Bipolar androgen therapy for treatment of metastatic castration-resistant prostate cancer: A case series.

INTRODUCTION: Advanced prostate cancer treatment has improved with androgen receptor signaling inhibitors (ARPI), yet many patients develop metastatic castration-resistant prostate cancer (mCRPC), characterized by sustained androgen receptor (AR) signaling. Bipolar androgen therapy (BAT) introduces supraphysiologic testosterone levels to inhibit tumor growth, offering novel treatment for mCRPC by exploiting AR-dependent mechanisms. CASE PRESENTATIONS: Case 1: A 53-year-old man with mCRPC, post multiple systemic therapies, initiated BAT and pembrolizumab, achieving PSA reduction and improved quality of life before progression. The patient exhibited AR amplification, which may have contributed to favorable response to BAT. Case 2: A 73-year-old man with recurrent prostate cancer, stable on ADT and abiraterone, experienced PSA decline with BAT to an undetectable level, maintaining stability post-therapy discontinuation. Case 3: A 73-year-old man with metastatic prostate cancer, initially resistant to enzalutamide, achieved clinical benefit and disease control with BAT, although he did not meet PSA response criteria, patient had remarkable response upon enzalutamide rechallenge. Case 4: A 90-year-old man with localized prostate cancer, refractory to multiple treatments, experienced symptom relief and PSA reduction with BAT before progression. CONCLUSION: BAT represents a promising treatment strategy for mCRPC. This case series underscores BAT's potential to induce significant clinical and biochemical responses, resensitize tumors to ARPIs, and improve patients' quality of life. Despite eventual progression in some cases, BAT offers a period of disease control. Further research is needed to optimize patient selection and understand the molecular determinants of BAT responsiveness.

The clock gene BHLHE40 and atypical CCNG2 control androgen-induced cellular senescence as a novel tumor suppressive pathway in prostate cancer.

BACKGROUND: The androgen receptor (AR) is a drug target used to inhibit AR and prostate cancer (PCa) growth. Surprisingly, treatment with supraphysiological androgen level (SAL), used in bipolar androgen therapy, inhibits growth of PCa suggesting a tumor-suppressive activity by SAL. SAL was shown to induce cellular senescence in PCa. METHODS: RNA-seq and transcriptome analysis, ChIP-seq, human 3D PCa spheroids, mouse xenografted castration-resistant PCa, knockdown and overexpression, Co-immunoprecipitation (Co-IP), translocation analysis, immune detection, qRT-PCR, protein-protein interaction modelling. RESULTS: Here, mice xenografts with castration-resistant PCa tumors show that SAL inhibits cancer growth in vivo suggesting that SAL activates a tumor-suppressive mechanism. RNA-seq and ChIP-seq revealed the clock gene BHLHE40 is a novel direct AR target. Compared to adjacent human prostate tissues, the expression of BHLHE40 is reduced in PCa tumors and associated with reduced survival. Knockdown suggests that BHLHE40 mediates SAL-induced cellular senescence including tumor spheroids. Interestingly, a large overlap of differentially expressed gene sets was identified between BHLHE40 and SAL leading to the identification of four classes of SAL-BHLHE40 transcriptome landscapes. Co-IP and modelling suggest binding of BHLHE40 to AR and their co-translocation into nucleus by SAL treatment. Further, RNA-seq and ChIP-seq analysis indicate that the atypical tumor suppressive cyclin G2 emerged as a novel downstream target of BHLHE40 and a mediator of SAL-induced cellular senescence. CONCLUSIONS: The data provide evidence of the tumor suppressive activity of SAL and a novel signaling by the AR-BHLHE40-CCNG2 axis for androgen-induced cellular senescence, linking circadian rhythm factor to androgen signaling as a novel tumor suppressive pathway.

Therapeutic Potential of Bipolar Androgen Therapy for Castration-Resistant Prostate Cancer: In Vitro and In Vivo Studies.

Androgen deprivation therapy (ADT) is a primary treatment for advanced prostate cancer (PCa), but resistance often leads to castration-resistant PCa (CRPC). CRPC remains androgen receptor (AR)-dependent, and AR overexpression causes vulnerability to high doses of androgen in CRPC. Bipolar androgen therapy (BAT) refers to the periodic administration of testosterone, resulting in oscillation between supraphysiologic and near-castrate serum testosterone levels. In this study, we evaluated the efficacy of BAT against CRPC in a preclinical setting. To emulate CRPC characteristics, PCa cell lines (LNCaP, VCaP, and 22Rv1) were cultured in phenol red-free RPMI-1640 medium supplemented with 10% dextran-coated charcoal treated FBS (A- cell line). Cell viability, AR, and AR-V7 expression were evaluated using the Cell Counting Kit-8 and Western blotting. In vivo studies involved 12 castrated NOG mice injected with LNCaP/A- cells, treated with testosterone pellets or controls in 2-week cycles. Tumor sizes were measured post a 6-week treatment cycle. Bicalutamide inhibited PCa cell viability but not in the adapted cell lines. Supraphysiologic androgen levels suppressed AR-expressing PCa cell growth in vitro. In vivo, high AR-expressing LNCaP cells proliferated under castrate conditions, while BAT-treated xenografts exhibited significant growth inhibition with low Ki-67 and mitotic indexes and a high cell death index. This study provides preliminary evidence that BAT is effective for the treatment of CRPC through rapid cycling between supraphysiologic and near-castrate serum testosterone levels, inducing an anti-tumor effect.

Bipolar Androgen Therapy: When Excess Fuel Extinguishes the Fire.

Androgen deprivation therapy (ADT) remains the cornerstone of advanced prostate cancer treatment. However, the progression towards castration-resistant prostate cancer is inevitable, as the cancer cells reactivate androgen receptor signaling and adapt to the castrate state through autoregulation of the androgen receptor. Additionally, the upfront use of novel hormonal agents such as enzalutamide and abiraterone acetate may result in long-term toxicities and may trigger the selection of AR-independent cells through "Darwinian" treatment-induced pressure. Therefore, it is crucial to develop new strategies to overcome these challenges. Bipolar androgen therapy (BAT) is one such approach that has been devised based on studies demonstrating the paradoxical inhibitory effects of supraphysiologic testosterone on prostate cancer growth, achieved through a variety of mechanisms acting in concert. BAT involves rapidly alternating testosterone levels between supraphysiological and near-castrate levels over a period of a month, achieved through monthly intramuscular injections of testosterone plus concurrent ADT. BAT is effective and well-tolerated, improving quality of life and potentially re-sensitizing patients to previous hormonal therapies after progression. By exploring the mechanisms and clinical evidence for BAT, this review seeks to shed light on its potential as a promising new approach to prostate cancer treatment.

Bipolar Androgen Therapy Followed by Androgen Receptor Inhibition as Sequential Therapy for Prostate Cancer.

Inhibition of androgen receptor (AR) signaling has been the mainstay of treatment of advanced prostate cancer (PCa) for the past 80 years. Combination and sequential AR-inhibiting therapies are highly effective palliative therapy, but they are not curative. All patients eventually develop resistance to primary castrating therapy [ie, castration-resistant PCa (CRPC)]. At this point, they are treated with subsequent lines of secondary AR inhibitory therapies. However, resistance to these agents also develops and patients progress to a state we have termed complete androgen inhibition-resistant PCa. This phase of the disease is associated with poor prognosis. At this point, treatment shifts to non-hormonal cytotoxic therapies (eg, chemotherapy and radiopharmaceuticals). However, the majority of PCas remain addicted to signaling through AR throughout the course of the disease. Resistant PCa cells adaptively upregulate AR activity, despite castration and AR inhibitors, via mechanisms such as AR overexpression, gene amplification, mutation, and expression of ligand-independent variants to permit sustained liganded and non-liganded AR signaling. Studies dating back nearly 30 years indicate that high expression of AR induced by prolonged castration becomes a vulnerability of CRPC cells in vitro and in mouse xenografts to supraphysiologic androgen (SPA), which induces cell death and growth arrest in this context. Based on these studies, we developed a counterintuitive treatment called bipolar androgen therapy (BAT) for patients with CRPC, in which SPA is administered intermittently to result in cycling of serum testosterone from the polar extremes of supraphysiologic to near-castrate levels. This rapid cycling is intended to disrupt the adaptive of AR regulation associated with chronic exposure to high or low levels of testosterone, while simultaneously targeting the spectrum of AR expression present in heterogeneous CRPC tumors. We have now tested BAT in >250 patients with CRPC. Here we present a review of these clinical studies, which have demonstrated collectively that BAT can be safely given to men with CRPC, improves quality of life, and produces therapeutic responses in ~30% of patients. As expected, resistance to BAT is associated with adaptive downregulation of AR expression. Intriguingly, this downregulation is associated with restoration of sensitivity to subsequent AR inhibitor therapies.

PSA provocation by bipolar androgen therapy may predict duration of response to first-line androgen deprivation: Updated results from the BATMAN study.

BACKGROUND: Previously, we reported results from the Phase II BATMAN study (Bipolar Androgen Therapy for Men with Androgen-ablation Naïve prostate cancer). This study (NCT01750398) was designed to evaluate the safety and efficacy of a treatment regimen consisting of a 6-month lead in-phase of androgen deprivation therapy (ADT) followed by alternating 3-month intervals of bipolar androgen therapy (BAT) and ADT alone. Here we report > 5-year follow-up related to the duration of subsequent ADT, response to first-line androgen receptor inhibitors, safety, and survival in men with castration-sensitive prostate cancer treated on the BATMAN study. METHODS: Univariate Cox regression was utilized to compare overall survival between Responders who achieved a prostate-specific antigen (PSA) level of <4 ng/ml and Non-Responders who achieved a PSA level of ≥4 ng/ml after BAT/ADT. Kaplan-Meier method and Cox regression were used to assess progression-free (PFS) and overall survival (OS) on BAT and on subsequent abiraterone or enzalutamide and on the association between PSA peak during BAT and each time to event outcome. RESULTS: Over median follow-up of 95 months, the median PFS on ADT for the entire cohort was 47.8. Median OS has not been reached (NR). Median OS for Non-Responders is 43 months versus NR (not reached) for responders (hazard ratio [HR]: 0.176, p = 0.002). Post-BAT, the PSA50 and PSA90 responses to abiraterone or enzalutamide were 94.4% and 66.7%, respectively and median PFS was 20.6 months. Patients with peak PSA level of ≥9 ng/ml after BAT had median PFS of 20.6 months versus NR for those having PSA < 9 ng/ml (HR: 0.122, p < 0.001). Median OS was 79.6 months for patients with PSA peak of ≥9 ng/ml versus NR for those having PSA peak of <9 ng/ml (HR: 0.409, p = 0.131). CONCLUSION: The use of BAT as part of first-line hormonal therapy strategy does not induce adversely affect long-term survival or induce any significant long-term adverse sequelae in patients with prostate cancer. Cycling BAT may extend the duration of ADT response and enhance response to subsequent androgen ablative therapies. The magnitude of BAT-provoked increase in PSA may predict duration of ADT response and warrants further study.

Androgen-Induced MIG6 Regulates Phosphorylation of Retinoblastoma Protein and AKT to Counteract Non-Genomic AR Signaling in Prostate Cancer Cells.

The bipolar androgen therapy (BAT) includes the treatment of prostate cancer (PCa) patients with supraphysiological androgen level (SAL). Interestingly, SAL induces cell senescence in PCa cell lines as well as ex vivo in tumor samples of patients. The SAL-mediated cell senescence was shown to be androgen receptor (AR)-dependent and mediated in part by non-genomic AKT signaling. RNA-seq analyses compared with and without SAL treatment as well as by AKT inhibition (AKTi) revealed a specific transcriptome landscape. Comparing the top 100 genes similarly regulated by SAL in two human PCa cell lines that undergo cell senescence and being counteracted by AKTi revealed 33 commonly regulated genes. One gene, ERBB receptor feedback inhibitor 1 (ERRFI1), encodes the mitogen-inducible gene 6 (MIG6) that is potently upregulated by SAL, whereas the combinatory treatment of SAL with AKTi reverses the SAL-mediated upregulation. Functionally, knockdown of ERRFI1 enhances the pro-survival AKT pathway by enhancing phosphorylation of AKT and the downstream AKT target S6, whereas the phospho-retinoblastoma (pRb) protein levels were decreased. Further, the expression of the cell cycle inhibitor p15INK4b is enhanced by SAL and ERRFI1 knockdown. In line with this, cell senescence is induced by ERRFI1 knockdown and is enhanced slightly further by SAL. Treatment of SAL in the ERRFI1 knockdown background enhances phosphorylation of both AKT and S6 whereas pRb becomes hypophosphorylated. Interestingly, the ERRFI1 knockdown does not reduce AR protein levels or AR target gene expression, suggesting that MIG6 does not interfere with genomic signaling of AR but represses androgen-induced cell senescence and might therefore counteract SAL-induced signaling. The findings indicate that SAL treatment, used in BAT, upregulates MIG6, which inactivates both pRb and the pro-survival AKT signaling. This indicates a novel negative feedback loop integrating genomic and non-genomic AR signaling.

[Bipolar androgen therapy followed by immune checkpoint inhibitors in metastatic castration resistant prostate cancer: A report of 4 cases].

The relationship between androgen and prostate cancer treatment has plagued the field of urologic oncology. To investigate the efficacy and safety of bipolar androgen therapy (BAT) followed by immune checkpoint inhibitor therapy in patients with metastatic castration resistant prostate cancer (mCRPC). In August 2020, Beijing Hospital conducted an investigator-initiated study: Bipolar androgen therapy followed by immune checkpoint inhibitor therapy in metastatic castration resistant prostate cancer. Up to now, the study has included 4 patients who completed the entire cycle of treatment. The mean age of the patients was 74.5 (68 to 82) years old, the mean prostate-specific antigen (PSA) was 20.8 (9.9 to 8.36) µg/L, the mean testosterone was 0.50 (0.00 to 1.81) µg/L, and the Gleason score were 10 and 9, 7, 7 respectively. The pain scale score before treatment was 1.5 (1 to 2). In this study, 4 patients completed the entire cycle of treatment, and the treatment effect of the patients showed great heterogeneity. PSA in case 1 decreased from 24.0 µg/L to 0.47 µg/L, testosterone increased from 0.175 6 µg/L to 2.62 µg/L. PSA in case 2 increased from 9.939 µg/L to 168.536 µg/L, and testosterone increased from 0.0 µg/L increased to 2.85 µg/L. PSA increased from 13.31 µg/L to 39.278 µg/L in case 3, testosterone increased from 0.0 µg/L to 2.54 µg/L. and PSA increased from 36.0 µg/L to 350.2 µg/L in the case 4, testosterone increased from 1.81 µg/L to 3.85 µg/L. Except for one patient who showed significant PSA remission, the PSA levels of the remaining three patients remained high overall. There were no adverse reactions reported in 4 patients. In the follow-up, case 1 continued to use PD-1 monoclonal antibody (median progression free survival time was 10 months). Two patients who had previously been resistant to enzalutamide received enzalutamide again after the whole cycle of treatment, and their PSA decreased again, which indicated that the patient was sensitive to enzalutamide again. BAT had a certain therapeutic effect on mCRPC patients, and the safety was controllable. Its tumor control effect still needed long-term follow-up verification in large-sample clinical trials. BAT has a certain therapeutic effect on mCRPC patient, especially the resensitivity of tumors to enzalutamide can be restored. Immune checkpoint inhibitors may have therapeutic potential in patients with prostate cancer treated with BAT and enzalutamide.

Maintenance of androgen deprivation therapy or testosterone supplementation in the management of castration-resistant prostate cancer: that is the question.

PURPOSE: Whether or not androgen receptor (AR) axis could still be targetable in castration resistant prostate cancer (CRPC) patients with disease progression to next generation hormonal agents (NGHAs) is a controversial issue. RESULTS: Serum testosterone in CRPC patients has a positive prognostic role and increasing testosterone levels after androgen deprivation therapy (ADT) withdrawal or testosterone supplementation, as part of a bipolar androgen therapy (BAT) strategy, has been shown to potentially restore sensitivity to previous lines of NGHAs. CONCLUSION: These data suggest that maintenance of ADT in CRPC patients receiving further lines of treatment, as recommended by current international guidelines, could be questionable. Conversely, testosterone supplementation aimed to re-sensitize CRPC to further hormonal manipulation is a strategy worth to be explored in future clinical trials.

Bipolar androgen therapy (BAT): A patient's guide.

Bipolar androgen therapy (BAT) is a new treatment concept for men whose prostate cancer has become resistant to standard hormone-blocking therapy. Over the past decade, we have performed a series of clinical studies testing BAT in asymptomatic men with castration-resistant prostate cancer. The key findings from these clinical studies are that BAT (a) can be safely administered to asymptomatic patients with metastatic castrate-resistant prostate cancer; (b) does not produce symptomatic disease progression; (c) produces sustained prostate-specific antigen and objective responses in 30%-40% of patients; and (d) can resensitize and prolong response to subsequent antiandrogen therapy. The concept of BAT has generated significant interest from men with prostate cancer, their families, and their physicians. Here we provide a "Patient's Guide" that answers questions about BAT in a form that is accessible to patients, their families, and physicians. Our goal is to provide information to help patients make the most informed decisions they can regarding their prostate cancer treatment.

Clinical response in metastatic castration-resistant prostate cancer (mCRPC) cases treated with supra-physiological doses of testosterone: Bipolar androgen therapy.

Androgen deprivation therapy is a standard of care for metastatic prostate cancer. A paradoxical approach utilizing high doses of testosterone in castration-resistant prostate cancer patients demonstrated clinical responses. Here, we report on four heavily pretreated Japanese patients (including one patient on hemodialysis) successfully treated with supra-physiological doses of testosterone.

Efficacy and safety of bipolar androgen therapy in mCRPC after progression on abiraterone or enzalutamide: A systematic review.

PURPOSE: To further determine the efficacy and safety of bipolar androgen therapy (BAT) on patients with metastatic castration-resistant prostate cancer (mCRPC) after progression on abiraterone (ABI) or enzalutamide (ENZA). MATERIALS AND METHODS: We systematically searched the Pubmed, Web of Science and ClinicalTrials.gov up to June 2021. Literature review, study selection, and data extraction were conducted by 2 reviewers. Risk of bias was assessed according to the methodology of the European Association of Urology (EAU). A systematic review and pooled analysis were performed. The primary outcomes were PSA50 after BAT and AR-targeted therapy rechallenge, objective response rate (ORR) after BAT, and AEs after BAT. The definition of PSA50 was that participants achieving a PSA decline ≥50% according to Prostate Cancer Working Group (PCWG2) criteria. The ORR determined by determined by Response Evaluation Criteria in Solid Tumors (RECIST) included patients experienced partial response (PR) or complete response (CR). RESULTS: In a total of 74 unique records, 5 studies were eligible for inclusion. Participants who underwent BAT achieved PSA50 of 0.26 (95% CI [0.20, 0.32]) and objective response rate (ORR) of 0.32 (95% CI [0.21, 0.44]). Patients completed BAT proceeded to AR-target therapy (ABI or ENZA) achieved moderate response (PSA50 0.54, 95% CI [0.30, 0.76]). Based on our multiple subgroup analysis, type of post-BAT AR-target therapy had a strong impact on PSA50 of AR-target therapy rechallenge. Most of adverse events (AEs) were low grade. CONCLUSIONS: The present study indicated that BAT could induce clinical responses in mCRPC patients after progression on ABI or ENZA, with an acceptable side effects profile. BAT could also be able to restore sensitivity to ABI and ENZA rechallenge in a subset of patients.

Efficacy and safety of bipolar androgen therapy in castration-resistant prostate cancer following abiraterone or enzalutamide resistance: A systematic review.

Bipolar androgen therapy (BAT) is a new endocrinologic treatment for castration-resistant prostate cancer (CRPC) that can restore some patients' sensitivity to drugs such as abiraterone (Abi) and enzalutamide (Enz). We performed a meta-analysis using STATA16. Sensitivity analyses were performed by examining the effects of individual studies using different effect models and detecting any publication bias using the Harbord test. In a total of 108 unique records, ten studies were included in the final meta-analysis. Participants who underwent BAT achieved a PSA50 response rate of 27% (95%CI [0.22,0.31], I2=17.98%), ORR of 34% (95%CI [0.24,0.43], I2=0), and incidence of AEs (grade≥3) of 14% (95%CI [0.09,0.19], I2=0). Patients who completed BAT proceeded to AR-targeted therapy (Abi or Enz) and achieved a PSA50 response rate of 57% (95% CI [0.36,0.78], I2=0). Patients with prior Enz resistance had a stronger impact on the PSA50 of AR-target therapy rechallenge. The results of this meta-analysis indicate that BAT is a safe and effective treatment for patients who have progressed after Abi or Enz. BAT can trigger the resensitization of patients with CRPC to subsequent endocrine therapy and improve the overall survival of patients and their quality of life.

Titration of Androgen Signaling: How Basic Studies Have Informed Clinical Trials Using High-Dose Testosterone Therapy in Castrate-Resistant Prostate Cancer.

Since the Nobel Prize-winning work of Huggins, androgen ablation has been a mainstay for treatment of recurrent prostate cancer. While initially effective for most patients, prostate cancers inevitably develop the ability to survive, grow, and metastasize further, despite ongoing androgen suppression. Here, we briefly review key preclinical studies over decades and include illustrative examples from our own laboratories that suggest prostate cancer cells titrate androgen signaling to optimize growth. Such laboratory-based studies argue that adaptations that allow growth in a low-androgen environment render prostate cancer sensitive to restoration of androgens, especially at supraphysiologic doses. Based on preclinical data as well as clinical observations, trials employing high-dose testosterone (HDT) therapy have now been conducted. These trials suggest a clinical benefit in cancer response and quality of life in a subset of castration-resistant prostate cancer patients. Laboratory studies also suggest that HDT may yet be optimized further to improve efficacy or durability of response. However, laboratory observations suggest that the cancer will inevitably adapt to HDT, and, as with prior androgen deprivation, disease progression follows. Nonetheless, the adaptations made to render tumors resistant to hormonal manipulations may reveal vulnerabilities that can be exploited to prolong survival and provide other clinical benefits.

Androgens in prostate cancer: A tale that never ends.

Androgens play an essential role in prostate cancer. Clinical treatments that target steroidogenesis and the androgen receptor (AR) successfully postpone disease progression. Abiraterone and enzalutamide, the next-generation androgen receptor pathway inhibitors (ARPI), emphasize the function of the androgen-AR axis even in castration-resistant prostate cancer (CRPC). However, with the increased incidence in neuroendocrine prostate cancer (NEPC) showing resistance to ARPI, the importance of androgen-AR axis in further disease management remains elusive. Herein we review the steroidogenic pathways associated with different disease stages and discuss the potential targets for disease management after manifesting resistance to abiraterone and enzalutamide.

Reversing the effects of androgen-deprivation therapy in men with metastatic castration-resistant prostate cancer.

OBJECTIVE: To investigate whether bipolar androgen therapy (BAT), involving rapid cyclic administration of high-dose testosterone, as a novel treatment for metastatic castration-resistant prostate cancer (mCRPC) promotes improvements in body composition and associated improvements in lipid profiles and quality of life. PATIENTS AND METHODS: Men from two completed trials with computed tomography imaging at baseline and after three cycles of BAT were included. Cross-sectional areas of psoas muscle, visceral and subcutaneous fat were measured at the L3 vertebral level. Functional Assessment of Chronic Illness Therapy - Fatigue questionnaire and 36-item short-form health survey were used to assess quality of life. RESULTS: The 60 included patients lost a mean (sd) of 7.8 (8.2)% of subcutaneous fat, 9.8 (18.2)% of visceral fat, and gained 12.2 (6.7)% muscle mass. Changes in subcutaneous and visceral fat were positively correlated with each other (Spearman's correlation coefficient 0.58, 95% confidence interval 0.35-0.71) independent of the effects of age, body mass index, and duration of androgen-deprivation therapy. Energy, physical function, and measures of limitations due to physical health were all significantly improved at 3 months. The improvements in body composition were not correlated with decreases in lipid levels or observed improvements in quality of life. CONCLUSIONS: In the present study, BAT was associated with significant improvements in body composition, lipid parameters, and quality of life. This has promising implications for the long-term health of men with mCRPC.

A Multicohort Open-label Phase II Trial of Bipolar Androgen Therapy in Men with Metastatic Castration-resistant Prostate Cancer (RESTORE): A Comparison of Post-abiraterone Versus Post-enzalutamide Cohorts.

BACKGROUND: Cyclic high-dose testosterone injections, also known as bipolar androgen therapy (BAT), is a novel treatment strategy for patients with metastatic castration-resistant prostate cancer (mCRPC). BAT has shown clinical activity in prior studies enrolling men with mCRPC and may potentially restore sensitivity to prior androgen receptor (AR)-targeted agents. OBJECTIVE: To evaluate the clinical activity of BAT in patients progressing on AR-targeted therapy as well as responses to abiraterone or enzalutamide upon rechallenge after BAT. DESIGN, SETTING, AND PARTICIPANTS: RESTORE is a multicohort phase II study enrolling asymptomatic mCRPC patients after abiraterone or enzalutamide at Johns Hopkins Hospital (NCT02090114). Participants (29 after abiraterone and 30 after enzalutamide) received 400 mg testosterone cypionate intramuscularly every 28 days, with ongoing luteinizing hormone-releasing hormone agonist/antagonist treatment (ie, BAT). Following progression on BAT, patients were rechallenged with their most recent AR-targeted therapy. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Coprimary endpoints were >50% decline in PSA from baseline (PSA50) responses to BAT and following AR-targeted therapy rechallenge. Outcomes in the post-abiraterone cohort are presented, as well as updated results from the post-enzalutamide cohort and an exploratory AR-V7 analysis. RESULTS AND LIMITATIONS: No statistically significant difference in PSA50 response rates to BAT was observed (30% [post-enzalutamide cohort] vs 17% [post-abiraterone cohort], p = 0.4). However, PSA50 responses to AR-targeted therapy rechallenge were higher in the post-enzalutamide cohort (68% vs 16%, p = 0.001). The median time from enrollment to progression following rechallenge with AR-targeted therapy (ie, progression-free survival 2; PFS2) was longer in the post-enzalutamide versus post-abiraterone patients (12.8 vs 8.1 mo, p = 0.04). Outcomes were worse in patients with detectable AR-V7 in circulating tumor cells (median PFS2: 10.3 vs 7.1 mo, p = 0.005). CONCLUSIONS: BAT shows clinical activity in mCRPC patients and may be more effective at resensitizing to enzalutamide versus abiraterone. PATIENT SUMMARY: BAT is well tolerated in metastatic castration-resistant prostate cancer patients. The type of prior AR-targeted therapy might affect response to BAT as well as AR-therapy rechallenge. BAT followed by AR-targeted therapy rechallenge did not improve outcomes in AR-V7-positive patients.

Bipolar androgen therapy sensitizes castration-resistant prostate cancer to subsequent androgen receptor ablative therapy.

BACKGROUND: Cyclical, high-dose testosterone administration, termed bipolar androgen therapy (BAT), can induce clinical responses and restore sensitivity to androgen signalling inhibition in patients with previously treated castration-resistant prostate cancer (PCa) (CRPC). This trial evaluated whether BAT is a safe and effective first-line hormonal therapy for patients with CRPC. PATIENTS AND METHODS: In cohort C of this single-centre, open-label, phase II, multi-cohort trial (RE-sensitizing with Supraphysiologic Testosterone to Overcome REsistance study), 29 patients with CRPC received first-line hormonal therapy with 400 mg of testosterone cypionate intramuscularly every 28 days concurrent with a luteinising hormone-releasing hormone agonist/antagonist. The primary end-point of the study was the PSA50 response rate to BAT treatment. RESULTS: After treatment with BAT, four of 29 patients (14%; 95% confidence interval [CI]: 4-32%) experienced a PSA50 response. The median radiographic progression-free survival to BAT was 8.5 months (95% CI: 6.9-15.1) for patients with metastatic CRPC. After progression on BAT, 17 of 18 patients (94%; 95% CI: 73-100%) achieved a PSA50 response and 15 of 18 patients (83%; 95% CI: 59-96) achieved a PSA90 response on abiraterone or enzalutamide. Twelve of 15 patients (80%; 95% CI: 52-96) with metastatic CRPC remain on abiraterone or enzalutamide with a median duration of follow-up of 11.2 months. CONCLUSION: As first-line hormonal treatment for CRPC, BAT was well tolerated and resulted in prolonged disease stabilisation. After progression on BAT, patients had favourable responses to second-generation androgen receptor-targeted therapy. TRIAL REGISTRATION: ClinicalTrials.gov NCT02090114.

Mechanisms of Androgen Receptor Agonist- and Antagonist-Mediated Cellular Senescence in Prostate Cancer.

The androgen receptor (AR) plays a leading role in the control of prostate cancer (PCa) growth. Interestingly, structurally different AR antagonists with distinct mechanisms of antagonism induce cell senescence, a mechanism that inhibits cell cycle progression, and thus seems to be a key cellular response for the treatment of PCa. Surprisingly, while physiological levels of androgens promote growth, supraphysiological androgen levels (SAL) inhibit PCa growth in an AR-dependent manner by inducing cell senescence in cancer cells. Thus, oppositional acting ligands, AR antagonists, and agonists are able to induce cellular senescence in PCa cells, as shown in cell culture model as well as ex vivo in patient tumor samples. This suggests a dual AR-signaling dependent on androgen levels that leads to the paradox of the rational to keep the AR constantly inactivated in order to treat PCa. These observations however opened the option to treat PCa patients with AR antagonists and/or with androgens at supraphysiological levels. The latter is currently used in clinical trials in so-called bipolar androgen therapy (BAT). Notably, cellular senescence is induced by AR antagonists or agonist in both androgen-dependent and castration-resistant PCa (CRPC). Pathway analysis suggests a crosstalk between AR and the non-receptor tyrosine kinase Src-Akt/PKB and the PI3K-mTOR-autophagy signaling in mediating AR-induced cellular senescence in PCa. In this review, we summarize the current knowledge of therapeutic induction and intracellular pathways of AR-mediated cellular senescence.