Role of the Androgen-Androgen Receptor Axis in the Treatment Resistance of Advanced Prostate Cancer: From Androgen-Dependent to Castration Resistant and Further

Non-steroidal CYP17A1 Inhibitors: Discovery and Assessment

CYP17A1 is an enzyme that plays a major role in steroidogenesis and is critically involved in the biosynthesis of steroid hormones. Therefore, it remains an attractive target in several serious hormone-dependent cancer diseases, such as prostate cancer and breast cancer. The medicinal chemistry community has been committed to the discovery and development of CYP17A1 inhibitors for many years, particularly for the treatment of castration-resistant prostate cancer. The current Perspective reflects upon the discovery and evaluation of non-steroidal CYP17A1 inhibitors from a medicinal chemistry angle. Emphasis is placed on the structural aspects of the target, key learnings from the presented chemotypes, and design guidelines for future inhibitors.

Therapeutic Strategies to Target the Androgen Receptor

The androgen receptor (AR) plays a key role in the maintenance of muscle and bone and the support of male sexual-related functions, as well as in the progression of prostate cancer. Accordingly, AR-targeted therapies have been developed for the treatment of related human diseases and conditions. AR agonists are an important class of drugs in the treatment of bone loss and muscle atrophy. AR antagonists have also been developed for the treatment of prostate cancer, including metastatic castration-resistant prostate cancer (mCRPC). Additionally, selective AR degraders (SARDs) have been reported. More recently, heterobifunctional degrader molecules of AR have been developed, and four such compounds are now in clinical development for the treatment of human prostate cancer. This review attempts to summarize the different types of compounds designed to target AR and the current frontiers of research on this important therapeutic target.

Designed, synthesized and biological evaluation of proteolysis targeting chimeras (PROTACs) as AR degraders for prostate cancer treatment

As a continuation of our research on developing potent and potentially safe androgen receptor (AR) degrader, a series of novel proteolysis targeting chimeras (PROTACs) containing the phthalimide degrons with different linker were designed, synthesized and evaluated for their AR degradation activity against LNCaP (AR+) cell line. Most of the synthesized compounds displayed moderate to satisfactory AR binding affinity and might lead to antagonist activity against AR. Among them, compound A16 exhibited the best AR binding affinity (85%) and degradation activity against AR. Due to the strong fluorescence properties of pomalidomide derivatives, B10 was found to be effectively internalized and visualized in LNCaP (AR + ) cells than PC-3 (AR-) cells. Moreover, the molecular docking of A16 with AR and the active site of DDB1-CRBN E3 ubiquitin ligase complex provides guidance to design new PROTAC degrons targeting AR for prostate cancer therapy. These results represent a step toward the development of novel and improved AR PROTACs.

A review of the effects and molecular mechanisms of dimethylcurcumin (ASC-J9) on androgen receptor-related diseases

Dimethylcurcumin (ASC-J9) is a curcumin analogue capable of inhibiting prostate cancer cell proliferation. The mechanism is associated with the unique role of ASC-J9 in enhancing androgen receptor (AR) degradation. So far, ASC-J9 has been investigated in typical AR-associated diseases such as prostate cancer, benign prostatic hypertrophy, bladder cancer, renal diseases, liver diseases, cardiovascular diseases, cutaneous wound, spinal and bulbar muscular atrophy, ovarian cancer and melanoma, exhibiting great potentials in disease control. In this review, the effects and molecular mechanisms of ASC-J9 on various AR-associated diseases are summarized. Importantly, the effects of ASC-J9 and AR antagonists enzalutamide/bicalutamide on prostate cancer are compared in detail and crucial differences are highlighted. At last, the pharmacological effects of ASC-J9 are summarized and the future applications of ASC-J9 in AR-associated disease control are discussed.

Pulmonary metastasis secondary to abiraterone-resistant prostate cancer with homozygous deletions of BRCA2: First Japanese case

INTRODUCTION

Most metastatic prostate cancers acquire the capacity for androgen-independent growth and become resistant to androgen deprivation therapy. A patient-focused treatment strategy is needed for aggressive castration-resistant prostate cancer.

CASE PRESENTATION

We report the case of a 62-year-old man who presented with prostatic adenocarcinoma who was treated by radiation and combined androgen blockade. After completion of first-line therapy, he was diagnosed with multiple metastatic castration-resistant prostate cancer in the lung. Second-line therapy with abiraterone acetate resulted in partial remission of the lung metastases. Thoracic surgery was performed to remove the single lung metastasis remaining. Next-generation sequencing of the specimens demonstrated homozygous loss of BRCA2. We note in this case a heterogeneous response to abiraterone acetate may be related to the somatic BRCA2 deletions.

CONCLUSIONS

We present the first Japanese case of a metastatic abiraterone acetate-resistant castration-resistant prostate cancer accompanied by BRCA2 mutation.

The long non-coding RNA PCAL7 promotes prostate cancer by strengthening androgen receptor signaling

BACKGROUND

The prostate cancer (PCa) has been a global problem to men health. Notably, the androgen receptor (AR) is essential for both normal development of prostate and prostate cancer progression.

METHODS

The RNA sequencing was used to identify the novel long non-coding RNA (lncRNA) termed PCAL7. The RT-qPCR was performed to quantify PCAL7 expression. Migration and proliferation assays were used to examine the function of PCAL7. Fluorescence in situ hybridization (FISH) was used to determine subcellular localization.

RESULTS

By RNA sequencing, the differentially expressed lncRNAs were identified (top 10 upregulated lncRNAs: PCAL7, AC083843.1, CTC-338M12.3, RP11-443B7.1, RP11-1008C21.2, RN7SL329P, RP4-773N10.4, RP11-264B17.2, KB-1507C5.2, and RP11-20B24.6; top 10 downregulated lncRNAs: RP11-77H9.2, RAB11FIP1P1, AP001625.6, CTA-217C2.1, RP11-603J24.7, RP11-315I20.1, AC092839.1, RP4-758J18.10, RP11-259O2.3, and HMGN2P17). PCAL7 was the lncRNA with the highest fold upregulation and significantly correlated with AR signaling during prostate cancer progression. The AR-regulated PCAL7 was abundantly overexpressed in prostate cancer tissues and AR-dependent cell lines. PCAL7 knockdown inhibited cell migration and proliferation. Consistently, the migration and proliferation were promoted by PCAL7 overexpression. PCAL7 depletion via antisense oligonucleotides (ASOs) markedly suppressed AR signaling and tumor growth. Mechanistically, PCAL7 interacted with Huntingtin-interacting protein 1 (HIP1) to stabilize HIP1. Therefore, PCAL7 could advance AR signaling via a novel positive feedback loop.

CONCLUSION

Our experiments support an oncogenic role for PCAL7 which promotes prostate cancer progression suggesting PCAL7 may serve as a potential therapeutic target.

Cancer stem cell and mesenchymal cell cooperative actions in metastasis progression and hormone resistance in prostate cancer: Potential role of androgen and gonadotropin‑releasing hormone receptors (Review)

Prostate cancer (PCa) is the leading cause of male cancer‑associated mortality worldwide. Mortality is associated with metastasis and hormone resistance. Cellular, genetic and molecular mechanisms underlying metastatic progression and hormone resistance are poorly understood. Studies have investigated the local effects of gonadotropin‑releasing hormone (GnRH) analogs (used for androgen deprivation treatments) and the presence of the GnRH receptor (GnRH‑R) on PCa cells. Furthermore, cell subpopulations with stem‑like properties, or cancer stem cells, have been isolated and characterized using a cell culture system derived from explants of human prostate tumors. In addition, the development of preclinical orthotopic models of human PCa in a nonobese diabetic/severe combined immunodeficiency mouse model of compromised immunity has enabled the establishment of a reproducible system of metastatic progression in vivo. There is increasing evidence that metastasis is a complex process involving the cooperative actions of different cancer cell subpopulations, in which cancer stem‑like cells would be responsible for the final step of colonizing premetastatic niches. It has been hypothesized that PCa cells with stemness and mesenchymal signatures act cooperatively in metastatic progression and the inhibition of stemness genes, and that overexpression of androgen receptor (AR) and GnRH‑R decreases the rate the metastasis and sensitizes tumors to hormone therapy. The aim of the present review is to analyze the evidence regarding this cooperative process and the possible influence of stem‑like cell phenotypes, AR and GnRH‑R in metastatic progression and hormone resistance. These aspects may represent an important contribution in the understanding of the mechanisms underlying metastasis and hormone resistance in PCa, and potential routes to blocking these processes, enabling the development of novel therapies that would be particularly relevant for patients with metastatic and castration‑resistant PCa.

Efficacy and safety of degarelix in patients with prostate cancer: Results from a phase III study in China

Objective

To establish non-inferiority of gonadotropin-releasing hormone degarelix compared with goserelin in suppressing and maintaining castrate testosterone levels from Day 28 to Day 364 in Chinese patients with prostate cancer.

Methods

This is an open-label, multi-centre study in which men aged ≥18 years were randomised in a 1:1 ratio to once-a-month subcutaneous injection of either degarelix (240/80 mg) or goserelin (3.6 mg) for 12 months. The primary endpoint was difference in 1-year cumulative probability of suppressing testosterone to ≤0.5 ng/mL. Non-inferiority was to be established if the lower 95% confidence interval (CI) limit for difference in cumulative probability between the treatment arms was greater than −10%. Secondary endpoints included cumulative probability of prostate-specific-antigen-progression-free-survival (PSA-PFS). Safety was also assessed.

Results

Baseline demographics and disease characteristics were similar between degarelix (n=142) and goserelin (n=141) treatment arms. The difference in cumulative probability of maintaining castrate levels from Day 28–364 was 3.6% (95% CI:−1.5%, 8.7%), demonstrating non-inferiority of degarelix. The cumulative probability of PSA-PFS at Day 364 was higher for degarelix (82.3%, 95% CI: 74.7%, 87.7%) versus goserelin (71.7%, 95% CI: 63.2%, 78.5%, p=0.038). Adverse events (AEs) were similar between treatment arms, except for more injection site reactions with degarelix versus goserelin. Four (2.8%) and nine (6.4%) patients discontinued due to AEs in degarelix and goserelin groups, respectively.

Conclusion

Degarelix was non-inferior to goserelin in achieving and maintaining testosterone suppression at castrate levels during 1-year treatment. PSA-PFS was significantly higher with degarelix, suggesting improved disease control. Both treatments were well tolerated.

A Novel Use of Olaparib for the Treatment of Metastatic Castration-Recurrent Prostate Cancer

Although mortality from prostate cancer has declined over the past 20 years as a result of early detection and treatment, the 5-year survival rate for men with prostate cancer who develop metastatic disease is only 29%. Current treatment options for metastatic castration-recurrent prostate cancer (mCRPC) are associated with toxicity and a limited durable response; therefore, additional lines of efficacious and minimally toxic therapy are needed. Olaparib, a poly(adenosine 5'-diphosphate) ribose polymerase (PARP) inhibitor, received a U.S. Food and Drug Administration breakthrough therapy designation in January 2016 for the treatment of patients with BRCA1/2 or ATM gene-mutated mCRPC based on results of a compelling phase II trial of olaparib in patients with advanced castration-resistant prostate cancer (TOPARP-A). This study found that men with mCRPC and genetic mutations in DNA damage repair genes had an overall response rate of nearly 90% with olaparib treatment. In this review, we describe current therapies for mCRPC, the rationale for anti-PARP therapies, the pharmacology of olaparib for prostate cancer, clinical trials of olaparib for mCRPC, our clinical experience with olaparib for prostate cancer at a comprehensive cancer center, and future directions of olaparib for the treatment of mCRPC. Olaparib may constitute a promising treatment to prolong survival in patients with mCRPC, with an acceptable adverse effect profile. As the role of PARP inhibition in prostate cancer and other malignancies becomes further elucidated, olaparib may be shown to be beneficial for other patient populations.

MicroRNA-744 promotes prostate cancer progression through aberrantly activating Wnt/β-catenin signaling

Accumulated evidence indicate that miR-744 functions as either tumor suppressor or oncogene in the progression of a variety of tumors, with a tumor type-specific way. However, little is known about how miR-744 impacts on the tumorigenesis of human prostate cancer. In this study, employing the analyses of microarray, qRT-PCR and re-analysis of MSKCC data, we found that CRPC tissues expressed much more miR-744 than ADPC tissues did, and the expression level of miR-744 was inversely associated with survival of CRPC patients. In vitro studies revealed that miR-744 promotes PCa cells proliferation, enhances migration, invasion; in vivo results demonstrated that silencing of miR-744 mediated by shRNA dramatically reduces PCa xenograft tumor growth. Importantly, through human gene expression array, pathway enrichment analysis and Western blot, we identified that miR-744 dramatically activated Wnt/β-catenin pathway by targeting multiple negative regulators of Wnt/β-catenin signaling, including SFRP1, GSK3β, TLE3 and NKD1. At molecular level, we further defined that NKD1 is a major functional target of miR-744. Our findings indicate that miR-744 acts as one of oncogenic factor in the progression of CRPC by recruiting a mechanism of aberrant activation of Wnt/β-catenin signaling.

Improving circulating tumor cells enumeration and characterization to predict outcome in first line chemotherapy mCRPC patients

INTRODUCTION

There is a critical need of new surrogate markers for improving the therapeutic selection and monitoring of metastatic prostate cancer patients. Nowadays clinical management of these patients is been driven by biochemical and clinical parameters without enough accuracy to allow a real personalized medicine. The present study was conducted to go insight the molecular profile of circulating tumor cells (CTCs) isolated from advanced metastatic castration-resistant prostate cancer (mCRPC) with the aim of identifying prognostic marker with potential utility for therapy selection and monitoring.

MATERIALS AND METHODS

CTCs isolation was carried out in peripheral blood samples from 29 mCRPC patients that undergo systemic chemotherapy based on taxanes (docetaxel/cabazitaxel) and 19 healthy controls using in parallel CellSearch and an alternative EpCAM-based immunoisolation followed by RT-qPCR analysis to characterize the CTC population. A panel of 17 genes related with prostate biology, hormone regulation, stem properties, tumor aggressiveness and taxanes responsiveness was analysed to identify an expression signature characterizing the CTCs.

RESULTS

Patients with ≥ 5 CTCs/7.5ml of peripheral blood at baseline and during the treatment showed lower progression free survival (PFS) and overall survival (OS). Changes of CTCs levels during the treatment were also associated with the patient's outcome. These results confirmed previous data obtained using CellSearch in mCRPC. In addition, we found a CTC profile mainly characterized by the expression of relevant genes for the hormone dependent regulation of PCa such as AR and CYP19 together with genes strongly implicated in PCa progression and resistance development such as BIRC5, TUB1A, GDF15, RAB7 and SPINK1. Our gene-expression profiling also permitted the identification of valuable prognostic biomarkers. Thus, high levels of AR, CYP19 and GDF15 were associated with poor PFS rates while AR, GDF15 and BIRC5 were also found as reliable predictors of OS. Besides, a logistic model using KLK3 and BIRC5 showed a high specificity and sensitivity compared to CellSearch to discriminate patients with a more aggressive evolution.

CONCLUSIONS

The molecular characterization of CTCs from advanced mCRPC patients provided with a panel of specific biomarkers, including genes related to taxanes resistance, with a promising applicability as "liquid biopsy" for the management of these patients.