title: Lack of association of the MDR1 C3435T polymorphism with susceptibility to gastric cancer and peptic ulcer: a systemic review and meta-analysis.
abstract: BACKGROUND
  The multidrug resistance 1 gene (MDR1) C3435T polymorphism has been demonstrated to influence the P-glycoprotein (P-gp) activity level which is related to inflammation and carcinogenesis. This meta-analysis was performed to estimate the association between the MDR1 C3435T polymorphism and the risk of gastric cancer (GC) and peptic ulcer (PU).
  
  
  METHODS
  A literature search was conducted with PubMed, Embase and the Cochrane library up to November 2013. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. Data were analyzed using Review Manager (Version 5.2), and Stata package (version 12.0) for estimation of publication bias.
  
  
  RESULTS
  Six case-control studies were included, of which five were for GC and two for PU. Overall, no evidence was found for any association between the MDR1 C3435T polymorphism and the susceptibility to GC and PU. In the stratified analysis by H. pylori infection status, stage and histology classification of GC, and PU type, there was still no significant association between them.
  
  
  CONCLUSIONS
  This meta-analysis suggested that the MDR1 C3435T polymorphism is not associated with susceptibility to GC and PU. Large and well-designed studies are warranted to validate our findings.
authors.affiliation: Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, China E-mail : dwg@whu.edu.cn.
authors.forename: Dan-Dan
authors.initials: DD
authors.lastname: Wu
authors.forename: Ji-Xiang
authors.initials: JX
authors.lastname: Zhang
authors.forename: Jiao
authors.initials: J
authors.lastname: Li
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Dong
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics; D063646:Carcinogenesis; D020022:Genetic Predisposition to Disease; D016481:Helicobacter Infections; D016480:Helicobacter pylori / Q000472:pathogenicity; D006801:Humans; D007249:Inflammation; D010437:Peptic Ulcer / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D013274:Stomach Neoplasms / Q000235:genetics*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1