Androgen Receptor Activity Research Articles

Abstract OT1-02-02: A phase 1/2 study to evaluate the safety and efficacy of EP0062, an oral Selective Androgen Receptor Modulator (SARM), for the treatment of AR+/HER2-/ER+ advanced breast cancer

Abstract There is growing interest in targeting the androgen receptor (AR) in advanced/metastatic breast cancer. It has been recently demonstrated preclinically that AR activation, rather than AR suppression, exerts potent antitumor activity across a number of ER+/AR+ breast tumors, including those resistant to standard-of-care endocrine therapy and CDK4/6 inhibitors (Hickey et al, Nature Medicine 2021 27: 310-320). Mechanistically, agonist activation of AR altered the genomic distribution of ER and essential co-activators resulting in repression of ER-regulated cell cycle genes and upregulation of AR target genes, including known tumor suppressors. EP0062 is an oral, non-steroidal, SARM currently being developed for the treatment of AR+/HER2-/ER+ advanced breast cancer. The efficacy and safety of EP0062 has previously been investigated in a Phase 1 clinical trial of AR+/HER2–/ER+ advanced breast cancer, and demonstrated that EP0062 has acceptable tolerability with evidence of clinical efficacy (LoRusso et al. Clinical Breast Cancer 2022 22;1 67-77). This new study is designed to further extend the evaluation of EP0062 as a potential therapy for AR+/HER2–/ER+ advanced breast cancer. The primary aim of the study is to assess tolerability and identify an optimal RP2D dose. The study will also explore the relationship between efficacy of EP0062 and AR expression, to establish a threshold for future patient selection, and undertake an initial evaluation of the safety and efficacy of EP0062 in combination with established standard of care therapies. The study will recruit up to 128 patients with AR+/HER2-/ER+ advanced breast cancer. Module A is a dose finding cohort to investigate safety, tolerability, PK and PD and to define the maximum tolerated dose (MTD) and/or Recommended Phase II Dose (RP2D). Dose finding will be based on a 3+3 design and is expected to recruit up to 32 patients. Once potential recommended doses are identified, approximately 60 evaluable patients will be randomised to two different dose cohorts in Module B in order to further optimise the RP2D dose, by further evaluation of safety and tolerability, as well as prospectively evaluate the relationship between efficacy and AR expression. In Module C, EP0062 will be combined with select standard of care targeted therapies in patients with relapsed AR+/HER2-/ER+ advanced breast cancer to confirm safety and explore efficacy. This will include approximately 36 patients across a number of single arm expansion cohorts. The key inclusion criteria are as follows: • Post-menopausal women, ≥18 years • ECOG performance status of 0 to 1 • Locally advanced or metastatic breast cancer • ER+, HER2- as per ASCO CAP guidelines • AR+, as defined as ≥ 10% AR nuclei staining by IHC • Endocrine-sensitive defined as greater than 3 years endocrine treatment prior to recurrence if recurrence occurred in the adjuvant setting, or ≥ 6 months treatment and response if recurrence occurred from primary treatment in the advanced setting • Relapsed, defined as clear and documented evidence of disease progression following ≥ 1 lines and ≤2 prior lines of previous endocrine therapy and ≤ 2 lines of chemotherapy in the advanced/metastatic setting • Measurable disease defined by RECIST version 1.1, or measurable bone-only disease EP0062 will be dosed to progression. Endpoints include incidence of DLTs during Cycle 1 of EP0062 treatment (28 days), MTD, RP2D (Module A), incidence and severity of AEs and SAEs, plasma PK parameters, Clinical Benefit Rate (complete response, partial response, or stable disease) at 24 weeks, ORR, duration of response, PFS, OS and quality of life. Clinic follow-up will be at 2 and 4 weeks, then every 4 weeks until disease progression. Recruitment is scheduled to initiate in Q4 2022. Citation Format: Elgene Lim, Erika Hamilton, Carlo Palmieri, Hendrik-Tobias Arkenau, Sue Brook, Geoff Fisher, Andrew Mazur. A phase 1/2 study to evaluate the safety and efficacy of EP0062, an oral Selective Androgen Receptor Modulator (SARM), for the treatment of AR+/HER2-/ER+ advanced 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 OT1-02-02.

Abstract P4-08-16: Selective Androgen Receptor Modulators in combination with CDK4/6 inhibitors demonstrate anti-cancer activity in preclinical treatment resistant ER+AR+ breast cancer models

Abstract Background: The Androgen Receptor (AR) is expressed in up to 90% of all ER+ breast cancers and has been associated with better patient outcome. While androgens were used at a high dose as an anticancer therapy historically, this was discontinued with the advent of Tamoxifen due to virilising effects. Non-steroidal, tissue selective AR modulators (SARMs) represent an attractive alternative, offering a targeted approach to AR activation. Recent compelling pre-clinical data has established that the AR is a tumour suppressor in ER+ breast cancers and that AR activation with a natural androgen or a SARM suppressed ER-driven tumour growth, in preclinical models of endocrine-sensitive and -resistant ER+ breast cancer. Here, we evaluate the efficacy of a SARM (enobosarm) and a natural AR ligand (dihydrotestosterone, DHT) in the context of metastatic, CDK4/6 inhibitor (CDK4/6i) resistant breast cancer. Methods: Enobosarm and palbociclib treatments were evaluated in vitro by colony forming assays using CDK4/6i resistant (MCF7 PalbR) and both endocrine and CDK4/6i resistant (MCF7 cTamPalbR) cell lines. Next, enobosarm or DHT and palbociclib treatment were evaluated in vivo using endocrine and CDK4/6i resistant ER+ patient derived xenograft models (PDX) and cell line xenograft models. IHC, RNA and ChIP sequencing (AR, ER, H3K27ac) were subsequently performed on the harvested tumours. Results: While in vitro and in vivo growth of CDK4/6i resistant preclinical models was inhibited by treatment with a SARM or DHT alone, growth inhibition was more potent and durable in combination with a CDK4/6i. Gene set enrichment analysis of RNA-seq data integrated with ChIP-seq data revealed upregulation of an AR gene signature associated with a better prognosis following treatment with SARM. Co-treatment with a SARM and a CDK4/6i also enhanced AR signalling compared to SARM alone indicating an interaction of the two signalling pathways. Conclusion: Our data indicates that combination treatment with an AR agonist and a CDK4/6i represents a novel therapeutic strategy for CDK4/6i resistant ER+AR+ breast cancers Citation Format: Allegra Freelander, Geraldine laven-Law, Leila Eshraghi, Nimmy Geetha, Peta Somerville, Marie Pickering, Sarah Alexandrou, C. Elizabeth Caldon, Wayne D. Tilley, Theresa E. Hickey, Elgene Lim. Selective Androgen Receptor Modulators in combination with CDK4/6 inhibitors demonstrate anti-cancer activity in preclinical treatment resistant ER+AR+ breast cancer models. [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 P4-08-16.

HSSB1 (NABP2/OBFC2B) modulates the DNA damage and androgen-induced transcriptional response in prostate cancer.

Activation and regulation of androgen receptor (AR) signaling and the DNA damage response impact the prostate cancer (PCa) treatment modalities of androgen deprivation therapy (ADT) and radiotherapy. Here, we have evaluated a role for human single-strand binding protein 1 (hSSB1/NABP2) in modulation of the cellular response to androgens and ionizing radiation (IR). hSSB1 has defined roles in transcription and maintenance of genome stability, yet little is known about this protein in PCa. We correlated hSSB1 with measures of genomic instability across available PCa cases from The Cancer Genome Atlas (TCGA). Microarray and subsequent pathway and transcription factor enrichment analysis were performed on LNCaP and DU145 prostate cancer cells. Our data demonstrate that hSSB1 expression in PCa correlates with measures of genomic instability including multigene signatures and genomic scars that are reflective of defects in the repair of DNA double-strand breaks via homologous recombination. In response to IR-induced DNA damage, we demonstrate that hSSB1 regulates cellular pathways that control cell cycle progression and the associated checkpoints. In keeping with a role for hSSB1 in transcription, our analysis revealed that hSSB1 negatively modulates p53 and RNA polymerase II transcription in PCa. Of relevance to PCa pathology, our findings highlight a transcriptional role for hSSB1 in regulating the androgen response. We identified that AR function is predicted to be impacted by hSSB1 depletion, whereby this protein is required to modulate AR gene activity in PCa. Our findings point to a key role for hSSB1 in mediating the cellular response to androgen and DNA damage via modulation of transcription. Exploiting hSSB1 in PCa might yield benefits as a strategy to ensure a durable response to ADT and/or radiotherapy and improved patient outcomes.

Adaptive and non-adaptive gene expression responses in prostate cancer during androgen deprivation.

Androgen deprivation therapy is the cornerstone treatment of advanced prostate cancer. Eventually prostate cancer cells overcome androgen deprivation therapy, giving rise to castration resistant prostate cancer (CRPC) characterized by increased androgen receptor (AR) activity. Understanding the cellular mechanisms leading to CRPC is needed for development of novel treatments. We used long-term cell cultures to model CRPC; a testosterone-dependent cell line (VCaP-T) and cell line adapted to grow in low testosterone (VCaP-CT). These were used to uncover persistent and adaptive responses to testosterone level. RNA was sequenced to study AR-regulated genes. Expression level changed due to testosterone depletion in 418 genes in VCaP-T (AR-associated genes). To evaluate significance for CRPC growth, we compared which of them were adaptive i.e., restored expression level in VCaP-CT. Adaptive genes were enriched to steroid metabolism, immune response and lipid metabolism. The Cancer Genome Atlas Prostate Adenocarcinoma data were used to assess the association with cancer aggressiveness and progression-free survival. Expressions of 47 AR-associated or association gaining genes were statistically significant markers for progression-free survival. These included genes related to immune response, adhesion and transport. Taken together, we identified and clinically validated multiple genes being linked with progression of prostate cancer and propose several novel risk genes. Possible use as biomarkers or therapeutic targets should be studied further.

Distinct genomic features and evolutionary relationships between concurrent intraductal carcinoma and adenocarcinoma of the prostate.

215 Background: Intraductal carcinoma of the prostate (IDC-P) is a lethal prostate cancer subtype that generally co-exists with invasive high-grade prostate acinar adenocarcinoma (PAC) but exhibits distinct biological features compared to concomitant adenocarcinoma. Till now, the genomic characteristics of IDC-P remain largely unknown. Methods: To explore the genomic features and evolutionary relationships between concurrent IDC-P and PAC, we isolated IDC-P, concurrent invasive high-grade PAC lesions, and adjuvant normal prostate tissues from 22 radical prostatectomy specimens. Whole-exome, RNA, and DNA-methylation sequencing were performed on the acquired tumoral and normal samples. The biological characteristics of IDC-P and concurrent PAC were compared at different molecular levels. Results: Three evolutionary patterns between concurrent IDC-P and PAC were identified. Tumors with clonally distant and early divergent evolutionary patterns showed higher genomic and pathological heterogeneities between concurrent IDC-P and PAC than those with the late-divergent pattern. Compared to co-existing PAC, increased adverse prognosis-associated genes were overexpressed in IDC-P. Besides, IDC-P was similar to Gleason pattern 5 PAC on the transcriptome profile. Survival analysis based on an independent cohort supported IDC-P resembled Gleason pattern 5 tumors. Furthermore, IDC-P exhibited robust cell-cycle progression and androgen receptor activities, characterized by an enrichment of cellular proliferation-associated master regulators and genes involved in intratumoral androgen biosynthesis. Conclusions: Our findings provide a molecular groundwork for the aggressive behavior of IDC-P and contribute to developing potential therapies for tumors with IDC-P.

Comparative transcriptomic analysis of DNA-damage response and androgen receptor pathway activity between biopsy and radical prostatectomy specimens before and after pre-operative real-time MRI-guided stereotactic body radiotherapy.

375 Background: Pre-Prostatectomy MRI-Guided Stereotactic Body Radiotherapy for High-Risk Prostate Cancer Trial (PREPARE SBRT; NCT03663218) is an ongoing clinical trial testing the safety of preoperative MRI-guided SBRT for men with clinically localized high-risk prostate cancer. We sought to compare transcriptomic profiles of biopsy (Bx) specimens to acutely irradiated radical prostatectomy (RP) specimens. Methods: Biopsy and post-irradiated RP specimens from 10 subjects were examined. The median interval between the end of RT and the date of RP was 5 days. Transcriptomic profiles were generated using Decipher GRID (Veracyte, Inc). Differences in transcriptional signatures were assessed between Bx samples taken before irradiation and RP samples post-irradiation using a paired T-Test. A control cohort of transcriptomic profiles of 803 untreated Bx samples and matching RP samples from the same patients were used to account for effects in tissue preservation from the procedure different of Bx vs RP. Linear regression model with the interaction effect of cohort (SBRT vs control) by procedure (Bx vs RP) to select signatures impacted by radiation treatment. Results: Transcriptomic signatures associated with Androgen Receptor (AR) activity were significantly downregulated (p=0.002) in irradiated RP specimens compared with pre-treatment biopsies. Analysis of DNA damage repair (DDR) pathways demonstrated that nucleotide excision repair (NER) and non-homologous end joining (NHEJ) signatures were increased (p=0.002 and p=0.02, respectively) after pre-operative RT whereas homologous recombination (p=0.06) and mismatch repair (p=0.08) were not significantly different between pre-treatment and irradiated tissues. Several metabolic-associated pathways were impacted by pre-operative RT including increased glycogen metabolism (p=0.008) and a NADH-NADPH conversion (p=0.001) signature indicative of RT-induced oxidative damage. Consistent upregulation of transcriptomic features associated with increased angiogenesis (p=0.0012) and stromal remodeling (p=0.0008) was observed in irradiated samples. Conclusions: Paired transcriptomic analysis following pre-operative RT demonstrated differential upregulation of specific DDR pathways including NHEJ and NER and metabolic alterations related to oxidative stress and glycogen metabolism. AR activity signatures were decreased in response to pre-operative RT.

Phase 1/2 study of EPI-7386 in combination with enzalutamide (enz) compared with enz alone in subjects with metastatic castration-resistant prostate cancer (mCRPC).

179 Background: EPI-7386 is a next generation aniten designed to inhibit androgen receptor (AR) activity by binding to the N-terminal domain (NTD) of the AR while effectively blocking transcription despite AR resistance mechanisms driven by the ligand-binding domain (LBD), including point mutations and splice variants. Preclinical models demonstrate the combination of EPI-7386 with enzalutamide (enz) results in a deeper blockade of the AR pathway (per RNAseq and ChIPseq data) and greater antitumor activity, prompting initiation of this trial. Methods: This Phase 1/2 multicenter, open-label clinical trial (NCT05075577) is enrolling mCRPC pts on androgen deprivation therapy and naïve to second-generation antiandrogens (one line of prior chemotherapy allowed). Phase 1 (P1) of the trial examines escalating doses of EPI-7386 in combination with a fixed dose of enz. The primary and secondary endpoints of P1 are to evaluate the safety and pharmacokinetics (PK) aspects of EPI-7386 and enz when administered in combination to establish the recommended Phase 2 combination doses (RP2CDs) and address any possible drug-drug interactions. Once the RP2CDs are established, Phase 2 of the trial will commence as a two -arm, 2:1 randomized trial evaluating the antitumor activity of EPI-7386 in combination with enz versus enz alone. Results: Seven pts have been enrolled in the first 2 cohorts: 3 in cohort 1 (600 mg QD EPI-7386 + 120 mg QD enz) and 4 in cohort 2 (800 mg QD EPI-7386 + 120 mg QD enz). No DLTs were observed, and the safety profile was consistent with second-generation antiandrogens (e.g., Grade 1 or 2 AEs of fatigue and hot flashes). PK results demonstrated enz exposure was minimally impacted by EPI-7386, while, as expected, EPI-7386 exposure was reduced 60-80% by enz (well-established CYP3A4 inducer). The observed EPI-7386 exposures remained in the clinically relevant range suggested by preclinical xenograft studies. 4/6 evaluable patients showed a PSA decrease >90% at/before week 12 regardless of the pt’s previous chemotherapy status and 5/6 evaluable patients achieved a PSA decrease of at least 85%; all 6 patients showed stable disease by imaging. Conclusions: With no safety concerns from cohorts 1 and 2, cohort 3 is enrolling at 600 mg BID EPI-7386 + 120 mg QD enz to assess if the exposure of EPI-7386 can be further increased in light of the augmented metabolism of the drug induced by enz. Clinical trial information: NCT05075577 .

Oral EPI-7386 in patients with metastatic castration-resistant prostate cancer.

177 Background: EPI-7386 is a next generation aniten, a novel class of compounds designed to inhibit androgen receptor (AR) activity by binding to the N-terminal domain. Preclinical data supports disruption of AR regulated gene transcription even in the presence of resistance mechanisms including ligand-binding domain point mutations and truncated splice variants. Here we report results of the Part 1a first-in-human trial of EPI-7386 in mCRPC (NCT04421222). Methods: This Phase 1, open-label, multicenter, dose escalation (Part 1a) and expansion (Part 1b) trial was designed to evaluate the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of EPI-7386 in mCRPC patients (pts) progressing on standard of care treatment, including next generation antiandrogen(s) and chemotherapy. Originally designed to assess up to 5 doses of EPI-7386 (200, 400, 600, 800, and 1000 mg QD), two additional cohorts were added examining 400 and 600 mg BID due to 600 mg QD showing exposure saturation while demonstrating a favorable safety profile. Results: 31 pts were enrolled in the QD cohorts and 8 in the BID cohorts. Pts had a median of 4 lines of prior therapy for mCRPC: 83% received abiraterone and at least one next generation AR inhibitor, and 58% had at least one line of prior chemotherapy. No DLTs were observed; EPI-7386 was safe and well tolerated at all doses/schedules evaluated. All related adverse events (AEs) were Grade 1 and 2 and consistent with AEs associated with second-generation antiandrogens. For doses above 400 mg QD, exposures were at or above those associated with antitumor activity in animal models. Evidence of antitumor activity (including significant and durable PSA responses and/or decreases in ctDNA, and/or radiographically documented tumor shrinkage) were observed in pts with fewer than 3 lines of treatment for mCRPC, no visceral metastases and no prior chemotherapy (9/31 pts). Conclusions: Part 1a treatment with EPI-7386 monotherapy was safe, well tolerated up to a daily dose of 1200 mg (600 mg BID), achieved target clinical exposures and showed preliminary signals of antitumor activity in heavily-pretreated mCRPC. Part 1b is open with enrollment focused on pre-chemotherapy, post-second generation antiandrogen treated mCRPC pts in one cohort, and treatment-naïve non-mCRPC pts in a window of opportunity proof-of-concept second cohort. Two doses will be evaluated (600 mg BID and QD) based on FDA Project Optimus recommendations. Clinical trial information: NCT04421222 .

Insulin-Induced AKR1C3 Induces Fatty Acid Synthase in a Model of Human PCOS Adipocytes.

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women. In PCOS, insulin resistance and hyperandrogenism could drive the increased risk for cardiometabolic disease. Aldo-keto reductase family 1 member C3 (AKR1C3) is induced by insulin in PCOS adipocytes and is the predominant enzyme for potent androgen formation causing ligand-dependent androgen receptor (AR) activation. AR induces fatty acid synthase (FASN), a central enzyme for de novo lipogenesis. To investigate how insulin signaling induces AKR1C3 to promote lipid overload through induction of FASN, we used differentiated human Simpson-Golabi-Behmel syndrome adipocytes as a model for PCOS adipocytes. Induction of AKR1C3 and FASN was shown to be dependent on phosphoinositide 3-kinase/protein kinase B/ mammalian target of rapamycin/nuclear factor-erythroid 2-related factor 2 using pharmacological and genetic manipulation. FASN induction was shown to be AKR1C3 and AR dependent. Monofunctional AKR1C3 inhibitors, which competitively inhibit AKR1C3, did not block FASN induction, whereas bifunctional inhibitors, which competitively inhibit AKR1C3 and attenuate AR signaling by increasing AR degradation and ubiquitination, did suggesting a nonenzymatic role for AKR1C3 to stabilize AR. AKR1C3 and AR interacted as seen by co-immunoprecipitation, proximity ligation assay, and co-occupancy on FASN locus using chromatin immunoprecipitation-quantitative polymerase chain reaction assays in a ligand-dependent and ligand-independent manner. In the absence of androgens, bifunctional inhibitors prevented lipid droplet formation, whereas monofunctional inhibitors did not. We propose that AKR1C3 has 2 roles in PCOS: to catalyze potent androgen formation in adipocytes promoting hyperandrogenism and to induce FASN by stabilizing AR in the absence of androgens. AKR1C3 may be a therapeutic target for bifunctional inhibitors to reduce cardiometabolic disease in PCOS women.

The androgen receptor as a potential regulator of prostate cancer contractility.

Prostate cancer (PCa) is a common health hazard for men that displays androgen-dependent growth at early stages through signalling mediated by the Androgen Receptor (AR). This has inspired androgen deprivation therapy (ADT) to be the gold standard treatment; however, in later stages, PCa displays a transition to androgen-independence and loss of AR, accompanied by a drastic increase in invasiveness. Critically, both the loss of AR and ADT have been shown to induce PCa invasiveness by promoting the epithelial-to-mesenchymal transition (EMT) which has been associated with biophysical changes in other cell models. Indeed, during metastasis cancers cells change their biophysical properties (reduced cell stiffness, increased contractility) facilitating migration through crowded microenvironments. Given AR's essential role in mediating PCa progression, we suspect that AR signalling may also regulate mechanical transitions required for PC metastasis and directed cell migration. In this study we characterize PCa biophysics in response to changes in AR signalling and expression. First, we applied Traction Force Microscopy on the metastatic PCa cell line LNCaP (AR-positive) to quantify contractile changes from androgen deprivation and supplementation, observing a non-monotonic contractile response with increasing androgen dose. These results suggest that the androgen-induced biophysical response shifts depending on the androgen availability, a finding consistent with past reports demonstrating that distinct pathways depend on both androgen concentration and AR expression. Regarding the latter, we then evaluated how AR expression and activity (nuclear localization) affects PCa biophysics by quantifying the contractility of highly metastatic PC3 cells with and without AR expression under varying androgen concentrations. We find that cell contractility is positively correlated with AR nuclear localization in androgen-containing media, yet negatively correlated in androgen-deprived media. These results complement emerging trends suggesting AR may have an important mechanobiological role in PCa migration and metastasis.

Abstract B008: The role of the androgen receptor in reciprocal activation of breast cancer metastases and the lung epithelium during metastatic outgrowth

Abstract The lung is one of the most common sites of breast cancer (BC) metastasis. A major gap in our ability to effectively treat BC patients with established lung metastases lies in our lack of knowledge regarding how the lung microenvironment is remodeled during metastasis and how this contributes to disease progression. Our data suggest that the lung epithelium, in particular lung type II alveolar epithelial (AT2) cells, contribute to metastatic outgrowth. We hypothesize that BC lung micrometastases activate surrounding lung epithelial cells which, in turn, support the survival and outgrowth of BC metastases within the lung. The overall goal of these studies is to identify factors secreted by resident lung cells that could be used as metastasis-specific therapeutic targets/agents. We utilized immunocompetent mouse metastasis models to study metastatic progression within the lung. Multispectral fluorescent imagining of metastases demonstrated that a wound repair-related phenotype, characterized by chronic inflammation, develops within the lung microenvironment during metastatic outgrowth. We observed an increase in the number and activation of AT2 cells surrounding metastases as they grow. To gain mechanistic insight into how growing metastases may impact AT2 cells, we conducted single-cell RNA-sequencing (scRNAseq) on mouse lungs with high vs. low metastatic burden. This investigation showed that metastatic outgrowth significantly changes AT2 gene expression resulting in a modified secretome. Cell culture experiments, using multiple AT2 cell models, indicated that no contact co-culture with TNBC also caused significant changes in AT2 gene expression. Upstream regulator analysis of these datasets predicted that the androgen receptor (AR) may contribute to AT2 activation during metastatic outgrowth. Compared to non-adjacent tumor-free MMTV-PyMT lung tissue, there was an increased percentage of AR+ cells in the lung adjacent to metastases, which was further associated with large metastases only. Co-immunofluorescence experiments demonstrated that these lung-specific AR+ cells were primarily AT2 cells and fibroblasts, while in human lungs the majority of AR+ cells were AT2 cells and macrophages. Interestingly, co-culturing of TNBC and AT2 cells enhanced BC proliferation, suggesting that following activation, AT2 secreted factors may reciprocally impact metastatic growth. In conclusion, these data indicate that a tumor supportive microenvironment develops as lung metastases grow and suggests that by the time patients present with established/detectable lung metastases, the lung microenvironment has already undergone fundamental alterations that promote metastatic progression. Future studies will elucidate how activated lung cells support metastatic progression and could lead to the development or repurposing of therapeutic strategies to prevent destructive metastatic outgrowth. Citation Format: Jessica L. Christenson, Nicole S. Spoelstra, G. Devon Trahan, Kathleen I. O'Neill, Michelle M. Williams, Jennifer K. Richer. The role of the androgen receptor in reciprocal activation of breast cancer metastases and the lung epithelium during metastatic outgrowth [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B008.

The functional implication of ATF6α in castration-resistant prostate cancer cells.

Stress in the endoplasmic reticulum (ER) may perturb proteostasis and activates the unfolded protein response (UPR). UPR activation is frequently observed in cancer cells and is believed to fuel cancer progression. Here, we report that one of the three UPR sensors, ATF6α, was associated with prostate cancer (PCa) development, while both genetic and pharmacological inhibition of ATF6α impaired the survival of castration-resistance PCa (CRPC) cells. Transcriptomic analyses identified the molecular pathways deregulated upon ATF6α depletion, and also discovered considerable disparity in global gene expression between ATF6α knockdown and Ceapin-A7 treatment. In addition, combined analyses of human CRPC bulk RNA-seq and single-cell RNA-seq (scRNA-seq) public datasets confirmed that CRPC tumors with higher ATF6α activity displayed higher androgen receptor (AR) activity, proliferative and neuroendocrine (NE) like phenotypes, as well as immunosuppressive features. Lastly, we identified a 14-gene set as ATF6α NE gene signature with encouraging prognostic power. In conclusion, our results indicate that ATF6α is correlated with PCa progression and is functionally relevant to CRPC cell survival. Both specificity and efficacy of ATF6α inhibitors require further refinement and evaluation.

Crosstalk between epigenetics and tumor promoting androgen signaling in prostate cancer.

Prostate cancer (PCa) is one of the major health burdens among all cancer types in men globally. Early diagnosis and efficacious treatment options are highly warranted as far as the incidence of PCa is concerned. Androgen-dependent transcriptional activation of androgen receptor (AR) is central to the prostate tumorigenesis and therefore hormonal ablation therapy remains the first line of treatment for PCa in the clinics. However, the molecular signaling engaged in AR-dependent PCa initiation and progression is infrequent and diverse. Moreover, apart from the genomic changes, non-genomic changes such as epigenetic modifications have also been suggested as critical regulator of PCa development. Among the non-genomic mechanisms, various epigenetic changes such as histones modifications, chromatin methylation and noncoding RNAs regulations etc. play decisive role in the prostate tumorigenesis. Given that epigenetic modifications are reversible using pharmacological modifiers, various promising therapeutic approaches have been designed for the better management of PCa. In this chapter, we discuss the epigenetic control of tumor promoting AR signaling that underlies the mechanism of prostate tumorigenesis and progression. In addition, we have discussed the approaches and opportunities to develop novel epigenetic modifications based therapeutic strategies for targeting PCa including castrate resistant prostate cancer (CRPC).

Inhibition of androgen receptor enhanced the anticancer effects of everolimus through targeting glucose transporter 12.

Everolimus was designed as a mammalian target of rapamycin (mTOR) inhibitor. It has been proven as a targeted drug for gastric cancer (GC) therapy. However, long-term treatment with everolimus may cause severe side effects for recipients. Decreasing the dosage and attenuating the associated risks are feasible to promote clinical translation of everolimus. This study aimed to identify the underlying mechanisms of responses to everolimus and develop novel regimens for GC treatment. Our findings proved that there was a significant dose-dependent relationship of everolimus-induced GC cell apoptosis and glycolysis inhibition. Then, we found that a member of glucose transporter (GLUT12) family, GLUT12, was actively upregulated to counteract the anticancer effects of everolimus. GLUT12 might be overexpressed in GC. High expression of GLUT12 might be correlated with tumor progression and short survival time of GC patients. Bioinformatic analysis suggested that GLUT12 might be involved in regulating cancer development and metabolism. The experiments proved that GLUT12 significantly promoted GC growth, glycolysis and impaired the anticancer effects of everolimus. Androgen receptor (AR) is a classical oncogenic factor in many types of cancer. Everolimus elevated GLUT12 expression in an AR-dependent manner. Inhibition of AR activity abrogated the promotive effects on GLUT12 expression. Both in-vitro and in-vivo experiments demonstrated that GLUT12 knockdown augmented anticancer effects of everolimus. Enzalutamide, an AR inhibitor, or AR knockdown was comparable to GLUT12 suppression. This study identified the role of the AR/GLUT12 pathway in the development of poor responses to everolimus. Interference with AR/GLUT12 pathway may serve as a promising approach to promoting the translational application of everolimus in GC therapy.

The role of activated androgen receptor in cofilin phospho-regulation depends on the molecular subtype of TNBC cell line and actin assembly dynamics.

Triple negative breast cancer (TNBC) is highly metastatic and of poor prognosis. Metastasis involves coordinated actin filament dynamics mediated by cofilin and associated proteins. Activated androgen receptor (AR) is believed to contribute to TNBC tumorigenesis. Our current work studied roles of activated AR and cofilin phospho-regulation during migration of three AR+ TNBC cell lines to determine if altered cofilin regulation can explain their migratory differences. Untreated or AR agonist-treated BT549, MDA-MB-453, and SUM159PT cells were compared to cells silenced for cofilin (KD) or AR expression/function (bicalutamide). Cofilin-1 was found to be the only ADF/cofilin isoform expressed in each TNBC line. Despite a significant increase in cofilin kinase caused by androgens, the ratio of cofilin:p-cofilin (1:1) did not change in SUM159PT cells. BT549 and MDA-MB-453 cells contain high p-cofilin levels which underwent androgen-induced dephosphorylation through increased cofilin phosphatase expression, but surprisingly maintain a leading-edge with high p-cofilin/total cofilin not found in SUM159PT cells. Androgens enhanced cell polarization in all lines, stimulated wound healing and transwell migration rates and increased N/E-cadherin mRNA ratios while reducing cell adhesion in BT549 and MDA-MB-453 cells. Cofilin KD negated androgen effects in MDA-MB-453 except for cell adhesion, while in BT549 cells it abrogated androgen-reduced cell adhesion. In SUM159PT cells, cofilin KD with and without androgens had similar effects in almost all processes studied. AR dependency of the processes were confirmed. In conclusion, cofilin regulation downstream of active AR is dependent on which actin-mediated process is being examined in addition to being cell line-specific. Although MDA-MB-453 cells demonstrated some control of cofilin through an AR-dependent mechanism, other AR-dependent pathways need to be further studied. Non-cofilin-dependent mechanisms that modulate migration of SUM159PT cells need to be investigated. Categorizing TNBC behavior as AR responsive and/or cofilin dependent can inform on decisions for therapeutic treatment.

The Impact of Indoles Activating the Aryl Hydrocarbon Receptor on Androgen Receptor Activity in the 22Rv1 Prostate Cancer Cell Line.

The activation of the aryl hydrocarbon receptor (AhR) by xenobiotic compounds was demonstrated to result in the degradation of the androgen receptor (AR). Since prostate cancer is often dependent on AR, it has become a significant therapeutic target. As a result of the emerging concept of bacterial mimicry, we tested whether compounds with indole scaffolds capable of AhR activation have the potential to restrict AR activity in prostate cancer cells. Altogether, 22 indolic compounds were tested, and all of them activated AhR. However, only eight decreased DHT-induced AR luciferase activity. All indoles, which met the AhR-activating and AR-suppressing criteria, decreased the expression of DHT-inducible AR target genes, specifically KLK3 and FKBP5 mRNAs. The reduced AR binding to the KLK3 promoter was confirmed by a chromatin immunoprecipitation (ChIP) assay. In addition, some indoles significantly decreased AR protein and mRNA level. By using CRISPR/Cas9 AhR knockout technology, no relationship between AhR and AR, measured as target gene expression, was observed. In conclusion, some indoles that activate AhR possess AR-inhibiting activity, which seems to be related to the downregulation of AR expression rather than to AR degradation alone. Moreover, there does not seem to be a clear relationship that would connect AhR activation with AR activity suppression in 22Rv1 cells.

Examining the Effect of PARP-1 Inhibitors on Transcriptional Activity of Androgen Receptor in Prostate Cancer Cells.

Since the early 1940s, androgen ablation has been the cornerstone of treatment for prostate cancer (PC). Importantly, androgen receptor (AR) signaling is vital not only for the initiation of PC, which is initially androgen-dependent, but also for castration-resistant disease. Recent studies demonstrated clear promise of the poly(ADP-ribose) polymerase 1 (PARP-1) inhibitors for targeting prostate cancer cells harboring mutations in DNA damage-repair genes. In addition, it has been established that PARP-1 inhibition suppresses growth of AR-positive prostate cancer cells in cell and animal models. Thus, prostate cancer represents a particularly promising disease site for targeting PARP-1, given that both DNA repair and AR-mediated transcription depend on PARP-1 function. Here, we describe the development and use of cell-based assay to evaluate the impact of PARP-1 inhibitors on the AR signaling in prostate cancer cells.

Plasma progastrin-releasing peptide level shows different predictive profiles for treatment response by androgen receptor axis-targeted agents in patients with metastatic castration-resistant prostate cancer.

The neuroendocrine (NE) pathway cannot be ignored as a mechanism for castration-resistant prostate cancer (CRPC) progression. The neuromediator, gastrin-releasing peptide (GRP) may be involved in the aberrant activation of the normal androgen receptor (AR) and increased AR variants. This study focused on plasma levels of progastrin-releasing peptide (ProGRP) and examined the treatment outcomes with androgen receptor axis-targeted (ARAT) agents. One hundred patients with metastatic CRPC were enrolled. Enzalutamide (ENZ) or abiraterone acetate/prednisone (AA/P) were administered to 50 patients each in a nonrandomized manner as a first-line or later choice. Plasma ProGRP levels were determined using a chemiluminescent enzyme immunoassay, and data were collected prospectively. The study endpoints were prostate-specific antigen (PSA) response and survival estimates. In the ENZ series, ProGRP levels correlated with the maximum PSA change from baseline (high ProGRP: -34.5% vs. low ProGRP: -85.7% p= .033). PSA progression-free survival (PFS), radiographic/symptomatic (r/s) PFS, and overall survival (OS) in patients with high ProGRP were significantly worse than those in patients with low ProGRP (median PSA-PFS: 3.3 vs. 10.0months, p =.001, r/s PFS: 5.0 vs. 15.0months, p< 0.001, and OS 17.5 vs. 49.0months, p< .001, respectively). In addition, ProGRP showed an independent predictive value for all survival estimates in multivariate analyses. In the AA/P series, ProGRP levels did not correlate with the PSA change or predict PSA-PFS and r/s PFS, but they maintained a significant difference in OS (19.0 vs. 48.0months, p= .003). Plasma ProGRP provides a consistent predictive value for OS in metastatic CRPC patients who underwent therapy with ARAT agents. Meanwhile, ProGRP showed different predictive profiles for PSA- and r/s PFS between ENZ and AA/P. These findings clinically suggest a mechanism for CRPC progression involving the NE pathway via the GRP. The underlying mechanism of different predictive profiles by the ARAT agent should be explored in future research.

Modulating the Activity of Androgen Receptor for Treating Breast Cancer

The androgen receptor (AR) is a steroid hormone receptor widely detected in breast cancer. Evidence suggests that the AR might be a tumor suppressor in estrogen receptor alpha-positive (ERα+ve) breast cancer but a tumor promoter in estrogen receptor alpha-negative (ERα-ve) breast cancer. Modulating AR activity could be a potential strategy for treating breast cancer. For ERα+ve breast cancer, activation of the AR had been demonstrated to suppress the disease. In contrast, for ERα-ve breast cancer, blocking the AR could confer better prognosis to patients. These studies support the feasibility of utilizing AR modulators as anti-cancer drugs for different subtypes of breast cancer patients. Nevertheless, several issues still need to be addressed, such as the lack of standardization in the determination of AR positivity and the presence of AR splice variants. In future, the inclusion of the AR status in the breast cancer report at the time of diagnosis might help improve disease classification and treatment decision, thereby providing additional treatment strategies for breast cancer.

Prenatal and postnatal exposure to polystyrene microplastics induces testis developmental disorder and affects male fertility in mice

Polystyrene microplastics (PS-MPs) can threaten human health, especially male fertility. However, most existing studies have focused on the adulthood stage of male reproduction toxicity caused by relatively short-term PS-MP exposure. This study aimed to investigate the toxic effect of PS-MPs on testicular development and reproductive function upon prenatal and postnatal exposure. Pregnant mice and their offspring were exposed to 0, 0.5 mg/L, 5 mg/L, and 50 mg/L PS-MPs through their daily drinking water from gestational day 1 to postnatal day (PND) 35 or PND70. We found that PS-MP exposure induced testis development disorder by PND35 and spermatogenesis dysfunction by PND70. By combining RNA sequencing results and bioinformatics analysis, the hormone-mediated signaling pathway, G1/S transition of the mitotic cell cycle, coregulation of androgen receptor activity, and Hippo signaling pathway were shown to be involved in testis development on PND35. The meiotic cell cycle, regulation of the immune effector process, neutrophil degranulation, and inflammation mediated by chemokine and cytokine signaling pathways were associated with disturbed spermatogenesis on PND70. These findings show that prenatal and postnatal exposure to PS-MPs resulted in testis development disorder and male subfertility, which may be regulated by the Hippo signaling pathway and involve an immune reaction.