hes1-protein--human and Neuroblastoma

Neuroblastoma is a childhood tumor originating from cells of the developing sympathetic nervous system. The disease exhibits a remarkable phenotypic diversity reflected in the outcome, ranging from spontaneous regression to fatal disease. Mammalian achaete-scute homologue 1 (MASH-1 or HASH-1 in humans), a basic helix-loop-helix transcription (bHLH) factor, is transiently expressed in migrating sympatho-adrenal precursor cells. This gene, which is essential for proper development of the sympathetic nervous system, is expressed in a majority of primary neuroblastomas and neuroblastoma cell lines indicating an embryonal origin of the tumor. One important negative regulator of MASH-1 expression is the bHLH factor hairy and Enhancer of split homolog-1 (HES-1), which in turn is under positive control of the Notch signaling cascade. When neuroblastoma cells are induced to differentiate, as indicated by neuronal morphology and upregulation of neuronal marker genes, the HASH-1 expression is rapidly downregulated with a concomitant, transient upregulation of HES-1. Furthermore, a constitutively active form of Notch-1 inhibits induced differentiation of neuroblastoma cells. In this review, the role of the Notch-signaling cascade in neuroblastoma, with focus on the bHLH factors HASH-1 and HES-1, will be discussed.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; DNA-Binding Proteins; Helix-Loop-Helix Motifs; Homeodomain Proteins; Humans; Membrane Proteins; Neuroblastoma; Receptors, Notch; Signal Transduction; Transcription Factor HES-1; Transcription Factors

Notch signaling and its downstream gene target HES1 play a critical role in regulating and maintaining cancer stem cells (CSCs), similar to as they do during embryonic development. Here, we report a unique subclass of Notch-independent Hes-1 (NIHes-1)-expressing CSCs in neuroblastoma. These CSCs maintain sustained HES1 expression by activation of HES1 promoter region upstream of classical CBF-1 binding sites, thereby completely bypassing Notch receptor-mediated activation. These stem cells have self-renewal ability and potential to generate tumors. Interestingly, we observed that NIHes-1 CSCs could transition to Notch-dependent Hes-1-expressing (NDHes-1) CSCs where HES1 is expressed by Notch receptor-mediated promoter activation. We observed that NDHes-1-expressing CSCs also had the potential to transition to NIHes-1 CSCs and during this coordinated bidirectional transition, both CSCs gave rise to the majority of the bulk cancer cells, which had an inactive HES1 promoter (PIHes-1). A few of these PIHes-1 cells were capable of reverting into a CSC state. These findings explain the existence of a heterogenic mode of HES1 promoter activation within the IMR-32 neuroblastoma cell line and the potential to switch between them. This article has an associated First Person interview with the first authors of the paper.

Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Line; Homeodomain Proteins; Humans; Neoplastic Stem Cells; Neuroblastoma; Promoter Regions, Genetic; Receptors, Notch; Transcription Factor HES-1

Notch pathway signaling has critical roles in differentiation, proliferation, and survival, and has oncogenic or tumor suppressor effects in a variety of malignancies. The goal of this study was to evaluate the effects of Notch activation on human neuroblastoma cells.. Quantitative RT-PCR, immunoblots, and immunohistochemistry were used to determine the expression of Notch receptors (Notch1-4), cleaved Notch1 (ICN1), and downstream targets (HES1-5) in human neuroblastoma cell lines and patient tumor samples. Notch pathway signaling was induced using intracellular Notch (ICN1-3) and HES gene constructs or direct culture on Notch ligands. Quantitative methylation-specific PCR was used to quantify methylation of the HES gene promoters, and the effects of treatment with decitabine were measured.. Neuroblastoma cells express varying levels of Notch receptors and low levels of HES genes at baseline. However, no endogenous activation of the Notch pathway was detected in neuroblastoma cell lines or patient tumor samples. Expression of activated Notch intracellular domains and HES gene products led to growth arrest. The HES2 and HES5 gene promoters were found to be heavily methylated in most neuroblastoma lines, and HES gene expression could be induced through treatment with decitabine.. We report that neuroblastoma cell lines express multiple Notch receptors, which are inactive at baseline. Activation of the Notch pathway via ligand binding consistently resulted in growth arrest. HES gene expression appears to be regulated epigenetically and could be induced with decitabine. These findings support a tumor suppressor role for Notch signaling in neuroblastoma.

Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Line, Tumor; Cell Proliferation; DNA Methylation; Homeodomain Proteins; Humans; Neuroblastoma; Promoter Regions, Genetic; Receptors, Notch; Repressor Proteins; Signal Transduction; Transcription Factor HES-1

Neuroblastoma (NB), a sympathetically derived childhood tumour, shows characteristics of neuronal precursor cells, suggesting a halted differentiation process. We have previously shown that the Notch signalling cascade, a key player during normal neurogenesis, also might be involved in NB differentiation. Valproic acid (VPA), a well-tolerated antiepileptic drug, has been shown to induce differentiation and cell death of NB cells, possibly associated with its recently described HDAC inhibiting activity. Stimulation of NB cells with VPA led to increased cell death and phenotypic changes associated with differentiation, that is, neurite extension and upregulation of neuronal markers. VPA treatment also led to an activated Notch signalling cascade as shown by increased levels of intracellular Notch-1 and Hes-1, mimicking the initial phase of induced differentiation. These results reinforce that VPA potentially could be used in differentiation therapy of NB and that the effects in part could be a consequence of interference with the Notch signalling cascade.

Topics: Anticonvulsants; Antineoplastic Agents; Apoptosis; Basic Helix-Loop-Helix Transcription Factors; Blotting, Northern; Blotting, Western; Cell Line, Tumor; DNA-Binding Proteins; DNA, Complementary; Enzyme Inhibitors; Flow Cytometry; Histone Deacetylase Inhibitors; Homeodomain Proteins; Humans; Luciferases; Membrane Proteins; Neuroblastoma; Phenotype; Receptor, Notch1; Receptors, Cell Surface; Receptors, Notch; Reverse Transcriptase Polymerase Chain Reaction; RNA, Neoplasm; Signal Transduction; Transcription Factor HES-1; Transcription Factors; Valproic Acid

Ras and Notch signaling have recently been shown to cooperate in the maintenance of neoplastic transformation. Here, we show that TGFalpha, a known activator of Ras signaling, can drive cell proliferation and at the same time induce the expression of the Notch target Hes-1 in the neuroblastoma cell line SK-N-BE(2)c. The up-regulation of Hes-1 occurred both at the transcriptional and protein levels and by use of EGFR and MEK inhibitors we could show that the Hes-1 response was dependent on activation of the MAP kinase ERK. Blocking Notch activation by gamma-secretase inhibition did not profoundly affect the Hes-1 levels, neither in untreated nor in TGFalpha treated cells. The up-regulation of Hes-1 was associated with down-regulation of its pro-neuronal target gene Hash-1. Taken together, these results show that TGFalpha is a potent mitogen of neuroblastoma cells and suggest a connection between activation of ERK and Hes-1, thus providing a link between the Ras and Notch signaling pathways.

Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Line, Tumor; Cell Proliferation; Enzyme Inhibitors; ErbB Receptors; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Neoplastic; Homeodomain Proteins; Humans; Membrane Proteins; Mitogen-Activated Protein Kinases; Neuroblastoma; ras Proteins; Receptors, Notch; Signal Transduction; Transcription Factor HES-1; Transforming Growth Factor alpha; Up-Regulation

Neuroblastoma is a childhood tumor that originates from the sympathetic nervous system. The tumor cells have embryonic features, presumably as a consequence of an impaired capacity to respond to signals and transcriptional control mechanisms operating during normal differentiation. Two basic helix-loop-helix transcription factors, human achaete-scute homologue-1 (HASH-1) and hairy/enhancer of split homologue-1 (HES-1), are crucial for proper development of some neuronal cells. Here, their potential roles during sympathetic differentiation of human neuroblastoma cells have been investigated. In all tested protocols for induction of differentiation of SH-SY5Y and SK-N-BE(2) neuroblastoma cells, HASH-1 expression was rapidly decreased with a concomitant, often transient, increase in HES-1 expression. In gel mobility shift assays, using extracts from neuroblastoma cells, HES-1 bound to an oligonucleotide corresponding to a sequence in the HASH-1 promoter including the so-called N-box, suggesting that the transiently increased HES-1 activity in differentiating neuroblastoma cells is involved in down-regulation of HASH-1. Constitutive expression of the intracellular domain of Notch1, which activates the HES-1 promoter in SH-SY5Y cells, inhibited spontaneous and induced morphological differentiation of these neuroblastoma cells. Our data show that functional sympathetic neuronal differentiation of neuroblastoma cells is associated with transient activation of HES-1 and down-regulation of HASH-1 expression.

Topics: Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; DNA; DNA-Binding Proteins; Drosophila Proteins; Homeodomain Proteins; Humans; Membrane Proteins; Neurites; Neuroblastoma; Promoter Regions, Genetic; Receptor, Notch1; Receptors, Cell Surface; Transcription Factor HES-1; Transcription Factors; Tumor Cells, Cultured