title: Chloroquine enhances gefitinib cytotoxicity in gefitinib-resistant nonsmall cell lung cancer cells.
abstract: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), including gefitinib, are effective for non-small cell lung cancer (NSCLC) patients with EGFR mutations. However, these patients eventually develop resistance to EGFR-TKI. The goal of the present study was to investigate the involvement of autophagy in gefitinib resistance. We developed gefitinib-resistant cells (PC-9/gef) from PC-9 cells (containing exon 19 deletion EGFR) after long-term exposure in gefitinib. PC-9/gef cells (B4 and E3) were 200-fold more resistant to gefitinib than PC-9/wt cells. Compared with PC-9/wt cells, both PC-9/gefB4 and PC-9/gefE3 cells demonstrated higher basal LC3-II levels which were inhibited by 3-methyladenine (3-MA, an autophagy inhibitor) and potentiated by chloroquine (CQ, an inhibitor of autophagolysosomes formation), indicating elevated autophagy in PC-9/gef cells. 3-MA and CQ concentration-dependently inhibited cell survival of both PC-9wt and PC-9/gef cells, suggesting that autophagy may be pro-survival. Furthermore, gefitinib increased LC3-II levels and autolysosome formation in both PC-9/wt cells and PC-9/gef cells. In PC-9/wt cells, CQ potentiated the cytotoxicity by low gefitinib (3 nM). Moreover, CQ overcame the acquired gefitinib resistance in PC-9/gef cells by enhancing gefitinib-induced cytotoxicity, activation of caspase 3 and poly (ADP-ribose) polymerase cleavage. Using an in vivo model xenografting with PC-9/wt and PC-9/gefB4 cells, oral administration of gefitinib (50 mg/kg) completely inhibited the tumor growth of PC-9/wt but not PC-9/gefB4cells. Combination of CQ (75 mg/kg, i.p.) and gefitinib was more effective than gefitinib alone in reducing the tumor growth of PC-9/gefB4. Our data suggest that inhibition of autophagy may be a therapeutic strategy to overcome acquired resistance of gefitinib in EGFR mutation NSCLC patients.
authors: National Center of Excellence for Clinical Trial and Research, National Taiwan University, Taipei, Taiwan.
authors: Mei-Chuan
authors: MC
authors: Tang
authors: Institute of Pharmacology, National Yang-Ming University, Taipei, Taiwan.
authors: Mei-Yi
authors: MY
authors: Wu
authors: Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan.
authors: Ming-Hung
authors: MH
authors: Hwang
authors: Institute of Pharmacology, National Yang-Ming University, Taipei, Taiwan.
authors: Ya-Ting
authors: YT
authors: Chang
authors: Department of Medical Research, Taipei-Veterans General Hospital, Taipei, Taiwan.
authors: Hui-Ju
authors: HJ
authors: Huang
authors: Institute of Pharmacology, National Yang-Ming University, Taipei, Taiwan; Department of Medical Research, Taipei-Veterans General Hospital, Taipei, Taiwan.
authors: Anya Maan-Yuh
authors: AM
authors: Lin
authors: National Center of Excellence for Clinical Trial and Research, National Taiwan University, Taipei, Taiwan; Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan; Graduate Institute of Oncology, National Taiwan University and Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors: James Chih-Hsin
authors: JC
authors: Yang
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001343:Autophagy / Q000187:drug effects*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D002738:Chloroquine / Q000494:pharmacology* / Q000627:therapeutic use; D066246:ErbB Receptors / Q000235:genetics*; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D011799:Quinazolines; C025946:3-methyladenine; D002738:Chloroquine; D066246:ErbB Receptors; D000225:Adenine; D000077156:Gefitinib