title: Upregulation of the inwardly rectifying potassium channel Kir2.1 (KCNJ2) modulates multidrug resistance of small-cell lung cancer under the regulation of miR-7 and the Ras/MAPK pathway.
abstract: BACKGROUND
  KCNJ2/Kir2.1, a member of the classical inwardly rectifying potassium channel family, is commonly expressed in a wide range of tissues and cell types. Previous studies indicated that Kir2.1 may be associated with SCLC multidrug resistance (MDR). However, whether Kir2.1 can regulate MDR and its underlying mechanisms remain poorly understood in SCLC.
  
  
  METHODS
  KCNJ2/Kir2.1 expression was examined in tissues from fifty-two SCLC cases by immunohistochemistry. Overexpression or knockdown of KCNJ2/Kir21 was performed in multidrug-resistant SCLC cell lines (H69AR and H446AR) and their parental cell lines (H69 and H446) to assess its influence on cell growth, apoptosis, the cell cycle and chemoresistance.
  
  
  RESULTS
  KCNJ2/Kir2.1 was expressed in 44.23% (23/52) of SCLC tissues. Overexpression of KCNJ2/Kir2.1 was correlated with the clinical stage and chemotherapy response in SCLC patients. Knockdown of KCNJ2/Kir2.1 expression using KCNJ2/Kir2.1 shRNA in H69AR and H446AR cells inhibited cell growth and sensitized the cancer cells to chemotherapeutic drugs by increasing cell apoptosis and cell cycle arrest. Forced KCNJ2/Kir2.1 expression in H69 and H446 cells promoted cell growth and enhanced multidrug resistance via reduced drug-induced apoptosis accompanied by cell cycle arrest. KCNJ2/Kir2.1 expression was also influenced by PKC and MEK inhibitors. In addition, multidrug resistance protein 1 (MRP1/ABCC1) was confirmed to interact with KCNJ2/Kir2.1 by Co-IP assays.
  
  
  CONCLUSIONS
  KCNJ2/Kir2.1 modulates cell growth and drug resistance by regulating MRP1/ABCC1 expression and is simultaneously regulated by the Ras/MAPK pathway and miR-7. KCNJ2/Kir2.1 may be a prognostic predictor and a potentially novel target for interfering with chemoresistance in SCLC.
authors.affiliation: Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China. liuhuanxin@smu.edu.cn.|Department of Pathology, Guangdong Provincial Corps Hospital of Chinese People's Armed Police Forces, Guangzhou Medical College, Guangzhou, China. liuhuanxin@smu.edu.cn.
authors.forename: Huanxin
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China. h_jie2008@aliyun.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China. 185881427@qq.com.|Department of Pathology, the Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China. 185881427@qq.com.
authors.forename: Juan
authors.initials: J
authors.lastname: Peng
authors.affiliation: Department of Pathology, Guangdong Provincial Corps Hospital of Chinese People's Armed Police Forces, Guangzhou Medical College, Guangzhou, China. 1013054401@qq.com.
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Pathology, Guangdong Provincial Corps Hospital of Chinese People's Armed Police Forces, Guangzhou Medical College, Guangzhou, China. 35507531@qq.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Oncology, Zhujiang Hospital, Southern Medical University, Guangzhou, China. 754640115@qq.com.
authors.forename: Weiliang
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China. linlangg@yahoo.com.
authors.forename: Linlang
authors.initials: L
authors.lastname: Guo
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D018432:Drug Resistance, Multiple / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D009367:Neoplasm Staging; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000378:metabolism; D011379:Prognosis; D011485:Protein Binding; D016283:Proto-Oncogene Proteins p21(ras); D034622:RNA Interference; D012307:Risk Factors; D015398:Signal Transduction; D055752:Small Cell Lung Carcinoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D035683:MicroRNAs; D020928:Mitogen-Activated Protein Kinases; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D024661:Potassium Channels, Inwardly Rectifying; D016283:Proto-Oncogene Proteins p21(ras); C489461:Kir2.1 channel; C549242:MIRN7-1 microRNA, human; C421109:multidrug resistance-associated protein 1