Androgen receptors in hormone-dependent and castration-resistant prostate cancer

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

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

USP16 regulates castration-resistant prostate cancer cell proliferation by deubiquitinating and stablizing c-Myc

Background

c-Myc, a well-established oncogene, plays an important role in the initiation and progression of various cancers, including prostate cancer. However, its mechanism in cancer cell remains largely unknown and whether there exist a deubiquitinase targeting c-Myc also remains elusive.

Methods

Bioinformatic analysis and shRNA screening methods were used to identify potential deubiquitinases that correlate with c-Myc gene signature. Cell proliferation and viability were measured by Cell-Counting-Kit 8 and colony formation assays. A mouse xenograft model of PC3 cells was established to confirm the function of USP16 in vivo. The interaction between USP16 and c-Myc protein was assessed by co-immunoprecipitation and protein co-localization assays. Immunohistochemistry staining was performed to detect the expression of USP16, Ki67, and c-Myc in xenograft tissues and clinical tumour tissues. Furthermore, the correlation between USP16 and c-Myc was confirmed by RNA sequencing.

Results

Functional analyses identified USP16, known as a deubiquitinase, was strongly correlated with the c-Myc gene signature. Depletion of USP16 was shown to significantly suppress the growth of PCa cells both in vitro and in vivo. Co-immunoprecipitation and ubiquitination assays confirmed that USP16 served as a novel deubiquitinase of c-Myc and overexpression of c-Myc significantly rescued the effects of USP16 disruption. Immunohistochemistry staining and RNA-seq tactics were further used to confirm the positive correlation between USP16 and c-Myc expression. Expression of USP16 in human PCa tissues was higher than that seen in normal prostate tissues and its high expression was found associated with poor prognosis.

Conclusions

USP16 serves as a novel deubiquitinase of c-Myc. Downregulation of USP16 markedly suppressed PCa cell growth both in vitro and in vivo. USP16 regulates PCa cell proliferation by deubiquitinating and stabilizing c-Myc, making it a potential therapeutic candidate for the treatment of PCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01843-8.

Treating Prostate Cancer by Antibody-Drug Conjugates

Prostate cancer is the most frequent malignancy in the worldwide male population; it is also one of the most common among all the leading cancer-related death causes. In the last two decades, the therapeutic scenario of metastatic castration-resistant prostate cancer has been enriched by the use of chemotherapy and androgen receptor signaling inhibitors (ARSI) and, more recently, by immunotherapy and poly(ADP–ribose) polymerase (PARP) inhibitors. At the same time, several trials have shown the survival benefits related to the administration of novel ARSIs among patients with non-castration-resistant metastatic disease along with nonmetastatic castration-resistant cancer too. Consequently, the therapeutic course of this malignancy has been radically expanded, ensuring survival benefits never seen before. Among the more recently emerging agents, the so-called “antibody–drug conjugates” (ADCs) are noteworthy because of their clinical practice changing outcomes obtained in the management of other malignancies (including breast cancer). The ADCs are novel compounds consisting of cytotoxic agents (also known as the payload) linked to specific antibodies able to recognize antigens expressed over cancer cells’ surfaces. As for prostate cancer, researchers are focusing on STEAP1, TROP2, PSMA, CD46 and B7-H3 as optimal antigens which may be targeted by ADCs. In this paper, we review the pivotal trials that have currently changed the therapeutic approach to prostate cancer, both in the nonmetastatic castration-resistant and metastatic settings. Therefore, we focus on recently published and ongoing trials designed to investigate the clinical activity of ADCs against prostate malignancy, characterizing these agents. Lastly, we briefly discuss some ADCs-related issues with corresponding strategies to overwhelm them, along with future perspectives for these promising novel compounds.

The Effects of Resveratrol on Prostate Cancer through Targeting the Tumor Microenvironment

Prostate cancer is one of the most common cancers diagnosed in men in the United States and the second leading cause of cancer-related deaths worldwide. Since over 60% of prostate cancer cases occur in men over 65 years of age, and this population will increase steadily in the coming years, prostate cancer will be a major cancer-related burden in the foreseeable future. Accumulating data from more recent research suggest that the tumor microenvironment (TME) plays a previously unrecognized role in every stage of cancer development, including initiation, proliferation, and metastasis. Prostate cancer is not only diagnosed in the late stages of life, but also progresses relatively slowly. This makes prostate cancer an ideal model system for exploring the potential of natural products as cancer prevention and/or treatment reagents because they usually act relatively slowly compared to most synthetic drugs. Resveratrol (RSV) is a naturally occurring stilbenoid and possesses strong anti-cancer properties with few adverse effects. Accumulating data from both in vitro and in vivo experiments indicate that RSV can interfere with prostate cancer initiation and progression by targeting the TME. Therefore, this review is aimed to summarize the recent advancement in RSV-inhibited prostate cancer initiation, proliferation, and metastasis as well as the underlying molecular mechanisms, with particular emphasis on the effect of RSV on TME. This will not only better our understanding of prostate cancer TMEs, but also pave the way for the development of RSV as a potential reagent for prostate cancer prevention and/or therapy.

LMO2 upregulation due to AR deactivation in cancer-associated fibroblasts induces non-cell-autonomous growth of prostate cancer after androgen deprivation

The androgen receptor (AR) is expressed in prostate fibroblasts in addition to normal prostate epithelial cells and prostate cancer (PCa) cells. Moreover, AR activation in fibroblasts dramatically influences prostate cancer (PCa) cell behavior. Androgen deprivation leads to deregulation of AR downstream target genes in both fibroblasts and PCa cells. Here, we identified LIM domain only 2 (LMO2) as an AR target gene in prostate fibroblasts using ChIP-seq and revealed that LMO2 can be repressed directly by AR through binding to androgen response elements (AREs), which results in LMO2 overexpression after AR deactivation due to normal prostate fibroblasts to cancer-associated fibroblasts (CAFs) transformation or androgen deprivation therapy. Next, we investigated the mechanisms of LMO2 overexpression in fibroblasts and the role of this event in non-cell-autonomous promotion of PCa cells growth in the androgen-independent manner through paracrine release of IL-11 and FGF-9. Collectively, our data suggest that AR deactivation deregulates LMO2 expression in prostate fibroblasts, which induces castration resistance in PCa cells non-cell-autonomously through IL-11 and FGF-9.

Androgen receptor and its splice variant, AR-V7, differentially induce mRNA splicing in prostate cancer cells

Prostate cancer (PCa) is dependent on the androgen receptor (AR). Advanced PCa is treated with an androgen deprivation therapy-based regimen; tumors develop resistance, although they typically remain AR-dependent. Expression of constitutively active AR variants lacking the ligand-binding domain including the variant AR-V7 contributes to this resistance. AR and AR-V7, as transcription factors, regulate many of the same genes, but also have unique activities. In this study, the capacity of the two AR isoforms to regulate splicing was examined. RNA-seq data from models that endogenously express AR and express AR-V7 in response to doxycycline were used. Both AR isoforms induced multiple changes in splicing and many changes were isoform-specific. Analyses of two endogenous genes, PGAP2 and TPD52, were performed to examine differential splicing. A novel exon that appears to be a novel transcription start site was preferentially induced by AR-V7 in PGAP2 although it is induced to a lesser extent by AR. The previously described AR induced promoter 2 usage that results in a novel protein derived from TPD52 (PrLZ) was not induced by AR-V7. AR, but not AR-V7, bound to a site proximal to promoter 2, and induction was found to depend on FOXA1.

Research Progress for the Clinical Application of Circulating Tumor Cells in Prostate Cancer Diagnosis and Treatment

Prostate cancer is a life-threatening and highly heterogeneous malignancy. In the past decade, circulating tumor cells (CTCs) have been suggested to play a critical role in the occurrence and progression of prostate cancer. In particular, as the “seed” of the cancer metastasis cascade, CTCs determine numerous biological behaviors, such as tumor invasion into adjacent tissues and migration to distant organs. Many studies have shown that CTCs are necessary in the processes of tumor progression, including tumorigenesis, invasion, metastasis, and colonization. Furthermore, CTCs express various biomarkers relevant to prostate cancer and thus can be applied clinically in noninvasive tests. Moreover, CTCs can serve as potential prognostic targets in prostate cancer due to their roles in regulating many processes associated with cancer metastasis. In this review, we discuss the isolation and detection of CTCs as predictive markers of prostate cancer, and we discuss their clinical application in the diagnosis and prognosis of prostate cancer and in monitoring the response to treatment and the prediction of metastasis.

Bruceantin targets HSP90 to overcome resistance to hormone therapy in castration-resistant prostate cancer

Rationale: Aberrant androgen receptor (AR) signaling via full-length AR (AR-FL) and constitutively active AR variant 7 (AR-V7) plays a key role in the development of castration-resistant prostate cancer (CRPC) and resistance to hormone therapies. Simultaneous targeting of AR-FL and AR-V7 may be a promising strategy to overcome resistance to hormone therapy. This study aimed to identify novel drug candidates co-targeting AR-FL and AR-V7 activities and elucidate their molecular mechanism of anti-CRPC activities.

Methods: Using a CRPC cell-based reporter assay system, we screened a small library of antimalarial agents to explore the possibility of repositioning them for CRPC treatment and identified bruceantin (BCT) as a potent anti-CRPC drug candidate. A series of cell-based, molecular, biochemical, and in vivo approaches were performed to evaluate the therapeutic potential and molecular mechanism of BCT in CRPC. These approaches include reporter gene assays, cell proliferation, RNA-seq, qRT-PCR, mouse xenografts, co-immunoprecipitation, GST pull-down, immobilized BCT pull-down, molecular modeling, and bioinformatic analyses.

Results: We identified BCT as a highly potent inhibitor co-targeting AR-FL and AR-V7 activity. BCT inhibits the transcriptional activity of AR-FL/AR-V7 and downregulates their target genes in CRPC cells. In addition, BCT efficiently suppresses tumor growth and metastasis of CRPC cells. Mechanistically, BCT disrupts the interaction of HSP90 with AR-FL/AR-V7 by directly binding to HSP90 and inhibits HSP90 chaperone function, leading to degradation of AR-FL/AR-V7 through the ubiquitin-proteasome system. Clinically, HSP90 expression is upregulated and correlated with AR/AR-V7 levels in CRPC.

Conclusion: Our findings suggest that BCT could serve as a promising therapeutic candidate against CRPC and highlight the potential benefit of targeting AR-FL/AR-V7-HSP90 axis to overcome resistance caused by aberrant AR-FL/AR-V7 signaling.

The androgen receptor expression and its activity have different relationships with prognosis in hepatocellular carcinoma

The role of the Androgen Receptor (AR) expression and its activity in the prognosis of hepatocellular carcinoma (HCC) remains inconclusive. The aim of this study is to analyze the role of the AR expression and its activity as prognostic biomarkers in HCC. Three-hundred and thirty-seven patients from The Cancer Genome Atlas (TCGA) (107 females; 59.42 years [SD = 13.0]) were included. To infer AR activity, the expression-profile of previously validated androgen responsive genes (ARGs) was included. AR activity was shown by the AR-Score-21 (21 ARGs) and AR-Score-13 (13 ARGs) that were computed based on the expression of the selected ARGs. Those ARGs whose expression was significantly different between histological grades were used for computing two new AR-Scores. HCC patients with higher AR expression showed a higher median overall survival (OS). AR-Score 21 and AR-Score-13 did not show any association with prognosis. Six of the 21 ARGs of the AR-Score-21 and 7 of the 13 ARGs of the AR-Score-13 showed a significant different expression profile among histological grades. Based on these differences, another two AR-Scores were computed (AR-Score-6 and AR-Score-7). They showed the relative increase of upregulated to downregulated ARGs in high-grade HCC. Higher AR activity inferred by these AR-Scores was associated with worse outcomes. The expression of AR is associated with a better prognosis in HCC. However, the activity of the AR seems to be qualitatively different among histological grades. The AR activity inferred by the shifted ARGs is associated with a worse prognosis in HCC patients.

Efficacy and Mechanism of Action of Marine Alkaloid 3,10-Dibromofascaplysin in Drug-Resistant Prostate Cancer Cells

Efficacy and mechanism of action of marine alkaloid 3,10-dibromofascaplysin (DBF) were investigated in human prostate cancer (PCa) cells harboring different levels of drug resistance. Anticancer activity was observed across all cell lines examined without signs of cross-resistance to androgen receptor targeting agents (ARTA) or taxane based chemotherapy. Kinome analysis followed by functional investigation identified JNK1/2 to be one of the molecular targets of DBF in 22Rv1 cells. In contrast, no activation of p38 and ERK1/2 MAPKs was observed. Inhibition of the drug-induced JNK1/2 activation or of the basal p38 activity resulted in increased cytotoxicity of DBF, whereas an active ERK1/2 was identified to be important for anticancer activity of the alkaloid. Synergistic effects of DBF were observed in combination with PARP-inhibitor olaparib most likely due to the induction of ROS production by the marine alkaloid. In addition, DBF intensified effects of platinum-based drugs cisplatin and carboplatin, and taxane derivatives docetaxel and cabazitaxel. Finally, DBF inhibited AR-signaling and resensitized AR-V7-positive 22Rv1 prostate cancer cells to enzalutamide, presumably due to AR-V7 down-regulation. These findings propose DBF to be a promising novel drug candidate for the treatment of human PCa regardless of resistance to standard therapy.

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

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

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

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

Structure-based virtual screening of perfluoroalkyl and polyfluoroalkyl substances (PFASs) as endocrine disruptors of androgen receptor activity using molecular docking and machine learning

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) pose a substantial threat as endocrine disruptors, and thus early identification of those that may interact with steroid hormone receptors, such as the androgen receptor (AR), is critical. In this study we screened 5,206 PFASs from the CompTox database against the different binding sites on the AR using both molecular docking and machine learning techniques. We developed support vector machine models trained on Tox21 data to classify the active and inactive PFASs for AR using different chemical fingerprints as features. The maximum accuracy was 95.01% and Matthew's correlation coefficient (MCC) was 0.76 respectively, based on MACCS fingerprints (MACCSFP). The combination of docking-based screening and machine learning models identified 29 PFASs that have strong potential for activity against the AR and should be considered priority chemicals for biological toxicity testing.

Involvement of the MEN1 Gene in Hormone-Related Cancers: Clues from Molecular Studies, Mouse Models, and Patient Investigations

MEN1 mutation predisposes patients to multiple endocrine neoplasia type 1 (MEN1), a genetic syndrome associated with the predominant co-occurrence of endocrine tumors. Intriguingly, recent evidence has suggested that MEN1 could also be involved in the development of breast and prostate cancers, two major hormone-related cancers. The first clues as to its possible role arose from the identification of the physical and functional interactions between the menin protein, encoded by MEN1, and estrogen receptor α and androgen receptor. In parallel, our team observed that aged heterozygous Men1 mutant mice developed cancerous lesions in mammary glands of female and in the prostate of male mutant mice at low frequencies, in addition to endocrine tumors. Finally, observations made both in MEN1 patients and in sporadic breast and prostate cancers further confirmed the role played by menin in these two cancers. In this review, we present the currently available data concerning the complex and multifaceted involvement of MEN1 in these two types of hormone-dependent cancers.

Protein phosphatase 1 in tumorigenesis: is it worth a closer look?

Cancer cells take advantage of signaling cascades to meet their requirements for sustained growth and survival. Cell signaling is tightly controlled by reversible protein phosphorylation mechanisms, which require the counterbalanced action of protein kinases and protein phosphatases. Imbalances on this system are associated with cancer development and progression. Protein phosphatase 1 (PP1) is one of the most relevant protein phosphatases in eukaryotic cells. Despite the widely recognized involvement of PP1 in key biological processes, both in health and disease, its relevance in cancer has been largely neglected. Here, we provide compelling evidence that support major roles for PP1 in tumorigenesis.

Novel small-molecule LG1836 inhibits the in vivo growth of castration-resistant prostate cancer

BACKGROUND

Androgen deprivation therapy (ADT) is the mainstay of treatment for castration-resistant prostate cancer (CRPC). Unfortunately, although ADT initially prolongs survival, most patients relapse and develop resistance. Clinical failure of these treatments in CRPC highlights the urgent need to develop novel strategies to more effectively block androgen receptor (AR) signaling and target other oncogenic factors responsible for ADT resistance.

METHODS

We developed a small-molecule compound LG1836 and investigated the in vitro and in vivo activity of LG1836 against CRPC in cellular and animal models.

RESULTS

LG1836 exhibits potent in vitro cytotoxicity in CRPC cells. Mechanistic studies demonstrated that LG1836 inhibits the expression of AR and AR variant 7, partially mediated via proteasome-dependent protein degradation. LG1836 also suppresses survivin expression and effectively induces apoptosis in CRPC cells. Significantly, as a single agent, LG1836 is therapeutically efficacious in suppressing the in vivo growth of CRPC in the subcutaneous and intraosseous models and extends the survival of tumor-bearing mice.

CONCLUSIONS

These preclinical studies indicate that LG1836 is a promising lead compound for the treatment of CRPC.

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

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

SETD1A Promotes Proliferation of Castration-Resistant Prostate Cancer Cells via FOXM1 Transcription

Androgen deprivation therapy eventually leads to the development of castration-resistant prostate cancer (CRPC). Here, we demonstrate for the first time that the histone H3K4 methyltransferase SETD1A is a major regulator for the proliferation of metastatic CRPC (mCRPC). The expression of SETD1A was significantly correlated with the survival rate of patients with prostate cancer. SETD1A, which is expressed at a higher level in mCRPC than in primary prostate cancer cells, promotes the expression of FOXM1, a gene encoding a cell proliferation-specific transcription factor. SETD1A is recruited to the promoter region of FOXM1 (forkhead box M1) upon binding to E2F1, a protein that regulates the transcription of FOXM1 and contributes to the trimethylation of H3K4 in the FOXM1 promoter region. In addition, SETD1A is essential for the expression of stem cell factor (e.g., OCT4, octamer-binding transcription factor 4) and stem cell formation in mCRPC, suggesting the importance of SETD1A expression in mCRPC tumor formation. Notably, poor prognosis is associated with high expression of the SETD1A-FOXM1 pair in clinical data sets. Therefore, our study suggests that SETD1A plays an important role in the proliferation of mCRPC by regulating FOXM1 transcription.

Imaging assisted evaluation of antitumor efficacy of a new histone deacetylase inhibitor in the castration-resistant prostate cancer

PURPOSE

Castration-resistant prostate cancer (CRPC) is the most common cause of death in men. The effectiveness of HDAC inhibitors has been demonstrated by preclinical models, but not in clinical studies, probably due to the ineffectively accumulation of HDACI in prostate cancer cells. The purpose of this work was to evaluate effects of a novel HDACI (CN133) on CRPC xenograft model and 22Rv1 cells, and develops methods, PET/CT imaging, to detect the therapeutic effects of CN133 on this cancer.

METHODS

We designed and performed study to compare the effects of CN133 with SAHA on the 22Rv1 xenograft model and 22Rv1 cells. Using PET/CT imaging with [¹¹C] Martinostat and [¹⁸F] FDG, we imaged mice bearing 22Rv1 xenografts before and after 21-day treatment with placebo and CN133 (1 mg/kg), and uptake on pre-treatment and post-treatment imaging was measured. The anti-tumor mechanisms of CN133 were investigated by qPCR, western blot, and ChIP-qPCR.

RESULTS

Our data showed that the CN133 treatment led to a 50% reduction of tumor volume compared to the placebo that was more efficacious than SAHA treatment in this preclinical model. [¹¹C] Martinostat PET imaging could identify early lesions of prostate cancer and can also be used to monitor the therapeutic effect of CN133 in CRPC. Using pharmacological approaches, we demonstrated that effects of CN133 showed almost 100-fold efficacy than SAHA treatment in the experiment of cell proliferation, invasion, and migration. The anti-tumor mechanisms of CN133 were due to the inhibition of AR signaling pathway activity by decreased HDAC 2 and 3 protein expressions.

CONCLUSION

Taken together, these studies provide not only a novel epigenetic approach for prostate cancer therapy but also offering a potential tool, [¹¹C] Martinostat PET/CT imaging, to detect the early phase of prostate cancer and monitor therapeutic effect of CN133. These results will likely lead to human trials in the future.

Urupocidin C: a new marine guanidine alkaloid which selectively kills prostate cancer cells via mitochondria targeting

New bicyclic guanidine alkaloid, urupocidin C (Ur-C) along with the previously known urupocidin A (Ur-A) were isolated from the rare deep-sea marine sponge Monanchora pulchra, harvested in Northwestern Pacific waters. The unique structure of Ur-C was elucidated using 1D and 2D NMR spectroscopy as well as mass spectra. We discovered a promising selectivity of both alkaloids for human prostate cancer (PCa) cells, including highly drug-resistant lines, compared to non-malignant cells. In cancer cells, marine derived compounds were able to induce G1- and S-cell cycle arrest as well as caspase-mediated cell death. For the first time we have identified mitochondrial targeting as a central mechanism of anticancer action for these and similar molecules. Thus, treatment with the isolated alkaloids resulted in mitochondrial membrane permeabilization consequently leading to the release of cytotoxic mitochondrial proteins to cellular cytoplasm, ROS upregulation, consequent activation of caspase-9 and -3, followed by PARP cleavage, DNA fragmentation, and apoptosis. Moreover, synergistic effects were observed when Ur-A and Ur-C were combined with clinically approved PARP inhibitor olaparib. Finally, these alkaloids exhibited additive effects in combination with docetaxel and androgen receptor inhibitor enzalutamide, both applied in PCa therapy. In conclusion, urupocidin-like compounds are promising lead molecules for the development of new drugs for the treatment of advanced PCa.

Microarray expression profiling of long noncoding RNAs in the progesterone-treated lung cancer cells

BACKGROUND

The increasing incidence and unique biological features of lung cancer in women has prompted renewed interest in the role of sex hormones in this disease. We previously showed that progesterone (P4) inhibited lung cancer tumorigenesis and progression. Here, we investigated the effects of P4 on expression of long noncoding RNAs (lncRNAs) and target mRNAs in lung cancer cells.

METHODS

We performed high-throughput microarray and bioinformatics analysis to identify differentially expressed lncRNAs and mRNAs in the untreated and the P4-treated A549 human lung cancer cells.

RESULTS

In total, 692 lncRNAs and 268 mRNAs were significantly differentially expressed in the P4-treated A549 cells compared to the untreated A549 cells (> 2-fold change, p < 0.05). Of the lncRNAs, 82 and 610 were up-regulated and down-regulated, respectively. Gene ontology, pathway and network analyses showed that many of the mRNAs were involved in the regulation of classical pathways, including Notch signaling. Differential expression of a lncRNA signature composed of NONHSAT000264, FR075921, FR324124, linc-TRIM58, RP1-93H18.7, RP11-120 K9.2, RP11-134F2.2 and NONHSAG024980 was validated by quantitatuve reverse transcriptase-polymerase chain reaction analysis.

CONCLUSIONS

This is the first report of differentially expressed lncRNAs in the P4-treated lung cancer cells. The results suggest that lncRNAs could serve as potential therapeutic targets for P4-sensitive lung cancer.

Over a century of cancer research: Inconvenient truths and promising leads

Despite over a century of intensive efforts, the great gains promised by the War on Cancer nearly 50 years ago have not materialized. Since 1999, we have analyzed the lack of progress in explaining and "curing" cancer by examining the merits of the premises that determine how cancer is understood and treated. Our ongoing critical analyses have aimed at clarifying the sources of misunderstandings at the root of the cancer puzzle while providing a plausible and comprehensive biomedical perspective as well as a new theory of carcinogenesis that is compatible with evolutionary theory. In this essay, we explain how this new theory, the tissue organization field theory (TOFT), can help chart a path to progress for cancer researchers by explaining features of cancer that remain unexplainable from the perspective of the still hegemonic somatic mutation theory (SMT) and its variants. Of equal significance, the premises underlying the TOFT offer new perspectives on basic biological phenomena.

The Prospect of Identifying Resistance Mechanisms for Castrate-Resistant Prostate Cancer Using Circulating Tumor Cells: Is Epithelial-to-Mesenchymal Transition a Key Player?

Prostate cancer (PCa) is initially driven by excessive androgen receptor (AR) signaling with androgen deprivation therapy (ADT) being a major therapeutic approach to its treatment. However, the development of drug resistance is a significant limitation on the effectiveness of both first-line and more recently developed second-line ADTs. There is a need then to study AR signaling within the context of other oncogenic signaling pathways that likely mediate this resistance. This review focuses on interactions between AR signaling, the well-known phosphatidylinositol-3-kinase/AKT pathway, and an emerging mediator of these pathways, the Hippo/YAP1 axis in metastatic castrate-resistant PCa, and their involvement in the regulation of epithelial-mesenchymal transition (EMT), a feature of disease progression and ADT resistance. Analysis of these pathways in circulating tumor cells (CTCs) may provide an opportunity to evaluate their utility as biomarkers and address their importance in the development of resistance to current ADT with potential to guide future therapies.

Lajis N, Abas F, Othman I, Naidu R. Mechanism of Anti-Cancer Activity of Curcumin on Androgen-Dependent and Androgen-Independent Prostate Cancer

Prostate cancer (PCa) is a heterogeneous disease and ranked as the second leading cause of cancer-related deaths in males worldwide. The global burden of PCa keeps rising regardless of the emerging cutting-edge technologies for treatment and drug designation. There are a number of treatment options which are effectively treating localised and androgen-dependent PCa (ADPC) through hormonal and surgery treatments. However, over time, these cancerous cells progress to androgen-independent PCa (AIPC) which continuously grow despite hormone depletion. At this particular stage, androgen depletion therapy (ADT) is no longer effective as these cancerous cells are rendered hormone-insensitive and capable of growing in the absence of androgen. AIPC is a lethal type of disease which leads to poor prognosis and is a major contributor to PCa death rates. A natural product-derived compound, curcumin has been identified as a pleiotropic compound which capable of influencing and modulating a diverse range of molecular targets and signalling pathways in order to exhibit its medicinal properties. Due to such multi-targeted behaviour, its benefits are paramount in combating a wide range of diseases including inflammation and cancer disease. Curcumin exhibits anti-cancer properties by suppressing cancer cells growth and survival, inflammation, invasion, cell proliferation as well as possesses the ability to induce apoptosis in malignant cells. In this review, we investigate the mechanism of curcumin by modulating multiple signalling pathways such as androgen receptor (AR) signalling, activating protein-1 (AP-1), phosphatidylinositol 3-kinases/the serine/threonine kinase (PI3K/Akt/mTOR), wingless (Wnt)/ß-catenin signalling, and molecular targets including nuclear factor kappa-B (NF-κB), B-cell lymphoma 2 (Bcl-2) and cyclin D1 which are implicated in the development and progression of both types of PCa, ADPC and AIPC. In addition, the role of microRNAs and clinical trials on the anti-cancer effects of curcumin in PCa patients were also reviewed.

The role of adrenal derived androgens in castration resistant prostate cancer

Castration resistant prostate cancer (CRPC) remains androgen dependant despite castrate levels of circulating testosterone following androgen deprivation therapy, the first line of treatment for advanced metstatic prostate cancer. CRPC is characterized by alterations in the expression levels of steroidgenic enzymes that enable the tumour to derive potent androgens from circulating adrenal androgen precursors. Intratumoral androgen biosynthesis leads to the localized production of both canonical androgens such as 5α-dihydrotestosterone (DHT) as well as less well characterized 11-oxygenated androgens, which until recently have been overlooked in the context of CRPC. In this review we discuss the contribution of both canonical and 11-oxygenated androgen precursors to the intratumoral androgen pool in CRPC. We present evidence that CRPC remains androgen dependent and discuss the alterations in steroidogenic enzyme expression and how these affect the various pathways to intratumoral androgen biosynthesis. Finally we summarize the current treatment strategies for targeting adrenal derived androgen biosynthesis.

Stevia eupatoria and Stevia pilosa Extracts Inhibit the Proliferation and Migration of Prostate Cancer Cells

Background and Objectives: Prostate cancer is the second most harmful disease in men worldwide and the number of cases is increasing. Therefore, new natural agents with anticancer potential should be examined and the response of existing therapeutic drugs must be enhanced. Stevia pilosa and Stevia eupatoria are two species that have been widely used in traditional medicine, but their effectiveness on cancer cells and their interaction with antineoplastic drugs have not been studied. The aim of this study was to evaluate the anticancer activity of Stevia pilosa methanolic root extract (SPME) and Stevia eupatoria methanolic root extract (SEME) and their effect, combined with enzalutamide, on prostate cancer cells. Materials and Methods: The study was conducted on a human fibroblast cell line, and on androgen-dependent (LNCaP) and androgen-independent (PC-3) prostate cancer cell lines. The cell viability was evaluated using a Trypan Blue exclusion test for 48 h, and the migration by a wound-healing assay for 24, 48, and 72 h. Results: The results indicate that SPME and SEME were not cytotoxic at concentrations less than 1000 μg/mL in the human fibroblasts. SPME and SEME significantly reduced the viability and migration of prostate cancer cells in all concentrations evaluated. The antiproliferative effect of the Stevia extracts was higher in cancer cells than in normal cells. The enzalutamide decreased the cell viability in all concentrations tested (10–50 µM). The combination of the Stevia extracts and enzalutamide produced a greater effect on the inhibition of the proliferation and migration of cancer cells than the Stevia extracts alone, but not of the enzalutamide alone. Conclusion: The results indicate that SPME and SEME have an inhibitory effect on the viability and migration of prostate cancer cells and do not interfere with the enzalutamide anticancer effect. The data suggest that Stevia extracts may be a potential source of molecules for cancer treatment.

RNA-binding protein Musashi2 stabilizing androgen receptor drives prostate cancer progression

The androgen receptor (AR) pathway is critical for prostate cancer carcinogenesis and development; however, after 18‐24 months of AR blocking therapy, patients invariably progress to castration‐resistant prostate cancer (CRPC), which remains an urgent problem to be solved. Therefore, finding key molecules that interact with AR as novel strategies to treat prostate cancer and even CRPC is desperately needed. In the current study, we focused on the regulation of RNA‐binding proteins (RBPs) associated with AR and determined that the mRNA and protein levels of AR were highly correlated with Musashi2 (MSI2) levels. MSI2 was upregulated in prostate cancer specimens and significantly correlated with advanced tumor grades. Downregulation of MSI2 in both androgen sensitive and insensitive prostate cancer cells inhibited tumor formation in vivo and decreased cell growth in vitro, which could be reversed by AR overexpression. Mechanistically, MSI2 directly bound to the 3′‐untranslated region (UTR) of AR mRNA to increase its stability and, thus, enhanced its transcriptional activity. Our findings illustrate a previously unknown regulatory mechanism in prostate cancer cell proliferation regulated by the MSI2‐AR axis and provide novel evidence towards a strategy against prostate cancer.

New insights of CYP1A in endogenous metabolism: a focus on single nucleotide polymorphisms and diseases

Cytochrome P450 1A (CYP1A), one of the major CYP subfamily in humans, not only metabolizes xenobiotics including clinical drugs and pollutants in the environment, but also mediates the biotransformation of important endogenous substances. In particular, some single nucleotide polymorphisms (SNPs) for CYP1A genes may affect the metabolic ability of endogenous substances, leading to some physiological or pathological changes in humans. This review first summarizes the metabolism of endogenous substances by CYP1A, and then introduces the research progress of CYP1A SNPs, especially the research related to human diseases. Finally, the relationship between SNPs and diseases is discussed. In addition, potential animal models for CYP1A gene editing are summarized. In conclusion, CYP1A plays an important role in maintaining the health in the body.

Structural Dynamics of Agonist and Antagonist Binding to the Androgen Receptor

Androgen receptor (AR) is a steroid hormone nuclear receptor which upon binding its endogenous androgenic ligands (agonists), testosterone and dihydrotestosterone (DHT), alters gene transcription, producing a diverse range of biological effects. Antiandrogens, such as the pharmaceuticals bicalutamide and hydroxyflutamide, act as agonists in the absence of androgens and as antagonists in their presence or in high concentration. The atomic level mechanism of action by agonists and antagonists of AR is less well characterized. Therefore, in this study, multiple 1 μs molecular dynamics (MD), docking simulations, and perturbation-response analyses were performed to more fully explore the nature of interaction between agonist or antagonist and AR and the conformational changes induced in the AR upon interaction with different ligands. We characterized the mechanism of the ligand entry/exit and found that helix-12 and nearby structural motifs respond dynamically in that process. Modeling showed that the agonist and antagonist/agonist form a hydrogen bond with Thr877/Asn705 and that this interaction is absent for antagonists. Agonist binding to AR increases the mobility of residues at allosteric sites and coactivator binding sites, while antagonist binding decreases mobility at these important sites. A new site was also identified as a potential surface for allosteric binding. These results shed light on the effect of agonists and antagonists on the structure and dynamics of AR.

Treatment of non-metastatic castration-resistant prostate cancer: focus on apalutamide

Androgen deprivation therapy (ADT) is an important component of systemic therapy in advanced prostate cancer; however, resistance to ADT is inevitable. Three large studies demonstrated the efficacy of novel androgen receptor (AR)-targeted therapies in prolonging metastasis-free survival and time to symptomatic progression in patients with non-metastatic castration-resistant prostate cancer (nmCRPC). Enzalutamide and apalutamide have been approved by the FDA in the nmCRPC setting. This review discusses the role of AR and ADT in prostate cancer, mechanism of ADT resistance and the nmCRPC stage. In addition, pharmacologic characteristics and clinical development of apalutamide, role of apalutamide in nmCRPC, and ongoing clinical studies of apalutamide in different stages of prostate cancer are discussed.

Single-Nucleotide Polymorphisms Sequencing Identifies Candidate Functional Variants at Prostate Cancer Risk Loci

Genome-wide association studies have identified over 150 risk loci that increase prostate cancer risk. However, few causal variants and their regulatory mechanisms have been characterized. In this study, we utilized our previously developed single-nucleotide polymorphisms sequencing (SNPs-seq) technology to test allele-dependent protein binding at 903 SNP sites covering 28 genomic regions. All selected SNPs have shown significant cis-association with at least one nearby gene. After preparing nuclear extract using LNCaP cell line, we first mixed the extract with dsDNA oligo pool for protein–DNA binding incubation. We then performed sequencing analysis on protein-bound oligos. SNPs-seq analysis showed protein-binding differences (>1.5-fold) between reference and variant alleles in 380 (42%) of 903 SNPs with androgen treatment and 403 (45%) of 903 SNPs without treatment. From these significant SNPs, we performed a database search and further narrowed down to 74 promising SNPs. To validate this initial finding, we performed electrophoretic mobility shift assay in two SNPs (rs12246440 and rs7077275) at CTBP2 locus and one SNP (rs113082846) at NCOA4 locus. This analysis showed that all three SNPs demonstrated allele-dependent protein-binding differences that were consistent with the SNPs-seq. Finally, clinical association analysis of the two candidate genes showed that CTBP2 was upregulated, while NCOA4 was downregulated in prostate cancer (p < 0.02). Lower expression of CTBP2 was associated with poor recurrence-free survival in prostate cancer. Utilizing our experimental data along with bioinformatic tools provides a strategy for identifying candidate functional elements at prostate cancer susceptibility loci to help guide subsequent laboratory studies.

Estrogen receptor α-NOTCH1 axis enhances basal stem-like cells and epithelial-mesenchymal transition phenotypes in prostate cancer

Background

Prostate cancer (PCa) is the second leading cause of mortality and a leading cause of malignant tumors in males. Prostate cancer stem cells (PCSCs) are likely the responsible cell types for cancer initiation, clinical treatment failure, tumor relapse, and metastasis. Estrogen receptor alpha (ERα) is mainly expressed in the basal layer cells of the normal prostate gland and has key roles in coordinating stem cells to control prostate organ development. Here, we investigated the roles of the estrogen-ERα signaling pathway in regulating PCSCs.

Methods

Correlation of CD49f and ERα/NOTCH1 was analyzed in human clinical datasets and tissue samples. Flow cytometry was used to sort CD49f^Hi and CD49f^Low cells. EZH2 recruitment by ERα and facilitation of ERα binding to the NOTCH1 promoter was validated by Co-IP and ChIP. Primary tumor growth, tumor metastasis and sensitivity to 17β-estradiol (E2) inhibitor (tamoxifen) were evaluated in castrated mice.

Results

ERα expression was significantly higher in CD49f^Hi prostate cancer basal stem-like cells (PCBSLCs), which showed basal and EMT features with susceptibility to E2 treatment. ERα-induced estrogen effects were suggested to drive the NOTCH1 signaling pathway activity via binding to the NOTCH1 promoter. Moreover, EZH2 was recruited by ERα and acted as a cofactor to assist ERα-induced estrogen effects in regulating NOTCH1 in PCa. In vivo, E2 promoted tumor formation and metastasis, which were inhibited by tamoxifen.

Conclusions

Our results implicated CD49f+/ERα + prostate cancer cells associated with basal stem-like and EMT features, named EMT-PCBSLCs, in heightened potential for promoting metastasis. NOTCH1 was regulated by E2 in CD49f^Hi EMT-PCBSLCs. These results contribute to insights into the metastatic mechanisms of EMT-PCBSLCs in PCa.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0367-x) contains supplementary material, which is available to authorized users.

Anti-Cancer Activity of Novel Dihydrotestosterone-Derived Ring A-Condensed Pyrazoles on Androgen Non-Responsive Prostate Cancer Cell Lines

Regioselective synthesis of novel ring A-fused arylpyrazoles of dihydrotestosterone (DHT) was carried out in two steps under facile reaction conditions. Aldol condensation of DHT with acetaldehyde afforded a 2-ethylidene derivative regio- and stereo-selectively, which was reacted with different arylhydrazines in the presence of iodine via microwave-assisted oxidative cyclization reactions. The 17-keto analogs of steroidal pyrazoles were also synthesized by simple oxidation in order to enlarge the compound library available for pharmacological studies and to obtain structure–activity relationship. The antiproliferative activities of the structurally related heteroaromatic compounds were tested in vitro on human cervical and breast adenocarcinoma cell lines (HeLa, MCF-7 and MDA-MB-231) and on two androgen-independent malignant prostate carcinoma cell lines (PC-3 and DU 145). Based on primary cytotoxicity screens and IC₅₀ assessment, a structure-function relationship was identified, as derivatives carrying a hydroxyl group on C-17 exhibit stronger activity compared to the 17-one counterparts. Cancer cell selectivity of the derivatives was also determined using non-cancerous MRC-5 cells. Furthermore, the proapoptotic effects of some selected derivatives were verified on androgen therapy refractive p53-deficient PC-3 cells. The present study concludes that novel DHT-derived arylpyrazoles exert cancer cell specific antiproliferative activity and activate apoptosis in PC-3 cells.

Upregulation of MicroRNA-21 promotes tumorigenesis of prostate cancer cells by targeting KLF5

Prostate cancer (PCa) is the second frequently newly diagnosed cancer in men. Androgen deprivation therapy has been widely used to inhibit PCa growth but eventually fails in many patients. Androgen receptor and its downstream molecules like microRNAs could be promising therapeutic targets. We aimed to investigate the involvement of miR-21 in PCa tumorigenesis. We found that miR-21 was an unfavorable factor and correlated positively with tumor grade in PCa patients from TCGA database. MiR-21 was more highly expressed in androgen-independent PCa cells than in androgen-dependent PCa cells. Overexpression of miR-21 promoted androgen-dependent and -independent PCa cell proliferation, migration, invasion, and resistance to apoptosis. Furthermore, increased miR-21 expression promoted mouse xenograft growth. We identified nine genes differentially expressed in PCa tumors and normal tissue which could be potential targets of miR-21 by bioinformatic analyses. We demonstrate that miR-21 directly targeted KLF5 and inhibited KLF5 mRNA and protein levels in PCa. STRING and functional enrichment analysis results suggest that GSK3B might be regulated by KLF5. Our findings demonstrate that miR-21 promotes the tumorigenesis of PCa cells by directly targeting KLF5. These biological effects are mediated through upregulation of GSK3B and activation of the AKT signaling pathway.

Discovery of Novel Androgen Receptor Ligands by Structure-based Virtual Screening and Bioassays

Androgen receptor (AR) is a ligand-activated transcription factor that plays a pivotal role in the development and progression of many severe diseases such as prostate cancer, muscle atrophy, and osteoporosis. Binding of ligands to AR triggers the conformational changes in AR that may affect the recruitment of coactivators and downstream response of AR signaling pathway. Therefore, AR ligands have great potential to treat these diseases. In this study, we searched for novel AR ligands by performing a docking-based virtual screening (VS) on the basis of the crystal structure of the AR ligand binding domain (LBD) in complex with its agonist. A total of 58 structurally diverse compounds were selected and subjected to LBD affinity assay, with five of them (HBP1-3, HBP1-17, HBP1-38, HBP1-51, and HBP1-58) exhibiting strong binding to AR-LBD. The IC₅₀ values of HBP1-51 and HBP1-58 are 3.96 µM and 4.92 µM, respectively, which are even lower than that of enzalutamide (Enz, IC₅₀ = 13.87 µM), a marketed second-generation AR antagonist. Further bioactivity assays suggest that HBP1-51 is an AR agonist, whereas HBP1-58 is an AR antagonist. In addition, molecular dynamics (MD) simulations and principal components analysis (PCA) were carried out to reveal the binding principle of the newly-identified AR ligands toward AR. Our modeling results indicate that the conformational changes of helix 12 induced by the bindings of antagonist and agonist are visibly different. In summary, the current study provides a highly efficient way to discover novel AR ligands, which could serve as the starting point for development of new therapeutics for AR-related diseases.

Omega-3 fatty acids decrease prostate cancer progression associated with an anti-tumor immune response in eugonadal and castrated mice

BACKGROUND

Several lines of evidence suggest effects of dietary fat on prostate cancer (PCa) development and progression. Targeting omega (ω)-3:ω6 fatty acids (FA) ratio could be beneficial against PCa by favorably modulating inflammation. Here, we studied the effects of ω3- and ω6-enriched diets on prostate tumor growth and inflammatory response in androgen-deprived and non-deprived conditions.

METHODS

Immune-competent eugonadal and castrated C57BL/6 mice were injected with TRAMP-C2 prostate tumor cells and daily fed with ω3- or ω6-enriched diet. FA and cytokine profiles were measured in blood and tumors using gas chromatography and multiplex immunoassay, respectively. Immune cell infiltration in tumors was profiled by multicolor flow cytometry.

RESULTS

ω3-enriched diet decreased prostate TRAMP-C2 tumor growth in immune-competent eugonadal and castrated mice. Cytokines associated with Th1 immune response (IL-12 [p70], IFN-γ, GM-CSF) and eosinophil recruitment (eotaxin-1, IL-5, and IL-13) were significantly elevated in tumors of ω3-fed mice. Using in vitro experiments, we confirmed ω3 FA-induced eotaxin-1 secretion by tumor cells and that eotaxin-1 secretion was regulated by androgens. Analysis of immune cell infiltrating tumors showed no major difference of immune cells' abundance between ω3- and ω6-enriched diets.

CONCLUSIONS

ω3-enriched diet reduces prostate tumor growth independently of androgen levels. ω3 FA can inhibit tumor cell growth and induce a local anti-tumor inflammatory response. These findings warrant further examination of dietary ω3's potential to slow down the progression of androgen-sensitive and castrate-resistant PCa by modulating immune cell function in tumors.

A magic drug target: Androgen receptor

Androgen receptor (AR) is closely associated with a group of hormone-related diseases including the cancers of prostate, breast, ovary, pancreas, etc and anabolic deficiencies such as muscle atrophy and osteoporosis. Depending on the specific type and stage of the diseases, AR ligands including not only antagonists but also agonists and modulators are considered as potential therapeutics, which makes AR an extremely interesting drug target. Here, we at first review the current understandings on the structural characteristics of AR, and then address why and how AR is investigated as a drug target for the relevant diseases and summarize the representative antagonists and agonists targeting five prospective small molecule binding sites at AR, including ligand-binding pocket, activation function-2 site, binding function-3 site, DNA-binding domain, and N-terminal domain, providing recent insights from a target and drug development view. Further comprehensive studies on AR and AR ligands would bring fruitful information and push the therapy of AR relevant diseases forward.

Histone demethylase KDM7A controls androgen receptor activity and tumor growth in prostate cancer

Prostate cancer can be controlled by androgen-hormone treatment until the cancer becomes refractory. It is believed that hormone sensitivity is largely dependent on androgen receptor (AR) activity. Here, we found the histone demethylase KDM7A which demethylates histone H3K27 to be overexpressed in enzalutamide resistant castration-resistant prostate cancer cell line C4-2b, and investigated the molecular mechanism whereby androgen receptor activity is regulated by KDM7A. We engineered AR-positive LNCaP cells to stably express a short-hairpin RNA against KDM7A mRNA from a lentiviral vector. By measuring AR downstream gene expression after androgen stimulation, we found that a KDM7A-deficient cell line showed lower AR downstream gene expression compared to a control cell. KDM7A knock-down in LNCaP cell line caused decreased cell proliferation. Western blot analysis with modified-histone antibody revealed that the KDM7A-knock-down LNCaP cell line had increased H3K27 di-methylation. We confirmed KDM7A binding on AR target-gene promoters after hormone stimulation in chromatin-immunoprecipitation experiments. And increased H3K27 di-methylation was observed in KDM7A knock-down LNCaP stable cell. Treatment with KDM7A inhibitor, TC-E 5002, reduced proliferation and induced apoptosis of prostate cancer cells. Finally, we observed that the KDM7A protein was significantly upregulated in prostate cancer tissue, and that this difference correlated with the Gleason score. These data suggested that KDM7A is potentially a good therapeutic target for prostate cancer drugs and can be used as potentially a good prognostic indicator for prostate cancer and related treatment strategies.

Perspectives on the current and emerging chemical androgen receptor antagonists for the treatment of prostate cancer

INTRODUCTION

 Prostate cancer is the most common cancer in men. Regardless of the initial treatment of localized disease, almost all patients develop castration resistant prostate cancer (CRPC). A better understanding of the molecular mechanisms behind castration resistance has led to the approval of novel oral androgen receptor (AR) antagonists, such as enzalutamide and apalutamide. Indeed, research has accelerated with numerous agents being studied for the management of CRPC. Areas covered: Herein, the authors present currently used and emerging AR antagonists for the treatment of CRPC. Emerging agents include darolutamide, EZN-4176, AZD-3514, and AZD-5312, apatorsen, galeterone, ODM-2014, TRC-253, BMS-641988, and proxalutamide. Expert opinion: Further understanding of the mechanisms leading to castration resistance in prostate cancer can reveal potential targets for the development of novel AR antagonists. Current novel agents are associated with modest clinical and survival benefit, while acquired resistance and safety issues are under continuous evaluation. The combination of AR antagonists used and ideal sequencing strategies are key tasks ahead, along with the investigation of molecular biomarkers for future personalized targeted therapies. In the future, the challenge will be to determine an AR antagonist with the best combination of outcome and tolerability.

Dioscin: A diverse acting natural compound with therapeutic potential in metabolic diseases, cancer, inflammation and infections

Currently, the numbers of patients with cancer, fibrosis, diabetes, chronic kidney disease, stroke and osteoporosis are increasing fast and fast. It's critical necessary to discovery lead compounds for new drug development. Dioscin, one active compound in some medicinal plants, has anti-inflammation, immunoregulation, hypolipidemic, anti-viral, anti-fungal and anti-allergic effects. In recent years, dioscin has reached more and more attention with its potent effects to treat liver, kidney, brain, stomach and intestine damages, and metabolic diseases including diabetes, osteoporosis, obesity, hyperuricemia as well as its anti-cancer activities through adjusting multiple targets and multiple signals. Therefore, dioscin is a promising multi-target candidate to treat various diseases. This review paper summarized the progress on pharmacological activities and mechanisms of dioscin, which may provide useful data for development and exploration of this natural product in the further.

11-Oxygenated androgen precursors are the preferred substrates for aldo-keto reductase 1C3 (AKR1C3): Implications for castration resistant prostate cancer

The progression of castration resistant prostate cancer (CRPC) is driven by the intratumoral conversion of adrenal androgen precursors to potent androgens. The expression of aldo-keto reductase 1C3 (AKR1C3), which catalyses the reduction of weak androgens to more potent androgens, is significantly increased in CRPC tumours. The oxidation of androgens to their inactive form is catalysed by 17β-hydroxysteroid dehydrogenase type 2 (17βHSD2), but little attention is given to the expression levels of this enzyme. In this study, we show that the 11-oxygenated androgen precursors of adrenal origin are the preferred substrate for AKR1C3. In particular we show that the enzymatic efficiency of AKR1C3 is 8- and 24-fold greater for 11-ketoandrostenedione than for the classic substrates androstenedione and 5α-androstanedione, respectively. Using three independent experimental systems and a computational model we subsequently show that increased ratios of AKR1C3:17βHSD2 significantly favours the flux through the 11-oxygenated androgen pathway as compared to the classical or 5α-androstanedione pathways. Our findings reveal that the flux through the classical and 5α-androstanedione pathways are limited by the low catalytic efficiently of AKR1C3 towards classical androgens combined with the high catalytic efficiency of 17βHSD2, and that the expression of the oxidative enzyme therefore plays a vital role in determining the steady state concentration of active androgens. Using microarray data from prostate tissue we confirm that the AKR1C3:17βHSD2 ratio is significantly increased in patients undergoing androgen deprivation therapy as compared to benign tissue, and further increased in patients with CRPC. Taken together this study therefore demonstrates that the ratio of AKR1C3:17βHSD2 is more important than AKR1C3 expression alone in determining intratumoral androgen levels and that 11-oxygenated androgens may play a bigger role in CRPC than previously anticipated.

Mechanism underlying the retarded nuclear translocation of androgen receptor splice variants

As shown in our previous study, two alternatively spliced androgen receptor (AR) variants, which are exclusively expressed in the granulosa cells of patients with polycystic ovary syndrome, exhibit retarded nuclear translocation compared with wild-type AR. However, researchers have not yet determined whether these abnormalities correlate with heat shock protein 90 (HSP90) and importin α (the former is a generally accepted co-chaperone of AR, and the latter is a component of classical nuclear import complexes). Here, these two variants were mainly retained in cytoplasm with HSP90 and importin α in the presence of dihydrotestosterone (DHT), and their levels in nucleus were significantly reduced, according to the immunofluorescence staining. The binding affinity of two AR variants for importin α was consistently decreased, while it was increased in WT-AR following DHT stimulation, leading to reduced nuclear import, particularly for the insertion-AR (Ins-AR). However, the binding affinities of two AR variants for HSP90 were increased in the absence of DHT compared with WT-AR, which functioned to maintain spatial structural stability, particularly for the deletion-AR (Del-AR). Therefore, the retarded nuclear translocation of two AR variants is associated with HSP90 and importin α, and the abnormal binding affinities for them play critical roles in this process.

ADT with antiandrogens in prostate cancer induces adverse effect of increasing resistance, neuroendocrine differentiation and tumor metastasis

Prostate cancer (PCa) is the most common cancer and the 2nd leading cause of cancer-related deaths among men in the United States. Androgen-deprivation-therapy (ADT) with antiandrogens to target the androgens/androgen receptor (AR) signals remains the standard therapy for advanced PCa. However, most of the PCa patients who received ADT with antiandrogens, including the recently developed Enzalutamide (Enz) that might extend PCa patients survival an extra 4.8 months, will still develop the castration (or antiandrogen) resistance. Mechanism dissection studies suggest these antiandrogen resistances may involve the induction of AR splicing variants and/or AR mutants. Further preclinical in vitro/in vivo studies suggest ADT-antiandrogens may also enhance the neuroendocrine differentiation (NED) and PCa cell invasion, and these unwanted side-effects may function through various mechanisms including altering the infiltrating inflammatory cells within the prostate tumor microenvironment. This review summarizes these unwanted ADT-induced side-effects and discusses multiple approaches to overcome these side-effects to better suppress the PCa at the castration resistant stage.

Role of Androgen Receptor in Prostate Cancer: A Review

Androgen receptor (AR) is a steroid receptor transcriptional factor for testosterone and dihydrotestosterone consisting of four main domains, the N-terminal domain, DNA-binding domain, hinge region, and ligand-binding domain. AR plays pivotal roles in prostate cancer, especially castration-resistant prostate cancer (CRPC). Androgen deprivation therapy can suppress hormone-naïve prostate cancer, but prostate cancer changes AR and adapts to survive under castration levels of androgen. These mechanisms include AR point mutations, AR overexpression, changes of androgen biosynthesis, constitutively active AR splice variants without ligand binding, and changes of androgen cofactors. Studies of AR in CRPC revealed that AR was still active in CRPC, and it remains as a potential target to treat CRPC. Enzalutamide is a second-generation antiandrogen effective in patients with CRPC before and after taxane-based chemotherapy. However, CRPC is still incurable and can develop drug resistance. Understanding the mechanisms of this resistance can enable new-generation therapies for CRPC. Several promising new AR-targeted therapies have been developed. Apalutamide is a new Food and Drug Administration-approved androgen agonist binding to the ligand-binding domain, and clinical trials of other new AR-targeted agents binding to the ligand-binding domain or N-terminal domain are underway. This review focuses on the functions of AR in prostate cancer and the development of CRPC and promising new agents against CRPC.

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

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

Therapeutic Potential of Leelamine, a Novel Inhibitor of Androgen Receptor and Castration-Resistant Prostate Cancer

Clinical management of castration-resistant prostate cancer (CRPC) resulting from androgen deprivation therapy remains challenging. CRPC is driven by aberrant activation of androgen receptor (AR) through mechanisms ranging from its amplification, mutation, post-translational modification, and expression of splice variants (e.g., AR-V7). Herein, we present experimental evidence for therapeutic vulnerability of CRPC to a novel phytochemical, leelamine (LLM), derived from pine tree bark. Exposure of human prostate cancer cell lines LNCaP (an androgen-responsive cell line with mutant AR), C4-2B (an androgen-insensitive variant of LNCaP), and 22Rv1 (a CRPC cell line with expression of AR-Vs), and a murine prostate cancer cell line Myc-CaP to plasma achievable concentrations of LLM resulted in ligand-dependent (LNCaP) and ligand-independent (22Rv1) growth inhibition in vitro that was accompanied by downregulation of mRNA and/or protein levels of full-length AR as well as its splice variants, including AR-V7. LLM treatment resulted in apoptosis induction in the absence and presence of R1881. In silico modeling followed by luciferase reporter assay revealed a critical role for noncovalent interaction of LLM with Y739 in AR activity inhibition. Substitution of the amine group with an isothiocyanate functional moiety abolished AR and cell viability inhibition by LLM. Administration of LLM resulted in 22Rv1 xenograft growth suppression that was statistically insignificant but was associated with a significant decrease in Ki-67 expression, mitotic activity, expression of full-length AR and AR-V7 proteins, and secretion of PSA. This study identifies a novel chemical scaffold for the treatment of CRPC. Mol Cancer Ther; 17(10); 2079-90. ©2018 AACR.

Suppressed epithelial-mesenchymal transition and cancer stem cell properties mediate the anti-cancer effects of ethyl pyruvate via regulation of the AKT/nuclear factor-κB pathway in prostate cancer cells

Castration-resistant prostate cancer (CRPC) is a leading cause of mortality among cases of prostate cancer (PCa). Current treatment options for CRPC are limited. Ethyl pyruvate (EP), a lipophilic derivative of pyruvic acid, has been reported to have antitumor activities. In the present study, the efficacy of EP against PCa was investigated using two human PCa cell lines and a mouse xenograft tumor model. PC3 and CWR22RV1 cells were treated with EP, and cytotoxicity was evaluated via Cell Counting Kit-8 and colony formation assays, while cell cycle distribution was assessed by flow cytometry. Changes in cell migration and invasion caused by EP treatment were also evaluated with Transwell and wound healing assays, and changes in the expression of intracellular signaling pathway components were detected by western blotting. EP treatment reduced cell viability, induced G1 arrest, and activated the intrinsic apoptosis pathway. Additionally, the in vivo experiments revealed that EP administration markedly inhibited tumor growth. EP also reversed epithelial-mesenchymal transition and suppressed cancer stem cell properties in part through negative regulation of AKT/nuclear factor-κB signaling. These results indicate that EP has anticancer activity in vitro and in vivo, and is therefore a promising therapeutic agent for the treatment of PCa.