Non-Cell-Autonomous Regulation of Prostate Epithelial Homeostasis by Androgen Receptor

Combined Sabal and Urtica Extracts (WS® 1541) Exert Anti-proliferative and Anti-inflammatory Effects in a Mouse Model of Benign Prostate Hyperplasia

WS^® 1541 is a phytopharmaceutical drug combination containing a lipophilic extract from fruits of Sabal serrulata (WS^® 1473) and an aqueous ethanolic extract from roots of Urtica dioica (WS^® 1031). It is approved in several countries worldwide for the treatment of lower urinary tract syndrome (LUTS) linked to benign prostate hyperplasia (BPH). Clinical studies have demonstrated the efficacy of this unique combination in the treatment of BPH-related LUTS. However, its mechanisms of action in vivo remain partly uncharacterized. The aim of this study was to take advantage of a validated mouse model of BPH to better characterize its growth-inhibitory and anti-inflammatory properties. We used the probasin–prolactin (Pb-PRL) transgenic mouse model in which prostate-specific overexpression of PRL results in several features of the human disease including tissue hypertrophy, epithelial hyperplasia, increased stromal cellularity, inflammation, and LUTS. Six-month-old heterozygous Pb-PRL male mice were randomly distributed to five groups (11–12 animals/group) orally treated for 28 consecutive days with WS^® 1541 (300, 600, or 900 mg/kg/day), the 5α-reductase inhibitor finasteride used as reference (5 mg/kg/day) or vehicle (olive oil 5 ml/kg/day). Administration of WS^® 1541 was well tolerated and caused a dose-dependent reduction of prostate weight (vs. vehicle) that was statistically significant at the two highest doses. This effect was accompanied by a reduction in prostate cell proliferation as assessed by lower Ki-67 expression (qPCR and immunohistochemistry). In contrast, finasteride had no or only a mild effect on these parameters. The growth-inhibitory activity of WS^® 1541 was accompanied by a strong anti-inflammatory effect as evidenced by the reduced infiltration of cells expressing the leukocyte common antigen CD45. In sharp contrast, finasteride significantly increased the prostate inflammatory status according to this readout. Molecular profiling (qPCR) of 23 selected pro-inflammatory genes confirmed the strong anti-inflammatory potency of WS^® 1541 compared to finasteride. Since treatment of WS^® 1541 did not interfere with transgene expression and activity in the prostate of Pb-PRL mice, the effects observed in this study are entirely attributable to the intrinsic pharmacological action of the drug combination.

5-ARI induces autophagy of prostate epithelial cells through suppressing IGF-1 expression in prostate fibroblasts

Objectives

5α‐reductase inhibitor (5‐ARI) is a commonly used medicine in the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH). Our study mainly focuses on the mechanism of BPH development after 5ARI treatment.

Materials and Methods

Prostate specimens from patients were collected. Insulin‐like growth factor 1 (IGF‐1), Beclin‐1, LC3 levels, was analysed by immunohistochemistry. The role IGF‐1 on autophagic flux in prostate epithelial cells was studied. Additionally, effect of autophagy on recombinant grafts consisting of prostate stromal and epithelial cells in nude mice was investigated.

Results

We demonstrated that IGF‐1 expression is down‐regulated in prostate fibroblasts after long‐term 5‐ARI application. A decrease in IGF‐1 levels was found to activate autophagic flux through the mTOR pathway in prostate epithelial cells, while the inhibition of IGF‐1 receptor function induced autophagy in prostate epithelial cells. In addition, we revealed that blocking autophagic flux initiation can reduce the volume of recombinant grafts in vivo. Finally, our findings suggest that long‐term 5‐ARI application reduces IGF‐1 secretion by prostatic stromal cells, thereby inducing autophagy of prostatic epithelial cells, which is one of the mechanisms underlying BPH pathogenesis and progression.

Conclusions

Focusing on the autophagy induced by low levels of IGF‐1 in prostatic epithelial cells, after elucidating AR signalling impairment of prostate stromal cells, might provide a novel strategy for the treatment and prevention of BPH development.

Genetically Engineered Mouse Models of Prostate Cancer in the Postgenomic Era

Recent genomic sequencing analyses have unveiled the spectrum of genomic alterations that occur in primary and advanced prostate cancer, raising the question of whether the corresponding genes are functionally relevant for prostate tumorigenesis, and whether such functions are associated with particular disease stages. In this review, we describe genetically engineered mouse models (GEMMs) of prostate cancer, focusing on those that model genomic alterations known to occur in human prostate cancer. We consider whether the phenotypes of GEMMs based on gain or loss of function of the relevant genes provide reliable counterparts to study the predicted consequences of the corresponding genomic alterations as occur in human prostate cancer, and we discuss exceptions in which the GEMMs do not fully emulate the expected phenotypes. Last, we highlight future directions for the generation of new GEMMs of prostate cancer and consider how we can use GEMMs most effectively to decipher the biological and molecular mechanisms of disease progression, as well as to tackle clinically relevant questions.

Cells of Origin for Prostate Cancer

Comprehensive knowledge of the normal prostate epithelial lineage hierarchy is a prerequisite to investigate the identity of the cells of origin for prostate cancer. The basal and luminal cells constitute most of the prostate epithelium and have been the major focuses of the study on the cells of origin for prostate cancer. Much progress has been made during the past few decades, mainly using mouse models, to understand the inter-lineage relationship and intra-lineage heterogeneity in adults as well as the lineage plasticity during conditions of stress. These studies have concluded that the adult mouse prostate basal and luminal cells are largely independently sustained under physiological conditions, but both types of cells possess the capacity for bipotent differentiation under stress or artificial experimental conditions. However, the existence or the identity of the putative progenitors within each lineage warrants further investigation. Whether the human prostate lineage hierarchy is completely the same as that of the mouse remains uncertain. Experiments from independent groups have demonstrated that both types of cells in mice and humans can serve as targets for transformation. But controversies remain whether the disease from distinct cells of origin display different clinical behaviors. Further investigation of the intra-lineage heterogeneity will provide new insights into this issue. Understanding the identity of the cells of origin for prostate cancer will help identify novel prognostic markers for early detection of aggressive prostate cancers, provide insights into the therapeutic vulnerability of these tumors, and inspire novel therapeutic strategies.

Single-Cell Analysis Identifies LY6D as a Marker Linking Castration-Resistant Prostate Luminal Cells to Prostate Progenitors and Cancer

The exact identity of castrate-resistant (CR) cells and their relation to CR prostate cancer (CRPC) is unresolved. We use single-cell gene profiling to analyze the molecular heterogeneity in basal and luminal compartments. Within the luminal compartment, we identify a subset of cells intrinsically resistant to castration with a bi-lineage gene expression pattern. We discover LY6D as a marker of CR prostate progenitors with multipotent differentiation and enriched organoid-forming capacity. Lineage tracing further reveals that LY6D+ CR luminal cells can produce LY6D- luminal cells. In contrast, in luminal cells lacking PTEN, LY6D+ cells predominantly give rise to LY6D+ tumor cells, contributing to high-grade PIN lesions. Gene expression analyses in patients' biopsies indicate that LY6D expression correlates with early disease progression, including progression to CRPC. Our studies thus identify a subpopulation of luminal progenitors characterized by LY6D expression and intrinsic castration resistance. LY6D may serve as a prognostic maker for advanced prostate cancer.

Prostate Luminal Progenitor Cells in Development and Cancer

Prostate cancer (PCa) has a predominantly luminal phenotype. Basal cells were previously identified as a cell of origin for PCa, but increasing evidence implicates luminal cells as a preferred cell of origin for PCa, as well as key drivers of tumor development and progression. Prostate luminal cells are understudied compared with basal cells. In this review, we describe the contribution of prostate luminal progenitor (LP) cells to luminal cell development and their role in prostate development, androgen-mediated regeneration of castrated prostate, and tumorigenesis. We also discuss the potential value of LP transcriptomics to identify new targets and therapies to treat aggressive PCa. Finally, we propose future research directions focusing on molecular mechanisms underlying LP cell biology and heterogeneity in normal and diseased prostate.

Inflammation and NF-κB Signaling in Prostate Cancer: Mechanisms and Clinical Implications

Prostate cancer is a highly prevalent form of cancer that is usually slow-developing and benign. Due to its high prevalence, it is, however, still the second most common cause of death by cancer in men in the West. The higher prevalence of prostate cancer in the West might be due to elevated inflammation from metabolic syndrome or associated comorbidities. NF-κB activation and many other signals associated with inflammation are known to contribute to prostate cancer malignancy. Inflammatory signals have also been associated with the development of castration resistance and resistance against other androgen depletion strategies, which is a major therapeutic challenge. Here, we review the role of inflammation and its link with androgen signaling in prostate cancer. We further describe the role of NF-κB in prostate cancer cell survival and proliferation, major NF-κB signaling pathways in prostate cancer, and the crosstalk between NF-κB and androgen receptor signaling. Several NF-κB-induced risk factors in prostate cancer and their potential for therapeutic targeting in the clinic are described. A better understanding of the inflammatory mechanisms that control the development of prostate cancer and resistance to androgen-deprivation therapy will eventually lead to novel treatment options for patients.

Identification of an IL-1-induced gene expression pattern in AR+ PCa cells that mimics the molecular phenotype of AR- PCa cells

BACKGROUND

In immunosurveillance, bone-derived immune cells infiltrate the tumor and secrete inflammatory cytokines to destroy cancer cells. However, cancer cells have evolved mechanisms to usurp inflammatory cytokines to promote tumor progression. In particular, the inflammatory cytokine, interleukin-1 (IL-1), is elevated in prostate cancer (PCa) patient tissue and serum, and promotes PCa bone metastasis. IL-1 also represses androgen receptor (AR) accumulation and activity in PCa cells, yet the cells remain viable and tumorigenic; suggesting that IL-1 may also contribute to AR-targeted therapy resistance. Furthermore, IL-1 and AR protein levels negatively correlate in PCa tumor cells. Taken together, we hypothesize that IL-1 reprograms AR positive (AR⁺ ) PCa cells into AR negative (AR^- ) PCa cells that co-opt IL-1 signaling to ensure AR-independent survival and tumor progression in the inflammatory tumor microenvironment.

METHODS

LNCaP and PC3 PCa cells were treated with IL-1β or HS-5 bone marrow stromal cell (BMSC) conditioned medium and analyzed by RNA sequencing and RT-QPCR. To verify genes identified by RNA sequencing, LNCaP, MDA-PCa-2b, PC3, and DU145 PCa cell lines were treated with the IL-1 family members, IL-1α or IL-1β, or exposed to HS-5 BMSC in the presence or absence of Interleukin-1 Receptor Antagonist (IL-1RA). Treated cells were analyzed by western blot and/or RT-QPCR.

RESULTS

Comparative analysis of sequencing data from the AR⁺ LNCaP PCa cell line versus the AR^- PC3 PCa cell line reveals an IL-1-conferred gene suite in LNCaP cells that is constitutive in PC3 cells. Bioinformatics analysis of the IL-1 regulated gene suite revealed that inflammatory and immune response pathways are primarily elicited; likely facilitating PCa cell survival and tumorigenicity in an inflammatory tumor microenvironment.

CONCLUSIONS

Our data supports that IL-1 reprograms AR⁺ PCa cells to mimic AR^- PCa gene expression patterns that favor AR-targeted treatment resistance and cell survival.

An Indispensable Role of Androgen Receptor in Wnt Responsive Cells During Prostate Development, Maturation, and Regeneration

Androgen signaling is essential for prostate development, morphogenesis, and regeneration. Emerging evidence indicates that Wnt/β-catenin signaling also contributes to prostate development specifically through regulation of cell fate determination. Prostatic Axin2-expressing cells are able to respond to Wnt signals and possess the progenitor properties to regenerate prostatic epithelium. Despite critical roles of both signaling pathways, the biological significance of androgen receptor (AR) in Axin2-expressing/Wnt-responsive cells remains largely unexplored. In this study, we investigated this important question using a series of newly generated mouse models. Deletion of Ar in embryonic Axin2-expressing cells impaired early prostate development in both ex vivo and tissue implantation experiments. When Ar expression was deleted in prostatic Axin2-expressing cells at pre-puberty stages, it results in smaller and underdeveloped prostates. A subpopulation of Axin2 expressing cells in prostate epithelium is resistant to castration and, following androgen supplementation, is capable to expand to prostatic luminal cells. Deletion of Ar in these Axin2-expressing cells reduces their regenerative ability. These lines of evidence demonstrate an indispensable role for the Ar in Wnt-responsive cells during the course of prostate development, morphogenesis, and regeneration, which also imply an underlying interaction between the androgen and Wnt signaling pathways in the mouse prostate. Stem Cells 2018;36:891-902.

Differential requirements of androgen receptor in luminal progenitors during prostate regeneration and tumor initiation

Master regulatory genes of tissue specification play key roles in stem/progenitor cells and are often important in cancer. In the prostate, androgen receptor (AR) is a master regulator essential for development and tumorigenesis, but its specific functions in prostate stem/progenitor cells have not been elucidated. We have investigated AR function in CARNs (CAstration-Resistant Nkx3.1-expressing cells), a luminal stem/progenitor cell that functions in prostate regeneration. Using genetically--engineered mouse models and novel prostate epithelial cell lines, we find that progenitor properties of CARNs are largely unaffected by AR deletion, apart from decreased proliferation in vivo. Furthermore, AR loss suppresses tumor formation after deletion of the Pten tumor suppressor in CARNs; however, combined Pten deletion and activation of oncogenic Kras in AR-deleted CARNs result in tumors with focal neuroendocrine differentiation. Our findings show that AR modulates specific progenitor properties of CARNs, including their ability to serve as a cell of origin for prostate cancer.

Serum Steroid Ratio Profiles in Prostate Cancer: A New Diagnostic Tool Toward a Personalized Medicine Approach

BACKGROUND

Serum steroids are crucial molecules altered in prostate cancer (PCa). Mass spectrometry (MS) is currently the elected technology for the analysis of steroids in diverse biological samples. Steroids have complex biological pathways and stoichiometry and it is important to evaluate their quantitative ratio. MS applications to patient hormone profiling could lead to a diagnostic approach.

METHODS

Here, we employed the Surface Activated Chemical Ionization-Electrospray-NIST (SANIST) developed in our laboratories, to obtain quantitative serum steroid ratio relationship profiles with a machine learning Bayesian model to discriminate patients with PCa. The approach is focused on steroid relationship profiles and disease association.

RESULTS

A pilot study on patients affected by PCa, benign prostate hypertrophy (BPH), and control subjects [prostate-specific antigen (PSA) lower than 2.5 ng/mL] was done in order to investigate the classification performance of the SANIST platform. The steroid profiles of 71 serum samples (31 controls, 20 patients with PCa and 20 subjects with benign prostate hyperplasia) were evaluated. The levels of 10 steroids were quantitated on the SANIST platform: Aldosterone, Corticosterone, Cortisol, 11-deoxycortisol, Androstenedione, Testosterone, dehydroepiandrosterone, dehydroepiandrosterone sulfate (DHEAS), 17-OH-Progesterone and Progesterone. We performed both traditional and a machine learning analysis.

CONCLUSION

We show that the machine learning approach based on the steroid relationships developed here was much more accurate than the PSA, DHEAS, and direct absolute value match method in separating the PCa, BPH and control subjects, increasing the sensitivity to 90% and specificity to 84%. This technology, if applied in the future to a larger number of samples will be able to detect the individual enzymatic disequilibrium associated with the steroid ratio and correlate it with the disease. This learning machine approach could be valid in a personalized medicine setting.

Histone 2B-GFP Label-Retaining Prostate Luminal Cells Possess Progenitor Cell Properties and Are Intrinsically Resistant to Castration

The existence of slow-cycling luminal cells in the prostate has been suggested, but their identity and functional properties remain unknown. Using a bigenic mouse model to earmark, isolate, and characterize the quiescent stem-like cells, we identify a label-retaining cell (LRC) population in the luminal cell layer as luminal progenitors. Molecular and biological characterizations show that these luminal LRCs are significantly enriched in the mouse proximal prostate, exhibit relative dormancy, display bipotency in both in vitro and in vivo assays, and express a stem/progenitor gene signature with resemblance to aggressive prostate cancer. Importantly, these LRCs, compared with bulk luminal cells, maintain a lower level of androgen receptor (AR) expression and are less androgen dependent and also castration resistant in vivo. Finally, analysis of phenotypic markers reveals heterogeneity within the luminal progenitor cell pool. Our study establishes luminal LRCs as progenitors that may serve as a cellular origin for castration-resistant prostate cancer.

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A bigenic mouse model to study prostatic slow-cycling luminal epithelial cells

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Prostate label-retaining cells (LRCs) exhibit stem/progenitor cell activities

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Luminal LRCs are developmentally bipotent and display a progenitor gene signature

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Luminal LRCs resist castration and molecularly resemble aggressive prostate cancer

Androgenic to oestrogenic switch in the human adult prostate gland is regulated by epigenetic silencing of steroid 5α-reductase 2

Benign prostatic hyperplasia is the most common proliferative abnormality of the prostate. All men experience some prostatic growth as they age, but the rate of growth varies among individuals. Steroid 5α-reductase 2 (SRD5A2) is a critical enzyme for prostatic development and growth. Previous work indicates that one-third of adult prostatic samples do not express SRD5A2, secondary to epigenetic modifications. Here we show that the level of oestradiol is dramatically elevated, concomitant with significant upregulation of oestrogen response genes, in prostatic samples with methylation at the SRD5A2 promoter. The phosphorylation of oestrogen receptor-α in prostatic stroma is upregulated when SRD5A2 expression is absent. We show that tumour necrosis factor (TNF)-α suppresses SRD5A2 mRNA and protein expression, and simultaneously promotes expression of aromatase, the enzyme responsible for conversion of testosterone to oestradiol. Concomitant suppression of SRD5A2 and treatment with TNF-α synergistically upregulate the aromatase levels. The data suggest that, in the absence of prostatic SRD5A2, there is an androgenic to oestrogenic switch. These findings have broad implications for choosing appropriate classes of medications for the management of benign and malignant prostatic diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Molecular determinants of prostate cancer metastasis

Metastatic cancer remains largely incurable and fatal. The general course of cancer, from the initiation of primary tumor formation and progression to metastasis, is a multistep process wherein tumor cells at each step must display specific phenotypic features. Distinctive capabilities required for primary tumor initiation and growth form the foundation, and sometimes may remain critical, for subsequent metastases. These phenotypic features must remain easily malleable during the acquisition of additional capabilities unique and essential to the metastatic process such as dissemination to distant tissues wherein tumor cells interact with foreign microenvironments. Thus, the metastatic phenotype is a culmination of multiple genetic and epigenetic alterations and subsequent selection for favorable traits under the pressure of ever-changing tumor microenvironments. Although our understanding of the molecular programs that drive cancer metastasis are incomplete, increasing evidence suggests that successful metastatic colonization relies on the dissemination of cancer stem cells (CSCs) with tumor-regenerating capacity and adaptive programs for survival in distant organs. In the past 2-3 years, a myriad of novel molecular regulators and determinants of prostate cancer metastasis have been reported, and in this Perspective, we comprehensively review this body of literature and summarize recent findings regarding cell autonomous molecular mechanisms critical for prostate cancer metastasis.

Transcriptional mechanisms coordinating tight junction assembly during epithelial differentiation

Epithelial tissues form a selective barrier via direct cell-cell interactions to separate and establish concentration gradients between the different compartments of the body. Proper function and formation of this barrier rely on the establishment of distinct intercellular junction complexes. These complexes include tight junctions, adherens junctions, desmosomes, and gap junctions. The tight junction is by far the most diverse junctional complex in the epithelial barrier. Its composition varies greatly across different epithelial tissues to confer various barrier properties. Thus, epithelial cells rely on tightly regulated transcriptional mechanisms to ensure proper formation of the epithelial barrier and to achieve tight junction diversity. Here, we review different transcriptional mechanisms utilized during embryogenesis and disease development to promote tight junction assembly and maintenance of intercellular barrier integrity. We focus particularly on the Grainyhead-like transcription factors and ligand-activated nuclear hormone receptors, two central families of proteins in epithelialization.

Targeting phenotypic heterogeneity in benign prostatic hyperplasia

Benign prostatic hyperplasia and associated lower urinary tract symptoms remain difficult to treat medically, resulting in hundreds of thousands of surgeries performed annually in elderly males. New therapies have not improved clinical outcomes since alpha blockers and 5 alpha reductase inhibitors were introduced in the 1990s. An underappreciated confounder to identifying novel targets is pathological heterogeneity. Individual patients display unique phenotypes, composed of distinct cell types. We have yet to develop a cellular or molecular understanding of these unique phenotypes, which has led to failure in developing targeted therapies for personalized medicine. This review covers the strategic experimental approach to unraveling the cellular pathogenesis of discrete BPH phenotypes and discusses how to incorporate these findings into the clinic to improve outcomes.

Molecular pathogenesis of human prostate basal cell hyperplasia

BACKGROUND

Understanding the molecular pathogenesis of distinct phenotypes in human benign prostatic hyperplasia (BPH) is essential to improving therapeutic intervention. Current therapies target smooth muscle and luminal epithelia for relief of lower urinary tract symptoms (LUTS) due to BPH, but basal cell hyperplasia (BCH) remains untargeted. The incidence of has been reported at 8-10%, but a molecular and cellular characterization has not been performed on this phenotype.

METHODS

Using freshly digested tissue from surgical specimens, we performed RNA-seq analysis of flow cytometry-purified basal epithelia from 3 patients with and 4 patients without a majority BCH phenotype. qPCR was performed on 28 genes identified as significant from 13 non-BCH and 7 BCH specimens to confirm transcriptomic analysis. IHC was performed on several non-BCH and BCH specimens for 3 proteins identified as significant by transcriptomic analysis.

RESULTS

A total of 141 human BPH specimens were analyzed for the presence of BCH. Clinical characteristics of non-BCH and BCH cohorts revealed no significant differences in age, PSA, prostate volume, medical treatment, or comorbidities. Quantitation of cellular subsets by flow cytometry in 11 BCH patients vs. 11 non-BCH patients demonstrated a significant increase in the ratio of basal to luminal epithelia in patients with BCH (P <0.05), but no significant differences in the total number of leukocytes. RNA-seq data from flow cytometry isolated basal epithelia from patients with and without BCH were subjected to gene set enrichment analysis of differentially expressed genes, which revealed increased expression of members of the epidermal differentiation complex. Transcriptomic data were complemented by immunohistochemistry for members of the epidermal differentiation complex, revealing a morphological similarity to other stratified squamous epithelial layers.

CONCLUSIONS

Increased expression of epidermal differentiation complex members and altered epithelial stratification resembles the progression of other metaplastic diseases. These data provide insight into the plasticity of the human prostate epithelium and suggest a classification of basal cell hyperplasia as a metaplasia.

Redirecting the focus of cancer immunotherapy to premalignant conditions

Much progress has been made in introducing immunological treatment approaches for cancer, with lessons learned from both the successes and failures of immunotherapy. Among the challenges of immunotherapeutic approaches for cancer are the multitudes of mechanisms by which cancers are known to subvert the immune defenses. This has led to the incorporation into the immunotherapeutic arsenal strategies by which to overcome the cancer’s immunological blockades. What has been only superficially explored is the immunological milieu of premalignant lesions and the possibility of immunological approaches for the treatment of premalignant lesions so as to prevent secondary premalignant lesions and their progression to cancer. This review discusses the immunological environment associated with premalignant lesions, and the possible missed opportunity of utilizing immunological treatment strategies in the less hostile environment of premalignant lesions as compared to the immune subversive cancer environment.