title: Induction of autophagy is an early response to gefitinib and a potential therapeutic target in breast cancer.
abstract: Gefitinib (Iressa(®), ZD1839) is a small molecule inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase. We report on an early cellular response to gefitinib that involves induction of functional autophagic flux in phenotypically diverse breast cancer cells that were sensitive (BT474 and SKBR3) or insensitive (MCF7-GFPLC3 and JIMT-1) to gefitinib. Our data show that elevation of autophagy in gefitinib-treated breast cancer cells correlated with downregulation of AKT and ERK1/2 signaling early in the course of treatment. Inhibition of autophagosome formation by BECLIN-1 or ATG7 siRNA in combination with gefitinib reduced the abundance of autophagic organelles and sensitized SKBR3 but not MCF7-GFPLC3 cells to cell death. However, inhibition of the late stage of gefitinib-induced autophagy with hydroxychloroquine (HCQ) or bafilomycin A1 significantly increased (p<0.05) cell death in gefitinib-sensitive SKBR3 and BT474 cells, as well as in gefitinib-insensitive JIMT-1 and MCF7-GFPLC3 cells, relative to the effects observed with the respective single agents. Treatment with the combination of gefitinib and HCQ was more effective (p<0.05) in delaying tumor growth than either monotherapy (p>0.05), when compared to vehicle-treated controls. Our results also show that elevated autophagosome content following short-term treatment with gefitinib is a reversible response that ceases upon removal of the drug. In aggregate, these data demonstrate that elevated autophagic flux is an early response to gefitinib and that targeting EGFR and autophagy should be considered when developing new therapeutic strategies for EGFR expressing breast cancers.
authors.affiliation: Department of Experimental Therapeutics, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
authors.forename: Wieslawa H
authors.initials: WH
authors.lastname: Dragowska
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Weppler
authors.forename: Jun Chih
authors.initials: JC
authors.lastname: Wang
authors.forename: Ling Yan
authors.initials: LY
authors.lastname: Wong
authors.forename: Anita I
authors.initials: AI
authors.lastname: Kapanen
authors.forename: Jenna S
authors.initials: JS
authors.lastname: Rawji
authors.forename: Corinna
authors.initials: C
authors.lastname: Warburton
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Qadir
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Donohue
authors.forename: Michel
authors.initials: M
authors.lastname: Roberge
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Gorski
authors.forename: Karen A
authors.initials: KA
authors.lastname: Gelmon
authors.forename: Marcel B
authors.initials: MB
authors.lastname: Bally
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology* / Q000648:ultrastructure; D002103:Cadaverine / Q000031:analogs & derivatives / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D000077156:Gefitinib; D055785:Gene Knockdown Techniques; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D006886:Hydroxychloroquine / Q000494:pharmacology / Q000627:therapeutic use; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013194:Staining and Labeling; D013629:Tamoxifen / Q000494:pharmacology / Q000627:therapeutic use; D016896:Treatment Outcome; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D011799:Quinazolines; D034741:RNA, Small Interfering; D013629:Tamoxifen; D006886:Hydroxychloroquine; C025946:3-methyladenine; D066246:ErbB Receptors; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; C008542:monodansylcadaverine; D000225:Adenine; D002103:Cadaverine; D000077156:Gefitinib