Are primary cultures realistic models of prostate cancer?

Cancer associated fibroblast: Mediators of tumorigenesis

It is well accepted that the tumor microenvironment plays a pivotal role in cancer onset, development, and progression. The majority of clinical interventions are designed to target either cancer or stroma cells. These emphases have been directed by one of two prevailing theories in the field, the Somatic Mutation Theory and the Tissue Organization Field Theory, which represent two seemingly opposing concepts. This review proposes that the two theories are mutually inclusive and should be concurrently considered for cancer treatments. Specifically, this review discusses the dynamic and reciprocal processes between stromal cells and extracellular matrices, using pancreatic cancer as an example, to demonstrate the inclusivity of the theories. Furthermore, this review highlights the functions of cancer associated fibroblasts, which represent the major stromal cell type, as important mediators of the known cancer hallmarks that the two theories attempt to explain.

Establishment and characterization of a novel cell line (cc‑006cpm8) of moderately/poorly differentiated colorectal adenocarcinoma derived from a primary tumor of a patient

In the present study, the cc‑006cpm8 novel colon cell line was established from a sample of right colorectal adenocarcinoma obtained from a woman with liver metastasis. It was possible to culture this cell line for ≥100 passages in vitro with vigorous growth. Morphologically, the cells grew as several layers with tight adhesion to the surface of the culture plate. The morphological, immunological and ultrastructural features of these cells suggested their epithelial origin. The characterization of this cell line indicated a doubling time of 27 h, a colony forming efficiency of 73.2% in semisolid media and a plate efficiency of 66.5% in liquid culture. The modal number of chromosomes was 50. In vivo, the cc‑006cpm8 cells underwent tumorigenesis in all nude mice used. Immunohistochemical analysis demonstrated that mutS homolog 2 (MSH2) and MSH6 were expressed; however, mutL homolog 1 and postmeiotic segregation 2 were downregulated in cc‑006cpm8 cells. To determine the mutation profile of the cell line analyzed, exome capture DNA sequencing was performed. The results revealed 20 hypermutated exons comprising single nucleotide polymorphisms, and insertion and deletions (InDels), including single nucleotide variants of mucin (MUC)19, MUC16, MUC12, filaggrin and AHNAK nucleoprotein 2, and InDels of β defensin‑126, microRNA‑3665, WNK lysine deficient protein kinase 1 and SLAIN motif‑containing protein 1. In addition, commonly mutated genes in colorectal cancer and exon mutations of genes in cc‑006cpm8 cells were analyzed, including adenomatous polyposis coli, tumor protein p53, Drosophila mothers against decapentaplegic 4, phosphatidylinositol‑4,5‑bisphosphate 3‑kinase catalytic subunit α and Kirsten rat sarcoma, and genes associated with the DNA mismatch repair pathway were investigated.

Prostate Stroma Increases the Viability and Maintains the Branching Phenotype of Human Prostate Organoids

The fibromuscular stroma of the prostate regulates normal epithelial differentiation and contributes to carcinogenesis in vivo. We developed and characterized a human 3D prostate organoid co-culture model that incorporates prostate stroma. Primary prostate stromal cells increased organoid formation and directed organoid morphology into a branched acini structure similar to what is observed in vivo. Organoid branching occurred distal to physical contact with stromal cells, demonstrating non-random branching. Stroma-induced phenotypes were similar in all patients examined, yet they maintained inter-patient heterogeneity in the degree of response. Stromal cells expressed growth factors involved in epithelial differentiation, which was not observed in non-prostatic fibroblasts. Organoids derived from areas of prostate cancer maintained differential expression of alpha-methylacyl-CoA racemase and showed increased viability and passaging when co-cultured with stroma. The addition of stroma to epithelial cells in vitro improves the ability of organoids to recapitulate features of the tissue and enhances the viability of organoids.

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Co-culture with human primary prostate stroma improves epithelial organoid viability

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Stromal cell contact in co-culture directs epithelial organoid branching

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Prostate stromal cells express morphogenic factors unique from non-prostate fibroblasts

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Co-culture with stroma maintains AMACR and increases survival of cancer derived-organoids

Modeling African American prostate adenocarcinoma by inducing defined genetic alterations in organoids

Genomic studies are rapidly identifying genetic alterations in human cancer, but functional validation of such alterations has been slow. Here, using human prostate cancer as a model, we have assessed the feasibility of engineering defined genetic alterations in well-known cancer driver genes to transform benign prostate epithelial organoids derived from African American men. Benign human prostate organoids were transduced with lentiviruses expressing MYC, shPTEN, shTP53 and AR, alone and in various combinations, to recapitulate prostate cancer development. Organoids expressing MYC, shPTEN, shTP53 and AR (denoted MPPA); MYC, shPTEN and shTP53 (MPP); or MYC (M) were significantly larger, had higher proliferation rates and demonstrated pathologically transformed morphology compared to organoids transduced with control lentivirus. Alterations in MYC, PTEN and TP53 also affected the rate of organoid basal-to-luminal differentiation in vitro. MPPA and MPP organoids expressed the clinical prostate cancer marker AMACR and developed prostate adenocarcinoma when grafted under the renal capsule in mice. These data indicate that genetic alterations commonly observed in human prostate cancer can be rapidly modeled in human organoid culture. Prostate cancer organoids provide a useful pre-clinical model for the evaluation of new candidate cancer genes, cancer disparities, and potentially for testing of novel therapeutic agents.

Rapid and Short-term Extracellular Matrix-mediated In Vitro Culturing of Tumor and Nontumor Human Primary Prostate Cells From Fresh Radical Prostatectomy Tissue

OBJECTIVE

To culture prostate cells from fresh biopsy core samples from radical prostatectomy (RP) tissue. Further, given the genetic heterogeneity of prostate cells, the ability to culture single cells from primary prostate tissue may be of importance toward enabling single-cell characterization of primary prostate tissue via molecular and cellular phenotypic biomarkers.

METHODS

A total of 260 consecutive tissue samples from RPs were collected between October 2014 and January 2016, transported at 4°C in serum-free media to an off-site central laboratory, dissociated, and cultured. A culture protocol, including a proprietary extracellular matrix formulation (ECMf), was developed that supports rapid and short-term single-cell culture of primary human prostate cells derived from fresh RP samples.

RESULTS

A total of 251 samples, derived from RP samples, yielded primary human tumor and nontumor prostate cells. Cultured cells on ECMf exhibit (1) survival after transport from the operating room to the off-site centralized laboratory, (2) robust (>80%) adhesion and survival, and (3) expression of different cell-type-specific markers. Cells derived from samples of increasing Gleason score exhibited a greater number of focal adhesions and more focal adhesion activation as measured by phospho-focal adhesion kinase (Y397) immunofluorescence when patient-derived cells were cultured on ECMf. Increased Ki67 immunofluorescence levels were observed in cells derived from cancerous RP tissue when compared to noncancerous RP tissue.

CONCLUSION

By utilizing a unique and defined extracellular matrix protein formulation, tumor and nontumor cells derived from primary human prostate tissue can be rapidly cultured and analyzed within 72 hours after harvesting from RP tissue.

miR-182, of the miR-183 cluster family, is packaged in exosomes and is detected in human exosomes from serum, breast cells and prostate cells

Members of the microRNA (miR)-183 family are expressed at high levels in the majority of cancer types, including breast and prostate, and are considered ‘oncomiRs’. The purpose of the present study was to investigate the role of exosomes in cell-to-cell transfer of the miR-183 family, which includes miRs-96, −182 and −183. Despite highly detectable levels of these three miRs within prostate and breast cells in vitro, only miR-182 was detectable in exosomes isolated from cell culture supernatant. Similar to the in vitro results, miR-182 was the only miR detected in exosomes isolated from fresh human serum. The packaging of miR-182 into exosomes was examined in MDA-MB-231 (MDA-182) breast cancer cells with miR-182 overexpression. Levels of mature miR-182 increased in exosomes in a dose-dependent manner compared to intracellular expression. Furthermore, co-culture of MDA-182 cells with naïve MDA-MB-231 cells resulted in an increase in mature miR-182 in the naïve cells, which was blocked by a chemical inhibitor of microvesicle formation. In summary, the present study demonstrates that of the miR-183 family members, miR-182 is preferentially packaged in exosomes, detectable in exosomes from human sera and may be transferred between cells via a microvesicle-dependent mechanism.

Differential expression and regulation of vitamin D hydroxylases and inflammatory genes in prostate stroma and epithelium by 1,25-dihydroxyvitamin D in men with prostate cancer and an in vitro model

Previous work on vitamin D in the prostate has focused on the prostatic epithelium, from which prostate cancer arises. Prostatic epithelial cells are surrounded by stroma, which has well-established regulatory control over epithelial proliferation, differentiation, and the inflammatory response. Here we examined the regulation of vitamin D-related genes and inflammatory genes by 1α,25-dihydroxyvitamin D3 (1,25(OH)2D) in laser-capture microdissected prostate tissue from a vitamin D3 clinical trial and in an in vitro model that facilitates stromal-epithelial crosstalk. Analysis of the trial tissues showed that VDR was present in both cell types, whereas expression of the hydroxylases was the highest in the epithelium. Examination of gene expression by prostatic (1,25(OH)2D) concentrations showed that VDR was significantly lower in prostate tissues with the highest concentration of 1,25(OH)2D, and down-regulation of VDR by 1,25(OH) 2D was confirmed in the primary cell cultures. Analysis of inflammatory genes in the patient tissues revealed that IL-6 expression was the highest in the prostate stroma while PTGS2 (COX2) levels were lowest in the prostate cancer tissues from men in the highest tertile of prostatic 1,25(OH)2D. In vitro, TNF-α, IL-6 and IL-8 were suppressed by 1,25 (OH)2D in the primary epithelial cells, whereas TNF-α and PTGS2 were suppressed by 1,25(OH) 2D in the stromal cells. Importantly, the ability of 1,25(OH)2D to alter pro-inflammatory-induced changes in epithelial cell growth were dependent on the presence of the stromal cells. In summary, whereas both stromal and epithelial cells of the prostate express VDR and can presumably respond to 1,25(OH)2D, the prostatic epithelium appears to be the main producer of 1,25(OH)2D. Further, while the prostate epithelium was more responsive to the anti-inflammatory activity of 1,25 (OH)2D than stromal cells, stroma-epithelial crosstalk enhanced the phenotypic effects of 1,25(OH)2D and the inflammatory process in the prostate gland.

Establishment of highly tumorigenic human colorectal cancer cell line (CR4) with properties of putative cancer stem cells

Background

Colorectal cancer (CRC) has the third highest mortality rates among the US population. According to the most recent concept of carcinogenesis, human tumors are organized hierarchically, and the top of it is occupied by malignant stem cells (cancer stem cells, CSCs, or cancer-initiating cells, CICs), which possess unlimited self-renewal and tumor-initiating capacities and high resistance to conventional therapies. To reflect the complexity and diversity of human tumors and to provide clinically and physiologically relevant cancer models, large banks of characterized patient-derived low-passage cell lines, and especially CIC-enriched cell lines, are urgently needed.

Principal Findings

Here we report the establishment of a novel CIC-enriched, highly tumorigenic and clonogenic colon cancer cell line, CR4, derived from liver metastasis. This stable cell line was established by combining 3D culturing and 2D culturing in stem cell media, subcloning of cells with particular morphology, co-culture with carcinoma associated fibroblasts (CAFs) and serial transplantation to NOD/SCID mice. Using RNA-Seq complete transcriptome profiling of the tumorigenic fraction of the CR4 cells in comparison to the bulk tumor cells, we have identified about 360 differentially expressed transcripts, many of which represent stemness, pluripotency and resistance to treatment. Majority of the established CR4 cells express common markers of stemness, including CD133, CD44, CD166, EpCAM, CD24 and Lgr5. Using immunocytochemical, FACS and western blot analyses, we have shown that a significant ratio of the CR4 cells express key markers of pluripotency markers, including Sox-2, Oct3/4 and c-Myc. Constitutive overactivation of ABC transporters and NF-kB and absence of tumor suppressors p53 and p21 may partially explain exceptional drug resistance of the CR4 cells.

Conclusions

The highly tumorigenic and clonogenic CIC-enriched CR4 cell line may provide an important new tool to support the discovery of novel diagnostic and/or prognostic biomarkers as well as the development of more effective therapeutic strategies.

Prostate cancer stem cell-targeted efficacy of a new-generation taxoid, SBT-1214 and novel polyenolic zinc-binding curcuminoid, CMC2.24

BACKGROUND

Prostate cancer is the second leading cause of cancer death among men. Multiple evidence suggests that a population of tumor-initiating, or cancer stem cells (CSCs) is responsible for cancer development and exceptional drug resistance, representing a highly important therapeutic target. The present study evaluated CSC-specific alterations induced by new-generation taxoid SBT-1214 and a novel polyenolic zinc-binding curcuminoid, CMC2.24, in prostate CSCs.

PRINCIPAL FINDINGS

The CD133(high)/CD44(high) phenotype was isolated from spontaneously immortalized patient-derived PPT2 cells and highly metastatic PC3MM2 cells. Weekly treatment of the NOD/SCID mice bearing PPT2- and PC3MM3-induced tumors with the SBT-1214 led to dramatic suppression of tumor growth. Four of six PPT2 and 3 of 6 PC3MM2 tumors have shown the absence of viable cells in residual tumors. In vitro, SBT-1214 (100 nM-1 µM; for 72 hr) induced about 60% cell death in CD133(high)/CD44(+/high) cells cultured on collagen I in stem cell medium (in contrast, the same doses of paclitaxel increased proliferation of these cells). The cytotoxic effects were increased when SBT-1214 was combined with the CMC2.24. A stem cell-specific PCR array assay revealed that this drug combination mediated massive inhibition of multiple constitutively up-regulated stem cell-related genes, including key pluripotency transcription factors. Importantly, this drug combination induced expression of p21 and p53, which were absent in CD133(high)/CD44(high) cells. Viable cells that survived this treatment regimen were no longer able to induce secondary spheroids, exhibited significant morphological abnormalities and died in 2-5 days.

CONCLUSIONS

We report here that the SBT-1214 alone, or in combination with CMC2.24, possesses significant activity against prostate CD133(high)/CD44(+/high) tumor-initiating cells. This drug combination efficiently inhibits expression of the majority of stem cell-related genes and pluripotency transcription factors. In addition, it induces a previously absent expression of p21 and p53 ("gene wake-up"), which can potentially reverse drug resistance by increasing sensitivity to anti-cancer drugs.

Influence of lycopene on cell viability, cell cycle, and apoptosis of human prostate cancer and benign hyperplastic cells

Prostate cancer is the most common malignancy in men and the second leading cause of cancer-related mortality in men of the Western world. Lycopene has received attention because of its expcted potential to prevent cancer. In the present study, we evaluated the influence of lycopene on cell viability, cell cycle, and apoptosis of human prostate cancer cells and benign prostate hyperplastic cells. Using MTT assay, we observed a decrease of cell viability in all cancer cell lines after treatment with lycopene, which decreased the percentage of cells in G0/G1 phase and increased in S and G2/M phases after 96 h of treatment in metastatic prostate cancer cell lineages. Flow citometry analysis of cell cycle revealed lycopene promoted cell cycle arrest in G0/G1 phase after 48 and 96 h of treatment in a primary cancer cell line. Using real time PCR assay, lycopene also induced apoptosis in prostate cancer cells with altered gene expression of Bax and Bcl-2. No effect was observed in benign prostate hyperplasia cells. These results suggest an effect of lycopene on activity of human prostate cancer cells.

Metabolic reprogramming and validation of hyperpolarized 13C lactate as a prostate cancer biomarker using a human prostate tissue slice culture bioreactor

BACKGROUND

The treatment of prostate cancer has been impeded by the lack of both clinically relevant disease models and metabolic markers that track tumor progression. Hyperpolarized (HP) (13) C MR spectroscopy has emerged as a new technology to investigate the metabolic shifts in prostate cancer. In this study, we investigate the glucose reprogramming using HP (13) C pyruvate MR in a patient-derived prostate tissue slice culture (TSC) model.

METHODS

The steady-state metabolite concentrations in freshly excised human prostate TSCs were assessed and compared to those from snap-frozen biopsy samples. The TSCs were then applied to a perfused cell (bioreactor) platform, and the bioenergetics and the dynamic pyruvate flux of the TSCs were investigated by (31) P and HP (13) C MR, respectively.

RESULTS

The prostate TSCs demonstrated steady-state glycolytic and phospholipid metabolism, and bioenergetics that recapitulate features of prostate cancer in vivo. (13) C spectra following injection of HP (13) C pyruvate showed significantly increased pyruvate to lactate flux in malignant as compared to the benign prostate TSCs. This increased flux in the malignant prostate TSCs correlated with both increased expression of monocarboxylate transporters (MCT) and activity of lactate dehydrogenase (LDH).

CONCLUSIONS

We provide the first mechanistic evidence for HP (13) C lactate as a prostate cancer biomarker in living human tissues, critical for the interpretation of in vivo studies. More broadly, the clinically relevant metabolic model system in combination with HP MR can facilitate the identification of clinically translatable biomarkers of prostate cancer presence, aggressiveness, and treatment response.

Effects of lycopene on protein expression in human primary prostatic epithelial cells

Clinical trials and animal studies have suggested that lycopene, the red carotenoid found in tomatoes, might be useful for the prevention of prostate cancer in the diet or as a dietary supplement through a variety of chemoprevention mechanisms. As most mechanism of action studies have used prostate cancer cells or males with existing prostate cancer, we investigated the effects of lycopene on protein expression in human primary prostatic epithelial cells. After treatment with lycopene at a physiologically relevant concentration (2 μmol/L) or placebo for 48 hours, the primary prostatic epithelial cells were lysed and fractionated using centrifugation into cytosolic/membrane and nuclear fractions. Proteins from lycopene-treated and placebo-treated cells were trypsinized and derivatized for quantitative proteomics using isobaric tags for relative and absolute quantitation (iTRAQ) reagent. Peptides were analyzed using two-dimensional microcapillary high-performance liquid chromatography-tandem mass spectrometry to identify proteins that were significantly upregulated or downregulated following lycopene exposure. Proteins that were most affected by lycopene were those involved in antioxidant responses, cytoprotection, apoptosis, growth inhibition, androgen receptor signaling, and the Akt/mTOR cascade. These data are consistent with previous studies suggesting that lycopene can prevent cancer in human prostatic epithelial cells at the stages of cancer initiation, promotion, and/or progression.

Effect of Serenoa repens (Permixon®) on the expression of inflammation-related genes: analysis in primary cell cultures of human prostate carcinoma

Background

To analyze the expression at basal level of inflammation-related cytokines and chemokines and the activation status of the NF-κB pathway, together with the proliferation and apoptosis indexes in two widely used in vitro tumor models, the androgen-dependent human Prostate Cancer (PC) cell line LNCaP and the androgen-independent PC3 , and in primary cultures of human PC cells. To assess in these models and primary cultures, the effects of Serenoa repens (LSESr, Permixon®) on proliferation/apoptosis ratio, inflammation-related genes expression and NF-κB pathway activation.

Methods

The expression of IL-6, CCL-5, CCL-2, COX-1, COX-2, iNOS inflammation-related genes has been evaluated at the mRNA level in two in vitro human PC models (LNCaP and PC3 cell lines) and in 40 independent human prostatic primary cultures obtained from PC patients undergoing radical prostatectomy. Tissue fragments were collected from both PC lesions and normal hyperplastic tissue counterparts for each case. All cultures were treated with two different amounts of Permixon® (44 and 88 μg/ml) for different time points (16, 24, 48 and 72 hours), depending on the cell type and the assay; the expression of inflammation-related genes, cell growth (proliferation/apoptosis ratio) and NF-κB activation has been analyzed in treated and untreated cells by means of semi-quantitative RNA-PCR, cell proliferation and immunofluorescence respectively.

Results

We detected a significant reduction (p <0.001) in PC and normal cells proliferation due to Permixon ® treatment. This result was related to an increase of the apoptotic activity showed by an increase in the number of anti-caspase-3 fluorescent cells. Almost all the inflammation-related genes (IL-6, CCL-5, CCL-2, COX-2 and iNOS) were expressed at the basal level in in vitro cultured cells and primary cultures and down-regulated by Permixon® treatment. This treatment interfered with NF-kB activation, detecting by the translocation of more than 30% of NF-κB p65 subunit to the nucleus.

Conclusions

The present study confirms the expression of inflammatory pattern in PC. We showed the effect of Permixon® on down-regulation of inflammatory-related genes in cell lines and in primary cultures. The inhibitory effect of Permixon® on cell growth could be partly associated to the down-regulation of inflammatory-related genes and to the activation of NF-κB pathway in prostate tissue.

Epcam, CD44, and CD49f distinguish sphere-forming human prostate basal cells from a subpopulation with predominant tubule initiation capability

BACKGROUND

Human prostate basal cells expressing alpha-6 integrin (CD49f(Hi)) and/or CD44 form prostaspheres in vitro. This functional trait is often correlated with stem/progenitor (S/P) activity, including the ability to self-renew and induce differentiated tubules in vivo. Antigenic profiles that distinguish tubule-initiating prostate stem cells (SCs) from progenitor cells (PCs) and mature luminal cells (LCs) with less regenerative potential are unknown.

METHODOLOGY/PRINCIPLE FINDINGS

Prostasphere assays and RT-PCR analysis was performed following FACS separation of total benign prostate cells based upon combinations of Epcam, CD44, and/or CD49f expression. Epithelial cell fractions were isolated, including Epcam(+)CD44(+) and Epcam+CD44+CD49f(Hi) basal cells that formed abundant spheres. When non-sphere-forming Epcam(+)CD44(-) cells were fractionated based upon CD49f expression, a distinct subpopulation (Epcam(+)CD44(-)CD49f(Hi)) was identified that possessed a basal profile similar to Epcam(+)CD44(+)CD49f(Hi) sphere-forming cells (p63(+)AR(Lo)PSA(-)). Evaluation of tubule induction capability of fractionated cells was performed, in vivo, via a fully humanized prostate tissue regeneration assay. Non-sphere-forming Epcam(+)CD44(-) cells induced significantly more prostate tubular structures than Epcam(+)CD44(+) sphere-forming cells. Further fractionation based upon CD49f co-expression identified Epcam(+)CD44(-)CD49f(Hi) (non-sphere-forming) basal cells with significantly increased tubule induction activity compared to Epcam(+)CD44(-)CD49f(Lo) (true) luminal cells.

CONCLUSIONS/SIGNIFICANCE

Our data delineates antigenic profiles that functionally distinguish human prostate epithelial subpopulations, including putative SCs that display superior tubule initiation capability and induce differentiated ductal/acini structures, sphere-forming PCs with relatively decreased tubule initiation activity, and terminally differentiated LCs that lack both sphere-forming and tubule-initiation activity. The results clearly demonstrate that sphere-forming ability is not predictive of tubule-initiation activity. The subpopulations identified are of interest because they may play distinct roles as cells of origin in the development of prostatic diseases, including cancer.

Vitamin D metabolism and action in the prostate: implications for health and disease

Prostate cancer (PCa) is the second most common cancer in men worldwide. Epidemiological, molecular, and cellular studies have implicated vitamin D deficiency as a risk factor for the development and/or progression of PCa. Studies using cell culture systems and animal models suggest that vitamin D acts to reduce the growth of PCa through regulation of cellular proliferation and differentiation. However, although preclinical studies provide a strong indication for anti-cancer activity, proof of therapeutic benefits in men is still lacking. The anti-proliferative and pro-differentiating properties of vitamin D have been attributed to calcitriol [1,25(OH)(2)D(3)], the hormonally active form of vitamin D, acting through the vitamin D receptor (VDR). Metabolism of vitamin D in target tissues is mediated by two key enzymes: 1α-hydroxylase (CYP27B1), which catalyzes the synthesis of calcitriol from 25(OH)D and 24-hydroxylase (CYP24), which catalyzes the initial step in the conversion of calcitriol to less active metabolites. Many factors affect the balance of calcitriol synthesis and catabolism and several maneuvers, like combination therapy of calcitriol with other drugs, have been explored to treat PCa and reduce its risk. The current paper is an overview addressing some of the key factors that influence the biological actions of vitamin D and its metabolites in the treatment and/or prevention of PCa.

Establishment and genomic characterization of mouse xenografts of human primary prostate tumors

Serum prostate-specific antigen screening has led to earlier detection and surgical treatment of prostate cancer, favoring an increasing incidence-to-mortality ratio. However, about one third of tumors that are diagnosed when still confined to the prostate can relapse within 10 years from the first treatment. The challenge is therefore to identify prognostic markers of aggressive versus indolent tumors. Although several preclinical models of advanced prostate tumors are available, a model that recapitulates the genetic and growth behavior of primary tumors is still lacking. Here, we report a complete histopathological and genomic characterization of xenografts derived from primary localized low- and high-grade human prostate tumors that were implanted under the renal capsule of immunodeficient mice. We obtained a tumor take of 56% and show that these xenografts maintained the histological as well as most genomic features of the parental tumors. Serum prostate-specific antigen levels were measurable only in tumor xenograft-bearing mice, but not in those implanted with either normal prostate tissue or in tumors that likely regressed. Finally, we show that a high proliferation rate, but not the pathological stage or the Gleason grade of the original tumor, was a fundamental prerequisite for tumor take in mice. This mouse xenograft model represents a useful preclinical model of primary prostate tumors for their biological characterization, biomarker discovery, and drug testing.

Investigations of prostate epithelial stem cells and prostate cancer stem cells

Although both prostate epithelial stem cells and prostate cancer stem cells are implicated in the differentiation of the normal prostate gland and carcinogenesis of prostate cancer, there has, until recently, been little information regarding their biology. This review summarizes the recent advancements in cell biological research including various in vitro culture systems that have offered the characterization and isolation of prostate epithelial stem cells and prostate cancer stem cells. In addition, the stromal niche or microenvironment of stem cells plays an essential role in proliferation and differentiation of normal stem cells. Stroma surrounding cancer cells, which also provide another unique niche, may involve the initiation and development of cancer stem cells. Investigation of stem cells and their microenvironments in the prostate should lead to the elucidation of biological features and the development of novel treatments for prostate cancer.

Cancer stem cells in prostate adenocarcinoma: a target for new anticancer strategies

Prostate cancer (PC) is major common malignancy in males in most industrialized Western countries, where it is the most commonly diagnosed cancer affecting men after middle age (>50 years). Over 90% of PC patients with incurable disease respond to primary treatment, which consists of intervention to lower serum testosterone. However, the duration of response is short (12-33 months) and in almost all patients, is followed by the emergence of a phenotype resistant to androgen deprivation in therapy (known as hormone or androgen-resistant PC). Considerable research efforts have been directed towards the identification of markers associated with the initiation and progression of PC, yet there is little consensus about the target cell within prostate epithelium that is susceptible to malignant transformation. Stem cells may represent a major target for mutations leading to cancer as their longevity assures continued presence during the long latency between carcinogenic agents exposure and cancer development. Therefore in order to allow the development of more effective treatment strategies for PC, a better understanding of the molecular changes that underlie cancer stem cells is required.

[Development of a three-dimensional primary prostate cancer cell culture model]

Much prostate cancer research is based on cell culture results. Recent genomic studies found major differences between primary prostate cancer tissue and established prostate cancer cell lines, which calls into question the clinical relevance of study results based on cell cultures.Using primary cultures of prostate cancer cells from prostatectomy specimens seems to be a reasonable solution, but primary cell cultures are much more difficult to establish. In this study, a primary cell culture model was combined with an invasion assay. With this combination it was possible not only to select invasive cell clones from the primary culture but also to culture these cells in a three-dimensional model, forming spheroids. A further characterization of this cell population was done by comparative genomic hybridization, showing numerous genetic alterations. The presented cell culture model offers, for the first time, an opportunity to isolate invasive growing cells from primary prostate cancer tissue and cultivate these cells for further analyses.

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.

A novel tissue-slice culture model for non-malignant human prostate

A novel tissue culture system was established for modeling the non-neoplastic human prostate in vitro. Precision-cut prostate slices were cultivated in culture plates with a gas-permeable base in a novel serum-free mixture. Cultivated specimens was evaluated by an immunohistochemical analysis of cytokeratins 18 and 14, androgen receptor (AR), prostate specific antigen (PSA), prostate acid phosphatase (PAP), and the endothelial cell marker von Willebrand factor. Epithelial viability in the presence and absence of dihydrotestosterone (DHT) was also assessed. Satisfactory maintenance of glandular cytoarchitecture was observed in the presence of DHT with approximately half of the glands displaying a columnar or cuboidal phenotype and an intact layer of basal cells. In the absence of DHT, the corresponding percentage was significantly lower. The occurrence of involutive changes and epithelial cell death was significantly higher in the absence of DHT. Glandular and stromal cells maintained their capacity to express AR. PSA and PAP were expressed throughout the culture period, albeit at a lower level than in uncultured tissue. The viability of endothelial cells differed markedly between individual samples. During culture, the tissue slices became covered with epithelial cells originating from glands that were cut open during tissue slicing. This cell layer consisted of a stratified basal compartment overlaid by cells with a luminal phenotype. The present culture system provides a novel in vitro setting in which to study normal human prostate biology and pathobiology and may help to obviate problems related to the use of established cancer cell lines and animal models.

Delta-like 1 (Dlk-1), a novel marker of prostate basal and candidate epithelial stem cells, is downregulated by notch signalling in intermediate/transit amplifying cells of the human prostate

BACKGROUND

There is a lack of understanding of the processes that regulate differentiation in the prostate.

OBJECTIVE

To determine localisation, activity, and regulation of cytodifferentiation-modulatory proteins in the human adult prostate.

DESIGN, SETTINGS, AND PARTICIPANTS

Eighteen volunteering patients with organ-confined prostate cancer were prospectively enrolled at a single university hospital.

INTERVENTION

All patients underwent radical prostatectomy, and normal/benign tissue was excised and obtained from the transition zone.

MEASUREMENTS

Expression and activity of Notch-protein family members, including the Notch-homologous protein Delta-like 1 (Dlk-1/Pref1), were investigated immunohistochemically in normal/benign tissue and explant cultures. The effect of the Notch inhibitor L-685,458 on Dlk-1 expression and cell number was investigated in primary cell cultures, and data were analysed with Student t test.

RESULTS AND LIMITATIONS

Mature luminal cells were found to co-express Notch-1 and its ligand Jagged1, but epithelia in normal/benign tissue showed no active Notch signalling. The basal cell layer, rare candidate epithelial stem cells, and a subpopulation of neuroendocrine cells expressed the differentiation protein Dlk-1. In explant cultures, luminal cells and Jagged1 expression were lost, whereas intermediate cells downregulated Dlk-1 concomitant with Notch-1 upregulation and activation. Notch inhibition in primary cell cultures led to lower cell densities (p<0.001) and suppressed downregulation of Dlk-1. This is a small study; current results need to be confirmed in larger investigations.

CONCLUSIONS

We demonstrate that Notch-1 is upregulated in differentiation of prostate epithelia, and that the novel prostate progenitor marker Dlk-1 is downregulated by Notch signalling in intermediate cells. The identification of Dlk-1-expressing candidate stem and neuroendocrine cells suggests a hierarchical relationship.

Telomerase-immortalized non-malignant human prostate epithelial cells retain the properties of multipotent stem cells

Understanding prostate stem cells may provide insight into the origin of prostate cancer. Primary cells have been cultured from human prostate tissue but they usually survive only 15-20 population doublings before undergoing senescence. We report here that RC-170N/h/clone 7 cells, a clonal cell line from hTERT-immortalized primary non-malignant tissue-derived human prostate epithelial cell line (RC170N/h), retain multipotent stem cell properties. The RC-170N/h/clone 7 cells expressed a human embryonic stem cell marker, Oct-4, and potential prostate epithelial stem cell markers, CD133, integrin alpha2beta1(hi) and CD44. The RC-170N/h/clone 7 cells proliferated in KGM and Dulbecco's Modified Eagle Medium with 10% fetal bovine serum and 5 microg/ml insulin (DMEM+10% FBS+Ins.) medium, and differentiated into epithelial stem cells that expressed epithelial cell markers, including CK5/14, CD44, p63 and cytokeratin 18 (CK18); as well as the mesenchymal cell markers, vimentin, desmin; the neuron and neuroendocrine cell marker, chromogranin A. Furthermore the RC170 N/h/clone 7 cells differentiated into multi tissues when transplanted into the sub-renal capsule and subcutaneously of NOD-SCID mice. The results indicate that RC170N/h/clone 7 cells retain the properties of multipotent stem cells and will be useful as a novel cell model for studying the mechanisms of human prostate stem cell differentiation and transformation.

Prostate cell cultures as in vitro models for the study of normal stem cells and cancer stem cells

Current existing therapies for prostate cancer eradicate the majority of cells within a tumor. However, most patients with advanced cancer still progress to androgen-independent metastatic disease that remains essentially incurable by current treatment strategies. Recent evidence has shown that cancer stem cells (CSCs) are a subset of the tumor cells that are responsible for initiating and maintaining the disease. Understanding normal stem cells and CSCs may provide insight into the origin of and new therapeutics for prostate cancer. Normal stem cells and CSCs have been identified in prostate tissue by the use of several markers or techniques. Although research on stem cells has been limited by the lack of suitable in vitro systems, recent studies show that not only primary cells but also several established cell lines may exhibit stem cell properties. This review discusses various in vitro culture systems to propagate normal prostate stem cells and prostate CSCs together with molecular markers. These in vitro cell culture models should be useful for elucidating the differentiation of prostatic epithelium and the biological features of prostate cancer.

Identification of putative stem cell markers, CD133 and CXCR4, in hTERT-immortalized primary nonmalignant and malignant tumor-derived human prostate epithelial cell lines and in prostate cancer specimens

Understanding normal and cancer stem cells may provide insight into the origin of and new therapeutics for prostate cancer. Normal and cancer stem cells in prostate have recently been identified with a CD44(+)/alpha(2)beta(1)(high)/CD133(+) phenotype. Stromal cell-derived factor-1 (SDF-1) and its receptor, CXCR4, have multiple essential functions, including homing of stem cells and metastasis of cancer cells. We show here that human telomerase reverse transcriptase (hTERT)-immortalized primary nonmalignant (RC-165N/hTERT) and malignant (RC-92a/hTERT) tumor-derived human prostate epithelial cell lines retain stem cell properties with a CD133(+)/CD44(+)/alpha(2)beta(1)(+)/34betaE12(+)/CK18(+)/p63(-)/androgen receptor (AR)(-)/PSA(-) phenotype. Higher CD133 expression was detected in the hTERT-immortalized cells than in primary prostate cells. These immortalized cells exhibited "prostaspheres" in nonadherent culture systems and also maintained higher CD133 expression. The CD133(+) cells from these immortalized cell lines had high proliferative potential and were able to differentiate into AR(+) phenotype. In three-dimensional culture, the CD133(+) cells from RC-165N/hTERT cells produced branched structures, whereas the CD133(+) cells from RC-92a/hTERT cells produced large irregular spheroids with less branched structures. SDF-1 induced, but anti-CXCR4 antibody inhibited, migration of CD133(+) cells from RC-92a/hTERT cells, which coexpressed CXCR4. CXCR4/SDF-1 may sustain tumor chemotaxis in cancer stem cells. Furthermore, immunostaining of clinical prostate specimens showed that CD133 expression was detected in a subpopulation of prostate cancer cells and corresponded to the loss of AR. Expression of CXCR4 was also detected in CD133(+) cancer cells. These novel in vitro models may offer useful tools for the study of the biological features and functional integration of normal and cancer stem cells in prostate.

Contrasting patterns of transcript abundance in tumour tissue and cancer cell lines

Comparison of data on transcript abundance in ovarian, prostate and colon tumours with the corresponding cancer cell lines was used to assess the similarities of expression profiles. Although transcript abundances in tumours and cell lines were positively correlated, there were substantial differences with respect to the overall expression pattern. Compared with tumours, cancer cell lines showed more variable patterns of transcript abundance among tissue types. In the ovary and colon, cancer cell lines showed greater overall transcript abundance than normal tissue; this increase was much more marked in the case of the colon. However, in the prostate, cancer cell lines showed overall reduced transcript abundance when compared with normal tissue. Principal component analyses, applied separately to each tissue type, showed that approximately 80% of the variance was explained by overall expression level differences, which were maintained across normal tissue, tumour tissue and cancer cell lines. The remaining variance ( approximately 20%) could be attributed to contrasts in expression pattern among normal tissue, tumour tissue and cancer cell lines. In each dataset and in a combined dataset of transcripts shared among the three datasets, principal components revealed both contrasts in expression pattern between tumour tissue and cancer cell lines, and common features in the expression pattern of cancer cell lines that were distinct from those of tumour tissue and were shared across the different tissue types. These results imply that data on gene expression in cancer cell lines should be used with caution in inferring gene expression of in vivo tumours.

An improved in vitro model to characterize invasive growing cancer cells simultaneously by function and genetic aberrations

Invasion into the surrounding tissue and bone metastasis is a common feature of advanced prostate cancer. Chromosomal and other genetic or epigenetic abnormalities were aligned to this behaviour mostly by using permanent cell lines, paraffin embedded tissue or primary tumour samples. Both attempts fail to reflect either the original situation or functional information in the patient's tissue. Thus, we developed an improved in vitro assay to follow invasion of prostate cancer cells derived from fresh samples of radical prostatectomy specimens. Fresh tumour samples were applied onto Matrigeltrade mark-coated invasion chambers using a cocultivation model. Invasive growing cells were harvested from the bottom of the membrane or from the underlying gel and further characterized using comparative genomic hybridization. Prostate cancer cells have the capability to invasively grow through the barrier of a Matrigeltrade mark and could easily be sampled in a pad of Matrigeltrade mark. Comparative genomic hybridization revealed characteristic chromosomal aberrations of the invasive growing cells. Noteworthy is their ability to spheroid formation, which allows for further cell propagation by standard cell culture methods. Thus, our improved invasion model is a tool for the sampling of invasive growing cancer cells from fresh human tumour material allowing for functional as well as genetic studies.

Epithelial-Restricted Gene Profile of Primary Cultures from Human Prostate Tumors: A Molecular Approach to Predict Clinical Behavior of Prostate Cancer

The histopathologic and molecular heterogeneity of prostate cancer and the limited availability of human tumor tissue make unraveling the mechanisms of prostate carcinogenesis a challenging task. Our goal was to develop an ex vivo model that could be reliably used to define a prognostic signature based on gene expression profiling of cell cultures that maintained the tumor phenotype. To this end, we derived epithelial cultures from tissue explanted from 59 patients undergoing radical prostatectomy or cistoprostatectomy because of prostate benign hyperplasia/prostate cancer or bladder carcinoma. Patient selection criteria were absence of hormonal neoadjuvant treatment before surgery and diagnosis of clinically localized disease. Using this unique experimental material, we analyzed expression of 22,500 transcripts on the Affymetrix Human U133A GeneChip platform (Affymetrix, Inc., High Wycombe, United Kingdom). Cultures from normal/hyperplastic tissues with a prevalent luminal phenotype and from normal prostate epithelial tissue with basal phenotype (PrEC) served as controls. We have established a large number of prostate primary cultures highly enriched in the secretory phenotype. From them, we derived an epithelial-restricted transcriptional signature that (a) differentiated normal from tumor cells and (b) clearly separated cancer-derived lines into two distinct groups, which correlated with indolent or aggressive clinical behavior of the disease. Our findings provide (a) a method to expand human primary prostate carcinoma cells with a luminal phenotype, (b) a powerful experimental model to study primary prostate cancer biology, and (c) a novel means to characterize these tumors from a molecular genetic standpoint for prognostic and/or predictive purposes.

Tissue Imprints or Primary Cultures

Touch preparations or imprints have been extensively used in cytogenetics to avoid primary cultures, especially when studying solid tumors which are hard to grow in vitro. Interphase nuclei studies by FISH have been validated in several sample types; however, to our knowledge, a comparison between both methods when studying clonality has not yet been published. We have performed a comparative FISH study between touch preparations and cultured cells to assess their reliability when studying the aneuploidy of chromosome Y in mosaicism. Our results in 23 samples indicate that aneuploidy of chromosome Y assessed in cells from tissue cultures versus cells obtained from touch preparations from seminal vesicles of patients with prostate cancer is not comparable. The percentage of aneuploid cells is higher in cultured cells. Attention, therefore, must be paid not to overestimating or underestimating the number of aneuploid cells detected when using interphase FISH studies, especially in solid tumors where clonality is very frequent. Also, according to our results, it is reasonable to extrapolate that when performing interphase nuclei studies in paraffin sections or tissue microarray, and therefore underestimations of aneuploidy could be reported. This might be of special relevance if the aneuploidy detected correlates with the tumor progression or might be used as a prognostic factor.

Comparative gene and protein expression in primary cultures of epithelial cells from benign prostatic hyperplasia and prostate cancer

Primary cultures are widely used to investigate the disease-specific biology of prostate cancer and benign prostatic hyperplasia (BPH). To identify genes differentially expressed between epithelial cells cultured from adenocarcinomas versus BPH tissues, we used probe array technology. Gene expression profiles were evaluated on Affymetrix Human Cancer G110 Array Chips containing approximately 1900 cancer-related genes. After defined statistical analysis, genes that were over-expressed in cancer cultures were identified. Protein expression of four of the differentially expressed genes was measured in immunoblots, and the expression of two other genes was measured by real-time reverse transcription-polymerase chain reaction (RT-PCR). While no gene or protein was consistently over-expressed in all cancer versus BPH cell cultures, cytokeratin 16 protein was highly elevated in several of the cancer cultures, suggesting that a hyperproliferative phenotype may be characteristic of prostate cancer cells.

A system for studying epithelial-stromal interactions reveals distinct inductive abilities of stromal cells from benign prostatic hyperplasia and prostate cancer

The development of normal and abnormal glandular structures in the prostate is controlled at the endocrine and paracrine levels by reciprocal interactions between epithelium and stroma. To study these processes, it is useful to have an efficient method of tissue acquisition for reproducible isolation of cells from defined histologies. Here we assessed the utility of a standardized system for acquisition and growth of prostatic cells from different regions of the prostate with different pathologies, and we compared the abilities of stromal cells from normal peripheral zone, benign prostatic hyperplasia (BPH-S), and cancer to induce the growth of a human prostatic epithelial cell line (BPH-1) in vivo. Using the tissue recombination method, we showed that grafting stromal cells (from any histology) alone or BPH-1 epithelial cells alone produced no visible grafts. Recombining stromal cells from normal peripheral zone with BPH-1 cells also produced no visible grafts (n = 15). Recombining BPH-S with BPH-1 cells generated small, well-organized, and sharply demarcated grafts approximately 3-4 mm in diameter (n = 9), demonstrating a moderate inductive ability of BPH-S. Recombining stromal cells from cancer with BPH-1 cells generated highly disorganized grafts that completely surrounded the host kidney and invaded into adjacent renal tissue, demonstrating induction of an aggressive phenotype. We conclude that acquisition of tissue from toluidine blue dye-stained specimens is an efficient method to generate high-quality epithelial and/or stromal cultures. Stromal cells derived by this method from areas of BPH and cancer induce epithelial cell growth in vivo, which mimics the natural history of these diseases.

Altered SMRT levels disrupt vitamin D3 receptor signalling in prostate cancer cells

We hypothesized that key antiproliferative target genes for the vitamin D receptor (VDR) were repressed by an epigenetic mechanism in prostate cancer cells resulting in apparent hormonal insensitivity. To explore this possibility, we examined nuclear receptor corepressor expression in a panel of nonmalignant and malignant cell lines and primary cultures, and found frequently elevated SMRT corepressor mRNA expression often associated with reduced sensitivity to 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)2D3). For example, PC-3 and DU-145 prostate cancer cell lines had 1.8-fold and twofold increases in SMRT mRNA relative to normal PrEC cells (P<0.05). Similarly, 10/15 primary tumour cultures (including three matched to normal cells from the same donors) had elevated SMRT mRNA levels; generally NCoR1 and Alien were not as commonly elevated. Corepressor proteins often have associated histone deacetylases (HDAC) and reflectively the antiproliferative action of 1alpha,25(OH)2D3 can be 'restored' by cotreatment with low doses of HDAC inhibitors such as trichostatin A (TSA, 15 nM) to induce apoptosis in prostate cancer cell lines. To decipher the transcriptional events that lead to these cellular responses, we undertook gene expression studies in PC-3 cells after cotreatment of 1alpha,25(OH)2D3 plus TSA after 6 h. Examination of known VDR target genes and cDNA microarray analyses revealed cotreatment of 1alpha,25(OH)2D3 plus TSA cooperatively upregulated eight (out of 1176) genes, including MAPK-APK2 and GADD45alpha. MRNA and protein time courses and inhibitor studies confirmed these patterns of regulation. Subsequently, we knocked down SMRT levels in PC-3 cells using a small interfering RNA (siRNA) approach and found that GADD45alpha induction by 1alpha,25(OH)2D3 alone became very significantly enhanced. The same distortion of gene responsiveness, with repressed induction of GADD45alpha was found in primary tumour cultures compared and to matched peripheral zone (normal) cultures from the same donor. These data demonstrate that elevated SMRT levels are common in prostate cancer cells, resulting in suppression of target genes associated with antiproliferative action and apparent 1alpha,25(OH)2D3-insensitivity. This can be targeted therapeutically by combination treatments with HDAC inhibitors.