Single Nucleotide Polymorphisms Within B7-H2Gene3’-UTR And Correlation With The Risk Of Gastric Cancer

Objective: To investigate the correlation between the single nucleotidepolymorphisms (SNPs) in the3’-UTR of B7-H2gene and gastric cancer development,and to further explore the mechanism of downregulation of B7-H2in gastric cancer.Methods: Firstly, the SNPs in the3’-UTR of the B7-H2gene and the possiblemiRNA binding-sites in the B7-H23’-UTR were obtained from the online softwares.The SNPs in the putative miRNA binding-sites with minor allele frequencies (MAF) ofnot less than10%were selected as candidate miRSNPs. Secondly, we determined theselected SNP in183gastric cancer patients and348healthy controls by usingpolymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP)method. Furthermore, we analyze the correlation between genotypes of the miRSNP andthe clinicopathological features of gastric cancer. Thirdly, dual luciferase reporter geneassay system was used to analyze the regulatory role of the potential miRNAs on theexpression of B7-H2.Results:1. Forty SNPs in the3’-UTR of B7-H2gene and their allele frequencieswere obtained from the SNP databases. Among them, the minor allele frequencies(MAF) of the SNPs rs15927, rs3804033, rs55769116, rs4819388and rs55769116areover10%. We found that the SNP rs4819388located in the binding-site of miR-24, sowe chose this SNP as research subject.2. Statistical analysis results showed that thers4819388genotypes were significantly related to the occurrence of gastric cancer.Compared with the GG homozygotes, the GA heterozygotes were significantly moreprevalent in the patients (55.7%vs32.8%, OR=1.60,95%CI=1.08–2.37). Comparedwith the GG homozygotes, AA homozygotes had higher possibility of lymphaticmetastasis (OR=9.27，95%CI=1.16–74.2，p=0.017), poorer tumor cell differentiation(OR=8.16，95%CI=0.98–67.8，p=0.043), more advanced TNM stage (OR=4.75，95%CI=1.01–22.4，p=0.046). The A allelic frequencies were significantly higher thanthat of the G allele in the patients with lymphatic metastasis (OR=1.76，95%CI =1.05-2.95， p=0.034) and/or advanced TNM stage (III/IV, OR=1.80，95%CI=1.07-3.04，p=0.032).3. Dualluciferase reporter assays showed that miR-24inhibitedthe expression of B7-H2through binding with the B7-H23’-UTR, and this inhibitoryrole of miR-24was impacted by rs4819388.Conclusion: Our findings suggest that the SNP rs4819388in B7-H23’-UTR,through disrupting the regulatory role of miR-24on B7-H2expression, contributes tothe occurrence of gastric cancer.