Evolving landscape and novel treatments in metastatic castrate-resistant prostate cancer

Investigation of the regulatory effects of synthesized antisense oligonucleotides on androgen receptor (AR) exon 3 splicing in prostate cancer cells

The Androgen Receptor (AR) gene plays a key role in castration-resistant prostate cancer (CRPC). Controlling the progression of CRPC by inhibiting AR gene expression is one of the core directions for prostate cancer (Pca) drug development. A 23-amino acids retention, named exon 3a, into the DNA binding domain of the splice variant AR23 has been shown to prevent AR from entering the nucleus and restore the sensitivity of cancer cells to related therapies. In this study, we conducted a preliminary investigation of the splicing modulation of the AR gene in order to develop a splice-switching therapy for Pca by promoting exon 3a inclusion. Using mutagenesis-coupled RT-PCR with AR minigene and over-expression of certain splicing factors, we found that serine/arginine-rich (SR) proteins are key factors facilitating the recognition of the 3' splice site of exon 3a (L-3' SS), while the deletion or blocking of the polypyrimidine tract (PPT) region of the original 3' splice site of exon 3 (S-3' SS) could strongly enhance exon 3a splicing without affecting the function of any SR protein. Furthermore, we designed a series of antisense oligonucleotides (ASOs) to screen drug candidates, and ASOs targeting S-3' SS and its PPT region or the exonic region of exon 3 turned out to be most effective in rescuing exon 3a splicing. A dose-response test indicated ASO12 as the lead candidate drug significantly promoting the inclusion of exon 3a to more than 85%. MTT assay confirmed that the cell proliferation was significantly inhibited after ASO treatment. Our results provide the first glance to AR splicing regulation. With several promising therapeutic ASO candidates obtained here, further development of ASO drugs to treat CRPC is strongly encouraged.

Recombinant Human Clusterin Seals Damage to the Ocular Surface Barrier in a Mouse Model of Ophthalmic Preservative-Induced Epitheliopathy

There is a significant unmet need for therapeutics to treat ocular surface barrier damage, also called epitheliopathy, due to dry eye and related diseases. We recently reported that the natural tear glycoprotein CLU (clusterin), a molecular chaperone and matrix metalloproteinase inhibitor, seals and heals epitheliopathy in mice subjected to desiccating stress in a model of aqueous-deficient/evaporative dry eye. Here we investigated CLU sealing using a second model with features of ophthalmic preservative-induced dry eye. The ocular surface was stressed by topical application of the ophthalmic preservative benzalkonium chloride (BAC). Then eyes were treated with CLU and sealing was evaluated immediately by quantification of clinical dye uptake. A commercial recombinant form of human CLU (rhCLU), as well as an rhCLU form produced in our laboratory, designed to be compatible with U.S. Food and Drug Administration guidelines on current Good Manufacturing Practices (cGMP), were as effective as natural plasma-derived human CLU (pCLU) in sealing the damaged ocular surface barrier. In contrast, two other proteins found in tears: TIMP1 and LCN1 (tear lipocalin), exhibited no sealing activity. The efficacy and selectivity of rhCLU for sealing of the damaged ocular surface epithelial barrier suggests that it could be of therapeutic value in treating BAC-induced epitheliopathy and related diseases.

The Androgen Regulated lncRNA NAALADL2-AS2 Promotes Tumor Cell Survival in Prostate Cancer

Castration resistance is the leading cause of death in men with prostate cancer. Recent studies indicate long noncoding RNAs (lncRNAs) to be important drivers of therapy resistance. The aim of this study was to identify differentially expressed lncRNAs in castration-resistant prostate cancer (CRPC) and to functionally characterize them in vitro. Tumor-derived RNA-sequencing data were used to quantify and compare the expression of 11,469 lncRNAs in benign, primary prostate cancer, and CRPC samples. CRPC-associated lncRNAs were selected for semi-quantitative PCR validation on 68 surgical tumor specimens. In vitro functional studies were performed by antisense-oligonucleotide-mediated lncRNA knockdown in hormone-sensitive prostate cancer (HSPC) and CRPC cell line models. Subsequently, cell proliferation, apoptosis, cell cycle, transcriptome and pathway analyses were performed using the appropriate assays. Transcriptome analysis of a prostate cancer tumor specimens unveiled NAALADL2-AS2 as a novel CRPC-upregulated lncRNA. The expression of NAALADL2-AS2 was found to be particularly high in HSPC in vitro models and to increase under androgen deprived conditions. NAALADL2-AS2 knockdown decreased cell viability and increased caspase activity and apoptotic cells. Cellular fractionization and RNA fluorescent in situ hybridization identified NAALADL2-AS2 as a nuclear transcript. Transcriptome and pathway analyses revealed that NAALADL2-AS2 modulates the expression of genes involved with cell cycle control and glycogen metabolism. We hypothesize that the nuclear lncRNA, NAALADL2-AS2, functions as a pro-survival signal in prostate cancer cells under pressure of targeted hormone therapy.

Clusterin, other extracellular chaperones, and eye disease

Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.

Transperineal Parallel Biopsy of the Prostate: A New Approach of Tissue Sampling for Precision Medicine

Purpose

Through an observational study to present a new approach for obtaining high-quality samples for the targeted therapy of prostate cancer.

Patients and Methods

Parallel biopsy, which was defined as collecting the tissue from the same site by two biopsies, was performed on patients with elevated PSA. Each tissue was stained by ink to identify the pathological characteristics, including Gleason score and tumor tissue ratio. Kendall tau-b test and intraclass correlation coefficient test were used to compare the consistency between each paired sample. Then, based on the pathology of the biopsies, high-quality tissues would be selected for sequencing, and PyClone model was used to track the clonal evolution.

Results

In total, 252 pairs of biopsies were collected. The consistency of Gleason score between each paired biopsy is 0.777 (p<0.01), and the consistency of tumor tissue ratio is 0.853 (p<0.01). With the application of parallel biopsy, on average five nonsynonymous mutations could be identified in patients with castration-resistant prostate cancer. Six out of eight had at least one biology-relevant alteration in patients, guiding further treatment. Meanwhile, clonal evolution was constructed to investigate the progress of tumor.

Conclusion

Parallel biopsy is a reliable approach to collect high-quality tissue and shows potential application in precision medicine.

RNA-binding protein Musashi2 stabilizing androgen receptor drives prostate cancer progression

The androgen receptor (AR) pathway is critical for prostate cancer carcinogenesis and development; however, after 18‐24 months of AR blocking therapy, patients invariably progress to castration‐resistant prostate cancer (CRPC), which remains an urgent problem to be solved. Therefore, finding key molecules that interact with AR as novel strategies to treat prostate cancer and even CRPC is desperately needed. In the current study, we focused on the regulation of RNA‐binding proteins (RBPs) associated with AR and determined that the mRNA and protein levels of AR were highly correlated with Musashi2 (MSI2) levels. MSI2 was upregulated in prostate cancer specimens and significantly correlated with advanced tumor grades. Downregulation of MSI2 in both androgen sensitive and insensitive prostate cancer cells inhibited tumor formation in vivo and decreased cell growth in vitro, which could be reversed by AR overexpression. Mechanistically, MSI2 directly bound to the 3′‐untranslated region (UTR) of AR mRNA to increase its stability and, thus, enhanced its transcriptional activity. Our findings illustrate a previously unknown regulatory mechanism in prostate cancer cell proliferation regulated by the MSI2‐AR axis and provide novel evidence towards a strategy against prostate cancer.

Neutrophil-to-lymphocyte Ratio as a Predictive Marker of Response to Abiraterone Acetate: A Retrospective Analysis of the COU302 Study

BACKGROUND

The neutrophil-lymphocyte ratio (NLR) is an inexpensive and accessible prognostic marker for many cancers, including metastatic castration-resistant prostate cancer (mCRPC).

OBJECTIVE

In this study, we assess the role of NLR as a predictive biomarker through a retrospective analysis of the pivotal COU302 study of abiraterone acetate (AA) as first-line therapy for men with asymptomatic or minimally symptomatic mCRPC.

DESIGN, SETTING, AND PARTICIPANTS

The COU302 study randomized asymptomatic or minimally symptomatic men with mCRPC to receive AA plus prednisone or prednisone as first-line treatment. Baseline NLR, overall survival, radiographic progression-free survival, and prostate-specific antigen (PSA) progression-free survival were evaluated.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Descriptive statistics, as well as Kaplan-Meier and Cox survival models were used to assess the effect of baseline NLR and changes in NLR on response to AA plus prednisone versus prednisone, with adjustment for important covariates.

RESULTS AND LIMITATIONS

Among the 1082 patients who received treatment, baseline NLR values showed no significant differences according to baseline covariates except for albumin. Baseline variables were similar between dichotomous groups with an NLR cutoff of 2.5, except for a lower proportion of patients with >10 bone metastases in the NLR <2.5 group. Our survival results demonstrate that higher NLR values corresponded to poorer overall survival and PSA response to AA but not to placebo, which was confirmed in our adjusted regression models. No significant differences were seen in time to radiographic progression. In separate analyses, an increase or decrease in NLR by 2 from treatment baseline did not clearly signal subsequent lack of benefit with continued AA.

CONCLUSIONS

Our results suggest that baseline NLR may be able to predict response to AA in men with asymptomatic mCRPC but that changes in NLR during treatment are insufficient to guide treatment. Further validation studies are warranted.

PATIENT SUMMARY

In this report, we look at the ratio of circulating immune cells as a predictor of response to abiraterone acetate (AA), using data from a large trial. Our results suggest that this ratio derived from routinely obtained bloodwork can predict which patients respond better to AA.

Apalutamide: the established and emerging roles in the treatment of advanced prostate cancer

INTRODUCTION

Prostate cancer (PCa) is the most common cancer in elderly males. Androgen deprivation therapy (ADT) is still the cornerstone of initial treatment; however, the vast majority of patients develop castration-resistant prostate cancer (CRPC). Several studies with numerous androgen receptor (AR)-directed agents have emerged since the approval of abiraterone acetate and enzalutamide. One of these agents is apalutamide, which seems to be a promising AR antagonist for the treatment of CRPC. Areas covered: The authors review Phase I, II, and III studies for apalutamide, in a large spectrum of PCa (from low-risk to metastatic CRPC [mCRPC]) patients as sole treatment or in the setting of combined therapy. Expert opinion: Apalutamide is an oral, investigational, AR antagonist that targets the AR ligand-binding domain and prevents AR nuclear translocation, DNA binding, and transcription of AR gene targets. It has shown favorable safety profile and therapeutic index in Phase I studies, good tolerance and efficacy in patients with high-risk CRPC in Phase II studies. Also, results were promising in a recent phase III study in patients with non-mCRPC who were at high risk for the development of metastasis. These data may offer potential advantages over the second-generation antiandrogens.

Exercise medicine for advanced prostate cancer

PURPOSE OF REVIEW

Exercise is a provocative medicine, known for its preventive, complimentary and rehabilitative role in the management of cancer. Impressively, exercise is also emerging as a synergistic and targeted medicine to enhance symptom control, modulate tumour biology and delay disease progression, with the potential to increase overall survival. Given the complex clinical presentation of advanced prostate cancer patients and their omnipresent comorbidities, this review describes the current and potential role of exercise medicine in advanced prostate cancer.

RECENT FINDINGS

Exercise has been shown to be safe, feasible and effective for advanced prostate cancer patients, inclusive of patients with bone metastases; a previously excluded population due to patient and clinician fear of adverse events. Preclinical data provide insight into the ability of exercise to modulate cancer-specific outcomes, may synergistically increase the potency of chemotherapy and radiotherapy and may endogenously and/or mechanically suppress tumour formation, growth and invasion in visceral and skeletal tissue. Epidemiological studies have also shown an association between physical activity and increased survival.

SUMMARY

Exercise oncology is rapidly evolving, with impressive possibilities that may directly improve patient outcomes in advanced prostate cancer. Research must focus on translating preclinical trials into human clinical trials and investigate the direct effect of exercise on overall survival.

The treatment patterns of castration-resistant prostate cancer in Japan, including symptomatic skeletal events and associated treatment and healthcare resource use

BACKGROUND

Real-world treatment patterns of bone metastatic castration-resistant prostate cancer (mCRPC) in Japan were examined, focusing on treatment patterns and resource use differences attributed to symptomatic skeletal events (SSEs).

METHODS

Urologists (N = 176) provided retrospective chart data for patients with mCRPC (N = 445) via online surveys. Descriptive analyses and chi-square tests evaluated treatment patterns and their differences by SSE presence; generalized linear mixed models examined healthcare resource utilization differences as a function of SSEs.

RESULTS

Patients were on average 73.6 years old (SD = 8.3), diagnosed with prostate cancer 5.1 years (SD = 6.2), castration-resistant 2.3 years (SD=2.0), and had 7.9 bone metastases sites (SD=12.4). Novel anti-hormones showed increased adoption as mCRPC treatment. Simultaneously, luteinizing hormone-releasing hormone (LHRH) agonist/antagonist use was common (43.6% of patients in 1^st line), even as CRPC treatment had started. SSEs were uncommon (2-3% per treatment line; 5% at any time), but were associated with increased opioids, strontium-89, bisphosphonates, and NSAIDs use, plus increased healthcare visits (all p < .05).

CONCLUSIONS

LHRH agonist/antagonist treatment combinations remain the mCRPC treatment mainstay in Japan. However, novel anti-hormone therapies are becoming well-accepted in practice. SSEs were associated with increased healthcare resource and analgesic use, highlighting the need for efficient symptom management.

Patient preferences for treatment of castration-resistant prostate cancer in Japan: a discrete-choice experiment

Background

Up to a fifth of patients diagnosed with prostate cancer (PC) will develop castration-resistant prostate cancer (CRPC), which has been associated with a poor prognosis. The aim of this study was to consider the patient perspective as part of the overall treatment decision-making process for CRPC, given that an alignment between patient preference and prescribing has been shown to benefit patient outcomes. This study examines preferences of patients with CRPC in Japan for treatment features associated with treatments like RA-223, abiraterone, and docetaxel and to examine the extent to which treatment preferences may vary between symptomatic and asymptomatic patients.

Methods

A two-phase research approach was implemented. In Phase 1, N = 8 patients with CRPC were recruited from a single hospital to complete a qualitative interview to provide feedback on the draft survey. In Phase 2, N = 134 patients with CRPC were recruited from five hospitals to complete a paper survey. The survey included 6 treatment choice questions, each asking patients to choose between two hypothetical treatments for their CRPC. Each treatment alternative was defined by the following attributes: length of overall survival (OS), time to a symptomatic skeletal event (SSE), method of administration, reduction in the risk of bone pain, treatment-associated risk of fatigue and lost work days. A hierarchical Bayesian logistic regression was used to estimate relative preference weights for each attribute level and mean relative importance.

Results

A total of N = 133 patients with CRPC completed the survey and were included in the final analysis. Patients had a mean age of 75.4 years (SD = 7.4) and had been diagnosed with PC a mean of 6.5 years prior (SD = 4.4). Over the attribute levels shown, fatigue (relative importance [RI] = 24.9 %, 95 % CI: 24.7 %, 25.1 %) was the most important attribute, followed by reduction in the risk of bone pain (RI = 23.2 %, 95 % CI: 23.0 %, 23.5 %), and OS (RI = 19.2 %, 95 % CI: 19.0 %, 19.4 %). Although symptomatic patients placed significantly more importance on delaying an SSE (p < .05), no other preference differences were observed.

Conclusions

CRPC patients were more concerned about reduced quality of life from side effects of treatment rather than extension of survival, which may have implications for shared decision-making between patients and physicians.

Clusterin in the eye: An old dog with new tricks at the ocular surface

The multifunctional protein clusterin (CLU) was first described in 1983 as a secreted glycoprotein present in ram rete testis fluid that enhanced aggregation ('clustering') of a variety of cells in vitro. It was also independently discovered in a number of other systems. By the early 1990s, CLU was known under many names and its expression had been demonstrated throughout the body, including in the eye. Its homeostatic activities in proteostasis, cytoprotection, and anti-inflammation have been well documented, however its roles in health and disease are still not well understood. CLU is prominent at fluid-tissue interfaces, and in 1996 it was demonstrated to be the most highly expressed transcript in the human cornea, the protein product being localized to the apical layers of the mucosal epithelia of the cornea and conjunctiva. CLU protein is also present in human tears. Using a preclinical mouse model for desiccating stress that mimics human dry eye disease, the authors recently demonstrated that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration in the tears. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to LGALS3 (galectin-3), a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. CLU depletion from the ocular surface epithelia is seen in a variety of inflammatory conditions in humans and mice that lead to squamous metaplasia and a keratinized epithelium. This suggests that CLU might have a specific role in maintaining mucosal epithelial differentiation, an idea that can now be tested using the mouse model for desiccating stress. Most excitingly, the new findings suggest that CLU could serve as a novel biotherapeutic for dry eye disease.

Clusterin Seals the Ocular Surface Barrier in Mouse Dry Eye

Dry eye is a common disorder caused by inadequate hydration of the ocular surface that results in disruption of barrier function. The homeostatic protein clusterin (CLU) is prominent at fluid-tissue interfaces throughout the body. CLU levels are reduced at the ocular surface in human inflammatory disorders that manifest as severe dry eye, as well as in a preclinical mouse model for desiccating stress that mimics dry eye. Using this mouse model, we show here that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. These findings define a fundamentally new mechanism for ocular surface protection and suggest CLU as a biotherapeutic for dry eye.

Cullin-1 promotes cell proliferation via cell cycle regulation and is a novel in prostate cancer

BACKGROUND

There is no reliable marker available for early detection, diagnostic confirmation, or disease prognosis available of prostate cancer (PCa). We aimed to evaluate the function of Cullin-1 and unravel its underlying molecular mechanism to develop novel treatment options equivalent to PCa.

METHOD

We used immunohistochemistry to analyze the correlation between Cullin-1 expression and clinicopathologic variables and patient survival. The Cullin-1 level was tested in PCa cells. The role of regulation of Cullin-1 in PCa was applied in vitro and vivo. In addition, we further investigated the signaling pathway of Cullin-1 in prostate cancer cell proliferation.

RESULT

We first discovered that Cullin-1 expression was upregulated in human PCa tissues and inversely related with PCa differentiation. We then found that high expression of Cullin-1 protein suggested a poor prognosis in PCa patients. Also, Cullin-1 promotes PCa cell proliferation in vitro and tumor growth in vivo. We then found that the mechanism of Cullin-1 regulation on cell-cycle progression is due to increased expression of p21 and p27, and decreased expression of cyclin D1 and cyclin E after Cullin-1 knockdown.

CONCLUSION

Cullin-1 exerts multiple biological effects in the PCa cell line. Through promoting proliferation and by countering cisplatin-induced apoptosis, Cullin-1 has been deeply implicated in the pathogenesis and development of PCa.

Serum tri- and tetra-antennary N-glycan is a potential predictive biomarker for castration-resistant prostate cancer

BACKGROUND

The U.S. FDA has approved several novel systemic agents including abiraterone acetate and taxoid cabazitaxel for metastatic castration-resistant prostate cancer (CRPC) result in a complicated decision-making while selecting an appropriate treatment. Therefore, a predictive biomarker for CRPC would provide useful information to physicians. The aim of this study is to evaluate the diagnostic potential of serum N-glycan profiling in CRPC.

METHODS

Serum N-glycomics was performed in 80 healthy volunteers and 286 benign prostatic hyperplasia, 258 early-stage PC, 46 PC with androgen deprivation therapy (ADT), and 68 CRPC patients using the glycoblotting method. A total of 36 types of N-glycan levels in each patient were analyzed using logistic regression analysis and receiver operating characteristic curves. We also examined the expression of N-glycan branching enzyme genes in PC cell lines using quantitative RT-PCR.

RESULTS

We observed that tri- and tetra-antennary N-glycans were significantly higher in CRPC patients than in any other groups. The longitudinal follow-up of tri- and tetra- antennary N-glycan levels revealed that one PC with ADT patient showed an increase that was more than the cut-off level and two consecutive increases in tri- and tetra-antennary N-glycan levels 3 months apart; resulted in biochemical recurrence despite the castrate level of testosterone, and the patient was defined as CRPC. Expression of N-glycan branching enzyme genes were significantly upregulated in CRPC cell lines.

CONCLUSIONS

These results suggest that the overexpression of tri- and tetra-antennary N-glycan may be associated with the castration-resistant status in PC and may be a potential predictive biomarker for CRPC.

Understanding the mechanisms of androgen deprivation resistance in prostate cancer at the molecular level

CONTEXT

Various molecular mechanisms play a role in the development of resistance to androgen deprivation therapy in castration-resistant prostate cancer (CRPC).

OBJECTIVE

To understand the mechanisms and biological pathways associated with the progression of prostate cancer (PCa) under systemic androgen depletion or administration of the novel antiandrogens abiraterone, enzalutamide, and ARN-509. This review also examines the introduction of novel combinational approaches for patients with CRPC.

EVIDENCE ACQUISITION

PubMed was the data source. Keywords for the search were castrate resistant prostate cancer, abiraterone, enzalutamide resistance mechanisms, resistance to androgen deprivation, AR mutations, amplifications, splice variants, and AR alterations. Papers published before 1990 were excluded from the review, and only English-language papers were included.

EVIDENCE SYNTHESIS

This review summarizes the current literature regarding the mechanisms implicated in the development of CRPC and the acquisition of resistance to novel antiandrogen axis agents. The review focuses on androgen biosynthesis in the tumor microenvironment, androgen receptor (AR) alterations and post-transcriptional modifications, the role of glucocorticoid receptor, and alternative oncogenic signaling that is derepressed on maximum AR inhibition and thus promotes cancer survival and progression.

CONCLUSIONS

The mechanisms implicated in the development of resistance to AR inhibition in PCa are multiple and complex, involving virtually all classes of genomic alteration and leading to a host of selective/adaptive responses. Combinational therapeutic approaches targeting both AR signaling and alternative oncogenic pathways may be reasonable for patients with CRPC.

PATIENT SUMMARY

We looked for mechanisms related to the progression of PCa in patients undergoing hormonal therapy and treatment with novel drugs targeting the AR. Based on recent data, combining maximal AR inhibition with novel agents targeting other tumor-compensatory, non-AR-related pathways may improve the survival and quality of life of patients with castration-resistant PCa.

From bench to bedside: immunotherapy for prostate cancer

The mainstay therapeutic strategy for metastatic castrate-resistant prostate cancer (CRPC) continues to be androgen deprivation therapy usually in combination with chemotherapy or androgen receptor targeting therapy in either sequence, or recently approved novel agents such as Radium 223. However, immunotherapy has also emerged as an option for the treatment of this disease following the approval of sipuleucel-T by the FDA in 2010. Immunotherapy is a rational approach for prostate cancer based on a body of evidence suggesting these cancers are inherently immunogenic and, most importantly, that immunological interventions can induce protective antitumour responses. Various forms of immunotherapy are currently being explored clinically, with the most common being cancer vaccines (dendritic-cell, viral, and whole tumour cell-based) and immune checkpoint inhibition. This review will discuss recent clinical developments of immune-based therapies for prostate cancer that have reached the phase III clinical trial stage. A perspective of how immunotherapy could be best employed within current treatment regimes to achieve most clinical benefits is also provided.

The many faces of neuroendocrine differentiation in prostate cancer progression

In normal prostate, neuroendocrine (NE) cells are rare and interspersed among the epithelium. These cells are believed to provide trophic signals to epithelial cell populations through the secretion of an abundance of neuropeptides that can diffuse to influence surrounding cells. In the setting of prostate cancer (PC), NE cells can also stimulate surrounding prostate adenocarcinoma cell growth, but in some cases adenocarcinoma cells themselves acquire NE characteristics. This epithelial plasticity is associated with decreased androgen receptor (AR) signaling and the accumulation of neuronal and stem cell characteristics. Transformation to an NE phenotype is one proposed mechanism of resistance to contemporary AR-targeted treatments, is associated with poor prognosis, and thought to represent up to 25% of lethal PCs. Importantly, the advent of high-throughput technologies has started to provide clues for understanding the complex molecular profiles of tumors exhibiting NE differentiation. Here, we discuss these recent advances, the multifaceted manner by which an NE-like state may arise during the different stages of disease progression, and the potential benefit of this knowledge for the management of patients with advanced PC.

The hurdle of antiandrogen drug resistance: drug design strategies

INTRODUCTION

Prostate cancer is the second most common cancer death in men after lung cancer, due to distant metastases. While distant prostate cancer is typically castrate resistant, it is not necessarily androgen independent. For this reason, a review of the literature regarding the pathways involved in androgen signaling and therapeutic regimens to treat distant metastases is beneficial to increasing the survival rate of prostate cancer patients.

AREAS COVERED

In this article, the author reviews the literature from the past decade covering metastatic hormone refractory prostate cancer with the aim to examine and identify pathways, therapeutic targets and current therapies for treating castrate-resistant disease. As this area is lacking, the author aims to provide the reader with knowledge of the molecular consequences of castrate resistant prostate cancer, the current treatment paradigms and future directions.

EXPERT OPINION

While there have been advances in the treatment of castrate resistant prostate cancer, only minimal advances have been made in overall survival rate. Due to aberrant mutations and activation in the androgen receptor gene, and the complexity of cell signaling within prostate cancer, the androgen receptor should remain a main target for drug discovery efforts. This author believes that designing compounds that will reduce the activation of the androgen receptor may hold the key to a cure in the future.

Combination of the PI3K inhibitor ZSTK474 with a PSMA-targeted immunotoxin accelerates apoptosis and regression of prostate cancer

The phosphoinositide 3-kinase (PI3K) pathway is activated in most advanced prostate cancers, yet so far treatments with PI3K inhibitors have been at best tumorostatic in preclinical cancer models and do not show significant antitumor efficacy in clinical trials. Results from tissue culture experiments in prostate cancer cells suggest that PI3K inhibitors should be combined with other cytotoxic agents; however, the general toxicity of such combinations prevents translating these experimental data into preclinical and clinical models. We investigated the emerging concept of tumor-targeted synthetic lethality in prostate cancer cells by using the pan-PI3K inhibitor ZSTK474 and the immunotoxin J591PE, a protein chimera between the single-chain variable fragment of the monoclonal antibody J591 against the prostate-specific membrane antigen (PSMA) and the truncated form of the Pseudomonas aeruginosa exotoxin A (PE38QQR). The combination of ZSTK474 and J591PE increased apoptosis within 6 hours and cell death (monitored at 24-48 hours) in the PSMA-expressing cells LNCaP, C4-2, and C4-2Luc but not in control cells that do not express PSMA (PC3 and BT549 cells). Mechanistic analysis suggested that induction of apoptosis requires Bcl-2-associated death promoter (BAD) dephosphorylation and decreased expression of myeloid leukemia cell differentiation protein 1 (MCL-1). A single injection of ZSTK474 and J591PE into engrafted prostate cancer C4-2Luc cells led to consistent and stable reduction of luminescence within 6 days. These results suggest that the combination of a PI3K inhibitor and a PSMA-targeted protein synthesis inhibitor toxin represents a promising novel strategy for advanced prostate cancer therapy that should be further investigated.

Real-World Corticosteroid Utilization Patterns in Patients with Metastatic Castration-Resistant Prostate Cancer in 2 Large US Administrative Claims Databases

BACKGROUND

Prostate cancer is the most common noncutaneous malignancy in men in the United States. Patients with metastatic castration-resistant prostate cancer (mCRPC) may be treated with secondary hormonal therapy or with chemotherapy, and potentially with concomitant corticosteroids. Corticosteroids can help manage the side effects of chemotherapy and secondary hormonal therapy and ameliorate prostate cancer-related symptoms, although corticosteroids are also associated with adverse effects. With an increasing number of available treatment options for mCRPC, evaluating the real-world concomitant use of corticosteroids in this patient population is important.

OBJECTIVE

To evaluate the utilization patterns of corticosteroids for the treatment of patients with mCRPC based on real-world data from 2 large claim databases.

METHODS

This retrospective analysis included medical and pharmacy claims from 2 large publicly available healthcare claims databases covering more than 31 million individuals to identify treatment patterns in adult patients with mCRPC. A total of 2593 patients with mCRPC were identified in data set 1 and 626 patients in data set 2 between 2005 and 2011. The appropriate treatment for castration-resistant prostate cancer (CRPC) was defined as chemotherapy, an antiandrogen, an adrenal androgen blocker, or estrogen. The index date was the date of the first CRPC treatment or the first metastasis diagnosis, whichever occurred later. The observation period spanned from the index date to the end of health insurance eligibility. Study end points included population characteristics, the distribution of mCRPC therapies, and corticosteroid utilization patterns.

RESULTS

The study population came from the 2 data sets and included 3219 men who were treated for mCRPC. Bone and lymph nodes were the predominant metastatic sites. Bicalutamide was the most common secondary hormonal therapy, and docetaxel was the most common chemotherapy used for these patients. Overall, 73.4% of the patients in data set 1 received concomitant corticosteroids, as did 71.6% of patients in population 2 during the entire period from the index date to the end of eligibility date. In addition, 62.8% and 60.4% of patients, respectively, received concomitant corticosteroids during the secondary hormonal therapy period, and 93.8% and 95.1% of patients, respectively, received concomitant corticosteroids during the chemotherapy period. Similar patterns of corticosteroid use were observed across geographic areas of the United States.

CONCLUSION

This study shows consistently similar utilization patterns of corticosteroids in patients with mCRPC in 2 large national databases. Using real-world data to inform concomitant corticosteroid use in the treatment of patients with mCRPC may assist healthcare providers with treatment selection and with sequencing decision. Future research is warranted to investigate evolving treatment options for patients with mCRPC.