Hey1, a mediator of notch signaling, is an androgen receptor corepressor

NOTCH and PTEN in prostate cancer

Over the past decade, our understanding of the role that Notch-signaling has in tumorigenesis has shifted from leukemogenesis into cancers of solid tumors. Emerging data suggests that in addition to direct effects mediated through the canonical Notch pathway, Notch may participate in epithelial tumor development through regulation of pathways such as PTEN/PI3K/Akt. Prostate cancer is a disease for which PTEN gene expression is especially essential. This review will summarize a role for Notch in prostate development and cancer with an emphasis on how the Notch pathway may intersect with PTEN/PI3K/Akt and mTOR signaling.

Hey bHLH transcription factors

Hey bHLH transcription factors are direct targets of canonical Notch signaling. The three mammalian Hey proteins are closely related to Hes proteins and they primarily repress target genes by either directly binding to core promoters or by inhibiting other transcriptional activators. Individual candidate gene approaches and systematic screens identified a number of Hey target genes, which often encode other transcription factors involved in various developmental processes. Here, we review data on interaction partners and target genes and conclude with a model for Hey target gene regulation. Furthermore, we discuss how expression of Hey proteins affects processes like cell fate decisions and differentiation, e.g., in cardiovascular, skeletal, and neural development or oncogenesis and how this relates to the observed developmental defects and phenotypes observed in various knockout mice.

Disruption of prostate epithelial differentiation pathways and prostate cancer development

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

Notch-induced transcription factors are predictive of survival and 5-fluorouracil response in colorectal cancer patients

Background:

The purpose of this study was to evaluate the expression of Notch-induced transcription factors (NTFs) HEY1, HES1 and SOX9 in colorectal cancer (CRC) patients to determine their clinicopathologic and prognostic significance.

Methods:

Levels of HEY1, HES1 and SOX9 protein were measured by immunohistochemistry in a nonmalignant and malignant tissue microarray of 441 CRC patients, and the findings correlated with pathologic, molecular and clinical variables.

Results:

The NTFs HEY1, HES1 and SOX9 were overexpressed in tumours relative to colonic mucosa (OR=3.44, P<0.0001; OR=7.40, P<0.0001; OR=4.08 P<0.0001, respectively). HEY1 overexpression was a negative prognostic factor for all CRC patients (HR=1.29, P=0.023) and strongly correlated with perineural and vascular invasion and lymph node (LN) metastasis. In 5-fluorouracil (5-FU)-treated patients, the tumour overexpression of SOX9 correlated with markedly poorer survival (HR=8.72, P=0.034), but had no predictive effect in untreated patients (HR=0.70, P=0.29). When HEY1, HES1 and SOX9 expression were combined to predict survival with chemotherapy, in treated patients there was an additive increase in the risk of death with each NTF overexpressed (HR=2.09, P=0.01), but no prognostic import in the untreated patient group (HR=0.74, P=0.19).

Conclusion:

The present study is the first to discover that HEY1 overexpression correlates with poorer outcome in CRC, and NTF expression is predictive of CRC patient survival with 5-FU chemotherapy. If confirmed in future studies, testing of NTF expression has the potential to enter routine pathological practice for the selection of patients to undergo chemotherapy alone or in combination with Notch inhibitors.

Hypoxia, notch signalling, and prostate cancer

The notch signalling pathway is involved in differentiation, proliferation, angiogenesis, vascular remodelling, and apoptosis. Deregulated expression of notch receptors, ligands, and targets is observed in many solid tumours, including prostate cancer. Hypoxia is a common feature of prostate tumours, leading to increased gene instability, reduced treatment response, and increased tumour aggressiveness. The notch signalling pathway is known to regulate vascular cell fate and is responsive to hypoxia-inducible factors. Evidence to date suggests similar, therapeutically exploitable, behaviour of notch-activated and hypoxic prostate cancer cells.

Mini-review: Foldosome regulation of androgen receptor action in prostate cancer

Steroid hormone receptors play diverse roles in many aspects of human physiology including cell division, apoptosis and homeostasis, tissue differentiation, sexual development and response to stress. These ligand-activated transcription factors require the functional activity of numerous chaperone and chaperone-associated proteins, collectively termed the foldosome, at the crucial step of ligand recognition and binding. Since the initial isolation of foldosome components and pioneering research by Pratt, Toft and colleagues we understand much regarding cytosolic receptor function. The classical view, that the role of foldosome components is restricted to the cytosol, has been modified over recent years by research highlighting additional roles of chaperone proteins in nuclear translocation and target gene expression. Further, dysregulation of chaperone activity and expression has been implicated in various cancers, including breast and prostate cancer. Consequently, the foldosome provides an attractive therapeutic target in steroid hormone receptor-driven malignancies. This review summarises current knowledge of how the foldosome impacts upon androgen receptor signalling, which is the key therapeutic target on prostate cancer, and how foldosome components may be used as biomarkers or therapeutic targets in this disease.

The transcription factor CREBZF is a novel positive regulator of p53

CREBZF is a member of the mammalian ATF/CREB family of transcription factors. Here, we describe a novel functional interaction between CREBZF and the tumor suppressor p53. CREBZF was identified in a yeast two-hybrid screen using HEY1, recently characterized as an indirect p53 activator, as bait. CREBZF interacts in vitro with both HEY1 and p53, and CREBZF expression stabilizes and activates p53. Moreover, CREBZF cooperates synergistically with HEY1 to enhance p53 transcriptional activity. On the other hand, partial depletion of endogenous CREBZF diminishes p53 protein levels and inhibits HEY1-mediated activation of p53. CREBZF-positive effects on p53 signaling may reflect, at least in part, an observed induction of posttranslational modifications in p53 known to prevent its degradation. CREBZF expression protects HCT116 cells from UV radiation-induced cell death. In addition, CREBZF expression confers sensitivity to 5-fluorouracil, a p53-activating chemotherapeutic drug. Our study suggests that CREBZF may participate in the modulation of p53 tumor suppressor function.

Androgen action and metabolism in prostate cancer

The transcriptional programs regulated through the activity of the androgen receptor (AR) modulate normal prostate development and the maintenance of prostatic functions at maturity. AR signaling also controls key survival and growth functions operative in prostate cancer. Inhibiting the AR program remains the key target in the treatment of advanced prostate cancer, and suppressing AR also holds great potential for preventing the development or progression of early stage prostate cancer. In this review, we detail molecular mechanisms of AR activity, cellular components contributing to the maintenance of AR signaling despite AR-ligand suppression, and discuss treatment strategies designed to target components of resistance to AR-directed therapeutics.

Biology of castration-recurrent prostate cancer

Although androgen-deprivation therapy is the standard therapy for advanced and metastatic prostate cancer, this treatment is only palliative. Prostate cancer recurs then grows despite low circulating testicular androgens, using several mechanisms that remain dependent on androgen-receptor signaling in most cases. This article reviews the diversity of mechanisms used for growth by castration-recurrent prostate cancer.

Castration-resistant prostate cancer: potential targets and therapies

The treatment landscape for patients with castration-resistant prostate cancer (CRPC) is undergoing significant changes with the advent of new therapies and multidisciplinary efforts by scientists and clinicians. As activation of multiple molecular pathways in the neoplastic prostate makes it impossible for single-target drugs to be completely effective in treating CRPC, this has led to combination therapy strategy, where several molecules involved in tumor growth and disease progression are targeted by a therapeutic regimen. In the present review, we provide an update on the molecular pathways that play an important role in the pathogenesis of CRPC and discuss the current wave of new treatments to combat this lethal disease.

Role of the HSP90-associated cochaperone p23 in enhancing activity of the androgen receptor and significance for prostate cancer

Prostate tumor growth initially depends on androgens, which act via the androgen receptor (AR). Despite androgen ablation therapy, tumors eventually progress to a castrate-resistant stage in which the AR remains active. The mechanisms are poorly understood but it may be that changes in levels or activity of AR coregulators affect trafficking and activation of the receptor. A key stage in AR signaling occurs in the cytoplasm, where unliganded receptor is associated with the heat shock protein (HSP)90 foldosome complex. p23, a key component of this complex, is best characterized as a cochaperone for HSP90 but also has HSP90-independent activity and has been reported as having differential effects on the activity of different steroid receptors. Here we report that p23 increases activity of the AR, and this appears to involve steps both in the cytoplasm (increasing ligand-binding capacity, possibly via direct interaction with AR) and the nucleus (enhancing AR occupancy at target promoters). We show, for the first time, that AR and p23 can interact, perhaps directly, when HSP90 is not present in the same complex. The effects of p23 on AR activity are at least partly HSP90 independent because a mutant form of p23, unable to bind HSP90, nevertheless increases AR activity. In human prostate tumors, nuclear p23 was higher in malignant prostate cells compared with benign/normal cells, supporting the utility of p23 as a therapeutic target in prostate cancer.

Transcriptomic analysis of the developing and adult mouse cochlear sensory epithelia

The adult mammalian cochlea lacks regenerative ability and the irreversible degeneration of cochlear sensory hair cells leads to permanent hearing loss. Previous data show that early postnatal cochlea harbors stem/progenitor-like cells and shows a limited regenerative/repair capacity. These properties are progressively lost later during the postnatal development. Little is known about the genes and pathways that are potentially involved in this difference of the regenerative/repair potentialities between early postnatal and adult mammalian cochlear sensory epithelia (CSE). The goal of our study is to investigate the transcriptomic profiles of these two stages. We used Mouse Genome 430 2.0 microarray to perform an extensive analysis of the genes expressed in mouse postnatal day-3 (P3) and adult CSE. Statistical analysis of microarray data was performed using SAM (Significance Analysis of Microarrays) software. We identified 5644 statistically significant differentially expressed transcripts with a fold change (FC) >2 and a False Discovery Rate (FDR) ≤0.05. The P3 CSE signature included 3,102 transcripts, among which were known genes in the cochlea, but also new transcripts such as, Hmga2 (high mobility group AT-hook 2) and Nrarp (Notch-regulated ankyrin repeat protein). The adult CSE overexpressed 2,542 transcripts including new transcripts, such as Prl (Prolactin) and Ar (Androgen receptor), that previously were not known to be expressed in the adult cochlea. Our comparative study revealed important genes and pathways differentially expressed between the developing and adult CSE. The identification of new candidate genes would be useful as potential markers of the maintenance or the loss of stem cells and regenerative/repair ability during mammalian cochlear development.

The androgen receptor facilitates inhibition of human dopamine transporter (DAT1) reporter gene expression by HESR1 and HESR2 via the variable number of tandem repeats

A functional genetic polymorphism in the 3'-untranslated region (UTR) within exon 15 of the human DAT gene (DAT1) has been described. This 3'-UTR contains a variable number of tandem repeats (VNTR) 40 bp in length; many association studies of psychiatric or developmental disorders with this VNTR have been conducted. We previously demonstrated that HESR1 (the Hairy/enhancer of split related transcriptional factor 1 with YRPW motif) and HESR2 reduced DAT reporter gene expression via this 3'-UTR. VNTR allele-dependent altered reporter gene expression was also observed. In the present study, we wanted to clarify the molecular characterization of HESR1 and HESR2, focusing on its cis-element and co-factor. Deletion of the VNTR domain increased reporter gene expression both with and without transfection of HESRs, suggesting that the VNTR inhibits DAT expression, and is responsive to HESRs. In the presence of transfected androgen receptor (AR), activity of the luciferase reporter with the nine-repeat allele (9r) decreased, while that with the ten-repeat allele (10r), the most frequent in the population, increased significantly. Furthermore, co-expression of HESR1 or HESR2 with AR increased the inhibitory effect of the HESRs. Our data indicate that a functional modification occurs when the HESRs are coupled with AR. This HESR-AR interaction could be the molecular basis of sexual dimorphisms in DAT expression, or other dopamine-related behavioral traits.

Notch activation by phenethyl isothiocyanate attenuates its inhibitory effect on prostate cancer cell migration

Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive component of edible cruciferous vegetables with in vivo efficacy against prostate cancer in experimental rodents. Cancer chemopreventive response to PEITC is characterized by its ability to inhibit multiple oncogenic signaling pathways, including nuclear factor-κB, Akt, and androgen receptor. The present study demonstrates, for the first time, that PEITC treatment activates Notch signaling in malignant as well as normal human prostate cells. Exposure of human prostate cancer cells (LNCaP, PC-3, and DU145) and a normal human prostate epithelial cell line (PrEC) to PEITC resulted in cleavage (active form) of Notch1 and Notch2, and increased transcriptional activity of Notch. In PC-3 and LNCaP cells, PEITC treatment caused induction of Notch ligands Jagged1 and Jagged2 (PC-3), overexpression of γ-secretase complex components Presenilin1 and Nicastrin (PC-3), nuclear enrichment of cleaved Notch2, and/or up-regulation of Notch1, Notch2, Jagged1, and/or Jagged2 mRNA. PEITC-induced apoptosis in LNCaP and PC-3 cells was significantly attenuated by RNA interference of Notch2, but not by pharmacological inhibition of Notch1. Inhibition of PC-3 and LNCaP cell migration resulting from PEITC exposure was significantly augmented by knockdown of Notch2 protein as well as pharmacological inhibition of Notch1 activation. Nuclear expression of cleaved Notch2 protein was significantly higher in PC-3 xenografts from PEITC-treated mice and dorsolateral prostates from PEITC-fed TRAMP mice compared with respective control. Because Notch signaling is implicated in epithelial-mesenchymal transition and metastasis, the present study suggests that anti-metastatic effect of PEITC may be augmented by a combination regimen involving a Notch inhibitor.

Differentiation of the ductal epithelium and smooth muscle in the prostate gland are regulated by the Notch/PTEN-dependent mechanism

We have shown previously that during branching morphogenesis of the mouse prostate gland, Bone morphogenetic protein 7 functions to restrict Notch1-positive progenitor cells to the tips of the prostate buds. Here, we employed prostate-specific murine bi-genic systems to investigate the effects of gain and loss of Notch function during prostate development. We show that Nkx3.1(Cre) and Probasin(Cre) alleles drive expression of Cre recombinase to the prostate epithelium and periepithelial stroma. We investigated the effects of gain of Notch function using the Rosa(NI1C) conditional allele, which carries a constitutively active intracellular domain of Notch1 receptor. We carried out the analysis of loss of Notch function in Nkx3.1(Cre/+);RBP-J(flox/flox) prostates, where RBP-J is a ubiquitous transcriptional mediator of Notch signaling. We found that gain of Notch function resulted in inhibition of the tumor suppressor PTEN, and increase in cell proliferation and progenitor cells in the basal epithelium and smooth muscle compartments. In turn, loss of Notch/RBP-J function resulted in decreased cell proliferation and loss of epithelial and smooth muscle progenitors. Gain of Notch function resulted in an early onset of benign prostate hyperplasia by three months of age. Loss of Notch function also resulted in abnormal differentiation of the prostate epithelium and stroma. In particular, loss of Notch signaling and increase in PTEN promoted a switch from myoblast to fibroblast lineage, and a loss of smooth muscle. In summary, we show that Notch signaling is necessary for terminal differentiation of the prostate epithelium and smooth muscle, and that during normal prostate development Notch/PTEN pathway functions to maintain patterned progenitors in the epithelial and smooth muscle compartments. In addition, we found that both positive and negative modulation of Notch signaling results in abnormal organization of the prostate tissue, and can contribute to prostate disease in the adult organ.

Repression of androgen receptor activity by HEYL, a third member of the Hairy/Enhancer-of-split-related family of Notch effectors

The Hairy/Enhancer-of-split-related with YRPW-like motif (HEY) family of proteins are transcriptional repressors and downstream effectors of Notch signaling. We previously reported that HEY1 and HEY2 selectively repress androgen receptor (AR) signaling in mammalian cell lines and have shown that in human tissue HEY1 is excluded from the nuclei in prostate cancer but not benign prostatic hyperplasia. We have now characterized a third member of this family, HEYL, which is a more potent repressor of AR activity. HEYL interacted with and repressed AR activation function-1 domain and competitively inhibited SRC1e activation of AR transcriptional activity. Using a cell line inducibly expressing exogenous HEYL, we showed that HEYL represses endogenous AR-regulated genes and reduces androgen-dependent prostate cancer cell growth. Using a trans-repression assay, we identified both trichostatin-sensitive and -insensitive domains within HEYL; however, analysis of endogenous AR target genes suggested that HEYL represses AR activity through histone deacetylase I/II-independent mechanisms. Immunohistochemical analyses of tissue indicated that, in a fashion similar to that previously reported for HEY1, HEYL is excluded from the nuclei in prostate cancer but not adjacent benign tissue. This suggests that nuclear exclusion of HEY proteins may be an important step in the progression of prostate cancer.

Notch signaling proteins: legitimate targets for cancer therapy

Proteins and small peptides (growth factors and hormones) are key molecules in maintaining cellular homeostasis. To that end, Notch signaling pathway proteins are known to play critical roles in maintaining the balance between cell proliferation, differentiation and apoptosis, and thus it has been suggested that Notch may be responsible for the development and progression of human malignancies. Therefore, the Notch signaling pathway proteins may present novel therapeutic targets, which could have promising therapeutic impact on eradicating human malignancies. This review describes the role of Notch signaling pathway proteins in cancer and how its deregulation is involved in tumor development and progression leading to metastasis and the ultimate demise of patients diagnosed with cancer. Further, we summarize the role of several Notch inhibitors especially "natural agents" that could represent novel therapeutic strategies targeting Notch signaling toward better treatment outcome of patients diagnosed with cancer.

Androgen receptor signalling in prostate cancer: the functional consequences of acetylation

The androgen receptor (AR) is a ligand activated transcription factor and member of the steroid hormone receptor (SHR) subfamily of nuclear receptors. In the early stages of prostate carcinogenesis, tumour growth is dependent on androgens, and AR directly mediates these effects by modulating gene expression. During transcriptional regulation, the AR recruits numerous cofactors with acetylation-modifying enzymatic activity, the best studied include p300/CBP and the p160/SRC family of coactivators. It is known that recruitment of histone acetyltransferases (HATs) and histone deacetylases (HDACs) is key in fine-tuning responses to androgens and is thus likely to play a role in prostate cancer progression. Further, these proteins can also modify the AR itself. The functional consequences of AR acetylation, the role of modifying enzymes in relation to AR transcriptional response, and prostate cancer will be discussed.

Genome-wide analysis of androgen receptor binding and gene regulation in two CWR22-derived prostate cancer cell lines

Prostate carcinoma (CaP) is a heterogeneous multifocal disease where gene expression and regulation are altered not only with disease progression but also between metastatic lesions. The androgen receptor (AR) regulates the growth of metastatic CaPs; however, sensitivity to androgen ablation is short lived, yielding to emergence of castrate-resistant CaP (CRCaP). CRCaP prostate cancers continue to express the AR, a pivotal prostate regulator, but it is not known whether the AR targets similar or different genes in different castrate-resistant cells. In this study, we investigated AR binding and AR-dependent transcription in two related castrate-resistant cell lines derived from androgen-dependent CWR22-relapsed tumors: CWR22Rv1 (Rv1) and CWR-R1 (R1). Expression microarray analysis revealed that R1 and Rv1 cells had significantly different gene expression profiles individually and in response to androgen. In contrast, AR chromatin immunoprecipitation (ChIP) combined with promoter DNA microarrays (ChIP-on-chip) studies showed that they have a similar AR-binding profile. Coupling of the microarray study with ChIP-on-chip analysis identified direct AR targets. The most prominent function of transcripts that were direct AR targets was transcriptional regulation, although only one transcriptional regulator, CCAAT/enhancer binding protein δ, was commonly regulated in both lines. Our results indicate that the AR regulates the expression of different transcripts in the two lines, and demonstrate the versatility of the AR-regulated gene expression program in prostate tumors.

Native functions of the androgen receptor are essential to pathogenesis in a Drosophila model of spinobulbar muscular atrophy

Spinobulbar muscular atrophy (SBMA) is a neurodegenerative disease caused by expansion of a polyglutamine tract in the androgen receptor (AR). This mutation confers toxic function to AR through unknown mechanisms. Mutant AR toxicity requires binding of its hormone ligand, suggesting that pathogenesis involves ligand-induced changes in AR. However, whether toxicity is mediated by native AR function or a novel AR function is unknown. We systematically investigated events downstream of ligand-dependent AR activation in a Drosophila model of SBMA. We show that nuclear translocation of AR is necessary, but not sufficient, for toxicity and that DNA binding by AR is necessary for toxicity. Mutagenesis studies demonstrated that a functional AF-2 domain is essential for toxicity, a finding corroborated by a genetic screen that identified AF-2 interactors as dominant modifiers of degeneration. These findings indicate that SBMA pathogenesis is mediated by misappropriation of native protein function, a mechanism that may apply broadly to polyglutamine diseases.

Primitive origins of prostate cancer: in vivo evidence for prostate-regenerating cells and prostate cancer-initiating cells

Tissue stem cells have been linked to cancers of epithelial origin including the prostate. There are three relevant issues concerning stem cells and cancer that rely solely on functional studies: 1. Are there tissue-regenerating stem cells in the adult organ? 2. Can tissue-regenerating cells serve as targets for transformation? 3. Do primary tumors contain tumor-propagating (cancer stem) cells? We will review the recent literature with respect to these critical issues to provide a direct link between primitive cells and prostate cancer.

Differential regulation of steroid nuclear receptor coregulator expression between normal and neoplastic prostate epithelial cells

BACKGROUND

Deregulated androgen receptor (AR) action is critical for prostate cancer (PCa) progression. Aberrant expression of AR-associated coregulators contributes to AR activity in PCa. The mechanisms underlying coregulator expression in PCa are under intense investigation as they may lead to alternative means of targeting AR activity in PCa cells. We have recently shown that over 30% of coregulator expression in the PCa cell line LNCaP is subject to androgen regulation.

METHODS

Using multiple PCa cell lines as well as xenograft models, non-malignant prostate epithelial cell lines and androgen-responsive tissues derived from a male Wistar rat model system, we explored the effect of androgen stimulation and androgen deprivation on the expression of the core coactivators SRC1, SRC2, SRC3, CBP, and p300.

RESULTS

Androgen stimulation of model systems representing PCa led to a decrease in the expression of SRC1, SRC2, SRC3, CBP, and p300, whereas androgen deprivation induced the expression of these coactivators. In contrast, expression of these coregulators remained largely unaffected following changes in the androgenic milieu in AR-positive models representing non-malignant prostate cells and tissues.

CONCLUSIONS

Our data indicate differences in the regulation of coregulator expression between neoplastic and normal prostate cells. These findings emphasize the important potential of targeting the mechanisms regulating coregulator expression for therapeutic intervention in PCa.

Partners in crime: deregulation of AR activity and androgen synthesis in prostate cancer

Prostate cancer remains a leading cause of cancer death, as there are no durable means to treat advanced disease. Treatment of non-organ-confined prostate cancer hinges on its androgen dependence. First-line therapeutic strategies suppress androgen receptor (AR) activity, via androgen ablation and direct AR antagonists, whereas initially effective, incurable, 'castration-resistant' tumors arise as a result of resurgent AR activity. Alterations of AR and/or associated regulatory networks are known to restore receptor activity and support resultant therapy-resistant tumor progression. However, recent evidence also reveals an unexpected contribution of the AR ligand, indicating that alterations in pathways controlling androgen synthesis support castration-resistant AR activity. In this report, the mechanisms underlying the lethal pairing of AR deregulation and aberrant androgen synthesis in prostate cancer progression will be discussed.

An exquisite cross-control mechanism among endothelial cell fate regulators directs the plasticity and heterogeneity of lymphatic endothelial cells

Arteriovenous-lymphatic endothelial cell fates are specified by the master regulators, namely, Notch, COUP-TFII, and Prox1. Whereas Notch is expressed in the arteries and COUP-TFII in the veins, the lymphatics express all 3 cell fate regulators. Previous studies show that lymphatic endothelial cell (LEC) fate is highly plastic and reversible, raising a new concept that all 3 endothelial cell fates may co-reside in LECs and a subtle alteration can result in a reprogramming of LEC fate. We provide a molecular basis verifying this concept by identifying a cross-control mechanism among these cell fate regulators. We found that Notch signal down-regulates Prox1 and COUP-TFII through Hey1 and Hey2 and that activated Notch receptor suppresses the lymphatic phenotypes and induces the arterial cell fate. On the contrary, Prox1 and COUP-TFII attenuate vascular endothelial growth factor signaling, known to induce Notch, by repressing vascular endothelial growth factor receptor-2 and neuropilin-1. We show that previously reported podoplanin-based LEC heterogeneity is associated with differential expression of Notch1 in human cutaneous lymphatics. We propose that the expression of the 3 cell fate regulators is controlled by an exquisite feedback mechanism working in LECs and that LEC fate is a consequence of the Prox1-directed lymphatic equilibrium among the cell fate regulators.

Ubiquitous overexpression of Hey1 transcription factor leads to osteopenia and chondrocyte hypertrophy in bone

The transcription factor Hey1, a known Notch target gene of the HES family, has recently been described as a target gene of bone morphogenetic protein-2 (BMP-2) during osteoblastic differentiation in vitro. As the role of Hey1 in skeletal physiology is unknown, we analyzed bones of mice ubiquitously lacking or overexpressing Hey1. This strategy enabled us to evaluate whether Hey1 modulation in the whole organism could serve as a drug or antibody target for therapy of diseases associated with bone loss. Hey1 deficiency resulted in modest osteopenia in vivo and increased number and activity of osteoclasts generated ex vivo. Hey1 overexpression resulted in distinct progressive osteopenia and inhibition of osteoblasts ex vivo, an effect apparently dominant to a mild inhibition of osteoclasts. In both Hey1 deficient and overexpressing mice, males were less affected than females and skeleton was not affected during development. Bone histomorphometry did not reveal major changes in animals at 20 weeks, suggesting that modulation had occurred before. Adult Hey1 transgenics also displayed increased type X collagen expression and an enlarged hypertrophic zone in the growth plate. Taken together, our data suggest that ubiquitous in vivo Hey1 regulation affects osteoblasts, osteoclasts and chondrocytes. Due to the complex role of Hey1 in bone, inhibition of Hey1 does not appear to be a straightforward therapeutic strategy to increase the bone mass.

The Notch effector Hey1 associates with myogenic target genes to repress myogenesis

Members of the Hey family of transcriptional repressors are basic helix-loop-helix proteins that are thought to act downstream of Notch in diverse tissues. Although forced expression of Hey1, a target of Notch in myoblasts, is sufficient to recapitulate inhibitory effects of the pathway on differentiation, how Hey1 interferes with myogenic transcription has not been fully elucidated. We provide multiple lines of evidence that Hey1 does not target the intrinsic transcriptional activity of the skeletal muscle master regulator MyoD. Our results indicate instead that Hey1 is recruited to the promoter regions of myogenin and Mef2C, two genes whose induction is critical for myogenesis. Expression of Hey1 in C2C12 myoblasts correlates with reduced recruitment of MyoD to these promoters, arguing that Hey1 inhibits myogenesis by associating with and repressing expression of key myogenic targets.

Notch-1 signaling is lost in prostate adenocarcinoma and promotes PTEN gene expression

Prostate tumorigenesis is associated with loss of PTEN gene expression. We and others have recently reported that PTEN is regulated by Notch-1 signaling. Herein, we tested the hypothesis that alterations of the Notch-1 signaling pathway are present in human prostate adenocarcinoma and that Notch-1 signaling regulates PTEN gene expression in prostate cells. Prostate adenocarcinoma cases were examined by immunohistochemistry for ligand cleaved (activated) Notch-1 protein. Tumor foci exhibited little cleaved Notch-1 protein, but expression was observed in benign tissue. Both tumor and benign tissue expressed total (uncleaved) Notch-1. Reduced Hey-1 expression was seen in tumor foci but not in benign tissue, confirming loss of Notch-1 signaling in prostate adenocarcinoma. Retroviral expression of constitutively active Notch-1 in human prostate tumor cell lines resulted in increased PTEN gene expression. Incubation of prostate cell lines with the Notch-1 ligand, Delta, resulted in increased PTEN expression indicating that endogenous Notch-1 regulates PTEN gene expression. Chromatin immunoprecipitation demonstrated that CBF-1 was bound to the PTEN promoter. These data collectively indicate that defects in Notch-1 signaling may play a role in human prostate tumor formation in part via a mechanism that involves regulation of the PTEN tumor suppressor gene.

HEY1 Leu94Met gene polymorphism dramatically modifies its biological functions

The hairy/enhancer-of-split related with YRPW motif 1 (HEY1) is a member of the basic-helix-loop-helix-Orange (bHLH-O) family of transcriptional repressors that mediate Notch signaling. Several cancer-related pathways also regulate HEY1 expression, and HEY1 itself acts as an indirect positive regulator of the p53 tumor suppressor protein and a negative regulator of androgen receptor activity. In this study we show how a naturally occurring non-synonymous polymorphism at codon 94 of HEY1, which results in a substitution of leucine by methionine (Leu94Met), converts HEY1 from an androgen receptor corepressor to an androgen receptor co-activator without affecting its intrinsic transcriptional repressive domains. The polymorphism Leu94Met also abolishes HEY1-mediated activation of p53 and suppresses the ability of HEY1 to induce p53-dependent cell-cycle arrest and aberrant cell differentiation in human osteosarcoma U2OS cells. Moreover, expression of HEY1, but not of the variant Leu94Met, confers sensitivity to p53-activating chemotherapeutic drugs on U2OS cells. In addition, we have identified motifs in HEY1 that are critical for the regulation of its subcellular localization and analysed how mutations in those motifs affect both HEY1 and HEY1-Leu94Met functions. These findings suggest that the polymorphism Leu94Met in HEY1 radically alters its biological activities and may affect oncogenic processes.

Estrogen receptor subtype beta2 is involved in neuromast development in zebrafish (Danio rerio) larvae

Estrogens are known to play a role in both reproductive and non-reproductive functions in mammals. Estrogens and their receptors are involved in the development of the central nervous system (brain development, neuronal survival and differentiation) as well as in the development of the peripheral nervous system (sensory-motor behaviors). In order to decipher possible functions of estrogens in early development of the zebrafish sensory system, we investigated the role of estrogen receptor beta(2) (ERbeta(2)) by using a morpholino (MO) approach blocking erbeta(2) RNA translation. We further investigated the development of lateral line organs by cell-specific labeling, which revealed a disrupted development of neuromasts in morphants. The supporting cells developed and migrated normally. Sensory hair cells, however, were absent in morphants' neuromasts. Microarray analysis and subsequent in situ hybridizations indicated an aberrant activation of the Notch signaling pathway in ERbeta(2) morphants. We conclude that signaling via ERbeta(2) is essential for hair cell development and may involve an interaction with the Notch signaling pathway during cell fate decision in the neuromast maturation process.

The Notch pathway in prostate development and cancer

The Notch family of transmembrane receptors are important mediators of cell fate determination. Accordingly, Notch signaling is intimately involved in the development of numerous tissues. Recent findings have highlighted a critical role for Notch signaling in normal prostate development. Notch signaling is required for embryonic and postnatal prostatic growth and development, for proper cell lineage specification within the prostate, as well as for adult prostate maintenance and regeneration following castration and hormone replacement. Evidence for Notch as a regulator of prostate cancer development, progression, and metastasis has also emerged. This review summarizes our current understanding of the role of Notch pathway elements, including members of the Jagged, Delta-like, hairy/enhancer-of-split, and hairy/enhancer-of-split related with YRPW motif families, in prostate development and tumorigenesis. Data supporting Notch pathway elements as oncogenes and tumor suppressors in prostate tumors, as well as data implicating Notch receptors and ligands as potential markers of normal prostate stem/progenitor cells and prostate cancer stem/initiating cells, are also presented.

Human ASH1 expression in prostate cancer with neuroendocrine differentiation

Neuroendocrine differentiation in prostate cancer correlates with overall prognosis and disease progression after androgen-deprivation therapy, although its specific mechanisms are currently poorly understood. A role of Notch pathway has been reported in determining neuroendocrine phenotype of normal and neoplastic tissues. The aim of this study was to analyze whether this pathway might affect neuroendocrine differentiation in prostate cancer. Human achaete-scute homolog 1 (hASH1), a pivotal member of the Notch pathway, was investigated in 80 prostate cancers selected and grouped according to chromogranin A immunohistochemistry, as follows: prostate cancers without neuroendocrine differentiation, untreated (25 cases); prostate cancers with neuroendocrine differentiation, untreated (40 cases); prostate cancers with previous androgen-deprivation therapy, all having neuroendocrine differentiation (15 cases). Human ASH1 protein was analyzed by immunohistochemistry, whereas the presence of hASH1 mRNA transcripts was investigated on paraffin material by real-time PCR. By immunohistochemistry, hASH1 was colocalized with chromogranin A in neuroendocrine cells of normal prostatic gland. It was absent in all but one prostate cancers without neuroendocrine differentiation, whereas it was positive in 25% of prostate cancers with neuroendocrine differentiation/untreated, with a significant correlation with the extent of neuroendocrine features (P=0.02). Moreover, comparing untreated and treated prostate cancers with neuroendocrine differentiation, a positive association with androgen-deprivation therapy was observed (P=0.01). In prostate cancers with neuroendocrine differentiation, RNA analysis confirmed the association of higher transcript levels in androgen deprivation-treated compared with untreated patients (P=0.01). In addition, hASH1 mRNA analysis in microdissected chromogranin A-positive and chromogranin A-negative areas within the same tumor demonstrated a two- to sevenfold increase of hASH1 mRNA expression in chromogranin A-positive tumor cell populations.

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.

Functional characterization of the native NH2-terminal transactivation domain of the human androgen receptor: binding kinetics for interactions with TFIIF and SRC-1a

The androgen receptor (AR) is a ligand-activated transcription factor that mediates the actions of the steroid hormones testosterone and dihydrotestosterone at the level of gene transcription. The main transactivation function is modular in structure, maps to the N-terminal domain (NTD), and is termed AF1. This region of the AR is structurally flexible and functions in multiple protein-protein interactions with coregulatory proteins and components of the general transcription machinery. Using surface plasmon resonance, the binding kinetics for the interaction of AR-AF1 with the large subunit of the general transcription factor TFIIF, termed RAP74, and the coactivator SRC-1a were measured. AR-AF1 interacts with both the NTD and CTD of RAP74 and the CTD of SRC-1a. The dissociation constants ( Kd) for the binding of polypeptides derived from RAP74 are in the submicromolar range, while a peptide from SRC-1a bound with a Kd of 14 microM. Significantly, the individual NTD and CTD of RAP74 interacted with AR-AF1 with distinct binding kinetics, with the NTD exhibiting slower on and off rates. TFIIF is involved in transcription initiation and elongation, and the CTD of RAP74 binds to the RNA polymerase II enzyme, the general transcription factor TFIIB, and a CTD phosphatase, FCP1. We have mutated hydrophobic residues in the RAP74-CTD structure to disrupt secondary structure elements and show that binding of AR-AF1 depends upon helix 3 in the winged-helix domain of the RAP74-CTD polypeptide. Altogether, a model is suggested for AR-AF1-dependent transactivation of receptor-target genes.

bHLH-Orange Transcription Factors in Development and Cancer

Basic helix-loop-helix (bHLH) proteins are a large superfamily of transcription factors that play critical roles in many physiological processes including cellular differentiation, cell cycle arrest and apoptosis. Based on structural and phylogenetic analysis, mammalian bHLH-Orange (bHLH-O) proteins, which constitute the repressor family of bHLH factors, can be grouped into four subfamilies: Hes, Hey, Helt and Stra13/Dec. In addition to the bHLH domain that mediates DNA-binding and protein dimerization, all members of this family are characterized by a distinctive motif called the "Orange domain" which is present exclusively in these factors. Genetic studies using targeted mutagenesis in mice have revealed essential roles for many bHLH-O genes in embryonic development, cell fate decisions, differentiation of a number of cell types and in apoptosis. Furthermore, growing evidence of crosstalk between bHLH-O proteins with the tumor suppressors p53 and hypoxia-inducible factor, have started to shed light on their possible roles in oncogenesis. Consistently, deregulated expression of several bHLH-O factors is associated with various human cancers. Here, we review the structure and biological functions of bHLH-O factors, and discuss recent studies that suggest a potential role for these factors in tumorigenesis and tumor progression.

Androgen receptor (AR) coregulators: a diversity of functions converging on and regulating the AR transcriptional complex

Androgens, acting through the androgen receptor (AR), are responsible for the development of the male phenotype during embryogenesis, the achievement of sexual maturation at puberty, and the maintenance of male reproductive function and behavior in adulthood. In addition, androgens affect a wide variety of nonreproductive tissues. Moreover, aberrant androgen action plays a critical role in multiple pathologies, including prostate cancer and androgen insensitivity syndromes. The formation of a productive AR transcriptional complex requires the functional and structural interaction of the AR with its coregulators. In the last decade, an overwhelming and ever increasing number of proteins have been proposed to possess AR coactivating or corepressing characteristics. Intriguingly, a vast diversity of functions has been ascribed to these proteins, indicating that a multitude of cellular functions and signals converge on the AR to regulate its function. The current review aims to provide an overview of the AR coregulator proteins identified to date and to propose a classification of these AR coregulator proteins according to the function(s) ascribed to them. Taken together, this approach will increase our understanding of the cellular pathways that converge on the AR to ensure an appropriate transcriptional response to androgens.

Low-calcium serum-free defined medium selects for growth of normal prostatic epithelial stem cells

Stage-specific differentiation markers were used to evaluate the cellular composition and the origin of nonimmortalized (PrEC) and immortalized (PZ-HPV7, CA-HPV10, RWPE-1, and 957E/hTERT) human prostate cell lines. These studies documented that immortalized and nonimmortalized prostate epithelial cells established and maintained in low (i.e., <300 micromol/L) Ca(2+) serum-free defined (SFD) medium were all derived from normal nonmalignant prostate tissues and contain CD133(+)/ABCG2(+)/alpha(2)beta(1)(Hi)/p63(-)/PSCA(-)/AR(-)/PSA(-) prostate stem cells. In these cultures, prostate stem cells are able to self-renew and generate two distinct cell lineages: the minor proliferatively quiescent neuroendocrine lineage and the major transit-amplifying cell lineage. Subsequently, CD133(-)/ABCG2(-)/alpha(2)beta(1)(Hi)/p63(+)/PSCA(-)/AR(-)/PSA(-) transit-amplifying cells proliferate frequently and eventually mature into proliferatively quiescent CD133(-)/ABCG2(-)/alpha(2)beta(1)(Lo)/p63(-)/PSCA(+)/AR(-)/PSA(-) intermediate cells. Such proliferatively quiescent intermediate cells, however, do not complete their full maturation into CD133(-)/ABCG2(-)/alpha(2)beta(1)(Lo)/p63(-)/PSCA(-)/AR(+)/PSA(+) luminal-secretory cells in low Ca(2+) SFD medium. Addition of universal type I IFN and synthetic androgen (R1881) to culture medium resulted in up-regulation of androgen receptor protein expression. However, it failed to induce full differentiation of intermediate cells into AR(+)/PSA(+) luminal-secretory cells. Our results indicate that such inability of prostate epithelial cells to complete their differentiation is due to continuous expression of Notch-1 receptor and its downstream effector, Hey-1 protein, which actively suppresses differentiation via its ability to transcriptionally repress a series of genes, including the GATA family of transcription factors.

Cyclin D3/CDK11p58 complex is involved in the repression of androgen receptor

Androgen receptor (AR) is essential for the maintenance of the male reproductive systems and is critical for the carcinogenesis of human prostate cancers (PCas). D-type cyclins are closely related to the repression of AR function. It has been well documented that cyclin D1 inhibits AR function through multiple mechanisms, but the mechanism of how cyclin D3 exerts its repressive role in the AR signaling pathway remains to be identified. In the present investigation, we demonstrate that cyclin D3 and the 58-kDa isoform of cyclin-dependent kinase 11 (CDK11p58) repressed AR transcriptional activity as measured by reporter assays of transformed cells and prostate-specific antigen expression in PCa cells. AR, cyclin D3, and CDK11p58 formed a ternary complex in cells and were colocalized in the luminal epithelial layer of the prostate. AR activity is controlled by phosphorylation at specific sites. We found that AR was phosphorylated at Ser-308 by cyclin D3/CDK11p58 in vitro and in vivo, leading to the repressed activity of AR transcriptional activation unit 1 (TAU1). Furthermore, androgen-dependent proliferation of PCa cells was inhibited by cyclin D3/CDK11p58 through AR repression. These data suggest that cyclin D3/CDK11p58 signaling is involved in the negative regulation of AR function.

Delta-Notch--and then? Protein interactions and proposed modes of repression by Hes and Hey bHLH factors

Hes and Hey genes are the mammalian counterparts of the Hairy and Enhancer-of-split type of genes in Drosophila and they represent the primary targets of the Delta–Notch signaling pathway. Hairy-related factors control multiple steps of embryonic development and misregulation is associated with various defects. Hes and Hey genes (also called Hesr, Chf, Hrt, Herp or gridlock) encode transcriptional regulators of the basic helix-loop-helix class that mainly act as repressors. The molecular details of how Hes and Hey proteins control transcription are still poorly understood, however.

Proposed modes of action include direct binding to N- or E-box DNA sequences of target promoters as well as indirect binding through other sequence-specific transcription factors or sequestration of transcriptional activators. Repression may rely on recruitment of corepressors and induction of histone modifications, or even interference with the general transcriptional machinery. All of these models require extensive protein–protein interactions. Here we review data published on protein–protein and protein–DNA interactions of Hairy-related factors and discuss their implications for transcriptional regulation. In addition, we summarize recent progress on the identification of potential target genes and the analysis of mouse models.

Androgen receptor coregulators and their involvement in the development and progression of prostate cancer

The androgen receptor signaling axis plays an essential role in the development, function and homeostasis of male urogenital structures including the prostate gland although the mechanism by which the AR axis contributes to the initiation, progression and metastatic spread of prostate cancer remains somewhat enigmatic. A number of molecular events have been proposed to act at the level of the AR and associated coregulators to influence the natural history of prostate cancer including deregulated expression, somatic mutation, and post-translational modification. The purpose of this article is to review the evidence for deregulated expression and function of the AR and associated coactivators and corepressors and how such events might contribute to the progression of prostate cancer by controlling the selection and expression of AR targets.

Crossing paths with Notch in the hyper-network

The development of complex and diverse metazoan morphologies is coordinated by a surprisingly small number of evolutionarily conserved signaling mechanisms. These signals can act in parallel but often appear to function as an integrated hyper-network. The nodes defining this complex molecular circuitry are poorly understood, but the biological significance of pathway cross-talk is profound. The importance of such large-scale signal integration is exemplified by Notch and its ability to cross-talk with all the major pathways to influence cell differentiation, proliferation, survival and migration. The Notch pathway is, thus, a useful paradigm to illustrate the complexity of pathway cross-talk: its pervasiveness, context dependency, and importance in development and disease.

Mechanisms of androgen receptor repression in prostate cancer

Anti-androgens used in prostate cancer therapy inhibit AR (androgen receptor) activity via largely unknown mechanisms. Although initially successful in most cases, they eventually fail and the disease progresses. We need to elucidate how anti-androgens work to understand why they fail, and prolong their effects or design further therapies. Using a cellular model, we found different anti-androgens have diverse effects on subcellular localization of AR, revealing that they work via different mechanisms and suggesting that an informed sequential treatment regime may benefit patients. In the presence of the anti-androgens bicalutamide and hydroxyflutamide, a significant proportion of the AR is translocated to the nucleus but remains inactive. Receptor inhibition under these conditions is likely to involve recruitment of co-repressor proteins, which interact with antagonist-occupied receptor but inhibit receptor-dependent transcription. Which co-repressors are required in vivo for AR repression by anti-androgens is not clear, but one candidate is the Notch effector Hey1. This inhibits ligand-dependent activity of the AR but not other steroid receptors. Further, it is excluded from the nucleus in most human prostate cancers, suggesting that abnormal subcellular distribution of co-repressors may contribute to the aberrant hormonal responses observed in prostate cancer. A decrease in co-repressor function is one possible explanation for the development of anti-androgen-resistant prostate cancer, and this suggests that it may not occur at the gross level of protein expression.

Persistent expression of Notch2 delays gonadotrope differentiation

Normal pituitary gland development requires coordination between maintenance of progenitor cell pools and selection of progenitors for differentiation. The spatial and temporal expression of Notch2 during pituitary development suggested that it could control progenitor cell differentiation in the pituitary. Consistent with this idea, Notch2 is not expressed in Prop1 mutants, and anterior pituitary progenitors in Prop1 mutants appear to be unable to transition from proliferation to differentiation properly, resulting in anterior lobe failed cell specification and evolving hypoplasia. To test the function of Notch2 directly, we used the alphaGSU subunit promoter to express activated NOTCH2 persistently in pre-gonadotropes and pre-thyrotropes of transgenic mice. At birth, there is a small reduction in the population of fully differentiated thyrotropes and almost no fully differentiated gonadotropes. The temporal and spatial expression of Hey1 suggests that it could be a mediator of this effect. Gonadotropes complete their differentiation program eventually, although expression of LH and FSH is mutually exclusive with NOTCH2 transgene expression. This demonstrates that activated Notch2 is sufficient to delay gonadotrope differentiation, and it supports the hypothesis that Notch2 regulates progenitor cell differentiation in the pituitary gland.

Notch signalling and voltage-gated Na+ channel activity in human prostate cancer cells: independent modulation of in vitro motility

This study tested the possible functional relationship of two signalling mechanisms shown previously to be involved in human prostate cancer (PCa), Notch and voltage-gated sodium channel. Notch1 and Notch2 were differentially expressed in PCa cell lines of varying metastatic potential (LNCaP, PC-3, PC-3M) in comparison to a normal prostate cell line (PNT2), whereas Notch3 and Notch4 were not expressed. The Notch ligand Jagged1, but not Jagged2, was increased in all cell lines, whereas the Notch downstream target Deltex was not expressed. In comparison to the LNCaP cell line, Hes1, another downstream target, showed elevated expression in the metastatic PC-3 and PC-3M cells and promoted lateral motility. In contrast, the Notch ligand Delta-like1 (Dll1) levels were higher in LNCaP compared with PC-3 and PC-3M cells. Importantly, decreasing Dll1 expression increased the lateral motility of PC-3 cells, whereas blocking voltage-gated Na(+) channel activity with tetrodotoxin decreased motility. However, the effect of Dll1 was independent of Notch signalling through Hes1 and voltage-gated Na(+) channel expression/activity.