-like receptor 2 (TLR2) and toll-like receptor 4(TLR4) polymorphisms and inflammatory bowel disease (IBD) susceptibility remain controversial. A meta-analysis was performed to assess these associations.A systematic search was performed to identify all relevant studies relating TLR2 and TLR4 polymorphisms and IBD susceptibility. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Subgroup analyses were performed by ethnicity and publication quality.Thirty-eight eligible studies, assessing 10970 cases and 7061 controls were included. No TLR2 Arg677Trp polymorphism was found. No significant association was observed between TLR2 Arg753Gln polymorphism and Crohn’s disease (CD) or ulcerative colitis (UC) in all genetic models. Interestingly, TLR4 Asp299Gly polymorphism was significantly associated with increased risk of CD and UC in all genetic models, except for the additive one in CD. In addition, a statistically significant association between TLR4 Asp299Gly polymorphism and IBD was observed among high quality studies evaluating Caucasians, but not Asians. Associations between TLR4 Thr399Ile polymorphisms and CD risk were found only in the allele and dominant models. The TLR4 Thr399Ile polymorphism was associated with UC risk in pooled results as well as subgroup analysis of high quality publications assessing Caucasians, in allele and dominant models.The meta-analysis provides evidence that TLR2 Arg753Gln is not associated with CD and UC susceptibility in Asians; TLR4 Asp299Gly is associated with CD and UC susceptibility in Caucasians, but not Asians. TLR4 Thr399Ile may be associated with IBD susceptibility in Caucasians only. Additional well-powered studies of Asp299Gly and other TLR4 variants are warranted. Inflammatory bowel disease (IBD), which mainly consists of ulcerative colitis (UC) and Crohn's disease (CD), is a group of chronic non-specific gastrointestinal inflammatory conditions. IncreasedIBD incidence and prevalence havebeen observed in different regions of the world. IBD is Toll-like receptors (TLRs) are transmembrane proteins usually expressed by antigen presenting cells; they are important immune receptors that participate in the recognition of pathogen-associated molecular patterns and activation of signal transduction pathways of antimicrobial genes, by identifying and binding to small molecular components on pathogens. TLRs alTLR2, located at 4q31.3, recognizes bacterial lipopeptides and lipoteichoic acid found abundantly in the cell wall of Gram positive bacteria. TLR4, lPopulation-based case-control show an association between TLR4 polymorphism and susceptibility to CD and UC. The association between TLR2 gene variantss and extensive colonic disease in UC and CD has also been discribed. TLR2 ArA systemic search was conducted on PubMed, Embase, Biosis Preview and China National Knowledge Infrastructure databases up to August 31, 2014 using the following keywords: (1) “toll-like receptor” or “TLR”; (2) “Crohn’s disease” or “CD” or “ulcerative colitis” or “UC” or “inflammatory bowel disease” or “IBD”; (3) “polymorphism” or “variant” or “genotype”. There was no language restriction and species were limited to human. References in the reviews and retrieved articles were hand-searched as well. For articles by the same author using the same case series, the study with the largest sample size was selected.The inclusion criteria were: (1) case-control study; (2) investigation evaluating the relationship between TLR2  and TLR4  genetic polymorphisms and IBD (CD or UC) susceptibility; (3) sufficient available published data for odds ratio (OR) estimation with 95% confidence interval (CI); (4) human study; (5) data not republished.Missing data were requested by contacting study authors through email. Data were blindly extracted from all selected publications by two investigators (Cheng and Zhu) separately. For each of the included articles, the first author name, publication year, study population (ethnicity), source of controls, total numbers of patients and controls, and polymorphism frequencies in patients and controls were extracted. For studies that included subjects of different ethnic groups, data were extracted for each one. Any disagreement on a given item of the extracted data was fully discussed to reach a consensus.Predefined criteria  based on2. A P value for heterogeneity < 0.10 or I2 > 50% was considered statistically significant. Sensitivity analysis was performed by sequentially excluding each single study to assess the stability of the results[Pooled crude odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined to assess the associations between TLR2  and TLR4  genetic polymorphisms and the risk of IBD under dominant, recessive, additive and allele models, based on the extracted data. The fixed-effects (random-effects) model was used depending on the heterogeneity among studies, 16. Sube results. Galbraie results. Hardy-We results. Potentie results. Funnel e results. Studiese results. All staThis meta-analysis was performed and reported according to the PRISMA guidelines. The search of PubMed, Biosis Previews, Embase and two Chinese databases  for relevant articles published up to July 2014 yielded 597 articles. A total of 36 articles–5823–58–5823–58 The basic information for each study, including authors and publication years, ethnicity, numbers of cases and controls, frequencies of various genotypes in IBD patients and healthy controls, and Hardy-Weinberg equilibrium (HWE) in healthy controls, are summarized in Of the 39 studies, 7 assessed the TLR2 Arg677Trp polymorphism, 10 studied the TLR2 Arg753Gln polymorphism, 37 evaluated the TLR4 Asp299Gly polymorphism and 17 studied the TLR4Thr399Ile polymorphism. There were 30 high quality and 9 low quality studies, respectively according to the set quality criteria . All lowAn estimation of the association between TLR2 Arg677Trp, Arg753Gln and TLR4Asp299Gly, Thr399Ile polymorphisms and susceptibility to CD and UC is presented in All studies evaluating the TLR2 Arg677Trp polymorphism were conducted among Asians. No variant allele A carrier or mutant homozygous was found in either the IBD patients or control population in the included studies. In addition, TLR2 Arg677Trp polymorphism did not show any association with CD  or UC  in Asian populations.Due to the rarity of the TLR2 Arg753Gln mutant homozygous genotype in the included studies, the data could only be pooled in the allele and dominant models. In the allele model, no association was found between the A allele and CDor UCsusceptibility. Similarly, the AA genotype was not associated with risk of CD  or UC .Subgroup analyses based on ethnic were performed to assess CD and UC susceptibility in Asians and Caucasians. No significant association was identified in both Asians and Caucasians .A significantly increased susceptibility was found between TLR4 D299G and CD in the allele model , dominant model , recessive model  and additive model . Similar results were also found between TLR4 D299G and UC in the allele model , dominant model , recessive model  and additive model .Stratified analyses by study quality and ethnicity were conducted to further explore the actual effect of TLR4 D299G polymorphism on the risk of CD and UC. Similar results were obtained with subgroup analyses by study quality. When ethnicity was restricted to Asians, no TLR4 D299G polymorphism was found in patients with CD or UC. However, when only studies with Caucasians were considered, a significant association with CD was obtained in all contrast models . Furthermore, significant associations with UC were found in the allele model , dominant model  and additive model . However, in the recessive model, only a marginal association  was found. Similar results were found in UC in Caucasians .The pooled results of all studies suggested that TLR4 T399I polymorphism was significantly associated with CD susceptibility in the dominant  and allele  models, whereas no significant association was found in the recessive  and additive  models. Similarly, the CC genotype significantly increased UC susceptibility in the dominant model  and the C allele was found associated with a higher UC susceptibility in the allele model ; no significant association was found in the recessive  and additive  models.Meta-analyses of high quality studies showed that TLR4 T399I polymorphism was not associated with the risk of CD in any genetic model and only the dominant model showed a significant association with the risk of UC.Stratified by ethnicity, neither Asians nor Caucasians were associated with CD susceptibility in all four genetic models. With respect to UC, a significant association was found for Caucasians in dominant  and allele  models, but not in recessive  and additive  models.2 values of heterogeneity> and P values< 0.10. To further investigate the heterogeneity in studies assessing TLR4 299 polymorphism in Caucasians, Galbraith plots were generated to identify the outliers which might contribute to this observation. Our results showed that the study published in 2008 by Rigoli was an outlier in both dominant and allele models , indicating that our results were statistically robust.There was no evidence of obvious asymmetry in the funnel plots. The Egger’s test was performed to access publication bias in the articles included in this meta-analysis, when the number of included studies was greater than 10. All p values obtained in the Egger’s test were more than 0.1 except for the dominant model of TLR4 399 in CD for both overall analysis and the assessment including only high quality studies. There were five unreported studies according to the Duval’s trim and full method . After pGenome-wide association studies(GWAS) has improved our knowledge of many common variants and molecular pathways leading to IBD. RecentlBoth TLR4 and TLR2 was not detected to be associated with IBD in the previous GWAS. Not surprisingly, uncommon genetic variation which may contribute significantly toward the heritability of IBD may not be captured by GWAS. PopulatAll studies assessing the TLR2 Arg677Trp polymorphism and IBD were carried out in Asia, and no TLR2 Arg677Trp polymorphism was found in Asians, as described above. This is the first meta-analysis evaluating TLR2 Arg677Trp polymorphism and IBD.In the case of TLR2 Arg753Gln, we only pooled data in the allele and dominant models due to the rarity of the TLR2 Arg753Gln mutant homozygous genotype in the included studies. All studies were of high quality. Our meta-analysis showed no association between the Arg753Gln polymorphism and UC or CD. We then restricted to ethnicity-specific data for subgroup analyses, and found that the Arg753Gln polymorphism was not associated with UC or CD susceptibility in Asians or Caucasians. These findings indicated that Arg753Gln with the mutant allele does not significantly increase IBD susceptibility.To our knowledge, this is the first meta-analysis evaluating TLR2 Arg753Gln polymorphism and IBD.Interestingly, this meta-analysis revealed a modest association between the TLR4 Asp299Gly polymorphism and IBD (CD and UC). This result was very well supported: sensitivity analyses excluding low quality studies did not significantly change the magnitude of the gene effect or genetic model. Next, we restricted to race-specific assessments to perform a subgroup analysis. Consistent with meta-studies reported by Hume and Shen, 52, ourThe current study indicates that the TLR4 399T allele might increase the risk of UC and CD. It is plausible that TLR4 Thr399Ile’s T allele affect TLR4 transcription and expression, further impacting TLR4 protein function. Further studies should focus on how the variant might impact gene expression and function. Subgroup analysis of high quality studies showed no association between TLR4 Thr 399Ile polymorphism and CD, and marginal association between TLR4 Thr399Ile polymorphism and UC. In the meta-analysis performed by Shen et al, TLR4 39The overall meta-analysis has little heterogeneity. When ethnicity sub-stratification was performed, heterogeneity was decreased or even removed among Asians while significant heterogeneity existed in study for TLR4 Asp299Gly polymorphism and UC in the dominant and allele models in Caucasions. Galbraith plot was used to identify heterogeneous records. One heterogeneous article for TLR Asp299Gly vs UC was detected by the Galbraith plot. The potA few limitations of this study need to be mentioned. First, a variety of confounding factors may be associated with increased damage to IBD, such as gender, age, smoking status, clinical phenotype, et al. Unfortunately, we were unable to obtain sufficient data to perform appropriate stratified analyses due to the limited information in the included studies. In addition, the number of cases and controls included was relatively small and most were included in Asians as far as studies on TLR2 Arg677Trp and Arg753Gln are concerned. Thus, the association between in different populations need to be confirmed by further studies. Finally, we could not identify the gene-gene and gene-environment interactions in this study. In conclusion, TLR2 Arg677Trp and Arg753Gln is not associated with the risk of UC or CD. The TLR4 Asp299Gly and Thr399Thr genotypes seem to be more susceptible to UC and CD in Caucasian populations but not in Asians. This finding needs to be further confirmed in future well-designed studies including different ethnicities.S1 PRISMA Checklist(DOC)Click here for additional data file.S1 Table(DOCX)Click here for additional data file.S2 Table(DOC)Click here for additional data file.


PDE4B single nucleotide polymorphisms (SNPs) have been reported to be associated with schizophrenia risk. However, current findings are ambiguous or even conflicting. To better facilitate the understanding the genetic role played by PDE4B in susceptibility to schizophrenia, we collected currently available data and conducted this meta-analysis.The PDE4B SNPs and schizophrenia was evaluated by odds ratios (ORs) and 95% confidence intervals (CIs) under allelic, dominant and recessive genetic models. The random effects model was utilized when high between-study heterogeneity (I2 > 50%) existed, otherwise the fixed effects model was used.A comprehensive electronic literature searching of PubMed, Embase, Web of Science and Cochrane Library was performed. The association between P = 0.04). The rs2180335 was significantly related with schizophrenia risk in Asian populations under allelic  and dominant  models. A significant association was also observed between rs4320761 and schizophrenia in Asian populations under allelic model . In addition, a strong association tendency was found between rs6588190 and schizophrenia in Asian populations under allelic model .Five studies comprising 2376 schizophrenia patients and 3093 controls were finally included for meta-analysis. The rs1040716 was statistically significantly associated with schizophrenia risk in Asian and Caucasian populations under dominant model (OR = 0.87, 95% CI: 0.76–0.99, PDE4B SNPs are genetically associated with susceptibility to schizophrenia. However, due to limited sample size, more large-scale, multi-racial association studies are needed to further clarify the genetic association between various PDE4B variants and schizophrenia.This meta-analysis suggests that  Susceptibility to schizophrenia has been considered to be inextricably related to genetic factors –4. Twin phosphodiesterase 4B (PDE4B), which is located on human chromosome 1 at 1p31 and composed of 17 exons spanning 580 kb [PDE4 families. Like other adenosine 3’, 5’-monophosphate (cAMP) phosphodiesterases, PDE4B participates in cAMP signaling process by specifically inactivating cAMP [dunce gene, encoding an ortholog of mammalian PDE4, resulted in high levels of cAMP and deficiencies in olfactory learning and memory [PDE4B was first implicated as a candidate risk gene for schizophrenia through investigating chromosomal abnormalities of two cousins, the proband of whom was diagnosed with schizophrenia [Among various candidate genes for schizophrenia, the gene g 580 kb , belongsing cAMP . Interesd memory . PDE4B wophrenia . Specifiophrenia . In addiophrenia –17, was ophrenia . TherefoPDE4B. Additionally, they identified 14 SNPs of PDE4B gene associated with schizophrenia under a nominal P value of 0.05 [PDE4B variations with predisposition to schizophrenia across multi-ethnic populations, including Caucasian populations , Asian uropeans , Japanesuropeans , Chineseuropeans  and Koreuropeans ), and Afuropeans ). The one’s study, which je’s study. AnotherWe conducted a comprehensive electronic literature searching of MEDLINE (PubMed), Embase (Ovid), Web of Science (Thomson-Reuters) and Cochrane Library (Wiley) from establishment date to August 2015. To maximize search scope and minimize the chance of missing relevant studies, we used a simple term combination strategy. The search terms and their combination manner were presented below: (“schizophrenia” OR “schizophrenic”) AND (“PDE4B” OR “phosphodiesterase 4B”). With this search strategy, there were 59, 86, 70, and 0 citations obtained from Pubmed, Embase, Web of Science and Cochrane Library, respectively. After excluding duplicates, there were 121 citations retrieved from these four electronic databases. In addition, to supplement the electronic search, we also manually searched reference lists of key studies and reviews for additional relevant studies, but no additional studies were obtained.The eligible studies should satisfy the following criteria: (1) case-control studies; (2) written in English; (3) providing sufficient data to calculate the odds ratios (ORs) and 95% confidence intervals (CIs); (4) allele frequency and genotype distribution of control population must be in Hardy-Weinberg equilibrium; (5) stating that well-informed consent was acquired from all participants.For each included study, the following data were collected: the first author’s last name, publication year, country, ethnicity, numbers of cases and controls, diagnosis criteria, gender distribution, age and Hardy-Weinberg equilibrium. We calculated the ORs and 95%CIs, if they are not provided in original studies. Two researchers independently performed data extraction and discrepancy was resolved through discussion or referred to a third researcher.The quality of the included studies was evaluated through a checklist originated from Strengthening the Reporting of Genetic Association (STREGA) recommendations for reports on genetic association studies  and modiQ test and I squared (I2) statistics. If substantial heterogeneity was detected (P < 0.1 or I2 > 50%), the random effects model (the DerSimonian-Laird method) was employed; otherwise the fixed effects model (the Mantel-Haenszel method or the Inverse Variance method) was utilized. We assessed the association strength by using ORs and 95% CIs and the significance of pooled ORs was examined by Z test. To reflect the influence of a single study on between-study heterogeneity and the pooled effect sizes, we excluded one study each time and then observed the corresponding changes. To estimate potential publication bias, we performed trim and fill analysis [Heterogeneity between studies was evaluated by Cochran’s analysis . The levanalysis . All anaThe PRISMA flow diagram of literature search was shown . In briePDE4B SNPs investigated in five studies are listed in Main characteristics of the five included studies were described in http://www.ncbi.nlm.nih.gov/snp/ and tabulated the information including locations and possible functions of these SNPs in We searched for SNPs included into our meta-analysis at P = 0.443; P = 0.941; For rs599381, no significant association was observed between this SNP and schizophrenia across Asian  and Caucasian (Northern Europeans) populations  and Caucasian (Northern Europeans) populations  and Caucasian (Northern Europeans) populations under either dominant  and Caucasian (Northern Europeans) populations in dominant model . Furthermore, when under recessive model, trim and fill analysis found one possible missing study and new meta-analysis after filling this study still showed no significant association (P = 0.601). For rs1040716 under allelic model, using trim and fill analysis, no potentially missing study was found, suggesting no publication bias. In dominant model, trim and fill analysis discovered one potentially missing study. Of note, after filling this study, new meta-analysis still revealed a significant association between rs1040716 and schizophrenia risk (P = 0.017). In addition, trim and fill analysis predicted no missing study when meta-analysis on rs1040716 is under recessive model.To evaluate the potential publication bias in our meta-analysis, we merely employed trim and fill method  due to lPDE4B was initially reported as a genetic susceptibility factor for schizophrenia in the exploration of chromosomal abnormalities of two psychiatric cousins [PDE4B gene locus. Regarding the underlying mechanistic role played by PDE4B in the pathogenesis of schizophrenia, Millar et al. [ cousins . Both cor et al.  demonstrr et al. . Therefor et al. , 32.PDE4B in the etiology of schizophrenia, to date to our knowledge, no comprehensive meta-analysis was conducted to systematically summarize the association of PDE4B polymorphisms and schizophrenia. In order to better understand the genetic role of PDE4B for schizophrenia susceptibility, we recapitulated the association of different PDE4B SNPs with schizophrenia risk in multi-ethnic populations under allelic, dominant and recessive models.Though there have been numerous association studies examining the genetic role of I2 = 3.6%) appeared in Asian populations. Sensitivity analysis demonstrated that the statistically significant association between rs1040716 and schizophrenia risk under dominant model was seemingly unstable and correspondingly changed with a certain study deleted  still existed. In addition, the new meta-analysis of association between rs1040716 and schizophrenia under dominant model after filling one possible missing study detected by trim and fill analysis remained significant (P = 0.017). Therefore, this result should be interpreted with caution and more large-scale replicative studies are necessary to ascertain the relationship. For analysis of rs472952, high heterogeneity was observed in allelic, dominant and recessive genetic models in Asian populations, suggesting that ethnicity may be not responsible for high heterogeneity. In addition, sensitivity analysis showed that heterogeneity dramatically decreased when Guan’s study was removed in allelic, dominant, and recessive models . We assume that this heterogeneity variation may be not coincidental because similar change was observed in three genetic models. It is highly probable that the significant heterogeneity between studies was attributable partly to geographic factors, age difference in samples . Two allelic haplotypes of PDE4B were observed in statistical significance (P = 0.0022 and P = 0.029), increasing or decreasing schizophrenia susceptibility [Besides the studies included into our meta-analysis, there are some other studies demonstrating the genetic association between d et al.  identifiol study  revealedophrenia . FurtherPDE4B SNPs and predisposition to schizophrenia.To conclude, our meta-analysis suggest that rs1040716, rs2180335 and rs4320761 may serve as genetic susceptibility factors for schizophrenia. Moreover, a strong association tendency between rs6588190 and schizophrenia risk was found. However, due to limitations in our meta-analysis, more large-scale studies from different ethnic populations are needed to further ascertain the underlying relationship between S1 Checklist(DOC)Click here for additional data file.S2 Checklist(DOCX)Click here for additional data file.S1 Text(DOCX)Click here for additional data file.


PPARG  and serum lipid levels, but the results were inconclusive. Hence, we conducted a meta-analysis to clarify the association. MEDLINE, EMBASE and the Cochrane Library databases were searched systematically. The subgroup analysis was performed based on ethnicity. Seventy-four studies with 54,953 subjects were included in this meta-analysis. In Pro12Ala, the group with the ‘PP’ (C/C genotype) genotype group had lower levels of total cholesterol (TC) , low-density lipoprotein cholesterol (LDL-C)  and higher levels of triglyceride (TG)  than the combined ‘PA+AA’  genotype group in Asian population, and the group with the ‘PP’ genotype had higher levels of TG  than the combined ‘PA+AA’ genotype group in non-Asian population. No statistically significant differences in the levels of TC, TG, high-density lipoprotein cholesterol, LDL-C were detected between different genotypes in C161T(Asian or non-Asian) and C1431T(Asian) polymorphisms. This meta-analysis was a renewed and confirmed study to assess the association between PPARG polymorphisms and serum lipid levels in Asian and non-Asian populations. There is a prominent association between Pro12Ala polymorphism and the levels of TC, LDL-C and TG in Asian population. No statistically significant differences in serum lipid levels were detected between different genotypes in C161T and C1431T polymorphisms.Considerable studies have been carried out to investigate the relationship between the polymorphisms of  Cardiovascular disease (CVD), a global health-threatening problem, is a complex disease resulting from many risk factors, such as genetic factor ,2 and dyPPAR) genes, which have three isotypes, namely α, γ and δ. PPARG (as known as PPARγ) is located at chromosome 3p25, and it encodes a member of the PPAR subfamily of nuclear receptors. Four PPARG isoforms have been identified: PPARγ1, PPARγ2, PPARγ3 and PPARγ4, which result from either alternative transcription start sites or alternative splicing [PPARG is potential transcriptional factors that are dietary lipid sensors [PPARG is cytosine–guanine exchange in exon B (codon12), which results in proline to alanine substitution in the protein. Several single-nucleotide polymorphisms (SNPs) in the PPARG have been reported to be associated with dyslipidaemia and CVD. These SNPs include Pro12Ala (rs1801282) [A large number of literatures have unravelled the correlation between genetic factors and dyslipidaemia –10. Amonsplicing –13. PPAR sensors ,15. The 1801282) –29, C1611801282) ,30–35.Various studies have investigated the association between these genetic variants and serum lipid levels in different races. However, the results were inconclusive ,18,36–39PPARG  and serum lipid levels published in English before May 2014 were identified by comprehensive computer-based searches of MEDLINE via PubMed, EMBASE, the Cochrane Library database and Web of Science. The following key words were used: ‘peroxisome proliferator-activated receptor γ’, ‘PPARγ or PPARG gene’, ‘Pro12Ala’, ‘C161T’, ‘C1431T’, ‘polymorphism’, ‘dyslipidemia’ and ‘serum lipid level’. The search strategy described was used to obtain titles and abstracts of studies of potential relevance for this meta-analysis. The titles and abstracts were screened independently by two authors (Q Li and R Chen), who discarded studies that were not applicable (Studies were discarded when (i) it was not possible to extract data from either the published results or by contacting the authors or (ii) appropriate outcomes were not reported). For multiple reports involving the same patients, only the study with the most complete data set was included in the meta-analysis. However, for patients included in two articles, where these had different types of data of outcomes, both were included. Any disagreements about article inclusion were arbitrated by discussion with a separate reviewer (J Hong).All studies reporting associations between the polymorphisms of i) case–control studies published in peer-reviewed journals with full text available in English; (ii) studies on the relationship between PPARG Pro12Ala, C161T and C1431T polymorphisms and serum lipid levels; (iii) reporting at least one relevant outcomes of association between genotype and serum lipid levels . Studies were excluded when (i) it was not possible to extract data from either the published results or by contacting the authors or (ii) appropriate outcomes were not reported.The five investigators  independently reviewed all studies identified by the search strategy, to determine whether an individual study was eligible for inclusion. The selection criteria for studies to be considered for this meta-analysis were as follows: (i) Relationship between serum lipid parameters and genotypes; (ii) Genotype frequency; and (iii) Serum lipid parameters: TC, TG, HDL-C and LDL-C., relationship between genotypes and serum lipid parameters. Discrepancies were resolved by discussion. When repeated publications of the same trial were identified, data were extracted from the repeated publications and reported as a single trial.P-values were ≤0.05. Heterogeneity was analysed using a chi-squared test and N − 1 degrees of freedom [I² values of 25%, 50% and 75% correspond to low, medium and high levels of heterogeneity respectively. Sensitivity analyses were performed by omitting a single study at a time or by analysis using another model. We carried out statistical analysis by the Review Manager software 5.2.0. Stratified analysis was performed according to the ethnicity of participants.Allele frequencies were determined by the allele counting method for each study. Relationships between continuous variables (lipid parameters) and genotypes were expressed as mean difference (MD) with 95% confidence intervals (CI). Pooled effects were calculated using a fixed effects model when there was no significant heterogeneity among the data from the contributing studies; however, a random effects model was used to ensure the robustness of the chosen model and susceptibility to outlier effects, or when there was significant heterogeneity among contributing study data, in which case a fixed effects model was used to ensure the robustness of the chosen model and examine susceptibility to outlier effects. Point estimates of MD were considered statistically significant when two-tailed  freedom . I² valuSeventy-four studies with 48,210 subjects –38,42–87PPARG) included 67 eligible studies, containing 45,831 participants. According to ethnic origin, two Subgroups (Asian and non-Asian) were divided from each comparison. For Asian subgroup, Pro12Ala (PPARG) included 24 eligible studies and 40 separate comparisons of the levels of TC [PPARG) included 36 eligible studies and 45 separate comparisons of the levels of TC [Thus, the meta-analysis of Pro12Ala  included 11 eligible studies, containing 3518 participants. Subgroup analysis was performed based on ethnicity (Asian and non-Asian). In Asian group, C161T (PPARG) included 6 eligible studies and 11 separate comparisons of the levels of TC [PPARG) included 3 eligible studies and 6 separate comparisons of the levels of TC, TG, HDL-C and LDL-C respectively [The meta-analysis of C161T  included 4 eligible studies, containing 5604 all Asian participants. A total of 3 eligible studies and 6 separate comparisons contained the levels of TC, LDL-C respectively [The meta-analysis of C1431T  in Asian population: Pooling of data from eligible compared groups indicated that the group with the ‘PP’ (C/C genotype) genotype group had lower levels of TC , LDL-C  and higher levels of TG  than the combined ‘PA+AA’  genotype group. No statistically significant difference in the levels of HDL-C  was detected between the ‘PP’ and ‘PA+AA’ groups  in non-Asian population: Pooling of data from eligible compared groups indicated that the group with the ‘PP’ genotype had higher levels of TG  than the combined ‘PA+AA’ genotype group. No statistically significant differences in the levels of TC , LDL-C  and HDL-C  were detected between the ‘PP’ and ‘PA+AA’ groups  in Asian population: In the subgroup analysis by ethnicity of study population, no statistically significant differences were detected in the levels of TC , TG , HDL-C  and LDL-C  between ‘CC’ (C/C genotype) and ‘CT + TT’ (C/T + T/T genotype) groups  in non-Asian population: No statistically significant differences were detected in the levels of TC , TG , HDL-C  and LDL-C  in non-Asian populations between ‘CC’ and ‘CT +TT’ groups : all the study population were Asian. As shown in Figure P = 0.13, I2 = 42%), TG , HDL-C , LDL-C  were detected between the CC and CT +TT groups.The outcomes of C1431T , C161T (Asian: TG) and C1431T (Asian: LDL-C) were medium. To explore the sources of heterogeneity, we performed subgroup analyses with stratification by case and control status; heterogeneity still existed, but the corresponding pooled MD was not substantially altered.For most of the outcomes of serum lipid levels, the PPARG as a member of the nuclear receptor superfamily regulates adipocyte differentiation, adipocyte-specific gene expression and insulin action. Recently, an increasing number of studies have been carried out to determine the association between the difference PPARG loci polymorphisms and serum lipid levels, but the results are inconclusive. Li et al. [et al. [et al. [Cardiovascular disease, a kind of chronic disease with high prevalence and morbidity, has attracted more and more researchers to study its related fields throughout the world . Previoui et al.  conclude [et al.  reported [et al. ,62,79. S [et al. ,45. Howe [et al.  tended t [et al. ,31. ThesPPARG), the group with the ‘PP’ genotype had lower levels of TC, LDL-C and higher levels of TG than the combined ‘PA+AA’ genotype group in Asian population, and the group with the ‘PP’ genotype had higher levels of TG than the combined ‘PA+AA’ genotype group in non-Asian population. No statistically significant differences in the levels of TC, TG, HDL-C, LDL-C were detected between different genotypes in C161T (Asian or non-Asian) and C1431T (Asian) polymorphisms.As the results in our meta-analysis showed, at Pro12Ala  indicated very significant effects, including TC, TG and LDL-C levels with Pro12Ala (PPARG) in Asian population, which demonstrate that the conclusions in our meta-analysis are robust.It is the first time that meta-analysis was conducted to explore the association between I2 values of heterogeneity in most of our outcomes were lower than 50%. Only the levels of heterogeneity in the outcomes of Pro12Ala (Asian: HDL-C and non-Asian: TG), C161T (Asian: TG) and C1431T (Asian: LDL-C) were medium. These indicate the reliability of the results in our meta-analysis. The medium heterogeneity may be because different groups of the included studies had different genetic backgrounds and environmental factors. It is well known that both serum lipid levels and CVD are affected by genetic and environmental factors, such as dietary patterns, lifestyle, obesity, physical inactivity.High heterogeneity is a potential problem that may affect the interpretation of the results. But heterogeneity analysis showed that the For better interpreting the results, some limitations of this meta-analysis should be acknowledged. Firstly, this meta-analysis focused only on papers published in English and the ones that reported in other languages may bias the present results. Secondly, we did not perform subgroup analysis by the factors such as smoking habits, diet pattern, alcohol use, case/control because insufficient data could be extracted. In addition, gene–gene and gene–environment interactions should also be considered in the analysis. However, heterogeneity in most of our outcomes was low, so that these limitations do not affect the reliability of the results in our meta-analysis.PPARG and serum lipid levels.Thus, it is necessary to conduct a study using standardized unbiased methods. Moreover, gene–gene and gene–environment interactions should also be considered in the analysis. Such studies taking these factors into account may eventually lead to better, more comprehensive understanding of the association between the common polymorphisms of the PPARG and serum lipid levels. As the results in our meta-analysis showed, there is a prominent association between Pro12Ala polymorphism and the levels of TC, LDL-C and TG in the Asian population. No statistically significant differences in the levels of TC, TG, HDL-C, LDL-C were detected between different genotypes in C161T (Asian or non-Asian population) and C1431T (Asian population) polymorphisms.This meta-analysis was a renewed and confirmed study to assess the association between common polymorphisms in


Objective. This meta-analysis aimed to investigate a comprehensive and reliable conclusion on the correlations of single nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor (VEGF) gene with the risk of diabetic nephropathy (DN) in patients with diabetes mellitus (DM). Methods. We screened PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, Google Scholar, CBM, and CNKI databases for those relevant studies that investigated the association of 14,945 subjects with clinicopathological parameters in gastric cancer. Results. Eleven case-control studies that met all inclusion criteria were included in this meta-analysis. A total of 14,945 subjects were involved, including 3,049 DN patients and 11,896 DM patients. Our meta-analysis results revealed that VEGF rs2010963 and rs3025039 polymorphisms might contribute to the risk of DN in DM patients. Ethnicity-stratified analysis suggested that VEGF genetic polymorphisms were associated with an increased risk of DN among Asians. However, we found no correlations of VEGF genetic polymorphisms with susceptibility to DN among Caucasians. Conclusion. Our findings suggest that VEGF rs2010963 and rs3025039 polymorphisms may contribute to the risk of DN in DM patients, especially among Asians. Thus, VEGF genetic polymorphisms could be useful biomarkers for early diagnosis of DN in DM patients. VEGF) has also been reported to be associated with the development and progression of DN  and [“diabetic nephropathies” or “DN” or “diabetic kidney disease”] and [“vascular endothelial growth factors” or “VEGF” or “vascular permeability factor” or “VPF”]. We also performed a manual search of the reference lists from the relevant articles to find other potential articles. VEGF genetic polymorphisms with the risk of DN in DM patients; (3) all patients must conform to the diagnostic criteria of DN; (4) the study must provide sufficient information about the frequencies of SNPs. If the study could not meet the inclusion criteria, it would be excluded. The most recent or the largest sample size publication was included when the authors published several studies using the same subjects.The eligible studies included in our meta-analysis should meet the following types of inclusion criteria: (1) the study design must be clinical cohort or case-control study; (2) the study must relate to the relationships ofTwo authors from each included study used a standardized form to systematically collect relevant data. The researchers collected the following data: the first author and publication year of article, language of publication, geographical location, design of study, sample size, the source of the subjects, allele frequencies, source of samples, genotyping method of SNP, evidence of Hardy-Weinberg equilibrium (HWE), and so forth.Methodological quality was independently assessed by two researchers according to the Newcastle-Ottawa Scale (NOS) criteria . The NOSZ test was used to estimate the statistical significance of pooled statistics. The Cochran's Q-statistic and I2 test were used to evaluate potential heterogeneity between studies [ Q-test shows a P < 0.05 or I2 test exhibits >50% which indicates significant heterogeneity, the random effect model was conducted or else the fixed effects model was used. We also performed subgroup and metaregression analyses to investigate potential sources of heterogeneity. In order to evaluate the influence of single studies on the overall estimate, sensitivity analysis was performed. We conducted Begger's funnel plots and Egger's linear regression test to investigate publication bias [The STATA version 12.0  software was used for meta-analysis. We calculated crude odds ratios (ORs) with their 95% confidence intervals (95% CI) to evaluate their relationships under 5 genetic models: the allele model , the dominant model (WM + MM versus WW), the recessive model (MM versus WW + WM), the homozygous model (MM versus WW), and the heterozygous model (MM versus WM). The  studies . If Q-teion bias .Initially, the searched keywords identified 308 articles. We reviewed the titles and abstracts of all articles and excluded 154 articles; full texts and data integrity were also reviewed and 142 articles were further excluded . Finally VEGF genetic polymorphisms with the risk of DN in DM patients were shown in  VEGF rs2010963  and rs3025039  polymorphisms might contribute to the risk of DN in DM patients .Meta-analysis findings on the relationships ofpatients . Neverth VEGF genetic polymorphisms were associated with an increased risk of DN among Asians  . Further subgroup analysis by genotyping method showed significant associations between VEGF genetic polymorphisms and DN risk in the PCR-RFLP subgroup  but not in the non-PCR-RFLP subgroup .Subgroup analysis by ethnicity suggested that; resp.) . Howevert = 2.92, P = 0.011 and dominant model: t = 2.53, P = 0.024, resp.).Metaregression analysis confirmed that SNP type and ethnicity might be the main sources of heterogeneity (as shown in  VEGF gene may result in the aberrancy of glomerular filtration barrier and renal tubular reabsorption, which can eventually lead to the occurrence of microalbuminuria and proteinuria [ VEGF genetic variants have been postulated to be clearly an excellent candidate for the pathogenesis of DN [VEGF is a potent multifunctional cytokine belonging to the multipotent cytokines family . The rolteinuria , 40. Theis of DN , 41. VEGF genetic polymorphisms with the risk of DN in DM patients. Finally, 11 independent case-control studies were included. Our meta-analysis results showed positive associations of VEGF rs2010963 and rs3025039 polymorphisms with susceptibility to DN in DM patients, indicating that these polymorphisms may be causative factors for the incidence of DN. Although the exact function of VEGF gene in the development of DN is not fully understood, a potential explanation might be that variants in the VEGF gene increased its expression level which was suspected to play a vital role in injury of podocytes by acting in a novel autocrine signaling mode to induce the podocytopathy of diabetes and the genesis of albuminuria related with DN. Our findings were in accordance with a previous study which attempted to show that VEGF genetic polymorphisms had a significantly higher frequency in DN patients with microalbuminuria or proteinuria than in DM patients [ VEGF genetic polymorphisms with an increased risk of DN among Asians and the PCR-RFLP subgroup but not among Caucasians and in the non-PCR-RFLP subgroup, which indicated that ethnic differences and genotype may be the main sources of heterogeneity. All in all, our findings were consistent with previous studies that found VEGF genetic polymorphisms may alter the risk of developing DN in DM patients, suggesting that these polymorphisms may be utilized as biomarkers for early diagnosis and prognosis of DN.In the present meta-analysis, we evaluated the relationships ofpatients . Since o VEGF genetic polymorphisms with the risk of DN in DM patients, our study still has some limitations. Firstly, our results had lacked sufficient statistical power to assess the correlations between genetic variants of VEGF and susceptibility to DN due to the relatively small sample size. Secondly, meta-analysis is a retrospective study that may lead to subject selection bias, thereby affecting the reliability of our results. Thirdly, our meta-analysis failed to obtain original data from the included studies, which may limit further evaluation of potential roles of VEGF genetic polymorphisms in the development and progression of DN. Importantly, the inclusion criteria of cases and controls were not well defined in all included studies, which might also influence our results.Although this is the first meta-analysis focused on the association of VEGF rs2010963 and rs3025039 polymorphisms may contribute to the risk of DN in DM patients, especially among Asians. Thus, VEGF genetic polymorphisms could be useful biomarkers for early diagnosis of DN in DM patients. However, due to the limitations mentioned above, more studies with larger sample sizes are still needed to provide a more representative statistical analysis accurately.In conclusion, our findings supply convincing evidence that


Background. Adenomatous polyposis coli (APC) is widely known as an antagonist of the Wnt signaling pathway via the inactivation of β-catenin. An increasing number of studies have reported that APC methylation contributes to the predisposition to breast cancer (BC). However, recent studies have yielded conflicting results.Methods. Herein, we systematically carried out a meta-analysis to assess the correlation between APC methylation and BC risk. Based on searches of the Cochrane Library, PubMed, Web of Science and Embase databases, the odds ratio (OR) with 95% confidence interval (CI) values were pooled and summarized.Results. A total of 31 articles involving 35 observational studies with 2,483 cases and 1,218 controls met the inclusion criteria. The results demonstrated that the frequency of APC methylation was significantly higher in BC cases than controls under a random effect model . Subgroup analysis further confirmed the reliable results, regardless of the sample types detected, methylation detection methods applied and different regions included. Interestingly, our results also showed that the frequency of APC methylation was significantly lower in early-stage BC patients than late-stage ones .Conclusion. APC methylation might play an indispensable role in the pathogenesis of BC and could be regarded as a potential biomarker for the diagnosis of BC. Breast cancer (BC) is the most common malignancy and the leading cause of cancer death among females in both well and poorly developed countries, accounting for approximately 15% of all cancer deaths in 2012 , 2015. IEpigenetic as well as genetic alterations are both stable and heritable and occur in tumor suppressor genes involved in tumourigenesis. The most common epigenetic alteration involving aberrant DNA methylation, a reliable and sensitive biomarker for nearly all types of cancer including breast cancer, often leads to the transcriptional silencing of tumor suppressor genes , 2013. Sβ-catenin, which is regarded as a transcriptional activator  gene is widely known as an antagonist of the Wnt signaling pathway via the inactivation of ctivator , 2001. Tctivator , 2008. Tctivator , 2013. Sctivator , 2009. T control , 1998. T control  reported control  also shoGiven these controversial results, we conducted this comprehensive meta-analysis of the current observational studies to evaluate the association between the aberrant methylation of the APC promoter and increased BC risk.Eligible studies were identified by searching the following databases until February 2016: the Cochrane Library, PubMed, Web of Science and Embase. No language restrictions or lower data limits were imposed; only abstracts, unpublished and incomplete studies were excluded. Titles, abstracts of potential references and reference lists from relevant studies were carefully checked. We performed the search strategy using the following search terms and their various combinations: “APC,” “Adenomatous polyposis coli,” “methylation,” “breast cancer,” “breast neoplasm” and “mammary carcinoma.”The studies included in the present meta-analysis addressed the association between APC methylation and increased BC risk. Our inclusion criteria were as follows: (1) provided sufficient data on the frequency of APC methylation in BC patients and controls; (2) original observational studies in full-text form; and (3) when several studies overlapped, the most recent or large-scale article was selected. The following were exclusion criteria: (1) data based on reviews, animal models, case reports or cell line studies; (2) studies lacking key information necessary for calculations; (3) duplicated studies; and (4) studies including BC patients or controls who underwent radiotherapy and chemotherapy which may influence APC promoter methylation levels.The relevant data were extracted from the eligible studies independently by two authors (D Zhou and WW Tang). Differing opinions, if any, were resolved by discussion in accordance with the original literature. The following information was extracted in a predefined table: the name of the first author, the year of publication, the country of origin, the sample type, the experimental methods used to detect APC methylation, sample size, tumor stage, tumor grade and APC methylation frequencies. Additionally, we classified stage 0, I and II as early-stage BC and stage III and IV as late-stage BC, as confirmed by the AJCC staging system. Furthermore, grades I and II were combined as low-grade BC; grade III was regarded as high-grade BC. This meta-analysis was performed following the statement of preferred reporting items set by the PRISMA Group  Moher e, 2009.Q-tests based on the chi-square test and I2 value. An I2 value >50% and a p < 0.10 denoted strong heterogeneity, an I2 value = 25–50% denoted a moderate degree of heterogeneity and an I2 value <25% or a p > 0.10 denoted mild heterogeneity (p < 0.1). Otherwise, the fixed effect model was employed  and Stata 12.0 (Stata Corporation) software. Forest plots were designed to estimate relative study-specific effects according to the 95% confidence interval (CI). The association between APC promoter methylation and BC risk was evaluated by calculating the odds ratio (OR) with corresponding 95% CI. For individual studies the OR was represented by a square and the 95% CI by a horizontal line in the centre of the forest plot. The OR and associated 95% CIs in the centre of the forest plot were plotted on a logarithmic scale. When a CI did not include 1.0, a correlation was deemed statistically significant. Heterogeneity between the included studies was quantified through ogeneity , 2003. Aemployed , 2014. MThe selection process is displayed as a flow chart in n = 10) (n = 13) (n = 2) (n = 9) (n = 1)  , 2007, E(n = 13) , 2011b,  (n = 2) , 2015, N (n = 9) , 2001 an (n = 1) , 2014. Fp < 0.00001, I2 = 65%), the random effect model was adopted to evaluate the combined effects of APC promoter methylation. The overall analysis indicated that the frequency of APC promoter methylation was remarkably higher in BC patients than in cancer-free controls. The combined OR for 35 included relevant studies showed that APC methylation was significantly correlated with increased BC risk and the absence of APC expression played an important role in BC pathogenesis .The pooled results of this meta-analysis reflected the association between APC promoter methylation and BC pathogenesis . Due to A sensitivity analysis was conducted by omitting one individual study every time to evaluate the stability of the pooled OR and to choose the heterogeneous study. As shown in p < 0.00001, I2 = 65%), subgroup analysis based on region, experimental methods for the detection of APC methylation and sample types were carried out to appraise the sources of the heterogeneity (I2 = 0%) and the pooled OR value was 24.48 . The I2 value representing heterogeneity in the European and North American subgroups decreased by 50% and 42%, compared with the overall I2 value. Furthermore, their OR values also decreased to 4.63  and 3.79 . In the African subgroup, the OR was 172.05  with higher heterogeneity (I2 = 80%) due to the small subset containing only 2 studies. These results indicated that the heterogeneity might result from different regions and APC methylation was remarkably related to increased BC risk without geographical restrictions. For the subgroup analyses based on sample types, the blood or serum group  made the largest contribution to the heterogeneity (I2 = 78%). In the tissue subgroup, the OR was 9.93  with lower heterogeneity (I2 = 50%). Moreover, heterogeneity in the NAF subgroups could be ignored (I2 = 6%). These results confirmed the stable association between APC methylation and BC risk in different sample types. For studies based on the methods used to detect the methylation of the APC promoter, the combined OR value was 18.18 for MSP (95% CI [7.96–41.52]), 3.93 for QMSP (95% CI [1.78–8.69]), 3.29 for MethyLight (95% CI [1.27–8.52]) and 31.81 for MS-MLPA (95% CI [5.30–191.06]). Heterogeneity in the QMSP (I2 = 36%) and MS-MLPA (I2 = 0%) subgroups was far lower than that of the MethyLight and MS-HRM subgroups (I2 = 83%).Due to the significant existence of inter-study heterogeneity (ogeneity . With reI2 = 34%). Meanwhile, the OR of 8 studies revealed that the association between APC methylation and tumor grade was not statistically significant .To assess the association between APC methylation and tumor stage, 11 studies comprising 681 BC patients were pooled to calculate the OR. The results showed that the frequency of APC promoter methylation was significantly lower in early-stage patients than in late-stage patients  suggested no significant publication bias (p > |t| = 0.000 < 0.05). Therefore, we carried out trim and fill analysis to identify and revise the bias. As shown in We used the funnel plot, Begg’s test and Egger’s test to evaluate the degree of publication bias. The shape of the funnel plot had no obvious asymmetry . Moreoveion bias . Interesβ-catenin accumulation and TCF/LEF-induced transcription  to ensure the reliability of the meta-analysis and minimize the potential publication bias.Surprisingly, only Egger’s linear regression showed an obvious publication bias other than Begg’s test and funnel plots. Although the meta-analysis indeed confirmed the significance of a correlation between APC methylation and BC pathogenesis, several limitations should be considered. First, the sample sizes used in several studies were small, which may have increased the risk of publication bias and limited the results of the meta-analysis. Second, the quality of the selected studies varied, as we included high-quality and low-quality studies. Therefore, heterogeneity likely existed. Third, the cut-off points of APC methylation and the primers based on CPG islands were difficult to unify. Thus, we were unable to calculate the pooled sensitivity and specificity of APC methylation.In conclusion, the results of our meta-analysis highlight the clinical significance and scientific value of APC promoter methylation in the diagnosis of BC. Consequently, APC methylation is a potential biomarker for monitoring BC development. However, given the limitations listed above, high-quality studies with large-scale and consistent standards should be carried out. The guidelines for the reporting of tumor marker studies recommended by the National Cancer Institute are necessary for adaptation to high-quality studies , 2005.10.7717/peerj.2203/supp-1File S1Click here for additional data file.10.7717/peerj.2203/supp-2File S2Click here for additional data file.