title: MiR-503 regulates cisplatin resistance of human gastric cancer cell lines by targeting IGF1R and BCL2.
abstract: BACKGROUND
  Studies have shown that the drug resistance of gastric cancer cells can be modulated by abnormal expression of microRNAs (miRNAs). We investigated the role of miR-503 in the development of cisplatin resistance in human gastric cancer cell lines.
  
  
  METHODS
  MiR-503 expression was measured by quantitative real-time PCR. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) and clonogenic assays were used to examine changes in cell viability and the drug resistance phenotype of cancer cells associated with upregulation or downregulation of the miRNA. A dual-luciferase activity assay was used to verify target genes of miR-503. Immunohistochemistry, Western blotting analysis, and a flow cytometric apoptosis assay were used to elucidate the mechanism by which miR-503 modulates drug resistance in cancer cells.
  
  
  RESULTS
  MiR-503 was significantly downregulated in gastric cancer tissues and several gastric cancer cell lines. Additionally, downregulation of miR-503 in the cisplatin (DDP)-resistant gastric cancer cell line SGC7901/DDP was concurrent with the upregulation of insulin-like growth factor-1 receptor (IGF1R) and B-cell lymphoma 2 (BCL2) expression compared with the parental SGC7901 cell line. An in vitro drug sensitivity assay showed that overexpression of miR-503 sensitized SGC7901/DDP cells to cisplatin. The luciferase activity of reporters driven by IGF1R and BCL2 3'-untranslated regions in SGC7901/DDP cells suggested that IGF1R and BCL2 were both direct target genes of miR-503. Enforced miR-503 expression in SGC7901/DDP cells reduced expression of the target proteins, inhibited proliferation, and sensitized the cells to DDP-induced apoptosis.
  
  
  CONCLUSIONS
  Our findings suggest that hsa-miR-503 modulates cisplatin resistance of human gastric cancer cells at least in part by targeting IGF1R and BCL2.
authors.affiliation: Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
authors.forename: Tongshan
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
authors.forename: Gaoxia
authors.initials: G
authors.lastname: Ge
authors.affiliation: State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, Jiangsu 210093, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
authors.forename: Zebo
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Department of Oncology, Jiangsu Province Hospital, Nanjing, Jiangsu 210029, China. Email: zhuwei1983213@163.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China.
authors.forename: Yongqian
authors.initials: Y
authors.lastname: Shu
authors.affiliation: Department of Oncology, First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, China. Email: liu-ping@csco.org.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D006801:Humans; D007150:Immunohistochemistry; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics
chemical_list: C545473:MIRN503 microRNA, human; D035683:MicroRNAs; D019253:Proto-Oncogene Proteins c-bcl-2; D002945:Cisplatin