Notch signaling and Notch signaling modifiers

Mechanism of Notch Signaling Pathway in Malignant Progression of Glioblastoma and Targeted Therapy

Glioblastoma multiforme (GBM) is the most aggressive form of glioma and the most common primary tumor of the central nervous system. Despite significant advances in clinical management strategies and diagnostic techniques for GBM in recent years, it remains a fatal disease. The current standard of care includes surgery, radiation, and chemotherapy, but the five-year survival rate for patients is less than 5%. The search for a more precise diagnosis and earlier intervention remains a critical and urgent challenge in clinical practice. The Notch signaling pathway is a critical signaling system that has been extensively studied in the malignant progression of glioblastoma. This highly conserved signaling cascade is central to a variety of biological processes, including growth, proliferation, self-renewal, migration, apoptosis, and metabolism. In GBM, accumulating data suggest that the Notch signaling pathway is hyperactive and contributes to GBM initiation, progression, and treatment resistance. This review summarizes the biological functions and molecular mechanisms of the Notch signaling pathway in GBM, as well as some clinical advances targeting the Notch signaling pathway in cancer and glioblastoma, highlighting its potential as a focus for novel therapeutic strategies.

Exploring novel protein biomarkers for early-stage diagnosis and prognosis of T-acute lymphoblastic leukemia (T-ALL)

BACKGROUND

Efficient classification of T-acute lymphoblastic leukemia (T-ALL) involves considering various factors, such as age, white blood cell count, and chromosomal alterations. However, studying protein markers are crucial to improving T-ALL patients' diagnosis and treatment. A study analyzing the expression of proteomes was conducted to identify promising early-stage biomarkers for T-ALL patients METHODS: Label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the blood proteins of both patients and healthy individuals to identify new biomarkers for T-ALL. The findings were validated by RT-PCR, ELISA and computational analysis RESULTS: The study identified 1467 proteins in the blood, of which nine were upregulated and 35 were downregulated by more than 2-fold. T-ALL patients showed a significant increase in specific disease-related proteins, such as eleven-nineteen lysine-rich leukemia protein, triggering receptor expressed on myeloid cells 1, cisplatin resistance-associated-overexpressed protein, X-ray radiation resistance-associated protein 1, tumor necrosis factor receptor superfamily member 10D, protein S100-A8, and copine-4, by more than 3-fold CONCLUSION: The findings of this study provide a valuable protein map of leukemic cells and identify potential biomarkers for leukemic aggressiveness. However, further studies using larger T-ALL patient samples must confirm these preliminary results.

Pathophysiological roles of thrombospondin-4 in disease development

Thrombospondin-4 (TSP-4) belongs to the extracellular matrix glycoprotein family of thrombospondins (TSPs). The multidomain, pentameric structure of TSP-4 allows its interactions with numerous extracellular matrix components, proteins and signaling molecules that enable its modulation to various physiological and pathological processes. Characterization of TSP-4 expression under development and pathogenesis of disorders has yielded important insights into mechanisms underlying the unique role of TSP-4 in mediating various processes including cell-cell, cell-extracellular matrix interactions, cell migration, proliferation, tissue remodeling, angiogenesis, and synaptogenesis. Maladaptation of these processes in response to pathological insults and stress can accelerate the development of disorders including skeletal dysplasia, osteoporosis, degenerative joint disease, cardiovascular diseases, tumor progression/metastasis and neurological disorders. Overall, the diverse functions of TSP-4 suggest that it may be a potential marker or therapeutic target for prognosis, diagnosis, and treatment of various pathological conditions upon further investigations. This review article highlights recent findings on the role of TSP-4 in both physiological and pathological conditions with a focus on what sets it apart from other TSPs.

The epigenetics orchestra of Notch signaling: a symphony for cancer therapy

The aberrant regulation of the Notch signaling pathway, which is a fundamental developmental pathway, has been implicated in a wide range of human cancers. The Notch pathway can be activated by both canonical and noncanonical Notch ligands, and its role can switch between acting as an oncogene or a tumor suppressor depending on the context. Epigenetic modifications have the potential to modulate Notch and its ligands, thereby influencing Notch signal transduction. Consequently, the utilization of epigenetic regulatory mechanisms may present novel therapeutic opportunities for both single and combined therapeutics targeted at the Notch signaling pathway. This review offers insights into the mechanisms governing the regulation of Notch signaling and explores their therapeutic potential.

Molecular insights of KMT2D and clinical aspects of Kabuki syndrome type 1

BACKGROUND

Kabuki syndrome type 1 (KS1), a rare multisystem congenital disorder, presents with characteristic facial features, intellectual disability, persistent fetal fingertip pads, skeletal abnormalities, and postnatal growth delays. KS1 results from pathogenic variants in the KMT2D gene, which encodes a histone methyltransferase protein involved in chromatin remodeling, promoter and enhancer regulation, and scaffold formation during early development. KMT2D also mediates cell signaling pathways, responding to external stimuli and organizing effector protein assembly. Research on KMT2D's molecular mechanisms in KS1 has primarily focused on its histone methyltransferase activity, leaving a gap in understanding the methyltransferase-independent roles in KS1 clinical manifestations.

METHODS

This scoping review examines KMT2D's role in gene expression regulation across various species, cell types, and contexts. We analyzed human pathogenic KMT2D variants using publicly available databases and compared them to research organism models of KS1. We also conducted a systematic search of healthcare and governmental databases for clinical trials, studies, and therapeutic approaches.

RESULTS

Our review highlights KMT2D's critical roles beyond methyltransferase activity in diverse cellular contexts and conditions. We identified six distinct groups of KMT2D as a cell signaling mediator, including evidence of methyltransferase-dependent and -independent activity. A comprehensive search of the literature, clinical databases, and public registries emphasizes the need for basic research on KMT2D's functional complexity and longitudinal studies of KS1 patients to establish objective outcome measurements for therapeutic development.

CONCLUSION

We discuss how KMT2D's role in translating external cellular communication can partly explain the clinical heterogeneity observed in KS1 patients. Additionally, we summarize the current molecular diagnostic approaches and clinical trials targeting KS1. This review is a resource for patient advocacy groups, researchers, and physicians to support KS1 diagnosis and therapeutic development.

Headache and NOTCH3 Gene Variants in Patients with CADASIL

Autosomal dominant cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited vascular disease characterized by recurrent strokes, cognitive impairment, psychiatric symptoms, apathy, and migraine. Approximately 40% of patients with CADASIL experience migraine with aura (MA). In addition to MA, CADASIL patients are described in the literature as having migraine without aura (MO) and other types of headaches. Mutations in the NOTCH3 gene cause CADASIL. This study investigated NOTCH3 genetic variants in CADASIL patients and their potential association with headache types. Genetic tests were performed on 30 patients with CADASIL (20 women aged 43.6 ± 11.5 and 10 men aged 39.6 ± 15.8). PCR-HRM and sequencing methods were used in the genetic study. We described three variants as pathogenic/likely pathogenic (p.Tyr189Cys, p.Arg153Cys, p.Cys144Arg) and two benign variants (p.Ala202=, p.Thr101=) in the NOTCH3 gene and also presented the NOTCH3 gene variant (chr19:15192258 G>T), which has not been previously described in the literature. Patients with pathogenic/likely pathogenic variants had similar headache courses. People with benign variants showed a more diverse clinical picture. It seems that different NOTCH3 variants may contribute to the differential presentation of a CADASIL headache, highlighting the diagnostic and prognostic value of headache characteristics in this disease.

Biomedical engineering approaches for the delivery of JAGGED1 as a potential tissue regenerative therapy

JAG1 is a ligand that activates the NOTCH signaling pathway which plays a crucial role in determining cell fate behavior through cell-to-cell signaling. JAG1-NOTCH signaling is required for mesenchymal stem cell (MSC) differentiation into cardiomyocytes and cranial neural crest (CNC) cells differentiation into osteoblasts, making it a regenerative candidate for clinical therapy to treat craniofacial bone loss and myocardial infarction. However, delivery of soluble JAG1 has been found to inhibit NOTCH signaling due to the requirement of JAG1 presentation in a bound form. For JAG1-NOTCH signaling to occur, JAG1 must be immobilized within a scaffold and the correct orientation between the NOTCH receptor and JAG1 must be achieved. The lack of clinically translatable JAG1 delivery methods has driven the exploration of alternative immobilization approaches. This review discusses the role of JAG1 in disease, the clinical role of JAG1 as a treatment, and summarizes current approaches for JAG1 delivery. An in-depth review was conducted on literature that used both in vivo and in vitro delivery models and observed the canonical versus non-canonical NOTCH pathway activated by JAG1. Studies were then compared and evaluated based on delivery success, functional outcomes, and translatability. Delivering JAG1 to harness its ability to control cell fate has the potential to serve as a therapeutic for many diseases.

A new model of Notch signalling: Control of Notch receptor cis-inhibition via Notch ligand dimers

All tissue development and replenishment relies upon the breaking of symmetries leading to the morphological and operational differentiation of progenitor cells into more specialized cells. One of the main engines driving this process is the Notch signal transduction pathway, a ubiquitous signalling system found in the vast majority of metazoan cell types characterized to date. Broadly speaking, Notch receptor activity is governed by a balance between two processes: 1) intercellular Notch transactivation triggered via interactions between receptors and ligands expressed in neighbouring cells; 2) intracellular cis inhibition caused by ligands binding to receptors within the same cell. Additionally, recent reports have also unveiled evidence of cis activation. Whilst context-dependent Notch receptor clustering has been hypothesized, to date, Notch signalling has been assumed to involve an interplay between receptor and ligand monomers. In this study, we demonstrate biochemically, through a mutational analysis of DLL4, both in vitro and in tissue culture cells, that Notch ligands can efficiently self-associate. We found that the membrane proximal EGF-like repeat of DLL4 was necessary and sufficient to promote oligomerization/dimerization. Mechanistically, our experimental evidence supports the view that DLL4 ligand dimerization is specifically required for cis-inhibition of Notch receptor activity. To further substantiate these findings, we have adapted and extended existing ordinary differential equation-based models of Notch signalling to take account of the ligand dimerization-dependent cis-inhibition reported here. Our new model faithfully recapitulates our experimental data and improves predictions based upon published data. Collectively, our work favours a model in which net output following Notch receptor/ligand binding results from ligand monomer-driven Notch receptor transactivation (and cis activation) counterposed by ligand dimer-mediated cis-inhibition.

Overview on Common Genes Involved in the Onset of Glioma and on the Role of Migraine as Risk Factor: Predictive Biomarkers or Therapeutic Targets?

Gliomas are relatively rare but fatal cancers, and there has been insufficient research to specifically evaluate the role of headache as a risk factor. Nowadays, gliomas are difficult to cure due to the infiltrative nature and the absence of specific adjuvant therapies. Until now, mutations in hundreds of genes have been identified in gliomas and most relevant discoveries showed specific genes alterations related to migraine as potential risk factors for brain tumor onset. Prognostic biomarkers are required at the time of diagnosis to better adapt therapies for cancer patients. In this review, we aimed to highlight the significant modulation of CLOCK, BMLA1 and NOTCH genes in glioma onset and development, praising these genes to be good as potentially attractive therapeutic markers for brain tumors. A improved knowledge regarding the role of these genes in triggering or modulating glioma maybe the key to early diagnosing brain tumor onset in patients affected by a simple headache. In addition, investigating on these genes we can suggest potential therapeutic targets for treating brain tumors. These considerations open up the possibility of personalized treatments that can target each brain tumor's specific genetic abnormality.

Computational analysis of the role of mechanosensitive Notch signaling in arterial adaptation to hypertension

Arteries grow and remodel in response to mechanical stimuli. Hypertension, for example, results in arterial wall thickening. Cell-cell Notch signaling between vascular smooth muscle cells (VSMCs) is known to be involved in this process, but the underlying mechanisms are still unclear. Here, we investigated whether Notch mechanosensitivity to strain may regulate arterial thickening in hypertension. We developed a multiscale computational framework by coupling a finite element model of arterial mechanics, including residual stress, to an agent-based model of mechanosensitive Notch signaling, to predict VSMC phenotypes as an indicator of growth and remodeling. Our simulations revealed that the sensitivity of Notch to strain at mean blood pressure may be a key mediator of arterial thickening in hypertensive arteries. Further simulations showed that loss of residual stress can have synergistic effects with hypertension, and that changes in the expression of Notch receptors, but not Jagged ligands, may be used to control arterial growth and remodeling and to intensify or counteract hypertensive thickening. Overall, we identify Notch mechanosensitivity as a potential mediator of vascular adaptation, and we present a computational framework that can facilitate the testing of new therapeutic and regenerative strategies.

Matricellular protein tenascin C: Implications in glioma progression, gliomagenesis, and treatment

Matricellular proteins are nonstructural extracellular matrix components that are expressed at low levels in normal adult tissues and are upregulated during development or under pathological conditions. Tenascin C (TNC), a matricellular protein, is a hexameric and multimodular glycoprotein with different molecular forms that is produced by alternative splicing and post-translational modifications. Malignant gliomas are the most common and aggressive primary brain cancer of the central nervous system. Despite continued advances in multimodal therapy, the prognosis of gliomas remains poor. The main reasons for such poor outcomes are the heterogeneity and adaptability caused by the tumor microenvironment and glioma stem cells. It has been shown that TNC is present in the glioma microenvironment and glioma stem cell niches, and that it promotes malignant properties, such as neovascularization, proliferation, invasiveness, and immunomodulation. TNC is abundantly expressed in neural stem cell niches and plays a role in neurogenesis. Notably, there is increasing evidence showing that neural stem cells in the subventricular zone may be the cells of origin of gliomas. Here, we review the evidence regarding the role of TNC in glioma progression, propose a potential association between TNC and gliomagenesis, and summarize its clinical applications. Collectively, TNC is an appealing focus for advancing our understanding of gliomas.

The Role of PTEN in Epithelial–Mesenchymal Transition

Simple Summary

The PTEN phosphatase is a ubiquitously expressed tumor suppressor, which inhibits the PI3K/AKT pathway in the cell. The PI3K/AKT pathway is considered to be one of the main signaling pathways that drives the proliferation of cancer cells. Furthermore, the same pathway controls the epithelial–mesenchymal transition (EMT). EMT is an evolutionarily conserved developmental program, which, upon aberrant reactivation, is also involved in the formation of cancer metastases. Importantly, metastasis is the leading cause of cancer-associated deaths. In this review, we discuss the literature data that highlight the role of PTEN in EMT. Based on this knowledge, we speculate about new possible strategies for cancer treatment.

Abstract

Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN) is one of the critical tumor suppressor genes and the main negative regulator of the PI3K pathway. PTEN is frequently found to be inactivated, either partially or fully, in various malignancies. The PI3K/AKT pathway is considered to be one of the main signaling cues that drives the proliferation of cells. Perhaps it is not surprising, then, that this pathway is hyperactivated in highly proliferative tumors. Importantly, the PI3K/AKT pathway also coordinates the epithelial–mesenchymal transition (EMT), which is pivotal for the initiation of metastases and hence is regarded as an attractive target for the treatment of metastatic cancer. It was shown that PTEN suppresses EMT, although the exact mechanism of this effect is still not fully understood. This review is an attempt to systematize the published information on the role of PTEN in the development of malignant tumors, with a main focus on the regulation of the PI3K/AKT pathway in EMT.

De novo brain arteriovenous malformation formation and development: A case report

BACKGROUND

Brain arteriovenous malformation (AVM), an aberrant vascular development during the intrauterine period, is traditionally considered a congenital disease. Sporadic reports of cases of de novo AVM formation in children and adults have challenged the traditional view of its congenital origin.

CASE SUMMARY

In this report, we have presented the case of a child with a de novo brain AVM. Magnetic resonance imaging and magnetic resonance angiography of the brain showed no AVM at the age of 5 years and 2 mo. Brain AVM was first detected in this child at the age of 7 years and 4 mo. The brain AVM was significantly advanced, and hemorrhage was seen for the first time at the age of 12 years and 8 mo. There was further progression in the AVM, and hemorrhage occurred again at the age of 13 years and 5 mo. Genetic analysis of this patient revealed a mutation in the NOTCH2 (p.Asp473Val) gene.

CONCLUSION

In short, our case has once again confirmed the view that brain AVM is an acquired disease and is the result of the interaction of genes, environment, and molecules.

Ehrlichia SLiM Ligand Mimetic Activates Notch Signaling in Human Monocytes

Ehrlichia chaffeensis evades innate host defenses by reprogramming the mononuclear phagocyte through mechanisms that involve the exploitation of multiple evolutionarily conserved cellular signaling pathways, including Notch. This immune evasion strategy is directed in part by tandem repeat protein (TRP) effectors. Specifically, the TRP120 effector activates and regulates Notch signaling through interactions with the Notch receptor and the negative regulator, F-Box and WD repeat domain-containing 7 (FBW7). However, the specific molecular interactions and motifs required for E. chaffeensis TRP120-Notch receptor interaction and activation have not been defined. To investigate the molecular basis of TRP120 Notch activation, we compared TRP120 with endogenous canonical/noncanonical Notch ligands and identified a short region of sequence homology within the tandem repeat (TR) domain. TRP120 was predicted to share biological function with Notch ligands, and a function-associated sequence in the TR domain was identified. To investigate TRP120-Notch receptor interactions, colocalization between TRP120 and endogenous Notch-1 was observed. Moreover, direct interactions between full-length TRP120, the TRP120 TR domain containing the putative Notch ligand sequence, and the Notch receptor LBR were demonstrated. To molecularly define the TRP120 Notch activation motif, peptide mapping was used to identify an 11-amino acid short linear motif (SLiM) located within the TRP120 TR that activated Notch signaling and downstream gene expression. Peptide mutants of the Notch SLiM or anti-Notch SLiM antibody reduced or eliminated Notch activation and NICD nuclear translocation. This investigation reveals a novel molecularly defined pathogen encoded Notch SLiM mimetic that activates Notch signaling consistent with endogenous ligands. IMPORTANCE E. chaffeensis infects and replicates in mononuclear phagocytes, but how it evades innate immune defenses of this indispensable primary innate immune cell is not well understood. This investigation revealed the molecular details of a ligand mimicry cellular reprogramming strategy that involved a short linear motif (SLiM), which enabled E. chaffeensis to exploit host cell signaling to establish and maintain infection. E. chaffeensis TRP120 is a moonlighting effector that has been associated with cellular activation and other functions, including ubiquitin ligase activity. Herein, we identified and demonstrated that a SLiM present within each tandem repeat of TRP120 activated Notch signaling. Notch is an evolutionarily conserved signaling pathway responsible for many cell functions, including cell fate, development, and innate immunity. This study is significant because it revealed the first molecularly defined pathogen encoded SLiM that appears to have evolved de novo to mimic endogenous Notch ligands. Understanding Notch activation during E. chaffeensis infection provides a model to study pathogen exploitation of signaling pathways and will be useful in developing molecularly targeted countermeasures for inhibiting infection by a multitude of disease-causing pathogens that exploit cell signaling through molecular mimicry.

Relationship between the Chromosome Structural Dynamics and Gene Expression—A Chicken and Egg Dilemma?

Prokaryotic transcription was extensively studied over the last half-century. A great deal of data has been accumulated regarding the control of gene expression by transcription factors regulating their target genes by binding at specific DNA sites. However, there is a significant gap between the mechanistic description of transcriptional control obtained from in vitro biochemical studies and the complexity of transcriptional regulation in the context of the living cell. Indeed, recent studies provide ample evidence for additional levels of complexity pertaining to the regulation of transcription in vivo, such as, for example, the role of the subcellular localization and spatial organization of different molecular components involved in the transcriptional control and, especially, the role of chromosome configurational dynamics. The question as to how the chromosome is dynamically reorganized under the changing environmental conditions and how this reorganization is related to gene expression is still far from being clear. In this article, we focus on the relationships between the chromosome structural dynamics and modulation of gene expression during bacterial adaptation. We argue that spatial organization of the bacterial chromosome is of central importance in the adaptation of gene expression to changing environmental conditions and vice versa, that gene expression affects chromosome dynamics.

Dissecting Tumor Growth: The Role of Cancer Stem Cells in Drug Resistance and Recurrence

Simple Summary

Cancer is one of the most debated problems all over the world. Cancer stem cells are considered responsible of tumor initiation, metastasis, drug resistance, and recurrence. This subpopulation of cells has been found into the tumor bulk and showed the capacity to self-renew, differentiate, up to generate a new tumor. In the last decades, several studies have been set on the molecular mechanisms behind their specific characteristics as the Wnt/β-catenin signaling, Notch signaling, Hedgehog signaling, transcription factors, etc. The most powerful part of CSCs is represented by the niches as “promoter” of their self-renewal and “protector” from the common oncological treatment as chemotherapy and radiotherapy. In our review article we highlighted the primary mechanisms involved in CSC tumorigenesis for the setting of further targets to control the metastatic process.

Abstract

Emerging evidence suggests that a small subpopulation of cancer stem cells (CSCs) is responsible for initiation, progression, and metastasis cascade in tumors. CSCs share characteristics with normal stem cells, i.e., self-renewal and differentiation potential, suggesting that they can drive cancer progression. Consequently, targeting CSCs to prevent tumor growth or regrowth might offer a chance to lead the fight against cancer. CSCs create their niche, a specific area within tissue with a unique microenvironment that sustains their vital functions. Interactions between CSCs and their niches play a critical role in regulating CSCs’ self-renewal and tumorigenesis. Differences observed in the frequency of CSCs, due to the phenotypic plasticity of many cancer cells, remain a challenge in cancer therapeutics, since CSCs can modulate their transcriptional activities into a more stem-like state to protect themselves from destruction. This plasticity represents an essential step for future therapeutic approaches. Regarding self-renewal, CSCs are modulated by the same molecular pathways found in normal stem cells, such as Wnt/β-catenin signaling, Notch signaling, and Hedgehog signaling. Another key characteristic of CSCs is their resistance to standard chemotherapy and radiotherapy treatments, due to their capacity to rest in a quiescent state. This review will analyze the primary mechanisms involved in CSC tumorigenesis, with particular attention to the roles of CSCs in tumor progression in benign and malignant diseases; and will examine future perspectives on the identification of new markers to better control tumorigenesis, as well as dissecting the metastasis process.

Epithelial-to-Mesenchymal Transition Signaling Pathways Responsible for Breast Cancer Metastasis

Breast carcinoma is highly metastatic and invasive. Tumor metastasis is a convoluted and multistep process involving tumor cell disseminating from their primary site and migrating to the secondary organ. Epithelial-mesenchymal transition (EMT) is one of the crucial steps that initiate cell progression, invasion, and metastasis. During EMT, epithelial cells alter their molecular features and acquire a mesenchymal phenotype. The regulation of EMT is centered by several signaling pathways, including primary mediators TGF-β, Notch, Wnt, TNF-α, Hedgehog, and RTKs. It is also affected by hypoxia and microRNAs (miRNAs). All these pathways are the convergence on the transcriptional factors such as Snail, Slug, Twist, and ZEB1/2. In addition, a line of evidence suggested that EMT and cancer stem like cells (CSCs) are associated. EMT associated cancer stem cells display mesenchymal phenotypes and resist to chemotherapy or targeted therapy. In this review, we highlighted recent discoveries in these signaling pathways and their regulation in breast cancer metastasis and invasion. While the clinical relevance of EMT and breast cancers remains controversial, we speculated a convergent signaling network pivotal to elucidating the transition of epithelial to mesenchymal phenotypes and onset of metastasis of breast cancer cells.

SUMOylated non-canonical polycomb PRC1.6 complex as a prerequisite for recruitment of transcription factor RBPJ

BACKGROUND

Notch signaling controls cell fate decisions in many contexts during development and adult stem cell homeostasis and, when dysregulated, leads to carcinogenesis. The central transcription factor RBPJ assembles the Notch coactivator complex in the presence of Notch signaling, and represses Notch target gene expression in its absence.

RESULTS

We identified L3MBTL2 and additional members of the non-canonical polycomb repressive PRC1.6 complex in DNA-bound RBPJ associated complexes and demonstrate that L3MBTL2 directly interacts with RBPJ. Depletion of RBPJ does not affect occupancy of PRC1.6 components at Notch target genes. Conversely, absence of L3MBTL2 reduces RBPJ occupancy at enhancers of Notch target genes. Since L3MBTL2 and additional members of the PRC1.6 are known to be SUMOylated, we investigated whether RBPJ uses SUMO-moieties as contact points. Indeed, we found that RBPJ binds to SUMO2/3 and that this interaction depends on a defined SUMO-interaction motif. Furthermore, we show that pharmacological inhibition of SUMOylation reduces RBPJ occupancy at Notch target genes.

CONCLUSIONS

We propose that the PRC1.6 complex and its conjugated SUMO-modifications provide a favorable environment for binding of RBPJ to Notch target genes.

Electrophilic and Drug-Induced Stimulation of NOTCH3 N-terminal Fragment Oligomerization in Cerebrovascular Pathology

Small vessel disease is a prevalent age-related condition linked to increased risk of dementia and stroke. We investigate the most commonly inherited form, CADASIL, caused by cysteine-involving mutations in NOTCH3. Recent studies highlight accumulation of NOTCH3 N-terminal fragmentation product (NTF) in disease. In vitro, NTF is capable of both spontaneous and catecholamine-enhanced cysteine-mediated oligomerization. Despite well-characterized genetic influence on CADASIL, environmental effects, including medication usage, on disease remain unclear. We studied effects of assorted electrophilic compounds and drugs on NTF oligomerization by SDS-PAGE and dynamic light scattering. We then examined direct proton pump inhibitor-NTF binding with antibodies designed against proton pump inhibitor-labeled proteins and mass spectrometry. Finally, we used monoclonal NTF antibodies with Proximity Ligation Assay to identify NTF oligomers in 3 CADASIL and 2 age-matched control brains. We identified enhancement of NTF oligomerization by two electrophilic cysteine-modifying compounds, N-ethylmaleimide and iodoacetamide, and an electrophilic compound capable of oxidizing cysteines, ferric chloride. Electrophilic clinical drugs (fenoldopam, omeprazole, tenatoprazole, lansoprazole, and rabeprazole) also promoted oligomerization, and we identified direct omeprazole-NTF and tenatoprazole-NTF complexes. Additionally, we provide novel evidence of NTF multimers in human CADASIL brains. A broad array of electrophilic chemicals, including clinically relevant drugs, influences oligomerization of a pathological CADASIL protein, providing mechanistic insight into disease protein oligomerization. We posit that environmental influences, which may include usage of electrophilic drugs, may affect CADASIL presentations.

A review: hippo signaling pathway promotes tumor invasion and metastasis by regulating target gene expression

BACKGROUND

The Hippo pathway is widely considered to inhibit cell growth and play an important role in regulating the size of organs. However, recent studies have shown that abnormal regulation of the Hippo pathway can also affect tumor invasion and metastasis. Therefore, finding out how the Hippo pathway promotes tumor development by regulating the expression of target genes provides new ideas for future research on targeted drugs that inhibit tumor progression.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were systematically searched.

RESULTS

The search strategy identified 1892 hits and 196 publications were finally included in this review. As the core molecule of the Hippo pathway, YAP/TAZ are usually highly expressed in tumors that undergo invasion and migration and are accompanied by abnormally strong nuclear metastasis. Through its interaction with nuclear transcription factors TEADs, it directly or indirectly regulates and the expressions of target genes related to tumor metastasis and invasion. These target genes can induce the formation of invasive pseudopodia in tumor cells, reduce intercellular adhesion, degrade extracellular matrix (ECM), and cause epithelial-mesenchymal transition (EMT), or indirectly promote through other signaling pathways, such as mitogen-activated protein kinases (MAPK), TGF/Smad, etc, which facilitate the invasion and metastasis of tumors.

CONCLUSION

This article mainly introduces the research progress of YAP/TAZ which are the core molecules of the Hippo pathway regulating related target genes to promote tumor invasion and metastasis. Focus on the target genes that affect tumor invasion and metastasis, providing the possibility for the selection of clinical drug treatment targets, to provide some help for a more in-depth study of tumor invasion and migration mechanism and the development of clinical drugs.

Drug Development in Neuroendocrine Tumors: What Is on the Horizon?

OPINION STATEMENT

Neuroendocrine neoplasms (NENs) constitute a heterogenous group of malignancies. Translational research into NEN cell biology is the cornerstone for drug development strategies in this field. Somatostatin receptor type 2 (SSTR2) expression is the hallmark of well-differentiated neuroendocrine tumors (NETs). Somatostatin analogs and peptide receptor radionuclide therapy (PRRT) form the basis of anti-SSTR2 treatment onto new combination strategies, antibody-drug conjugates and bispecific antibodies. Classical pathways involved in NET development (PI3K-Akt-mTOR and antiangiogenics) are reviewed but new potential targets for NET treatment will be explored. Epigenetic drugs have shown clinical activity in monotherapy and preclinical combination strategies are more than attractive. Immunotherapy has shown opposite results in different NEN settings. Although the NOTCH pathway has been targeted with disappointing results, new strategies are being developed. Finally, after years of solid preclinical evidence on different genetically engineered oncolytic viruses, clinical trials for refractory NET patients are now ongoing.

Relevance of Notch Signaling for Bone Metabolism and Regeneration

Notch1-4 receptors and their signaling pathways are expressed in almost all organ systems and play a pivotal role in cell fate decision by coordinating cell proliferation, differentiation and apoptosis. Differential expression and activation of Notch signaling pathways has been observed in a variety of organs and tissues under physiological and pathological conditions. Bone tissue represents a dynamic system, which is constantly remodeled throughout life. In bone, Notch receptors have been shown to control remodeling and regeneration. Numerous functions have been assigned to Notch receptors and ligands, including osteoblast differentiation and matrix mineralization, osteoclast recruitment and cell fusion and osteoblast/osteoclast progenitor cell proliferation. The expression and function of Notch1-4 in the skeleton are distinct and closely depend on the temporal expression at different differentiation stages. This review addresses the current knowledge on Notch signaling in adult bone with emphasis on metabolism, bone regeneration and degenerative skeletal disorders, as well as congenital disorders associated with mutant Notch genes. Moreover, the crosstalk between Notch signaling and other important pathways involved in bone turnover, including Wnt/β-catenin, BMP and RANKL/OPG, are outlined.

The aging endothelium

Cellular senescence is now recognized as one of the hallmarks of aging. Herein, we examine current findings on senescence of the vascular endothelium and its impacts on age-related vascular diseases. Endothelial senescence can result in systemic metabolic changes, implicating senescence in chronic diseases such as diabetes, obesity and atherosclerosis. Senolytics, drugs that eliminate senescent cells, afford new therapeutic strategies for control of these chronic diseases.

Overlapping Protein Accumulation Profiles of CADASIL and CAA: Is There a Common Mechanism Driving Cerebral Small-Vessel Disease?

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and cerebral amyloid angiopathy (CAA) are two distinct vascular angiopathies that share several similarities in clinical presentation and vascular pathology. Given the clinical and pathologic overlap, the molecular overlap between CADASIL and CAA was explored. CADASIL and CAA protein profiles from recently published proteomics-based and immuno-based studies were compared to investigate the potential for shared disease mechanisms. A comparison of affected proteins in each disease highlighted 19 proteins that are regulated in both CADASIL and CAA. Functional analysis of the shared proteins predicts significant interaction between them and suggests that most enriched proteins play roles in extracellular matrix structure and remodeling. Proposed models to explain the observed enrichment of extracellular matrix proteins include both increased protein secretion and decreased protein turnover by sequestration of chaperones and proteases or formation of stable protein complexes. Single-cell RNA sequencing of vascular cells in mice suggested that the vast majority of the genes accounting for the overlapped proteins between CADASIL and CAA are expressed by fibroblasts. Thus, our current understanding of the molecular profiles of CADASIL and CAA appears to support potential for common mechanisms underlying the two disorders.

Deubiquitinating Enzyme-Mediated Signaling Networks in Cancer Stem Cells

Cancer stem cells (CSCs) have both the capacity for self-renewal and the potential to differentiate and contribute to multiple tumor properties, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Thus, CSCs are considered to be promising therapeutic targets for cancer therapy. The function of CSCs can be regulated by ubiquitination and deubiquitination of proteins related to the specific stemness of the cells executing various stem cell fate choices. To regulate the balance between ubiquitination and deubiquitination processes, the disassembly of ubiquitin chains from specific substrates by deubiquitinating enzymes (DUBs) is crucial. Several key developmental and signaling pathways have been shown to play essential roles in this regulation. Growing evidence suggests that overactive or abnormal signaling within and among these pathways may contribute to the survival of CSCs. These signaling pathways have been experimentally shown to mediate various stem cell properties, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation. In this review, we focus on the DUBs involved in CSCs signaling pathways, which are vital in regulating their stem-cell fate determination.

Tenascin-C Function in Glioma: Immunomodulation and Beyond

First identified in the 1980s, tenascin-C (TNC) is a multi-domain extracellular matrix glycoprotein abundantly expressed during the development of multicellular organisms. TNC level is undetectable in most adult tissues but rapidly and transiently induced by a handful of pro-inflammatory cytokines in a variety of pathological conditions including infection, inflammation, fibrosis, and wound healing. Persistent TNC expression is associated with chronic inflammation and many malignancies, including glioma. By interacting with its receptor integrin and a myriad of other binding partners, TNC elicits context- and cell type-dependent function to regulate cell adhesion, migration, proliferation, and angiogenesis. TNC operates as an endogenous activator of toll-like receptor 4 and promotes inflammatory response by inducing the expression of multiple pro-inflammatory factors in innate immune cells such as microglia and macrophages. In addition, TNC drives macrophage differentiation and polarization predominantly towards an M1-like phenotype. In contrast, TNC shows immunosuppressive function in T cells. In glioma, TNC is expressed by tumor cells and stromal cells; high expression of TNC is correlated with tumor progression and poor prognosis. Besides promoting glioma invasion and angiogenesis, TNC has been found to affect the morphology and function of tumor-associated microglia/macrophages in glioma. Clinically, TNC can serve as a biomarker for tumor progression; and TNC antibodies have been utilized as an adjuvant agent to deliver anti-tumor drugs to target glioma. A better mechanistic understanding of how TNC impacts innate and adaptive immunity during tumorigenesis and tumor progression will open new therapeutic avenues to treat brain tumors and other malignancies.

Regulation of GDNF expression in Sertoli cells

Sertoli cells regulate male germ cell proliferation and differentiation and are a critical component of the spermatogonial stem cell (SSC) niche, where homeostasis is maintained by the interplay of several signaling pathways and growth factors. These factors are secreted by Sertoli cells located within the seminiferous epithelium, and by interstitial cells residing between the seminiferous tubules. Sertoli cells and peritubular myoid cells produce glial cell line-derived neurotrophic factor (GDNF), which binds to the RET/GFRA1 receptor complex at the surface of undifferentiated spermatogonia. GDNF is known for its ability to drive SSC self-renewal and proliferation of their direct cell progeny. Even though the effects of GDNF are well studied, our understanding of the regulation its expression is still limited. The purpose of this review is to discuss how GDNF expression in Sertoli cells is modulated within the niche, and how these mechanisms impact germ cell homeostasis.

Aspartate β-hydroxylase as a target for cancer therapy

As metastasis is a major cause of death in cancer patients, new anti-metastatic strategies are needed to improve cancer therapy outcomes. Numerous pathways have been shown to contribute to migration and invasion of malignant tumors. Aspartate β-hydroxylase (ASPH) is a key player in the malignant transformation of solid tumors by enhancing cell proliferation, migration, and invasion. ASPH also promotes tumor growth by stimulation of angiogenesis and immunosuppression. These effects are mainly achieved via the activation of Notch and SRC signaling pathways. ASPH expression is upregulated by growth factors and hypoxia in different human tumors and its inactivation may have broad clinical impact. Therefore, small molecule inhibitors of ASPH enzymatic activity have been developed and their anti-metastatic effect confirmed in preclinical mouse models. ASPH can also be targeted by monoclonal antibodies and has also been used as a tumor-associated antigen to induce both cluster of differentiation (CD) 8+ and CD4+ T cells in mice. The PAN-301-1 vaccine against ASPH has already been tested in a phase 1 clinical trial in patients with prostate cancer. In summary, ASPH is a promising target for anti-tumor and anti-metastatic therapy based on inactivation of catalytic activity and/or immunotherapy.

The oncogenic role of Jagged1/Notch signaling in cancer

Aberrant activation of Notch signaling plays an oncogenic role in cancer development. Jagged1 (JAG1) is an important Notch ligand that triggers Notch signaling through cell-cell interactions. JAG1 overexpression has been reported in many different types of cancer and correlates with a poor clinical prognosis. JAG1/Notch signaling controls oncogenic processes in different cell types and cellular contexts. Furthermore, JAG1/Notch signaling cascades activate a number of oncogenic factors that regulate cellular functions such as proliferation, metastasis, drug-resistance, and angiogenesis. To suppress the severe toxicity of pan-Notch inhibitors, JAG1 is attracting increasing attention as a source of therapeutic targets for cancers. In this review, the oncogenic role of JAG1/Notch signaling in cancer is discussed, as well as implications of strategies to inhibit JAG1/Notch signaling activity.

The Role of DLLs in Cancer: A Novel Therapeutic Target

Delta-like ligands (DLLs) control Notch signaling. DLL1, DLL3 and DLL4 are frequently deregulated in cancer and influence tumor growth, the tumor vasculature and tumor immunity, which play different roles in cancer progression. DLLs have attracted intense research interest as anti-cancer therapeutics. In this review, we discuss the role of DLLs in cancer and summarize the emerging DLL-relevant targeting methods to aid future studies.

Lateral induction limits the impact of cell connectivity on Notch signaling in arterial walls

It is well known that arteries grow and remodel in response to mechanical stimuli. Vascular smooth muscle cells are the main mediators of this process, as they can switch phenotype from contractile to synthetic, and vice-versa, based on the surrounding bio-chemo-mechanical stimuli. A correct regulation of this phenotypic switch is fundamental to obtain and maintain arterial homeostasis. Notch, a mechanosensitive signaling pathway, is one of the main regulators of the vascular smooth muscle cell phenotype. Therefore, understanding Notch dynamics is key to elucidate arterial growth, remodeling, and mechanobiology. We have recently developed a one-dimensional agent-based model to investigate Notch signaling in arteries. However, due to its one-dimensional formulation, the model cannot be adopted to study complex nonsymmetrical geometries and, importantly, it cannot capture the realistic "cell connectivity" in arteries, here defined as the number of cell neighbors. Notch functions via direct cell-cell contact; thus, the number of cell neighbors could be an essential feature of Notch dynamics. Here, we extended the agent-based model to a two-dimensional formulation, to investigate the effects of cell connectivity on Notch dynamics and cell phenotypes in arteries. The computational results, supported by a sensitivity analysis, indicate that cell connectivity has marginal effects when Notch dynamics is dominated by the process of lateral induction, which induces all cells to have a uniform phenotype. When lateral induction is weaker, cells exhibit a nonuniform phenotype distribution and the percentage of synthetic cells within an artery depends on the number of neighbors.

Self-Renewal Signalling Pathway Inhibitors: Perspectives on Therapeutic Approaches for Cancer Stem Cells

The poor survival and prognosis of individuals with cancer are often attributed to tumour relapse and metastasis, which may be due to the presence of cancer stem cells (CSCs). CSCs have the characteristics of self-renewal, differentiation potential, high carcinogenicity, and drug resistance. In addition, CSCs exhibit many characteristics similar to those of embryonic or tissue stem cells while displaying persistent abnormal activation of self-renewal pathways associated with development and tissue homeostasis, including the Wnt, Notch, Hedgehog (Hh), TGF-β, JAK/STAT3, and NF-κB pathways. Therefore, we can eliminate CSCs by targeting these self-renewal pathways to constrain stem cell replication, survival and differentiation. At the same time, we cannot neglect the ping-pong effect of the tumour microenvironment, which releases cytokines and promotes self-renewal pathways in CSCs. Recently, meaningful progress has been made in the study of inhibitors of self-renewal pathways in tumours. This review primarily summarizes several representative and novel agents targeting these self-renewal signalling pathways and the tumour microenvironment and that represent a promising strategy for treating refractory and recurrent cancer.

Altered expression of Notch1 in Alzheimer's disease

Notch signaling is an evolutionarily conserved pathway that regulates cell-cell interactions through binding of Notch family receptors to their cognate ligands. Notch signaling has an essential role in vascular development and angiogenesis. Recent studies have reported that Notch may be implicated in Alzheimer's disease (AD) pathophysiology. We measured the levels of soluble Notch1 (sNotch1) in the plasma samples from 72 dementia patients (average age 75.1 y), 89 subjects with amnestic mild cognitive impairment (MCI) (average age 73.72 y), and 150 cognitively normal controls (average age 72.34 y). Plasma levels of sNotch1 were 25.27% lower in dementia patients as compared to healthy control subjects. However, the level of Notch1 protein was significantly increased in human brain microvascular endothelial cells (HBMECs) after amyloid-beta treatment. Also, Notch1 mRNA level was significantly increased in HBMECs and iPSC-derived neuronal cells from AD patient compared to normal control. These results indicate that altered expression of Notch1 might be associated with the risk of Alzheimer's disease.

A modifier in the 129S2/SvPasCrl genome is responsible for the viability of Notch1[12f/12f] mice

Background

Mouse NOTCH1 carries a highly conserved O-fucose glycan at Thr466 in epidermal growth factor-like repeat 12 (EGF12) of the extracellular domain. O-Fucose at this site has been shown by X-ray crystallography to be recognized by both DLL4 and JAG1 Notch ligands. We previously showed that a Notch1 Thr466Ala mutant exhibits very little ligand-induced NOTCH1 signaling in a reporter assay, whereas a Thr466Ser mutation enables the transfer of O-fucose and reverts the NOTCH1 signaling defect. We subsequently generated a mutant mouse with the Thr466Ala mutation termed Notch1[12f](Notch1^tm2Pst). Surprisingly, homozygous Notch1[12f/12f] mutants on a mixed background were viable and fertile.

Results

We now report that after backcrossing to C57BL/6 J mice for 11–15 generations, few homozygous Notch1[12f/12f] embryos were born. Timed mating showed that embryonic lethality occurred by embryonic day (E) ~E11.5, somewhat delayed compared to mice lacking Notch1 or Pofut1 (the O-fucosyltransferase that adds O-fucose to Notch receptors), which die at ~E9.5. The phenotype of C57BL/6 J Notch1[12f/12f] embryos was milder than mutants affected by loss of a canonical Notch pathway member, but disorganized vasculogenesis in the yolk sac, delayed somitogenesis and development were characteristic. In situ hybridization of Notch target genes Uncx4.1 and Dll3 or western blot analysis of NOTCH1 cleavage did not reveal significant differences at E9.5. However, qRT-PCR of head cDNA showed increased expression of Dll3, Uncx4.1 and Notch1 in E9.5 Notch1[12f/12f] embryos. Sequencing of cDNA from Notch1[12f/12f] embryo heads and Southern analysis showed that the Notch1[12f] locus was intact following backcrossing. We therefore looked for evidence of modifying gene(s) by crossing C57BL/6 J Notch1 [12f/+] mice to 129S2/SvPasCrl mice. Intercrosses of the F1 progeny gave viable F2 Notch1[12f/12f] mice.

Conclusion

We conclude that the 129S2/SvPasCrl genome contains a dominant modifying gene that rescues the functions of NOTCH1[12f] in signaling. Identification of the modifying gene has the potential to illuminate novel factor(s) that promote Notch signaling when an O-fucose glycan is absent from EGF12 of NOTCH1.

Gene expression profiles and bioinformatics analysis of insulin-like growth factor-1 promotion of osteogenic differentiation

Background

Insulin‐like growth factor‐1 (IGF‐1) promotes osteoblast differentiation and mineralization. The objective of this study was to investigate the effects of IGF‐1 on proliferation, mineralization, alkaline phosphatase (ALP) synthesis, and gene expression of osteoblast differentiation in MC3T3‐E1 osteoblasts cells, and to explore gene expression profiling differential genes.

Methods

MC3T3‐E1 osteoblasts cells were cultured in medium with or without IGF‐1. The ALP assay was employed to determine the osteoblast mineralization, and Alizarin red S to stain for calcium deposits, which were the indicators of mature osteocytes. The living cell number was assessed by the Cell Counting Kit‐8 method. RNA‐seq analysis was applied to identify genes that were differentially expressed in with or without IGF‐1 as well as genes that varied between these two groups. The expression of osteogenic marker genes was determined by quantitative real‐time polymerase chain reaction (qRT‐PCR) and western blot analysis.

Result

The cell number of osteoblasts exposed to IGF‐1 at 200 μg/L significantly increased compared with the control group. The ALP activity in IGF‐1‐treated cells was higher than that in the control group. IGF‐1 can increase ALP synthesis in osteoblasts in vitro. RNA‐seq analysis showed that 677 triggered differentially expressed genes by IGF, of which 383 genes were downregulated and 294 genes were upregulated. Gene ontology (GO) analysis showed that IGF‐1 caused a significant change in gene expression patterns.

Conclusions

This result suggested that IGF‐1 could probably promote the synthesis of organic matrix and mineralize action of bone. Osteogenic‐related genes (DMP1, PHEX, SOST, BMP2, RUNX2, OPN, and OCN) were significantly upregulated both in GO analysis and in pathway analysis to perform qRT‐PCR. Western blot analysis demonstrated that the Notch pathway was highly upregulated in MC3T3‐E1 cells.

Modulation of Nerve Cell Differentiation: Role of Polyphenols and of Contactin Family Components

In this study the mechanisms are explored, which modulate expression and function of cell surface adhesive glycoproteins of the Immunoglobulin Supergene Family (IgSF), and in particular of its Contactin subset, during neuronal precursor developmental events. In this context, a specific topic concerns the significance of the expression profile of such molecules and their ability to modulate signaling pathways activated through nutraceuticals, in particular polyphenols, administration. Both in vitro and in vivo approaches are chosen. As for the former, by using as a model the human SH-SY5Y neuroblastoma line, the effects of grape seed polyphenols are evaluated on proliferation and commitment/differentiation events along the neuronal lineage. In SH-SY5Y cell cultures, polyphenols were found to counteract precursor proliferation while promoting their differentiation, as deduced by studying their developmental parameters through the expression of cell cycle and neuronal commitment/differentiation markers as well as by measuring neurite growth. In such cultures, Cyclin E expression and BrdU incorporation were downregulated, indicating reduced precursor proliferation while increased neuronal differentiation was inferred from upregulation of cell cycle exit (p27^–Kip) and neuronal commitment (NeuN) markers as well as by measuring neurite length through morphometric analysis. The polyphenol effects on developmental parameters were also explored in vivo, in cerebellar cortex, by using as a model the TAG/F3 transgenic line, which undergoes delayed neural development as a consequence of Contactin1 adhesive glycoprotein upregulation and premature expression under control of the Contactin2 gene (Cntn-2) promoter. In this transgenic line, a Notch pathway activation is known to occur and polyphenol treatment was found to counteract such an effect, demonstrated through downregulation of the Hes-1 transcription factor. Polyphenols also downregulated the expression of adhesive glycoproteins of the Contactin family themselves, demonstrated for both Contactin1 and Contactin2, indicating the involvement of changes in the expression of the underlying genes in the observed phenotype. These data support the hypothesis that the complex control exerted by polyphenols on neural development involves modulation of expression and function of the genes encoding cell adhesion molecules of the Contactin family and of the associated signaling pathways, indicating potential mechanisms whereby such compounds may control neurogenesis.

Circulating delta-like Notch ligand 1 is correlated with cardiac allograft vasculopathy and suppressed in heart transplant recipients on everolimus-based immunosuppression

Cardiac allograft vasculopathy (CAV) causes heart failure after heart transplantation (HTx), but its pathogenesis is incompletely understood. Notch signaling, possibly modulated by everolimus (EVR), is essential for processes involved in CAV. We hypothesized that circulating Notch ligands would be dysregulated after HTx. We studied circulating delta-like Notch ligand 1 (DLL1) and periostin (POSTN) and CAV in de novo HTx recipients (n = 70) randomized to standard or EVR-based, calcineurin inhibitor-free immunosuppression and in maintenance HTx recipients (n = 41). Compared to healthy controls, plasma DLL1 and POSTN were elevated in de novo (P < .01; P < .001) and maintenance HTx recipients (P < .001; P < .01). Use of EVR was associated with a treatment effect for DLL1. For de novo HTx recipients, a change in DLL1 correlated with a change in CAV at 1 (P = .021) and 3 years (P = .005). In vitro, activation of T cells increased DLL1 secretion, attenuated by EVR. In vitro data suggest that also endothelial cells and vascular smooth muscle cells (VSMCs) could contribute to circulating DLL1. Immunostaining of myocardial specimens showed colocalization of DLL1 with T cells, endothelial cells, and VSMCs. Our findings suggest a role of DLL1 in CAV progression, and that the beneficial effect of EVR on CAV could reflect a suppressive effect on DLL1. Trial registration numbers-SCHEDULE trial: ClinicalTrials.gov NCT01266148; NOCTET trial: ClinicalTrials.gov NCT00377962.

Role of Notch Signaling Pathway in Glioblastoma Pathogenesis

Notch signaling is an evolutionarily conserved pathway that regulates important biological processes, such as cell proliferation, apoptosis, migration, self-renewal, and differentiation. In mammals, Notch signaling is composed of four receptors (Notch1–4) and five ligands (Dll1-3–4, Jagged1–2) that mainly contribute to the development and maintenance of the central nervous system (CNS). Neural stem cells (NSCs) are the starting point for neurogenesis and other neurological functions, representing an essential aspect for the homeostasis of the CNS. Therefore, genetic and functional alterations to NSCs can lead to the development of brain tumors, including glioblastoma. Glioblastoma remains an incurable disease, and the reason for the failure of current therapies and tumor relapse is the presence of a small subpopulation of tumor cells known as glioma stem cells (GSCs), characterized by their stem cell-like properties and aggressive phenotype. Growing evidence reveals that Notch signaling is highly active in GSCs, where it suppresses differentiation and maintains stem-like properties, contributing to Glioblastoma tumorigenesis and conventional-treatment resistance. In this review, we try to give a comprehensive view of the contribution of Notch signaling to Glioblastoma and its possible implication as a target for new therapeutic approaches.

BMP9 Promotes the Extracellular Matrix of Nucleus Pulposus Cells via Inhibition of the Notch Signaling Pathway

Intervertebral disk degeneration (IDD) is a common disease that is caused by degeneration of the nucleus pulposus (NP). One goal in the treatment of IDD is delaying or reversing the degeneration of NP via the transformation of exogenous genes. This study first investigated the role of BMP9 in the extracellular matrix (ECM) of nucleus pulposus cells (NPCs) and its mechanism. We found that BMP9 promotes the expression of ECM in NPCs, and the key molecules of Notch signaling, namely, NICD-1, hes and hey, and it was significantly altered in BMP9-transfected NPCs, which suggests that BMP9 may regulate the ECM via the Notch signaling pathway. We verified the expression of Notch ligands and receptors in NPCs infected with Ad-BMP9 and demonstrated a significant decrease in DLL1 and Notch1; then, NPCs were transfected with Ad-dnNotch1, Ad-Jagged1, and Ad-DLL1, and different multiple groups were established to further identify the ligands or receptors that affected ECM expression. The results demonstrated that Ad-dnNotch1, Jagged1 and DLL1 inhibited ECM expression, and dnNotch1 promoted expression. Therefore, we demonstrated that BMP9 promoted the expression of ECM in NPCs via inhibition of Notch1 and DLL1. This study provides a possible method for IDD treatment.

Regulation of melanocyte stem cells in the pigmentation of skin and its appendages: Biological patterning and therapeutic potentials

Skin evolves essential appendages and indispensable types of cells that synergistically insulate the body from environmental insults. Residing in the specific regions in the skin such as epidermis, dermis and hair follicle, melanocytes perform an array of vital functions including defending the ultraviolet radiation and diversifying animal appearance. As one of the adult stem cells, melanocyte stem cells in the hair follicle bulge niche can proliferate, differentiate and keep quiescence to control and coordinate tissue homeostasis, repair and regeneration. In synchrony with hair follicle stem cells, melanocyte stem cells in the hair follicles undergo cyclic activation, degeneration and resting phases, to pigment the hairs and to preserve the stem cells. Disorder of melanocytes results in severe skin problems such as canities, vitiligo and even melanoma. Here, we compare and summarize recent discoveries about melanocyte in the skin, particularly in the hair follicle. A better understanding of the physiological and pathological regulation of melanocyte and melanocyte stem cell behaviours will help to guide the clinical applications in regenerative medicine.

Notch signal pathway - therapeutic target for regulation of reparative processes in the heart

Notch signaling pathway is a universal regulator of cell fate in embryogenesis and in maintaining the cell homeostasis of adult tissue. Through local cell-cell interactions, he controls neighboring cells behavior and determines their capacity for self-renewal, growth, survival, differentiation, and apoptosis. Recent studies have shown that the control of regenerative processes in the heart is also carried out with the participation of Notch system. At the heart of Notch regulates migration bone marrow progenitors and stimulates the proliferation of cardiomyocytes, cardiac progenitor cell activity, limits cardiomyocyte hypertrophy and fibrosis progression and stimulates angiogenesis. Notch signaling pathway may be regarded as a very promising target for the development of drugs for the stimulation of regeneration in the myocardium.

Notch3 is involved in adipogenesis of human adipose-derived stromal/stem cells

Human adipose-derived stromal/stem cells (hASCs) have tremendous therapeutic potential and the ability to offer insight into human development and disease. Here we subject human ASCs to siRNA-mediated knockdown of Notch3 cultured under both self-renewing and adipogenic differentiation conditions. Self-renewal was monitored by assessing viability and proliferation rates through staining and alamarBlue assays, respectively. Adipogenesis was measured through Oil-Red O staining, western blot, and quantitative real-time RT-PCR that determined expression levels of multipotency and adipogenic markers over time. Notch3 was expressed in self-renewing hASCs but knockdown, as validated by qRT-PCR and western blot, showed no impact on cell viability, as measured through live-dead staining, or cell proliferation rates, as measured through alamarBlue assays. However, although Notch3 expression was observed to increase during adipogenesis, in the absence of Notch3 there was a significant increase in hASC adipogenesis as demonstrated through an increased number of lipid vesicles, and increased expression of adipogenic markers ppar-γ, adiponectin, fabp4, and plin2. Although Notch3 is only one of four Notch receptors expressed on the surface of hASCs, this receptor appears important for proper regulation of adipogenic differentiation, possibly serving as a negative regulator to prevent inappropriate adipogenesis or promote other lineage commitments of ASCs.

Novel Insights on Notch signaling pathways in liver fibrosis

Liver fibrosis is characterized by an increased and altered deposition of extracellular matrix (ECM) proteins that make up excessive tissue scarring and promote chronic liver injury. Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in the progression of liver fibrosis. However, the mechanisms involved in the development of liver fibrosis are only now beginning to be unveiled. The Notch pathway is a fundamental and highly conserved pathway able to control cell-fate, including cell proliferation, differentiation, apoptosis, regeneration and other cellular activities. Recently, the deregulation of Notch cascade has been found involved in many pathological processes, including liver fibrosis. These data give evidence for a role for Notch signaling in liver fibrosis. In addition，more and more date are available on the role of Notch pathways in the process. Therefore, this review focuses on the current knowledge about the Notch signaling pathway, which dramatically takes part in HSC activation and liver fibrosis, and look ahead on new perspectives of Notch signaling pathway research. Furthermore, we will summarize this new evidence on the different interactions in Notch signaling pathway-regulated liver fibrosis, and support the potentiality of putative biomarkers and unique therapeutic targets.

Crosstalk between Notch and Sonic hedgehog signaling in a mouse model of amyotrophic lateral sclerosis

The developmental morphogen Sonic hedgehog (Shh) may continue to play a sustaining role in adult motor neurons, of potential relevance to motor neuron diseases including amyotrophic lateral sclerosis. The Shh signaling pathway is incompletely understood and interactions with other signaling pathways are possible. We focus here on Notch, and first show that there is an almost linear reduction in light output from a Gli reporter in Shh Light II cells in the presence of increasing concentrations of the Notch inhibitor DAPT (r²=0.982). Second, in the spinal cord of mutant superoxide dismutase mice, but not control mice, a key marker of Notch signaling changes with age. Before the onset of clinical signs, the Notch intracellular domain is expressed predominantly in motor neurons, but by 125 days of age, Notch intracellular domain expression is markedly reduced in motor neurons and increased in neighboring astroglia. Third, there is a parallel reduction in Gli protein expression in mutant superoxide dismutase mouse spinal motor neurons, consistent with the observed reduction in Notch signaling and also a redistribution of Gli away from the nucleus. Thus, there is a reduction in motor neuronal Notch signaling and associated changes in Shh signaling, occurring coincidentally with disease expression, that may contribute toward the dysfunction and death of motor neurons in amyotrophic lateral sclerosis.

AKAP200 promotes Notch stability by protecting it from Cbl/lysosome-mediated degradation in Drosophila melanogaster

AKAP200 is a Drosophila melanogaster member of the “A Kinase Associated Protein” family of scaffolding proteins, known for their role in the spatial and temporal regulation of Protein Kinase A (PKA) in multiple signaling contexts. Here, we demonstrate an unexpected function of AKAP200 in promoting Notch protein stability. In Drosophila, AKAP200 loss-of-function (LOF) mutants show phenotypes that resemble Notch LOF defects, including eye patterning and sensory organ specification defects. Through genetic interactions, we demonstrate that AKAP200 interacts positively with Notch in both the eye and the thorax. We further show that AKAP200 is part of a physical complex with Notch. Biochemical studies reveal that AKAP200 stabilizes endogenous Notch protein, and that it limits ubiquitination of Notch. Specifically, our genetic and biochemical evidence indicates that AKAP200 protects Notch from the E3-ubiquitin ligase Cbl, which targets Notch to the lysosomal pathway. Indeed, we demonstrate that the effect of AKAP200 on Notch levels depends on the lysosome. Interestingly, this function of AKAP200 is fully independent of its role in PKA signaling and independent of its ability to bind PKA. Taken together, our data indicate that AKAP200 is a novel tissue specific posttranslational regulator of Notch, maintaining high Notch protein levels and thus promoting Notch signaling.

AKAP200 belongs to a family of scaffolding proteins best known for their regulation of PKA localization. In this study, we have identified a novel role of AKAP200 in Notch protein stability and signaling. In Drosophila melanogaster, AKAP200’s loss and gain-of-function (LOF/GOF) phenotypes are characteristic of Notch signaling defects. Furthermore, we demonstrated genetic interactions between AKAP200 and Notch. Consistent with this, AKAP200 stabilizes the endogenous Notch protein and limits its ubiquitination. AKAP200 exerts its effects on Notch by antagonizing Cbl-mediated ubiquitination and thus lysosome targeting of Notch. Based on these data, we postulate a novel PKA independent mechanism of AKAP200 to achieve optimal Notch protein levels, with AKAP200 preventing Cbl-mediated lysosomal degradation of Notch.

Stanniocalcin-1 augments stem-like traits of glioblastoma cells through binding and activating NOTCH1

Glioblastoma (GBM) is a fatal tumor and comprises heterogeneous cells in which a subpopulation with stem cell-like properties is included. Cancer cells with stem cell-like properties account for tumor initiation, drug resistance and recurrence. To identify and characterize specific factors in regulating stem-like traits is critical for GBM therapeutic. Here, we showed that Stanniocalcin-1 (STC1), a secretory glycoprotein, functions as a novel stimulator for stem-like traits of GBM cells. We found STC1 was prominently expressed in glioma spheres which are mainly comprised of glioma stem-like cells. The stem-like traits of GBM cells, as determined by the expression of stem cell markers, tumor-sphere formation efficiency and colony-forming ability, were enhanced by STC1 overexpression and inhibited by STC1 knockdown. Furthermore, introduction of STC1 enhanced tumorigenesis in vivo while knockdown of STC1 showed reverse effect. Finally, we demonstrated that STC1 interacted with the extracellular domain of NOTCH1 to activate NOTCH1-SOX2 signaling pathway, by which STC1 augmented the stem-like traits of GBM cells. Taken together, our data herein indicate that STC1 is a novel non-canonical NOTCH ligand and acts as a crucial regulator of stemness in GBM.

Crocodile choline from Crocodylus siamensis induces apoptosis of human gastric cancer

Crocodile choline, an active compound isolated from Crocodylus siamensis, was found to exert potent anti-cancer activities against human gastric cancer cells in vitro and in vivo. Our study revealed that crocodile choline led to cell cycle arrest at the G2/M phase through attenuating the expressions of cyclins, Cyclin B1, and CDK-1. Furthermore, crocodile choline accelerated apoptosis through the mitochondrial apoptotic pathway with the decrease in mitochondrial membrane potential, the increase in reactive oxygen species production and Bax/Bcl-2 ratio, and the activation of caspase-3 along with the release of cytochrome c. In addition, this study, for the first time, shows that Notch pathway is remarkably deregulated by crocodile choline. The combination of crocodile choline and Notch1 short interfering RNA led to dramatically increased cytotoxicity than observed with either agent alone. Notch1 short interfering RNA sensitized and potentiated the capability of crocodile choline to suppress the cell progression and invasion of gastric cancer. Taken together, these data suggested that crocodile choline was a potent progression inhibitor of gastric cancer cells, which was correlated with mitochondrial apoptotic pathway and Notch pathway. Combining Notch1 inhibitors with crocodile choline might represent a novel approach for gastric cancer.