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1.  Characterization of Notch1 Antibodies That Inhibit Signaling of Both Normal and Mutated Notch1 Receptors 
PLoS ONE  2010;5(2):e9094.
Notch receptors normally play a key role in guiding a variety of cell fate decisions during development and differentiation of metazoan organisms. On the other hand, dysregulation of Notch1 signaling is associated with many different types of cancer as well as tumor angiogenesis, making Notch1 a potential therapeutic target.
Principal Findings
Here we report the in vitro activities of inhibitory Notch1 monoclonal antibodies derived from cell-based and solid-phase screening of a phage display library. Two classes of antibodies were found, one directed against the EGF-repeat region that encompasses the ligand-binding domain (LBD), and the second directed against the activation switch of the receptor, the Notch negative regulatory region (NRR). The antibodies are selective for Notch1, inhibiting Jag2-dependent signaling by Notch1 but not by Notch 2 and 3 in reporter gene assays, with EC50 values as low as 5±3 nM and 0.13±0.09 nM for the LBD and NRR antibodies, respectively, and fail to recognize Notch4. While more potent, NRR antibodies are incomplete antagonists of Notch1 signaling. The antagonistic activity of LBD, but not NRR, antibodies is strongly dependent on the activating ligand. Both LBD and NRR antibodies bind to Notch1 on human tumor cell lines and inhibit the expression of sentinel Notch target genes, including HES1, HES5, and DTX1. NRR antibodies also strongly inhibit ligand-independent signaling in heterologous cells transiently expressing Notch1 receptors with diverse NRR “class I” point mutations, the most common type of mutation found in human T-cell acute lymphoblastic leukemia (T-ALL). In contrast, NRR antibodies failed to antagonize Notch1 receptors bearing rare “class II” or “class III” mutations, in which amino acid insertions generate a duplicated or constitutively sensitive metalloprotease cleavage site. Signaling in T-ALL cell lines bearing class I mutations is partially refractory to inhibitory antibodies as compared to cell-penetrating gamma-secretase inhibitors.
Antibodies that compete with Notch1 ligand binding or that bind to the negative regulatory region can act as potent inhibitors of Notch1 signaling. These antibodies may have clinical utility for conditions in which inhibition of signaling by wild-type Notch1 is desired, but are likely to be of limited value for treatment of T-ALLs associated with aberrant Notch1 activation.
PMCID: PMC2817004  PMID: 20161710
2.  Nicastrin and Notch4 drive endocrine therapy resistance and epithelial to mesenchymal transition in MCF7 breast cancer cells 
Resistance to anti-estrogen therapies is a major cause of disease relapse and mortality in estrogen receptor alpha (ERα)-positive breast cancers. Tamoxifen or estrogen withdrawal increases the dependence of breast cancer cells on Notch signalling. Here, we investigated the contribution of Nicastrin and Notch signalling in endocrine-resistant breast cancer cells.
We used two models of endocrine therapies resistant (ETR) breast cancer: tamoxifen-resistant (TamR) and long-term estrogen-deprived (LTED) MCF7 cells. We evaluated the migratory and invasive capacity of these cells by Transwell assays. Expression of epithelial to mesenchymal transition (EMT) regulators as well as Notch receptors and targets were evaluated by real-time PCR and western blot analysis. Moreover, we tested in vitro anti-Nicastrin monoclonal antibodies (mAbs) and gamma secretase inhibitors (GSIs) as potential EMT reversal therapeutic agents. Finally, we generated stable Nicastrin overexpessing MCF7 cells and evaluated their EMT features and response to tamoxifen.
We found that ETR cells acquired an epithelial to mesenchymal transition (EMT) phenotype and displayed increased levels of Nicastrin and Notch targets. Interestingly, we detected higher level of Notch4 but lower levels of Notch1 and Notch2 suggesting a switch to signalling through different Notch receptors after acquisition of resistance. Anti-Nicastrin monoclonal antibodies and the GSI PF03084014 were effective in blocking the Nicastrin/Notch4 axis and partially inhibiting the EMT process. As a result of this, cell migration and invasion were attenuated and the stem cell-like population was significantly reduced. Genetic silencing of Nicastrin and Notch4 led to equivalent effects. Finally, stable overexpression of Nicastrin was sufficient to make MCF7 unresponsive to tamoxifen by Notch4 activation.
ETR cells express high levels of Nicastrin and Notch4, whose activation ultimately drives invasive behaviour. Anti-Nicastrin mAbs and GSI PF03084014 attenuate expression of EMT molecules reducing cellular invasiveness. Nicastrin overexpression per se induces tamoxifen resistance linked to acquisition of EMT phenotype. Our finding suggest that targeting Nicastrin and/or Notch4 warrants further clinical evaluation as valid therapeutic strategies in endocrine-resistant breast cancer.
PMCID: PMC4095694  PMID: 24919951
3.  Negative Regulation of Notch Signaling by Xylose 
PLoS Genetics  2013;9(6):e1003547.
The Notch signaling pathway controls a large number of processes during animal development and adult homeostasis. One of the conserved post-translational modifications of the Notch receptors is the addition of an O-linked glucose to epidermal growth factor-like (EGF) repeats with a C-X-S-X-(P/A)-C motif by Protein O-glucosyltransferase 1 (POGLUT1; Rumi in Drosophila). Genetic experiments in flies and mice, and in vivo structure-function analysis in flies indicate that O-glucose residues promote Notch signaling. The O-glucose residues on mammalian Notch1 and Notch2 proteins are efficiently extended by the addition of one or two xylose residues through the function of specific mammalian xylosyltransferases. However, the contribution of xylosylation to Notch signaling is not known. Here, we identify the Drosophila enzyme Shams responsible for the addition of xylose to O-glucose on EGF repeats. Surprisingly, loss- and gain-of-function experiments strongly suggest that xylose negatively regulates Notch signaling, opposite to the role played by glucose residues. Mass spectrometric analysis of Drosophila Notch indicates that addition of xylose to O-glucosylated Notch EGF repeats is limited to EGF14–20. A Notch transgene with mutations in the O-glucosylation sites of Notch EGF16–20 recapitulates the shams loss-of-function phenotypes, and suppresses the phenotypes caused by the overexpression of human xylosyltransferases. Antibody staining in animals with decreased Notch xylosylation indicates that xylose residues on EGF16–20 negatively regulate the surface expression of the Notch receptor. Our studies uncover a specific role for xylose in the regulation of the Drosophila Notch signaling, and suggest a previously unrecognized regulatory role for EGF16–20 of Notch.
Author Summary
In multi-cellular organisms, neighboring cells need to communicate with each other to ensure proper cell fate decisions and differentiation. Signaling through the Notch receptors is the primary means by which local cell-cell communication is accomplished in animals. Given the broad usage of Notch signaling in animals and the host of human disease caused by Notch pathway misregulation, sophisticated mechanisms are required to adjust the strength of Notch signaling in each context. We have previously shown that addition of glucose residues to the Notch receptor promotes Notch signaling. Since these glucose residues on Notch can be extended by addition of xylose residues, we sought to determine whether xylose also plays a role in the regulation of Notch signaling. In contrast to glucose, we determine that xylose residues decrease Notch signaling in certain contexts by controlling Notch surface levels. Moreover, the xylose residues reside in a specific domain of Notch, unlike the glucose residues which are distributed throughout the Notch extracellular domain. Our data provide an example of signaling pathway regulation by altering the distribution of the short or elongated forms of a saccharide on a receptor protein, and offer a potential avenue for modulating Notch signaling as both a therapeutic modality and a tool in regenerative medicine.
PMCID: PMC3675014  PMID: 23754965
4.  Notch3 Interactome Analysis Identified WWP2 as a Negative Regulator of Notch3 Signaling in Ovarian Cancer 
PLoS Genetics  2014;10(10):e1004751.
The Notch3 signaling pathway is thought to play a critical role in cancer development, as evidenced by the Notch3 amplification and rearrangement observed in human cancers. However, the molecular mechanism by which Notch3 signaling contributes to tumorigenesis is largely unknown. In an effort to identify the molecular modulators of the Notch3 signaling pathway, we screened for Notch3-intracellular domain (N3-ICD) interacting proteins using a human proteome microarray. Pathway analysis of the Notch3 interactome demonstrated that ubiquitin C was the molecular hub of the top functional network, suggesting the involvement of ubiquitination in modulating Notch3 signaling. Thereby, we focused on functional characterization of an E3 ubiquitin-protein ligase, WWP2, a top candidate in the Notch3 interactome list. Co-immunoprecipitation experiments showed that WWP2 interacted with N3-ICD but not with intracellular domains from other Notch receptors. Wild-type WWP2 but not ligase-deficient mutant WWP2 increases mono-ubiquitination of the membrane-tethered Notch3 fragment, therefore attenuating Notch3 pathway activity in cancer cells and leading to cell cycle arrest. The mono-ubiquitination by WWP2 may target an endosomal/lysosomal degradation fate for Notch3 as suggested by the fact that the process could be suppressed by the endosomal/lysosomal inhibitor. Analysis of The Cancer Genome Atlas dataset showed that the majority of ovarian carcinomas harbored homozygous or heterozygous deletions in WWP2 locus, and there was an inverse correlation in the expression levels between WWP2 and Notch3 in ovarian carcinomas. Furthermore, ectopic expression of WWP2 decreased tumor development in a mouse xenograft model and suppressed the Notch3-induced phenotypes including increase in cancer stem cell-like cell population and platinum resistance. Taken together, our results provide evidence that WWP2 serves as a tumor suppressor by negatively regulating Notch3 signaling in ovarian cancer.
Author Summary
Notch pathway is important for many cellular activities, and its dysregulation leads to several diseases in humans, including cancer. Although Notch hyperactivity has been observed in many types of cancers, the interactome of Notch receptor remains largely unknown, especially for Notch3, which is involved in ovarian cancer pathogenesis. This article is the first study, to our knowledge, that delineates the Notch3 interacting network, and demonstrates that one of the Notch3 interacting proteins, WWP2, an E3 ubiquitin-protein ligase, plays a major role in negative regulation of Notch3 signaling in cancer cells. WWP2 locus was found to be deleted, and its mRNA down-regulated in a significant fraction of ovarian carcinomas. Ectopic expression of WWP2 reduced tumorigenicity of ovarian cancer cells, and counteracted Notch3-mediated phenotypes, including promotion of cancer stem-like cell phenotype and platinum resistance, further supporting its tumor suppressor role. The results from this study provide new insights into how Notch3 signaling contributes to cancer development, and should have implications for the design of Notch3-based cancer therapy.
PMCID: PMC4214668  PMID: 25356737
5.  NOTCH-1 and NOTCH-4 are novel gene targets of PEA3 in breast cancer: novel therapeutic implications 
Women with triple-negative breast cancer have the worst prognosis, frequently present with metastatic tumors and have few targeted therapy options. Notch-1 and Notch-4 are potent breast oncogenes that are overexpressed in triple-negative and other subtypes of breast cancer. PEA3, an ETS transcription factor, is also overexpressed in triple-negative and other breast cancer subtypes. We investigated whether PEA3 could be the critical transcriptional activator of Notch receptors in MDA-MB-231 and other breast cancer cells.
Real-time PCR and Western blot analysis were performed to detect Notch-1, Notch-2, Notch-3 and Notch-4 receptor expression in breast cancer cells when PEA3 was knocked down by siRNA. Chromatin immunoprecipitation was performed to identify promoter regions for Notch genes that recruited PEA3. TAM-67 and c-Jun siRNA were used to identify that c-Jun was necessary for PEA3 enrichment on the Notch-4 promoter. A Notch-4 luciferase reporter was used to confirm that endogenous PEA3 or AP-1 activated the Notch-4 promoter region. Cell cycle analysis, trypan blue exclusion, annexin V flow cytometry, colony formation assay and an in vivo xenograft study were performed to determine the biological significance of targeting PEA3 via siRNA, Notch signaling via a γ-secretase inhibitor, or both.
Herein we provide new evidence for transcriptional regulation of Notch by PEA3 in breast cancer. PEA3 activates Notch-1 transcription in MCF-7, MDA-MB-231 and SKBr3 breast cancer cells. PEA3 activates Notch-4 transcription in MDA-MB-231 cells where PEA3 levels are endogenously high. In SKBr3 and BT474 breast cancer cells where PEA3 levels are low, overexpression of PEA3 increases Notch-4 transcripts. Chromatin immunoprecipitation confirmed the enrichment of PEA3 on Notch-1 and Notch-4 promoters in MDA-MB-231 cells. PEA3 recruitment to Notch-1 was AP-1-independent, whereas PEA3 recruitment to Notch-4 was c-JUN-dependent. Importantly, the combined inhibition of Notch signaling via a γ-secretase inhibitor (MRK-003 GSI) and knockdown of PEA3 arrested growth in the G1 phase, decreased both anchorage-dependent and anchorage-independent growth and significantly increased apoptotic cells in vitro. Moreover, either PEA3 knockdown or MRK-003 GSI treatment significantly reduced tumor growth of MDA-MB-231 xenografts in vivo.
Taken together, the results from this study demonstrate for the first time that Notch-1 and Notch-4 are novel transcriptional targets of PEA3 in breast cancer cells. Targeting of PEA3 and/or Notch pathways might provide a new therapeutic strategy for triple-negative and possibly other breast cancer subtypes.
PMCID: PMC3218952  PMID: 21679465
6.  NOTCH1 inhibition in vivo results in mammary tumor regression and reduced mammary tumorsphere-forming activity in vitro 
Breast Cancer Research : BCR  2012;14(5):R126.
NOTCH activation has been recently implicated in human breast cancers, associated with a poor prognosis, and tumor-initiating cells are hypothesized to mediate resistance to treatment and disease relapse. To address the role of NOTCH1 in mammary gland development, transformation, and mammary tumor-initiating cell activity, we developed a doxycycline-regulated mouse model of NOTCH1-mediated mammary transformation.
Mammary gland development was analyzed by using whole-mount analysis and by flow cytometry in nulliparous transgenic mice maintained in the presence/absence of doxycycline (or intracellular NOTCH1). Mammary tumors were examined histologically and immunophenotyped by staining with antibodies followed by flow cytometry. Tumors were transplanted into mammary fat pads under limiting dilution conditions, and tumor-initiating cell frequency was calculated. Mammary tumor cells were also plated in vitro in a tumorsphere assay in the presence/absence of doxycycline. RNA was isolated from mammary tumor cell lines cultured in the presence/absence of doxycycline and used for gene-expression profiling with Affymetrix mouse arrays. NOTCH1-regulated genes were identified and validated by using quantitative real-time polymerase chain reaction (PCR). Mammary tumor-bearing mice were treated with doxycycline to suppress NOTCH1 expression, and disease recurrence was monitored.
Similar to published studies, we show that constitutive expression of human intracellular NOTCH1 in the developing mouse mammary gland inhibits side branching and promotes luminal cell fate. These mice develop mammary adenocarcinomas that express cytokeratin (CK) 8/18. In vivo limiting-dilution analyses revealed that these mammary tumors exhibit functional heterogeneity and harbor a rare (1/2,978) mammary tumor-initiating cell population. With this dox-regulated NOTCH1 mammary tumor model, we demonstrate that NOTCH1 inhibition results in mammary tumor regression in vivo and prevents disease recurrence in four of six tumors tested. Consistent with the in vivo data, NOTCH1 inhibition reduces mammary tumorsphere activity in vitro. We also identify the embryonic stem cell transcription factor Nanog as a novel NOTCH1-regulated gene in tumorspheres and in mouse and human breast cancer cell lines.
These data indicate that NOTCH1 inhibition results in mammary tumor regression in vivo and interferes with disease recurrence. We demonstrate that NOTCH1-transformed mouse mammary tumors harbor a rare mammary tumor-initiating population and that NOTCH1 contributes to mammary tumor-initiating activity. This work raises the possibility that NOTCH therapeutics may target mammary tumor-initiating cells in certain human breast cancer subtypes.
PMCID: PMC4053103  PMID: 22992387
7.  Targeted knockdown of Notch1 Inhibits Invasion of Human Prostate Cancer Cells Concomitant with Inhibition of MMP9 and uPA 
Notch, a type 1 transmembrane protein, plays a key role in the development of many tissues and organ types. Aberrant Notch signaling found in a wide variety of human cancers contributes to tumor development. Since Notch1 was found to be over-expressed in prostate cancer (PCa) cells, and human PCa tissue we, therefore tested our hypothesis that over-expression of Notch1 in PCa promotes tumor invasion.
Experimental design
Notch1 expression was evaluated in human PCa cells and in human PCa tissues. PCa cells were transiently transfected with Notch1 specific siRNAs in concentrations ranging from 30-120 nM and subsequently evaluated for effects on invasion and expression analysis for molecules involved in invasion.
Small interfering RNA mediated knockdown of Notch1 in PCa PC3 and 22Rν1 cells dramatically decreased their invasion. Focused cDNA array revealed that Notch1 knockdown resulted in significant reduction in the expression of urokinase plasminogen activator (uPA) and matrix metalloproteinase (MMP)-9 gene transcripts. These data were further verified by RT-PCR, real- time RT-PCR and immunoblot analysis. Knockdown of Notch1 was also observed to significantly reduce the mRNA expression and protein levels of uPA and its receptor uPAR. A significant reduction in MMP9 expression in Notch1 knockdown cells suggested a role for Notch1 in augmenting MMP9 transcription.
Our data demonstrate involvement of Notch1 in human PCa invasion and that silencing of Notch1 inhibits invasion of human PCa cells by inhibiting the expression of MMP9 and uPA. Thus, targeting of Notch1 could be an effective therapeutic approach against PCa.
PMCID: PMC2951134  PMID: 19147749
8.  Activated NOTCH1 induces lung adenomas in mice and cooperates with MYC in the generation of lung adenocarcinoma 
Cancer research  2011;71(18):6010-6018.
NOTCH1 encodes the canonical member of the mammalian Notch receptor family. Activating lesions frequently affect NOTCH1 in T-cell acute lymphoblastic leukemia (T-ALL) and recently have been found in non-small cell lung cancer (NSCLC) as well. We explored the oncogenic potential of activated NOTCH1 in the lung by developing a transgenic mouse model in which activated NOTCH1 was overexpressed in the alveolar epithelium. The initial response to activated NOTCH1 was proliferation and the accumulation of alveolar hyperplasia, which was then promptly cleared by apoptosis. After an extended latency period, however, pulmonary adenomas arose in the transgenic mice, but failed to progress to carcinoma. Interestingly, MYC and MYCL1 were expressed in the adenomas, suggesting that selection for enhanced MYC activity may facilitate tumorigenesis. Using mice engineered to co-express activated NOTCH1 and MYC, we found that supplementing MYC expression increased the frequency of N1ICD-induced adenomas and enabled progression to adenocarcinoma and metastases. Cooperation stemmed from synergistic activation of tumor cell cycling, a process that apparently countered any impedance to tumorigenesis posed by MYC and/or activated NOTCH1-induced apoptosis. Significantly, cooperation was independent of RAS activation. Taken together, the data suggest that activated NOTCH1 substitutes for RAS activation in cooperation with MYC in the development of NSCLC. These tumor models should be valuable for exploring the role of activated NOTCH1 in the genesis of NSCLC and for testing therapies targeting either activated NOTCH1 or its downstream effectors.
PMCID: PMC3174331  PMID: 21803744
Calcified Tissue International  2011;90(2):69-75.
Notch signaling mediates cell to cell interactions that are critical for embryonic development and tissue renewal. In the canonical signaling pathway, the Notch receptor is cleaved following ligand binding, resulting in the release and nuclear translocation of the Notch intracellular domain (NICD). NICD induces gene expression by forming a ternary complex with the DNA binding protein CBF1/Rbp-Jk, Suppressor of Hairless, Lag1 (CSL) and Mastermind-Like (Maml). Hairy Enhancer of Split (Hes) and Hes related with YRPW motif (Hey) are classic Notch target genes. Notch canonical signaling plays a central role in skeletal development and bone remodeling by suppressing the differentiation of skeletal cells. The skeletal phenotype of mice misexpressing Hes1 phenocopies partially the effects of Notch misexpression, suggesting that Hey proteins mediate most of the skeletal effects of Notch. Dysregulation of Notch signaling is associated with diseases affecting human skeletal development, such as Alagille Syndrome, Brachydactyly and Spondylocostal Dysostosis. Somatic mutations in Notch receptors and ligands are found in tumors of the skeletal system. Overexpression of NOTCH1 is associated with osteosarcoma, and overexpression of NOTCH3 or JAGGED1 in breast cancer cells favors the formation of osteolytic bone metastasis. Activating mutations in NOTCH2 cause Hajdu Cheney syndrome, which is characterized by skeletal defects and fractures, and JAG1 polymorphisms are associated with variations in bone mineral density. In conclusion, Notch is a regulator of skeletal development and bone remodeling and abnormal Notch signaling is associated with developmental and postnatal skeletal disorders.
PMCID: PMC3272107  PMID: 22002679
10.  Molecular Pathways: Context-dependent approaches to Notch targeting as cancer therapy 
Recent high throughput genomic sequencing studies of solid tumors, including head and neck squamous cell carcinoma (SCC), ovarian cancer, lung adenocarcinoma, glioblastoma, breast cancer and lung SCC, have highlighted DNA mutation as a mechanism for aberrant Notch signaling. A primary challenge of targeting Notch for treatment of solid malignancies is determining whether Notch signaling is cancer-promoting or tumor-suppressing for a specific cancer. We compiled reported Notch receptor and ligand missense and nonsense mutations in order glean insights into aberrant Notch signaling.
Frequencies of coding mutations differed for the four Notch genes. 4.7% of tumors harbored NOTCH1 missense or nonsense mutations. NOTCH2 and NOTCH3 had similar overall mutation rates of 1.5% and 1.3%, respectively, while NOTCH4 mutations were rarer. Notch ligand genes were rarely mutated.
The combined mutation frequency and position spectra of the four Notch paralogs across the different cancers provide an opportunity to begin to illuminate the different contributions of each Notch paralog to each tumor type and to identify opportunities for therapeutic targeting. Notch signaling pathway activators and inhibitors are currently in early clinical development for treatment of solid malignancies. Defining the status and consequences of altered Notch signaling will be important for selection of appropriate treatment.
PMCID: PMC3463728  PMID: 22773520
11.  Prostate tumor OVerexpressed-1 (PTOV1) down-regulates HES1 and HEY1 notch targets genes and promotes prostate cancer progression 
Molecular Cancer  2014;13:74.
PTOV1 is an adaptor protein with functions in diverse processes, including gene transcription and protein translation, whose overexpression is associated with a higher proliferation index and tumor grade in prostate cancer (PC) and other neoplasms. Here we report its interaction with the Notch pathway and its involvement in PC progression.
Stable PTOV1 knockdown or overexpression were performed by lentiviral transduction. Protein interactions were analyzed by co-immunoprecipitation, pull-down and/or immunofluorescence. Endogenous gene expression was analyzed by real time RT-PCR and/or Western blotting. Exogenous promoter activities were studied by luciferase assays. Gene promoter interactions were analyzed by chromatin immunoprecipitation assays (ChIP). In vivo studies were performed in the Drosophila melanogaster wing, the SCID-Beige mouse model, and human prostate cancer tissues and metastasis. The Excel package was used for statistical analysis.
Knockdown of PTOV1 in prostate epithelial cells and HaCaT skin keratinocytes caused the upregulation, and overexpression of PTOV1 the downregulation, of the Notch target genes HEY1 and HES1, suggesting that PTOV1 counteracts Notch signaling. Under conditions of inactive Notch signaling, endogenous PTOV1 associated with the HEY1 and HES1 promoters, together with components of the Notch repressor complex. Conversely, expression of active Notch1 provoked the dismissal of PTOV1 from these promoters. The antagonist role of PTOV1 on Notch activity was corroborated in the Drosophila melanogaster wing, where human PTOV1 exacerbated Notch deletion mutant phenotypes and suppressed the effects of constitutively active Notch. PTOV1 was required for optimal in vitro invasiveness and anchorage-independent growth of PC-3 cells, activities counteracted by Notch, and for their efficient growth and metastatic spread in vivo. In prostate tumors, the overexpression of PTOV1 was associated with decreased expression of HEY1 and HES1, and this correlation was significant in metastatic lesions.
High levels of the adaptor protein PTOV1 counteract the transcriptional activity of Notch. Our evidences link the pro-oncogenic and pro-metastatic effects of PTOV1 in prostate cancer to its inhibitory activity on Notch signaling and are supportive of a tumor suppressor role of Notch in prostate cancer progression.
PMCID: PMC4021398  PMID: 24684754
PTOV1/HES1/HEY1/Notch signaling/prostate cancer progression
12.  Role of Notch and its oncogenic signaling crosstalk in breast cancer 
Biochimica et biophysica acta  2010;1815(2):197-213.
The Notch signaling plays a key role in cell differentiation, survival, and proliferation through diverse mechanisms. Notch signaling is also involved in vasculogenesis and angiogenesis. Moreover, Notch expression is regulated by hypoxia and inflammatory cytokines (IL-1, IL-6 and leptin). Entangled crosstalk between Notch and other developmental signaling (Hedgehog and Wnt), and signaling triggered by growth factors, estrogens and oncogenic kinases, could impact on Notch targeted genes. Thus, alterations of the Notch signaling can lead to a variety of disorders, including human malignancies. Notch signaling is activated by ligand binding, followed by ADAM/Tumor necrosis factor-α-converting enzyme (TACE) metalloprotease and γ-secretase cleavages that produce the Notch intracellular domain (NICD). Translocation of NICD into the nucleus induces the transcriptional activation of Notch target genes. The relationships between Notch deregulated signaling, cancer stem cells and the carcinogenesis process reinforced by Notch crosstalk with many oncogenic signaling pathways suggest that Notch signaling may be a critical drug target for breast and other cancers. Since current status of knowledge in this field changes quickly, our insight should be continuously revised. In this review, we will focus on recent advancements in identification of aberrant Notch signaling in breast cancer and the possible underlying mechanisms, including potential role of Notch in breast cancer stem cells, tumor angiogenesis, as well as its crosstalk with other oncogenic signaling pathways in breast cancer. We will also discuss the prognostic value of Notch proteins and therapeutic potential of targeting Notch signaling for cancer treatment.
PMCID: PMC3060666  PMID: 21193018
Notch; Breast cancer; Leptin; Tumor angiogenesis; Carcinogenesis; Cancer stem cell; NILCO; IL-1
13.  Notch Activation Is Dispensable for D, L-Sulforaphane-Mediated Inhibition of Human Prostate Cancer Cell Migration 
PLoS ONE  2012;7(9):e44957.
D, L-Sulforaphane (SFN), a synthetic racemic analog of broccoli constituent L-sulforaphane, is a highly promising cancer chemopreventive agent with in vivo efficacy against chemically-induced as well as oncogene-driven cancer in preclinical rodent models. Cancer chemopreventive effect of SFN is characterized by G2/M phase cell cycle arrest, apoptosis induction, and inhibition of cell migration and invasion. Moreover, SFN inhibits multiple oncogenic signaling pathways often hyperactive in human cancers, including nuclear factor-κB, Akt, signal transducer and activator of transcription 3, and androgen receptor. The present study was designed to determine the role of Notch signaling, which is constitutively active in many human cancers, in anticancer effects of SFN using prostate cancer cells as a model. Exposure of human prostate cancer cells (PC-3, LNCaP, and/or LNCaP-C4-2B) to SFN as well as its naturally-occurring thio-, sulfinyl-, and sulfonyl-analogs resulted in cleavage (activation) of Notch1, Notch2, and Notch4, which was accompanied by a decrease in levels of full-length Notch forms especially at the 16- and 24-hour time points. The SFN-mediated cleavage of Notch isoforms was associated with its transcriptional activation as evidenced by RBP-Jk-, HES-1A/B- and HEY-1 luciferase reporter assays. Migration of PC-3 and LNCaP cells was decreased significantly by RNA interference of Notch1 and Notch2, but not Notch4. Furthermore, SFN-mediated inhibition of PC-3 and LNCaP cell migration was only marginally affected by knockdown of Notch1 and Notch2. Strikingly, SFN administration to Transgenic Adenocarcinoma of Mouse Prostate transgenic mice failed to increase levels of cleaved Notch1, cleaved Notch2, and HES-1 proteins in vivo in prostatic intraepithelial neoplasia, well-differentiated carcinoma or poorly-differentiated prostate cancer lesions. These results indicate that Notch activation is largely dispensable for SFN-mediated inhibition of cell migration, which should be viewed as a therapeutic advantage as Notch activation is frequent in human prostate cancers.
PMCID: PMC3436754  PMID: 22970326
14.  Yes-Associated Protein Upregulates Jagged-1 and Activates the NOTCH Pathway in Human Hepatocellular Carcinoma 
Gastroenterology  2013;144(7):1530-1542.e12.
Background & Aims
Cancer cells often lose contact inhibition to undergo anchorage-independent proliferation and become resistant to apoptosis by inactivating the Hippo signaling pathway, resulting in activation of the transcriptional co-activator yes-associated protein (YAP). However, the oncogenic mechanisms of YAP are unclear.
Using cross-species analysis of expression data, the Notch ligand Jagged-1 (Jag-1) was identified as downstream target of YAP in hepatocytes and hepatocellular carcinoma (HCC) cells. We analyzed the functions of YAP in HCC cells via overexpression and RNA silencing experiments. We used transgenic mice that overexpressed a constitutively activated form of YAP (YAPS127A), and measured protein levels in HCC and colorectal and pancreatic tumor samples from patients.
Human HCC cell lines and mouse hepatocytes that overexpress YAPS127A upregulated Jag-1, leading to activation of the Notch pathway and increased proliferation. Induction of Jag-1, activation of Notch, and cell proliferation required binding of YAP to its transcriptional partner TEAD4; TEAD4 binding required Mst1/2, but not WNT-β-catenin signaling. Levels of YAP correlated with Jag-1 expression and Notch signaling in human tumor samples and shorter survival times of patients with HCC or colorectal cancer.
The transcriptional regulator YAP upregulates Jag-1 to activate Notch signaling in HCC cells and mouse hepatocytes. YAP-dependent activity of Jag-1 and Notch correlate in human HCC and colorectal tumor samples with patient survival times, suggesting the use of YAP and Notch inhibitors as therapeutics for gastrointestinal cancer.
PMCID: PMC3665638  PMID: 23419361
transcriptional regulators; liver cancer; colorectal cancer; pancreatic cancer
15.  Cooperation of Notch and Ras/MAPK signaling pathways in human breast carcinogenesis 
Molecular Cancer  2009;8:128.
Recent studies have implicated aberrant Notch signaling in breast cancers. Yet, relatively little is known about the pattern of expression of various components of the Notch pathway, or its mechanism of action. To better understand the role of the Notch pathway in breast cancer, we have undertaken a detailed expression analysis of various Notch receptors, their ligands, and downstream targets at different stages of breast cancer progression.
We report here that there is a general increase in the expression levels of Notch 1, 2, 4, Jagged1, Jagged2, and Delta-like 4 proteins in breast cancers, with simultaneous upregulation of multiple Notch receptors and ligands in a given cancer tissue. While Notch3 and Delta-like1 were undetectable in normal tissues, moderate to high expression was detected in several cancers. We detected the presence of active, cleaved Notch1, along with downstream targets of the Notch pathway, Hes1/Hes5, in ~75% of breast cancers, clearly indicating that in a large proportion of breast cancers Notch signaling is aberrantly activated. Furthermore, we detected cleaved Notch1 and Hes1/5 in early precursors of breast cancers - hyperplasia and ductal carcinoma in situ - suggesting that aberrant Notch activation may be an early event in breast cancer progression. Mechanistically, while constitutively active Notch1 alone failed to transform immortalized breast cells, it synergized with the Ras/MAPK pathway to mediate transformation. This cooperation is reflected in vivo, as a subset of cleaved Notch positive tumors additionally expressed phopsho-Erk1/2 in the nuclei. Such cases exhibited high node positivity, suggesting that Notch-Ras cooperation may lead to poor prognosis.
High level expression of Notch receptors and ligands, and its increased activation in several breast cancers and early precursors, places Notch signaling as a key player in breast cancer pathogenesis. Its cooperation with the Ras/MAPK pathway in transformation offers combined inhibition of the two pathways as a new modality for breast cancer treatment.
PMCID: PMC2809056  PMID: 20030805
16.  The Significance of Notch1 Compared with Notch3 in High Metastasis and Poor Overall Survival in Hepatocellular Carcinoma 
PLoS ONE  2013;8(2):e57382.
The prognosis for patients with hepatocellular carcinoma (HCC) is poor, and the mechanisms underlying the development of HCC remain unclear. Notch1 and Notch3 may be involved in malignant transformation, although their roles remain unknown.
Materials and Methods
HCC tissues were stained with anti-Notch1 or -Notch3 antibody. The migration and invasion capacities of the cells were measured with transwell cell culture chambers. RT-PCR was used to measure the expression of Notch1 and Notch3 mRNA. Additionally, western blot analysis was used to assess the protein expression of Notch1, Notch3, CD44v6, E-cadherin, matrix metalloproteinase-2 (MMP-2), MMP-9, and urokinase-type plasminogen activator (uPA). RNA interference was used to down-regulate the expression of Notch1 and Notch3. Cell viability was assessed using MTT.
Based on immunohistochemistry, high Notch1 expression was correlated with tumor size, tumor grade, metastasis, venous invasion and AJCC TNM stage. High Notch3 expression was only strongly correlated with metastasis, venous invasion and satellite lesions. Kaplan-Meier curves demonstrated that patients with high Notch1 or Notch3 expression were at a significantly increased risk for shortened survival time. In vitro, the down-regulation of Notch1 decreased the migration and invasion capacities of HCC cells by regulating CD44v6, E-cadherin, MMP-2, MMP-9, and uPA via the COX-2 and ERK1/2 pathways. Down-regulation of Notch3 only decreased the invasion capacity of HCC cells by regulating MMP-2 and MMP-9 via the ERK1/2 pathway.
Based on the migration and invasion of HCC, we hypothesize that targeting Notch1 may be more useful than Notch3 for designing novel preventive and therapeutic strategies for HCC in the near future.
PMCID: PMC3585338  PMID: 23468978
17.  Crosstalk between PKCα and Notch-4 in endocrine-resistant breast cancer cells 
Oncogenesis  2013;2(8):e60-.
The Notch pathway is functionally important in breast cancer. Notch-1 has been reported to maintain an estrogen-independent phenotype in estrogen receptor α (ERα)+ breast cancer cells. Notch-4 expression correlates with Ki67. Notch-4 also plays a key role in breast cancer stem-like cells. Estrogen-independent breast cancer cell lines have higher Notch activity than estrogen-dependent lines. Protein kinase Cα (PKCα) overexpression is common in endocrine-resistant breast cancers and promotes tamoxifen (TAM)-resistant growth in breast cancer cell lines. We tested whether PKCα overexpression affects Notch activity and whether Notch signaling contributes to endocrine resistance in PKCα-overexpressing breast cancer cells.Analysis of published microarray data from ERα+ breast carcinomas shows that PKCα expression correlates strongly with Notch-4. Real-time reverse transcription PCR and immunohistochemistry on archival specimens confirmed this finding. In a PKCα-overexpressing, TAM-resistant T47D model, PKCα selectively increases Notch-4, but not Notch-1, expression in vitro and in vivo. This effect is mediated by activator protein-1 (AP-1) occupancy of the Notch-4 promoter. Notch-4 knockdown inhibits estrogen-independent growth of PKCα-overexpressing T47D cells, whereas Notch-4IC expression stimulates it. Gene expression profiling shows that multiple genes and pathways associated with endocrine resistance are induced in Notch-4IC- and PKCα-expressing T47D cells. In PKCα-overexpressing T47D xenografts, an orally active γ-secretase inhibitor at clinically relevant doses significantly decreased estrogen-independent tumor growth, alone and in combination with TAM. In conclusion, PKCα overexpression induces Notch-4 through AP-1. Notch-4 promotes estrogen-independent, TAM-resistant growth and activates multiple pathways connected with endocrine resistance and chemoresistance. Notch inhibitors should be clinically evaluated in PKCα- and Notch-4-overexpressing, endocrine-resistant breast cancers.
PMCID: PMC3759125  PMID: 23917222
Notch; breast cancer; endocrine therapy; PKCα
18.  Analysis of the expression of the Notch3 receptor protein in adult lung cancer 
Oncology Letters  2012;5(2):499-504.
Abnormalities in the Notch signaling system are considered to play a role in the tumorigenesis of bronchiogenic carcinoma. The present study aimed to investigate the expression of Notch3 in adult lung cancer patients and its role in the pathogenesis of primary bronchiogenic carcinoma. The expression of the Notch3 protein in lung squamous cell carcinoma, adenocarcinoma, small cell carcinoma and corresponding non-tumor tissues was detected by immunohistochemistry. To investigate the expression of Notch3 in adenocarcinoma tissues, Notch3 mRNA and protein expression were measured with reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, respectively. It was demonstrated that Notch3 had a stronger positive degree of expression in lung squamous cell carcinoma and adenocarcinoma compared with the corresponding non-tumor tissue (P<0.01). The expression of Notch3 in small cell carcinoma tissue was lower compared with that of the corresponding non-tumor tissue (P<0.01). The expression of Notch3 in the lung adenocarcinoma group was the highest of the three lung carcinoma groups (P<0.01). RT-PCR revealed that the expression of Notch3 mRNA in the lung adenocarcinoma group was higher than that of the normal lung group, but there was no statistically significant difference (P=0.05). The expression of Notch1 protein in the lung adenocarcinoma group was significantly higher compared with the normal lung group (P<0.01), as shown by western blot analysis. Notch3 may be involved in the pathogenesis of bronchogenic carcinoma, in particular in the promotion of the lung cancer oncogene, and a difference in its expression may exist in the various pathological types.
PMCID: PMC3573152  PMID: 23420695
bronchiogenic carcinoma; Notch3; lung cancer
19.  Visfatin promotes cell and tumor growth by upregulating Notch1 in breast cancer 
Oncotarget  2014;5(13):5087-5099.
Overexpression of Notch1 has been associated with breast cancer. We recently showed that visfatin stimulates breast cancer cell proliferation and invasion. The present study was undertaken to determine whether Notch1 signaling is affected by visfatin and to characterize the functional role of the visfatin-Notch1 axis in breast cancer. Visfatin and Notch1 were expressed at higher levels in breast tumors than in matched control tissues. Visfatin induced Notch1 expression in MDA-MB-231 breast cancer cell line and in nontransformed MCF10A mammary epithelial cells, whereas visfatin depletion reduced Notch1 mRNA and protein levels. Depletion of Notch1 in MDA-MB-231 cells attenuated cell growth in vitro and in vivo; visfatin depletion produced similar effects, but was less potent. Additionally, Notch1 depletion inhibited cell proliferation induced by visfatin. Analysis of the signaling pathways underlying visfatin-mediated Notch1 upregulation revealed that visfatin activated NF-κB p65. Blockade of NF-κB signaling suppressed the effects of visfatin on Notch1 upregulation and breast cancer cell proliferation. Breast tumors expressing high levels of NF-κB p65 exhibited increased expression of Notch1. Our results demonstrate that the visfatin-Notch1 axis contributes to breast tumor growth through the activation of the NF-κB pathway. Study of the visfatin-Notch1 axis may offer new therapeutic directions for breast cancer.
PMCID: PMC4148124  PMID: 24970818
Visfain; Notch1; NF- κB; breast cancer cells
20.  A switch in Notch Gene Expression Parallels Stem Cell to Endothelial Transition in Infantile Hemangioma 
Angiogenesis  2010;13(1):15-23.
Infantile hemangioma (IH) is the most common benign tumor of infancy, yet its pathogenesis is poorly understood. Notch family members are known to play a role in vascular development during embryogenesis and postnatal tumor angiogenesis, yet the role of Notch signaling in the pathogenesis of IH has not been investigated. This study aims to survey Notch expression in IH.
Materials & Methods
RNA from resected hemangioma tissue and hemangioma-derived stem cells (HemSCs) and endothelial cells (HemECs) were used for gene expression analyses by real-time PCR. Results were confirmed with immunofluorescence (IF) for protein expression in tissue.
Real-time PCR showed that Notch family gene expression in IH is distinct from placenta and skin. Notch3 is expressed in HemSCs, but not in HemECs, indicating Notch3 is downregulated as HemSCs differentiate into HemECs. Moreover, expression of endothelial-associated Notch proteins, Notch1, -4, and Jagged-1 are increased in involuting hemangiomas and HemECs, suggesting that as hemangioma progresses towards involution, it acquires more differentiated endothelium. A subset of cells stained double positive for Notch3 and CD31, pointing to a potential intermediate between the HemSC cellular differentiation into HemEC.
HemSCs have distinct Notch expression patterns from differentiated HemECs and from normal human endothelial cells. Notch3 is expressed in HemSCs while Notch1, Notch4, and Jagged-1 have higher expression levels in HemECs. Notch3 was localized to the interstitial cells outside of the nascent vascular channels in proliferating IH tissue sections, but became more apparent in the perivascular cells in involuting IH. In summary, the pattern of Notch gene expression mirrors the progression from immature cells to endothelial-lined vascular channels (i.e., endothelial differentiation) that characterizes the growth and involution of IH.
PMCID: PMC2846229  PMID: 20069356
endothelial cell; infantile hemangioma; Notch gene expression; stem cell
21.  Complex interplay between β-catenin signalling and Notch effectors in intestinal tumorigenesis 
Gut  2011;60(2):166-176.
The activation of β-catenin signalling is a key step in intestinal tumorigenesis. Interplay between the β-catenin and Notch pathways during tumorigenesis has been reported, but the mechanisms involved and the role of Notch remain unclear.
Notch status was analysed by studying expression of the Notch effector Hes1 and Notch ligands/receptors in human colorectal cancer (CRC) and mouse models of Apc mutation. A genetic approach was used, deleting the Apc and RBP-J or Atoh1 genes in murine intestine. CRC cell lines were used to analyse the control of Hes1 and Atoh1 by β-catenin signalling.
Notch signalling was found to be activated downstream from β-catenin. It was rapidly induced and maintained throughout tumorigenesis. Hes1 induction was mediated by β-catenin and resulted from both the induction of the Notch ligand/receptor and Notch-independent control of the Hes1 promoter by β-catenin. Surprisingly, the strong phenotype of unrestricted proliferation and impaired differentiation induced by acute Apc deletion in the intestine was not rescued by conditional Notch inactivation. Hyperactivation of β-catenin signalling overrode the forced differention induced by Notch inhibition, through the downregulation of Atoh1, a key secretory determinant factor downstream of Notch. This process involves glycogen synthase kinase 3 β (GSK3β) and proteasome-mediated degradation. The restoration of Atoh1 expression in CRC cell lines displaying β-catenin activation was sufficient to increase goblet cell differentiation, whereas genetic ablation of Atoh1 greatly increased tumour formation in Apc mutant mice.
Notch signalling is a downstream target of β-catenin hyperactivation in intestinal tumorigenesis. However, its inhibition had no tumour suppressor effect in the context of acute β-catenin activation probably due to the downregulation of Atoh1. This finding calls into question the use of γ-secretase inhibitors for the treatment of CRC and suggests that the restoration of Atoh1 expression in CRC should be considered as a therapeutic approach.
PMCID: PMC3022366  PMID: 21205878
Intestine; β-catenin; RBP-J; Hes1; Atoh1; proliferation; differentiation; cell proliferation; cell signalling; colorectal cancer genes; differentiation; molecular carcinogenesis
22.  Notch-1 stimulates survival of lung adenocarcinoma cells during hypoxia by activating the IGF-1R pathway 
Oncogene  2010;29(17):2488-2498.
Hypoxic microenvironment supports cancer stem cell survival, causes poor response to anticancer therapy and tumor recurrence. Inhibition of Notch-1 signaling in adenocarcinoma of the lung (ACL) cells causes apoptosis specifically under hypoxia. Here we found that Akt-1 activation is a key mediator of Notch-1 pro-survival effects under hypoxia. Notch-1 activates Akt-1 through repression of phosphatase and tensin homolog (PTEN) expression and induction of the Insulin-like Growth Factor 1 Receptor (IGF-1R). The latter seems to be the major determinant of Akt-1 stimulation, since Notch-1 signaling affects Akt-1 activation in PTEN−/− ACL cells. Both downregulation of Insulin Receptor Substrate 1 (IRS-1) and dominant-negative IGF-1R sensitized ACL cells to γ-secretase inhibitor (GSI)-induced apoptosis. Conversely, overexpression of IGF-1R protected ACL cells from GSI toxicity. Inhibition of Notch-1 caused reduced IGF-1R expression, while forced Notch-1 expression yielded opposite effects. ChIP experiments suggested Notch-1 direct regulation of the IGF-1R promoter. Experiments in which human ACL cells were injected in mice confirmed elevated and specific co-expression of Notch-1IC, IGF-1R and pAkt-1 in hypoxic tumor areas.
Our data provide a mechanistic explanation for Notch-1 mediated pro-survival function in hypoxic ACL tumor microenvironment. The results identify additional targets that may synergize with Notch-1 inhibition for ACL treatment.
PMCID: PMC2861728  PMID: 20154720
Notch signaling; lung cancer; hypoxia; IGF-1R; cancer cell survival
23.  A Notch1 Ectodomain Construct Inhibits Endothelial Notch Signaling, Tumor Growth, and Angiogenesis 
Cancer research  2008;68(12):4727-4735.
Notch signaling is required for vascular development and tumor angiogenesis. Although inhibition of the Notch ligand Delta-like 4 can restrict tumor growth and disrupt neo-vasculature, the effect of inhibiting Notch receptor function on angiogenesis has yet to be defined. In this study, we generated a soluble form of the Notch1 receptor (Notch1 decoy) and assessed its effect on angiogenesis in vitro and in vivo. Notch1 decoy expression reduced signaling stimulated by the binding of three distinct Notch ligands to Notch1 and inhibited morphogenesis of endothelial cells overexpressing Notch4. Thus, Notch1 decoy functioned as an antagonist of ligand-dependent Notch signaling. In mice, Notch1 decoy also inhibited vascular endothelial growth factor–induced angiogenesis in skin, establishing a role for Notch receptor function in this process. We tested the effects of Notch1 decoy on tumor angiogenesis using two models: mouse mammary Mm5MT cells overexpressing fibroblast growth factor 4 (Mm5MT-FGF4) and NGP human neuroblastoma cells. Exogenously expressed FGF4 induced Notch ligand expression in Mm5MT cells and xenografts. Notch1 decoy expression did not affect tumorigenicity of Mm5MT-FGF4 cells in vitro but restricted Mm5MT-FGF4 xenograft growth in mice while markedly impairing neoangiogenesis. Similarly, Notch1 decoy expression did not affect NGP cells in vitro but disrupted vessels and decreased tumor viability in vivo. These results strongly suggest that Notch receptor signaling is required for tumor neoangiogenesis and provides a new target for tumor therapy.
PMCID: PMC3690602  PMID: 18559519
24.  Expression of Notch-1 and its clinical significance in different histological subtypes of human lung adenocarcinoma 
According to the International Multidisciplinary Classification of Lung Adenocarcinoma (LAD) by International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) in 2011, the diagnosis of LAD is changing from simple morphology into a comprehensive multidisciplinary classification. The aim of this study is to detect the expression of Notch-1 and analyze its clinicopathological or prognostic significance in different histological subtypes of Lung Adenocarcinomas (LADs).
Western blot and Semi-quantitative Reverse transcription-polymerase chain reaction (RT-PCR) assays, as well as immunohisitochemistry, were performed to detect the expression of Notch-1 in LAD cells and tissue samples. Kaplan-Meier and multivariate Cox regression analyses were performed to evaluate the correlation of Notch-1 expression with clinicopathological factors and prognosis of LAD patients.
The expression level of Notch-1 protein in LAD cell lines or tissues was significantly lower than that in normal human bronchial epithelial cell line (16HBE) or nontumor tissues (P < 0.05). By statistical analyses, it was observed that negative Notch-1 expression was significantly associated with advanced clinical stage (P = 0.001) and lymph node metastasis (P = 0.026) in LAD patients. Also, the recurrence rate of Notch-1-positive group was higher than the Notch-1-negative group (P = 0.001), and patients with positive Notch-1 expression have a prolonged progression of overall survival (P = 0.033). More interestingly, the expression of Notch-1 protein was often observed to be negative in solid predominant adenocarcinoma (SPA) tissues, but highly expressed in papillary predominant adenocarcinoma (PPA) and micropapillary predominant adenocarcinoma (MPA) tissues. Kaplan-Meier survival analysis showed that patients with positive Notch-1 expression had a prolonged progression of overall survival compared with those with negative Notch-1 expression (P = 0.033). The median survival time of Notch-1-positive or negative patients was 64.6 months (95% CI: 31.497-97.703 months) or 36.0 months (95% CI: 12.132-59.868 months).
Notch-1 could be used as a predictable biomarker to be detected in different pathological and histological subtypes in LAD for diagnosis or prognosis.
PMCID: PMC3818984  PMID: 24423157
Lung adenocarcinoma; Notch-1; Immunohistochemistry; Histological subtypes; Prognosis
25.  Notch Pathway Activation Induces Neuroblastoma Tumor Cell Growth Arrest 
Pediatric blood & cancer  2011;58(5):682-689.
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 or downstream HES gene expression 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.
PMCID: PMC3264695  PMID: 21744479
neuroblastoma; Notch; ICN; HES

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