KIAA0319 at the DYX2 locus is one of the most extensively studied candidate genes for developmental dyslexia (DD) owing to its important role in neuronal migration. Previous research on associations between KIAA0319 genetic variations and DD has yielded inconsistent results. It is important to establish a more precise estimate of the DD risk associated with these genetic variations. We carried out a meta-analysis of association studies involving KIAA0319 polymorphisms and DD risk. The results of pooled analysis indicated that none of the six investigated markers in or near the KIAA0319 gene are associated with DD. However, a stratified analysis by the study population revealed opposite associations involving KIAA0319 rs4504469 in European and Asian subgroups. The stratified analysis also showed that the KIAA0319 rs9461045 minor allele  has a protective effect in Asians. This meta-analysis has allowed us to establish the effects of specific KIAA0319 polymorphisms on DD risk with greater precision, as they vary across populations; analyzing one single nucleotide polymorphism at a time could not fully explain the genetic association for DD. KIAA0319 has emerged as one of the two strongest candidates (the other is DCDC2) for DD161718192021Developmental dyslexia (DD) is one of the most common learning disorders affecting 5–10% of school-aged children worldwide23457610121314KIAA0319 have been identified in independent DD samples. An early study by Francks et al. identified an underlying quantitative trait locus at chromosome 6p22.2, a 77 kb region spanning the entire TTRAP and the first four exons of KIAA0319, which was found to be related to DD in two independent UK samples and one US sample; the authors suggested that a three-marker risk haplotype (rs4504469-rs2038137-rs2143340) in this region was associated with DDKIAA0319 as a DD-associated gene. Following this study, rs4504469, rs6935076 and their haplotype were observed to be associated with DD in a UK sampleet al. not only confirmed that rs4504469 and rs6935076 influenced DD risk, but also identified another promising single nucleotide polymorphism (SNP) candidate for association with DD, rs761100, in a larger UK sampleet al.et al.2327During the past decade some noteworthy genetic variants in KIAA0319 seems to be an important risk factor for DD, and this conclusion is supported by functional analysis. KIAA0319 encodes for an integral membrane protein containing a large extracellular domain with four polycystic kidney disease domains, a single transmembrane domain and a small intracellular C-terminus263031Kiaa0319 knockdown resulted in disruption to the migration of neocortical neurons leading to the formation of heterotopia in white matter in a subset of animals which also displayed an array of behavioral deficits, including impairments in rapid auditory processing, simple spatial learningNonetheless, et al.17Several SNPs are involved in regulation of KIAA0319 expression. The risk haplotype rs4504469-rs2038137-rs2143340 identified by Francks KIAA0319 gene  studies in order to derive a more precise estimate of the association between six markers in or near the 319 gene  and DD ret al. in ref. et al. in ref. et al. in ref. et al. in ref. et al.et al.KIAA0319. In addition, the Eicher et al.192124252728394041et al.The literature search and study selection procedures are shown in KIAA0319 gene in association with DD risk. Significant heterogeneity was found for rs4504469, rs761100 and rs6935076 (shown in P = 0.706) for rs4504469, 0.95  for rs761100, 1.01  for rs6935076, 0.94  for rs3212236, 0.93  for rs9461045, and 1.03  for rs2143340.shown in ; thus, tP = 0.028), but in Asians the T allele conferred an increased risk of DD . The stratified analysis also revealed that the rs9461045 minor allele  had a protective effect in the Asian subgroup . The other four markers, rs761100, rs6935076, rs3212236 and rs2143340, were all negatively associated with DD risk in all subgroups.The data were stratified into three subgroups  according to the study population. The results are shown in https://www.broadinstitute.org/mpg/snap. The results are shown in Given that the analysis stratified by the study population explains the opposite direction of effects for rs4504469 but not the rest of the analyzed SNPs, and that this rs4504469 is located further in the 3′ of the gene  and DD risk was based on seven case-control studies comprising a total of 2,711 cases and 2,991 controls and five TDT studies involving 943 families. The results of pooled analysis demonstrated that none of the six markers was associated with DD. A stratified analysis with the study population as the stratification factor revealed that KIAA0319 rs4504469 had opposite associations with DD risk in European and Asian subgroups. The stratified analysis also revealed that the KIAA0319 rs9461045 minor allele had a protective effect in the Asian subgroup, but was a risk allele for UK samplesKIAA0319 polymorphism on DD risk with greater precision, revealing that they vary with the study population.This meta-analysis of associations between six markers in or near the KIAA0319 gene on the risk of DD also showed opposite association trends in different samples. Specifically, although under-transmitted haplotypes of rs4504469–rs6935076 were associated with DD in the samples from CardiffKIAA0319 gene on reading skills in the general population drew opposite conclusions about the relationship of the 1-1-2 haplotype (rs4504469–rs2038137–rs2143340) to reading performance  with rs4504469 is not captured by the rest of the analyzed SNPs, and the LD patterns for rs4504469 are different in European and Asian populations. We therefore speculate that there is a functional element in this region and that ethnic differences in inter-marker LD in this region account for the opposite effects of rs4504469, but not the rest of the analyzed SNPs. Of course, differences in inter-marker LD across samples may be due to sampling variationLin et al. found that SNP rs761100 interacted with DCDC2 haplotype rs793862−rs807701 to affect the quantitative subdimension ‘word reading’et al. studyNeither rs761100 nor rs6935076 were associated with DD risk in the meta-analysis, but these results should be treated with caution because of the repeated presence of heterogeneity suggested by the sensitivity analysis and the stratified analysis. Although we do not know the source of the heterogeneity, it seems arbitrary to simply assume that it is due to false positives. The two SNPs might be correlated, through interactive effects or linkage disequilibrium, with a causal variant, which causing flip-flop associations between these two SNPs and DD risk as discussed above. For example, Ludwig KIAA0319 expression, rs9461045, rs3212236 and rs2143340, were not associated with DD as a discrete trait in each included association studies or in the pooled analysis (see 2437http://snpinfo.niehs.nih.gov/snpinfo/snpfunc.htm). Rs2143340 is located in the TTRAP gene, which encodes a tumor necrosis factor receptor-associated protein which inhibits nuclear factor-kappa B (NF-κB) transcriptionKIAA0319 markers on quantitative reading-related traits should be priority for future research.The other three SNPs that were included in this meta-analysis because of their potential effect on ysis see . HoweverKIAA0319 polymorphisms and DD risk and suggested that the associations between single SNPs and DD risk vary according to the study population. There may be multiple genetic variants (rather than a single SNP) that contribute to DD risk. Further primary research and updated meta-analysis of findings on KIAA0319 is needed to explore the combined effect of multiple genetic polymorphisms and environmental factors on DD risk. In complex diseases the effect of single causal variant is very weak, and the sample sizes in our analysis were relatively small, especially in the stratified analysis. More studies with larger samples in a particular ethnic group are needed to confirm our findings and identify true causal variants via fine-mapping.In summary, the meta-analysis clarified the associations between We searched PubMed, EMBASE, and ISI Web of Science databases for published articles up to May 2015 using the keywords “KIAA0319”, “dyslexia or reading disability”, “polymorphism or variant” without language restrictions. References of the retrieved articles were also scanned. Reviews, comments, and letters were also checked for additional studies.KIAA0319 polymorphisms and DD risk; (3) allele frequencies on KIAA0319 polymorphisms in case and control groups for case–control studies, and numbers of transmitted alleles from heterozygous parents to affected offspring for family-based studies. For the study that only meet the first two conditions, we emailed its corresponding author to asking for the original data mentioned in the third condition. Animal studies, reviews, simple commentaries and meetings were excluded. Study overlap was eliminated by selecting the report with a complete design or larger sample size.The following inclusion criteria had to be fulfilled: (1) either case-control or TDT study design; (2) KIAA0319 polymorphisms. The counts of alleles in case and control groups in case-control studies and the number of transmitted alleles from heterozygous parents to affected offspring in family-based studies were extracted or calculated in the included studies.All data were extracted in dependently by two reviewers (S. Shao & X. Zhang). The following information was extracted from the eligible studies: first author’s name, year of publication, study population, study design, and http://www.r-project.org/). Briefly, data from each case-control and TDT study were extracted and sorted as per the metafor package instructions. Odds ratios (ORs), 95% confidence intervals (95%CIs) and standard errors (SEs) were calculated for individual study based on allele data. The between-study heterogeneity was assessed by a χ2-based Cochran’s Q-statistic test (the heterogeneity was considered significant at P < 0.10). A fixed-effects model was used to apply data from studies when heterogeneity was negligible; otherwise, a random-effects model was applied. For the synthesis of case-control and TDT studies, Kazeem and FarrallP values were two-tailed with a significance level at 0.05, except for Cochran’s Q-statistic test.All statistical analyses were conducted using the metafor package (version 1.9-5) in R .


Introduction. Diabetes mellitus as the most prevalent metabolic disease is a multifactorial disease which is influenced by environmental and genetic factors. In this systematic review, we assessed the association between genetic variants and diabetes/its complications in studies with Iranian populations. Methods. Google Scholar, PubMed, Scopus, and Persian web databases were systematically searched up to January 2014. The search terms were “gene,” “polymorphism,” “diabetes,” and “diabetic complications”; nephropathy, retinopathy, neuropathy, foot ulcer, and CAD (coronary artery diseases); and Persian equivalents. Animal studies, letters to editor, and in vitro studies were excluded. Results. Out of overall 3029 eligible articles, 88 articles were included. We found significant association between CTLA-4, IL-18, VDR, TAP2, IL-12, and CD4 genes and T1DM, HNFα and MODY, haptoglobin, paraoxonase, leptin, TCF7L2, calreticulin, ERα, PPAR-γ2, CXCL5, calpain-10, IRS-1 and 2, GSTM1, KCNJ11, eNOS, VDR, INSR, ACE, apoA-I, apo E, adiponectin, PTPN1, CETP, AT1R, resistin, MMP-3, BChE K, AT2R, SUMO4, IL-10, VEGF, MTHFR, and GSTM1 with T2DM or its complications. Discussion. We found some controversial results due to heterogeneity in ethnicity and genetic background. We thought genome wide association studies on large number of samples will be helpful in identifying diabetes susceptible genes as an alternative to studying individual candidate genes in Iranian populations. Diabetes mellitus, as the most prevalent metabolic disorder, is characterized by chronic hyperglycemia due to defect in insulin secretion by beta cells of Langerhans islets or resistance against insulin action –3. More A systematic review showed that between years 1996 and 2004 the prevalence of type 2 diabetes in Iran was 24% and the risk was 1.7% greater in women. According to this report the prevalence of T2DM in Iran seems to be highest amongst developing countries. Previous reports on total urban population of Middle Eastern countries show the prevalence of T2DM as 3.4% in Sudan, 20% in United Arab Emirates, 8.5% in Bahrain, and 12.1% in India [Diabetes Mellitus is categorized into the following groups.Type 1 diabetes mellitus (T1DM) includes 5–10% of diabetic patients. Cellular-mediated autoimmune destruction of the beta-cells of the pancreas results in T1DM. It classically occurs in juveniles and affected patients are dependent on insulin injection in their lifetime and are very prone to ketosis , 9.T2DM includes 90–95% of patients with diabetes. Patients with type 2 diabetes may be asymptomatic for long period of time. Vascular complications such as nephropathy, neuropathy, retinopathy, and cardiovascular disease may develop in these patients. The impact of genetic component appears to be stronger in T2DM compared to T1DM , 9.Gestational diabetes mellitus (GDM) is another type which is observed during pregnancy and the prevalence may range from 1 to 14% in all pregnancies , 9. HNF4α (hepatocyte nuclear factor), HNF1β, IPF1 (insulin promoter factor), and neuro-D1 [MODY (maturity onset diabetes of young) is monogenic form of diabetes comprised of several types with various features which is consisting of 1–5% of patients diagnosed as T2DM. The onset of this type of diabetes is normally before 25 years and its treatment is independent of insulin. MODY in its different forms is inherited in autosomal dominant pattern and presents as a result of mutation in transcription factors genes includingneuro-D1 , 9.There are also other types of diabetes which are considered as secondary to other conditions, for example, any damage to pancreas such as removal of pancreatic tissue, trauma, pancreatic carcinoma, and infection, or underlying diseases including endocrine diseases that alter different hormones secretion which are antagonist to insulin resulting in various clinical manifestations such as acromegaly, Cushing's syndrome, pheochromocytoma, glucagonoma, somatostatinoma, and diabetes. Diabetes (or carbohydrate intolerance) is also found in increased frequency with a large number of genetic syndromes such as Wolfram syndrome, which causes diabetes mellitus, diabetes insipidus, and other neurodegenerative disorders, MELAS  which is presented with myopathy and encephalopathy caused by mitochondrial mutation, MIDD  which causes diabetes, and IPEX  which is X-linked and alters immune system and causes multiple endocrine problems , 8, 9. PPRAG (peroxisome proliferator-activates receptor gamma), IRS1 and 2 (insulin receptor substrate), KCNJ11 (potassium inwardly rectifying channel), and HNFA are associated with T2DM. Genome wide association studies (GWAS) showed that many genes including Calpain 10 and TCF7L2 (transcription factor 7-like 2) are associated with T2DM. HHEX , SLC30A8 (solute carrier family 30 (zinc transporter), member 8), CDK2A/B (cyclin-dependent kinase inhibitor 2A/B), and IG2BP2 (insulin-like growth factor 2) are other genes which have been shown to be associated with T2DM based on GWAS. Some of these genes are expressed in beta cells or involved in insulin secretion pathways [γ, ACE (angiotensin converting enzyme), MTHFR (methylene tetrahydrofolate reductase), FABP2 (fatty acid binding protein-2), and FTO (fat mass and obesity associated gene) [α (peroxisome proliferator-activated receptor gamma coactivator-1α) and adiponectin with T2DM [INS) gene VNTRs (variable number of tandem repeats) with a protective effect is a variants related to T1DM. In addition PTPN22 (protein tyrosin phosphatase), CTLA4, and IL2RA genes have also been shown as candidates for T1DM due to their role in T-cell signaling. Studies have also confirmed the association between IFIH1, CYP27B1, and CLEC16, which are important in immune system and T1DM [Diabetes mellitus is a multifactorial disease with both environmental and genetic causes affecting its presence and incidence. Genome wide association studies revealed the genetic heterogeneity of diabetes and the fact that difference in ethnicity can result in different susceptible genes associated with diabetes , 11. Stupathways , 13. Othed gene) . GWAS waed gene) . Systemaith T2DM , 17. Theand T1DM .There is no inclusive information for genetic association studies of diabetes in Middle Eastern population including Iranian population. In order to make a comprehensive approach, we aimed to collectively investigate and gather data for association between genetic variants and type 2 diabetes in Iranian population in a systematic review study.This study is reported according to PRISMA  guideline .We systematically searched international web databases: Google Scholar, PubMed, Scopus, and Persian web databases; IranMedex; and Magiran to investigate the association of genetic variants with diabetes and its complications in Iranian population up to January 2014. The search terms were “gene,” “polymorphism,” “diabetes,” “diabetes' complications,” nephropathy, retinopathy, neuropathy, foot ulcer, and CAD (coronary artery disease) and their MeSH terms and Persian equivalents with diabetes. At least three emails were sent to the corresponding author of articles which were not accessible as full text or had insufficient data. Duplicate articles and multiple publications from the same population were excluded and the most relevant data were used for the investigation. The references of all selected articles were investigated.We included all observational population-based studies ≥100 sample size, which were conducted as case-control, cohort, or cross sectional. According to WHO criteria, diabetes mellitus was defined as FBS ≥ 7 mmol/L (126 mg/dL) or 2 h plasma glucose ≥11.1 mmol/L 200 mg/dL) [0 mg/dL [The following data were extracted and presented in an excel sheet: author(s), year, genes and SNPs, patients' characteristics , city, study design, genotyping method, and significant association. Six selected items from the STROBE  checklist  was usedDue to heterogeneity in genotyping techniques and also differences in genetic variants studied in assessed included articles performing a meta-analysis was impossible.A summary of the literature review process performed in this study is presented in a flow chart in Overall 27,396 diabetics and healthy subjects were studied in this systematic review. All of the subjects were recruited from total urban population. T2DM was the most investigated type of diabetes (42 studies) –75. AmonDetails of the included studies are described as below.All the studies in this subgroup including 12 studies –33 were P = 0.037, P = 0.0001) while no significant relation was observed between −607A/C variant of this gene and T1DM [P = 0.035) [Association of interleukins including IL-18 (interleukin) and IL-12 with T1DM revealed that the −137C/G polymorphism of IL-18 had significant association with T1DM  .P = 0.01, P < 0.001) [In 2 studies the association of +49A/G variant of CTLA-4 (cytotoxic T lymphocyte associated antigen 4) was investigated and it was revealed that there was a positive significant association between AG genotype and T1DM (< 0.001) , 32. One FokI, BsmI, ApaI, and TaqI variants of VDR with T1DM. In one study which was performed on 114 subjects, Aa (P = 0.003), FF (P = 0.008) and Bb (P = 0.014) genotypes were shown to be positively associated with T1DM but no significant association was observed between TaqI polymorphism and T1DM [ FokI, BsmI, and ApaI. However TT genotype was observed to be more frequent in controls (P = 0.007) and negatively associated with T1DM [Vitamin D receptor (VDR) was investigated in 2 studies , 26. Botand T1DM . AnotherP = 0.001 and P = 0.013, resp.). Other variants of TAP2 (transporter 2 ATP-binding cassette) including Ala565Thr, Arg651Cys, and Ala665Thr were not associated with T1DM significantly [Different polymorphisms of TAP2 and their association with T1DM were investigated in 191 subjects. It was shown that Ile379Val and Stop687Gln had significant association with T1DM (ficantly .P = 0.025) and A5 had positive (P = 0.001) significant association with T1DM [Association of alleles A2–A9 of CD4 with T1DM was assessed in 200 subjects. It was revealed that A3 allele had negative (ith T1DM .α4 (rs1449263 polymorphism), CD44 (rs8193 polymorphism), and TGFβ (transforming growth factor) (+915C/G polymorphism) was also investigated in 2 studies and no significant relation was observed between these variants and T1DM [Association of some other genes including osteopontin (rs1126772 polymorphism), integrin and T1DM , 29.α and diabetes was investigated in 101 subjects including MODY subjects, their relatives, and healthy controls [In this category only one study was found  and the controls . The stuIn this subgroup 42 studies were assessed and all of them were designed as case control association studies , 70–75 eP = 0.045) [P = 0.008) [P = 0.014) [Association between two polymorphisms of TCF7L2 including rs7903146 (C/T) and rs12255372 (G/T) was assessed in three studies , 48, 53.= 0.045) . HoweverInvestigating the association of calreticulin with T2DM in 650 subjects showed two mutations, only in case group, 9 bp deletion of 397–399 codons and G>T mutation at IVSII-142 [α and its PvuII and XbaI polymorphism with T2DM in two studies was assessed [ PvuII and XbaI polymorphisms with T2DM was observed  [P = 0.001 and P = 0.026, resp.) [Association of estrogen receptor assessed , 49. In , resp.) . In anotγ with T2DM was investigated in three studies [P = 0.003) [P < 0.001 and P = 0.003, resp.). However in the third study no significant association was observed between Pro12Ala polymorphism of PPARγ and T2DM [Association of Pro12Ala polymorphism of PPAR studies , 69, 75.= 0.003) , 75. Ala= 0.003)  and nega ApoAI with T2DM was investigated in two studies [ MSPI polymorphism showed no significant association with T2DM [ ApoAI was not associated with T2DM while a significant association was found between C+83T polymorphism and T2DM (P = 0.028) [Association of different polymorphisms of studies , 72. In ith T2DM . In anotP = 0.006) and negative association of GG carriers (P = 0.01) was found between diabetic patients and healthy controls [P = 0.009) [Two studies assessed the association of −156G>C polymorphism of CXCL5 with T2DM , 65. In controls  and in a= 0.009) .P = 0.04) [Adiponectin and its association with T2DM were investigated in two studies , 73. In In one study that investigated insulin receptor gene, the following mutations were found only in T2DM: 511C>A, 514T>G, 586, and 628T>A on exon 2, 694G>C, 680G>A on exon 3, 1627A>T on exon 8, AT>TG on intron 9, 2007C>C/T on exon 9, 2595C>C/T and 2669G>C/G on exon 13, 2706 and 2717C>G, 2752C>T, and 2753C>G on exon 14, and 3471T>A and 3516T>G on exon 19. These mutations were not seen in control subjects [Other variants which had significant association with T2DM included haptoglobin , leptin (G-2548A polymorphism), paraoxonase 2 (Ser311Cys polymorphism), GST (glutathione-S-transferase) M1 and GSTM1/GSTT1 interaction, calpain-10 (SNP (single nucleotide polymorphism) 43), IRS-1 (G972R polymorphism) and IRS-2 (G1057D polymorphism), VDR (vitamin D receptor) (TaqI polymorphism), KCNJ11 (E23K polymorphism), eNOS  VNTR (intron 4 a/b polymorphism), resistin (−420C/G polymorphism), and ACE (Insertion/Deletion) , 64, 70.α , GLP-1R (glucagon-like peptid 1 receptor) (Thr149Met polymorohism), SLC30A8 (Arg325Trp polymorphism), GSTP1 , glucokinase (−30G/A polymorphism), SDF-1β  (G801A polymorphism), ApoE (apolipoprotein E), ENPP1 (ectoenzyme nucleotide pyrophosphate phosphodiesterase 1) (K121Q polymorphism), SUMO4  Met55Val polymorphism), MTHFR (C677T polymorphism), UCP2 (uncoupling protein 2) (−866G/A polymorphism), 5HTTLPR, IL-4 (−590C/T polymorphism), IFN-γ (interferon γ) (+874T/A polymorphism), CCR5 (C-C chemokine receptor type 5) (δ32mutation), HFE (hemochromatosis gene) /−51delA, −451A>G, −467T>C, −1023C>A, −1045G>A, −1286 3 bp del ACA, −1291 9 bp del CTAGACTAA polymorphisms) were not significantly associated with T2DM [In contrast to above variants, CTLA4 (+49A/G polymorphism), HNF-1ith T2DM , 74.In this subgroup, four studies were assessed and all were designed as case-control association studies. Three studies used PCR-RFL , 78, 79 P = 0.032) and Ala allele carriers of Pro12Ala polymorphism of PPARγ (P = 0.036) with T2DM [FokI polymorphism) (P = 0.02) and negative association of 148insG carriers of PTPN1 (148insG polymorphism) (P = 0.041) with insulin resistance index [The studies assessed in this subgroup showed a positive association of TG carriers of +45T/G polymorphism of adiponectin  [Paraoxonase 1 (163T/A polymorphism) was the only variant in this subgroup which was not significantly associated with atherosclerosis risk in T2DM . Investi < 0.05) . TaqI B allele in 400 subjects showed that pooling of B1B1+B1B2 and B1B1 genotypes had significant association with T2DM and CAD (P < 0.01). On the other hand assessing the G894T polymorphism of eNOS showed positive significant association between TG and TT carriers and CAD (P < 0.05). It was also shown that concomitant presence of NOS3 T allele and CEPT B1 allele was significantly associated with T2DM (P = 0.004) and CAD (P = 0.002) [Investigating B1 and B2 alleles of CETP= 0.002) .P < 0.001) [P < 0.05) [Investigation of apolipoprotein E  alleles showed the association of E2 and E4 alleles with CAD (< 0.001) , 87. AlsP = 0.023 and 0.033, resp.) [P = 0.008) [Adiponectin +276G/T and +45T/G were significantly associated with CAD   while in= 0.008) .P = 0.01 and P = 0.009, respectively [In addition A1166C polymorphism of AT1R (angiotensin I receptor) and −420C/G polymorphism of resistin in diabetic patients with CAD revealed significant association with diabetes, ectively , 85.P = 0.026) [Another study showed insertion(I)/deletion(D) polymorphism of angiotensin converting enzyme (ACE) DD genotype was significantly associated with higher blood pressure (= 0.026) .Factor V Leiden (G1691A polymorphism), prothrombin (G20210A polymorphism), and MTHFR (methylenetetrahydrofolate reductase) (C677T polymorphism) were the variants which were not significantly associated with CAD and T2DM in this subgroup .All of 15 studies in this subgroup were designed as case-control association studies –106. In P < 0.05) [Studying the association of 163A/G polymorphism of SUMO4 showed a positive significant association between AA carriers and diabetic nephropathy ( < 0.05) .P = 0.01, P = 0.02, resp.) [P = 0.035) [Studying the interaction of eNOS/4a/b and G894T revealed positive significant association between 4a or 894T allele carriers and macro- and microalbuminuria  . It was = 0.035) .P < 0.05) was shown in this study [It has also been shown that interaction of eNOS (G894T polymorphisms) and MTHFR (C677T and A1298C polymorphisms), eNOS T/1298 C, and eNOS T/677 T carriers had positive significant association with macroalbuminuria. In addition significant association of eNOS GT+TT carriers with lipid profile (is study .P < 0.001). Positive significant association when pooling CT+TT genotypes and 677T/1298C was also found with microalbuminuria (P < 0.001) [P = 0.035) and ACE D/1298C (P = 0.012) genotypes with macroalbuminuria [C677T and A1298C polymorphisms of MTHFR were also investigated in another study revealing that 677T, 1298C, and 677T/1298C carriers were significantly associated with macroalbuminuria (< 0.001) . Investiuminuria .P < 0.01) between DD carriers and progression but not development of albuminuria was observed [P = 0.006) but not nephropathy was revealed [ACE  polymorphisms were investigated in three studies. In one study positive significant association  [P < 0.001) [Association of interleukins including IL-4 and IL-10 with diabetic nephropathy was also investigated in two studies. Study of −592C/A polymorphism of IL-10 revealed positive significant association between CC carriers and nephropathy (= 0.001)  and stud< 0.001) .TaqI polymorphism) [ ApaI polymorphism of VDR was not significantly associated with diabetic nephropathy [Other significant associations between variants and diabetic nephropathy included AT2R (angiotensin II receptor) (−1332G/A polymorphism), VEGF (vascular epithelium growth factor) (+405G/C polymorphism), and VDR (orphism) , 95, 102All of the 3 studies in this subgroup were conducted as case-control association studies –108.P < 0.05) [Investigating null/positive genotype of GSTM1 in a study, which used ARMS-PCR for genotyping, revealed that null genotype is significantly associated with diabetic retinopathy ( < 0.05) . This re < 0.05) , althoug < 0.05) .P = 0.005) [Investigating +405G/C polymorphism of VEGF also revealed positive significant association between GG carriers and diabetic retinopathy (= 0.005) .P = 0.03) was observed. But no significant association was found between −7C/T of VEGF and DFU [In this subgroup only one study was found  which wa and DFU .Diabetes mellitus is the eighth most frequent disease leading cause of death throughout the world and now ranks the fifth, following communicable diseases, cardiovascular disease, cancer, and injuries . PrevaleType 2 diabetes is the most frequent type of diabetes mellitus , 111. MuMTHFR is another important gene in association with T2DM and other related complications. No association of C677T polymorphism of MTHFR gene was found in Africans, Asians, and Caucasians . MTHFR iInterleukins especially IL-10 are shown to have significant association with T2DM in different ethnic groups. Significant association between −592C/A and −819C/T polymorphisms of IL-10 and T2DM risk in Africans was shown . Also −1Investigation of different polymorphisms of adiponectin and their association with T2DM in a meta-analysis study revealed −11391G>A and −11426A>G polymorphisms of adiponectin as risk factor for T2DM in Europeans and −11377C>G variant of adiponectin as risk factor of T2DM in Europeans and Asians . It was Among candidate genes in association with T2DM, TCF7L2 is one of the strongest genes related to diabetes. In a meta-analysis study after pooling all data of European, African, and Asian populations, it has been revealed that rs12255372 polymorphism of TCF7L2 significantly increases the risk of T2DM. However no data from Iranian population as a type of Asian population was included in this meta-analysis . In lineγ is found to be as a protective variant especially in Asian population although the results were highly heterogeneous [Pro12Ala polymorphism of PPARogeneous . In our ogeneous  while inogeneous , 75. The BsmI and FokI polymorphisms of VDR increased the risk of T1DM in East and West Asians, respectively [ BsmI was shown to be associated with T1DM [ FokI was not associated with T1DM in our study in contrast to previous studies which might be due to difference in ethnicity and genetic background or insufficient clinical data [Type 1 diabetes mellitus is another type of diabetes in which HLA (human lymphocyte antigen), IR1R1 (interleukin-1 receptor type 1), CTLA-4, and VDR are some important genes studied in association with T1DM . VDR is ectively . In our ith T1DM  while inith T1DM . FokI wacal data , 26.Among diabetic complications, CAD and DN are the most studied complications. Meta-analysis studies showed that rs2010963 and rs3025039 polymorphisms of VEGF, 4b/a, T-786C, and G894T polymorphisms of eNOS and ACE are associated with DN –123. In γ, TCF7L2, ACE, TNF-α, adiponectin, and IRS1 [The most investigated genes in association with CAD include PPARand IRS1 . In our and IRS1 .Overall it seems that more studies are needed to identify diabetes susceptibility genes in Iranian population. Investigation of candidate genes is one way to understand these genes, but the method with the least expenses and error is GWAS which scans a set of loci in association with a disease in many people. GWAS in different populations such as Americans, Caucasians, Australians, West Africans, and Europeans revealed multiple loci in association with T2DM –128. In However, there are some strength and some limitations in our study. Firstly, this systematic review, for the first time, assessed the association between genetic variants and diabetes in Iranian population. Moreover, the studies included in this systematic review were assessed for quality and selected as high quality (scored ≥ 3). For limitations it should be considered that all included studies were observational, which does not allow reliable inferences about causality. Moreover due to methodological heterogeneity, we were not able to pool the data and perform the meta-analysis.α gene had significant association with MODY. The following genes showed significant association with T2DM: haptoglobin, paraoxonase, leptin, TCF7L2, calreticulin, ERα, PPAR-γ2, CXCL5, calpain-10, IRS-1 and 2, GSTM1, KCNJ11, eNOS, VDR, resistin, INSR, ACE, ApoA-I, adiponectin, and PTPN1. In assessment of association between CAD and diabetes in Iranian population the following genes showed significant association: paraoxonase 1, adiponectin, eNOS, CETP, AT1R, resistin, MMP-3, BChE K, Apo E, ACE. The following genes had significant association with diabetic nephropathy: eNOS, AT2R, SUMO4, IL-10, VEGF, MTHFR, ACE, and VDR. The following genes had significant association with diabetic retinopathy: GSTM1 and VEGF and also VEGF had significant association with diabetic foot ulcer.Our study showed significant association between CTLA-4, IL-18, VDR, TAP2, IL-12, and CD4 genes and T1DM. HNFInsufficient data might cause the conflicting results; therefore GWAS on defined population with large sample size is suggested as a more comprehensive approach answering many more questions.


Background: Multiple studies indicate that the matrix metalloproteinase-9 (MMP-9)-1562C>T gene polymorphism may be associated with an increased risk of coronary artery disease (CAD) in the Chinese Han population. However, a clear consensus has yet to be established.Objective and methods: A meta-analysis of 5468 subjects from 10 separate studies was performed to explore the possible relationship between the MMP-9-1562C>T gene polymorphism and CAD within the Chinese Han population. Pooled odds ratio (ORs) for the association and the corresponding 95% confidence intervals (CIs) were evaluated by a random or fixed-effect model.Results: Our analysis confirms the association between the MMP-9-1562C>T gene polymorphism and an increased risk of CAD within the Chinese Han population under allelic , recessive , dominant , homozygous , heterozygous , and additive genetic models .Conclusions: In the Chinese Han population, the MMP-9-1562C>T gene polymorphism is correlated with an increased risk of CAD. Therefore, Han Chinese carriers of the -1562T allele may be at an increased risk of CAD. Coronary artery disease (CAD) is a chronic condition with both hereditary and environmental factors. The increasing prevalence of unhealthy lifestyles in China , the general aging of the Chinese population, and the increasing rates of hypertension and diabetes have damaged the quality of life of many Chinese people and sharply increased CAD-associated morbidity and mortality Li, . HoweverMMP-9  is one the most extensively researched MMPs and exhibits enhanced expression in atherosclerosis injury sites. It has been also found that there were many gene sequence variations in MMP-9 gene, of which the locus rs3918242 (-1562C>T) in the promoter region was the most reported gene locus.Matrix metalloproteinases (MMPs), a large family of zinc-dependent proteolytic enzymes that have special functions in extracellular matrix (ECM) degradation have been a particular rich area of research. MMPs play a role in multiple pathophysiological processes such as ECM degradation, inflammation response, tumor metastasis, and atherosclerosis  for thymine (T). This mutation may increase MMP-9 gene expression and risk of CAD development by reducing the binding affinity with transcription inhibition proteins.MMP-9-1562C>T gene polymorphism and CAD have been performed in China, the composite of these studies fail to provide a consensus. In 2005, Tang et al found that MMP-9-1562C>T gene polymorphism was significantly associated with CAD in a Zhejiang population and T allele increased the CAD risk  diagnose CAD according to the clinical symptoms combined with examination results  with a minimal stenosis rate of the major coronary artery diameter of more than 50% (c) be a case-control or cohort study published in an official journals or as a postgraduate dissertation.To meet our inclusion criteria, studies had to (a) evaluate the association between Data was extracted according to a standardized protocol. Two investigators searched for duplicates while a third served as an arbiter to resolve possible disagreements. Duplicate papers, those that violated the inclusion criteria, or those that provided deficient data were removed. Identical data sets used in different studies by the same authors were used once. Abstracted data consisted of the following items: the first author's name, publication year, region, number of genotypes, genotyping method, study design, age, gender, and total number of cases and controls.MMP-9-1562C>T gene polymorphism and CAD. The Chi-square-based Q-test was adopted to measure the effects between-studies heterogeneity (P < 0.05 level)   and its corresponding to 95% confidence interval (CI) were used to measure the association between Cochran, . VariatiP < 0.05). Potential publication bias was assessed by Egger′s linear regression test on the natural log scale of the OR to detect funnel plot asymmetry (P < 0.05 level)  , recessive , dominant , homozygous , heterozygous , and additive genetic models . , dominant , heterozygous  and additive genetic models . Subsequent meta-regressions explored the source of this heterogeneity under their respective genetic models.There was also significant heterogeneity under the allelic (P = 0.006), CT sample size of CAD group , TT sample size of CAD group , CC sample size of control group , total sample size of control group , and weight (%) (P = 0.030)were possible confounding factors that could partially explain heterogeneity between studies.Under the allelic genetic model, CC sample size of CAD group , CT1 (P = 0.012), and TT1 (P = 0.016) were the confounding factors. In the allelic and additive genetic models, CT1 plays a central role in explaining the source of heterogeneity. According to CT1, the whole population was separated into two subgroups. The studies with CT1 < 30 were grouped into subgroup 1 and the residual studies with CT1 ≥ 60 belonged to subgroup 2.Under the additive genetic model, CC1  . No significant heterogeneity was fond in subgroup 1 , but significant heterogeneity was detected in subgroup 2 . This identifies CT1 as the primary confounding factor under the allelic and additive genetic models , CT1 (P = 0.009), TT1 (P = 0.009), CC sample size of control group , CT sample size of control group , TT sample size of control group , and weight (P = 0.001) could partly explain the heterogeneity source. In a subgroup analysis stratified by CC0, significant increased CAD risk was observed in both subgroups . Although heterogeneity was still detected in both subgroups, it was significantly reduced in subgroup 2 , suggesting that CC0 was the main confounding factor , total sample size of CAD group , and CT0 (P = 0.004) could partly explain the heterogeneity. In a subgroup analysis stratified by T1, significant increase in CAD risk was detected in both subgroups . No significant heterogeneity existed in subgroup 1 any longer , but significant heterogeneity was still observed in subgroup 2 .The publication bias of the studies was evaluated by funnel plot and Egger's test. There was no visual publication bias in the funnel plot Figure . No statMMP-9-1562C>T gene polymorphism and CAD in the Chinese Han population under allelic (OR: 1.60), recessive (OR: 3.05), dominant (OR: 2.23), homozygous (OR: 3.41), heterozygous (OR: 2.03), and additive genetic models (OR: 1.78). Hence, it has been concluded that in Chinese Han population, the MMP-9-1562C>T gene polymorphism may be associated with the increased CAD susceptibility among Han Chinese.In the present meta-analysis, we found a significant association between MMP-9-1562C>T gene polymorphism and CAD? The meta-regression used to reveal the source of the heterogeneity detected under allelic, dominant, heterozygous and additive genetic models (Pheterogeneity < 0.05) suggests that patient number may have been the confounding factor. In the heterogeneity source analysis, CT1 was possibly indicated to be the main heterogeneity source under allelic and additive genetic models. Although the subgroup analysis stratified by CT1 showed a significantly increased risk of CAD in both subgroups, only one subgroup exhibited heterogeneity. Hence, CT1 was the main confounding factor contributing to the heterogeneity under the allelic and additive models. Similarly, T1 and CC0 were major confounding factors under heterozygous and dominant models, respectively. CT1, T1, CC0 may be better matched between the CAD and control groups under these genetic models.What contributed to the recent controversy over the association between Sensitivity analysis showed that our meta-analysis was most sensitive to the Wu et al study. Although the pooled analysis result without Wu et al study was different from the original result , and endothelial cells. The relative molecular weight of MMP-9 is 92KD. In its active form its molecular weight is 84KD. MMP-9 can degrade extensive ECM substrates, including Type IV collagen, which plays a key role in the revascularization, inflammation response, and atherosclerosis progression. Research has shown an increased MMP-9 expression level in the atherosclerotic arteries of human and animals compared to normal arteries. The MMP-9 degradation activity was most located in the shoulder regions of plaque, the lipid core margin, and micro-vessels formation regions. This suggests that MMP-9 may be associated with the coronary artery plaque stability and myocardial infarction , a potential binding site for transcription inhibition proteins (Zhang et al., MMP-9-1562C allele was replaced by -1562T allele (Cho et al., MM9 is regulated primarily at the transcriptional level. The MMP-9 expression may contribute CAD development through a number of pathways. It may promote the VSMCs proliferation and migration, promote the injured vascular remodeling, and/or promote the plaque rupture and lead to the thrombosis, resulting in the acute coronary syndrome known as myocardial infarction (Galis et al., Increased MMP-9-1562C>T gene polymorphism and CAD (Li et al., Past meta-analyses on the association of MMP-9-1562C>T gene polymorphism and CAD. The CAD susceptibility is also influenced by environmental factors, such as smoking, diabetes, dyslipidaemia, air pollution, inflammation, and psychological factors (Wang et al., MMP-9-1562C>T gene polymorphism interact with a risk factor that was not within the scope of this study. There are also many other MMP-9 gene polymorphisms as P574R, R+279Q, and R668Q that influence the MMP-9 serum level (Zhi et al., However, this meta-analysis is not without limitations. The large-scale studies present in the analysis were not adequate to fully elucidate the complex relationship between the MMP-9-1562T allele may increase the CAD risk among the Chinese population. This result has the potential to guide the therapy strategy for a CAD patient. Taking into account the limitations mentioned above, it remains necessary for these results to be verified by future studies.In conclusion, the current meta-analysis indicates that the YL researched data. YL and CZ wrote manuscript, researched data. YL, YZ, XY, HK, and GG reviewed/edited manuscript. YL, HG, and YQ contributed to discussion, reviewed/edited manuscript. YL, JW, and XW researched data, contributed discussion.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The VEGF in low oxygen conditions are reported to prolong the survival of malignant cell, and thus this gene has a critical role in tumor growth and invasion as well as development of malignant tumor. We aimed to assess the association between the six common SNPs and the risk of osteosarcoma, and their association with environmental factors.176 subjects with osteosarcoma and 176 gender- and sex-matched healthy control individuals were enrolled into our study. The VEGF -2578C/A, -1156G/A, +1612G/A, +936C/T, -634G/C and -460T/C gene polymorphisms were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay according to manufacturer’s instructionsBy conditional logistic regression analysis, AA and CA+AA genotypes of VEGF -2578C/A were associated with significant increased risk of osteosarcoma compared with CC genotype, and the ORs(95%CI) were 2.32(1.18-4.60) and 1.68(1.07-2.64), respectively. Moreover, individuals with CC and TC+CC genotypes of VEGF-460T/C had significant increased risk of osteosarcoma compared with those carrying with the TT genotype, and ORs(95%CI) were 2.15(1.10-4.21) and 1.60(1.0-2.58), respectively. By stratified analysis, we did not find statistically significant associated between VEGF -2578C/A and -460T/C gene polymorphisms and cancer risk by stratification analysis.Our results suggested that VEGF -2578C/A and -460T/C gene polymorphisms may be association with an increased risk of osteosarcoma. Osteosarcoma is the most common type of primary bone cancer, and this cancer is a malignant tumor arising from mesenchymal tissues. Osteosarcoma mostly occurs in the long bones of the body, such as distal and proximal tibia and proximal humerus.9It is well known that vascular endothelial growth factors (VEGF), a potent angiogenic growth factor, plays an important role in altering proliferation to inflammatory and ischemic processes.The VEGF in low oxygen conditions are reported to prolong the survival of malignant cell, and thus this gene has a critical role in tumor growth and invasion as well as development of malignant tumor.In the present hospital-based case-control study, 176 subjects with osteosarcoma and 176 gender- and sex-matched healthy control individuals were collected from the Department of Orthopedics of Beijing Hospital between May 2011 and December 2013. The osteosarcoma patients were newly diagnosed and histologically confirmed by two pathologists. The control subjects were randomly selected from a pool of individuals who were attending a clinic for routine examination during the same period. The controls were frequency matched to the cancer cases by age and gender, and the control subjects were free from any cancer or other chronic disease, and unrelated to the patients.The written informed consent before participating into this study was obtained from all study participants, and this study was approved by the ethics committee of the Department of Orthopedics of Beijing Hospital.The general demographic and clinical characteristics of osteosarcoma cases and control subjects were collected from medical records, including age, gender, family history of cancer, tumor location, therapy and stage of tumor.Peripheral venous blood was collected from each osteosarcoma case and control subject. According to the manufacturer’s instructions, genomic DNA was extarcted from collected peripheral blood mononuclear cells using TIANamp Blood DNA Kit . The VEGF -2578C/A, -1156G/A, +1612G/A, +936C/T, -634G/C and -460T/C gene polymorphisms were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay according to manufacturer’s instructions . The PCR primers of VEGF -2578C/A, -1156G/A, +1612G/A, +936C/T, -634G/C and -460T/C were designed by Sequenom Assay Design 3.1 software . The PCR reaction conditions were as follows: 95 °C for one minute, then 40 cycles of 95 °C for 20 sec, 60 °C for 1 min and 72 °C for 1 min, and a final extension step at 72 °C for 10 min. The digested PCR products were visualized by ultraviolet (UV) light.2-test. The Hardy–Weinberg equilibriums of VEGF -2578C/A, -1156G/A, +1612G/A, +936C/T, -634G/C and -460T/C genotype frequencies in controls were tested using goodness-of-fit χ2-test. The odds ratio (OR) and their corresponding 95% confidence intervals (CI) for the association between the six VEGF gene polymorphisms and osteosarcoma risk were assessed by conditional logistic regression. Interaction between genotypes of the six VEGF gene polymorphisms and general demographic characteristics was assessed by conditional logistic regression. All P-values were two sided, and a P-value less than 0.05 was considered as statistical significant. All analyses were performed using SPSS version 16.0 statistical software .Comparison of general demographic and clinical characteristics between groups was performed using χSelected demographic and clinical characteristics of the osteosarcoma patients and controls are shown in P>0.05), but the genotype frequencies of +936C/T were not (P<0.05). By conditional logistic regression analysis, AA and CA+AA genotypes of VEGF -2578C/A were associated with significant increased risk of osteosarcoma compared with CC genotype, and the ORs(95%CI) were 2.32(1.18-4.60) and 1.68(1.07-2.64), respectively. Moreover, individuals with CC and TC+CC genotypes of -460T/C had significant increased cancer risk of osteosarcoma compared with those carrying with the TT genotype, and ORs(95%CI) were 2.15(1.10-4.21) and 1.60(1.0-2.58), respectively. However, no significant association was found between -1156G/A, +1612G/A, +936C/T and -634G/C and osteosarcoma risk in multivariate logistic regression analysis.The association of VEGF -2578C/A, -1156G/A, +1612G/A, +936C/T, -634G/C and -460T/C with risk of osteosarcoma are shown in We assessed the association between VEGF -2578C/A and -460T/C gene polymorphisms and risk of osteosarcoma stratified by age, gender and family history of cancer . HoweverIt is reported that many environmental and genetic factors can influence the individuals susceptibility to the carcinogenesis of osteosarcoma.15Several case-controls studies have reported the association of functional polymorphisms in VEGF with increased risk of several tumors, including osteosarcoma.For the association between VEGF gene polymorphisms and development of osteosarcoma, three previous studies have reported their association.Two limitations should be considered in this study. First, the cases and controls were selected from on hospital, and distributions of VEGF +936C/T gene polymorphism in controls were not in line with Hardy–Weinberg equilibrium. The cases and controls may not represent the entire general population. Second, the small sample size of this study may limit the statistical power to find the difference between groups. Therefore, further studies with more different populations and larger sample size could help to verify the role of VEGF gene polymorphisms in the development of osteosarcoma.In this case-control study, our results suggested that VEGF -2578C/A and -460T/C gene polymorphisms may be associated with an increased risk of osteosarcoma. Further large sample studies are greatly needed to confirm these associations.


Studies have reported inconsistent results concerning the existence of associations of folate intake and serum folate levels with prostate cancer risk. This study sought to summarise the evidence regarding these relationships using a dose–response meta-analysis approach.In January 2014, we performed electronic searches of PubMed, Embase, and the Cochrane Library to identify studies examining the effect of folate on the incidence of prostate cancer. Only prospective studies that reported effect estimates with 95% confidence intervals (CIs) of the incidence of prostate cancer for more than 2 categories of folate were included.Overall, we included 10 prospective studies reporting data on 202,517 individuals. High dietary folate intake had little or no effect on prostate cancer risk . The dose–response meta-analysis suggested that a 100 μg per day increase in dietary folate intake has no significant effect on the risk of prostate cancer . However, high serum folate levels were associated with an increased risk of prostate cancer . The dose–response meta-analysis indicated that a 5 nmol/L increment of serum folate levels was also associated with an increased risk of prostate cancer .Our study indicated that dietary folate intake had little or no effect on prostate cancer risk. However, increased serum folate levels have potentially harmful effects on the risk of prostate cancer.The online version of this article (doi:10.1186/1471-2458-14-1326) contains supplementary material, which is available to authorized users. Prostate cancer is the second most common non-skin cancer among men globally, and with markedly higher incidence rates in developed countries, 2. OverThe results of a previous prospective study indicateIn 2012, Wien used a sIn this study, we attempted a large-scale examination of the available prospective studies to determine the association between dietary folate intake or serum folate levels and prostate morbidity. We also performed a dose–response meta-analysis to quantify the risk of prostate cancer associated with incremental increases in dietary folate intake and serum folate levels for the general population.This review was conducted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Statement issued in 2009 , with no language restrictions for studies in humans. We included all studies investigating an association between dietary folate intake or serum folate levels and prostate cancer incidence. Our core search included the following terms: (“folate” OR “folic acid”) AND (“prostate cancer” OR “prostate neoplasm” OR “prostate carcinoma”) AND (“cohort” OR “cohort studies” OR “nest case–control studies”). If a site-specific dataset had been published more than once, we used the most recent publication. We reviewed the reference lists of the identified reports, reviews, meta-analyses, and other relevant publications to find additional pertinent studies. The medical subject heading, methods, population, study design, exposure, and outcome variables of these articles were used to identify relevant studies.A study was eligible for inclusion if the following criteria were met: (1) the study had a prospective observational design (prospective cohort or prospective nested case–control study); (2) the study investigated the association between dietary folate intake or serum folate levels and the risk of prostate cancer; and (3) the authors reported effect estimates  and 95% confidence intervals (CIs) for comparisons between high and low dietary folate intake or serum folate levels (with more than 2 categories). We excluded all retrospective case–control studies because various confounding factors could bias the results.The literature search was independently undertaken by 2 authors (RW and YZ) using a standardised approach. Any inconsistencies were resolved by discussion with the primary author (YHZ) and a consensus was reached.The following data elements were collected: name of the first author or study group, publication year, country, study design, assessment of folate levels, sample size, age at baseline, effect estimate, comparison categories, follow-up duration, and covariates in the fully adjusted model. We also extracted the numbers of cases per person or per person-year, effect of the different exposed categories, and 95% CIs. For studies that reported several multivariable adjusted RRs, we selected the effect estimate that was maximally adjusted for potential confounders.The Newcastle-Ottawa Scale (NOS) was used to evaluate methodological quality, 20. The2 statistic to measure the proportion of total estimate variation that was attributable to study heterogeneity; I2 values of 25%, 50%, and 75% were used as cut-off points for low, moderate, and high degrees of heterogeneity, respectively[We examined the relationship between dietary folate intake or serum folate levels and the risk of prostate cancer based on the effect estimate  and its 95% CI published in each study. We first used the random-effects model to calculate summary RRs and 95% CIs for the highest folate levels compared to the lowest folate levels, 22. We ectively. Subgrouectively. Severalectively and Beggectively were alsThe results of the study selection process are shown in Figure Five prospective cohort studies–12 invol2 = 0.0%; P = 0.959). The findings of the dose–response meta-analysis also suggested no association between the risk of prostate cancer and a 100 μg/day increment of dietary folate intake  different cooking methods may moderate the effect of dietary folate intake and (2) different types of prostate cancer might provide a biased view of the study question. Previous studiesSubgroup analyses indicated that the harmful effect of increased serum folate levels was more evident in studies with follow-up periods of less than 15 years than in those with longer follow-up periods. The reason for this difference could be that studies with longer follow-up periods (greater than 15 years) did not reach statistical significance owing to the low incidence of prostate cancer. This conclusion may be unreliable because smaller cohorts were included in each subset. Similar explanations may apply to subgroup analyses based on other potential biases factors.Two strengths of our study compared with previous meta-analyses should be highlighted. First, only prospective studies were included, which should eliminate selection and recall bias. Second, the dose–response analysis included a wide range of dietary folate intake levels and statuses, which permitted an accurate assessment of the dose relationship between dietary folate intake or status and prostate cancer risk.The limitations of our study are as follows: (1) publication bias is possible in meta-analyses of published studies; (2) data on prostate cancer type were not available, and thus, we could not differentiate the effects of dietary folate intake or status by prostate cancer type; and (3) the analysis used pooled data , which restricted us from performing a more detailed relevant analysis and obtaining more comprehensive results.In conclusion, the findings of this study suggest that increased dietary folate intake was not associated with prostate cancer risk. However, increased serum folate levels were associated with an increased risk of prostate cancer. These findings need to be confirmed in future studies. Future studies should (1) ascertain the specific type of prostate cancer and analyse effects by type, (2) consider the effects of the cooking method when assessing dietary folate intake and its effects on clinical outcomes, and (3) consider the effects of alcohol consumption and smoking status.Checklist S1. PRISMA Checklist. (DOC 70 KB)Additional file 1:Additional file 2: Table S1: Quality scores of prospective cohort studies using Newcastle-Ottawa Scale. (DOC 44 KB)


To explore the association between maternal alcohol consumption and/or binge drinking and congenital heart defects (CHDs), we conducted a meta-analysis for more sufficient evidence on this issue.We searched Medline, EMBASE, and the Cochrane Library from their inceptions to December 2014 for case-control and cohort studies that assessed the association between maternal alcohol consumption and CHD risk. Study-specific relative risk estimates were calculated using random-effect or fixed-effect models.A total of 19 case-control studies and 4 cohort studies were included in the meta-analysis. We observed a null association between maternal alcohol consumption during pregnancy and the risk of CHDs. Even in the analysis of different trimesters of pregnancy, we found little association between the two.This meta-analysis suggests that maternal alcohol consumption is modestly not associated with the risk of CHDs. However, further investigation is needed to confirm this conclusion. Congenital heart defects (CHDs) are the most common group of congenital malformations, affecting nearly 1 % of live births throughout the world . AlthougA number of chromosomal anomalies, certain maternal illnesses, and prenatal exposures to specific therapeutic drugs are recognized risk factors. It is difficult to establish the role of a single factor because in many cases, the cause of a defect is believed to be multifactorial, including environmental teratogens with genetic and chromosomal conditions . Maternaet al.  where P0 stands for the incidence of CHDs [The corresponding risk estimates (including RRs and ORs) and 95 % CIs were extracted from each study for CHDs overall, CHD subtypes and the period of maternal alcohol consumption during pregnancy. We selected the main confounder-adjusted RRs or ORs whenever possible. Otherwise, unadjusted effect estimates were extracted from each study. We conducted meta-analyses for specific CHD subtypes  if at least two studies had available data. The RRs were used as the common measure of association across studies. ORs were transformed into RRs according to the formula RR = OR/[. We calculated summary RR estimates and 95 % CIs using both fixed- and random-effects models for CHDs overall and for the CHD subtypes.Q and I2 statistics [P < 0.05 or I 2≧ 50 %), we used a random-effects model, which provided a more appropriate summary effect estimate between heterogeneous study-specific estimates. If the Cochran Q and I2 statistics showed no evidence of heterogeneity, we used a fixed-effects analysis, applying inverse variance weighting to calculate summary RR estimates [We first tested for heterogeneity across studies using Cochran atistics . If therstimates .Meta-analyses of total maternal alcohol consumption and binge drinking were both included. Subgroup analysis of CHDs was conducted by CHD subtype , study design (cohort and case-control studies), geographic region (Europe and America) and study adjustments . In the main analyses that examined the association between maternal alcohol consumption and the risk of CHDs overall, we calculated a summary effect estimate for CHDs overall limited to the studies that examined the association between maternal periconceptional drinking  and CHDs.P value of <0.05 for the two aforementioned tests was considered representative of significant statistical publication bias. All statistical analyses were performed using STATA .Publication bias was evaluated by generating funnel plots for a visual examination, conducting correlation and regression tests for significance, and using Egger’s linear regression  and BeggThe search strategy generated 4181 citations, of which 23 were identified in the final analysis  showed no evidence of publication bias for the period of maternal alcohol consumption during pregnancy. In the subgroup analyses by geographic region, we observed null results among both European  and North American  populations. In the adjustment models, we chose smoking as important, but unfortunately, a null result was found for smoking . Eight other studies were about the dose-response data on maternal alcohol consumption and risk of CHDs. It showed that with the increase of alcohol consumption, the corresponding risk of CHDs did not increase , although no publication bias was indicated from Egger’s test (P = 0.156) while Begg’s test (P = 0.037) indicated a publication bias , and as many as 54 % of live-born children with FAS present with some form of cardiac anomalies , e.g., sOur study has a number of strengths, including the large sample  used to estimate the effect of maternal alcohol consumption on CHDs as a group. Additionally, because the suspected heterogeneous etiologies can affect CHD risk during different times in pregnancy, we divided pregnancy into stages; still, no association was found in any of the stages. However, our study must also be considered in light of certain limitations. First, our analysis is limited to studies published in English. Evidence of publication bias was found, and there was heterogeneity in the component studies, which could have been attributable to study design, study populations, analytic strategies or other unknown factors. Second, we derived most of our data from case-control studies, which may be more prone to information bias than cohort studies. Third, the consumption quantity in each study varied, including times/week, drinks/week, drinks/occasion, etc. The highest and lowest intakes varied across studies, and the highest intake in one study could have been similar to the median or lowest intake in another, which could have biased the overall results. Additionally, based on the different methods that were used to assess and report alcohol consumption across studies, we established the dose-response relationship between alcohol consumption and CHDs. It showed that the risk of CHDs did not influence with the increase of alcohol consumption, even binge drinking. Fourth, because of our inability to fully adjust for various confounders, associations between alcohol consumption and CHDs could be attributed to other factors, such as maternal smoking, ethnicity, age, and education. Fifth, our analysis included a wide range of exposure periods, but heart anomalies develop during weeks 2–7 of gestation . We suspIn conclusion, our analysis indicates that maternal alcohol consumption has no association with CHD risk. However, the findings from our study need to be confirmed in future research in well-designed cohort or intervention studies. In addition, the underlying mechanisms call for further elucidation.Although its effects are modest, drinking is relatively common among women of reproductive age and could have important public health consequences. Young women continue to drink although the adverse effects of drinking on reproductive health are known, and some women continue to drink even after they learn that they are pregnant. Decreased maternal alcohol consumption during pregnancy would result in improved reproductive outcomes and could contribute to reduced infant mortality and morbidity.


RET/PTC rearrangements have been identified as a specific genetic event in papillary thyroid cancer (PTC). We conducted this meta-analysis to identify an enriched population who were more likely to occur RET/PTC fusion genes.All relevant studies in the PubMed, Web of Science, and Embase databases were searched up to June 2015. The studies found were screened according to our inclusion and exclusion criteria. All analyses were performed using STATA software.RET/PTC risk . Stratified analysis according to RET/PTC subtype and geographical area showed that this association was restricted to the RET/PTC3 subtype  in the Western population. In addition, age < 18 years, i.e., young age, was associated with higher prevalence of RET/PTC3 , especially in the radiation-exposure subpopulation . The association between female gender and RET/PTC1 risk was more significant in the PTC patients without radiation exposure .Eventually, 38 eligible studies comprising 2395 participants were included. Overall analysis indicated that radiation exposure contributed to increased RET/PTC3 and that female gender is associated with higher prevalence of RET/PTC1 in the subpopulation without radiation exposure. The RET/PTC status in combination with radiation exposure, age, and sex should be considered in the differential diagnosis of suspicious PTC.Both radiation exposure and young age are associated with increased risk of  RET proto-oncogene, referred to RET/PTC (the rearranged during transfection/papillary thyroid carcinoma tyrosine kinase) fusion genes, is one of the best-known mutations in papillary thyroid carcinoma (PTC) [RET/PTC is identified as a specific genetic event in patients with PTC, which forms the basis of differential diagnosis and novel therapeutic approaches to this disease [RET/PTC subtypes in different ethnicities and their correlation with the clinicopathologic features of PTC remains controversial and as yet are not routinely investigated in clinical practice.Rearrangement involving the ma (PTC) . RET/PTC disease . HoweverRET as a proto-oncogene that can be activated by interchromosomal rearrangement [RET rearrangement, of which RET/PTC1 and RET/PTC3 are the most common, resulting from the fusion of RET with H4 and of RET with RFG/ELE1 respectively [RET/PTCrearrangement risk. Accordingly, several studies have detected RET/PTC rearrangements more frequently in PTC in children than in adults [RET/PTC rearrangements was reported in radiation-induced PTC [RET/PTC rearrangement [The receptor tyrosine kinase RET plays a critical role in cell differentiation and proliferation, which is required for normal development of several tissues, especially in early embryogenesis . In 1985angement . Subsequectively , 7. As ruced PTC . In addiangement -13. To dRET/PTC1 or RET/PTC3 and radiation exposure, sex, age, and ethnicity.In this study, we aimed to identify an enriched population who were more likely to occur RET/PTC1 and RET/PTC3 fusion genes and to provide more useful information on candidate selection for PTC prevention, diagnosis, and treatment. Therefore, we performed this meta-analysis to investigate the association between the presence/absence of The article selection flowchart is depicted in Figure RET/PTC fusion gene in the original studies were detected by PCR combined with reverse transcription (RT), Southern Blot or fluorescence in situ hybridization (FISH). The included studies involved populations from different geographical regions, namely Asia, Europe, and America; therefore, we divided the studies into Asian and Western subgroups.The main characteristics of the studies included in this meta-analysis are summarized in Table RET/PTC from each original study (Table RET/PTC was relatively higher in the Western populations (42.19%) than in the Asian populations (36.73%). A similar tendency was observed for the RET/PTC1 subtype, whereas the Asian populations demonstrated a higher positive rate for the RET/PTC3 subtype (Asian vs. Western populations: 26.50% vs. 17.05%). In the Asian studies, the positive rates of RET/PTC3 in the studies by Lam et al. [RET/PTC3 that ranged from 0% to 20.79% [We also summarized the positive rates of dy Table . The ovem et al.  and Rao tions 36.3%. A simions 42.1% than ino 20.79% , 20-23.RET/PTC rearrangement . Stratified analysis according to geographical region decreased the heterogeneity slightly, and increased risk for RET/PTC rearrangement persisted in the Western subpopulation, demonstrating an increased OR of 3.97 .As radiation exposure is the best-known risk factor for PTC, we initially investigated the effect of radiation on nt Table . FourteeRET/PTC1 and RET/PTC3 subtypes were considered separately, radiation exposure conferred significantly higher risk for RET/PTC3 rearrangement .Different age effects have been observed in the development of PTC, and we therefore explored whether young age affected the penetrance of thets Table . In thist Figure  but peneRET/PTC rearrangement in patients with PTC. As suggested by the findings in Table RET/PTC status in the combined analysis. In subgroup analysis, a pooled analysis of 13 studies showed that female gender was associated with RET/PTC1 development in the subpopulation without radiation exposure. Female patients had 1.69-fold greater risk for RET/PTC1 rearrangement than male patients did . Only slight inter-study heterogeneity was observed in all of the above analyses .Females are more likely to develop PTC, therefore we investigated whether female gender increases the chance of RET/PTC1 and RET/PTC3 fusion genes demonstrated moderate heterogeneity. To explore the source of heterogeneity, subgroup analyses based on ethnicity and RET/PTC subtype were performed. Heterogeneity was decreased in the subgroup analysis and may be partly explained by the different ethnicities and RET/PTC subtypes  among homogeneous studies. For the effect of young age on RET/PTC rearrangement, the outlier studies appeared to be the studies of Smida et al. (1999)[2= 34.0%, Phet = 0.181), and similar estimates (OR = 1.10 vs. 1.53) were generated before and after these data were removed, indicating the relatively high stability of the results.Sensitivity analysis was also conducted to assess the influence of individual studies on the overall risk of i et al. , Nakazawi et al. , and Boui et al.  reportedl. (1999) and Hiebl. (1999). After rBegg's test and Egger's test were performed to quantitatively evaluate the publication bias of the studies; the results are listed in Table RET/PTC rearrangement were controversial. To our knowledge, this is the first meta-analysis evaluating the effect of radiation exposure, female gender, and young age on RET/PTC rearrangement. By performing the present meta-analysis, we found that radiation exposure contributed to increased risk of RET/PTC rearrangement, especially for the RET/PTC3 subtype. Young age was also associated with higher prevalence of RET/PTC3, and this association was more significant in the subpopulation exposed to radiation. Our pooled estimate also demonstrated an association between female gender and higher prevalence of the RET/PTC1 subtype in the subpopulation that had not been exposed to radiation. These results identify an enriched population of RET/PTC fusion genes in patients with PTC and provide novel insights into the utility of RET/PTC rearrangement in the differential diagnosis of suspicious PTC.Previous study results on the relationship between PTC-related risk factors and RET/PTC rearrangement. Our pooled estimates provide clear evidence that radiation exposure could be responsible for the difference in RET/PTC3 prevalence between sporadic and radiation-associated tumors, whereas the rate of RET/PTC1 prevalence was similar between the two groups. The corresponding pooled OR for RET/PTC3 was up to 8.30, and this association was evident in the Western populations. However, we could not derive a negative or null association in the Asian population because of a lack of original studies from the Asian region. There are valid reasons to believe that there is a causative link between radiation exposure and RET/PTC rearrangements. For example, Nikiforov et al. reported much higher RET/PTC3 prevalence in post-Chernobyl PTC than in subjects without radiation exposure [RET/PTC rearrangement, predominantly RET/PTC3, in thyroid cells, can be induced by ionizing radiation [RET/PTC rearrangement in thyroid cancer.Exposure to ionizing radiation is a well-known risk factor for thyroid cancer, particularly for papillary carcinoma , 49. Theexposure . In addiadiation . This maadiation , 51. ThiRET/PTC3 in PTC in young people. Our observations further indicate that young patients who exposed to radiation have higher RET/PTC3 risk than young patients who have not been exposed to radiation. Original studies have shown that RET/PTC3 is more common in children and adolescents compared to adults [RET/PTC3 was indicated as the most common form of rearrangement in radiation-associated childhood PTC [RET/PTC prevalence in young people [RET/PTC rearrangement remains inconclusive, which would require further validation. By setting a cutoff age of 18 years in this meta-analysis, the corresponding results may indicate the relatively low defense ability of children against pathogenic factors.The data synthesis in the present meta-analysis also demonstrated increased risk of o adults , 9. Whenhood PTC , 25, 52.g people . NeverthRET/PTC1 risk was more significant in patients who had not been exposed to radiation. For unknown reasons, thyroid cancer is three times more prevalent in women than in men [RET/PTC is an estrogen-dependent gene required for breast cancer cell growth [RET rearrangements.Concerning the impact of sex, we observed that the association between female gender and increased n in men . One posn in men . There il growth . The aboRET/PTC3 were from the Western countries, thus the generalizability of our conclusions is limited. In the future, more studies are needed to confirm this association in Asian regions. Third, only two common RET/PTC subtypes, RET/PTC1 and RET/PTC3, were considered in this study, mainly due to the limitation of current laboratory techniques for simultaneously detecting all RET/PTC subtypes.Nevertheless, this study has some limitations. First, although we included all available relevant articles in this meta-analysis, the sample sizes remain insufficiently large. Second, most studies in relation to the association between radiation exposure and RET/PTC3 rearrangement. In addition, female gender is associated with higher prevalence of the RET/PTC1 subtype in the subpopulation not exposed to radiation. We suggest that RET/PTC status in combination with radiation exposure, age, and sex should be considered when differential diagnoses are suggested for suspicious patients. Further large-scale studies concerning the relationship between radiation exposure and RET/PTC in the Asian population are required to confirm our meta-analysis results.In conclusion, both radiation exposure and young age, i.e., age < 18 years, are associated with increased risk of RET/PTC fusion gene and PTC up to June 2015. The published date of available articles in this study was from 1959 to 2015. The keywords used for the search were “RET/PTC”, “RET/PTC fusion gene”, or “RET/PTC fusion oncoproteins” in combination with “Thyroid Cancer”, “Thyroid Carcinoma”, “Thyroid Neoplasms”, or “Thyroid Papillary Carcinoma”. The references of the articles acquired were also searched manually to broaden the search. When there was overlapping data, only the largest and most recent study was selected for this meta-analysis. If the data presented in an article were unclear, we contacted the author for specific raw data.We searched the PubMed, Web of Science, and Embase databases for all articles on the association between the RET/PTC fusion gene and the clinicopathological features of patients with PTC was explored; (2) PTC diagnosis was made according to the pathology results; (3) studies were full-text articles; and (4) there was sufficient data for estimating an odds ratio (OR) with a 95% confidence interval (CI). The exclusion criteria were: (1) duplicate publication; (2) article was an abstract, comment, review, conference proceeding, or editorial; (3) insufficient data were reported; and (4) study was not in English or Chinese.Eligible studies had to meet the following criteria: (1) the association between the RET/PTC fusion gene; detection method; whether study subjects were children or adults; and clinicopathological features . The above information was carefully extracted by two independent investigators (Xuan Su and Zhaoqu Li). If the two investigators could not reach a consensus, the result was reviewed by a third investigator (Caiyun He).The following items were collected: first name of first author; year of publication; population of study; number of enrolled patients; frequency of RET/PTC and radiation exposure, age, and sex was estimated by OR and 95%CI. Two-sided P-values were evaluated in this meta-analysis, and P < 0.05 was considered statistically significant. The chi-square–based Q test and I2 statistic were used to assess the statistical heterogeneity among studies. For the Q statistic, P < 0.10 was considered statistically significant for heterogeneity. When there was heterogeneity, a random-effects model based on the DerSimonian and Laird method was used to calculate the pooled OR of each study [The strength of the association between ch study ; otherwich study . Publicach study , 60, whe


The association between epidermal growth factor (EGF) gene +61A/G polymorphism (rs4444903) and hepatocellular carcinoma (HCC) susceptibility has been widely reported, but the results were inconsistent. To clarify the effect of this polymorphism on HCC risk, a meta-analysis was performed.The PubMed, Embase, Cochrane Library, Web of Science, Chinese BioMedical Literature (CBM), Wanfang and Chinese National Knowledge Infrastructure (CNKI) databases were systematically searched to identify relevant studies published up to December 2013. Data were extracted independently by two authors. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to assess the strength of association.P < 0.001, 95% CI: 1.174-1.629; GG vs. GA + AA: OR = 1.484, P < 0.001, 95% CI: 1.198-1.838; GG + GA vs. AA: OR = 1.530, P < 0.001, 95% CI: 1.217-1.924; GG vs. AA: OR = 1.958, P < 0.001, 95% CI: 1.433-2.675; GA vs. AA: OR = 1.215, P = 0.013, 95% CI: 1.041-1.418). In the subgroup analyses by ethnicity, a significant association with HCC risk was found in Asian populations , European populations , respectively.A total of 16 studies including 2475 HCC cases and 5381 controls were included in this meta-analysis. Overall, a significantly increased HCC risk was observed under all genetic models  contains supplementary material, which is available to authorized users. Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer-related death worldwide . The estEpidermal growth factor (EGF) was first isolated in 1962 ,8. EGF iMeta-analysis offers a powerful means of overcoming the problems associated with small sample sizes, and particularly, of overcoming the inadequate statistical powers of genetic studies on complex traits . TherefoThis meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) criteria .We conducted a computerized literature search of PubMed, Embase, Cochrane Library, Web of Science, Chinese BioMedical Literature (CBM), Wanfang and Chinese National Knowledge Infrastructure (CNKI) databases to identify all potential studies published up to December 31, 2013. The following keywords and subject terms were included in searching: “EFG” or “Epidermal growth factor”, “liver cancer” or “hepatocellular carcinoma” or “HCC”, and “polymorphism” or “variant” or “allele”. References of retrieved articles and review articles were also screened.Studies included in the meta-analysis had to meet all the following criteria: (1) evaluating the association between EGF +61A/G polymorphism and HCC risk, (2) using unrelated individuals, (3) providing sufficient data for estimating an odds ratio (OR) with its 95% confidence interval (CI), (4) using case–control, cohort or cross-sectional design, (5) published in English or Chinese. The corresponding authors were contacted to obtain missing information, and some studies were excluded if critical missing information was not obtained. Reviews, case reports, family-based studies, case-only studies, and studies without sufficient data were all excluded. When a study reported results on different subpopulations based on ethnicity or geographical region, we treated each subpopulation as a separate comparison. If more than one article was published using the same subjects, only the study with the largest sample size was selected.All data were extracted independently by two investigators (Lifang Shao and Xiaobo Yu). Disagreement was resolved by discussion. The following data were extracted: authors, name of journal, year of publication, ethnicity and country of study population, inclusion and exclusion criteria, characteristics of cases and controls, numbers of HCC cases and controls, matching criteria, source of controls, HCC confirmation, study design, genotyping methods, genotype frequencies of cases and controls, and interactions between environment factors or genes.Quality of studies was independently assessed by the same two investigators (Lifang Shao and Xiaobo Yu) according to a set of predetermined criteria  was considered representative of significant statistical heterogeneity because of the low power of the statistic. I2 ranges between 0 and 100%, and represents the proportion of between-study variability that can be attributed to heterogeneity rather than chance. I2 values of 25%, 50%, and 75% were defined as low, moderate, and high estimates. If the significant Q-statistic indicated heterogeneity across studies, the random-effects model (DerSimonian and Laird method) was used, otherwise the fixed-effects model (Mantel-Haenszel method) was adopted [Z test was used to assess the significance of the pooled OR and a P-value less than 0.05 (P < 0.05) was considered significant.The unadjusted OR with 95% CI was used to assess the strength of the association between EGF +61A/G polymorphism and HCC risk. The pooled ORs were performed under the allelic contrast (G versus A), co-dominant model , dominant model (GG + GA versus AA), and recessive model (GG versus GA + AA), respectively. Between-study heterogeneity was measured using a tic test  and an Itatistic . P less  adopted . The Z tP-value less than 0.10 (P < 0.10) because of the relatively weak statistical power.Subgroup analyses were stratified by racial descent, study quality, source of controls, type of controls, and number of cases, respectively. Furthermore, meta-regression analysis  was perfχ2 test. All P-values were two-sided. Data analyses were performed using the software Stata version 11.0 .To evaluate the stability of the results, sensitivity analyses were performed by sequential omission of individual studies under various comparisons in overall and Asian populations, respectively. Publication bias was investigated by funnel plot. Funnel plot asymmetry was assessed by the method of Egger’s linear regression test . Hardy-WThe present study met the PRISMA statement  . Table P = 0.001, 95% CI: 1.056-1.255, I2 = 4.6%, Pheterogeneity = 0.397), European populations , and African populations , respectively  and in low-quality studies . In the subgroup analyses by source of controls, the results showed that EGF +61A/G polymorphism was significantly associated with HCC risk in hospital-based studies , but not in population-based studies . Furthermore, according to chronic liver disease status in Asian controls, a significant association between EGF +61A/G polymorphism and HCC risk was obtained in patients with chronic liver diseases , and in healthy controls  , but not in Asian populations   were finally included in this meta-analysis. Overall, the EGF +61A/G polymorphism was significantly associated with an increased HCC risk under all genetic models. However, considerable heterogeneity was detected across studies. Meta-regression showed that both ethnicity and study quality significantly contributed to the heterogeneity for EGF +61A/G polymorphism. Nevertheless, in the subgroup analyses by ethnicity and study quality, this significant association still existed in each subgroup, and the between-study heterogeneity became insignificant in Asian, European or African populations. Moreover, sensitivity analysis further strengthened the validity of the positive association in overall populations, and in Asian populations, indicating robustness of our results.It is possible that the effects of genetic factors related to cancer are different across various ethnic populations. In this study, ethnicity was identified as a potential source of between-study heterogeneity by meta-regression and subgroup analyses. Although the reason for these discrepancies was not well known, some possibilities should be considered. First, there were significant differences in terms of +61G allele frequency among the three major ethnicities. The frequency of EGF +61G allele was greatest in Asian populations (65%), intermediate in European populations (42%), and lowest in African populations (30%). The higher HCC prevalence among Asian populations may be partly ascribed to the higher prevalence of EGF +61G allele. The frequency of EGF +61G among the controls of all studies was consistent with that in 1000 Genome Project, except for two studies ,28. The Study design is an area of concern and can influence the interpretation of the results of meta-analysis. Among the eligible studies, there were 15 hospital-based studies, but only 5 population-based studies. Our results showed that EGF +61A/G polymorphism was significantly associated with HCC risk in hospital-based studies, but not in population-based studies. Therefore, the results should be treated with caution, because controls from hospital-based studies may not represent the general population. Larger population-based studies were required to further confirm the association between EGF +61A/G polymorphism and HCC susceptibility. Furthermore, according to chronic liver disease status in Asian controls, a significant association between EGF +61A/G polymorphism and HCC risk was obtained both in controls with chronic liver diseases, and in healthy controls, indicating reliability of the pooled results in Asian populations. Besides, all Asian studies were based on Chinese populations except for one Japanese study . The freEpidermal growth factor is a mitogen for hepatocytes, and plays a critical role in liver tissue regeneration, malignant transformation, tumor growth and progression . TransgeTo our knowledge, this present meta-analysis is the most comprehensive one related to the relationship between EGF +61A/G polymorphism and HCC risk. Compared with the previous meta-analysis , anotherDespite our efforts in performing a comprehensive analysis, several limitations should be considered. Firstly, obvious publication bias was detected in overall populations. Bias may result from our exclusion of unpublished data, as well as studies published in languages other than English and Chinese. Secondly, the controls were not uniformly defined. Some studies were population-based, while others were hospital-based. Considering the overwhelming impact of chronic liver diseases on HCC development, controls were divided into healthy controls and controls with chronic liver diseases. The subgroup analyses showed that the significant association between EGF +61A/G and HCC was present both in healthy controls and in patients with chronic liver diseases, indicating the role of EGF +61A/G in the risk of HCC, regardless of type of controls. Moreover, the pooled ORs for individuals with chronic liver diseases were higher than those for healthy controls under all genetic models. Therefore, the chronic liver diseases may change the environment in vivo and mediate the ability of genetic factors to contribute to HCC. More studies should be designed to investigate the role of EGF polymorphisms in combination with chronic liver diseases in HCC pathogenesis. Thirdly, our meta-analysis was based on unadjusted estimates. If individual data were available, adjusted estimates by confounding factors could be obtained to conduct a more precise analysis. Fourthly, gene-gene and gene-environment interactions were not addressed in our meta-analysis due to lack of sufficient data. Aside from genetic factors, other factors such as exposure to aflatoxin B1, high cigarette smoking, and habitual alcohol abuse might also play vital roles in the development of HCC. However, we could not perform subgroup analyses based on environmental exposure owing to the limited reported information on such associations in those included studies. Finally, the number of studies included in the meta-analysis for European populations and African populations was relatively small, which may lead to low statistical power and generate fluctuation in estimation.In summary, this meta-analysis suggests that EGF gene +61A/G polymorphism is significantly associated with the increased risk of HCC, particularly in Asian populations. Further well-designed and large-scale studies with the consideration of gene-gene and gene-environment interactions should be conducted to investigate the association in different ethnic populations.