Cryptotanshinone targets tumor-initiating cells through down-regulation of stemness genes expression.

Recent evidence indicates that tumor-initiating cells (TICs), also called cancer stem cells (CSCs), are responsible for tumor initiation and progression, therefore representing an important cell population that may be used as a target for the development of future anticancer therapies. In the present study, Cryptotanshinone (CT), a traditional Chinese herbal medicine, was demonstrated to regulate the behaviors of LNCaP prostate cells and prostate LNCaP TICs. The results demonstrate that treatment with CT alters cellular proliferation, cell cycle status, migration, viability, colony formation and notably, sphere formation and down-regulation of stemness genes (Nanog, OCT4, SOX2, ß-catenin, CXCR4) in TICs. The present study demonstrates that CT targets the LNCaP CD44+CD24- population that is representative of prostate TICs and also affects total LNCaP cells as well via down-regulation of stemness genes. The strong effect with which CT has on prostate TICs suggests that CT may potentially function as a novel natural anticancer agent that specifically targets TICs.

Identification of a long non-coding RNA as a novel biomarker and potential therapeutic target for metastatic prostate cancer.

Metastatic prostate cancer (PCa) is still an incurable disease. Long non-coding RNAs (lncRNAs) may be an overlooked source of cancer biomarkers and therapeutic targets. We therefore performed RNA sequencing on paired metastatic/non-metastatic PCa xenografts derived from clinical specimens. The most highly up-regulated transcript was LOC728606, a lncRNA now designated PCAT18. PCAT18 is specifically expressed in the prostate compared to 11 other normal tissues (p<0.05) and up-regulated in PCa compared to 15 other neoplasms (p<0.001). Cancer-specific up-regulation of PCAT18 was confirmed on an independent dataset of PCa and benign prostatic hyperplasia samples (p<0.001). PCAT18 was detectable in plasma samples and increased incrementally from healthy individuals to those with localized and metastatic PCa (p<0.01). We identified a PCAT18-associated expression signature (PES), which is highly PCa-specific and activated in metastatic vs. primary PCa samples (p<1E-4, odds ratio>2). The PES was significantly associated with androgen receptor (AR) signalling. Accordingly, AR activation dramatically up-regulated PCAT18 expression in vitro and in vivo. PCAT18 silencing significantly (p<0.001) inhibited PCa cell proliferation and triggered caspase 3/7 activation, with no effect on non-neoplastic cells. PCAT18 silencing also inhibited PCa cell migration (p<0.01) and invasion (p<0.01). These results position PCAT18 as a potential therapeutic target and biomarker for metastatic PCa.

Epigenetic regulation of SOX9 by the NF-κB signaling pathway in pancreatic cancer stem cells.

Pancreatic cancer is the fourth leading cause of cancer-related mortality in the world. Pancreatic cancer can be localized, locally advanced, or metastatic. The median 1- and 5-year survival rates are 25% and 6%, respectively. Epigenetic modifications such as DNA methylation play a significant role during both normal human development and cancer progression. To investigate epigenetic regulation of genes in the tumor-initiating population of pancreatic cancer cells, which are also termed cancer stem cells (CSCs), we conducted epigenetic arrays in PANC1 and HPAC pancreatic cancer cell lines and compared the global DNA methylation status of CpG promoters in invasive cells, demonstrated to be CSCs, to their noninvasive counterparts, or non-CSCs. Our results suggested that the NF-κB pathway is one of the most activated pathways in pancreatic CSCs. In agreement with this, we determined that upon treatment with NF-κB pathway inhibitors, the stem cell-like properties of cells are significantly disrupted. Moreover, SOX9, demethylated in CSCs, is shown to play a crucial role in the invasion process. Additionally, we found a potential NF-κB binding site located in the SOX9 promoter and determined that the NF-κB subunit p65 positively regulates SOX9 expression by binding to its promoter directly. This interaction can be efficiently blocked by NF-κB inhibitors. Thus, our work establishes a link between the classic NF-κB signaling transduction pathway and the invasiveness of pancreatic CSCs, which may result in the identification of novel signals and molecules that function at an epigenetic level, and could potentially be targeted for pharmaceutical investigations and clinical trials.

The differentiation of pancreatic tumor-initiating cells by vitronectin can be blocked by cilengitide.

OBJECTIVE: Pancreatic cancer is a leading cancer type and its molecular pathology is poorly understood. The only potentially curative therapeutic option available is complete surgical resection; however, this is inadequate as most of the patients are diagnosed at an advanced or metastatic stage. Tumor-initiating cells (TICs) constitute a subpopulation of cells within a solid tumor that sustain tumor growth, metastasis, and chemo/radioresistance. Within pancreatic cancer, TICs have been identified based on the expression of specific cell surface markers. METHODS: We use a sphere formation assay to enrich putative TICs and use human serum as a driver of differentiation. We demonstrate by using specific blocking reagents that we can inhibit the differentiation process and maintain TIC-associated markers and genes. RESULTS: We can induce differentiation of pancreatospheres with the addition of human serum, and we identified vitronectin as an inducer of differentiation. We inhibit differentiation by human serum using an arginine-glycine-aspartate-specific peptide, which is Cilengitide; hence, demonstrating this differentiation is mediated via specific integrin receptors. CONCLUSIONS: Overall, our studies further the definition of pancreatic TICs and provide further insight into both the maintenance and differentiation of this lethal population.

Genomic Analysis of Invasive Human Bone Marrow Derived Mesenchymal Stem Cells.

BACKGROUND: Human bone marrow derived mesenchymal stem cells (hMSCs) are capable of differentiation into multiple cell lineages and demonstrate a wide variety of use in various therapeutic applications. Only recently has research begun to understand the gene expression profiles of hMSCs and their differentiated counterparts in vivo and ex vivo. PURPOSE: The research presented here aimed at gaining a better understanding of gene expression patterns present during hMSC invasion through a basement membrane. METHODS: Changes in gene expression were evaluated between invasive and non-invasive cells using Agilent's gene expression arrays and Matrigel invasion chambers. The cells were specifically attracted to a defined stem cell media called SCM. RESULTS: A total 435 genes were up-regulated by 2- fold or more in the invasive population of cells and classified into developmental programs and immunological/inflammatory signaling pathways determined by Ingenuity Pathway Analysis (IPA). This list included a variety of regulators of growth and differentiation including NANOG, STAT3 and STAT5A and members of the polycomb repressive complex-2 (PCRC2) EZH2 and SUZ12. The known regulator of inflammation and hypoxia HIF-1α was also increased suggesting that regulation of the microenvironment is important during this process. Finally, the invasion process could be reversed using the STAT3 inhibitor Static. CONCLUSIONS: Overall these data will increase the understanding of the genetic pathways functioning during hMSC invasion and aid in the development of their therapeutic applications.

Histone lysine demethylases in breast cancer.

Histone lysine demethylases (KDMs) have been recently discovered in mammals and have been nicknamed "erasers" for their ability to remove methyl groups from histone substrates. In cancer cells, KDMs can activate or repress gene transcription, behaving as oncogenes or tumor suppressors depending upon the cellular context. In order to investigate the potential role of KDMs in Breast Cancer (BC), we queried the Oncomine database and determined that the expression of KDMs correlates with BC prognosis. High expression of KDM3B and KDM5A is associated with a better prognosis (no recurrence after mastectomy p=0.005 and response to docetaxel p=0.005); conversely, KDM6A is overexpressed in BC patients with an unfavorable prognosis (mortality at 1 year, p=8.65E-7). Our findings suggest that KDMs could be potential targets for BC therapy. Further, altering the interactions between KDMs and Polycomb Group genes (PcG) may provide novel avenues for therapy that specifically targets these genes in BC.

The emerging role of histone lysine demethylases in prostate cancer.

Early prostate cancer (PCa) is generally treatable and associated with good prognosis. After a variable time, PCa evolves into a highly metastatic and treatment-refractory disease: castration-resistant PCa (CRPC). Currently, few prognostic factors are available to predict the emergence of CRPC, and no curative option is available. Epigenetic gene regulation has been shown to trigger PCa metastasis and androgen-independence. Most epigenetic studies have focused on DNA and histone methyltransferases. While DNA methylation leads to gene silencing, histone methylation can trigger gene activation or inactivation, depending on the target amino acid residues and the extent of methylation (me1, me2, or me3). Interestingly, some histone modifiers are essential for PCa tumor-initiating cell (TIC) self-renewal. TICs are considered the seeds responsible for metastatic spreading and androgen-independence. Histone Lysine Demethylases (KDMs) are a novel class of epigenetic enzymes which can remove both repressive and activating histone marks. KDMs are currently grouped into 7 major classes, each one targeting a specific methylation site. Since their discovery, KDM expression has been found to be deregulated in several neoplasms. In PCa, KDMs may act as either tumor suppressors or oncogenes, depending on their gene regulatory function. For example, KDM1A and KDM4C are essential for PCa androgen-dependent proliferation, while PHF8 is involved in PCa migration and invasion. Interestingly, the possibility of pharmacologically targeting KDMs has been demonstrated. In the present paper, we summarize the emerging role of KDMs in regulating the metastatic potential and androgen-dependence of PCa. In addition, we speculate on the possible interaction between KDMs and other epigenetic effectors relevant for PCa TICs. Finally, we explore the role of KDMs as novel prognostic factors and therapeutic targets. We believe that studies on histone demethylation may add a novel perspective in our efforts to prevent and cure advanced PCa.

EZH2 inhibition: targeting the crossroad of tumor invasion and angiogenesis.

Tumor angiogenesis and metastatic spreading are two highly interconnected phenomena, which contribute to cancer-associated deaths. Thus, the identification of novel strategies to target angiogenesis and metastatic spreading is crucial. Polycomb genes are a set of epigenetic effectors, structured in multimeric repressive complexes. EZH2 is the catalytic subunit of Polycomb repressive complex 2 (PRC2), which methylates histone H3 lysine 27, thereby silencing several tumor-suppressor genes. EZH2 is essential for cancer stem cell self-renewal. Interestingly, cancer stem cells are thought to be the seeds of metastatic spreading and are able to differentiate into tumor-associated endothelial cells. Pre-clinical studies showed that EZH2 is able to silence several anti-metastatic genes (e.g., E-cadherin and tissue inhibitors of metalloproteinases), thereby favoring cell invasion and anchorage-independent growth. In addition, EZH2 seems to play a crucial role in the regulation of tumor angiogenesis. High EZH2 expression predicts poor prognosis, high grade, and high stage in several cancer types. Recently, a small molecule inhibitor of PRC2 (DZNeP) demonstrated promising anti-tumor activity, both in vitro and in vivo. Interestingly, DZNeP was able to inhibit cancer cell invasion and tumor angiogenesis in prostate and brain cancers, respectively. At tumor-inhibiting doses, DZNeP is not harmful for non-transformed cells. In the present manuscript, we review current evidence supporting a role of EZH2 in metastatic spreading and tumor angiogenesis. Using Oncomine datasets, we show that DZNeP targets are specifically silenced in some metastatic cancers, and some of them may inhibit angiogenesis. Based on this evidence, we propose the development of EZH2 inhibitors as anti-angiogenic and anti-metastatic therapy.

Long-term recovery of irradiated prostate cancer increases cancer stem cells.

BACKGROUND: Despite improvements in treatment, prostate cancer (PC) remains the second-leading cause of cancer death in men. Radiotherapy is among the first-line treatments for PC, but a significant number of patients relapse. Recent evidence supports the idea that PC is initiated by a subset of cells, termed cancer stem cells (CSCs). CSCs have also been implicated in radioresistance in various malignancies, but their role in PC has not yet been investigated. METHODS: We compared the relative radiosensitivity of isolated CSCs to the total population of their corresponding cell lines, and examined the relative numbers of CSCs in irradiated cell lines following long-term recovery and in recurrent human PC. RESULTS: Here, we show that while irradiation does not immediately favor increased survival of CSCs, irradiated PC cell lines showed an increase in CSC properties with long-term recovery. These data suggest that, although CSCs are initially damaged by radiation, they possess a greater capacity for recovery and regrowth. CONCLUSIONS: The combination of radiotherapy with a CSC-targeted therapeutic strategy may prevent tumor recurrence.

The role of upregulated miRNAs and the identification of novel mRNA targets in prostatospheres.

TICs are characterized by their ability to self-renew, differentiate and initiate tumor formation. miRNAs are small noncoding RNAs that bind to mRNAs resulting in regulation of gene expression and biological functions. The role of miRNAs and TICs in cancer progression led us to hypothesize that miRNAs may regulate genes involved in TIC maintenance. Using whole genome miRNA and mRNA expression profiling of TICs from primary prostate cancer cells, we identified a set of up-regulated miRNAs and a set of genes down-regulated in PSs. Inhibition of these miRNAs results in a decrease of prostatosphere formation and an increase in target gene expression. This study uses genome-wide miRNA profiling to analyze expression in TICs. We connect aberrant miRNA expression and deregulated gene expression in TICs. These findings can contribute to a better understanding of the molecular mechanisms governing TIC development/maintenance and the role that miRNAs have in the fundamental biology of TICs.

The cancer stem cell niche--there goes the neighborhood?

The niche is the environment in which stem cells reside and is responsible for the maintenance of unique stem cell properties such as self-renewal and an undifferentiated state. The heterogeneous populations which constitute a niche include both stem cells and surrounding differentiated cells. This network of heterogeneity is responsible for the control of the necessary pathways that function in determining stem cell fate. The concept that cancer stem cells, a subpopulation of cells responsible for tumor initiation and formation, reside in their own unique niche is quickly evolving and it is of importance to understand and identify the processes occurring within this environment. The necessary intrinsic pathways that are utilized by this cancer stem cell population to maintain both self-renewal and the ability to differentiate are believed to be a result of the environment where cancer stem cells reside. The ability of a specific cancer stem cell niche to provide the environment in which this population can flourish is a critical aspect of cancer biology that mandates intense investigation. This review focuses on current evidence demonstrating that homeostatic processes such as inflammation, epithelial to mesenchymal transition, hypoxia and angiogenesis contribute to the maintenance and control of cancer stem cell fate by providing the appropriate signals within the microenvironment. It is necessary to understand the key processes occurring within this highly specialized cancer stem cell niche to identify potential therapeutic targets that can serve as the basis for development of more effective anticancer treatments.

Increased expression of DNA repair genes in invasive human pancreatic cancer cells.

OBJECTIVE: Pancreatic cancer was the fourth leading cause of cancer death in the United States in 2010. Recurrence of disease after resection occurs because of neoplastic cell survival. To better understand these highly aggressive cells, gene expression microarrays were performed. METHODS: Using the established lines HPAC and PANC1 and a Matrigel assay, genome expression arrays were performed to analyze patterns between invasive and total cells. RESULTS: Significant increases in the expression of genes related to DNA repair were observed. A number of the same genes also demonstrated an increase in expression when comparing bulk cells to a putative tumor-initiating cell (TIC) population. The TIC population was isolated using the spheroid technique, and compared with bulk cells, spheroid cells functionally repair breaks in DNA faster after challenge with the drug gemcitabine. Finally, using Oncomine, we observed a significant increase in DNA copy number of BRCA1 and RAD51 in tissue isolated from metastatic pancreatic cancer compared with tissue isolated from the primary site. CONCLUSIONS: From these data, we conclude that the most invasive cells within a pancreatic tumor are able to thrive because of their increased genomic stability. These cells have also been linked to the TIC population in a tumor.

Pharmacogenomics and cancer stem cells: a changing landscape?

Pharmacogenomics in oncology holds the promise to personalize cancer therapy. However, its clinical application is still limited to a few genes, and, in the large majority of cancers, the correlation between genotype and clinical outcome has been disappointing. One possible explanation is that current pharmacogenomic studies do not take into account the emerging role of cancer stem cells (CSCs) in drug sensitivity and resistance. CSCs are a subpopulation of cells driven by specific signal-transduction pathways, but genetic variants affecting their activity are generally neglected in current pharmacogenomic studies. Moreover, in several malignancies, CSCs represent a rare sub-population; therefore, whole tumor profiling might mask CSC gene expression patterns. This article reviews current evidence on CSC chemoresistance and shows how common genetic variations in CSC-related genes may predict individual response to anti-cancer agents. Furthermore, we provide insights into the design of pharmacogenomic studies to address the clinical usefulness of CSC genetic profiling.

Pharmacologic disruption of Polycomb Repressive Complex 2 inhibits tumorigenicity and tumor progression in prostate cancer.

BACKGROUND: Polycomb repressive complex 2 (PRC2) mediates gene silencing through histone H3K27 methylation. PRC2 components are over-expressed in metastatic prostate cancer (PC), and are required for cancer stem cell (CSC) self-renewal. 3-Dezaneplanocin-A (DZNeP) is an inhibitor of PRC2 with broad anticancer activity. METHOD: we investigated the effects of DZNeP on cell proliferation, tumorigenicity and invasive potential of PC cell lines (LNCaP and DU145). RESULTS: Exploring GEO and Oncomine databases, we found that specific PRC2 genes (EED, EZH2, SUZ12) predict poor prognosis in PC. Non-toxic DZNeP concentrations completely eradicated LNCaP and DU145 prostatosphere formation, and significantly reduced the expression of CSC markers. At comparable doses, other epigenetic drugs were not able to eradicate CSCs. DZNeP was also able to reduce PC cell invasion. Cells pre-treated with DZNeP were significantly less tumorigenic (LNCaP) and formed smaller tumors (DU145) in immunocompromised mice. CONCLUSION: DZNeP is effective both in vitro and in vivo against PC cells. DZNeP antitumor activity is in part mediated by inhibition of CSC tumorigenic potential.

DNA repair: the culprit for tumor-initiating cell survival?

The existence of "tumor-initiating cells" (TICs) has been a topic of heated debate for the last few years within the field of cancer biology. Their continuous characterization in a variety of solid tumors has led to an abundance of evidence supporting their existence. TICs are believed to be responsible for resistance against conventional treatment regimes of chemotherapy and radiation, ultimately leading to metastasis and patient demise. This review summarizes DNA repair mechanism(s) and their role in the maintenance and regulation of stem cells. There is evidence supporting the hypothesis that TICs, similar to embryonic stem (ES) cells and hematopoietic stem cells (HSCs), display an increase in their ability to survive genotoxic stress and injury. Mechanistically, the ability of ES cells, HSCs and TICs to survive under stressful conditions can be attributed to an increase in the efficiency at which these cells undergo DNA repair. Furthermore, the data presented in this review summarize the results found by our lab and others demonstrating that TICs have an increase in their genomic stability, which can allow for TIC survival under conditions such as anticancer treatments, while the bulk population of tumor cells dies. We believe that these data will greatly impact the development and design of future therapies being engineered to target and eradicate this highly aggressive cancer cell population.

BMI1 silencing enhances docetaxel activity and impairs antioxidant response in prostate cancer.

The BMI1 oncogene promotes prostate cancer (PC) progression. High B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) expression predicts poor prognosis in PC patients. Recent evidence suggests that BMI1 may also play a role in docetaxel chemoresistance. However, mechanisms and clinical significance of BMI1-related chemoresistance have not been investigated. For this purpose, BMI1 was silenced in 2 PC cell lines (LNCaP and DU 145). Cell proliferation and apoptosis after docetaxel treatment were measured. Guanine oxidation was assessed by in-cell western. Global gene expression analysis was performed on BMI1 silenced cells. Oncomine database was used to compare in vitro data with gene expression in PC samples. BMI1 silencing had no effect on cell proliferation but significantly enhanced docetaxel-induced antitumor activity. Gene expression analysis demonstrated that BMI1 silencing downregulates a set of antioxidant genes. Docetaxel treatment increased guanine oxidation, whereas the antioxidant N-acetyl cysteine rescued docetaxel-induced cell death. Examination of clinical datasets revealed a positive correlation of BMI1 and antioxidant gene expression. BMI1-controlled antioxidant genes were predictive of poor prognosis in PC patients. In conclusion, BMI1 enhances antioxidant response, thereby allowing PC survival after docetaxel-based chemotherapy. BMI1-controlled antioxidant genes are overexpressed in aggressive PC and should be tested as predictors of chemotherapy failure.

Epigenetic regulation of CpG promoter methylation in invasive prostate cancer cells.

BACKGROUND: Recently, much attention has been focused on gaining a better understanding of the different populations of cells within a tumor and their contribution to cancer progression. One of the most commonly used methods to isolate a more aggressive sub-population of cells utilizes cell sorting based on expression of certain cell adhesion molecules. A recently established method we developed is to isolate these more aggressive cells based on their properties of increased invasive ability. These more invasive cells have been previously characterized as tumor initiating cells (TICs) that have a stem-like genomic signature and express a number of stem cell genes including Oct3/4 and Nanog and are more tumorigenic compared to their 'non-invasive' counterpart. They also have a profile reminiscent of cells undergoing a classic pattern of epithelial to mesenchymal transition or EMT. Using this model of invasion, we sought to investigate which genes are under epigenetic control in this rare population of cells. Epigenetic modifications, specifically DNA methylation, are key events regulating the process of normal human development. To determine the specific methylation pattern in these invasive prostate cells, and if any developmental genes were being differentially regulated, we analyzed differences in global CpG promoter methylation. RESULTS: Differentially methylated genes were determined and select genes were chosen for additional analyses. The non-receptor tyrosine kinase BMX and transcription factor SOX1 were found to play a significant role in invasion. Ingenuity pathway analysis revealed the methylated gene list frequently displayed genes from the IL-6/STAT3 pathway. Cells which have decreased levels of the targets BMX and SOX1 also display loss of STAT3 activity. Finally, using Oncomine, it was determined that more aggressive metastatic prostate cancers in humans also have higher levels of both Stat3 and Sox1. CONCLUSIONS: Using this method we can begin to understand which genes are epigenetically regulated in the invasive population compared to the bulk tumor cells. These aggressive sub-populations of cells may be linked to the cancer stem cell hypothesis, making their patterns of epigenetic regulation very attractive for biomarker analysis.

Clinical significance of Polycomb gene expression in brain tumors.

Polycomb group (PcG) proteins are crucial for neural cancer stem cell (NCSC) self-renewal. However, the relative expression levels of PcG genes in different subtypes of brain tumors, their prognostic role and their effects on cellular pathways have not been investigated. For this purpose, we queried the Oncomine database and found that 4 PcG genes (EZH2, RBBP7, SUZ12, YY1) are specifically expressed in brain tumors. EZH2 expression increases with tumor grade in adult and pediatric brain tumors, and is a poor prognostic factor. In glioblastoma, EZH2 inhibits differentiation, and activates cancer-, cell cycle- and cellular movement-related genes. In keeping with previously published data, our results suggest that EZH2 is both a prognostic factor and a promising therapy target in brain tumors.

Survivin is not induced by novel taxanes.

Taxanes are a critical component of chemotherapy for breast, prostate, lung and other cancers. Initial or acquired tumor resistance to taxanes is therefore one of the most important issues in oncology. Survivin is a prosurvival gene whose expression is a poor prognostic feature. Survivin is induced acutely upon exposure to taxanes and coordinates resistance to taxane-mediated cell death, although the exact mechanism of taxane-mediated survivin induction is not clear. Here, we describe the synthesis of a series of novel taxanes, with modifications on the 7- or 10-position of the taxane backbone, as well as the side chain. We found that the novel taxanes with modifications at the 10-position have robust tubulin binding and tubulin polymerization activity. Gene expression profiling and quantitative PCR of cells treated with the 10-position conjugates reveals that the effect of treatment with a subset of these novel taxanes lacks a gene expression signature, including survivin induction, which is characteristically induced with paclitaxel treatment. Furthermore, we show that this gene expression signature is not due to differences in G2/M arrest. Cell sensitivity studies suggest that the inability to induce survivin is associated with increased drug cytotoxicity and apoptosis. This work suggests that taxanes that effectively bind tubulin need not invariably induce survivin as a mechanism of drug resistance.

Genomic profiling of tumor initiating prostatospheres.

BACKGROUND: The cancer stem cell (CSC) hypothesis proposes that a population of tumor cells bearing stem cell properties is responsible for the origin and maintenance of tumors. Normal and cancer stem cells possess the ability to grow in vitro as self-renewing spheres, but the molecular basis of this phenotype remains largely unknown. We intended to establish a comprehensive culture system to grow prostatospheres (PSs) from both cancer cell lines and patient tumors. We then used gene expression microarrays to gain insight on the molecular pathways that sustain the PS tumor initiating cell (TIC) phenotype. RESULTS: Traditional stem cell medium (SCM) supplemented with KnockoutSR (KO) allows the propagation of monoclonal PSs from cell lines and primary cells. PSs display gene expression and tumorigenicity hallmarks of TICs. Gene expression analysis defined a gene signature composed of 66 genes that characterize LNCaP and patient PSs. This set includes novel prostate TIC growth factors (NRP1, GDF1, JAG1), proteins implicated in cell adhesion and cytoskeletal maintenance, transcriptional regulators (MYCBP, MYBL1, ID1, ID3, FOS, ELF3, ELF4, KLF2, KLF5) and factors involved in protein biosynthesis and metabolism. Meta-analysis in Oncomine reveals that some of these genes correlate with prostate cancer status and/or progression. Reporter genes and inhibitors indicate that the Notch pathway contributes to prostatosphere growth. CONCLUSIONS: We have developed a model for the culture of PSs, and provide a genomic profile that support CSCs identity. This signature identifies novel markers and pathways that are predicted to correlate with prostate cancer evolution.