Differentiation of prostate epithelial cell cultures by matrigel/ stromal cell glandular reconstruction

Characterisation of cell lines derived from prostate cancer patients with localised disease

BACKGROUND

Prostate cancer is a broad-spectrum disease, spanning from indolent to a highly aggressive lethal malignancy. Prostate cancer cell lines are essential tools to understanding the basic features of this malignancy, as well as in identifying novel therapeutic strategies. However, most cell lines routinely used in prostate cancer research are derived from metastatic disease and may not fully elucidate the molecular events underlying the early stages of cancer development and progression. Thus, there is a need for new cell lines derived from localised disease to better span the disease spectrum.

METHODS

Prostatic tissue from the primary site, and adjacent non-cancerous tissue was obtained from four patients with localised disease undergoing radical prostatectomy. Epithelial cell outgrowths were immortalised with human papillomavirus type 16 (HPV16) E6 and E7 to establish monoclonal cell lines. Chromosomal ploidy was imaged and STR profiles were determined. Cell morphology, colony formation and cell proliferation characteristics were assessed. Androgen receptor (AR) expression and AR-responsiveness to androgen treatment were analysed by immunofluorescence and RT-qPCR, respectively. RNA-seq analysis was performed to identify prostate lineage markers and expression of prostate cancer tumorigenesis-related genes.

RESULTS

Two benign cell lines derived from non-cancer cells (AQ0420 and AQ0396) and two tumour tissue derived cancer cell lines (AQ0411 and AQ0415) were immortalised from four patients with localised prostatic adenocarcinoma. The cell lines presented an epithelial morphology and a slow to moderate proliferative rate. None of the cell lines formed anchorage independent colonies or displayed AR-responsiveness. Comparative RNA-seq expression analysis confirmed the prostatic lineage of the four cell lines, with a distinct gene expression profile from that of the metastatic prostate cancer cell lines, PC-3 and LNCaP.

CONCLUSIONS

Comprehensive characterization of these cell lines may provide new in vitro tools that could bridge the current knowledge gap between benign, early-stage and metastatic disease.

Single luminal epithelial progenitors can generate prostate organoids in culture

The intrinsic ability to display self-organizing morphogenetic properties in ex vivo culture may represent a general property of tissue stem cells. Here we show that single luminal stem/progenitor cells can generate prostate organoids in a three-dimensional culture system in the absence of stroma. Organoids generated from CARNs (castration-resistant Nkx3.1-expressing cells) or normal prostate epithelium exhibit tissue architecture containing luminal and basal cells, undergo long-term expansion in culture, and display functional androgen receptor signaling. Lineage-tracing demonstrates that luminal cells are favored for organoid formation, and generate basal cells in culture. Furthermore, tumor organoids can initiate from CARNs after oncogenic transformation, and from mouse models of prostate cancer, and can facilitate analyses of drug response. Finally, we provide evidence supporting the feasibility of organoid studies of human prostate tissue. Our studies underscore the progenitor properties of luminal cells, and identify in vitro approaches for studying prostate biology.

Cancer cell lines for drug discovery and development

Despite the millions of dollars spent on target validation and drug optimization in preclinical models, most therapies still fail in phase III clinical trials. Our current model systems, or the way we interpret data from them, clearly do not have sufficient clinical predictive power. Current opinion suggests that this is because the cell lines and xenografts that are commonly used are inadequate models that do not effectively mimic and predict human responses. This has become such a widespread belief that it approaches dogma in the field of drug discovery and optimization and has spurred a surge in studies devoted to the development of more sophisticated animal models such as orthotopic patient-derived xenografts in an attempt to obtain more accurate estimates of whether particular cancers will respond to given treatments. Here, we explore the evidence that has led to the move away from the use of in vitro cell lines and toward various forms of xenograft models for drug screening and development. We review some of the pros and cons of each model and give an overview of ways in which the use of cell lines could be modified to improve the predictive capacity of this well-defined model.

Conserved two-step regulatory mechanism of human epithelial differentiation

Human epithelia are organized in a hierarchical structure, where stem cells generate terminally differentiated cells via intermediate progenitors. This two-step differentiation process is conserved in all tissues, but it is not known whether a common gene set contributes to its regulation. Here, we show that retinoic acid (RA) regulates early human prostate epithelial differentiation by activating a tightly coexpressed set of 80 genes (e.g., TMPRSS2). Response kinetics suggested that some of these genes could be direct RA targets, whereas others are probably responding indirectly to RA stimulation. Comparative bioinformatic analyses of published tissue-specific microarrays and a large-scale transcriptomic data set revealed that these 80 genes are not only RA responsive but also significantly coexpressed in many human cell systems. The same gene set preferentially responds to androgens during terminal prostate epithelial differentiation, implying a cell-type-dependent interplay between RA and tissue-specific transcription factor-mediated signaling in regulating the two steps of epithelial differentiation.

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Four sets of coexpressed genes mark primary human prostate stem cell differentiation

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These gene sets are also tightly coexpressed in >150 human cell types

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Retinoic acid induces early differentiation while upregulating one of the gene sets

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Androgens preferentially regulate the same gene set during terminal differentiation

DNA hypermethylation in prostate cancer is a consequence of aberrant epithelial differentiation and hyperproliferation

Prostate cancer (CaP) is mostly composed of luminal-like differentiated cells, but contains a small subpopulation of basal cells (including stem-like cells), which can proliferate and differentiate into luminal-like cells. In cancers, CpG island hypermethylation has been associated with gene downregulation, but the causal relationship between the two phenomena is still debated. Here we clarify the origin and function of CpG island hypermethylation in CaP, in the context of a cancer cell hierarchy and epithelial differentiation, by analysis of separated basal and luminal cells from cancers. For a set of genes (including GSTP1) that are hypermethylated in CaP, gene downregulation is the result of cell differentiation and is not cancer specific. Hypermethylation is however seen in more differentiated cancer cells and is promoted by hyperproliferation. These genes are maintained as actively expressed and methylation-free in undifferentiated CaP cells, and their hypermethylation is not essential for either tumour development or expansion. We present evidence for the causes and the dynamics of CpG island hypermethylation in CaP, showing that, for a specific set of genes, promoter methylation is downstream of gene downregulation and is not a driver of gene repression, while gene repression is a result of tissue-specific differentiation.

Nuclear targeting of dystroglycan promotes the expression of androgen regulated transcription factors in prostate cancer

Dystroglycan is frequently lost in adenocarcinoma, but the mechanisms and consequences are poorly understood. We report an analysis of β-dystroglycan in prostate cancer in human tissue samples and in LNCaP cells in vitro. There is progressive loss of β-dystroglycan immunoreactivity from basal and lateral surfaces of prostate epithelia which correlates significantly with increasing Gleason grade. In about half of matched bone metastases there is significant dystroglycan re-expression. In tumour tissue and in LNCaP cells there is also a tyrosine phosphorylation-dependent translocation of β-dystroglycan to the nucleus. Analysis of gene expression data by microarray, reveals that nuclear targeting of β-dystroglycan in LNCaP cells alters the transcription of relatively few genes, the most unregulated being the transcription factor ETV1. These data suggest that proteolysis, tyrosine phosphorylation and translocation of dystroglycan to the nucleus resulting in altered gene transcription could be important mechanisms in the progression of prostate cancer.

Different expression patterns and functions of acetylated and unacetylated Klf5 in the proliferation and differentiation of prostatic epithelial cells

KLF5 is a basic transcription factor that regulates multiple biological processes. While it was identified as a putative tumor suppressor in prostate cancer, likely due to its function as an effector of TGF-β in the inhibition of cell proliferation, KLF5 is unacetylated and promotes cell proliferation in the absence of TGF-β. In this study, we evaluated the expression and function of KLF5 in prostatic epithelial homeostasis and tumorigenesis using mouse prostates and human prostate epithelial cells in 3-D culture. Histological and molecular analyses demonstrated that unacetylated-Klf5 was expressed in basal or undifferentiated cells, whereas acetylated-Klf5 was expressed primarily in luminal and/or differentiated cells. Androgen depletion via castration increased both the level of Klf5 expression and the number of Klf5-positive cells in the remaining prostate. Functionally, knockdown of KLF5 in the human RWPE-1 prostate cell line decreased the number of spheres formed in 3-D culture. In addition, knockout of Klf5 in prostate epithelial cells, mediated by probasin promoter-driven Cre expression, did not cause neoplasia but promoted cell proliferation and induced hyperplasia when one Klf5 allele was knocked out. Knockout of both Klf5 alleles however, caused apoptosis rather than cell proliferation in the epithelium. In castrated mice, knockout of Klf5 resulted in more severe shrinkage of the prostate. These results suggest that KLF5 plays a role in the proliferation and differentiation of prostatic epithelial cells, yet loss of KLF5 alone is insufficient to induce malignant transformation in epithelial cells.

In vitro model systems to study androgen receptor signaling in prostate cancer

Prostate cancer (PCa) is one of the most common causes of male cancer-related death in Western nations. The cellular response to androgens is mediated via the androgen receptor (AR), a ligand-inducible transcription factor whose dysregulation plays a key role during PCa development and progression following androgen deprivation therapy, the current mainstay systemic treatment for advanced PCa. Thus, a better understanding of AR signaling and new strategies to abrogate AR activity are essential for improved therapeutic intervention. Consequently, a large number of experimental cell culture models have been established to facilitate in vitro investigations into the role of AR signaling in PCa development and progression. These different model systems mimic distinct stages of this heterogeneous disease and exhibit differences with respect to AR expression/status and androgen responsiveness. Technological advances have facilitated the development of in vitro systems that more closely reflect the physiological setting, for example via the use of three-dimensional coculture to study the interaction of prostate epithelial cells with the stroma, endothelium, immune system and tissue matrix environment. This review provides an overview of the most commonly used in vitro cell models currently available to study AR signaling with particular focus on their use in addressing key questions relating to the development and progression of PCa. It is hoped that the continued development of in vitro models will provide more biologically relevant platforms for mechanistic studies, drug discovery and design ensuring a more rapid transfer of knowledge from the laboratory to the clinic.

Primary culture and propagation of human prostate epithelial cells

Basic and translational (or preclinical) prostate cancer research has traditionally been conducted with a limited repertoire of immortalized cell lines, which have homogeneous phenotypes and have adapted to long-term tissue culture. Primary cell culture provides a model system that allows a broader spectrum of cell types from a greater number of patients to be studied, in the absence of artificially induced genetic mutations. Nevertheless, primary prostate epithelial cell culture can be technically challenging, even for laboratories experienced in immortalized cell culture. Therefore, we provide methods to isolate and culture primary epithelial cells directly from human prostate tissue. Initially, we describe the isolation of bulk epithelial cells from benign or tumor tissues. These cells have a predominantly basal/intermediate phenotype and co-express cytokeratin 8/18 and high molecular weight cytokeratins. Since prostatic stem cells play a major role in disease progression and are considered to be a therapeutic target, we also describe a prospective approach to specifically isolate prostatic basal cells that include both stem and transit-amplifying basal populations, which can be studied independently or subsequently differentiated to supply luminal cells. This approach allows the study of stem cells for the development of new therapeutics for prostate cancer.

A transductionally retargeted adenoviral vector for virotherapy of Her2/neu-expressing prostate cancer

The efficacy of adenovirus (Ad)-based gene therapy of solid tumors, such as prostate cancer, is limited. One of the many problems is that the virus infects many different cell types in the body, resulting in high toxicity, whereas the target cancer cells are often less prone to wild-type Ad infection. Our aim was to develop genetically de- and retargeted Ad vectors to reduce off-target effects and increase target infection for prostate cancer. We have previously reported an Ad5 vector specific for the cancer-associated receptor Her2/neu, created by inserting Her2/neu-reactive Affibody(®) molecules (ZH) into the HI loop of a coxsackievirus and adenovirus receptor binding-ablated fiber (Ad[ZH/1]). In addition to virus retargeting to Her2/neu, this virus was further modified from wild-type Ad by changing the RGD motif in the penton base to EGD and by substitution of the KKTK motif in the third shaft repeat to RKSK, resulting in the vector Ad[ZH/3]. The ZH-containing vectors could be produced to high titers and were specific for their target, resulting in efficient infection and killing of Her2/neu-positive androgen-dependent PC346C prostate cancer cells in vitro. Here we show that the oncolytic Ad[ZH/3] vector significantly prolonged survival time and reduced serum prostate-specific antigen levels in an orthotopic prostate tumor model in nude mice to the same extent as wild-type Ad5. Our results show that Her2/neu targeting using Ad-based vectors for prostate cancer is feasible and may serve as a basis for the development of gene therapy of human prostate cancer as well as other Her2/neu-expressing cancers.

Estrogen-initiated transformation of prostate epithelium derived from normal human prostate stem-progenitor cells

The present study sought to determine whether estrogens with testosterone support are sufficient to transform the normal human prostate epithelium and promote progression to invasive adenocarcinoma using a novel chimeric prostate model. Adult prostate stem/early progenitor cells were isolated from normal human prostates through prostasphere formation in three-dimensional culture. The stem/early progenitor cell status and clonality of prostasphere cells was confirmed by immunocytochemistry and Hoechst staining. Normal prostate progenitor cells were found to express estrogen receptor α, estrogen receptor β, and G protein-coupled receptor 30 mRNA and protein and were responsive to 1 nm estradiol-17β with increased numbers and prostasphere size, implicating them as direct estrogen targets. Recombinants of human prostate progenitor cells with rat urogenital sinus mesenchyme formed chimeric prostate tissue in vivo under the renal capsule of nude mice. Cytodifferentiation of human prostate progenitor cells in chimeric tissues was confirmed by immunohistochemistry using epithelial cell markers (p63, cytokeratin 8/18, and androgen receptor), whereas human origin and functional differentiation were confirmed by expression of human nuclear antigen and prostate-specific antigen, respectively. Once mature tissues formed, the hosts were exposed to elevated testosterone and estradiol-17β for 1-4 months, and prostate pathology was longitudinally monitored. Induction of prostate cancer in the human stem/progenitor cell-generated prostatic tissue was observed over time, progressing from normal histology to epithelial hyperplasia, prostate intraepithelial neoplasia, and prostate cancer with local renal invasion. These findings provide the first direct evidence that human prostate progenitor cells are estrogen targets and that estradiol in an androgen-supported milieu is a carcinogen for human prostate epithelium.

Evidence of epithelial to mesenchymal transition associated with increased tumorigenic potential in an immortalized normal prostate epithelial cell line

BACKGROUND

The majority of established human prostate cancer cell lines are derived from metastatic lesions and are already tumorigenic in vivo, therefore immortalized normal prostate cell lines may provide a more relevant model to unveil the mechanisms associated with cancer progression and metastasis.

METHODS

PZ-HPV-7, an immortalized human prostate epithelial cell line was used to generate xenograft tumors in mice. A subline designated HPV-PZ-7T was subsequently derived from the subrenal capsule xenograft of a nude mouse. These cells were further characterized using karyotyping, immunofluorescence, qRT-PCR, Western blotting, and three-dimensional cultures in Matrigel.

RESULTS

The PZ-HPV-7 cell line possesses a typical epithelial morphology, expresses basal cell markers, and is capable of forming web-like structures with evidence of budding on Matrigel. PZ-HPV-7 is non-tumorigenic in immunocompromised mice by either subcutaneous injection or subrenal grafting. In contrast, the PZ-HPV-7T cells, derived from a xenograft tumor induced by co-inoculation with matrigel using subrenal grafting, possess a mesenchymal phenotype as well as luminal cell markers and are highly tumorigenic and metastatic in nude mice. Functionally and biochemically, the PZ-HPV-7T subline appears to have undergone an epithelial-to-mesenchymal transition (EMT) from the parental PZ-HPV-7 line.

CONCLUSION

We have developed a novel EMT model using an immortalized normal prostate epithelial cell line and generated a new prostate cancer cell line, PZ-HPV-7T, which may represent an excellent system to study mechanisms associated with prostate cancer progression and metastasis.

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.

Development of a three-dimensional culture model of prostatic epithelial cells and its use for the study of epithelial-mesenchymal transition and inhibition of PI3K pathway in prostate cancer

BACKGROUND

Appropriate 3D culture models of human prostatic epithelial cells resembling normal growth pattern and architecture of prostate gland and its malignant development are scarce.

METHODS

Here, we optimized the 3D culture conditions of the immortalized non-transformed human prostatic epithelial cell line BPH-1 in Matrigel and developed a 3D culture model closely mimicking prostatic glandular structure.

RESULTS

Our results showed that BPH-1 cells cultured in Matrigel formed acinus-like spheroids with lumen formation and polarized differentiation. To establish an androgen-stimulated differentiation in AR-negative BPH-1, we generated AR-transduced BPH-1 cells, which displayed androgen-induced secretory differentiation and growth suppression in 3D culture. We also evaluated the spheroid forming capacity of tumorigenic derivative BPH-1(CAFTD) sublines in 3D culture and their responses to PI3K inhibitor LY294002. Results showed that these tumorigenic BPH-1(CAFTD) sublines did not exhibit polarized differentiation in Matrigel culture. Interestingly, polarization could be restored by LY294002 treatment of BPH-1(CAFTD1) but not of BPH-1(CAFTD3) subline. Finally, we employed this 3D culture model to examine the significance of an EMT-regulatory transcription factor Snail in prostate cancer development by its stable transduction into BPH-1 cells. Results showed that BPH-1-Snail cells lost their spheroid forming capacity and exhibited an invasive phenotype.

CONCLUSIONS

Taken together, we established a 3D culture model of human prostatic epithelial cells with structural and functional relevance to normal prostate gland and prostate cancer development and also demonstrated that this 3D model might be useful to assess the ability of drugs to restore differentiation as a potential surrogate measure of efficacy for prostate cancer therapy.

Identification of secreted glycoproteins of human prostate and bladder stromal cells by comparative quantitative proteomics

BACKGROUND

Functional development of the prostate is governed by stromal mesenchyme induction and epithelial response. Stromal/epithelial signaling can be mediated through direct cell-cell contact and diffusible factors and their cell surface receptors. These inducers are likely secreted or membrane-associated extracellular proteins. Given the importance of intercellular communication, it is possible that diseases like cancer could arise from a loss of this communication. One approach to gain a molecular understanding of stromal cells is to identify, as a first step, secreted stromal signaling factors. We proposed to do this by comparative analysis between bladder and prostate.

METHODS

Secreted proteins were identified from cultured normal prostate and bladder stromal mesenchyme cells by glycopeptide-capture method followed by mass spectrometry. Differences in protein abundance between prostate and bladder were quantified from calculated peptide ion current area (PICA) followed by Western validation. Functional and pathway analyses of the proteins were carried out by Gene Ontology (GO) and Teranode software.

RESULTS

This analysis produced a list of 116 prostate and 84 bladder secreted glycoproteins with ProteinProphet probability scores > or =0.9. Stromal proteins upregulated in the prostate include cathepsin L, follistatin-related protein, neuroendocrine convertase, tumor necrosis factor receptor, and others that are known to be involved in signal transduction, extracellular matrix interaction, differentiation and transport.

CONCLUSIONS

We have identified a number of potential proteins for stromal signaling and bladder or prostate differentiation program. The prostate stromal/epithelial signaling may be accomplished through activation of the ECM-receptor interaction, complement and coagulation cascades, focal adhesion and cell adhesion pathways.

Polarized fluid movement and not cell death, creates luminal spaces in adult prostate epithelium

There are two predominant theories for lumen formation in tissue morphogenesis; cavitation driven by cell death, and membrane separation driven by epithelial polarity. To define the mechanism of lumen formation in prostate acini we examined both theories in several cell lines grown in 3D Matrigel culture. Lumen formation occurred early in culture and preceded the expression of cell death markers for apoptosis (active caspase 3) and autophagy (LC-3). Active caspase 3 was expressed by very few cells and inhibition of apoptosis did not suppress lumen formation. Despite LC-3 expression in all cells within a spheroid, this was not associated with cell death. However, expression of the prostate secretory protein coincided with lumen formation and subsequent disruption of polarized fluid movement led to significant inhibition of lumen formation. This work indicates that lumen formation is driven by the polarized movement of fluids and proteins in 3D prostate epithelial models and not by cavitation.

Prostate cancer stem cells: a new target for therapy

The existence of prostate cancer stem cells offers a theoretical explanation for many of the enduring uncertainties surrounding the etiology and treatment of the most commonly diagnosed tumor in US males. The study of cancer stem cells in prostate, as in other complex tissues, is critically dependent on the availability of pure cell populations, a situation complicated by the heterogeneity of prostate tumors. However, selection of cells with a CD133(+)/alpha 2 beta 1 integrin/ CD44(+) phenotype enriches for a tumor-initiating population from human prostate cancers. Among the most pressing needs is for enduring therapy in patients who have experienced failure of hormonal treatments. Because the putative cancer stem cell does not express androgen receptor, it is likely to be immune from most androgen-based therapies, and an inherent genetic instability would enable the tumor to develop the new variants present in hormone-refractory disease. Prostate cancer stem cells have a unique gene expression signature that can also be related to Gleason grade and patient outcome. The scarcity of cancer stem cells in a prostate tumor will probably limit their usefulness in cancer diagnosis and prognosis. However, the emergence of new stem-cell therapeutic targets not only will require new assays for efficacy (because of their relatively quiescent nature), but also holds real promise of more lasting treatments to augment those currently directed against the remaining tumor cells, which comprise 99.9% of tumor mass, but paradoxically have a poor tumor-initiating capacity.

Inhibition of monoamine oxidase A promotes secretory differentiation in basal prostatic epithelial cells

Monoamine oxidase A (MAO-A) expression is associated with high-grade prostate cancer. Immunohistochemistry showed that MAO-A is also expressed in the basal epithelial cells of normal prostate glands. Using cultured primary prostatic epithelial cells as a model, we showed that MAO-A prevents basal epithelial cells from differentiating into secretory cells. Under differentiation-promoting conditions, clorgyline, an irreversible MAO-A inhibitor, induced secretory cell-like morphology and repressed expression of cytokeratin 14, a basal cell marker. More importantly, clorgyline induced mRNA and protein expression of androgen receptor (AR), a hallmark of secretory epithelial cells. In clorgyline-treated cells, androgen induced luciferase activity controlled by the promoter of prostate-specific antigen, an AR target gene, in a dose-dependent manner. This activity was blocked by the AR antagonist Casodex, showing that AR is functional. In turn, androgen decreased MAO-A expression in clorgyline-treated, secretory-like cells. Our results demonstrated that cultured basal epithelial cells have the potential to differentiate into secretory cells, and that inhibition of MAO-A is a key factor in promoting this process. Increased expression of MAO-A in high-grade prostate cancer may be an important contributor to its de-differentiated phenotype, raising the possibility that MAO-A inhibition may restore differentiation and reverse the aggressive behavior of high-grade cancer.