Castration-resistant prostate cancer: from new pathophysiology to new treatment

An Inherited Allele Confers Prostate Cancer Progression and Drug Resistance via RFX6/HOXA10-Orchestrated TGFβ Signaling

Genetic and epigenetic alterations are cancer hallmark characteristics. However, the role of inherited cancer predisposition alleles in co-opting lineage factor epigenetic reprogramming and tumor progression remains elusive. Here the FinnGen cohort phenome-wide analysis, along with multiple genome-wide association studies, has consistently identified the rs339331-RFX6/6q22 locus associated with prostate cancer (PCa) risk across diverse populations. It is uncovered that rs339331 resides in a reprogrammed androgen receptor (AR) binding site in PCa tumors, with the T risk allele enhancing AR chromatin occupancy. RFX6, an AR-regulated gene linked to rs339331, exhibits synergistic prognostic value for PCa recurrence and metastasis. This comprehensive in vitro and in vivo studies demonstrate the oncogenic functions of RFX6 in promoting PCa cell proliferation and metastasis. Mechanistically, RFX6 upregulates HOXA10 that profoundly correlates with adverse PCa outcomes and is pivotal in RFX6-mediated PCa progression, facilitating the epithelial-mesenchymal transition (EMT) and modulating the TGFβ/SMAD signaling axis. Clinically, HOXA10 elevation is associated with increased EMT scores, tumor advancement and PCa recurrence. Remarkably, reducing RFX6 expression restores enzalutamide sensitivity in resistant PCa cells and tumors. This findings reveal a complex interplay of genetic and epigenetic mechanisms in PCa pathogenesis and drug resistance, centered around disrupted prostate lineage AR signaling and abnormal RFX6 expression.

Design and Synthesis of Dual-Target Inhibitors Targeting Androgen Receptors and Glucocorticoid Receptors to Overcome Antiandrogen Resistance in Castration-Resistant Prostate Cancer

Androgen receptor (AR) antagonists play important roles in the treatment of castration-resistant prostate cancer (CRPC). The glucocorticoid receptor (GR) upregulation leads to drug resistance for clinically used antiandrogens. Therefore, blocking AR/GR signaling simultaneously has become an efficient strategy to overcome the drug resistance of CRPC. Our previous work indicated that Z19 could inhibit the activity of both AR and GR. Herein, we optimized the structure of Z19 and identified GA32 as a potent AR/GR dual inhibitor. GA32 efficiently reduced the mRNA and protein levels of AR/GR downstream genes. GA32 efficiently inhibited the proliferation of enzalutamide resistance CRPC both in vitro and in vivo. GA32 could directly bind to AR and GR, and the predicted binding modes for GA32 with AR/GR suggested that GA32 binds to the AR or GR hormone binding pocket. This work provides a potential lead compound with dual AR/GR inhibitory activity to conquer the drug resistance of CRPC.

Clinical characteristics of patients with metastatic castration-resistant prostate cancer after treatment with combined androgen blockade

BACKGROUND

Although the second-generation androgen receptor inhibitors and taxanes have recently been recommended for the initial treatment of metastatic prostate cancer, bicalutamide and flutamide are still used in a large number of cases. Therefore, it is important to elucidate the clinical characteristics of these treated CRPC cases and their sensitivity to the currently used therapeutic agents. We aimed to examine the outcomes of metastatic castration-resistant prostate cancer following combined androgen blockade as initial therapy at our institution.

METHODS

Ninety-four patients who developed metastatic castration-resistant prostate cancer after hormonal treatment with combined nonsteroidal androgen receptor antagonists and continuous androgen deprivation therapy between January 2015 and December 2020 were included. The presence of visceral metastases, duration of efficacy of each treatment, and overall survival after castration-resistant prostate cancer were evaluated.

RESULTS

Patients with a longer duration of castration-resistant prostate cancer tended to have a longer response duration to subsequent enzalutamide administration (p = 0.003). Patients who achieved a 90% reduction in prostate-specific antigen levels with enzalutamide had a significantly better castration-resistant prostate cancer prognosis (p = 0.002). Meanwhile, those with visceral metastases at the time of castration-resistant prostate cancer diagnosis had a significantly poorer prognosis (p < 0.001). A positive correlation was observed between the treatment efficacy of abiraterone and taxanes for castration-resistant prostate cancer.

CONCLUSION

The study provides scientific evidence to support that patients with longer time to castration-resistant prostate cancer are more sensitive to enzalutamide, and the use of abiraterone between docetaxel and cabazitaxel has favorable prognostic impact. These findings provide instrumental evidence that can enable better treatment selection for prostate cancer patients.

Research progress on non-protein-targeted drugs for cancer therapy

Non-protein target drugs, especially RNA-based gene therapies for treating hereditary diseases, have been recognized worldwide. As cancer is an insurmountable challenge, no miracle drug is currently available. With the advancements in the field of biopharmaceuticals, research on cancer therapy has gradually focused on non-protein target-targeted drugs, especially RNA therapeutics, including oligonucleotide drugs and mRNA vaccines. This review mainly summarizes the clinical research progress in RNA therapeutics and highlights that appropriate target selection and optimized delivery vehicles are key factors in increasing the effectiveness of cancer treatment in vivo.

Preclinical Efficacy of a PARP-1 Targeted Auger-Emitting Radionuclide in Prostate Cancer

There is an unmet need for better therapeutic strategies for advanced prostate cancer. Poly (ADP-ribose) polymerase-1 (PARP-1) is a chromatin-binding DNA repair enzyme overexpressed in prostate cancer. This study evaluates whether PARP-1, on account of its proximity to the cell's DNA, would be a good target for delivering high-linear energy transfer Auger radiation to induce lethal DNA damage in prostate cancer cells. We analyzed the correlation between PARP-1 expression and Gleason score in a prostate cancer tissue microarray. A radio-brominated Auger emitting inhibitor ([77Br]Br-WC-DZ) targeting PARP-1 was synthesized. The ability of [77Br]Br-WC-DZ to induce cytotoxicity and DNA damage was assessed in vitro. The antitumor efficacy of [77Br]Br-WC-DZ was investigated in prostate cancer xenograft models. PARP-1 expression was found to be positively correlated with the Gleason score, thus making it an attractive target for Auger therapy in advanced diseases. The Auger emitter, [77Br]Br-WC-DZ, induced DNA damage, G2-M cell cycle phase arrest, and cytotoxicity in PC-3 and IGR-CaP1 prostate cancer cells. A single dose of [77Br]Br-WC-DZ inhibited the growth of prostate cancer xenografts and improved the survival of tumor-bearing mice. Our studies establish the fact that PARP-1 targeting Auger emitters could have therapeutic implications in advanced prostate cancer and provides a strong rationale for future clinical investigation.

Targeting prolyl isomerase Pin1 as a promising strategy to overcome resistance to cancer therapies

The development of tumor therapeutic resistance is one of the important reasons for the failure of antitumor therapy. Starting with multiple targets and multiple signaling pathways is helpful in understanding the mechanism of tumor resistance. The overexpression of prolyl isomerase Pin1 is highly correlated with the malignancy of cancer, since Pin1 controls many oncogenes and tumor suppressors, as well as a variety of cancer-driving signaling pathways. Strikingly, numerous studies have shown that Pin1 is directly involved in therapeutic resistance. In this review, we mainly summarize the functions and mechanisms of Pin1 in therapeutic resistance of multifarious cancers, such as breast, liver, and pancreatic carcinomas. Furtherly, from the perspective of Pin1-driven cancer signaling pathways including Raf/MEK/ERK, PI3K/Akt, Wnt/β-catenin, NF-κB, as well as Pin1 inhibitors containing juglone, epigallocatechin-3-gallate (EGCG), all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), it is better to demonstrate the important potential role and mechanism of Pin1 in resistance and sensitization to cancer therapies. It will provide new therapeutic approaches for clinical reversal and prevention of tumor resistance by employing synergistic administration of Pin1 inhibitors and chemotherapeutics, implementing combination therapy of Pin1-related cancer signaling pathway inhibitors and Pin1 inhibitors, and exploiting novel Pin1-specific inhibitors.

Advances in the Current Understanding of the Mechanisms Governing the Acquisition of Castration-Resistant Prostate Cancer

Despite aggressive treatment and androgen-deprivation therapy, most prostate cancer patients ultimately develop castration-resistant prostate cancer (CRPC), which is associated with high mortality rates. However, the mechanisms governing the development of CRPC are poorly understood, and androgen receptor (AR) signaling has been shown to be important in CRPC through AR gene mutations, gene overexpression, co-regulatory factors, AR shear variants, and androgen resynthesis. A growing number of non-AR pathways have also been shown to influence the CRPC progression, including the Wnt and Hh pathways. Moreover, non-coding RNAs have been identified as important regulators of the CRPC pathogenesis. The present review provides an overview of the relevant literature pertaining to the mechanisms governing the molecular acquisition of castration resistance in prostate cancer, providing a foundation for future, targeted therapeutic efforts.

Incidence of dural metastases in castrate-resistant prostate cancer

Purpose:

The natural history and clinical manifestations of dural metastases (DM) in castrate-resistant prostate cancer (CRPC) will change with advances in new hormonal therapy. Here, we characterised the incidence, clinical presentation, and outcomes of patients with DM in a contemporary patient cohort with CRPC.

Methods:

We retrospectively reviewed our CRPC database from 2012 to 2020. The primary outcome was the diagnosis of DM, defined as metastasis to the dura mater in the brain or spine. We describe the presenting symptoms, biochemistry, radiologic findings, and therapy sequence for all DM patients. Multivariable logistic regression was performed to identify predictors of DM.

Results:

Six of the 275 patients (2.2%) with CRPC developed DM. The average age of CRPC diagnosis for patients with DM was 65.6 years. Mean patient survival was 4.5 months after the diagnosis of DM. At the time of CRPC diagnosis, patients who developed DM were significantly younger, had lower baseline haemoglobin, higher lactate dehydrogenase (LDH), and elevated alkaline phosphatase (ALP) compared to those without DM. On multivariable analysis, younger age of CRPC diagnosis was found to be a predictor for DM.

Conclusion:

The presence of neurological symptoms in the context of younger age, anaemia, and elevated baseline LDH and ALP are associated with DM in CRPC.

Level of Evidence:

4

CX-5461 Sensitizes DNA Damage Repair-proficient Castrate-resistant Prostate Cancer to PARP Inhibition

Monotherapy with PARP inhibitors is effective for the subset of castrate-resistant prostate cancer (CRPC) with defects in homologous recombination (HR) DNA repair. New treatments are required for the remaining tumors, and an emerging strategy is to combine PARP inhibitors with other therapies that induce DNA damage. Here we tested whether PARP inhibitors are effective for HR-proficient CRPC, including androgen receptor (AR)-null tumors, when used in combination with CX-5461, a small molecule that inhibits RNA polymerase I transcription and activates the DNA damage response, and has antitumor activity in early phase I trials. The combination of CX-5461 and talazoparib significantly decreased in vivo growth of patient-derived xenografts of HR-proficient CRPC, including AR-positive, AR-null, and neuroendocrine tumors. CX-5461 and talazoparib synergistically inhibited the growth of organoids and cell lines, and significantly increased the levels of DNA damage. Decreased tumor growth after combination therapy was maintained for 2 weeks without treatment, significantly increasing host survival. Therefore, combination treatment with CX-5461 and talazoparib is effective for HR-proficient tumors that are not suitable for monotherapy with PARP inhibitors, including AR-null CRPC. This expands the spectrum of CRPC that is sensitive to PARP inhibition.

Androgen receptor variant shows heterogeneous expression in prostate cancer according to differentiation stage

Quantitation of androgen receptor variant (AR-V) expression in circulating tumor cells (CTCs) from patients with metastatic castration-resistant prostate cancer (mCRPC) has great potential for treatment customization. However, the absence of a uniform CTC isolation platform and consensus on an analytical assay has prevented the incorporation of these measurements in routine clinical practice. Here, we present a single-CTC sensitive digital droplet PCR (ddPCR) assay for the quantitation of the two most common AR-Vs, AR-V7, and AR-v567es, using antigen agnostic CTC enrichment. In a cohort of 29 mCRPC patients, we identify AR-V7 in 66% and AR-v567es in 52% of patients. These results are corroborated using another gene expression platform (NanoString^TM) and by analysis of RNA-Seq data from patients with mCRPC (SU2C- PCF Dream Team). We next quantify AR-V expression in matching EpCAM-positive vs EpCAM-negative CTCs, as EpCAM-based CTC enrichment is commonly used. We identify lower AR-V prevalence in the EpCAM-positive fraction, suggesting that EpCAM-based CTC enrichment likely underestimates AR-V prevalence. Lastly, using single CTC analysis we identify enrichment for AR-v567es in patients with neuroendocrine prostate cancer (NEPC) indicating that AR-v567es may be involved in lineage plasticity, which warrants further mechanistic interrogation.

Ada Gjyrezi et al. show that ddPCR can be used to accurately measure androgen receptor variant (AR-V) expression levels in single circulating tumor cells (CTCs) from prostate cancer patients. They show that current methods for isolating CTCs tend to underestimate the prevalence of AR-V and that a specific variant, AR-v567es, could be potentially used as a biomarker for an aggressive subtype of prostate cancer.

The Role of PARP Inhibitors in the Treatment of Prostate Cancer: Recent Advances in Clinical Trials

Poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPis) belong to a class of targeted drugs developed for the treatment of homologous recombination repair (HRR)-defective tumors. Preclinical and limited clinical data suggest that PARP inhibition is effective against prostate cancer (PC) in patients with HRR-deficient tumors and that PARPis can improve the mortality rate of PC in patients with BRCA1/2 mutations through a synthetic lethality. Olaparib has been approved by the FDA for advanced ovarian and breast cancer with BRCA mutations, and as a maintenance therapy for ovarian cancer after platinum chemotherapy. PARPis are also a new and emerging clinical treatment for metastatic castration-resistant prostate cancer (mCRPC). Although PARPis have shown great efficacy, their widespread use is restricted by various factors, including drug resistance and the limited population who benefit from treatment. It is necessary to study the combination of PARPis and other therapeutic agents such as anti-hormone drugs, USP7 inhibitors, BET inhibitors, and immunotherapy. This article reviews the mechanism of PARP inhibition in the treatment of PC, the progress of clinical research, the mechanisms of drug resistance, and the strategies of combination treatments.

Liquid Biopsy: From Discovery to Clinical Application

Over the past 10 years, circulating tumor cells (CTC) and circulating tumor DNA (ctDNA) have received enormous attention as new biomarkers and subjects of translational research. Although both biomarkers are already used in numerous clinical trials, their clinical utility is still under investigation with promising first results. Clinical applications include early cancer detection, improved cancer staging, early detection of relapse, real-time monitoring of therapeutic efficacy, and detection of therapeutic targets and resistance mechanisms. Here, we propose a conceptual framework of CTC and ctDNA assays and point out current challenges of CTC and ctDNA research, which might structure this dynamic field of translational cancer research. SIGNIFICANCE: The analysis of blood for CTCs or cell-free nucleic acids called "liquid biopsy" has opened new avenues for cancer diagnostics, including early detection of tumors, improved risk assessment and staging, as well as early detection of relapse and monitoring of tumor evolution in the context of cancer therapies.

Distinct DNA methylation patterns associated with treatment resistance in metastatic castration resistant prostate cancer

Androgens are a major driver of prostate cancer (PCa) and continue to be a critical treatment target for advanced disease, which includes castration therapy and antiandrogens. However, resistance to these therapies leading to metastatic castration-resistant prostate cancer (mCRPC), and the emergence of treatment-induced neuroendocrine disease (tNEPC) remains an ongoing challenge. Instability of the DNA methylome is well established as a major hallmark of PCa development and progression. Therefore, investigating the dynamics of the methylation changes going from the castration sensitive to the tNEPC state would provide insights into novel mechanisms of resistance. Using an established xenograft model of CRPC, genome-wide methylation analysis was performed on cell lines representing various stages of PCa progression. We confirmed extensive methylation changes with the development of CRPC and tNEPC using this model. This included key genes and pathways associated with cellular differentiation and neurodevelopment. Combined analysis of methylation and gene expression changes further highlighted genes that could potentially serve as therapeutic targets. Furthermore, tNEPC-related methylation signals from this model were detectable in circulating cell free DNA (cfDNA) from mCRPC patients undergoing androgen-targeting therapies and were associated with a faster time to clinical progression. These potential biomarkers could help with identifying patients with aggressive disease.

Pin1 inhibition improves the efficacy of ralaniten compounds that bind to the N-terminal domain of androgen receptor

Therapies for lethal castration-resistant prostate cancer (CRPC) are an unmet medical need. One mechanism underlying CRPC and resistance to hormonal therapies is the expression of constitutively active splice variant(s) of androgen receptor (AR-Vs) that lack its C-terminus ligand-binding domain. Transcriptional activities of AR-Vs and full-length AR reside in its N-terminal domain (NTD). Ralaniten is the only drug proven to bind AR NTD, and it showed promise of efficacy in Phase 1 trials. The peptidyl-prolyl isomerase Pin1 is frequently overexpressed in prostate cancer. Here we show that Pin1 interacted with AR NTD. The inhibition of Pin1 expression or its activity selectively reduced the transcriptional activities of full-length AR and AR-V7. Combination of Pin1 inhibitor with ralaniten promoted cell cycle arrest and had improved antitumor activity against CRPC xenografts in vivo compared to individual monotherapies. These findings support the rationale for therapy that combines a Pin1 inhibitor with ralaniten for treating CRPC.

Anti-prostate cancer activity of a nanoformulation of the spleen tyrosine kinase (SYK) inhibitor C61

Patients with advanced or metastatic castration-resistant prostate cancer have a dismal prognosis and are therefore in urgent need for therapeutic innovations. Spleen tyrosine kinase has emerged as a new molecular target for castration-resistant prostate cancer. This study was done to test the cytotoxicity of the lead nanoformulation of a potent spleen tyrosine kinase inhibitor, C61-LNP, against the human prostatic carcinoma cell line, PC-3. PC-3 cells were treated with various concentrations of C61-LNP either alone or in combination with cisplatin (CDDP) for 24, 48 and 72 hours. The cell viability was evaluated by MTS assay. Cellular expression levels of various regulatory proteins in treated PC-3 cells were evaluated by Western blot analyses. C61-LNP exhibited dose-dependent cytotoxicity against PC-3 cells. C61-LNP, as well as C61-LNP + CDDP treatments, caused pro-apoptotic proteomic changes including an increase in cleaved fragments of caspases-3 and -9 consistent with caspase activation as well as an improvement in the anti-apoptotic Bcl2 and Bax levels. The combination of C61-LNP and CDDP changed in alterations of the cell cycle regulatory proteins p53, p21, p27, cyclin D1 and cyclin E levels. C61-LNP exhibited cytotoxicity against the castration-resistant prostate cancer cell line PC3. It also caused alterations in expression levels of regulatory proteins involved in apoptosis and cell cycle regulation and these effects were not abrogated by the standard chemotherapy drug CDDP. We are planning to further develop C61-LNP as a selective spleen tyrosine kinase inhibitor as part of a multi-modality treatment strategy for advanced/metastatic castration-resistant prostate cancer.

Dynamics of the cell-free DNA methylome of metastatic prostate cancer during androgen-targeting treatment

Aim: We examined methylation changes in cell-free DNA (cfDNA) in metastatic castration-resistant prostate cancer (mCRPC) during treatment. Patients & methods: Genome-wide methylation analysis of sequentially collected cfDNA samples derived from mCRPC patients undergoing androgen-targeting therapy was performed. Results: Alterations in methylation states of genes previously implicated in prostate cancer progression were observed and patients that maintained methylation changes throughout therapy tended to have a longer time to clinical progression. Importantly, we also report that markers associated with a highly aggressive form of the disease, neuroendocrine-CRPC, were associated with a faster time to clinical progression. Conclusion: Our findings highlight the potential of monitoring the cfDNA methylome during therapy in mCRPC, which may serve as predictive markers of response to androgen-targeting agents.

Estimation of [177Lu]PSMA-617 tumor uptake based on voxel-wise 3D Monte Carlo tumor dosimetry in patients with metastasized castration resistant prostate cancer

OBJECTIVE

 Patients with advanced prostate cancer are suitable candidates for [177Lu]PSMA-617 therapy. Integrated SPECT/CT systems have the potential to improve the accuracy of patient-specific tumor dosimetry. We present a novel patient-specific Monte Carlo based voxel-wise dosimetry approach to determine organ and total tumor doses (TTD).

METHODS

 13 patients with histologically confirmed metastasized castration-resistant prostate cancer were treated with a total of 18 cycles of [177Lu]PSMA-617 therapy. In each patient, dosimetry was performed after the first cycle of [177Lu]PSMA-617 therapy. Regions of interest were defined manually on the SPECT/CT images for the kidneys, spleen and all 295 PSMA-positive tumor lesions in the field of view. The absorbed dose to normal organs and to all tumor lesions were calculated by a three dimensional dosimetry method based on Monte Carlo Simulations.

RESULTS

 The average dose values yielded the following results: 2.59 ± 0.63 Gy (1.67-3.92 Gy) for the kidneys, 0.79 ± 0.46 Gy (0.31-1.90 Gy) for the spleen and 11.00 ± 11.97 Gy (1.28-49.10 Gy) for all tracer-positive tumor lesions. A trend towards higher TTD was observed in patients with Gleason Scores > 8 compared to Gleason Scores ≤ 8 and in lymph node metastases compared to bone metastases. A significant correlation was determined between the serum-PSA level before RLT and the TTD (r = -0.57, p < 0.05), as well as between the TTD with the percentage change of serum-PSA levels before and after therapy was observed (r = -0.57, p < 0.05). Patients with higher total tumor volumes of PSMA-positive lesions demonstrated significantly lower kidney average dose values (r = -0.58, p < 0.05).

CONCLUSION

 The presented novel Monte Carlo based voxel-wise dosimetry calculates a patient specific whole-body dose distribution, thus taking into account individual anatomies and tissue compositions showing promising results for the estimation of radiation doses of normal organs and PSMA-positive tumor lesions.

Annexin A1 promotes the nuclear localization of the epidermal growth factor receptor in castration-resistant prostate cancer

Epidermal growth factor receptor is a cancer driver whose nuclear localization has been associated with the progression of prostate cancer to the castration-resistant phenotype. Previous reports indicated a functional interaction between this receptor and the protein Annexin A1, which has also been associated with aggressive tumors. The molecular pathogenesis of castration-resistant prostate cancer remains largely unresolved, and herein we have demonstrated the correlation between the expression levels and localization of the epidermal growth factor receptor and Annexin A1 in prostate cancer samples and cell lines. Interestingly, a higher expression of both proteins was detected in castration-resistant prostate cancer cell lines and the strongest correlation was seen at the nuclear level. We verified that Annexin A1 interacts with the epidermal growth factor receptor, and by using prostate cancer cell lines knocked down for Annexin A1, we succeeded in demonstrating that Annexin A1 promotes the nuclear localization of epidermal growth factor receptor. Finally, we showed that Annexin A1 activates an autocrine signaling in castration-resistant prostate cells through the formyl peptide receptor 1. The inhibition of such signaling by Cyclosporin H inhibits the nuclear localization of epidermal growth factor receptor and its downstream signaling. The present work sheds light on the functional interaction between nuclear epidermal growth factor receptor and nuclear Annexin A1 in castration-resistant prostate cancer. Therefore, strategies to inhibit the nuclear localization of epidermal growth factor receptor through the suppression of the Annexin A1 autocrine loop could represent an important intervention strategy for castration-resistant prostate cancer.

Plasma cell-free DNA-based predictors of response to abiraterone acetate/prednisone and prognostic factors in metastatic castration-resistant prostate cancer

Background:

The combination of abiraterone acetate and prednisone (AA/P) is used to treat metastatic prostate cancer, but molecular predictors of treatment response are not well elucidated. We evaluated plasma circulating tumor DNA– (ctDNA-) based copy number alterations (CNAs) to determine treatment-related predictive and prognostic biomarkers for metastatic castration-resistant prostate cancer (mCRPC).

Methods:

Serial plasma specimens were prospectively collected from 88 chemotherapy-naive mCRPC patients before and after 12 weeks of AA/P treatment. Sequencing-based CNA analyses were performed on 174 specimens. We evaluated CNA-associated 12-week responses for primary resistance, time to treatment change (TTTC) for secondary resistance, and overall survival for prognosis (P < .05). Associations with primary resistance were analyzed using the Fisher exact test. Kaplan–Meier survival curves and Cox regression analyses were used to determine the associations of CNAs with acquired resistance and overall survival.

Results:

ctDNA reduced by 3.89% in responders and increased by 0.94% in nonresponders (P = .0043). Thirty-one prostate cancer–related genes from whole genome CNAs were tested. AR and AR enhancer amplification were associated with primary resistance (P = .0039) and shorter TTTC (P = .0003). ZFHX3 deletion and PIK3CA amplification were associated with primary resistance (P = .026 and P = .017, respectively), shorter TTTC (P = .0008 and P= .0016, respectively), and poor survival (P = .0025 and P = .0022, respectively). CNA-based risk scores combining selected significant associations (AR, NKX3.1, and PIK3CA) at the univariate level with TTTC were predictive of secondary resistance (P = .0002). and established prognoses for survival based on CNAs in ZFHX3, RB1, PIK3CA, and OPHN1 (P = .002). Multigene risk scores were more predictive than individual genes or clinical risk factors (P < .05).

Conclusion:

Plasma ctDNA CNAs and risk scores can predict mCRPC-state treatment and survival outcomes.

Preliminary results of targeted prostate-specific membrane antigen imaging in evaluating the efficacy of a novel hormone agent in metastatic castration-resistant prostate cancer

To investigate the feasibility and effectiveness of prostate‐specific membrane antigen (PSMA) imaging to make response assessment regarding novel hormone treatment and to predict the outcomes for metastatic castration‐resistant prostate cancer (mCRPC) patients. This retrospective study enrolled 68 mCRPC patients who had daily received a novel hormone agent named abiraterone. Tc‐99m PSMA single‐photon emission computed tomography (SPECT/CT) was performed at the baseline (SPECT/CT1) and after 3‐6 months of treatment (SPECT/CT2). The treatment response was determined by visual analysis based on molecular imaging PSMA (miPSMA) scores framework and was compared with conventional biochemical analysis. We chose either the hottest lesion (target A) or five of the hottest lesions (target B) to calculate the tumor/background ratio (TBR) and the maximum standardized uptake value (SUVmax) and compared their performances in predicting progression‐free survival (PFS). Changes in PSMA expression between SPECT/CT1 and SPECT/CT2 were well associated with the results of the visual analysis. The TBR and the SUVmax of both targets were significantly associated with the baseline serum PSA level (P < .0001). The biochemical and radiological responses were concordant in 56 of the 68 patients (P < .001). The median PFS of the nonresponse group patients was significantly shorter than that of the patients in the response group (6.8 vs 12.1 months, P = .012). For predicting PFS, most of the indexes tested were significant on SPECT/CT2, with %ΔTBR being the most significant prognostic factor. Our preliminary results suggest that molecular imaging‐targeted PSMA is of great value for treatment response assessment and clinical outcome prediction in mCRPC patients with long‐term abiraterone treatment.

Landmarks in prostate cancer

The field of prostate cancer has been the subject of extensive research that has resulted in important discoveries and shaped our appreciation of this disease and its management. Advances in our understanding of the epidemiology, natural history, anatomy, detection, diagnosis, grading, staging, imaging, and management of prostate cancer have changed clinical practice and influenced guideline recommendations. The development of the Gleason score and subsequent modifications enabled accurate prediction of prognosis. Increased anatomical understanding and improved surgical techniques resulted in the development of nerve-sparing surgery for radical prostatectomy. The advent of active surveillance has changed the management of low-risk disease, and chemotherapy and hormonal therapy have improved the outcomes of patients with distant disease. Ongoing research and clinical trials are expected to yield more practice-changing results in the near future.

COMMD3:BMI1 Fusion and COMMD3 Protein Regulate C-MYC Transcription: Novel Therapeutic Target for Metastatic Prostate Cancer

Gene rearrangement is reported to be associated to the aggressive phenotype and poor prognosis in prostate cancer. We identified a gene fusion between a transcription repressor (BMI1) and transcriptional factor (COMMD3) in human prostate cancer. We show that COMMD3:BMI1 fusion expression is significantly increased in prostate cancer disease in an order: normal tissue < primary < metastatic tumors (Mets). Although elevated TMPRSS-ERG/ETV fusion is reported in prostate cancer, we identified a subtype of Mets exhibiting low TMPRSS:ETV and high COMMD3:BMI1 We delineated the mechanism and function of COMMD3 and COMMD3:BMI1 in prostate cancer. We show that COMMD3 level is elevated in prostate cancer cell models, PDX models (adenocarcinoma, NECaP), and Mets. The analysis of TCGA/NIH/GEO clinical data showed a positive correlation between increased COMMD3 expression to the disease recurrence and poor survival in prostate cancer. We show that COMMD3 drives proliferation of normal cells and promotes migration/invasiveness of neoplastic cells. We show that COMMD3:BMI1 and COMMD3 regulate C-MYC transcription and C-MYC downstream pathway. The ChIP analysis showed that COMMD3 protein is recruited at the promoter of C-MYC gene. On the basis of these data, we investigated the relevance of COMMD3:BMI1 and COMMD3 as therapeutic targets using in vitro and xenograft mouse models. We show that siRNA-mediated targeting of COMMD3:BMI1 and COMMD3 significantly decreases (i) C-MYC expression in BRD/BET inhibitor-resistant cells, (ii) proliferation/invasion in vitro, and (iii) growth of prostate cancer cell tumors in mice. The IHC analysis of tumors confirmed the targeting of COMMD3-regulated molecular pathway under in vivo conditions. We conclude that COMMD3:BMI1 and COMMD3 are potential progression biomarkers and therapeutic targets of metastatic prostate cancer.

Identification of Novel Biomarkers of Homologous Recombination Defect in DNA Repair to Predict Sensitivity of Prostate Cancer Cells to PARP-Inhibitors

One of the most common malignancies in men is prostate cancer, for which androgen deprivation is the standard therapy. However, prostate cancer cells become insensitive to anti-androgen treatment and proceed to a castration-resistant state with limited therapeutic options. Therefore, besides the androgen deprivation approach, novel biomarkers are urgently required for specific targeting in this deadly disease. Recently, germline or somatic mutations in the homologous recombination (HR) DNA repair genes have been identified in at least 20–25% of metastatic castration-resistant prostate cancers (mCRPC). Defects in genes involved in HR DNA repair can sensitize cancer cells to poly(ADP-ribose) polymerase (PARP) inhibitors, a class of drugs already approved by the Food and Drug Administration (FDA) for breast and ovarian cancer carrying germline mutations in BRCA1/2 genes. For advanced prostate cancer carrying Breast cancer1/2 (BRCA1/2) or ataxia telengiectasia mutated (ATM) mutations, preclinical studies and clinical trials support the use of PARP-inhibitors, which received breakthrough therapy designation by the FDA. Based on these assumptions, several trials including DNA damage response and repair (DDR) targeting have been launched and are ongoing for prostate cancer. Here, we review the state-of-the-art potential biomarkers that could be predictive of cancer cell synthetic lethality with PARP inhibitors. The identification of key molecules that are affected in prostate cancer could be assayed in future clinical studies to better stratify prostate cancer patients who might benefit from target therapy.

New Insights into the Role of Polybromo-1 in Prostate Cancer

The human protein Polybromo-1 (PBMR1/BAF180) is a component of the SWI/SNF chromatin-remodeling complex that has been reported to be deregulated in tumors. However, its role in prostate cancer (PCa) is largely unknown. In this study, we described the PBRM1 transcriptional levels and the protein expression/localization in tissues of PCa patients and in prostatic cell lines. Increased PBRM1 mRNA levels were found in PCa samples, when compared to benign disease, and were correlated with higher Gleason score. We also verified that only the nuclear localization of PBRM1 protein is correlated with a more aggressive disease and high Prostate-Specific Antigen (PSA) levels in tissue microarrays. Intriguing expression patterns of mRNA and protein were identified in the cell lines. Although PBRM1 protein was restricted to the nuclei, in tumor cell lines in non-neoplastic cells, it was also present in vesicular-like structures that were dispersed within the cytoplasm. We knocked-down PBRM1 in the castration-resistant PCa (CRPC) cell line PC-3 and we verified that PBRM1 promotes the expression of several markers of aggressiveness, including EpCAM, TGF-β, and N-Cadherin. Therefore, our data supported the hypothesis that PBRM1 displays a pivotal role in the promotion and maintenance of the malignant behavior of PCa, especially in CRPC.

Evaluation of response in patients of metastatic castration resistant prostate cancer undergoing systemic radiotherapy with lutetium177-prostate-specific membrane antigen: A comparison between response evaluation criteria in solid tumors, positron-emission tomography response criteria in solid tumors, European organization for research and treatment of cancer, and MDA criteria assessed by gallium 68-prostate-specific membrane antigen positron-emission tomography-computed tomography

Introduction

We evaluated various morphological and molecular response criteria in metastatic castration-resistant prostate cancer (PCa) patient undergoing peptide receptor radioligand therapy (PRLT) with Lutetium177-prostate-specific membrane antigen (PSMA) by using Gallium 68-PSMA positron-emission tomography-computed tomography (Ga68-PSMA PET-CT).

Methods

A total of 46 pre- and 8-12 weeks' post-PRLT Ga68-PSMA PET-CT studies were reanalyzed (23 comparisons). Prostate-specific antigen drop of ≥50% and ≥25% increase was considered as partial response (PR) and progressive disease (PD), respectively, for biochemical response (BR) while change in-between was considered as stable disease (SD). Response evaluation criteria in solid tumors 1.1 (RECIST 1.1) and MD Anderson (MDA) criteria for morphological response while PET response criteria in solid tumors 1.0 (PERCIST 1.0) and European organization for research and treatment of cancer (EORTC) criteria for molecular response were used. Kappa coefficient was derived to see the level of agreement.

Results

The proportion of PD, PR, and SD by BR and RECIST criteria was 9 (39.13%), 3 (13.04%), and 11 (47.83%) and 5 (21.74%), 2 (8.70%), and 16 (69.57%), respectively. The proportion of PD, PR, and SD was same by PERCIST and EORTC criteria and which were 8 (34.78%), 5 (21.74%), and 10 (43.48%). The proportion of PD, PR, and SD by MDA criteria was 1 (4.35%), 1 (4.35%), and 21 (91.30%), respectively. Poor agreement between BR and both morphological criteria while a statistically significant agreement with both molecular criteria seen.

Conclusion

We concluded that molecular criteria performed better than morphological criteria in response assessment by Ga68-PSMA PET-CT in metastatic castration resistant PCa patients undergoing PRLT.

Patient-derived, three-dimensional spheroid cultures provide a versatile translational model for the study of organ-confined prostate cancer

PURPOSE

To generate and characterize 3D spheroid suspension cultures from radical prostatectomy (RP) specimens as a versatile model system for organ-confined prostate cancer (PCa).

METHODS

Cancerous tissue samples from RP specimens were excised by a uropathologist. Preparation of 3D spheroids was done by mechanical disintegration and limited enzymatic digestion followed by serial filtration through 100 μm- and 40 μm-cell strainers. Thereafter, spheroids were cultured in a modified stem cell medium and characterized by a live/dead assay, whole-spheroid immunohistochemistry (IHC; CK5, CK8, AMACR, PSA, Ki67, AR, αSMA, Vimentin, E-Cadherin) and PSA-measurements in culture medium. Furthermore, their response to pharmaceutical treatment with docetaxel, bicalutamide, enzalutamide and abiraterone was tested.

RESULTS

173 RP cases were included. The median preoperative PSA-level was 16.12 ng/ml [range 0.99;345], the median Gleason score was 7b [6;10]. 64 cases were excluded due to low tumor content in frozen sections (43) or to insufficient spheroid formation (21). In the remaining 109 cases, spheroids formed successfully and stayed viable for up to several months. IHC analysis revealed AR-, CK8-, and AMACR-positivity in nearly all cases, while CK5-positive cells were detectable only occasionally as were α-SMA and Vimentin. E-Cadherin was positive in most cases. Furthermore, spheroids proved to be amenable to cryopreservation. While abiraterone had no effect and docetaxel only a moderate effect, spheroid viability was markedly reduced upon bicalutamide and enzalutamide treatment.

CONCLUSIONS

Multicellular 3D spheroids can be generated from patient-derived RP tissue samples and serve as an innovative in vitro model of organ-confined PCa.

Perspectives on the current and emerging chemical androgen receptor antagonists for the treatment of prostate cancer

INTRODUCTION

 Prostate cancer is the most common cancer in men. Regardless of the initial treatment of localized disease, almost all patients develop castration resistant prostate cancer (CRPC). A better understanding of the molecular mechanisms behind castration resistance has led to the approval of novel oral androgen receptor (AR) antagonists, such as enzalutamide and apalutamide. Indeed, research has accelerated with numerous agents being studied for the management of CRPC. Areas covered: Herein, the authors present currently used and emerging AR antagonists for the treatment of CRPC. Emerging agents include darolutamide, EZN-4176, AZD-3514, and AZD-5312, apatorsen, galeterone, ODM-2014, TRC-253, BMS-641988, and proxalutamide. Expert opinion: Further understanding of the mechanisms leading to castration resistance in prostate cancer can reveal potential targets for the development of novel AR antagonists. Current novel agents are associated with modest clinical and survival benefit, while acquired resistance and safety issues are under continuous evaluation. The combination of AR antagonists used and ideal sequencing strategies are key tasks ahead, along with the investigation of molecular biomarkers for future personalized targeted therapies. In the future, the challenge will be to determine an AR antagonist with the best combination of outcome and tolerability.

The human oncogene SCL/TAL1 interrupting locus (STIL) promotes tumor growth through MAPK/ERK, PI3K/Akt and AMPK pathways in prostate cancer

The morbidity and mortality of prostate cancer (PCa) in China have increased obviously, which became the second leading cause of death in men with cancer. Hedgehog (Hh) signaling pathway is a key signaling pathway involved in the prostate cancer progression. The human oncogene SCL/TAL1 interrupting locus (STIL) can modulate the Hh signaling pathway, but its function in PCa has not been reported. Here, we showed that STIL was increased in high grade prostate cancer tissue. Knockdown of STIL in prostate cancer cells PC-3 and DU 145 significantly decreased the proliferation of cells and induced cellular apoptosis through casepase3/7 mediated pathway. Moreover, the colony formation ability was also inhibited when knockdown of STIL by lentivirus-mediated shRNA. Furthermore, the cellular signaling antibody array analysis revealed which signaling pathway was affected when silencing STIL. Altogether, we found that STIL could affect MAPK/ERK, PI3K/Akt and AMPK signaling pathways, thus promoting cellular proliferation, colony formation and suppressing cellular apoptosis in prostate cancer.

Evaluation of RECIST, PERCIST, EORTC, and MDA Criteria for Assessing Treatment Response with Ga68-PSMA PET-CT in Metastatic Prostate Cancer Patient with Biochemical Progression: a Comparative Study

Purpose

The aim of the study was to compare response evaluation criteria in solid tumours 1.1 (RECIST 1.1), positron emission tomography response criteria in solid tumours (PERCIST), European organisation for research and treatment of cancer (EORTC), and MD Anderson (MDA) criteria for response assessment by Gallium 68-prostate-specific membrane antigen positron emission tomography-computed tomography (Ga68-PSMA PET-CT) in metastatic adenocarcinoma prostate cancer (mPCa) patients with biochemical progression.

Methods

Eighty-eight mPCa patients with pre and post treatment Ga68-PSMA PET-CT were included. A ≥ 25% increase and ≥ 2 ng/ml above the nadir if prostate specific antigen (PSA) drop or ≥ 2 ng/ml above the baseline if PSA does not drop was considered as biochemical progression. RECIST 1.1 and MDA criteria for morphology and PERCIST and EORTC criteria for molecular response were investigated. Percentages of progressive disease (PD), partial response (PR), and stable disease (SD) were calculated. Chi-square test was used for statistical significance.

Results

Proportion of PD, SD, and PR by RECIST 1.1 and MDA criteria were 44 (50.57%), 39 (44.83%), 4 (4.6%), and 33 (39.76%), 48 (57.83%), 2 (2.41%) respectively. Proportion of PD, SD, and PR by PERCIST and EORTC criteria were 71 (80.68%), 11 (12.50%), 6 (6.82%), and 74 (84.09%), 8 (9.09%), 6 (6.82%) respectively. Chi-square test showed statistically significant (P < 0.05) higher proportion of progression detected by both molecular criteria as compare to both morphological criteria.

Conclusion

We concluded that for Ga68-PSMA PET-CT response evaluation, molecular criteria performed better than morphological criteria in mPCa patient with PSA progression.

Patient-derived Models of Abiraterone- and Enzalutamide-resistant Prostate Cancer Reveal Sensitivity to Ribosome-directed Therapy

BACKGROUND

The intractability of castration-resistant prostate cancer (CRPC) is exacerbated by tumour heterogeneity, including diverse alterations to the androgen receptor (AR) axis and AR-independent phenotypes. The availability of additional models encompassing this heterogeneity would facilitate the identification of more effective therapies for CRPC.

OBJECTIVE

To discover therapeutic strategies by exploiting patient-derived models that exemplify the heterogeneity of CRPC.

DESIGN, SETTING, AND PARTICIPANTS

Four new patient-derived xenografts (PDXs) were established from independent metastases of two patients and characterised using integrative genomics. A panel of rationally selected drugs was tested using an innovative ex vivo PDX culture system.

INTERVENTION

The following drugs were evaluated: AR signalling inhibitors (enzalutamide and galeterone), a PARP inhibitor (talazoparib), a chemotherapeutic (cisplatin), a CDK4/6 inhibitor (ribociclib), bromodomain and extraterminal (BET) protein inhibitors (iBET151 and JQ1), and inhibitors of ribosome biogenesis/function (RNA polymerase I inhibitor CX-5461 and pan-PIM kinase inhibitor CX-6258).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Drug efficacy in ex vivo cultures of PDX tissues was evaluated using immunohistochemistry for Ki67 and cleaved caspase-3 levels. Candidate drugs were also tested for antitumour efficacy in vivo, with tumour volume being the primary endpoint. Two-tailed t tests were used to compare drug and control treatments.

RESULTS AND LIMITATIONS

Integrative genomics revealed that the new PDXs exhibited heterogeneous mechanisms of resistance, including known and novel AR mutations, genomic structural rearrangements of the AR gene, and a neuroendocrine-like AR-null phenotype. Despite their heterogeneity, all models were sensitive to the combination of ribosome-targeting agents CX-5461 and CX-6258.

CONCLUSIONS

This study demonstrates that ribosome-targeting drugs may be effective against diverse CRPC subtypes including AR-null disease, and highlights the potential of contemporary patient-derived models to prioritise treatment strategies for clinical translation.

PATIENT SUMMARY

Diverse types of therapy-resistant prostate cancers are sensitive to a new combination of drugs that inhibit protein synthesis pathways in cancer cells.

Glyoxalase 1 sustains the metastatic phenotype of prostate cancer cells via EMT control

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Effective therapeutic intervention in metastatic PCa is undermined by our poor understanding of its molecular aetiology. Defining the mechanisms underlying PCa metastasis may lead to insights into how to decrease morbidity and mortality in this disease. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a potent precursor of advanced glycation end products (AGEs). Hydroimidazolone (MG-H1) and argpyrimidine (AP) are AGEs originating from MG-mediated post-translational modification of proteins at arginine residues. AP is involved in the control of epithelial to mesenchymal transition (EMT), a crucial determinant of cancer metastasis and invasion, whose regulation mechanisms in malignant cells are still emerging. Here, we uncover a novel mechanism linking Glo1 to the maintenance of the metastatic phenotype of PCa cells by controlling EMT by engaging the tumour suppressor miR-101, MG-H1-AP and TGF-β1/Smad signalling. Moreover, circulating levels of Glo1, miR-101, MG-H1-AP and TGF-β1 in patients with metastatic compared with non-metastatic PCa support our in vitro results, demonstrating their clinical relevance. We suggest that Glo1, together with miR-101, might be potential therapeutic targets for metastatic PCa, possibly by metformin administration.

Radium-223 in the treatment of bone metastasis in patients with castration-resistant prostate cancer. Review and procedure

Bone metastatic disease is the main cause of morbidity / mortality in patients with prostate cancer, presenting frequently as bone pain, pathological fractures or spinal cord compression, which requires early and timely therapy. Although, for the moment, the therapeutic window for its use has not been definitively established, radium-223 (²²³Ra), an alpha particle emitter, has proved to be an effective therapeutic tool, pre or post-chemotherapy, in patients with castration-resistant prostate cancer with symptomatic bone metastases and absence of visceral metastases, significantly modifying the prognosis of the disease. It is therefore imperative to define the ideal scenarios and the correct protocol for the use of this therapy and thus offer the greatest possible clinical benefit to the patient.

Prognostic and predictive clinical factors in patients with metastatic castration-resistant prostate cancer treated with cabazitaxel

INTRODUCTION

Cabazitaxel is one of several treatment options available for patients with metastatic castration-resistant prostate cancer who have progressed on docetaxel. Little is known about clinical factors that influence prognosis or treatment response for patients receiving cabazitaxel. Identifying prognostic and predictive factors could contribute to the optimal selection of patients for treatment after docetaxel.

METHODS

A retrospective review of patients enrolled on the cabazitaxel Canadian Early Access Program (C-EAP) was performed. Clinical factors were analyzed by univariable and multivariable Cox proportional hazards and logistic regression analysis to identify independent predictors of prognosis and response.

RESULTS

Forty-five patients from five centres in Canada were included in this study. On multivariable analysis, lower hemoglobin was associated with shorter survival. No other factors were independently associated with survival, prostate-specific antigen (PSA) response, or primary PSA progression.

CONCLUSIONS

Clinical factors predicting survival or treatment response were not identified for men with castration-resistant prostate cancer receiving cabazitaxel. Larger studies may be necessary to identify clinical factors and biomarkers that identify whether patients should or should not receive cabazitaxel.

Present and Future Prospects of Radiation Therapy Using α-Emitting Nuclides

Therapy with α-radiation has issues associated with internal exposure; its clinical use has been avoided. However, phase III clinical tests of the α-emitting nuclide ²²³Ra on patients with cancer have been conducted, and results were reported in 2011 to 2012. Since then, research has being carried out on targeted internal therapy by introducing α-emitting nuclides directly into the cancers. For many decades, nontargeted radon therapy has been carried out and is controversial because its mechanism of action is stimulation. The low-level radiation sends powerful signals to upregulate many biological protection systems, which protect against the effects of radiogenic and nonradiogenic toxins. These vital systems prevent, repair, and remove DNA and other biomolecular damage being produced endogenously at a very high rate by the very abundant reactive oxygen species associated with aerobic metabolism. Stimulation of protection systems results in beneficial effects, including a lower risk of cancer. This article reports the results of treatments on 4 patients with cancer and reviews the clinical use of α-radiation from ²²³Ra and radon. It discusses the prospect of using the novel ²²⁵Ac-prostate-specific membrane antigen ligand-617 ligand as a therapeutic agent for prostate cancer. It presents a new treatment system that we developed, α-Radiorespiro-Rn, which seems to be extremely effective in treating cancer.

Prognostic and Therapeutic Implications of Circulating Androgen Receptor Gene Copy Number in Prostate Cancer Patients Using Droplet Digital Polymerase Chain Reaction

BACKGROUND

Resistance mechanisms in the androgen receptor (AR) signaling pathway remain key drivers in the progression to castration-resistant prostate cancer (CRPC) and relapse under antihormonal therapy.

MATERIALS AND METHODS

We evaluated the circulating AR gene copy number (CN) gain using droplet digital polymerase chain reaction in 21 control and 91 prostate cancer serum samples and its prognostic and therapeutic implications in prostate cancer.

RESULTS

In CRPC, AR CN gain was associated with faster progression to CRPC (P = .026), a greater number of previous treatments (P = .045), and previous chemotherapy (P = .016). Comparing patients with and without CN gain, the median progression-free survival (PFS) in the abiraterone subgroup was 1.7 months versus not reached (P = .004), and the median overall survival (OS) was 7 months versus 20.9 months (P = .020). In the enzalutamide subgroup, PFS was 1.7 versus 10.8 months (P = .006), and OS was 6.1 versus 16.5 months (P = .042). In the taxane subgroup, PFS was 3.2 versus 6.5 months (P = .093), and OS was 3.9 months versus not reached (P = .026). The presence of more AR copies correlated with shorter androgen deprivation (P = .002), abiraterone (P = .022), enzalutamide (P = .008), and taxane (P = .039) therapy.

CONCLUSION

Circulating AR CN gain predicts for a poor prognosis in CRPC. It is a promising biomarker predetermining rapid CRPC progression and predicting worse abiraterone and enzalutamide outcomes. Furthermore, it is associated with multiple previous treatments and previous chemotherapy.

Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer

Castrate-resistant prostate cancer (CRPC) is the fatal form of prostate cancer. Although reactivation of androgen receptor (AR) occurs following androgen deprivation, the precise mechanism involved is unclear. Here we show that the receptor tyrosine kinase, RON alters mechanical properties of cells to influence epithelial to mesenchymal transition and functions as a transcription factor to differentially regulate AR signaling. RON inhibits AR activation and subset of AR-regulated transcripts in androgen responsive LNCaP cells. However in C4-2B, a castrate-resistant sub-line of LNCaP and AR-negative androgen independent DU145 cells, RON activates subset of AR-regulated transcripts. Expression of AR in PC-3 cells leads to activation of RON under androgen deprivation but not under androgen proficient conditions implicating a role for RON in androgen independence. Consistently, RON expression is significantly elevated in castrate resistant prostate tumors. Taken together our results suggest that RON activation could aid in promoting androgen independence and that inhibition of RON in combination with AR antagonist(s) merits serious consideration as a therapeutic option during hormone deprivation therapy.

Oxibendazole inhibits prostate cancer cell growth

Prostate cancer (PCa) is one of the most common malignancies among men and is the second leading cause of cancer-associated mortality in the developed world. Androgen deprivation therapy (ADT) is the most common treatment for PCa. However, the majority of androgen-sensitive PCa patients will eventually develop resistance to ADT and the disease will become androgen-independent. There is, therefore, an immediate requirement to develop effective therapeutic techniques towards the treatment of recurrent PCa. Oxibendazole (OBZ) is an anthelmintic drug that has also shown promise in the treatment of malignancies. In the present study, the capability of OBZ to repress the growth of PCa cells was assessed in human androgen-independent PCa 22Rv1 and PC-3 cell lines. The growth of the 22Rv1 and PC-3 cell lines, as assessed with a trypan blue exclusion assay, was markedly inhibited by OBZ treatment in vitro, with half-maximal inhibitory concentration values of 0.25 and 0.64 µM, respectively. The mean size of 22Rv1 tumors in nude mice treated with OBZ (25 mg/kg/day) was 47.96% smaller than that of the control mice. Treatment with OBZ increased the expression of microRNA-204 (miR-204), as determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and the level of p53 as determined with western blotting, two well-characterized tumor suppressor genes. When miR-204 expression was knocked down by introduction of an miR-204 inhibitor, the inhibitory effect of OBZ was markedly reduced; however, when it was overexpressed, the inhibitory efficiency of OBZ was markedly higher, indicating that upregulation of miR-204 is key for the efficacy of OBZ. Additionally, OBZ was demonstrated with RT-qPCR to repress the expression of the androgen receptor, and by western blotting to reduce prostate-specific androgen in 22Rv1 cells. The results suggest that OBZ has potential for clinical use in the treatment of recurrent PCa.

Regulation of HMGB3 by antitumor miR-205-5p inhibits cancer cell aggressiveness and is involved in prostate cancer pathogenesis

Our recent determination of a microRNA (miRNA) expression signature in prostate cancer (PCa) revealed that miR-205-5p was significantly reduced in PCa tissues and that it acted as an antitumor miRNA. The aim of this study was to identify oncogenic genes and pathways in PCa cells that were regulated by antitumor miR-205-5p. Genome-wide gene expression analyses and in silico miRNA database searches showed that 37 genes were putative targets of miR-205-5p regulation. Among those genes, elevated expression levels of seven in particular (HMGB3, SPARC, MKI67, CENPF, CDK1, RHOU, and POLR2D) were associated with a shorter disease-free survival in a large number of patients in the The Cancer Genome Atlas (TCGA) database. We focused on high-mobility group box 3 (HMGB3) because it was the most downregulated by ectopic expression of miR-205-5p in PC3 cells and its expression was involved in PCa pathogenesis. Luciferase reporter assays showed that HMGB3 was directly regulated by miR-205-5p in PCa cells. Knockdown studies using si-HMGB3 showed that expression of HMGB3 enhanced PCa cell aggressiveness. Overexpression of HMGB3/HMGB3 was confirmed in naive PCa and castration-resistant PCa (CRPC) clinical specimens. Novel approaches to analysis of antitumor miRNA-regulated RNA networks in PCa cells may provide new insights into the pathogenic mechanisms of the disease.

Phase 1 study of darolutamide (ODM-201): a new-generation androgen receptor antagonist, in Japanese patients with metastatic castration-resistant prostate cancer

PURPOSE

This trial assessed the safety, pharmacokinetics, and efficacy of darolutamide (ODM-201), a new-generation nonsteroidal androgen receptor antagonist, in Japanese patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

In this open-label, nonrandomized, two-cohort, dose-escalating phase 1 study, Japanese patients with mCRPC were enrolled after a screening period. In the single-dose period (≈1 week), darolutamide was administered at 300 mg (Cohort 1) or 600 mg (Cohort 2) on day -5 (fasting state) and day -2 (fed condition). In the subsequent multiple-dose period (fed condition), patients received darolutamide 300 mg twice daily (Cohort 1) or 600 mg twice daily (Cohort 2) for 12 weeks. Primary endpoints: evaluate safety and pharmacokinetics of darolutamide.

RESULTS

Of 12 patients enrolled, 9 received darolutamide (Cohort 1, n = 3; Cohort 2, n = 6). All 9 patients experienced ≥1 treatment-emergent adverse event (TEAE; majority Grade 1/2). Incidence of drug-related TEAEs (DR-TEAEs) was 44% (all grades; n = 4); most common DR-TEAE was decreased appetite (22%), and 1 serious DR-TEAE (Grade 3 nausea) was observed. No Grade ≥4 DR-TEAEs or new safety signals were observed. C max and AUC (0-t last) were dose-dependent; pharmacokinetics of each dose appeared to be linear over time. Prostate-specific antigen response was observed in 11% (1/9) of patients. Compared with fasting status, geometric mean C max increased 2.5-fold after 300 mg and 2.8-fold after 600 mg; geometric mean AUC (0-t last) increased 2.5-fold after both doses under fed conditions.

CONCLUSIONS

Darolutamide was well tolerated at the examined doses in Japanese patients with mCRPC, without differences in safety and pharmacokinetics relative to Western patients.

Preliminary results on response assessment using 68Ga-HBED-CC-PSMA PET/CT in patients with metastatic prostate cancer undergoing docetaxel chemotherapy

PURPOSE

To investigate the value of ⁶⁸Ga-HBED-CC PSMA (⁶⁸Ga-PSMA) PET/CT for response assessment in metastatic castration-sensitive and castration-resistant prostate cancer (mCSPC and mCRPC) during docetaxel chemotherapy.

METHODS

⁶⁸Ga-PSMA PET/CT was performed in seven mCSPC patients before and after six cycles of upfront docetaxel chemotherapy and in 16 mCRPC patients before and after three cycles of palliative docetaxel chemotherapy. Radiographic treatment response was evaluated separately on the ⁶⁸Ga-PSMA PET and CT datasets. Changes in ⁶⁸Ga-PSMA uptake (SUVmean) were assessed on a per-patient and a per-lesion basis using the PERCIST scoring system with slight modification. Treatment response was defined as absence of any PSMA uptake in all target lesions on posttreatment PET (complete response, CR) or a decrease in summed SUVmean of ≥30% (partial response, PR). The appearance of a new PET-positive lesion or an increase in summed SUVmean of ≥30% (progressive disease, PD) indicated nonresponse. A moderate change in summed SUVmean (between -30% and +30%) without a change in the number of target lesions was defined as stable disease (SD). For treatment response assessment on CT, RECIST1.1 criteria were used. Radiographic responses on ⁶⁸Ga-PSMA PET [RR(PET)] and on CT [RR(CT)] were compared and correlated with biochemical response (BR). A decrease in serum PSA level of ≥50% was defined as biochemical PR.

RESULTS

Biochemical PR was found in six of seven patients with mCSPC (86%, 95% confidence interval 42% to 99.6%). The concordance rate was higher between BR and RR(PET) than between BR and RR(CT) (6/7 vs. 3/6 patients. ⁶⁸Ga-PSMA PET and CT were concordant in only three patients (50%, 12% to 88%). In mCRPC patients, biochemical PR was found in six of 16 patients (38%, 15% to 65%). Outcome prediction was concordant between BR and RR(PET) in nine of 16 patients (56%), and between BR and RR(CT) in only four of 12 patients (33%) with target lesions on CT. ⁶⁸Ga-PSMA PET and CT results corresponded in seven of 12 patients (58%, 28% to 85%).

CONCLUSION

Our preliminary results suggest that ⁶⁸Ga-PSMA PET might be a promising method for treatment response assessment in mCSPC and mCRPC. The data indicate that for different metastatic sites, the performance of ⁶⁸Ga-PSMA PET in response assessment might be superior to that of the conventional CT approach and could help differentiate between progressive disease and treatment response. Because of the limited number of patients, the differences revealed in our study were not statistically significant. Thus larger and prospective studies are clearly needed and warranted to confirm the value of ⁶⁸Ga-PSMA PET as an imaging biomarker for response assessment.

High expression of PDLIM5 facilitates cell tumorigenesis and migration by maintaining AMPK activation in prostate cancer

PDZ and LIM domain 5 (PDLIM5) is a cytoskeleton-associated protein and has been shown to bind to a variety of proteins through its specific domain, thereby acting to regulate cell migration and tumor progression. Here, we found that PDLIM5 was abnormally upregulated in prostate cancer (PCa) tissues as compared with that in normal prostate tissue. ONCOMINE microarray data mining showed that PDLIM5 was closely correlated with the prognosis of PCa in terms of Gleason score, tumor metastasis and biochemical recurrence. Lentivirus-mediated short hairpin RNA (shRNA) knockdown of PDLIM5 inhibited cell proliferation and colony formation, arrested hormone independent PCa cells DU145 and PC-3 in G2/M phase, and induced apoptosis. Meanwhile, silencing PDLIM5 inhibited migration and invasion of tumor cells by reversing the mesenchymal phenotype and a similar result was confirmed in a xenograft nude mouse model. Finally, we found PDLIM5 plays a crucial role in regulating malignant tumor cell proliferation, invasion and migration by binding to AMPK and affecting its activation and degradation, and may therefore prove to be a potential oncogenic gene in the development and progression of PCa.

Effect of dihydroartemisinin on UHRF1 gene expression in human prostate cancer PC-3 cells

As the second most common cancer in men around the world, prostate cancer is increasingly gaining more attention. Dihydroartemisinin (DHA) has been proven to be a promising anticancer agent in vitro as well as in vivo in accumulating data. However, the detailed mechanisms of how DHA action in human prostate cancer PC-3 cells remain elusive. This study aimed to investigate the effects of DHA, a novel anticancer agent, by inhibiting the expression of ubiquitin like containing PHD and ring finger 1 (UHRF1) in PC-3 cells. The apoptosis and cell-cycle distribution were detected by flow cytometry. Quantitative real-time PCR was performed to examine both UHRF1 and DNA methyltransferase 1 (DNMT1) expressions at mRNA levels, whereas the expressions of UHRF1, DNMT1, and p16 proteins at protein levels were detected by Western blotting. Methylation levels of p16 CpG islands were determined by bisulfite genomic sequencing. We showed that DHA induced the downregulation of UHRF1 and DNMT1, accompanied by an upregulation of p16 in PC-3 cells. Decreased p16 promoter methylation levels in DHA-treated groups were also observed in PC-3 cells. Furthermore, DHA significantly induced apoptosis and G1/S cell-cycle arrest in PC-3 cells. Our results suggested that downregulation of UHRF1/DNMT1 is upstream to many cellular events, including G1 cell arrest, demethylation of p16, and apoptosis. Together, our study provides new evidence that DHA may serve as a potential therapeutic agent in the treatment of prostate cancer.

Treatment with the WNT5A-mimicking peptide Foxy-5 effectively reduces the metastatic spread of WNT5A-low prostate cancer cells in an orthotopic mouse model

Prostate cancer patients with high WNT5A expression in their tumors have been shown to have more favorable prognosis than those with low WNT5A expression. This suggests that reconstitution of Wnt5a in low WNT5A-expressing tumors might be an attractive therapeutic approach. To explore this idea, we have in the present study used Foxy-5, a WNT5A mimicking peptide, to investigate its impact on primary tumor and metastasis in vivo and on prostate cancer cell viability, apoptosis and invasion in vitro. We used an in vivo orthotopic xenograft mouse model with metastatic luciferase-labeled WNT5A-low DU145 cells and metastatic luciferase-labeled WNT5A-high PC3prostate cancer cells. We provide here the first evidence that Foxy-5 significantly inhibits the initial metastatic dissemination of tumor cells to regional and distal lymph nodes by 90% and 75%, respectively. Importantly, this effect was seen only with the WNT5A-low DU145 cells and not with the WNT5A-high PC3 cells. The inhibiting effect in the DU145-based model occurred despite the fact that no effects were observed on primary tumor growth, apoptosis or proliferation. These findings are consistent with and supported by the in vitro data, where Foxy-5 specifically targets invasion without affecting apoptosis or viability of WNT5A-low prostate cancer cells. To conclude, our data indicate that the WNT5A-mimicking peptide Foxy-5, which has been recently used in a phase 1 clinical trial, is an attractive candidate for complimentary anti-metastatic treatment of prostate cancer patients with tumors exhibiting absent or low WNT5A expression.