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Dual Inhibition of mTOR and Estrogen Receptor Signaling In vitro Induces Cell Death in Models of Breast Cancer

Dual Inhibition of mTOR and Estrogen Receptor Signaling In vitro Induces Cell Death in Models of... Purpose: RAD001 (everolimus), a mammalian target of rapamycin (mTOR) pathway inhibitor in phase II clinical trials in oncology, exerts potent antiproliferative/antitumor activities. Many breast cancers are dependent for proliferation on estrogens synthesized from androgens (i.e., androstenedione) by aromatase. Letrozole (Femara) is an aromatase inhibitor used for treatment of postmenopausal women with hormone-dependent breast cancers. The role of the mTOR pathway in estrogen-driven proliferation and effects of combining RAD001 and letrozole were examined in vitro in two breast cancer models. Experimental Design: The role of the mTOR pathway in estrogen response was evaluated in aromatase-expressing MCF7/Aro breast cancer cells by immunoblotting. Effects of RAD001 and letrozole (alone and in combination) on the proliferation and survival of MCF7/Aro and T47D/Aro cells were evaluated using proliferation assays, flow cytometry, immunoblotting, and apoptosis analyses. Results: Treatment of MCF7/Aro cells with estradiol or androstenedione caused modulation of the mTOR pathway, a phenomenon reversed by letrozole or RAD001. In MCF7/Aro and T47D/Aro cells, both agents inhibited androstenedione-induced proliferation; however, in combination, this was significantly augmented ( P < 0.001, two-way ANOVA, synergy by isobologram analysis). Increased activity of the combination correlated with more profound effects on G 1 progression and a significant decrease in cell viability ( P < 0.01, two-way ANOVA) defined as apoptosis ( P < 0.05, Friedman test). Increased cell death was particularly evident with optimal drug concentrations. Conclusion: mTOR signaling is required for estrogen-induced breast tumor cell proliferation. Moreover, RAD001-letrozole combinations can act in a synergistic manner to inhibit proliferation and trigger apoptotic cell death. This combination holds promise for the treatment of hormone-dependent breast cancers. RAD001 everolimus letrozole Femara mTOR estrogen receptor estradiol breast aromatase http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clinical Cancer Research American Association of Cancer Research

Dual Inhibition of mTOR and Estrogen Receptor Signaling In vitro Induces Cell Death in Models of Breast Cancer

Dual Inhibition of mTOR and Estrogen Receptor Signaling In vitro Induces Cell Death in Models of Breast Cancer

Clinical Cancer Research , Volume 11 (14): 5319 – Jul 15, 2005

Abstract

Purpose: RAD001 (everolimus), a mammalian target of rapamycin (mTOR) pathway inhibitor in phase II clinical trials in oncology, exerts potent antiproliferative/antitumor activities. Many breast cancers are dependent for proliferation on estrogens synthesized from androgens (i.e., androstenedione) by aromatase. Letrozole (Femara) is an aromatase inhibitor used for treatment of postmenopausal women with hormone-dependent breast cancers. The role of the mTOR pathway in estrogen-driven proliferation and effects of combining RAD001 and letrozole were examined in vitro in two breast cancer models. Experimental Design: The role of the mTOR pathway in estrogen response was evaluated in aromatase-expressing MCF7/Aro breast cancer cells by immunoblotting. Effects of RAD001 and letrozole (alone and in combination) on the proliferation and survival of MCF7/Aro and T47D/Aro cells were evaluated using proliferation assays, flow cytometry, immunoblotting, and apoptosis analyses. Results: Treatment of MCF7/Aro cells with estradiol or androstenedione caused modulation of the mTOR pathway, a phenomenon reversed by letrozole or RAD001. In MCF7/Aro and T47D/Aro cells, both agents inhibited androstenedione-induced proliferation; however, in combination, this was significantly augmented ( P < 0.001, two-way ANOVA, synergy by isobologram analysis). Increased activity of the combination correlated with more profound effects on G 1 progression and a significant decrease in cell viability ( P < 0.01, two-way ANOVA) defined as apoptosis ( P < 0.05, Friedman test). Increased cell death was particularly evident with optimal drug concentrations. Conclusion: mTOR signaling is required for estrogen-induced breast tumor cell proliferation. Moreover, RAD001-letrozole combinations can act in a synergistic manner to inhibit proliferation and trigger apoptotic cell death. This combination holds promise for the treatment of hormone-dependent breast cancers. RAD001 everolimus letrozole Femara mTOR estrogen receptor estradiol breast aromatase

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References (53)

Publisher
American Association of Cancer Research
Copyright
Copyright © 2010 American Association for Cancer Research
ISSN
1078-0432
eISSN
1557-3265
DOI
10.1158/1078-0432.CCR-04-2402
pmid
16033851
Publisher site
See Article on Publisher Site

Abstract

Purpose: RAD001 (everolimus), a mammalian target of rapamycin (mTOR) pathway inhibitor in phase II clinical trials in oncology, exerts potent antiproliferative/antitumor activities. Many breast cancers are dependent for proliferation on estrogens synthesized from androgens (i.e., androstenedione) by aromatase. Letrozole (Femara) is an aromatase inhibitor used for treatment of postmenopausal women with hormone-dependent breast cancers. The role of the mTOR pathway in estrogen-driven proliferation and effects of combining RAD001 and letrozole were examined in vitro in two breast cancer models. Experimental Design: The role of the mTOR pathway in estrogen response was evaluated in aromatase-expressing MCF7/Aro breast cancer cells by immunoblotting. Effects of RAD001 and letrozole (alone and in combination) on the proliferation and survival of MCF7/Aro and T47D/Aro cells were evaluated using proliferation assays, flow cytometry, immunoblotting, and apoptosis analyses. Results: Treatment of MCF7/Aro cells with estradiol or androstenedione caused modulation of the mTOR pathway, a phenomenon reversed by letrozole or RAD001. In MCF7/Aro and T47D/Aro cells, both agents inhibited androstenedione-induced proliferation; however, in combination, this was significantly augmented ( P < 0.001, two-way ANOVA, synergy by isobologram analysis). Increased activity of the combination correlated with more profound effects on G 1 progression and a significant decrease in cell viability ( P < 0.01, two-way ANOVA) defined as apoptosis ( P < 0.05, Friedman test). Increased cell death was particularly evident with optimal drug concentrations. Conclusion: mTOR signaling is required for estrogen-induced breast tumor cell proliferation. Moreover, RAD001-letrozole combinations can act in a synergistic manner to inhibit proliferation and trigger apoptotic cell death. This combination holds promise for the treatment of hormone-dependent breast cancers. RAD001 everolimus letrozole Femara mTOR estrogen receptor estradiol breast aromatase

Journal

Clinical Cancer ResearchAmerican Association of Cancer Research

Published: Jul 15, 2005

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