title: Regulation of microtubule-associated protein tau (MAPT) by miR-34c-5p determines the chemosensitivity of gastric cancer to paclitaxel.
abstract: BACKGROUND
  Human miR-34c has been reported to be associated with various human malignancies; however, it remains unknown whether miR-34c is involved in chemoresistance in gastric cancer. The aim of this study was to investigate the role of miR-34c in gastric cancer.
  
  
  METHODS
  The adenosine triphosphate-based tumor chemosensitivity assay was used to measure drug sensitivity in gastric cancer samples. The expression levels of miRNA were determined by reverse transcriptase polymerase chain reaction (PCR) and those of protein were by Western blot analysis. Luciferase activity assay was used to verify the target genes of miRNAs. MTT assay was used to test the drug-resistant phenotype changes in cancer cells via overregulation of miRNAs. The methylation status of neighboring CpG islands of miR-34c-5p was analyzed by Bisulfite Sequencing PCR and methylation-specific PCR.
  
  
  RESULTS
  Quantitative real-time polymerase chain reaction demonstrated that expression of miR-34c-5p was downregulated in paclitaxel-resistant gastric cancer samples (p < 0.01). Cells derived from gastric cancer tissues with low miR-34c-5p expression and high microtubule-associated protein tau (MAPT) protein expression tended to have increased chemoresistance to paclitaxel in vitro. Luciferase activity assay confirmed that the 3'-UTR of MAPT mRNA contains a functional miR-34c-5p binding site. Overexpression of miR-34c-5p significantly downregulated MAPT protein expression and increased the chemosensitivity of paclitaxel-resistant gastric cancer cells. Further investigation demonstrated that differential methylation of CpG islands neighboring the miR-34c promoter regulated the expression of miR-34c-5p in gastric cancer cell lines.
  
  
  CONCLUSIONS
  DNA methylation, dysregulation of miR-34c-5p, and MAPT expression are critical factors in the chemoresistance of gastric cancer to paclitaxel.
authors: Department of Oncology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 Jiangsu Province, People's Republic of China.
authors: Hao
authors: H
authors: Wu
authors: Min
authors: M
authors: Huang
authors: Mingjie
authors: M
authors: Lu
authors: Wei
authors: W
authors: Zhu
authors: Yongqian
authors: Y
authors: Shu
authors: Peng
authors: P
authors: Cao
authors: Ping
authors: P
authors: Liu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001665:Binding Sites; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D017239:Paclitaxel / Q000494:pharmacology*; D016133:Polymerase Chain Reaction / Q000379:methods; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000473:pathology; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C054369:MAPT protein, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D016875:tau Proteins; D000255:Adenosine Triphosphate; D008156:Luciferases; D017239:Paclitaxel