Notch signaling in leukemias and lymphomas

Epigenetically dysregulated NOTCH-Delta-HES signaling cascade can serve as a subtype classifier for acute lymphoblastic leukemia

The NOTCH-Delta-HES signaling cascade is regarded as a double-edged sword owing to its dual tumor-suppressor and oncogenic roles, in different cellular environments. In the T-cells, it supports leukemogenesis by promoting differentiation while in B-cells, it controls leukemogenesis by inhibiting early differentiation/inducing growth arrest in the lead to apoptosis. The present study was undertaken to assess if this bi-faceted behavior of NOTCH family can be exploited as a diagnostic biomarker or subtype classifier of acute lymphoblastic leukemia (ALL). In this pursuit, expression of seven NOTCH cascade genes was analyzed in bone marrow (BM) biopsy and blood plasma (BP) of pediatric ALL patients using quantitative PCR (qPCR). Further, promoter DNA methylation status of the differentially expressed genes (DEGs) was assessed by methylation-specific qMSP and validated through bisulphite amplicon sequencing. Whereas hypermethylation of JAG1, DLL1, and HES-2, HES-4, and HES-5 was observed in all patients, NOTCH3 was found hypermethylated specifically in Pre-B ALL cases while DLL4 in Pre-T ALL cases. Aberrant DNA methylation strongly correlated with downregulated gene expression, which restored at complete remission stage as observed in "follow-up/post-treatment" subjects. The subtype-specific ROC curve analysis and Kaplan-Meier survival analysis predicted a clinically applicable diagnostic and prognostic potential of the panel. Moreover, the logistic regression model (Pre-B vs Pre-T ALL) was found to be the best-fitted model (McFadden's R2 = 0.28, F1 measure = 0.99). Whether analyzed in BM-aspirates or blood plasma, the NOTCH epigenetic signatures displayed comparable results (p < 0.001), advocating the potential of NOTCH-Delta-HES cascade, as a subtype classifier, in minimally invasive diagnosis of ALL.

Relapsed/Refractory Peripheral T-Cell Lymphoma-Associated Hemophagocytic Lymphohistiocytosis With UNC13D and CD27 Germline Mutations

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory disease characterized by familial and acquired forms. Here, we present the case of a 26-year-old male patient with relapsed/refractory peripheral T-cell lymphoma and concurrent HLH. Whole-exon sequencing revealed germline mutations associated with HLH, including those in critical genes such as CD27 and UNC13D and other germline heterozygous variants (NOTCH2, NOTCH3, IL2RA, TYK2, AGL, CFD, and F13A1). CD107a analyses consistently demonstrated impaired degranulation of cytotoxic T-lymphocytes and natural killer (NK) cells. Examination of the patient's family pedigree revealed that his father and mother harbored UNC13D and CD27 mutations, respectively; his brother carried the same CD27 heterozygous mutation. However, none of them manifested the disease. Despite the missense mutation of CD27 (c.779C>T; p.Pro260Leu) lacking previous documentation in databases, comprehensive analysis suggested non-pathogenic mutations in the CD27 variant, indicating minimal impact on T- and NK-cell functions. These results ultimately supported the option of hematopoietic stem cell transplantation (HSCT) as a successful curative therapeutic approach. As of this report, the patient has remained free of lymphoma and quiescent HLH 15.2 months post-HSCT. This study underscores the efficacy of genetic tests in identifying significant mutations and confirming their etiologies, providing an early basis for treatment decisions and the selection of suitable transplant donors.

In silico modelling of the function of disease-related CAZymes

In silico modelling of proteins comprises a diversity of computational tools aimed to obtain structural, electronic, and/or dynamic information about these biomolecules, capturing mechanistic details that are challenging to experimental approaches, such as elusive enzyme-substrate complexes, short-lived intermediates, and reaction transition states (TS). The present article gives the reader insight on the use of in silico modelling techniques to understand complex catalytic reaction mechanisms of carbohydrate-active enzymes (CAZymes), along with the underlying theory and concepts that are important in this field. We start by introducing the significance of carbohydrates in nature and the enzymes that process them, CAZymes, highlighting the conformational flexibility of their carbohydrate substrates. Three commonly used in silico methods (classical molecular dynamics (MD), hybrid quantum mechanics/molecular mechanics (QM/MM), and enhanced sampling techniques) are described for nonexpert readers. Finally, we provide three examples of the application of these methods to unravel the catalytic mechanisms of three disease-related CAZymes: β-galactocerebrosidase (GALC), responsible for Krabbe disease; α-mannoside β-1,6-N-acetylglucosaminyltransferase V (MGAT5), involved in cancer; and O-fucosyltransferase 1 (POFUT1), involved in several human diseases such as leukemia and the Dowling-Degos disease.

Comprehensive Molecular Analyses of Notch Pathway-Related Genes to Predict Prognosis and Immunotherapy Response in Patients with Gastric Cancer

Gastric cancer (GC) is a highly molecular heterogeneous tumor with unfavorable outcomes. The Notch signaling pathway is an important regulator of immune cell differentiation and has been associated with autoimmune disorders, the development of tumors, and immunomodulation caused by tumors. In this study, by developing a gene signature based on genes relevant to the Notch pathway, we could improve our ability to predict the outcome of patients with GC. From the TCGA database, RNA sequencing data of GC tumors and associated normal tissues were obtained. Microarray data were collected from GEO datasets. The Molecular Signature Database (MSigDB) was accessed in order to retrieve sets of human Notch pathway-related genes (NPRGs). The LASSO analysis performed on the TCGA cohort was used to generate a multigene signature based on prognostic NPRGs. In order to validate the gene signature, the GEO cohort was utilized. Using the CIBERSORT method, we were able to determine the amounts of immune cell infiltration in the GC. In this study, a total of 21 differentially expressed NPRGs were obtained between GC specimens and nontumor specimens. The construction of a prognostic prediction model for patients with GC involved the identification and selection of three different NPRGs. According to the appropriate cutoff value, the patients with GC were divided into two groups: those with a low risk and those with a high risk. The time-dependent ROC curves demonstrated that the new model had satisfactory performance when it came to prognostic prediction. Multivariate assays confirmed that the risk score was an independent marker that may be used to predict the outcome of GC. In addition, the generated nomogram demonstrated a high level of predictive usefulness. Moreover, the scores of immunological infiltration of the majority of immune cells were distinctly different between the two groups, and the low-risk group responded to immunotherapy in a significantly greater degree. According to the results of a functional enrichment study of candidate genes, there are multiple pathways and processes associated with cancer. Taken together, a new gene model associated with the Notch pathway may be utilized for the purpose of predicting the prognosis of GC. One potential method of treatment for GC is to focus on NPRGs.

Asparagine Tautomerization in Glycosyltransferase Catalysis. The Molecular Mechanism of Protein O-Fucosyltransferase 1

O-glycosylation is a post-translational protein modification essential to life. One of the enzymes involved in this process is protein O-fucosyltransferase 1 (POFUT1), which fucosylates threonine or serine residues within a specific sequence context of epidermal growth factor-like domains (EGF-LD). Unlike most inverting glycosyltransferases, POFUT1 lacks a basic residue in the active site that could act as a catalytic base to deprotonate the Thr/Ser residue of the EGF-LD acceptor during the chemical reaction. Using quantum mechanics/molecular mechanics (QM/MM) methods on recent crystal structures, as well as mutagenesis experiments, we uncover the enzyme catalytic mechanism, revealing that it involves proton shuttling through an active site asparagine, conserved among species, which undergoes tautomerization. This mechanism is consistent with experimental kinetic analysis of Caenorhabditis elegans POFUT1 Asn43 mutants, which ablate enzyme activity even if mutated to Asp, the canonical catalytic base in inverting glycosyltransferases. These results will aid inhibitor development for Notch-associated O-glycosylation disorders.

Leukaemia Infection Diagnosis and Intestinal Flora Disorder

Leukaemia is the most common malignant tumor in childhood and can be cured by chemotherapy. Infection is an important cause of treatment-related death and treatment failure in childhood leukaemia. Recent studies have shown that the correlation between the occurrence of leukaemia infection and the intestinal flora has attracted more and more attention. Intestinal flora can affect the body's physiological defense and immune function. When intestinal microflora disorder occurs, metabolites/microorganisms related to intestinal flora alterations and even likely the associated morpho-functional alteration of the epithelial barrier may be promising diagnostic biomarkers for the early diagnosis of leukaemia infection. This review will focus on the interaction between leukaemia infection and intestinal flora, and the influence of intestinal flora in the occurrence and development of leukaemia infection.

Deltex-1 is indispensible for the IL-6 and TGF-β treatment-triggered differentiation of Th17 cells

CSL(CBF1, Su(H) and LAG-1)-dependent Hes-1 signaling plays an important part in regulating Th17 cell differentiation. However, little is known about influence of CSL-independent Deltex-1 signaling on this subset. The current focus is on roles of the Deltex-1 signaling in the Th17 cell differentiation. IL-17-producing CD4⁺ T cell subpopulation could be induced in vitro by treatment of both IL-6 and TGF-β. This could be reversed by knockdown of the deltex-1 gene, following the attenuation of retinoic acid-related orphan receptor γt (RORγt) and its DNA-binding activity in nuclei. Subsequently, Th17-associated cytokines generated by the treated cells were also diminished by the inhibition of Deltex-1 signaling, but the production of IL-10 was enhanced. Contrary to the alteration of RORγt, both zinc-finger transcription factor-3 (GATA3) and transcription factor Forkhead box P3 (Foxp3) were augmented at their mRNA and protein levels as well as DNA-binding activities with the emerging phenotypes of the corresponding cellular subpopulation and T-bet (encoded by TBX21) was not changed. These results reveal for the first time that Deltex-1 is indispensible for the IL-6 and TGF-β treatment-triggered differentiation of Th17 cells, indicating that CSL-independent Deltex-1 signaling favors naïve CD4⁺ T cells to deviate into Th17 cells via the enhancement of RORγt/IL-17A.

Knockdown of MAML1 inhibits proliferation and induces apoptosis of T-cell acute lymphoblastic leukemia cells through SP1-dependent inactivation of TRIM59

Notch exerts important functions in cell proliferation, survival, and differentiation, which plays a critical role in tumor development when aberrantly activated. Mastermind-like protein 1 (MAML1) has been functioning as crucial coactivators of Notch receptors and is required for stable formation of Notch transcriptional complexes. However, the mechanism whereby MAML1 induces T-cell acute lymphoblastic leukemia (T-ALL) tumorigenesis is largely unknown. The CCK-8 and flow cytometry assay were performed to examine the effect of MAML1 knockdown on T-ALL cell proliferation, apoptosis, and cell cycle. The expression of MAML1, cell cycle, and apoptosis-related gene, as well as TRIM family members and specific protein 1 (SP1) was measured by western blot analysis and qPCR. Our results showed that MAML1 knockdown significantly inhibited cell proliferation and induced G0/G1 cell cycle arrest and apoptosis in Jurkat and MOLT-4 cells. Cell cycle and apoptosis-related gene expression, including CDK2, Bcl-2, Bax, and Bad, was modified by the MAML1 knockdown. MAML1 knockdown obviously inhibited the CDK2 and Bcl-2 expression and increased the Bax, p53, and Bad expression. Moreover, the TRIM family members, including TRIM13, TRIM32, TRIM44, and TRIM59, were significantly decreased by the MAML1 knockdown, with the highest decrease detected in TRIM59 expression. Interesting, overexpression of SP1 not only increased the expression of MAML1 and TRIM59, but also promoted the promoter activation of TRIM59. Taken together, knockdown of MAML1 inhibits proliferation and induces apoptosis of T-ALL cells through SP1-dependent inactivation of TRIM59, and therefore suggest that MAML1-SP1-TRIM59 axis may serve as potentially interesting therapeutic targets for treatment of T-ALL.

A multi-arm phase I dose escalating study of an oral NOTCH inhibitor BMS-986115 in patients with advanced solid tumours

Background Inhibiting Notch is a promising anti-cancer strategy as it plays a critical role in cancer stem cells maintenance and tumour angiogenesis. BMS-986115 is an orally active, selective inhibitor of gamma-secretase mediated Notch signalling. Method Two dose escalation schedules (Arm-A continuous daily schedule and Arm-B intermittent 2 times weekly schedule) of BMS-986115 were evaluated in advanced solid tumour patients. The primary objective was to establish the safety, tolerability and Maximum Tolerated Dose (MTD) of BMS-986115. Results Thirty six patients (24 in Arm A and 12 in Arm B) were treated. The most frequent treatment related adverse advents were diarrhoea (72%), hypophosphataemia (64%), and nausea (61%). The MTD was 1.5 mg daily in Arm A but not established in Arm B. Four patients in Arm A and 2 in Arm B experienced dose limiting toxicities (grade 3 nausea, diarrhoea, pruritus/urticaria and ileus). BMS-986115 showed dose related increase in exposure within the dose range tested. Target inhibition of Notch pathway related genes was observed. Three patients in Arm A and 2 in Arm B achieved stable disease for more than 6 months. Conclusion The daily oral dosing of BMS-986115 is safe and tolerable with biological activity demonstrated by continuous target engagement and Notch signalling inhibition.

Significance of Inactivated Genes in Leukemia: Pathogenesis and Prognosis

Epigenetic and genetic alterations are two mechanisms participating in leukemia, which can inactivate genes involved in leukemia pathogenesis or progression. The purpose of this review was to introduce various inactivated genes and evaluate their possible role in leukemia pathogenesis and prognosis. By searching the mesh words "Gene, Silencing AND Leukemia" in PubMed website, relevant English articles dealt with human subjects as of 2000 were included in this study. Gene inactivation in leukemia is largely mediated by promoter's hypermethylation of gene involving in cellular functions such as cell cycle, apoptosis, and gene transcription. Inactivated genes, such as ASPP1, TP53, IKZF1 and P15, may correlate with poor prognosis in acute lymphoid leukemia (ALL), chronic lymphoid leukemia (CLL), chronic myelogenous leukemia (CML) and acute myeloid leukemia (AML), respectively. Gene inactivation may play a considerable role in leukemia pathogenesis and prognosis, which can be considered as complementary diagnostic tests to differentiate different leukemia types, determine leukemia prognosis, and also detect response to therapy. In general, this review showed some genes inactivated only in leukemia (with differences between B-ALL, T-ALL, CLL, AML and CML). These differences could be of interest as an additional tool to better categorize leukemia types. Furthermore; based on inactivated genes, a diverse classification of Leukemias could represent a powerful method to address a targeted therapy of the patients, in order to minimize side effects of conventional therapies and to enhance new drug strategies.

Growth inhibitory effect of rapamycin in Hodgkin-lymphoma cell lines characterized by constitutive NOTCH1 activation

Growing evidence suggests that deregulation of signalling elements of Notch and mammalian target of rapamycin (mTOR) pathways contribute to tumorigenesis. These signals play important roles in cellular functions and malignancies. Their tumorigenic role in T-cell acute lymphoblastic leukaemia (T-ALL) is well known; however, their potential interactions and functions are poorly characterized in Hodgkin lymphoma (HL). The aim of our study was to characterize mTOR and Notch signalling elements in HL cell lines (DEV, L1236, KMH2) and human biopsies and to investigate their cross-talk in the tumorous process. High mTOR activity and constitutive NOTCH1 activation was confirmed in HL cell lines, without any known oncogenic mutations in key elements, including those common to both pathways. The anti-tumour effect of Notch inhibitors are well known from several preclinical models but resistance and side effects occur in many cases. Here, we tested mTOR and Notch inhibitors and their combinations in gamma-secretase inhibitor (GSI) resistant HL cells in vitro and in vivo. mTOR inhibitor alone or in combination was able to reduce tumour growth; furthermore, it was more effective in xenograft models in vivo. Based on these results, we suggest that constitutively activated NOTCH1 may be a potential target in HL therapy; furthermore, mTOR inhibitors may be effective for decreasing tumour growth if resistance to Notch inhibitors develop.

Notch1 pathway in adrenocortical carcinomas: correlations with clinical outcome

Previous SNP array analyses have revealed genomic alterations of the Notch pathway as being the most frequent abnormality in adrenocortical tumors (ACTs). The aim of the present study was to evaluate the expression of components of Notch signaling in ACTs and to correlate them with clinical outcome. The mRNA expression of JAG1, NOTCH1, and selected target genes of NOTCH1 (HES1, HES5, and HEY2) was evaluated in 80 fresh frozen samples (28 normal adrenal glands (NAGs), 24 adenomas (ACAs), and 28 carcinomas (ACCs)) by quantitative RT-PCR. Immunohistochemistry was performed in 221 tissues on paraffin slides (16 NAGs, 27 ACAs, and 178 ACCs) for JAG1, activated NOTCH1 (aNOTCH1), and HEY2. An independent ACC validation cohort (n=77) was then also investigated. HEY2 mRNA expression was higher in ACCs than it was in ACAs (P<0.05). The protein expression of all of the factors was high (H-score 2-3) in a larger proportion of ACCs as compared to ACAs and NAGs (JAG1 in 27, 15, and 10%; aNOTCH1 in 13, 8, and 0%; HEY2 in 66, 61, and 33% respectively, all P<0.001). High JAG1 expression was associated with earlier tumor stages and lower numbers of metastases in ACCs (both P=0.08) and favorably impacted overall and progression-free survival (PFS) (131 vs 30 months, hazard ratio (HR) 0.45, and 37 vs 9 months, HR 0.51, both P<0.005). This impact on overall survival (OS) was confirmed in the validation cohort. No such association was observed for aNOTCH1 or HEY2. In conclusion, different components of the Notch1 signaling pathway are overexpressed in ACCs, which suggests a role for the pathway in malignant transformation. However, JAG1 is overexpressed in a subgroup of ACCs with a better clinical outcome.

3D hotspots of recurrent retroviral insertions reveal long-range interactions with cancer genes

Genomically distal mutations can contribute to the deregulation of cancer genes by engaging in chromatin interactions. To study this, we overlay viral cancer-causing insertions obtained in a murine retroviral insertional mutagenesis screen with genome-wide chromatin conformation capture data. Here we find that insertions tend to cluster in 3D hotspots within the nucleus. The identified hotspots are significantly enriched for known cancer genes, and bear the expected characteristics of bona fide regulatory interactions, such as enrichment for transcription factor-binding sites. In addition, we observe a striking pattern of mutual exclusive integration. This is an indication that insertions in these loci target the same gene, either in their linear genomic vicinity or in their 3D spatial vicinity. Our findings shed new light on the repertoire of targets obtained from insertional mutagenesis screening and underline the importance of considering the genome as a 3D structure when studying effects of genomic perturbations.

The Link between Autoimmunity and Lymphoma: Does NOTCH Signaling Play a Contributing Role?

An association between certain autoimmune conditions and increased risk of developing lymphoma is well documented. Recent evidence points to NOTCH signaling as a strong driver of autoimmunity. Furthermore, a role for NOTCH in various lymphomas, including classical Hodgkin lymphoma, non-Hodgkin lymphoma, and T cell lymphoma has also been described. In this mini-review, we will outline what is known about involvement of NOTCH signaling in those autoimmune conditions, such as rheumatoid arthritis and primary Sjörgren’s syndrome, which show an increased risk for subsequent diagnosis of lymphoma. Furthermore, we will detail what is known about the lymphomas associated with these autoimmune conditions and how aberrant or sustained NOTCH signaling in the immune cells that mediate these diseases may contribute to lymphoma.

Notch signaling in the malignant bone marrow microenvironment: implications for a niche-based model of oncogenesis

Fueled by the growing interest in stem cell biology and the promise of regenerative medicine, study of the hematopoietic stem cell (HSC) microenvironment has provided critical insights into normal and malignant hematopoiesis. Notch receptor signaling in this microenvironment is a critical regulator of HSC fate and differentiation. Notch signaling also has the potential to modulate the growth of various malignant cell types, as evidenced by the growing list of hematologic cancers and other malignancies associated with either mutations in Notch genes or alterations in Notch signaling. In both health and disease, activation of Notch signaling predominantly exerts influence through stromal cell interactions with the tumor or stem cell microenvironments. Definitive evidence from transgenic mouse models has shown that alterations in stromal cell signaling from the bone marrow niche can induce malignant outgrowth of preleukemic clones and leukemia. Understanding how Notch receptor signals in the bone marrow microenvironment govern stem cell behavior will advance our understanding of cancer pathogenesis in hematologic malignancies and may have implications for treating metastatic solid tumors involving bone. These microenvironmental interactions are potential therapeutic targets for treating and preventing a variety of diseases, including bone marrow failure disorders, myelodysplastic syndromes, leukemia, and lymphoma.

Interaction between gastric cancer stem cells and the tumor microenvironment

Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are selectively capable of tumor initiation and are implicated in tumor relapse and metastasis, thus, governing the prognosis of GC patients. Stromal cells and extracellular matrix adjacent to cancer cells are known to form a supportive environment for cancer progression. CSC properties are also regulated by their microenvironment through cell signaling and related factors. This review presents the current findings regarding the influence of the tumor microenvironment on GC stem cells, which will support the development of novel therapeutic strategies for patients with GC.

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.

Epigenetic inactivation of Notch-Hes pathway in human B-cell acute lymphoblastic leukemia

The Notch pathway can have both oncogenic and tumor suppressor roles, depending on cell context. For example, Notch signaling promotes T cell differentiation and is leukemogenic in T cells, whereas it inhibits early B cell differentiation and acts as a tumor suppressor in B cell leukemia where it induces growth arrest and apoptosis. The regulatory mechanisms that contribute to these opposing roles are not understood. Aberrant promoter DNA methylation and histone modifications are associated with silencing of tumor suppressor genes and have been implicated in leukemogenesis. Using methylated CpG island amplification (MCA)/DNA promoter microarray, we identified Notch3 and Hes5 as hypermethylated in human B cell acute lymphoblastic leukemia (ALL). We investigated the methylation status of other Notch pathway genes by bisulfite pyrosequencing. Notch3, JAG1, Hes2, Hes4 and Hes5 were frequently hypermethylated in B leukemia cell lines and primary B-ALL, in contrast to T-ALL cell lines and patient samples. Aberrant methylation of Notch3 and Hes5 in B-ALL was associated with gene silencing and was accompanied by decrease of H3K4 trimethylation and H3K9 acetylation and gain of H3K9 trimethylation and H3K27 trimethylation. 5-aza-2′-deoxycytidine treatment restored Hes5 expression and decreased promoter hypermethylation in most leukemia cell lines and primary B-ALL samples. Restoration of Hes5 expression by lentiviral transduction resulted in growth arrest and apoptosis in Hes5 negative B-ALL cells but not in Hes5 expressing T-ALL cells. These data suggest that epigenetic modifications are implicated in silencing of tumor suppressor of Notch/Hes pathway in B-ALL.

Notch1 signaling is involved in regulating Foxp3 expression in T-ALL

Background

T-cell acute lymphoblastic leukemia (T-ALL) is a highly aggressive hematologic malignancy. Immune tolerance induced by CD4⁺CD25⁺ regulatory T cells (Tregs) with high expression of Foxp3 is an important hypothesis for poor therapy response. Notch1 signaling is thought to be involved in the pathogenesis of this disease. Crosstalk between Notch and Foxp3⁺Tregs induced immune tolerance is unknown in T-ALL. We studied Foxp3 and Notch1 expression in vivo and in vitro, and analyzed the biological characteristics of T-ALL cell line systematically after Notch inhibition and explored the crosstalk between Notch signaling and Foxp3 expression.

Methods

In vivo, we established T-ALL murine model by Jurkat cells transplantation to severe combined immunodeficiency (SCID) mice. Notch1 and Foxp3 expression was detected. In vitro, we used γ-secretase inhibitor N-S-phenyl-glycine-t-butyl ester (DAPT) to block Notch1 signaling in Jurkat cells. Notch1, Hes-1 and Foxp3 genes and protein expression were detected by PCR and western blotting, respectively. The proliferation pattern, cell cycle and viability of Jurkat cells after DAPT treatment were studied. Protein expression of Notch1 target genes including NF-κB, p-ERK1/2 and STAT1 were determined.

Results

We show that engraftment of Jurkat cells in SCID mice occurred in 8 of 10 samples (80%), producing disseminated human neoplastic lymphocytes in PB, bone marrow or infiltrated organs. Notch1 and Foxp3 expression were higher in T-ALL mice than normal mice. In vitro, Jurkat cells expressed Notch1 and more Foxp3 than normal peripheral blood mononuclear cells (PBMCs) in both mRNA and protein levels. Blocking Notch1 signal by DAPT inhibited the proliferation of Jurkat cells and induced G0/G1 phase cell cycle arrest and apoptosis. Foxp3 as well as p-ERK1/2, STAT1 and NF-κB expression was down regulated after DAPT treatment.

Conclusions

These findings indicate that regulation of Foxp3 expression does involve Notch signaling, and they may cooperatively regulate T cell proliferation in T-ALL.

Notch activation inhibits AML growth and survival: a potential therapeutic approach

Activating Notch with a Notch agonist peptide induces apoptosis in AML patient samples.

Although aberrant Notch activation contributes to leukemogenesis in T cells, its role in acute myelogenous leukemia (AML) remains unclear. Here, we report that human AML samples have robust expression of Notch receptors; however, Notch receptor activation and expression of downstream Notch targets are remarkably low, suggesting that Notch is present but not constitutively activated in human AML. The functional role of these Notch receptors in AML is not known. Induced activation through any of the Notch receptors (Notch1–4), or through the Notch target Hairy/Enhancer of Split 1 (HES1), consistently leads to AML growth arrest and caspase-dependent apoptosis, which are associated with B cell lymphoma 2 (BCL2) loss and enhanced p53/p21 expression. These effects were dependent on the HES1 repressor domain and were rescued through reexpression of BCL2. Importantly, activated Notch1, Notch2, and HES1 all led to inhibited AML growth in vivo, and Notch inhibition via dnMAML enhanced proliferation in vivo, thus revealing the physiological inhibition of AML growth in vivo in response to Notch signaling. As a novel therapeutic approach, we used a Notch agonist peptide that led to significant apoptosis in AML patient samples. In conclusion, we report consistent Notch-mediated growth arrest and apoptosis in human AML, and propose the development of Notch agonists as a potential therapeutic approach in AML.

Low SGK1 expression in human adrenocortical tumors is associated with ACTH-independent glucocorticoid secretion and poor prognosis

CONTEXT

Using single-nucleotide polymorphism analysis, we observed allelic loss of the gene for serum glucocorticoid (GC) kinase 1 (SGK1), a GC-responsive kinase involved in multiple cellular functions, in a subset of cortisol-secreting adenomas.

OBJECTIVE

Our objective was to analyze SGK1 expression in adrenocortical tumors and to further characterize its role in ACTH-independent cortisol secretion, tumor progression, and prognosis.

DESIGN AND SETTING

Gene expression levels of SGK1, SGK3, and CTNNB1 (coding for β-catenin) and protein expression levels of SGK1, nuclear β-catenin, and phosphorylated AKT were determined in adrenocortical tumors and normal adrenal glands.

PATIENTS

A total of 227 adrenocortical tumors (40 adenomas and 187 carcinomas) and 25 normal adrenal tissues were included. Among them, 62 frozen tumor samples were used for mRNA analysis and 203 tumors were investigated on tissue microarrays or full standard slides by immunohistochemistry.

MAIN OUTCOME MEASURES

We evaluated the relationship between SGK1 mRNA and/or protein levels and clinical parameters.

RESULTS

SGK1 mRNA levels were lower in cortisol-secreting than in nonsecreting tumors (P < 0.005). Nonsecreting neoplasias showed a significant correlation between SGK1 and CTNNB1 mRNA levels (P < 0.001; r = 0.57). Low SGK1 protein levels, but not nuclear β-catenin and phosphorylated AKT, were associated with poor overall survival in patients with adrenocortical carcinoma (P < 0.005; hazard ratio = 2.0; 95% confidence interval = 1.24-3.24), independent of tumor stage and GC secretion.

CONCLUSION

Low SGK1 expression is related to ACTH-independent cortisol secretion in adrenocortical tumors and is a new prognostic factor in adrenocortical carcinoma.

Notch Signaling during Oogenesis in Drosophila melanogaster

The Notch signaling pathway is an evolutionarily conserved intercellular signaling mechanism that is required for embryonic development, cell fate specification, and stem cell maintenance. Discovered and studied initially in Drosophila melanogaster, the Notch pathway is conserved and functionally active throughout the animal kingdom. In this paper, we summarize the biochemical mechanisms of Notch signaling and describe its role in regulating one particular developmental pathway, oogenesis in Drosophila.

The molecular basis of Notch signaling: a brief overview

The Notch signaling pathway is evolutionarily conserved and has been associated with numerous developmental processes, including stem cell maintenance and adult tissue homeostasis. Notably, both abnormal increases and deficiencies of Notch signaling result in human developmental anomalies and cancer development implying that the precise regulation of the intensity and duration of Notch signals is imperative. Numerous studies have demonstrated that the aberrant gain or loss of Notch signaling pathway components is critically linked to multiple human diseases. In this chapter, we will briefly summarize the molecular basis of Notch signaling, focusing on the modulation of Notch signals, and its developmental outcomes including vessel formation and the onset of cancer.

Structural insights into the mechanism of protein O-fucosylation

Protein O-fucosylation is an essential post-translational modification, involved in the folding of target proteins and in the role of these target proteins during embryonic development and adult tissue homeostasis, among other things. Two different enzymes are responsible for this modification, Protein O-fucosyltransferase 1 and 2 (POFUT1 and POFUT2, respectively). Both proteins have been characterised biologically and enzymatically but nothing is known at the molecular or structural level. Here we describe the first crystal structure of a catalytically functional POFUT1 in an apo-form and in complex with GDP-fucose and GDP. The enzyme belongs to the GT-B family and is not dependent on manganese for activity. GDP-fucose/GDP is localised in a conserved cavity connected to a large solvent exposed pocket, which we show is the binding site of epidermal growth factor (EGF) repeats in the extracellular domain of the Notch Receptor. Through both mutational and kinetic studies we have identified which residues are involved in binding and catalysis and have determined that the Arg240 residue is a key catalytic residue. We also propose a novel S(N)1-like catalytic mechanism with formation of an intimate ion pair, in which the glycosidic bond is cleaved before the nucleophilic attack; and theoretical calculations at a DFT (B3LYP/6-31+G(d,p) support this mechanism. Thus, the crystal structure together with our mutagenesis studies explain the molecular mechanism of POFUT1 and provide a new starting point for the design of functional inhibitors to this critical enzyme in the future.

Insights into intermediate filament regulation from development to ageing

Intermediate filament (IF) proteins comprise a large family with more than 70 members. Initially, IFs were assumed to provide only structural reinforcement for the cell. However, IFs are now known to be dynamic structures that are involved in a wide range of cellular processes during all stages of life, from development to ageing, and during homeostasis and stress. This Commentary discusses some lesser-known functional and regulatory aspects of IFs. We specifically address the emerging roles of nestin in myogenesis and cancer cell migration, and examine exciting evidence on the regulation of nestin and lamin A by the notch signalling pathway, which could have repercussions for our understanding of the roles of IF proteins in development and ageing. In addition, we discuss the modulation of the post-translational modifications of neuronally expressed IFs and their protein-protein interactions, as well as IF glycosylation, which not only has a role in stress and ageing, but might also regulate IFs during development. Although many of these recent findings are still preliminary, they nevertheless open new doors to explore the functionality of the IF family of proteins.

Genistein inhibited proliferation and induced apoptosis in acute lymphoblastic leukemia, lymphoma and multiple myeloma cells in vitro

Genistein is one of the major isoflavones in soy products. It has been reported that genistein has apoptotic effects on certain hematological malignancies. However, so far there have been no completely comparative studies of the effect of genistein on malignant hematological diseases, especially multiple myeloma. We investigated genistein's inhibitory effect on the growth of acute lymphoblastic leukemia (RS4;11 and CEM), lymphoma (Toledo and GA10) and multiple myeloma (OPM-2 and U266) cell lines in vitro. We observed that genistein dose- and time-dependently inhibited proliferation of these cells. The cell line sensitivity to genistein treatment based on the 50% inhibitory concentration (IC(50)) values in decreasing order of toxicity was found to be as follows: RS4;11 (4.89 ± 4.28 μM) > GA10 (13.08 ± 3.49 μM) > Toledo (16.94 ± 3.89 μM) > CEM (17.31 ± 0.72 μM) > OPM-2 (46.76 ± 2.26 μM) > U266 (128.82 ± 1.90 μM). The mechanism of growth inhibition was through induction of apoptosis and cell cycle arrest. The concomitant altered expression of apoptosis pathway proteins and cell cycle modulators (caspases 9, 3, 7, PARP [poly(ADP-ribose) polymerase], cIAP1 [inhibitor of apoptosis protein 1], Bcl-2 and cyclin B1) were observed by Western blot and real-time polymerase chain reaction (PCR) analyses. In addition, some malignancy-related embryologic pathway proteins, e.g. Notch1 and Gli1, were modulated by genistein treatment in sensitive cell lines.

Essential gene pathways for glioblastoma stem cells: clinical implications for prevention of tumor recurrence

Glioblastoma (World Health Organization/WHO grade IV) is the most common and most aggressive adult glial tumor. Patients with glioblastoma, despite being treated with gross total resection and post-operative radiation/chemotherapy, will almost always develop tumor recurrence. Glioblastoma stem cells (GSC), a minor subpopulation within the tumor mass, have been recently characterized as tumor-initiating cells and hypothesized to be responsible for post-treatment recurrence because of their enhanced radio-/chemo-resistant phenotype and ability to reconstitute tumors in mouse brains. Genome-wide expression profile analysis uncovered molecular properties of GSC distinct from their differentiated, proliferative progeny that comprise the majority of the tumor mass. In contrast to the hyperproliferative and hyperangiogenic phenotype of glioblastoma tumors, GSC possess neuroectodermal properties and express genes associated with neural stem cells, radial glial cells, and neural crest cells, as well as portray a migratory, quiescent, and undifferentiated phenotype. Thus, cell cycle-targeted radio-chemotherapy, which aims to kill fast-growing tumor cells, may not completely eliminate glioblastoma tumors. To prevent tumor recurrence, a strategy targeting essential gene pathways of GSC must be identified and incorporated into the standard treatment regimen. Identifying intrinsic and extrinsic cues by which GSC maintain stemness properties and sustain both tumorigenesis and anti-apoptotic features may provide new insights into potentially curative strategies for treating brain cancers.

Notch signaling proteins: legitimate targets for cancer therapy

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

Notch ligand delta-like 4 regulates development and pathogenesis of allergic airway responses by modulating IL-2 production and Th2 immunity

Activation of the canonical Notch pathways has been implicated in Th cell differentiation, but the role of specific Notch ligands in Th2-mediated allergic airway responses has not been completely elucidated. In this study, we show that delta-like ligand 4 (Dll4) was upregulated on dendritic cells in response to cockroach allergen. Blocking Dll4 in vivo during either the primary or secondary response enhanced allergen-induced pathogenic consequences including airway hyperresponsiveness and mucus production via increased Th2 cytokines. In vitro assays demonstrated that Dll4 regulates IL-2 in T cells from established Th2 responses as well as during primary stimulation. Notably, Dll4 blockade during the primary, but not the secondary, response increased IL-2 levels in lung and lymph node of allergic mice. The in vivo neutralization of Dll4 was associated with increased expansion and decreased apoptosis during the primary allergen sensitization. Moreover, Dll4-mediated Notch activation of T cells during primary stimulation in vitro increased apoptosis during the contraction/resting phase of the response, which could be rescued by exogenous IL-2. Consistent with the role for Dll4-mediated IL-2 regulation in overall T cell function, the frequency of IL-4-producing cells was also significantly altered by Dll4 both in vivo and in vitro. These data demonstrate a regulatory role of Dll4 both in initial Th2 differentiation and in Th2 cytokine production in established allergic responses.

Characterization of an atypical gamma-secretase complex from hematopoietic origin

Gamma-secretase is a widely expressed multisubunit enzyme complex which is involved in the pathogenesis of Alzheimer disease and hematopoietic malignancies through its aberrant processing of the amyloid precursor protein (APP) and Notch1, respectively. While gamma-secretase has been extensively studied, there is a dearth of information surrounding the activity, composition, and function of gamma-secretase expressed in distinct cellular populations. Here we show that endogenous gamma-secretase complexes of hematopoietic origin are distinct from epithelial derived gamma-secretase complexes. Hematopoietic gamma-secretase has reduced activity for APP and Notch1 processing compared to epithelial gamma-secretase. Characterization of the active complexes with small molecule affinity probes reveals that hematopoietic gamma-secretase has an atypical subunit composition with significantly altered subunit stoichiometry. Furthermore, we demonstrate that these discrete complexes exhibit cell-line specific substrate selectivity suggesting a possible mechanism of substrate regulation. These data underscore the need for studying endogenous gamma-secretase to fully understand of the biology of gamma-secretase and its complexity as a molecular target for the development of disease therapeutics.

Hematopoietic stem cells and retroviral infection

Retroviral induced malignancies serve as ideal models to help us better understand the molecular mechanisms associated with the initiation and progression of leukemogenesis. Numerous retroviruses including AEV, FLV, M-MuLV and HTLV-1 have the ability to infect hematopoietic stem and progenitor cells, resulting in the deregulation of normal hematopoiesis and the development of leukemia/lymphoma. Research over the last few decades has elucidated similarities between retroviral-induced leukemogenesis, initiated by deregulation of innate hematopoietic stem cell traits, and the cancer stem cell hypothesis. Ongoing research in some of these models may provide a better understanding of the processes of normal hematopoiesis and cancer stem cells. Research on retroviral induced leukemias and lymphomas may identify the molecular events which trigger the initial cellular transformation and subsequent maintenance of hematologic malignancies, including the generation of cancer stem cells. This review focuses on the role of retroviral infection in hematopoietic stem cells and the initiation, maintenance and progression of hematological malignancies.

Myeloid translocation gene 16 (MTG16) interacts with Notch transcription complex components to integrate Notch signaling in hematopoietic cell fate specification

The Notch signaling pathway regulates gene expression programs to influence the specification of cell fate in diverse tissues. In response to ligand binding, the intracellular domain of the Notch receptor is cleaved by the gamma-secretase complex and then translocates to the nucleus. There, it binds the transcriptional repressor CSL, triggering its conversion to an activator of Notch target gene expression. The events that control this conversion are poorly understood. We show that the transcriptional corepressor, MTG16, interacts with both CSL and the intracellular domains of Notch receptors, suggesting a pivotal role in regulation of the Notch transcription complex. The Notch1 intracellular domain disrupts the MTG16-CSL interaction. Ex vivo fate specification in response to Notch signal activation is impaired in Mtg16-/- hematopoietic progenitors, and restored by MTG16 expression. An MTG16 derivative lacking the binding site for the intracellular domain of Notch1 fails to restore Notch-dependent cell fate. These data suggest that MTG16 interfaces with critical components of the Notch transcription complex to affect Notch-dependent lineage allocation in hematopoiesis.

Nutlin-3 up-regulates the expression of Notch1 in both myeloid and lymphoid leukemic cells, as part of a negative feedback antiapoptotic mechanism

The small molecule inhibitor of the MDM2/p53 interaction Nutlin-3 significantly up-regulated the steady-state mRNA and protein levels of Notch1 in TP53wild-type (OCI, SKW6.4) but not in TP53deleted (HL-60) or TP53mutated (BJAB) leukemic cell lines. A direct demonstration that NOTCH1 was a transcriptional target of p53 in leukemic cells was obtained in experiments carried out with siRNA for p53. Moreover, inhibition of Notch1 expression using Notch1-specific siRNA significantly increased cytotoxicity in TP53wild-type leukemic cells. Of note, Nutlin-3 up-regulated Notch1 expression also in primary TP53wild-type B-chronic lymphocytic leukemia (B-CLL) cells and the combined use of Nutlin-3 plus pharmacological γ-secretase inhibitors of the Notch signaling showed a synergistic cytotoxicity in both TP53wild-type leukemic cell lines and primary B-CLL cells. A potential drawback of γ-secretase inhibitors was their ability to enhance osteoclastic maturation of normal circulating preosteoclasts induced by RANKL + M-CSF. Notwithstanding, Nutlin-3 completely suppressed osteoclastogenesis irrespective of the presence of γ-secretase inhibitors. Taken together, these data indicate that the p53-dependent up-regulation of Notch1 in response to Nutlin-3 represents an antiapoptotic feedback mechanism able to restrain the potential therapeutic efficacy of Nutlin-3 in hematologic malignancies. Therefore, therapeutic combinations of Nutlin-3 + γ-secretase inhibitors might potentiate the cytotoxicity of Nutlin-3 in p53wild-type leukemic cells.

A Notch updated

Cell–cell signaling mediated by the Notch receptor is iteratively involved in numerous developmental contexts, and its dysregulation has been associated with inherited genetic disorders and cancers. The core components of the signaling pathway have been identified for some time, but the study of the modulation of the pathway in different cellular contexts has revealed many layers of regulation. These include complex sugar modifications in the extracellular domain as well as transit of Notch through defined cellular compartments, including specific endosomes.

Notch signaling and diseases: an evolutionary journey from a simple beginning to complex outcomes

Notch signaling pathway regulates a wide variety of cellular processes during development and it also plays a crucial role in human diseases. This important link is firmly established in cancer, since a rare T-ALL-associated genetic lesion has been initially reported to result in deletion of Notch1 ectodomain and constitutive activation of its intracellular region. Interestingly, the cellular response to Notch signaling can be extremely variable depending on the cell type and activation context. Notch signaling triggers signals implicated in promoting carcinogenesis and autoimmune diseases, whereas it can also sustain responses that are critical to suppress carcinogenesis and to negatively regulate immune response. However, Notch signaling induces all these effects via an apparently simple signal transduction pathway, diversified into a complex network along evolution from Drosophila to mammals. Indeed, an explanation of this paradox comes from a number of evidences accumulated during the last few years, which dissected the intrinsic canonical and non-canonical components of the Notch pathway as well as several modulatory extrinsic signaling events. The identification of these signals has shed light onto the mechanisms whereby Notch and other pathways collaborate to induce a particular cellular phenotype. In this article, we review the role of Notch signaling in cells as diverse as T lymphocytes and epithelial cells of the epidermis, with the main focus on understanding the mechanisms of Notch versatility.