Preventing Estrogen Receptor Alpha-Positive Breast Cancer Outgrowth with the Use of Hormone Replacement Therapy

Menopause occurs in all women, typically between the ages of 45 and 55. As a result of menopause, women often experience undesirable symptoms such as hot flashes, vaginal dryness and atrophy, and osteoporosis. These symptoms can be alleviated with hormone replacement therapy (HRT). The Women’s Health Initiative (WHI) trial concluded that PremPro, a HRT formulation that combines conjugated equine estrogens (CE) with medroxyprogesterone acetate, increases the risk of breast cancer. Over the years, the number of women taking HRT has dramatically decreased due to the perceived risk based mainly on the results of the WHI trial. Follow-up studies suggest that breast cancer cases from PremPro treatment were primarily due to the outgrowth of undetectable occult tumors, not the formation of new disease. Duavee, a more recent form of HRT that combines CE and bazedoxifene (BZA), a selective estrogen receptor modulator (SERM) and degrader (SERD), has been approved by the FDA for treatment of hot flashes and to reduce the risk of osteoporosis. More importantly, this CE+BZA mixture not only relieves symptoms associated with menopause, but it also does not stimulate the breast or endometrium. Several preclinical studies suggest that CE+BZA might be protective in the breast; however, the mechanism of action of this new combination therapy is not known. Our goal, therefore, is to elucidate the underlying molecular mechanisms by which CE+BZA differentially affects estrogen receptor alpha (ER) action in the mammary gland, using transcriptome and cistrome analysis in breast cancer cell lines. RNA-Seq and ChIP-Seq studies suggest that CE+BZA increases pathways related to cell death and decreases activation of pathways related to cell proliferation and survival. BZA was found to exert its action through the aryl hydrocarbon receptor (AHR) pathway, further clarifying the role of AHR in breast cancer. We are also studying the effects of CE+BZA on early mammary cancer progression in the estrogen-sensitive polyoma middle T antigen (PyMT) transgenic mouse model and have observed that treatment with CE+BZA delayed the onset of tumors and decreased their rate of growth. Mice treated with CE+BZA also survived longer. In addition, CE+BZA was able to decrease the rate of tumor growth in an ER-positive patient-derived xenograft (PDX) mouse model. An improved understanding of the molecular mechanisms of CE+BZA action in hormone-sensitive breast cancer cell and animal models should have important implications for women considering HRT and for physicians prescribing it

Genomic agonism and phenotypic antagonism between estrogen and progesterone receptors in breast cancer

The functional role of progesterone receptor (PR) and its impact on estrogen signaling in breast cancer remain controversial. In primary ER+ (estrogen receptor-positive)/PR+ human tumors, we report that PR reprograms estrogen signaling as a genomic agonist and a phenotypic antagonist. In isolation, estrogen and progestin act as genomic agonists by regulating the expression of common target genes in similar directions, but at different levels. Similarly, in isolation, progestin is also a weak phenotypic agonist of estrogen action. However, in the presence of both hormones, progestin behaves as a phenotypic estrogen antagonist. PR remodels nucleosomes to noncompetitively redirect ER genomic binding to distal enhancers enriched for BRCA1 binding motifs and sites that link PR and ER/PR complexes. When both hormones are present, progestin modulates estrogen action, such that responsive transcriptomes, cellular processes, and ER/PR recruitment to genomic sites correlate with those observedwith PR alone, but not ER alone. Despite this overall correlation, the transcriptome patterns modulated by dual treatment are sufficiently different from individual treatments, such that antagonism of oncogenic processes is both predicted and observed. Combination therapies using the selective PRmodulator/antagonist (SPRM) CDB4124 in combination with tamoxifen elicited 70% cytotoxic tumor regression of T47D tumor xenografts, whereas individual therapies inhibited tumor growth without net regression. Our findings demonstrate that PR redirects ER chromatin binding to antagonize estrogen signaling and that SPRMs can potentiate responses to antiestrogens, suggesting that cotargeting of ER and PR in ER+/PR+ breast cancers should be explored

Abstract 5044: Reducing breast cancer risk with hormone replacement therapy

Abstract Menopause occurs in women between the ages of 45 and 55 and often results in symptoms that can be alleviated with hormone replacement therapy (HRT). HRT improves the symptoms associated with menopause that negatively affect quality of life, such as hot flashes, difficulty sleeping, fatigue, and vaginal atrophy. HRT also prevents osteoporosis. A current HRT formulation, which includes conjugated equine estrogens (CE) and medroxyprogesterone acetate, unfortunately increases the risk of breast cancer. Over the years, the number of women taking HRT has decreased due to this perceived increased risk. A new form of HRT, which contains CE and bazedoxifene (BZA), a selective estrogen receptor modulator, has recently been approved by the FDA for treatment of moderate to severe hot flashes and for the reduction of osteoporosis development. The CE/BZA mixture has been shown to not only relieve symptoms associated with menopause, but also does not stimulate the breast or uterus. Various studies show that CE/BZA may be protective in the breast. Currently, the mechanism of action of this new combination therapy is not known. Our goal is to identify the molecular mechanism of action of CE/BZA through transcriptome and whole genome occupancy analysis in breast cancer cell lines. In addition, we are determining the effects of the combination therapy on breast cancer progression in a transgenic mouse model. The overall hypothesis of our project is that the ability of CE/BZA to delay the onset of mammary tumors and decrease the number of lesions in the polyoma middle T antigen transgenic mouse model is due to its action as an estrogen receptor α antagonist in the mammary gland. We have determined that CE stimulates gene expression in MCF7 cells at a similar rate to 17β-estradiol, and that BZA is able to decrease this stimulation. Similarly, we have found that CE increases ERα occupancy at promoters of some estrogen target genes, while a combination of CE and BZA decreases this occupancy. Through understanding the molecular mechanism of CE/BZA and by determining whether it reduces the incidence of invasive breast cancer in a transgenic mouse model, we will be able to improve quality of life for many women by relieving menopausal symptoms in a safe manner. Citation Format: Anna Dembo, Geoffrey Greene. Reducing breast cancer risk with hormone replacement therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5044. doi:10.1158/1538-7445.AM2015-5044</jats:p

Abstract 1802: ER-positive breast cancer prevention with the use of hormone replacement therapy

Abstract Menopause occurs in women between the ages of 45 and 55 and often results in undesirable vasomotor symptoms. Hormone replacement therapy (HRT) alleviates these symptoms, including hot flashes, difficulty sleeping, fatigue, and vaginal atrophy. HRT also prevents osteoporosis. PremPro, a currently available HRT formulation that combines conjugated equine estrogens (CE) with medroxyprogesterone acetate, increases the risk of breast cancer. Due to the perceived risk based largely on the results of the Women's Health Initiative (WHI) trial, the number of women taking HRT has decreased dramatically. Duavee, a new form of HRT that combines CE and bazedoxifene (BZA), a selective estrogen receptor modulator (SERM) and degrader (SERD), has recently been approved by the FDA for treatment of moderate to severe hot flashes and to reduce the risk of osteoporosis. Importantly, this CE/BZA mixture not only relieves symptoms associated with menopause, but it also does not stimulate the breast or uterus. Although several preclinical studies suggest that CE/BZA might be protective in the breast, the mechanism of action of this new combination therapy is not known. Our goal, therefore, is to elucidate the underlying molecular mechanisms by which CE/BZA differentially affects estrogen receptor alpha (ERα) action in the mammary gland, using transcriptome and whole genome occupancy analysis in breast cancer cell lines. We are also studying the effects of CE/BZA on early mammary cancer progression in the polyoma middle T antigen (PyMT) transgenic mouse model, which has been shown to be sensitive to estrogens. In addition, we are studying the effects in an ERα-positive patient-derived xenograft mouse model. We have determined that CE modulates gene expression in MCF7 cells similar to 17β-estradiol (E2), and that BZA is able to inhibit these effects. We have also observed that CE increases ERα occupancy versus E2 at response elements associated with some estrogen target genes, whereas CE/BZA decreases this occupancy. In the PyMT mouse model, we have determined that CE/BZA significantly delays the onset of mammary tumors in ovariectomized mice and prolongs their survival when compared to E2 and CE treatment alone. An improved understanding of the molecular mechanisms of CE/BZA action in hormone sensitive breast cancer cell and animal models should have important implications for women considering HRT. Citation Format: Anna G. Dembo, Geoffrey L. Greene. ER-positive breast cancer prevention with the use of hormone replacement therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1802.</jats:p

Cerebral blood flow responses to exercise are enhanced in left ventricular assist device patients after an exercise rehabilitation program

Cerebral blood flow during exercise is impaired in patients with heart failure implanted with left ventricular assist devices (LVADs). Our aim was to determine whether a 3-mo exercise training program could mitigate cerebrovascular dysfunction. Internal carotid artery (ICA) blood flow and intracranial middle (MCA v) and posterior cerebral (PCA v) artery velocities were measured continuously using Doppler ultrasound, alongside cardiorespiratory measures at rest and in response to an incremental cycle ergometer exercise protocol in 12 LVAD participants (5 female, 53.6 ± 11.8 yr; 84.2 ± 15.7 kg; 1.73 ± 0.08) pre- (PreTR) and post- (PostTR) completion of a 3-mo supervised exercise rehabilitation program. At rest, only PCAv was different PostTR (38.1 ± 10.4 cm/s) compared with PreTR (43.0 ± 10.8 cm/s; P &lt; 0.05). PreTR, the reduction in PCAv observed from rest to exercise (5.2 ± 1.8%) was mitigated PostTR ( P &lt; 0.001). Similarly, exercise training enhanced ICA flow during submaximal exercise (~8.6 ± 13.7%), resulting in increased ICA flow PostTR compared with a reduced flow PreTR ( P &lt; 0.001). Although both end-tidal partial pressure of carbon dioxide and mean arterial pressure responses during incremental exercise were greater PostTR than PreTR, only the improved [Formula: see text] was related to the improved ICA flow ( R2 = 0.14; P &lt; 0.05). Our findings suggest that short-term exercise training improves cerebrovascular function during exercise in patients with LVADs. This finding should encourage future studies investigating long-term exercise training and cerebral and peripheral vascular adaptation. NEW &amp; NOTEWORTHY Left ventricular assist devices, now used as destination therapy in end-stage heart failure, enable patients to undertake rehabilitative exercise training. We show, for the first time in humans, that training improves cerebrovascular function during exercise in patients with left ventricular assist devices. This finding may have implications for cerebrovascular health in patients with heart failure. </jats:p

Abstract 3308: Endothelin 3/endothelin receptor B signaling pathway blockade depletes radio-chemoresistant glioblastoma stem cells

Abstract Background: Patients with glioblastoma multiforme (GBM) despite being treated with gross total resection and post-operative temozolomide (TMZ) plus radiation therapy (RT), will almost always develop tumor recurrence. Hypothesis and objective: We hypothesize GBM stem cells (GSC) are responsible for post-treatment tumor recurrence and blockade of endothelin-3 (EDN3)/endothelin receptor B(EDNRB) signaling, a signaling pathway for neural crest development that hyperactivated in GSC, will enhance TMZ/RT treatment efficacy for GSC. Materials and Methods: Patient tumor-derived GSC were seeded at clonal density and subjected to radiochemotherapy at dose and schedule comparable to patient treatment. Treatment efficacy and synergy of EDNRB antagonist (BQ788) plus TMZ/RT were evaluated by the clonogenic efficiency, cell proliferation, and cell apoptosis of GSCs. Results: GSC are resistant to TMZ treatment alone (10μM), while treatment with BQ788 (75μM) alone can restrict cell migration, decrease clonogenic efficiency, and induce cell apoptosis. The RT displays the highest treatment efficacy on GSC when compared to TMZ or BQ788 alone and addition of TMZ to RT is slightly synergistic. Although only few small tumor spheres were detected when treated with RT or RT/TMZ, the survival clones regain proliferative activity and possess enhanced clonogenicity and anti-apoptotic ability when compared to untreated GSC. Treatment efficacy was greatly improved when GSC treated with BQ788 combined with RT/TMZ and no cells with self- renewal capacity were detected or recovered from the treatment. Conclusion: Subsets of GSC clones are resistance to standard RT/TMZ treatment and possess enhanced tumor sphere-forming capacity. Incorporate EDN3/EDNRB antagonist to a standard radiochemotherapy provide a significant treatment synergy in depletion of functional GSC and thus highlights a novel therapeutic strategy for the prevention of GSC-mediated tumor occurrence and recurrence. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3308. doi:10.1158/1538-7445.AM2011-3308</jats:p