A conditionally immortalized cell line model for the study of human prostatic epithelial cell differentiation

A role for class 3 semaphorins in prostate cancer

BACKGROUND

Class 3 semaphorins are secreted proteins that act as guidance cues for migrating cells via their transmembrane receptors plexins and neuropilins. Semaphorins have a role in cancer affecting tumor progression both directly, and indirectly by affecting angiogenesis.

METHODS

The expression of semaphorins and their receptors in prostate cancer cell lines and tissue was determined by RT-PCR, Western blotting and immunohistochemistry. The effect of Sema3E on prostate cancer cell lines was determined by adhesion assays and transwell migration assays.

RESULTS

Semaphorins and their receptors, plexins and neuropilins, are widely co-expressed in prostate cancer cell lines and tissue with a significant overexpression of Sema3E in tumor tissue. Sema3E affected integrin-mediated adhesion to fibronectin of prostate cancer cells, and inhibited their motility. Expression of Sema3C was upregulated and Sema3A and Sema3E were down regulated in prostate cells by hypoxia, consistent with an additional role for Sema3A and 3E as anti-angiogenic factors in prostate cancer.

CONCLUSIONS

Semaphorin 3E is aberrantly expressed in prostate cancer and affects adhesion and motility of prostate cancer cells, indicating a role for the Sema3E/PlexinD1 signaling pathway in prostate cancer and identifying a new possible target for therapy.

Stemness markers characterize IGR-CaP1, a new cell line derived from primary epithelial prostate cancer

Deciphering molecular pathways involved in the early steps of prostate oncogenesis requires both in vitro and in vivo models derived from human primary tumors. However the few recognized models of human prostate epithelial cancer originate from metastases. To date, very few models are proposed from primary tumors and immortalizing normal human prostate cells does not recapitulate the natural history of the disease. By culturing human prostate primary tumor cells onto human epithelial extra-cellular matrix, we successfully selected a new prostate cancer cell line, IGR-CaP1, and clonally-derived subclones. IGR-CaP1 cells, that harbor a tetraploid karyotype, high telomerase activity and mutated TP53, rapidly induced subcutaneous xenografts in nude mice. Furthermore, IGR-CaP1 cell lines, all exhibiting negativity for the androgen receptor and PSA, express the specific prostate markers alpha-methylacyl-CoA racemase and a low level of the prostate-specific membrane antigen PSMA, along with the prostate basal epithelial markers CK5 and CK14. More importantly, these clones express high CD44, CD133, and CXCR4 levels associated with high expression of α2β1-integrin and Oct4 which are reported to be prostate cancer stemness markers. RT-PCR data also revealed high activation of the Sonic Hedgehog signalling pathway in these cells. Additionally, the IGR-CaP1 cells possess a 3D sphere-forming ability and a renewal capacity by maintaining their CSC potential after xenografting in mice. As a result, the hormone-independent IGR-CaP1 cellular clones exhibit the original features of both basal prostate tissue and cancer stemness. Tumorigenic IGR-CaP1 clones constitute invaluable human models for studying prostate cancer progression and drug assessment in vitro as well as in animals specifically for developing new therapeutic approaches targeting prostate cancer stem cells.

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.

TEAD1 and c-Cbl are novel prostate basal cell markers that correlate with poor clinical outcome in prostate cancer

Prostate cancer is the most frequently diagnosed male cancer, and its clinical outcome is difficult to predict. The disease may involve the inappropriate expression of genes that normally control the proliferation of epithelial cells in the basal layer and their differentiation into luminal cells. Our aim was to identify novel basal cell markers and assess their prognostic and functional significance in prostate cancer. RNA from basal and luminal cells isolated from benign tissue by immunoguided laser-capture microdissection was subjected to expression profiling. We identified 112 and 267 genes defining basal and luminal populations, respectively. The transcription factor TEAD1 and the ubiquitin ligase c-Cbl were identified as novel basal cell markers. Knockdown of either marker using siRNA in prostate cell lines led to decreased cell growth in PC3 and disrupted acinar formation in a 3D culture system of RWPE1. Analyses of prostate cancer tissue microarray staining established that increased protein levels of either marker were associated with decreased patient survival independent of other clinicopathological metrics. These data are consistent with basal features impacting on the development and clinical course of prostate cancers.

Expression profiling of CD133+ and CD133- epithelial cells from human prostate

BACKGROUND

Recent evidence suggests that prostate stem cells in benign and tumor tissue express the cell surface marker CD133, but these cells have not been well characterized. The aim of our study was to gene expression profile CD133-expressing cells.

METHODS

We analyzed CD133-positive (CD133+) and -negative (CD133-) sub-populations of high-integrin expressing epithelial cells isolated from benign human prostate tissue and hormone-refractory prostate cancer (HRPC).

RESULTS

CD133+ cells freshly isolated from benign prostate tissue exhibited an expression profile characteristic of a putative stem/progenitor cell population, with transcripts involved in biological processes ranging from development and ion homeostasis to cell communication. The profile of CD133- cells was consistent with that of a transit amplifying population, suggesting up-regulated proliferation and metabolism. Comparison of benign populations to those from HRPC showed some similarities between CD133+ profiles but also revealed significant differences that provide a tumor-specific pattern, which included evidence of increased metabolic activity and active proliferation. Subsequently, we demonstrated protein expression of a number of candidate genes in these cell populations and in benign tissue. In a novel observation we also found expression of some of these markers in prostate tumors, including the oligodendrocyte lineage transcription factor OLIG1.

CONCLUSIONS

This study provides a unique genome-wide molecular signature of CD133+ and CD133- human prostate epithelial cells. This will provide a valuable resource for prostate stem cell biology research and the identification of novel therapeutic targets for the treatment of prostate cancer.

Prostate stromal and urogenital sinus mesenchymal cell lines for investigations of stromal-epithelial interactions

Bidirectional signaling between the urogenital sinus epithelium and mesenchyme is an essential element of prostate development that regulates ductal morphogenesis, growth, and differentiation. Comparable interactions between the epithelium and stroma in the adult prostate appear to regulate normal growth homeostasis. Alterations in the stromal-epithelial dialogue that recapitulate features of the mesenchymal-epithelial interactions of development may play a critical role in the development of benign prostatic hyperplasia and in the progression of prostate cancer. For this reason, the mesenchymal-epithelial interactions of development are of considerable interest. In this review, we provide an overview of the mesenchymal contribution to rodent prostate development with an emphasis on the stage just before ductal budding (embryonic day 16; E16) and describe the isolation, characterization and utility of a newly established E16 urogenital sinus mesenchymal cell line.

Gene expression profiling identifies lobe-specific and common disruptions of multiple gene networks in testosterone-supported, 17beta-estradiol- or diethylstilbestrol-induced prostate dysplasia in Noble rats

The xenoestrogen diethylstilbestrol (DES) is commonly believed to mimic the action of the natural estrogen 17beta-estradiol (E2). To determine if these two estrogens exert similar actions in prostate carcinogenesis, we elevated circulating levels of estrogen in Noble (NBL) rats with E(2/DES-filled implants, while maintaining physiological levels of testosterone (T) in the animals with T-filled implants. The two estrogens induced dysplasia in a lobe-specific manner, with E2 targeting only the lateral prostate (LP) and DES impacting only the ventral prostate (VP). Gene expression profiling identified distinct and common E2-disrupted versus DES-disrupted gene networks in each lobe. More importantly, hierarchical clustering analyses revealed that T + E2 treatment primarily affected the gene expression pattern in the LP, whereas T + DES treatment primarily affected the gene expression profile in the VP. Gene ontology analyses and pathway mapping suggest that the two hormone treatments disrupt unique and/or common cellular processes, including cell development, proliferation, motility, apoptosis, and estrogen signaling, which may be linked to dysplasia development in the rat prostate. These findings suggest that the effects of xenoestrogens and natural estrogens on the rat prostate are more divergent than previously suspected and that these differences may explain the lobe-specific carcinogenic actions of the hormones.

Culture requirements of prostatic epithelial cell lines for acinar morphogenesis and lumen formation in vitro: role of extracellular calcium

BACKGROUND

Three-dimensional (3D) culture of benign prostatic epithelial cell lines can recapitulate acinar morphogenesis in vitro, but the broad applicability of this approach has not been described. The present studies examine the culture conditions important for prostatic acinar morphogenesis in vitro and the role of extracellular calcium in this process.

METHODS

With optimized culture conditions, RWPE-1, pRNS-1-1, PZ-HPV-7, PNT1A, BPH-1, and PrEC were analyzed for their ability to undergo acinar morphogenesis in 3D culture and by immunoblotting. RWPE-1 cells were further examined for the effects of calcium on morphology, E-cadherin membrane localization and multicellular layering in 2D culture and for acinar morphogenesis, luminal apoptosis, and luminal filling in 3D.

RESULTS

Cell lines grown in low-calcium medium have the ability to form acinar structures with lumens, which correlates with E-cadherin expression, but low calcium is not required for this process. Adding CaCl(2) to the medium strongly inhibits lumen formation, luminal apoptosis and induces luminal filling, and luminal filling is blocked by an interfering antibody.

CONCLUSIONS

Optimized medium composition allows nearly all seeded RWPE-1 cells to undergo acinar morphogenesis, forming consistent structures representative of normal adult prostate glands. Low-calcium-containing medium appears selective for cells capable of undergoing acinar morphogenesis in vitro, and branching and luminal space within the acini are strongly influenced by extracellular calcium levels, likely through the actions of E-cadherin. These results provide important information about a relevant in vitro model with which to study prostate development and carcinogenesis and highlight the importance of extracellular calcium in regulating 3D morphology.

Differential gene expression in the peripheral zone compared to the transition zone of the human prostate gland

Gene expression profiles may lend insight into whether prostate adenocarcinoma (CaP) predominantly occurs in the peripheral zone (PZ) compared to the transition zone (TZ). From human prostates, tissue sets consisting of PZ and TZ were isolated to investigate whether there is a differential level of gene expression between these two regions of this gland. Gene expression profiling using Affymetrix Human Genome U133 plus 2.0 arrays coupled with quantitative real-time reverse transcriptase-PCR was employed. Genes associated with neurogenesis, signal transduction, embryo implantation and cell adhesion were found to be expressed at a higher level in the PZ. Those overexpressed in the TZ were associated with neurogenesis development, signal transduction, cell motility and development. Whether such differential gene expression profiles may identify molecular mechanisms responsible for susceptibility to CaP remains to be ascertained.