Targeting the adaptive molecular landscape of castration-resistant prostate cancer

Design, synthesis, and biological evaluation of 2-(naphthalen-1-yloxy)-N-phenylacetamide derivatives as TRPM4 inhibitors for the treatment of prostate cancer

Transient receptor potential melastatin 4 (TRPM4) is considered to be a potential target for cancer and other human diseases. Herein, a series of 2-(naphthalen-1-yloxy)-N-phenylacetamide derivatives were designed and synthesized as new TRPM4 inhibitors, aiming to improve cellular potency. One of the most promising compounds, 7d (ZX08903), displayed promising antiproliferative activity against prostate cancer cell lines. 7d also suppressed colony formation and the expression of androgen receptor (AR) protein in prostate cancer cells. Furthermore, 7d can concentration-dependently induce cell apoptosis in prostate cancer cells. Collectively, these findings indicated that compound 7d may serve as a promising lead compound for further anticancer drug development.

Discovery of Novel Inhibitors of BRD4 for Treating Prostate Cancer: A Comprehensive Case Study for Considering Water Networks in Virtual Screening and Drug Design

Androgen receptor (AR) is the primary target for treating prostate cancer (PCa), which inevitably progresses due to drug-resistant mutations. Bromodomain-containing protein 4 (BRD4) has been a new potential drug target for PCa treatment. Herein, we report the rational design and discovery of novel BRD4 inhibitors through computer-aided drug design (CADD), and a hit compound SQ-1 (IC50 = 676 nM) was identified by structure-based virtual screening (SBVS) with the conserved water network. To optimize the structure of SQ-1, the free energy landscape was constructed, and the binding mechanism was explored by characterizing the water profile and the dissociation mechanism. Finally, the compound SQ-17 with improved inhibitory activity (IC50 < 100 nM) was discovered, which showed potent antiproliferative activity against LNCaP. These data highlighted a successful attempt to identify and optimize a small molecule by comprehensive CADD application and provided essential clues for developing novel therapeutics for PCa treatment.

The functional roles of m6A modification in prostate cancer

Prostate cancer (PCa) is the most prevalent malignancy of the male genitourinary system, and its etiology suggests that genetics is an essential risk factor for its development and progression, while exogenous factors may have an significant impact on this risk. Initial diagnosis of advanced PCa is relatively frequent, and androgen deprivation therapy (ADT) is the predominant standard of care for PCa and the basis for various novel combination therapy regimens, and is often required throughout the patient's subsequent treatment. Although diagnostic modalities and treatment options are evolving, some patients suffer from complications, including biochemical relapse, metastasis and treatment resistance. Mechanisms of PCa pathogenesis and progression have been the focus of research. N6-methyladenosine (m6A) is an RNA modification involved in cell physiology and tumor metabolism. It has been observed to affect the evolution of diverse cancers through the regulation of gene expression. Genes associated with m6A are prominent in PCa and are involved in multiple aspects of desmoresistant PCa occurrence, progression, PCa bone metastasis (BM), and treatment resistance. Here, we explore the role of m6A modifications in promoting PCa.

Heat Shock Factor 1 Inhibition: A Novel Anti-Cancer Strategy with Promise for Precision Oncology

Heat shock factor 1 (HSF1) is a transcription factor crucial for regulating heat shock response (HSR), one of the significant cellular protective mechanisms. When cells are exposed to proteotoxic stress, HSF1 induces the expression of heat shock proteins (HSPs) to act as chaperones, correcting the protein-folding process and maintaining proteostasis. In addition to its role in HSR, HSF1 is overexpressed in multiple cancer cells, where its activation promotes malignancy and leads to poor prognosis. The mechanisms of HSF1-induced tumorigenesis are complex and involve diverse signaling pathways, dependent on cancer type. With its important roles in tumorigenesis and tumor progression, targeting HSF1 offers a novel cancer treatment strategy. In this article, we examine the basic function of HSF1 and its regulatory mechanisms, focus on the mechanisms involved in HSF1's roles in different cancer types, and examine current HSF1 inhibitors as novel therapeutics to treat cancers.

Castration-Resistant Prostate Cancer: From Uncovered Resistance Mechanisms to Current Treatments

Prostate cancer (PC) is the second most common cancer in men worldwide. Despite recent advances in diagnosis and treatment, castration-resistant prostate cancer (CRPC) remains a significant medical challenge. Prostate cancer cells can develop mechanisms to resist androgen deprivation therapy, such as AR overexpression, AR mutations, alterations in AR coregulators, increased steroidogenic signaling pathways, outlaw pathways, and bypass pathways. Various treatment options for CRPC exist, including androgen deprivation therapy, chemotherapy, immunotherapy, localized or systemic therapeutic radiation, and PARP inhibitors. However, more research is needed to combat CRPC effectively. Further investigation into the underlying mechanisms of the disease and the development of new therapeutic strategies will be crucial in improving patient outcomes. The present work summarizes the current knowledge regarding the underlying mechanisms that promote CRPC, including both AR-dependent and independent pathways. Additionally, we provide an overview of the currently approved therapeutic options for CRPC, with special emphasis on chemotherapy, radiation therapy, immunotherapy, PARP inhibitors, and potential combination strategies.

A GATA2-CDC6 axis modulates androgen receptor blockade-induced senescence in prostate cancer

BACKGROUND

Prostate cancer is a major cause of cancer morbidity and mortality in men worldwide. Androgen deprivation therapy (ADT) has proven effective in early-stage androgen-sensitive disease, but prostate cancer gradually develops into an androgen-resistant metastatic state in the vast majority of patients. According to our oncogene-induced model for cancer development, senescence is a major tumor progression barrier. However, whether senescence is implicated in the progression of early-stage androgen-sensitive to highly aggressive castration-resistant prostate cancer (CRPC) remains poorly addressed.

METHODS

Androgen-dependent (LNCaP) and -independent (C4-2B and PC-3) cells were treated or not with enzalutamide, an Androgen Receptor (AR) inhibitor. RNA sequencing and pathway analyses were carried out in LNCaP cells to identify potential senescence regulators upon treatment. Assessment of the invasive potential of cells and senescence status following enzalutamide treatment and/or RNAi-mediated silencing of selected targets was performed in all cell lines, complemented by bioinformatics analyses on a wide range of in vitro and in vivo datasets. Key observations were validated in LNCaP and C4-2B mouse xenografts. Senescence induction was assessed by state-of-the-art GL13 staining by immunocytochemistry and confocal microscopy.

RESULTS

We demonstrate that enzalutamide treatment induces senescence in androgen-sensitive cells via reduction of the replication licensing factor CDC6. Mechanistically, we show that CDC6 downregulation is mediated through endogenous activation of the GATA2 transcription factor functioning as a CDC6 repressor. Intriguingly, GATA2 levels decrease in enzalutamide-resistant cells, leading to CDC6 stabilization accompanied by activation of Epithelial-To-Mesenchymal Transition (EMT) markers and absence of senescence. We show that CDC6 loss is sufficient to reverse oncogenic features and induce senescence regardless of treatment responsiveness, thereby identifying CDC6 as a critical determinant of prostate cancer progression.

CONCLUSIONS

We identify a key GATA2-CDC6 signaling axis which is reciprocally regulated in enzalutamide-sensitive and -resistant prostate cancer environments. Upon acquired resistance, GATA2 repression leads to CDC6 stabilization, with detrimental effects in disease progression through exacerbation of EMT and abrogation of senescence. However, bypassing the GATA2-CDC6 axis by direct inhibition of CDC6 reverses oncogenic features and establishes senescence, thereby offering a therapeutic window even after acquiring resistance to therapy.

Rational Design, Synthesis and Biological Evaluation of Benzo[d]isoxazole Derivatives as Potent BET Bivalent Inhibitors for Potential Treatment of Prostate Cancer

Multivalency is an attractive strategy for effective binding to target protein. Bromodomain and extra-terminal (BET) family features two tandem bromodomains (BD1, BD2), which are considered to be potential new targets for prostate cancer. Herein, we report the rational design, optimization, and evaluation of a class of novel BET bivalent inhibitors based on our monovalent BET inhibitor 7 (Y06037). The representative bivalent inhibitor 17b effectively inhibited the cell growth of LNCaP, exhibiting 32 folds more potency than monovalent inhibitor 7. Besides, 17b induced 95.1 % PSA regression in LNCaP cell at 2 μM. Docking study was further carried out to reveal the potential binding mode of 17b with two BET bromodomains. Our study demonstrates that 17b (Y13021) is a promising BET bivalent inhibitor for the treatment of prostate cancer.

Preclinical models of prostate cancer - modelling androgen dependency and castration resistance in vitro, ex vivo and in vivo

Prostate cancer is well known to be dependent on the androgen receptor (AR) for growth and survival. Thus, AR is the main pharmacological target to treat this disease. However, after an initially positive response to AR-targeting therapies, prostate cancer will eventually evolve to castration-resistant prostate cancer, which is often lethal. Tumour growth was initially thought to become androgen-independent following treatments; however, results from molecular studies have shown that most resistance mechanisms involve the reactivation of AR. Consequently, tumour cells become resistant to castration - the blockade of testicular androgens - and not independent of AR per se. However, confusion still remains on how to properly define preclinical models of prostate cancer, including cell lines. Most cell lines were isolated from patients for cell culture after evolution of the tumour to castration-resistant prostate cancer, but not all of these cell lines are described as castration resistant. Moreover, castration refers to the blockade of testosterone production by the testes; thus, even the concept of "castration" in vitro is questionable. To ensure maximal transfer of knowledge from scientific research to the clinic, understanding the limitations and advantages of preclinical models, as well as how these models recapitulate cancer cell androgen dependency and can be used to study castration resistance mechanisms, is essential.

The functional implication of ATF6α in castration-resistant prostate cancer cells

Stress in the endoplasmic reticulum (ER) may perturb proteostasis and activates the unfolded protein response (UPR). UPR activation is frequently observed in cancer cells and is believed to fuel cancer progression. Here, we report that one of the three UPR sensors, ATF6α, was associated with prostate cancer (PCa) development, while both genetic and pharmacological inhibition of ATF6α impaired the survival of castration-resistance PCa (CRPC) cells. Transcriptomic analyses identified the molecular pathways deregulated upon ATF6α depletion, and also discovered considerable disparity in global gene expression between ATF6α knockdown and Ceapin-A7 treatment. In addition, combined analyses of human CRPC bulk RNA-seq and single-cell RNA-seq (scRNA-seq) public datasets confirmed that CRPC tumors with higher ATF6α activity displayed higher androgen receptor (AR) activity, proliferative and neuroendocrine (NE) like phenotypes, as well as immunosuppressive features. Lastly, we identified a 14-gene set as ATF6α NE gene signature with encouraging prognostic power. In conclusion, our results indicate that ATF6α is correlated with PCa progression and is functionally relevant to CRPC cell survival. Both specificity and efficacy of ATF6α inhibitors require further refinement and evaluation.

Targeting HSF1 for cancer treatment: mechanisms and inhibitor development

Heat Shock Factor 1 (HSF1) is a master regulator of heat shock responsive signaling. In addition to playing critical roles in cellular heat shock response, emerging evidence suggests that HSF1 also regulates a non-heat shock responsive transcriptional network to handle metabolic, chemical, and genetic stress. The function of HSF1 in cellular transformation and cancer development has been extensively studied in recent years. Due to important roles for HSF1 for coping with various stressful cellular states, research on HSF1 has been very active. New functions and molecular mechanisms underlying these functions have been continuously discovered, providing new targets for novel cancer treatment strategies. In this article, we review the essential roles and mechanisms of HSF1 action in cancer cells, focusing more on recently discovered functions and their underlying mechanisms to reflect the new advances in cancer biology. In addition, we emphasize new advances with regard to HSF1 inhibitors for cancer drug development.

Comparative Proteomic and Transcriptomic Analysis of the Impact of Androgen Stimulation and Darolutamide Inhibition

Several inhibitors of androgen receptor (AR) function are approved for prostate cancer treatment, and their impact on gene transcription has been described. However, the ensuing effects at the protein level are far less well understood. We focused on the AR signaling inhibitor darolutamide and confirmed its strong AR binding and antagonistic activity using the high throughput cellular thermal shift assay (CETSA HT). Then, we generated comprehensive, quantitative proteomic data from the androgen-sensitive prostate cancer cell line VCaP and compared them to transcriptomic data. Following treatment with the synthetic androgen R1881 and darolutamide, global mass spectrometry-based proteomics and label-free quantification were performed. We found a generally good agreement between proteomic and transcriptomic data upon androgen stimulation and darolutamide inhibition. Similar effects were found both for the detected expressed genes and their protein products as well as for the corresponding biological programs. However, in a few instances there was a discrepancy in the magnitude of changes induced on gene expression levels compared to the corresponding protein levels, indicating post-transcriptional regulation of protein abundance. Chromatin immunoprecipitation DNA sequencing (ChIP-seq) and Hi-C chromatin immunoprecipitation (HiChIP) revealed the presence of androgen-activated AR-binding regions and long-distance AR-mediated loops at these genes.

Acetylated HOXB13 Regulated Super Enhancer Genes Define Therapeutic Vulnerabilities of Castration-Resistant Prostate Cancer

PURPOSE

Androgen receptor (AR) antagonism is exacerbated by HOXB13 in castration-resistant prostate cancers (CRPC). However, it is unclear when and how HOXB13 primes CRPCs for AR antagonism. By mass-spectrometry analysis of CRPC extract, we uncovered a novel lysine 13 (K13) acetylation in HOXB13 mediated by CBP/p300. To determine whether acetylated K13-HOXB13 is a clinical biomarker of CRPC development, we characterized its role in prostate cancer biology.

EXPERIMENTAL DESIGN

We identified tumor-specific acK13-HOXB13 signal enriched super enhancer (SE)-regulated targets. We analyzed the effect of loss of HOXB13K13-acetylation on chromatin binding, SE proximal target gene expression, self-renewal, enzalutamide sensitivity, and CRPC tumor growth by employing isogenic parental and HOXB13K13A mutants. Finally, using primary human prostate organoids, we evaluated whether inhibiting an acK13-HOXB13 target, ACK1, with a selective inhibitor (R)-9b is superior to AR antagonists in inhibiting CRPC growth.

RESULTS

acK13-HOXB13 promotes increased expression of lineage (AR, HOXB13), prostate cancer diagnostic (FOLH1), CRPC-promoting (ACK1), and angiogenesis (VEGFA, Angiopoietins) genes early in prostate cancer development by establishing tumor-specific SEs. acK13-HOXB13 recruitment to key SE-regulated targets is insensitive to enzalutamide. ACK1 expression is significantly reduced in the loss of function HOXB13K13A mutant CRPCs. Consequently, HOXB13K13A mutants display reduced self-renewal, increased sensitivity to enzalutamide, and impaired xenograft tumor growth. Primary human prostate tumor organoids expressing HOXB13 are significantly resistant to AR antagonists but sensitive to (R)-9b.

CONCLUSIONS

In summary, acetylated HOXB13 is a biomarker of clinically significant prostate cancer. Importantly, PSMA-targeting agents and (R)-9b could be new therapeutic modalities to target HOXB13-ACK1 axis regulated prostate cancers.

Structure-Based Study to Overcome Cross-Reactivity of Novel Androgen Receptor Inhibitors

The mutation-driven transformation of clinical anti-androgen drugs into agonists of the human androgen receptor (AR) represents a major challenge for the treatment of prostate cancer patients. To address this challenge, we have developed a novel class of inhibitors targeting the DNA-binding domain (DBD) of the receptor, which is distanced from the androgen binding site (ABS) targeted by all conventional anti-AR drugs and prone to resistant mutations. While many members of the developed 4-(4-phenylthiazol-2-yl)morpholine series of AR-DBD inhibitors demonstrated the effective suppression of wild-type AR, a few represented by 4-(4-(3-fluoro-2-methoxyphenyl)thiazol-2-yl)morpholine (VPC14368) exhibited a partial agonistic effect toward the mutated T878A form of the receptor, implying their cross-interaction with the AR ABS. To study the molecular basis of the observed cross-reactivity, we co-crystallized the T878A mutated form of the AR ligand binding domain (LBD) with a bound VPC14368 molecule. Computational modelling revealed that helix 12 of AR undergoes a characteristic shift upon VPC14368 binding causing the agonistic behaviour. Based on the obtained structural data we then designed derivatives of VPC14368 to successfully eliminate the cross-reactivity towards the AR ABS, while maintaining significant anti-AR DBD potency.

A Drug Repurposing Screen Identifies Fludarabine Phosphate as a Potential Therapeutic Agent for N-MYC Overexpressing Neuroendocrine Prostate Cancers

Neuroendocrine prostate cancer (NEPC) represents a highly aggressive form of prostate tumors. NEPC results from trans-differentiated castration-resistant prostate cancer (CRPC) with increasing evidence indicating that the incidence of NEPC often results from the adaptive response to androgen deprivation therapy. Recent studies have shown that a subset of NEPC exhibits overexpression of the MYCN oncogene along with the loss of tumor suppressing TP53 and RB1 activities. N-MYC is structurally disordered with no binding pockets available on its surface and so far, no clinically approved drug is available. We adopted a drug-repurposing strategy, screened ~1800 drug molecules, and identified fludarabine phosphate to preferentially inhibit the proliferation of N-MYC overexpressing NEPC cells by inducing reactive oxygen species (ROS). We also show that fludarabine phosphate affects N-MYC protein levels and N-MYC transcriptional targets in NEPC cells. Moreover, enhanced ROS production destabilizes N-MYC protein by inhibiting AKT signaling and is responsible for the reduced survival of NEPC cells and tumors. Our results indicate that increasing ROS production by the administration of fludarabine phosphate may represent an effective treatment option for patients with N-MYC overexpressing NEPC tumors.

Trpm8 Expression in Human and Mouse Castration Resistant Prostate Adenocarcinoma Paves the Way for the Preclinical Development of TRPM8-Based Targeted Therapies

Metastatic prostate cancer (mPCa) is one of the leading causes of cancer-related mortality in both the US and Europe. Androgen deprivation is the first-line therapy for mPCa; however, resistance to therapy inevitably occurs and the disease progresses to the castration resistant stage, which is uncurable. A definition of novel targeted therapies is necessary for the establishment of innovative and more effective protocols of personalized oncology. We employed genetically engineered mouse models of PCa and human samples to characterize the expression of the TRPM8 cation channel in both hormone naïve and castration resistant tumors. We show that Trpm8 expression marks both indolent (Pten-null) and aggressive (Pten/Trp53 double-null and TRAMP) mouse prostate adenocarcinomas. Importantly, both mouse and human castration-resistant PCa preserve TRPM8 protein expression. Finally, we tested the effect of TRPM8 agonist D-3263 administration in combination with enzalutamide or docetaxel on the viability of aggressive mouse PCa cell lines. Our data demonstrate that D-3263 substantially enhances the pro-apoptotic activity of enzalutamide and docetaxel in TRAMP-C1 e TRAMP-C2 PCa cell lines. To conclude, this study provides the basis for pre-clinical in vivo testing of TRPM8 targeting as a novel strategy to implement the efficacy of standard-of-care treatments for advanced PCa.

Design, Synthesis, and Biological Evaluation of 1-(Indolizin-3-yl)ethan-1-ones as CBP Bromodomain Inhibitors for the Treatment of Prostate Cancer

CREB (cyclic-AMP responsive element binding protein) binding protein (CBP) is a potential target for prostate cancer treatment. Herein, we report the structural optimization of a series of 1-(indolizin-3-yl)ethan-1-one compounds as new selective CBP bromodomain inhibitors, aiming to improve cellular potency and metabolic stability. This process led to compound 9g (Y08284), which possesses good liver microsomal stability and pharmacokinetic properties (F = 25.9%). Furthermore, the compound is able to inhibit CBP bromodomain as well as the proliferation, colony formation, and migration of prostate cancer cells. Additionally, the new inhibitor shows promising antitumor efficacy in a 22Rv1 xenograft model (TGI = 88%). This study provides new lead compounds for further development of drugs for the treatment of prostate cancer.

Regulation of AR mRNA translation in response to acute AR pathway inhibition

We report a new mechanism of androgen receptor (AR) mRNA regulation and cytoprotection in response to AR pathway inhibition (ARPI) stress in prostate cancer (PCA). AR mRNA translation is coordinately regulated by RNA binding proteins, YTHDF3 and G3BP1. Under ambient conditions m6A-modified AR mRNA is bound by YTHDF3 and translationally stimulated, while m6A-unmodified AR mRNA is bound by G3BP1 and translationally repressed. When AR-regulated PCA cell lines are subjected to ARPI stress, m6A-modified AR mRNA is recruited from actively translating polysomes (PSs) to RNA-protein stress granules (SGs), leading to reduced AR mRNA translation. After ARPI stress, m6A-modified AR mRNA liquid–liquid phase separated with YTHDF3, while m6A-unmodified AR mRNA phase separated with G3BP1. Accordingly, these AR mRNA messages form two distinct YTHDF3-enriched or G3BP1-enriched clusters in SGs. ARPI-induced SG formation is cell-protective, which when blocked by YTHDF3 or G3BP1 silencing increases PCA cell death in response to ARPI stress. Interestingly, AR mRNA silencing also delays ARPI stress-induced SG formation, highlighting its supportive role in triggering this stress response. Our results define a new mechanism for stress adaptive cell survival after ARPI stress involving SG-regulated translation of AR mRNA, mediated by m6A RNA modification and their respective regulatory proteins.

Mechanistic Insights into the Selective Dual BET and PLK1 Inhibitory Activity of a Novel Benzamide Compound in Castration-Resistant Prostrate Cancer

Though multifactorial, BET and PLK1 proteins have been found to be key players in the oncogenic process leading to castration-resistant prostate cancer through regulation of AR and MYC-mediated transcription. Hence, dual inhibition of these proteins appears to be an auspicious approach for CRPC therapy. WNY0824 has been reported to exhibit nanomolar range inhibition as well as significant anti-proliferative activity on AR-positive CRPC cells in vitro. However, structural, and mechanistic events associated with its dual inhibitory and anti-proliferative mechanisms remain unclear. Utilizing integrative computer-assisted atomistic techniques, analyses revealed that the dual-inhibitory activity of WNY0824 against BRD4 and PLK1 proteins is mediated by conserved residues present in the binding cavities of both proteins which are shown to elicit various strong intermolecular interactions and thus favour binding affinity. Also, binding orientation of the ligand at the protein binding cavities allowed for important hydrophobic interactions which resulted in high binding free energy of -42.50 kcal/mol and -51.64 kcal/mol towards BRD4 and PLK1, respectively. While van der Waals interactions are very important to ligand binding in BRD4-WNY complex, electrostatic interactions are pertinent to PLK1-WNY complex. Intriguingly, WNY0824 triggered conformational alterations in both proteins through increased structural instability, decreased structural compactness and mitigation in exposure of residues to solvent surface area. Consequently, critical interactions peculiar to the oncogenic activities of BRD4 and PLK1 were inhibited, a phenomenon that results in an antagonism of CRPC progression. The mechanistic insights presented in this report would further assist in the structure-based design of improved inhibitors useful in CRPC therapy.

Wnt/β-catenin signal transduction pathway in prostate cancer and associated drug resistance

Globally, prostate cancer ranks second in cancer burden of the men. It occurs more frequently in black men compared to white or Asian men. Usually, high rates exist for men aged 60 and above. In this review, we focus on the Wnt/β-catenin signal transduction pathway in prostate cancer since many studies have reported that β-catenin can function as an oncogene and is important in Wnt signaling. We also relate its expression to the androgen receptor and MMP-7 protein, both critical to prostate cancer pathogenesis. Some mutations in the androgen receptor also impact the androgen-β-catenin axis and hence, lead to the progression of prostate cancer. We have also reviewed MiRNAs that modulate this pathway in prostate cancer. Finally, we have summarized the impact of Wnt/β-catenin pathway proteins in the drug resistance of prostate cancer as it is a challenging facet of therapy development due to the complexity of signaling pathways interaction and cross-talk.

Androgens alter the heterogeneity of small extracellular vesicles and the small RNA cargo in prostate cancer

Proliferation and survival of prostate cancer cells are driven by the androgen receptor (AR) upon binding to androgen steroid hormones. Manipulating the AR signalling axis is the focus for prostate cancer therapy; thus, it is crucial to understand the role of androgens and AR on extracellular vesicle (EV) secretion and cargo. In this study, we report that plasma-derived circulating vesicles consisting of CD9 and double-positive for CD9 and Prostate Specific Membrane Antigen (PSMA) are increased in patients with advanced metastatic prostate cancer, whereas double positives for CD9 and CD63 small extracellular vesicles (S-EVs) are significantly higher in patients with localised prostate cancer. Androgen manipulation by dihydrotestosterone (DHT) and the clinical antagonist enzalutamide (ENZ) altered the heterogeneity and size of CD9 positive S-EVs in AR expressing prostate cancer cells, while assessment of the total number and protein cargo of total S-EVs was unaltered across different treatment groups. Furthermore, hormone stimulation caused strong and specific effects on the small RNA cargo of S-EVs. A total of 543 small RNAs were found to be regulated by androgens including miR-19-3p and miR-361-5p. Analysis of S-EVs heterogeneity and small RNA cargo may provide clinical utility for prostate cancer and be informative to understand further the mechanism of resistance to androgen targeted therapy in castration-resistant prostate cancer.

Androgen receptor (AR) antagonism triggers acute succinate-mediated adaptive responses to reactivate AR signaling

Treatment-induced adaptive pathways converge to support androgen receptor (AR) reactivation and emergence of castration-resistant prostate cancer (PCa) after AR pathway inhibition (ARPI). We set out to explore poorly defined acute adaptive responses that orchestrate shifts in energy metabolism after ARPI and identified rapid changes in succinate dehydrogenase (SDH), a TCA cycle enzyme with well-known tumor suppressor activity. We show that AR directly regulates transcription of its catalytic subunits (SDHA, SDHB) via androgen response elements (AREs). ARPI acutely suppresses SDH activity, leading to accumulation of the oncometabolite, succinate. Succinate triggers calcium ions release from intracellular stores, which in turn phospho-activates the AR-cochaperone, Hsp27 via p-CaMKK2/p-AMPK/p-p38 axis to enhance AR protein stabilization and activity. Activation of this pathway was seen in tissue microarray analysis on prostatectomy tissues and patient-derived xenografts. This adaptive response is blocked by co-targeting AR with Hsp27 under both in vitro and in vivo studies, sensitizing PCa cells to ARPI treatments.

Cerebral Cavernous Malformation 1 Determines YAP/TAZ Signaling-Dependent Metastatic Hallmarks of Prostate Cancer Cells

Enhanced Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling is correlated with the extraprostatic extension of prostate cancer. However, the mechanism by which YAP/TAZ signaling becomes hyperactive and drives prostate cancer progression is currently unclear. In this study, we revealed that higher expression of CCM1, which is uniquely found in advanced prostate cancer, is inversely correlated with metastasis-free and overall survival in patients with prostate cancer. We also demonstrated that CCM1 induces the metastasis of multiple types of prostate cancer cells by regulating YAP/TAZ signaling. Mechanistically, CCM1, a gene mutated in cerebral cavernous malformation, suppresses DDX5, which regulates the suppression of YAP/TAZ signaling, indicating that CCM1 and DDX5 are novel upstream regulators of YAP/TAZ signaling. Our findings highlight the importance of CCM1-DDX5-YAP/TAZ signaling in the metastasis of prostate cancer cells.

The long non-coding RNA GHSROS reprograms prostate cancer cell lines toward a more aggressive phenotype

It is now appreciated that long non-coding RNAs (lncRNAs) are important players in orchestrating cancer progression. In this study we characterized GHSROS, a human lncRNA gene on the opposite DNA strand (antisense) to the ghrelin receptor gene, in prostate cancer. The lncRNA was upregulated by prostate tumors from different clinical datasets. Transcriptome data revealed that GHSROS alters the expression of cancer-associated genes. Functional analyses in vitro showed that GHSROS mediates tumor growth, migration and survival, and resistance to the cytotoxic drug docetaxel. Increased cellular proliferation of GHSROS-overexpressing PC3, DU145, and LNCaP prostate cancer cell lines in vitro was recapitulated in a subcutaneous xenograft model. Conversely, in vitro antisense oligonucleotide inhibition of the lncRNA reciprocally regulated cell growth and migration, and gene expression. Notably, GHSROS modulates the expression of PPP2R2C, the loss of which may drive androgen receptor pathway-independent prostate tumor progression in a subset of prostate cancers. Collectively, our findings suggest that GHSROS can reprogram prostate cancer cells toward a more aggressive phenotype and that this lncRNA may represent a potential therapeutic target.

Targeting therapy-resistant prostate cancer via a direct inhibitor of the human heat shock transcription factor 1

Heat shock factor 1 (HSF1) is a cellular stress-protective transcription factor exploited by a wide range of cancers to drive proliferation, survival, invasion, and metastasis. Nuclear HSF1 abundance is a prognostic indicator for cancer severity, therapy resistance, and shortened patient survival. The HSF1 gene was amplified, and nuclear HSF1 abundance was markedly increased in prostate cancers and particularly in neuroendocrine prostate cancer (NEPC), for which there are no available treatment options. Despite genetic validation of HSF1 as a therapeutic target in a range of cancers, a direct and selective small-molecule HSF1 inhibitor has not been validated or developed for use in the clinic. We described the identification of a direct HSF1 inhibitor, Direct Targeted HSF1 InhiBitor (DTHIB), which physically engages HSF1 and selectively stimulates degradation of nuclear HSF1. DTHIB robustly inhibited the HSF1 cancer gene signature and prostate cancer cell proliferation. In addition, it potently attenuated tumor progression in four therapy-resistant prostate cancer animal models, including an NEPC model, where it caused profound tumor regression. This study reports the identification and validation of a direct HSF1 inhibitor and provides a path for the development of a small-molecule HSF1-targeted therapy for prostate cancers and other therapy-resistant cancers.

ABT-737 and erufosine combination against castration-resistant prostate cancer: a promising but cell-type specific response associated with the modulation of anti-apoptotic signaling

A deeper understanding of the molecular basis of castration-resistant prostate cancer (CRPC) paved the way for the rational design and development of targeted therapies, which yielded promising preclinical results. However, translation of these potentially promising agents into clinics has usually failed, partly because of tumor heterogeneity. In this study, anticancer activities of the Bcl-2 inhibitor ABT-737 and the Akt-inhibitor erufosine (ErPC3) alone and in combination were compared between CRPC (PC-3 and DU-145) and healthy (PNT-1A) cell lines. The combination of ABT-737 and ErPC3 showed synergistic antiproliferative, antimigratory, and apoptotic effects in PC-3 cells. In DU-145 cells, ErPC3 showed a resistant profile, with half-maximal inhibitory concentration (IC50) values more than two-fold of PC-3, and combining ErPC3 with ABT-737 yielded no added benefit for all the incubation periods compared with ErPC3 alone. In PNT-1A cells, ABT-737 and ErPC3 alone and in combination reduced cell survival slightly and only at the highest concentrations. Apoptosis analysis showed that ABT-737 induced increased Akt expression and ErPC3 induced increased Mcl-1 expression in DU-145 cells. In conclusion, the ABT-737 and ErPC3 combination seems to be promising against CRPC, with a favorable safety profile in healthy cells. However, CRPC cell-type-specific resistance may be induced by enhancement of antiapoptotic signaling.

Alternative splicing regulation by the androgen receptor in prostate cancer cells

The androgen receptor (AR) is a transcription factor that drives prostate cancer (PCa) by modulating the expression of thousands of genes to promote proliferation and survival and to reprogram metabolism. However, how AR activation controls alternative splicing is mostly unknown. Our objective was to define its role in the transcriptome-wide regulation of alternative splicing. Three human PCa models-LNCaP, LAPC4, and 22Rv1 cells-were treated with and without androgens, and RNA was purified for deep-sequencing analyses (RNA-seq). Several bioinformatic tools were then used to study alternative splicing. We demonstrate that in the absence of androgens, alternative splicing complexity is similar among AR-positive PCa cells, with 48 % of all transcripts having various levels of alternative splicing. We also describe alternative splicing differences among cell lines, such as specific splicing of AR, REST, TSC2, and CTBP1. Interestingly, AR activation changed the alternative splicing of thousands of genes in all the PCa cell lines tested. Overlap between AR-sensitive alternative splicing events revealed that genes linked to cell metabolism are major targets for this specific modulation. These genes encode metabolic enzymes such as the prostate-specific membrane antigen, encoded by FOLH1, and the malate dehydrogenase 1 (MDH1). Overall, our study presents a comprehensive analysis of the PCa cell transcriptome and its modulation by AR, revealing a significant enrichment of metabolic genes in this AR-dependent regulation of alternative splicing.

YB-1 variant and androgen receptor axis-targeted agents in metastatic castration-resistant prostate cancer patients

Aim: To evaluate the influence of YB-1 rs10493112 variant as a genetic marker for response to second-generation androgen receptor axis-target agents. Methods: A hospital-based cohort study of 78 patients with metastatic castration-resistant prostate cancer was conducted. Genotyping was performed by TaqMan^® allelic discrimination technology. Main results: In abiraterone-treated and high-risk patients, YB-1 rs10493112 AA genotype carriers showed lower progression-free survival than C allele genotype patients (4 vs 17 months; p = 0.009). For carriers of AA genotype, multivariate Cox regression analysis revealed a fivefold increased risk of progression (p = 0.035). Conclusion: The study findings suggest that, for metastatic and castration-resistant prostate cancer patients, this polymorphism might be a putative marker for the clinical outcome.

Novel Dual BET and PLK1 Inhibitor WNY0824 Exerts Potent Antitumor Effects in CRPC by Inhibiting Transcription Factor Function and Inducing Mitotic Abnormality

Castration-resistant prostate cancer (CRPC) is a lethal disease with few treatment alternatives once patients become resistant to second-generation antiandrogens. In CRPC, BET proteins are key regulators of AR- and MYC-mediated transcription, while the PLK1 inhibitor potentially downregulates AR and MYC besides influencing the cell cycle. Therefore, synchronous inhibition of BET and PLK1 would be a promising approach for CRPC therapy. This study developed a dual BET and PLK1 inhibitor WNY0824 with nanomolar and equipotent inhibition of BRD4 and PLK1. In vitro, WNY0824 exhibited excellent antiproliferation activity on AR-positive CRPC cells and induced apoptosis. These activities are attributable to its disruption of the AR-transcriptional program and the inhibition of the ETS pathway. Furthermore, WNY0824 downregulated MYC and induced mitotic abnormality. In vivo, oral WNY0824 administration suppressed tumor growth in the CRPC xenograft model of enzalutamide resistance. These findings suggest that WNY0824 is a selective dual BET and PLK1 inhibitor with potent anti-CRPC oncogenic activity and provides insights into the development of other novel dual BET- and PLK1-inhibiting drugs.

MYC and the unfolded protein response in cancer: synthetic lethal partners in crime?

The transcription factors of the MYC family play pivotal roles in the initiation and progression of human cancers. High oncogenic level of MYC invades low‐affinity sites and enhancer sequences, which subsequently alters the transcriptome, causes metabolic imbalance, and induces stress response. The endoplasmic reticulum (ER) not only plays a central role in maintaining proteostasis, but also contributes to other key biological processes, including Ca²⁺ metabolism and the synthesis of lipids and glucose. Stress conditions, such as shortage in glucose or oxygen and disruption of Ca²⁺ homeostasis, may perturb proteostasis and induce the unfolded protein response (UPR), which either restores homeostasis or triggers cell death. Crucial roles of ER stress and UPR signaling have been implicated in various cancers, from oncogenesis to treatment response. Here, we summarize the current knowledge on the interaction between MYC and UPR signaling, and its contribution to cancer development. We also discuss the potential of targeting key UPR signaling nodes as novel synthetic lethal strategies in MYC‐driven cancers.

[Palmitoylome profiling indicates that androgens promote the palmitoylation of metabolism-related proteins in prostate cancer-derived LNCaP cells]

OBJECTIVE

To explore potential therapeutic targets other than androgen-deprivation treatment for prostate cancer by screening the proteins induced by androgen at palmitoylation modification level in LNCaP cells.

METHODS

The LNCaP cells were treated with androgen (Methyltrienolone, R1881, 5 nmol/L) or dimethyl sulfoxide (DMSO) for 24 h, and then labeled with alkynyl palmitic acid Alk-C16 (100 μmol/L). After that, the cells were collected, lysed, the total protein was extracted, agarose beads labeled with azide (1 mmol/L) were added, and the click-chemistry reaction was carried out at room temperature for 1 h. The covalent bond formed by click-chemistry reaction of azide and alkynyl group was used to enrich the palmitoylated proteins on agarose beads. Label-free quantitation (LFQ) was used to compare the protein palmitoylation level of R1881 treated and untreated cells to screen the proteins induced by androgen at palmitoylation modification level.

RESULTS

In this experiment, 907 potential palmitoylated proteins (mascot score>2, P<0.05) were identified, among which 430 proteins had LFQ values not zero at least twice. Among the 430 proteins, the palmitoylation levels of 92 candidates were increased by androgen treatment, and their LFQ values were significantly upregulated (>1.5-fold, P<0.05) in ≥2 samples of androgen-treated vs. untreated LNCaP cells. We also used the software of cytoscape to classify the 92 proteins, and found that the known functional proteins of them could be divided into three categories: metabolism related, protein folding related and translation initiation related. Among them, metabolism related proteins included lipid metabolism (6), glucose metabolism (7) and respiratory electron transport chain (8), and a small amount of amino acid metabolism (2) and other metabolism related proteins (2). Notably, the ratio of LFQ of cytochrome b-c1 complex subunit 2 (UQCRC2) was significantly (>3-fold, P<0.05) higher in androgen-treated cells compared with untreated cells, indicating that the palmitoylation level of UQCRC2 was enhanced by androgen most significantly than that of others. The second was long-chain acyl CoA dehydrogenase (ACADVL) related to lipid metabolism and glucose 6-phosphate dehydrogenase (PGD) related to glucose metabolism, but the LFQ ratio of them was less than 3-fold.

CONCLUSION

The research on palmitoylation mechanism of metabolism, especially the proteins related to respiratory electron transport chain, will provide a new guidance for the diagnosis and treatment of prostate cancer and the development of targeted drugs.

Discovery of pyridine tetrahydroisoquinoline thiohydantoin derivatives with low blood-brain barrier penetration as the androgen receptor antagonists

Prostate cancer (PC) is the most diagnosed type of malignancy in men and the major frequently cause of cancer-related death worldwide. The androgen receptor (AR) has become a promising drug target for the treatment of PC. Here, we reported the design, optimization and evaluation of pyridine tetrahydroisoquinoline thiohydantoin derivatives with improved activity and safety as potent AR antagonists. The most promising compound 42f exhibited potent inhibitory activity on AR and strongly blocked AR nuclear translocation. Moreover, 42f displayed promising in vitro antitumor activity toward AR-dependent prostate cancer cell lines (LNCaP) and also demonstrated therapeutic effects in LNCaP xenograft tumor model in mice (TGI: 79%) with no apparent toxicity observed in vivo. More importantly, 42f showed negligible penetration of the brain-blood barrier (BBB) compared with enzalutamide. These results provide a foundation for the development of a new class of androgen receptor antagonists for potential therapeutics against PC with lower seizurogenic risk for patients.

Notch signalling is a potential resistance mechanism of progenitor cells within patient-derived prostate cultures following ROS-inducing treatments

Low Temperature Plasma (LTP) generates reactive oxygen and nitrogen species, causing cell death, similarly to radiation. Radiation resistance results in tumour recurrence, however mechanisms of LTP resistance are unknown. LTP was applied to patient-derived prostate epithelial cells and gene expression assessed. A typical global oxidative response (AP-1 and Nrf2 signalling) was induced, whereas Notch signalling was activated exclusively in progenitor cells. Notch inhibition induced expression of prostatic acid phosphatase (PAP), a marker of prostate epithelial cell differentiation, whilst reducing colony forming ability and preventing tumour formation. Therefore, if LTP is to be progressed as a novel treatment for prostate cancer, combination treatments should be considered in the context of cellular heterogeneity and existence of cell type-specific resistance mechanisms.

A novel CRISPR-engineered prostate cancer cell line defines the AR-V transcriptome and identifies PARP inhibitor sensitivities

Resistance to androgen receptor (AR)-targeted therapies in prostate cancer (PC) is a major clinical problem. A key mechanism of treatment resistance in advanced PC is the generation of alternatively spliced forms of the AR termed AR variants (AR-Vs) that are refractory to targeted agents and drive tumour progression. Our understanding of how AR-Vs function is limited due to difficulties in distinguishing their discriminate activities from full-length AR (FL-AR). Here we report the development of a novel CRISPR-derived cell line which is a derivative of CWR22Rv1 cells, called CWR22Rv1-AR-EK, that has lost expression of FL-AR, but retains all endogenous AR-Vs. From this, we show that AR-Vs act unhindered by loss of FL-AR to drive cell growth and expression of androgenic genes. Global transcriptomics demonstrate that AR-Vs drive expression of a cohort of DNA damage response genes and depletion of AR-Vs sensitises cells to ionising radiation. Moreover, we demonstrate that AR-Vs interact with PARP1 and PARP2 and are dependent upon their catalytic function for transcriptional activation. Importantly, PARP blockade compromises expression of AR-V-target genes and reduces growth of CRPC cell lines suggesting a synthetic lethality relationship between AR-Vs and PARP, advocating the use of PARP inhibitors in AR-V positive PC.

Inhibiting Heat Shock Factor 1 in Cancer: A Unique Therapeutic Opportunity

The ability of cancer cells to cope with stressful conditions is critical for their survival, proliferation, and metastasis. The heat shock transcription factor 1 (HSF1) protects cells from stresses such as chemicals, radiation, and temperature. These properties of HSF1 are exploited by a broad spectrum of cancers, which exhibit high levels of nuclear, active HSF1. Functions for HSF1 in malignancy extend well beyond its central role in protein quality control. While HSF1 has been validated as a powerful target in cancers by genetic knockdown studies, HSF1 inhibitors reported to date have lacked sufficient specificity and potency for clinical evaluation. We review the roles of HSF1 in cancer, its potential as a prognostic indicator for cancer treatment, evaluate current HSF1 inhibitors and provide guidelines for the identification of selective HSF1 inhibitors as chemical probes and for clinical development.

Plasma Androgen Receptor in Prostate Cancer

The therapeutic landscape of prostate cancer has expanded rapidly over the past 10 years, and there is now an even greater need to understand the biological mechanisms of resistance and to develop noninvasive biomarkers to guide treatment. The androgen receptor (AR) is known to be involved in the pathogenesis and progression of prostate cancer. Recently, highly sensitive next-generation sequencing and PCR-based methods for analyzing androgen receptor gene (AR) copy numbers (CN) and mutations in plasma were established in cell-free DNA (cfDNA) of patients with castration-resistant prostate cancer (CRPC) treated with different drugs. The study of cfDNA holds great promise for improving treatment in CRPC, especially in the advanced stage of the disease. Recent findings showed the significant association of plasma AR aberrations with clinical outcome in CRPC patients treated with AR-directed therapies, whereas no association was observed in patients treated with taxanes. This suggests the potential for using plasma AR as a biomarker for selecting treatment, i.e., hormone therapy or chemotherapy, and the possibility of modulating taxane dose. In recent years, plasma AR status has also been investigated in association with novel agents, such as 177Lu-PSMA radioligand therapy and PARP inhibitors. This review will focus on AR testing in plasma that may have clinical utility for treatment selection in advanced prostate cancer.

Resolution of Cellular Heterogeneity in Human Prostate Cancers: Implications for Diagnosis and Treatment

Prostate cancers have a justified reputation as one of the most heterogeneous human tumours. Indeed, there are some who consider that advanced and castration-resistant prostate cancers are incurable, as a direct result of this heterogeneity. However, tumour heterogeneity can be defined in different ways. To a clinician, prostate cancer is a number of different diseases, the treatments for which remain equally heterogeneous and uncertain. To the pathologist, the histopathological appearances of the tumours are notoriously heterogeneous. Indeed, the genius of Donald Gleason in the 1960s was to devise a classification system designed to take into account the heterogeneity of the tumours both individually and in the whole prostate context. To the cell biologist, a prostate tumour consists of multiple epithelial cell types, inter-mingled with various fibroblasts, neuroendocrine cells, endothelial cells, macrophages and lymphocytes, all of which interact to influence treatment responses in a patient-specific manner. Finally, genetic analyses of prostate cancers have been compromised by the variable gene rearrangements and paucity of activating mutations observed, even in large numbers of patient tumours with consistent clinical diagnoses and/or outcomes. Research into familial susceptibility has even generated the least tractable outcome of such studies: the genetic loci are of low penetrance and are of course heterogeneous. By fractionating the tumour (and patient-matched non-malignant tissues) heterogeneity can be resolved, revealing homogeneous markers of patient outcomes.

A molecule inducing androgen receptor degradation and selectively targeting prostate cancer cells

A new molecule induces AR sumoylation and degradation resulting in selective growth inhibition in AR-dependent prostate cancer cells, but its activity is blunted by interference with proteasomes.

Aberrant androgen signaling drives prostate cancer and is targeted by drugs that diminish androgen production or impede androgen–androgen receptor (AR) interaction. Clinical resistance arises from AR overexpression or ligand-independent constitutive activation, suggesting that complete AR elimination could be a novel therapeutic strategy in prostate cancers. IRC117539 is a new molecule that targets AR for proteasomal degradation. Exposure to IRC117539 promotes AR sumoylation and ubiquitination, reminiscent of therapy-induced PML/RARA degradation in acute promyelocytic leukemia. Critically, ex vivo, IRC117539-mediated AR degradation induces prostate cancer cell viability loss by inhibiting AR signaling, even in androgen-insensitive cells. This approach may be beneficial for castration-resistant prostate cancer, which remains a clinical issue. In xenograft models, IRC117539 is as potent as enzalutamide in impeding growth, albeit less efficient than expected from ex vivo studies. Unexpectedly, IRC117539 also behaves as a weak proteasome inhibitor, likely explaining its suboptimal efficacy in vivo. Our studies highlight the feasibility of AR targeting for degradation and off-target effects’ importance in modulating drug activity in vivo.

Upregulation of Scavenger Receptor B1 Is Required for Steroidogenic and Nonsteroidogenic Cholesterol Metabolism in Prostate Cancer

Aberrant cholesterol metabolism is increasingly appreciated to be essential for prostate cancer initiation and progression. Transcript expression of the high-density lipoprotein-cholesterol receptor scavenger receptor B1 (SR-B1) is elevated in primary prostate cancer. Hypothesizing that SR-B1 expression may help facilitate malignant transformation, we document increased SR-B1 protein and transcript expression in prostate cancer relative to normal prostate epithelium that persists in lethal castration-resistant prostate cancer (CRPC) metastasis. As intratumoral steroid synthesis from the precursor cholesterol can drive androgen receptor (AR) pathway activity in CRPC, we screened androgenic benign and cancer cell lines for sensitivity to SR-B1 antagonism. Benign cells were insensitive to SR-B1 antagonism, and cancer line sensitivity inversely correlated with expression levels of full-length and splice variant AR. In androgen-responsive CRPC cell model C4-2, SR-B1 antagonism suppressed cholesterol uptake, de novo steroidogenesis, and AR activity. SR-B1 antagonism also suppressed growth and viability and induced endoplasmic reticulum stress and autophagy. The inability of exogenous steroids to reverse these effects indicates that AR pathway activation is insufficient to overcome cytotoxic stress caused by a decrease in the availability of cholesterol. Furthermore, SR-B1 antagonism decreased cholesterol uptake, growth, and viability of the AR-null CRPC cell model PC-3, and the small-molecule SR-B1 antagonist block lipid transport-1 decreased xenograft growth rate despite poor pharmacologic properties. Overall, our findings show that SR-B1 is upregulated in primary and castration-resistant disease and is essential for cholesterol uptake needed to drive both steroidogenic and nonsteroidogenic biogenic pathways, thus implicating SR-B1 as a novel and potentially actionable target in CRPC. SIGNIFICANCE: These findings highlight SR-B1 as a potential target in primary and castration-resistant prostate cancer that is essential for cholesterol uptake needed to drive steroidogenic and nonsteroidogenic biogenic pathways.

Functional genomic studies reveal the androgen receptor as a master regulator of cellular energy metabolism in prostate cancer

Sex-steroid hormones have been investigated for decades for their oncogenic properties in hormone-dependent cancers. The increasing body of knowledge on the biological actions of androgens in prostate cancer has led to the development of several targeted therapies that still represent the standard of care for cancer patients to this day. In the prostate, androgens promote cellular differentiation and proper tissue development. These hormones also promote the aberrant proliferation and survival of prostate cancer cells. Over the past few years, sequencing technologies for functional genomic analyses have rapidly expanded, revealing novel functions of sex-steroid hormone receptors other than their classic roles. In this article, we will focus on transcriptomic- and genomic-based evidence that demonstrates the importance of the androgen receptor signaling in the regulation of prostate cancer cell metabolism. This is significant because the reprogramming of cell metabolism is a hallmark of cancer. In fact, it is clear now that the androgen receptor contributes to the reprogramming of specific cellular metabolic pathways that promote tumor growth and disease progression, including aerobic glycolysis, mitochondrial respiration, fatty acid ß-oxidation, and de novo lipid synthesis. Overall, beyond regulating development, differentiation, and proliferation, the androgen receptor is also a master regulator of cellular energy metabolism.

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

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

Stress-induced tunneling nanotubes support treatment adaptation in prostate cancer

Tunneling nanotubes (TNTs) are actin-based membranous structures bridging distant cells for intercellular communication. We define roles for TNTs in stress adaptation and treatment resistance in prostate cancer (PCa). Androgen receptor (AR) blockade and metabolic stress induce TNTs, but not in normal prostatic epithelial or osteoblast cells. Co-culture assays reveal enhanced TNT formation between stressed and unstressed PCa cells as well as from stressed PCa to osteoblasts. Stress-induced chaperones clusterin and YB-1 localize within TNTs, are transported bi-directionally via TNTs and facilitate TNT formation in PI3K/AKT and Eps8-dependent manner. AR variants, induced by AR antagonism to mediate resistance to AR pathway inhibition, also enhance TNT production and rescue loss of clusterin- or YB-1-repressed TNT formation. TNT disruption sensitizes PCa to treatment-induced cell death. These data define a mechanistic network involving stress induction of chaperone and AR variants, PI3K/AKT signaling, actin remodeling and TNT-mediated intercellular communication that confer stress adaptative cell survival.

Computer-Aided Discovery of Small Molecules Targeting the RNA Splicing Activity of hnRNP A1 in Castration-Resistant Prostate Cancer

The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a versatile RNA-binding protein playing a critical role in alternative pre-mRNA splicing regulation in cancer. Emerging data have implicated hnRNP A1 as a central player in a splicing regulatory circuit involving its direct transcriptional control by c-Myc oncoprotein and the production of the constitutively active ligand-independent alternative splice variant of androgen receptor, AR-V7, which promotes castration-resistant prostate cancer (CRPC). As there is an urgent need for effective CRPC drugs, targeting hnRNP A1 could, therefore, serve a dual purpose of preventing AR-V7 generation as well as reducing c-Myc transcriptional output. Herein, we report compound VPC-80051 as the first small molecule inhibitor of hnRNP A1 splicing activity discovered to date by using a computer-aided drug discovery approach. The inhibitor was developed to target the RNA-binding domain (RBD) of hnRNP A1. Further experimental evaluation demonstrated that VPC-80051 interacts directly with hnRNP A1 RBD and reduces AR-V7 messenger levels in 22Rv1 CRPC cell line. This study lays the groundwork for future structure-based development of more potent and selective small molecule inhibitors of hnRNP A1–RNA interactions aimed at altering the production of cancer-specific alternative splice isoforms.

Meta-analysis of efficacy and safety of custirsen in patients with metastatic castration-resistant prostate cancer

Custirsen is the second-generation antisense oligonucleotide (ASO), which can reduce cellular levels of clusterin to increase the cytotoxic effect of chemotherapeutic drugs. Our study assessed the efficacy and safety of custirsen in patients with metastatic castration-resistant prostate cancer (mCRPC).We conducted a comprehensive search to identify all the randomized controlled trials (RCTs) of custirsen for the treatment of mCRPC. The reference lists of the retrieved studies were investigated.Three publications involving a total of 1709 patients were used in the analysis. We found that overall survival (OS) (P = .25) was not statistically significant in the comparison. Safety assessments indicated custirsen were often associated with complications resulting from neutropenia (P < .001), anaemia (P < .001), thrombocytopenia (P < .001), and diarrhea (P = .002).Our meta-analysis shows that custirsen has no obvious effect on improving the OS of patients with mCRPC. Adverse reactions were more common among those patients treated with custirsen as compared to those treated with placebo.

Targeting the turnover of oncoproteins as a new avenue for therapeutics development in castration-resistant prostate cancer

The current therapeutic armamentarium for castration-resistant prostate cancer (CRPC) includes second-generation agents such as the Androgen Receptor (AR) inhibitor enzalutamide and the androgen synthesis inhibitor abiraterone acetate, immunotherapies like sipuleucel-T, chemotherapies including docetaxel and cabazitaxel and the radiopharmaceutical radium 223 dichloride. However, relapse of CRPC resistant to these therapeutic modalities occur rapidly. The mechanisms of resistance to these treatments are complex, including specific mutations or alternative splicing of oncogenic proteins. An alternative approach to treating CRPC may be to target the turnover of these molecular drivers of CRPC. In this review, the mechanisms by which protein stability of several oncoproteins such as AR, ERG, GR, CYP17A1 and MYC, will be discussed, as well as how these findings could be translated into novel therapeutic agents.

DNA repair defects in prostate cancer: impact for screening, prognostication and treatment

Failure of effective DNA damage repair is a hallmark of cancer, but was previously underappreciated as a driver of aggressive prostate cancer. However, recent international sequencing efforts have revealed that both germline and somatic alterations within the homologous recombination and mismatch repair pathways are relatively common in lethal metastatic disease. BRCA2 gene alterations are particularly prevalent and are linked to poor prognosis as well as poor responses to systemic therapy for castration-resistant prostate cancer, although there is conflicting support for the latter. Defective DNA repair contributes to tumour heterogeneity, evolution and progression, but there are high hopes that management of this aggressive subset will be transformed by biomarker-driven use of poly-ADP ribose polymerase (PARP) inhibitors and platinum-based chemotherapy. In this review, we detail the relationship between DNA repair defects and prostate cancer, highlighting the prevalence of mutations in key genes and their controversial association with clinical outcomes.

Computer-aided drug discovery of Myc-Max inhibitors as potential therapeutics for prostate cancer

While Myc is an essential regulator of growth in normal cells, it is also frequently associated with cancer progression, therapy-resistance and lethal outcomes in most human cancers. In prostate cancer (PCa), Myc transcription factors are implicated in the pathogenesis and progression of the full spectrum of PCa, from adenocarcinoma to advanced castration-resistant and neuroendocrine phenotypes. Though a high-value therapeutic target, clinically approved anti-Myc drugs have yet to be discovered. To elicit its oncogenic effects, Myc must form a heterodimer with its partner Max, which together bind DNA and activate transcription of a spectrum of target genes that promote cell growth, proliferation, metabolism, and apoptosis while blocking differentiation. In this study, we identified a binding site on the DNA-binding domain of the structurally ordered Myc-Max complex and employed a computer-aided rational drug discovery approach to identify small molecules that effectively inhibit Myc-Max functionality. A large-scale virtual screening protocol implementing structure-based methodologies was utilized to select a set of top-ranked compounds that were subsequently evaluated experimentally and characterized mechanistically for their ability to inhibit Myc-Max transcriptional activity and subsequent downstream functions, to reduce viability in PCa cell lines, disrupt protein-DNA interactions and to induce apoptosis as their mechanism of action. Among compounds identified that effectively inhibit Myc-Max activity with low to mid-micromolar range potency and no or minimal generic cytotoxicity, VPC-70067, a close analog of the previously identified Myc inhibitor 10058-F4, served as proof-of-concept that our in silico drug discovery strategy performed as expected. Compound VPC-70063, of a chemically different scaffold, was the best performer in a panel of in vitro assays, and the forerunner for future hit-to-lead optimization efforts. These findings lay a foundation for developing more potent, specific and clinically optimized Myc-Max inhibitors that may serve as promising therapeutics, alone or in combination with current anti-cancer treatments, for treatment of specific phenotypes or heterogeneous tumors.

Androgen receptor: what we know and what we expect in castration-resistant prostate cancer

Androgen deprivation therapy is an important therapy for prostate cancer (PCa) in aging men. Under the background of castration, it is inevitable that prostate cancer will develop into castration-resistant prostate cancer (CRPC), which has a high mortality rate, after 2-3 years. Androgen receptor (AR) plays a key role in PCa development and is essential to CRPC. More recent research studies have reported that the development of CRPC is largely due to altered mechanisms related to AR, so it is important for us to understand the roles of AR and detailed AR-related mechanisms in CRPC. The multiple AR-related mechanisms promoting the development of CRPC are as follows: (1) enhanced transformation and increased synthesis of intratumoral androgen; (2) AR overexpression, which enables CRPC to be hypersensitive to low levels of androgen; (3) AR cofactors, which enhanced AR transactivation; (4) AR-spliced variants, which mediated downstream gene expression without androgen; (5) the interaction between the AR pathway and classic tumor-related pathways; and» (6) AR mutations, which reduced AR specificity and enhanced AR transcription.

Overexpression of Periostin in Tumor Biopsy Samples Is Associated With Prostate Cancer Phenotype and Clinical Outcome

BACKGROUND

Overexpression of periostin (POSTN) is associated with prostate cancer (PCa) aggressiveness. We investigated the prognostic significance of POSTN expression in tumor biopsy samples of patients with PCa.

METHODS

We scored POSTN expression by immunohistochemistry analysis on 215 PCa biopsy samples using an anti-POSTN-specific antibody. A total immunoreactive score (T-IRS) was calculated by adding the POSTN staining scores of stromal and epithelial tumor cells. Prostate-specific antigen (PSA) progression/recurrence-free survival (PFS), radiographic progression/recurrence-free survival (rPFS), and overall survival (OS) were the study end points.

RESULTS

A total of 143 patients received therapy with radical attempt, whereas 72 had locally advanced or metastatic disease and received hormone therapy alone. Median T-IRS was 9 and 12 (range, 0-20), respectively (P = .001). Overall, we found a weak positive correlation of T-IRS with prebiopsy PSA levels (r = 0.166, P = .016) and Gleason score (r = 0.266, P < .000). T-IRS ≥ 8 independently predicted for shorter PSA-PFS and OS (hazard ratio [HR] [95% confidence interval (CI)] ≥ 8 versus < 8: 1.50 [1.06-2.14], P = .024 and 1.92 [1.20-3.07], P = .007, respectively). In the subgroup analysis, the association between T-IRS and patient outcome was retained in patients who received therapy with radical attempt (HR [95% CI] ≥ 8 vs. < 8: rPFS: 2.06 [1.18-3.58], P = .01; OS: 2.36 [1.24-4.50], P = .009) and in those with low to intermediate Gleason scores (HR [95% CI] ≥ 8 vs. < 8: PSA-PFS: 1.65 [1.06-2.59], P = .028; rPFS: 2.09 [1.14-3.87], P = .018; OS: 2.57 [1.31-5.04], P = .006).

CONCLUSION

POSTN T-IRS on PCa biopsy samples independently predicted the risk of recurrence, progression, and death in patients with localized disease and in those with low to intermediate Gleason scores.