title: MicroRNA-29a contributes to drug-resistance of breast cancer cells to adriamycin through PTEN/AKT/GSK3β signaling pathway.
abstract: OBJECTIVE
  Acquisition of resistance to adriamycin (ADR) during the treatment of breast cancer is still a major clinical obstacle. MicroRNAs (miRNAs) are a class of short noncoding RNAs which associate with cancer chemoresistance through regulating gene expression by targeting mRNAs. Our previous microarray found that miR-29a may strongly confer the ADR resistance of breast cancer cells. Here, we aim to explore the possible mechanism by which miR-29a affects sensitivity to ADR.
  
  
  METHODS
  ADR-resistant MCF-7 breast cancer cell subline (MCF-7/ADR) was successfully established in vitro through a stepwise increase of ADR concentrations in the culture based on parental MCF-7 cell lines (MCF-7/S). We used TargetScan (a wide use of target prediction algorithms) in conjunction with pathway enrichment analyses to predict the mRNAs that were most likely to involve in miR-29a-mediated drug resistance in cancers. We confirmed the effects of miR-29a-mediated ADR resistance through MTT and apoptosis assays, and further investigated the activities of two target genes, PTEN and GSK3β, by RT-qPCR analyses and western blot assays.
  
  
  RESULTS
  The expression level of miR-29a in MCF-7/ADR cells was remarkablely higher than in MCF-7/S cells. Further MTT and apoptosis assays revealed that transfection of miR-29a inhibitors into MCF-7/ADR cells resulted in prominent reduction of the drug resistance, in contrast, transfection of miR-29a mimics into MCF-7/S cells obviously increased their drug resistance. Through pathway enrichment analyses for miR-29a, we found that PTEN/AKT/GSK3β signaling pathway may be of importance. RT-qPCR and Western blot results showed that downregulation of miR-29a expression in MCF-7/ADR cells increased PTEN expression levels, resulting in decreased phospho-Akt (p-Akt) and phospho-GSK3β (p-GSK3β) expression. Conversely, upregulation of miR-29a expression in MCF-7/S cells is associated with decreasing PTEN expression and increasing p-Akt and p-GSK3β expression.
  
  
  CONCLUSIONS
  PTEN and GSK3β are targeted by miR-29a, and miR-29a may contribute to ADR resistance through inhibition of the PTEN/AKT/GSK3β pathway in breast cancer cells. Thus, miR-29a may be a potential target for the patients who acquired ADR-resistance during the treatment of breast cancer.
authors: The Fourth Clinical School of Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors: Hongyu
authors: H
authors: Shen
authors: Department of Thoracic and Cardiovascular Surgery, Nanjing First Hospital, Nanjing Medical University, Changle Road 68, Nanjing 210006, Jiangsu, China.
authors: Liangpeng
authors: L
authors: Li
authors: The Fourth Clinical School of Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors: Sujin
authors: S
authors: Yang
authors: Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors: Dandan
authors: D
authors: Wang
authors: Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors: Shanliang
authors: S
authors: Zhong
authors: Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. Electronic address: lcjyjhzhao@163.com.
authors: Jianhua
authors: J
authors: Zhao
authors: The Fourth Clinical School of Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. Electronic address: njmujhtang@163.com.
authors: Jinhai
authors: J
authors: Tang
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D005260:Female; D000071679:Glycogen Synthase Kinase 3 beta / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics
chemical_list: C532045:MIRN29a microRNA, human; D035683:MicroRNAs; D012334:RNA, Neoplasm; D004317:Doxorubicin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human
keywords: Breast cancer; Drug-resistance; GSK3β; PTEN; miR-29a