Cell-lineage specificity and role of AP-1 in the prostate fibroblast androgen receptor cistrome

Androgen-regulated stromal complement component 7 (C7) suppresses prostate cancer growth

The complement system is a major component of the innate immune system that works through the cytolytic effect of the membrane attack complex (MAC). Complement component 7 (C7) is essential for MAC assembly and its precisely regulated expression level is crucial for the cytolytic activity of MAC. We show that C7 is specifically expressed by the stromal cells in both mouse and human prostates. The expression level of C7 inversely correlates with clinical outcomes in prostate cancer. C7 is positively regulated by androgen signaling in the mouse prostate stromal cells. The androgen receptor directly transcriptionally regulates the mouse and human C7. Increasing C7 expression in the C57Bl/6 syngeneic RM-1 and Pten-Kras allografts suppresses tumor growth in vivo. Conversely, C7 haploinsufficiency promotes tumor growth in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Interestingly, replenishing C7 in androgen-sensitive Pten-Kras tumors during androgen depletion only slightly enhances cellular apoptosis, highlighting the diverse mechanisms employed by tumors to counteract complement activity. Collectively, our research indicates that augmenting complement activity could be a promising therapeutic approach to impede the development of castration resistance in prostate cancer.

Rewiring of master transcription factor cistromes during high-grade serous ovarian cancer development

The transcription factors MECOM, PAX8, SOX17 and WT1 are candidate master regulators of high-grade serous 'ovarian' cancer (HGSC), yet their cooperative role in the hypothesized tissue of origin, the fallopian tube secretory epithelium (FTSEC) is unknown. We generated 26 epigenome (CUT&TAG, CUT&RUN, ATAC-seq and HiC) data sets and 24 profiles of RNA-seq transcription factor knock-down followed by RNA sequencing in FTSEC and HGSC models to define binding sites and gene sets regulated by these factors in cis and trans. This revealed that MECOM, PAX8, SOX17 and WT1 are lineage-enriched, super-enhancer associated master regulators whose cooperative DNA-binding patterns and target genes are re-wired during tumor development. All four TFs were indispensable for HGSC clonogenicity and survival but only depletion of PAX8 and WT1 impaired FTSEC cell survival. These four TFs were pharmacologically inhibited by transcriptional inhibitors only in HGSCs but not in FTSECs. Collectively, our data highlights that tumor-specific epigenetic remodeling is tightly related to MECOM, PAX8, SOX17 and WT1 activity and these transcription factors are targetable in a tumor-specific manner through transcriptional inhibitors.

Cancer-Associated Fibroblast Heterogeneity, Activation and Function: Implications for Prostate Cancer

The continuous remodeling of the tumor microenvironment (TME) during prostate tumorigenesis is emerging as a critical event that facilitates cancer growth, progression and drug-resistance. Recent advances have identified extensive communication networks that enable tumor-stroma cross-talk, and emphasized the functional importance of diverse, heterogeneous stromal fibroblast populations during malignant growth. Cancer-associated fibroblasts (CAFs) are a vital component of the TME, which mediate key oncogenic events including angiogenesis, immunosuppression, metastatic progression and therapeutic resistance, thus presenting an attractive therapeutic target. Nevertheless, how fibroblast heterogeneity, recruitment, cell-of-origin and differential functions contribute to prostate cancer remains to be fully delineated. Developing our molecular understanding of these processes is fundamental to developing new therapies and biomarkers that can ultimately improve clinical outcomes. In this review, we explore the current challenges surrounding fibroblast identification, discuss new mechanistic insights into fibroblast functions during normal prostate tissue homeostasis and tumorigenesis, and illustrate the diverse nature of fibroblast recruitment and CAF generation. We also highlight the promise of CAF-targeted therapies for the treatment of prostate cancer.

Elevated expression of the colony-stimulating factor 1 (CSF1) induces prostatic intraepithelial neoplasia dependent of epithelial-Gp130

Macrophages are increased in human benign prostatic hyperplasia and prostate cancer. We generate a Pb-Csf1 mouse model with prostate-specific overexpression of macrophage colony-stimulating factor (M-Csf/Csf1). Csf1 overexpression promotes immune cell infiltration into the prostate, modulates the macrophage polarity in a lobe-specific manner, and induces senescence and low-grade prostatic intraepithelial neoplasia (PIN). The Pb-Csf1 prostate luminal cells exhibit increased stem cell features and epithelial-to-mesenchymal transition. Human prostate cancer patients with high CSF-1 expression display similar transcriptional alterations with the Pb-Csf1 model. P53 knockout alleviates senescence but fails to progress PIN lesions. Ablating epithelial Gp130 but not Il1r1 substantially blocks PIN lesion formation. The androgen receptor (AR) is downregulated in Pb-Csf1 mice. ChIP-Seq analysis reveals altered AR binding in 2482 genes although there is no significant widespread change in global AR transcriptional activity. Collectively, our study demonstrates that increased macrophage infiltration causes PIN formation but fails to transform prostate cells.

Cellular specificity of androgen receptor, coregulators, and pioneer factors in prostate cancer

Androgen signalling, through the transcription factor androgen receptor (AR), is vital to all stages of prostate development and most prostate cancer progression. AR signalling controls differentiation, morphogenesis, and function of the prostate. It also drives proliferation and survival in prostate cancer cells as the tumour progresses; given this importance, it is the main therapeutic target for disseminated disease. AR is also essential in the surrounding stroma, for the embryonic development of the prostate and controlling epithelial glandular development. Stromal AR is also important in cancer initiation, regulating paracrine factors that excite cancer cell proliferation, but lower stromal AR expression correlates with shorter time to progression/worse outcomes. The profile of AR target genes is different between benign and cancerous epithelial cells, between castrate-resistant prostate cancer cells and treatment-naïve cancer cells, between metastatic and primary cancer cells, and between epithelial cells and fibroblasts. This is also true of AR DNA-binding profiles. Potentially regulating the cellular specificity of AR binding and action are pioneer factors and coregulators, which control and influence the ability of AR to bind to chromatin and regulate gene expression. The expression of these factors differs between benign and cancerous cells, as well as throughout disease progression. The expression profile is also different between fibroblast and mesenchymal cell types. The functional importance of coregulators and pioneer factors in androgen signalling makes them attractive therapeutic targets, but given the contextual expression of these factors, it is essential to understand their roles in different cancerous and cell-lineage states.

The antiandrogen enzalutamide downregulates TMPRSS2 and reduces cellular entry of SARS-CoV-2 in human lung cells

SARS-CoV-2 attacks various organs, most destructively the lung, and cellular entry requires two host cell surface proteins: ACE2 and TMPRSS2. Downregulation of one or both of these is thus a potential therapeutic approach for COVID-19. TMPRSS2 is a known target of the androgen receptor, a ligand-activated transcription factor; androgen receptor activation increases TMPRSS2 levels in various tissues, most notably prostate. We show here that treatment with the antiandrogen enzalutamide—a well-tolerated drug widely used in advanced prostate cancer—reduces TMPRSS2 levels in human lung cells and in mouse lung. Importantly, antiandrogens significantly reduced SARS-CoV-2 entry and infection in lung cells. In support of this experimental data, analysis of existing datasets shows striking co-expression of AR and TMPRSS2, including in specific lung cell types targeted by SARS-CoV-2. Together, the data presented provides strong evidence to support clinical trials to assess the efficacy of antiandrogens as a treatment option for COVID-19.

TMPRSS2 is regulated by androgen receptor signalling in the prostate, however it is unclear if blocking this signalling is beneficial in the context of SARS-CoV-2 lung infection. Here the authors show that antiandrogen treatment downregulates TMPRSS2 in the lung and reduces viral entry and infection.

Characteristics and possible mechanisms of 46, XY differences in sex development caused by novel compound variants in NR5A1 and MAP3K1

Background

Dozens of genes are involved in 46, XY differences in sex development (DSD). Notably, about 3/4 of patients cannot make a clear etiology diagnosis and single gene variant identified cannot fully explain the clinical heterogeneity of 46, XY DSD.

Materials and methods

We conducted a systematic clinical analysis of a 46, XY DSD patient, and applied whole-exome sequencing for the genetic analysis of this pedigree. The identified variants were analyzed by bioinformatic analysis and in vitro studies were performed in human embryonic kidney 293T (HEK-293T) cells which were transiently transfected with wild type or variant NR5A1 and MAP3K1 plasmid. Furthermore, protein production of SRY-box transcription factor 9 (SOX9) was analyzed in cell lysates.

Results

A novel NR5A1 variant (c.929A > C, p. His310Pro) and a rare MAP3K1 variant (c.2282T > C, p. Ile761Thr) were identified in the proband, whereas the proband's mother and sister who only carry rare MAP3K1 variant have remained phenotypically healthy to the present. These two variants were predicted to be pathogenic by bioinformatic analysis. In vitro, NR5A1 variant decreased the SOX9 production by 82.11% compared to wild type NR5A1, while MAP3K1 variant had little effect on the SOX9 production compared to wild type MAP3K1. Compared to wild type NR5A1 transfection, the SOX9 production of cells transfected with both wild type plasmids decreased by about 17.40%. Compared to variant NR5A1 transfection, the SOX9 production of cells transfected with both variant plasmids increased by the 36.64%.

Conclusions

Our findings suggested the novel compound variants of NR5A1 and MAP3K1 can alter the expression of SOX9 and ultimately lead to abnormality of sex development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01908-z.

Novel compound variants of the AR and MAP3K1 genes are related to the clinical heterogeneity of androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS; OMIM 300068) is the most frequent cause of 46, XY disorders of sex development (DSD). However, the correlation between genotype and phenotype has not been determined. We conducted a systematic analysis of the clinical characteristics, hormone levels, ultrasonography data and histopathology of a 46, XY Chinese patient with AIS. The family was followed up for nearly 8 years. We applied whole-exome sequencing (WES) for genetic analysis of the pedigree and performed bioinformatic analysis of the identified variants. Human embryonic kidney 293T/17 (HEK293T/17) cells were transiently transfected with wild-type or mutant AR and MAP3K1 plasmid. Cell lysates were used to analyze androgen receptor (AR) production. A novel hemizygous AR variant (c.2070C>A, p. His690Glu) and a rare heterozygous MAP3K1 variant (c.778C>T, p. Arg260Cys) were identified by WES in the proband and her mother. Bioinformatic analysis predicted these two variants to be pathogenic. Multiple amino acid sequence alignments showed that p. His690 and p. Arg260 are conserved among various species. His690Glu is a mutation that decreased the AR production, whereas the Arg260Cys mutation increased the AR production. The novel compound variants of the AR and MAP3K1 genes also increased the production of AR protein. Thus, the phenotype of the patient may be caused by defects in both the AR and MAP3K1 signaling pathways. Compound variants of the AR and MAP3K1 genes resulted in a specific phenotype in this patient with AIS. WES might reveal genetic variants that explain the heterogeneity of AIS.

Androgen Signaling in the Tumor Microenvironment

The key function of mesenchymal/stromal androgen receptor (AR) signaling for prostate development has been well documented by tissue recombination experiments. Some studies have addressed the expression and function of AR in stromal cells in prostate cancer, yet our understanding of the role of stromal AR in other tissues beyond prostate is still insufficient.Genomic analysis has revealed that cellular responses to androgens differ between epithelial and stromal cells. AR in stromal cells seems not to act via classical AR transcription factors such as FOXA1 but rather depends on the JUN/AP1 complex. Stromal AR appears to have tumor-promoting and tumor-protective functions depending on tumor stage. Loss of AR signaling in fibroblasts has been detected already in premalignant lesions in the skin and prostate and has been associated with tumor induction in xenografts of skin cancer and aggressive disease features and poor patient prognosis in prostate cancer. Moreover, AR expression is found on virtually all tissue-infiltrating immune cells and plays critical roles in immune cell function. These findings suggest a potential deleterious impact of current androgen deprivation therapies which inhibit both epithelial and stromal AR, highlighting the need to develop tissue-specific AR inhibitors.

Stroma Transcriptomic and Proteomic Profile of Prostate Cancer Metastasis Xenograft Models Reveals Prognostic Value of Stroma Signatures

Resistance acquisition to androgen deprivation treatment and metastasis progression are a major clinical issue associated with prostate cancer (PCa). The role of stroma during disease progression is insufficiently defined. Using transcriptomic and proteomic analyses on differentially aggressive patient-derived xenografts (PDXs), we investigated whether PCa tumors predispose their microenvironment (stroma) to a metastatic gene expression pattern. RNA sequencing was performed on the PCa PDXs BM18 (castration-sensitive) and LAPC9 (castration-resistant), representing different disease stages. Using organism-specific reference databases, the human-specific transcriptome (tumor) was identified and separated from the mouse-specific transcriptome (stroma). To identify proteomic changes in the tumor (human) versus the stroma (mouse), we performed human/mouse cell separation and subjected protein lysates to quantitative Tandem Mass Tag labeling and mass spectrometry. Tenascin C (TNC) was among the most abundant stromal genes, modulated by androgen levels in vivo and highly expressed in castration-resistant LAPC9 PDX. The tissue microarray of primary PCa samples (n = 210) showed that TNC is a negative prognostic marker of the clinical progression to recurrence or metastasis. Stroma markers of osteoblastic PCa bone metastases seven-up signature were induced in the stroma by the host organism in metastatic xenografts, indicating conserved mechanisms of tumor cells to induce a stromal premetastatic signature. A 50-gene list stroma signature was identified based on androgen-dependent responses, which shows a linear association with the Gleason score, metastasis progression and progression-free survival. Our data show that metastatic PCa PDXs, which differ in androgen sensitivity, trigger differential stroma responses, which show the metastasis risk stratification and prognostic biomarker potential.

ARe we there yet? Understanding androgen receptor signaling in breast cancer

The role of androgen receptor (AR) activation and expression is well understood in prostate cancer. In breast cancer, expression and activation of AR is increasingly recognized for its role in cancer development and its importance in promoting cell growth in the presence or absence of estrogen. As both prostate and breast cancers often share a reliance on nuclear hormone signaling, there is increasing appreciation of the overlap between activated cellular pathways in these cancers in response to androgen signaling. Targeting of the androgen receptor as a monotherapy or in combination with other conventional therapies has proven to be an effective clinical strategy for the treatment of patients with prostate cancer, and these therapeutic strategies are increasingly being investigated in breast cancer. This overlap suggests that targeting androgens and AR signaling in other cancer types may also be effective. This manuscript will review the role of AR in various cellular processes that promote tumorigenesis and metastasis, first in prostate cancer and then in breast cancer, as well as discuss ongoing efforts to target AR for the more effective treatment and prevention of cancer, especially breast cancer.

Androgen receptor signalling in macrophages promotes TREM-1-mediated prostate cancer cell line migration and invasion

The androgen receptor (AR) is the master regulator of prostate cancer (PCa) development, and inhibition of AR signalling is the most effective PCa treatment. AR is expressed in PCa cells and also in the PCa-associated stroma, including infiltrating macrophages. Macrophages have a decisive function in PCa initiation and progression, but the role of AR in macrophages remains largely unexplored. Here, we show that AR signalling in the macrophage-like THP-1 cell line supports PCa cell line migration and invasion in culture via increased Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) signalling and expression of its downstream cytokines. Moreover, AR signalling in THP-1 and monocyte-derived macrophages upregulates IL-10 and markers of tissue residency. In conclusion, our data suggest that AR signalling in macrophages may support PCa invasiveness, and blocking this process may constitute one mechanism of anti-androgen therapy.

Anti-androgen therapy inhibits prostate cancer (PC) progression, and is thought to act directly on cancer cells. Here the authors show that androgen receptor is expressed on normal and PC-associated macrophages, and its stimulation alters macrophage secretome to promote migration of cultured PC cell lines.

The role of the androgen receptor in prostate development and benign prostatic hyperplasia: A review

Benign prostatic hyperplasia (BPH) is a benign enlargement of the prostate in which incidence increases linearly with age, beginning at about 50 years old. BPH is a significant source of morbidity in aging men by causing lower urinary tract symptoms and acute urinary retention. Unfortunately, the etiology of BPH incidence and progression is not clear. This review highlights the role of the androgen receptor (AR) in prostate development and the evidence for its involvement in BPH. The AR is essential for normal prostate development, and individuals with defective AR signaling, such as after castration, do not experience prostate enlargement with age. Furthermore, decreasing dihydrotestosterone availability through therapeutic targeting with 5α-reductase inhibitors diminishes AR activity and results in reduced prostate size and symptoms in some BPH patients. While there is some evidence that AR expression is elevated in certain cellular compartments, how exactly AR is involved in BPH progression has yet to be elucidated. It is possible that AR signaling within stromal cells alters intercellular signaling and a "reawakening" of the embryonic mesenchyme, loss of epithelial AR leads to changes in paracrine signaling interactions, and/or chronic inflammation aids in stromal or epithelial proliferation evident in BPH. Unfortunately, a subset of patients fails to respond to current medical approaches, forcing surgical treatment even though age or associated co-morbidities make surgery less attractive. Fundamentally, new therapeutic approaches to treat BPH are not currently forthcoming, so a more complete molecular understanding of BPH etiology is necessary to identify new treatment options.

Factors that influence the androgen receptor cistrome in benign and malignant prostate cells

The androgen receptor (AR) plays key roles in the development of prostate tissue and the development and progression of prostate cancer (PC). AR guides cytodifferentiation and homeostasis in benign luminal epithelial cells; however, in PC, AR instead drives the uncontrolled proliferation of these cells. This ‘AR malignancy shift’ (AMS) is a central event in tumorigenesis. Using a ChIP‐seq approach in primary human tissues, cell lines, and mouse models, we demonstrate that the AMS occurs in every sample analyzed, suggesting that it is necessary for PC development. Using molecular and genetic techniques, we demonstrate that forkhead box (FOX)A1, HOXB13, GATA2, and c‐JUN are involved in the regulation of the AMS. AR‐binding sites (ARBS) are enriched for FOX, HOX, and GATA motifs in PC cells but not for c‐JUN motifs in benign cells. We show that the SPOP mutation commonly found in localized PCs can cause the AMS but is not transformative on its own and must be coupled to another mutation to transform cells. We show that the AMS occurs in mouse models of PC as well and that chronic low T, which is associated with increased PC risk and aggressiveness in humans, also causes the AMS in mice. We have discovered a previously unrecognized, fundamental tenet of PC, one which explains how and why AR signaling is different in cancer and benign cells. Our work has the potential to be used to stratify patients with localized PC for specific treatments. Furthermore, our work suggests that the AMS is a novel target for the treatment and/or prevention of PC.

Tissue-specific progesterone receptor-chromatin binding and the regulation of progesterone-dependent gene expression

Progesterone receptor (PGR) co-ordinately regulates ovulation, fertilisation and embryo implantation through tissue-specific actions, but the mechanisms for divergent PGR action are poorly understood. Here we characterised PGR activity in mouse granulosa cells using combined ChIP-seq for PGR and H3K27ac and gene expression microarray. Comparison of granulosa, uterus and oviduct PGR-dependent genes showed almost complete tissue specificity in PGR target gene profiles. In granulosa cells 82% of identified PGR-regulated genes bound PGR within 3 kb of the gene and PGR binding sites were highly enriched in proximal promoter regions in close proximity to H3K27ac-modified active chromatin. Motif analysis showed highly enriched PGR binding to the PGR response element (GnACAnnnTGTnC), but PGR also interacted significantly with other transcription factor binding motifs. In uterus PGR showed far more tendency to bind intergenic chromatin regions and low evidence of interaction with other transcription factors. This is the first genome-wide description of PGR action in granulosa cells and systematic comparison of diverse PGR action in different reproductive tissues. It clarifies finely-tuned contextual PGR-chromatin interactions with implications for more targeted reproductive medicine.

Androgen receptor enhancer usage and the chromatin regulatory landscape in human prostate cancers

The androgen receptor (AR) is commonly known as a key transcription factor in prostate cancer development, progression and therapy resistance. Genome-wide chromatin association studies revealed that transcriptional regulation by AR mainly depends on binding to distal regulatory enhancer elements that control gene expression through chromatin looping to gene promoters. Changes in the chromatin epigenetic landscape and DNA sequence can locally alter AR-DNA-binding capacity and consequently impact transcriptional output and disease outcome. The vast majority of reports describing AR chromatin interactions have been limited to cell lines, identifying numerous other factors and interacting transcription factors that impact AR chromatin interactions. Do these factors also impact AR cistromics - the genome-wide chromatin-binding landscape of AR - in vivo? Recent technological advances now enable researchers to identify AR chromatin-binding sites and their target genes in human specimens. In this review, we provide an overview of the different factors that influence AR chromatin binding in prostate cancer specimens, which is complemented with knowledge from cell line studies. Finally, we discuss novel perspectives on studying AR cistromics in clinical samples.

Neural Transcription Factors in Disease Progression

Progression to the malignant state is fundamentally dependent on transcriptional regulation in cancer cells. Optimum abundance of cell cycle proteins, angiogenesis factors, immune evasion markers, etc. is needed for proliferation, metastasis or resistance to treatment. Therefore, dysregulation of transcription factors can compromise the normal prostate transcriptional network and contribute to malignant disease progression.The androgen receptor (AR) is considered to be a key transcription factor in prostate cancer (PCa) development and progression. Consequently, androgen pathway inhibitors (APIs) are currently the mainstay in PCa treatment, especially in castration-resistant prostate cancer (CRPC). However, emerging evidence suggests that with increased administration of potent APIs, prostate cancer can progress to a highly aggressive disease that morphologically resembles small cell carcinoma, which is referred to as neuroendocrine prostate cancer (NEPC), treatment-induced or treatment-emergent small cell prostate cancer. This chapter will review how neuronal transcription factors play a part in inducing a plastic stage in prostate cancer cells that eventually progresses to a more aggressive state such as NEPC.

Genome-wide analysis of AR binding and comparison with transcript expression in primary human fetal prostate fibroblasts and cancer associated fibroblasts

The androgen receptor (AR) is a transcription factor, and key regulator of prostate development and cancer, which has discrete functions in stromal versus epithelial cells. AR expressed in mesenchyme is necessary and sufficient for prostate development while loss of stromal AR is predictive of prostate cancer progression. Many studies have characterized genome-wide binding of AR in prostate tumour cells but none have used primary mesenchyme or stroma. We applied ChIPseq to identify genomic AR binding sites in primary human fetal prostate fibroblasts and patient derived cancer associated fibroblasts, as well as the WPMY1 cell line overexpressing AR. We identified AR binding sites that were specific to fetal prostate fibroblasts (7534), cancer fibroblasts (629), WPMY1-AR (2561) as well as those common among all (783). Primary fibroblasts had a distinct AR binding profile versus prostate cancer cell lines and tissue, and showed a localisation to gene promoter binding sites 1 kb upstream of the transcriptional start site, as well as non-classical AR binding sequence motifs. We used RNAseq to define transcribed genes associated with AR binding sites and derived cistromes for embryonic and cancer fibroblasts as well as a cistrome common to both. These were compared to several in vivo ChIPseq and transcript expression datasets; which identified subsets of AR targets that were expressed in vivo and regulated by androgens. This analysis enabled us to deconvolute stromal AR targets active in stroma within tumour samples. Taken together, our data suggest that the AR shows significantly different genomic binding site locations in primary prostate fibroblasts compared to that observed in tumour cells. Validation of our AR binding site data with transcript expression in vitro and in vivo suggests that the AR target genes we have identified in primary fibroblasts may contribute to clinically significant and biologically important AR-regulated changes in prostate tissue.

Loss of androgen receptor signaling in prostate cancer-associated fibroblasts (CAFs) promotes CCL2- and CXCL8-mediated cancer cell migration

Fibroblasts are abundantly present in the prostate tumor microenvironment (TME), including cancer‐associated fibroblasts (CAFs) which play a key role in cancer development. Androgen receptor (AR) signaling is the main driver of prostate cancer (PCa) progression, and stromal cells in the TME also express AR. High‐grade tumor and poor clinical outcome are associated with low AR expression in the TME, which suggests a protective role of AR signaling in the stroma against PCa development. However, the mechanism of this relation is not clear. In this study, we isolated AR‐expressing CAF‐like cells. Testosterone (R1881) exposure did not affect CAF‐like cell morphology, proliferation, or motility. PCa cell growth was not affected by culturing in medium from R1881‐exposed CAF‐like cells; however, migration of PCa cells was inhibited. AR chromatin immune precipitation sequencing (ChIP‐seq) was performed and motif search suggested that AR in CAF‐like cells bound the chromatin through AP‐1‐elements upon R1881 exposure, inducing enhancer‐mediated AR chromatin interactions. The vast majority of chromatin binding sites in CAF‐like cells were unique and not shared with AR sites observed in PCa cell lines or tumors. AR signaling in CAF‐like cells decreased expression of multiple cytokines; most notably CCL2 and CXCL8 and both cytokines increased migration of PCa cells. These results suggest direct paracrine regulation of PCa cell migration by CAFs through AR signaling.

Androgen receptor moonlighting in the prostate cancer microenvironment

Androgen receptor (AR) signaling is vital for the normal development of the prostate and is critically involved in prostate cancer (PCa). AR is not only found in epithelial prostate cells but is also expressed in various cells in the PCa-associated stroma, which constitute the tumor microenvironment (TME). In the TME, AR is expressed in fibroblasts, macrophages, lymphocytes and neutrophils. AR expression in the TME was shown to be decreased in higher-grade and metastatic PCa, suggesting that stromal AR plays a protective role against PCa progression. With that, the functionality of AR in stromal cells appears to deviate from the receptor's classical function as described in PCa cells. However, the biological action of AR in these cells and its effect on cancer progression remains to be fully understood. Here, we systematically review the pathological, genomic and biological literature on AR actions in various subsets of prostate stromal cells and aim to better understand the consequences of AR signaling in the TME in relation to PCa development and progression.

Enduring epigenetic landmarks define the cancer microenvironment

The growth and progression of solid tumors involves dynamic cross-talk between cancer epithelium and the surrounding microenvironment. To date, molecular profiling has largely been restricted to the epithelial component of tumors; therefore, features underpinning the persistent protumorigenic phenotype of the tumor microenvironment are unknown. Using whole-genome bisulfite sequencing, we show for the first time that cancer-associated fibroblasts (CAFs) from localized prostate cancer display remarkably distinct and enduring genome-wide changes in DNA methylation, significantly at enhancers and promoters, compared to nonmalignant prostate fibroblasts (NPFs). Differentially methylated regions associated with changes in gene expression have cancer-related functions and accurately distinguish CAFs from NPFs. Remarkably, a subset of changes is shared with prostate cancer epithelial cells, revealing the new concept of tumor-specific epigenome modifications in the tumor and its microenvironment. The distinct methylome of CAFs provides a novel epigenetic hallmark of the cancer microenvironment and promises new biomarkers to improve interpretation of diagnostic samples.

Myofibroblast androgen receptor expression determines cell survival in co-cultures of myofibroblasts and prostate cancer cells in vitro

Fibroblasts express androgen receptor (AR) in the normal prostate and during prostate cancer development. We have reported that loss of AR expression in prostate cancer-associated fibroblasts is a poor prognostic indicator. Here we report outcomes of direct and indirect co-cultures of immortalised AR-positive (PShTert-AR) or AR-negative (PShTert) myofibroblasts with prostate cancer cells.

In the initial co-cultures the AR-negative PC3 cell line was used so AR expression and signalling were restricted to the myofibroblasts. In both direct and indirect co-culture with PShTert-AR myofibroblasts, paracrine signalling to the PC3 cells slowed proliferation and induced apoptosis. In contrast, PC3 cells proliferated with PShTert myofibroblasts irrespective of the co-culture method. In direct co-culture PC3 cells induced apoptosis in and destroyed PShTerts by direct signalling. Similar results were seen in direct co-cultures with AR-negative DU145 and AR-positive LNCaP and C4-2B prostate cancer cell lines. The AR ligand 5α-dihydrotestosterone (DHT) inhibited the proliferation of the PShTert-AR myofibroblasts, thereby reducing the extent of their inhibitory effect on cancer cell growth.

These results suggest loss of stromal AR would favour prostate cancer cell growth in vivo, providing an explanation for the clinical observation that reduced stromal AR is associated with a poorer outcome.

Stromal Androgen Receptor in Prostate Cancer Development and Progression

Prostate cancer development and progression is the result of complex interactions between epithelia cells and fibroblasts/myofibroblasts, in a series of dynamic process amenable to regulation by hormones. Whilst androgen action through the androgen receptor (AR) is a well-established component of prostate cancer biology, it has been becoming increasingly apparent that changes in AR signalling in the surrounding stroma can dramatically influence tumour cell behavior. This is reflected in the consistent finding of a strong association between stromal AR expression and patient outcomes. In this review, we explore the relationship between AR signalling in fibroblasts/myofibroblasts and prostate cancer cells in the primary site, and detail the known functions, actions, and mechanisms of fibroblast AR signaling. We conclude with an evidence-based summary of how androgen action in stroma dramatically influences disease progression.