Antiestrogen Treatment Research Articles

8523 An Unconventional Estrogen Receptor Conformation Induces SUMO Expression In Breast Cancer Cells

Abstract Disclosure: G.R. Hancock: None. K. Young: None. G.L. Greene: None. S.W. Fanning: None. An Unconventional Estrogen Receptor Conformation Induces SUMO Expression in Breast Cancer Cells Govinda Hancock, Kristen Young, Geoffrey L. Greene, Sean W. Fanning Competitive allosteric regulators, selective estrogen receptor modulators (SERMs)/degraders (SERDs) differentially manipulate receptor structure to treat and prevent metastatic breast cancers. However, their utility is limited by the ∼40% rate of disease progression due to acquired therapy resistance. In this study, a new SERM based on a tetrahydro-6-isoquinoline (T6I) scaffold reveals the relationship between ERα conformation and therapeutic transcriptional pathways in drug-resistant breast cancers. Optimization of structure-activity relationships produced unique lead compound that engages transcriptional programs similar to the clinically approved SERD fulvestrant. Notably, both drugs induce the expression of small ubiquitin-like modifier-1 (SUMO1), in opposition to the pathogenic hormone 17β-estradiol. SUMOylation is a post-translational modification affecting protein-protein interactions, localization, stability and functional properties. High expression of SUMO1 is associated with better patient prognosis in ERα+ disease. SUMOylation in breast cancer will be elucidated through understanding how it’s induced, its structural basis, and its role in therapeutic response of antiestrogen treatments. Presentation: 6/3/2024

WEE1 inhibition delays resistance to CDK4/6 inhibitor and antiestrogen treatment in estrogen receptor-positive breast cancer.

Although endocrine therapies and Cdk4/6 inhibitors have produced significantly improved outcomes for patients with estrogen receptor positive (ER+) breast cancer, continuous application of these drugs often results in resistance. We hypothesized that cancer cells acquiring drug resistance might increase their dependency on negative regulators of the cell cycle. Therefore, we investigated the effect of inhibiting WEE1 on delaying the development of resistance to palbociclib and fulvestrant. We treated ER+ MCF7 breast cancer cells with palbociclib alternating with a combination of fulvestrant and a WEE1 inhibitor AZD1775 for 12 months. We found that the alternating treatment prevented the development of drug resistance to palbociclib and fulvestrant compared to monotherapies. Furthermore, we developed a mathematical model that can simulate cell proliferation under monotherapy, combination or alternating drug treatments. Finally, we showed that the mathematical model can be used to minimize the number of fulvestrant plus AZD1775 treatment periods while maintaining its efficacy.

Estrogen Regulated Genes Compel Apoptosis in Breast Cancer Cells, Whilst Stimulate Antitumor Activity in Peritumoral Immune Cells in a Janus-Faced Manner.

Background: Breast cancer incidence and mortality exhibit a rising trend globally among both premenopausal and postmenopausal women, suggesting that there are serious errors in our preventive and therapeutic measures. Purpose: Providing a series of valuable, but misunderstood inventions highlighting the role of increasing estrogen signaling in prevention and therapy of breast cancer instead of its inhibition. Results: 1. Breast cells and breast cancer cells with germline BRCA1/2 mutations similarly show defects in liganded estrogen receptor (ER) signaling, demonstrating its role in genomic instability and cancer initiation. 2. In breast tumors, the increased expression of special receptor family maybe an effort for self-directed improvement of genomic defects, while the weakness or loss of receptors indicates a defect requiring medical repair. 3. ER overexpression in breast cancer cells is capable of strengthening estrogen signaling and DNA repair, while in ER negative tumors, HER2 overexpression tries to upregulate unliganded ER activation and genome stabilization. 4. ER-positive breast cancers responsive to endocrine therapy may show a compensatory ER overexpression resulting in a transient tumor response. Breast cancers non-responsive to antiestrogen treatment exhibit HER2-overexpression for compensating the complete inhibition of hormonal ER activation. 5. In breast tumors, somatic mutations serve upregulation of ER activation via liganded or unliganded pathway helping genome stabilization and apoptotic death. 6. The mutual communication between breast cancer and its inflammatory environment is a wonderful partnership among cells fighting for genome stabilization and apoptotic death of tumor. 7. In breast cancers, there is no resistance to genotoxic or immune blocker therapies, but rather, the nonresponsive tumor cells exhaust all compensatory possibilities against therapeutic damages. Conclusions: Understanding the behavior and ambition of breast cancer cells may achieve a turn in therapy via applying supportive care instead of genotoxic measures.

Enhanced desmosome assembly driven by acquired high-level desmoglein-2 promotes phenotypic plasticity and endocrine resistance in ER+ breast cancer

Acquired resistance to endocrine treatments remains a major clinical challenge. In this study, we found that desmoglein-2 (DSG2) plays a major role in acquired endocrine resistance and cellular plasticity in ER+ breast cancer (BC). By analysing the well-established fulvestrant-resistant ER+ BC model using single-cell RNA-seq, we revealed that ER inhibition leads to a specific increase in DSG2 in cancer cell populations, which in turn enhances desmosome formation in vitro and in vivo and cell phenotypic plasticity that promotes resistance to treatment. DSG2 depletion reduced tumorigenesis and metastasis in fulvestrant-resistant xenograft models and promoted fulvestrant efficiency. Mechanistically, DSG2 forms a desmosome complex with JUP and Vimentin and triggers Wnt/PCP signalling. We showed that elevated DSG2 levels, along with reduced ER levels and an activated Wnt/PCP pathway, predicted poor survival, suggesting that a DSG2high signature could be exploited for therapeutic interventions. Our analysis highlighted the critical role of DSG2-mediated desmosomal junctions following antiestrogen treatment.

Abstract PS15-06: Results of the window-of-opportunity PIONEER trial evaluating addition of the progesterone receptor (PR) agonist megestrol to letrozole for early stage estrogen receptor (ER) positive breast cancer: exploiting ER-PR interaction

Abstract Background: Pre-clinical data suggest that combining anti-estrogen treatment with a progesterone receptor agonist leads to greater inhibition of tumor proliferation, due to molecular interactions between ER and PR [1]. A high dose of the PR agonist megestrol (160mg daily) is approved as monotherapy for the treatment of ER positive metastatic breast cancer. A lower dose of megestrol (20-40mg daily) can be an effective treatment for severe hot flashes associated with endocrine therapy [2] but whether this dose has anti-tumor activity is unknown. The PIONEER trial evaluated the potential anti-proliferative effect of low and high dose megestrol in combination with letrozole, relative to letrozole alone, using a short-term preoperative ‘window’ trial design assessing the direct effects of the trial treatment on tumor tissue before and after treatment. Methods: Eligible patients were post-menopausal women with histologically confirmed ER+ (Allred ≥ 3) HER2 negative breast cancer at least 10mm in size, with an ECOG performance status ≤ 2, planned for primary surgery or endocrine therapy. Enrolled patients were randomised 2:3:3 to Arm A: letrozole alone, Arm B: letrozole + lower-dose megestrol (40mg) or Arm C: letrozole + higher-dose megestrol (160mg). Treatment was given for 15 (13-19) days prior to surgery or end of treatment (EOT) core biopsy. The primary endpoint was change in tumor proliferation between baseline and EOT in Arm A vs (Arms B+C combined), measured by Ki67 immunohistochemistry (IHC). Secondary endpoints were comparison of Ki67 change in high versus low dose megestrol arms, absolute Ki67 at EOT, and change in tumor apoptosis (cleaved caspase 3 IHC), proliferation (Aurora Kinase A IHC), PR and androgen receptor expression. Exploratory analysis of ER chromatin binding (ChIP-Seq) was conducted on paired fresh-frozen samples from a subset of patients. Results: A total of 243 patients were randomised from July 2017 to October 2022 with recruitment paused for 3 months at onset of the COVID pandemic. 198 patients completed treatment and had evaluable tissue samples at baseline and EOT (Arm A: n = 51, Arm B: n = 74, Arm C: n = 73). Baseline mean Ki67 values were well balanced. Therapy was well tolerated and adverse events ≥ grade 3 were similarly rare across arms (A: 3.3%, B+C: 3.5%). The mean % reduction in Ki67 for each arm was: Arm A (letrozole): 71%, Arm B (letrozole + 40mg megestrol): 79%, Arm C (letrozole + 160mg megestrol): 80%. There was a statistically significantly greater reduction in Ki67 with megestrol combinations (B+C) versus letrozole alone (A) (P = 0.013). Analyses of secondary IHC endpoints and ER ChIP-Seq are ongoing and will be presented. Conclusion: Addition of the PR agonist megestrol enhanced the anti-proliferative effect of letrozole in this window-of opportunity trial. Megestrol combinations were well tolerated, and the anti-proliferative effect was observed in both low and high dose arms. These data support the potential use of low-dose megestrol as an inexpensive and well-tolerated means of improving aromatase inhibitor efficacy. Low dose megestrol can also ameliorate hot flashes and therefore might be a strategy to improve both treatment adherence and clinical outcomes for patients taking adjuvant endocrine therapy.

Autophagy and senescence facilitate the development of antiestrogen resistance in ER positive breast cancer.

Estrogen receptor positive (ER+) breast cancer is the most common breast cancer diagnosed annually in the US with endocrine-based therapy as standard-of-care for this breast cancer subtype. Endocrine therapy includes treatment with antiestrogens, such as selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators (SERDs), and aromatase inhibitors (AIs). Despite the appreciable remission achievable with these treatments, a substantial cohort of women will experience primary tumor recurrence, subsequent metastasis, and eventual death due to their disease. In these cases, the breast cancer cells have become resistant to endocrine therapy, with endocrine resistance identified as the major obstacle to the medical oncologist and patient. To combat the development of endocrine resistance, the treatment options for ER+, HER2 negative breast cancer now include CDK4/6 inhibitors used as adjuvants to antiestrogen treatment. In addition to the dysregulated activity of CDK4/6, a plethora of genetic and biochemical mechanisms have been identified that contribute to endocrine resistance. These mechanisms, which have been identified by lab-based studies utilizing appropriate cell and animal models of breast cancer, and by clinical studies in which gene expression profiles identify candidate endocrine resistance genes, are the subject of this review. In addition, we will discuss molecular targeting strategies now utilized in conjunction with endocrine therapy to combat the development of resistance or target resistant breast cancer cells. Of approaches currently being explored to improve endocrine treatment efficacy and patient outcome, two adaptive cell survival mechanisms, autophagy, and "reversible" senescence, are considered molecular targets. Autophagy and/or senescence induction have been identified in response to most antiestrogen treatments currently being used for the treatment of ER+ breast cancer and are often induced in response to CDK4/6 inhibitors. Unfortunately, effective strategies to target these cell survival pathways have not yet been successfully developed. Thus, there is an urgent need for the continued interrogation of autophagy and "reversible" senescence in clinically relevant breast cancer models with the long-term goal of identifying new molecular targets for improved treatment of ER+ breast cancer.

Systemic and Local Strategies for Primary Prevention of Breast Cancer.

One in eight women will develop breast cancer in the US. For women with moderate (15-20%) to average (12.5%) risk of breast cancer, there are few options available for risk reduction. For high-risk (>20%) women, such as BRCA mutation carriers, primary prevention strategies are limited to evidence-based surgical removal of breasts and/or ovaries and anti-estrogen treatment. Despite their effectiveness in risk reduction, not many high-risk individuals opt for surgical or hormonal interventions due to severe side effects and potentially life-changing outcomes as key deterrents. Thus, better communication about the benefits of existing strategies and the development of new strategies with minimal side effects are needed to offer women adequate risk-reducing interventions. We extensively review and discuss innovative investigational strategies for primary prevention. Most of these investigational strategies are at the pre-clinical stage, but some are already being evaluated in clinical trials and others are expected to lead to first-in-human clinical trials within 5 years. Likely, these strategies would be initially tested in high-risk individuals but may be applicable to lower-risk women, if shown to decrease risk at a similar rate to existing strategies, but with minimal side effects.

A Novel Metastatic Estrogen Receptor-Expressing Breast Cancer Model with Antiestrogen Responsiveness.

Most women diagnosed with breast cancer (BC) have estrogen receptor alpha-positive (ER+) disease. The current mouse models of ER+ BC often rely on exogenous estrogen to encourage metastasis, which modifies the immune system and the function of some tissues like bone. Other studies use genetically modified or immunocompromised mouse strains, which do not accurately replicate the clinical disease. To create a model of antiestrogen responsive BC with spontaneous metastasis, we developed a mouse model of 4T1.2 triple-negative (TN) breast cancer with virally transduced ER expression that metastasizes spontaneously without exogenous estrogen stimulation and is responsive to antiestrogen drugs. Our mouse model exhibited upregulated ER-responsive genes and multi-organ metastasis without exogenous estrogen administration. Additionally, we developed a second TN BC cell line, E0771/bone, to express ER, and while it expressed ER-responsive genes, it lacked spontaneous metastasis to clinically important tissues. Following antiestrogen treatment (tamoxifen, ICI 182,780, or vehicle control), 4T1.2- and E0771/bone-derived tumor volumes and weights were significantly decreased, exemplifying antiestrogen responsivity in both cell lines. This 4T1.2 tumor model, which expresses the estrogen receptor, metastasizes spontaneously, and responds to antiestrogen treatment, will allow for further investigation into the biology and potential treatment of metastasis.

Effects of Non-Ablative Solid-State Vaginal Laser (SSVL) for the Treatment of Vulvovaginal Atrophy in Breast Cancer Survivors after Adjuvant Aromatase Inhibitor Therapy: Preliminary Results.

One of the side effects of anti-estrogen treatments in breast cancer survivors (BCSs), especially with aromatase inhibitor (AI) treatment, is the frequent appearance of vulvo-vaginal atrophy (VVA). We aim to evaluate the efficacy, safety and feasibility of a new type of non-ablative Solid-State Vaginal Laser (SSVL) treatment in BCSs with VVA. A total of 30 BCSs with a history of AI use and symptoms of VVA were treated with a non-ablative SSVL (LASEmaR 1500™-EUFOTON)in this non-randomized pilot study. The effects of the laser have been evaluated at baseline, 10 wk and 24 wk using a visual analogue scale (VAS), the Vaginal Health Index (VHI), the Vulvar Health Index (VuHI), the Female Sexual Function Index (FSFI), the EORTC QLQ-BR23, the Vaginal Maturation Index (VMI) and vaginal pH. At 10-week follow-up vs. baseline there were no statistically significant differences in FSFI, lubrication and EORTC QLQ-BR23. In all the subjective (dyspareunia, VHI, VuHI, FSFI, QLQ) and objective parameters (VMI and pH) there was a statistically significant improvement at the 6-month follow-up. Satisfaction was very high (4.7 out of 5), with 95.7% of patients being satisfied, more than or very satisfied. Preliminary results of SSVL treatment of VVA and dyspareunia in BCSs after AI treatment suggest clinical improvement, without relevant side effects and with a high degree of satisfaction.

Tolerability and effectiveness of fulvestrant as first-line endocrine therapy in unselected patients with advanced breast cancer (ABC): Results of a multicenter, single arm, non-interventional study.

e13061 Background: Fulvestrant, a selective estrogen receptor (ER) down-regulator, is a standard of care for first-line treatment in hormone receptor-positive (HR+) advanced breast cancer. This study is to assess the safety profile and effectiveness of fulvestrant 500mg as the first-line endocrine therapy of post-menopausal women with HR+ locally advanced or metastatic breast cancer. Methods: The study is an open-label, multicentre, prospective, observational study in China. Chinese patients receiving fulvestrant 500mg as the first endocrine agent after relapse according to investigator’s clinical practice were enrolled. Primary variable is the frequency and severity of adverse events (AEs). Secondary variables were objective response rate (ORR), clinical benefit rate (CBR), progress free survival (PFS) and overall survival (OS). Predictive effects of endocrine resistance, chemotherapy for advanced disease and adjuvant endocrine therapy on the effectiveness were prespecified as exploratory variables. Results: From November 2017 to December 2020, 461 patients were enrolled by 29 Chinese centers. Median age was 56 years and the ECOG score was: 0, 165 (35.8%); 1, 281 (60.9%); 2, 12 (2.6%); and 3, 3 (0.7%). 20 (4.3%) patients had the Kaplan-Feinstein index ≥2. Majority (77.0%) of the patients were ER+ and PgR+, and 190 (41.2%) had visceral metastasis. In total, 91 (19.7%) patients were primary endocrine resistant, 202 (43.8%) were secondary endocrine resistant and 123 (26.7%) were endocrine-therapy naïve. 147 (31.9%) patients received previous chemotherapy for advanced disease, while 101 (21.9%) patients had anti-estrogen drugs as adjuvant therapy. 54 (11.7%) patients had concurrent CDK4/6 inhibitors. After a median follow-up of 26.8 months (IQR 18.7-38.2), median PFS was 13.0 months (95% CI 9.8-16.4) and median OS was 41.2 months (95% CI 37.3-NE). ORR was 11.3% (95% CI 8.2-15.1) and CBR was 60.6% (95%CI 55.2-65.8). Patients with endocrine-therapy naïve tumor, no previous chemotherapy for advanced disease and adjuvant anti-estrogen treatment had a longer PFS of first-line fulvestrant 500mg. 67 (14.5%) patients had at least one AE, with 1 (0.2%) patient withdrawing because of AEs. Drug-related serious AEs (SAEs) were rare, occurring in 2 (0.4%) patients. No patient died as a result of a drug-related AE. Neutropenia, increased ALT/AST, and anemia were the most commonly reported AEs in this study. Conclusions: This is the first prospective real-world study confirming that fulvestrant 500mg is a well-tolerated treatment option in unselected ABC in China. In the real clinical practice, fulvestrant 500mg can achieve the consistent anti-tumor activity as in clinical trials. Patients with endocrine-therapy naïve status and no prior chemotherapy tend to have a longer control time. Clinical trial information: NCT02909361 .

Pulmonary benign metastasizing leiomyoma in patients aged 45 years and younger: clinical features and novelty in treatment

BackgroundPulmonary benign metastasizing leiomyoma (PBML) is the most common extrauterine spread of uterine leiomyoma, and its biological behavior is traditionally thought to be hormone dependent. Studies on older PBML patients have been previously reported, but limited literature has been published regarding the clinical features and treatment of PBML in young women.MethodsA total of 65 cases of PBML in women aged 45 years and younger were reviewed, including 56 cases selected from PubMed and 9 cases from our hospital. The clinical characteristics and management of these patients were analyzed.ResultsThe median age of all the patients at diagnosis was 39.0 years. PBML most commonly presented as bilateral solid lesions (60.9%), with other rare imaging manifestations. The median interval time from a pertinent gynecologic procedure to diagnosis was 6.0 years. A total of 16.7% of patients received careful observation, and all achieved stable status in a median follow-up time of 18.0 months. A total of 71.4% of patients were administered anti-estrogen therapies, including surgical castration (33.3%), gonadotropin-releasing hormone analog (23.8%) and anti-estrogen drugs (14.3%). Eight of 42 patients underwent surgical resection of metastatic lesions. Patients who underwent curative surgery for the removal of pulmonary lesions combined with adjuvant anti-estrogen therapies had favorable outcomes compared with those who only underwent surgical resection. The disease control rates of surgical castration, gonadotropin-releasing hormone analog, and anti-estrogen drugs were 85.7%, 90.0%, and 50.0%, respectively. For two patients, sirolimus (rapamycin) achieved successful relief of symptoms and control of pulmonary lesions without lowering hormone levels and causing estrogen deficiency symptoms.ConclusionsIn the absence of standard treatment guidelines for PBML, maintaining a low-estrogen environment using different kinds of antiestrogen therapies has been the mainstream strategy and has satisfying curative effects. A wait-and-see strategy might be an option, but therapeutic approaches must be contemplated when complications or symptoms progress. For PBML in young women, the negative effect on ovarian function of anti-estrogen treatment, especially surgical castration, should be considered. Sirolimus might be a new treatment option for young PBML patients, especially for those who want to preserve ovarian function.

Abstract 3890: TMPRSS2 serin protease is a novel biomarker for ER+ breast cancer patient prognosis and survival and mediates resistance to anti-estrogen treatment in ER+ breast cancer

Abstract Breast cancer (BC) is the most commonly diagnosed cancer in women and the second leading cause of cancer related deaths in the US. About 70-80% of patients have ER+ BC and initially respond to anti-estrogen (ie, Tamoxifen) or endocrine/homonal treatments. However, about 60% of the patients inevitably develops resistance to anti-estrogen therapies (due to intrinsic (15-20%) and acquire resistance (30-40%), representing a major clinical problem, resulting in relapses and metastasis, leading to significant patient mortality. Therefore, understanding the underlying mechanisms causing resitance to hormonal or anti-estrogen treatments is needed the for developing highly effective threapies and improving patient survival. Cell surface proteases, including serine proteases, are proteolytic modifiers of particular targets, including growth factors and protease-activated receptors, which are critical for the activation of oncogenic signaling pathways. TMPRSS2, a member of type II transmembrane serine protease (TTSP) family, has been shown to be highly expressed in prostate cancer cells and its role in carcinogenesis. We found that TMPRSS2 is highly upregulated well established tamoxifene resistant cell lines derivative of MCF7 (LCC2 and LCC9) compared to MCF7 cells. Performing Kaplan-Meier survival analyses in TCGA-BC database we also found that TMPRSS2 expression is associated with poor prognosis and significantly shorter patient survival in ER+ BC patients (p=0.015, n=221 patients). In addition, we found that TMPRSS2 is regulated by Estrogen/Estrogen Receptor-alpha (ERα) signaling as in vitro inhibition of estrogen/ERα signaling by ERα siRNA, tamoxifen or faslodex reduced TMPRSS2 protein expression ER+ MCF7 BC cells. Moreover, we found that inhibition of TMPRSS2 by 3 different siRNA molecules suppressed cell proliferation of MCF7 cells and reduced expression critical proteins for cell cycle and proliferation, including cyclin D1, c-Myc and pERK/MAPK signaling, suggesting that TMPRSS2 promotes the oncogenic signaling pathways in ER+ BC cells. Currently, we are targeting TMPRSS2 in in vitro and in vivo Tamox-resistant LCC2 and LCC9 models in mice by siRNA alone and in combination with Tamoxifen or faslodex to demostrate inhibition of TMPRSS2 sensitize tumors to anti-estrogen treatments. In conclusion, TMPRSS2 is a potential biomarker for poor patient survival and anti-estrogen resistance, and targeting TMPRSS2 alone as a monothreapy and in combination with anti- Tamoxifen or faslodex may be a promising approach for overcoming resistance to estrogen thereapies in ER+ BC patients. Citation Format: Rumeysa Ozyurt, Nermin Kahraman, Pinar Atalay Dundar, Bulent Ozpolat. TMPRSS2 serin protease is a novel biomarker for ER+ breast cancer patient prognosis and survival and mediates resistance to anti-estrogen treatment in ER+ breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3890.

Abstract 3445: Immune cells infiltration and activation are higher in breast cancers resistant to antiestrogen therapy

Abstract We investigated the tumor microenvironment (TME) in estrogen receptor positive (ER+) primary breast cancers from stage I-III patients treated with estrogen deprivation (ED, induced with letrozole) for 10-21 days. We used primary breast cancer biopsies, collected from 198 patients, to assess tumor-infiltrating lymphocytes (TILs), transcriptomic profiles, and TME composition. Diagnostic biopsy and surgical on-treatment tumor specimens were collected; Ki67, ERα, PR, and HER2 expression were measured using automated quantitative analysis (AQUA). Tumors were categorized as estrogen deprivation-sensitive (ED-S) or -resistant (ED-R) based on the natural log (ln) of the Ki67 score (ln ≤1.0 or ≤2.7% Ki67+ cells vs. ln ≥2.0 or ≥7.4%, respectively) in the on-treatment (surgical) biopsy. Scoring of stromal (s)TILs, using hematoxylin and eosin staining of on-treatment specimens, revealed that sTILs were elevated in ED-R compared to ED-S tumors (p<0.0001). We next constructed tissue microarrays (TMAs) of on-treatment tumor sections and performed cyclic immunofluorescence (CyCIF) with 38 antibodies, including markers of hormone receptors, immune cells, signaling pathways, proliferation, DAPI (nuclei), and others. We then segmented single cells from each tumor core and designated them as immune, cancer, or stromal cells based on expression of a set of markers. Briefly, cells that stained strongly for CD45 (leukocyte marker), and/or CD4 (T lymphocyte marker), or CD68 (macrophage marker) were considered immune cells. CD45/CD4/CD68-negative cells were categorized as tumor, if E-cadherin and/or cytokeratin-positive, or stromal cells, if -negative. To investigate the TME composition, we next assessed cell specific spatial enrichment by quantifying the expression of immune markers in the area immediately adjacent to each tumor cell. Relative to ED-S, ED-R samples exhibited higher CD45+ cells (p<0.0001) and higher CD8+ T cells (p=0.0329), while CD4+ T cells showed no difference. Conversely, immune-suppressive T-reg (CD4+FOXP3+) cells were enriched in the ED-S samples (p=0.0004). In addition, PD1, a marker for T cell exhaustion, was higher in the ED-S group (p=0.0004), as were CD68+ cells (p<0.0001). To confirm and expand upon these findings, RNA-sequencing was performed on the on-treatment tumor sections. Gene set enrichment analysis of hallmark gene signatures revealed that immune-related gene sets, such as “IFNα response”, “IFNɣ response”, “allograft rejection”, and “inflammatory response” were enriched in ED-R vs. ED-S tumors. In summary, our study shows that activated anti-tumor immune cells are enriched in the TME of ER+ breast tumors resistant to estrogen deprivation, whereas ED-sensitive tumors show a more immunosuppressed or immune cold milieu. These data suggest a potential causal link between antiestrogen treatment and modulation of antitumor immunity in ER+ breast cancers. Citation Format: Fabiana Napolitano, Dhivya R. Sudhan, Yunguan Wang, Paula I. González-Ericsson, Luigi Formisano, Kyung-Min Lee, Chang-Ching Lin, María Rosario Chica-Parrado, Hongli Ma, Nathaniel Evans, Alberto Servetto, Saurabh Mendiratta, Spencer Barnes, Yisheng V. Fang, Justin M. Balko, Gordon B. Mills, Marilyne Labrie, Ariella B. Hanker, Carlos L. Arteaga. Immune cells infiltration and activation are higher in breast cancers resistant to antiestrogen therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3445.

BAP18 facilitates CTCF-mediated chromatin accessible to regulate enhancer activity in breast cancer.

The estrogen receptor alpha (ERα) signaling pathway is a crucial target for ERα-positive breast cancer therapeutic strategies. Co-regulators and other transcription factors cooperate for effective ERα-related enhancer activation. Recent studies demonstrate that the transcription factor CTCF is essential to participate in ERα/E2-induced enhancer transactivation. However, the mechanism of how CTCF is achieved remains unknown. Here, we provided evidence that BAP18 is required for CTCF recruitment on ERα-enriched enhancers, facilitating CTCF-mediated chromatin accessibility to promote enhancer RNAs transcription. Consistently, GRO-seq demonstrates that the enhancer activity is positively correlated with BAP18 enrichment. Furthermore, BAP18 interacts with SMARCA1/BPTF to accelerate the recruitment of CTCF to ERα-related enhancers. Interestingly, BAP18 is involved in chromatin accessibility within enhancer regions, thereby increasing enhancer transactivation and enhancer-promoter looping. BAP18 depletion increases the sensitivity of anti-estrogen and anti-enhancer treatment in MCF7 cells. Collectively, our study indicates that BAP18 coordinates with CTCF to enlarge the transactivation of ERα-related enhancers, providing a better understanding of BAP18/CTCF coupling chromatin remodeling and E-P looping in the regulation of enhancer transcription.

Upregulation of the EGFR/MEK1/MAPK1/2 signaling axis as a mechanism of resistance to antiestrogen‑induced BimEL dependent apoptosis in ER+ breast cancer cells.

The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimEL‑dependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the pro‑apoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL pro‑apoptotic action in an antiestrogen‑resistant breast cancer cell model. In addition, the present study identified a pro‑survival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogen‑resistant breast cancer cells survive EGFR targeting by pro‑survival autophagy. These pre‑clinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and pro‑survival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimEL‑dependent apoptosis.

Contemporary Use of Hormonal Therapy in Endometrial Cancer: a Literature Review.

Most endometrial cancers are estrogen receptor and progesterone receptor positive. Hormonal therapy in endometrial cancer is best used in patients with low-grade disease and hormone receptor positivity. Though not standard of care, hormonal treatment can be considered in endometrial cancer treatment in both the early-stage upfront setting for patients who are not surgical candidates and in advanced and recurrent endometrial cancer. In patients who desire fertility preservation or who are not surgical candidates, levonorgestrel intrauterine device and oral progesterone are preferred treatment options. In patients with advanced and metastatic disease, there is no standard-of-care second-line treatment, and hormonal treatment is a widely accepted option for low-grade disease. Beyond progesterone, selective estrogen receptor modulators, aromatase inhibitors, gonadotropin-releasing hormone agonists, and fulvestrant are hormonal treatment options. New therapies, such as MTOR inhibitors and CDK 4/6 inhibitors, have been extensively studied in breast cancer and are shown to be useful in conjunction with hormonal therapies particularly when there is suspected resistance to anti-estrogen treatment. Hormonal therapies also tend to be better tolerated than chemotherapy agents, making them a desirable option particularly in patients with lower performance status. Results from ongoing clinical trials will hopefully help shed light on the use of combination treatment in patients with hormone receptor-positive, low-grade metastatic, and recurrent endometrial cancer.

Pregnancy outcomes after oral and injectable ovulation induction in women with infertility with a low antimüllerian hormone level compared with those with a normal antimüllerian hormone level

To determine the ongoing pregnancy rate among patients with infertility with a low antimüllerian (AMH) level compared with those with a normal AMH level after oral and injectable ovulation induction (OI)/intrauterine insemination (IUI). Retrospective cohort. Academic center. Patients completing ≥1 medicated OI/IUI cycle at our center between 2015 and 2019 were included. The AMH levels were measured within 12 months of treatment initiation. The cohort was stratified into low AMH (AMH level, <1.0 ng/mL) and normal AMH (AMH level, ≥1.0 ng/mL) groups. All subsequent medicated OI/IUI cycles occurring within 1 year of initial cycle start date were included up to the third completed cycle or until an ongoing pregnancy was recorded. Patients were stratified by age (<35, 35-40, and >40 years), and the relationship between the low and normal AMH groups and each binary endpoint were quantified as risk ratios using the age-adjusted Poisson models. None. Ongoing pregnancy. A total of 3,122 patients completed 5,539 oral antiestrogen cycles, and 1,060 completed 1,630 injectable gonadotropin cycles. For oral antiestrogen treatment, pregnancy outcomes, including ongoing pregnancy rate per cycle, for patients with a low AMH level were comparable with those for patients with a normal AMH level (<35 years, 15.4% vs. 14.9%; 35-40 years, 10.0% vs. 11.0%; and >40 years, 2.8% vs. 3.3%). For injectable gonadotropin treatment, the ongoing pregnancy rate was lower in the low AMH group than in the normal AMH group for the ages of <35 (12.1% vs. 23.5%; relative risk [RR], 0.52 [95% confidence interval {CI}, 0.28-0.97]) and 35-40 (12.5% vs. 18.5%; RR, 0.70 [95% CI, 0.49-0.99]) years but comparable with that for patients aged >40 years (3.0% vs. 4.0%; RR, 0.86 [95% CI, 0.31-2.35]). The proportion of multifetal gestations was similar between the low and normal AMH groups treated with oral antiestrogens (13.1% vs. 10.8%); however, for injectable gonadotropin treatment, patients with a normal AMH level had a higher proportion of multifetal gestations (18.6% vs. 31.1%). Compared with normal ovarian reserve, treatment with oral antiestrogens for OI/IUI for patients with low ovarian reserve results in comparable follicular development and ongoing pregnancy rates for all age groups. When patients with low ovarian reserve are treated with gonadotropins for OI/IUI, multifollicular recruitment is less likely resulting in a significantly decreased ongoing pregnancy rate for patients aged <35 and 35-40 years but also a decrease in multifetal gestations. Overall, the ongoing pregnancy rates of 8.7% per oral antiestrogen cycle and 8.1% per injectable gonadotropin cycle in patients with low ovarian reserve are comparable with the expected rates in the general infertility population.

Abstract 3006: Effects of JNK/Jun blockade on breast cancer cell autophagy are dependent on breast cancer subtype

Abstract Our long-term goal is to elucidate the role of JNK/Jun signaling in breast cancer cell autophagy induced by anti-estrogen treatment and/or chemotherapy in ERα expressing and TNBC cells, respectively. In this study, we analyzed the role of JNK/Jun signaling in regulating the high basal autophagy levels in TNBC. To do so, we utilized the highly metastatic murine 4T1 and the human MDA-MB-231 TNBC models. In addition, we performed autophagic flux assays after treating breast cancer cells with JNK-IN8, a non-reversible small molecule JNK1/2 inhibitor. Treatments were performed for various times in the presence and absence of chloroquine (CQ) to allow analysis of steady state levels of atg8 (LC3-II) and sequestosome-1 (p62). These LC3-II and p62 proteins are involved in autophagosome formation and function, and are catabolized during autolysosomal turnover. To impair this process, CQ is a lysosomotropic agent that raises the pH of the lysosome and blocks such turnover. We also determined the effect of JNK-IN-8 on 4T1 and MDA-MB-231 cell number (proliferation). These studies determined that JNK-IN8 was an effective inhibitor of autophagic flux in the TNBC cells when used at concentrations that effectively blocked cJun phosphorylation, the downstream readout of JNK-IN8 efficacy used for our experiments. Blockade of autophagic flux by JNK-1/2 inhibition in TNBC was in stark contrast to results obtained with JNK-IN-8 treatment of ERα expressing MCF-7 and T47-D breast cancer cells, in which JNK-IN-8 induced a robust autophagy response with elevations in the steady state levels and flux of LC3-II and p62. Induction of autophagy by JNK-IN-8 in ERα expressing breast cancer cells occurred concomitantly with a substantial reduction in cell proliferation but minimal induction of apoptosis. Overall, these pre-clinical in vitro studies support the following conclusions: (1) JNK1/2 targeting in TNBC effectively blocks autophagic flux and may be particularly effective when used in combination with chemotherapies that induce pro-survival autophagy which is a current focus of our studies; and (2) JNK1/2 targeting in ERα expressing breast cancers has the potential to mediate a pro-survival autophagic activity in response to endocrine therapy or chemotherapy and should be cautiously approached. Ongoing studies are aimed at understanding the underlying mechanisms of the differential effects of JNK/Jun signaling on autophagy in TNBC versus ERα expressing breast cancer. Such an understanding should provide important information to aid in the ongoing interest in utilizing JNK1/2 as a molecular target for improved treatment of TNBC. Citation Format: Michael K. McGrath, McKenzie L. Hagan, Timmothy Summers, Jesse Wayson, Carol Joseph, Amanda C. Barrett, John T. Barrett, Patricia V. Schoenlein. Effects of JNK/Jun blockade on breast cancer cell autophagy are dependent on breast cancer subtype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3006.

Abstract 2562: eIF4E modulators to address breast cancer resistance

Abstract ER+/HER2- advanced or metastatic breast cancers represents a large patient population served by CDK4/6 inhibitors combined with hormonal therapy as standard of care. As acquired resistance emerges, molecular profiling indicates about &amp;gt; 100 different mutations render resistance, creating challenges for treating physicians, patients, and the healthcare system broadly. The aim of our work is to maintain consolidation of this large patient population by developing targeted therapies to a key fundamental mechanism at the convergence of many oncogenic signaling pathways through which resistance arises. The regulation of CAP dependent protein translation is a central element in oncogenesis. One of a family of CAP binding proteins, eIF4E serves to anchor the m7GTP CAP of RNA into several protein complexes and regulates multiple aspects of mRNA processing such as nuclear export and ribosomal translation. Our efforts focused on simultaneously developing potent small molecule modulators of eIF4E and patient hypotheses through which to direct their initial clinical use. By aligning medicinal chemistry tools with patient directed pharmacology, we optimized our inhibitors to identify orally bioavailable, nM modulators of eIF4E. Biochemical assays demonstrated direct binding and allosteric modulation of eIF4E activity by PICRN941, along with Proximity Ligation Assays (PLA) demonstrating reduced eIF4E and 4G association in cells. Western analysis demonstrated that PICRN941 induced simultaneous and significant modulation of a number of key oncogenes that have been postulated to drive intrinsic or acquired resistance in response to standard of care including anti-estrogen treatment, CDK4/6 inhibitors or PI3K inhibitors combined with hormonal therapy, including MYC, CDK2, CDK4, CCND1 and eIF4E itself. Treatment of ER+ breast cancer cell lines including ZR-75-1, T47D, and ZR-75-30 with PICRN941 induced a dose dependent reduction in the levels of hyper-phosphorylated 4E-BP1 commensurate to increases in unphosphorylated 4E-BP1, and dose-dependent reduction in protein expression of Cyclin D1, CDK4, ER alpha, phosphorylated Rb and eIF4E. Reduced protein expression correlated with subsequent cell cycle arrest and apoptosis. We further studied our inhibitors in primary patient derived organoids in collaboration with the Hubrecht Institute, where we observed potent and complete responses in breast cancer organoids that represent patient populations where unmet needs remain high including PTEN and RB null organoid models. Markers of target engagement correlated well with organoid model sensitivity, including Cyclin D1 responses. Our findings suggest that our allosteric eIF4E modulators may provide a unique and efficient therapeutic approach to address multiple resistance mechanisms across cancer patient populations, toward fulfilling the promise of this elusive target. Citation Format: Lisa Sturla, Bassil Dekky, Xuemei Zhang, Katherine S. Bowdish, Chris VanDeusen. eIF4E modulators to address breast cancer resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2562.

Abstract 5375: Precision run-on sequencing (PRO-seq) analysis of a treatment time course in ER+ breast cancer cell lines reveals the transcriptional changes underlying response to complete estrogen receptor antagonist (CERAN) OP-1250

Abstract OP-1250 is an orally-bioavailable complete estrogen receptor antagonist (CERAN) previously shown to shrink wild-type and Y537S mutant estrogen receptor-positive (ER+) tumors in multiple preclinical xenograft models. To better understand the effects of OP-1250 treatment on ER+ breast cancer cells, we used precision run-on sequencing (PRO-seq) to profile the direct transcriptional effects of OP-1250 in two commonly used breast cancer cell lines, MCF7 and CAMA-1. PRO-seq detects nascent RNA, and thus can detect changes at shorter timescales than traditional RNA-seq methods. We conducted PRO-seq 15 minutes, 1 hour, 6 hours and 24 hours after administration of OP-1250, estradiol, fulvestrant and tamoxifen to compare the effects of these compounds across the two cell lines. OP-1250 was administered in the absence of estradiol and after estradiol pretreatment to generate a detailed profile of the time course of its activity. We identified genes that display early transcriptional changes in response to the compounds tested, many of which have been previously identified as estrogen response genes. At later time points we observed transcriptional changes consistent with modulation of pathways involved in cell cycle progression. We show that OP-1250 treatment reverses the estradiol-induced transcriptional changes associated with estrogen receptor activation and chronicle the time course of these changes. Finally, we show greater similarity in the transcriptional changes induced by CERANs OP-1250 and fulvestrant compared to tamoxifen, as well as cell line-specific differences in estrogen response and response to anti-estrogen treatment. These data provide additional insights into the mechanisms of OP-1250 action on ER+ cell lines and patient tumors. OP-1250 is currently in a Phase I/II clinical trial for the treatment of ER+ breast cancer. Citation Format: Alison D. Parisian, Caitlin Miller, Fabian Ortega, Leslie Hodges-Gallagher, Susanna Barratt, Joey Azofeifa, Peter J. Kushner, David Kulp, Cyrus L. Harmon. Precision run-on sequencing (PRO-seq) analysis of a treatment time course in ER+ breast cancer cell lines reveals the transcriptional changes underlying response to complete estrogen receptor antagonist (CERAN) OP-1250 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5375.