title: MiR-21 overexpression is associated with acquired resistance of EGFR-TKI in non-small cell lung cancer.
abstract: OBJECTIVE
  With the increasing use of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) in patients with advanced non-small cell lung cancer (NSCLC), its acquired resistance has become a major clinical problem. Recent studies revealed that miR-21 was involved into the resistance of cytotoxic agents. The aim of this study was to investigate its role in the acquired resistance of NSCLC to EGFR-TKI.
  
  
  METHODS
  EGFR-TKI-sensitive human lung adenocarcinoma cell line PC9 and the acquired resistant cell line, PC9R, were used. Lentiviral vectors were used to infect PC9 or PC9R to regulate the miR-21 expression. The expression of targeted proteins PTEN and PDCD4 was controlled by RNA interference. MicroRNA array, RT-PCR and TaqMan MicroRNA Assays were used to detect miR-21 expression. The MTT and Annexin V assays were used to determine proliferation and apoptosis. Western Blot and immunohistochemistry were used to analyze target protein expression (PTEN, PDCD4, Akt, p-Akt). We also constructed PC9R xenograft tumor model to observe the relationship between miR-21 and EGFR-TKI resistance in vivo and validated it in the clinical serum specimens of NSCLC patients treated with EGFR-TKI.
  
  
  RESULTS
  MiR-21 was overexpressed in the EGFR-TKI resistant cell line PC9R relative to PC9. The level of miR-21 was reversely correlated with the expression of PTEN and PDCD4 and positive correlated with PI3K/Akt pathway. Inhibiting miR-21 with lentivirus vector induces apoptosis in PC9R cell line and inhibiting miR-21with ASO suppressed tumor growth in nude mice treated with EGFR-TKI. Furthermore, serum miR-21 expression in NSCLC patients treated with EGFR-TKI was significantly higher at the time of acquiring resistance than at baseline (p<0.01).
  
  
  CONCLUSIONS
  miR-21 is involved in acquired resistance of EGFR-TKI in NSCLC, which is mediated by down-regulating PTEN and PDCD4 and activating PI3K/Akt pathway.
authors: Tongji University Medical School Cancer Institute, Shanghai 200433, People's Republic of China.
authors: Bing
authors: B
authors: Li
authors: Tongji University Medical School Cancer Institute, Shanghai 200433, People's Republic of China.
authors: Shengxiang
authors: S
authors: Ren
authors: Tongji University Medical School Cancer Institute, Shanghai 200433, People's Republic of China.
authors: Xuefei
authors: X
authors: Li
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Yongsheng
authors: Y
authors: Wang
authors: ProMed Cancer Center, Shanghai 200020, People's Republic of China.
authors: David
authors: D
authors: Garfield
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Songwen
authors: S
authors: Zhou
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Xiaoxia
authors: X
authors: Chen
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Chunxia
authors: C
authors: Su
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Mo
authors: M
authors: Chen
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Peng
authors: P
authors: Kuang
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Guanghui
authors: G
authors: Gao
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Yayi
authors: Y
authors: He
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Lihong
authors: L
authors: Fan
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China.
authors: Ke
authors: K
authors: Fei
authors: Department of Medical Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai 200433, People's Republic of China; Tongji University Medical School Cancer Institute, Shanghai 200433, People's Republic of China. Electronic address: caicunzhou@yahoo.com.cn.
authors: Caicun
authors: C
authors: Zhou
authors: Interdisciplinary Thoracic Oncology, University Medical Center Mannheim of Heidelberg University, Mannheim, Germany.
authors: Gerald
authors: G
authors: Schmit-Bindert
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000628:therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics; D005260:Female; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000628:therapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use*; D034622:RNA Interference; D016601:RNA-Binding Proteins / Q000235:genetics; D019076:Transgenes / Q000235:genetics; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D051017:Apoptosis Regulatory Proteins; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D016601:RNA-Binding Proteins; C512478:EGFR protein, human; D066246:ErbB Receptors; D051059:PTEN Phosphohydrolase; D000077156:Gefitinib
keywords: Acquired resistance; EGFR-TKI; Non-small cell lung cancer; PDCD4; PI3K/Akt; PTEN; miR-21