Androgen receptor rediscovered: the new biology and targeting the androgen receptor therapeutically

Therapeutic prospects of sex hormone receptor signaling in hormone-responsive cancers

Globally, hormone-responsive cancers afflict millions of people contributing to cancer-related morbidity and mortality. While hormone-responsive cancers overburden patients, their close families, and even health budgets at the local levels, knowledge of these cancers particularly their biology and possible avenues for therapy remains poorly exploited. Herewith, this review highlights the role of sex hormones (estrogens and androgens) in the pathophysiology of hormone-responsive cancers and the exploration of therapeutic targets. Major scientific databases including but not limited to Scopus, PubMed, Science Direct, Web of Science core collections, and Google Scholar were perused using a string of search terms: Hormone-responsive cancers, androgens and cancers, estrogens and cancer, androgen receptor signalling, estrogen receptor signalling, etc.

The polyunsaturated fatty acid docosahexaenoic affects mitochondrial function in prostate cancer cells

BACKGROUND

Prostate cancer (PCa) shows a rewired metabolism featuring increased fatty acid uptake and synthesis via de novo lipogenesis, both sharply related to mitochondrial physiology. The docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (PUFA) that exerts its antitumoral properties via different mechanisms, but its specific action on mitochondria in PCa is not clear. Therefore, we investigated whether the DHA modulates mitochondrial function in PCa cell lines.

METHODS

Here, we evaluated mitochondrial function of non-malignant PNT1A and the castration-resistant (CRPC) prostate 22Rv1 and PC3 cell lines in response to DHA incubation. For this purpose, we used Seahorse extracellular flux assay to assess mitochondria function, [14C]-glucose to evaluate its oxidation as well as its contribution to fatty acid synthesis, 1H-NMR for metabolite profile determination, MitoSOX for superoxide anion production, JC-1 for mitochondrial membrane polarization, mass spectrometry for determination of phosphatidylglycerol levels and composition, staining with MitoTracker dye to assess mitochondrial morphology under super-resolution in addition to Transmission Electron Microscopy, In-Cell ELISA for COX-I and SDH-A protein expression and flow cytometry (Annexin V and 7-AAD) for cell death estimation.

RESULTS

In all cell lines DHA decreased basal respiratory activity, ATP production, and the spare capacity in mitochondria. Also, the omega-3 induced mitochondrial hyperpolarization, ROS overproduction and changes in membrane phosphatidylglycerol composition. In PNT1A, DHA led to mitochondrial fragmentation and it increased glycolysis while in cancer cells it stimulated glucose oxidation, but decreased de novo lipogenesis specifically in 22Rv1, indicating a metabolic shift. In all cell lines, DHA modulated several metabolites related to energy metabolism and it was incorporated in phosphatidylglycerol, a precursor of cardiolipin, increasing the unsaturation index in the mitochondrial membrane. Accordingly, DHA triggered cell death mainly in PNT1A and 22Rv1.

CONCLUSION

In conclusion, mitochondrial metabolism is significantly affected by the PUFA supplementation to the point that cells are not able to proliferate or survive under DHA-enriched condition. Moreover, combination of DHA supplementation with inhibition of metabolism-related pathways, such as de novo lipogenesis, may be synergistic in castration-resistant prostate cancer.

Stat5 induces androgen receptor (AR) gene transcription in prostate cancer and offers a druggable pathway to target AR signaling

Androgen receptor (AR) drives prostate cancer (PC) growth and progression, and targeting AR signaling is the mainstay of pharmacological therapies for PC. Resistance develops relatively fast as a result of refueled AR activity. A major gap in the field is the lack of understanding of targetable mechanisms that induce persistent AR expression in castrate-resistant PC (CRPC). This study uncovers an unexpected function of active Stat5 signaling, a known promoter of PC growth and clinical progression, as a potent inducer of AR gene transcription. Stat5 suppression inhibited AR gene transcription in preclinical PC models and reduced the levels of wild-type, mutated, and truncated AR proteins. Pharmacological Stat5 inhibition by a specific small-molecule Stat5 inhibitor down-regulated Stat5-inducible genes as well as AR and AR-regulated genes and suppressed PC growth. This work introduces the concept of Stat5 as an inducer of AR gene transcription in PC. Pharmacological Stat5 inhibitors may represent a new strategy for suppressing AR and CRPC growth.

Supraphysiological Androgens Promote the Tumor Suppressive Activity of the Androgen Receptor through cMYC Repression and Recruitment of the DREAM Complex

The androgen receptor (AR) pathway regulates key cell survival programs in prostate epithelium. The AR represents a near-universal driver and therapeutic vulnerability in metastatic prostate cancer, and targeting AR has a remarkable therapeutic index. Though most approaches directed toward AR focus on inhibiting AR signaling, laboratory and now clinical data have shown that high dose, supraphysiological androgen treatment (SPA) results in growth repression and improved outcomes in subsets of patients with prostate cancer. A better understanding of the mechanisms contributing to SPA response and resistance could help guide patient selection and combination therapies to improve efficacy. To characterize SPA signaling, we integrated metrics of gene expression changes induced by SPA together with cistrome data and protein-interactomes. These analyses indicated that the dimerization partner, RB-like, E2F, and multivulval class B (DREAM) complex mediates growth repression and downregulation of E2F targets in response to SPA. Notably, prostate cancers with complete genomic loss of RB1 responded to SPA treatment, whereas loss of DREAM complex components such as RBL1/2 promoted resistance. Overexpression of MYC resulted in complete resistance to SPA and attenuated the SPA/AR-mediated repression of E2F target genes. These findings support a model of SPA-mediated growth repression that relies on the negative regulation of MYC by AR leading to repression of E2F1 signaling via the DREAM complex. The integrity of MYC signaling and DREAM complex assembly may consequently serve as determinants of SPA responses and as pathways mediating SPA resistance.

SIGNIFICANCE

Determining the molecular pathways by which supraphysiological androgens promote growth arrest and treatment responses in prostate cancer provides opportunities for biomarker-selected clinical trials and the development of strategies to augment responses.

GATA2 co-opts TGFβ1/SMAD4 oncogenic signaling and inherited variants at 6q22 to modulate prostate cancer progression

BACKGROUND

Aberrant somatic genomic alteration including copy number amplification is a hallmark of cancer genomes. We previously profiled genomic landscapes of prostate cancer (PCa), yet the underlying causal genes with prognostic potential has not been defined. It remains unclear how a somatic genomic event cooperates with inherited germline variants contribute to cancer predisposition and progression.

METHODS

We applied integrated genomic and clinical data, experimental models and bioinformatic analysis to identify GATA2 as a highly prevalent metastasis-associated genomic amplification in PCa. Biological roles of GATA2 in PCa metastasis was determined in vitro and in vivo. Global chromatin co-occupancy and co-regulation of GATA2 and SMAD4 was investigated by coimmunoprecipitation, ChIP-seq and RNA-seq assays. Tumor cellular assays, qRT-PCR, western blot, ChIP, luciferase assays and CRISPR-Cas9 editing methods were performed to mechanistically understand the cooperation of GATA2 with SMAD4 in promoting TGFβ1 and AR signaling and mediating inherited PCa risk and progression.

RESULTS

In this study, by integrated genomics and experimental analysis, we identified GATA2 as a prevalent metastasis-associated genomic amplification to transcriptionally augment its own expression in PCa. Functional experiments demonstrated that GATA2 physically interacted and cooperated with SMAD4 for genome-wide chromatin co-occupancy and co-regulation of PCa genes and metastasis pathways like TGFβ signaling. Mechanistically, GATA2 was cooperative with SMAD4 to enhance TGFβ and AR signaling pathways, and activated the expression of TGFβ1 via directly binding to a distal enhancer of TGFβ1. Strinkingly, GATA2 and SMAD4 globally mediated inherited PCa risk and formed a transcriptional complex with HOXB13 at the PCa risk-associated rs339331/6q22 enhancer, leading to increased expression of the PCa susceptibility gene RFX6.

CONCLUSIONS

Our study prioritizes causal genomic amplification genes with prognostic values in PCa and reveals the pivotal roles of GATA2 in transcriptionally activating the expression of its own and TGFβ1, thereby co-opting to TGFβ1/SMAD4 signaling and RFX6 at 6q22 to modulate PCa predisposition and progression.

Adapting to hormone-therapy resistance for adopting the right therapeutic strategy in advanced prostate cancer

INTRODUCTION

The androgen/androgen receptor (AR) axis represents a key driver of treatment resistance in prostate cancer (PCa) patients receiving androgen deprivation therapy (ADT) and targeted agents, and a deeper comprehension of resistance mechanisms is fundamental to adopt effective therapeutic strategies.

AREAS COVERED

We review the mechanisms of primary or secondary resistance to hormone therapy (HT) in PCa, especially focusing on available data and emerging evidence.

EXPERT OPINION

First- and second-generation HT resistance has been associated with several AR-dependent and AR-independent mechanisms, ranging from the amplification of the AR gene locus to somatic AR mutations and the intratumoral synthesis of androgens from adrenal steroids and cholesterol. As reported in the current review, the development of novel and effective treatments is needed to personalize anticancer therapies in this setting and to finally improve clinical outcomes in patients with HT resistant disease.

Interstitial pneumonia after regression by olaparib for neuroendocrine prostate cancer with BRCA1 mutation: a case report

A 67-year-old man with metastatic prostate cancer was treated with leuprorelin and enzalutamide, but presented radiographic progression after 1 year. Although docetaxel chemotherapy was initiated, liver metastasis appeared with elevation of nerve-specific enolase in serum. Pathological findings of needle biopsy of lymph node metastasis in the right inguinal region showed neuroendocrine carcinoma. FoundationOne CDx® using a biopsy sample of the prostate at initial diagnosis detected the BRCA1 mutation (deletion of intron 3-7), but BRACAnalysis® test revealed no BRCA mutation in germline. Then, olaparib treatment was initiated, resulting in remarkable remission of tumors, but comorbidity with interstitial pneumonia. This case suggested that olaparib could be effective for neuroendocrine prostate cancer with BRCA1 gene mutation, but may cause interstitial pneumonia.

Effectiveness and safety of radium-223 dichloride in patients with castration-resistant prostate cancer and bone metastases in real-world practice: A multi-institutional study

OBJECTIVE

Radium-223 (Ra-223) dichloride is the bone-targeted radioligand therapy that prolongs overall survival (OS) in patients with bone-metastatic castration-resistant prostate cancer (CRPC). We aimed to evaluate the safety and effectiveness of this treatment in real-world practice.

METHODS

We included Japanese men treated with Ra-223 for bone-metastatic CRPC from 10 institutions, retrospectively. Primary endpoint was OS. Secondary endpoint was maximum decline of alkaline phosphatase (ALP), lactate dehydrogenase, and prostate-specific antigen values, the rate of adverse events, and time to pathological fracture after Ra-223 treatment. Exploratory endpoint was the associations between clinical parameters and OS.

RESULTS

In total, 73 men with bone metastatic CRPC treated with Ra-223 were enrolled. The median OS was 20.9 months. ALP levels decreased significantly from pre-treatment (p = 0.03). Anemia occurred in three (4.1%) patients. Grade ≥ 3 non-pathological fractures occurred in four (5.5%) men. Nine (12.3%) patients presented pathological fracture; 7/30 (23.3%) were in men without concomitant use of a bone-modifying agent (BMA) while 2/43 (4.7%) were in patients with concomitant BMA (p = 0.03). The median OS in patients with ≥3 cycles treatment (27.2 months, p < 0.001) or hemoglobin ≥12 g/dl (27.2 months, p = 0.001) or absence of bone pain (36.3 months, p = 0.004) was significantly longer compared to those who with ≤2 cycles or hemoglobin<12 g/dl or presence of bone paint, respectively.

CONCLUSIONS

This study has shown the outcomes of Ra-223 treatment in real-world practice, where the number of treatment cycles, baseline anemia and bone pain may be useful to predict OS in Ra-223 treatment.

AR-regulated ZIC5 contributes to the aggressiveness of prostate cancer

The mechanisms by which prostate cancer (PCa) progresses to the aggressive castration-resistant stage remain uncertain. Zinc finger of the cerebellum 5 (ZIC5), a transcription factor belonging to the ZIC family, is involved in the pathology of various cancers. However, the potential effect of ZIC5 on PCa malignant progression has not been fully defined. Here, we show that ZIC5 is upregulated in PCa, particularly in metastatic lesions, in positive association with poor prognosis. Genetic inhibition of ZIC5 in PCa cells obviously attenuated invasion and metastasis and blunted the oncogenic properties of colony formation. Mechanistically, ZIC5 functioned as a transcription factor to promote TWIST1-mediated EMT progression or as a cofactor to strengthen the β-catenin-TCF4 association and stimulate Wnt/β-catenin signaling. Importantly, ZIC5 and the androgen receptor (AR) form a positive feed-forward loop to mutually stimulate each other’s expression. AR, in cooperation with its steroid receptor coactivator 3 (SRC-3), increased ZIC5 expression through binding to the miR-27b-3p promoter and repressing miR-27b-3p transcription. In turn, ZIC5 potentiated AR, AR-V7, and AR targets’ expression. Besides, ZIC5 inhibition reduced AR and AR-V7 protein expression and enhanced the sensitivity of PCa to enzalutamide (Enz) treatment, both in vitro and in vivo. These findings indicate that the reciprocal activation between AR and ZIC5 promotes metastasis and Enz resistance of PCa and suggest the therapeutic value of cotargeting ZIC5 and AR for the treatment of advanced PCa.

Role of Olaparib in the Management of Metastatic Castration-Resistant Prostate Cancer: A Japanese Clinician's Perspective

Several studies have identified various targetable genomic alterations in prostate cancer, which accumulate during carcinogenesis and cancer progression. Genomic alterations in genes involved in DNA damage repair by homologous recombination repair may predict increased sensitivity to poly-ADP ribose polymerase (PARP) inhibitors. The Phase 3 PROfound trial has shown that treatment with the PARP inhibitor olaparib was associated with an improved radiographic progression-free survival and overall survival among patients with homologous recombination repair-deficient metastatic castration-resistant prostate cancer (mCRPC) after the treatment with androgen receptor targeting therapy, especially in men with BRCA1 or BRCA2 mutation. In Japan, olaparib was approved in December 2020 for the treatment of mCRPC with BRCA1 or BRCA2 mutation. In addition, genetic tests to detect BRCA1 or BRCA2 mutation to select patients who are likely to benefit from olaparib were also approved. This review summarizes the status of olaparib treatment for mCRPC, focusing on the situation in Japan.

Targeting signaling pathways in prostate cancer: mechanisms and clinical trials

Prostate cancer (PCa) affects millions of men globally. Due to advances in understanding genomic landscapes and biological functions, the treatment of PCa continues to improve. Recently, various new classes of agents, which include next-generation androgen receptor (AR) signaling inhibitors (abiraterone, enzalutamide, apalutamide, and darolutamide), bone-targeting agents (radium-223 chloride, zoledronic acid), and poly(ADP-ribose) polymerase (PARP) inhibitors (olaparib, rucaparib, and talazoparib) have been developed to treat PCa. Agents targeting other signaling pathways, including cyclin-dependent kinase (CDK)4/6, Ak strain transforming (AKT), wingless-type protein (WNT), and epigenetic marks, have successively entered clinical trials. Furthermore, prostate-specific membrane antigen (PSMA) targeting agents such as ¹⁷⁷Lu-PSMA-617 are promising theranostics that could improve both diagnostic accuracy and therapeutic efficacy. Advanced clinical studies with immune checkpoint inhibitors (ICIs) have shown limited benefits in PCa, whereas subgroups of PCa with mismatch repair (MMR) or CDK12 inactivation may benefit from ICIs treatment. In this review, we summarized the targeted agents of PCa in clinical trials and their underlying mechanisms, and further discussed their limitations and future directions.

Effectiveness of GnRH Antagonists and Agonists in Patients with Hormone-Sensitive Prostate Cancer: A Retrospective Study

Objective

To assess the effectiveness of gonadotropin-releasing hormone (GnRH) antagonists and agonists in the treatment of patients with hormone-sensitive prostate cancer (HSPC), thus providing valid data support for their clinical treatment.

Methods

We collected 52 and 65 HSPC patients treated with GnRH antagonists and agonists, respectively, in Tongji Hospital, Tongji Medical College of HUST between May 2019 and April 2021. Prostate-specific antigen (PSA) levels before and after treatment were recorded and analyzed. Further, univariate and multivariate logistic regressions were used to analyze the influencing factors of PSA control rate in HSPC patients.

Results

In patients receiving antagonist, the control rate of prostate-specific antigen (PSA) was 54.28% and 88% without and with abiraterone, respectively, and 47.91% and 72% in patients treated using agonist without and with abiraterone. In 32 pairs of patients obtained via propensity score matching, the PSA control rates were 84.38% and 53.13% for those receiving antagonists and agonists, respectively, and 66.67% and 50% for those without abiraterone, respectively. In addition, univariate logistic regression analysis showed that the type of androgen deprivation therapy (ADT) drugs and combined use of abiraterone had a significant effect on the control rate of PSA. Further multivariate logistic regression revealed that GnRH antagonists in ADT drugs were risk factors for PSA control rate.

Conclusion

The PSA control rate of HSPC patients treated with GnRH antagonist is significantly higher than that of the agonist group, and the use of GnRH antagonist is an independent predictor of PSA control rate.

Review of second-generation androgen receptor inhibitor therapies and their role in prostate cancer management

PURPOSE OF REVIEW

We review the published literature on the indications of second-generation androgen receptor inhibitors, Poly(ADP-Ribose) Polymerase (PARP) inhibitors, combination therapies, and their evolution throughout the advanced prostate cancer continuum.

RECENT FINDINGS

Enzalutamide trials have published data supporting its use in metastatic hormone-sensitive prostate cancer (mHSPC), nonmetastatic castration-resistant prostate cancer (nmCRPC), and metastatic castration-resistant prostate cancer (mCRPC). Apalutamide trials have supported its indication for mHSPC and nmCRPC. Darolutamide trials currently support its use for nmCRPC. Abiraterone trials have supported its use in mCRPC and mHSPC. Olaparib and rucaparib have shown clinical benefit in heavily pretreated patients with mCRPC and DNA repair mutation genes.

SUMMARY

Phase 3 trials and peer-reviewed literature demonstrate that enzalutamide, apalutamide, and darolutamide prolong overall survival (OS) in men with nmCRPC. Abiraterone, enzalutamide, and apalutamide improve OS in men with mHSPC. Abiraterone and enzalutamide have data supporting improvement in OS in men with mCRPC.

RASAL2 suppresses the proliferative and invasive ability of PC3 prostate cancer cells

The RAS protein activator like 2 (RASAL2) negatively regulates RAS proto-oncogene which is activated by high mutation rate in cancer. Thus, RASAL2 expression could potentially limit the function of RAS in prostate cancer (PCa). Genome-wide DNA methylation analysis demonstrated that RASAL2 is differentially hypermethylated in PCa tissues compared to benign prostate tissues. The PCR analysis of RASAL2 mRNA transcript showed differential expression in a panel of prostate cell lines with most PCa showing lower RASAL2 expression compared to benign prostatic epithelial cells. In PCa PC3 cells, the ectopic expression of RASAL2 significantly inhibited cell proliferation and invasion and induced an S phase plus G2/M phase cell cycle arrest. Ingenuity Pathway Analysis (IPA) demonstrated a cross talk between RASAL2 and TNFα, a key cytokine in immune signaling pathway that is relevant in PCa. Over-expression of RASAL2 downregulated TNFα expression whereas the knockdown of RASAL2 caused increased expression of TNFα. Taken together, our data demonstrates tumor suppressor role for RASAL2 in human PCa cells, despite increased RAS oncogenic activity. Our observation provides a new mechanistic insight of RASAL2 expression in aberrant Ras expression and immune signaling in PCa cells suggesting a potential novel therapeutic target for PCa.

Current treatment options for newly diagnosed metastatic hormone-sensitive prostate cancer-a narrative review

Prostate cancer continues to be one of the most commonly diagnosed cancers in men globally and a leading cause of male cancer deaths. The landscape of metastatic hormone-sensitive prostate cancer has significantly changed over the past decade. For many years, androgen deprivation therapy alone through surgical or chemical castration was the mainstay of treatment yielding limited 5-year survival rates. New treatment approaches using Docetaxel chemotherapy or androgen receptor pathway inhibitors to intensify upfront systemic therapy have resulted in significantly improved survival rates compared to androgen deprivation therapy alone. Clinicians are now equipped with an arsenal of drugs capable of prolonging life for metastatic hormone-sensitive prostate cancer patients. Furthermore, new treatment modalities are being tested in clinical trials making treatment of metastatic hormone-sensitive prostate cancer an extremely dynamic space. In this narrative review, we provide an overview of the key systemic treatments for metastatic hormone-sensitive prostate cancer, namely androgen deprivation therapy, novel androgen receptor pathway inhibitors and Docetaxel. We summarise a series of landmark trials that have led to the integration of novel androgen receptor pathway inhibitors and docetaxel into the treatment paradigm for metastatic hormone-sensitive prostate cancer. Lastly, we discuss nursing, financial and side-effect considerations pertaining to the use of these drugs. This article aims to give its readers an understanding of the evidence and clinical aspects of novel therapies in metastatic hormone-sensitive prostate cancer as they become increasingly available for use around the world.

Opposing transcriptional programs of KLF5 and AR emerge during therapy for advanced prostate cancer

Endocrine therapies for prostate cancer inhibit the androgen receptor (AR) transcription factor. In most cases, AR activity resumes during therapy and drives progression to castration-resistant prostate cancer (CRPC). However, therapy can also promote lineage plasticity and select for AR-independent phenotypes that are uniformly lethal. Here, we demonstrate the stem cell transcription factor Krüppel-like factor 5 (KLF5) is low or absent in prostate cancers prior to endocrine therapy, but induced in a subset of CRPC, including CRPC displaying lineage plasticity. KLF5 and AR physically interact on chromatin and drive opposing transcriptional programs, with KLF5 promoting cellular migration, anchorage-independent growth, and basal epithelial cell phenotypes. We identify ERBB2 as a point of transcriptional convergence displaying activation by KLF5 and repression by AR. ERBB2 inhibitors preferentially block KLF5-driven oncogenic phenotypes. These findings implicate KLF5 as an oncogene that can be upregulated in CRPC to oppose AR activities and promote lineage plasticity.

Molecular Basis of Prostate Cancer and Natural Products as Potential Chemotherapeutic and Chemopreventive Agents

Prostate cancer is the second most common malignant cancer in males. It involves a complex process driven by diverse molecular pathways that closely related to the survival, apoptosis, metabolic and metastatic characteristics of aggressive cancer. Prostate cancer can be categorized into androgen dependent prostate cancer and castration-resistant prostate cancer and cure remains elusive due to the developed resistance of the disease. Natural compounds represent an extraordinary resource of structural scaffolds with high diversity that can offer promising chemical agents for making prostate cancer less devastating and curable. Herein, those natural compounds of different origins and structures with potential cytotoxicity and/or in vivo anti-tumor activities against prostate cancer are critically reviewed and summarized according to the cellular signaling pathways they interfere. Moreover, the anti-prostate cancer efficacy of many nutrients, medicinal plant extracts and Chinese medical formulations were presented, and the future prospects for the application of these compounds and extracts were discussed. Although the failure of conventional chemotherapy as well as involved serious side effects makes natural products ideal candidates for the treatment of prostate cancer, more investigations of preclinical and even clinical studies are necessary to make use of these medical substances reasonably. Therefore, the elucidation of structure-activity relationship and precise mechanism of action, identification of novel potential molecular targets, and optimization of drug combination are essential in natural medicine research and development.

Radium-223 Treatment of Patients with Metastatic Castration Resistant Prostate Cancer: Biomarkers for Stratification and Response Evaluation

Simple Summary

Radium-223 dichloride ([²²³Ra]RaCl₂; Ra-223) is an alpha-emitting radiopharmaceutical treatment for patients with metastatic castration resistant prostate cancer (mCRPC) with predominantly bone metastases. While responses to chemotherapeutic and antihormonal mCRPC treatments can be assessed by serum PSA levels, a decrease of serum PSA levels is not expected during Ra-223 therapy. Moreover, radiographic evaluation of bone metastases response is challenging. Therefore, novel biomarkers to select patients for Ra-223 treatment and monitoring response are urgently needed. In this review, we discuss the currently used and exploratory biomarkers for this purpose, including soluble and cellular factors detected in the peripheral blood, genetic defects and radiographic assessments. We conclude that some biomarkers, including metabolic products of collagen degradation and novel PET scan techniques, might hold promise as predictors of response to Ra-223 treatment. However, these biomarkers have not been extensively studied. Consequently, currently, no biomarker has established a place in patient stratification and response evaluation.

Abstract

Radium-223 dichloride ([²²³Ra]RaCl₂; Ra-223) is a targeted alpha-emitting radiopharmaceutical which results in an overall survival and health related quality of life (HRQoL) benefit in symptomatic patients with metastatic castration resistant prostate cancer (mCRPC) and predominantly bone metastasis. Although effective, options to select patients who will derive treatment benefit and to monitor and predict treatment outcomes are limited. PSA response and radiographic evaluation are commonly used in mCRPC treatment assessment but are not informative in Ra-223 treated patients. Consequently, there is a clear need for predictive and prognostic tools. In this review, we discuss the physiology of bone metastases and the mechanism of action and efficacy of Ra-223 treatment, as well as offering an outline of current innovative prognostic and predictive biomarkers.

Current and emerging gonadotropin-releasing hormone (GnRH) antagonists for the treatment of prostate cancer

Introduction:Androgen deprivation therapy (ADT) is currently the backbone treatment of metastatic prostate cancer and is also used in combination with external beam radiotherapy (EBRT). Castration may be achieved either by bilateral orchiectomy or by administration of LHRH agonists or GnRH antagonists.Areas covered: In this article, the authors assess the current and emerging role of GnRH antagonists for the treatment of prostate cancer focusing on oncological results and safety (i.e. cardiovascular risk). In addition, updated data regarding the first orally administered GnRH antagonist, relugolix, is presented.Expert opinion: Studies demonstrate that GnRH antagonists are at least equal with LHRH agonists in terms of testosterone suppression and PSA progression free survival with a major advantage being rapid testosterone suppression. Thus, the optimal group of patients included symptomatic metastatic prostate cancer patients especially if cardiovascular comorbidities or LUTS are also present. Emerging data regarding benefit of the use of GnRH antagonists in patients with concomitant cardiovascular disease are of great interest. Relugolix has emerged as the first orally administered GnRH antagonist able to achieve and maintain testosterone castration levels and it is associated with a profound reduction of major cardiovascular events.

A new flavonoid derivative exerts antitumor effects against androgen-sensitive to cabazitaxel-resistant prostate cancer cells

BACKGROUND

Our previous report has shown that the flavonoid 2'-hydroxyflavanone (2'-HF) showed inhibition of androgen receptor (AR) activity against androgen-sensitive prostate cancer (PCa) cells, LNCaP, and exhibited antitumor effects against androgen-insensitive PCa cells, PC-3, and DU145. In the present study, we prepared a derivative of 2'-HF, 16MS7F1924, and confirmed the effects of this derivative on PCa cells.

METHODS

The antiproliferation effects of 16MS7F1924 were investigated in PCa cells using LNCaP, PC-3, DU145 and docetaxel-resistant and cabazitaxel-resistant cell lines of PC-3-TxR/CxR and DU145-TxR/CxR. Prostate-specific antigen (PSA) and AR expression level in whole cells and the nucleus were confirmed in LNCaP by reverse transcriptase polymerase chain reaction and Western blot analysis. AR activity in LNCaP cells was confirmed by luciferase assay using PSA promoter-driven reporter. To analyze the antiproliferative effects, cell-based assays using flow cytometry, immunocytochemistry, and TUNEL assay as well as Western blot analysis were employed. Furthermore, PC-3, DU145 and each chemoresistant strain of human PCa cells were subcutaneously xenografted. The antitumor effects of 16MS7F1924 were evaluated in vivo.

RESULTS

16MS7F1924 showed antitumor effect on all PCa cells in a dose-dependent manner. 16MS7F1924 reduced the expression of PSA messenger RNA (mRNA) and protein and inhibited AR activity in a dose-dependent manner, while expression of AR protein and mRNA was reduced by 16MS7F1924. 16MS7F1924 induced mitotic catastrophe and apoptosis. Apoptotic cells were increased in a dose-dependent manner, and the apoptosis was mediated through the Akt pathway. Tumor growth was safely and significantly inhibited by both intraperitoneal and oral administration of 16MS7F1924 in vivo.

CONCLUSION

16MS7F1924 had sufficient antitumor activity against androgen-sensitive and cabazitaxel-resistant PCa cells and may be useful as a novel therapeutic agent overcoming hormone- and chemoresistant PCas.

Hormone-Dependent Prostate Cancers are Dependent on Rac Signaling for Growth and Survival

Prostate cancer remains a common cause of cancer mortality in men. Initially, cancers are dependent of androgens for growth and survival. First line therapies reduce levels of circulating androgens or target the androgen receptor (AR) directly. Although most patients show durable responses, many patients eventually progress to castration-resistant prostate cancer (CRPC) creating a need for alternative treatment options. The Rac1 signaling pathway has previously been implicated as a driver of cancer initiation and disease progression. We investigated the role of HACE1, the E3 ubiquitin ligase for Rac1, in prostate cancer and found that HACE1 is commonly lost resulting in hyperactive Rac signaling leading to enhanced cellular proliferation, motility and viability. Importantly, we show that a Rac inhibitor can attenuate the growth and survival of prostate cancer cells. Rac signaling was also found to be critical in prostate cancers that express the AR. Rac inhibition in androgen dependent cells resulted in reduction of AR target gene expression suggesting that targeting Rac1 may be an alternative method for blocking the AR signaling axis. Finally, when used in combination with AR antagonists, Rac inhibition enhanced the suppression of AR target gene expression. Therefore, targeting Rac in prostate cancer has the potential to enhance the efficacy of approved AR therapies.

Resveratrol inhibits proliferation and promotes apoptosis via the androgen receptor splicing variant 7 and PI3K/AKT signaling pathway in LNCaP prostate cancer cells

Prostate cancer is a common malignant tumor of the male genitourinary system and its incidence increases with age. Studies have shown that resveratrol (Res) inhibits cancer cell proliferation, migration, invasion and promotes apoptosis. The present study evaluated the effect of Res in two human prostate cancer cell lines (the androgen-dependent LNCaP cell line and the non-androgen-independent LNCaP-B cell line) on proliferation and apoptosis. A proliferation assay was used to demonstrate that Res inhibited proliferation of LNCaP and LNCaP-B cells in the range of 25-100 µM, and the effect was time- and dose-dependent. Using flow cytometry, it was reported that various concentrations of Res induced apoptosis in LNCaP and LNCaP-B cells, and that the apoptotic effect of Res was dose-dependent. A chemiluminescence assay showed that Res inhibited prostate specific antigen levels in LNCaP and LNCaP-B cells. Reverse transcription quantitative-PCR showed that Res inhibited the expression of androgen receptor (AR) in LNCaP and LNCaP-B cells at the mRNA level. Western blot analysis showed that Res suppressed the expression of AR protein as well as protein kinase B (AKT) phosphorylation. To study the effect of Res on the expression of AR splicing variant 7 (ARV7) and the PI3K/AKT signaling pathway in prostate cancer cells, as well as the underlying molecular mechanisms, the recombinant ARV7 expression vector Pcdna3.1-ARV7 was transfected into LNCaP and LNCaP cells and the aforementioned experiments were repeated. It was revealed that Res acted via the ARV7 and the AKT pathways. Taken together, the present results suggested that Res suppresses the proliferation of prostate cancer cells, promotes apoptosis and inhibits the expression of AR mRNA and protein. These effects likely resulted from inhibition of ARV7 and the AKT signaling pathway.

Impact of antiandrogen withdrawal syndrome in castration-resistant prostate cancer patients treated with abiraterone or enzalutamide

OBJECTIVES

To assess the impact of antiandrogen withdrawal syndrome after bicalutamide withdrawal in castration-resistant prostate cancer patients treated with androgen receptor-axis targeted agents.

METHODS

The study cohort comprised 94 patients treated with abiraterone (n = 34) or enzalutamide (n = 60) as a first-line androgen receptor-axis targeted agent for castration-resistant prostate cancer despite combined androgen blockade by castration with bicalutamide as the first-line therapy. The association between clinicopathological factors (including antiandrogen withdrawal syndrome) and therapeutic outcome after using abiraterone and enzalutamide was investigated.

RESULTS

The decline in the prostate-specific antigen level after use of abiraterone or enzalutamide was comparable between patients with and without antiandrogen withdrawal syndrome. Antiandrogen withdrawal syndrome (hazard ratio 3.84, 95% confidence interval 1.29-11.45; P = 0.016) was associated with a higher risk of progression on multivariate analysis, but not all-cause death after abiraterone use. Progression-free survival and overall survival after enzalutamide use did not differ between patients with and without antiandrogen withdrawal syndrome.

CONCLUSIONS

The present data suggest a modest therapeutic efficacy of abiraterone in castration-resistant prostate cancer patients with anti-androgen withdrawal syndrome after bicalutamide withdrawal.

Development of Novel AKR1C3 Inhibitors as New Potential Treatment for Castration-Resistant Prostate Cancer

Aldo-keto reductase (AKR) 1C3 catalyzes the synthesis of active androgens that promote the progression of prostate cancer. AKR1C3 also contributes to androgen-independent cell proliferation and survival through the metabolism of prostaglandins and reactive aldehydes. Because of its elevation in castration-resistant prostate cancer (CRPC) tissues, AKR1C3 is a promising therapeutic target for CRPC. In this study, we found a novel potent AKR1C3 inhibitor, N-(4-fluorophenyl)-8-hydroxy-2-imino-2H-chromene-3-carboxamide (2d), and synthesized its derivatives with IC₅₀ values of 25-56 nM and >220-fold selectivity over other AKRs (1C1, 1C2, and 1C4). The structural factors for the inhibitory potency were elucidated by crystallographic study of AKR1C3 complexes with 2j and 2l. The inhibitors suppressed proliferation of prostate cancer 22Rv1 and PC3 cells through both androgen-dependent and androgen-independent mechanisms. Additionally, 2j and 2l prevented prostate tumor growth in a xenograft mouse model. Furthermore, the inhibitors significantly augmented apoptotic cell death induced by anti-CRPC drugs (abiraterone or enzalutamide).

Chelerythrine suppresses proliferation and metastasis of human prostate cancer cells via modulating MMP/TIMP/NF-κB system

Chelerythrine is a natural benzo[c]phenanthridine alkaloid found in many herbs and displays a wide range of antitumor activities. Here, the present study tested their effects on prostate cancer cells. The addition of chelerythrine can significantly inhibit the proliferation of androgen-independent prostate cancer DU145 and PC-3 cells at the concentration of 5 and 10 μM, but not on androgen-dependent prostate cancer LNCaP cells as well as normal prostate epithelial cell line PrEC cells. Wound migration and transwell invasion assay showed the similar inhibitory effect of chelerythrine on the migration and invasion of DU145 and PC-3 cells in the same condition. Western blot analysis further confirmed that chelerythrine not only dramatically decreased MMP-2, MMP-9, and uPA protein expression, but also augmented the expression of their endogenous inhibitors (TIMP-1 and TIMP-2) and plasminogen activator inhibitors (PAI-1 and PAI-2) in both cancer cells. Meanwhile, NF-κB and AP-1 transcription factors were all suppressed as evidenced by the decline of p-p65, c-Fos, and c-Jun protein expression in both cells. Taken together, these findings suggested that chelerythrine could reduce the metastasis of androgen-independent prostate cancer cells via modulation of MMP/TIMP system and inactivation of NF-κB pathway.

Glycolysis inhibition and apoptosis induction in human prostate cancer cells by FV-429-mediated regulation of AR-AKT-HK2 signaling network

Prostate cancer (PCa) depends on androgen receptor (AR) signaling to regulate cell metabolism, including glycolysis, and thereby promotes tumor growth. Glycolysis is overactive in PCa and associated with poor prognosis, but the therapeutic efficacy of glycolysis inhibitors has thus far been limited by their inability to induce cell death. FV-429, a flavonoid derivative of Wogonin, is a glycolysis inhibitor that has shown anti-cancer promise. In this study, we used FV-429 as an anti-PCa agent and investigated its mechanisms of action. In vitro, both the glycolytic ability and the viability of PCa cells were inhibited by FV-429. We found that FV-429 could induce mitochondrial dysfunction and apoptosis, with AKT-HK2 signaling pathway playing a key role. In addition, FV-429 had a pro-apoptotic effect on human prostate cancer cells that relied on the inhibition of AR expression and activity. In vivo, FV-429 exerted significant tumor-repressing activity with high safety in the xenograft model using LNCaP cells. In summary, we demonstrated that FV-429 induced glycolysis inhibition and apoptosis in human prostate cancer cells by downregulating the AR-AKT-HK2 signaling network, making FV-429 a promising candidate as one therapeutic agent for advanced PCa.

Diverse AR Gene Rearrangements Mediate Resistance to Androgen Receptor Inhibitors in Metastatic Prostate Cancer

PURPOSE

Prostate cancer is the second leading cause of male cancer deaths. Castration-resistant prostate cancer (CRPC) is a lethal stage of the disease that emerges when endocrine therapies are no longer effective at suppressing activity of the androgen receptor (AR) transcription factor. The purpose of this study was to identify genomic mechanisms that contribute to the development and progression of CRPC.

EXPERIMENTAL DESIGN

We used whole-genome and targeted DNA-sequencing approaches to identify mechanisms underlying CRPC in an aggregate cohort of 272 prostate cancer patients. We analyzed structural rearrangements at the genome-wide level and carried out a detailed structural rearrangement analysis of the AR locus. We used genome engineering to perform experimental modeling of AR gene rearrangements and long-read RNA sequencing to analyze effects on expression of AR and truncated AR variants (AR-V).

RESULTS

AR was among the most frequently rearranged genes in CRPC tumors. AR gene rearrangements promoted expression of diverse AR-V species. AR gene rearrangements occurring in the context of AR amplification correlated with AR overexpression. Cell lines with experimentally derived AR gene rearrangements displayed high expression of tumor-specific AR-Vs and were resistant to endocrine therapies, including the AR antagonist enzalutamide.

CONCLUSIONS

AR gene rearrangements are an important mechanism of resistance to endocrine therapies in CRPC.

Effects and mechanisms of pyrethroids on male reproductive system

Synthetic pyrethroids are used as insecticides in agriculture and a variety of household applications worldwide. Pyrethroids are widely distributed in all environmental compartments and the general populations are exposed to pyrethroids through various routes. Pyrethroids have been identified as endocrine-disrupting chemicals (EDCs) which are responsible for the male reproductive impairments. The data confirm pyrethroids cause male reproductive damages. The insecticides exert the toxic effects on male reproductive system through various complex mechanisms including antagonizing androgen receptor (AR), inhibiting steroid synthesis, affecting the hypothalamic-pituitary-gonadal (HPG) axis, acting as estrogen receptor (ER) modulators and inducing oxidative stress. The mechanisms of male reproductive toxicity of pyrethroids involve multiple targets and pathways. The review will provide further insight into pyrethroid-induced male reproductive toxicity and mechanisms, which is crucial to preserve male reproductive health.

Liver tests increase on abiraterone acetate in men with metastatic prostate cancer: Natural history, management and outcome

BACKGROUND

Abiraterone acetate (abiraterone) combined with prednisone is a standard of care in metastatic castration-resistant prostate cancer. Recently, benefit in overall survival was reported in metastatic castration-sensitive prostate cancer also, and an extension of indication has been granted. Abiraterone is seldom associated with liver toxicity. The clinical management and the outcome of patients with transaminase increase while on abiraterone have not been described.

PATIENTS AND METHOD

We identified 25 men with metastatic prostate cancer and liver function test disorders occurring while on abiraterone treatment from December 2009 to September 2017 in three oncology centres in France.

RESULTS

Forty-six liver disorder events occurred in 25 patients while on abiraterone treatment. The median age at liver function test increase was 67 (55-85) years. The incidence of aspartate aminotransférase (AST) (24 events) and that of alanine aminotransférase (ALT) (22 events) increases were similar. Liver toxicity was of grade 1, 2 and 3 (Common Terminology Criteria for Adverse Events. version 4) in 7 (32%), 6 (27%) and 9 (41%) patients for ALT, and in 12 (50%), 6 (25%) and 6 (25%) for AST, respectively. The median time from abiraterone initiation to the detection of liver toxicity was 7.1 (4-95) weeks. The median time from highest ALT/AST increase to normalisation was 6.2 [2-14] weeks. In 13 patients (52%), liver tests spontaneously returned to baseline values, while abiraterone was continued at full dose.

CONCLUSION

Liver function test increase is a rare event that typically occurs within the first two months on abiraterone. Most patients experience normalisation of the tests, either spontaneously or after dose reduction/discontinuation.

Sin1 promotes proliferation and invasion of prostate cancer cells by modulating mTORC2-AKT and AR signaling cascades

AIMS

Prostate cancer (PCa) is the most common type of cancer and a major cause of death in men worldwide. Aberrant Androgen receptor (AR) and PI3K-AKT signaling are very frequent in PCa patients and, therefore, considered as therapeutic targets in the clinic. Sin1 is an essential component of mTORC2 complex, which determines full AKT activation and PCa development in PTEN^-/- mice. Here we examined the role of Sin1 in human PCa cell lines and respective tumor samples.

MAIN METHODS

Western blotting and immunohistochemistry (IHC) were performed to analyze the expression of Sin1-mTORC2-AKT related proteins in human PCa cells, as well as prostate tumors and normal tissue counterparts. Cell viability and invasion assays were also pursued in the presence or not of Sin1 in PCa cells. Immunoprecipitation assays were additionally carried out to examine the interaction of Sin1 with AR.

KEY FINDINGS

We have presently demonstrated that high levels of Sin1 expression in human PCa tissues correlate with cancer progression. Sin1-mediated cell proliferation and invasion of PCa cells occurs by regulating mTORC2-AKT signaling, epithelial-mesenchymal transition and matrix metalloproteinases. Moreover, androgens are able to induce Sin1 expression, which is further translocated to the nucleus of PCa cells. Finally, Sin1 interacts with AR to suppress its transcriptional activity.

SIGNIFICANCE

Taken together, these data indicate that both Sin1-mediated mTORC2-AKT signaling and Sin1-AR interaction regulate PCa development. Hence, Sin1 may be considered a novel biomarker of PCa progression.

The ternary complex factor protein ELK1 is an independent prognosticator of disease recurrence in prostate cancer

BACKGROUND

Both hormone-sensitive and castration- and enzalutamide-resistant prostate cancers (PCa) depend on the ternary complex factor (TCF) protein ELK1 to serve as a tethering protein for the androgen receptor (AR) to activate a critical set of growth genes. The two sites in ELK1 required for AR binding are conserved in other members of the TCF subfamily, ELK3 and ELK4. Here we examine the potential utility of the three proteins as prognosticators of disease recurrence in PCa.

METHODS

Transcriptional activity assays; Retrospective analysis of PCa recurrence using data on 501 patients in The Cancer Genome Atlas (TCGA) database; Unpaired Wilcoxon rank-sum test and multiple comparison correction using the Holm's method; Spearman's correlations; Kaplan-Meier methods; Univariable and multivariable Cox regression analyses; LASSO-based penalized Cox regression models; Time-dependent area under the receiver operating characteristic (ROC) curve.

RESULTS

ELK4 but not ELK3 was coactivated by AR similar to ELK1. Tumor expression of neither ELK3 nor ELK4 was associated with disease-free survival (DFS). ELK1 was associated with higher clinical T-stage, pathology T-stage, Gleason score, prognostic grade, and positive lymph node status. ELK1 was a negative prognosticator of DFS, independent of ELK3, ELK4, clinical T-stage, pathology T-stage, prognostic grade, lymph node status, age, and race. Inclusion of ELK1 increased the abilities of the Oncotype DX and Prolaris gene panels to predict disease recurrence, correctly predicting disease recurrence in a unique subset of patients.

CONCLUSIONS

ELK1 is a strong, independent prognosticator of disease recurrence in PCa, underscoring its unique role in PCa growth. Inclusion of ELK1 may enhance the utility of currently used prognosticators for clinical decision making in prostate cancer.

Bioguided identification of daucosterol, a compound that contributes to the cytotoxicity effects of Crateva adansonii DC (capparaceae) to prostate cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Crateva adansonii DC (Capparaceae) is a shrub used to treat tumors in Cameroon. In our previous reports, a Crateva adansonii dichloromethane-methanol (DCM/MeOH) extract was shown to prevent chemically induced tumors in Wistar rats.

AIM OF STUDY

To determine the bioactive principle of Crateva adansonii extract and to elucidate its underlying mechanism.

MATERIALS AND METHODS

An activity-guided fractionation was realized using MTT assay. To investigate if the bioactive compound daucosterol (CA2) accounted for the previously observed anticancer effects of the C. adansonii extract, it was tested on cell growth, cell proliferation, cell cycle, cell death mechanism and cell migration. In addition, cell cycle- and apoptosis-regulating proteins were assessed by Western blotting.

RESULTS

Daucosterol (CA2), a steroid saponin, was identified as major anticancer principle of the C. adansonii extract. Daucosterol significantly inhibited LNCaP, DU145 and PC3 prostate carcinoma cell growth and proliferation at the optimal concentration of 1 μg/mL. It also significantly increased the number of late apoptotic (DU145) and apoptotic (PC3) cells. The number of cells in S phase increased in DU145, while the number of G0/G1 cells decreased. Cell cycle proteins (cdk1, pcdk1, cyclin A and B) were down-regulated in DU145 and PC3 cells, whereas only cdk2 was down-regulated in PC3 cells. Moreover, the anti-apoptotic Akt, pAKT and Bcl-2 proteins were down-regulated, while the pro-apoptotic protein Bax was up-regulated. CA2 induced anti-metastatic effects by decreasing chemotaxis and cell migration, while it increased cell adhesion to fibronectin and collagen matrix.

CONCLUSION

These results suggest that daucosterol is the major active principle responsible at least in part for the anticancer effect of the extract of Crateva adansonii.

Prognostic value of testosterone for the castration-resistant prostate cancer patients: a systematic review and meta-analysis

INTRODUCTION

This systematic review and meta-analysis aimed to assess the prognostic value of testosterone in patients with castration-resistant prostate cancer (CRPC).

MATERIALS AND METHODS

PubMed, Web of Science, and Scopus databases were systematically searched until December 2019, according to the Preferred Reporting Items for Systemic Review and Meta-analysis statement. The endpoints were progression-free survival (PFS) and overall survival (OS).

RESULTS

We identified 11 articles with 4206 patients for systematic review and nine articles with 4136 patients for meta-analysis. Higher testosterone levels were significantly associated with better OS (pooled HR 0.74, 95% CI 0.58-0.95) and better PFS (pooled HR 0.51, 95% CI 0.30-0.87). Subgroup analyses based on the treatment type revealed that higher testosterone levels were significantly associated with better OS in CRPC patients treated with androgen receptor-targeted agents (ARTAs) (pooled HR 0.64, 95% CI 0.55-0.75), but not in those treated with chemotherapy (pooled HR 0.78, 95% CI 0.53-1.14).

CONCLUSION

This meta-analysis demonstrated that the PFS and OS were significantly greater in patients with CRPC in those with higher testosterone levels than that of those with lower testosterone levels. In the subgroup analyses, lower testosterone levels were a consistently poor prognostic factor for OS in patients treated with ARTAs, but not in those treated with chemotherapy. Therefore, higher testosterone levels could be a useful biomarker to identify patient subgroups in which ARTAs should be preferentially recommended in the CRPC setting.

Androgen-induced expression of DRP1 regulates mitochondrial metabolic reprogramming in prostate cancer

Androgen receptor (AR) signaling plays a central role in metabolic reprogramming for prostate cancer (PCa) growth and progression. Mitochondria are metabolic powerhouses of the cell and support several hallmarks of cancer. However, the molecular links between AR signaling and the mitochondria that support the metabolic demands of PCa cells are poorly understood. Here, we demonstrate increased levels of dynamin-related protein 1 (DRP1), a mitochondrial fission mediator, in androgen-sensitive and castration-resistant AR-driven PCa. AR signaling upregulates DRP1 to form the VDAC-MPC2 complex, increases pyruvate transport into mitochondria, and supports mitochondrial metabolism, including oxidative phosphorylation and lipogenesis. DRP1 inhibition activates the cellular metabolic stress response, which involves AMPK phosphorylation, induction of autophagy, and the ER unfolded protein response, and attenuates androgen-induced proliferation. Additionally, DRP1 expression facilitates PCa cell survival under diverse metabolic stress conditions, including hypoxia and oxidative stress. Moreover, we found that increased DRP1 expression was indicative of poor prognosis in patients with castration-resistant PCa. Collectively, our findings link androgen signaling-mediated mitochondrial dynamics to metabolic reprogramming; moreover, they have important implications for understanding PCa progression.

Breast cancer stem cells: The role of sex steroid receptors

Breast cancer (BC) is the most common cancer among women, and current available therapies often have high success rates. Nevertheless, BC might acquire drug resistance and sometimes relapse. Current knowledge about the most aggressive forms of BC points to the role of specific cells with stem properties located within BC, the so-called “BC stem cells” (BCSCs). The role of BCSCs in cancer formation, growth, invasiveness, therapy resistance and tumor recurrence is becoming increasingly clear. The growth and metastatic properties of BCSCs are regulated by different pathways, which are only partially known. Sex steroid receptors (SSRs), which are involved in BC etiology and progression, promote BCSC proliferation, dedifferentiation and migration. However, in the literature, there is incomplete information about their roles. Particularly, there are contrasting conclusions about the expression and role of the classical BC hormonal biomarkers, such as estrogen receptor alpha (ERα), together with scant, albeit promising information concerning ER beta (ERβ) and androgen receptor (AR) properties that control different transduction pathways in BCSCs. In this review, we will discuss the role that SRs expressed in BCSCs play to BC progression and recurrence and how these findings have opened new therapeutic possibilities.

Influence of the HDAC Inhibitor Valproic Acid on the Growth and Proliferation of Temsirolimus-Resistant Prostate Cancer Cells In Vitro

The mechanistic target of rapamycin (mTOR) is elevated in prostate cancer, making this protein attractive for tumor treatment. Unfortunately, resistance towards mTOR inhibitors develops and the tumor becomes reactivated. We determined whether epigenetic modulation by the histone deacetylase (HDAC) inhibitor, valproic acid (VPA), may counteract non-responsiveness to the mTOR inhibitor, temsirolimus, in prostate cancer (PCa) cells. Prostate cancer cells, sensitive (parental) and resistant to temsirolimus, were exposed to VPA, and tumor cell growth behavior compared. Temsirolimus resistance enhanced the number of tumor cells in the G2/M-phase, correlating with elevated cell proliferation and clonal growth. The cell cycling proteins cdk1 and cyclin B, along with Akt-mTOR signaling increased, whereas p19, p21 and p27 decreased, compared to the parental cells. VPA significantly reduced cell growth and up-regulated the acetylated histones H3 and H4. Cdk1 and cyclin B decreased, as did phosphorylated mTOR and the mTOR sub-complex Raptor. The mTOR sub-member Rictor and phosphorylated Akt increased under VPA. Knockdown of cdk1, cyclin B, or Raptor led to significant cell growth reduction. HDAC inhibition through VPA counteracts temsirolimus resistance, probably by down-regulating cdk1, cyclin B and Raptor. Enhanced Rictor and Akt, however, may represent an undesired feedback loop, which should be considered when designing future therapeutic regimens.

Reduced T-cell Numbers and Elevated Levels of Immunomodulatory Cytokines in Metastatic Prostate Cancer Patients De Novo Resistant to Abiraterone and/or Enzalutamide Therapy

Currently, there are two Food and Drug Administration (FDA)-approved drugs for androgen deprivation therapy (ADT) of metastatic castration-resistant prostate cancer (mCRPC) patients: abiraterone and enzalutamide. However, our understanding of the effect of these therapies on the immune system in mCRPC patients remains limited. Here, we examined how abiraterone and enzalutamide treatment affects levels of soluble immune mediators in plasma and in circulating immune cells of 44 mCRPC patients. We found that the baseline levels of cytokines fibroblast growth factor (FGF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 10 (IL-10), and IL-6 were significantly lower in ADT-sensitive compared to de novo resistant patients. In addition, resistant patients showed significantly lower T cell frequencies. When comparing the levels of cytokines over the course of treatment, we observed that the levels of proinflammatory mediators, such as interferon-γ (IFN-γ), IL-5, macrophage inflammatory protein 1 alpha (MIP-1α), and tumor necrosis factor alpha (TNFα), were significantly increased in the ADT-sensitive patients. At the same time, the abiraterone/enzalutamide therapy did not reduce the percentage of tolerogenic myeloid cell populations, such as polymorphonuclear myeloid-derived suppressor cells, which retained unaltered expression of programmed death-ligand 1 (PD-L1) and B7-H3. Overall, our results suggest that certain immune markers, such as IL-6 and the frequency of effector T cells, could be predictive of therapeutic response to ADT therapies in mCRPC patients.

Precision oncology in Latin America: current situation, challenges and perspectives

BACKGROUND

Anti-cancer cytotoxic treatments like platinum-derived compounds often show low therapeutic efficacy, high-risk side effects and resistance. Hence, targeted treatments designed to attack only tumour cells avoiding these harmful side effects are highly needed in clinical practice. Due to this, precision oncology has arisen as an approach to specifically target alterations present only in cancer cells, minimising side effects for patients. It involves the use of molecular biomarkers present in each kind of tumour for diagnosis, prognosis and treatment. Since these biomarkers are specific for each cancer type, physicians use them to stratify, diagnose or take the best therapeutic options for each patient depending on the features of the specific tumour.

AIM

This review aims to describe the current situation, limitations, advantages and perspectives about precision oncology in Latin America.

MAIN BODY

For many years, many biomarkers have been used in a clinical setting in developed countries. However, in Latin American countries, their broad application has not been affordable partially due to financial and technical limitations associated with precarious health systems and poor access of low-income populations to quality health care. Furthermore, the genetic mixture in Latin American populations could generate differences in treatment responses from one population to another (pharmacoethnicity) and this should be evaluated before establishing precision therapy in particular populations. Some research groups in the region have done a lot of work in this field and these data should be taken as a starting point to establish networks oriented to finding clinically useful cancer biomarkers in Latin American populations.

CONCLUSION

Latin America must create policies allowing excluded populations to gain access to health systems and next generation anti-cancer drugs, i.e. high-cost targeted therapies to improve survival. Also, cancer clinical research must be oriented to establish cancer biomarkers adapted to specific populations with different ethnicity, allowing the improvement of patient outcomes.

Halogen-substituted anthranilic acid derivatives provide a novel chemical platform for androgen receptor antagonists

Androgen receptor (AR) antagonists are used for hormone therapy of prostate cancer (PCa). However resistance to the treatment occurs eventually. One possible reason is the occurrence of AR mutations that prevent inhibition of AR-mediated transactivation by antagonists. To offer in future more options to inhibit AR signaling, novel chemical lead structures for new AR antagonists would be beneficial. Here we analyzed structure-activity relationships of a battery of 36 non-steroidal structural variants of methyl anthranilate including 23 synthesized compounds. We identified structural requirements that lead to more potent AR antagonists. Specific compounds inhibit the transactivation of wild-type AR as well as AR mutants that render treatment resistance to hydroxyflutamide, bicalutamide and the second-generation AR antagonist enzalutamide. This suggests a distinct mode of inhibiting the AR compared to the clinically used compounds. Competition assays suggest binding of these compounds to the AR ligand binding domain and inhibit PCa cell proliferation. Moreover, active compounds induce cellular senescence despite inhibition of AR-mediated transactivation indicating a transactivation-independent AR-pathway. In line with this, fluorescence resonance after photobleaching (FRAP) - assays reveal higher mobility of the AR in the cell nuclei. Mechanistically, fluorescence resonance energy transfer (FRET) - assays indicate that the amino-carboxy (N/C)-interaction of the AR is not affected, which is in contrast to known AR-antagonists. This suggests a mechanistically novel mode of AR-antagonism. Together, these findings indicate the identification of a novel chemical platform as a new lead structure that extends the diversity of known AR antagonists and possesses a distinct mode of antagonizing AR-function.

Androgens Induce Invasiveness of Triple Negative Breast Cancer Cells Through AR/Src/PI3-K Complex Assembly

Breast cancer (BC) is still characterized by high morbidity and mortality. A specific BC subtype named triple negative BC (TNBC) lacks estrogen and progesterone receptors (ER and PR, respectively) and is characterized by the absence of overexpression/amplification of human epidermal growth factor receptor 2 (HER2). The androgen receptor (AR) is expressed in TNBC, although its function in these cancers is still debated. Moreover, few therapeutic options are currently available for the treatment of TNBC. In this study, we have used TNBC-derived MDA-MB231 and MDA-MB453 cells that, albeit at different extent, both express AR. Androgen challenging induces migration and invasiveness of these cells. Use of the anti-androgen bicalutamide or AR knockdown experiments show that these effects depend on AR. Furthermore, the small peptide, S1, which mimics the AR proline-rich motif responsible for the interaction of AR with SH3-Src, reverses the effects in both cell lines, suggesting that the assembly of a complex made up of AR and Src drives the androgen-induced motility and invasiveness. Co-immunoprecipitation experiments in androgen-treated MDA-MB231 and MDA-MB453 cells show that the AR/Src complex recruits p85α, the regulatory subunit of PI3-K. In such a way, the basic machinery leading to migration and invasiveness is turned-on. The S1 peptide inhibits motility and invasiveness of TNBC cells and disrupts the AR/Src/p85α complex assembly in MDA-MB231 cells. This study shows that the rapid androgen activation of Src/PI3-K signaling drives migration and invasiveness of TNBC cells and suggests that the S1 peptide is a promising therapeutic option for these cancers.

Estrogens Modulate Somatostatin Receptors Expression and Synergize With the Somatostatin Analog Pasireotide in Prostate Cells

Prostate cancer (PC) is one of the most frequently diagnosed cancers and a leading cause of cancer-related deaths in Western society. Current PC therapies prevalently target the functions of androgen receptor (AR) and may only be effective within short time periods, beyond which the majority of PC patients progress to castration-resistant PC (CRPC) and metastatic disease. The role of estradiol/estradiol receptor (ER) axis in prostate transformation and PC progression is well established. Further, considerable efforts have been made to investigate the mechanism by which somatostatin (SST) and somatostatin receptors (SSTRs) influence PC growth and progression. A number of therapeutic strategies, such as the combination of SST analogs with other drugs, show, indeed, strong promise. However, the effect of the combined treatment of SST analogs and estradiol on proliferation, epithelial mesenchyme transition (EMT) and migration of normal- and cancer-derived prostate cells has not been investigated so far. We now report that estradiol plays anti-proliferative and pro-apoptotic effect in non-transformed EPN prostate cells, which express both ERα and ERβ. A weak apoptotic effect is observed in transformed CPEC cells that only express low levels of ERβ. Estradiol increases, mainly through ERα activation, the expression of SSTRs in EPN, but not CPEC cells. As such, the hormone enhances the anti-proliferative effect of the SST analog, pasireotide in EPN, but not CPEC cells. Estradiol does not induce EMT and the motility of EPN cells, while it promotes EMT and migration of CPEC cells. Addition of pasireotide does not significantly modify these responses. Altogether, our results suggest that pasireotide may be used, alone or in combination with other drugs, to limit the growth of prostate proliferative diseases, provided that both ER isoforms (α and β) are present. Further investigations are needed to better define the cross talk between estrogens and SSTRs as well as its role in PC.

Inhibition of de novo lipogenesis targets androgen receptor signaling in castration-resistant prostate cancer

Standard of care for metastatic castration-resistant prostate cancer (mCRPC) mainly relies on suppression of androgen receptor (AR) signaling. This approach has no lasting benefit due to the emergence of resistance mechanisms, such as ligand-independent splicing variant AR-V7. A metabolic feature of mCRPC is the upregulation of de novo lipogenesis to provide substrates and fuel for metastatic spread. Whether increased levels of fats affect AR signaling to promote an aggressive disease remains to be determined. Using a selective and potent inhibitor of fatty acid synthase we demonstrate that suppression of this key enzyme inhibits AR, most importantly AR-V7, and reduces mCRPC growth. Our findings offer a therapeutic opportunity for mCRPC and a potential mechanism to overcome resistance to AR inhibitors.

A hallmark of prostate cancer progression is dysregulation of lipid metabolism via overexpression of fatty acid synthase (FASN), a key enzyme in de novo fatty acid synthesis. Metastatic castration-resistant prostate cancer (mCRPC) develops resistance to inhibitors of androgen receptor (AR) signaling through a variety of mechanisms, including the emergence of the constitutively active AR variant V7 (AR-V7). Here, we developed an FASN inhibitor (IPI-9119) and demonstrated that selective FASN inhibition antagonizes CRPC growth through metabolic reprogramming and results in reduced protein expression and transcriptional activity of both full-length AR (AR-FL) and AR-V7. Activation of the reticulum endoplasmic stress response resulting in reduced protein synthesis was involved in IPI-9119–mediated inhibition of the AR pathway. In vivo, IPI-9119 reduced growth of AR-V7–driven CRPC xenografts and human mCRPC-derived organoids and enhanced the efficacy of enzalutamide in CRPC cells. In human mCRPC, both FASN and AR-FL were detected in 87% of metastases. AR-V7 was found in 39% of bone metastases and consistently coexpressed with FASN. In patients treated with enzalutamide and/or abiraterone FASN/AR-V7 double-positive metastases were found in 77% of cases. These findings provide a compelling rationale for the use of FASN inhibitors in mCRPCs, including those overexpressing AR-V7.

Strategy for Tumor-Selective Disruption of Androgen Receptor Function in the Spectrum of Prostate Cancer

PURPOSE

Testosterone suppression in prostate cancer is limited by serious side effects and resistance via restoration of androgen receptor (AR) functionality. ELK1 is required for AR-dependent growth in various hormone-dependent and castration-resistant prostate cancer models. The amino-terminal domain of AR docks at two sites on ELK1 to coactivate essential growth genes. This study explores the ability of small molecules to disrupt the ELK1-AR interaction in the spectrum of prostate cancer, inhibiting AR activity in a manner that would predict functional tumor selectivity.

EXPERIMENTAL DESIGN

Small-molecule drug discovery and extensive biological characterization of a lead compound.

RESULTS

We have discovered a lead molecule (KCI807) that selectively disrupts ELK1-dependent promoter activation by wild-type and variant ARs without interfering with ELK1 activation by ERK. KCI807 has an obligatory flavone scaffold and functional hydroxyl groups on C5 and C3'. KCI807 binds to AR, blocking ELK1 binding, and selectively blocks recruitment of AR to chromatin by ELK1. KCI807 primarily affects a subset of AR target growth genes selectively suppressing AR-dependent growth of prostate cancer cell lines with a better inhibitory profile than enzalutamide. KCI807 also inhibits in vivo growth of castration/enzalutamide-resistant cell line-derived and patient-derived tumor xenografts. In the rodent model, KCI807 has a plasma half-life of 6 hours, and maintenance of its antitumor effect is limited by self-induced metabolism at its 3'-hydroxyl.

CONCLUSIONS

The results offer a mechanism-based therapeutic paradigm for disrupting the AR growth-promoting axis in the spectrum of prostate tumors while reducing global suppression of testosterone actions. KCI807 offers a good lead molecule for drug development.

Abiraterone in metastatic castration-resistant prostate cancer: Efficacy and safety in unselected patients

BACKGROUND

Abiraterone acetate (AA), an androgen biosynthesis inhibitor, is now a standard of care for men with metastatic, castration-sensitive and castration-resistant prostate cancer (mCRPC). Data exploring real-world toxicity and outcomes are scarce.

METHODS

Retrospective study on unselected patients with mCRPC on AA plus steroids.

RESULTS

93 patients were included in the study. Median duration of treatment by AA was 7.5 months (95% CI 5.7-12) among the 58 patients pretreated with chemotherapy, versus 12.7 months ( 95% CI 8.2-35.9) among the 33 chemo-naive patients. Median survivals would reach 13.4 months (95% CI 10.2-19.1) and 36.4 months (95% CI 24.7-41.5) respectively. Rates of hypokalemia, peripheral edema, hypertension, cardiac failure, and overall survival assessments in patients with and without prior chemotherapy were similar to that previously reported in phase 3 randomized trials. The median survival time without adverse event of special interest was 7.5 months for hypokalemia and hypertension, and 5.3 months for liver-function test abnormalities (it was not reached for cardiac disorders).

CONCLUSION

Our findings provide further evidence for the survival benefits of AA with a low frequency of additional adverse events among unselected patients. In patients who have not developed hypokalemia or a transaminase increase within 7.5 and 5.3 months respectively, a lighter systematic monitoring may be considered.

Constitutive Aryl Hydrocarbon Receptor Signaling in Prostate Cancer Progression

Research on the aryl hydrocarbon receptor (AhR) has largely focused on its activation by various environmental toxins. Consequently, only limited inferences have been made regarding its constitutive activity in the absence of an exogenous ligands. Evidence has shown that AhR is constitutively active in advanced prostate cancer cell lines which model castration resistant prostate cancer (CRPC). CRPC cells can thrive in an androgen depleted environment. However, AR signaling still plays a major role. Although several mechanisms have been suggested for the sustained AR signaling, much is still unknown. Recent studies suggest that crosstalk between constitutive AhR and Src kinase may sustained AR signaling in CRPC. AhR forms a protein complex with Src and plays a role in regulating Src activity. Several groups have reported that tyrosine phosphorylation of AR protein by Src leads to AR activation, thereby promoting the development of CRPC. This review evaluates reports that implicate constitutive AhR as a key regulator of AR signaling in CRPC by utilizing Src as a signaling intermediate.

Lifestyle interventions to alleviate side effects on prostate cancer patients receiving androgen deprivation therapy: a meta-analysis

Background

Prostate cancer (PCa) patients receiving androgen deprivation therapy (ADT) are prone to suffer a series of potential side effects, including metabolic change, declining physical strength and worsening fatigue. Recent studies found that the change of lifestyle interventions can help to alleviate some adverse reactions, but the results were controversial. Therefore, the aim of this review was to comprehensively evaluate the effects of these lifestyle interventions on the side effects on PCa patients who received ADT.

Methods

We searched several electronic databases, including ScienceDirect, PubMed, Cochrane library, CNKI and Wanfang database, without language restrictions. Among the literature, such lifestyle interventions as dietary advice, exercise and physical activities were carried out in the way of randomized controlled trials (RCTs) on PCa patients taking ADT. Pooled estimates were performed using fixed-effects or random-effects model.

Results

Eleven RCTs involving 905 participants were included in this review. Compared with usual care group, exercise intervention could significantly improve the quality of life (QoL) of PCa patients undergoing ADT (P = 0.05, SMD = 0.17, 95% CI -0.00 to 0.34), but exercise plus dietary advice could not significantly improve the QoL (P = 0.15, SMD = 0.45, 95% CI -0.17 to 1.08). Moreover, lifestyle intervention could significantly change body composition (P = 0.03, SMD = -0.1, 95% CI -0.19 to -0.01). However, there showed no obvious difference in mitigating fatigue and depression (P = 0.46, SMD = 0.11, 95% CI -0.18 to 0.39; P = 0.31, SMD = -0.18, 95% CI -0.54 to 0.17).

Conclusions

The results of this meta-analysis from present study indicated that exercise interventions can better improve the QoL and alleviate treatment-related side effects on prostate cancer patients taking ADT, and better therapeutic regimens for PCa patients are likely to emerge in the process.