Notch pathway activation induces neuroblastoma tumor cell growth arrest

Notch signaling pathway in cancer: from mechanistic insights to targeted therapies

Notch signaling, renowned for its role in regulating cell fate, organ development, and tissue homeostasis across metazoans, is highly conserved throughout evolution. The Notch receptor and its ligands are transmembrane proteins containing epidermal growth factor-like repeat sequences, typically necessitating receptor-ligand interaction to initiate classical Notch signaling transduction. Accumulating evidence indicates that the Notch signaling pathway serves as both an oncogenic factor and a tumor suppressor in various cancer types. Dysregulation of this pathway promotes epithelial-mesenchymal transition and angiogenesis in malignancies, closely linked to cancer proliferation, invasion, and metastasis. Furthermore, the Notch signaling pathway contributes to maintaining stem-like properties in cancer cells, thereby enhancing cancer invasiveness. The regulatory role of the Notch signaling pathway in cancer metabolic reprogramming and the tumor microenvironment suggests its pivotal involvement in balancing oncogenic and tumor suppressive effects. Moreover, the Notch signaling pathway is implicated in conferring chemoresistance to tumor cells. Therefore, a comprehensive understanding of these biological processes is crucial for developing innovative therapeutic strategies targeting Notch signaling. This review focuses on the research progress of the Notch signaling pathway in cancers, providing in-depth insights into the potential mechanisms of Notch signaling regulation in the occurrence and progression of cancer. Additionally, the review summarizes pharmaceutical clinical trials targeting Notch signaling for cancer therapy, aiming to offer new insights into therapeutic strategies for human malignancies.

MYCN Amplification Is Associated with Reduced Expression of Genes Encoding γ-Secretase Complex and NOTCH Signaling Components in Neuroblastoma

Amplification of the MYCN oncogene is found in ~20% of neuroblastoma (NB) cases and correlates with high-risk disease and poor prognosis. Despite the plethora of studies describing the role of MYCN in NB, the exact molecular mechanisms underlying MYCN's contribution to high-risk disease are not completely understood. Herein, we implemented an integrative approach combining publicly available RNA-Seq and MYCN ChIP-Seq datasets derived from human NB cell lines to define biological processes directly regulated by MYCN in NB. Our approach revealed that MYCN-amplified NB cell lines, when compared to non-MYCN-amplified cell lines, are characterized by reduced expression of genes involved in NOTCH receptor processing, axoneme assembly, and membrane protein proteolysis. More specifically, we found genes encoding members of the γ-secretase complex, which is known for its ability to liberate several intracellular signaling molecules from membrane-bound proteins such as NOTCH receptors, to be down-regulated in MYCN-amplified NB cell lines. Analysis of MYCN ChIP-Seq data revealed an enrichment of MYCN binding at the transcription start sites of genes encoding γ-secretase complex subunits. Notably, using publicly available gene expression data from NB primary tumors, we revealed that the expression of γ-secretase subunits encoding genes and other components of the NOTCH signaling pathway was also reduced in MYCN-amplified tumors and correlated with worse overall survival in NB patients. Genetic or pharmacological depletion of MYCN in NB cell lines induced the expression of γ-secretase genes and NOTCH-target genes. Chemical inhibition of γ-secretase activity dampened the expression of NOTCH-target genes upon MYCN depletion in NB cells. In conclusion, this study defines a set of MYCN-regulated pathways that are specific to MYCN-amplified NB tumors, and it suggests a novel role for MYCN in the suppression of genes of the γ-secretase complex, with an impact on the NOTCH-target gene expression in MYCN-amplified NB.

NOTCH Signaling in Osteosarcoma

The combination of neoadjuvant chemotherapy and surgery has been promoted for the treatment of osteosarcoma; however, the local recurrence and lung metastasis rates remain high. Therefore, it is crucial to explore new therapeutic targets and strategies that are more effective. The NOTCH pathway is not only involved in normal embryonic development but also plays an important role in the development of cancers. The expression level and signaling functional status of the NOTCH pathway vary in different histological types of cancer as well as in the same type of cancer from different patients, reflecting the distinct roles of the Notch pathway in tumorigenesis. Studies have reported abnormal activation of the NOTCH signaling pathway in most clinical specimens of osteosarcoma, which is closely related to a poor prognosis. Similarly, studies have reported that NOTCH signaling affected the biological behavior of osteosarcoma through various molecular mechanisms. NOTCH-targeted therapy has shown potential for the treatment of osteosarcoma in clinical research. After the introduction of the composition and biological functions of the NOTCH signaling pathway, the review paper discussed the clinical significance of dysfunction in osteosarcoma. Then the paper reviewed the recent relevant research progress made both in the cell lines and in the animal models of osteosarcoma. Finally, the paper explored the potential of the clinical application of NOTCH-targeted therapy for the treatment of osteosarcoma.

Genomic Analysis Made It Possible to Identify Gene-Driver Alterations Covering the Time Window between Diagnosis of Neuroblastoma 4S and the Progression to Stage 4

Neuroblastoma (NB) is a tumor of the developing sympathetic nervous system. Despite recent advances in understanding the complexity of NB, the mechanisms that determine its regression or progression are still largely unknown. Stage 4S NB is characterized by a favorable course of disease and often by spontaneous regression, while progression to true stage 4 is a very rare event. Here, we focused on genomic analysis of an NB case that progressed from stage 4S to stage 4 with a very poor outcome. Array-comparative genomic hybridization (a-CGH) on tumor-tissue DNA, and whole-exome sequencing (WES) on exosomes DNA derived from plasma collected at the onset and at the tumor progression, pointed out relevant genetic changes that can explain this clinical worsening. The combination of a-CGH and WES data allowed for the identification iof somatic copy number aberrations and single-nucleotide variants in genes known to be responsible for aggressive NB. KLRB1, MAPK3 and FANCA genes, which were lost at the time of progression, were studied for their possible role in this event by analyzing in silico the impact of their expression on the outcome of 786 NB patients.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

Targeting Notch in oncology: the path forward

Notch signalling is involved in many aspects of cancer biology, including angiogenesis, tumour immunity and the maintenance of cancer stem-like cells. In addition, Notch can function as an oncogene and a tumour suppressor in different cancers and in different cell populations within the same tumour. Despite promising preclinical results and early-phase clinical trials, the goal of developing safe, effective, tumour-selective Notch-targeting agents for clinical use remains elusive. However, our continually improving understanding of Notch signalling in specific cancers, individual cancer cases and different cell populations, as well as crosstalk between pathways, is aiding the discovery and development of novel investigational Notch-targeted therapeutics.

The Relevance of Notch Signaling in Cancer Progression

The Notch signaling pathway controls normal embryonic development and tissue homeostasis of many cell types. It regulates cell proliferation, fate, differentiation, and cell death by short-range signaling between nearby cells that come in contact. The Notch pathway has also been critically involved in the pathobiology of a variety of malignancies, regulating cancer initiation and development, as well as early stages of cancer progression, by adjusting conserved cellular programs. Fibroblasts, an essential for tumor growth component of stroma, have also been affected by Notch regulation. Sequencing Notch gene mutations have been identified in a number of human tumors, revealing information on the progression of specific cancer types, such as ovarian cancer and melanoma, immune-associated tumors such as myeloid neoplasms, but especially in lymphocytic leukemia. Activation of the Notch can be either oncogenic or it may contain growth-suppressive functions, acting as a tumor suppressor in other hematopoietic cells, hepatocytes, skin, and pancreatic epithelium.

Notch Signaling in Thyroid Cancer

Thyroid cancer is the most common malignancy of the endocrine system with a steadily rising incidence. The term "thyroid cancer" encompasses a spectrum of subtypes, namely papillary thyroid cancer, follicular thyroid cancer, anaplastic thyroid cancer, and medullary thyroid cancer. Each subtype differs histopathologically and in degrees of cellular differentiation, which may be in part due to signaling of the Notch pathway. The Notch pathway is an evolutionarily conserved signal transduction mechanism that regulates cell proliferation, differentiation, survival, stem cell maintenance, embryonic and adult development, epithelial-mesenchymal transition, and angiogenesis. Its role in cancer biology is controversial, as it has been shown to play both an oncogenic and tumor-suppressive role in many different types of cancers. This discordance holds true for each subtype of thyroid cancer, indicating that Notch signaling is likely cell type and context dependent. Whether oncogenic or not, Notch signaling has proven to be significantly involved in the tumorigenesis of thyroid cancer and has thus earned interest as a therapeutic target. Advancement in the understanding of Notch signaling in thyroid cancer holds great promise for the development of novel treatment strategies to benefit patients.

A Wnt-BMP4 Signaling Axis Induces MSX and NOTCH Proteins and Promotes Growth Suppression and Differentiation in Neuroblastoma

The Wnt and bone morphogenetic protein (BMP) signaling pathways are known to be crucial in the development of neural crest lineages, including the sympathetic nervous system. Surprisingly, their role in paediatric neuroblastoma, the prototypic tumor arising from this lineage, remains relatively uncharacterised. We previously demonstrated that Wnt/b-catenin signaling can have cell-type-specific effects on neuroblastoma phenotypes, including growth inhibition and differentiation, and that BMP4 mRNA and protein were induced by Wnt3a/Rspo2. In this study, we characterised the phenotypic effects of BMP4 on neuroblastoma cells, demonstrating convergent induction of MSX homeobox transcription factors by Wnt and BMP4 signaling and BMP4-induced growth suppression and differentiation. An immunohistochemical analysis of BMP4 expression in primary neuroblastomas confirms a striking absence of BMP4 in poorly differentiated tumors, in contrast to a high expression in ganglion cells. These results are consistent with a tumor suppressive role for BMP4 in neuroblastoma. RNA sequencing following BMP4 treatment revealed induction of Notch signaling, verified by increases of Notch3 and Hes1 proteins. Together, our data demonstrate, for the first time, Wnt-BMP-Notch signaling crosstalk associated with growth suppression of neuroblastoma.

Novel Notch signaling inhibitor NSI‑1 suppresses nuclear translocation of the Notch intracellular domain

The Notch receptor serves a fundamental role in the regulation of cell fate determination through intracellular signal transmission. Mutation of the Notch receptor results in abnormal active signaling, leading to the development of diseases involving abnormal cell growth, including malignant tumors. Therefore, the Notch signaling pathway is a useful pharmacological target for the treatment of cancer. In the present study, a compound screening system was designed to identify inhibitors of the Notch signaling targeting Notch intracellular domain (NICD). A total of 9,600 compounds were analyzed using the Michigan Cancer Foundation‑7 (MCF7) human breast adenocarcinoma cell line and the SH‑SY5Y human neuroblastoma cell line with the reporter assay system using an artificial protein encoding a partial Notch carboxyl‑terminal fragment fused to the Gal4 DNA‑binding domain. The molecular mechanism underlying the inhibition of Notch signaling by a hit compound was further validated using biochemical and cell biological approaches. Using the screening system, a potential candidate, Notch signaling inhibitor‑1 (NSI‑1), was isolated which showed 50% inhibition at 6.1 µM in an exogenous Notch signaling system. In addition, NSI‑1 suppressed the nuclear translocation of NICD and endogenous gene expression of hairy and enhancer of split‑1, indicating that NSI‑1 specifically targets Notch. Notably, NSI‑1 suppressed the cell viability of MCF7 cells and another human breast adenocarcinoma cell line, MDA‑MB‑231 exhibiting constitutive and high Notch signaling activity, whereas no significant effect was observed in the SH‑SY5Y cells bearing a lower Notch signaling activity. NSI‑1 significantly suppressed the viability of SH‑SY5Y cells expressing exogenous human Notch1. These results indicate that NSI‑1 is a novel Notch signaling inhibitor and suggest its potential as a useful drug for the treatment of diseases induced by constitutively active Notch signaling.

Expression of NOTCH1 in thyroid cancer is mostly restricted to papillary carcinoma

The NOTCH signaling is an evolutionarily conserved signaling pathway that regulates cell-cell interactions. NOTCH family members play a fundamental role in a variety of processes during development in particular in cell fate decisions. As other crucial factors during embryogenesis, NOTCH signaling is aberrantly reactivated in cancer where it has been linked to context-dependent effects. In thyroid cancer, NOTCH1 expression has been associated to aggressive features even if its in vivo expression within the entire spectrum of thyroid tumors has not definitively established. A series of 106 thyroid specimens including non-neoplastic lesions, benign and malignant tumors of common and rare histotypes, were investigated by immunohistochemistry to assess NOTCH1 expression. Extent of positivity and protein localization were investigated and correlated with clinical and morphological parameters. NOTCH1 positivity was predominantly associated with papillary carcinomas and only occasionally found in follicular carcinomas. Poorly differentiated and undifferentiated thyroid carcinomas showed only a partial positivity. NOTCH1 expression pattern also seemed differently distributed according to histotype. Our data confirm a role of NOTCH1 in thyroid cancer and highlight for the first time the specific involvement of this pathway in papillary carcinomas. Our data also indicate that other thyroid malignancies do not rely on NOTCH1 signaling for development and progression.

Defining the "Metastasome": Perspectives from the genome and molecular landscape in colorectal cancer for metastasis evolution and clinical consequences

Metastasis still poses the highest challenge for personalized therapy in cancer, partly due to a still incomplete understanding of its molecular evolution. We recently presented the most comprehensive whole-genome study of colorectal metastasis vs. matched primary tumors and suggested novel components of disease progression and metastasis evolution, some of them potentially relevant for targeted therapy. In this review, we try to put these findings into perspective with latest discoveries of colleagues and recent literature, and propose a systematic international team effort to collectively define the "metastasome", a term we introduce to summarize all genomic, epigenomic, transcriptomic, further -omic, molecular and functional characteristics rendering metastases different from primary tumors. Based on recent discoveries, we propose a revised metastasis model for colorectal cancer which is based on a common ancestor clone, early dissemination but flexible early or late stage clonal separation paralleling stromal interactions. Furthermore, we discuss hypotheses on site-specific metastasis, colorectal cancer progression, metastasis-targeted diagnosis and therapy, and metastasis prevention based on latest metastasome data.

Dual functionality of the antimicrobial agent taurolidine which demonstrates effective anti-tumor properties in pediatric neuroblastoma

High-risk, relapsed and refractory neuroblastoma are associated with poor 5-years survival rates, demonstrating the need for investigational therapeutic agents to treat this disease. Taurolidine is derived from the aminosulfoacid taurine and has known anti-microbial and anti-inflammatory properties. Taurolidine has also demonstrated anti-neoplastic effects in a range of cancers, providing the rationale to investigate the activity of taurolidine against neuroblastoma in preclinical studies. We investigated the in vitro activity of taurolidine against neuroblastoma using the alamar blue cytotoxicity assay, phase-contrast light microscopy, western blotting and analysis of global gene expression by RNA-Seq. In vivo activity of taurolidine was evaluated using mouse xenograft models. In vitro pre-clinical data show that taurolidine is cytotoxic to neuroblastoma cell lines, inducing cell death by apoptosis. Analysis of global gene expression and determination of signaling pathway activation scores using the in silico Pathway Activation Network Decomposition Analysis (iPANDA) platform indicates that taurolidine has an effect on the Notch, mitogen-activated protein kinase (MAPK) and interleukin-10 (IL-10) signaling pathways. In vivo experiments in xenograft mouse models show that taurolidine decreases tumor growth and improves survival. These results provide supportive pre-clinical data on the activity of taurolidine against neuroblastoma. The findings support the rationale for further evaluation of taurolidine for the treatment of relapsed/refractory neuroblastoma patients in an early phase clinical trial.

γ-Secretase inhibitor I inhibits neuroblastoma cells, with NOTCH and the proteasome among its targets

As high-risk neuroblastoma (NB) has a poor prognosis, new therapeutic modalities are needed. We therefore investigated the susceptibility of NB cells to γ-secretase inhibitor I (GSI-I). NOTCH signaling activity, the cellular effects of GSI-I and its mechanisms of cytotoxicity were evaluated in NB cells in vitro and in vivo. The results show that NOTCH signaling is relevant for human NB cells. Of the GSIs screened in vitro GSI-I was the most effective inhibitor of NB cells. Both MYCN-amplified and non-amplified NB cells were susceptible to GSI-I. Among the targets of GSI-I in NB cells were NOTCH and the proteasome. GSI-I caused G2/M arrest that was enhanced by acute activation of MYCN and led to mitotic dysfunction. GSI-I also induced proapoptotic NOXA. Survival of mice bearing an MYCN non-amplified orthotopic patient-derived NB xenograft was significantly prolonged by systemic GSI-I, associated with mitotic catastrophe and reduced angiogenesis, and without evidence of intestinal toxicity. In conclusion, the activity of GSI-I on multiple targets in NB cells and the lack of gastrointestinal toxicity in mice are advantageous and merit further investigations of GSI-I in NB.

Antiproliferative and apoptotic effect of LY2090314, a GSK-3 inhibitor, in neuroblastoma in vitro

Background

Neuroblastoma (NB) is a devastating disease. Despite recent advances in the treatment of NB, about 60% of high-risk NB will have relapse and therefore long-term event free survival is very minimal. We have reported that targeting glycogen synthase kinase-3 (GSK-3) may be a potential strategy to treat NB. Consequently, investigating LY2090314, a clinically relevant GSK-3 inhibitor, on NB cellular proliferation and may be beneficial for NB treatment.

Methods

The effect of LY2090314 was compared with a previously studied GSK-3 inhibitor, Tideglusib. Colorimetric, clonogenic, and live-cell image confluency assays were used to study the proliferative effect of LY2090314 on NB cell lines (NGP, SK-N-AS, and SH-SY-5Y). Western blotting and caspase glo assay were performed to determine the mechanistic function of LY2090314 in NB cell lines.

Results

LY2090314 treatment exhibited significant growth reduction starting at a 20 nM concentration in NGP, SK-N-AS, and SH-SY-5Y cells. Western blot analysis indicated that growth suppression was due to apoptosis as evidenced by an increase in pro-apoptotic markers cleaved PARP and cleaved caspase-3 and a reduction in the anti-apoptotic protein, survivin. Further, treatment significantly reduced the level of cyclin D1, a key regulatory protein of the cell cycle and apoptosis. Functionally, this was confirmed by an increase in caspase activity. LY2090314 treatment reduced the expression levels of phosphorylated GSK-3 proteins and increased the stability of β-catenin in these cells.

Conclusions

LY2090314 effectively reduces growth of both human MYCN amplified and non-amplified NB cell lines in vitro. To our knowledge, this is the first study to look at the effect of LY2090314 in NB cell lines. These results indicate that GSK-3 may be a therapeutic target for NB and provide rationale for further preclinical analysis using LY2090314.

TP-0903 inhibits neuroblastoma cell growth and enhances the sensitivity to conventional chemotherapy

Neuroblastoma (NB) is an embryonal tumor with low cure rate for patients classified as high-risk. This class of NB tumors shows a very complex genomic background and requires aggressive treatment strategies. In this work we evaluated the efficacy of the novel multi-kinase inhibitor TP-0903 in impairing NB cells' growth, proliferation and motility. In vitro studies were performed using cell lines with different molecular background, and in vivo studies were done using the zebrafish experimental model. Our results confirmed a strong cytotoxicity of TP-0903 already at the sub-micro molar concentrations. The observed cytotoxicity of TP-0903 was irreversible and the resulting apoptosis was caspase dependent. In addition, TP-0903 impaired colony formation and neurosphere creation. Depending on the molecular background of the selected NB cell lines, TP-0903 influenced either their capacity to migrate, to complete their cell cycle or both. Likewise, TP-0903 reduced NB cells intravasation in vitro and in vivo. Importantly, TP-0903 showed remarkable pharmacological efficacy not only as a mono-treatment, but also in combination with conventional chemotherapy drugs (ATRA, cisplatin, and VP16) in different types of NB cells. In conclusion, the multi-kinase activity of TP-0903 allowed the impairment of several biological processes required for expansion of NB cells, making them more vulnerable to the conventional chemotherapeutics. Altogether, our results support the eligibility of TP-0903 for further (pre)clinical assessments in NB.

Research progress of neuroblastoma related gene variations

Neuroblastoma, the most common extracranial solid tumor among children, is an embryonal tumor originating from undifferentiated neural crest cell. Neuroblastomas are highly heterogeneous, represented by the wide range of clinical presentations and likelihood of cure, ranging from spontaneous regression to relentless progression despite rigorous multimodal treatments. Approximately, 50% of cases are high-risk with overall survival rates less than 40%. With the efforts to collect large numbers of clinically annotated specimens and the advancements in technologies, researchers have revealed numerous genetic alterations that may drive tumor growth. However, the most lack mutations in genes that are recurrently mutated, which inspires researchers to identify disrupted pathways instead of single mutated genes to unearth biological systems perturbed in neuroblastoma. Stratification of patients and target therapy based on their molecular signatures have been the center of focus. This review provides a comprehensive summary of the recent advances in identification of candidate genes variations, targeted approaches to high-risk neuroblastoma and evaluates the methods utilized for detection, which will provide new avenues to develop therapies and further genetic researches.

Loss of Polycomb Group Protein Pcgf1 Severely Compromises Proper Differentiation of Embryonic Stem Cells

The Polycomb repressive complex 1 (PRC1) is essential for fate decisions of embryonic stem (ES) cells. Emerging evidence suggests that six major variants of PRC1 complex, defined by the mutually exclusive presence of Pcgf subunit, regulate distinct biological processes, yet very little is known about the mechanism by which each version of PRC1 instructs and maintains cell fate. Here, we disrupted the Pcgf1, also known as Nspc1 and one of six Pcgf paralogs, in mouse ES cells by the CRISPR/Cas9 technology. We showed that although these mutant cells were viable and retained normal self-renewal, they displayed severe defects in differentiation in vitro. To gain a better understanding of the role of Pcgf1 in transcriptional control of differentiation, we analysed mRNA profiles from Pcgf1 deficient cells using RNA-seq. Interestingly, we found that Pcgf1 positively regulated expression of essential transcription factors involved in ectoderm and mesoderm differentiation, revealing an unexpected function of Pcgf1 in gene activation during ES cell lineage specification. Chromatin immunoprecipitation experiments demonstrated that Pcgf1 deletion caused a decrease in Ring1B and its associated H2AK119ub1 mark binding to target genes. Altogether, our results suggested an unexpected function of Pcgf1 in gene activation during ES cell maintenance.

Neuroblastoma patient outcomes, tumor differentiation, and ERK activation are correlated with expression levels of the ubiquitin ligase UBE4B

BACKGROUND

UBE4B is an E3/E4 ubiquitin ligase whose gene is located in chromosome 1p36.22. We analyzed the associations of UBE4B gene and protein expression with neuroblastoma patient outcomes and with tumor prognostic features and histology.

METHODS

We evaluated the association of UBE4B gene expression with neuroblastoma patient outcomes using the R2 Platform. We screened neuroblastoma tumor samples for UBE4B protein expression using immunohistochemistry. FISH for UBE4B and 1p36 deletion was performed on tumor samples. We then evaluated UBE4B expression for associations with prognostic factors and with levels of phosphorylated ERK in neuroblastoma tumors and cell lines.

RESULTS

Low UBE4B gene expression is associated with poor outcomes in patients with neuroblastoma and with worse outcomes in all patient subgroups. UBE4B protein expression was associated with neuroblastoma tumor differentiation, and decreased UBE4B protein levels were associated with high-risk features. UBE4B protein levels were also associated with levels of phosphorylated ERK.

CONCLUSIONS

We have demonstrated associations between UBE4B gene expression and neuroblastoma patient outcomes and prognostic features. Reduced UBE4B protein expression in neuroblastoma tumors was associated with high-risk features, a lack of differentiation, and with ERK activation. These results suggest UBE4B may contribute to the poor prognosis of neuroblastoma tumors with 1p36 deletions and that UBE4B expression may mediate neuroblastoma differentiation.

Involvement of Notch-1 in Resistance to Regorafenib in Colon Cancer Cells

Regorafenib, an oral small-molecule multi kinase inhibitor, is able to block Vascular Endothelial Growth Factor Receptors (VEGFR-1, 2, and 3), Platelet-Derived Growth Factor Receptors (PDGF), Fibroblast Growth Factor (FGF) receptor 1, Raf, TIE-2, and the kinases KIT, RET, and BRAF. Different studies have displayed its antitumor activity in several cancer models (both in vitro and in vivo), particularly in colorectal and gastrointestinal stromal cancers. The mechanism of resistance to regorafenib is largely unknown. In our investigation, we have generated regorafenib-resistant SW480 cells (Reg-R-SW480 cells) by culturing such cells with increasing concentration of regorafenib. Examination of intracellular signaling found that Akt signaling was activated in Reg-R-SW480 cells but not in wild-type SW480 cells, after regorafenib treatment as measured by Western Blot. The Notch pathway is a fundamental signaling system in the development and homeostasis of tissues since it regulates different cellular process such as proliferation, differentiation, and apoptosis and it can be a potential driver of resistance to a wide array of targeted therapies. In this study, we found that Notch-1 was significantly up-regulated in resistant tumor cells as well as HES1 and HEY. Additionally, inhibition of Notch-1 in resistant cells partially restored sensitivity to regorafenib treatment in vitro. Collectively, these data suggest a key role of Notch-1 in mediating the resistant effects of regorafenib in colorectal cancer cells, and also provide a rationale to improve the therapeutic efficacy of regorafenib.

Peptides of presenilin-1 bind the amyloid precursor protein ectodomain and offer a novel and specific therapeutic approach to reduce ß-amyloid in Alzheimer's disease

β-Amyloid (Aβ) accumulation in the brain is widely accepted to be critical to the development of Alzheimer's disease (AD). Current efforts at reducing toxic Aβ40 or 42 have largely focused on modulating γ-secretase activity to produce shorter, less toxic Aβ, while attempting to spare other secretase functions. In this paper we provide data that offer the potential for a new approach for the treatment of AD. The method is based on our previous findings that the production of Aβ from the interaction between the β-amyloid precursor protein (APP) and Presenilin (PS), as part of the γ-secretase complex, in cell culture is largely inhibited if the entire water-soluble NH2-terminal domain of PS is first added to the culture. Here we demonstrate that two small, non-overlapping water-soluble peptides from the PS-1 NH2-terminal domain can substantially and specifically inhibit the production of total Aβ as well as Aβ40 and 42 in vitro and in vivo in the brains of APP transgenic mice. These results suggest that the inhibitory activity of the entire amino terminal domain of PS-1 on Aβ production is largely focused in a few smaller sequences within that domain. Using biolayer interferometry and confocal microscopy we provide evidence that peptides effective in reducing Aβ give a strong, specific and biologically relevant binding with the purified ectodomain of APP 695. Finally, we demonstrate that the reduction of Aβ by the peptides does not affect the catalytic activities of β- or γ-secretase, or the level of APP. P4 and P8 are the first reported protein site-specific small peptides to reduce Aβ production in model systems of AD. These peptides and their derivatives offer new potential drug candidates for the treatment of AD.

NOTCH mutations: multiple faces in human malignancies

NOTCH proteins have been implicated in multiple cellular functions, such as stem cell maintenance and cell fate determination. Initially identified as proto-oncogenes because they promote the development of certain types of leukemia, inactivating mutations of NOTCH were later reported. Together with the potential distinct functions of NOTCH family members, their ligands and associated niches, the precise roles of NOTCH in human cancers, particularly solid tumors, remain unsettled. In oral squamous cell carcinoma (OSCC), mutations of NOTCH1 are found in 10% to 15% tumors from Caucasian patients, mostly inactivating mutations. Recent studies of OSCC from Chinese patients, however, showed mutation rates of NOTCH1 about 50% with a considerable portion of potential activating mutations. These findings add another twist into the already complex picture of NOTCH alterations in human cancers, calling for further investigation to uncover what role exactly these molecules play in cancer initiation and progression to develop strategies targeting NOTCH signaling for cancer prevention and treatment.

Involvement of midkine in neuroblastoma tumourigenesis

Midkine is highly expressed in various cancers, including neuroblastoma, one of the most malignant paediatric solid tumours known. Also, it has been shown to be useful as a tumour marker, a prognosis factor and a target of molecular therapy. Several molecular tools (e.g. siRNA, antibodies and RNA aptamer) have been used to establish a midkine-targeted therapy. The involvement of midkine in tumourigenesis has been demonstrated in vivo in a mouse neuroblastoma model, where targeting it with an RNA aptamer was shown to be an effective treatment for xenografted tumours. Chemoresistance is one of the notable phenotypes regulated by midkine in various cancer cell types. In pancreatic tumours and glioma cells, midkine is expressed in chemoresistant cells and is involved in the survival of these cells in the presence of anticancer drugs. In contrast to these tumours, midkine was found to be expressed in every neuroblastoma cell line tested and the knockdown of midkine alone was sufficient to suppress their growth. These results indicate that neuroblastoma cells are highly dependent on midkine and that a midkine-targeted therapy could exert a significant effect in these cells. However, to achieve a midkine-targeted therapy for high-risk neuroblastoma patients, the further refinement of the RNA aptamer or antibody as tools and the elucidation of midkine signalling are immediate issues that need to be resolved. Regarding the latter, although it has been shown that Notch2 functions as a receptor in neuroblastoma cells, it is likely that other receptors (e.g. anaplastic lymphoma kinase) are also involved in midkine signalling.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Notch ligand Delta-like 1 promotes the metastasis of melanoma by enhancing tumor adhesion

Notch signaling plays a vital role in tumorigenicity and tumor progression by regulating proliferation, invasion, and the tumor microenvironment. Previous research by our group indicated that Notch ligand Delta-like 1 (Dll1) is involved in angiogenesis in melanoma, and we noticed that it took a longer time to trypsinize Dll1-expressing B16 melanoma cells than the control cells. In this article, we extended our study to investigate the effects of Dll1 on tumor cell adhesion and metastasis. Dll1 overexpression activated Notch signaling in B16 tumor cells and significantly enhanced the adhering capacity of B16 tumor cells both in vitro and in vivo. B16-Dll1 cells also had a higher metastatic potential than their counterpart in the mouse model of lung metastasis. Along with increased Dll1 expression, N-cadherin, but not E-cadherin, was upregulated in B16-Dll1 cells. These data suggested that Notch ligand Dll1 may enhance the adhesion and metastasis of melanoma cells by upregulation of N-cadherin.

Specific glycogen synthase kinase-3 inhibition reduces neuroendocrine markers and suppresses neuroblastoma cell growth

OBJECTIVE

Neuroblastoma is a common neuroendocrine (NE) tumor that presents in early childhood, with a high incidence of malignancy and recurrence. The glycogen synthase kinase-3 (GSK-3) pathway is a potential therapeutic target, as this pathway has been shown to be crucial in the management of other NE tumors. However, it is not known which isoform is necessary for growth inhibition. In this study, we investigated the effect of the GSK-3 inhibitor AR-A014418 on the different GSK-3 isoforms in neuroblastoma.

METHODS

NGP and SH-5Y-SY cells were treated with 0-20 μM of AR-A014418 and cell viability was measured by MTT assay. Expression levels of NE markers CgA and ASCL1, GSK-3 isoforms, and apoptotic markers were analyzed by western blot.

RESULTS

Neuroblastoma cells treated with AR-A014418 had a significant reduction in growth at all doses and time points (P<0.001). A reduction in growth was noted in cell lines on day 6, with 10 μM (NGP-53% vs. 0% and SH-5Y-SY-38% vs. 0%, P<0.001) treatment compared to control, corresponding with a noticeable reduction in tumor marker ASCL1 and CgA expression.

CONCLUSION

Treatment of neuroblastoma cell lines with AR-A014418 reduced the level of GSK-3α phosphorylation at Tyr279 compared to GSK-3β phosphorylation at Tyr216, and attenuated growth via the maintenance of apoptosis. This study supports further investigation to elucidate the mechanism(s) by which GSK-3α inhibition downregulates the expression of NE tumor markers and growth of neuroblastoma.

Hesperetin activates the Notch1 signaling cascade, causes apoptosis, and induces cellular differentiation in anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is characterized by very aggressive growth with undifferentiated features. Recently, it has been reported that the Notch1 signaling pathway, which affects thyrocyte proliferation and differentiation, is inactivated in ATC. However, it remains largely unknown whether using Notch1 activating compounds can be an effective therapeutic strategy in ATC. Therefore, in this study, we aimed to evaluate the drug effects of a potential Notch activator hesperetin on ATC cell.

METHODS

A unique ATC cell line HTh7 was used to evaluate the drug effects of hesperetin. The Notch1 activating function and cell proliferation were evaluated. The mechanism of growth regulation was investigated by the detection of apoptotic markers. The expression levels of thyrocyte-specific genes were quantified for ATC redifferentiation.

RESULTS

Upregulated expression of Notch1 and its downstream effectors hairy and enhancer of split 1 (Hes1) and Hes1 related with YRPW motif was observed in hesperetin-treated ATC cells. The enhanced luciferase signal also confirmed the functional activity of hesperetin-induced Notch1 signaling. Hesperetin led to a time- and dose-dependent decrease in ATC cell proliferation. The cell-growth inhibition was mainly caused by apoptosis as evidenced by increased levels of cleaved poly ADP ribose polymerase and cleaved caspase-3 as well as decreased survivin. Additionally, hesperetin induced the expression levels of thyrocyte-specific genes including thyroid transcription factor 1 (TTF1), TTF2, paired box gene 8, thyroid stimulating hormone receptor, and sodium/iodide symporter.

CONCLUSIONS

Hesperetin activates the Notch1 signaling cascade and suppresses ATC cell proliferation mainly via apoptosis. Hesperetin also induces cell redifferentiation of ATC, which could be useful clinically.

Understanding the role of Notch in osteosarcoma

The Notch pathway has been described as an oncogene in osteosarcoma, but the myriad functions of all the members of this complex signaling pathway, both in malignant cells and nonmalignant components of tumors, make it more difficult to define Notch as simply an oncogene or a tumor suppressor. The cell-autonomous behaviors caused by Notch pathway manipulation may vary between cell lines but can include changes in proliferation, migration, invasiveness, oxidative stress resistance, and expression of markers associated with stemness or tumor-initiating cells. Beyond these roles, Notch signaling also plays a vital role in regulating tumor angiogenesis and vasculogenesis, which are vital aspects of osteosarcoma growth and behavior in vivo. Further, osteosarcoma cells themselves express relatively low levels of Notch ligand, making it likely that nonmalignant cells, especially endothelial cells and pericytes, are the major source of Notch activation in osteosarcoma tumors in vivo and in patients. As a result, Notch pathway expression is not expected to be uniform across a tumor but likely to be highest in those areas immediately adjacent to blood vessels. Therapeutic targeting of the Notch pathway is likewise expected to be complicated. Most pharmacologic approaches thus far have focused on inhibition of gamma secretase, a protease of the presenilin complex. This enzyme, however, has numerous other target proteins that would be expected to affect osteosarcoma behavior, including CD44, the WNT/β-catenin pathway, and Her-4. In addition, Notch plays a vital role in tissue and organ homeostasis in numerous systems, and toxicities, especially GI intolerance, have limited the effectiveness of gamma secretase inhibitors. New approaches are in development, and the downstream targets of Notch pathway signaling also may turn out to be good targets for therapy. In summary, a full understanding of the complex functions of Notch in osteosarcoma is only now unfolding, and this deeper knowledge will help position the field to better utilize novel therapies as they are developed.

The challenge of targeting notch in hematologic malignancies

Notch signaling can play oncogenic and tumor suppressor roles depending on cell type. Hematologic malignancies encompass a wide range of transformed cells, and consequently the roles of Notch are diverse in these diseases. For example Notch is a potent T-cell oncogene, with >50% of T-cell acute lymphoblastic leukemia (T-ALL) cases carry activating mutations in the Notch1 receptor. Targeting Notch signaling in T-ALL with gamma-secretase inhibitors, which prevent Notch receptor activation, has shown pre-clinical activity, and is under evaluation clinically. In contrast, Notch signaling inhibits acute myeloblastic leukemia growth and survival, and although targeting Notch signaling in AML with Notch activators appears to have pre-clinical activity, no Notch agonists are clinically available at this time. As such, despite accumulating evidence about the biology of Notch signaling in different hematologic cancers, which provide compelling clinical promise, we are only beginning to target this pathway clinically, either on or off. In this review, we will summarize the evidence for oncogenic and tumor suppressor roles of Notch in a wide range of leukemias and lymphomas, and describe therapeutic opportunities for now and the future.

Common and complex Notch1 mutations in Chinese oral squamous cell carcinoma

PURPOSE

To determine Notch1 mutation status in oral squamous cell carcinoma (OSCC) from Chinese population and its potential clinical implications.

EXPERIMENTAL DESIGN

Surgically resected OSCC tissues from 51 Chinese patients and 13 head and neck squamous cell carcinoma (HNSCC) cell lines were sequenced for mutations in the entire coding regions of Notch1 and TP53 using a next-generation sequencing platform. Sequences of the genes were also determined in corresponding normal tissues from 46 of the 51 patients. Mutations and their association with clinical parameters were analyzed.

RESULTS

Six mutations in Notch1 and 11 mutations in TP53 coding regions were detected in 4 (31%) and 10 (77%) of the 13 HNSCC cell lines, respectively. Forty-two somatic Notch1 mutations, including 7 nonsense mutations and 11 mutations within the domain commonly harboring potential activating mutations in acute lymphoblastic leukemia, were detected in 22 (43%) of the 51 Chinese OSCC tumors. In comparison, 25 somatic TP53 mutations were observed in 21 (41%) of the 51 tumors. Patients whose tumors carried Notch1 mutation had significantly shorter overall and disease-free survivals (P = 0.004 and P = 0.001, respectively, by log-rank test) compared with those whose tumors carried no Notch1 mutation. Multivariate analysis showed that both Notch1 mutation and lymph node metastasis are independent prognostic factors in the patient population (P = 0.001). All 15 patients with both Notch1 mutation and nodal metastasis recurred or metastasized within 2 years after surgery.

CONCLUSIONS

Notch1 mutation is common in Chinese OSCC and associates with clinical outcomes. The complexity of the mutation spectrum warrants further investigation of Notch1 in Chinese patients with OSCC.

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.

HES1, a target of Notch signaling, is elevated in canine osteosarcoma, but reduced in the most aggressive tumors

BACKGROUND

Hairy and enhancer of split 1 (HES1), a basic helix-loop-helix transcriptional repressor, is a downstream target of Notch signaling. Notch signaling and HES1 expression have been linked to growth and survival in a variety of human cancer types and have been associated with increased metastasis and invasiveness in human osteosarcoma cell lines. Osteosarcoma (OSA) is an aggressive cancer demonstrating both high metastatic rate and chemotherapeutic resistance. The current study examined expression of Notch signaling mediators in primary canine OSA tumors and canine and human osteosarcoma cell lines to assess their role in OSA development and progression.

RESULTS

Reverse transcriptase - quantitative PCR (RT-qPCR) was utilized to quantify HES1, HEY1, NOTCH1 and NOTCH2 gene expression in matched tumor and normal metaphyseal bone samples taken from dogs treated for appendicular OSA at the Colorado State University Veterinary Teaching Hospital. Gene expression was also assessed in tumors from dogs with a disease free interval (DFI) of <100 days compared to those with a DFI > 300 days following treatment with surgical amputation followed by standard chemotherapy. Immunohistochemistry was performed to confirm expression of HES1. Data from RT-qPCR and immunohistochemical (IHC) experiments were analyzed using REST2009 software and survival analysis based on IHC expression employed the Kaplan-Meier method and log rank analysis. Unbiased clustered images were generated from gene array analysis data for Notch/HES1 associated genes. Gene array analysis of Notch/HES1 associated genes suggested alterations in the Notch signaling pathway may contribute to the development of canine OSA. HES1 mRNA expression was elevated in tumor samples relative to normal bone, but decreased in tumor samples from dogs with a DFI < 100 days relative to those with a DFI > 300 days. NOTCH2 and HEY1 mRNA expression was also elevated in tumors relative to normal bone, but was not differentially expressed between the DFI tumor groups. Survival analysis confirmed an association between decreased HES1 immunosignal and shorter DFI.

CONCLUSIONS

Our findings suggest that activation of Notch signaling occurs and may contribute to the development of canine OSA. However, association of low HES1 expression and shorter DFI suggests that mechanisms that do not alter HES1 expression may drive the most aggressive tumors.

A NOTCH3 transcriptional module induces cell motility in neuroblastoma

PURPOSE

Neuroblastoma is a childhood tumor of the peripheral sympathetic nervous system with an often lethal outcome due to metastatic disease. Migration and epithelial-mesenchymal transitions have been implicated in metastasis but they are hardly investigated in neuroblastoma.

EXPERIMENTAL DESIGN

Cell migration of 16 neuroblastoma cell lines was quantified in Transwell migration assays. Gene expression profiling was used to derive a migration signature, which was applied to classify samples in a neuroblastoma tumor series. Differential expression of transcription factors was analyzed in the subsets. NOTCH3 was prioritized, and inducible transgene expression studies in cell lines were used to establish whether it functions as a master switch for motility.

RESULTS

We identified a 36-gene expression signature that predicts cell migration. This signature was used to analyse expression profiles of 88 neuroblastoma tumors and identified a group with distant metastases and a poor prognosis. This group also expressed a known mesenchymal gene signature established in glioblastoma. Neuroblastomas recognized by the motility and mesenchymal signatures strongly expressed genes of the NOTCH pathway. Inducible expression of a NOTCH intracellular (NOTCH3-IC) transgene conferred a highly motile phenotype to neuroblastoma cells. NOTCH3-IC strongly induced expression of motility- and mesenchymal marker genes. Many of these genes were significantly coexpressed with NOTCH3 in neuroblastoma, as well as colon, kidney, ovary, and breast tumor series.

CONCLUSION

The NOTCH3 transcription factor is a master regulator of motility in neuroblastoma. A subset of neuroblastoma with high expression of NOTCH3 and its downstream-regulated genes has mesenchymal characteristics, increased incidence of metastases, and a poor prognosis.

UBE4B levels are correlated with clinical outcomes in neuroblastoma patients and with altered neuroblastoma cell proliferation and sensitivity to epidermal growth factor receptor inhibitors

BACKGROUND

The UBE4B gene, which is located on chromosome 1p36, encodes a ubiquitin ligase that interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), a protein involved in epidermal growth factor receptor (EGFR) trafficking, suggesting a link between EGFR trafficking and neuroblastoma pathogenesis. The authors analyzed the roles of UBE4B in the outcomes of patients with neuroblastoma and in neuroblastoma tumor cell proliferation, EGFR trafficking, and response to EGFR inhibition.

METHODS

The association between UBE4B expression and the survival of patients with neuroblastoma was examined using available microarray data sets. UBE4B and EGFR protein levels were measured in patient tumor samples, EGFR degradation rates were measured in neuroblastoma cell lines, and the effects of UBE4B on neuroblastoma tumor cell growth were analyzed. The effects of the EGFR inhibitor cetuximab were examined in neuroblastoma cells that expressed wild-type and mutant UBE4B.

RESULTS

Low UBE4B gene expression is associated with poor outcomes in patients with neuroblastoma. UBE4B overexpression reduced neuroblastoma tumor cell proliferation, and UBE4B expression was inversely related to EGFR expression in tumor samples. EGFR degradation rates correlated with cellular UBE4B levels. Enhanced expression of catalytically active UBE4B resulted in reduced sensitivity to EGFR inhibition.

CONCLUSIONS

The current study demonstrates associations between UBE4B expression and the outcomes of patients with neuroblastoma and between UBE4B and EGFR expression in neuroblastoma tumor samples. Moreover, levels of UBE4B influence neuroblastoma tumor cell proliferation, EGFR degradation, and response to EGFR inhibition. These results suggest UBE4B-mediated growth factor receptor trafficking may contribute to the poor prognosis of patients who have neuroblastoma tumors with 1p36 deletions and that UBE4B expression may be a marker that can predict responses of neuroblastoma tumors to treatment.

Whole-genome sequencing identifies recurrent somatic NOTCH2 mutations in splenic marginal zone lymphoma

NOTCH2 mutations in splenic marginal zone lymphoma are associated with poor prognosis.

Splenic marginal zone lymphoma (SMZL), the most common primary lymphoma of spleen, is poorly understood at the genetic level. In this study, using whole-genome DNA sequencing (WGS) and confirmation by Sanger sequencing, we observed mutations identified in several genes not previously known to be recurrently altered in SMZL. In particular, we identified recurrent somatic gain-of-function mutations in NOTCH2, a gene encoding a protein required for marginal zone B cell development, in 25 of 99 (∼25%) cases of SMZL and in 1 of 19 (∼5%) cases of nonsplenic MZLs. These mutations clustered near the C-terminal proline/glutamate/serine/threonine (PEST)-rich domain, resulting in protein truncation or, rarely, were nonsynonymous substitutions affecting the extracellular heterodimerization domain (HD). NOTCH2 mutations were not present in other B cell lymphomas and leukemias, such as chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL; n = 15), mantle cell lymphoma (MCL; n = 15), low-grade follicular lymphoma (FL; n = 44), hairy cell leukemia (HCL; n = 15), and reactive lymphoid hyperplasia (n = 14). NOTCH2 mutations were associated with adverse clinical outcomes (relapse, histological transformation, and/or death) among SMZL patients (P = 0.002). These results suggest that NOTCH2 mutations play a role in the pathogenesis and progression of SMZL and are associated with a poor prognosis.

Genome-wide DNA methylation studies suggest distinct DNA methylation patterns in pediatric embryonal and alveolar rhabdomyosarcomas

Rhabdomyosarcoma is the most common soft-tissue sarcoma in children. While cytogenetic abnormalities have been well characterized in this disease, aberrant epigenetic events such as DNA hypermethylation have not been described in genome-wide studies. We have analyzed the methylation status of 25,500 promoters in normal skeletal muscle, and in cell lines and tumor samples of embryonal and alveolar rhabdomyosarcoma from pediatric patients. We identified over 1,900 CpG islands that are hypermethylated in rhabdomyosarcomas relative to skeletal muscle. Genes involved in tissue development, differentiation, and oncogenesis such as DNAJA4, HES5, IRX1, BMP8A, GATA4, GATA6, ALX3, and P4HTM were hypermethylated in both RMS cell lines and primary samples, implicating aberrant DNA methylation in the pathogenesis of rhabdomyosarcoma. Furthermore, cluster analysis revealed embryonal and alveolar subtypes had distinct DNA methylation patterns, with the alveolar subtype being enriched in DNA hypermethylation of polycomb target genes. These results suggest that DNA methylation signatures may aid in the diagnosis and risk stratification of pediatric rhabdomyosarcoma and help identify new targets for therapy.

Oncogenic and tumor suppressor functions of Notch in cancer: it's NOTCH what you think

Notch signaling is often considered a model hematopoietic proto-oncogene because of its role as the main trigger of T cell acute lymphoblastic leukemia (T-ALL). Although its role in T-ALL is well characterized and further supported by a high frequency of activating NOTCH1 mutations in T-ALL patients, it still remains an open question whether the effects of Notch signaling are causative in other types of cancer, including solid tumors. Growing evidence supported by recent studies unexpectedly shows that Notch signaling can also have a potent tumor suppressor function in both solid tumors and hematological malignancies. We discuss the intriguing possibility that the pleiotropic functions of Notch can be tumor suppressive or oncogenic depending on the cellular context.