title: miR-34a mediates oxaliplatin resistance of colorectal cancer cells by inhibiting macroautophagyviatransforming growth factor-β/Smad4 pathway.
abstract: OBJECTIVE
  To investigate whether microRNA (miR)-34a mediates oxaliplatin (OXA) resistance of colorectal cancer (CRC) cells by inhibiting macroautophagyviathe transforming growth factor (TGF)-β/Smad4 pathway.
  
  
  METHODS
  miR-34a expression levels were detected in CRC tissues and CRC cell lines by quantitative real-time polymerase chain reaction. Computational search, functional luciferase assay and western blotting were used to demonstrate the downstream target of miR-34a in CRC cells. Cell viability was measured with Cell Counting Kit-8. Apoptosis and macroautophagy of CRC cells were analyzed by flow cytometry and transmission electron microscopy, and expression of beclin I and LC3-II was detected by western blotting.
  
  
  RESULTS
  Expression of miR-34a was significantly reduced while expression of TGF-β and Smad4 was increased in CRC patients treated with OXA-based chemotherapy. OXA treatment also resulted in decreased miR-34a levels and increased TGF-β and Smad4 levels in both parental cells and the OXA-resistant CRC cells. Activation of macroautophagy contributed to OXA resistance in CRC cells. Expression levels of Smad4 and miR-34a in CRC patients had a significant inverse correlation and overexpressing miR-34a inhibited macroautophagy activation by directly targeting Smad4 through the TGF-β/Smad4 pathway. OXA-induced downregulation of miR-34a and increased drug resistance by activating macroautophagy in CRC cells.
  
  
  CONCLUSIONS
  miR-34a mediates OXA resistance of CRC by inhibiting macroautophagyviathe TGF-β/Smad4 pathway.
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Sun
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Fu-Jing
authors.initials: FJ
authors.lastname: Wang
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Hao-Gang
authors.initials: HG
authors.lastname: Zhang
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Xun-Zheng
authors.initials: XZ
authors.lastname: Xu
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Rui-Chun
authors.initials: RC
authors.lastname: Jia
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Yao
authors.affiliation: Chen Sun, Fu-Jing Wang, Hao-Gang Zhang, Xun-Zheng Xu, Lei Yao, Peng-Fei Qiao, Department of General Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, Heilongjiang Province, China.
authors.forename: Peng-Fei
authors.initials: PF
authors.lastname: Qiao
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000235:genetics*; D000071186:Beclin-1 / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000235:genetics / Q000503:physiopathology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005434:Flow Cytometry; D019073:HT29 Cells; D006801:Humans; D035683:MicroRNAs / Q000187:drug effects / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008875:Middle Aged; D009944:Organoplatinum Compounds / Q000008:administration & dosage / Q000627:therapeutic use*; D000077150:Oxaliplatin; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D051901:Smad4 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C491997:BECN1 protein, human; D000071186:Beclin-1; C477012:MAP1LC3A protein, human; C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D008869:Microtubule-Associated Proteins; D009944:Organoplatinum Compounds; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D000077150:Oxaliplatin
keywords: Colorectal cancer; Macroautophagy; Oxaliplatin; Transforming growth factor-β/Smad pathway; miR-34a