Inhibition Of Estrogen Production Research Articles

Effect of daily alcohol intake on sex hormone levels among postmenopausal breast cancer survivors on aromatase inhibitor therapy: a randomized controlled crossover pilot study

BackgroundAlcohol intake is associated with a higher risk of estrogen receptor-positive (ER+) breast cancer (BC), presumably through its confirmed ability to increase sex hormone levels. Whether consuming alcohol within the recommended limit of one serving per day increases sex hormone levels among postmenopausal women taking aromatase inhibitors (AI) to inhibit estrogen production remains unknown. Therefore, we compared sex hormone levels following white wine to levels following white grape juice among ER + BC survivors taking AIs.MethodsIn this 10-week randomized controlled two-period crossover trial conducted from September 2022 to July 2023 among 20 postmenopausal women on AIs, we examined within-person changes in sex hormone levels following 3 weeks of 5 ounces of white wine daily versus 3 weeks of 6 ounces of white grape juice daily, with each drinking period preceded by two-week washouts and drinking period sequence allocated by randomization.ResultsAll 20 participants completed the trial. Compared to daily grape juice, daily wine led to decreases in total estradiol (11.1%, 95%confidence interval[CI] -49.8%,57.2%), free estradiol index (0.7%, 95%CI -2%,0.7%), and free estradiol concentration (7.7%, 95%CI -48%, 63.9%) but increases in estrone (13.8%, 95%CI -9.5%,43.1%), dehydroepiandrosterone sulfate (DHEAS; 11.4%, 95%CI -3.3%,28.4%), and testosterone (12.6%, 95%CI -0.8%,27.7%) and decreased sex hormone-binding globulin (SHBG; -2.7%, 95%CI -21.9%,21.2%).ConclusionsFive ounces of white wine daily did not lead to statistically significant increases in estradiol, but it led to changes in other sex hormones suggesting higher BC risk. Whether this level of alcohol intake diminishes AI effectiveness warrants further investigation.Trials RegistrationClinicaltrials.gov NCT05423730 registered June 14, 2022.

Virtual Screening of Apigenin and Luteolin as Natural Aromatase Inhibitors for the Treatment of Breast Cancer Patients

Aromatase is an enzyme that converts androgens (like testosterone) to estrogens (like 17- estradiol). It is also a highly successful therapeutic target for endocrine-responsive breast cancer. Aromatase inhibitors, which suppress estrogen synthesis in postmenopausal women, have been useful in the treatment of individuals with estrogen receptor-positive breast cancer. Anastrozole is an aromatase inhibitor medication that is used in the management and treatment of breast cancer. Flavonoids inhibit cancer cell proliferation by causing apoptosis, encouraging autophagy, and changing the cell cycle. Although several dietary flavonoids (like in parsley, celery and Broccoli) can inhibit aromatase, the tissue specificity and mechanism of binding are uncertain. According to several researches, flavonoids (apigenin and luteolin) dramatically suppress estrogen production. The study aims to examine binding of 3EQM (Aromatase) in the A chain with both of flavonoid (Apigenin and luteolin) and Anastrozole, using an in silico approach. PyRx default program was used to detect docking accuracy. Virtually, results showed that flavonoids have higher binding strength for apigenin and luteolin (which was -8.2 and -8.3) than Anastrozole (which was -7.6) with chain A of Aromatase. So, flavonoids can potentially be used as a natural medication to reduce breast cancer incidence. However, clinical trial studies are needed to investigate the role of apigenin and luteolin in the treatment of breast cancer.

Novel Treatment Strategies for Hormone Receptor (HR)-Positive, HER2-Negative Metastatic Breast Cancer.

Estrogen receptor (ER)-positive breast cancer (BC) is the most common BC subtype. Endocrine therapy (ET) targeting ER signaling still remains the mainstay treatment option for hormone receptor (HR)-positive BC either in the early or in advanced setting, including different strategies, such as the suppression of estrogen production or directly blocking the ER pathway through SERMs-selective estrogen receptor modulators-or SERDs-selective estrogen receptor degraders. Nevertheless, the development of de novo or acquired endocrine resistance still remains challenging for oncologists. The use of novel ET combined with targeted drugs, such as cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, has significantly improved long-term outcome rates, thus changing the therapeutic algorithm for metastatic BC (MBC) and recently the therapeutic strategy in the adjuvant setting for early high-risk BC. Eluding the resistance to CDK4/6 inhibitors combined with ET is currently an unmet medical need, and there is disagreement concerning the best course of action for patients who continue to progress after this combination approach. Genetic changes in the tumor along its growth uncovered by genomic profiling of recurrent and/or metastatic lesions through tumor and/or liquid biopsies may predict the response or resistance to specific agents, suggesting the best therapeutic strategy for each patient by targeting the altered ER-dependent pathway (novel oral SERDs and a new generation of anti-estrogen agents) or alternative ER-independent signaling pathways such as PI3K/AKT/mTOR or tyrosine kinase receptors (HER2 mutations or HER2 low status) or by inhibiting pathways weakened through germline BRCA1/2 mutations. These agents are being investigated as single molecules and in combination with other target therapies, offering promising weapons to overcome or avoid treatment failure and propose increasingly more personalized treatment approaches. This review presents novel insights into ET and other targeted therapies for managing metastatic HR+/HER2- BC by exploring potential strategies based on clinical evidence and genomic profiling following the failure of the CDK4/6i and ET combination.

Discovery of Novel ERα and Aromatase Dual-Targeting PROTAC Degraders to Overcome Endocrine-Resistant Breast Cancer.

Estrogen receptor α (ERα) plays a pivotal role in the proliferation, differentiation, and migration of breast cancer (BC) cells, and aromatase (ARO) is a crucial enzyme in estrogen synthesis. Hence, it is necessary to inhibit estrogen production or the activity of ERα for the treatment of estrogen receptor-positive (ER+) BC. Herein, we present a new category of dual-targeting PROTAC degraders designed to specifically target ERα and ARO. Among them, compound 18c bifunctionally degrades and inhibits ERα/ARO, thus effectively suppressing the proliferation of MCF-7 cells while showing negligible cytotoxicity to normal cells. In vivo, 18c promotes the degradation of ERα and ARO and inhibits the growth of MCF-7 xenograft tumors. Finally, compound 18c demonstrates promising antiproliferative and ERα degradation activity against the ERαMUT cells. These findings suggest that 18c, being the inaugural dual-targeting degrader for ERα and ARO, warrants further advancement for the management of BC and the surmounting of endocrine resistance.

Next generation selective estrogen receptor degraders in postmenopausal women with advanced-stage hormone receptors-positive, HER2-negative breast cancer.

Breast cancer is the most prevalent malignancy in women, and is characterized by its heterogeneity; exhibiting various subgroups identifiable through molecular biomarkers that also serve as predictive indicators. More than two thirds of breast tumors are classified as luminal with positive hormone receptors (HR), indicating that cancer cells proliferation is promoted by hormones. Endocrine therapies play a vital role in the effective treatment of breast cancer by manipulating the signaling of estrogen receptors (ER), leading to a reduction in cell proliferation and growth rate. Selective estrogen receptor modulators (SERMs), such as tamoxifen and toremifene, function by blocking estrogen's effects. Aromatase inhibitors (AI), including anastrozole, letrozole and exemestane, suppress estrogen production. On the other hand, selective estrogen receptor degraders (SERDs), like fulvestrant, act by blocking and damaging estrogen receptors. Tamoxifen and AI are widely used both in early- and advanced-stage disease, while fulvestrant is used as a single agent or in combination with other agents like the cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors (palbociclib, abemaciclib, ribociclib) or alpelisib for advanced-stage disease. Currently, SERDs are recognized as an effective therapeutic approach for the treatment of ER-positive breast cancer, showing proficiency in reducing and blocking ER signaling. This review aims to outline the ongoing development of novel oral SERDs from a practical therapeutic perspective, enhancing our understanding of the mechanisms of action underlying these compounds.

Repurposing of approved drugs for targeting CDK4/6 and aromatase protein using molecular docking and molecular dynamics studies.

Breast cancer is a leading cause of cancer-related morbidity and mortality worldwide, with the highest incidence among women. Among the various subtypes of breast cancer, estrogen-receptor positive (ER+) is the most diagnosed. Estrogen upregulates cyclin D1, which in turn promotes the activity of CDK4/6 and facilitates cell cycle progression. To address this, the first-line treatment for ER+ breast cancer focuses on inhibiting estrogen production by targeting aromatase, the enzyme responsible for the rate-limiting step in estrogen synthesis. Thus, combining CDK4/6 inhibitors with aromatase inhibitors has emerged as a crucial treatment strategy for this type of breast cancer. This approach effectively suppresses estrogen biosynthesis and controls uncontrolled cell proliferation, significantly improving overall survival rates and delayed disease progression. This study aimed to identify compounds that are likely to inhibit CDK4/6 and aromatase simultaneously by using a structure-based drug design strategy. 12,432 approved and investigational drugs were prepared and docked into the active site of CDK6 using HTVS and XP docking modes of Glide resulting in 277 compounds with docking scores ≤ -7 kcal/mol. These compounds were docked into aromatase enzyme using XP mode to give seven drugs with docking scores≤ -6.001 kcal/mol. Furthermore, the shortlisted drugs were docked against CDK4 showing docking scores ranging from -3.254 to -8.254 kcal/mol. Moreover, MM-GBSA for the top seven drugs was calculated. Four drugs, namely ellagic acid, carazolol, dantron, and apomorphine, demonstrated good binding affinity to all three protein targets CDK4/6 and aromatase. Specifically, they exhibited favourable binding free energy with CDK6, with values of -51.92, -53.90, -50.22, and -60.97 kcal/mol, respectively. Among these drugs, apomorphine displayed the most favourable binding free energy with all three protein targets. To further evaluate the stability of the interaction, apomorphine was subjected to a 100 ns molecular dynamics simulation with CDK6. The results indicated the formation of a stable ligand-protein complex. While the results obtained from the MM-GBSA calculation of the binding free energies of the MD conformations of apomorphine showed less favourable binding free energy compared to that obtained post-docking. All these computational findings will provide better structural insight for the development of CDK4/6 and aromatase multi-target inhibitors.

Abstract A32: Exemestane inhibits survival and cell cycle regulators and retards AML cell proliferation

Abstract Acute myeloid leukemia (AML) is the most common type of leukemia with poor prognosis. Although estrogen plays important roles in female cancers, the recent reports indicate that estrogen and its receptors also attribute to the development of non-gender cancers and AML is one of those. Therefore, the inhibition of estrogen production becomes a potential strategy for AML treatment. Exemestane is an aromatase inhibitor and commonly used for reducing estrogen production in breast cancer patients. Our data showed that Exemestane treatment significantly decreased the proliferation of both KG-1 and HL-60 AML cell lines. Since STAT3 and AKT closely collaborate with estrogen receptor in breast cancer cells, their activations are next to be monitored. In KG-1 cells, the phosphorylations of STAT3 (Y705 and S727) and AKT (S473) were both inhibited by Exemestane treatment. Regarding the cell cycle control, p21 was increased by Exemestane in KG-1 cells in which Cyclin E was reduced. It suggests that CDK2 might be inactivated by Exemestane-reduced Cyclin E and therefore p21 escaped from the CDK2-dependent degradation. Although the signaling findings of Exemestane in KG-1 were interesting, no similar results were found in HL-60 cells except the growth inhibition, suggesting the distinct regulation mechanisms between two cell lines. In summary, these results not only suggest, again, the importance of estrogen demand for AML cells, but also show the novel and potential treatment of AML using blockade of estrogen supply, which could be helpful to uncover novel AML treatments in the future. Citation Format: Mei-chih Chen, Pang-Ting Cheng, Yu-Chiao Cheng, Ho Lin, Chieh-Lin Jerry Teng. Exemestane inhibits survival and cell cycle regulators and retards AML cell proliferation [abstract]. In: Proceedings of the AACR Special Conference: Acute Myeloid Leukemia and Myelodysplastic Syndrome; 2023 Jan 23-25; Austin, TX. Philadelphia (PA): AACR; Blood Cancer Discov 2023;4(3_Suppl):Abstract nr A32.

Abstract P2-26-17: Establishment of an in vitro preclinical platform: A living biobank of patient-derived organoids with ER+ breast cancer

Abstract Introduction and objectives Estrogen receptor positive (ER+) tumors are the most common form of breast cancer and are responsible for most of the deaths from the disease. Treatment of ER+ breast cancer comprises interventions that suppress estrogen production and/or target the ER directly. While endocrine therapy has considerably reduced recurrence and mortality from breast cancer, de novo and acquired resistance to this treatment remains a major challenge. In this context, patient-derived organoids (PDOs), 3D structures composed of epithelial cells, are changing our understanding of cancer heterogeneity and its implications for personalized medicine. Our aim was to establish and characterize a PDO platform of ER+ breast cancer as preclinical tool to decipher and target this heterogeneity in order to tailor effective treatments based on the precise molecular makeup of the tumor. Material and Methods Surgical resections were collected from patients diagnosed with ER+ breast cancer. Organoid generation from patient material were divided in three main steps: 1) mechanical fragmentation of tissue pieces; 2) digestion of fragments into single-cell suspension; and 3) plating of cell preparations into matrigel domes to mimic the extracellular matrix. Organoids were passaged every 7–21 days based on confluency. Each newly organoid line was cryopreserved for further expansion. Results We have successfully achieved an outgrowth efficiency of almost 50% for PDOs from patients diagnosed with breast cancer. Characterization of PDO cultures is essential to validate its predictive potential. To asses that PDOs represent the tumor of the patient, for each organoid line, expression levels of the main histological markers (ER, PR, HER2, Ki67) were evaluated and correlated with the tissue of origin. In parallel, we have performed immunofluorescence on paraffin-embedded organoid samples with routinely used cancer stem cell markers. Potential contamination with normal cells (present in the resection used to establish the culture) should be considered. To address the tumor purity of the culture we have performed targeted DNA sequencing in both the original tissue and established PDOs. Conclusions PDOs represent a superior preclinical system compared to previous models due to their inherent heterogeneity, long-term stability, applicability for high-throughput screens and enhanced capacity to capture tumor characteristics. Therefore, the implementation of a well-annotated patient-derived organoid biobank will be of great interest for drug discovery and personalized therapy. Understanding the sources and implications of tumor heterogeneity will undoubtedly improve our evolving definition of cancer and aid in the design of effective patient-specific treatment strategies. Citation Format: Maria A Dominguez-Cejudo, Raquel Chapresto, Ana Gil-Torralvo, Francisco Javier Salvador Bofill, Sonia Molina-Pinelo. Establishment of an in vitro preclinical platform: A living biobank of patient-derived organoids with ER+ breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-26-17.

Neoadjuvant endocrine therapy expands stromal populations that predict poor prognosis in estrogen receptor-positive breast cancer.

The tumor microenvironment (TME) is an important modulator of response and resistance to endocrine therapy in estrogen receptor alpha (ER) positive breast cancer. Endocrine therapy is highly effective at reducing tumor burden and preventing recurrence in most estrogen receptor alpha (ER) positive breast cancers. Existing drugs work either directly by targeting tumor-cell ER or indirectly by inhibiting estrogen production in stromal cells with aromatase inhibitors (AI). However, many stromal cells also express ER and the direct impact of endocrine therapies on ER + stromal cells remain unclear. In this study, we investigated how neoadjuvant endocrine therapy (NET) directly effects stromal cells by measuring changes in stomal components of the TME that favor tumor progression. We previously defined two major subsets of tumor-associated stromal cells (TASCs): CD146 positive/CDCP1 negative (TASCCD146 ), CD146 negative/CDCP1 positive (TASCCDCP1 ), and generated a differentially expressed genes list associated with each type. Here, we applied the TASC gene list for classification and an algorithm that estimates immune cell abundance (TIMEx) to METABRIC transcriptomic data for ER + breast cancer patients coupled with multiplex imaging and analysis of paired tissue samples pre- and post- NET with the AI exemestane. TASCCDCP1 composition predicted for decreased patient survival in the METABRIC cohort. Exemestane treatment significantly increased expression of TASCCDCP1 and decreased expression of TASCCD146 . The posttreatment shift toward TASCCDCP1 composition correlated with increased macrophage infiltration and increased CD8+ T-cell, B cell, and general stromal components. The effectiveness of NET is currently based solely on the reduction of ER+ breast cancer cells. Here, we show NET displays clear TME effects that promote the expansion of the less favorable TASCCDCP1 population which are correlated with TME remodeling and reshaping immune infiltration supportive of tumor progression. Our findings highlight the need to further understand the role of endocrine therapy on TME remodeling, tumor progression, and patient outcomes.

Aromatase Inhibitor Induced Bone Loss: Do International Guidelines Accurately Stratify Fracture Risk and Selection of Anti-Osteoporosis Treatment?

Abstract Introduction: Aromatase inhibitors (AI) are used for adjunctive treatment of estrogen receptor-positive (ER+) breast cancer. Aromatase converts androgens to estrogens in the ovaries and peripheral tissues such as adipose, liver, muscle, and breast. In breast, estrogens increase cell proliferation in both normal and ER+ malignant tissue. AIs globally suppress estrogen production, and thereby can decrease tumor progression. However, in bone, estrogens suppress osteoclast activity and decrease bone resorption so AI use results in increased bone resorption and decreased bone mineral density (BMD). Several guidelines exist to direct management of AI-associated bone loss, but it is unclear whether adherence to these guidelines translates to decreased fracture risk. The International Osteoporosis Foundation (IOF) et al 2017 guidelines for the prevention of osteoporotic fractures in patients treated with AI recommended BMD measurement at the onset of AI use and use of anti-osteoporosis therapy (anti-OP) in those who met T-score and clinical risk factor (CRF) criteria. Hypothesis: We explored application of these guidelines and whether they were able to stratify patients according to risk, initiation of treatment, and fracture outcomes. Methods: 1517 charts were extracted from the electronic medical record (EMR) of a tertiary academic medical center based on history of breast cancer and use of AIs between 2008 and 2017. Charts were retrospectively analyzed to determine baseline BMD, osteoporosis risk factors, duration of AI use, duration of anti-OP therapy, and fractures. The IOF criteria were applied to each patient to determine applicability of anti-OP therapy. Fracture rates were compared using chi square test or Fisher’s exact test. Results: 1517 patients were included in the analysis. Regardless of whether criteria were met for treatment based on baseline BMD and CRF, the fracture rate was significantly higher in the treated versus the untreated group, 13.78% (CI: 9.56–18.99) versus 2.24% (p < 0.0001, CI: 1.51–3.21). Similarly, among those that met criteria, the fracture rate was significantly higher in the treated versus the untreated group, 10.24% (CI: 5.56–16.87) versus 2.61% (p = 0.0005, CI: 1.20–4.89). There was no significant difference in fractures between those who did versus did not meet treatment criteria, 4.66% (CI: 2.94–6.97) versus 3.64% (p = 0.34, CI 2.59–4.96). Conclusions: This retrospective EMR analysis of 1517 breast cancer patients on AIs between 2008 and 2017 observed a higher fracture incidence in patients who received anti-OP treatment compared to those who did not, regardless of meeting criteria for treatment per the IOF guidelines. It is possible that patients who initiated anti-OP therapy had additional CRFs not captured in the EMR and not factored into our analyses.

Prenatal aromatase inhibition alters postnatal immunity in domestic chickens (Gallus gallus)

In birds, exposure to exogenous testosterone during embryonic development can suppress measures of immune function; however, it is unclear whether these effects are due to direct or indirect action via aromatization. Estradiol (E2) is synthesized from testosterone by the enzyme aromatase, and this conversion is a necessary step in many signaling pathways that are ostensibly testosterone-dependent. Many lines of evidence in mammals indicate that E2 can affect immune function. We tested the hypothesis that some of the immunomodulatory effects observed in response to in ovo testosterone exposure in birds are mediated by conversion to E2 by aromatase, by using fadrozole to inhibit aromatization of endogenous testosterone during a crucial period of embryonic immune system development in domestic chickens (Gallus gallus). We then measured total IgY antibody count, response to PHA challenge, mass of thymus and bursa of Fabricius, and plasma testosterone post-hatch on days 3 and 18. Because testosterone has a reputation for immunosuppression, we predicted that if modulation of an immune measure by testosterone is dependent on aromatization, then inhibition of estrogen production by fadrozole treatment would lead to elevated measures of that parameter. Conversely, if testosterone inhibits an immune measure directly, then fadrozole treatment would likely not alter that parameter. Fadrozole treatment reduced circulating E2 in female embryos, but had no effect on males or on testosterone in either sex. Fadrozole-treated chicks had decreased day 3 plasma IgY antibody titers and a strong trend towards increased day 18 thymic mass. Furthermore, fadrozole treatment generated a positive relationship between testosterone and thymic mass in males, and tended to increase day 18 IgY levels for a given bursal mass in females. There was no effect on PHA response, bursal mass, or plasma testosterone at either age post-hatch. The alteration of several indicators of immune function in fadrozole-treated chicks implicates aromatization as a relevant pathway through which developmental exposure to testosterone can affect immunity in birds.

Rational design of allosteric modulators of the aromatase enzyme: An unprecedented therapeutic strategy to fight breast cancer

Estrogens play a key role in cellular proliferation of estrogen-receptor-positive (ER+) breast cancers (BCs). Suppression of estrogen production by competitive inhibitors of the enzyme aromatase (AIs) is currently one of the most effective therapies against ER + BC. Yet, the development of acquired resistance, after prolonged treatments with AIs, represents a clinical major concern. Serendipitous findings indicate that aromatase may be non-competitively inhibited by clinically employed drugs and/or industrial chemicals. Here, by performing in silico screening on two putative allosteric sites, molecular dynamics and free energy simulations, supported by enzymatic and cell-based assays, we identified five leads inhibiting the enzyme via a non-active site-directed mechanism. This study provides new compelling evidences for the existence of an allosteric regulation of aromatase and for the possibility of exploiting it to modulate estrogens biosynthesis. Such modulation can aptly reduce side effects caused by the complete estrogen deprivation therapy, and, possibly, delay/avoid the onset of resistance.

Treatment of Girls and Boys with McCune-Albright Syndrome with Precocious Puberty - Update 2017.

The most common endocrinopathy associated with McCune-Albright Syndrome (MAS) is peripheral precocious puberty (PP) which occurs far more often in girls than in boys. We will discuss the latest advancements in the treatment of precocious puberty in MAS that have been achieved during the past 10 years. However, due to the rarity of the condition and the heterogeneity of the disease, research in this field is limited particularly in regards to treatment in boys. In girls, a period of watchful waiting is recommended prior to initiating therapy due to extreme variability in the clinical course. This article will review in detail current pharmacologic treatment in girls, which typically consists of either inhibiting estrogen production or blocking estrogen action at the level of the end-organ. The two treatments with the most evidence at this time are Tamoxifen (which is an estrogen receptor modulator) and Letrozole (which is a 3rd generation aromatase inhibitor). This article will also review the current treatment strategies in boys which typically include using an androgen receptor blocker and an aromatase inhibitor. Due to the rarity of the condition, large multicenter collaborative studies are needed to further investigate efficacy and safety with the goal of establishing the gold standard for treatment of PP in children with MAS.

Rapid effects of the aromatase inhibitor fadrozole on steroid production and gene expression in the ovary of female fathead minnows (Pimephales promelas)

Cytochrome P450 aromatase catalyzes conversion of C19 androgens to C18 estrogens and is critical for normal reproduction in female vertebrates. Fadrozole is a model aromatase inhibitor that has been shown to suppress estrogen production in the ovaries of fish. However, little is known about the early impacts of aromatase inhibition on steroid production and gene expression in fish. Adult female fathead minnows (Pimephales promelas) were exposed via water to 0, 5, or 50µg fadrozole/L for a time-course of 0.5, 1, 2, 4, and 6h, or 0 or 50µg fadrozole/L for a time-course of 6, 12, and 24h. We examined ex vivo ovarian 17β-estradiol (E2) and testosterone (T) production, and plasma E2 concentrations from each study. Expression profiles of genes known or hypothesized to be impacted by fadrozole including aromatase (cytochrome P450 [cyp] 19a1a), steriodogenic acute regulatory protein (star), cytochrome P450 side-chain cleavage (cyp11a), cytochrome P450 17 alpha hydroxylase/17,20 lyase (cyp17), and follicle stimulating hormone receptor (fshr) were measured in the ovaries by quantitative real-time polymerase chain reaction (QPCR). In addition, broader ovarian gene expression was examined using a 15k fathead minnow microarray. The 5µg/L exposure significantly reduced ex vivo E2 production by 6h. In the 50µg/L treatment, ex vivo E2 production was significantly reduced after just 2h of exposure and remained depressed at all time-points examined through 24h. Plasma E2 concentrations were significantly reduced as early as 4h after initiation of exposure to either 5 or 50µg fadrozole/L and remained depressed throughout 24h in the 50µg/L exposure. Ex vivo T concentrations remained unchanged throughout the time-course. Expression of transcripts involved in steroidogenesis increased within the first 24h suggesting rapid induction of a mechanism to compensate for fadrozole inhibition of aromatase. Microarray results also showed fadrozole exposure caused concentration- and time-dependent changes in gene expression profiles in many HPG-axis pathways as early as 4h. This study provides insights into the very rapid effects of aromatase inhibition on steroidogenic processes in fish.

Gsdf is a downstream gene of dmrt1 that functions in the male sex determination pathway of the Nile tilapia.

Gonadal soma-derived factor (gsdf) is critical for testicular differentiation in teleosts, yet detailed analysis of Gsdf on testicular differentiation is lacking. In the present study, we knocked out tilapia gsdf using CRISPR/Cas9. F0 gsdf-deficient XY fish with high mutation rate (≥58%) developed as intersex, with ovotestes 90 days after hatching (dah), and become completely sex-reversed with ovaries at 180 and 240 dah. Those individuals with a low mutation rate (<58%) and XY gsdf(+/-) fish developed as males with normal testes. In F2 XY gsdf(-/-) fish, the gonads first expressed Dmrt1, which initiated the male pathway at 10 dah, then both male and female pathways were activated, as reflected by the simultaneous expression of Dmrt1 and Cyp19a1a in different cell populations at 18 dah, shifted to the female pathway expressing only Cyp19a1a at 36 dah, and finally developed into functional ovaries as adults. The male pathway and Dmrt1 expression was initiated, but failed to be maintained, in the absence of Gsdf. Aromatase-inhibitor treatment from 10 to 35 dah, however, rescued the phenotype, resulting in XY gsdf(-/-) with normal testes that expressed Dmrt1 and Cyp11b2. In vitro promoter analyses demonstrated that Dmrt1 activated gsdf expression in a dose-dependent manner in the presence of Sf1, even though Dmrt1 alone could not. Taken together, our results demonstrated that gsdf is a downstream gene of dmrt1. Gsdf probably inhibits estrogen production to trigger testicular differentiation. Mol. Reprod. Dev. 83: 497-508, 2016. © 2016 Wiley Periodicals, Inc.

Aromatase expression and regulation in breast and endometrial cancer.

Long-term exposure to excess estrogen increases the risk of breast cancer and type 1 endometrial cancer. Most of the estrogen in premenopausal women is synthesized by the ovaries, while extraovarian subcutaneous adipose tissue is the predominant tissue source of estrogen after menopause. Estrogen and its metabolites can cause hyperproliferation and neoplastic transformation of breast and endometrial cells via increased proliferation and DNA damage. Several genetically modified mouse models have been generated to help understand the physiological and pathophysiological roles of aromatase and estrogen in the normal breast and in the development of breast cancers. Aromatase, the key enzyme for estrogen production, is comprised of at least ten partially tissue-selective and alternatively used promoters. These promoters are regulated by distinct signaling pathways to control aromatase expression and estrogen formation via recruitment of various transcription factors to their cis-regulatory elements. A shift in aromatase promoter use from I.4 to I.3/II is responsible for the excess estrogen production seen in fibroblasts surrounding malignant epithelial cells in breast cancers. Targeting these distinct pathways and/or transcription factors to modify aromatase activity may lead to the development of novel therapeutic remedies that inhibit estrogen production in a tissue-specific manner.

Clinical utility of letrozole in the treatment of breast cancer: a Chinese perspective.

The incidence rate of breast cancers in People’s Republic of China has increased in the last decade, and many cases are responsive to hormone therapies. The third-generation aromatase inhibitor letrozole inhibits estrogen production, and is more efficacious than the estrogen receptor inhibitor tamoxifen. In recent years, letrozole has been widely used to treat postmenopausal breast cancers in People’s Republic of China. Also, metastatic, premenopausal, and male breast cancers have been effectively treated by a combination of letrozole with cytotoxic, radiation, or other therapies. In this review, we provide a perspective and summary of recent advances in the use of letrozole for breast cancer in Chinese patients.

Abstract OT2-01-10: A phase 1 study of RAD1901, a novel, orally available, selective estrogen receptor degrader, for the treatment of ER positive advanced breast cancer

Abstract The current NCCN treatment guidelines for ER+ breast cancer involves the use of approved agents such as fulvestrant, tamoxifen and aromatase inhibitors that either inhibit estrogen production or block estrogen receptor binding. While the initial treatment regimens with these selective estrogen receptor modulators (SERMs) and selective estrogen receptor degraders (SERDs) is often successful, many women eventually relapse with more aggressive forms of endocrine-resistant disease. To begin to overcome some of the challenges associated with current therapies including exposure limitations and intramuscular administration, we have developed RAD1901, a novel, non-steroidal, orally available SERD. Preclinical studies with RAD1901 have demonstrated potent dose dependent ER degradation consistent with a SERD mechanism of action, as well as potent inhibition of proliferation in vitro in breast cancer cell lines. RAD1901 also demonstrated significant anti-tumor efficacy in vivo, and notably single agent regressions in both MCF7 and a primary patient derived xenograft models harboring an ESR1 mutations. A phase 1 monotherapy study conducted in healthy postmenopausal female volunteers evaluated forty four subjects treated once daily with RAD1901 with doses ranging from 200 mg/day up to 1000 mg/day for 7 days. All dose levels were generally well tolerated and pharmacokinetic analysis demonstrated plasma exposures consistent with preclinical efficacy in ER+ breast cancer models. Furthermore, 18F-estradiol positron emission tomography (FES-PET) was also performed at baseline and after 7 days of RAD1901 treatment, to evaluate estrogen receptor engagement. Standardized uptake values (SUV) pre- and post-treatment with RAD1901 demonstrated complete attenuation of FES-PET signal in ER+ tissues such as the uterus from the 200 mg/day dose level. Taken together, these results provide strong preclinical and clinical rationale for the development of RAD1901 as a potent and selective oral SERD for the treatment of hormone driven and hormone resistant ER + metastatic breast cancers. RAD1901-005 is a Phase 1 study currently enrolling ER+ advanced metastatic breast cancer patients. The study consists of two parts: a monotherapy dose escalation followed by a safety expansion at the maximum tolerated dose (MTD). The dose escalation will follow a standard 3+3 design with once daily dosing to establish, safety, tolerability, and PK. Once the MTD for RAD1901 has been established, the safety expansion will further evaluate the safety, tolerability, biomarkers and preliminary efficacy at the recommended phase 2 dose (RP2D) following a continuous once daily schedule. Key inclusion criteria include post-menopausal women aged 18 years or older, with advanced ER positive, HER2 negative breast cancer, who have received ≤ 2 prior chemotherapy regimens in the metastatic setting and &amp;gt; 6 months of prior endocrine therapy. Patient enrollment started in early 2015, and is currently ongoing. ClinicalTrials.gov identifier: NCT02338349. Citation Format: Harb W, Garner F, McDermott J, Zimmerman T, Williams G, Hattersley G, Purandare D. A phase 1 study of RAD1901, a novel, orally available, selective estrogen receptor degrader, for the treatment of ER positive advanced breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT2-01-10.

RAD1901: a novel, orally bioavailable selective estrogen receptor degrader that demonstrates antitumor activity in breast cancer xenograft models.

Agents that inhibit estrogen production, such as aromatase inhibitors or those that directly block estrogen receptor (ER) activity, such as selective estrogen receptor modulators and selective estrogen receptor degraders, are routinely used in the treatment of ER-positive breast cancers. However, although initial treatment with these agents is often successful, many women eventually relapse with drug-resistant breast cancers. To overcome some of the challenges associated with current endocrine therapies and to combat the development of resistance, there is a need for more durable and more effective ER-targeted therapies. Here we describe and characterize a novel, orally bioavailable small-molecule selective estrogen receptor degrader, RAD1901, and evaluate its therapeutic potential for the treatment of breast cancer. RAD1901 selectively binds to and degrades the ER and is a potent antagonist of ER-positive breast cancer cell proliferation. Importantly, RAD1901 produced a robust and profound inhibition of tumor growth in MCF-7 xenograft models. In an intracranial MCF-7 model, RAD1901-treated animals survived longer than those treated with either control or fulvestrant, suggesting the potential benefit of RAD1901 in the treatment of ER-positive breast cancer that has metastasized to the brain. Finally, RAD1901 preserved ovariectomy-induced bone loss and prevented the uterotropic effects of E2, suggesting that it may act selectively as an agonist in bone but as an antagonist in breast and uterine tissues. RAD1901 is currently under clinical study in postmenopausal women with ER-positive advanced breast cancer.

Abstract ES5-1: Adherence and persistence with adjuvant aromatase inhibitor therapy

Abstract Aromatase inhibitors (AI) are medications that inhibit the aromatase enzyme, which converts androgens to estrogens, resulting in suppression of estrogen production in postmenopausal women. Treatment of postmenopausal women diagnosed with hormone receptor positive breast cancer with adjuvant AI therapy for 5 years has resulted in significant improvements in disease free and overall survival. Despite their proven benefit, however, adherence to and persistence with AI therapy is poor. A key reason for non-persistence with therapy is the development of bothersome side effects that can have a negative impact on quality of life. Retrospective analyses have identified possible predictors of poor tolerance of therapy. Studies have also suggested that development of toxicity may be associated with better response to therapy. Because of the concern about non-persistence with therapy, especially in the setting of prescription of an oral medication for many years, there has been considerable research into understanding the mechanism underlying development of toxicity as well as treatment of these side effects. Ultimately the goal is to improve breast cancer survival outcomes while minimizing the negative impact of therapy on quality of life. Citation Format: Norah Lynn Henry. Adherence and persistence with adjuvant aromatase inhibitor therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr ES5-1.