title: Cooperative effect of gefitinib and fumitremorgin c on cell growth and chemosensitivity in estrogen receptor alpha negative fulvestrant-resistant MCF-7 cells.
abstract: The selective ER downregulator, fulvestrant, is currently approved as a second line endocrine therapy after onset of resistance to prior antiestrogen therapy in postmenopausal breast cancer patients. Resistance to antihormonal therapies is common and, therefore, we anticipate that fulvestrant-resistance will occur as well. The current study was undertaken to investigate the underlying molecular changes after fulvestrant-resistance and find new therapeutic targets and agents for fulvestrant-resistant breast cancer cells. We developed a unique fulvestrant-resistant cell line (MCF-7/F), derived from MCF-7 estrogen receptor alpha (ERalpha)-positive human breast cancer cells, by culturing them in 1 microM fulvestrant containing medium for approximately 18 months. MCF-7/F cells became irreversibly ERalpha negative as withdrawal of fulvestrant did not alter the ERalpha-negative phenotype, determined by real-time PCR, Western blot analysis, and ERE-luciferase transfection assays. MCF-7/F cells grew in a hormone-independent manner. Interestingly, MCF-7/F cells overexpressed both epidermal growth factor receptor (EGFR) and breast cancer resistant protein (BCRP). Gefitinib, a specific EGFR tyrosine kinase inhibitor, preferentially inhibited the growth of MCF-7/F cells relative to MCF-7 cells by inhibiting both MAPK44/42 and Akt phosphorylation. MCF-7/F cells became less sensitive to chemotherapeutic agents such as mitoxantrone. Moreover, fumitremorgin C, a specific BCRP inhibitor, significantly increased the efficacy of mitoxantrone in MCF-7/F cells. Gefitinib increased the inhibitory effect of mitoxantrone on cell growth. Similarly, fumitremorgin C increased the inhibitory effect of gefitinib on cell growth, suggesting that there is a bidirectional crosstalk between EGFR and BCRP. More importantly, these results provide a molecular basis for using gefitinib, BCRP inhibitors, and chemotherapeutic agents as combination therapy approaches in fulvestrant-resistant breast cancer.
authors.affiliation: Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Dong
authors.initials: D
authors.lastname: Cheng
authors.forename: Alyssa K
authors.initials: AK
authors.lastname: Weichel
authors.forename: Clodia
authors.initials: C
authors.lastname: Osipo
authors.forename: Laura K
authors.initials: LK
authors.lastname: Wing
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Teresa E
authors.initials: TE
authors.lastname: Louis
authors.forename: V Craig
authors.initials: VC
authors.lastname: Jordan
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004958:Estradiol / Q000031:analogs & derivatives / Q000627:therapeutic use; D047628:Estrogen Receptor alpha / Q000032:analysis; D005260:Female; D000077267:Fulvestrant; D000077156:Gefitinib; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008942:Mitoxantrone / Q000819:agonists / Q000627:therapeutic use; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology / Q000627:therapeutic use*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D047628:Estrogen Receptor alpha; D009363:Neoplasm Proteins; D010879:Piperazines; D011799:Quinazolines; C100698:demethoxyfumitremorgin C; D000077267:Fulvestrant; D004958:Estradiol; D008942:Mitoxantrone; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000077156:Gefitinib