title: MiR-222 promotes drug-resistance of breast cancer cells to adriamycin via modulation of PTEN/Akt/FOXO1 pathway.
abstract: OBJECTIVE
  Acquisition of resistance to adriamycin (ADR) is one of the most important clinical obstacles in the treatment of breast cancer, but the molecular mechanisms underlying sensitivity to ADR remain elusive. In our previous study, through miRNA microarray and experiments, we have emphasized that miR-222 could promote the ADR-resistance in breast cancer cells. The aim of this study was to explore the possible mechanism by which miR-222 affects sensitivity to ADR.
  
  
  METHODS
  Through pathway enrichment analyses for miR-222, we found that PTEN/Akt/FOXO1 signaling pathway may be of importance. RT-qPCR analyses and western blot assays confirmed the relationship between miR-222 expression and target genes. Immunofluorescence further visually displayed the location of FOXO1. When blocking PTEN/Akt/FOXO1 signaling pathway, we demonstrated the effects of miR-222-mediated ADR resistance by MTT and apoptosis assays.
  
  
  RESULTS
  RT-qPCR and Western blot results showed that miR-222 expression was negatively correlated with FOXO1 expression. In addition, the subcellular translocation of FOXO1 due to the altered expression of miR-222 was observed from immunofluorescence. Moreover, upregulation of miR-222 expression in MCF-7/S cells is associated with decreased PTEN expression levels and increased phospho-Akt (p-Akt) expression. Conversely in MCF-7/ADR cells, inhibition of miR-222 resulted in increased PTEN expression and decreased p-Akt expression. For further validation, results of the present study also demonstrated that PTEN/Akt/FOXO1 signaling was responsible for the ADR-resistance of breast cancer cells since LY294002, an inhibitor of Akt signaling, partially increased the sensitivity of MCF-7/S cells to ADR. More importantly, we postulated that high expression of miR-222 is closely related to poor overall survival by TCGA database validation.
  
  
  CONCLUSIONS
  Taken together, these data elucidated that miR-222 mediated ADR-resistance of breast cancer cells partly through regulation of PTEN/Akt/FOXO1 signaling pathway and inhibition of miR-222 may improve the prognosis of breast cancer patients.
authors.affiliation: 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.forename: Hongyu
authors.initials: H
authors.lastname: Shen
authors.affiliation: Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Nanjing First Hospital, Nanjing Medical University, Changle Road 68, Nanjing 210006, Jiangsu, China.
authors.forename: Liangpeng
authors.initials: L
authors.lastname: Li
authors.affiliation: 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.forename: Sujin
authors.initials: S
authors.lastname: Yang
authors.affiliation: 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.forename: Xiu
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Nanjing University of Traditional Chinese Medicine, Xianlin Road 138, Nanjing, China.
authors.forename: Siying
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China.
authors.forename: Shanliang
authors.initials: S
authors.lastname: Zhong
authors.affiliation: 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.forename: Jianhua
authors.initials: J
authors.lastname: Zhao
authors.affiliation: 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.forename: Jinhai
authors.initials: J
authors.lastname: Tang
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D000071161:Forkhead Box Protein O1 / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D061986:MCF-7 Cells; D035683:MicroRNAs / Q000235:genetics*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D004317:Doxorubicin; D000071161:Forkhead Box Protein O1; D035683:MicroRNAs; D051059:PTEN Phosphohydrolase; D051057:Proto-Oncogene Proteins c-akt; C085126:FOXO1 protein, human; C525710:MIR222, human; C494929:PTEN protein, human
keywords: Breast cancer; Drug resistance; PTEN/Akt/FOXO1pathway; miR-222