Mechanisms of Therapeutic Resistance in Prostate Cancer

Identification of Somatic Gene Signatures in Circulating Cell-Free DNA Associated with Disease Progression in Metastatic Prostate Cancer by a Novel Machine Learning Platform

PURPOSE

Progression from metastatic castration-sensitive prostate cancer (mCSPC) to a castration-resistant (mCRPC) state heralds the lethal phenotype of prostate cancer. Identifying genomic alterations associated with mCRPC may help find new targets for drug development. In the majority of patients, obtaining a tumor biopsy is challenging because of the predominance of bone-only metastasis. In this study, we hypothesize that machine learning (ML) algorithms can identify clinically relevant patterns of genomic alterations (GAs) that distinguish mCRPC from mCSPC, as assessed by next-generation sequencing (NGS) of circulating cell-free DNA (cfDNA).

EXPERIMENTAL DESIGN

Retrospective clinical data from men with metastatic prostate cancer were collected. Men with NGS of cfDNA performed at a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory at time of diagnosis of mCSPC or mCRPC were included. A combination of supervised and unsupervised ML algorithms was used to obtain biologically interpretable, potentially actionable insights into genomic signatures that distinguish mCRPC from mCSPC.

RESULTS

GAs that distinguish patients with mCRPC (n = 187) from patients with mCSPC (n = 154) (positive predictive value = 94%, specificity = 91%) were identified using supervised ML algorithms. These GAs, primarily amplifications, corresponded to androgen receptor, Mitogen-activated protein kinase (MAPK) signaling, Phosphoinositide 3-kinase (PI3K) signaling, G1/S cell cycle, and receptor tyrosine kinases. We also identified recurrent patterns of gene- and pathway-level alterations associated with mCRPC by using Bayesian networks, an unsupervised machine learning algorithm.

CONCLUSION

These results provide clinical evidence that progression from mCSPC to mCRPC is associated with stereotyped concomitant gain-of-function aberrations in these pathways. Furthermore, detection of these aberrations in cfDNA may overcome the challenges associated with obtaining tumor bone biopsies and allow contemporary investigation of combinatorial therapies that target these aberrations.

IMPLICATIONS FOR PRACTICE

The progression from castration-sensitive to castration-resistant prostate cancer is characterized by worse prognosis and there is a pressing need for targeted drugs to prevent or delay this transition. This study used machine learning algorithms to examine the cell-free DNA of patients to identify alterations to specific pathways and genes associated with progression. Detection of these alterations in cell-free DNA may overcome the challenges associated with obtaining tumor bone biopsies and allow contemporary investigation of combinatorial therapies that target these aberrations.

Detection of Cross-Resistance Between Methotrexate and Azoles in Candida albicans and Meyerozyma guilliermondii: An In Vitro Study

In recent years, there has been a rapid increase in the incidence of Candida infections. The different species of the genus Candida vary in their virulence abilities and susceptibility to antifungal agents, depending on several external factors. The result of such modifications may be cross-resistance, which is understood as an acquired resistance to a certain antimicrobial agent after exposure to another drug. The aim of this study was to determine the possibility of cross-resistance between fluconazole, voriconazole, itraconazole, and methotrexate in Candida albicans and Meyerozyma guilliermondii (syn. Candida guilliermondii ). Fifteen strains of M. guilliermondii and eight strains of C. albicans , including the standard strains, were tested. For all strains, the minimum inhibitory concentrations (MICs) for fluconazole, voriconazole, and itraconazole were determined before and after stimulation with methotrexate. The median MICs in M. guilliermondii before and after stimulation were 9.333 and 64 mg/L ( p = 0.005) for fluconazole; 0.917 and 1.667 mg/L ( p = 0.001) for itraconazole, respectively. No significant change in MIC was observed for voriconazole. For C. albicans strains, the median MICs before and after stimulation were 0.917 and 64 mg/L ( p = 0.012) for fluconazole; 0.344 and 1.135 mg/L ( p = 0.018) for voriconazole, respectively. There was no significant change in MIC values for itraconazole. Thus, this study demonstrates the presence of cross-resistance between voriconazole, itraconazole, fluconazole, and methotrexate for the selected strains. Methotrexate exposure induces different responses when certain drugs are used for various species. Therefore, if a patient was previously exposed to methotrexate, there may be a higher risk of treatment failure with fluconazole than with other azoles such as voriconazole for fungemia caused by M. guilliermondii or itraconazole for C. albicans infection.

Antitumor Activity of NLG207 (Formerly CRLX101) in Combination with Enzalutamide in Preclinical Prostate Cancer Models

Effective treatments for patients with metastatic castration-resistant prostate cancer following disease progression on enzalutamide are currently an unmet clinical need. Simultaneous inhibition of the hypoxia-inducible factor (HIF)-1α and androgen receptor (AR) pathways has been previously shown to overcome enzalutamide resistance in vitro Combination treatment with NLG207, a nanoparticle-drug conjugate of camptothecin and inhibitor of HIF-1α, and enzalutamide was evaluated in preclinical prostate cancer models of enzalutamide resistance. The effect of NLG207 and enzalutamide on average tumor volume and tumor re-growth after 3 weeks of treatment was evaluated in vivo using the subcutaneous 22Rv1 xenograft and castrated subcutaneous VCaP xenograft models. Correlative assessments of antitumor activity were evaluated in vitro using cell proliferation and qPCR assays. NLG207 8 mg/kg alone and in combination with enzalutamide reduced average tumor volume by 93% after 3 weeks of treatment (P < 0.05) in comparison with vehicle control in the subcutaneous 22Rv1 xenograft model. Notably, the addition of NLG207 also enhanced the efficacy of enzalutamide alone in the castrated subcutaneous VCaP xenograft model, decreasing the median rate of tumor growth by 51% (P = 0.0001) in comparison with enzalutamide alone. In vitro assessments of cell proliferation and gene expression further demonstrated antitumor activity via AR-HIF-1α crosstalk inhibition. Combination treatment with NLG207 and enzalutamide was shown to be effective in preclinical prostate cancer models of enzalutamide resistance. Clinical investigation of this treatment combination is ongoing (NCT03531827).

Cross-resistance and drug sequence in prostate cancer

The treatment landscape of advanced prostate cancer has widely expanded over the past years with androgen receptor signaling inhibitors (ARSIs) and taxane chemotherapy moving to earlier disease stages in the treatment of prostate cancer. With the increasing use of ARSIs in earlier disease stages, cross-resistance between treatments has emerged, which is a dominant impediment in current clinical practice. To overcome cross-resistance in the treatment of prostate cancer, it is of paramount importance to decipher the mechanisms of cross-resistance between ARSIs and between ARSIs and chemotherapy. Here, molecular mechanisms of resistance to the available therapies including androgen receptor (AR) splice variants, AR overexpression, AR mutations and glucocorticoid receptor upregulation are described. Based on these underlying mechanisms, clinical data of cross-resistance between ARSIs and chemotherapy have been reported. Only recently these data have been confirmed in prospective randomized trials. From these studies, it has become clear that sequential ARSI treatment has no place in the treatment of advanced prostate cancer due to emerging drug resistance. In addition, based on prospective evidence, we argue that it is worth considering an early switch to cabazitaxel treatment in case of lack of benefit on docetaxel regimen after an ARSI treatment. Based on these new insights from randomized trials, several recommendations for treatment sequence are proposed.

Resistance to second-generation androgen receptor antagonists in prostate cancer

The introduction of second-generation androgen receptor antagonists (SG-ARAs) has greatly impacted the treatment of metastatic prostate cancer, providing tolerable and efficacious alternatives to chemotherapy. SG-ARAs provide similar therapeutic benefit to abiraterone, a potent CYP17 inhibitor, and do not require the co-administration of prednisone. Despite considerable improvements in clinical outcomes in the settings of both castration sensitivity and castration resistance, the durability of clinical response to the SG-ARAs enzalutamide, apalutamide and darolutamide, similar to abiraterone, is limited by inevitable acquired resistance. Genomic aberrations that confer resistance to SG-ARAs or provide potential alternative treatment modalities have been identified in numerous studies, including alterations of the androgen receptor, DNA repair, cell cycle, PI3K-AKT-mTOR and Wnt-β-catenin pathways. To combat resistance, researchers have explored approaches to optimizing the utility of available treatments, as well as the use of alternative agents with a variety of targets, including AR-V7, AKT, EZH2 and HIF1α. Ongoing research to establish predictive biomarkers for the treatment of tumours with resistance to SG-ARAs led to the approval of the PARP inhibitors olaparib and rucaparib in pre-treated metastatic castration-resistant prostate cancer. The results of ongoing studies will help to shape precision medicine in prostate cancer and further optimize treatment paradigms to maximize clinical outcomes.

V-ATPase Inhibition Decreases Mutant Androgen Receptor Activity in Castrate-resistant Prostate Cancer

Prostate cancer is critically dependent on androgen receptor (AR) signaling. Despite initial responsiveness to androgen deprivation, most patients with advanced prostate cancer subsequently progress to a clinically aggressive castrate-resistant prostate cancer (CRPC) phenotype, typically associated with expression of splice-variant or mutant AR forms. Although current evidence suggests that the vacuolar-ATPase (V-ATPase), a multiprotein complex that catalyzes proton transport across intracellular and plasma membranes, influences wild-type AR function, the effect of V-ATPase inhibition on variant AR function is unknown.Inhibition of V-ATPase reduced AR function in wild-type and mutant AR luciferase reporter models. In hormone-sensitive prostate cancer cell lines (LNCaP, DuCaP) and mutant AR CRPC cell lines (22Rv1, LNCaP-F877L/T878A), V-ATPase inhibition using bafilomycin-A1 and concanamycin-A reduced AR expression, and expression of AR target genes, at mRNA and protein levels. Furthermore, combining chemical V-ATPase inhibition with the AR antagonist enzalutamide resulted in a greater reduction in AR downstream target expression than enzalutamide alone in LNCaP cells. To investigate the role of individual subunit isoforms, siRNA and CRISPR-Cas9 were used to target the V1C1 subunit in 22Rv1 cells. Whereas transfection with ATP6V1C1-targeted siRNA significantly reduced AR protein levels and function, CRISPR-Cas9-mediated V1C1 knockout showed no substantial change in AR expression, but a compensatory increase in protein levels of the alternate V1C2 isoform.Overall, these results indicate that V-ATPase dysregulation is directly linked to both hormone-responsive prostate cancer and CRPC via impact on AR function. In particular, V-ATPase inhibition can reduce AR signaling regardless of mutant AR expression.

Synthesis and anticancer evaluation of 6-azacyclonol-2,4,6-trimethylpyridin-3-ol derivatives: M3 muscarinic acetylcholine receptor-mediated anticancer activity of a cyclohexyl derivative in androgen-refractory prostate cancer

We recently reported 2,4,5-trimethylpyridin-3-ol with C(6)-azacyclonol, whose code name is BJ-1207, showing a promising anticancer activity by inhibiting NOX-derived ROS in A549 human lung cancer cells. The present study was focused on structural modification of the azacyclonol moiety of BJ-1207 to find a compound with better anticancer activity. Ten new compounds (3A-3J) were prepared and evaluated their inhibitory actions against proliferation of eighteen cancer cell lines as a primary screening. Among the ten derivatives of BJ-1207, the effects of compounds 3A and 3J on DU145 and PC-3, androgen-refractory cancer cell lines (ARPC), were greater than the parent compound, and compound 3A showed better activity than 3J. Antitumor activity of compound 3A was also observed in DU145-xenografted chorioallantoic membrane (CAM) tumor model. In addition, the ligand-based target prediction and molecular docking study using DeepZema® server showed compound 3A was a ligand to M3 muscarinic acetylcholine receptor (M3R) which is overexpressed in ARPC. Carbachol, a muscarinic receptor agonist, concentration dependently increased proliferation of DU145 in the absence of serum, and it also activated NADPH oxidase (NOX). The carbachol-induced proliferation and NOX activity was significantly blocked by compounds 3A in a concentration-dependent manner. This finding might become a new milestone in the development of pyridinol-based anti-cancer agents against ARPC.

A National Multicenter Study on overall survival in elderly metastatic castrate-resistant prostate cancer patients treated with Radium-223

BACKGROUND

Radium-223 prolongs overall survival (OS) and delays time to the first symptomatic skeletal events in patients with symptomatic metastatic castration-resistant prostate cancer (mCRPC). There is a lack of evidence on the safety and efficacy of Radium-223 treatment in the very elderly population.

AIMS

Aim of this multicentre study is to analyze mCRPC patients treated with Radium-223 in terms of OS and to assess whether there are differences between young and elderly, as well as to verify efficacy and safety in patients ≥ 75 years of age.

METHODS

430 mCRPC patients of six Italian Centres were analyzed in this multicenter retrospective study. At baseline and after each cycle were collected clinical and diagnostic patients' parameters. The whole cohort was divided into two groups based on the age of the patients (< 75 years old and ≥ 75 years old).

RESULTS

47% of the patients were < 75 years old and 53% were ≥ 75 years old. The primary outcome, OS, does not show significant differences between the two subgroups if other basal parameters are considered. Considering clinical covariates in univariate models (p < 0.05) several clinical aspects have an impact on OS, except for age (p = 0.072). Age continues to have no significant impact on the OS (p = 0.274) even in multivariate models in the two groups. The toxic effects are similar in the two groups.

CONCLUSIONS

Radium-223 prolongs survival in both younger and older patients at the same baseline condition and is a good option in the symptomatic mCRPC setting compared to other agents.

Non-Coding RNAs Set a New Phenotypic Frontier in Prostate Cancer Metastasis and Resistance

Prostate cancer (PCa) mortality remains a significant public health problem, as advanced disease has poor survivability due to the development of resistance in response to both standard and novel therapeutic interventions. Therapeutic resistance is a multifaceted problem involving the interplay of a number of biological mechanisms including genetic, signaling, and phenotypic alterations, compounded by the contributions of a tumor microenvironment that supports tumor growth, invasiveness, and metastasis. The androgen receptor (AR) is a primary regulator of prostate cell growth, response and maintenance, and the target of most standard PCa therapies designed to inhibit AR from interacting with androgens, its native ligands. As such, AR remains the main driver of therapeutic response in patients with metastatic castration-resistant prostate cancer (mCRPC). While androgen deprivation therapy (ADT), in combination with microtubule-targeting taxane chemotherapy, offers survival benefits in patients with mCRPC, therapeutic resistance invariably develops, leading to lethal disease. Understanding the mechanisms underlying resistance is critical to improving therapeutic outcomes and also to the development of biomarker signatures of predictive value. The interconversions between epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) navigate the prostate tumor therapeutic response, and provide a novel targeting platform in overcoming therapeutic resistance. Both microRNA (miRNA)- and long non-coding RNA (lncRNA)-mediated mechanisms have been associated with epigenetic changes in prostate cancer. This review discusses the current evidence-based knowledge of the role of the phenotypic transitions and novel molecular determinants (non-coding RNAs) as contributors to the emergence of therapeutic resistance and metastasis and their integrated predictive value in prostate cancer progression to advanced disease.

Optimal control to reach eco-evolutionary stability in metastatic castrate-resistant prostate cancer

In the absence of curative therapies, treatment of metastatic castrate-resistant prostate cancer (mCRPC) using currently available drugs can be improved by integrating evolutionary principles that govern proliferation of resistant subpopulations into current treatment protocols. Here we develop what is coined as an 'evolutionary stable therapy', within the context of the mathematical model that has been used to inform the first adaptive therapy clinical trial of mCRPC. The objective of this therapy is to maintain a stable polymorphic tumor heterogeneity of sensitive and resistant cells to therapy in order to prolong treatment efficacy and progression free survival. Optimal control analysis shows that an increasing dose titration protocol, a very common clinical dosing process, can achieve tumor stabilization for a wide range of potential initial tumor compositions and volumes. Furthermore, larger tumor volumes may counter intuitively be more likely to be stabilized if sensitive cells dominate the tumor composition at time of initial treatment, suggesting a delay of initial treatment could prove beneficial. While it remains uncertain if metastatic disease in humans has the properties that allow it to be truly stabilized, the benefits of a dose titration protocol warrant additional pre-clinical and clinical investigations.

Study on the cellular internalization mechanisms and in vivo anti-bone metastasis prostate cancer efficiency of the peptide T7-modified polypeptide nanoparticles

Bone-metastasis prostate cancer (BMPCa)-targeting gene therapy is gaining increasing concern in recent years. The peptide T7-modified polypeptide nanoparticles for delivery DNA (CRD-PEG-T7/pPMEPA1) was prepared as our previous study. However, the feasibility of CRD-PEG-T7/pPMEPA1 for BMPCa treatment, the mechanisms underlying cellular uptake, anti-BMPCa effect, and administration safety requires further research. LNCaP cells treated with endocytosis inhibitors and excessive T7 under different culture condition were carried out to investigate the mechanisms of cellular uptake of the CRD-PEG-T7-pPMEPA1. A transwell assay was applied to evaluate the cell migration ability. Besides, the tumor volume and survival rates of the PCa xenograft mice model were recorded to estimate the anti-tumor effect. In addition, the weight profiles of the PCa tumor-bearing mice, the blood chemistry, and the HE analysis of visceral organs and tumor was conducted to investigate the administration safety of CRD-PEG-T7/pPMEPA1. The results showed that PCa cellular uptake was decreased after treating with excessive free T7, endocytosis inhibitors and lower incubation temperature. Besides, CRD-PEG-T7/pPMEPA1 could inhibit the LNCaP cells chemotaxis and tumor growth. In addition, the survival duration of the PCa tumor-bearing mice treating with CRD-PEG-T7/pPMEPA1 was significantly prolonged with any systemic toxicity or damage to the organs. In conclusion, this research proposes a promising stratagem for treatment BMPCa by providing the biocompatible and effective carrier for delivery DNA therapeutic agents.

Modifying Adaptive Therapy to Enhance Competitive Suppression

Adaptive therapy is a promising new approach to cancer treatment. It is designed to leverage competition between drug-sensitive and drug-resistant cells in order to suppress resistance and maintain tumor control for longer. Prompted by encouraging results from a recent pilot clinical trial, we evaluate the design of this initial test of adaptive therapy and identify three simple modifications that should improve performance. These modifications are designed to increase competition and are easy to implement. Using the mathematical model that supported the recent adaptive therapy trial, we show that the suggested modifications further delay time to tumor progression and also increase the range of patients who can benefit from adaptive therapy.

Super-enhancer in prostate cancer: transcriptional disorders and therapeutic targets

Abnormal activity of oncogenic and tumor-suppressor signaling pathways contributes to cancer and cancer risk in humans. Transcriptional dysregulation of these pathways is commonly associated with tumorigenesis and the development of cancer. Genetic and epigenetic alterations may mediate dysregulated transcriptional activity. One of the most important epigenetic alternations is the non-coding regulatory element, which includes both enhancers and super-enhancers (SEs). SEs, characterized as large clusters of enhancers with aberrant high levels of transcription factor binding, have been considered as key drivers of gene expression in controlling and maintaining cancer cell identity. In cancer cells, oncogenes acquire SEs and the cancer phenotype relies on these abnormal transcription programs driven by SEs, which leads to cancer cells often becoming addicted to the SEs-related transcription programs, including prostate cancer. Here, we summarize recent findings of SEs and SEs-related gene regulation in prostate cancer and review the potential pharmacological inhibitors in basic research and clinical trials.

Immune molecular profiling of a multiresistant primary prostate cancer with a neuroendocrine-like phenotype: a case report

Background

Understanding the drivers of recurrence in aggressive prostate cancer requires detailed molecular and genomic understanding in order to aid therapeutic interventions. We provide here a case report of histological, transcriptional, proteomic, immunological, and genomic features in a longitudinal study of multiple biopsies from diagnosis, through treatment, and subsequent recurrence.

Case presentation

Here we present a case study of a male in 70 s with high-grade clinically-localised acinar adenocarcinoma treated with definitive hormone therapy and radiotherapy. The patient progressed rapidly with rising PSA and succumbed without metastasis 52 months after diagnosis. We identified the expression of canonical histological markers of neuroendocrine PC (NEPC) including synaptophysin, neuron-specific enolase and thyroid transcription factor 1, as well as intact AR expression, in the recurrent disease only. The resistant disease was also marked by an extremely low immune infiltrate, extensive genomic chromosomal aberrations, and overactivity in molecular hallmarks of NEPC disease including Aurora kinase and E2F, as well as novel alterations in the cMYB pathway. We also observed that responses to both primary treatments (high dose-rate brachytherapy and androgen deprivation therapies) were consistent with known optimal responses—ruling out treatment inefficacy as a factor in relapse.

Conclusions

These data provide novel insights into a case of locally recurrent aggressive prostate cancer harbouring NEPC pathology, in the absence of detected metastasis.

Senescence and castration resistance in prostate cancer: A review of experimental evidence and clinical implications

The development of Castration-Resistant Prostate Cancer (CRPC) remains a major challenge in the treatment of this disease. While Androgen Deprivation Therapy (ADT) can result in tumor shrinkage, a primary response of Prostate Cancer (PCa) cells to ADT is a senescent growth arrest. As a response to cancer therapies, senescence has often been considered as a beneficial outcome due to its association with stable growth abrogation, as well as the potential for immune system activation via the Senescence-Associated Secretory Phenotype (SASP). However, there is increasing evidence that not only can senescent cells regain proliferative capacity, but that senescence contributes to deleterious effects of cancer chemotherapy, including disease recurrence. Notably, the preponderance of work investigating the consequences of therapy-induced senescence on tumor progression has been performed in non-PCa models. Here, we summarize the evidence that ADT promotes a senescent response in PCa and postulate mechanisms by which senescence may contribute to the development of castration-resistance. Primarily, we suggest that ADT-induced senescence may support CRPC development via escape from senescence, by cell autonomous-reprogramming, and by the formation of a pro-tumorigenic SASP. However, due to the scarcity of direct evidence from PCa models, the consequences of ADT-induced senescence outlined here remain speculative until the relationship between senescence and CRPC can be experimentally defined.

Perinatal exposure to Bisphenol A disturbs the early differentiation of male germ cells

Understanding the effects of Bisphenol A (BPA) on early germ cell differentiation and their consequences in adult life is an area of growing interest in the field of endocrine disruption. Herein, we investigate whether perinatal exposure to BPA affects the differentiation of male germ cells in early life using a transgenic mouse expressing the GFP reporter protein under the Oct4 promoter. In this model, the expression of GFP reflects the expression of the Oct4 gene. This pluripotency gene is required to maintain the spermatogonial stem cells in an undifferentiated stage. Thus, GFP expression was used as a parameter to evaluate the effect of BPA on early germ cell development. Female pregnant transgenic mice were exposed to BPA by oral gavage, from embryonic day 5.5 to postnatal day 7 (PND7). The effects of BPA on male germ cell differentiation were evaluated at PND7, while sperm quality, testicular morphology, and protein expression of androgen receptor and proliferating cell nuclear antigen were studied at PND130. We found that perinatal/lactational exposure to BPA up-regulates the expression of Oct4-driven GFP in testicular cells at PND7. This finding suggests a higher proportion of undifferentiated spermatogonia in BPA-treated animals compared with non-exposed mice. Moreover, in adulthood, the number of spermatozoa per epididymis was reduced in those animals perinatally exposed to BPA. This work shows that developmental exposure to BPA disturbed the normal differentiation of male germ cells early in life, mainly by altering the expression of Oct4 and exerted long-lasting sequelae at the adult stage, affecting sperm count and testis.

Resetting the Bar of Castration Resistance - Understanding Androgen Dynamics in Therapy Resistance and Treatment Choice in Prostate Cancer

This review discusses impact of advancements in biologic understanding of prostate cancer (PCa) on definition and diagnosis of castration-resistant PCa (CRPC), predictive factors for progression to CRPC and treatment strategies. More sensitive assays confirm that bilateral orchiectomy reduces serum testosterone (T) closer to < 20 ng/dL than < 50 ng/dL, and evidence suggests that achieving T < 20 ng/dL improves outcomes and delays CRPC emergence. Regular T assessments will evaluate whether T is adequately suppressed in the setting of potential progression to CRPC, given that late dosing may result in T escape. More advanced imaging modalities and biomarker assays allow earlier detection of disease progression. Predictive factors for progression to CRPC include Gleason grade, extent of metastatic spread, germline hereditary factors such as gene mutations affecting androgen receptor amplification or DNA repair deficiency mutations, prostate-specific antigen kinetics, and biomarker analyses. Treatment options for CRPC have expanded beyond androgen deprivation therapy to include therapies that suppress T or inhibit its activity through varying mechanisms. Future directions include therapies with novel biological targets, drug combinations and personalized treatments. Advanced PCa management aims to delay progression to CRPC and prolong survival. With redefinition of castration and advancements in understanding of the biology of disease progression, diagnosis and treatment strategies should be re-evaluated. Definition of CRPC could be updated to reflect the T < 20 ng/dL requirement as this is a 'true' castrate level and may improve outcomes. It is important that androgen deprivation therapy as foundational therapy is continued even as new CRPC therapies are introduced.

Mismatch repair deficiency in metastatic prostate cancer: Response to PD-1 blockade and standard therapies

Background

While response rates to anti-PD1 therapy are low in unselected metastatic castration resistant prostate cancer (mCRPC) patients, those with inactivating mutations in mismatch repair (MMR) genes (i.e. MMR deficiency; MMRd) or microsatellite instability (MSI) are thought likely to respond favorably. To date, there is limited published data on this biologically distinct and clinically relevant subgroup’s natural history and response to treatment.

Methods

We retrospectively identified patients at two academic institutions who had MMRd/MSI-high metastatic prostate cancer (PC). Clinical and pathologic characteristics at the time of diagnosis as well as response to standard therapies and immune checkpoint therapy were abstracted. Descriptive statistics, including PSA50 response (≥50% decline in PSA from baseline) and clinical/radiographic progression free survival (PFS), are reported.

Results

27 men with MMRd and/or MSI-high metastatic PC were identified. 13 (48%) men had M1 disease at diagnosis and 19 of 24 (79%) men that underwent prostate biopsy had a Gleason score ≥8. Median overall survival from time of metastasis was not reached (95% CI: 33.6-NR mos) after a median follow up of 33.6 mos (95% CI: 23.8–50.5 mos). Seventeen men received pembrolizumab, of which 15 had PSA response data available. PSA50 responses to pembrolizumab occurred in 8 (53%) men. Median PFS was not reached (95% CI: 1.87-NR mos) and the estimated PFS at 6 months was 64.1% (95% CI: 33.7%-83.4%). Of those who achieved a PSA50 response, 7 (87.5%) remain on treatment without evidence of progression at a median follow up of 12 months (range 3–20 months).

Conclusions

MMRd PC is associated with high Gleason score and advanced disease at presentation. Response rates to standard therapies are comparable to those reported in unselected patients and response rate to checkpoint blockade is high. Our study is limited by small sample size, and more research is needed to identify additional factors that may predict response to immunotherapy.

Metastasis-directed therapy in castration-refractory prostate cancer (MEDCARE): a non-randomized phase 2 trial

Background

Patients diagnosed with metastatic castration-refractory prostate cancer (mCRPC) rely on a limited number of therapeutic agents resulting in a median survival of 2–3 years. A subgroup of those patients with mCRPC presents with oligoprogressive disease, with a limited number of progressive lesions while other metastases are still controlled by ongoing systemic treatment.

Methods

In this single arm prospective phase II trial, we aim to include 18 patients with oligoprogressive mCRPC (1–3 metastases and/or local recurrence) who will be treated with metastasis-directed therapy to all visible progressive lesions. Progression is based on conventional imaging, as the use of PSMA PET-CT is considered investigational. However all patients will undergo PSMA PET-CT and the images will be blinded until progression. Primary endpoint is the postponement of the start of next-line systemic treatment (NEST) and the additional clinical value of PSMA PET-CT. Recruitment of patients for this trial started in January 2020 and will be completed approximately by December 2020.

Discussion

In this phase 2 trial on oligoprogressive mCRPC, we will investigate the benefit of progression-directed therapy while continuing ongoing systemic treatment. We hypothesize that progression-directed therapy (PDT) with surgery or stereotactic body radiation therapy for these oligoprogressive lesions will postpone the start of next-line systemic treatment and therefore serve as a new or add-on therapy in the spectrum of treatments available for mCRPC. The results of this trial will serve as guidance for a later randomized phase 3 trial. All participants are given an information sheet and are required to give written informed consent. Results will be published in a peer-reviewed journal.

Trial registration

This study is registered at ClinicalTrials.gov: NCT04222634 (December 18th 2019).

Impact of nuclear YAP1 expression in residual cancer after neoadjuvant chemohormonal therapy with docetaxel for high-risk localized prostate cancer

Background

Although docetaxel-based chemohormonal therapy (CHT) is one of the standard treatments for castration-resistant prostate cancer (CRPC), pertinent biomarkers and precise mechanisms involved in the resistance for CHT for CRPC remain unknown. We investigated the relationship between chemohormonal resistance and the expression of steroid receptors and Hippo pathway proteins using a docetaxel-resistant prostate cancer (PCa) cell line and human PCa tissues in patients who underwent surgery with and without neoadjuvant therapy.

Methods

A docetaxel-resistant subline (22Rv1-DR) was generated to assess Hippo pathway protein expression and the effect of YAP1 inhibition on cellular characteristics. A tissue microarray with 203 cores from 70 high-risk localized PCa tissues was performed to assess steroid receptor and Hippo pathway protein expressions.

Results

Nuclear YAP (nYAP) expression was higher in 22RV-1-DR than in parental 22Rv-1 and YAP1 knockdown suppressed cell proliferation of 22Rv1-DR. Steroid receptor and Hippo pathway protein expressions varied among three different neoadjuvant groups, and nYAP1 expression was the highest in the CHT group. The patients with high nYAP in residual cancer after neoadjuvant CHT had a significantly higher biochemical recurrence (BCR) rate than those with low nYAP1. On multivariate analysis, the high nYAP1 was an independent prognostic factor for BCR.

Conclusions

nYAP expression is a potential biomarker in high-risk patients treated with docetaxel-based CHT. Steroid receptors and Hippo pathway proteins may play a role in the chemohormonal resistance in advanced PCa.

Reversal of Apalutamide and Darolutamide Aldo-Keto Reductase 1C3-Mediated Resistance by a Small Molecule Inhibitor

The antiandrogen therapeutics apalutamide and darolutamide entered the clinic in 2018 and 2019, respectively, for the treatment of castration-resistant prostate cancer (CRPC). Increased expression of the enzyme aldo-keto reductase 1C3 (AKR1C3) is phenotypic of CRPC. The enzyme acts to circumvent castration by producing potent androgens that drive proliferation. Furthermore, AKR1C3 mediates chemotherapeutic resistance to the standard of care, enzalutamide, a structural analogue of apalutamide. Resistance develops in almost all CRPC patients within three months of beginning treatment. Herein, we report that both apalutamide and the structurally distinct darolutamide induce AKR1C3 expression in in vitro models of prostate cancer and are susceptible to AKR1C3-mediated resistance. This effect is countered by pretreatment with a potent and highly selective AKR1C3 inhibitor, sensitizing high AKR1C3 expressing prostate cancer cell lines to the action of both chemotherapeutics with a concomitant reduction in expression of AKR1C3 and the biomarker prostate-specific antigen.

RELA is sufficient to mediate interleukin-1 repression of androgen receptor expression and activity in an LNCaP disease progression model

BACKGROUND

The androgen receptor (AR) nuclear transcription factor is a therapeutic target for prostate cancer (PCa). Unfortunately, patients can develop resistance to AR-targeted therapies and progress to lethal disease, underscoring the importance of understanding the molecular mechanisms that underlie treatment resistance. Inflammation is implicated in PCa initiation and progression and we have previously reported that the inflammatory cytokine, interleukin-1 (IL-1), represses AR messenger RNA (mRNA) levels and activity in AR-positive (AR⁺ ) PCa cell lines concomitant with the upregulation of prosurvival biomolecules. Thus, we contend that IL-1 can select for AR-independent, treatment-resistant PCa cells.

METHODS

To begin to explore how IL-1 signaling leads to the repression of AR mRNA levels, we performed comprehensive pathway analysis on our RNA sequencing data from IL-1-treated LNCaP PCa cells. Our pathway analysis predicted nuclear factor kappa B (NF-κB) p65 subunit (RELA), a canonical IL-1 signal transducer, to be significantly active and potentially regulate many genes, including AR. We used small interfering RNA (siRNA) to silence the NF-κB family of transcription factor subunits, RELA, RELB, c-REL, NFKB1, or NFKB2, in IL-1-treated LNCaP, C4-2, and C4-2B PCa cell lines. C4-2 and C4-2B cell lines are castration-resistant LNCaP sublines and represent progression toward metastatic PCa disease, and we have previously shown that IL-1 represses AR mRNA levels in C4-2 and C4-2B cells.

RESULTS

siRNA revealed that RELA alone is sufficient to mediate IL-1 repression of AR mRNA and AR activity. Intriguingly, while LNCaP cells are more sensitive to IL-1-mediated repression of AR than C4-2 and C4-2B cells, RELA siRNA led to a more striking derepression of AR mRNA levels and AR activity in C4-2 and C4-2B cells than in LNCaP cells.

CONCLUSIONS

These data indicate that there are RELA-independent mechanisms that regulate IL-1-mediated AR repression in LNCaP cells and suggest that the switch to RELA-dependent IL-1 repression of AR in C4-2 and C4-2B cells reflects changes in epigenetic and transcriptional programs that evolve during PCa disease progression.

Therapeutic Targeting of MDR1 Expression by RORγ Antagonists Resensitizes Cross-Resistant CRPC to Taxane via Coordinated Induction of Cell Death Programs

Overexpression of ATP-binding cassette subfamily B member 1 (ABCB1)-encoded multidrug resistance protein 1 (MDR1) constitutes a major mechanism of cancer drug resistance including docetaxel (DTX) and cabazitaxel (CTX) resistance in castration-resistant prostate cancer (CRPC). However, no therapeutics that targets MDR1 is available at clinic for taxane sensitization. We report here that retinoic acid receptor-related orphan receptor γ (RORγ), a nuclear receptor family member, unexpectedly mediates MDR1/ABCB1 overexpression. RORγ plays an important role in controlling the functions of subsets of immune cells and has been an attractive target for autoimmune diseases. We found that its small-molecule antagonists are efficacious in resensitizing DTX and CTX cross-resistant CRPC cells and tumors to taxanes in both androgen receptor-positive and -negative models. Our mechanistic analyses revealed that combined treatment with RORγ antagonists and taxane elicited a robust synergy in killing the resistant cells, which involves a coordinated alteration of p53, Myc, and E2F-controlled programs critical for both intrinsic and extrinsic apoptosis, survival, and cell growth. Our results suggest that targeting RORγ with small-molecule inhibitors is a novel strategy for chemotherapy resensitization in tumors with MDR1 overexpression.

Sulfiredoxin as a Potential Therapeutic Target for Advanced and Metastatic Prostate Cancer

The incidence of prostate cancer (PCa) is increasing, and it is currently the second most frequent cause of death by cancer in men. Despite advancements in cancer therapies, new therapeutic approaches are still needed for treatment-refractory advanced metastatic PCa. Cross-species analysis presents a robust strategy for the discovery of new potential therapeutic targets. This strategy involves the integration of genomic data from genetically engineered mouse models (GEMMs) and human PCa datasets. Considering the role of antioxidant pathways in tumor initiation and progression, we searched oxidative stress-related genes for a potential therapeutic target for PCa. First, we analyzed RNA-sequencing data from Pb-Cre4; Pten^f/f mice and discovered an increase in sulfiredoxin (Srxn1) mRNA expression in high-grade prostatic intraepithelial neoplasia (PIN), well-differentiated adenocarcinoma (medium-stage tumors), and poor-differentiated adenocarcinoma (advanced-stage prostate tumors). The increase of SRXN1 protein expression was confirmed by immunohistochemistry in mouse prostate tumor paraffin samples. Analyses of human databases and prostate tissue microarrays demonstrated that SRXN1 is overexpressed in a subset of high-grade prostate tumors and correlates with aggressive PCa with worse prognosis and decreased survival. Analyses in vitro showed that SRXN1 expression is also higher in most PCa cell lines compared to normal cell lines. Furthermore, siRNA-mediated downregulation of SRXN1 led to decreased viability of PCa cells LNCaP. In conclusion, we identified the antioxidant enzyme SRXN1 as a potential therapeutic target for PCa. Our results suggest that the use of specific SRXN1 inhibitors may be an effective strategy for the adjuvant treatment of castration-resistant PCa with SRXN1 overexpression.

Contribution of Inherited DNA-Repair Gene Mutations to Hormone-Sensitive and Castrate-Resistant Metastatic Prostate Cancer and Implications for Clinical Outcome

PURPOSE

To compare the prevalence of germline mutations in metastatic hormone-sensitive prostate cancer (mHSPC) and metastatic castrate-resistant prostate cancer (mCRPC) and assess the impact of mutations on progression to castration resistance and overall survival.

METHODS

Targeted sequencing of germline DNA from 704 men (221 at the time of mHSPC and 483 at the time of mCRPC) enrolled in two advanced prostate cancer registries at Mayo Clinic between 2003 and 2013 was performed for 21 predisposition genes. Frequencies of pathogenic mutations were compared in patients and reference controls to identify genes enriched in metastatic prostate cancer. Multivariable Cox proportional hazards regression was used to identify predictors of progression to mCRPC and overall survival.

RESULTS

Sixty-eight germline mutations in 12 genes were identified in 66 men (9.4%). Mutations in ATM, BRCA2, CHEK2, FANCM, and TP53 were significantly enriched (odds ratio greater than 2.0) in the metastatic cohorts compared with reference controls. The frequency of germline mutations was similar for patients with mHSPC and mCRPC (11.8% v 8.3%; P = .16). The median time to progression from mHSPC to mCRPC was 23.1 and 32.5 months for patients with and without mutations, respectively (P = .96). Although older age at diagnosis, Gleason score greater than 7, elevated alkaline phosphatase level, and high volume of disease were associated with shorter duration of progression to mCRPC and poor overall survival, mutation status was not (progression to mCRPC hazard ratio, 0.81; 95% CI, 0.61 to 1.09; P = .17; overall survival hazard ratio, 1.00; 95% CI, 0.75 to 1.34; P = .98).

CONCLUSION

Similarly elevated rates of germline predisposition gene mutations in mHSPC and mCRPC suggest that germline genetic testing may help to guide medical management for all patients with advanced metastatic prostate cancer. Mutation status was not associated with shorter progression to mCRPC or poor overall survival.

Personalization of prostate cancer therapy through phosphoproteomics

Castration-resistant prostate cancer (CRPC) remains incurable despite the approval of several new treatments. Identification of new biomarkers and therapeutic targets to enable personalization of CRPC therapy, with the aim of maximizing therapeutic responses and minimizing toxicity in patients, is urgently needed. Prostate cancer progression and therapeutic resistance are frequently driven by aberrantly activated kinase signalling pathways that are amenable to pharmacological inhibition. Personalized phosphoproteomics, which enables the analysis of signalling networks in individual tumours, is a promising approach to advance personalized therapy by discovering biomarkers of pathway activity and clinically actionable targets. Several technologies for global and targeted phosphoproteomic analysis exist, each with its own strengths and shortcomings. Global discovery phosphoproteomics is predominantly conducted using liquid chromatography-tandem mass spectrometry coupled with data-dependent or data-independent acquisition technologies. Multiplexed targeted phosphoproteomics can be divided into platforms based on mass spectrometry or antibodies, including selected or parallel reaction monitoring and triggered by offset, multiplexed, accurate mass, high-resolution, absolute quantification (known as TOMAHAQ) or forward-phase or reverse-phase protein arrays, respectively. Several obstacles still need to be overcome before the full potential of phosphoproteomics can be realized in routine clinical practice, but a future phosphoproteomics-centric trans-omic profiling approach should enable optimized personalized CRPC management through improved biomarkers and targeted treatments.

Steroid receptor/coactivator binding inhibitors: An update

The purpose of this review is to highlight recent developments in small molecules and peptides that block the binding of coactivators to steroid receptors. These coactivator binding inhibitors bind at the coregulator binding groove, also known as Activation Function-2, rather than at the ligand-binding site of steroid receptors. Steroid receptors that have been targeted with coactivator binding inhibitors include the androgen receptor, estrogen receptor and progesterone receptor. Coactivator binding inhibitors may be useful in some cases of resistance to currently prescribed therapeutics. The scope of the review includes small-molecule and peptide coactivator binding inhibitors for steroid receptors, with a particular focus on recent compounds that have been assayed in cell-based models.

Predictive and targeting value of IGFBP-3 in therapeutically resistant prostate cancer

BACKGROUND

Our previous studies demonstrated that a novel quinazoline derivative, DZ-50, inhibited prostate cancer epithelial cell invasion and survival by targeting insulin-like-growth factor binding protein-3 (IGFBP-3) and mediating epithelial-mesenchymal transition (EMT) conversion to mesenchymal-epithelial transition (MET). This study investigated the therapeutic value of DZ-50 agent in in vitro and in vivo models of advanced prostate cancer and the ability of the compound to overcome resistance to antiandrogen (enzalutamide) in prostate tumors.

APPROACH

LNCaP and LNCaP-enzalutamide resistant human prostate cancer (LNCaP-ER) cells, as well as 22Rv1 and enzalutamide resistant, 22Rv1-ER were used as cell models. The effects of DZ-50 and the antiandrogen, enzalutamide (as single agents or in combination) on cell death, EMT-MET interconversion, and expression of IGFBP3 and the androgen receptor (AR), were examined. The TRAMP mouse model of prostate cancer progression was used as a pre-clinical model. Transgenic mice (20-wks of age) were treated with DZ-50 (100 mg/kg for 2 wks, oral gavage daily) and prostate tumors were subjected to immunohistochemical assessment of apoptosis, cell proliferation, markers of EMT and differentiation and IGFBP-3 and AR expression. A tissue microarray (TMA) was analyzed for expression of IGBP-3, the target of DZ-50 and its association with tumor progression and biochemical recurrence.

RESULTS

We found that treatment with DZ-50 enhanced the anti-tumor response to the antiandrogen via promoting EMT to MET interconversion, in vitro. This DZ-50-mediated phenotypic reversal to MET leads to prostate tumor re-differentiation in vivo, by targeting nuclear IGFBP-3 expression (without affecting AR). Analysis of human prostate cancer specimens and TCGA patient cohorts revealed that overexpression of IGBP-3 protein correlated with tumor recurrence and poor patient survival.

CONCLUSIONS

These findings provide significant new insights into (a) the predictive value of IGFBP-3 in prostate cancer progression and (b) the antitumor action of DZ-50, [in combination or sequencing with enzalutamide] as a novel approach for the treatment of therapeutically resistant prostate cancer.

Androgen receptor plasticity and its implications for prostate cancer therapy

Acquired resistance to a drug treatment is a common problem across many cancers including prostate cancer (PCa) - one of the major factors for male mortality. The androgen receptor (AR) continues to be the main therapeutic PCa target and despite the success of modern targeted therapies such as enzalutamide, resistance to these drugs eventually develops. The AR has found many ways to adapt to treatments including overexpression and production of functional, constitutively active splice variants. However, of particular importance are point mutations in the ligand binding domain of the protein that convert anti-androgens into potent AR agonists. This mechanism appears to be especially prevalent with the AR in spite of some distant similarities to other hormone nuclear receptors. Despite the AR being one of the most studied and attended targets in cancer, those gain-of-function mutations in the receptor remain a significant challenge for the development of PCa therapies. This drives the need to fully characterize such mutations and to consistently screen PCa patients for their occurrence to prevent adverse reactions to anti-androgen drugs. Novel treatments should also be developed to overcome this resistance mechanism and more attention should be given to the possibility of similar occurrences in other cancers.

Computational modelling of resistance and associated treatment response heterogeneity in metastatic cancers

Metastatic cancer patients invariably develop treatment resistance. Different levels of resistance lead to observed heterogeneity in treatment response. The main goal was to evaluate treatment response heterogeneity with a computation model simulating the dynamics of drug-sensitive and drug-resistant cells. Model parameters included proliferation, drug-induced death, transition and proportion of intrinsically resistant cells. The model was benchmarked with imaging metrics extracted from 39 metastatic prostate cancer patients who had ¹⁸F-NaF-PET/CT scans performed at baseline and at three cycles into chemotherapy or hormonal therapy. Two initial model assumptions were evaluated: considering only inter-patient heterogeneity and both inter-patient and intra-patient heterogeneity in the proportion of intrinsically resistant cells. The correlation between the median proportion of intrinsically resistant cells and baseline patient-level imaging metrics was assessed with Spearman's rank correlation coefficient. The impact of model parameters on simulated treatment response was evaluated with a sensitivity study. Treatment response after periods of six, nine, and 12 months was predicted with the model. The median predicted range of response for patients treated with both therapies was compared with a Wilcoxon rank sum test. For each patient, the time was calculated when the proportion of disease with a non-favourable response outperformed a favourable response. By taking into account inter-patient and intra-patient heterogeneity in the proportion of intrinsically resistant cells, the model performed significantly better ([Formula: see text]) than by taking into account only inter-patient heterogeneity ([Formula: see text]). The median proportion of intrinsically resistant cells showed a moderate correlation (ρ  =  0.55) with mean patient-level uptake, and a low correlation (ρ  =  0.36) with the dispersion of mean metastasis-level uptake in a patient. The sensitivity study showed a strong impact of the proportion of intrinsically resistant cells on model behaviour after three cycles of therapy. The difference in the median range of response (MRR) was not significant between cohorts at any time point (p   >  0.15). The median time when the proportion of disease with a non-favourable response outperformed the favourable response was eight months, for both cohorts. The model provides an insight into inter-patient and intra-patient heterogeneity in the evolution of treatment resistance.

Synergistic effects of hormone therapy drugs and usnic acid on hormone receptor-positive breast and prostate cancer cells

The aim of this study was to investigate the combined effects of usnic acid (UA) and Tamoxifen (Tam) or Enzalutamide (Enz) on hormone receptor-positive breast and prostate cancer (BC and PC), respectively. The antiproliferative and apoptotic effects of Tam or Enz alone and in combination with UA on MCF7 and LNCaP cancer cells were detected. The results of the WST-1 assay indicated that UA was a promising anticancer compound that significantly enhanced the effectiveness of hormone therapy drugs compared with each drug alone (combination index < 1). In addition, the combination of UA with Tam or Enz remarkably induced more cell cycle arrest at the G0/G1 phase and apoptosis than only drug-treated cells (P < 0.01). Consequently, our findings suggest that the combination of UA with Tam or Enz may be a potential therapeutic approach for the treatment of BC and PC and further studies are required to exploit the potential mechanisms of synergistic effects.

The Response of Prostate Cancer to Androgen Deprivation and Irradiation Due to Immune Modulation

This study investigated changes in the immune system and the biological consequences of androgen deprivation therapy (ADT) and radiotherapy (RT) for augmenting the treatment response in prostate cancer, particularly for castration-resistant prostate cancer (CRPC). Human and murine prostate cancer cell lines were used to examine the response to ADT and RT in vitro and in vivo. Biological changes following treatment and related immune modulation in the tumor microenvironment were examined. Our results showed that CRPC cells were demonstrated to be more resistant to the RT and ADT treatments. ADT increased tumor inhibition following irradiation. The underlying changes included increased cell death, attenuated myeloid-derived suppressor cell recruitment, and an increase in the number of tumor-infiltrating T cells (TILs). Furthermore, when high-dose fractionated RT was given to the primary CRPC tumor, a smaller size of secondary non-irradiated tumor associated with increased TILs was noted in ADT-treated mice. In conclusion, treatment resistance in CRPC was associated with a more immunosuppressive microenvironment. Enhanced antitumor immunity was responsible for the augmented RT-induced tumoricidal effect induced by ADT. Immune modulation could be a promising strategy for prostate cancer, especially for metastatic CRPC.

Peptide T7-modified polypeptide with disulfide bonds for targeted delivery of plasmid DNA for gene therapy of prostate cancer

Background

Vectors are essential for successful gene delivery. In the present study, a tumor-targeting cationic gene vector, known as the disulfide cross-linked arginine-aspartic acid peptide modified by HAIYPRH (T7) peptide (CRD-PEG-T7), was designed for targeted delivery of plasmid DNA (pDNA) for gene therapy of prostate cancer (PCa).

Methods

The structure of CRD-PEG-T7 was determined and the cellular uptake efficacy, gene transfection efficacy, cytotoxicity, and the targeting effect of the CRD-PEG-T7–plasmid DNA complex were examined.

Results

The results demonstrated that the CRD-PEG-T7–plasmid DNA complex was nanosized and had a positively charged surface, good cellular uptake efficacy, minimal cytotoxicity, and a dual-targeting effect as compared with the CRD-PEG–plasmid DNA complex. The peptide T7-modifed new delivery system was able to target the highly expressed transferrin receptor (TfR) on tumor cells with an efficiency four-fold higher than that of the non-modified system.

Conclusion

The results above indicatd that the CRD-PEG-T7–plasmid DNA complex may prove to be a promising gene delivery system targeting bone-metastatic tumor.

Chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating expression of ephrin-B1

Advanced solid tumors are exposed to hypoxic conditions over longer periods of time as they grow. Tumor hypoxia is a major factor that induces malignant progression, but most previous studies on tumor hypoxia were performed under short-term hypoxia for up to 72 hours and few studies have focused on tumor response to chronic hypoxic conditions. Here we show a molecular mechanism by which chronic hypoxia promotes invasive behavior in prostate cancer cells. We found that an epithelial-mesenchymal transition (EMT)-driving transcription factor, slug, is specifically upregulated under chronic hypoxia and promotes tumor cell migration and invasion. Unexpectedly, processes associated with EMT, such as loss of E-cadherin, are not observed under chronic hypoxia. Instead, expression of ephrin-B1, a ligand of Eph-related receptor tyrosine kinases, is markedly induced by slug through E-box motifs and promotes cell migration and invasion. Furthermore, slug and ephrin-B1 are highly coexpressed in chronic hypoxic cells of human prostate adenocarcinoma tissues after androgen deprivation, which is known to cause tumor hypoxia. Taken together, these results indicate that chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating the expression of ephrin-B1. In addition, ephrin-B1 may be a novel therapeutic target in combination with androgen deprivation therapy for aggressive prostate cancer.

A dose finding clinical trial of cabozantinib (XL184) administered in combination with abiraterone acetate in metastatic castration-resistant prostate cancer

BACKGROUND

Cabozantinib can enhance the effect of abiraterone in preclinical prostate cancer models. This study aimed to define the recommended phase 2 dose (RP2D) and preliminary efficacy of abiraterone + cabozantinib in mCRPC.

METHODS

Patients with progressive mCRPC with 0-2 prior chemotherapy regimens but no prior CYP17A1 or MET inhibitor received abiraterone acetate at 1000 mg daily with prednisone 5 mg BID in combination with cabozantinib at 20, 40, or 60 mg daily in a dose-escalation 3 + 3 open-label phase 1 design (Part A). After tolerable doses were defined, cohorts were expanded to better define toxicity and efficacy (Part B).

RESULTS

There were no dose-limiting toxicities (DLTs) in the first 4 weeks at any of the three dose levels in Part A. Two of the three patients at the 60 mg dose level required dose reductions beyond cycle 2 due to fatigue. In Part B, nine more patients were accrued to each of the 20 and 40 mg doses. Of the 12 patients treated at the 40 mg dose, only one DLT (grade 3 Lipase elevation) was observed in cycle 1. The median time to radiographic progression was 12.88 months (95% CI:5.42- not estimated [NE]) in the 20 mg cohort and 22.01 months (95% CI:15.44-NE) in the 40 mg cohort. Median overall survival was 23.29 months (95% CI:19.06-NE) in the 20 mg cohort and 39.08 months (95% CI:17.38-NE) in the 40 mg cohort.

CONCLUSIONS

Based on tolerability and preliminary efficacy, 40 mg cabozantinib plus 1000 mg abiraterone daily is the RP2D.

New NO- and H2S-releasing doxorubicins as targeted therapy against chemoresistance in castration-resistant prostate cancer: in vitro and in vivo evaluations

Chemotherapy for castration-resistant prostate cancer (CRPC) is only temporarily effective due to the onset of chemoresistance. We investigated the efficacy of NO- and H2S-releasing doxorubicins (NitDox and H2SDox) in overcoming drug resistance and evaluated their safety. New and innovative NO- and H₂S-releasing doxorubicins (NitDox and H₂SDox) showed a good intracellular accumulation and high cytotoxic activity in vitro in an androgen-independent and doxorubicin-resistant DU-145 prostate cancer cell line. Nude mice were subcutaneously injected with 4*10⁶ DU-145 cells and treated once a week for 3 weeks with 5 mg/kg doxorubicin, NitDox, H₂SDox or vehicle, i.p. Animal weight, tumor volume, intra-tumoral drug accumulation, apoptosis and the presence of nitrotyrosine and sulfhydryl (SH) groups within the tumor, were evaluated. Cardiotoxicity was assessed by measuring troponin plasma levels and the left ventricular wall thickness. In vivo, NitDox and H₂SDox accumulated inside the tumors, significantly reduced tumor volumes by 60%, increased the percentage of apoptotic cells in both the inner and the outer parts of the tumors and the presence of nitrotyrosine and SH groups. Doxorubicin treatment was associated with reduced body weight and cardiotoxicity. On the contrary, NitDox and H₂SDox were well tolerated and had a better safety profile. Combining efficacy with reduced cardiovascular side effects, NitDox and H₂SDox are promising novel therapeutic agents for reversing chemoresistance in CRCP.

Profiling Prostate Cancer Therapeutic Resistance

The major challenge in the treatment of patients with advanced lethal prostate cancer is therapeutic resistance to androgen-deprivation therapy (ADT) and chemotherapy. Overriding this resistance requires understanding of the driving mechanisms of the tumor microenvironment, not just the androgen receptor (AR)-signaling cascade, that facilitate therapeutic resistance in order to identify new drug targets. The tumor microenvironment enables key signaling pathways promoting cancer cell survival and invasion via resistance to anoikis. In particular, the process of epithelial-mesenchymal-transition (EMT), directed by transforming growth factor-β (TGF-β), confers stem cell properties and acquisition of a migratory and invasive phenotype via resistance to anoikis. Our lead agent DZ-50 may have a potentially high efficacy in advanced metastatic castration resistant prostate cancer (mCRPC) by eliciting an anoikis-driven therapeutic response. The plasticity of differentiated prostate tumor gland epithelium allows cells to de-differentiate into mesenchymal cells via EMT and re-differentiate via reversal to mesenchymal epithelial transition (MET) during tumor progression. A characteristic feature of EMT landscape is loss of E-cadherin, causing adherens junction breakdown, which circumvents anoikis, promoting metastasis and chemoresistance. The targetable interactions between androgens/AR and TGF-β signaling are being pursued towards optimized therapeutic regimens for the treatment of mCRPC. In this review, we discuss the recent evidence on targeting the EMT-MET dynamic interconversions to overcome therapeutic resistance in patients with recurrent therapeutically resistant prostate cancer. Exploitation of the phenotypic landscape and metabolic changes that characterize the prostate tumor microenvironment in advanced prostate cancer and consequential impact in conferring treatment resistance are also considered in the context of biomarker discovery.

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.

LincRNA-p21 suppresses development of human prostate cancer through inhibition of PKM2

OBJECTIVES

Previously, we found that long intergenic non-coding RNA-p21 (lincRNA-p21) inhibited the development of human prostate cancer. However, the underlying molecular mechanisms are poorly understood. Here, we attempted to investigate the downstream targets of lincRNA-p21 in prostate cancer.

MATERIALS AND METHODS

Expression of lincRNA-p21 and PKM2 was determined by qRT-PCR and Western blot. Lentivirus expressing shPKM2 or shCtrl was used to explore the role of PKM2 on the enhanced cell proliferation and glycolysis of lincRNA-p21-silenced prostate cancer cells. A xenograft mouse model was performed to investigate the effect of PKM2 suppression, glycolytic or mammalian target of rapamycin (mTOR) inhibitor on the tumorigenic capacity of lincRNA-p21-silenced prostate cancer cells.

RESULTS

We revealed that lincRNA-p21 silencing in DU145 and LNCaP cells induced up-regulation of PKM2 and activation of glycolysis, which could be reversed by PKM2 knockdown or rapamycin treatment. We also found that the proliferation and tumorigenesis of lincRNA-p21-silenced prostate cancer cells were significantly inhibited after knocking down PKM2. 3-bromopyruvate (3-Brpa) or rapamycin treatment largely decreased the tumour burden. Importantly, PKM2 expression was inversely correlated with the lincRNA-p21 level and the survival of prostate cancer patients.

CONCLUSIONS

We demonstrated that lincRNA-p21 blunted the prostate cancer cell proliferation and tumorigenic capacity through down-regulation of PKM2. Therefore, targeting PKM2 or glycolysis might be a therapeutic strategy in prostate cancer patients with lowly expressed lincRNA-p21.

Efficacy of Abiraterone and Enzalutamide in Pre- and Postdocetaxel Castration-Resistant Prostate Cancer: A Trial-Level Meta-Analysis

We examined the comparative efficacies of first-line abiraterone and enzalutamide in pre- and postdocetaxel settings in castration-resistant prostate cancer (CRPC) through a trial level meta-analysis. A mixed method approach was applied to 19 unique studies containing 17 median overall survival (OS) estimates and 13 median radiographic progression-free survival (PFS) estimates. We employed a random-effects meta-analysis to compare efficacies of abiraterone and enzalutamide with respect to OS and PFS. In the predocetaxel setting, enzalutamide use was associated with an increase in median OS of 5.9 months (p < 0.001), hazard ratio (HR) = 0.81, and an increase in median PFS of 8.3 months (p < 0.001), HR = 0.47 compared to abiraterone. The advantage of enzalutamide improved after adjusting for baseline Gleason score to 19.5 months (p < 0.001) and 14.6 months (p < 0.001) in median OS and PFS, respectively. In the postdocetaxel setting, the advantage of enzalutamide use was nominally significant for median PFS (1.2 months p = 0.02 without adjustment and 2.2 months and p = 0.0007 after adjustment); there was no significant difference in median OS between the two agents. The results from this comprehensive meta-analysis suggest a survival advantage with the use of first-line enzalutamide over abiraterone in CRPC and highlight the need for prospective clinical trials.

Resveratrol, piceatannol and analogs inhibit activation of both wild-type and T877A mutant androgen receptor

Prostate cancer growth and progression are mainly dependent on androgens and many current prostate cancer treatment options target the synthesis or function of androgens. We have previously reported that resveratrol and synthetic analogs of resveratrol with a higher bioavailability inhibit the synthesis of androgens in human adrenocortical H295R cells. Now we have studied the antiandrogenic properties of resveratrol, piceatannol and analogs in two different prostate cell lines; LNCaP and RWPE. LNCaP carry a T877A mutation in the androgen receptor while RWPE has a wild-type androgen receptor. We found that resveratrol, piceatannol and all studied analogs were able to inhibit a dihydrotestosterone-induced activation of the androgen receptor, showing that they act as antiandrogens. In LNCaP cells, all studied compounds were able to statistically significantly decrease the androgenic signaling in concentrations ≥1μM and the synthetic analogs trimethylresveratrol (RSVTM) and tetramethylpiceatannol (PICTM) were the most potent compounds. RWPE cells were not as responsive to the studied compounds as the LNCaP cells. A statistically significant decrease in the androgenic signaling was observed at concentrations ≤5μM for most compounds and RSVTM was found to be the most potent compound. Further, we studied the effects of resveratrol, piceatannol and analogs on the levels of prostate-specific antigen (PSA) in LNCaP cells and found that all studied compounds decreased the level of PSA and that the synthetic analogs diacetylresveratrol (RSVDA), triacetylresveratrol (RSVTA) and RSVTM were the most potent compounds, decreasing the PSA level by approx. 50% at concentrations ≥10μM. In a cell-free receptor binding assay we were unable to show binding of resveratrol or analogs to the ligand binding domain of the androgen receptor, indicating that the observed effects are mediated via other mechanisms than direct ligand competition. We conclude that the resveratrol, piceatannol and analogs are highly interesting for chemoprevention of prostate cancer, since they have a high potency both as inhibitors of androgen synthesis and androgen receptor activation.

Implications of Bcl-2 and its interplay with other molecules and signaling pathways in prostate cancer progression

INTRODUCTION

Among several genetic alterations involved in the progression of prostate cancer, B cell lymphoma gene number 2 (BCL-2) is an important target molecule in the progression of androgen-independent prostate cancer (AIPC) after androgen ablation or castration. Nevertheless, the molecular mechanism of BCL-2 in prostate cancer progression remains elusive and controversial. In the current review, we discuss the critical role of BCL-2 in the carcinogenesis of prostate cancer with experimental evidences on the BCL-2 molecular networks in AIPC and androgen-dependent prostate cancer (ADPC) and subsequently suggest perspective research targeting BCL-2. Areas covered: This review focused on the molecular implications of BCL-2 in association with other molecules and signaling pathways involved in the progression and carcinogenesis of prostate cancer. Expert opinion: BCL-2 plays a pivotal role in the progression of AIPC than in ADPC since androgen represses BCL-2. BCL-2 acts as a pro-survival molecule in association with androgen-related signaling in the progression of ADPC, while BCL-2 upregulation, PTEN loss, PI3K/AKT phosphorylation and receptor tyrosine kinase (RTK) activation are primarily involved in AIPC. To identify more effective prostate cancer therapy, further mechanistic studies are required with BCL-2 inhibitors in AIPC and ADPC, considering a multi-target therapy against BCL-2 and its related signaling.