Pfizer presentations at ENDO 2012 on Aprela - licensed from Ligand Pharma $LGND
[SAT-30] A Pooled Analysis of the Effects of Bazedoxifene/Conjugated Estrogens on Lipid Parameters from the Selective Estrogens, Menopause, and Response to Therapy Trials
Sebastian Mirkin, Kelly A Ryan, Kaijie Pan, Arkadi A Chines, Rogerio A Lobo. Pfizer Inc, Collegeville, PA; Columbia University Medical Center, New York, NY.
Objective: Bazedoxifene (BZA)/conjugated estrogens (CE) is the first tissue selective estrogen complex in clinical development. The Selective estrogens, Menopause, And Response to Therapy (SMART) trials showed that BZA/CE reduced menopausal symptoms and bone loss and was well tolerated in postmenopausal women with a uterus. The effects of BZA/CE on lipid parameters were assessed based on pooled data from the SMART-1, SMART-2, SMART-3, SMART-4, and SMART-5 trials.
Methods: The SMART trials were randomized, double-blind, placebo (PBO)-controlled, phase 3 studies in non-hysterectomized postmenopausal women. Lipid parameters were assessed at 12 and 24 months for the SMART-1 trial, 3 months for the SMART-2 and SMART-3 trials, and 12 months for the SMART-4 and SMART-5 trials; pooled data were analyzed for women treated with BZA 20 mg/CE 0.45 or 0.625 mg or PBO (N = 4,735).
Results: BZA 20 mg/CE 0.45 and 0.625 mg were associated with decreases from baseline in total cholesterol (mean changes [95% confidence intervals (CI)] of –0.3 [–1.7, 1.1] and –0.3 [–1.6, 1.0] mmol/L, respectively, at 12 months; –0.1 [–1.6, 1.3] mmol/L for PBO). BZA 20 mg/CE 0.45 and 0.625 mg also reduced levels of low-density lipoprotein cholesterol (LDL-C) from baseline (mean changes [95% CI] of –0.4 [–1.6, 0.9] and –0.4 [–1.5, 0.7] mmol/L, respectively, at 12 months; –0.1 [–1.3, 1.1] mmol/L for PBO). Similar results for total cholesterol and LDL-C were seen at 3 and 24 months. Changes in high-density lipoprotein cholesterol were similar among groups at all time points. The BZA/CE doses showed slight increases in triglycerides at 3, 12, and 24 months. Mean changes (95% CI) in triglycerides for BZA 20 mg/CE 0.45 and 0.625 mg and PBO at 12 months were 0.1 (–0.9, 1.2), 0.1 (–0.9, 1.2), and –0.01 (–1.0, 1.0) mmol/L, respectively. At 3, 12, and 24 months, the BZA/CE doses showed slight increases in apolipoprotein A (0.13-0.14, 0.16-0.18, and 0.14-0.15 g/L, respectively) compared with minimal changes for PBO, and slight decreases in apolipoprotein B (–0.05 to –0.07, –0.02 to –0.03, and –0.02 to –0.03 g/L, respectively) compared with an increase of 0.03 g/L for PBO at 12 and 24 months.
Conclusion: Based on this pooled analysis of the SMART studies, BZA 20 mg/CE 0.45 and 0.625 mg were associated with a favorable overall lipid profile in postmenopausal women over 2 years of treatment.
Sebastian Mirkin, Kelly A Ryan, Kaijie Pan, Arkadi A Chines, Rogerio A Lobo. Pfizer Inc, Collegeville, PA; Columbia University Medical Center, New York, NY.
Objective: Bazedoxifene (BZA)/conjugated estrogens (CE) is the first tissue selective estrogen complex in clinical development. The Selective estrogens, Menopause, And Response to Therapy (SMART) trials showed that BZA/CE reduced menopausal symptoms and bone loss and was well tolerated in postmenopausal women with a uterus. The effects of BZA/CE on lipid parameters were assessed based on pooled data from the SMART-1, SMART-2, SMART-3, SMART-4, and SMART-5 trials.
Methods: The SMART trials were randomized, double-blind, placebo (PBO)-controlled, phase 3 studies in non-hysterectomized postmenopausal women. Lipid parameters were assessed at 12 and 24 months for the SMART-1 trial, 3 months for the SMART-2 and SMART-3 trials, and 12 months for the SMART-4 and SMART-5 trials; pooled data were analyzed for women treated with BZA 20 mg/CE 0.45 or 0.625 mg or PBO (N = 4,735).
Results: BZA 20 mg/CE 0.45 and 0.625 mg were associated with decreases from baseline in total cholesterol (mean changes [95% confidence intervals (CI)] of –0.3 [–1.7, 1.1] and –0.3 [–1.6, 1.0] mmol/L, respectively, at 12 months; –0.1 [–1.6, 1.3] mmol/L for PBO). BZA 20 mg/CE 0.45 and 0.625 mg also reduced levels of low-density lipoprotein cholesterol (LDL-C) from baseline (mean changes [95% CI] of –0.4 [–1.6, 0.9] and –0.4 [–1.5, 0.7] mmol/L, respectively, at 12 months; –0.1 [–1.3, 1.1] mmol/L for PBO). Similar results for total cholesterol and LDL-C were seen at 3 and 24 months. Changes in high-density lipoprotein cholesterol were similar among groups at all time points. The BZA/CE doses showed slight increases in triglycerides at 3, 12, and 24 months. Mean changes (95% CI) in triglycerides for BZA 20 mg/CE 0.45 and 0.625 mg and PBO at 12 months were 0.1 (–0.9, 1.2), 0.1 (–0.9, 1.2), and –0.01 (–1.0, 1.0) mmol/L, respectively. At 3, 12, and 24 months, the BZA/CE doses showed slight increases in apolipoprotein A (0.13-0.14, 0.16-0.18, and 0.14-0.15 g/L, respectively) compared with minimal changes for PBO, and slight decreases in apolipoprotein B (–0.05 to –0.07, –0.02 to –0.03, and –0.02 to –0.03 g/L, respectively) compared with an increase of 0.03 g/L for PBO at 12 and 24 months.
Conclusion: Based on this pooled analysis of the SMART studies, BZA 20 mg/CE 0.45 and 0.625 mg were associated with a favorable overall lipid profile in postmenopausal women over 2 years of treatment.
[SAT-29] Effects of Bazedoxifene/Conjugated Estrogens on Coagulation Parameters in a 1-Year, Randomized, Placebo- and Active-Controlled, Phase 3 Trial of Postmenopausal Women
Sebastian Mirkin, Kelly A Ryan, John R Thompson, Arkadi A Chines. Pfizer Inc, Collegeville, PA.
Objective: In phase 3 clinical trials, bazedoxifene (BZA)/conjugated estrogens (CE) demonstrated efficacy in treating menopausal symptoms and preventing osteoporosis in postmenopausal women with a favorable safety/tolerability profile, including no increase in the risk of coronary heart disease or stroke. The risk of venous thromboembolism for BZA/CE appears to be similar to that for CE and BZA alone. The effects of BZA/CE on coagulation parameters were evaluated in the Selective estrogens, Menopause, And Response to Therapy (SMART)-5 trial.
Methods: The SMART-5 trial was a 1-year, randomized, double-blind, placebo (PBO)- and active-controlled, phase 3 study in non-hysterectomized, postmenopausal women aged 40 to 65 years (N = 1,843). Coagulation parameters were assessed in a subset of randomized subjects who received BZA 20 mg/CE 0.45 mg (n = 135), BZA 20 mg/CE 0.625 mg (n = 154), BZA 20 mg (n = 73), CE 0.45 mg/medroxyprogesterone acetate (MPA) 1.5 mg (n = 70), or PBO (n = 158).
Results: Coagulation parameters were evaluated in 590 dosed subjects (mean age ± standard deviation [SD], 52.9 years ± 3.4 years; mean years since last menstrual period ± SD, 2.5 years ± 1.5 years). At 12 months, BZA 20 mg/CE 0.45 and 0.625 mg and BZA 20 mg showed decreases from baseline in antithrombin III while PBO showed an increase (mean percent change of –2.3%, –4.7%, –3.4%, and 3.7% for BZA 20 mg/CE 0.45 and 0.625 mg, BZA 20 mg, and PBO, respectively; P <0.0001 for BZA/CE and BZA alone vs PBO). The change in antithrombin III for CE 0.45 mg/MPA 1.5 mg (1.8%) was similar to that for PBO. There were no differences among the BZA 20-mg/CE 0.45- and 0.625-mg, BZA 20-mg, CE 0.45-mg/MPA 1.5-mg, and PBO groups in the mean percent changes in Protein C activity (19.3%, 10.8%, –5.1%, 5.2%, and 1.5%, respectively) or Protein S activity (–9.3%, –8.9%, –5.4%, 5.7%, and –4.5%, respectively). Compared with PBO, both BZA/CE doses showed decreases in fibrinogen and PAI-1 activity, and an increase in plasminogen (P <0.05 for all). Changes in D-dimer, PAI-1 antigen, prothrombin time, and partial thromboplastin time were generally similar among groups.
Conclusion: Overall, there was no evidence of clinically meaningful changes in coagulation parameters for BZA 20 mg/CE 0.45 and 0.625 mg compared with PBO at 12 months. Together with the efficacy of BZA/CE on menopausal symptoms and bone preservation, these findings indicate that BZA/CE may be a promising option for postmenopausal women.
Sebastian Mirkin, Kelly A Ryan, John R Thompson, Arkadi A Chines. Pfizer Inc, Collegeville, PA.
Objective: In phase 3 clinical trials, bazedoxifene (BZA)/conjugated estrogens (CE) demonstrated efficacy in treating menopausal symptoms and preventing osteoporosis in postmenopausal women with a favorable safety/tolerability profile, including no increase in the risk of coronary heart disease or stroke. The risk of venous thromboembolism for BZA/CE appears to be similar to that for CE and BZA alone. The effects of BZA/CE on coagulation parameters were evaluated in the Selective estrogens, Menopause, And Response to Therapy (SMART)-5 trial.
Methods: The SMART-5 trial was a 1-year, randomized, double-blind, placebo (PBO)- and active-controlled, phase 3 study in non-hysterectomized, postmenopausal women aged 40 to 65 years (N = 1,843). Coagulation parameters were assessed in a subset of randomized subjects who received BZA 20 mg/CE 0.45 mg (n = 135), BZA 20 mg/CE 0.625 mg (n = 154), BZA 20 mg (n = 73), CE 0.45 mg/medroxyprogesterone acetate (MPA) 1.5 mg (n = 70), or PBO (n = 158).
Results: Coagulation parameters were evaluated in 590 dosed subjects (mean age ± standard deviation [SD], 52.9 years ± 3.4 years; mean years since last menstrual period ± SD, 2.5 years ± 1.5 years). At 12 months, BZA 20 mg/CE 0.45 and 0.625 mg and BZA 20 mg showed decreases from baseline in antithrombin III while PBO showed an increase (mean percent change of –2.3%, –4.7%, –3.4%, and 3.7% for BZA 20 mg/CE 0.45 and 0.625 mg, BZA 20 mg, and PBO, respectively; P <0.0001 for BZA/CE and BZA alone vs PBO). The change in antithrombin III for CE 0.45 mg/MPA 1.5 mg (1.8%) was similar to that for PBO. There were no differences among the BZA 20-mg/CE 0.45- and 0.625-mg, BZA 20-mg, CE 0.45-mg/MPA 1.5-mg, and PBO groups in the mean percent changes in Protein C activity (19.3%, 10.8%, –5.1%, 5.2%, and 1.5%, respectively) or Protein S activity (–9.3%, –8.9%, –5.4%, 5.7%, and –4.5%, respectively). Compared with PBO, both BZA/CE doses showed decreases in fibrinogen and PAI-1 activity, and an increase in plasminogen (P <0.05 for all). Changes in D-dimer, PAI-1 antigen, prothrombin time, and partial thromboplastin time were generally similar among groups.
Conclusion: Overall, there was no evidence of clinically meaningful changes in coagulation parameters for BZA 20 mg/CE 0.45 and 0.625 mg compared with PBO at 12 months. Together with the efficacy of BZA/CE on menopausal symptoms and bone preservation, these findings indicate that BZA/CE may be a promising option for postmenopausal women.
[SAT-31] Low Risk of Thrombophilia with Bazedoxifene/Conjugated Estrogens: Summary of Pooled Coagulation Data from the Selective Estrogens, Menopause, and Response to Therapy Trials
Sven O Skouby, Rogerio A Lobo, Kelly A Ryan, John R Thompson, Barry S Komm, Arkadi A Chines, Sebastian Mirkin. Herlev Hospital, Herlev, Denmark; University of Copenhagen, Copenhagen, Denmark; University of Southern Denmark, Esbjerg, Denmark; Columbia University Medical Center, New York, NY; Pfizer Inc, Collegeville, PA.
Objective: Bazedoxifene (BZA)/conjugated estrogens (CE) is a menopausal therapy in development and has shown efficacy in reducing menopausal symptoms and bone loss in the Selective estrogens, Menopause, And Response to Therapy (SMART) trials in postmenopausal women. The effects of BZA/CE on coagulation parameters were assessed based on pooled data from the SMART-1, SMART-4, and SMART-5 trials.
Methods: The SMART-1, SMART-4, and SMART-5 trials were randomized, double-blind, placebo (PBO)- and active-controlled, phase 3 studies in postmenopausal women with a uterus. Mean changes in coagulation parameters were assessed at 12 months in the SMART-4 and SMART-5 trials and at 12 and 24 months in the SMART-1 trial; pooled data were analyzed for women who received BZA 20 mg/CE 0.45 or 0.625 mg or PBO.
Results: Across the 3 trials, coagulation parameters were assessed in 1,978 randomized and dosed subjects. At 12 months, BZA 20 mg/CE 0.45 and 0.625 mg showed decreases from baseline in antithrombin III compared with an increase for PBO (–0.05, –0.06 and 0.02 L/L, respectively; P <0.01 vs baseline for all). At 24 months, BZA 20 mg/CE 0.45 and 0.625 mg and PBO showed similar decreases in antithrombin III (–0.27, –0.26, and –0.21 L/L, respectively; P <0.001 vs baseline for all). Changes in Protein C activity at 12 and 24 months were –0.01 to –0.03 and 0.05 L/L, respectively, for the BZA/CE doses compared with –0.02 and 0.04 L/L, respectively, for PBO (P <0.01 vs baseline for all except BZA 20 mg/CE 0.625 mg and PBO at 12 months). For the 2 BZA/CE doses and PBO, changes in Protein S activity were –0.02 to –0.03 and –0.02 L/L, respectively, at 12 months and 0.06 to 0.08 and 0.15 L/L, respectively, at 24 months (P <0.05 vs baseline for all except PBO at 12 months). There were no apparent changes in fibrinogen, prothrombin time, partial thromboplastin time, PAI-1 activity, plasminogen, and D-dimer for BZA/CE compared with PBO. Pooled incidences of venous thromboembolic and cerebrovascular events were low (≤0.2%) and similar among groups.
Conclusion: BZA 20 mg/CE 0.45 and 0.625 mg showed an overall favorable coagulation profile in postmenopausal women, as changes in coagulation parameters were generally comparable to those for PBO over 2 years. Combined with the demonstrated efficacy and safety of BZA/CE in treating menopausal symptoms and preventing osteoporosis, these findings show that BZA/CE may be a promising alternative for non-hysterectomized women.
Sven O Skouby, Rogerio A Lobo, Kelly A Ryan, John R Thompson, Barry S Komm, Arkadi A Chines, Sebastian Mirkin. Herlev Hospital, Herlev, Denmark; University of Copenhagen, Copenhagen, Denmark; University of Southern Denmark, Esbjerg, Denmark; Columbia University Medical Center, New York, NY; Pfizer Inc, Collegeville, PA.
Objective: Bazedoxifene (BZA)/conjugated estrogens (CE) is a menopausal therapy in development and has shown efficacy in reducing menopausal symptoms and bone loss in the Selective estrogens, Menopause, And Response to Therapy (SMART) trials in postmenopausal women. The effects of BZA/CE on coagulation parameters were assessed based on pooled data from the SMART-1, SMART-4, and SMART-5 trials.
Methods: The SMART-1, SMART-4, and SMART-5 trials were randomized, double-blind, placebo (PBO)- and active-controlled, phase 3 studies in postmenopausal women with a uterus. Mean changes in coagulation parameters were assessed at 12 months in the SMART-4 and SMART-5 trials and at 12 and 24 months in the SMART-1 trial; pooled data were analyzed for women who received BZA 20 mg/CE 0.45 or 0.625 mg or PBO.
Results: Across the 3 trials, coagulation parameters were assessed in 1,978 randomized and dosed subjects. At 12 months, BZA 20 mg/CE 0.45 and 0.625 mg showed decreases from baseline in antithrombin III compared with an increase for PBO (–0.05, –0.06 and 0.02 L/L, respectively; P <0.01 vs baseline for all). At 24 months, BZA 20 mg/CE 0.45 and 0.625 mg and PBO showed similar decreases in antithrombin III (–0.27, –0.26, and –0.21 L/L, respectively; P <0.001 vs baseline for all). Changes in Protein C activity at 12 and 24 months were –0.01 to –0.03 and 0.05 L/L, respectively, for the BZA/CE doses compared with –0.02 and 0.04 L/L, respectively, for PBO (P <0.01 vs baseline for all except BZA 20 mg/CE 0.625 mg and PBO at 12 months). For the 2 BZA/CE doses and PBO, changes in Protein S activity were –0.02 to –0.03 and –0.02 L/L, respectively, at 12 months and 0.06 to 0.08 and 0.15 L/L, respectively, at 24 months (P <0.05 vs baseline for all except PBO at 12 months). There were no apparent changes in fibrinogen, prothrombin time, partial thromboplastin time, PAI-1 activity, plasminogen, and D-dimer for BZA/CE compared with PBO. Pooled incidences of venous thromboembolic and cerebrovascular events were low (≤0.2%) and similar among groups.
Conclusion: BZA 20 mg/CE 0.45 and 0.625 mg showed an overall favorable coagulation profile in postmenopausal women, as changes in coagulation parameters were generally comparable to those for PBO over 2 years. Combined with the demonstrated efficacy and safety of BZA/CE in treating menopausal symptoms and preventing osteoporosis, these findings show that BZA/CE may be a promising alternative for non-hysterectomized women.
[SAT-18] The Effect of a Tissue-Specific Estrogen Complex (TSEC) on Normal Mammary Gland and Breast Cancer Xenografts in Mice: Rationale for Use of a Tissue-Selective Estrogen Complex
Yan Song, Wei Yue, Jiping Wang, Richard J Santen. University of Virginia, Charlottesville, VA.
The Women's Health Initiative (WHI) studies showed that the combination of an estrogen plus a progestin increased the risk of breast cancer in postmenopausal women while estrogen alone did not. As a novel means of eliminating the need for a progestin as menopausal hormone therapy (MHT), use of a tissue selective estrogen complex (TSEC) has been proposed. The most studied TSEC in women involves the pairing of a SERM, bazedoxifene (BZA) with conjugated estrogens (CE). Our hypothesis is that this combination may prevent the growth of occult breast cancers in women. To systematically examine the effects of this TSEC on breast, we quantified its effects on mouse mammary gland and occult human breast cancer xenografts. We initially used computerized morphometry to examine the effects of estradiol (E2) and CE alone or in combination with BZA on ductal development in immature castrate mice. BZA completely blocked CE or E2 stimulated ductal and terminal end bud growth (P<0.05). We then examined human breast tumor proliferation. Occult, undiagnosed breast cancer is present at autopsy in 7% of women between the ages of 40 and 80 (Santen et al JCEM 95:S1-66, 2010). Using a MCF-7 mouse xenograft model to mimic occult tumors in women, we demonstrated that plasma levels of 80 pg/ml of E2 (estrogen clamp method) stimulated growth of small tumors. This effect was completely blocked with BZA (2 mg/kg) (p<0.05). BZA also inhibited E2 stimulation of PR, pS2, cMyC and AREG; the enhancement of Ki67 and PCNA as proliferation markers; and the anti-apoptotic effect of estrogen. CE was much less potent than E2 on reducing apoptosis and on stimulation of Ki67 expression. In addition, gene expression analysis showed less stimulation of proliferation related genes (AREG, cyclin D1, and cMyc) by CE compared to E2 but all effects were blocked by BZA. Surprisingly CE alone did not stimulate tumor growth but did cause a 6-fold increase in uterine weight. This uterine weight bioassay confirmed that CE were effectively absorbed, de-conjugated in vivo, and capable of exerting an estrogenic effect on uterus but not on breast cancer. In summary, these results demonstrate that BZA can abrogate the growth of E2 stimulated occult human breast tumors. The estrogenic effects of CE on cellular markers could be blocked by BZA. These data support our hypothesis that the CE/BZA TSEC exerts anti-estrogenic effects on benign and malignant breast tissue.
Yan Song, Wei Yue, Jiping Wang, Richard J Santen. University of Virginia, Charlottesville, VA.
The Women's Health Initiative (WHI) studies showed that the combination of an estrogen plus a progestin increased the risk of breast cancer in postmenopausal women while estrogen alone did not. As a novel means of eliminating the need for a progestin as menopausal hormone therapy (MHT), use of a tissue selective estrogen complex (TSEC) has been proposed. The most studied TSEC in women involves the pairing of a SERM, bazedoxifene (BZA) with conjugated estrogens (CE). Our hypothesis is that this combination may prevent the growth of occult breast cancers in women. To systematically examine the effects of this TSEC on breast, we quantified its effects on mouse mammary gland and occult human breast cancer xenografts. We initially used computerized morphometry to examine the effects of estradiol (E2) and CE alone or in combination with BZA on ductal development in immature castrate mice. BZA completely blocked CE or E2 stimulated ductal and terminal end bud growth (P<0.05). We then examined human breast tumor proliferation. Occult, undiagnosed breast cancer is present at autopsy in 7% of women between the ages of 40 and 80 (Santen et al JCEM 95:S1-66, 2010). Using a MCF-7 mouse xenograft model to mimic occult tumors in women, we demonstrated that plasma levels of 80 pg/ml of E2 (estrogen clamp method) stimulated growth of small tumors. This effect was completely blocked with BZA (2 mg/kg) (p<0.05). BZA also inhibited E2 stimulation of PR, pS2, cMyC and AREG; the enhancement of Ki67 and PCNA as proliferation markers; and the anti-apoptotic effect of estrogen. CE was much less potent than E2 on reducing apoptosis and on stimulation of Ki67 expression. In addition, gene expression analysis showed less stimulation of proliferation related genes (AREG, cyclin D1, and cMyc) by CE compared to E2 but all effects were blocked by BZA. Surprisingly CE alone did not stimulate tumor growth but did cause a 6-fold increase in uterine weight. This uterine weight bioassay confirmed that CE were effectively absorbed, de-conjugated in vivo, and capable of exerting an estrogenic effect on uterus but not on breast cancer. In summary, these results demonstrate that BZA can abrogate the growth of E2 stimulated occult human breast tumors. The estrogenic effects of CE on cellular markers could be blocked by BZA. These data support our hypothesis that the CE/BZA TSEC exerts anti-estrogenic effects on benign and malignant breast tissue.
[SUN-544] Genomics and Integration of Estrogen Receptor Alpha and Protein Kinase Chromatin Binding and Regulation of Gene Expression and Cell Properties with a Tissue-Selective Estrogen Complex (TSEC)
Zeynep Madak-Erdogan, Ping Gong, Benita S Katzenellenbogen. University of Illinois and College of Medicine at Urbana-Champaign, Urbana, IL.
Estrogens act through estrogen receptors (ERs) in the nucleus of target cells to regulate gene expression, but they also act through ERs at extranuclear sites, where they activate kinase cascades. Recent work (e.g., Madak-Erdogan et al., Mol. Cell. Biol. 31:226, 2011) has revealed that estrogen action in target cells requires genomic collaboration between ERs and protein kinases in the control of gene expression and cell phenotypic properties. Therefore, in the current study, we have investigated the actions of estrogens, selective estrogen receptor modulators (SERMs), and a Tissue-Selective Estrogen Complex (TSEC), and the involvement of nuclear and extranuclear pathways in their activities. Chromatin immunoprecipitation (ChIP) and gene expression analyses were utilized to monitor the recruitment of ERα and the extracellular signal-regulated kinase 2 (ERK2) to ER binding sites in chromatin of estrogen-regulated genes, and these were correlated with changes in cell phenotypic properties.
We found that conjugated estrogen (CE, which is a mix of 10 estrogens as present in Premarin®) was much less effective than estradiol (E2) in ERK2 recruitment to the same chromatin binding sites, whereas recruitment of ERα to chromatin binding sites by E2 and CE was relatively similar, although lower for CE at certain sites. Likewise, MAPK activation was lower for CE vs E2. CE was also much less agonistic than E2 in stimulation of the proliferation of MCF-7 breast cancer cells. The SERM bazedoxifene (BZA, 1 µM) fully suppressed any cell proliferation stimulated by E2 or CE (at 1 pM – 1 µM), and it reversed gene stimulation by CE or E2, with BZA being as or more suppressive than Faslodex. The findings suggest that the balance of biological activities mediated through direct nuclear vs. kinase-mediated pathways is different for CE vs. E2, with CE having less potency in the kinase-mediated pathways. These studies provide a molecular underpinning for the basis by which a TSEC functions and is most effective. They also expand our understanding of the mechanisms and different modes by which estrogens and SERMs support or antagonize one another in regulating chromatin binding, gene expression, and cell phenotypic properties, such as proliferation, and they illuminate how the combined actions of these two classes of hormones (as present in TSECs) can achieve unique modes of regulation and efficacy.
Zeynep Madak-Erdogan, Ping Gong, Benita S Katzenellenbogen. University of Illinois and College of Medicine at Urbana-Champaign, Urbana, IL.
Estrogens act through estrogen receptors (ERs) in the nucleus of target cells to regulate gene expression, but they also act through ERs at extranuclear sites, where they activate kinase cascades. Recent work (e.g., Madak-Erdogan et al., Mol. Cell. Biol. 31:226, 2011) has revealed that estrogen action in target cells requires genomic collaboration between ERs and protein kinases in the control of gene expression and cell phenotypic properties. Therefore, in the current study, we have investigated the actions of estrogens, selective estrogen receptor modulators (SERMs), and a Tissue-Selective Estrogen Complex (TSEC), and the involvement of nuclear and extranuclear pathways in their activities. Chromatin immunoprecipitation (ChIP) and gene expression analyses were utilized to monitor the recruitment of ERα and the extracellular signal-regulated kinase 2 (ERK2) to ER binding sites in chromatin of estrogen-regulated genes, and these were correlated with changes in cell phenotypic properties.
We found that conjugated estrogen (CE, which is a mix of 10 estrogens as present in Premarin®) was much less effective than estradiol (E2) in ERK2 recruitment to the same chromatin binding sites, whereas recruitment of ERα to chromatin binding sites by E2 and CE was relatively similar, although lower for CE at certain sites. Likewise, MAPK activation was lower for CE vs E2. CE was also much less agonistic than E2 in stimulation of the proliferation of MCF-7 breast cancer cells. The SERM bazedoxifene (BZA, 1 µM) fully suppressed any cell proliferation stimulated by E2 or CE (at 1 pM – 1 µM), and it reversed gene stimulation by CE or E2, with BZA being as or more suppressive than Faslodex. The findings suggest that the balance of biological activities mediated through direct nuclear vs. kinase-mediated pathways is different for CE vs. E2, with CE having less potency in the kinase-mediated pathways. These studies provide a molecular underpinning for the basis by which a TSEC functions and is most effective. They also expand our understanding of the mechanisms and different modes by which estrogens and SERMs support or antagonize one another in regulating chromatin binding, gene expression, and cell phenotypic properties, such as proliferation, and they illuminate how the combined actions of these two classes of hormones (as present in TSECs) can achieve unique modes of regulation and efficacy.