title: miR-638 suppresses cell proliferation in gastric cancer by targeting Sp2.
abstract: BACKGROUND
  MicroRNAs play important roles in the development and progression of various cancers. Recent studies have shown that miR-638 was downregulated in several tumors; however, its role in gastric cancer (GC) has not been investigated in detail.
  
  
  OBJECTIVE
  The purpose of this study was to determine the role of miR-638 and to elucidate its regulatory mechanism in GC.
  
  
  METHODS
  The expression levels of miR-638 and specificity protein 2 (Sp2) were detected by real-time PCR and Western blotting in GC. After pcDNA6.2-GW/EmGFP-miR-638 vector, miR-638 inhibitor and Sp2-siRNA transfection, the AGS cell proliferation was investigated by MTT assay and cell cycle, and apoptosis was detected using the Annexin V/PI. In addition, the regulation of Sp2 by miR-638 was evaluated by real-time RT-PCR, Western blot and luciferase reporter assays; cyclin D1 expression was measured by Western blotting.
  
  
  RESULTS
  The expression of miR-638 is dramatically down-regulated and Sp2 expression is remarkably up-regulated in GC tissues. Luciferase assays revealed that miR-638 inhibited Sp2 expression by targeting the 3'-UTR of Sp2 mRNA. Overexpression of miR-638 and Sp2-siRNA reduced Sp2 expression at both the mRNA and protein levels in vitro, and inhibition of miR-638 increased Sp2 expression. Moreover, we found that miR-638 overexpression and Sp2-siRNA markedly suppressed cell proliferation with decreasing expression of cyclin D1 and inducing G1-phase cell-cycle arrest in vitro; inhibition of miR-638 significantly promoted cell proliferation by increasing expression of cyclin D1 and leading more cells into the S and G2/M phase.
  
  
  CONCLUSIONS
  Our results demonstrated that miR-638 suppressed GC cell proliferation by targeting Sp2 with influence on the expression of cyclin D1. We suggest that miR-638 might be a candidate predictor or an anticancer therapeutic target for GC patients.
authors.affiliation: Department of Genetics and Cell Biology, Environment and Genes Related to Diseases Key Laboratory of Education Ministry, College of Medicine, Xi'an Jiaotong University, Xi'an, 710061, People's Republic of China, lingyuzhao@aliyun.com.
authors.forename: Ling Yu
authors.initials: LY
authors.lastname: Zhao
authors.forename: Yu
authors.initials: Y
authors.lastname: Yao
authors.forename: Jia
authors.initials: J
authors.lastname: Han
authors.forename: Juan
authors.initials: J
authors.lastname: Yang
authors.forename: Xiao Fei
authors.initials: XF
authors.lastname: Wang
authors.forename: Dong Dong
authors.initials: DD
authors.lastname: Tong
authors.forename: Tu Sheng
authors.initials: TS
authors.lastname: Song
authors.forename: Chen
authors.initials: C
authors.lastname: Huang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Shao
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000235:genetics; D056742:Cyclin D2 / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D055785:Gene Knockdown Techniques; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D051704:Sp2 Transcription Factor / Q000037:antagonists & inhibitors* / Q000235:genetics; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology
chemical_list: C530104:CCND1 protein, human; C080336:CCND2 protein, human; D056742:Cyclin D2; C572154:MIRN638 microRNA, human; D035683:MicroRNAs; C497119:SP2 protein, human; D019938:Cyclin D1; D051704:Sp2 Transcription Factor