Prognostic Value of Androgen Receptor Splice Variant 7 in the Treatment of Castration-resistant Prostate Cancer with Next generation Androgen Receptor Signal Inhibition: A Systematic Review and Meta-analysis

Dissecting the Significance of Acid Phosphatase 1 Gene Alterations in Prostate Cancer

PURPOSE

The acid phosphatase 1 (ACP1) gene encodes low-molecular-weight protein tyrosine phosphatase, which is overexpressed in prostate cancer (PC) and a potential therapeutic target. We analyzed ACP1 expression in primary/metastatic PC and its association with molecular profiles and clinical outcomes.

METHODS

NextGen sequencing of DNA (592-gene/whole-exome sequencing)/RNA(whole-transcriptome sequencing) was performed for 5,028 specimens. ACP1-High/ACP1-Low expression was defined as quartile (Q4/1) of RNA transcripts per million (TPM). DNA mutational profiles were analyzed for ACP1-quartile-stratified samples. Gene set enrichment analysis was used for Hallmark collection of pathways. PD-L1+(≥2+, ≥5%; SP142) was tested by immunohistochemistry. Tumor microenvironment's (TME) immune cell fractions were estimated by RNA deconvolution/quanTIseq. Overall survival (OS) was assessed from initial diagnosis/treatment initiation to death/last follow-up.

RESULTS

We included 3,058 (60.8%) samples from the prostate, 634 (12.6%) from lymph node metastases (LNMs), and 1,307 (26.0%) from distant metastases (DMs). ACP1 expression was higher in LNM/DM than prostate (49.8/47.9 v 44.1 TPM; P < .0001). TP53 mutations were enriched in ACP1-Q4 (37.9%[Q4] v 27.0%[Q1]; P < .001) among prostate samples. Pathways associated with cell cycle regulation and oxidative phosphorylation were enriched in ACP1-Q4, whereas epithelial-mesenchymal transition and tumor necrosis factor-alpha signaling via nuclear factor kappa-light-chain-enhancer of activated B-cell pathways were enriched in ACP1-Q1. Neuroendocrine and androgen receptor signaling was increased in ACP1-Q4. M2 macrophages and natural killer cell fractions were increased, whereas T cells and M1 macrophages were decreased in ACP1-Q4. While OS differences between ACP1-Q1/Q4 were not statistically significant, there was a trend for worse OS among ACP1-Q4 prostate samples (Q4 v Q1: hazard ratio [HR], 1.19 [95% CI, 0.99 to 1.42]; P = .06) and DM (HR, 1.12 [95% CI, 0.93 to 1.36]; P = .22) but not LNM (HR, 0.98 [95% CI, 0.74 to 1.29]; P = .87).

CONCLUSION

ACP1-High tumors exhibit a distinct molecular profile and cold TME, highlighting ACP1's potential role in PC pathogenesis and novel therapeutic targeting.

CD44 and CD133 protein expression might serve as a prognostic factor for early occurrence castration-resistant prostate cancer

BACKGROUND

The occurrence of castration-resistant prostate cancer (CRPC) varies in patients with advanced prostate cancer (PCa) undergoing androgen deprivation therapy (ADT). The rate of occurrence of CRPC may be related to the presence of prostate cancer stem cells (CSC). Thus, this study aims to evaluate the presence of CSC markers (CD44 and CD133) in histopathology tissue at the time of diagnosis and their correlation with the occurrence of CRPC in patients with advanced PCa within 2 years of ADT.

METHOD

A retrospective case-control study was conducted to evaluate the incidence of CRPC within 2 years. The inclusion criteria were patients with PCa who had received treatment with ADT and a first-generation anti-androgen (AA) for 2 years. We classified patients based on whether they developed CRPC within 2 years (CRPC) of the therapy or did not experience CRPC within 2 years (non-CRPC) of the therapy. We performed immunohistochemical (IHC) staining for CD44 and CD133 on the prostate biopsy tissue samples.

RESULTS

Data were collected from records spanning 2011-2019. We analyzed a total of 65 samples, including 22 patients with CRPC and 43 patients with non-CRPC who had received treatment with LHRH agonists and AA for up to 2 years. Our findings showed a significant H-score difference in CD44 protein expression between CRPC prostate adenocarcinoma samples 869 (200-1329) and non-CRPC 524 (154-1166) (p = 0.033). There was no significant difference in CD133 protein expression between the two groups (p = 0.554). However, there was a significant difference in the nonoccurrence of CRPC between the high expressions of both CD44 and CD133 groups with other expressions of CD44/CD133 groups (25% vs. 75%; p = 0.011; odds ratio = 4.29; 95% confidence interval [1.34, 13.76]).

CONCLUSION

This study found a low expression of at least one CD44/CD133 protein in the patients without early occurrence of CRPC. This result might suggest that CD44/CD133 may function as a potential prognostic marker for PCa, especially in a low expression, to identify patients who have a better prognosis regarding the occurrence of early CRPC.

Natural course of metastatic castration-resistant prostate cancer in the era of intensified androgen deprivation therapy in the hormone-sensitive setting

BACKGROUND

Androgen deprivation therapy (ADT) intensification (ADTi) (i.e., ADT with androgen receptor pathway inhibitor or docetaxel, or both) has significantly improved survival outcomes of patients with metastatic hormone-sensitive prostate cancer (mHSPC). However, the impact of prior ADTi in the mHSPC setting on the disease presentation and survival outcomes in metastatic castration-resistant prostate cancer (mCRPC) is not well characterized. In this study, our objective was to compare the disease characteristics and survival outcomes of patients with new mCRPC with respect to receipt of intensified or nonintensified ADT in the mHSPC setting.

METHODS

In this institutional review board-approved retrospective study, eligibility criteria were as follows: patients diagnosed with mCRPC, treated with an approved first-line mCRPC therapy, and who received either intensified or nonintensified ADT in the mHSPC setting. Progression-free survival (PFS) was defined from the start of first-line therapy for mCRPC to progression per Prostate Cancer Working Group 2 criteria or death, and overall survival (OS) was defined from the start of first-line therapy for mCRPC to death or censored at the last follow-up. A multivariable analysis using the Cox proportional hazards model was used, adjusting for potential confounders.

RESULTS

Patients (n = 387) treated between March 20, 2008, and August 18, 2022, were eligible and included: 283 received nonintensified ADT, whereas 104 were treated with ADTi. At mCRPC diagnosis, patients in the ADTi group were significantly younger, had more visceral metastasis, lower baseline prostate-specific antigen (all p < 0.01), and lower hemoglobin (p = 0.027). Furthermore, they had significantly shorter PFS (median 4.8 vs. 8.4 months, adjusted hazard ratio [HR]: 1.46, 95% confidence interval [95% CI]: 1.07-2, p = 0.017) and OS (median 21.3 vs. 33.1 months, adjusted HR: 1.53, 95% CI: 1.06-2.21, p = 0.022) compared to patients in the nonintensified ADT group.

CONCLUSION

Patients treated with ADTi in the mHSPC setting and experiencing disease progression to mCRPC had more aggressive disease features of mCRPC (characterized by a higher number of poor prognostic factors at mCRPC presentation). They also had shorter PFS on first-line mCRPC treatment and shorter OS after the onset of mCRPC compared to those not receiving ADTi in the mHSPC setting. Upon external validation, these findings may impact patient counseling, prognostication, treatment selection, and design of future clinical trials in the mCRPC setting. There remains an unmet need to develop novel life-prolonging therapies with new mechanisms of action to improve mCRPC prognosis in the current era.

Androgen Receptor Upregulates Mucosa-Associated Lymphoid Tissue 1 to Induce NF-κB Activity via Androgen-Dependent and -Independent Pathways in Prostate Carcinoma Cells

The androgen-dependent or -independent pathways are regarded as primary therapeutic targets for the neoplasm of the prostate. Mucosa-associated lymphoid tissue 1 (MALT1) acting as a paracaspase in the regulation of nuclear factor κB (NF-κB) signal transduction plays a central role in inflammation and oncogenesis in cancers. This study confirmed the potential linkages between androgen and NF-κB activation by inducing MALT1 in the androgen receptor-full length (ARFL)-positive LNCaP and 22Rv1 prostate cancer cells. Although androgen did not stimulate MALT1 expression in AR-null or ectopic ARFL-overexpressed PC-3 cells, the ectopic overexpression of the AR splicing variant 7 (ARv7) upregulated MALT1 to activate NF-κB activities in 22Rv1 and PC-3 cells. Since the nuclear translocation of p50 and p65 was facilitated by ARv7 to motivate NF-κB activity, the expressions of MALT1, prostate-specific antigen (PSA), and N-myc downstream regulated 1 (NDRG1) were therefore induced in ectopic ARv7-overexpressed prostate cancer cells. Ectopic ARv7 overexpression not only enhanced 22Rv1 or PC-3 cell growth and invasion in vitro but also the tumor growth of PC-3 cells in vivo. These results indicate that an androgen receptor induces MALT1 expression androgen-dependently and -independently in ARFL- or ARv7-overexpressed prostate cancer cells, suggesting a novel ARv7/MALT1/NF-κB-signaling pathway may exist in the cells of prostate cancer.

The STAT3 inhibitor GPB730 enhances the sensitivity to enzalutamide in prostate cancer cells

Enzalutamide is a second-generation anti-androgen which has shown increased survival in patients with metastatic prostate cancer. However, some patients do not respond to this therapy or will develop resistance to treatment over time. Signal Transducer and Activator of Transcription 3 (STAT3) is known to be involved in castration-resistant prostate cancer and to interact with androgen receptor (AR)-signaling. This study aims to investigate the combination enzalutamide and the small molecule STAT3 inhibitor GPB730 for enhanced therapeutic effect in advanced prostate cancer in vitro. The prostate cancer cell lines LNCaP (androgen dependent) and C4-2 (androgen insensitive) were used. The effect of enzalutamide and GPB730, alone and in combination, was investigated on viability and IC₅₀ values calculated. Enzalutamide and GPB730 treated LNCaP and C4-2 cells were subjected to western blot and QPCR analyses in order to investigate the expression of AR, STAT3 and down-stream targets. C4-2 were less sensitive to growth inhibition by enzalutamide than LNCaP cells. GPB730 enhanced the growth inhibitory effect of enzalutamide in LNCaP and C4-2 cells. The addition of GPB730 to enzalutamide decreased the IC₅₀ values for enzalutamide by 3.3-fold for LNCaP and by 12-fold for C4-2. In C4-2 cells, GPB730 alone decreased PSA expression and enhanced the enzalutamide induced decrease in NKX3.1 expression. GPB730 and enzalutamide in combination enhanced inhibition of c-myc and survivin expression. This study suggests that enzalutamide may be combined with the STAT3 inhibitor GPB730 in order to enhance the efficacy of enzalutamide, offering a new therapeutic approach in advanced prostate cancer.

Clinicopathological characteristics of androgen receptor splicing variant 7 (AR-V7) expression in patients with castration resistant prostate cancer: A systematic review and meta-analysis

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Studies have shown that AR-V7 may be correlated with the poor prognosis of castration resistant prostate cancer (CRPC), however, clinicopathological characteristics of AR-V7 have not been fully elucidated.

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We enrolled 24 studies with 2307 eligible patients for a systemic review and meta-analysis.

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AR-V7 positivity was associated with higher Gleason score, bone or any site metastasis, presence of pain and worse ECOG performance score in CRPC.

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Therefore, AR-V7 positivity may be a particular type of prostate cancer subtype in CRPC.

Background

 Studies have shown that AR-V7 may be correlated with the poor prognosis of castration resistant prostate cancer (CRPC), however, clinicopathological characteristics of AR-V7 have not been fully elucidated.

Objective

This study aimed at evaluating the clinicopathological features of AR-V7 in CRPC patients.

Materials and methods

To evaluate the clinicopathological features of AR-V7 in CRPC patients. A search of PubMed, Embase, and Web of Science was performed using the keywords prostate cancer, prostate tumor, prostate neoplasm, prostate carcinoma, AR-V7, AR3, androgen receptor splicing variant-7, or androgen receptor-3. Twenty-four trials published by February 2020 were included in this study.

Results

The proportion of Gleason score ≥ 8 was found to be significantly higher in AR-V7-positive CRPC (69.5%) than negative (54.9%) (OR 1.68, 95% CI 1.25–2.25, p < 0.001), while the rates of T3/T4 stage (OR 1.16, 95% CI 0.60–2.24, p = 0.65) and N1 stage (OR 0.99, 95% CI 0.65–1.51, p = 0.96) were not statistically correlated with AR-V7 status. The AR-V7-positive patients exhibited a significantly higher proportion of any site metastasis (61.3% versus 35.0%; OR 2.19, 95% CI 1.57–3.05, p < 0.001) and bone metastasis (81.7% versus 69.0%; OR 1.97, 95% CI 1.44–2.69, p < 0.001), and a trend close to significance was expected in visceral metastasis (28.8% versus 22.1%; OR 1.29, 95% CI 0.96–1.74, p = 0.09). Incidences of pain in AR-V7-positive CRPC (54.6%) were significantly higher than in negative CRPC (28.1%; OR 4.23, 95% CI 2.52–7.10, p < 0.001), line with worse ECOG performance status (56.7% versus 35.0%, OR 2.18, 95% CI 1.51–3.16, P < 0.001). Limitations of the study include differences in sample sizes and designs, AR-V7 detection assays, as well as disease characteristics of the included studies.

Conclusions

AR-V7 positivity is associated with a higher Gleason score, bone or any site metastasis, pain and worse ECOG performance scores in CRPC. However, it is not correlated with tumor stage or lymph node metastasis. More studies are needed to confirm these findings.

AR-V7 in Metastatic Prostate Cancer: A Strategy beyond Redemption

Metastatic prostate cancer is the most common cancer in males and the fifth cause of cancer mortality worldwide. Despite the major progress in this field, leading to the approval of novel anti-androgens, the prognosis is still poor. A significant number of patients acquire an androgen receptor splice variant 7 (AR-V7), which is constitutively activated and lacks the ligand-binding domain (LBD) while maintaining the nuclear localization signal and DNA-binding domain (DBD). This conformational change, even in the absence of the ligand, allows its retention within the nucleus, where it acts as a transcription factor repressing crucial tumor suppressor genes. AR-V7 is an important oncogenic driver and plays a role as an early diagnostic and prognostic marker, as well as a therapeutic target for antagonists such as niclosamide and TAS3681. Anti-AR-V7 drugs have shown promise in recent clinical investigations on this subset of patients. This mini-review focuses on the relevance of AR-V7 in the clinical manifestations of castration-resistant prostate cancer (CRPC) and summarizes redemptive therapeutic strategies.

Neoisoliquiritin exerts tumor suppressive effects on prostate cancer by repressing androgen receptor activity

BACKGROUND

Prostate cancer (PCa) is a major cause of morbidity and mortality in men in both developed and developing countries. Androgens and the androgen receptor (AR) play predominant roles in the progression of PCa. Neoisoliquiritin (NEO) belongs to the class of licorice (Glycyrrhiza) flavonoids, which have a variety of biological activities including anti-depressant, anti-tumor-promoting, and anti-inflammation properties. Licorice root has cancer chemopreventive effects and has been given to PCa patients as an ingredient of PC-SPES, a commercially available combination of eight herbs. Therefore, we determined if NEO can suppress the proliferation of PCa cells.

PURPOSE

We investigated whether and how NEO exerts its anti-neoplastic activity against PCa.

METHODS

The Cell Counting Kit 8 and flow cytometry were used to evaluate the effects of NEO on the proliferation and cell cycle progression of AR-dependent (LNCaP) and AR-independent (PC3) PCa cells. RNA sequencing was employed to examine the genome-wide changes in responsiveness to NEO in LNCaP cells. Quantitative PCR, Western blotting, docking, chromatin immunoprecipitation, and dual-luciferase reporter assays were conducted to determine the mechanism of action of NEO and its potential cross-talk with AR. A LNCaP xenograft nude mouse model was used to determine the inhibitory effects of NEO on AR-dependent PCa tumors in vivo.

RESULTS

NEO inhibited LNCaP cell proliferation in vitro by inducing G0/G1 phase cell cycle arrest. Conversely, NEO treatment had no effect on PC3 cells. Transcriptomic analysis indicated that AR signaling might be the key target of NEO in preventing PCa. NEO regulated AR-mediated cell growth suppression and AR-sensitized cell cycle arrest in LNCaP cells. NEO also blocked several key steps in the AR signaling pathway, including proposed targeting to the ligand binding pocket of AR by computer modeling, modulating AR-androgen response element DNA-binding activity, inhibiting the expression and transcriptional activity of AR, and suppressing downstream AR signaling.

CONCLUSIONS

NEO negatively regulates AR expression and activity, thus supporting the tumor suppressive role for NEO in AR-dependent PCa.

Hong Kong Urological Association-Hong Kong Society of Uro-Oncology consensus statements on the management of advanced prostate cancer-2019 Updates

BACKGROUND

To update the Hong Kong Urological Association-Hong Kong Society of Uro-Oncology consensus statements on the management of advanced prostate cancer, the same panelists as in the previous consensus panel held a series of meetings to discuss updated clinical evidence and experiences.

METHODS

The previous consensus statements were retained, deleted, or revised, and new statements were added. At the final meeting, all statements were reviewed and amended as appropriate, followed by panel voting.

RESULTS

There were significant changes and additions to the previous consensus statements, primarily driven by the advances in androgen receptor signaling inhibitors, treatment sequencing in metastatic castration-resistant prostate cancer, and increasing recognition of oligometastatic prostate cancer since the introduction of prostate-specific membrane antigen positron emission tomography. In this update, a total of 59 consensus statements were accepted and established.

CONCLUSIONS

The consensus panel updated consensus statements on the management of advanced prostate cancer, aiming to allow physicians in the region to keep abreast of the recent evidence on optimal clinical practices.

The Prognostic Value of Androgen Receptor Splice Variant 7 in Castration-Resistant Prostate Cancer Treated With Novel Hormonal Therapy or Chemotherapy: A Systematic Review and Meta-analysis

Purpose

This study aimed to evaluate the prognostic role of AR-V7 in terms of prostate-specific antigen (PSA) response, progression-free survival (PFS), and overall survival (OS) in CRPC patients treated with novel hormonal therapy (NHT) (Abiraterone and Enzalutamide) or taxane-based chemotherapy (Docetaxel and Cabazitaxel).

Methods

A comprehensive literature search was conducted on PubMed, Embase, and the Web of Science from inception to February 2020. Studies focusing on the prognostic values of AR-V7 in CRPC patients treated with NHT or chemotherapy were included in our meta-analysis. The OS and PFS were analyzed based on Hazard ratios (HRs) and 95% confidence intervals (CIs). Furthermore, Odds ratios (ORs) and 95% CIs were summarized for the AR-V7 conversion after treatment and the PSA response.

Results

The AR-V7 positive proportion increased significantly after NHT treatment (OR 2.56, 95% CI 1.51–4.32, P<0.001), however, it declined after chemotherapy (OR 0.51, 95% CI 0.28–0.93, P=0.003). AR-V7-positive patients showed a significantly decreased PSA response rate after NHT (OR 0.13, 95% CI 0.09–0.19, P<0.001) but not statistically significant for chemotherapy (OR 0.63, 95% CI 0.40-1.01, P=0.06). Notably, PFS (HR 3.56, 95% CI 2.53–5.01, P<0.001) and OS (HR 4.47, 95% CI 3.03–6.59, P<0.001) were worse in AR-V7-positive ttreated with NHT. Similarly, AR-V7 positivity correlated with poor prognosis after chemotherapy as evidenced by shorter OS (HR 1.98, 95% CI 1.48-2.66, P<0.001) and a significantly shorter PFS (HR 1.35, 95% CI 0.97-1.87, P=0.07).

Conclusion

NHT treatment increased AR-V7 positive proportion whereas chemotherapy decreased it. Moreover, AR-V7 positivity correlated with lower PSA response, poorer PFS, and OS in CRPC treated with NHT, and shorter OS in patients receiving chemotherapy.

A Systematic Review and Meta-Analysis on the Predictive Value of Cell-Free DNA–Based Androgen Receptor Copy Number Gain in Patients With Castration-Resistant Prostate Cancer

PURPOSE

It has been suggested that androgen receptor copy number gain ( AR gain) detected in cell-free DNA (cfDNA) can predict treatment response to androgen receptor signaling inhibitors (ARSIs) in patients with castration-resistant prostate cancer (CRPC). But it is unclear whether cfDNA-based AR gain is a true resistance mechanism to ARSIs or mainly a reflection of the tumor burden. In this systematic review, we aim to summarize current literature and comment on the potential of cfDNA-based AR gain as a predictive biomarker to guide therapy choices.

METHODS

A literature search was conducted in PubMed/Medline, Cochrane, Embase, and Web of Science databases. Sixteen articles published before November 2019 were selected for the meta-analysis, representing more than 1,000 patients. By using a random effects model, the progression-free survival (PFS) and overall survival (OS) were compared between patients with and without cfDNA-based AR gain who had been treated with ARSIs or with taxane chemotherapy.

RESULTS

Upon treatment with ARSIs, the PFS (hazard ratio [HR], 2.33; 95% CI, 2.00 to 2.72; P < .0001) and the OS (HR, 3.83; 95% CI, 3.11 to 4.70; P < .0001) were worse for patients with cfDNA-based AR gain, independent of the line and type of ARSIs. The OS and PFS in patients treated with first-line docetaxel or second-line or third-line cabazitaxel seemed to be unaffected by AR gain, despite a higher disease burden in patients with AR gain. AR gain was associated with reduced response with later lines of docetaxel.

CONCLUSION

In patients with CRPC, cfDNA-based AR gain is associated with a worse response to ARSIs. The effect on patients who are receiving taxane chemotherapy seems to be dependent on the type and line, although data are limited. Future prospective studies are essential to assess the true potential of cfDNA-based AR gain as a minimally invasive biomarker to guide therapy choice.

AR-V7 as a Biomarker for Resistance to Treatment with Abiraterone/Enzalutamide in Three Latin American Countries: A Hypothetical Cost-Saving Analysis

BACKGROUND

Prostate cancer is the most incident and one of the deadliest male cancers in Latin America. Treatment for patients with metastatic castration-resistant prostate cancer (mCRPC) includes androgen receptor signaling inhibitors such as abiraterone and enzalutamide, for which androgen receptor splice variant 7 (AR-V7) has emerged as a biomarker for primary resistance. Our study sought to analyze the potential economic impact of the use of AR-V7 detection as a treatment indicator in patients with mCRPC in three Latin American countries.

MATERIALS AND METHODS

A hypothetical cost prediction model for the use of noninvasive circulating tumor cell-based AR-V7 testing as a treatment indicator for patients eligible for treatment with abiraterone/enzalutamide was conducted using available information on treatment and testing costs from Mexico, Argentina, and Colombia.

RESULTS

At an estimated prevalence of AR-V7 positivity of 20%, the use of upfront AR-V7 genetic testing resulted in annual net savings of $9,801,669.97, $6,390,055.75, and $3,096,780.91 in Mexico, Argentina, and Colombia, respectively. A direct relationship between AR-V7 positivity prevalence and net savings was found.

CONCLUSION

The use of a noninvasive AR-V7 detection assay as a treatment indicator tool in patients eligible for treatment with abiraterone or enzalutamide in Latin America could be a cost-effective approach for the management of these patients. Additional efforts are needed to accurately determine the incidence of castration-resistant prostate cancer cases and the prevalence of AR-V7 positivity in Latin America in order to predict the potential economic benefit of its clinical use.

IMPLICATIONS FOR PRACTICE

In Latin America, prostate cancer is the most frequently diagnosed cancer in men, and the burden of this disease is expected to double in this region by 2030. Noninvasive detection of androgen receptor splice variant 7 (AR-V7) is being currently validated as a predictive biomarker for benefit with androgen receptor signaling inhibitor therapy in patients with metastatic castration-resistant prostate cancer (mCRPC). This hypothetical cost-saving analysis shows that AR-V7 testing in peripheral blood of patients with CRPC eligible for treatment with abiraterone or enzalutamide might represent a cost-effective strategy to select patients who will benefit from AR-axis-directed treatment in three Latin American countries.

Combination therapy with androgen receptor N-terminal domain antagonist EPI-7170 and enzalutamide yields synergistic activity in AR-V7-positive prostate cancer

Resistance of castration-resistant prostate cancer (CRPC) to enzalutamide and abiraterone involves the expression of constitutively active, truncated androgen receptor (AR) splice variants (AR-Vs) that lack a C-terminal ligand-binding domain (LBD). Both full-length AR and truncated AR-Vs require a functional N-terminal domain (NTD) for transcriptional activity thereby providing rationale for the development of ralaniten (EPI-002) as a first-in-class antagonist of the AR-NTD. Here, we evaluated the antitumor effect of a next-generation analog of ralaniten (EPI-7170) as a monotherapy or in combination with enzalutamide in prostate cancer cells that express AR-V7 that were resistant to enzalutamide. EPI-7170 had 8-9 times improved potency compared to ralaniten. Enzalutamide increased levels of AR-V7 and expression of its target genes. Knockdown of AR-V7 restored sensitivity to enzalutamide, indicating a role for AR-V7 in the mechanism of resistance. EPI-7170 inhibited expression of genes transcriptionally regulated by full-length AR and AR-V7. A combination of EPI-7170 and enzalutamide resulted in synergistic inhibition of proliferation of enzalutamide-resistant cells that was consistent with results from cell cycle and clonogenic assays. In addition, this drug enhanced the antitumor effect of enzalutamide in enzalutamide-resistant CRPC preclinical models. Thus, a combination therapy targeting both the NTD and LBD of AR, and thereby blocking both full-length AR and AR-Vs, has potential for the treatment of enzalutamide-resistant CRPC.

Combined Cell-free DNA and RNA Profiling of the Androgen Receptor: Clinical Utility of a Novel Multianalyte Liquid Biopsy Assay for Metastatic Prostate Cancer

BACKGROUND

The androgen receptor (AR) remains a critical driver in metastatic castration-resistant prostate cancer (mCRPC). Profiling AR aberrations in both circulating DNA and RNA may identify key predictive and/or prognostic biomarkers in the context of contemporary systemic therapy.

OBJECTIVE

To profile AR aberrations in circulating nucleic acids and correlate with clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS

We prospectively enrolled 67 mCRPC patients commencing AR pathway inhibitors (ARPIs; n = 41) or taxane chemotherapy (n = 26). Using a first-in-class next-generation sequencing-based assay, we performed integrated cell-free DNA (cfDNA) and cell-free RNA (cfRNA) profiling from a single 10 ml blood tube.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Kaplan-Meier survival estimates and multivariable Cox regression analyses were used to assess associations between clinical outcomes and the following AR aberrations: copy number variation, splice variants (AR-V7 and AR-V9) and somatic mutations.

RESULTS AND LIMITATIONS

Cell-free DNA and cfRNA were successfully sequenced in 67 (100%) and 59 (88%) patients, respectively. Thirty-six (54%) patients had one or more AR aberrations. AR gain and cumulative number of AR aberrations were independently associated with clinical/radiographic progression-free survival (PFS; hazard ratio [HR] 3.2, p = 0.01 and HR 3.0 for 0 vs ≥2, p = 0.04) and overall survival (HR 2.8, p = 0.04 and HR 2.9 for 0 vs ≥2, p = 0.03). Notably, concurrent AR gain and AR splice variant expression (AR gain/AR-V+) was associated with shorter prostate-specific antigen PFS on both ARPIs (HR 6.7, p = 0.009) and chemotherapy (HR 3.9, p = 0.04). Importantly, key findings were validated in an independent cohort of mCRPC patients (n = 40), including shorter OS in AR gain/AR-V+ disease (HR 3.3, p = 0.02). Limitations include sample size and follow-up period.

CONCLUSIONS

We demonstrate the utility of a novel, multianalyte liquid biopsy assay capable of simultaneously detecting AR alterations in cfDNA and cfRNA. Concurrent profiling of cfDNA and cfRNA may provide vital insights into disease biology and resistance mechanisms in mCRPC.

PATIENT SUMMARY

In this study of men with advanced prostate cancer, DNA and RNA abnormalities in the androgen receptor detected in blood were associated with poor outcomes on available drug treatments. This information could be used to better guide treatment of advanced prostate cancer.

The characteristics of androgen receptor splice variant 7 in the treatment of hormonal sensitive prostate cancer: a systematic review and meta-analysis

BACKGROUND

Accumulating evidence suggests androgen receptor splice variant 7 (AR-V7) may be associated with the prognosis of castration-resistant prostate cancer (CRPC) received novel hormonal therapy while its characteristic and prognosis value in hormonal sensitive prostate cancer is unclear.

METHODS

We aimed to evaluate the prognostic role of AR-V7 by progression free survival (PFS) and overall survival (OS) in hormonal sensitive prostate cancer (HSPC), and the AR-V7-positive-proportion difference in HSPC and CRPC. A search of PubMed, Embase, and the Web of Science was performed using the keywords prostate cancer, prostate tumor, prostate neoplasm, prostate carcinoma; AR-V7, AR3, androgen receptor splicing variant-7, or androgen receptor-3. Seventeen trials published due December 2019 were enrolled.

RESULTS

AR-V7-positive proportion in CRPC was significantly larger than newly diagnosed prostate cancer (PCa) (odds ratio [OR] 7.06, 95% confidence interval [CI] 2.52-19.83, P < 0.001). Subgroup analyses indicated significantly higher AR-V7-positive proportion in CRPC derived from RNA in situ hybridization (OR 65.23, 95% CI 1.34-3171.43, P = 0.04), exosome RNA (OR 3.88, 95% CI 0.98-15.39, P = 0.05) and tissue RNA (OR 10.89, 95% CI 4.13-28.73, P < 0.001). AR-V7-positive patients had a significantly shorter PFS than those who were AR-V7-negative treated with first-line hormonal therapy (hazard ratio [HR] 3.63, 95% CI 1.85-7.10, P < 0.001) and prostatectomy (HR 2.49, 95% CI 1.33-4.64, P = 0.004). OS (HR 5.59, 95% CI 2.89-10.80, P < 0.001) were better in AR-V7-negative than AR-V7-positive HSPC patients treated with first-line hormonal therapy. The limitations of our meta-analysis were differences in study sample size and design, AR-V7 detection assay, and disease characteristics.

CONCLUSION

AR-V7-positive proportion was significantly higher in CRPC than that in newly diagnosed PCa. AR-V7 positive HSPC patients portend worse prognosis of first-line hormonal therapy and prostatectomy. Additional studies are warranted to confirm these findings.

A candidate androgen signalling signature predictive of response to abiraterone acetate in men with metastatic castration-resistant prostate cancer

BACKGROUND

The unmet need for predictive biomarkers emerged from the unpredictable pattern of response to androgen signalling inhibition in metastatic castration-resistant prostate cancer (mCRPC). Here, we report on the testing of a previously identified candidate androgen signalling signature associated with response to androgen signalling inhibition.

PATIENTS AND METHODS

We report on the outcome of the first module of a phase II trial on abiraterone acetate (AA) followed by combination with dasatinib or sunitinib. Bone marrow biopsies (BMBs) with matched bone marrow aspirate and blood samples were collected at baseline and upon progression. End-points included assessment of a prespecified molecular signature consisting of nuclear androgen receptor (AR) overexpression, cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17) expression, and AR-C-/N terminal expression ratio of ≥0.8 by immunohistochemistry (IHC) in patients with benefit versus primary resistance to AA (i.e. progression within 4 months). Tumour markers also included v-ets avian erythroblastosis virus E26 oncogene homologue (ERG), androgen receptor splice variant (ARV7) by IHC and steroids by liquid chromatography-tandem mass spectrometry.

RESULTS

Of 170 patients accrued from 03/2011 to 02/2015, 44 (26%) were primary resistant to AA. Forty-eight patients had tumour infiltrated BMB at baseline. Pretreatment androgen signalling signature was linked to benefit from AA (p < 0.001). Presence of ERG was associated with benefit (p = 0.05), whereas nuclear ARV7 presence and 20 or more bone lesions at baseline with primary resistance (p = 0.04 and p = 0.0006, respectively).

CONCLUSION

Testing of a prespecified androgen signalling signature was highly supportive of its predictive value in maximal androgen deprivation strategies in mCRPC. Further validation is under way.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01254864.

Androgen Receptor and Its Splicing Variant 7 Expression in Peripheral Blood Mononuclear Cells and in Circulating Tumor Cells in Metastatic Castration-Resistant Prostate Cancer

Androgen receptor (AR) signaling remains crucial in castration-resistant prostate cancer (CRPC). Since it is also essential in immune cells, we studied whether the expression of AR full-length (ARFL) and its splicing variant ARV7 in peripheral blood mononuclear cells (PBMC) predicts systemic treatment response in mCRPC in comparison with circulating-tumor cells (CTC). We measured ARFL and ARV7 mRNA in PBMC and CTC from patients prior to receiving abiraterone (AA), enzalutamide (E), or taxanes by a pre-amplification plus quantitative reverse-transcription PCR. They were also tested in LNCaP-ARV7-transfected and in 22RV1 docetaxel-resistant (22RV1DR) cells. We studied 171 PBMC from 136 patients and from 24 non-cancer controls, and 47 CTC from 22 patients. High PBMC ARV7 levels correlated with worse AA/E and better taxane response. In taxane-treated patients high PBMC ARFL also correlated with longer progression-free survival (PFS). High ARV7 and ARFL expression were independently associated with better biochemical-PFS. Conversely, high CTC ARV7 and ARFL correlated with shorter radiological-PFS and overall survival, respectively. High ARV7 in 22RV1DR and LNCaP-ARV7 cells correlated with taxane resistance. In conclusion, ARFL and ARV7 at PBMC or CTC have a different predictive role in the taxane response, suggesting a potential influence of the AR pathway from PBMC in such response modulation.

The Immune Checkpoint Regulator PDL1 is an Independent Prognostic Biomarker for Biochemical Recurrence in Prostate Cancer Patients Following Adjuvant Hormonal Therapy

Background: The programmed death 1 (PD1)/programmed death ligand 1 (PDL1) targeted therapies have gained positive outcomes in several tumors, but the evidence of the expression and prognosis value of PD1/PDL1 in high risk prostate cancer was rare.

Methods: Immunohistochemical analysis of PDL1/PD1 expression by a validated antibody was performed in a retrospectively collected high risk prostate cancer cohort who received adjuvant hormonal therapy (AHT) after radical prostatectomy (RP). The association between PDL1/PD1 expression and prognosis was determined.

Results: In total, 127 patients were enrolled. 49.6% patients were considered PDL1-high expression while the PD1-positive expression proportion was 24.4%. High PDL1 and negative PD1 expression were significantly associated with lower prostate specific antigen (PSA) density (p=0.010 and p=0.033, respectively). Compared with the PDL1-low expression patients, the PDL1-high expression patients had significantly shorter time to PSA nadir (TTN) (P=0.001) and biochemical recurrence (BCR) (P=0.004). In Kaplan-Meier analysis, the PDL1-high expression group (p<0.0001) and the PDL1-high/PD1-negative expression group (p<0.0001) showed markedly lower BCR-free survival in localized disease. Univariate cause-specific Cox proportional hazard regression model concluded total PSA (p=0.047), PDL1-high-expression (p<0.001), PDL1-high/PD1-negative expression (p<0.001) were significant risk factors of shorter progression time to BCR in localized disease. PDL1-high-expression was the independent predictor of time to BCR in multiple Cox regression of all patients (Hazard ratio [HR]: 3.901; 95% Confidence interval [CI]: 1.287-11.824; p=0.016).

Conclusions: PDL1 expression is not only highly prevalent in high-risk prostate cancer, but is also an independent biomarker in the prognosis of high-risk prostate cancer received AHT after RP. PDL1/PD1 targeted therapy might be a potentially adjuvant treatment option for high-risk prostate cancer after RP.

miR-103a-2-5p/miR-30c-1-3p inhibits the progression of prostate cancer resistance to androgen ablation therapy via targeting androgen receptor variant 7

Androgens and androgen receptors are vital factors involved in prostate cancer progression, and androgen ablation therapies are commonly used to treat advanced prostate cancer. However, the acquisition of androgen ablation therapy resistance remains a challenge. Recently, androgen receptor splicing variants lacking the ligand-binding domain have been reported to play a critical role in the acquisition of androgen ablation therapy resistance. In the present study, we revealed that the messenger RNA expression and the protein levels of an androgen receptor variant 7 (AR-V7) were higher in prostate cancer tissue samples and in the AR-positive prostate cancer cell line, VCaP. In contrast, microRNA (miR)-30c-1-3p/miR-103a-2-5p expression was significantly downregulated in tumor tissues and cells. miR-30c-1-3p/miR-103a-2-5p overexpression could inhibit AR-V7 expression, suppress VCaP cell growth, and inhibit AR-V7 downstream factor expression by directly targeting the 3'-untranslated region of AR-V7. Under enzalutamide (Enza) treatment, the effects of AR-V7 overexpression were the opposite of those of miR-103a-2-5p/miR-30c-1-3p overexpression; more importantly, the effects of miR-103a-2-5p/miR-30c-1-3p overexpression could be significantly reversed by AR-V7 overexpression under Enza. In summary, we demonstrated a novel mechanism of the miR-30c-1-3p/miR-103a-2-5p/AR-V7 axis modulating the cell proliferation of AR-positive prostate cancer cells via AR downstream targets. The clinical application of miR-30c-1-3p/miR-103a-2-5p needs further in vivo validation.

Splicing Factors Have an Essential Role in Prostate Cancer Progression and Androgen Receptor Signaling

Although inhibition of the androgen–androgen receptor (AR) axis effectively represses the growth of prostate cancer, most of all cases eventually become castration-resistant prostate cancers (CRPCs). Enhancement of the expression of AR and its variants along with the downstream signals is important for disease progression. AR-V7, a constitutive active form of AR, is generated as a result of RNA splicing. RNA splicing creates multiple transcript variants from one pre-messenger RNA (mRNA) by removing introns/exons to allow mRNA translation. The molecular mechanisms leading to marked increases of AR and generation of AR-V7 have been unclear. However, recent papers highlighted the roles of RNA splicing factors which promote AR expression and production of variants. Notably, a broad range of splicing components were aberrantly regulated in CRPC tissues. Interestingly, expression of various spliceosome genes is enhanced by RNA-binding protein splicing factor proline- and glutamine-rich (PSF/SFPQ), leading to changes in the expression of AR transcript variants. Moreover, inhibition of several splicing factors repressed tumor growth in vivo. Altered expression of splicing factors is correlated to biochemical recurrence in prostate cancer patients. Thus, these findings suggest that splicing factors would be a potential therapeutic target. This review focuses on the emerging roles of splicing factors in prostate cancer progression and AR signaling.

New Opportunities for Targeting the Androgen Receptor in Prostate Cancer

Recent genomic analyses of metastatic prostate cancer have provided important insight into adaptive changes in androgen receptor (AR) signaling that underpin resistance to androgen deprivation therapies. Novel strategies are required to circumvent these AR-mediated resistance mechanisms and thereby improve prostate cancer survival. In this review, we present a summary of AR structure and function and discuss mechanisms of AR-mediated therapy resistance that represent important areas of focus for the development of new therapies.

Nuclear loss and cytoplasmic expression of androgen receptor in penile carcinomas: role as a driver event and as a prognosis factor

Androgen receptor (AR) is a member of the steroid and nuclear family receptor that acts as transcription factor. AR signaling plays pivotal role in the development and progression of prostate cancer. However, the role of AR in penile cancer (PeCa) is poorly explored. Our previous molecular studies unveiled frequent AR mRNA loss in PeCa, which was further predicted as a major driver alteration in this neoplasm. Herein, we assessed the AR protein expression in 59 usual PeCa tissues and 42 surrounding normal tissues (SNT) by immunohistochemistry using a tissue microarray. In a paired analysis, we found a total absence of nuclear AR expression in PeCa while 95.2% of SNT samples presented strong nuclear AR expression (P < 0.001). Interestingly, 17 of 42 PeCa presented weak or moderate cytoplasmic AR staining, contrasting with 5 of 42 SNT (P = 0.008). Increased levels of AR cytoplasmic expression were related with poor prognosis features including advanced clinical staging (P = 0.044), compromised surgical margins (P = 0.005), and pathological inguinal node status (P = 0.047). Furthermore, AR cytoplasmic expression was also related with shorter overall survival (P = 0.032). In conclusion, the frequent loss of nuclear AR protein levels suggests a potential function in PeCa development. Based on this result, the androgen deprivation therapy is not indicated for PeCa patients. In addition, the AR cytoplasmic expression found in a significant number of cases (40.5%) showed prognostic value and pathways activated by the non-genomic AR signaling may represent a promising therapeutic strategy.

Inhibition of autophagy significantly increases the antitumor effect of Abiraterone in prostate cancer

PURPOSE

Abiraterone acetate (AA) plus prednisone is an approved treatment of advanced prostate cancer (PCa). Autophagy is linked to drug resistance in numerous types of cancers. We hypothesized, that upregulation of autophagy is one of the mechanisms by which PCa cells survive AA anti-tumor treatment and therefore evaluated the potential effect of a combination with autophagy inhibition.

METHODS

Human PCa LNCaP cell lines were cultured in steroid-free medium and treated with AA. Autophagy was inhibited by 3-methyladenine, chloroquine and ATG5 siRNA knock-down. Cell viability and apoptosis was assessed by flow cytometry and fluorescence microscopy, and autophagy was monitored by immunohistochemistry, AUTOdot and Western blotting.

RESULTS

Western blot revealed upregulation of ATG5 and LC3 II with a reduction of p62 protein expression in AA-treated cells, indicating upregulation of autophagy. These data were supported by results obtained with immunocytochemistry and AUTOdot assays. Using flow cytometry, we showed that combining AA with autophagy inhibition significantly impaired cell viability (1.3-1.6-fold, p < 0.001) and increased apoptosis (1.4-1.5-fold, p < 0.001) compared to AA treatment alone.

CONCLUSIONS

AA activates autophagy as a cytoprotective mechanism in LNCaP prostate cancer cells and targeting of autophagy enhances the antitumor effect of the compound.

CTC-derived AR-V7 detection as a prognostic and predictive biomarker in advanced prostate cancer

INTRODUCTION

Prostate cancer is a highly heterogeneous disease, with remarkably different prognosis across all stages. Increased circulating tumor cell (CTC) count (≥ 5) using the CellSearch assay has been identified as one of the markers that can be used to predict survival, with added value beyond currently available prognostic factors. Recently, androgen receptor splice variant 7 (AR-V7) detection has been associated with worse outcomes for patients with castration-resistant prostate cancer (CRPC) treated with novel androgen receptor-signaling (ARS) inhibitors such as abiraterone and enzalutamide but not taxane chemotherapies. Areas covered: In this manuscript, the authors review the available biomarkers in CRPC and discuss emerging data on the value of CTC-derived AR-V7 status to assess prognosis and its potential role to guide treatment selection for patients with advanced prostate cancer. Expert commentary: Current evidence supports AR-V7 status as a prognostic biomarker and also as a potential predictive biomarker for patients with mCRPC. The authors expect that the incorporation of AR-V7 status and other biomarkers (e.g. AR mutations) in the sequential assessment of patients with advanced prostate cancer will lead to a more rational use of available and future therapies, with significant improvements in outcomes for our patients.