Role of mesenchymal-epithelial interactions in normal and abnormal development of the mammary gland and prostate

The cancer-inhibitory effects of proliferating tumor-residing fibroblasts

Initiation, local progression, and metastasis of cancer are associated with specific morphological, molecular, and functional changes in the extracellular matrix and the fibroblasts within the tumor microenvironment (TME). In the early stages of tumor development, fibroblasts are an obstacle that cancer cells must surpass or nullify to progress. Thus, in early tumor progression, specific signaling from cancer cells activates bio-pathways, which abolish the innate anticancer properties of fibroblasts and convert a high proportion of them to tumor-promoting cancer-associated fibroblasts (CAFs). Following this initial event, a wide spectrum of gene expression changes gradually leads to the development of a stromal fibroblast population with complex heterogeneity, creating fibroblast subtypes with characteristic profiles, which may alternate between being tumor-promotive and tumor-suppressive, topologically and chronologically in the TME. These fibroblast subtypes form the tumor's histological landscape including areas of cancer growth, inflammation, angiogenesis, invasion fronts, proliferating and non-proliferating fibroblasts, cancer-cell apoptosis, fibroblast apoptosis, and necrosis. These features reflect general deregulation of tissue homeostasis within the TME. This review discusses fundamental and current knowledge that has established the existence of anticancer fibroblasts within the various interacting elements of the TME. It is proposed that the maintenance of fibroblast proliferation is an essential parameter for the activation of their anticancer capacity, similar to that by which normal fibroblasts would be activated in wound repair, thus maintaining tissue homeostasis. Encouragement of research in this direction may render new means of cancer therapy and a greater understanding of tumor progression.

Microenvironmental control of cell fate decisions in mammary gland development and cancer

Cell fate decisions are critical for adequate tissue development, maintenance and regeneration. In the mammary gland, epithelial cell fates are tightly controlled by the microenvironment. Here, we review how cell fate decisions are regulated by components of the microenvironment during mammary gland development and how pathological changes in the microenvironment can alter cell fates, leading to malignancy. Specifically, we describe the current understanding of how mammary cell fate is controlled and directed by three elements: the extracellular matrix, the immune microenvironment, and hormones-and how these elements can converge to create microenvironments that promote a fourth element: DNA damage.

Tumor Microenvironment-Derived NRG1 Promotes Antiandrogen Resistance in Prostate Cancer

Despite the development of second-generation antiandrogens, acquired resistance to hormone therapy remains a major challenge in treating advanced prostate cancer. We find that cancer-associated fibroblasts (CAFs) can promote antiandrogen resistance in mouse models and in prostate organoid cultures. We identify neuregulin 1 (NRG1) in CAF supernatant, which promotes resistance in tumor cells through activation of HER3. Pharmacological blockade of the NRG1/HER3 axis using clinical-grade blocking antibodies re-sensitizes tumors to hormone deprivation in vitro and in vivo. Furthermore, patients with castration-resistant prostate cancer with increased tumor NRG1 activity have an inferior response to second-generation antiandrogen therapy. This work reveals a paracrine mechanism of antiandrogen resistance in prostate cancer amenable to clinical testing using available targeted therapies.

Spatial Regulation of Mitochondrial Heterogeneity by Stromal Confinement in Micropatterned Tumor Models

Heterogeneity of mitochondrial activities in cancer cells exists across different disease stages and even in the same patient, with increased mitochondrial activities associated with invasive cancer phenotypes and circulating tumor cells. Here, we use a micropatterned tumor-stromal assay (μTSA) comprised of MCF-7 breast cancer cells and bone marrow stromal cells (BMSCs) as a model to investigate the role of stromal constraints in altering the mitochondrial activities of cancer cells within the tumor microenvironment (TME). Using microdissection and RNA sequencing, we revealed a differentially regulated pattern of gene expression related to mitochondrial activities and metastatic potential at the tumor-stromal interface. Gene expression was confirmed by immunostaining of mitochondrial mass, and live microscopic imaging of mitochondrial membrane potential (ΔΨ_m) and optical redox ratio. We demonstrated that physical constraints by the stromal cells play a major role in ΔΨ_m heterogeneity, which was positively associated with nuclear translocation of the YAP/TAZ transcriptional co-activators. Importantly, inhibiting actin polymerization and Rho-associated protein kinase disrupted the differential ΔΨ_m pattern. In addition, we showed a positive correlation between ΔΨ_m level and metastatic burden in vivo in mice injected with MDA-MB-231 breast cancer cells. This study supports a new regulatory role for the TME in mitochondrial heterogeneity and metastatic potential.

Transdifferentiation of bovine epithelial towards adipocytes in the presence of myoepithelium

Objective

Orchastric changes in the mammary glands are vital, especially during lactation. The secretary epithelial cells together with the supporting myoepithelial and stromal cells function cordially to secrete milk. Increase in the number of luminal epithelial cells and a decrease in adipocytes are visible during lactation, whereas the reverse happens in the involution. However, an early involution occurs if the epithelial cells transdifferentiate towards adipocytes during the lactation period. We aimed to inhibit the adipocyte transdifferentiation of luminal cells by restraining the peroxisomal proliferator-activated receptor γ (PPARγ) pathway.

Methods

Linolenic acid (LA) and thiazolidinediones (TZDs) induced adipogenesis in mammary epithelial cells were conducted in monolayer, mixed culture as well as in transwell plate co-culture with mammary myoepithelial cells.

Results

Co-culture with myoepithelial cells showed higher adipogenic gene expression in epithelial cells under LA+TZDs treatment. Increase in the expressions of PPARγ, CCAAT/enhancer-binding protein α and vimentin in both mRNA as well as protein levels were observed. Whereas, bisphenol A diglycidyl ether treatment blocked LA+TZDs induced adipogenesis, as it could not show a significant rise in adipose related markers. Although comparative results were found in both mixed culture and monolayer conditions, co-culture technic was found to work better than the others.

Conclusion

Antagonizing PPARγ pathway in the presence of myoepithelial cells can significantly reduce the adipogenisis in epithelial cells, suggesting therapeutic inhibition of PPARγ can be considered to counter early involution or excessive adipogenesis in mammary epithelium in animals.

Androgen excess in breast cancer development: implications for prevention and treatment

The aim of this review is to highlight the pivotal role of androgen excess in the development of breast cancer. Available evidence suggests that testosterone controls breast epithelial growth through a balanced interaction between its two active metabolites: cell proliferation is promoted by estradiol while it is inhibited by dihydrotestosterone. A chronic overproduction of testosterone (e.g. ovarian stromal hyperplasia) results in an increased estrogen production and cell proliferation that are no longer counterbalanced by dihydrotestosterone. This shift in the androgen/estrogen balance partakes in the genesis of ER-positive tumors. The mammary gland is a modified apocrine gland, a fact rarely considered in breast carcinogenesis. When stimulated by androgens, apocrine cells synthesize epidermal growth factor (EGF) that triggers the ErbB family receptors. These include the EGF receptor and the human epithelial growth factor 2, both well known for stimulating cellular proliferation. As a result, an excessive production of androgens is capable of directly stimulating growth in apocrine and apocrine-like tumors, a subset of ER-negative/AR-positive tumors. The key role of androgen excess in the genesis of different subtypes of breast cancer has significant clinical implications for both treatment and prevention. Our belief stems from a thorough analysis of the literature, where an abundance of evidence is present to justify a clinical trial that would investigate the effectiveness of treating the underlying excessive androgen production.

Testosterone regulates myosin II isoforms expression and functional activity in the rat prostate

BACKGROUND

Benign prostatic hyperplasia (BPH) is mainly caused by increased prostatic smooth muscle (SM) tone and prostatic volume. At the molecular level, SM myosin II (SMM II) and non-muscle myosin II (NMM II) mediate SM tone and cell proliferation while testosterone (T) plays a permissive role in the development of BPH.

AIMS

The novel objective of this study was to elucidate the effects of T on the proliferation and apoptosis of rat prostatic cells and SM contractility as well as related regulatory signaling pathways.

MATERIALS AND METHODS

Briefly, 36 male rats were divided into three groups (sham-operated, surgically castrated, and castrated with T supplementation). In vitro organ bath studies, competitive RT-PCR, Western-blotting analysis, Masson's trichrome staining, and immunofluorescence staining were performed.

RESULTS

Our data showed that castration dramatically increased prostatic SM contractility and SM MHC immunostaining revealed a relatively increased SM cell numbers in the stroma. T deprivation altered prostate SMM II isoform composition with upregulation of SM-B and SM2 but downregulation of LC17a, favoring a faster more phasic-type contraction. Moreover, protein expressions of MLCK, p-MLCP, RhoB, ROCK1, and ROCK2 increased in castrated rats. Meanwhile NMM II heavy chain isoforms A, B, and C (NMMHC-A, B, and C isoforms) were altered by castration which may be linked to decreased cell proliferation and increased apoptosis.

CONCLUSION

Our novel data demonstrated T regulates SMM II and NMM II and their functional activities in rat prostate and T ablation not only decreases prostate size (static component) but also changes the prostatic SM tone (dynamic component).

E-cadherin bridges cell polarity and spindle orientation to ensure prostate epithelial integrity and prevent carcinogenesis in vivo

Cell polarity and correct mitotic spindle positioning are essential for the maintenance of a proper prostate epithelial architecture, and disruption of the two biological features occurs at early stages in prostate tumorigenesis. However, whether and how these two epithelial attributes are connected in vivo is largely unknown. We herein report that conditional genetic deletion of E-cadherin, a key component of adherens junctions, in a mouse model results in loss of prostate luminal cell polarity and randomization of spindle orientations. Critically, E-cadherin ablation causes prostatic hyperplasia which progresses to invasive adenocarcinoma. Mechanistically, E-cadherin and the spindle positioning determinant LGN interacts with the PDZ domain of cell polarity protein SCRIB and form a ternary protein complex to bridge cell polarity and cell division orientation. These findings provide a novel mechanism by which E-cadherin acts an anchor to maintain prostate epithelial integrity and to prevent carcinogenesis in vivo.

Luminal cells are the most abundant type of the prostate epithelial cells. Most prostate cancers also display a luminal phenotype. Horizontal cell division of luminal cells allows the surface expansion of the secretory prostate lumen and meanwhile maintains the monolayer and polarized epithelial architecture. Disruption of the epithelial integrity and appearance of multilayer epithelia are early events in prostate adenocarcinoma development. However, the molecular mechanism that ensures the horizontal division in luminal cells remains largely unknown. Here, we generated a genetically engineered mouse model in which E-cadherin, a key component of the adherens junction that serves to connect the lateral plasma membrane of neighboring epithelial cells, was knocked out in the prostate luminal cells. E-cadherin deletion leads to loss of cell polarity and disoriented cell division, which subsequently causes dysregulated cell proliferation and strongly predisposes mice for prostate tumorigenesis. Importantly, we revealed that E-cadherin acts as an anchor to recruit cell polarity protein SCRIB and spindle positioning determinant LGN to the lateral cell membrane, thereby ensure a proper alignment of the cell division plane. All these findings uncover a novel mechanism by which E-cadherin links cell polarity and spindle orientation to keep prostate epithelial integrity and prevent carcinogenesis.

Role of Stromal Paracrine Signals in Proliferative Diseases of the Aging Human Prostate

Androgens are essential for the development, differentiation, growth, and function of the prostate through epithelial–stromal interactions. However, androgen concentrations in the hypertrophic human prostate decrease significantly with age, suggesting an inverse correlation between androgen levels and proliferative diseases of the aging prostate. In elderly males, age- and/or androgen-related stromal remodeling is spontaneously induced, i.e., increased fibroblast and myofibroblast numbers, but decreased smooth muscle cell numbers in the prostatic stroma. These fibroblasts produce not only growth factors, cytokines, and extracellular matrix proteins, but also microRNAs as stromal paracrine signals that stimulate prostate epithelial cell proliferation. Surgical or chemical castration is the standard systemic therapy for patients with advanced prostate cancer. Androgen deprivation therapy induces temporary remission, but the majority of patients eventually progress to castration-resistant prostate cancer, which is associated with a high mortality rate. Androgen deprivation therapy-induced stromal remodeling may be involved in the development and progression of castration-resistant prostate cancer. In the tumor microenvironment, activated fibroblasts stimulating prostate cancer cell proliferation are called carcinoma-associated fibroblasts. In this review, we summarize the role of stromal paracrine signals in proliferative diseases of the aging human prostate and discuss the potential clinical applications of carcinoma-associated fibroblast-derived exosomal microRNAs as promising biomarkers.

Crosstalk between the Androgen Receptor and PPAR Gamma Signaling Pathways in the Prostate

Nuclear receptors are a superfamily of ligand-activated transcription factors that play critical roles in the regulation of normal biological processes and several disease states. Of the nuclear receptors expressed within the prostate, the androgen receptor (AR) promotes the differentiation of prostatic epithelial cells and stimulates production of enzymes needed for liquefaction of semen. Multiple forms of AR also promote the growth of both early and late stage prostate cancers. As a result, drugs that target the AR signaling pathway are routinely used to treat patients with advanced forms of prostate cancer. Data also suggest that a second member of the nuclear receptor superfamily, the peroxisome proliferator activated receptor gamma (PPARγ), is a tumor suppressor that regulates growth of normal prostate and prostate cancers. Recent studies indicate there is a bidirectional interaction between AR and PPARγ, with each receptor influencing the expression and/or activity of the other within prostatic tissues. In this review, we examine how AR and PPARγ each regulate the growth and development of normal prostatic epithelial cells and prostate cancers. We also discuss interactions between the AR and PPARγ signaling pathways and how those interactions may influence prostate biology.

The expression and functional activities of smooth muscle myosin and non-muscle myosin isoforms in rat prostate

Benign prostatic hyperplasia (BPH) is mainly caused by increased prostatic smooth muscle (SM) tone and volume. SM myosin (SMM) and non-muscle myosin (NMM) play important roles in mediating SM tone and cell proliferation, but these molecules have been less studied in the prostate. Rat prostate and cultured primary human prostate SM and epithelial cells were utilized. In vitro organ bath studies were performed to explore contractility of rat prostate. SMM isoforms, including SM myosin heavy chain (MHC) isoforms (SM1/2 and SM-A/B) and myosin light chain 17 isoforms (LC_17a/b ), and isoform ratios were determined via competitive RT-PCR. SM MHC and NM MHC isoforms (NMMHC-A, NMMHC-B and NMMHC-C) were further analysed via Western blotting and immunofluorescence microscopy. Prostatic SM generated significant force induced by phenylephrine with an intermediate tonicity between phasic bladder and tonic aorta type contractility. Correlating with this kind of intermediate tonicity, rat prostate mainly expressed LC_17a and SM1 but with relatively equal expression of SM-A/SM-B at the mRNA level. Meanwhile, isoforms of NMMHC-A, B, C were also abundantly present in rat prostate with SMM present only in the stroma, while NMMHC-A, B, C were present both in the stroma and endothelial. Additionally, the SMM selective inhibitor blebbistatin could potently relax phenylephrine pre-contracted prostate SM. In conclusion, our novel data demonstrated the expression and functional activities of SMM and NMM isoforms in the rat prostate. It is suggested that the isoforms of SMM and NMM could play important roles in BPH development and bladder outlet obstruction.

Prognostic and functional role of subtype-specific tumor-stroma interaction in breast cancer

None of the clinically relevant gene expression signatures available for breast cancer were specifically developed to capture the influence of the microenvironment on tumor cells. Here, we attempted to build subtype‐specific signatures derived from an in vitro model reproducing tumor cell modifications after interaction with activated or normal stromal cells. Gene expression signatures derived from HER2+, luminal, and basal breast cancer cell lines (treated by normal fibroblasts or cancer‐associated fibroblasts conditioned media) were evaluated in clinical tumors by in silico analysis on published gene expression profiles (GEPs). Patients were classified as microenvironment‐positive (μENV+ve), that is, with tumors showing molecular profiles suggesting activation by the stroma, or microenvironment‐negative (μENV−ve) based on correlation of their tumors' GEP with the respective subtype‐specific signature. Patients with estrogen receptor alpha (ER)+/HER2−/μENV+ve tumors were characterized by 2.5‐fold higher risk of developing distant metastases (HR = 2.546; 95% CI: 1.751–3.701, P = 9.84E‐07), while μENV status did not affect, or only suggested the risk of distant metastases, in women with HER2+ (HR = 1.541; 95% CI: 0.788–3.012, P = 0.206) or ER‐/HER2− tumors (HR = 1.894; 95% CI: 0.938–3.824; P = 0.0747), respectively. In ER+/HER2− tumors, the μENV status remained significantly associated with metastatic progression (HR = 2.098; CI: 1.214–3.624; P = 0.00791) in multivariable analysis including size, age, and Genomic Grade Index. Validity of our in vitro model was also supported by in vitro biological endpoints such as cell growth (MTT assay) and migration/invasion (Transwell assay). In vitro‐derived gene signatures tracing the bidirectional interaction with cancer activated fibroblasts are subtype‐specific and add independent prognostic information to classical prognostic variables in women with ER+/HER2− tumors.

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.

Exosomes from the tumor microenvironment as reciprocal regulators that enhance prostate cancer progression

Distant organ metastasis of prostate cancer is a puzzle, and various theories have successively arisen to explain the mechanism of lethal cancer progression. While perhaps agreeable to many cancer biologists, the very statement of "seed and soil" proposed by Stephan Paget in 1881 is arguably still the major statement for organ-specific cancer metastasis. Since recent studies showed important correlations of regulation of cancer cells and the microenvironment, exosomes from cancer and stromal cells seem to create another important niche for metastasis. Stromal cells pretreated with exosomes from metastatic cancer cells increase the potential of change stromal cells. The poorly metastatic cancer cells could also enhance malignancy through transfer of proteins, microribonucleic acid and messenger ribonucleic acid to recipient cancer cells. Herein, we reviewed extracellular exosomes as a factor involved in cross-talk between stromal and prostate cancer epithelial cells.

In touch with your feminine side: how oestrogen metabolism impacts prostate cancer

Prostate cancer is the primary cancer in males, with increasing global incidence rates making this malignancy a significant healthcare burden. Androgens not only promote normal prostate maturity but also influence the development and progression of prostate cancer. Intriguingly, evidence now suggests endogenous and exogenous oestrogens, in the form of phytoestrogens, may be equally as relevant as androgens in prostate cancer growth. The prostate gland has the molecular mechanisms, catalysed by steroid sulphatase (STS), to unconjugate and utilise circulating oestrogens. Furthermore, prostate tissue also expresses enzymes essential for local oestrogen metabolism, including aromatase (CYP19A1) and 3β- and 17β-hydroxysteroid dehydrogenases. Increased expression of these enzymes in malignant prostate tissue compared with normal prostate indicates that oestrogen synthesis is favoured in malignancy and thus may influence tumour progression. In contrast to previous reviews, here we comprehensively explore the epidemiological and scientific evidence on how oestrogens impact prostate cancer, particularly focusing on pre-receptor oestrogen metabolism and subsequent molecular action. We analyse how molecular mechanisms and metabolic pathways involved in androgen and oestrogen synthesis intertwine to alter prostate tissue. Furthermore, we speculate on whether oestrogen receptor status in the prostate affects progression of this malignancy.

Expression of androgen receptor and cyclooxygenase-2 in the vesicular glands of castrated and intact goat

This study was conducted to demonstrate the effect of castration on the structure of vesicular glands of the Egyptian Nubian (Zaraibi) goat. Vesicular glands of castrated (n=4) and intact (n=6) goat were used for histological and immunohistochemical evaluations. In this study, we report the difference in cell specific expression of androgen receptor (AR) and cyclooxygenase-2 (COX-2) in the vesicular glands of castrated and intact goats. In both castrated and intact goats, the present study revealed no immunopositive cells for AR or COX-2 in the fibromuscular stroma meanwhile, AR and COX-2 containing immunoreactive cells were restricted only to the epithelium of the secretory acini of the vesicular gland. Such finding suggests androgen and COX-2 as important regulators for the growth and secretory activity of epithelial cells in the vesicular gland of goats. Overall, the vesicular gland of castrated goats showed significantly (P<0.05) lower AR and COX-2 immuno-expression than intact goats indicating that both AR and COX-2 are androgen dependent.

Novel In Vivo model for combinatorial fluorescence labeling in mouse prostate

BACKGROUND

The epithelial layer of prostate glands contains several types of cells, including luminal and basal cells. Yet there is paucity of animal models to study the cellular origin of normal or neoplastic development in the prostate to facilitate the treatment of heterogenous prostate diseases by targeting individual cell lineages.

METHODS

We developed a mouse model that expresses different types of fluorescent proteins (XFPs) specifically in prostatic cells. Using an in vivo stochastic fluorescent protein combinatorial strategy, XFP signals were expressed specifically in prostate of Protein Kinase D1 (PKD1) knock-out, K-Ras(G) (12) (D) knock-in, and Phosphatase and tensin homolog (PTEN) and PKD1 double knock-out mice under the control of PB-Cre promoter.

RESULTS

In vivo XFP signals were observed in prostate of PKD1 knock-out, K-Ras(G) (12) (D) knock-in, and PTEN PKD1 double knock-out mice, which developed normal, hyperplastic, and neoplastic prostate, respectively. The patchy expression pattern of XFPs in neoplasia tissue indicated the clonal origin of cancer cells in the prostate.

CONCLUSIONS

The transgenic mouse models demonstrate combinatorial fluorescent protein expression in normal and cancerous prostatic tissues. This novel prostate-specific fluorescent labeled mouse model, which we named Prorainbow, could be useful in studying benign and malignant pathology of prostate.

RANK-mediated signaling network and cancer metastasis

Cancer metastasis is highly inefficient and complex. Common features of metastatic cancer cells have been observed using cancer cell lines and genetically reconstituted mouse and human tumor xenograft models. These include cancer cell interaction with the tumor microenvironment and the ability of cancer cells to sense extracellular stimuli and adapt to adverse growth conditions. This review summarizes the coordinated response of cancer cells to soluble growth factors, such as RANKL, by a unique feed forward mechanism employing coordinated upregulation of RANKL and c-Met with downregulation of androgen receptor. The RANK-mediated signal network was found to drive epithelial to mesenchymal transition in prostate cancer cells, promote osteomimicry and the ability of prostate cancer cells to assume stem cell and neuroendocrine phenotypes, and confer the ability of prostate cancer cells to home to bone. Prostate cancer cells with activated RANK-mediated signal network were observed to recruit and even transform the non-tumorigenic prostate cancer cells to participate in bone and soft tissue colonization. The coordinated regulation of cancer cell invasion and metastasis by the feed forward mechanism involving RANKL, c-Met, transcription factors, and VEGF-neuropilin could offer new therapeutic opportunities to target prostate cancer bone and soft tissue metastases.

A human fetal prostate xenograft model of developmental estrogenization

Prostate cancer is a common disease in older men. Rodent models have demonstrated that an early and later-life exposure to estrogen can lead to cancerous lesions and implicated hormonal dysregulation as an avenue for developing future prostate neoplasia. This study utilizes a human fetal prostate xenograft model to study the role of estrogen in the progression of human disease. Histopathological lesions were assessed in 7-, 30-, 90-, 200-, and 400-day human prostate xenografts. Gene expression for cell cycle, tumor suppressors, and apoptosis-related genes (ie, CDKN1A, CASP9, ESR2, PTEN, and TP53) was performed for 200-day estrogen-treated xenografts. Glandular hyperplasia was observed in xenografts given both an initial and secondary exposure to estradiol in both 200- and 400-day xenografts. Persistent estrogenic effects were verified using immunohistochemical markers for cytokeratin 10, p63, and estrogen receptor α. This model provides data on the histopathological state of the human prostate following estrogenic treatment, which can be utilized in understanding the complicated pathology associated with prostatic disease and early and later-life estrogenic exposures.

Stromal androgen receptor in prostate development and cancer

The androgen receptor (AR) in stromal cells contributes significantly to the development and growth of prostate during fetal stages as well as during prostate carcinogenesis and cancer progression. During prostate development, stromal AR induces and promotes epithelial cell growth, as observed from tissue recombinant and mouse knockout studies. During prostate carcinogenesis and progression, the stromal cells begin to lose AR expression as early as at the stage of high-grade prostatic intraepithelial neoplasia. The extent of loss of stromal AR is directly proportional to the degree of differentiation (Gleason grade) and progression of prostate cancer (PCa). Co-culture studies suggested that stromal AR inhibits the growth of malignant epithelial cells, possibly through expression of certain paracrine factors in the presence of androgens. This functional reversal of stromal AR, from growth promotion during fetal prostate development to mediating certain growth-inhibiting effects in cancer, explains to some extent the reason that loss of AR expression in stromal cells may be crucial for development of resistance to androgen ablation therapy for PCa. From a translational perspective, it generates the need to re-examine the current therapeutic options and opens a fundamental new direction for therapeutic interventions, especially in advanced PCa.

Differentiation of human umbilical cord mesenchymal stem cells into prostate-like epithelial cells in vivo

Although human umbilical cord mesenchymal stem cells (hUC-MSCs) have been identified as a new source of MSCs for potential application in regenerative medicine, their full potential of differentiation has not been determined. In particular, whether they have the capability to differentiate into epithelial cells of endodermal origin such as the prostate epithelial cells is unknown. Here we report that when hUC-MSCs were combined with rat urogenital sinus stromal cells (rUGSSs) and transplanted into the renal capsule in vivo, they could differentiate into prostate epithelial-like cells that could be verified by prostate epithelial cell-specific markers including the prostate specific antigen. The prostatic glandular structures formed in vivo displayed similar cellular architecture with lumens and branching features as seen for a normal prostate. In addition, the human origin of the hUC-MSCs was confirmed by immunocytochemistry for human nuclear antigen. These findings together indicate that hUC-MSCs have the capability to differentiate into epithelial-like cells that are normally derived from the endoderm, implicating their potential applications in tissue repair and regeneration of many endoderm-derived internal organs.

Role of the adjacent stroma cells in prostate cancer development and progression: synergy between TGF-β and IGF signaling

This review postulates the role of transforming growth factor-beta (TGF-β) and insulin-like growth factor (IGF-I/IGF-II) signaling in stromal cells during prostate carcinogenesis and progression. It is known that stromal cells have a reciprocal relationship to the adjacent epithelial cells in the maintenance of structural and functional integrity of the prostate. An interaction between TGF-β and IGF signaling occupies a central part in this stromal-epithelial interaction. An increase in TGF-β and IGF signaling will set off the imbalance of this relationship and will lead to cancer development. A continuous input from TGF-β and IGF in the tumor microenvironment will result in cancer progression. Understanding of these events can help prevention, diagnosis, and therapy of prostate cancer.

Androgens and mammalian male reproductive tract development

One of the main functions of androgen is in the sexually dimorphic development of the male reproductive tissues. During embryogenesis, androgen determines the morphogenesis of male specific organs, such as the epididymis, seminal vesicle, prostate and penis. Despite the critical function of androgens in masculinization, the downstream molecular mechanisms of androgen signaling are poorly understood. Tissue recombination experiments and tissue specific androgen receptor (AR) knockout mouse studies have revealed epithelial or mesenchymal specific androgen-AR signaling functions. These findings also indicate that epithelial-mesenchymal interactions are a key feature of AR specific activity, and paracrine growth factor action may mediate some of the effects of androgens. This review focuses on mouse models showing the interactions of androgen and growth factor pathways that promote the sexual differentiation of reproductive organs. Recent studies investigating context dependent AR target genes are also discussed. This article is part of a Special Issue entitled: Nuclear receptors in animal development.

Evidence of TGF-β1 mediated epithelial-mesenchymal transition in immortalized benign prostatic hyperplasia cells

Expression of epithelial-mesenchymal transition (EMT) markers has been detected clinically in benign prostatic hyperplasia (BPH) tissues. To understand the molecular basis, we investigated the role of stromal microenvironment in the progression of EMT in BPH cells. First, we used cell culture supernatant from normal prostate stromal WPMY-1 cells to provide supernatant-conditioned medium (WSCM) to culture the BPH-1 cell line. Then, the morphological changes and migratory capacity were detected in BPH-1 cells. The expression of EMT markers was examined in BPH-1 cells by Western blot and immunofluorescent analysis. Finally, to investigate the role of transforming growth factor beta 1 (TGF-β1) in this process, the WSCM-cultured cells were treated with monoclonal antibody against TGF-β1 to study its effect on EMT. We found that the morphology of BPH-1 cells changed to a spindle-like shape after cultured in WSCM, and the levels of E-cadherin and cytokeratin 5/8 (CK5/8) were significantly lower than the cells cultured in ordinary medium. These BPH-1 cells were also tested positive for mesenchymal markers vimentin and a-smooth muscle actin (SMA) as well as Snail. We also found WSCM can increase the migratory capacity of BPH-1 cells. In addition, when they were treated with anti-TGF-β1, upregulation of E-cadherin and CK5/8 levels was observed but no expression of vimentin, alpha-SMA or Snail was detected. Furthermore, phosphorylated-Smad3 expression in WSCM-cultured BPH-1 cells was also suppressed by anti-TGF-β1 treatment. Our results demonstrated that stromal cell supernatant was able to induce EMT in BPH-1 cells, possibly through secreting TGF-β1 to activate Smad signaling. Our results suggest novel molecular targets for clinical treatment of BPH by modification of stromal microenvironment through inhibiting TGF-β1/Smad expression.

Interaction of tumour cells with their microenvironment: ion channels and cell adhesion molecules. A focus on pancreatic cancer

Cancer must be viewed as a 'tissue', constituted of both transformed cells and a heterogeneous microenvironment, the 'tumour microenvironment' (TME). The TME undergoes a complex remodelling during the course of multistep tumourigenesis, hence strongly contributing to tumour progression. Ion channels and transporters (ICTs), being expressed on both tumour cells and in the different cellular components of the TME, are in a strategic position to sense and mediate signals arising from the TME. Often, this transmission is mediated by integrin adhesion receptors, which are the main cellular receptors capable of mediating cell-to-cell and cell-to-matrix bidirectional signalling. Integrins can often operate in conjunction with ICT because they can behave as functional partners of ICT proteins. The role of integrin receptors in the crosstalk between tumour cells and the TME is particularly relevant in the context of pancreatic cancer (PC), characterized by an overwhelming TME which actively contributes to therapy resistance. We discuss the possibility that this occurs through integrins and ICTs, which could be exploited as targets to overcome chemoresistance in PC.

Maturation of the developing human fetal prostate in a rodent xenograft model

BACKGROUND

Prostate cancer is the most commonly diagnosed nonskin cancer in men. The etiology of prostate cancer is unknown, although both animal and epidemiologic data suggest that early life exposures to various toxicants, may impact DNA methylation status during development, playing an important role.

METHODS

We have developed a xenograft model to characterize the growth and differentiation of human fetal prostate implants (gestational age 12-24 weeks) that can provide new data on the potential role of early life stressors on prostate cancer. The expression of key immunohistochemical markers responsible for prostate maturation was evaluated, including p63, cytokeratin 18, α-smooth muscle actin, vimentin, caldesmon, Ki-67, prostate-specific antigen, estrogen receptor-α, and androgen receptor. Xenografts were separated into epithelial and stromal compartments using laser capture microdissection (LCM), and the DNA methylation status was assessed in >480,000 CpG sites throughout the genome.

RESULTS

Xenografts demonstrated growth and maturation throughout the 200 days of post-implantation evaluation. DNA methylation profiles of laser capture microdissected tissue demonstrated tissue-specific markers clustered by their location in either the epithelium or stroma of human prostate tissue. Differential methylated promoter region CpG-associated gene analysis revealed significantly more stromal than epithelial DNA methylation in the 30- and 90-day xenografts. Functional classification analysis identified CpG-related gene clusters in methylated epithelial and stromal human xenografts.

CONCLUSION

This study of human fetal prostate tissue establishes a xenograft model that demonstrates dynamic growth and maturation, allowing for future mechanistic studies of the developmental origins of later life proliferative prostate disease.

A novel model of urinary tract differentiation, tissue regeneration, and disease: reprogramming human prostate and bladder cells into induced pluripotent stem cells

BACKGROUND

Primary culture and animal and cell-line models of prostate and bladder development have limitations in describing human biology, and novel strategies that describe the full spectrum of differentiation from foetal through to ageing tissue are required. Recent advances in biology demonstrate that direct reprogramming of somatic cells into pluripotent embryonic stem cell (ESC)-like cells is possible. These cells, termed induced pluripotent stem cells (iPSCs), could theoretically generate adult prostate and bladder tissue, providing an alternative strategy to study differentiation.

OBJECTIVE

To generate human iPSCs derived from normal, ageing, human prostate (Pro-iPSC), and urinary tract (UT-iPSC) tissue and to assess their capacity for lineage-directed differentiation.

DESIGN, SETTING, AND PARTICIPANTS

Prostate and urinary tract stroma were transduced with POU class 5 homeobox 1 (POU5F1; formerly OCT4), SRY (sex determining region Y)-box 2 (SOX2), Kruppel-like factor 4 (gut) (KLF4), and v-myc myelocytomatosis viral oncogene homolog (avian) (MYC, formerly C-MYC) genes to generate iPSCs.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The potential for differentiation into prostate and bladder lineages was compared with classical skin-derived iPSCs. The student t test was used.

RESULTS AND LIMITATIONS

Successful reprogramming of prostate tissue into Pro-iPSCs and bladder and ureter into UT-iPSCs was demonstrated by characteristic ESC morphology, marker expression, and functional pluripotency in generating all three germ-layer lineages. In contrast to conventional skin-derived iPSCs, Pro-iPSCs showed a vastly increased ability to generate prostate epithelial-specific differentiation, as characterised by androgen receptor and prostate-specific antigen induction. Similarly, UT-iPSCs were shown to be more efficient than skin-derived iPSCs in undergoing bladder differentiation as demonstrated by expression of urothelial-specific markers: uroplakins, claudins, and cytokeratin; and stromal smooth muscle markers: α-smooth-muscle actin, calponin, and desmin. These disparities are likely to represent epigenetic differences between individual iPSC lines and highlight the importance of organ-specific iPSCs for tissue-specific studies.

CONCLUSIONS

IPSCs provide an exciting new model to characterise mechanisms regulating prostate and bladder differentiation and to develop novel approaches to disease modelling. Regeneration of bladder cells also provides an exceptional opportunity for translational tissue engineering.

Zeranol induces deleterious effects on the testes and the prostate gland of mature rats

BACKGROUND

Endocrine disrupters have been shown to affect the male and female reproductive systems and to alter potential fertility.

OBJECTIVES

This study was conducted to evaluate the effect of a continuous-release pellet containing 12 mg of zeranol for 30 days on the testes and the prostate gland of mature male rats.

RESULTS

Zeranol treatment induced significant decrease of the testes and the prostate gland weights which were associated with a remarkable atrophy of the testicular seminiferous tubules and prominent regression of the glandular compartment of the prostate gland. However, zeranol treatment increased the thickness of the periductal layer of stromal cells of the prostate gland from a thin layer that express intense immunostaining of SM-actin and mild vimentin to a thicker layer of cells that exhibited intense immunostaining for both SM-actin and vimentin.

CONCLUSION

These findings suggest that zeranol-induced changes to the prostate gland could result from either a direct effect of zeranol on the prostate gland or an indirect effect by interfering with testosterone production through disruption of testicular function.

From Reductionism to Holism: Systems-oriented Approaches in Cancer Research

Somatic mutation theory of cancer has directed cancer research during the last century. A deluge of information on cellular, molecular, and genetic behavior was uncovered, but so was a mind-numbing complexity that still challenges research and concepts, and expectations in the war on cancer have by and large not been fulfilled. A change of paradigm beyond reductionism has been called for, especially as research ubiquitously points at the importance of tissue, microenvironment, extracellular matrix, embryonic and morphogenetic fields, and fields of tissue maintenance and organization in the processes of carcinogenesis, cancer control, and cancer progression, as well as in the control of cellular and genetic behavior. Holistic, organismic systems concepts open new perspectives for cancer research and treatment, as well as general biological understanding.

17α-androstenediol-mediated oncophagy of tumor cells by different mechanisms is determined by the target tumor

Δ5-androstene-3β,17α-diol (17α-AED) mediates oncophagy of human myeloid, glioma, and breast tumor cells by apoptotic- and autophagic-programmed cell death pathways, whereas the 17β-epimer does not. In hematologically derived myeloid tumor cells, 17α-AED induced apoptosis, as determined by TUNEL staining, caspase, PARP activation, and electron microscopy. In contrast, 17α-AED treatment of glioma cells of neuroectodermal lineaged induced autophagy, evident by the presence of acidic vesicular organelles, LC3 processing, and upregulation of beclin-1. Proliferation inhibition studies on primary and established glioma cells demonstrated that the IC-50 of the steroid is ∼15 μM. In the case of breast cancer cells, the bioactivity of 17α-AED is independent of the expression of estrogen or androgen receptors. Collectively, oncophagy is induced by 17α-AED treatment in human tumor cells and proceeds by the induction of either autophagy or apoptosis. The neoplastic cell determines which oncophagic pathway is utilized.

Reversal of the low-affinity neurotrophin receptor stromal-epithelial expression pattern between benign and malignant human prostate

Reduced expression of the low-affinity p75 neurotrophin receptor (p75(NTR)) occurs in prostate epithelial cells during malignant transformation. Recent studies indicating that the p75(NTR) can transduce signals that induce apoptosis suggest that diminished p75(NTR) in transformed prostate cells may contribute to immortalization. Mutations in the transmembrane domain of the p75(NTR) gene have been associated with decreased p75(NTR) protein expression and may block the ability of the p75(NTR) to induce apoptosis. Therefore, we used Western blot to analyze prostate cancer (PC) cell lines for p75(NTR) protein expression and gene single strand conformation polymorphism (SSCP) analysis and direct DNA sequencing to analyze mutations in the transmembrane domain of the p75(NTR). p75(NTR) Protein was present in all cell lines, and mutations in the p75(NTR) gene were not detected in cDNA derived from any cell line. To define the expression pattern of p75(NTR) in PCs in vivo, we used immunohistochemical techniques to examine tissue specimens from 20 benign, 19 malignant primary, and 14 metastatic prostate specimens. In benign prostate tissues, expression of p75(NTR) was universally detected in basal cells but not in secretory epithelial or stromal cells. In both primary and metastatic PC tissues, p75(NTR) immunoreactivity could not be detected in malignant prostate epithelial cells. However, in contrast to the benign prostate, p75(NTR) protein was expressed in stromal cells surrounding malignant epithelial cells. Stromal p75(NTR) expression was present in 84% (16 of 19) primary and in 86% (12 of 14) metastatic specimens. These data show that in the benign prostate p75(NTR) protein is expressed by basal cells and not stromal cells whereas in malignant prostate p75(NTR) protein is expressed by stromal cells but not prostatic carcinoma cells. Reversal of the p75(NTR) stromal-epithelial pattern of expression between benign and malignant prostate suggests that p75(NTR) may contribute to the development and maintenance of prostate cancer.

JNK and PTEN cooperatively control the development of invasive adenocarcinoma of the prostate

The c-Jun NH(2)-terminal kinase (JNK) signal transduction pathway is implicated in cancer, but the role of JNK in tumorigenesis is poorly understood. Here, we demonstrate that the JNK signaling pathway reduces the development of invasive adenocarcinoma in the phosphatase and tensin homolog (Pten) conditional deletion model of prostate cancer. Mice with JNK deficiency in the prostate epithelium (ΔJnk ΔPten mice) develop androgen-independent metastatic prostate cancer more rapidly than control (ΔPten) mice. Similarly, prevention of JNK activation in the prostate epithelium (ΔMkk4 ΔMkk7 ΔPten mice) causes rapid development of invasive adenocarcinoma. We found that JNK signaling defects cause an androgen-independent expansion of the immature progenitor cell population in the primary tumor. The JNK-deficient progenitor cells display increased proliferation and tumorigenic potential compared with progenitor cells from control prostate tumors. These data demonstrate that the JNK and PTEN signaling pathways can cooperate to regulate the progression of prostate neoplasia to invasive adenocarcinoma.

Breast epithelial tissue morphology is affected in 3D cultures by species-specific collagen-based extracellular matrix

Collagen-based gels have been widely used to determine the factors that regulate branching morphogenesis in the mammary gland. The patterns of biomechanical gradients and collagen reorganization influence the shape and orientation of epithelial structures in three-dimensional (3D) conditions. We explored in greater detail whether collagen type I fibers with distinct biomechanical and fiber-assembling properties, isolated from either bovine or rat tail tendon, differentially affected the epithelial phenotype in a tissue culture model of the human breast. Rat tail collagen fibers were densely packed into significantly longer and thicker bundles compared to those of the bovine type (average fascicle length 7.35 and 2.29 μm, respectively; p = 0.0001), indicating increased fiber alignment and biomechanical enablement in the former. MCF10A epithelial cells formed elaborated branched tubular structures in bovine but only nonbranched ducts and acini in rat tail collagen matrices. Ductal branching in bovine collagen was associated with interactions between neighboring structures mediated through packed collagen fibers; these fiber-mediated interactions were absent in rat tail collagen gels. Normal breast fibroblasts increased the final size and number of ducts only in rat tail collagen gels while not affecting branching. Our results suggest that the species of origin of collagen used in organotypic cultures may influence epithelial differentiation into alveolar or ductal structures and the patterns of epithelial branching. These observations underscore the importance of considering the species of origin and fiber alignment properties of collagen when engineering branching organs in 3D matrices and interpreting their role in the tissue phenotype.

QTL region-specific microarrays reveal differential expression of positional candidate genes of signaling pathways associated with the liability for the inverted teat defect

The inverted teat defect is the most common disorder of the mammary complex in pigs. It is characterized by the failure of teats to protrude from the udder surface, preventing normal milk flow and thus limiting the rearing capacity and increasing the risk of mastitis. The inverted teat defect is a liability trait with a complex mode of inheritance. We previously identified QTL for inverted teats. As a complementary approach that integrates map-based efforts to identify candidate genes for the inverted teat defect with function-driven expression analysis, application-specific microarrays were constructed that cover 1525 transcripts mapping in QTL regions on pig chromosomes 2, 3, 4, 6 and 11. About 950 transcripts were expressed in epithelial and mesenchymal teat tissue. The expression of three categories of teats was compared: normal teats of both non-affected and affected animals and inverted teats of affected animals. In epithelium and mesenchyme, 62 and 24 genes respectively were significantly differentially expressed (DE). The majority of biofunctions to which a significant number of DE genes were assigned are related to the following: (1) cell maintenance, proliferation, differentiation and replacement; (2) organismal, organ and tissue development; or (3) genetic information and nucleic acid processing. Moreover, the DE genes belong almost exclusively to canonical pathways related to signaling rather than metabolic pathways. This is in line with findings obtained by genome-wide catalogue microarrays. This study adds another piece to the puzzle of the etiology of inverted teats by indicating that causal genetic variation leading to the disorder is likely among the genes encoding for members of the signaling cascades of growth factors.

A local paracrine and endocrine network involving TGFβ, Cox-2, ROS, and estrogen receptor β influences reactive stromal cell regulation of prostate cancer cell motility

The tumor microenvironment plays a critical role in supporting cancer cells particularly as they disengage from limitations on their growth and motility imposed by surrounding nonreactive stromal cells. We show here that stromal-derived androgenic precursors are metabolized by DU145 human prostate cancer (PCa) cells to generate ligands for estrogen receptor-β, which act to limit their motility through transcriptional regulation of E-cadherin. Although primary human PCa-associated fibroblasts and the human WPMY-1-reactive prostate stromal cell line maintain this inherent estrogen receptor (ER)β-dependent motility inhibitor activity, they are subverted by TGF-β1 pro-oxidant signals derived from cocultured DU145 PCa cells. Specifically, stromal-produced H(2)O(2), which requires Cox-2, acts as a second paracrine factor to inhibit ERβ activity in adjacent DU145 cells. Chromatin immunoprecipitation analysis reveals that ERβ recruitment to the E-cadherin promoter is inhibited when H(2)O(2) is present. Both neutralization of H(2)O(2) with catalase and prevention of its production by silencing Cox-2 expression in stromal cells restore the motility-suppression activity of stromal-derived ERβ ligand precursors. These data suggest that reactive stromal cells may still have a capacity to limit cancer cell motility through a local endocrine network but must be protected from pro-oxidant signals triggered by cancer cell-derived TGF-β1 to exhibit this cancer-suppressive function.

Gene expression analysis of mammary tissue during fetal bud formation and growth in two pig breeds--indications of prenatal initiation of postnatal phenotypic differences

BACKGROUND

The mammary gland is key to all mammal species; in particular in multiparous species like pigs the number and the shape of functional mammary gland complexes are major determinants of fitness. Accordingly, we aimed to catalog the genes relevant to mammogenesis in pigs. Moreover, we aimed to address the hypothesis that the extent and timing of proliferation, differentiation, and maturation processes during prenatal development contribute to postnatal numerical, morphological and functional properties of the mammary gland. Thus we focused on differentially expressed genes and networks relevant to mammary complex development in two breeds that are subject to different selection pressure on number, shape and function of teats and show largely different prevalence of non-functional inverted teats. The expression patterns of fetal mammary complexes obtained at 63 and 91 days post conception (dpc) from German Landrace (GL) and Pietrain (PI) were analyzed by Affymetrix GeneChip Porcine Genome Arrays.

RESULTS

The expression of 11,731 probe sets was analysed between the two stages within and among breeds. The analysis showed the largest distinction of samples of the breed GL at 63 dpc from all other samples. According to Ingenuity Pathways Analysis transcripts with abundance at the four comparisons made (GL63-GL91, PI63-PI93, GL63-PI63 and GL91-PI91) were predominantly assigned to biofunctions relevant to 'cell maintenance, proliferation, differentiation and replacement', 'organismal, organ and tissue development' and 'genetic information and nucleic acid processing'. Moreover, these transcripts almost exclusively belong to canonical pathways related to signaling rather than metabolic pathways. The accumulation of transcripts that are up-regulated in GL compared to PI indicate a higher proliferating activity in GL, whereas processes related to differentiation, maturation and maintenance of cells are more prominent in PI. Differential expression was validated by quantitative RT-PCR of five genes (GAB1, MAPK9, PIK3C2B, PIK3C3 and PRKCH) that are involved in several relevant signaling pathways.

CONCLUSIONS

The results indicate that mammary complex development in PI precedes GL. The differential expression between the two breeds at fetal stages likely reflects the prenatal initiation of postnatal phenotypes concerning the number and shape as well as functionality of teats.

Effects of castration on the expression of the NGF and TrkA in the vas deferens and accessory male genital glands of the rat

Nerve Growth Factor (NGF) is a member of the neurotrophin family. Neurotrophins exert their effects by binding to corresponding receptors, which are formed by the tyrosine protein kinases TrkA, TrkB, and TrkC, and the low affinity p75NTR receptor. The role of neurotrophins in the biology of male genital organs is far from clear. In particular, little is known about the influence of sex hormones on the expression of neurotrophins and their receptors. In the present study, using immunohistochemistry and real time RT-PCR, we investigated the expression of NGF and TrkA in the vas deferens and accessory male genital glands in normal and castrated rats.In normal rats, both NGF- and TrkA-immunoreactivities (IR) were localized in the epithelial layer of the vas deferens. NGF-IR was also found in the stroma and epithelium of the vesicular gland and prostate. TrkA-IR was distributed in the epithelial cells of vesicular and prostate glands. The nerves were weakly immunoreactive in all the examined organs. After castration the immunoreactivities increased. Real-time RT-PCR experiments indicated that NGF and TrkA mRNA levels increased significantly after castration. These results suggest that NGF and TrkA are expressed in the internal male genital organs of the rat and that their expression is downregulated by androgen hormones. We hypothesize NGF and TrkA play a role in the processes that regulate the involution of these organs under conditions of androgen deprivation.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

Bone marrow-derived macrophages are associated with androgen modulated prostate regeneration

BACKGROUND

Recent studies have reported that bone marrow-derived cells (BMDCs) can be cellular components of tissue undergoing remodeling. However, the types of BMDCs that contribute to prostate regeneration are unclear. Elucidating the association between BMDCs and prostate regeneration will help to identify the mechanism responsible for abnormal prostate tissue remodeling in conditions such as benign prostate hyperplasia, proliferative inflammatory atrophy, and prostate cancer.

METHODS

We used a bone marrow transplantation (BMT) technique involving green fluorescent protein (GFP)-expressing bone marrow cells and a murine model of prostate regeneration induced by androgen modulation. Immunophenotypes of recruited GFP-positive cells at days 3, 14, and 28 after regeneration were analyzed in the prostate tissue of mice that had undergone BMT.

RESULTS

During the regenerating process, the most abundant BMDC phenotype was the F4/80-positive macrophage followed by the CD3-positive T lymphocyte. The proportion of all nucleated cells that were F4/80-positive BMDCs was greatest at day 3 after regeneration and was lower at days 14 and 28. By contrast, the proportion of F4/80-positive/GFP-negative cells remained unchanged at days 3, 14, and 28. Macrophage-colony stimulating factor mRNA expression level was the highest in the regenerating prostate. The number of F4/80-positive BMDCs, but not CD3-positive BMDCs, correlated with the proliferative activity of epithelial cells of the regenerating prostate at day 14.

CONCLUSIONS

The observation that bone marrow-derived macrophages are recruited into the prostate where they associate with prostate regeneration suggests that bone marrow-derived macrophages are involved in prostate regeneration.

Dual regulation of breast tubulogenesis using extracellular matrix composition and stromal cells

Epithelial-mesenchymal interactions during embryogenesis are critical in defining the phenotype of tissues and organs. The initial elongation of the mammary bud represents a central morphological event requiring extensive epithelial-mesenchymal crosstalk. The precise mechanism orchestrating this outgrowth is still unknown and mostly animal models have been relied upon to explore this process. Highly tunable three-dimensional (3D) culture models are a complementary approach to address the question of phenotypic determination. Here, we used a 3D in vitro culture to study the roles of stromal cells and extracellular matrix components during mammary tubulogenesis. Fibroblasts, adipocytes, and type I collagen actively participated in this process, whereas reconstituted basement membrane inhibited tubulogenesis by affecting collagen organization. We conclude that biochemical and biomechanical signals mediate the interaction between cells and matrix components and are necessary to induce tubulogenesis in vitro.

Reduced levels of 5-α reductase 2 in adult prostate tissue and implications for BPH therapy

BACKGROUND

5-α reductase 2 (5-AR 2) is a key enzyme that is responsible of proper development of prostate tissue. Inhibition of 5-AR 2 has proven to be efficacious for management of urinary symptoms secondary benign prostatic hyperplasia (BPH). However, some patients are resistant to the therapeutic effects of 5-AR 2 inhibitor. We wished to determine why some benign non-cancerous adult human prostates do not express 5-AR 2, and hypothesized that methylation of 5-AR 2 promoter region correlated with low expression of 5-AR 2 protein.

METHODS

The transition zone of 42 human prostate tissues after radical prostatectomy was used for evaluation. Initially, 21 paraffin embedded samples were used to assess immunoreactivity to 5-AR 2 antibody in non-cancerous BPH samples. In the next 21 samples, fresh frozen prostate transition zone samples without cancer were assessed for immunoreactivity and methylation of the 5-AR 2 promoter using methyl-specific PCR.

RESULTS

We show that 6/21 (29%) of benign human prostate samples did not express the 5-AR 2 protein. Moreover, the promoter region of 5-AR 2 contains a CpG island that is methylated in benign prostate epithelial cells in culture and also in 39% (7/18) human prostate tissues. We show a strong correlation between methylation of the 5-AR 2 promoter region and absence of 5-AR 2 protein expression (P = 0.0025, Fisher's exact test).

CONCLUSIONS

Methylation of 5-AR 2 promoter may account for low or absent expression of 5-AR 2 in some human adult prostate tissues.

Cell autonomous role of PTEN in regulating castration-resistant prostate cancer growth

Alteration of the PTEN/PI3K pathway is associated with late-stage and castrate-resistant prostate cancer (CRPC). However, how PTEN loss is involved in CRPC development is not clear. Here, we show that castration-resistant growth is an intrinsic property of Pten null prostate cancer (CaP) cells, independent of cancer development stage. PTEN loss suppresses androgen-responsive gene expressions by modulating androgen receptor (AR) transcription factor activity. Conditional deletion of Ar in the epithelium promotes the proliferation of Pten null cancer cells, at least in part, by downregulating the androgen-responsive gene Fkbp5 and preventing PHLPP-mediated AKT inhibition. Our findings identify PI3K and AR pathway crosstalk as a mechanism of CRPC development, with potentially important implications for CaP etiology and therapy.

Androgen-induced PSA expression requires not only activation of AR but also endogenous IGF-I or IGF-I/PI3K/Akt signaling in human prostate cancer epithelial cells

BACKGROUND

Prostate cancer (PrCa) risk is positively associated with levels of insulin-like growth factor I (IGF-I) and prostate specific antigen (PSA), both androgen receptor (AR) signaling target genes in PrCa cells. Although activated AR is required for androgen-induction of expression of both genes, effects of the IGF-I signaling pathways on the androgen-induction of PSA have not been studied.

METHODS

Human prostate stromal and epithelial cancer cells were treated alone or in coculture with steroid hormone and/or inhibitors. Gene or protein expression was analyzed by real time RT-PCR or Western blotting of lysates, nuclear extracts, or immunoprecipitated products.

RESULTS

In PrCa epithelial cells, endogenous IGF-I, significantly induced by R1881, was required for R1881-induction of PSA. Increased IGF-I correlated with accumulation of cytoplasmic dephospho β-catenin (CPDP β-catenin), a co-activator of AR signaling. Exogenous IGF-I enhanced R1881-induced PSA and accumulation of CPDP β-catenin in LAPC-4 cells. Functional depletion of IGF-I or IGF-I receptor diminished PSA induction. Induction of IGF-I reached a plateau while PSA consecutively increased. Inhibiting PI3K abolished R1881-induced Akt phosphorylation, CPDP and nuclear β-catenin and nuclear association of AR/β-catenin, consequently abrogating R1881-induced expression of IGF-I and/or PSA.

CONCLUSIONS

By integrating androgen, IGF-I and β-catenin signaling pathways, these data reveal that androgen-induced PSA expression requires activation of AR and endogenous IGF-I or IGF-I/PI3K/Akt signaling, suggesting a positive feedback cycle for increased production of PSA associated with PrCa.

Disruption of reelin signaling alters mammary gland morphogenesis

Reelin signaling is required for appropriate cell migration and ductal patterning during mammary gland morphogenesis. Dab1, an intracellular adaptor protein activated in response to reelin signaling, is expressed in the developing mammary bud and in luminal epithelial cells in the adult gland. Reelin protein is expressed in a complementary pattern, first in the epithelium overlying the mammary bud during embryogenesis and then in the myoepithelium and periductal stroma in the adult. Deletion in mouse of either reelin or Dab1 induced alterations in the development of the ductal network, including significant retardation in ductal elongation, decreased terminal branching, and thickening and disorganization of the luminal wall. At later stages, some mutant glands overcame these early delays, but went on to exhibit enlarged and chaotic ductal morphologies and decreased terminal branching: these phenotypes are suggestive of a role for reelin in spatial patterning or structural organization of the mammary epithelium. Isolated mammary epithelial cells exhibited decreased migration in response to exogenous reelin in vitro, a response that required Dab1. These observations highlight a role for reelin signaling in the directed migration of mammary epithelial cells driving ductal elongation into the mammary fat pad and provide the first evidence that reelin signaling may be crucial for regulating the migration and organization of non-neural tissues.

Atypical fetal prostate development is associated with ipsilateral hypoplasia of the wolffian ducts in the ACI rat

For over a half century, the ACI (August x Copenhagen) rat has been a primary model for studying renal agenesis and ipsilateral hypoplasia (IHP) of the Wolffian-derived structures (WDS). Because the ACI rat is also used as a model for prostate research, it is important to examine the relationship of IHP and urogenital sinus (UGS) development. The prostate is dependent on androgens for proper growth and differentiation. Alteration in androgen production and/or delivery to the UGS has the potential to perturbate normal development. In this study, we investigate whether the ipsilateral loss of the WDS is associated with altered prostate development. Digital images of serial-sectioned fetal ACI rat UGS were used to create three-dimensional (3-D) surface-rendered models of the developing prostate, seminal vesicle, vas deferens, and utricle on gestational day 21. The number and volume of prostate ducts developing from the UGS were calculated from the 3-D model data. Animals exhibiting IHP had a significant decrease in total fetal prostate volume (40%; P < 0.005) with significant regional specific differences when compared with normal male ACI rats. Anatomical and histological differences in the utricle, abnormal histology of the ipsilateral testes, and a truncation of the ipsilateral Wolffian ductal mesenchyme were also seen in the animals with IHP. Additional research is needed to further understand the mechanisms and consequences of IHP on prostate growth and development. Alterations to normal prenatal development of the male accessory sex organs can have important consequences for the growth and morphology of the adult gland.

The developmental expression profile of PAX2 in the murine prostate

BACKGROUND

Nine transcription factors comprise the PAX gene family that regulate organogenesis. The urogenital system of PAX2 null male mice fails to develop properly. PAX2 is overexpressed in PC3 cells. Therefore, PAX2 is implicated in both prostate organogenesis and cancer. However, the expression pattern/profile of PAX2 in the prostate is unknown.

METHODS

PAX2/5/8 expression was surveyed in E16.5 male urogenital sinus (UGS) by RT-PCR. Prostate samples from 10 developmental stages in C3H male mice were used in quantitative reverse-transcript PCR (Q-PCR) and Western blotting (WB). RT-PCR and WB measured PAX2 expression in prostatic lobes or UGS layers, to identify local-regional expression patterns. Cytoplasmic versus nuclear expression was examined by WB. A castration series in adult C3H male mice and R1881 treatment in serum-free LNCaP cells examined androgen control of PAX2.

RESULTS

PAX2 mRNA levels are higher in early developmental stages as compared to postpubertal prostates. RT-PCR and/or WB indicated a dorsal epithelial-nuclear localization of PAX2. PAX2 mRNA and protein increase postcastration. R1881 decreases expression of PAX2 mRNA in LNCaP cells as compared to controls.

CONCLUSIONS

The expression profile of PAX2 indicates that it may regulate early, androgen-independent stages of murine prostate development, particularly for dorsally derived prostate glands. PAX2 expression appears to be associated with a dorsally localized epithelial cell population that is castration insensitive and retains proliferative and differentiative potential. Such a population of cells may represent a subset of stem-like cells having some characteristics in common with castrate-resistant prostate cancer cells.