BACKGROUND: Multidrug resistance (MDR) is associated with over expression of the P-glycoprotein (P-gp) drug transporter, which is encoded by the MDR1 gene. Estradiol (E2) is thought to regulate P-gp expression in breast cancer and the aim of this study was to determine the role of estrogen receptor subtypes (ERalpha and ERbeta) in modulating drug resistance and P-gp expression in cultured breast carcinoma cells. MATERIALS AND METHODS: The cytotoxic effects of doxorubicin and P-gp concentrations were determined in E2-treated and untreated T47D and MCF7 breast carcinoma cells. Western blot and mobility shift/super shift analyses were used to determine estrogen receptor subtype interaction with AP1 and Sp1 transcription factors. RESULTS: ERalpha-positive MCF7 cells were resistant to doxorubicin cytotoxicity, while ERbeta-expressing T47D cells were sensitive to doxorubicin treatment. E2 increased the cytoplasmic concentration of P-gp in MCF7 cells but not in T47D cells. ERalpha binds both AP1 and Sp1 transcription factors in extracts from MCF7 cells, while ERbeta binds AP1 in extracts from T47D cells. CONCLUSION: These interactions of the ER subtypes with transcription factors correlates with their functional effects on the MDR1 promoter and the observed effects of E2 on drug resistance.
BACKGROUND: Multidrug resistance (MDR) is associated with over expression of the P-glycoprotein (P-gp) drug transporter, which is encoded by the MDR1 gene. Estradiol (E2) is thought to regulate P-gp expression in breast cancer and the aim of this study was to determine the role of estrogen receptor subtypes (ERalpha and ERbeta) in modulating drug resistance and P-gp expression in cultured breast carcinoma cells. MATERIALS AND METHODS: The cytotoxic effects of doxorubicin and P-gp concentrations were determined in E2-treated and untreated T47D and MCF7 breast carcinoma cells. Western blot and mobility shift/super shift analyses were used to determine estrogen receptor subtype interaction with AP1 and Sp1 transcription factors. RESULTS:ERalpha-positive MCF7 cells were resistant to doxorubicincytotoxicity, while ERbeta-expressing T47D cells were sensitive to doxorubicin treatment. E2 increased the cytoplasmic concentration of P-gp in MCF7 cells but not in T47D cells. ERalpha binds both AP1 and Sp1 transcription factors in extracts from MCF7 cells, while ERbeta binds AP1 in extracts from T47D cells. CONCLUSION: These interactions of the ER subtypes with transcription factors correlates with their functional effects on the MDR1 promoter and the observed effects of E2 on drug resistance.
Authors: Anjaiah Srirangam; Ranjana Mitra; Mu Wang; J Christopher Gorski; Sunil Badve; LeeAnn Baldridge; Justin Hamilton; Hiromitsu Kishimoto; John Hawes; Lang Li; Christie M Orschell; Edward F Srour; Janice S Blum; David Donner; George W Sledge; Harikrishna Nakshatri; David A Potter Journal: Clin Cancer Res Date: 2006-03-15 Impact factor: 12.531
Authors: Nalinie S Wickramasinghe; Tissa T Manavalan; Susan M Dougherty; Krista A Riggs; Yong Li; Carolyn M Klinge Journal: Nucleic Acids Res Date: 2009-03-05 Impact factor: 16.971