Emerging mechanisms of resistance to androgen receptor inhibitors in prostate cancer

Identification and Validation of Three Hub Genes Involved in Cell Proliferation and Prognosis of Castration-Resistant Prostate Cancer

Background

The acquisition of castration resistance is lethal and inevitable in most prostate cancer patients under hormone therapy. However, effective biomarkers and therapeutic targets for castration-resistant prostate cancer remain to be defined.

Methods

Comprehensive bioinformatics tools were used to screen hub genes in castration-resistant prostate cancer and were verified in androgen-dependent prostate cancer and castration-resistant prostate cancer in TCGA and the SU2C/PCF Dream Team database, respectively. Gene set enrichment analysis and in vitro experiments were performed to determine the potential functions of hub genes involved in castration-resistant prostate cancer progression.

Results

Three hub genes were screened out by bioinformatics analysis: MCM4, CENPI, and KNTC1. These hub genes were upregulated in castration-resistant prostate cancer and showed high diagnostic and prognostic value. Moreover, the expression levels of the hub genes were positively correlated with neuroendocrine prostate cancer scores, which represent the degree of castration-resistant prostate cancer aggression. Meanwhile, in vitro experiments confirmed that hub gene expression was increased in castration-resistant prostate cancer cell lines and that inhibition of hub genes hindered cell cycle transition, resulting in suppression of castration-resistant prostate cancer cell proliferation, which confirmed the gene set enrichment analysis results.

Conclusions

MCM4, CENPI, and KNTC1 could serve as candidate diagnostic and prognostic biomarkers of castration-resistant prostate cancer and may provide potential preventive and therapeutic targets.

Reformation of the chondroitin sulfate glycocalyx enables progression of AR-independent prostate cancer

Lineage plasticity of prostate cancer is associated with resistance to androgen receptor (AR) pathway inhibition (ARPI) and supported by a reactive tumor microenvironment. Here we show that changes in chondroitin sulfate (CS), a major glycosaminoglycan component of the tumor cell glycocalyx and extracellular matrix, is AR-regulated and promotes the adaptive progression of castration-resistant prostate cancer (CRPC) after ARPI. AR directly represses transcription of the 4-O-sulfotransferase gene CHST11 under basal androgen conditions, maintaining steady-state CS in prostate adenocarcinomas. When AR signaling is inhibited by ARPI or lost during progression to non-AR-driven CRPC as a consequence of lineage plasticity, CHST11 expression is unleashed, leading to elevated 4-O-sulfated chondroitin levels. Inhibition of the tumor cell CS glycocalyx delays CRPC progression, and impairs growth and motility of prostate cancer after ARPI. Thus, a reactive CS glycocalyx supports adaptive survival and treatment resistance after ARPI, representing a therapeutic opportunity in patients with advanced prostate cancer.

Chondroitin sulfate (CS) is one of the most abundant glycosaminoglycans in prostate cancers. Here the authors show that inhibition of the androgen receptor pathway leads to the upregulation of CS, which promotes prostate cancer growth and metastasis.

Transcriptomic Signature and Growth Factor Regulation of Castration-Tolerant Prostate Luminal Progenitor Cells

Background: The molecular and cellular mechanisms that drive castration-resistant prostate cancer (CRPC) remain poorly understood. LSCmed cells defines an FACS-enriched population of castration-tolerant luminal progenitor cells that has been proposed to promote tumorigenesis and CRPC in Pten-deficient mice. The goals of this study were to assess the relevance of LSCmed cells through the analysis of their molecular proximity with luminal progenitor-like cell clusters identified by single-cell (sc)RNA-seq analyses of mouse and human prostates, and to investigate their regulation by in silico-predicted growth factors present in the prostatic microenvironment. Methods: Several bioinformatic pipelines were used for pan-transcriptomic analyses. LSCmed cells isolated by cell sorting from healthy and malignant mouse prostates were characterized using RT-qPCR, immunofluorescence and organoid assays. Results: LSCmed cells match (i) mouse luminal progenitor cell clusters identified in scRNA-seq analyses for which we provide a common 15-gene signature including the previously identified LSCmed marker Krt4, and (ii) Club/Hillock cells of the human prostate. This transcriptional overlap was maintained in cancer contexts. EGFR/ERBB4, IGF-1R and MET pathways were identified as autocrine/paracrine regulators of progenitor, proliferation and differentiation properties of LSCmed cells. The functional redundancy of these signaling pathways allows them to bypass the effect of receptor-targeted pharmacological inhibitors. Conclusions: Based on transcriptomic profile and pharmacological resistance to monotherapies that failed in CRPC patients, this study supports LSCmed cells as a relevant model to investigate the role of castration-tolerant progenitor cells in human prostate cancer progression.

Exosomes derived from myeloid-derived suppressor cells facilitate castration-resistant prostate cancer progression via S100A9/circMID1/miR-506-3p/MID1

Background

Castration-resistant prostate cancer (CRPC) is a major cause of recurrence and mortality among prostate cancer (PCa) patients. Myeloid-derived suppressor cells (MDSCs) regulate castration resistance in PCa. Previously, it was shown that intercellular communication was efficiently mediated by exosomes (Exos), but the role and the mechanism of MDSC-derived Exos in CRPC progression was unclear.

Methods

In this study, the circRNA expression profiles in PC3 cells treated with MDSC-Exo and control cells were investigated using a circRNA microarray.

Results

The data showed that circMID1 (hsa_circ_0007718) expression was elevated in PC3 cells treated with MDSC-Exo. Moreover, high circMID1 expression was found in PCa compared with benign prostatic hyperplasia (BPH) tissues and in CRPC patients compared with hormone sensitive prostate cancer (HSPC) patients. Further studies showed that MDSC-Exo accelerated PCa cell proliferation, migration, and invasion, while circMID1 deficiency inhibited MDSC-Exo-regulated CRPC progression in vitro and in vivo. Mechanistically, MDSC-derived exosomal S100A9 increased circMID1 expression to sponge miR-506-3p, leading to increased MID1 expression and accelerated tumor progression.

Conclusion

Together, our results showed that a S100A9/circMID1/miR-506-3p/MID1 axis existed in MDSC-Exo-regulated CRPC progression, which provided novel insights into MDSC-Exo regulatory mechanisms in CRPC progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03494-5.

MicroRNA-375 is a therapeutic target for castration-resistant prostate cancer through the PTPN4/STAT3 axis

The functional role of microRNA-375 (miR-375) in the development of prostate cancer (PCa) remains controversial. Previously, we found that plasma exosomal miR-375 is significantly elevated in castration-resistant PCa (CRPC) patients compared with castration-sensitive PCa patients. Here, we aimed to determine how miR-375 modulates CRPC progression and thereafter to evaluate the therapeutic potential of human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes loaded with miR-375 antisense oligonucleotides (e-375i). We used miRNA in situ hybridization technique to evaluate miR-375 expression in PCa tissues, gain- and loss-of-function experiments to determine miR-375 function, and bioinformatic methods, dual-luciferase reporter assay, qPCR, IHC and western blotting to determine and validate the target as well as the effects of miR-375 at the molecular level. Then, e-375i complexes were assessed for their antagonizing effects against miR-375. We found that the expression of miR-375 was elevated in PCa tissues and cancer exosomes, correlating with the Gleason score. Forced expression of miR-375 enhanced the expression of EMT markers and AR but suppressed apoptosis markers, leading to enhanced proliferation, migration, invasion, and enzalutamide resistance and decreased apoptosis of PCa cells. These effects could be reversed by miR-375 silencing. Mechanistically, miR-375 directly interfered with the expression of phosphatase nonreceptor type 4 (PTPN4), which in turn stabilized phosphorylated STAT3. Application of e-375i could inhibit miR-375, upregulate PTPN4 and downregulate p-STAT3, eventually repressing the growth of PCa. Collectively, we identified a novel miR-375 target, PTPN4, that functions upstream of STAT3, and targeting miR-375 may be an alternative therapeutic for PCa, especially for CRPC with high AR levels.

Androgen receptor signaling and spatial chromatin organization in castration-resistant prostate cancer

Prostate cancer is one of the leading causes of cancer death and affects millions of men in the world. The American Cancer Society estimated about 34,500 deaths from prostate cancer in the United States in year 2022. The Androgen receptor (AR) signaling is a major pathway that sustains local and metastatic prostate tumor growth. Androgen-deprivation therapy (ADT) is the standard of care for metastatic prostate cancer patient and can suppress the tumor growth for a median of 2–3 years. Unfortunately, the malignancy inevitably progresses to castration-resistant prostate cancer (CRPC) which is more aggressive and no longer responsive to ADT. Surprisingly, for most of the CPRC patients, cancer growth still depends on androgen receptor signaling. Accumulating evidence suggests that CRPC cells have rewired their transcriptional program to retain AR signaling in the absence of androgens. Besides AR, other transcription factors also contribute to the resistance mechanism through multiple pathways including enhancing AR signaling pathway and activating other complementary signaling pathways for the favor of AR downstream genes expression. More recent studies have shown the role of transcription factors in reconfiguring chromatin 3D structure and regulating topologically associating domains (TADs). Pioneer factors, transcription factors and coactivators form liquid-liquid phase separation compartment that can modulate transcriptional events along with configuring TADs. The role of AR and other transcription factors on chromatin structure change and formation of condensate compartment in prostate cancer cells has only been recently investigated and appreciated. This review intends to provide an overview of transcription factors that contribute to AR signaling through activation of gene expression, governing 3D chromatin structure and establishing phase to phase separation. A more detailed understanding of the spatial role of transcription factors in CRPC might provide novel therapeutic targets for the treatment of CRPC.

Aptamers as Theragnostic Tools in Prostate Cancer

Despite of the capacity that several drugs have for specific inhibition of the androgen receptor (AR), in most cases, PCa progresses to an androgen-independent stage. In this context, the development of new targeted therapies for prostate cancer (PCa) has remained as a challenge. To overcome this issue, new tools, based on nucleic acids technology, have been developed. Aptamers are small oligonucleotides with a three-dimensional structure capable of interacting with practically any desired target, even large targets such as mammalian cells or viruses. Recently, aptamers have been studied for treatment and detection of many diseases including cancer. In PCa, numerous works have reported their use in the development of new approaches in diagnostics and treatment strategies. Aptamers have been joined with drugs or other specific molecules such as silencing RNAs (aptamer–siRNA chimeras) to specifically reduce the expression of oncogenes in PCa cells. Even though these studies have shown good results in the early stages, more research is still needed to demonstrate the clinical value of aptamers in PCa. The aim of this review was to compile the existing scientific literature regarding the use of aptamers in PCa in both diagnosis and treatment studies. Since Prostate-Specific Membrane Antigen (PSMA) aptamers are the most studied type of aptamers in this field, special emphasis was given to these aptamers.

A comprehensive analysis of ncRNA-mediated interactions reveals potential prognostic biomarkers in prostate adenocarcinoma

As one of common malignancies, prostate adenocarcinoma (PRAD) has been a growing health problem and a leading cause of cancer-related death. To obtain expression and functional relevant RNAs, we firstly screened candidate hub mRNAs and characterized their associations with cancer. Eight deregulated genes were identified and used to build a risk model (AUC was 0.972 at 10 years) that may be a specific biomarker for cancer prognosis. Then, relevant miRNAs and lncRNAs were screened, and the constructed primarily interaction networks showed the potential cross-talks among diverse RNAs. IsomiR landscapes were surveyed to understand the detailed isomiRs in relevant homologous miRNA loci, which largely enriched RNA interaction network due to diversities of sequence and expression. We finally characterized TK1, miR-222-3p and SNHG3 as crucial RNAs, and the abnormal expression patterns of them were correlated with poor survival outcomes. TK1 was found synthetic lethal interactions with other genes, implicating potential therapeutic target in precision medicine. LncRNA SNHG3 can sponge miR-222-3p to perturb RNA regulatory network and TK1 expression. These results demonstrate that TK1:miR-222-3p:SNHG3 axis may be a potential prognostic biomarker, which will contribute to further understanding cancer pathophysiology and providing potential therapeutic targets in precision medicine.

Structural and molecular insights into the mechanism of resistance to enzalutamide by the clinical mutants in androgen receptor (AR) in castration-resistant prostate cancer (CRPC) patients

Androgen receptor (AR) is a key contributing element in the prostate cancer (PCa) instigation, progression and it is among the vastly discovered target for prostate cancer. Numerous mechanisms trigger the expansion of CRPC among which the aberrant AR gene is considered as the prime factor. Recently three essential substitutions H875Y, F877L, and T878A are reported to cause resistance to Enzalutamide. However, no detailed study is available to explore the key events that contribute to the resistance. Hence, considering the applicability of structural bioinformatics and molecular simulation-based methods in the current study, we assessed the impact of these mutations on the binding of Enzalutamide. Using a long-run simulation approach the binding stability, residues flexibility, hydrogen bonding, and protein compactness for each complex were determined to reveal the dynamic variations induced by these mutations. We discovered that the binding mode of Enzalutamide is altered by these mutations which misstarget the key residues required for the antagonistic activity. Molecular simulation of each complex revealed that the wild type H11 and H12 are more flexible moving outside and provides more volume for the ligand optimization. In the mutant complexes, the H12 remained tighter pushing out enzalutamide from the key residues which then essentially misstarget the correct orientation for the antagonist activity. The binding free energy (BFE) for the wild type was computed to be -59.92 ± 0.18 kcal/mol, for H875Y the BFE was -55.92 ± 0.18 kcal/mol, -54.82 ± 0.15 kcal/mol for F877L and -53.87 ± 0.18 kcal/mol for T878A, which further demonstrate that these mutations have destabilized the binding of enzalutamide. The proteins' motion and FEL further validated the aforementioned findings where the wild type reported different dynamic features than the mutant complexes. In conclusion, this study provides a structural basis for the resistance to Enzalutamide, which can be used to design novel effective drugs using structure-based and rationale approaches.

Second generation androgen receptor antagonists and challenges in prostate cancer treatment

Prostate cancer is a hormone-dependent malignancy, whose onset and progression are closely related to the activity of the androgen receptor (AR) signaling pathway. Due to this critical role of AR signaling in driving prostate cancer, therapy targeting the AR pathway has been the mainstay strategy for metastatic prostate cancer treatment. The utility of these agents has expanded with the emergence of second-generation AR antagonists, which began with the approval of enzalutamide in 2012 by the United States Food and Drug Administration (FDA). Together with apalutamide and darolutamide, which were approved in 2018 and 2019, respectively, these agents have improved the survival of patients with prostate cancer, with applications for both androgen-dependent and castration-resistant disease. While patients receiving these drugs receive a benefit in the form of prolonged survival, they are not cured and ultimately progress to lethal neuroendocrine prostate cancer (NEPC). Here we summarize the current state of AR antagonist development and highlight the emerging challenges of their clinical application and the potential resistance mechanisms, which might be addressed by combination therapies or the development of novel AR-targeted therapies.

AR-V7 exhibits non-canonical mechanisms of nuclear import and chromatin engagement in castrate-resistant prostate cancer

Expression of the AR splice variant, androgen receptor variant 7 (AR-V7), in prostate cancer is correlated with poor patient survival and resistance to AR targeted therapies and taxanes. Currently, there is no specific inhibitor of AR-V7, while the molecular mechanisms regulating its biological function are not well elucidated. Here, we report that AR-V7 has unique biological features that functionally differentiate it from canonical AR-fl or from the second most prevalent variant, AR-v567. First, AR-V7 exhibits fast nuclear import kinetics via a pathway distinct from the nuclear localization signal dependent importin-α/β pathway used by AR-fl and AR-v567. We also show that the dimerization box domain, known to mediate AR dimerization and transactivation, is required for AR-V7 nuclear import but not for AR-fl. Once in the nucleus, AR-V7 is transcriptionally active, yet exhibits unusually high intranuclear mobility and transient chromatin interactions, unlike the stable chromatin association of liganded AR-fl. The high intranuclear mobility of AR-V7 together with its high transcriptional output, suggest a Hit-and-Run mode of transcription. Our findings reveal unique mechanisms regulating AR-V7 activity, offering the opportunity to develop selective therapeutic interventions.

Machine learning-based tissue of origin classification for cancer of unknown primary diagnostics using genome-wide mutation features

Cancers of unknown primary (CUP) origin account for ∼3% of all cancer diagnoses, whereby the tumor tissue of origin (TOO) cannot be determined. Using a uniformly processed dataset encompassing 6756 whole-genome sequenced primary and metastatic tumors, we develop Cancer of Unknown Primary Location Resolver (CUPLR), a random forest TOO classifier that employs 511 features based on simple and complex somatic driver and passenger mutations. CUPLR distinguishes 35 cancer (sub)types with ∼90% recall and ∼90% precision based on cross-validation and test set predictions. We find that structural variant derived features increase the performance and utility for classifying specific cancer types. With CUPLR, we could determine the TOO for 82/141 (58%) of CUP patients. Although CUPLR is based on machine learning, it provides a human interpretable graphical report with detailed feature explanations. The comprehensive output of CUPLR complements existing histopathological procedures and can enable improved diagnostics for CUP patients.

Role of prostate cancer stem-like cells in the development of antiandrogen resistance

Androgen deprivation therapy (ADT) is the standard of care treatment for advance stage prostate cancer. Treatment with ADT develops resistance in multiple ways leading to the development of castration-resistant prostate cancer (CRPC). Present research establishes that prostate cancer stem-like cells (CSCs) play a central role in the development of treatment resistance followed by disease progression. Prostate CSCs are capable of self-renewal, differentiation, and regenerating tumor heterogeneity. The stemness properties in prostate CSCs arise due to various factors such as androgen receptor mutation and variants, epigenetic and genetic modifications leading to alteration in the tumor microenvironment, changes in ATP-binding cassette (ABC) transporters, and adaptations in molecular signaling pathways. ADT reprograms prostate tumor cellular machinery leading to the expression of various stem cell markers such as Aldehyde Dehydrogenase 1 Family Member A1 (ALDH1A1), Prominin 1 (PROM1/CD133), Indian blood group (CD44), SRY-Box Transcription Factor 2 (Sox2), POU Class 5 Homeobox 1(POU5F1/Oct4), Nanog and ABC transporters. These markers indicate enhanced self-renewal and stemness stimulating CRPC evolution, metastatic colonization, and resistance to antiandrogens. In this review, we discuss the role of ADT in prostate CSCs differentiation and acquisition of CRPC, their isolation, identification and characterization, as well as the factors and pathways contributing to CSCs expansion and therapeutic opportunities.

Sex Differences in Taxane Toxicities

Simple Summary

Clinically observed sex differences in acute and long-term taxane chemotherapy-induced normal tissue toxicity are routinely documented but remain poorly understood despite the significant impact such toxicities have on treatment tolerance and quality of life outcomes in cancer survivors. This review draws from pre-clinical and clinical literature to highlight sex-specific mechanisms of action in taxane drug toxicity and proposes hypotheses for sex-specific clinical discrepancies in taxane-induced acute and long-term toxicities. To our knowledge, this is the first review exploring how sex as a biological variable impacts taxane-mediated mechanisms of action and clinical outcomes. In doing so, we have provided a novel framework to investigate and understand common sex differences observed in clinical and pre-clinical research.

Abstract

The taxane family of microtubule poisons and chemotherapeutics have been studied for over 50 years and are among the most frequently used antineoplastic agents today. Still, limited research exists characterizing taxane-induced sex-specific mechanisms of action and toxicities in cancer and non-cancerous tissue. Such research is important to advance cancer treatment outcomes as well as to address clinically observed sex-differences in short- and long-term taxane-induced toxicities that have disproportionate effects on female and male cancer patients. To gain more insight into these underlying differences between the sexes, the following review draws from pre-clinical and clinical paclitaxel and taxane oncology literature, examines sex-discrepancies, and highlights uncharacterized sex-dependent mechanisms of action and clinical outcomes. To our knowledge, this is the first literature review to provide a current overview of the basic and clinical sex dimorphisms of taxane-induced effects. Most importantly, we hope to provide a starting point for improving and advancing sex-specific personalized chemotherapy and cancer treatment strategies as well as to present a novel approach to review sex as a biological variable in basic and clinical biology.

Lipid nanoparticles to silence androgen receptor variants for prostate cancer therapy

Advanced-stage prostate cancer remains an incurable disease with poor patient prognosis. There is an unmet clinical need to target androgen receptor (AR) splice variants, which are key drivers of the disease. Some AR splice variants are insensitive to conventional hormonal or androgen deprivation therapy due to loss of the androgen ligand binding domain at the C-terminus and are constitutively active. Here we explore the use of RNA interference (RNAi) to target a universally conserved region of all AR splice variants for cleavage and degradation, thereby eliminating protein level resistance mechanisms. To this end, we tested five siRNA sequences designed against exon 1 of the AR mRNA and identified several that induced potent knockdown of full-length and truncated variant ARs in the 22Rv1 human prostate cancer cell line. We then demonstrated that 2'O methyl modification of the top candidate siRNA (siARv^m) enhanced AR and AR-V7 mRNA silencing potency in both 22Rv1 and LNCaP cells, which represent two different prostate cancer models. For downstream in vivo delivery, we formulated siARv^m-LNPs and functionally validated these in vitro by demonstrating knockdown of AR and AR-V7 mRNA in prostate cancer cells and loss of AR-mediated transcriptional activation of the PSA gene in both cell lines following treatment. We also observed that siARv^m-LNP induced cell viability inhibition was more potent compared to LNP containing siRNA targeting full-length AR mRNA (siARfl-LNP) in 22Rv1 cells as their proliferation is more dependent on AR splice variants than LNCaP and PC3 cells. The in vivo biodistribution of siARv^m-LNPs was determined in 22Rv1 tumor-bearing mice by incorporating ¹⁴C-radiolabelled DSPC in LNP formulation, and we observed a 4.4% ID/g tumor accumulation following intravenous administration. Finally, treatment of 22Rv1 tumor bearing mice with siARv^m-LNP resulted in significant tumor growth inhibition and survival benefit compared to siARfl-LNP or the siLUC-LNP control. To best of our knowledge, this is the first report demonstrating therapeutic effects of LNP-siRNA targeting AR splice variants in prostate cancer.

MicroRNA-99b-5p targets mTOR/AR axis, induces autophagy and inhibits prostate cancer cell proliferation

OBJECTIVES: MicroRNAs (miRNAs) are the small non-coding regulatory RNA molecules involved in gene regulation via base-pairing with complementary sequences in mRNAs. The dysregulation of specific miRNAs, such as miR-99b-5p (miR-99b), is associated with prostate cancer (PCa) progression. However, the mechanistic role of miR-99b in PCa remains to be determined. In this study, we aimed to investigate the functional and clinical significance of miR-99b in PCa. STUDY DESIGN: The expression of miR-99b and its downstream targets mTOR/AR in the PCa samples were analyzed by RT/qPCR. The effects of miR-99b overexpression/inhibition on PCa cell survival/proliferation, spheroid formation, and cell migration were examined by specific assays. Luciferase reporter assays were performed to determine the binding of miR-99b to 3′ untranslated region (UTR) of the mTOR gene. The effects of miR-99b on the expression of mTOR, AR, and PSA proteins, as well as on AKT/mTOR signaling, autophagy, and neuroendocrine differentiation markers were analyzed by western blotting. The expression of miR-99b, mTOR, AR, PSA in AR-negative PC3 and AR-positive LNCaP cells was analyzed by RT/qPCR. The effect of miR-99b on global gene expression in PC3 cells was analyzed by RNA-seq. RESULTS: The expression of miR-99b was downregulated in tumor samples from PCa patients, whereas the expression of mTOR and AR was upregulated. In PCa cell lines, overexpression of miR-99b inhibited cell proliferation and cell colony/spheroid formation; induced apoptosis, and increased sensitivity towards docetaxel (DTX). In contrast, inhibition of miR-99b by miR-99b inhibitor resulted in increased cell growth in PCa cells. Mechanistically, miR-99b inhibited the expression of the mammalian target of the rapamycin (mTOR) gene by binding to its 3′ UTR and induced autophagy. Furthermore, miR-99b inhibited androgen receptor (AR) activity in LNCaP cells and induced apoptosis. Activation of AR signaling by dihydrotestosterone (DHT) downregulated miR-99b expression and promoted cell PCa cell growth/survival, whereas inactivation of mTOR by rapamycin or AR by enzalutamide decreased miR-99b mediated PCa cell growth. CONCLUSION: Our data suggest that miR-99b functions as a tumor suppressor by targeting the mTOR/AR axis in PCa cells, implicating miR-99b as a novel biomarker and therapeutic target for PCa management.

Prostate Cancer Drug Therapy: What Have Clinicians Missed During the COVID-19 Pandemic

Due to the COVID-19 pandemic, major congresses and many teaching opportunities as well as the usual visits from medical advisors of pharmaceutical firms have been postponed and canceled. The major trials of prostate cancer in the last 5 years in each state are shortly discussed providing a panoramic overview of the available evidence and data on prostate cancer treatment. Apalutamide, enzalutamide, and darolutamide have proven to have clinical benefits when added to androgen deprivation therapy for patients with nonmetastatic castration-resistant prostate cancer. In patients in the metastatic hormone-sensitive setting, next to docetaxel, abiraterone, enzalutamide, and apalutamide have been shown to significantly improve overall survival and progression-free survival in comparison to standard hormone therapy. In addition, docetaxel abiraterone and enzalutamide are widely used in the metastatic setting. For second-line therapy of metastasized prostate cancer patients who have received either docetaxel or abiraterone or enzalutamide, olaparib, cabazitaxel, radium, and lutetium therapy have been shown to be beneficial in selected patient groups.

Clonal evolution and expansion associated with therapy resistance and relapse of colorectal cancer

Colorectal cancer (CRC) arises by a continuous process of genetic diversification and clonal evolution. Multiple genes and pathways have a role in tumor initiation and progression. The gradual accumulation of genetic and epigenetic processes leads to the establishment of adenoma and cancer. The important 'driver' mutations in tumor suppressor genes (such as TP53, APC, and SMAD4) and oncogenes (such as KRAS, NRAS, MET, and PIK3CA) confer selective growth advantages and cause CRC advancement. Clonal evolution induced by therapeutic pressure, as well as intra-tumoral heterogeneity, has been a great challenge in the treatment of metastatic CRC. Tumors often develop resistance to treatments as a result of intra-tumor heterogeneity, clonal evolution, and selection. Hence, the development of a multidrug personalized approach should be prioritized to pave the way for therapeutics repurposing and combination therapy to arrest tumor progression. This review summarizes how selective drug pressure can impact tumor evolution, resulting in the formation of polyclonal resistance mechanisms, ultimately promoting cancer progression. Current strategies for targeting clonal evolution are described. By understanding sources and consequences of tumor heterogeneity, customized and effective treatment plans to combat drug resistance may be devised.

Genomic Profiling of Prostate Cancer: An Updated Review

Understanding the genomic profiling of prostate cancer is crucial, owing to the emergence of precision medicine to guide therapeutic approaches. Over the last decade, integrative genomic profiling of prostate tumors has provided insights that improve the understanding and treatment of the disease. Minimally invasive liquid biopsy procedures have emerged to investigate cancer-related molecules with the advantage of detecting heterogeneity as well as acquired resistance in cancer. The metastatic castration-resistant prostate cancer (mCRPC) tumors have a highly complex genomic landscape compared to primary prostate tumors; a number of mCRPC harbor clinically actionable molecular alterations, including DNA damage repair (e.g., BRCA1/2 and ATM) and PTEN/phosphoinositide 3-kinase signaling. Heterogeneity in the genomic landscape of prostate cancer has become apparent and genomic alterations of TP53, RB1, AR, and cell cycle pathway are associated with poor clinical outcomes in patients. Prostate cancer with mutant SPOP shows a distinct pattern of genomic alterations, associating with better clinical outcomes. Several genomic profiling tests, which can be used in the clinic, are approved by the U.S. Food and Drug Administration, including MSK-IMPACT, FoundationOne CDx, and FoundationOne Liquid CDx. Here, we review emerging evidence for genomic profiling of prostate cancer, especially focusing on associations between genomic alteration and clinical outcome, liquid biopsy, and actionable molecular alterations.

Targeting Ferroptosis Pathway to Combat Therapy Resistance and Metastasis of Cancer

Ferroptosis is an iron-dependent regulated form of cell death caused by excessive lipid peroxidation. This form of cell death differed from known forms of cell death in morphological and biochemical features such as apoptosis, necrosis, and autophagy. Cancer cells require higher levels of iron to survive, which makes them highly susceptible to ferroptosis. Therefore, it was found to be closely related to the progression, treatment response, and metastasis of various cancer types. Numerous studies have found that the ferroptosis pathway is closely related to drug resistance and metastasis of cancer. Some cancer cells reduce their susceptibility to ferroptosis by downregulating the ferroptosis pathway, resulting in resistance to anticancer therapy. Induction of ferroptosis restores the sensitivity of drug-resistant cancer cells to standard treatments. Cancer cells that are resistant to conventional therapies or have a high propensity to metastasize might be particularly susceptible to ferroptosis. Some biological processes and cellular components, such as epithelial–mesenchymal transition (EMT) and noncoding RNAs, can influence cancer metastasis by regulating ferroptosis. Therefore, targeting ferroptosis may help suppress cancer metastasis. Those progresses revealed the importance of ferroptosis in cancer, In order to provide the detailed molecular mechanisms of ferroptosis in regulating therapy resistance and metastasis and strategies to overcome these barriers are not fully understood, we described the key molecular mechanisms of ferroptosis and its interaction with signaling pathways related to therapy resistance and metastasis. Furthermore, we summarized strategies for reversing resistance to targeted therapy, chemotherapy, radiotherapy, and immunotherapy and inhibiting cancer metastasis by modulating ferroptosis. Understanding the comprehensive regulatory mechanisms and signaling pathways of ferroptosis in cancer can provide new insights to enhance the efficacy of anticancer drugs, overcome drug resistance, and inhibit cancer metastasis.

Chronologically modified androgen receptor in recurrent castration-resistant prostate cancer and its therapeutic targeting

Resistance to second-generation androgen receptor (AR) antagonists such as enzalutamide is an inevitable consequence in patients with castration-resistant prostate cancer (CRPC). There are no effective therapeutic options for this recurrent disease. The expression of truncated AR variant 7 (AR-V7) has been suggested to be one mechanism of resistance; however, its low frequency in patients with CRPC does not explain the almost universal acquisition of resistance. We noted that the ability of AR to translocate to nucleus in an enzalutamide-rich environment opens up the possibility of a posttranslational modification in AR that is refractory to enzalutamide binding. Chemical proteomics in enzalutamide-resistant CRPC cells revealed acetylation at Lys609 in the zinc finger DNA binding domain of AR (acK609-AR) that not only allowed AR translocation but also galvanized a distinct global transcription program, conferring enzalutamide insensitivity. Mechanistically, acK609-AR was recruited to the AR and ACK1/TNK2 enhancers, up-regulating their transcription. ACK1 kinase-mediated AR Y267 phosphorylation was a prerequisite for AR K609 acetylation, which spawned positive feedback loops at both the transcriptional and posttranslational level that regenerated and sustained high AR and ACK1 expression. Consistent with these findings, oral and subcutaneous treatment with ACK1 small-molecule inhibitor, (R)-9b, not only curbed AR Y267 phosphorylation and subsequent K609 acetylation but also compromised enzalutamide-resistant CRPC xenograft tumor growth in mice. Overall, these data uncover chronological modification events in AR that allows prostate cancer to evolve through progressive stages to reach the resilient recurrent CRPC stage, opening up a therapeutic vulnerability.

Prostate organogenesis

Prostate organogenesis begins during embryonic development and continues through puberty when the prostate becomes an important exocrine gland of the male reproductive system. The specification and growth of the prostate is regulated by androgens and is largely a result of cell-cell communication between the epithelium and mesenchyme. The fields of developmental and cancer biology have long been interested in prostate organogenesis because of its relevance for understanding prostate diseases, and research has expanded in recent years with the advent of novel technologies, including genetic-lineage tracing, single-cell RNA sequencing and organoid culture methods, that have provided important insights into androgen regulation, epithelial cell origins and cellular heterogeneity. We discuss these findings, putting them into context with what is currently known about prostate organogenesis.

The Extracellular Matrix Stiffening: A Trigger of Prostate Cancer Progression and Castration Resistance?

Despite advancements made in diagnosis and treatment, prostate cancer remains the second most diagnosed cancer among men worldwide in 2020, and the first in North America and Europe. Patients with localized disease usually respond well to first-line treatments, however, up to 30% develop castration-resistant prostate cancer (CRPC), which is often metastatic, making this stage of the disease incurable and ultimately fatal. Over the last years, interest has grown into the extracellular matrix (ECM) stiffening as an important mediator of diseases, including cancers. While this process is increasingly well-characterized in breast cancer, a similar in-depth look at ECM stiffening remains lacking for prostate cancer. In this review, we scrutinize the current state of literature regarding ECM stiffening in prostate cancer and its potential association with disease progression and castration resistance.

PROTACs: great opportunities for academia and industry (an update from 2020 to 2021)

PROteolysis TArgeting Chimeras (PROTACs) technology is a new protein-degradation strategy that has emerged in recent years. It uses bifunctional small molecules to induce the ubiquitination and degradation of target proteins through the ubiquitin–proteasome system. PROTACs can not only be used as potential clinical treatments for diseases such as cancer, immune disorders, viral infections, and neurodegenerative diseases, but also provide unique chemical knockdown tools for biological research in a catalytic, reversible, and rapid manner. In 2019, our group published a review article “PROTACs: great opportunities for academia and industry” in the journal, summarizing the representative compounds of PROTACs reported before the end of 2019. In the past 2 years, the entire field of protein degradation has experienced rapid development, including not only a large increase in the number of research papers on protein-degradation technology but also a rapid increase in the number of small-molecule degraders that have entered the clinical and will enter the clinical stage. In addition to PROTAC and molecular glue technology, other new degradation technologies are also developing rapidly. In this article, we mainly summarize and review the representative PROTACs of related targets published in 2020–2021 to present to researchers the exciting developments in the field of protein degradation. The problems that need to be solved in this field will also be briefly introduced.

Allosteric interactions prime androgen receptor dimerization and activation

The androgen receptor (AR) is a nuclear receptor that governs gene expression programs required for prostate development and male phenotype maintenance. Advanced prostate cancers display AR hyperactivation and transcriptome expansion, in part, through AR amplification and interaction with oncoprotein cofactors. Despite its biological importance, how AR domains and cofactors cooperate to bind DNA has remained elusive. Using single-particle cryo-electron microscopy, we isolated three conformations of AR bound to DNA, showing that AR forms a non-obligate dimer, with the buried dimer interface utilized by ancestral steroid receptors repurposed to facilitate cooperative DNA binding. We identify novel allosteric surfaces which are compromised in androgen insensitivity syndrome and reinforced by AR's oncoprotein cofactor, ERG, and by DNA-binding motifs. Finally, we present evidence that this plastic dimer interface may have been adopted for transactivation at the expense of DNA binding. Our work highlights how fine-tuning AR's cooperative interactions translate to consequences in development and disease.

Novel forms of prostate cancer chemoresistance to successful androgen deprivation therapy demand new approaches: Rationale for targeting BET proteins

In patients with prostate cancer, the duration of remission after treatment with androgen deprivation therapies (ADTs) varies dramatically. Clinical experience has demonstrated difficulties in predicting individual risk for progression due to chemoresistance. Drug combinations that inhibit androgen biosynthesis (e.g., abiraterone acetate) and androgen signaling (e.g., enzalutamide or apalutamide) have proven so effective that new forms of ADT resistance are emerging. In particular, prostate cancers with a neuroendocrine transcriptional signature, which demonstrate greater plasticity, and potentially, increased predisposition to metastasize, are becoming more prevalent. Notably, these subtypes had in fact been relatively rare before the widespread success of novel ADT regimens. Therefore, better understanding of these resistance mechanisms and potential alternative treatments are necessary to improve progression-free survival for patients treated with ADT. Targeting the bromodomain and extra-terminal (BET) protein family, specifically BRD4, with newer investigational agents may represent one such option. Several families of chromatin modifiers appear to be involved in ADT resistance and targeting these pathways could also offer novel approaches. However, the limited transcriptional and genomic information on ADT resistance mechanisms, and a serious lack of patient diversity in clinical trials, demand profiling of a much broader clinical and demographic range of patients, before robust conclusions can be drawn and a clear direction established.

Addition of Standard Enzalutamide Medication Shows Synergistic Effects on Response to [177Lu]Lu-PSMA-617 Radioligand Therapy in mCRPC Patients with Imminent Treatment Failure-Preliminary Evidence of Pilot Experience

Simple Summary

In this study, we investigated co-medication with enzalutamide, a well-established newer androgen axis drug, as a potential re-sensitizer for prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) in n = 10 patients with imminent treatment failure on standard ¹⁷⁷Lu-based PSMA-RLT. After the introduction of enzalutamide medication, all patients showed a PSA decrease (7/10 patients with partial remission). This pilot experience suggests the synergistic potential of adding enzalutamide to PSMA-RLT derived from the intra-individual comparison of ¹⁷⁷Lu-based PSMA-RLT ± enzalutamide.

Abstract

Well-received strong efficacy of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) does not prevent patients from either early or eventual disease progression under this treatment. In this study, we investigated co-medication with enzalutamide as a potential re-sensitizer for PSMA-RLT in patients with imminent treatment failure on standard ¹⁷⁷Lu-based PSMA-RLT. Ten mCRPC patients who exhibited an insufficient response to conventional [¹⁷⁷Lu]Lu-PSMA-617 RLT received oral medication of enzalutamide 160 mg/d as an adjunct to continued PSMA-RLT. Prostate-specific antigen (PSA) and standard toxicity screening lab work-up were performed to assess the treatment efficacy and safety in these individuals. The mean PSA increase under PSMA-RLT before starting the re-sensitizing procedure was 22.4 ± 26.5%. After the introduction of enzalutamide medication, all patients experienced a PSA decrease, –43.4 ± 20.0% and –48.2 ± 39.0%, after one and two cycles of enzalutamide-augmented PSMA-RLT, respectively. A total of 70% of patients (7/10) experienced partial remission, with a median best PSA response of –62%. Moreover, 5/6 enzalutamide-naïve patients and 2/4 patients who had previously failed enzalutamide exhibited a partial remission. There was no relevant enzalutamide-induced toxicity observed in this small cohort. This pilot experience suggests the synergistic potential of adding enzalutamide to PSMA-RLT derived from the intra-individual comparison of ¹⁷⁷Lu-based PSMA-RLT ± enzalutamide.

Chromatin profiles classify castration-resistant prostate cancers suggesting therapeutic targets

In castration-resistant prostate cancer (CRPC), the loss of androgen receptor (AR) dependence leads to clinically aggressive tumors with few therapeutic options. We used ATAC-seq (assay for transposase-accessible chromatin sequencing), RNA-seq, and DNA sequencing to investigate 22 organoids, six patient-derived xenografts, and 12 cell lines. We identified the well-characterized AR-dependent and neuroendocrine subtypes, as well as two AR-negative/low groups: a Wnt-dependent subtype, and a stem cell-like (SCL) subtype driven by activator protein-1 (AP-1) transcription factors. We used transcriptomic signatures to classify 366 patients, which showed that SCL is the second most common subtype of CRPC after AR-dependent. Our data suggest that AP-1 interacts with the YAP/TAZ and TEAD proteins to maintain subtype-specific chromatin accessibility and transcriptomic landscapes in this group. Together, this molecular classification reveals drug targets and can potentially guide therapeutic decisions.

Stromal AR inhibits prostate tumor progression by restraining secretory luminal epithelial cells

Androgen receptor (AR) is expressed in both the prostate epithelium and the prostate stroma and plays diverse roles in prostate physiology. Although low expression of stromal AR is clinically associated with advanced cancer stage and worse outcome, whether stromal AR inhibits or promotes prostate cancer progression remains controversial. Here, we specifically delete AR in smooth muscle cells of the adult mouse prostate under two tumorigenic conditions, namely, the Hi-Myc genetic model and the T + E2 hormonal carcinogenesis model. Histology analyses show that stromal AR deletion exacerbates tumor progression phenotypes in both models. Furthermore, single-cell analyses of the tumor samples reveal that secretory luminal cells are the cell population particularly affected by stromal AR deletion, as they transition to a cellular state of potentiated PI3K-mTORC1 activities. Our results suggest that stromal AR normally inhibits prostate cancer progression by restraining secretory luminal cells and imply possible unintended negative effects of androgen deprivation therapy.

Whether stromal androgen receptor (AR) promotes or inhibits prostate cancer progression is controversial. Liu et al. report that AR loss in smooth muscle cells exacerbates tumor phenotypes by potentiating the PI3K pathway activity in a subset of luminal epithelial cells, suggesting a tumor-suppressing role for AR in the prostate stroma.

Prostate cancer addiction to oxidative stress defines sensitivity to anti-tumor neutrophils

Bone metastatic prostate cancer (BM-PCa) remains one of the most difficult cancers to treat due to the complex interactions of cancer and stromal cells. We previously showed that bone marrow neutrophils elicit an anti-tumor immune response against BM-PCa. Further, we demonstrated that BM-PCa induces neutrophil oxidative burst, which has previously been identified to promote primary tumor growth of other cancers, and a goal of this study was to define the importance of neutrophil oxidative burst in BM-PCa. To do this, we first examined the impact of depletion of reactive oxygen species (ROS), via systemic deletion of the main source of ROS in phagocytes, NADPH oxidase (Nox)2, which we found to suppress prostate tumor growth in bone. Further, using pharmacologic ROS inhibitors and Nox2-null neutrophils, we found that ROS depletion specifically suppresses growth of androgen-insensitive prostate cancer cells. Upon closer examination using bulk RNA sequencing analysis, we identified that metastatic prostate cancer induces neutrophil transcriptomic changes that activates pathways associated with response to oxidative stress. In tandem, prostate cancer cells resist neutrophil anti-tumor response via extracellular (i.e., regulation of neutrophils) and intracellular alterations of glutathione synthesis, the most potent cellular antioxidant. These findings demonstrate that BM-PCa thrive under oxidative stress conditions and such that regulation of ROS and glutathione programming could be leveraged for targeting of BM-PCa progression.

Management of prostate cancer by targeting 3βHSD1 after enzalutamide and abiraterone treatment

Novel strategies for prostate cancer therapy are required to overcome resistance to abiraterone and enzalutamide. Here, we show that increasing 3βHSD1 after abiraterone and enzalutamide treatment is essential for drug resistance, and biochanin A (BCA), as an inhibitor of 3βHSD1, overcomes drug resistance. 3βHSD1 activity increases in cell lines, biopsy samples, and patients after long-term treatment with enzalutamide or abiraterone. Enhanced steroidogenesis, mediated by 3βHSD1, is sufficient to impair enzalutamide function. In patients, accelerated abiraterone metabolism results in a decline of plasma abiraterone as disease progresses. BCA inhibits 3βHSD1 and suppresses prostate cancer development alone or together with abiraterone and enzalutamide. Daidzein, a BCA analog of dietary origin, is associated with higher plasma abiraterone concentrations and prevented prostate-specific antigen (PSA) increases in abiraterone-resistant patients. Overall, our results show that 3βHSD1 is a promising target to overcome drug resistance, and BCA suppresses disease progression as a 3βHSD1 inhibitor even after abiraterone and enzalutamide resistance.

MYC drives aggressive prostate cancer by disrupting transcriptional pause release at androgen receptor targets

c-MYC (MYC) is a major driver of prostate cancer tumorigenesis and progression. Although MYC is overexpressed in both early and metastatic disease and associated with poor survival, its impact on prostate transcriptional reprogramming remains elusive. We demonstrate that MYC overexpression significantly diminishes the androgen receptor (AR) transcriptional program (the set of genes directly targeted by the AR protein) in luminal prostate cells without altering AR expression. Analyses of clinical specimens reveal that concurrent low AR and high MYC transcriptional programs accelerate prostate cancer progression toward a metastatic, castration-resistant disease. Data integration of single-cell transcriptomics together with ChIP-seq uncover an increase in RNA polymerase II (Pol II) promoter-proximal pausing at AR-dependent genes following MYC overexpression without an accompanying deactivation of AR-bound enhancers. Altogether, our findings suggest that MYC overexpression antagonizes the canonical AR transcriptional program and contributes to prostate tumor initiation and progression by disrupting transcriptional pause release at AR-regulated genes.

Correlation of NTRK1 Downregulation with Low Levels of Tumor-Infiltrating Immune Cells and Poor Prognosis of Prostate Cancer Revealed by Gene Network Analysis

Prostate cancer (PCa) is a life-threatening heterogeneous malignancy of the urinary tract. Due to the incidence of prostate cancer and the crucial need to elucidate its molecular mechanisms, we searched for possible prognosis impactful genes in PCa using bioinformatics analysis. A script in R language was used for the identification of Differentially Expressed Genes (DEGs) from the GSE69223 dataset. The gene ontology (GO) of the DEGs and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed. A protein–protein interaction (PPI) network was constructed using the STRING online database to identify hub genes. GEPIA and UALCAN databases were utilized for survival analysis and expression validation, and 990 DEGs (316 upregulated and 674 downregulated) were identified. The GO analysis was enriched mainly in the “collagen-containing extracellular matrix”, and the KEGG pathway analysis was enriched mainly in “focal adhesion”. The downregulation of neurotrophic receptor tyrosine kinase 1 (NTRK1) was associated with a poor prognosis of PCa and had a significant positive correlation with infiltrating levels of immune cells. We acquired a collection of pathways related to primary PCa, and our findings invite the further exploration of NTRK1 as a biomarker for early diagnosis and prognosis, and as a future potential molecular therapeutic target for PCa.

Transcriptome profiling reveals that VNPP433-3β, the lead next-generation galeterone analog inhibits prostate cancer stem cells by downregulating epithelial-mesenchymal transition and stem cell markers

Cancer stem cells (CSCs) virtually present in all tumors albeit in small numbers are primarily responsible for driving cancer progression, metastasis, drug resistance, and recurrence. Prostate cancer (PCa) is the second most frequent cancer in men worldwide, and castration resistant prostate cancer (CRPC) remains a major challenge despite the tremendous advancements in medicine. Currently, none of the available treatment options are effective in treating CRPC. We earlier reported that VNPP433-3β, the lead next-generation galeterone analog is effective in treating preclinical in vivo models of CRPC. In this study using RNA-seq, cytological, and biochemical methods, we report that VNPP433-3β inhibits prostate CSCs by targeting key pathways critical to stemness and epithelial-mesenchymal transition. VNPP433-3β inhibits CSCs in PCa, presumably by degrading the androgen receptor (AR) thereby decreasing the AR-mediated transcription of several stem cell markers including BMI1 and KLF4. Transcriptome analyses by RNA-seq, Ingenuity Pathway Analysis, and Gene Set Enrichment Analysis demonstrate that VNPP433-3β inhibits transcription of several genes and functional pathways critical to the prostate CSCs thereby inhibiting CSCs in PCa besides targeting the bulk of the tumor.

Targeting CDCP1 gene transcription coactivated by BRD4 and CBP/p300 in castration-resistant prostate cancer

CUB domain-containing protein 1 (CDCP1), a transmembrane protein with tumor pro-metastatic activity, is highly expressed in late-stage and castrate-resistant prostate cancer (CRPC). However, the molecular mechanism driving CDCP1 overexpression in CRPC progress remains elusive. Here we report that transcription cofactors BRD4 and CBP/p300 co-regulate transcriptional expression of CDCP1 in CRPC tumorigenesis. In contrast to androgen receptor (AR) in CRPC, increased expression of BRD4 and CBP/p300 is strongly correlated with CDCP1 gene amplification. Combined knockdown or dual-inhibition of BRD4 and CBP/p300 down-regulated CDCP1 transcription and downstream PI3K/AKT and/or SRC/MAPK signaling pathways in CRPC cells much more so than single-protein perturbation. Our biochemical and structural analyses further showed that NEO2734, a dual-inhibitor targeting BRD4 and p300 bromodomains exhibits greater efficacy than single inhibitors for BRD4 or CBP/p300 in suppressing CDCP1 transcriptional expression and its downstream signaling pathways in CRPC cell proliferation and metastasis. Our study illustrates that targeting CDCP1 through dual-inhibition of BRD4 and CBP/p300 represents a synergistic therapeutic strategy for new treatment of CRPC.

RUVBL1 promotes enzalutamide resistance of prostate tumors through the PLXNA1-CRAF-MAPK pathway

Although enzalutamide improves the overall survival of patients with metastatic prostate cancers, enzalutamide resistance (ENZR) will be inevitably developed. Emerging evidence support that alternative oncogenic pathways may bypass the androgen receptor (AR) signaling to promote ENZR progression, however, the underpinning mechanisms remain poorly defined. Here, we report that the expression of RuvB like AAA ATPase 1 (RUVBL1) is upregulated in ENZR cells and xenograft models and prostate tumors in patients. Enzalutamide increases RUVBL1 accumulation in the cytoplasm, which in turn enhances the recruitment of CRAF proto-oncogene serine/threonine kinase protein to plexin A1 (PLXNA1) and the subsequent activation of the downstream MAPK pathway. Co-overexpression of RUVBL1 and PLXNA1 defines a subgroup of prostate cancer (PCa) patients with a poor prognosis. Furthermore, pharmacological inhibition of RUVBL1 by CB-6644 suppresses ENZR cell proliferation and xenograft growth and allows re-sensitization of ENZR cells and xenografts to enzalutamide, indicating that RUVBL1 may act to substitute the AR signaling to promote cancer cell survival and ENZR development. Together, these findings may lead to the identification of RUVBL1 as a potential therapeutic target for ENZR tumors.

HDL-mediated reduction of cholesterol content inhibits the proliferation of prostate cancer cells induced by LDL: Role of ABCA1 and proteasome inhibition

High-density lipoproteins (HDL) are well known for their atheroprotective function, mainly due to their ability to remove cell cholesterol and to exert antioxidant and anti-inflammatory activities. Through the same mechanisms HDL could also affect the development and progression of tumors. Cancer cells need cholesterol to proliferate, especially in hormone-dependent tumors, as prostate cancer (PCa). Aim of the study was to investigate the ability of HDL to modulate cholesterol content and metabolism in androgen receptor (AR)-positive and AR-null PCa cell lines and the consequences on cell proliferation. HDL inhibited colony formation of LNCaP and PC3 cells. HDL reduced cell cholesterol content and proliferation of LNCaP cells loaded with low-density lipoproteins but were not effective on PC3 cells. Here, the expression of the ATP-binding cassette transporter A1 (ABCA1) was markedly reduced due to proteasome degradation. Bortezomib, a proteasome inhibitor, restored ABCA1 expression and HDL ability to promote cholesterol removal from PC3; consequently, HDL inhibited the proliferation of PC3 cells induced by LDL only after bortezomib pre-treatment. In conclusion, the antiproliferative activity of HDL on AR-positive and AR-null PCa cells also rely on cholesterol removal, a process in which the ABCA1 transporter plays a key role.

βArrestin1 regulates glucocorticoid receptor mitogenic signaling in castration-resistant prostate cancer

BACKGROUND

Prostate cancer (PC) is the most commonly diagnosed malignancy and the second leading cause of cancer-related deaths in males. The disease is initially treated with methods that inhibit androgen receptor (AR) signal transduction. Laboratory-based and clinical studies have identified alternative pathways that cause the failure of AR signal inhibition and consequent development of castration-resistant prostate cancer (CRPC). Glucocorticoid receptor (GR) signaling is activated in certain PC patients and promotes the emergence of CRPC, although by as yet incompletely understood mechanisms. We have previously demonstrated that ubiquitous βarrestin1 (βArr1) expression levels are linked to PC progression. Here, we consider the possibility that βArr1 interacts with and activates GR in model CRPC cells.

METHODS

Bioinformatic analysis of tumor xenograft and human PC datasets was used to correlate the expression of βArr1 and GR. Western blot, immunohistochemistry and immunofluorescence microscopy, and subcellular fractionation were used to determine protein expression level and localization. Immunoprecipitation was applied to detect protein-protein interactions. RNA expression levels were determined using quantitative reverse transcription-polymerase chain reaction. Prostate sphere analysis was used to assess the rate of growth and invasion. The xenograft tumor implantation method was used to determine the tumor growth rate, local invasion, and metastasis.

RESULTS

Elevated expression of βArr1 positively correlated with increased GR expression and function in CRPC xenograft and in human PC patients. βArr1 is expressed in the cell cytosol and nucleus, and it formed a complex with GR in the nucleus and not cytosol. Depletion of βArr1 in AR-null CRPC cells inhibited GR function and CRPC growth and invasion in both in vitro and in vivo settings.

CONCLUSIONS

βArr1 binds GR that initiates mitogenic signaling cascades involved in the progression of PC to CRPC. The targeting of the βArr1-GR axis may provide a new opportunity to better manage the CRPC disease.

Targeting KDM1B-dependent miR-215-AR-AGR2-axis promotes sensitivity to enzalutamide-resistant prostate cancer

Post-translational modifications of histones by histone demethylases plays an important role in the regulation of gene transcription and are implicated in cancers. Castrate resistant prostate cancer (CRPC) is often driven by constitutively active androgen receptor and commonly becomes resistant to established hormonal therapy strategies such as enzalutamide as a result. However, the role of KDM1B involved in next generation anti-enzalutamide resistance and the mechanisms of KDM1B regulation are poorly defined. Here, we show that KDM1B is upregulated and correlated with prostate cancer progression and poor prognosis. Downregulation of miR-215 is correlated with overexpression of KDM1B in enzalutamide-resistant prostate cancer cells, which promotes AR-dependent AGR2 transcription and regulates the sensitivity to next generation AR-targeted therapy. Inhibition of KDM1B significantly inhibits prostate tumor growth and improves enzalutamide treatments through AGR2 suppression. Our studies demonstrate inhibition of KDM1B can offer a viable therapeutic option to overcome enzalutamide resistance in tumors with deregulated miR-215-KDM1B-AR-AGR2 signaling axis.

Baseline Plasma Tumor DNA (ctDNA) Correlates with PSA Kinetics in Metastatic Castration-Resistant Prostate Cancer (mCRPC) Treated with Abiraterone or Enzalutamide

Background: Baseline high circulating tumor DNA (ctDNA) fraction in plasma and androgen receptor (AR) copy number (CN) gain identify mCRPC patients with worse outcomes. This study aimed to assess if ctDNA associates with PSA kinetics. Methods: In this prospective biomarker study, we evaluate ctDNA fraction and AR CN from plasma samples. We divided patients into high and low ctDNA level and in AR gain and AR normal. Results: 220 baseline samples were collected from mCRPC treated with abiraterone (n = 140) or enzalutamide (n = 80). A lower rate of PSA decline ≥ 50% was observed in patients with high ctDNA (p = 0.017) and AR gain (p = 0.0003). Combining ctDNA fraction and AR CN, we found a different median PSA progression-free survival (PFS) among four groups: (1) low ctDNA/AR normal, (2) high ctDNA/AR normal, (3) low ctDNA/AR gain, and (4) high ctDNA/AR gain (11.4 vs. 5.0 vs. 4.8 vs. 3.7 months, p < 0.0001). In a multivariable analysis, high ctDNA, AR gain, PSA DT, PSA DT velocity remained independent predictors of PSA PFS. Conclusions: Elevated ctDNA levels and AR gain are negatively and independently correlated with PSA kinetics in mCRPC men treated with abiraterone or enzalutamide.

Novel MDM2 Inhibitor XR-2 Exerts Potent Anti-Tumor Efficacy and Overcomes Enzalutamide Resistance in Prostate Cancer

Background: The inactivation of tumor-suppressor p53 plays an important role in second generation anti-androgens (SGAs) drug resistance and neuroendocrine differentiation in castration-resistant prostate cancer (CRPC). The reactivation of p53 by blocking the MDM2–p53 interaction represents an attractive therapeutic remedy in cancers with wild-type or functional p53. Whether MDM2-p53 inhibitor could overcome SGAs drug resistance in CRPC is still needed further research. Here, we investigated the anti-tumor efficacy and mechanisms of a novel MDM2-p53 inhibitor XR-2 in CRPC.

Methods: To investigate the functions and mechanisms of XR-2 in prostate cancer, in vitro and in vivo biofunctional assays were performed. Western blot and qRT-PCR assay were performed to detect the protein and mRNA expression levels of indicated genes. CCK8, colony formation, flow cytometry and senescence assays were performed for cell function identifications. RNA-sequencing and bioinformatics analysis were mainly used to identify the influence of XR-2 on prostate cancer cells transcriptome. Subcutaneous 22Rv1 derived xenografts mice model was used to investigate the in vivo anti-tumor activity of XR-2. In addition, the broad-spectrum anti-tumor activities in vivo of XR-2 were evaluated by different xenografts mice models.

Results: XR-2 could directly bind to MDM2, potently reactivate the p53 pathway and thus induce cell cycle arrest and apoptosis in wild-type p53 CRPC cell lines. XR-2 also suppresses the AR pathway as p53 regulates AR transcription inhibition and MDM2 participates in AR degradation. As a result, XR-2 efficiently inhibited CRPC cell viability, showed a synergistic effect with enzalutamide and overcame enzalutamide resistance both in vitro and in vivo. Moreover, results illustrated that XR-2 possesses broad-spectrum anti-tumor activities in vivo with favourable safety.

Conclusion: MDM2-p53 inhibitor (XR-2) possesses potently prostate cancer progresses inhibition activity both in vitro and in vivo. XR-2 shows a synergistic effect with enzalutamide and overcomes enzalutamide resistance.

SIRT1 inhibition-induced senescence as a strategy to prevent prostate cancer progression

Emerging evidence suggests an important role for SIRT1, a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase in cancer development, progression and therapeutic resistance; making it a viable therapeutic target. Here, we examined the impact of resveratrol-mediated pharmacological activation of SIRT1 on the progression of HGPIN lesions (using the Pten^-/- mouse model) and on prostate tumor development (using an orthotopic model of prostate cancer cells stably silenced for SIRT1). We show that precise SIRT1 modulation could benefit both cancer prevention and treatment. Positive effect of SIRT1 activation can prevent Pten deletion-driven development of HGPIN lesions in mice if resveratrol is administered early (pre-cancer stage) with little to no benefit after the establishment of HGPIN lesions or tumor cell implantation. Mechanistically, our results show that under androgen deprivation conditions, SIRT1 inhibition induces senescence as evidenced by decreased gene signature associated with negative regulators of senescence and increased senescence-associated β-galactosidase activity. Furthermore, pharmacological inhibition of SIRT1 potentiated growth inhibitory effects of clinical androgen receptor blockade agents and radiation. Taken together, our findings provide an explanation for the discrepancy regarding the role of SIRT1 in prostate tumorigenesis. Our results reveal that the bifurcated roles for SIRT1 may occur in stage and context-dependent fashion by functioning in an antitumor role in prevention of early-stage prostate lesion development while promoting tumor development and disease progression post-lesion development. Clinically, these data highlight the importance of precise SIRT1 modulation to provide benefits for cancer prevention and treatment including sensitization to conventional therapeutic approaches.

Single-cell proteomics defines the cellular heterogeneity of localized prostate cancer

Localized prostate cancer exhibits multiple genomic alterations and heterogeneity at the proteomic level. Single-cell technologies capture important cell-to-cell variability responsible for heterogeneity in biomarker expression that may be overlooked when molecular alterations are based on bulk tissue samples. This study aims to identify prognostic biomarkers and describe the heterogeneity of prostate cancer and the associated microenvironment by simultaneously quantifying 36 proteins using single-cell mass cytometry analysis of over 1.6 million cells from 58 men with localized prostate cancer. We perform this task, using a high-dimensional clustering pipeline named Franken to describe subpopulations of immune, stromal, and prostate cells, including changes occurring in tumor tissues and high-grade disease that provide insights into the coordinated progression of prostate cancer. Our results further indicate that men with localized disease already harbor rare subpopulations that typically occur in castration-resistant and metastatic disease.

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Single-cell proteomics of localized prostate cancer defines disease heterogeneity

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Malignant and benign prostate tissues differ in rare cell-type proportional shifts

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T cells and proliferating macrophages are associated with high-grade PCa

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Rare CD15⁺ epithelial cells are amplified in high-grade PCa

Understanding Drug Sensitivity and Tackling Resistance in Cancer

Decades of research into the molecular mechanisms of cancer and the development of novel therapeutics have yielded a number of remarkable successes. However, our ability to broadly assign effective, rationally targeted therapies in a personalized manner remains elusive for many patients, and drug resistance persists as a major problem. This is in part due to the well-documented heterogeneity of cancer, including the diversity of tumor cell lineages and cell states, the spectrum of somatic mutations, the complexity of microenvironments, and immune-suppressive features and immune repertoires, which collectively require numerous different therapeutic approaches. Here, we describe a framework to understand the types and biological causes of resistance, providing translational opportunities to tackle drug resistance by rational therapeutic strategies.

Influence of statins in metastatic castration-resistant prostate cancer patients treated with new antiandrogen therapies: a systematic review and meta-analysis

Objective

To evaluate whether the addition of statins to the new antiandrogens (enzalutamide or abiraterone) affects overall survival in patients with metastatic castration-resistant prostate cancer.

Methods

We searched studies in English language including the keywords statins, overall survival, and metastatic castration-resistant prostate cancer, at PubMed^® (MEDLINE^®), Embase and Cochrane databases.

Results

A total of 195 articles were initially identified, but only four met the inclusion criteria and were selected for the meta-analysis. A total of 955 patients, 632 on the new antiandrogens only group, and 323 on the new antiandrogens + statins group, were analyzed. In all four studies the combination therapy (new antiandrogens + statin) was well tolerated, regardless of which new antiandrogens were used. Neither the type of statin nor the doses and duration of use were well specified in the studies. The combination therapy in metastatic castration-resistant prostate cancer was associated with an overall survival improvement, and a 46% reduction in death (hazard ratio of 0.54; 95%CI 0.34-0.87; p<0.01) in multivariate analysis.

Conclusion

There seems to be a clinical benefit with the association of statins to the new antiandrogens in patients with metastatic castration-resistant prostate cancer, suggesting longer overall survival with no important collateral effect. However, due to fragility of the studies available in the literature, we are not yet capable of recommending this combination of drugs in the clinical practice. Further randomized prospective studies are warranted to confirm these beneficial outcomes.

Mesenchymal and stem-like prostate cancer linked to therapy-induced lineage plasticity and metastasis

Bioinformatic analysis of 94 patient-derived xenografts (PDXs), cell lines, and organoids (PCOs) identifies three intrinsic transcriptional subtypes of metastatic castration-resistant prostate cancer: androgen receptor (AR) pathway + prostate cancer (PC) (ARPC), mesenchymal and stem-like PC (MSPC), and neuroendocrine PC (NEPC). A sizable proportion of castration-resistant and metastatic stage PC (M-CRPC) cases are admixtures of ARPC and MSPC. Analysis of clinical datasets and mechanistic studies indicates that MSPC arises from ARPC as a consequence of therapy-induced lineage plasticity. AR blockade with enzalutamide induces (1) transcriptional silencing of TP53 and hence dedifferentiation to a hybrid epithelial and mesenchymal and stem-like state and (2) inhibition of BMP signaling, which promotes resistance to AR inhibition. Enzalutamide-tolerant LNCaP cells re-enter the cell cycle in response to neuregulin and generate metastasis in mice. Combined inhibition of HER2/3 and AR or mTORC1 exhibits efficacy in models of ARPC and MSPC or MSPC, respectively. These results define MSPC, trace its origin to therapy-induced lineage plasticity, and reveal its sensitivity to HER2/3 inhibition.

Advances in neuroendocrine prostate cancer research: From model construction to molecular network analyses

Prostate cancer is the most common cancer among men and has a high incidence and associated mortality worldwide. It is an androgen-driven disease in which tumor growth is triggered via ligand-mediated signaling through the androgen receptor (AR). Recent evidence suggests that the widespread use of effective AR pathway inhibitors may increase the occurrence of neuroendocrine prostate cancer (NEPC), an aggressive and treatment-resistant AR-negative variant; however, mechanisms controlling NEPC development remain to be elucidated. Various preclinical models have recently been developed to investigate the mechanisms driving the NEPC differentiation. In the present study, we summarized strategies for the development of NEPC models and proposed a novel method for model evaluation, which will help in the timely and accurate identification of NEPC by virtue of its ability to recapitulate the heterogeneity of prostate cancer. Moreover, we discuss the origin and the mechanism of NEPC. The understanding of the regulatory network mediating neuroendocrine differentiation presented in this review could provide valuable insights into the identification of novel drug targets for NEPC as well as into the causes of antiandrogenic drug resistance.