title: Metformin sensitizes EGFR-TKI-resistant human lung cancer cells in vitro and in vivo through inhibition of IL-6 signaling and EMT reversal.
abstract: OBJECTIVE
  The EGF receptor tyrosine kinase inhibitors (EGFR-TKI) have become a standard therapy in patients with EGFR-activating mutations. Unfortunately, acquired resistance eventually limits the clinical effects and application of EGFR-TKIs. Studies have shown that suppression of epithelial-mesenchymal transition (EMT) and the interleukin (IL)-6/STAT3 pathway may abrogate this acquired mechanism of drug resistance of TKIs. This study aims to investigate the effect of metformin on sensitizing EGFR-TKI-resistant human lung cancer cells in vitro and in vivo through inhibition of IL-6 signaling and EMT reversal.
  
  
  METHODS
  The effect of metformin on reversing TKI resistance was examined in vitro and in vivo using MTT, BrdUrd incorporation assay, invasion assay, flow cytometry analysis, immunostaining, Western blot analysis, and xenograft implantation.
  
  
  RESULTS
  In this study, metformin, a widely used antidiabetic agent, effectively increased the sensitivity of TKI-resistant lung cancer cells to erlotinib or gefitinib. Metformin reversed EMT and decreased IL-6 signaling activation in TKI-resistant cells, while adding IL-6 to those cells bypassed the anti-TKI-resistance effect of metformin. Furthermore, overexpression or addition of IL-6 to TKI-sensitive cells induced TKI resistance, which could be overcome by metformin. Finally, metformin-based combinatorial therapy effectively blocked tumor growth in xenografts with TKI-resistant cancer cells, which was associated with decreased IL-6 secretion and expression, EMT reversal, and decreased IL-6-signaling activation in vivo.
  
  
  CONCLUSIONS
  Metformin, generally considered nontoxic and remarkably inexpensive, might be used in combination with TKIs in patients with non-small cell lung cancer, harboring EGFR mutations to overcome TKI resistance and prolong survival.
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, ChinaAuthors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Han
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Hualiang
authors.initials: H
authors.lastname: Xiao
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Caiyu
authors.initials: C
authors.lastname: Lin
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Kunlin
authors.initials: K
authors.lastname: Li
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Hengyi
authors.initials: H
authors.lastname: Chen
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Fenfen
authors.initials: F
authors.lastname: Sun
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Zhenzhou
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Authors' Affiliations: Departments of Respiratory Disease, Thoracic Surgery, Pathology, and Oncology; and State Key Laboratory of Trauma, Burns and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, China heyong@dphospital.tmmu.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: He
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D000077156:Gefitinib; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008687:Metformin / Q000008:administration & dosage / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D011799:Quinazolines / Q000008:administration & dosage / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D023041:Xenograft Model Antitumor Assays
chemical_list: D015850:Interleukin-6; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D008687:Metformin; D066246:ErbB Receptors; D000077156:Gefitinib