DPYD) gene and 5-fluorouracil (5-FU) toxicities in patients with colorectal cancer (CRC). The MEDLINE (1966∼2013), the Cochrane Library Database , EMBASE (1980∼2013), CINAHL (1982∼2013), Web of Science (1945∼2013), and the Chinese Biomedical Database (CBM) (1982∼2013) were searched without language restrictions. Meta-analyses were conducted with the use of STATA software . Seven clinical cohort studies with a total of 946 CRC patients met our inclusion criteria, and NOS scores of each of the included studies were ≥5. Our findings showed that DPYD genetic polymorphisms were significantly correlated with high incidences of 5-FU-related toxicity in CRC patients. SNP-stratified analysis indicated that there were remarkable connections of IVS14+1G>A, 464T>A, and 2194G>A polymorphisms with the incidence of marrow suppression in CRC patients receiving 5-FU chemotherapy. Furthermore, we found that IVS14+1G>A, 496A>G, and 2194G>A polymorphisms were correlated with the incidence of gastrointestinal reaction. Ethnicity-stratified analysis also revealed that DPYD genetic polymorphisms might contribute to the development of marrow suppression and gastrointestinal reaction among Asians, but not among Caucasians. The present meta-analysis suggests that DPYD genetic polymorphisms may be correlated with the incidence of 5-FU-related toxicity in CRC patients.Our meta-analysis aggregated existing results from relevant studies to comprehensively investigate the correlations between genetic polymorphisms in dihydropyrimidine dehydrogenase ( Colorectal cancer (CRC) is a malignant tumor caused by uncontrolled cell growth in the colon or rectum, or in the appendix, which is typically manifested by rectal bleeding, anemia, weight loss, and changes in bowel habits . Accordi DPYD gene has been identified to play a crucial role in the pharmacology of 5-FU in CRC patients receiving chemotherapy [ DPYD gene is located on chromosome 1p22, encompassing 23 exons and spanning approximately 843 kb [ DPYD gene may contribute to decreased activations of DPD enzyme which result in reduced clearance of 5-FU and thereby conduce to increased toxicity of 5-FU in CRC patients [ DPYD gene have been investigated to be related to toxicity of 5-FU chemotherapy in CRC patients [ DPYD gene in CRC patients with partial or complete DPD deficiency is a G to A point mutation within the 5′-splicing donor site of intron 14 [ DPYD genetic polymorphisms are potentially useful markers of the response to 5-FU chemotherapy [ DPYD gene are correlated with 5-FU-related toxicity in CRC patients.DPYD, acting as a pyrimidine catabolic enzyme, is suggested to be the initial and rate-limiting factor in the catabolism pathway of 5-FU toxic metabolites . It has otherapy . Consequotherapy , 13. Humy 843 kb . Geneticpatients . In recepatients , 16. Thentron 14 . Furtherotherapy , 11, butotherapy , 18. TheThe MEDLINE (1966~2013), the Cochrane Library Database , EMBASE (1980~2013), CINAHL (1982~2013), Web of Science (1945~2013), and the Chinese Biomedical Database (CBM) (1982~2013) were searched without language restrictions. We used the following keywords and MeSH terms in conjunction with a highly sensitive search strategy: (“genetic polymorphism” or “single nucleotide polymorphism” or “polymorphism“ or “SNP” or “mutation” or “variation” or “variant”) and (“dihydrouracils dehydrogenase” or “NADP” or “DPYD” or “DPD”) and . A manual search on the basis of references identified in the included articles was performed to obtain other potential articles. DPYD genetic polymorphisms and toxicity of 5-FU in CRC patients; (2) all patients involved in the meta-analysis received 5-FU chemotherapy regimen for the first time, and they did not develop chronic liver disease or any liver dysfunction that may have an impact on the metabolism of 5-FU; (3) sufficient information about the frequency of DPYD genetic polymorphisms should be provided in the article. The articles that were not in accordance with our inclusion criteria must be excluded. If authors published several studies of the same subjects, either the most recent or the largest sample size publication was included.The following criteria were utilized to identify the eligibility of included studies: (1) the study must concern the correlations betweenTwo authors from each included study systematically collected relevant data by using a standardized form. The most relevant items were documented in the form for data extraction, including language of publication, publication year of article, the first author's surname, geographical location, design of study, total number of cases, sample size, the source of the subjects, type of sample, detection method of genotypes, the frequency of genetic polymorphisms, gastrointestinal reaction, and adverse drug reaction.Methodological quality was evaluated separately by two observers using the Newcastle-Ottawa Scale (NOS) criteria . The NOSZ test was used to estimate the statistical significance of pooled ORs. Between-study heterogeneity was assessed by Cochran's Q-statistic and I2 tests [ Q-test exhibited a P < 0.05 or the I2 test showed >50%, which means that these studies were heterogeneous, the random-effect model was conducted; otherwise, the fixed-effects model was used. We also make use of subgroup analyses to explore sources of heterogeneity. In order to evaluate the influence of single studies on the overall estimate, a sensitivity analysis was performed. Potential publication bias was investigated with the use of Funnel plots and Egger's linear regression test [The STATA statistical software  was employed in the meta-analysis to achieve rigorous statistical analysis. Odds ratios (OR) with their corresponding 95% confidence interval (95% CI) were calculated. The 2 tests . If the ion test . DPYD gene were assessed, including IVS14+1G>A, 85T>C, 464T>A, 2194G>A, 496A>G, 1896T>C, and 1627A>G. None of the studies deviated from the HWE . NOS scores of each of the included studies were ≥5. The characteristics and methodological quality of included studies were collected in Initially, our highly sensitive search strategy identified 145 articles. We reviewed the titles and abstracts of all articles and excluded 68 articles; then we systematically reviewed full texts and 66 articles were further excluded. Another 4 studies were also excluded due to lack of data integrity . Finally DPYD genetic polymorphisms had a higher incidence of marrow suppression than those without DPYD genetic variants . Furthermore, we observed that there were significant correlations between DPYD genetic polymorphisms and the occurrence of gastrointestinal reaction  and hand-foot syndrome  in CRC patients  (P > 0.05). Furthermore, we found that IVS14+1G>A, 496A>G, and 2194G>A polymorphisms were correlated with the occurrence of gastrointestinal reaction , but similar correlations were not found in other polymorphisms . Among different ethnicities, the findings revealed that DPYD genetic polymorphisms might contribute to the development of marrow suppression and gastrointestinal reaction among Asians , but no similar results were found among Caucasians   . However > 0.05) . MoreoveP > 0.05).A sensitivity analysis was performed to assess the influence of each individual study on the pooled estimates by omitting individual studies. The outcomes suggested that no single study could influence the pooled ORs . Funnel  DPYD genetic polymorphisms and toxicity of 5-FU in CRC patients. The results of our meta-analysis showed significant correlations between DPYD genetic polymorphisms and the incidence of adverse drug events in CRC patients receiving 5-FU chemotherapy, including marrow suppression, gastrointestinal reaction, and hand-foot syndrome, implying that DPYD genetic polymorphisms may be significantly related to toxicity of 5-FU chemotherapy in CRC. Nevertheless, the precise mechanism by which DPYD genetic polymorphisms lead to enhanced toxicity of 5-FU in CRC patients is still largely unknown. It is well established that 5-FU is an important component of many standard treatments in the multimodal therapy of CRC, which always induces side effects and toxicity-related death unfortunately [ DPYD genetic polymorphisms might alter the expression and function of DPYD and may decrease its ability in clearance of 5-FU [ DPYD genetic polymorphisms may contribute to reinforced 5-FU toxicity. The findings are in accordance with a previous study which demonstrated an allele-dose dependent association of the nonsynonymous sequence aberration c.496A>G and indicated that the methionine-valine exchange caused by the c.496A>G transition has posed a deleterious effect on DPYD deficient patients [ DPYD gene may influence the breakdown of the common anticancer drug 5-FU and provoke severe drug adverse effects in CRC patients receiving 5-FU therapy [In the current meta-analysis, we evaluated the relationships betweentunately . It shoutunately . In parttunately . We ther of 5-FU . Thus, ipatients . Moreove DPYD genetic polymorphisms showed a close relationship with the development of marrow suppression and gastrointestinal reaction in Asians, revealing that there was ethnic difference in the effects of DPYD genetic polymorphisms on clinical outcome of 5-FU chemotherapy. Although the potential mechanism of ethnicity differences is still not fully understood, we supposed that ethnicity may result in differences in alleles and genotypes among different ethnic populations.To investigate the influence of potential factors on the specific marrow suppression and gastrointestinal reaction of CRC patients receiving 5-FU chemotherapy, we carried out stratified analysis based on SNP and ethnicity. In the subgroup stratified by SNP, our results indicated that there was a significant association of IVS14+1G>A, 464T>A, and 2194G>A polymorphisms with the incidence of marrow suppression in CRC patients receiving 5-FU chemotherapy. In addition, we found that IVS14+1G>A, 496A>G, and 2194G>A polymorphisms were associated with the occurrence of gastrointestinal reaction. Among different ethnicities, DPYD genetic polymorphisms and toxicity of 5-FU in CRC patients, which may have a negative effect on the general applicability of our findings. Consequently, the cognitive function of our meta-analysis should be considered elementary. A second limitation of our meta-analysis is the fact that, as a retrospective study, there are no guidelines as to how much information a meta-analysis should include to be reliable, which may explain why many controversies occur when the results of meta-analysis and large trials were not consistent. Another potential limitation is that our meta-analysis was unable to acquire original data from the included studies. Even though our meta-analysis has the above limitations, this is the first meta-analysis on the association between DPYD genetic polymorphisms and toxicity of 5-FU in CRC patients. More importantly, our meta-analysis has a clear selection criterion in literature search strategy. In order to achieve strong objectivity, all the research methods were based on strict inclusion and exclusion criteria. Besides, meta-analysis undertaken according to these rigorous statistical analyses will lead to a more reliable conclusion.Our meta-analysis also has a number of potential limitations. Firstly, due to the small number of studies, our results did not include all the data from all trials to assess the correlations between DPYD genetic polymorphisms might be correlated with the incidence of marrow suppression, gastrointestinal reaction, and hand-foot syndrome. Therefore, DPYD genetic polymorphisms may be valuable in predicting toxicity of 5-FU in CRC patients. However, for the fact that several limitations existed in our meta-analysis, larger sample size studies with more integral data are needed to obtain a more profound and representative statistical analysis.To sum up, the present meta-analysis suggested that


Although many epidemiologic studies have investigated the CYP1A1 MspI gene polymorphisms and their associations with esophageal cancer (EC), definite conclusions cannot be drawn. To clarify the effects of CYP1A1 MspI polymorphisms on the risk of EC, a meta-analysis was performed in Chinese population.Related studies were identified from PubMed, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) till October 2014. Pooled ORs and 95% CIs were used to assess the strength of the associations.vs. T: OR = 1.25, 95% CI = 1.04 to 1.51; CC + CT vs. TT: OR = 1.35, 95% CI = 1.06 to 1.72; CC vs. TT + CT: OR = 1.35, 95% CI = 1.03 to 1.76). When we performed stratified analyses by geographical locations, histopathology type, and source of control, significantly increased risks were found in North China , in the population-based studies  and ESCC .A total of 13 studies including 1,519 EC cases and 1,962 controls were involved in this meta-analysis. Overall, significant association was found between CYP1A1 MspI polymorphism and EC risk when all studies in the Chinese population pooled into this meta-analysis (C This meta-analysis provides the evidence that CYP1A1 MspI polymorphism may contribute to the EC development in the Chinese population. Esophageal cancer (EC) is the eighth most common cancer and sixth most deadly cancer worldwide, with an estimated 482,300 new esophageal cancer cases and 406,800 deaths in 2008 . Its incCYP1A1 enzyme is a member of the CYP superfamily and prone to mutation . AgundezA comprehensive literature search was performed using the PubMed, Springer Link, Ovid, Chinese Wanfang Data Knowledge Service Platform, Chinese National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) for relevant articles published with the following Mesh terms:  and (‘P4501A1’ or ‘CYP1A1’) and (China or Chinese or Taiwan). An upper date limit of 28 December 2014 was applied, and no lower date limit was used. The search was performed without any restrictions on language and focused on studies conducted in humans. Concurrently, the reference lists of reviews and retrieved articles were searched manually.For inclusion, the studies must have met the following criteria: (1) case–control study or cohort study studying on association between the CYP1A1 MspI polymorphisms and EC susceptibility; (2) all patients with the diagnosis of EC confirmed by pathological or histological examination; (3) sufficient published data about sample size, odds ratio (OR), and their 95% confidence interval (CI); (4) all participants were Chinese; (5) containing complete information about all genotype frequencies. Studies were excluded when they were: (1) not case–control study or cohort study; (2) duplicate of previous publication; (3) based on incomplete data; (4) meta-analyses, letters, reviews, or editorial articles.Information was extracted carefully from all eligible studies independently by two investigators according to the inclusion criteria listed above. Disagreements were resolved by discussion. The title and abstract of all potentially relevant articles were screened to determine their relevance. Full articles were also scrutinized if the title and abstract were ambiguous. The following data was collected from each study: first author’s surname, year of publication, geographical location, histopathology type, source of control, total numbers of cases and controls, and the numbers of cases and controls who harbored the MspI genotypes. If data from any category were not reported in the primary study, the items were designated ‘not stated’. We did not contact the author of the primary study to request the information.vs. T), dominant model (CT + CC vs. TT), recessive model (CC vs. CT + TT), heterozygous model (CC vs. CT), and homozygous model (CC vs. TT), respectively. Between-study heterogeneity was assessed by the Q-statistics with P values <0.1. Dependent on the results of heterogeneity test among individual studies, the fixed effect model (Mantel-Haenszel) or random effect model (DerSimonian and Laird) was selected to summarize the combined OR and their 95% CI. Hardy-Weinberg equilibrium (HWE) was calculated by using the goodness-of-fit test, and deviation was considered when P < 0.05. The significance of the pooled OR was determined by the z test. Sensitivity analysis was conducted to verify stability of the meta-analysis using both models (the fixed effect model and random effect model). Begg’s funnel plots and Egger’s linear regression test were used to assess publication bias. In addition to the comparison among all subjects, we also performed stratification analyses by geographical locations, histopathology type, and source of control. All the statistical analysis was conducted by using STATA statistical package .Crude odds ratios (ORs) together with their corresponding 95% CIs were used to assess the strength of association between the CYP1A1 MspI polymorphism and the risk of EC. The pooled ORs were performed for allele model . For the allele C vs. allele T, the pooled OR was 1.25   but not found in the South. In the stratified analysis by source of controls, significantly increased risks were found in the population-based studies  but not found in the hospital-based studies. In the subgroup analysis by histopathology type, significantly increased association was found in esophageal squamous cell carcinoma (ESCC) .Table P = 0.550).In order to compare the difference and evaluate the sensitivity of the meta-analyses, we used both models (the fixed effect model and random effect model) to evaluate the stability of the meta-analysis. All the significant results were not materially altered Table . Hence, CYP genes are large families of endoplasmic and cytosolic enzymes that catalyze the activation and detoxification, respectively, of reactive electrophilic compounds, including many environmental carcinogens . CYP1A1 is a phase I enzyme that regulates the metabolic activation of major classes of tobacco procarcinogens, such as aromatic amines and PAHs . Thus, CWhen we performed stratified analyses by geographical locations, histopathology type, and source of control, significant association with susceptibility for the development of EC was found in North China, in ESCC, and population-based studies; however, it was not found in South China and hospital-based studies. These can be influenced by some factors. First, the hospital-based studies usually have some biases because such controls may just represent a sample of ill-defined reference population and may not be representative of the general population. Second, genetic risk factors for EC in North and South China are different . Last buThe pathways of carcinogen metabolism are complex, mediated by the activity of multiple enzymes. The effect of any single gene might have a limited impact on EC risk than have so far been anticipated. EC has some known major environmental determinants other than tobacco smoke, and large studies with detailed exposure information are needed to evaluate reliably any moderate genetic effects. Otherwise, some limitations should be acknowledged. Firstly, we did not perform subgroup analysis on smoking status because of the lack of sufficient data. Another potential limitation was that our results were based on unadjusted estimates. More precise analyses can be conducted if individual data were available, which would allow for the adjustment by other covariates including age, sex, race, and other factors. Finally, heterogeneity can interfere with the interpretation of the results of a meta-analysis. Although we minimized this likelihood by performing a careful search of published studies and subgroup analyses, significant inter-study heterogeneity nevertheless existed in the comparison of geographical locations. In spite of these limitations, our meta-analysis still had some advantages. We obeyed the inclusion and exclusion criteria strictly to reduce selection bias. A funnel plot and Egger’s linear regression test was used to assess publication bias. In addition, the impact of different genetic background was lessened by means of including the studies performed in the Chinese population only, and the test of the Hardy-Weinberg equilibrium for distribution of the genotypes in control groups suggested that there was almost no significantly different genetic background among the participants.In conclusion, our meta-analysis supports that CYP1A1 MspI polymorphism might contribute to individual susceptibility to EC in the Chinese population. Concerning EC with multifactorial etiology, to further evaluate gene-gene and gene-environment interactions on CYP1A1 MspI polymorphism and EC, larger studies in selected populations with different environmental background or other risk factors are required. Such studies may eventually lead to have a better, comprehensive understanding of the association between the CYP1A1 MspI polymorphism and EC risk.


BCL-2 genetic polymorphisms, such as rs2279115, rs1801018 and rs1564483, have been identified previously and might be involved in cancer development through deregulating BCL-2 expression. Therefore, we examined associations between these three polymorphisms and esophageal squamous cell carcinoma (ESCC) susceptibility as well as its biological function in vivo. Genotypes were determined in two independent case-control sets consisted of 1588 ESCC patients and 1600 controls from two regions of China. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression. The impact of the rs2279115 polymorphism on BCL-2 expression was detected using esophagus tissues. Our results demonstrated that the BCL-2 rs2279115 AA genotype was significantly associated with decreased ESCC risk compared with the CC genotype , especially in nonsmokers  or nondrinkers . Genotype-phenotype correlation studies demonstrated that subjects with the rs2279115 CA and AA genotypes had a statistically significant decrease of BCL-2 mRNA expression compared to the CC genotype in both normal and cancerous esophagus tissues. Our results indicate that the BCL-2 rs2279115 polymorphism contributes to ESCC susceptibility in Chinese populations.B-cell lymphoma-2 (BCL-2) prevents apoptosis and its overexpression could promote cancer cell survival. Multiple functional  BCL-2 was firstly identified during the investigation of t chromosome translocation in B-cell lymphomaApoptosis has been widely recognized as a well controlled and conserved process which is crucial for the normal development and function of multiple organisms2As one of the most common and fatal malignancies worldwide, esophageal squamous cell carcinoma (ESCC) shows a relatively high incidence in Asian including China7910111213BCL-2 gene locus which is located on chromosome 18q21.3 and consists of three exons and two promoters. These two promoters show different functional properties. That is, BCL-2 mRNA transcription is driven by the P1 promoter, while the P2 promoter acts as a negative regulatory element16BCL-2 functional polymorphisms  might be also involved in ESCC development through deregulating BCL-2 expression. To test this hypothesis, we conducted a two-stage case-control study of ESCC. To validate the biological function of BCL-2 rs2279115 genetic variant in vivo, we detected the association between its genotypes and BCL-2 mRNA expression levels in normal and cancerous esophagus tissues.In ESCC, BCL-2 plays its role in regulating cancer cell growth, especially in the early stage. Additionally, BCL-2 expression has been positively associated with cancer cell differentiation and inversely with disease progressionTwo case-control sets were included in the current study. Huaian case-control set consists of 588 ESCC cases from Huaian No. 2 Hospital  and sex- and age-matched 600 healthy controls. Jinan case-control set contains 540 patients with ESCC from Shandong Cancer Hospital, Shandong Academy of Medical Sciences  and sex- and age-matched (±5 years) 550 controls. We used the group match considering sex- and age-match between cases and controls. The detailed information about the two case-control sets has been reported previously2122BCL-2 candidate SNPs were analyzed by the MassArray system . A 5% blind, random sample of study subjects was genotyped in duplicates and the reproducibility was 98.8%. To reduce the costs of the study, we genotyped the BCL-2 rs2279115 SNP in the validation set using PCR-based restriction fragment length polymorphism (RFLP). The genotyping primers used for amplifying DNA segments with the SNP site were 5′-GCATTTGCTGTTCGGAGTTT-3′ and 5′-TTCGCAGAAGTCCTGTGATG-3′. The 25 μL PCR reaction mixture contains 0.2 mmol/L of deoxynucleoside triphosphate, 0.1 mmol/L of each primer, 100 ng of DNA, 1.0 U of rTaq DNA polymerase (TaKaRa), 1.5 mmol/L MgCl2, and 1 × reaction buffer. The PCR profile included an initial 2 minutes melting step at 95 °C, followed by 35 cycles of 30 seconds at 94 °C, 30 seconds at 60 °C, 30 seconds at 72 °C, and a final 10 minutes elongation step at 72 °C. Restriction enzyme BccI (New England Biolabs) was used to distinguish the rs2279115 C > A genotypes. A 15% random sample was reciprocally tested by different person, and the reproducibility was 99.0%.Three BCL-2 mRNA expression in cancerous and normal esophagus tissues was examined using the SYBR-Green real-time quantity PCR (qPCR) method as described previously2324BCL-2 and β-actin as an internal reference gene was carried out using the ABI 7500 real-time PCR system in triplicates. The primers used for BCL-2 were 5′-TCGCCCTGTGGATGACTGA-3′ and 5′-CAGAGACAGCCAGGAGAAATCA-3′; and for β-actin were 5′-GGCGGCACCACCATGTACCCT-3′ and 5′-AGGGGCCGGACTCGTCATACT-3′. The samples size of each qPCR assay is 10 μL. Relative gene quantitation for BCL-2 was calculated by -delta delta ct methods. To control quality of the qPCR data, we repeated the qPCR assays for some specific sample if the ct values of the triplicates for this sample showed variations more than 0.5 in very few cases. Paired t-test was used to calculate the differences between individuals with different genotypes.Total RNA was extracted from ESCC tissue samples using TRIzol Reagent (Invitrogen) and converted to cDNA using the ReverTra Ace qPCR RT Kit (TOYOBO). BCL-2 SNPs between ESCC cases and controls were examined using Pearson’s χ2 test. Unconditional logistic regression model was utilized to estimate associations between BCL-2 genotypes and ESCC risk by odds ratio (OR) and their 95% confidence intervals (CIs). During calculating associations between functional SNP candidates in BCL-2 and ESCC risk in Huaian case-control set, we used the common genotypes of rs2279115 (CC), rs1801018 (AA) and rs1564483 (GG) as the reference genotype. All ORs were adjusted for age, sex, drinking and smoking status, where it was appropriate. A P value of less than 0.05 was used as the criterion of statistical significance, and all statistical tests were two-sided. All analyses were performed with SPSS software package .The differences in demographic variables and genotype distributions of P > 0.05), which indicated that the frequency matching of age and sex was adequate . Similarly, there were more alcohol drinkers among patients than among control subjects in these two sets .There were no statistically significant differences between cases and controls for both case-control sets in terms of median age and sex distribution  are summarized in 2 = 8.68, P = 0.013, df = 2), with the frequency of AA homozygote being significantly lower among patients than among controls (13.7% vs. 15.0%). However, no statistically significant differences of rs1801018 and rs1564483 genotypes were observed between cases and control subjects (both P > 0.05) (The genotype frequencies of  > 0.05) . TherefoBCL-2 rs2279115 C > A SNP and ESCC risk were calculated using unconditional logistic regression analyses  for developing ESCC in Huaian Set, compared with individual having the rs2279115 CC genotype. However, the rs2279115 AA genotypes had a marginally decreased risk for ESCC compared with the rs2279115 CC genotype . In Jinan set, carriers of the rs2279115 CA or AA genotypes were significantly associated with decreased ESCC risk    . In the = 0.005) . All ORsBCL-2 rs2279115 genetic variant and ESCC risk was further examined by stratifying for age, sex, smoking and alcohol drinking status using the pooled data of two Chinese case-control sets , but not among females . However, the BCL-2 rs2279115 CC genotype was not significantly associated with ESCC susceptibility in males or females . In age-stratified analyses, either rs2279115 CA or AA genotype was significantly associated with decreased risk in subjects aged older than 57 years . However, among subjects aged 57 years or younger, neither rs2279115 CA nor AA genotype showed impacts on ESCC risk .Associations between genotypes of rol sets . CompareBCL-2 rs2279115 genetic variant influence ESCC susceptibility in combination with these pathogenic factors . There was no significantly decreased risk for smokers with CA or AA genotype compared with CC smokers (both P > 0.05). Nondrinkers carrying rs2279115 CA or AA genotype showed significantly decreased risk to develop ESCC compared with CC carriers who did not drink . However, there were no association between rs2279115 CA and AA genotypes and ESCC risk in drinkers (both P > 0.05)  .BCL-2 P2 promoter activity and gene expression in cancer cells, we investigated whether there is an allele-specific effect of rs2279115 SNP on BCL-2 expression in esophagus tissues. We found that there were significantly lower BCL-2 mRNA levels (mean ± SE) among carriers of the rs2279115 CA and AA genotypes compared to carriers of the CC genotype in normal esophagus tissues  (P = 0.040) (Due to rs2279115 C-to-A change could influence = 0.031) . Similar= 0.040) .BCL-2 functional candidate SNPs and ESCC susceptibility through a case-control approach. We found that only BCL-2 rs2279115 polymorphism is significantly associated with decreased ESCC susceptibility in Chinese populations, with the rs2279115 AA genotype as the protective genotype. Genotype-phenotype correlation studies demonstrated that subjects with the rs2279115 CA and AA genotypes had a statistically significant decrease of BCL-2 mRNA expression compared to the CC genotype in both normal and cancerous esophagus tissues. Our data support the hypothesis that SNPs in gene expression regulatory elements of tumor suppressor genes or oncogenes might impact genetic susceptibility of cancers.In the current study, we investigated the association between three BCL-2 rs2279115 polymorphism has been extensively studied in multiple cancer types, including ESCC. Liu et al. reported in a case-control study conducted in western China including 205 esophageal cancer patients and 224 controlsBCL-2 rs2279115 AA genotype was significantly associated with increased risk of developing esophageal cancer. In contrast, we found that subjects with the rs2279115 AA genotype have significantly decreased risk to develop ESCC in both Northern and Southern Chinese populations. There are several possible explanations for the insistent results. Firstly, Liu et al. only recruited 205 esophageal cancer patients to evaluate association between rs2279115 and esophageal cancer risk. The relative large sample size of the present study (1588 ESCC patients and 1600 controls) may provide more statistic power to the moderate effect of this genetic polymorphism on ESCC susceptibility. Secondly, we only included ESCC, but not esophageal adenocarcinoma in this study. Considering the distinct etiology and clinical behaviors of these two subtypes of esophageal cancer, we believe that mixed study subjects might also lead to the discrepancy.The et al. recently reported that hierarchical clustering analyses of whole-genome sequencing in 17 ESCC cases and whole-exome sequencing in 71 cases indicate that ESCC and HNSCC mutation spectra were intermingled, whereas esophageal adenocarcinomas were clearly distinctive from ESCCBCL-2 rs2279115 polymorphism influence ESCC genetics thoroughly through regulating BCL-2 expression and apoptosis in vivo.Our results are consistent to functional relevance of rs2279115 polymorphism in SCCHNBCL-2 rs2279115 polymorphism showed a consistent association with ESCC risk in two independent case-control cohorts. Additionally, our results are unlikely to be attributable to unknown confounding factors due to having relatively large sample sizes, significantly increased odd ratios with small P values. More importantly, our results on the genotype-phenotype relationship between the rs2279115 polymorphism and gene expression supports our conclusion. However, there might be several limitations in the current case-control study. For instance, since all ESCC cases were recruited from the hospital, inherent selection bias may exist. Therefore, the findings of our study warrant to be validated in a population-based prospective study in the future. In addition, relatively small sample size for non-smokers and non-drinkers should be further analyzed in a larger population.The BCL-2 rs2279115 SNP was associated with a significantly decreased risk of ESCC in Chinese populations, especially in nonsmokers or nondrinkers. Our data may support the hypothesis that genetic variants can influence gene regulation might be important modifiers of ESCC susceptibility. These results may lead to better understanding of ESCC etiology in different populations.In conclusion, we demonstrated that functional How to cite this article: Pan, W. et al. Functional BCL-2 regulatory genetic variants contribute to susceptibility of esophageal squamous cell carcinoma. Sci. Rep.5, 11833; doi: 10.1038/srep11833 (2015).


However, some studies yielded conflicting results. To clarify precise association, we performed a comprehensive meta-analysis of 42 case-control studies involving 43,000 subjects . The overall results suggested that the -94 ins/del ATTG polymorphism had a decreased risk for cancer, reaching significant levels in five genetic models . Furthermore, the -94 ins/del ATTG polymorphism could confer a decreased or increased risk for cancer development among Asians and Caucasians, respectively. Additionally, the stratification analysis revealed a significant association between the variant and decreased risk of oral, ovarian, and nasopharyngeal cancer in Asians. After we adjusted p values using the Benjamini-Hochberg false discovery rate method to account for multiple comparisons, these associations remained.Accumulating evidences have indicated that the functional  NFKB1)56789Characterized by angiogenesis and inflammation, cancer is a major public health problem and a complex terminal disease worldwide, which is injurious to human health and lives12NFKB1 gene, mapped to chromosome 4q24, encodes p105/p50 isoforms of NF-κB, involved in cancer initiation and progression. The -94 insertion/deletion (ins/del) ATTG polymorphism within the promoter region of the NFKB1 gene could potentially affect the transcription of the gene and the function of NF-κB protein, sequentially leading to loss of binding capacity to nuclear proteins and reduced promoter activityThere is mounting evidence that inflammatory cytokines and carcinogens closely related to cancer development are involved in activating the common cell survival signaling pathways11121416-94 ins/del ATTG (rs28362491) polymorphism that involves deletion of four nucleotides in the promoter region of NFKB1 gene consists of three genotypes: homozygote insertion or wild-type (WW), homozygote deletion or variant (DD), and heterozygous ins/del (DW)771019202122232526282920The TG rs283691 polymoTG rs283691 polymoet al.et al.-94 ins/del ATTG polymorphism was significantly associated with decreased cancer risk in Asian populations, but not in Caucasian populations. Unfortunately, the two previous meta-analyses included some studies, in which the genotype distributions of control groups were not consistent with Hardy–Weinberg equilibrium (HWE). In addition, obviously high heterogeneity was detected under all five genetic models in their studies, but they only conducted subgroup analysis based on ethnicity to investigate the origin of the high heterogeneity. Furthermore, the authors did not perform tests to access statistical significance of multiple null hypotheses232425262730363738394041Up to now, some earlier meta-analyses based on different strategies have tried to investigate the link between the polymorphism and cancer risk. Yang NFKB1 -94 ins/del ATTG promoter polymorphism and cancer risk by precise results.Due to the inconsistency of past studies and the critical role of the variant in the pathogenesis of cancer, we conducted an updated meta-analysis to investigate the association of NFKB1 -94 ins/del ATTG polymorphism and susceptibility to cancer . The search terms were used as follows: ‘cancer’ or ‘carcinoma’ or ‘tumor’ or ‘carcinogenesis’ or ‘neoplasm’ And ‘NF-κB’ or ‘Nuclear factor-κB 1’ or ‘NFKB1” And ‘polymorphism’ or ‘variant’ or ‘mutation’ or ‘polymorphisms’ or ‘variants’ or ‘mutations’. No publication date or languages restrictions were imposed. Studies eligible for this meta-analysis must fulfill the following inclusion criteria: (a) studies using a case-control design; (b) studies evaluating the association between NFKB1 -94 ins/del ATTG polymorphism and cancer risk; (c) genotype distributions should be available for estimating the odds ratios (OR) with 95% confidence interval (CI); (d) the genotype distributions among control groups must be consistent with HWE. For multiple reports based on overlapping samples, only the most recent study or the study with the largest number of subjects were retained. Exclusion criteria were defined as follows: (a) abstracts, conferences, reviews, letters, case reports, and non-human studies; (b) repeated or overlapping publications; (c) studies reporting neither genotype distributions nor allele frequency; (d) the studies that do not follow HWE. We also inspected the references list of reviews or previous meta-analyses for potentially relevant publications. Two investigators independently screened all abstracts and citations to extract potentially eligible studies.A systematic search of PubMed, Embase, ISI Web of Science, and Chinese National Knowledge Infrastructure (CNKI) database was conducted by two independent reviewers to identify relevant articles, which had investigated the association between Two investigators independently collected the information of each eligible study based on the inclusion and exclusion criteria. First author, publication year, country, ethnicity, control source, genotyping technology, genotype and allele distributions, total number of cases and controls, and cancer type were extracted. In case of discrepancies, we checked the collected data and reached a consensus through discussion to ensure accuracy of the data. The information is shown in http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp). The scale use a ‘-’ rating system to evaluate quality based on three points including the selection of the study groups, comparability of the groups, and the ascertainment of the exposure or outcome of interest in the case-control study. Total scores range from 0 to 9 points. A study with scores of more than 7 points was considered to be a high quality study , homozygous deletion or variant (DD), and heterozygous ins/del (DW). The pooled OR was estimated in five genetic models: (1) dominant model: del/del + del/ins versus ins/ins (DD+DW vs. WW); (2) recessive model: del/del versus del/ins + ins/ins (DD vs. DW+WW); (3) homozygous model: del/del versus ins/ins (DD vs. WW); (4) heterozygous del/ins versus ins/ins (DW vs. WW); and (5) allelic model: deletion allele versus insertion allele (D vs. W), which was considered statistically significant when the P value of the Z test was less than 0.05.In this meta-analysis, all of the data in eligible studies were calculated as odds ratios (OR) with 95% confidence interval (CI) to assess the strength of association between 2 statistics, which confirmed the heterogeneity at P-value < 0.10. If no or low heterogeneity existed (P < 0.10), the random-effects model (REM) was applied to estimate pooled OR. Otherwise, the fixed-effects model (FEM) was used. Moreover, HWE was recalculated in control groups by Pearson’s χ2 test before this meta-analysis was conducted. To explore the potential heterogeneity among studies, we conducted subgroup analysis based on ethnicity (Asian and Caucasian), control source  and population-based (PB) population), genotyping method (TaqMan and others), quality score of studies, and type of cancer. In addition, sensitivity analyses were also conducted through sequentially excluded individual studies to investigate the potential origin of heterogeneity and to assess the stability of the results.Heterogeneity among studies was evaluated by Chi-squared-based Q-test and IP < 0.05 was considered statistically significant. Benjamini–Hochberg false discovery rate (FDR) test was used to correct for multiple comparisons yielding Pcorr value less than 0.05 was considered as significant. All statistical analyses were performed with STATA 12.0 software .Potential publication bias was tested by several methods. Visual inspection of asymmetry in funnel plots was carried out. Furthermore, Egger’ regression and Begg’s test were also utilized to detect publication bias, and et al.et al.-94 ins/del ATTG polymorphism and the risk of three different cancer types, respectively. Therefore, we treated them as six separate comparisons. In addition, Huang et al.et al.810131920212223242526272829303236373839404142434445464748495051525354This meta-analysis design was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) prospectively. The process of study selection was showed in NFKB1 -94 ins/del ATTG polymorphism in all five genetic models   . In addinificant .NFKB1 -94 ins/del ATTG polymorphism was significantly associated with decreased cancer susceptibility among HB population in all genetic models, among which the most obvious is for dominant model , and weakest for recessive model . Corrected P values for multiple testing remained significant. However, no such significant relationship was detected for PB population in any genetic model  and 95% confidence interval (CI) from further subgroup analyses of ethnicity, control source, genotyping method, cancer type, and quality score. When stratified by control source, REM was utilized due to the presence of heterogeneity in all above genetic models . Consistic model .NFKB1 -94 ins/del ATTG polymorphism and decreased cancer risk was seen for Asian population in all genetic models  , homozygous , heterozygous , and allelic  models  . In cont) models , with lo) models . MoreoveNFKB1 -94 ins/del ATTG promoter variant and cancer risk were identified, among which the most obvious is for recessive model in the two groups , respectively. In contrast, no relationship was detected in TaqMan, MassARRAY, PCR-CGE, and Pyrosequencing group (P = 0.013), recessive , homozygous , and allelic  model  group and polymerase chain reaction-polyacrylamide gel electrophoresis (PCR-PAGE) group, significantly decreased association between ng group . When st2) model .P < 0.0001; DD vs. DW+WW: OR = 0.63, P < 0.0001; DD vs. WW: OR = 0.49, P < 0.0001; DW vs. WW: OR = 0.67, P = 0.004; D vs. W: OR = 0.70, P < 0.0001), OC , and NPC  in genetic models. Moreover, significantly decreased relationship between the polymorphism and LC risk was only found in heterozygous model . In addition, corrected p values for multiple testing remained significant  further provided no evidence of significant publication bias. Our observation of symmetric funnel plots and non-significant statistical tests confirmed no publication bias . Therefore, our conclusion in this meta-analysis was stable and credible.The NF-κB family constitutes a class of pleiotropic transcription factors, which seems to contribute to tumor angiogenesis and progression by regulating the transcription of genes involved in immune response, cell proliferation, apoptosis, and angiogenesis1758-94 ins/del ATTG (rs28362491) polymorphism in the promoter region of the p50/p105-encoding NFKB1 gene located between two received key promoter regulatory elements modulates its transcription and then affects the production of protein subunits18NFKB1 transcript level and hence, reduce p50/p105 protein production18A functional -94 ins/del ATTG on NFKB1 gene locus with 42 separate case-control studies  focusing on the relationship of this variant to cancer risk. The overall results revealed a significant association between -94 del/del variant genotype carriers and decreased cancer risk. Despite the mechanism remains unclear, considering the critical role of NF-κB in various biological pathways, we could hypothesize that ATTG deletion causes the loss of binding to nuclear proteins, which leads to reduced promoter activityIn this meta-analysis, we investigated the However, we must treat these results cautiously when referring to the findings, because moderate heterogeneity was detected in this meta-analysis, which may be attributed to different characteristics of the cohort, environmental exposure, clinical information and intrinsic complexity of cancer architecture. In addition, there are 30 studies for the Asian population and 12 studies for the Caucasian population. The high proportion of over-represented studies of the Asian population in the combined analysis clearly resulted in a bias, which affected the overall results. Therefore, we conducted a subgroup analysis to identify the origin of heterogeneity by ethnicity, control source, genotyping method, cancer type, and quality score.NFKB1 -94 ins/del ATTG polymorphism and the risk of cancer in Caucasians. The contradictory results are interpreted by the following reasons: (1) the small sample was included in the previous two meta-analyses. Therefore, the results may reduce the power to reveal a reliable relationship. There were twelve case-control studies eligible for this meta-analysis among Caucasians, so the result may be closer to the real value; (2) the previous studies included many studies, which do not follow HWE. These studies may make the result incredible; (3) the sensitivity analysis was conducted through three different methods in this meta-analysis, and the results were consistent with the previous results, suggesting the results of this study were stable; (4) different clinicopathological features of cases included, different experimental designs and genotyping methods utilized in these studies; (5) we used Benjamini–Hochberg procedures to adjust for multiple comparisons in setting the level of significance. There were no significant variables after corrections for multiple comparisons.When analysis was restricted to ethnicity, the variant del allele could confer a decreased or increased risk of developing cancer to its carriers among Asians and Caucasians, respectively. Natural selection and balance to other genetic variants may result in different genotype frequencies in different ethnicities. In addition, accumulated evidence demonstrated that individuals with the same genotype living in the different areas with different environments and life style might have a different cancer risk7206033The stronger and significantly decreased risk of cancer when analysis was restricted to hospital-based (HB) group was observed in all genetic model, but such association was not seen in population-based (PB) group. Interestingly, it was noted that moderate heterogeneity appeared in the HB group, which may result from selection bias. Additionally, HB controls were selected from hospital, which may not validly represent the exposure situation of the overall population. Therefore, results from the PB controls were thought to be more reliable.et al.et al.-94 ins/del ATTG polymorphism remained when analyses were done according to gender and smoking status in lung cancer among Asian population. The study by Oltulu et al.et al.94 ins/del ATTG polymorphism was not present in nonsmokers and younger subjects in prostate cancer. Consequently, only increasing the number of populations, without taking into clinical and demographic information into account, will not guarantee the validity of the results. We tried to collect some subsets of clinical information and demographic data from the eligible publications to conduct further analysis. However, on one side, the relatively small sample size could reduce the statistical power of this study and result in unreliable association. On the other side, these data were collected from various cancers and ethnicities, which may give rise to confounding variables to reveal an unreliable association. Therefore, in my opinion, a better result can be given exclusively from a case-control study of large sample size, the same cancer type, and the same ethnicity.Cancer was an overly broad collection of different types, which may have confounding factors to not reveal a reliable association. Therefore, further stratification analysis by cancer type was also conducted. The decreased risk of cancer also remained in the subgroups of oral, ovarian, and nasopharyngeal carcinoma in Asian populations. Moreover, the clinical and demographic information are essential factors affecting the overall results. Zhang We note several potential limitations of this meta-analysis when interpreting these results. First, we were unable to perform further analysis to investigate other risk factors of cancer risk for insufficient original data, such as age, tumor location, and gene-environment/gene-gene interaction. Second, moderate between-study heterogeneity was checked in some genetic comparisons. Further subgroup analysis showed that cancer type and control source might be the source of heterogeneity. Nevertheless, there is other inexplicable heterogeneity affecting the results. Third, publication bias might have occurred for only including published articles. Some relevant published studies or unpublished studies with null results were missed, which may affect our results. Fourth, many studies included in this meta-analysis were performed in Asian and Caucasian populations, so the association needs to be verified in other ethnicities. Despite these limitations, we created a strict protocol, and performed study selection, data identification and statistical analysis to reduce potential bias through the whole process. Thus, the objectivity and reliability of the results are guaranteed.NFKB1 -94 ins/del ATTG polymorphism and cancer risk. Our results indicated that the -94 ins/del ATTG polymorphism was significantly associated with decreased cancer risk in Asian populations, but increased cancer risk in Caucasian populations. However, due to the limitations of this current meta-analysis, the conclusion might be not conclusive. Therefore, in the future, there will be a need for larger sample size and more ethnic groups to further confirm the results of this meta-analysis.In conclusion, to the best of our knowledge, this is a comprehensive study to assess the relationship between How to cite this article: Wang, D. et al. Genetic association between NFKB1 −94 ins/del ATTG Promoter Polymorphism and cancer risk: a meta-analysis of 42 case-control studies. Sci. Rep.6, 30220; doi: 10.1038/srep30220 (2016).


Interleukin-10 (IL-10) is an important immunomodulatory cytokine. Several studies focused the association between IL-10 promoter gene polymorphisms and graft rejection risk in kidney transplantation recipients. However, the results of these studies remain inconclusive. The aim of this study was to conduct a meta-analysis to further assess the associations.The PubMed, Embase, and Ovid Medline databases were searched. Two independent authors extracted data, and the effects were estimated from an odds ratio (OR) with 95% confidence intervals (CIs). Subgroup and sensitivity analyses identified sources of heterogeneity.A total of 16 studies including 595 rejection patients and 1239 stable graft patients were included in order to study the IL-10 -1082 (rs1800896 G/A), -819 (rs1800871 C/T), -592 (rs1800872 C/A) and IL-10  polymorphisms. The -1082 G/A polymorphism was not associated with an increased graft rejection risk . Moreover, all of the -819 C/T , -592 C/A  and IL-10  polymorphisms  did not increase the graft rejection risk. In addition, we also performed subgroup analysis by ethnic group (mainly in Europeans or Asians) and rejection type (acute or chronic). There was also lack of evidence of a significant association between the IL-10 gene polymorphism and graft rejection risk. The present meta-analysis indicated that the IL-10 gene polymorphism was not associated with graft rejection risk in kidney transplantation recipients.This meta-analysis found evidence that the IL-10 polymorphism does not increase the risk of graft rejection in kidney transplantation recipients. Further chronic rejection and other ethnic population studies are needed to confirm our results. Worldwide, kidney transplantation (KTx) is recognized as a treatment for end-stage renal disease (ESRD) . It provPrevious studies show that patients’ genetic background was associated with allograft outcome , which cThe aim of the present study was to determine whether analysis of IL-10 gene polymorphisms can be used to identify patients at increased risk for acute rejection or delayed graft function. We performed this meta-analysis to evaluate the association between IL-10 gene polymorphisms and graft rejection in recipients after kidney transplantation.We performed a search to identify the studies that examined the associations between Interleukin-10 gene polymorphisms and graft rejection risk in kidney transplantation recipients. Literature was identified by searching the Ovid Medline, Embase, and PubMed databases. The last updated search was performed in August 2014. The searching terms used were ‘‘Interleukin-10 gene or IL-10”, ‘‘polymorphism”, ‘‘rejection or graft failure”, and “renal transplantation or kidney transplantation or renal transplant”. The search was carried out without restriction on language but was limited to studies that had been conducted on human subjects.The included studies met the following criteria: (1) evaluated IL-10 gene polymorphism and graft rejection risk , -819 (rs1800871 C/T), -592 (rs1800872 C/A), IL-10); (2) for case–control studies, the clinical outcome were defined as acute rejection or chronic rejection; (3) supplied the number of individual genotypes in rejection cases and no rejection cases, having a stable graft function group as a comparator; and (4) indicated that the distributions of genotypes in cases and controls were available for estimating odds ratio (OR) with a 95% confidence interval (CI).Two authors independently extracted the information from all eligible publications using standard data extraction forms. Disagreements were resolved by discussion between the two authors or through consultation with a third reviewer. A standardized data form was used for data collection and included the following: first author, year of publication, country of origin, ethnicity of the study population, definition of rejection cases, no rejection cases, genotyping methods, and genotype distribution in cases and controls.The publication bias was evaluated using Egger’s linear regression test, which measures funnel plot asymmetry using a natural logarithm scale of odds ratios (ORs), and subgroup analyses were also performed to determine the heterogeneities.2 test. I2 values of 25%, 50% and 75% correspond to low, medium and high levels of heterogeneity, respectively. A random-effects model was used if the studies exhibited heterogeneity ; otherwise, the fixed-effects model was selected. To evaluate the ethnicity-specific effects, subgroup analysis was performed by ethnicity and by acute rejection or delayed graft dysfunction. The Begg’s test and the Egger’s test were used to assess publication bias statistically. Hardy-Weinberg equilibrium (HWE) was tested with the Pearson’s v2 test. STATA software (version 12.0) was used to perform all statistical analyses.We performed meta-analysis on (1) allelic contrast, (2) recessive, (3) dominant, and (4) additive models. And we use dominant model as a representative model to explain the results. Point estimates of risks, ORs, and 95% confidence intervals (CI) were estimated for each study. We also assessed within- and between-study variations and heterogeneities using Cochran’s Q-statistic. Heterogeneity was analyzed using a chi squared test on N-1 degrees of freedom, with an alpha of 0.05 used for statistical significance and with the IThe flow diagram for the literature search is shown in There were a total of 407 rejection cases and 675 controls in 11 case-control studies that were included in the meta-analysis on the relationship between the -1082 G/A polymorphism and the risk of graft rejection. The study numbers for acute rejection and chronic graft rejection were 8 and 3, respectively. Five studies were from a European population, 5 were from an Asian population, and 1 was from mix ethnic population. We found that there was no association between the -1082 G/A polymorphism and graft rejection risk  polymorphisms and the risk of graft rejection. Five studies were performed on acute rejection and 1 was performed on chronic graft rejection. Among them, 3 were from European populations, 1 was from Asia, and 2 were performed with other ethnic populations. The high/intermediate/low expression of the IL-10 was according to the level of production based on the references , 26, theAs reflected by the funnel plots  and the Allograft rejection is mediated by complex immunologic mechanisms . CytokinThe association between the IL-10 gene polymorphism and graft rejection risk has been studied in liver transplantation , heart tIn the subgroup analysis based on different types of rejection, we also found there was no association between the IL-10 gene polymorphism and acute graft rejection or chronic graft rejection. Furthermore, considering that the results produced were from different genetic backgrounds, subgroup analyses based on ethnicity were also performed and had similar results. The ethnic populations were mainly from European and Asian countries. Whether other ethnic populations have an association was beyond the explanation of our meta-analysis.Publication bias did not exist in the overall comparisons, indicating that the results of the present meta-analysis were statistically robust. In addition, subgroup meta-analyses were also performed to determine the heterogeneity of the ethnicity or rejection type, and we found similar results.For better interpretation of the results, some limitations should be considered in this meta-analysis. We studied the association only in KTx in recipients, while the association between IL-10 polymorphism and the donors was not included. Second, due to a lack of original information for each included subject, we were unable to perform further stratified analyses, such as gender and age. Third, the included studies involved mainly European and Asian populations for subgroup meta-analysis by ethnicity. Data concerning other ethnicities were limited.In conclusion, the present meta-analysis including 595 rejection patients and 1239 stable graft patients suggested that the IL-10 gene polymorphism was not associated with an increased graft rejection risk. However, due to its limitations, our findings in the present meta-analysis should be confirmed by further chronic rejection and other ethnic population studies.S1 Fig(TIF)Click here for additional data file.S2 Fig(TIF)Click here for additional data file.S3 Fig(TIF)Click here for additional data file.S4 Fig(TIF)Click here for additional data file.S1 File(DOCX)Click here for additional data file.


The vitamin D receptor (VDR) mediates the major cellular activities of vitamin D and regulates various signaling pathways implicated in cancer development and progression. VDR variants have been found associated with the risk of developing melanoma; however, previous epidemiological studies are inconsistent. We have systematically reviewed the published epidemiological literature and conducted a meta-analysis to assess associations between common VDR variants and melanoma risk.2 = 22%) for Ff vs. FF and 1.19  for ff vs. FF. The dominant genetic model suggested the allele f carriers showed an 18%  increased risk for melanoma compared to homozygote FF. In contrast, the Bsm1 was found to be associated with a decreased risk for melanoma with the pooled OR was 0.85  for Bb vs. bb and 0.83  for BB vs. bb. Under the dominant genetic model, a 15%  decrease of melanoma risk was found for those with BB or Bb genotype compared to those of bb genotype.We identified 10 eligible studies that evaluated six VDR variants  in a total of 4,961 melanoma patients and 4,605 controls. The pooled estimates identified two variants—Fok1 and Bsm1—as significantly associated with melanoma risk, but not for the other four variants Apa1, Cdx2, EcorV and Taq1. For Fok1, the pooled OR was 1.18 (95% CI = 1.06-1.30; IThe VDR variants Fok1 and Bsm1 may influence the susceptibility to developing melanoma, though further studies are needed to verify these conclusions. Melanoma is one of the most aggressive skin cancers and is responsible for approximately 75% of skin cancer-related deaths worldwide . An esti2D) are mediated by the nuclear vitamin D receptor (VDR), which regulates the transcription of target genes. The VDR gene is located on chromosome 12q12-q14 and comprises 11 exons and 11 introns, with more than 600 single nucleotide polymorphisms having been identified within its coding region [Vitamin D is a fat-soluble essential vitamin metabolised from 7-dehydrocholesterol in skin cells following UV light exposure or obtained from dietary sources. Vitamin D promotes calcium and phosphate absorption to affect bone metabolism, and plays important roles in the regulation of cellular proliferation, differentiation, apoptosis, migration, and the immune response. Vitamin D deficiency is a worldwide problem, with insufficient vitamin D levels increasing the risk of developing obesity, diabetes, asthma, autoimmune disorders, infectious diseases, and some cancers . Most big region . Many epg region . Given tThe meta-analysis studies were performed following the MOOSE statement.Two individuals independently performed a systematic search and comprehensive review of the literature to identify eligible studies. Epidemiological studies deposited in the PubMed database to September, 2014 were searched using the terms “VDR” or “vitamin D receptor” in combination with “melanoma” to identify studies that have reported associations between the VDR variants and melanoma risk. Only the studies that are reported in English were included in the current meta-analysis studies. Following this systematic search, citations within the discovered epidemiological studies and related reviews were checked to identify any missing studies. Figure Individual studies that are included in the current meta-analysis studies had to meet the following criteria: 1) determine an association between VDR variant(s) and melanoma risk; 2) be a hospital- or population-based case–control, cross-sectional, or prospective study; 3) provide the genotype distribution within cases and controls ; 4) the variant was directly genotyped and not imputed; 5) if two or more studies had overlapping participant populations, only the most complete study was included; 6) only those variants with at least three studies examining their association with the melanoma risk were included to reduce potential bias. Studies that did not provide detailed information regarding allele distribution in the cases and controls were excluded. Any study that was reported in language other English was also excluded.For each study, two investigators independently extracted the following information: first author’s last name, year of publication, study region, participant ethnicity, origin of controls, number of participants, studied variants, and genotyping methods. For the purposes of meta-analysis, subgroup studies from an individual report were treated as independent studies.2 statistic, which indicates the percentage of variability across the studies that is caused by heterogeneity rather than by chance alone. A p value < 0.05 for the Q-test and/or I2 > 25% was recognised as significant and heterogeneity between the studies was noted. Publication bias was assessed graphically through funnel plots and further examined with Egger’s linear regression. Where a significant publication bias was noticed, the trim and fill method was applied. All statistical analyses were performed with STATA 11.0 and Review Manager 5.2. A two-sided p value < .05 was considered statistically significant.Associations between individual VDR variants and melanoma risk were determined as a pooled odds ratio (OR) together with a 95% confidence interval (CI). Additive and dominant genetic models were applied for each variant and the DerSimonian–Laird method  used to p = .001). The study performed by Randerson-Moor et al. [We identified 10 suitable studies with a total of 4,961 melanoma patients and 4,605 controls which have described associations between common VDR variants and melanoma risk  for the GA vs. AA genotype and 1.09  for the GG vs. AA genotype. Moderate heterogeneity between the studies was detected. No significant change in risk between GA or GG carriers and AA carriers was identified  by the dominant genetic model. A forest plot and an Egger’s linear regression test suggested that significant publication bias existed  are not. As a nuclear receptor phosphoprotein, VDR binds to its ligand 1,25(OH)ogenesis , and VDRogenesis . Moreoveogenesis . Taken t2D [2D compared with the longer VDR isoform [Fok1 is located in exon 2 of the VDR coding region. The F to f transition alters the translation start site for the VDR protein, making the f allele three amino acids longer. This larger VDR molecule is less active than the regular-sized receptor following stimulation with 1,25(OH)2D . Moreove2D . Etten e isoform . Additio isoform . Whereas isoform  and ovar isoform . Althoug2D levels compared with bb individuals [Bsm1 is located within the 3′-UTR region of VDR and is in high linkage disequilibrium with Apa1 and Taq1. Previous studies identified the baT and Bat haplotypes as the most frequent in the population, with baT mRNA having lower stability than Bat transcripts . Chudek ividuals . We repoividuals , while Xividuals . Xu et aividuals . These dVDR promoter region where they may influence gene transcription [We detected a high linkage disequilibrium between the Cdx2 and EcoRV variants, both of which are located in the cription . The G tcription . Our curcription . GATA-3 cription . Our curThere are several limitations to our current meta-analysis. First, the sample size used to determine associations between individual variants and melanoma risk was relatively small. Therefore, the lack of an association between some variants and melanoma risk may result from low statistical power. Second, nearly all of the eligible studies were performed in Western countries, and whether the associations identified are present in other populations remains unknown. Third, the method we employed did not take into account other co-factors such as age, sex, smoking, vitamin D level, or the latitude at which participants reside, all of which may modify the associations between specific VDR variants and melanoma risk.This meta-analysis identified that the VDR variants Bsm1 and Fok1 are significantly associated with melanoma risk, whereas four other variants—Apa1, Cdx2, EcoRV, and Taq1—are not. Nevertheless, more studies are warranted to validate these results and further understand the mechanisms underlying these associations.


Subgroup analysis showed elevated PLR did not predict poor OS in patients included in large sample studies  whereas petients with Caucasian ethnicity  and PLR cut-off value >180  had enhanced prognostic efficiency for OS. Subgroup analysis also demonstrated that high PLR did not predict poor DFS/PFS in Asian patients. In conclusion, our meta-analysis suggested that elevated PLR was associated with poor OS and DFS/PFS in NSCLC. In addition, high PLR especially predicted poor OS in Caucasians but had no association with poor DFS/PFS in Asians.This study was designed to explore the association between elevated platelet to lymphocyte ratio (PLR) and prognosis of patients with non-small cell lung cancer (NSCLC) by meta-analysis. A total of 11 studies with 3,430 subjects were included and the combined hazard ratio (HR) and 95% confidence intervals (95% CI) were calculated. The data showed that elevated PLR predicted poor overall survival (OS) (HR = 1.42; 95% CI: 1.25–1.61, p < 0.001; I Lung cancer is one of the most commonly diagnosed cancer forms and the leading cause of cancer related mortality in both developed and developing countries246et al.Accumulated evidence show that host’s inflammatory response plays an important role in cancer progression and prognosis810et al.et al.et al.Cannon The literature selection process of the eligible studies was presented in 151617181920212223241518201619211518161720212324161718211519202223192015161718192021222324181920241820211516171922232 = 63.6, Ph = 0.002; Eleven studies151617181920212223242 = 46.8, Ph = 0.111; There were five studies181920242 = 80.8, Ph = 0.001), however, elevated PLR had enhanced prognostic efficiency for poor OS in Caucasians  and when the cut-off value of PLR was more than 180 . As for the PLR in DFS/PFS, the results showed that elevated PLR did not predict poor DFS/PFS in Asians  whereas high PLR was correlated with shortened DFS/PFS in small sample studies  .Each single study was omitted every time to estimate the influence of individual data sets on the combined HR. The results showed that the pooled HRs for OS and DFS/PFS were not substantially changed , indicatBegg’s test suggested no evidence of obvious publication bias .In the present study, using the method of meta-analysis, we explored the prognostic impact of pretreatment PLR on OS and DFS/PFS in patients with NSCLC. By combining the HRs and 95% CIs from eleven primary studies15161718192021222324Inflammation and immune responses were recognized as important stimulators for tumorigenesis since it was first proposed by Virchow2732The results of this meta-analysis provided evidence supporting elevated PLR as a prognostic factor for OS in NSCLC, which was in line with a previous meta-analysis182021The present study had several limitations. First, obvious heterogeneity existed in this meta-analysis. Although sensitivity analysis and publication bias test indicated the credibility of the results, we could not rule out that different study criteria used in the primary resulted in the discrepancies between studies. Second, the nonuniform cutoff value defining elevated PLR may not be applicable for clinical use, an identical cutoff value was needed. Finally, the summary HR and 95% CI rather than individual patient data were used for calculation of pooled HR and 95% CI in this meta-analysis.In conclusion, our study for the first demonstrated the prognostic role of elevated PLR for poor OS and DFS/PFS in NSCLC by meta-analysis. Considering the limitations of our study, further well-designed studies using uniform PLR cutoff value are warranted to test our results.The databases of Web of Science, Embase and Pubmed were thoroughly searched until December, 2015. The following terms were used in separation or in combination: “PLR”, “platelet-lymphocyte ratio”, “platelet to lymphocyte ratio”, “lung cancer”, “lung carcinoma” or “NSCLC”. Reviews and reference lists were also manually retrieved for additional publications. The publication language was limited to English.The inclusion criteria were: 1) patients pathologically diagnosed as NSCLC; 2) PLR was measured by blood-based methods before formal treatment; 3) HRs and 95% CIs for PLR in OS and (or) DFS/PFS were reported in text or sufficient data was provided for the calculation of HRs and 95% CIs. 4) full text papers published in English.The exclusion criteria were as follows: 1) review, meeting abstract, letter, not full text in English; 2) duplicate data; 3) nonhuman studies; 4) did not present the cut-off value for elevated PLR.Two independent reviewers  extracted the following information from the eligible studies: the surname of the first author, year of publication, study country, sample size, treatment methods, cut-off value of high PLR and survival data. Disagreements were resolved by joint discussion.http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp). This scale is composed of three parts: selection, comparability and outcome assessment. The full mark is 9 points and studies labeled with ≥6 points were regarded as high-quality researches.The quality assessment of primary studies was performed according to Newcastle-Ottawa quality assessment Scale (NOS) was used to calculate the pooled HR and 95% CI. Otherwise, the fixed effects model (Mantel-Haenszel method) was used. Studies with sample size >200 were considered as large sample studies, otherwise was regarded as small sample size. Subgroup analyses stratified by ethnicity, sample size, treatment methods and PLR cut-off were carried out.The hazard ratio (HR) with 95% confidence intervals(95% CI) were directly obtained from the articles or estimated according to the methods reported by Tierney Sensitivity analysis was conducted by omitting each single study and recalculating their HRs. Publication bias was evaluated using Begg’s testHow to cite this article: Gu, X. et al. Prognostic value of platelet to lymphocyte ratio in non-small cell lung cancer: evidence from 3,430 patients. Sci. Rep.6, 23893; doi: 10.1038/srep23893 (2016).


CYP1A1 MspI and Ile462Val polymorphisms and renal cell carcinoma (RCC) risk, but the results have been conflicting. To more precisely evaluate the potential association, we carried out a meta-analysis of seven published case-control studies. The meta-analysis indicated that the MspI polymorphism was associated with an increased RCC risk . No significant associations were found for the Ile462Val polymorphism for all genetic models. When stratified by smoking status, smokers carrying the variant Vt and Val allele were more susceptible to RCC . These data indicate that the CYP1A1 MspI polymorphism significantly increased RCC risk, while the Ile462Val polymorphism was not associated with RCC. Among smokers, individuals with the CYP1A1 Vt allele and Val allele showed a significantly increased risk of RCC. More well-designed studies with larger samples are warranted to show the underlying mechanisms of CYP1A1 in the development of RCC.Cytochrome P450 1A1 (CYP1A1) usually metabolizes carcinogens to their inactive derivatives but occasionally converts the chemicals to more potent carcinogens. To date, many studies have evaluated the association between the  In 2014, an estimated 63,920 people in the United States will be diagnosed with cancers of the kidney and renal pelvis, the vast majority of which are renal cell carcinoma (RCC), with an estimated 13,860 deaths3CYP1A1 gene have been recently studied: a thymine (T) to cytosine (C) transition in the noncoding 3′-flanking region , and an adenine (A) to guanine (G) substitution at codon 462 in exon 7 CYP1A1 is a member of the CYP1 family and plays a key role in the metabolism of drugs and environmental chemicals. The human CYP1A1 enzyme is the most active among the CYPs in metabolizing pro-carcinogens, particularly the polycyclic aromatic hydrocarbons, into highly reactive intermediatesMspI, rs446903, anCYP1A1 and various cancers, including prostate, esophageal, lung, cervical, head and neck cancers891011CYP1A1 MspI and Ile462Val polymorphisms and RCC risk has not been performed. Here we performed a meta-analysis of all currently available publications to examine whether the genotype status of the two polymorphisms in CYP1A1 is associated with RCC risk.To date, a number of meta-analyses have been performed to explore the association between the MspI and Ile462Val polymorphisms of CYP1A1 MspI and Ile462Val polymorphisms, so they were regarded as two independent studies. Seven case-control studies were eligible according to the inclusion criteria, among which three studies (531 cases and 739 controls) examined the CYP1A1 MspI polymorphism and four studies (742 cases and 975 controls) examined the CYP1A1 Ile462Val polymorphism. Of the five publications, three were published in English and two were written in Chinese, and four were conducted in China and one was based in India. A list of details from the studies included in the meta-analysis is provided in After a literature search, five publications were eligible for the meta-analysis13141516CYP1A1 MspI and Ile462Val polymorphisms with RCC is shown in The summary of meta-analysis for Overall, MspI polymorphism was significantly associated with the increased risk of RCC under three genetic comparison models  . When stNo significant association was found between the Ile462Val polymorphism and RCC risk for all genetic models . When stratified by HWE test and country, the polymorphism was not significantly associated with RCC risk. Obvious heterogeneity was observed in all genetic models. Neither the HWE test or country could explain the heterogeneity, which could have been caused by the limited number of included studies.CYP1A1 polymorphisms and smoking on RCC is shown in CYP1A1 Vt allele and Val allele showed a significantly increased risk of RCC . However, no significant interaction was found between smoking and the CYP1A1 Vt allele or Val allele .The impact of the combination of P = 0.405 for allele model). The leave-one-out sensitivity analysis indicated that no single study qualitatively changed the pooled ORs (data not shown). The results of sensitivity analyses indicated that the data of our meta-analysis are relatively stable and credible.Begg's funnel plot and Egger's test were performed to assess the publication bias of included studies. As shown in CYP1A1 enzymes may contribute to the variable susceptibility to carcinogenesis by altering the level of gene expression or messenger RNA stability, resulting in highly inducible activity of the enzyme.CYP1A1 is a member of the CYP1 family and participates in the metabolism of a vast number of xenobiotics, as well as endogenous substratesCYP1A1 MspI and Ile462Val polymorphisms and RCC risk. Our results suggested an important role of the CYP1A1 MspI polymorphism in the risk of developing RCC. The overall pooled ORs suggested that individuals carrying the variant C allele and the homozygous genotype CC were significantly more susceptible to RCC compared with those carrying the wild-type TT genotype . However, our results showed that the CYP1A1 Ile462Val polymorphism was not associated with RCC. Several studies have suggested the CYP1A1 polymorphisms were associated with elevated risks of prostate cancer, esophageal cancer, and head and neck cancer89CYP1A1 polymorphisms and risks for gastric cancer and colorectal cancer were found in other studies20CYP1A1 might exert different effects in different types of cancers.To the best of our knowledge, this is the first meta-analysis to assess the association between the CYP1A1 genotypes and smoking in patients with RCC. In our meta-analysis, we found that individuals with the CYP1A1 Vt allele and Val allele showed a significantly increased risk of RCC among smokers. This implied that polymorphisms in metabolic genes might greatly increase susceptibility carcinogens to RCC in smokers.Epidemiological studies have shown that cigarette smoking is an important risk factor for RCC. In the subgroup analysis based on smoking status, we evaluated the interaction between CYP1A1 polymorphisms and RCC risk, especially in Caucasians and Africans. Third, several studies departed from the HWE, which may have led to a bias for the overall estimates of the meta-analysis. Finally, the gene-gene and gene-environment interplays play crucial roles in the development of RCC. Previous research implicated a variety of risk factors in RCC development, including obesity, smoking, hypertension, renal disease and viral hepatitis22Several limitations should be taken into consideration when analyzing the results of our meta-analysis. First, only seven independent case-control studies with 885 cases and 1,128 controls were included in our study. More studies with larger samples are needed to take further power of meta-analysis and obtain more reliable results. Second, all seven studies were performed in Asians, and there was no study involving Caucasians or Africans. Therefore, further studies are needed to investigate the association between CYP1A1 MspI polymorphism significantly increased RCC risk, while the Ile462Val polymorphism was not associated with RCC. Among smokers, individuals with the CYP1A1 Vt allele and Val allele showed a significant highly increased risk of RCC. Considering the limited sample size and ethnicities included in the meta-analysis, further larger scale studies are necessary to enrich the present findings, especially in Caucasians and Africans.In conclusion, our meta-analysis suggests that the CYP1A1 MspI and Ile462Val polymorphisms and RCC risk up to July 20, 2014. We used the following keywords and subject terms: “polymorphism” or “SNP” or “gene mutation” or “genetic variants”, and “renal cell cancer” or “renal cell tumor” or “renal cell carcinoma”, and “Cytochrome P450 1A1” or “CYP1A1” or “MspI” or “Ile462Val”. References of all primary studies and review articles were reviewed to obtain additional references. When multiple publications reported on the same or overlapping data, the largest or most complete study was chosen.We performed a literature search of the PubMed, Embase, China National Knowledge Infrastructure (CNKI) and Web of Science databases to identify individual studies on the association between the CYP1A1 MspI and Ile462Val polymorphisms and RCC risk; and (3) sufficient information to estimate the odds ratio (OR) and a 95% confidence interval (CI). Articles were excluded based on the following: (1) an irrelevant study; (2) a duplicate publication; (3) based on incomplete data; or (4) case-only studies, letters and reviews.Publications were selected if they satisfied the following inclusion criteria: (1) a case-control study; (2) an evaluation of the association between the p-values for Hardy-Weinberg equilibrium (HWE), and genotype distribution in cases and controls.Based on the inclusion criteria, two investigators (Meng and Tian) independently reviewed and extracted data from all eligible studies. The following items were extracted: first author, year of publication, ethnicity, country of origin, source of controls , sample size, genotyping method, CYP1A1 gene polymorphisms and the risk of RCC under four genetic models: the allele model (A vs. G), homozygous model (AA vs. GG), recessive model (AA vs. GG + GA), and dominant model (AA + GA vs. GG). We tested whether genotype frequencies of controls were in HWE using the χ2 test. The heterogeneity between the studies was evaluated with the χ2-based Q (Cochran's Q test) and I2 statistic tests. Heterogeneity between studies was considered to be significant when P < 0.05 for Q-tests or when I2 was more than 80%2428The pooled ORs with corresponding 95% CIs were calculated to assess the association between the Designed the study: J.Y. and M.F. Searched databases and collected full-text papers: M.P., S.C. and T.X. Extracted and analyzed the data: J.Y., M.F. and T.X. Statistical analyses: J.Y. and M.F. Wrote the main manuscript text: J.Y., M.F. and M.P. All authors reviewed the manuscript.


It is unclear whether an ‘obesity survival paradox’ exists for pneumonia. Therefore, we conducted a meta-analysis to assess the associations between increased body mass index (BMI), pneumonia risk, and mortality risk.Cohort studies were identified from the PubMed and Embase databases. Summary relative risks (RRs) with their corresponding 95% confidence intervals (CIs) were calculated using a random effects model.P = 0.02, I2 = 87%). In the dose–response analysis, the estimated summary RR of pneumonia per 5 kg/m2 increase in BMI was 1.04 . Inversely, overweight and obese subjects were significantly associated with reduced risk of pneumonia mortality . The estimated summary RR of mortality per 5 kg/m2 increase in BMI was 0.95 .Thirteen cohort studies on pneumonia risk , and ten cohort studies on mortality  were included. Overweight and obese individuals were significantly associated with an increased risk of pneumonia (RR = 1.33, 95% CI 1.04 to 1.71, This meta-analysis suggests that an ‘obesity survival paradox’ exists for pneumonia. Because this meta-analysis is based on observational studies, more studies are required to confirm the results. The ideal BMI is between 18.5 and 24.9. Being overweight is considered as having a BMI between 25 and 29.9, and being classified as obese falls into a BMI of 30.0 or greater [The prevalence of obesity has dramatically increased in the last two decades . The dia greater . This phet al.[et al.[et al.[Pneumonia is one of the most common infectious diseases; however, there is uncertainty about the association between obesity and pneumonia risk or pneumonia mortality -28. For et al. suggestel.[et al. did not l.[et al. indicatel.[et al.-28. ThusTo date, no meta-analysis has shown whether an ‘obesity survival paradox’ exists for pneumonia. The aim of this meta-analysis was to investigate the relationships between elevated BMI, pneumonia risk, and mortality.This meta-analysis was performed according to a predetermined protocol described in the following paragraphs, using standard systematic review techniques, as outlined by the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) criteria .A literature search was performed (WN and YZ) using the PubMed search engine, with the database being last accessed on 15 June 2013. The Embase database was also searched for relevant studies published up to June 2013. References from relevant articles were manually checked for further studies. The detailed search strategy is presented in the Additional file Two reviewers (WN and YZ) independently screened the abstracts of papers identified by the literature search, retrieved potentially relevant studies and determined study eligibility. Studies were included if: (1) the study design was a prospective or retrospective cohort study; (2) the exposure of interest was BMI; (3) they reported adjusted relative risks (RRs), hazard ratios (HRs) or odds ratios (ORs) with corresponding 95% confidence intervals (CIs), or provided a RR/HR/OR with corresponding 95% CI per unit increment in BMI; and (4) the outcome was pneumonia incidence or mortality. If the same cohort was used in more than one publication, we included the publication that reported the results in greater detail or, if similar, the one with the largest number of cases. Data published only in abstract form were excluded. Case reports, review articles and commentary articles were also excluded. Studies with pediatric participants or pregnant populations were not included.From each study, two reviewers (WN and YZ) independently extracted the first author, publication year, study design, location where the study was performed, number of cases and cohort size, gender and age of study participants, follow-up duration, method for assessing height and weight, ascertainment of pneumonia, type of pneumonia, BMI category, adjusted RR/HR/OR and the corresponding 95% CI, and covariates controlled for multivariable analysis. The authors of the relevant studies were contacted by Email if more information was needed.Two independent reviewers (WN and YZ) completed the quality assessment. The Newcastle–Ottawa Scale (NOS) was used to evaluate the methodological quality, which scored studies by the selection of the study groups, the comparability of the groups and the ascertainment of the outcome of interest . Discrepversus normal weight. The random effects model was utilized. HRs and ORs were regarded as equivalent to RRs in cohort studies. If a study reported results specifically for men and women, respectively, we combined the sex-specific RR estimates using a fixed-effects model before combining with other studies.For pneumonia risk and pneumonia mortality risk, we calculated summary RRs and 95% CIs for overweight and obesity P < 0.05 was considered statistically significant. We also combined the sex-specific estimates using a fixed-effects model to generate an estimate for both genders combined. The method described by Greenland and Longnecker [2 BMI increment.In dose–response analysis, we calculated the RR per 5-unit increase in the BMI levels for each study. The average of the natural logarithm of the RRs was estimated and the RR from each study was weighted by the inverse of its variance. A two-tailed ngnecker  was usedNonlinear dose–response curves were plotted using restricted cubic splines for each study, using knots fixed at percentiles 10%, 50% and 90% through the distribution; then these were combined using multivariate meta-analysis -34.I2 statistics. For the I2 metric, we considered low, moderate and high I2 values to be 25%, 50% and 75%, respectively. We examined the role of several potential sources of heterogeneity by subgroup analyses according to study design, gender, ascertainment of case, pneumonia type, assessment of anthropometry, and duration of follow-up. Meta-regression was also performed to find the sources of heterogeneity. Sensitivity analysis was conducted by excluding one study at a time to explore whether the results were driven by one large study or by a study with an extreme result. Potential small study effects, such as publication bias, were investigated with funnel plots.Statistical heterogeneity among studies was evaluated using the Q and P < 0.1 was used to decide whether heterogeneity was present. In other cases, P values were two sided with a significance level of 0.05.All statistical analyses were performed with the Stata software . A threshold of The process of identifying relevant studies is shown in Figure Twelve cohort studies n = 1,536,623) investigated the association between BMI and pneumonia risk -19, and ,536,623 P = 0.02, I2 = 87%). A small-study effect was demonstrated using a funnel plot [see Additional file P = 0.01, I2 = 84%; Figure P > 0.05; Figure Compared with normal weight individuals, overweight and obese individuals were associated with a significantly increased risk of pneumonia . The potential sources of heterogeneity were explored by stratifying analyses. Studies comparing overweight and obese subjects with normal weight subjects, and studies assessing dose–response associations were explored, respectively. The positive relationship between BMI and risk of pneumonia was significant in subgroups by ascertainment of case and assessment of weight and height [see Additional file P < 0.01, I2 = 34%). A small-study effect was revealed by the funnel plot [see Additional file Overweight and obese individuals were associated with decreased mortality risk . Stratified analyses were defined by study design, gender, assessment of weight and height, and follow-up duration. Studies comparing overweight and obese subjects with normal weight subjects, and studies assessing dose–response associations were explored, respectively. The inverse relationship between BMI and risk of mortality was significant in subgroups that were defined by ascertainment of case and study design. However, in the female subgroup or studies with shorter follow-up duration, the inverse relationship was not statistically significant [see Additional file In this meta-analysis, we showed that an ‘obesity survival paradox’ might exist for pneumonia. On the one hand, there was a positive association of obesity with pneumonia risk. On the other hand, pneumonia mortality was lower for patients with high BMI compared to normal BMI.In a recent meta-analysis, Phung and coworkers found a J-shaped relationship between BMI and risk of CAP and a U-shaped relationship between BMI and risk of influenza-related pneumonia . Our res3 levels [3 concentration had a higher risk of pneumonia [ob/ob) and leptin receptor (db/db) deficient mice showed severe immune abnormalities and greater susceptibility to viral and bacterial infection [There were several potential explanations for why obese individuals may have higher risk of pneumonia. First, obesity is often accompanied by co-morbid conditions, such as gastroesophageal reflux disease . When re3 levels . More reneumonia . Fourth,nfection . Individnfection . Therefonfection . Taken tet al. showed that the risk of pneumonia mortality was 2.6 times higher in men of the lowest BMI quartile compared to the highest quartile [et al. indicated that the highest two quartiles of BMI had a significantly reduced risk of mortality compared with the lowest quartile [et al.[This present meta-analysis suggested a survival advantage for obese patients with pneumonia. A study by LaCroix quartile . Anotherquartile . We propquartile . Thus, oe [et al. indicatee [et al.. Additioe [et al.,28. ThirThere are several limitations of the current study. First, a meta-analysis of observational studies inherits the limitation of the original studies. Although most studies adjusted for potential confounders, such as age, gender, smoking and underlying diseases, the possibility of residual confounding cannot be ruled out. Because this meta-analysis investigated only BMI, we cannot exclude the possibility that the observed associations may be confounded by other lifestyle factors, such as lower physical activity or dietary factors. Second, the number of available studies that were included in this meta-analysis was moderate. Therefore, the results could be influenced by some factors,such as random error. Third, most of the studies used International Classification of Diseases (ICD)-9 or ICD-10 codes to classify pneumonia. van de Garde and coworkers suggested that ICD-9 codes showed modest sensitivity for detecting CAP, leaving at least one quarter of pneumonia cases undetected . Fourth,This meta-analysis suggests that obese individuals may be at higher risk for pneumonia, but they might have a lower mortality risk. Additional prospective studies with adjustment for more confounding factors are warranted before a conclusion can be drawn.BMI: body mass index; CAP: community-acquired pneumonia; CI: confidence interval; HAP: hospital-acquired pneumonia; ICD: International Classification of Diseases; NOS: Newcastle–Ottawa Scale; RR: risk ratio; TNF-α: tumor necrosis factor-alpha.The authors declare that they have no competing interests.WN searched the papers, created tables, and wrote the manuscript. YZ searched the papers, created tables, and wrote the manuscript. SHJ analyzed and provided data. KJJ analyzed and provided data. BL reviewed the study proposal and contributed to the manuscript writing. QX reviewed the study proposal and contributed to the manuscript writing. All authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1741-7015/12/61/prepubSearch strategy.Click here for fileCheck list for methodological quality assessment and quality scores of cohort studies using the Newcastle-Ottawa Scale.Click here for filePRISMA checklist.Click here for fileFunnel plot of the association between obesity and pneumonia risk.Click here for fileFunnel plot of the association between obesity and pneumonia risk in dose-response analysis.Click here for fileSubgroup analyses of pneumonia risk, overweight and obesity versus normal weight and dose–response analyses, respectively.Click here for fileFunnel plot of the association between obesity and pneumonia mortality risk.Click here for fileFunnel plot of the association between obesity and pneumonia mortality risk in dose-response analysis.Click here for fileSubgroup analyses of pneumonia mortality risk, overweight and obesity versus normal weight and dose–response analyses, respectively.Click here for file