The Crucial Role of AR-V7 in Enzalutamide-Resistance of Castration-Resistant Prostate Cancer

Novel Skp1 inhibitor has potent preclinical efficacy against castration-resistant prostate cancer

BACKGROUND

Metastatic, castration-resistant prostate cancer (mCRPC) directly contributes to the mortality and morbidity of prostate cancer. It is imperative to identify new molecular targets and discover effective therapeutic agents against lethal mCRPC.

METHODS

The anticancer activities and mechanism of action of the small-molecule lead compound were investigated in preclinical models of human prostate cancer. Immunohistochemistry was employed to determine the expression of S-phase kinase-associated protein 1 (Skp1) in human prostate tissues.

RESULTS

GH501 demonstrates nanomolar potency in the NCI-60 human cancer cell panel and multiple mCRPC cell lines with diverse genetic backgrounds, including those resistant to androgen deprivation therapy drugs. Mechanistically, GH501 may bind Skp1 and disrupt the physical interaction between Skp1 and S-phase kinase-associated protein 2 (Skp2) within the Skp1-Cullin1-F-box protein ubiquitin ligase complexes (SCF), thereby affecting multiple oncogenic signals implicated in mCRPC progression, including p21, p27, β-catenin, cyclin D1, enhancer of zeste homolog 2 (EZH2), c-Myc, and survivin. GH501 exhibits excellent in vitro and in vivo safety pharmacology, and GH501 monotherapy effectively inhibits the in vivo growth of cell- and patient-derived xenografts in intraosseous and subcutaneous models. Skp1 expression is significantly increased in human prostate cancer specimens.

CONCLUSION

These results indicate that interrupting Skp1-Skp2 interaction is an effective approach to target mCRPC and warrant further preclinical development of GH501 as a promising therapeutic candidate.

Prostate Cancer: De-regulated Circular RNAs With Efficacy in Preclinical In Vivo Models

Therapy resistance, including castration-resistance and metastasis, remains a major hurdle in the treatment of prostate cancer. In order to identify novel therapeutic targets and treatment modalities for prostate cancer, we conducted a comprehensive literature search on PubMed to identify de-regulated circular RNAs that influence treatment efficacy in preclinical prostate cancer-related in vivo models. Our analysis identified 49 circular RNAs associated with various processes, including treatment resistance, transmembrane and secreted proteins, transcription factors, signaling cascades, human antigen R, nuclear receptor binding, ubiquitination, metabolism, epigenetics and other target categories. The identified targets and circular RNAs can be further scrutinized through target validation approaches. Down-regulated circular RNAs are candidates for reconstitution therapy, while up-regulated RNAs can be inhibited using small interfering RNA (siRNA), antisense oligonucleotides (ASO) or clustered regularly interspaced short palindromic repeats/CRISPR associated (CRISPR-CAS)-related approaches.

Androgen receptor dynamics in prostate cancer: from disease progression to treatment resistance

Prostate cancer is the most common cancer among men worldwide, especially in those over 65, and is a leading cause of cancer-related mortality. The disease typically advances from an androgen-dependent state to castration-resistant prostate cancer (CRPC), which poses significant treatment challenges. The androgen receptor (AR) on the X chromosome is a central driver in this process, activating genes that govern proliferation and survival. Mutations and amplifications of the AR are closely associated with disease progression and treatment resistance. While traditional therapies such as androgen deprivation therapy (ADT) and AR antagonists like enzalutamide have been effective, resistance persists due to reactivation of AR signaling through mechanisms like ligand-independent activation. Recent research highlights the role of epigenetic modifications in enhancing AR activity and drug resistance. The tumor microenvironment, particularly interactions with cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs), further complicates treatment by promoting aggressive tumor behavior and immune evasion. Future directions include developing next-generation AR antagonists, identifying AR-related biomarkers for personalized therapy, and exploring combinations with immune checkpoint inhibitors. Additionally, basal cell-lumen-derived organoids provide innovative models that can enhance understanding and treatment strategies in prostate cancer.

Insulin-Like Growth Factor 2 mRNA-Binding Protein 2 (IGF2BP2) Promotes Castration-Resistant Prostate Cancer Progression by Regulating AR-V7 mRNA Stability

BACKGROUND

The emergence of constitutively active androgen receptor (AR) splice variant AR-V7 poses a formidable challenge in treating prostate cancer, as it lacks the ligand binding region targeted by androgen-deprivation therapies such as enzalutamide and abiraterone. AR-V7 is critical for castration-resistant prostate cancer (CRPC) development and progression; however, the molecular mechanisms regulating its expression and biological function remain poorly understood. Here, we investigate the role of IGF2BP2 in regulating AR-V7 expression and CRPC progression.

METHODS

To determine the clinical relevance of IGF2BP2 in CRPC, we analyzed the mRNA expression data for prostate cancer patients available in the Genomic Data Commons (GDC) Data Portal and cBioPortal. Next to investigate the role of IGF2BP2 in regulating AR-V7 expression and enzalutamide resistance, we performed shRNA-mediated IGF2BP2 knockdown and overexpression experiments followed by qRT-PCR, immunoblot, colony-formation, and MTT assays. Finally, we performed RIP-qPCR, actinomycin-D, and IGF2BP2 domain-deletion analysis to study the mechanism by which IGF2BP2 regulates AR-V7 stability, expression, and enzalutamide resistance in CRPC cells.

RESULTS

Our analysis revealed that IGF2BP2 is upregulated in CRPC patients and its expression positively correlates with increasing Gleason score in patients with CRPC. We demonstrate that IGF2BP2 silencing leads to downregulation of AR-V7 and its downstream target genes without affecting AR levels. Additionally, IGF2BP2 knockdown also enhances the sensitivity of CRPC cells to enzalutamide while overexpression increases AR-V7 expression and confers increased resistance to enzalutamide. Mechanistically, our experiments demonstrate that IGF2BP2 binds to the intronic splicing enhancer (ISE) region of AR-V7, thereby enhancing its mRNA stability. Furthermore, our domain-deletion analysis pinpoints the role of KH3 and KH4 domains of IGF2BP2 in regulating AR-V7 stability and enzalutamide resistance.

CONCLUSIONS

Taken together, our findings suggest that IGF2BP2 plays a critical role in regulating AR-V7 expression and stability, offering a novel target for developing therapeutic interventions for CRPC.

ECM-mimicking hydrogel models of human adipose tissue identify deregulated lipid metabolism in the prostate cancer-adipocyte crosstalk under antiandrogen therapy

Antiandrogen therapies are effectively used to treat advanced prostate cancer, but eventually cancer adaptation drives unresolved metastatic castration-resistant prostate cancer (mCRPC). Adipose tissue influences metabolic reprogramming in cancer and was proposed as a contributor to therapy resistance. Using extracellular matrix (ECM)-mimicking hydrogel coculture models of human adipocytes and prostate cancer cells, we show that adipocytes from subcutaneous or bone marrow fat have dissimilar responses under the antiandrogen Enzalutamide. We demonstrate that androgen receptor (AR)-dependent cancer cells (LNCaP) are more influenced by human adipocytes than AR-independent cells (C4-2B), with altered lipid metabolism and adipokine secretion. This response changes under Enzalutamide, with increased AR expression and adipogenic and lipogenic genes in cancer cells and decreased lipid content and gene dysregulation associated with insulin resistance in adipocytes. This is in line with the metabolic syndrome that men with mCRPC under Enzalutamide experience. The all-human, all-3D, models presented here provide a significant advance to dissect the role of fat in therapy response for mCRPC.

A study of the role of androgen receptor and androgen receptor variant 7 in TNBC patients and the effect of their targeting by Enzalutamide and EPI-001 in MDA-MB-231

The lack of targeted therapy for triple-negative breast cancer (TNBC) is among the mainsprings of its poor prognosis. This study aimed to elucidate the role of the androgen receptor (AR) and its splice variant 7 (ARv7) in TNBC patients. Further, the molecular impact of their blockers, Enzalutamide and EPI-001, on the TNBC cell line MDA-MB-231 was investigated. Thereby, immunohistochemical expression of AR/ARv7 was assessed for TNBC Egyptian patients. Moreover, bioinformatics analysis of AR/ARv7 RNA status was carried out on TNBC patients from The Cancer Genome Atlas Breast Carcinoma project (TCGA-BRCA). Data from both groups was correlated with patients' clinicopathological features. Besides, scratch wound healing assay and ELISA were employed to assess the effect of AR/ARv7 blockers on several metastasis markers in MDA-MB-231 cell line. In the Egyptian-TNBC patients, AR expression was associated with worse 7-year DFS (40.6 ± 18.6 %). In addition, ARv7 showed cytoplasmic and nuclear patterns, and both cytoplasmic and nuclear ARv7+ patients demonstrated a worse 7-year DFS (22.7 ± 17.7 % and 20 ± 17.9 %) and overall survival (63.6 ± 14.5 % and 40 ± 21.8 %). Importantly, 80 % of the nuclear ARv7+ patients developed distant metastasis. The data of the TCGA-TNBC patients showed a tendency for poor outcomes in the high ARv7-expressing patients. Molecularly, in MDA-MB-231, both inhibitors modulated metastasis and epithelial to mesenchymal transition (EMT) markers ROCK1, ROCK2, c-Myc, E-cadherin and N-cadherin, with EPI-001 downregulating NF-ĸB level as well. We concluded that ARv7 indicated poor prognosis in the studied cohorts and that blocking of AR/ARv7 abated metastasis and key regulators of EMT in MDA-MB-231, at least in part by targeting ROCK/NF-ĸB/c-Myc axis.

The Emerging Roles of the Stress Epigenetic Reader LEDGF/p75 in Cancer Biology and Therapy Resistance: Mechanisms and Targeting Opportunities

The lens epithelium derived growth factor of 75 kD (LEDGF/p75) is a transcription co-activator and epigenetic reader that has emerged as a stress oncoprotein in multiple human cancers. Growing evidence indicates that it promotes tumor cell survival against certain therapeutic drugs. The amino (N)-terminal region of LEDGF/p75 contains a PWWP domain that reads methylated histone marks, critical for recognizing transcriptionally active chromatin sites. Its carboxyl (C)-terminus has an integrase binding domain (IBD) that serves as the binding site for the HIV-1 integrase and multiple oncogenic transcription factors. Acting as hubs for protein-protein interactions, both domains facilitate the tethering of oncogenic transcription factors and regulators to active chromatin to regulate mRNA splicing, promote DNA repair, and enhance the expression of stress and cancer-related genes that contribute to tumor cell aggressiveness and chemoresistance. This review summarizes our current knowledge of the emerging roles of LEDGF/p75 in cancer biology and therapy resistance and discusses its potential as a novel oncotherapeutic target in combinatorial treatments.

Prognostic role of Androgen Receptor splice variant 7 (AR-V7) in the pathogenesis of breast cancer

BACKGROUND

The Androgen Receptor (AR) has emerged as an endocrine therapy target in Breast Cancer, exhibiting up to 80% expression in clinical cases. AR-V7, a constitutively activated splice variant of AR with a truncated ligand-binding domain (LBD), demonstrates ligand-independent transcriptional activity and resistance to nonsteroidal antiandrogens like Bicalutamide or Enzalutamide, targeting the LBD. In metastatic prostate cancer, elevated AR-V7 levels lead to therapeutic resistance and increased metastasis.

METHODS

In this study, we evaluated the expression of AR and AR-V7 in cell lines and a cohort of 89 patients undergoing surgical intervention for treatment-naïve breast cancer. Further clinicopathological correlations and survival analysis were performed to evaluate the relationship between the AR and AR-V7 expression and clinical outcomes.

RESULTS

AR-V7/AR-FL ratio was elevated in the TNBC cell line and downregulation of AR-FL upon AR antagonists' treatment led to a compensatory increase in AR-V7. Clinical samples showed significantly elevated expression of AR and AR-V7 in tumors compared to control cases. Further clinicopathological correlation revealed aggressive clinical traits, higher pathological grades, and poor survival with AR-V7 expression.

CONCLUSIONS

Our study unravels AR-V7 as a marker for poor clinical outcomes, predicting breast cancer aggressiveness, and encourages consideration of AR-V7 as a probable target for therapeutic intervention.

Vaccination Against Androgen Receptor Splice Variants to Immunologically Target Prostate Cancer

Background/Objectives: Androgen receptor (AR) expression and signaling are critical for the progression of prostate cancer and have been the therapeutic focus of prostate cancer for over 50 years. While a variety of agents have been developed to target this axis, many of these fail due to the emergent expression of AR RNA splice variants, such as AR-V7, that can signal independently of ligand binding. Other therapies, such as vaccination against prostate-specific antigens, have achieved FDA approvals but have fallen short of being incorporated as standard-of-care therapies for advanced prostate cancer. This may be due to the elevated level of immunosuppression observed in prostate cancer, which remains largely refractory to immune checkpoint blockade. Methods: We developed a vaccine targeting AR-V7, a common isoform associated with treatment resistance, and demonstrated its ability to elicit AR-V7-specific immunity and enable anti-tumor responses against AR-V7+ cancers in subcutaneous tumor models. Results: Our studies also revealed that AR-V7 expression conferred an immune suppressive phenotype that was significant in a non-AR-dependent prostate cancer model. Notably, in this model, we found that vaccination in combination with enzalutamide, an AR antagonist, suppressed these aggressive immune suppressive cancers and resulted in enhanced survival in comparison to control vaccinated and enzalutamide-treated mice. While anti-PD-1 immune checkpoint inhibition (ICI) alone slowed tumor growth, the majority of vaccinated mice that received anti-PD-1 therapy showed complete tumor elimination. Conclusions: Collectively, these results validate the importance of AR signaling in prostate cancer immune suppression and suggest the potential of AR-V7-specific vaccines as therapeutic strategies against prostate cancer, offering significant protective and therapeutic anti-tumor responses, even in the presence of androgen signaling inhibitors.

Prebiotic stachyose inhibits PRDX5 activity and castration-resistant prostate cancer development

Stachyose (STA) is a prebiotic with poor oral bioavailability. In this study, we developed stachyose caproate (C6-STA), as a novel STA derivative, to demonstrate its high adsorption rate via oral administration. Pharmacokinetic analysis reveals that after absorption, the STA derived from C6-STA reaches its highest peak in the blood, liver, and kidney at 20 min, 30 min, and 12-24 h, with approximate levels of 1200 μg/mL, 0.14 μg/mL, and 0.2-0.3 μg/mL, respectively. In addition, the accumulation of STA in prostate tissues of mice with castration-resistant prostate cancer (CRPC) (1.75 μg/mg) is 10-fold higher than that in normal prostate tissues (0.14 μg/mg). The analysis also reveals that C6-STA has t1/2 of 12.8 h and Tmax of 0.25 h, indicating that it has the potential to be used as a promising drug in clinical practice. The toxicological evaluation shows no obvious side effects of C6-STA in mice administered with a 0.2 g/kg intragastric dose. Pharmacodynamic analysis and mechanism investigation of C6-STA show its ability to inhibit peroxiredoxin 5 (PRDX5) enzyme activity, disrupt PRDX5-nuclear factor erythroid 2-related factor 2 (NRF2) interaction, and decrease NAD(P)H quinone dehydrogenase 1 (NQO1) levels. NQO1 decrease further causes the accumulation of quinone radicals, which ultimately leads to the apoptosis of LNCaP cell-derived drug-tolerant persister (DTP) cells and slows CRPC progression. Our study discovered the anti-tumor activity of stachyose and shows that prebiotics have biological functions in vivo besides in the gut. Further investigation of C6-STA, especially in CRPC patients, is warranted.

The m6A regulators in prostate cancer: molecular basis and clinical perspective

Prostate cancer (PCa) is the second leading cause of cancer-related death among men in western countries. Evidence has indicated the significant role of the androgen receptor (AR) as the main driving factor in controlling the development of PCa, making androgen receptor inhibition (ARI) therapy a pivotal management approach. In addition, AR independent signaling pathways also contribute to PCa progression. One such signaling pathway that has garnered our attention is N6-Methyladenosine (m6A) signaling, which refers to a chemical modification on RNA with crucial roles in RNA metabolism and disease progression, including PCa. It is important to comprehensively summarize the role of each individual m6A regulator in PCa development and understand its interaction with AR signaling. This review aims to provide a thorough summary of the involvement of m6A regulators in PCa development, shedding light on their upstream and downstream signaling pathways. This summary sets the stage for a comprehensive review that would benefit the scientific community and clinical practice by enhancing our understanding of the biology of m6A regulators in the context of PCa.

MED12 and CDK8/19 Modulate Androgen Receptor Activity and Enzalutamide Response in Prostate Cancer

Prostate cancer progression is driven by androgen receptor (AR) activity, which is a target for therapeutic approaches. Enzalutamide is an AR inhibitor that prolongs the survival of patients with advanced prostate cancer. However, resistance mechanisms arise and impair its efficacy. One of these mechanisms is the expression of AR-V7, a constitutively active AR splice variant. The Mediator complex is a multisubunit protein that modulates gene expression on a genome-wide scale. MED12 and cyclin-dependent kinase (CDK)8, or its paralog CDK19, are components of the kinase module that regulates the proliferation of prostate cancer cells. In this study, we investigated how MED12 and CDK8/19 influence cancer-driven processes in prostate cancer cell lines, focusing on AR activity and the enzalutamide response. We inhibited MED12 expression and CDK8/19 activity in LNCaP (AR+, enzalutamide-sensitive), 22Rv1 (AR-V7+, enzalutamide-resistant), and PC3 (AR-, enzalutamide-insensitive) cells. Both MED12 and CDK8/19 inhibition reduced cell proliferation in all cell lines, and MED12 inhibition reduced proliferation in the respective 3D spheroids. MED12 knockdown significantly inhibited c-Myc protein expression and signaling pathways. In 22Rv1 cells, it consistently inhibited the AR response, prostate-specific antigen (PSA) secretion, AR target genes, and AR-V7 expression. Combined with enzalutamide, MED12 inhibition additively decreased the AR activity in both LNCaP and 22Rv1 cells. CDK8/19 inhibition significantly decreased PSA secretion in LNCaP and 22Rv1 cells and, when combined with enzalutamide, additively reduced proliferation in 22Rv1 cells. Our study revealed that MED12 and CDK8/19 regulate AR activity and that their inhibition may modulate response to enzalutamide in prostate cancer.

Combination of Blood Adiponectin and Leptin Levels Is a Predictor of Biochemical Recurrence in Prostate Cancer Invading the Surrounding Adipose Tissue

Biochemical recurrence is a process that progresses to castration-resistant prostate cancer (CRPC) and prediction of biochemical recurrence is useful in determining early therapeutic intervention and disease treatment. Prostate cancer is surrounded by adipose tissue, which secretes adipokines, affecting cancer progression. This study aimed to investigate the correlation between blood adipokines and CRPC biochemical recurrence. We retrospectively analyzed the clinical data, including preoperative serum adipokine levels, of 99 patients with pT3a pN0 prostate cancer who underwent proctectomy between 2011 and 2019. The primary outcome was biochemical recurrence (prostate-specific antigen: PSA > 0.2). We identified 65 non-recurrences and 34 biochemical recurrences (one progressed to CRPC). The initial PSA level was significantly higher (p = 0.006), but serum adiponectin (p = 0.328) and leptin (p = 0.647) levels and their ratio (p = 0.323) were not significantly different in the biochemical recurrence group compared with the non-recurrence group. In contrast, significantly more biochemical recurrences were observed in the group with adiponectin < 6 μg/mL and Leptin < 4 ng/mL (p = 0.046), initial PSA > 15 ng/mL, clinical Gleason pattern ≥ 4, and positive resection margin. A significant difference was also observed in the multivariate analysis (hazard ratio: 4.04, 95% confidence interval: 1.21-13.5, p = 0.0232). Thus, low preoperative serum adiponectin and high leptin levels were significantly associated with biochemical recurrence in adipose tissue-invasive prostate cancer, suggesting that they may be useful predictors of biochemical recurrence. Further studies with larger cases are needed to increase the validity of this study.

Prostate cancer stem cells and their targeted therapies

Prostate cancer (PCa) is the most common malignancy among men worldwide. Through androgen receptor signaling inhibitor (ARSI) treatment, patients eventually succumb to castration-resistant prostate cancer (CRPC). For this, the prostate cancer stem cells (PCSCs), as a minor population of tumor cells that can promote tumor relapse, ARSI resistance, and disease progression, are gaining attention. Therefore, specific therapy targeting PCSCs has momentum. This study reviewed the identification and characterization of PCSCs and PCSC-based putative biomarkers and summarized their mechanisms of action. We further discussed clinical trials of novel therapeutic interventions focused on PCSC-related pathways, the PCSC microenvironment, cutting-edge miRNA therapy, and immunotherapy approaches from a mechanistic standpoint. This review provides updated insights into PCSC plasticity, identifying new PCSC biomarkers and optimized treatments for patients with advanced PCa.

Promising therapy for neuroendocrine prostate cancer: current status and future directions

Neuroendocrine prostate cancer (NEPC) is a highly aggressive variant of castration-resistant prostate cancer. It is characterized by low or no expression of the androgen receptor (AR), activation of AR-independent signaling, and increased neuroendocrine phenotype. Most of NEPC is induced by treatment of androgen deprivation therapy and androgen receptor pathway inhibitors (ARPIs). Currently, the treatment of NEPC follows the treatment strategy for small-cell lung cancer, lacking effective drugs and specific treatment options. This review summarizes potential novel targets and therapies for NEPC treatment, including epigenetic regulators (zeste homolog 2 inhibitors, lysine-specific demethylase 1 inhibitors), aurora kinase A inhibitors, poly-ADP-ribose polymerase inhibitors, delta-like ligand 3 targeted therapies, a combination of immunotherapies, etc. Other promising targets and future directions are also discussed in this review. These novel targets and therapies may provide new opportunities for the treatment of NEPC.

Synergistic Strategies for Castration-Resistant Prostate Cancer: Targeting AR-V7, Exploring Natural Compounds, and Optimizing FDA-Approved Therapies

Castration-resistant prostate cancer (CRPC) remains a significant therapeutic challenge due to its resistance to standard androgen deprivation therapy (ADT). The emergence of androgen receptor splice variant 7 (AR-V7) has been implicated in CRPC progression, contributing to treatment resistance. Current treatments, including first-generation chemotherapy, androgen receptor blockers, radiation therapy, immune therapy, and PARP inhibitors, often come with substantial side effects and limited efficacy. Natural compounds, particularly those derived from herbal medicine, have garnered increasing interest as adjunctive therapeutic agents against CRPC. This review explores the role of AR-V7 in CRPC and highlights the promising benefits of natural compounds as complementary treatments to conventional drugs in reducing CRPC and overcoming therapeutic resistance. We delve into the mechanisms of action underlying the anti-CRPC effects of natural compounds, showcasing their potential to enhance therapeutic outcomes while mitigating the side effects associated with conventional therapies. The exploration of natural compounds offers promising avenues for developing novel treatment strategies that enhance therapeutic outcomes and reduce the adverse effects of conventional CRPC therapies. These compounds provide a safer, more effective approach to managing CRPC, representing a significant advancement in improving patient care.

Hydrophobic tagging of small molecules: an overview of the literature and future outlook

INTRODUCTION

Hydrophobic tagging (HyT) technology presents a distinct therapeutic strategy diverging from conventional small molecule drugs, providing an innovative approach to drug design. This review aims to provide an overview of the HyT literature and future outlook to offer guidance for drug design.

AREAS COVERED

In this review, the authors introduce the composition, mechanisms and advantages of HyT technology, as well as summarize the detailed applications of HyT technology in anti-cancer, neurodegenerative diseases (NDs), autoimmune disorders, cardiovascular diseases (CVDs), and other fields. Furthermore, this review discusses key aspects of the future development of HyT molecules.

EXPERT OPINION

HyT emerges as a highly promising targeted protein degradation (TPD) strategy, following the successful development of proteolysis targeting chimeras (PROTAC) and molecular glue. Based on exploring new avenues, modification of the HyT molecule itself potentially enhances the technology. Improved synthetic pathways and emphasis on pharmacokinetic (PK) properties will facilitate the development of HyT. Furthermore, elucidating the biochemical basis by which the compound's hydrophobic moiety recruits the protein homeostasis network will enable the development of more precise assays that can guide the optimization of the linker and hydrophobic moiety.

Deciphering the genetic and epigenetic architecture of prostate cancer

Prostate cancer, one of the most frequently diagnosed cancers in men, leads to significant mortality worldwide. Its study is important due to the complexity and diversity in its progression, highlighting the urgent need for improved therapeutic strategies. This chapter probes into the genetic and epigenetic factors influencing prostate cancer progression, underscoring the importance of understanding the disease's molecular fundamentals for the development of targeted therapies. It specifically reviews the role of key genetic mutations in genes such as Androgen Receptor, TP53, SPOP, FOXA1 and PTEN which are crucial for the disease onset and a progression. Furthermore, it examines the impact of epigenetic modifications, including DNA methylation and histone modification, which contribute to the cancer's progression by affecting gene expression and cellular behavior. Further, in this chapter we delve into the underlying signaling mechanism, the advancements in targeting genetic and epigenetic alterations in prostate cancer. These findings have revealed promising targets for therapeutic advancements, aiming to understand and identify promising avenues for future therapies. This chapter improves our current understanding of prostate cancer genetic and epigenetic landscape, emphasizing the necessity of advancing our knowledge to refine and expand treatment options for prostate cancer patients.

The interplay between autophagy and ferroptosis presents a novel conceptual therapeutic framework for neuroendocrine prostate cancer

In American men, the incidence of prostate cancer (PC) is the highest among all types of cancer, making it the second leading cause of mortality associated with cancer. For advanced or metastatic PC, antiandrogen therapies are standard treatment options. The administration of these treatments unfortunately carries the potential risk of inducing neuroendocrine prostate cancer (NEPC). Neuroendocrine differentiation (NED) serves as a crucial indicator of prostate cancer development, encompassing various factors such as phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), Yes-associated protein 1 (YAP1), AMP-activated protein kinase (AMPK), miRNA. The processes of autophagy and ferroptosis (an iron-dependent form of programmed cell death) play pivotal roles in the regulation of various types of cancers. Clinical trials and preclinical investigations have been conducted on many signaling pathways during the development of NEPC, with the deepening of research, autophagy and ferroptosis appear to be the potential target for regulating NEPC. Due to the dual nature of autophagy and ferroptosis in cancer, gaining a deeper understanding of the developmental programs associated with achieving autophagy and ferroptosis may enhance risk stratification and treatment efficacy for patients with NEPC.

CRISPR genome-wide screening identifies PAK1 as a critical driver of ARSI cross-resistance in prostate cancer progression

Next-generation androgen receptor signaling inhibitors (ARSIs), such as enzalutamide (Enza) and darolutamide (Daro), are initially effective for the treatment of advanced prostate cancer (PCa) and castration-resistant prostate cancer (CRPC). However, patients often relapse and develop cross-resistance, which consequently makes drug resistance an inevitable cause of CRPC-related mortality. By conducting a comprehensive analysis of GEO datasets, CRISPR genome-wide screening results, ATAC-seq data, and RNA-seq data, we systemically identified PAK1 as a significant contributor to ARSI cross-resistance due to the activation of the PAK1/RELA/hnRNPA1/AR-V7 axis. Inhibition of PAK1 followed by suppression of NF-κB pathways and AR-V7 expression effectively overcomes ARSI cross-resistance. Our findings indicate that PAK1 represents a promising therapeutic target gene for the treatment of ARSI cross-resistant PCa patients in the clinic. STATEMENT OF SIGNIFICANCE: PAK1 drives ARSI cross-resistance in prostate cancer progression.

Development of a Double-Stapled Peptide Stabilizing Both α-Helix and β-Sheet Structures for Degrading Transcription Factor AR-V7

Peptide drugs offer distinct advantages in therapeutics; however, their limited stability and membrane penetration abilities hinder their widespread application. One strategy to overcome these challenges is the hydrocarbon peptide stapling technique, which addresses issues such as poor conformational stability, weak proteolytic resistance, and limited membrane permeability. Nonetheless, while peptide stapling has successfully stabilized α-helical peptides, it has shown limited applicability for most β-sheet peptide motifs. In this study, we present the design of a novel double-stapled peptide capable of simultaneously stabilizing both α-helix and β-sheet structures. Our designed double-stapled peptide, named DSARTC, specifically targets the androgen receptor (AR) DNA binding domain and MDM2 as E3 ligase. Serving as a peptide-based PROTAC (proteolysis-targeting chimera), DSARTC exhibits the ability to degrade both the full-length AR and AR-V7. Molecular dynamics simulations and circular dichroism analysis validate the successful constraint of both secondary structures, demonstrating that DSARTC is a "first-in-class" heterogeneous-conformational double-stapled peptide drug candidate. Compared to its linear counterpart, DSARTC displays enhanced stability and an improved cell penetration ability. In an enzalutamide-resistant prostate cancer animal model, DSARTC effectively inhibits tumor growth and reduces the levels of both AR and AR-V7 proteins. These results highlight the potential of DSARTC as a more potent and specific peptide PROTAC for AR-V7. Furthermore, our findings provide a promising strategy for expanding the design of staple peptide-based PROTAC drugs, targeting a wide range of "undruggable" transcription factors.

Experimental treatment efficacy of dmrFABP5 on prostate cancer singly or in combination with drugs in use

Enzalutamide is a drug used to treat prostate cancer (PC) and docetaxel is a drug for chemotherapeutic treatment of diverse cancer types, including PC. The effectiveness of these drugs in treating castration-resistant prostate cancer (CRPC) is poor and therefore CRPC is still largely incurable. However, the bio-inhibitor of fatty acid-binding protein 5 (FABP5), dmrFABP5, which is a mutant form of FABP5 incapable of binding to fatty acids, has been shown recently to be able to suppress the tumorigenicity and metastasis of cultured CRPC cells. The present study investigated the possible synergistic effect of dmrFABP5 combined with either enzalutamide or docetaxel on suppressing the tumorigenic properties of PC cells, including cell viability, migration, invasion and colony proliferation in soft agar. A highly significant synergistic inhibitory effect on these properties was observed when dmrFABP5 was used in combination with enzalutamide on androgen-responsive PC 22RV1 cells. Moreover, a highly significant synergistic inhibitory effect was also observed when dmrFABP5 was combined with docetaxel, and added to 22RV1 cells and to the highly malignant, androgen-receptor (AR)-negative Du145 cells. DmrFABP5 alone failed to produce any suppressive effect when added to the FABP5-negative cell line LNCaP, although enzalutamide could significantly suppress LNCaP cells when used as a single agent. These synergistic inhibitory effects of dmrFABP5 were produced by interrupting the FABP5-related signal transduction pathway in PC cells. Thus, dmrFABP5 appears to be not only a potential single therapeutic agent, but it may also be used in combination with existing drugs to suppress both AR-positive and AR-negative PC.

Molecular Insight into Prostate Cancer: Preventive Role of Selective Bioactive Molecules

Prostate cancer (CaP) is one of the most prevalent male malignancies, accounting for a considerable number of annual mortalities. However, the prompt identification of early-stage CaP often faces delays due to diverse factors, including socioeconomic inequalities. The androgen receptor (AR), in conjunction with various other signaling pathways, exerts a central influence on the genesis, progression, and metastasis of CaP, with androgen deprivation therapy (ADT) serving as the primary therapeutic strategy. Therapeutic modalities encompassing surgery, chemotherapy, hormonal intervention, and radiotherapy have been formulated for addressing early and metastatic CaP. Nonetheless, the heterogeneous tumor microenvironment frequently triggers the activation of signaling pathways, culminating in the emergence of chemoresistance, an aspect to which cancer stem cells (CSCs) notably contribute. Phytochemicals emerge as reservoirs of bioactive agents conferring manifold advantages against human morbidity. Several of these phytochemicals demonstrate potential chemoprotective and chemosensitizing properties against CaP, with selectivity exhibited towards malignant cells while sparing their normal counterparts. In this context, the present review aims to elucidate the intricate molecular underpinnings associated with metastatic CaP development and the acquisition of chemoresistance. Moreover, the contributions of phytochemicals to ameliorating CaP initiation, progression, and chemoresistance are also discussed.

siRNA-based approaches for castration-resistant prostate cancer therapy targeting the androgen receptor signaling pathway

Androgen deprivation therapy is a common treatment method for metastatic prostate cancer through lowering androgen levels; however, this therapy frequently leads to the development of castration-resistant prostate cancer (CRPC). This is attributed to the activation of the androgen receptor (AR) signaling pathway. Current treatments targeting AR are often ineffective mostly due to AR gene overexpression and mutations, as well as the presence of splice variants that accelerate CRPC progression. Thus there is a critical need for more specific medication to treat CRPC. Small interfering RNAs have shown great potential as a targeted therapy. This review discusses prostate cancer progression and the role of AR signaling in CRPC, and proposes siRNA-based targeted therapy as a promising strategy for CRPC.

Glucocorticoid Receptor Regulates and Interacts with LEDGF/p75 to Promote Docetaxel Resistance in Prostate Cancer Cells

Patients with advanced prostate cancer (PCa) invariably develop resistance to anti-androgen therapy and taxane-based chemotherapy. Glucocorticoid receptor (GR) has been implicated in PCa therapy resistance; however, the mechanisms underlying GR-mediated chemoresistance remain unclear. Lens epithelium-derived growth factor p75 (LEDGF/p75, also known as PSIP1 and DFS70) is a glucocorticoid-induced transcription co-activator implicated in cancer chemoresistance. We investigated the contribution of the GR-LEDGF/p75 axis to docetaxel (DTX)-resistance in PCa cells. GR silencing in DTX-sensitive and -resistant PCa cells decreased LEDGF/p75 expression, and GR upregulation in enzalutamide-resistant cells correlated with increased LEDGF/p75 expression. ChIP-sequencing revealed GR binding sites in the LEDGF/p75 promoter. STRING protein-protein interaction analysis indicated that GR and LEDGF/p75 belong to the same transcriptional network, and immunochemical studies demonstrated their co-immunoprecipitation and co-localization in DTX-resistant cells. The GR modulators exicorilant and relacorilant increased the sensitivity of chemoresistant PCa cells to DTX-induced cell death, and this effect was more pronounced upon LEDGF/p75 silencing. RNA-sequencing of DTX-resistant cells with GR or LEDGF/p75 knockdown revealed a transcriptomic overlap targeting signaling pathways associated with cell survival and proliferation, cancer, and therapy resistance. These studies implicate the GR-LEDGF/p75 axis in PCa therapy resistance and provide a pre-clinical rationale for developing novel therapeutic strategies for advanced PCa.

Aldo-Keto Reductase 1C3 Inhibitor Prodrug Improves Pharmacokinetic Profile and Demonstrates In Vivo Efficacy in a Prostate Cancer Xenograft Model

Aldo-keto reductase 1C3 (AKR1C3) is overexpressed in castration-resistant prostate cancer where it acts to drive proliferation and aggressiveness by producing androgens. The reductive action of the enzyme leads to chemoresistance development against various clinical antineoplastics across a range of cancers. Herein, we report the continued optimization of selective AKR1C3 inhibitors and the identification of 5r, a potent AKR1C3 inhibitor (IC50 = 51 nM) with >1216-fold selectivity for AKR1C3 over closely related isoforms. Due to the cognizance of the poor pharmacokinetics associated with free carboxylic acids, a methyl ester prodrug strategy was pursued. The prodrug 4r was converted to free acid 5r in vitro in mouse plasma and in vivo. The in vivo pharmacokinetic evaluation revealed an increase in systemic exposure and increased the maximum 5r concentration compared to direct administration of the free acid. The prodrug 4r demonstrated a dose-dependent effect to reduce the tumor volume of 22Rv1 prostate cancer xenografts without observed toxicity.

Allosteric inhibition of HSP70 in collaboration with STUB1 augments enzalutamide efficacy in antiandrogen resistant prostate tumor and patient-derived models

Ubiquitin proteasome activity is suppressed in enzalutamide resistant prostate cancer cells, and the heat shock protein 70/STIP1 homology and U-box-containing protein 1 (HSP70/STUB1) machinery are involved in androgen receptor (AR) and AR variant protein stabilization. Targeting HSP70 could be a viable strategy to overcome resistance to androgen receptor signaling inhibitor (ARSI) in advanced prostate cancer. Here, we showed that a novel HSP70 allosteric inhibitor, JG98, significantly suppressed drug-resistant C4-2B MDVR and CWR22Rv1 cell growth, and enhanced enzalutamide treatment. JG98 also suppressed cell growth in conditional reprogramed cell cultures (CRCs) and organoids derived from advanced prostate cancer patient samples. Mechanistically, JG98 degraded AR/AR-V7 expression in resistant cells and promoted STUB1 nuclear translocation to bind AR-V7. Knockdown of the E3 ligase STUB1 significantly diminished the anticancer effects and partially restored AR-V7 inhibitory effects of JG98. JG231, a more potent analog developed from JG98, effectively suppressed the growth of the drug-resistant prostate cancer cells, CRCs, and organoids. Notably, the combination of JG231 and enzalutamide synergistically inhibited AR/AR-V7 expression and suppressed CWR22Rv1 xenograft tumor growth. Inhibition of HSP70 using novel small-molecule inhibitors coordinates with STUB1 to regulate AR/AR-V7 protein stabilization and ARSI resistance.

Niclosamide in prostate cancer: An inhibitor of AR-V7, a mitochondrial uncoupler, or more?

A recent phase Ib study investigating the use of reformulated niclosamide in combination with abiraterone and prednisone in patients with castration-resistant prostate cancer (CRPC) demonstrated encouraging preliminary efficacy with low toxicity. Preclinical studies have reported that niclosamide at clinically relevant concentrations inhibits androgen receptor splice variant 7 (AR-V7), a known tumor driver in CRPC. However, the magnitude of anti-tumor effects of niclosamide either used alone or in combination with abiraterone in these experimental models, far exceeded what could have been explained as a simple AR-V7 inhibition. Niclosamide at clinically relevant concentrations also acts as an oxidative phosphorylation (OxPhos) uncoupler in mitochondria. This raises the question whether the observed effects of niclosamide were partly mediated by OxPhos inhibition. Most OxPhos inhibitors did not demonstrate selectivity towards cancer cells and failed to enter clinical practice due to unacceptable toxicity. However, some mitochondrial uncouplers have greater cytotoxicity against cancerous cells compared to non-cancerous. Hyperpolarization of cancer cell mitochondria, or the more alkaline mitochondrial matrix of cancer cells could be potential reasons for this. Niclosamide can also alter Wnt/β-catenin, mTOR, Notch, NF-kB and STAT3 signaling pathways. Hence, the mechanism of action of reformulated niclosamide in CRPC patients requires further investigation. This will potentially lead to new opportunities to develop and investigate even more selective and effective treatments against prostate cancer.