KGF suppresses α2β1 integrin function and promotes differentiation of the transient amplifying population in human prostatic epithelium

AR loss in prostate cancer stroma mediated by NF-κB and p38-MAPK signaling disrupts stromal morphogen production

Androgen Receptor (AR) activity in prostate stroma is required to maintain prostate homeostasis. This is mediated through androgen-dependent induction and secretion of morphogenic factors that drive epithelial cell differentiation. However, stromal AR expression is lost in aggressive prostate cancer. The mechanisms leading to stromal AR loss and morphogen production are unknown. We identified TGFβ1 and TNFα as tumor-secreted factors capable of suppressing AR mRNA and protein expression in prostate stromal fibroblasts. Pharmacological and RNAi approaches identified NF-κB as the major signaling pathway involved in suppressing AR expression by TNFα. In addition, p38α- and p38δ-MAPK were identified as suppressors of AR expression independent of TNFα. Two regions of the AR promoter were responsible for AR suppression through TNFα. FGF10 and Wnt16 were identified as androgen-induced morphogens, whose expression was lost upon TNFα treatment and enhanced upon p38-MAPK inhibition. Wnt16, through non-canonical Jnk signaling, was required for prostate basal epithelial cell survival. These findings indicate that stromal AR loss is mediated by secreted factors within the TME. We identified TNFα/TGFβ as two possible factors, with TNFα mediating its effects through NF-κB or p38-MAPK to suppress AR mRNA transcription. This leads to loss of androgen-regulated stromal morphogens necessary to maintain normal epithelial homeostasis.

The FGF/FGFR system in the physiopathology of the prostate gland

Fibroblast growth factors (FGFs) are a family of proteins possessing paracrine, autocrine, or endocrine functions in a variety of biological processes, including embryonic development, angiogenesis, tissue homeostasis, wound repair, and cancer. Canonical FGFs bind and activate tyrosine kinase FGF receptors (FGFRs), triggering intracellular signaling cascades that mediate their biological activity. Experimental evidence indicates that FGFs play a complex role in the physiopathology of the prostate gland that ranges from essential functions during embryonic development to modulation of neoplastic transformation. The use of ligand- and receptor-deleted mouse models has highlighted the requirement for FGF signaling in the normal development of the prostate gland. In adult prostate, the maintenance of a functional FGF/FGFR signaling axis is critical for organ homeostasis and function, as its disruption leads to prostate hyperplasia and may contribute to cancer progression and metastatic dissemination. Dissection of the molecular landscape modulated by the FGF family will facilitate ongoing translational efforts directed toward prostate cancer therapy.

Human stroma and epithelium co-culture in a microfluidic model of a human prostate gland

The prostate is a walnut-sized gland that surrounds the urethra of males at the base of the bladder comprising a muscular portion, which controls the release of urine, and a glandular portion, which secretes fluids that nourish and protect sperms. Here, we report the development of a microfluidic-based model of a human prostate gland. The polydimethylsiloxane (PDMS) microfluidic device, consisting of two stacked microchannels separated by a polyester porous membrane, enables long-term in vitro cocultivation of human epithelial and stromal cells. The porous separation membrane provides an anchoring scaffold for long-term culturing of the two cell types on its opposite surfaces allowing paracrine signaling but not cell crossing between the two channels. The microfluidic device is transparent enabling high resolution bright-field and fluorescence imaging. Within this coculture model of a human epithelium/stroma interface, we simulated the functional development of the in vivo human prostate gland. We observed the successful differentiation of basal epithelial cells into luminal secretory cells determined biochemically by immunostaining with known differentiation biomarkers, particularly androgen receptor expression. We also observed morphological changes where glandlike mounds appeared with relatively empty centers reminiscent of prostatic glandular acini structures. This prostate-on-a-chip will facilitate the direct evaluation of paracrine and endocrine cross talk between these two cell types as well as studies associated with normal vs disease-related events such as prostate cancer.

Downregulation of C-Terminal Tensin-Like Protein (CTEN) Suppresses Prostate Cell Proliferation and Contributes to Acinar Morphogenesis

C-terminal tensin-like protein (CTEN) is a member of tensin family, which is crucial for the assembly of cell-matrix adhesome. Unlike other tensins, CTEN is selectively expressed only in a few tissues such as the prostate. However, the biological relevance of CTEN in normal prostate is poorly understood. In this study, we revealed that CTEN is selectively expressed in the prostate epithelial cells and enriched in the basal compartment. Knockdown of CTEN in RWPE-1 cells suppresses cell proliferation and results in G1/S cell cycle arrest as well as the accumulation of cyclin-dependent kinase (CDK) inhibitors, p21 and p27. Moreover, the expression of CTEN is decreased during acinar morphogenesis using Matrigel-based three-dimensional (3D) culture. In the course of acinar formation, induction of CTEN reactivates focal adhesion kinase (FAK) Y³⁹⁷ phosphorylation and disrupts the acini structure. This study, to our knowledge, is the first report demonstrating that downregulation of CTEN is required for luminal differentiation and acinar formation.

Multipotent Basal Stem Cells, Maintained in Localized Proximal Niches, Support Directed Long-Ranging Epithelial Flows in Human Prostates

Sporadic mitochondrial DNA mutations serve as clonal marks providing access to the identity and lineage potential of stem cells within human tissues. By combining quantitative clonal mapping with 3D reconstruction of adult human prostates, we show that multipotent basal stem cells, confined to discrete niches in juxta-urethral ducts, generate bipotent basal progenitors in directed epithelial migration streams. Basal progenitors are then dispersed throughout the entire glandular network, dividing and differentiating to replenish the loss of apoptotic luminal cells. Rare lineage-restricted luminal stem cells, and their progeny, are confined to proximal ducts and provide only minor contribution to epithelial homeostasis. In situ cell capture from clonal maps identified delta homolog 1 (DLK1) enrichment of basal stem cells, which was validated in functional spheroid assays. This study establishes significant insights into niche organization and function of prostate stem and progenitor cells, with implications for disease.

Human prostate luminal cell differentiation requires NOTCH3 induction by p38-MAPK and MYC

Many pathways dysregulated in prostate cancer are also involved in epithelial differentiation. To better understand prostate tumor initiation, we sought to investigate specific genes and mechanisms required for normal basal to luminal cell differentiation. Utilizing human prostate basal epithelial cells and an in vitro differentiation model, we tested the hypothesis that regulation of NOTCH3 by the p38 MAPK family (hereafter p38-MAPK), via MYC, is required for luminal differentiation. Inhibition (SB202190 and BIRB796) or knockdown of p38α (also known as MAPK14) and/or p38δ (also known as MAPK13) prevented proper differentiation. Additionally, treatment with a γ-secretase inhibitor (RO4929097) or knockdown of NOTCH1 and/or NOTCH3 greatly impaired differentiation and caused luminal cell death. Constitutive p38-MAPK activation through MKK6(CA) increased NOTCH3 (but not NOTCH1) mRNA and protein levels, which was diminished upon MYC inhibition (10058-F4 and JQ1) or knockdown. Furthermore, we validated two NOTCH3 enhancer elements through a combination of enhancer (e)RNA detection (BruUV-seq) and luciferase reporter assays. Finally, we found that the NOTCH3 mRNA half-life increased during differentiation or upon acute p38-MAPK activation. These results reveal a new connection between p38-MAPK, MYC and NOTCH signaling, demonstrate two mechanisms of NOTCH3 regulation and provide evidence for NOTCH3 involvement in prostate luminal cell differentiation.

Advances in prostate cancer research models: From transgenic mice to tumor xenografting models

The identification of the origin and molecular characteristics of prostate cancer (PCa) has crucial implications for personalized treatment. The development of effective treatments for PCa has been limited; however, the recent establishment of several transgenic mouse lines and/or xenografting models is better reflecting the disease in vivo. With appropriate models, valuable tools for elucidating the functions of specific genes have gone deep into prostate development and carcinogenesis. In the present review, we summarize a number of important PCa research models established in our laboratories (PSA-Cre-ER^T2/PTEN transgenic mouse models, AP-OX model, tissue recombination-xenografting models and PDX models), which represent advances of translational models from transgenic mouse lines to human tumor xenografting. Better understanding of the developments of these models will offer new insights into tumor progression and may help explain the functional significance of genetic variations in PCa. Additionally, this understanding could lead to new modes for curing PCa based on their particular biological phenotypes.

Harvesting Human Prostate Tissue Material and Culturing Primary Prostate Epithelial Cells

In order to fully explore the biology of a complex solid tumor such as prostate cancer, it is desirable to work with patient tissue. Only by working with cells from a tissue can we take into account patient variability and tumor heterogeneity. Cell lines have long been regarded as the workhorse of cancer research and it could be argued that they are of most use when considered within a panel of cell lines, thus taking into account specified mutations and variations in phenotype between different cell lines. However, often very different results are obtained when comparing cell lines to primary cells cultured from tissue. It stands to reason that cells cultured from patient tissue represents a close-to-patient model that should and does produce clinically relevant data. This chapter aims to illustrate the methods of processing, storing and culturing cells from prostate tissue, with a description of potential uses.

The many ways to make a luminal cell and a prostate cancer cell

Research in the area of stem/progenitor cells has led to the identification of multiple stem-like cell populations implicated in prostate homeostasis and cancer initiation. Given that there are multiple cells that can regenerate prostatic tissue and give rise to prostate cancer, our focus should shift to defining the signaling mechanisms that drive differentiation and progenitor self-renewal. In this article, we will review the literature, present the evidence and raise important unanswered questions that will help guide the field forward in dissecting critical mechanisms regulating stem-cell differentiation and tumor initiation.

Type 2 Fibroblast Growth Factor Receptor Signaling Preserves Stemness and Prevents Differentiation of Prostate Stem Cells from the Basal Compartment

Prostate stem cells (P-SCs) are capable of giving rise to all three lineages of prostate epithelial cells, which include basal, luminal, and neuroendocrine cells. Two types of P-SCs have been identified in both human and mouse adult prostates based on prostasphere or organoid cultures, cell lineage tracing, renal capsule implantation, and expression of luminal- and basal-specific proteins. The sphere-forming P-SCs are from the basal cell compartment that express P63, and are therefore designated as basal P-SCs (P-bSCs). Luminal P-SCs (P-lSCs) express luminal cytokeratins and Nkx3.1. Herein, we report that the type 2 FGF receptor (FGFR2) signaling axis is crucial for preserving stemness and preventing differentiation of P-bSCs. FGFR2 signaling mediated by FGFR substrate 2α (FRS2α) is indispensable for formation and maintenance of prostaspheres derived from P63(+) P-bSCs. Ablation of Fgfr2 in P63(+) cells in vitro causes the disintegration of prostaspheres. Ablation of Fgfr2 in vivo reduces the number of P63-expressing basal cells and enriches luminal cells. This suggests a basal stem cell-to-luminal cell differentiation. In addition, ablation of Fgfr2 in P63(+) cells causes defective postnatal development of the prostate. Therefore, the data indicate that FGFR2 signaling is critical for preserving stemness and preventing differentiation of P-bSCs.

Glial cell line-derived neurotrophic factor induces cell proliferation in the mouse urogenital sinus

Glial cell line-derived neurotrophic factor (GDNF) is a TGFβ family member, and GDNF signals through a glycosyl-phosphatidylinositol-linked cell surface receptor (GFRα1) and RET receptor tyrosine kinase. GDNF signaling plays crucial roles in urogenital processes, ranging from cell fate decisions in germline progenitors to ureteric bud outgrowth and renal branching morphogenesis. Gene ablation studies in mice have revealed essential roles for GDNF signaling in urogenital development, although its role in prostate development is unclear. We investigated the functional role of GDNF signaling in the urogenital sinus (UGS) and the developing prostate of mice. GDNF, GFRα1, and RET show time-specific and cell-specific expression during prostate development in vivo. In the UGS, GDNF and GFRα1 are expressed in the urethral mesenchyme (UrM) and epithelium (UrE), whereas RET is restricted to the UrM. In each lobe of the developing prostate, GDNF and GFRα1 expression declines in the epithelium and becomes restricted to the stroma. Using a well-established organ culture system, we determined that exogenous GDNF increases proliferation of UrM and UrE cells, altering UGS morphology. With regard to mechanism, GDNF signaling in the UrM increased RET expression and phosphorylation of ERK1/2. Furthermore, inhibition of RET kinase activity or ERK kinases suppressed GDNF-induced proliferation of UrM cells but not UrE cells. We therefore propose that GDNF signaling in the UGS increases proliferation of UrM and UrE cells by different mechanisms, which are distinguished by the role of RET receptor tyrosine kinase and ERK kinase signaling, thus implicating GDNF signaling in prostate development and growth.

Disruption of prostate epithelial differentiation pathways and prostate cancer development

One of the foremost problems in the prostate cancer (PCa) field is the inability to distinguish aggressive from indolent disease, which leads to difficult prognoses and thousands of unnecessary surgeries. This limitation stems from the fact that the mechanisms of tumorigenesis in the prostate are poorly understood. Some genetic alterations are commonly reported in prostate tumors, including upregulation of Myc, fusion of Ets genes to androgen-regulated promoters, and loss of Pten. However, the specific roles of these aberrations in tumor initiation and progression are poorly understood. Likewise, the cell of origin for PCa remains controversial and may be linked to the aggressive potential of the tumor. One important clue is that prostate tumors co-express basal and luminal protein markers that are restricted to their distinct cell types in normal tissue. Prostate epithelium contains layer-specific stem cells as well as rare bipotent cells, which can differentiate into basal or luminal cells. We hypothesize that the primary oncogenic cell of origin is a transient-differentiating bipotent cell. Such a cell must maintain tight temporal and spatial control of differentiation pathways, thus increasing its susceptibility for oncogenic disruption. In support of this hypothesis, many of the pathways known to be involved in prostate differentiation can be linked to genes commonly altered in PCa. In this article, we review what is known about important differentiation pathways (Myc, p38MAPK, Notch, PI3K/Pten) in the prostate and how their misregulation could lead to oncogenesis. Better understanding of normal differentiation will offer new insights into tumor initiation and may help explain the functional significance of common genetic alterations seen in PCa. Additionally, this understanding could lead to new methods for classifying prostate tumors based on their differentiation status and may aid in identifying more aggressive tumors.

Characterisations of human prostate stem cells reveal deficiency in class I UGT enzymes as a novel mechanism for castration-resistant prostate cancer

Background:

Evidence increasingly supports that prostate cancer is initiated by the malignant transformation of stem cells (SCs). Furthermore, many SC-signalling pathways are shown to be shared in prostate cancer. Therefore, we planned transcriptome characterisation of adult prostate SCs as a strategy to consider new targets for cancer treatment.

Methods:

Intuitive pathway analysis was used for putative target discovery in 12 matched selections of human prostate SCs, transiently amplifying cells and terminally differentiated cells. These were pooled into three groups according to the stage of differentiation for mRNA microarray analysis. Targets identified were validated using uncultured primary tissue (n=12), functional models of prostate cancer and a tissue microarray consisting of benign (n=42) and malignant prostate (n=223).

Results:

A deficiency in class 1 UDP glucuronosyltransferase (UGT) enzymes (UGT1A) was identified in prostate SCs, which are involved in androgen catabolism. Class 1 UGT enzyme expression was also downregulated in cancer SCs and during progression to metastatic castration-resistant prostate cancer (CRPC). Reduction of UGT1A expression in vitro was seen to improve cell survival and increase androgen receptor (AR) activity, as shown by upregulation of prostate-specific antigen expression.

Interpretation:

Inactivation of intracellular androgen catabolism represents a novel mechanism to maintain AR activity during CRPC.

Effects of keratinocyte growth factor on skin epithelial differentiation of human amnion epithelial cells

The aim of the present study was to determine the effects of KGF on the differentiation of cultured human amnion epithelial cells (HAECs) towards skin keratinocyte. HAECs at passage 1 were cultured in medium HAM's F12: Dulbecco's Modified Eagles Medium (1:1) supplemented with different concentrations of KGF (0, 5, 10, 20, 30 and 50 ng/ml KGF). Dose-response of KGF on HAECs was determined by morphological assessment; growth kinetic evaluation; immunocytochemical analysis; stemness and epithelial gene expression quantification with two step real time RT-PCR. KGF promotes the proliferation of HAECs with maximal effect observed at 10 ng/ml KGF. However, KGF decreased the stemness genes expression: Oct-3/4, Sox-2, Nanog3, Rex-1, FGF-4, FZD-9 and BST-1. KGF also down-regulates epithelial genes expression: CK3, CK18, CK19, Integrin-β1, p63 and involucrin in cultured HAECs. No significant difference on the gene expression was detected for each Nestin, ABCG-2, CK1 and CK14 in KGF-treated HAECs. Immunocytochemical analysis for both control and KGF-treated HAECs demonstrated positive staining against CK14 and CK18 but negative staining against involucrin. The results suggested that KGF stimulates an early differentiation of HAECs towards epidermal cells. Differentiation of KGF-treated HAECs to corneal lineage is unfavourable. Therefore, further studies are needed to elucidate the roles of KGF in the differentiation of HAECs towards skin keratinocytes.

Human α(2)β(1)(HI) CD133(+VE) epithelial prostate stem cells express low levels of active androgen receptor

Stem cells are thought to be the cell of origin in malignant transformation in many tissues, but their role in human prostate carcinogenesis continues to be debated. One of the conflicts with this model is that cancer stem cells have been described to lack androgen receptor (AR) expression, which is of established importance in prostate cancer initiation and progression. We re-examined the expression patterns of AR within adult prostate epithelial differentiation using an optimised sensitive and specific approach examining transcript, protein and AR regulated gene expression. Highly enriched populations were isolated consisting of stem (α₂β₁^HI CD133^+VE), transiently amplifying (α₂β₁^HI CD133^–VE) and terminally differentiated (α₂β₁^LOW CD133^–VE) cells. AR transcript and protein expression was confirmed in α₂β₁^HI CD133^+VE and CD133^–VE progenitor cells. Flow cytometry confirmed that median (±SD) fraction of cells expressing AR were 77% (±6%) in α₂β₁^HI CD133^+VE stem cells and 68% (±12%) in α₂β₁^HI CD133^–VE transiently amplifying cells. However, 3-fold lower levels of total AR protein expression (peak and median immunofluorescence) were present in α₂β₁^HI CD133^+VE stem cells compared with differentiated cells. This finding was confirmed with dual immunostaining of prostate sections for AR and CD133, which again demonstrated low levels of AR within basal CD133^+VE cells. Activity of the AR was confirmed in prostate progenitor cells by the expression of low levels of the AR regulated genes PSA, KLK2 and TMPRSS2. The confirmation of AR expression in prostate progenitor cells allows integration of the cancer stem cell theory with the established models of prostate cancer initiation based on a functional AR. Further study of specific AR functions in prostate stem and differentiated cells may highlight novel mechanisms of prostate homeostasis and insights into tumourigenesis.

NGF/γ-IFN inhibits androgen-independent prostate cancer and reverses androgen receptor function through downregulation of FGFR2 and decrease in cancer stem cells

Androgen-independent prostate cancer (AIPC) is difficult to treat. Present study is to explore the inhibitory effect of a cytokine environment on AIPC and its mechanism. We utilized nerve growth factor (NGF)/γ-interferon (γ-IFN) to change the cytokine environment. Animal models and 2 androgen receptor (AR)-negative prostate cancer cell lines were used to evaluate the effect of NGF/γ-IFN. Flow cytometry, immunocytochemistry, western blotting, Tunel assay, colony formation efficiency, gene microarray, and in vivo bioluminescence were used to discern the mechanisms within NGF/γ-IFN that effect the environment. In vitro, NGF/γ-IFN effectively inhibited the proliferation of AIPC cell lines and promoted the apoptosis of the cancer cells. In vivo, NGF/γ-IFN suppressed the growth and metastasis of a tumor mass that arose from the AIPC cell line. After NGF/γ-IFN treatment, the AR-negative cell lines re-expressed AR and were then able to respond to the androgen. Contrary to expectations, the proliferation of cells was inhibited after dihydrotestosterone was added, and the results indicated that NGF/γ-IFN decreased the proportion of cancer stem cells. NGF/γ-IFN worked mainly through the downregulation of fibroblast growth factor receptor 2.

β1 integrin deletion enhances progression of prostate cancer in the TRAMP mouse model

β1 integrin regulates the response of both normal and cancer cells to their local environment. Although mis-localised in prostate cancer, the role β1 integrin plays in prostate development and carcinogenesis remains unknown. To assess the role of β1 integrin in vivo, we conditionally deleted β1 integrin from prostate epithelium and subsequently crossed these mice to the TRAMP prostate carcinogenesis model. Deletion of β1 integrin following castration and subsequent androgen supplementation resulted in an expansion of the p63-positive basal cell population and decreased differentiation. Consistent with these findings, deletion of β1 integrin in TRAMP mice decreased animal survival, decreased retention of normal prostate morphology, increased the percentage of tissue with poorly differentiated carcinoma, and increased cell proliferation. This study demonstrates that β1 integrin regulates several aspects of normal prostate development and in contrast to its role in several other tissues, its loss is associated with increased rates of prostate tumour progression.

Hunterian Lecture. Characterisation of human prostate epithelial progenitor differentiation in response to androgens

INTRODUCTION

A stem cell model of prostate cancer tumourigenesis explains progression to castration resistant prostate cancer (CRPC) and offers novel perspectives in targeting this cancer in its more advanced forms. Androgen receptor (AR) regulated pathways are central mechanisms in progression to CRPC. However, AR was thought to be lacking in prostate stem cell enriched fractions. Potential low levels of AR expression in stem cell enriched cells were investigated and potential direct effects of androgen were examined.

METHODS

Human prostate stem cell enriched populations, based on high α(2)β(1) integrin expression (α(2)β(1)(hi)), were selected from primary human prostate tissue in men undergoing transurethral prostatectomy or cystoprostatectomy. Effects on differentiation were assayed with flow cytometry using differentiation-specific markers.

RESULTS

Low levels of AR were demonstrable in α(2)β(1)(hi) cells following inhibition of the proteasome using MG132. Furthermore, a direct effect of androgen was shown in stabilising/inducing AR expression. Androgen treatment of α(2)β(1)(hi) cells was associated with the induction of differentiation using a number of differentiation-specific markers (prostatic acid phosphatase, cytokeratin 18 and AR) with increases ranging from 49% to 67% (p<0.05). These effects were blocked with the AR-specific inhibitor bicalutamide (p<0.05). These data support a role of direct androgen activity on stem cell enriched cells in the prostate and the implications of these findings are discussed.

In situ lineage tracking of human prostatic epithelial stem cell fate reveals a common clonal origin for basal and luminal cells

Stem cells accumulate mitochondrial DNA (mtDNA) mutations resulting in an observable respiratory chain defect in their progeny, allowing the mapping of stem cell fate. There is considerable uncertainty in prostate epithelial biology where both basal and luminal stem cells have been described, and in this study the clonal relationships within the human prostate epithelial cell layers were explored by tracing stem cell fate. Fresh-frozen and formalin-fixed histologically-benign prostate samples from 35 patients were studied using sequential cytochrome c oxidase (COX)/succinate dehydrogenase (SDH) enzyme histochemistry and COX subunit I immunofluorescence to identify areas of respiratory chain deficiency; mtDNA mutations were identified by whole mitochondrial genome sequencing of laser-captured areas. We demonstrated that cells with respiratory chain defects due to somatic mtDNA point mutations were present in prostate epithelia and clonally expand in acini. Lineage tracing revealed distinct patterning of stem cell fate with mtDNA mutations spreading throughout the whole acinus or, more commonly, present as mosaic acinar defects. This suggests that individual acini are typically generated from multiple stem cells, and the presence of whole COX-deficient acini suggests that a single stem cell can also generate an entire branching acinar subunit of the gland. Significantly, a common clonal origin for basal, luminal and neuroendocrine cells is demonstrated, helping to resolve a key area of debate in human prostate stem cell biology.

Characterisation of human prostate epithelial progenitor differentiation in response to androgens

INTRODUCTION

A stem cell model of prostate cancer tumourigenesis explains progression to castration resistant prostate cancer (CRPC) and offers novel perspectives in targeting this cancer in its more advanced forms. Androgen receptor (AR) regulated pathways are central mechanisms in progression to CRPC. However, AR was thought to be lacking in prostate stem cell enriched fractions. Potential low levels of AR expression in stem cell enriched cells were investigated and potential direct effects of androgen were examined.

METHODS

Human prostate stem cell enriched populations, based on high α2β1 integrin expression (α2β1hi), were selected from primary human prostate tissue in men undergoing transurethral prostatectomy or cystoprostatectomy. Effects on differentiation were assayed with flow cytometry using differentiation-specific markers.

RESULTS

Low levels of AR were demonstrable in α2β1hi cells following inhibition of the proteasome using MG132. Furthermore, a direct effect of androgen was shown in stabilising/inducing AR expression. Androgen treatment of α2β1hi cells was associated with the induction of differentiation using a number of differentiation-specific markers (prostatic acid phosphatase, cytokeratin 18 and AR) with increases ranging from 49% to 67% (p<0.05). These effects were blocked with the AR-specific inhibitor bicalutamide (p<0.05). These data support a role of direct androgen activity on stem cell enriched cells in the prostate and the implications of these findings are discussed.

Modeling the prostate stem cell niche: an evaluation of stem cell survival and expansion in vitro

The goal of this work was to engineer a clinically relevant in vitro model of human prostate stem cells (PSCs) that could be used to interrogate the mechanisms of stem cell control. We, therefore, compared the growth potential of stem cells in 3D culture (where the conditions would favor a quiescent state) with monolayer culture that has previously been demonstrated to induce PSC division. We found a fundamental difference between cultures of primary, adult PSCs grown as monolayers compared to those grown as spheres. The first supported the expansion and maintenance of PSCs from single cells while the latter did not. In an attempt to determine the mechanisms governing stem cell control, several known stem cell activators (including IFNalpha, FGF2, anti-TGFbeta, and dihydrotestosterone) were studied. However, cell division was not observed. CD133+ cells derived from a prostate cell line did not grow as spheres from single cells but did grow from aggregates. We conclude that PSCs can be expanded and maintained in monolayer culture from single cells, but that PSCs are growth quiescent when grown as spheres. It is likely that the physical arrangement of cells in monolayer provides an injury-type response, which can activate stem cells into cycle.

E-cadherin-mediated survival of androgen-receptor-expressing secretory prostate epithelial cells derived from a stratified in vitro differentiation model

The androgen receptor (AR) is expressed in differentiated secretory prostate epithelial cells in vivo. However, in the human prostate, it is unclear whether androgens directly promote the survival of secretory cells, or whether secretory cells survive through androgen-dependent signals from the prostate stroma. Biochemical and mechanistic studies have been hampered by inadequate cell-culture models. In particular, large-scale differentiation of prostate epithelial cells in culture has been difficult to achieve. Here, we describe the development of a differentiation system that is amenable to functional and biochemical analysis and its application to deciphering the survival pathways in differentiated AR-expressing epithelial cells. Confluent prostate epithelial cell cultures were treated with keratinocyte growth factor (KGF) and dihydrotestosterone. After 2 weeks, a suprabasal cell layer was formed in which cells no longer expressed alpha2, alpha3, alpha6, alphav, beta1 or beta4 integrins or p63, K5, K14, EGFR, FGFR2IIIb or Bcl-2, but instead expressed AR and androgen-induced differentiation markers, including K18, K19, TMPRSS2, Nkx3.1, PMSA, KLK2 and secreted prostate-specific antigen (PSA). Differentiated prostate cell survival depended on E-cadherin and PI3K, but not KGF, androgen, AR or MAPK. Thus survival of differentiated prostate epithelial cells is mediated by cell-cell adhesion, and not through androgen activity or prostate stroma-derived KGF.

Epithelial-stromal interaction 1 (EPSTI1) substitutes for peritumoral fibroblasts in the tumor microenvironment

Tumor cells can activate stroma, yet the implication of this activation in terms of reciprocal induction of gene expression in tumor cells is poorly understood. Epithelial Stromal Interaction 1 (EPSTI1) is an interferon response gene originally isolated from heterotypic recombinant cultures of human breast cancer cells and activated breast myofibroblasts. Here we describe the first immunolocalization of EPSTI1 in normal and cancerous breast tissue, and we provide evidence for a role of this molecule in the regulation of tumor cell properties and epithelial-mesenchymal transition. In general, no EPSTI1 staining was observed in normal breast epithelial cells from reduction mammoplasties (n=25). However, in carcinomas, staining was positive in 22 of 40 biopsies and inversely correlated with the level of differentiation. To address the function of EPSTI1, we expressed EPSTI1 ectopically in one cell line and silenced endogenous EPSTI1 by RNA interference in another. Irrespective of the experimental approach, EPSTI1 expression led to an increase in tumorsphere formation-a property associated with breast stem/progenitor cells. Most remarkably, we show that EPSTI1, by conveying spread of tumor cells, can replace peritumoral activated fibroblasts in a tumor environment assay. These observations implicate EPSTI1 as a hitherto unappreciated regulator of tumor cell properties.

Laminin enhances the growth of human neural stem cells in defined culture media

Background

Human neural stem cells (hNSC) have the potential to provide novel cell-based therapies for neurodegenerative conditions such as multiple sclerosis and Parkinson's disease. In order to realise this goal, protocols need to be developed that allow for large quantities of hNSC to be cultured efficiently. As such, it is important to identify factors which enhance the growth of hNSC. In vivo, stem cells reside in distinct microenvironments or niches that are responsible for the maintenance of stem cell populations. A common feature of niches is the presence of the extracellular matrix molecule, laminin. Therefore, this study investigated the effect of exogenous laminin on hNSC growth.

Results

To measure hNSC growth, we established culture conditions using B27-supplemented medium that enable neurospheres to grow from human neural cells plated at clonal densities. Limiting dilution assays confirmed that neurospheres were derived from single cells at these densities. Laminin was found to increase hNSC numbers as measured by this neurosphere formation. The effect of laminin was to augment the proliferation/survival of the hNSC, rather than promoting the undifferentiated state. In agreement, apoptosis was reduced in dissociated neurospheres by laminin in an integrin β1-dependent manner.

Conclusion

The addition of laminin to the culture medium enhances the growth of hNSC, and may therefore aid their large-scale production.

Androgen receptor signalling in prostate: effects of stromal factors on normal and cancer stem cells

The prostate gland is the most common site for cancer in males within the developed world. Androgens play a vital role in prostate development, maintenance of tissue function and pathogenesis of prostate disease. The androgen receptor signalling pathway facilitates that role in both the epithelial compartment and in the underlying stroma. Stroma is a key mediator of androgenic effects upon the epithelium and can regulate both the fate of the epithelial stem cell and potentially the initiation and progression of prostate cancer. Different groups of growth factors are expressed by stroma, which control proliferation, and differentiation of prostate epithelium demonstrating a critical role for stroma in epithelial growth and homeostasis. Paracrine stromal proteins may offer the possibility to control tumour stem cell growth and could permit prostate specific targeting of both therapies and of androgen responsive proteins. The effect of 5alpha-dihydrotestosterone, the more potent metabolite of testosterone, on expression of androgen-regulated genes in stroma from benign prostatic hyperplasia is a key mediator of epithelial cell fate. Global gene expression arrays have recently identified new candidate genes in androgen responsive stroma, some of which have androgen receptor binding sites in their promoter regions. Some of these genes have direct androgen receptor binding ability.

Functions of normal and malignant prostatic stem/progenitor cells in tissue regeneration and cancer progression and novel targeting therapies

This review summarizes the recent advancements that have improved our understanding of the functions of prostatic stem/progenitor cells in maintaining homeostasis of the prostate gland. We also describe the oncogenic events that may contribute to their malignant transformation into prostatic cancer stem/progenitor cells during cancer initiation and progression to metastatic disease stages. The molecular mechanisms that may contribute to the intrinsic or the acquisition of a resistant phenotype by the prostatic cancer stem/progenitor cells and their differentiated progenies with a luminal phenotype to the current therapies and disease relapse are also reviewed. The emphasis is on the critical functions of distinct tumorigenic signaling cascades induced through the epidermal growth factor system, hedgehog, Wnt/beta-catenin, and/or stromal cell-derived factor-1/CXC chemokine receptor-4 pathways as well as the deregulated apoptotic signaling elements and ATP-binding cassette multidrug transporter. Of particular therapeutic interest, we also discuss the potential beneficial effects associated with the targeting of these signaling elements to overcome the resistance to current treatments and prostate cancer recurrence. The combined targeted strategies toward distinct oncogenic signaling cascades in prostatic cancer stem/progenitor cells and their progenies as well as their local microenvironment, which could improve the efficacy of current clinical chemotherapeutic treatments against incurable, androgen-independent, and metastatic prostate cancers, are also described.

Development-related expression of KGF and FGF-10 mRNA in the canine prostate gland

Keratinocyte growth factor (KGF) and fibroblast growth factor 10 (FGF-10) are stromal-derived growth factors that interact with their epithelial FGFR2 receptors to mediate stromal--epithelial cell interaction within the prostate gland. This study was conducted to compare the development-related mRNA expression of KGF, FGF-10 and their receptor FGFR2 in immature and mature canine prostate glands. In addition, their expression levels were correlated with the differentiation of stromal cells using vimentin as a mesenchymal cell marker. Quantitative mRNA expression was assessed by real-time polymerase chain reaction (PCR) and the results were expressed as relative mRNA expression of the target gene, which was normalized to the GAPDH reference gene. mRNA analysis revealed a differential expression of KGF, FGF-10 and FGFR2 receptor by the prostate glands of immature and mature dogs. The results showed a 7.3- and 9-fold decrease in mRNA expression of KGF and FGF-10 by mature and immature prostate glands respectively. However, there was no significant change in FGFR2 receptor mRNA expression by mature or immature prostate glands. This downregulation of KGF and FGF-10 expression was associated with a 15-fold decrease in vimentin expression. These results indicate that KGF and FGF-10 expression varied according to the differentiation status of stromal cells and might reflect differential developmental requirements of immature and mature canine prostate glands.

The role of androgen in determining differentiation and regulation of androgen receptor expression in the human prostatic epithelium transient amplifying population

Abnormal differentiation in epithelial stem cells or their immediate proliferative progeny, the transiently amplifying population (TAP), may explain malignant pathogenesis in the human prostate. These models are of particular importance as differing sensitivities to androgen among epithelial cell subpopulations during differentiation are recognised and may account for progression to androgen independent prostate cancer. Androgens are crucial in driving terminal differentiation and their indirect effects via growth factors from adjacent androgen responsive stroma are becoming better characterised. However, direct effects of androgen on immature cells in the context of a prostate stem cell model have not been investigated in detail and are studied in this work. In alpha2beta1hi stem cell enriched basal cells, androgen analogue R1881 directly promoted differentiation by the induction of differentiation-specific markers CK18, androgen receptor (AR), PSA and PAP. Furthermore, treatment with androgen down-regulated alpha2beta1 integrin expression, which is implicated in the maintenance of the immature basal cell phenotype. The alpha2beta1hi cells were previously demonstrated to lack AR expression and the direct effects of androgen were confirmed by inhibition using the anti-androgen bicalutamide. AR protein expression in alpha2beta1hi cells became detectable when its degradation was repressed by the proteosomal inhibitor MG132. Stratifying the alpha2beta1hi cells into stem (CD133(+)) and transient amplifying population (TAP) (CD133(-)) subpopulations, AR mRNA expression was found to be restricted to the CD133(-) (TAP) cells. The presence of a functional AR in the TAP, an androgen independent subpopulation for survival, may have particular clinical significance in hormone resistant prostate cancer, where both the selection of immature cells and functioning AR regulated pathways are involved.

KGF promotes integrin alpha5 expression through CCAAT/enhancer-binding protein-beta

Keratinocyte growth factor (KGF) and alpha(5)beta(1)-integrin are not expressed in normal skin but they are both highly upregulated in the migrating epidermis during wound healing. Here we report that KGF increased alpha(5) mRNA and protein levels in epidermoid carcinoma cells and stratified bioengineered epidermis. Interestingly, KGF increased integrin alpha(5) in the basal as well as suprabasal cell epidermal layers. Promoter studies indicated that KGF-induced integrin alpha(5) promoter activation was dependent on the C/EBP transcription factor binding site. Accordingly, KGF induced sustained phosphorylation of C/EBP-beta that was dependent on activation of ERK1/2. In addition, a dominant negative form of C/EBP-beta inhibited alpha(5) promoter activity and blocking C/EBP-beta with siRNA diminished integrin alpha(5) expression. Taken together, our data indicate that KGF increased integrin alpha(5) expression by phosphorylating C/EBP-beta. Interestingly, KGF-induced upregulation of integrin alpha(5) was more pronounced in three-dimensional tissue analogues than in conventional two-dimensional culture suggesting that stratified epidermis may be useful in understanding the effects of growth factors in the local tissue microenvironment.

Keratinocyte growth factor improves repair in the injured tracheal epithelium

Keratinocyte growth factor (KGF) is a critical growth factor in lung development and is a protective agent after lung injury, although the exact mechanisms of this protective effect have not yet been elucidated. Our laboratory has shown that circulating epithelial progenitor cells can traffic to the airway and that they appear to be derived from the bone marrow. On this basis, we hypothesized that KGF and its putative receptor (KGFR) would be important to these cells. We showed that the KGFR, which is found almost exclusively on epithelial cells, was present on cells in the bone marrow and circulation of mice that identified a subpopulation of cytokeratin 5+ circulating epithelial progenitor cells (CEPC). In addition, the KGFR co-localized with a population of cytokeratin 5+ basal cells in the repairing proximal airway. Systemic administration of KGF resulted in a significant increase in mobilization of cytokeratin 5+ CEPC at 6 h after injection. Administration of KGF to mouse recipients of heterotopic syngeneic tracheal transplants resulted in protection and more rapid repair of the tracheal epithelium, with an increase in the number of CEPC in the epithelium of the airway, and this effect was abrogated by blocking CEPC with anti-CXCL12 antibodies. KGF therefore appears to be an important growth factor for local resident progenitor epithelial cell repair and for mobilization and enhanced engraftment of CEPC to the injured proximal airway epithelium.

Progenitor cells are responsible for formation primary epithelial cultures in the prostate epithelial model

The adult stem cells (ASC) are supposed to regenerate epithelium. We hypothesized prostate epithelial CD133-positive ASC to be responsible for establishing the primary cell culture. The prostate epithelial stem cells were isolated using anti-CD133 microbeads in order to form different cell populations. The morphology of cultures developed from CD133(+) and CD133(-) prostate epithelial cells were compared with prostate epithelium cell culture obtained after simple isolation procedure. Four 8-week-old Wistar rats were used in the experiment and six cultures were obtained. Double CD133(+) and CD133(-) cultures from two rats were established after enzymatic digestion and positive selection by SuperMACS device, and two non-selected CD133(+)/CD133(-) cultures were developed by simple prostate epithelial cell isolation from two other rats. The epithelial nature was confirmed by anti-cytokeratine antibodies. It was observed that growth of the CD133(+)/CD133(-) and CD133(+)culture resembled epithelial-like prostate cell culture. It was not possible to establish epithelial-like culture from CD133(-) cell population. The primary epithelial cell culture collapsed in a few days after the CD133-positive ASC were removed. We concluded that the epithelial progenitor cells are responsible for establishing primary prostate epithelial cultures in vitro.

Fibroblast growth factor receptor 2 tyrosine kinase is required for prostatic morphogenesis and the acquisition of strict androgen dependency for adult tissue homeostasis

The fibroblast growth factor (FGF) family consists of 22 members and regulates a broad spectrum of biological activities by activating diverse isotypes of FGF receptor tyrosine kinases (FGFRs). Among the FGFs, FGF7 and FGF10 have been implicated in the regulation of prostate development and prostate tissue homeostasis by signaling through the FGFR2 isoform. Using conditional gene ablation with the Cre-LoxP system in mice, we demonstrate a tissue-specific requirement for FGFR2 in urogenital epithelial cells--the precursors of prostatic epithelial cells--for prostatic branching morphogenesis and prostatic growth. Most Fgfr2 conditional null (Fgfr2(cn)) embryos developed only two dorsal prostatic (dp) and two lateral prostatic (lp) lobes. This contrasts to wild-type prostate, which has two anterior prostatic (ap), two dp, two lp and two ventral prostatic (vp) lobes. Unlike wild-type prostates, which are composed of well developed epithelial ductal networks, the Fgfr2(cn) prostates, despite retaining a compartmented tissue structure, exhibited a primitive epithelial architecture. Moreover, although Fgfr2(cn) prostates continued to produce secretory proteins in an androgen-dependent manner, they responded poorly to androgen with respect to tissue homeostasis. The results demonstrate that FGFR2 is important for prostate organogenesis and for the prostate to develop into a strictly androgen-dependent organ with respect to tissue homeostasis but not to the secretory function, implying that androgens may regulate tissue homeostasis and tissue function differently. Therefore, Fgfr2(cn) prostates provide a useful animal model for scrutinizing molecular mechanisms by which androgens regulate prostate growth, homeostasis and function, and may yield clues as to how advanced-tumor prostate cells escape strict androgen regulations.