Gliotoxin is a potent NOTCH2 transactivation inhibitor and efficiently induces apoptosis in chronic lymphocytic leukaemia (CLL) cells

Mechanisms underlying linear ubiquitination and implications in tumorigenesis and drug discovery

Linear ubiquitination is a distinct type of ubiquitination that involves attaching a head-to-tail polyubiquitin chain to a substrate protein. Early studies found that linear ubiquitin chains are essential for the TNFα- and IL-1-mediated NF-κB signaling pathways. However, recent studies have discovered at least sixteen linear ubiquitination substrates, which exhibit a broader activity than expected and mediate many other signaling pathways beyond NF-κB signaling. Dysregulation of linear ubiquitination in these pathways has been linked to many types of cancers, such as lymphoma, liver cancer, and breast cancer. Since the discovery of linear ubiquitin, extensive effort has been made to delineate the molecular mechanisms of how dysregulation of linear ubiquitination causes tumorigenesis and cancer development. In this review, we highlight newly discovered linear ubiquitination-mediated signaling pathways, recent advances in the role of linear ubiquitin in different types of cancers, and the development of linear ubiquitin inhibitors. Video Abstract.

NOTCH Signaling in Mantle Cell Lymphoma: Biological and Clinical Implications

Despite major progress in mantle cell lymphoma (MCL) therapeutics, MCL remains a deadly disease with a median survival not exceeding four years. No single driver genetic lesion has been described to solely give rise to MCL. The hallmark translocation t(11;14)(q13;q32) requires additional genetic alterations for the malignant transformation. A short list of recurrently mutated genes including ATM, CCND1, UBR5, TP53, BIRC3, NOTCH1, NOTCH2, and TRAF2 recently emerged as contributors to the pathogenesis of MCL. Notably, NOTCH1 and NOTCH2 were found to be mutated in multiple B cell lymphomas, including 5-10% of MCL, with most of these mutations occurring within the PEST domain of the protein. The NOTCH genes play a critical role in the early and late phases of normal B cell differentiation. In MCL, mutations in the PEST domain stabilize NOTCH proteins, rendering them resistant to degradation, which subsequently results in the upregulation of genes involved in angiogenesis, cell cycle progression, and cell migration and adhesion. At the clinical level, mutated NOTCH genes are associated with aggressive features in MCL, such as the blastoid and pleomorphic variants, a shorter response to treatment, and inferior survival. In this article, we explore in detail the role of NOTCH signaling in MCL biology and the ongoing efforts toward targeted therapeutic interventions.

Natural epidithiodiketopiperazine alkaloids as potential anticancer agents: Recent mechanisms of action, structural modification, and synthetic strategies

Cancer has become a grave health crisis that threatens the lives of millions of people worldwide. Because of the drawbacks of the available anticancer drugs, the development of novel and efficient anticancer agents should be encouraged. Epidithiodiketopiperazine (ETP) alkaloids with a 2,5-diketopiperazine (DKP) ring equipped with transannular disulfide or polysulfide bridges or S-methyl moieties constitute a special subclass of fungal natural products. Owing to their privileged sulfur units and intriguing architectural structures, ETP alkaloids exhibit excellent anticancer activities by regulating multiple cancer proteins/signaling pathways, including HIF-1, NF-κB, NOTCH, Wnt, and PI3K/AKT/mTOR, or by inducing cell-cycle arrest, apoptosis, and autophagy. Furthermore, a series of ETP alkaloid derivatives obtained via structural modification showed more potent anticancer activity than natural ETP alkaloids. To solve supply difficulties from natural resources, the total synthetic routes for several ETP alkaloids have been designed. In this review, we summarized several ETP alkaloids with anticancer properties with particular emphasis on their underlying mechanisms of action, structural modifications, and synthetic strategies, which will offer guidance to design and innovate potential anticancer drugs.

The Intricate Notch Signaling Dynamics in Therapeutic Realms of Cancer

The Notch pathway is remarkably simple without the interventions of secondary messengers. It possesses a unique receptor-ligand interaction that imparts signaling upon cleavage of the receptor followed by the nuclear localization of its cleaved intracellular domain. It is found that the transcriptional regulator of the Notch pathway lies at the intersection of multiple signaling pathways that enhance the aggressiveness of cancer. The preclinical and clinical evidence supports the pro-oncogenic function of Notch signaling in various tumor subtypes. Owing to its oncogenic role, the Notch signaling pathway assists in enhanced tumorigenesis by facilitating angiogenesis, drug resistance, epithelial to mesenchymal transition, etc., which is also attributed to the poor outcome in patients. Therefore, it is extremely vital to discover a suitable inhibitor to downregulate the signal-transducing ability of Notch. The Notch inhibitory agents, such as receptor decoys, protease (ADAM and γ-secretase) inhibitors, and monoclonal/bispecific antibodies, are being investigated as candidate therapeutic agents. Studies conducted by our group exemplify the promising results in ablating tumorigenic aggressiveness by inhibiting the constituents of the Notch pathway. This review deals with the detailed mechanism of the Notch pathways and their implications in various malignancies. It also bestows us with the recent therapeutic advances concerning Notch signaling in the context of monotherapy and combination therapy.

Role of Notch2 pathway in mature B cell malignancies

In recent decades, the Notch pathway has been characterized as a key regulatory signaling of cell-fate decisions evolutionarily conserved in many organisms and different tissues during lifespan. At the same time, many studies suggest a link between alterations of this signaling and tumor genesis or progression. In lymphopoiesis, the Notch pathway plays a fundamental role in the correct differentiation of T and B cells, but its deregulated activity leads to leukemic onset and evolution. Notch and its ligands Delta/Jagged exhibit a pivotal role in the crosstalk between leukemic cells and their environment. This review is focused in particular on Notch2 receptor activity. Members of Notch2 pathway have been reported to be mutated in Chronic Lymphocytic Leukemia (CLL), Splenic Marginal Zone Lymphoma (SMZL) and Nodal Marginal Zone Lymphoma (NMZL). CLL is a B cell malignancy in which leukemic clones establish supportive crosstalk with non-malignant cells of the tumor microenvironment to grow, survive, and resist even the new generation of drugs. SMZL and NMZL are indolent B cell neoplasms distinguished by a distinct pattern of dissemination. In SMZL leukemic cells affect mainly the spleen, bone marrow, and peripheral blood, while NMZL has a leading nodal distribution. Since Notch2 is involved in the commitment of leukemic cells to the marginal zone as a major regulator of B cell physiological differentiation, it is predominantly affected by the molecular lesions found in both SMZL and NMZL. In light of these findings, a better understanding of the Notch receptor family pathogenic role, in particular Notch2, is desirable because it is still incomplete, not only in the physiological development of B lymphocytes but also in leukemia progression and resistance. Several therapeutic strategies capable of interfering with Notch signaling, such as monoclonal antibodies, enzyme or complex inhibitors, are being analyzed. To avoid the unwanted multiple "on target" toxicity encountered during the systemic inhibition of Notch signaling, the study of an appropriate pharmaceutical formulation is a pressing need. This is why, to date, there are still no Notch-targeted therapies approved. An accurate analysis of the Notch pathway could be useful to drive the discovery of new therapeutic targets and the development of more effective therapies.

Establishment and characterization of a new mantle cell lymphoma cell line with a NOTCH2 mutation, Arbo

Cell lines represent an essential tool used in preclinical research. Most hematologic malignancies have a wide array of cell lines representing their respective molecular and pathologic spectra. In mantle cell lymphoma (MCL), cell lines become specifically valuable in view of the heterogeneity of this disease. Unfortunately, the number of MCL cell lines that are available for the research community remains small, with only nine cell lines available for purchase through the American Type Culture Collection (ATCC). We have established a novel blastoid MCL cell line, isolated from the malignant pleural effusion of a 69-year-old male with refractory MCL. Arbo was fully characterized with cytogenetics, immunophenotyping, whole exome sequencing and drug sensitivity assays. One of the most notable mutations identified in Arbo (but not in normal tissue) was the missense mutation NOTCH2 R2400*, which has been proposed as a clinically significant mutation in MCL seen in 5% of cases. NOTCH2 R2400* results in a truncated Notch2 protein, leading to a more stable and active protein. Using pharmacologic inhibition of Notch2, we showed a dependence of Arbo on NOTCH2 signaling, as well as a link between CD23 expression on Arbo and NOTCH2 activity. Arbo represents a NOTCH2 mutated model that is useful in MCL as well as other lymphomas with such mutation. We plan to deposit Arbo at the ATCC to be available for the research community.

Cancer metabolism control by natural products: Pyruvate kinase M2 targeting therapeutics

Glycolysis is the primary source of energy for cancer growth and metastasis. The shift in metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis is called the Warburg effect. Cancer progression due to aerobic glycolysis is often associated with the activation of oncogenes or the loss of tumor suppressors. Therefore, inhibition of glycolysis is one of the effective strategies in cancer control. Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme overexpressed in breast, prostate, lung, colorectal, and liver cancers. Here, we discuss published studies regarding PKM2 inhibitors from natural products that are promising drug candidates for cancer therapy. We have highlighted the potential of natural PKM2 inhibitors for various cancer types. Moreover, we encourage researchers to evaluate the combinational effects between natural and synthetic PKM2 inhibitors. Also, further high-quality studies are needed to firmly establish the clinical efficacy of natural products.

RNF144B stimulates the proliferation and inhibits the apoptosis of human spermatogonial stem cells via the FCER2/NOTCH2/HES1 pathway and its abnormality is associated with azoospermia

Studies on gene regulation and signaling transduction pathways of human spermatogonial stem cells (SSCs) are of the utmost significance for unveiling molecular mechanisms underlying human spermatogenesis and gene therapy of male infertility. We have demonstrated, for the first time, that RNF144B stimulated cell proliferation and inhibited the apoptosis of human SSCs. The target of RNF144B was identified as FCER2 by RNA sequencing. We revealed that RNF144B interacted with FCER2 by immunoprecipitation. Consistently, overexpression of FCER2 reversed the phenotype of proliferation and apoptosis of human SSCs caused by RNF144B knockdown. Interestingly, FCER2 pulled down N2ICD (NOTCH2 intracellular domain), while N2ICD could bind to FCER2 in human SSCs. The levels of NOTCH2, FCER2, HES1, and HEY1 were reduced by RNF144B siRNA in human SSCs. Significantly, RNF144B was expressed at a lower level in nonobstructive azoospermia (NOA) patients than in the obstructive azoospermia (OA) patients with normal spermatogenesis, and 52 patients with heterozygous mutations of RNF144B were detected in 1,000 NOA patients. These results implicate that RNF144B promotes the proliferation of human SSCs and suppresses their apoptosis via the FCER2/NOTCH2/HES1 pathway and that the abnormality of RNF144B is associated with spermatogenesis failure. This study thus provides novel molecular mechanisms regulating the fate determinations of human SSCs, and it offers new biomarkers for the diagnosis and treatment of male infertility.

Notch2 Increases the Resistance to Venetoclax-Induced Apoptosis in Chronic Lymphocytic Leukemia B Cells by Inducing Mcl-1

Chronic lymphocytic leukemia (CLL) has experienced a clinical revolution—thanks to the discovery of crucial pathogenic mechanisms. CLL is still an incurable disease due to intrinsic or acquired resistance of the leukemic clone. Venetoclax is a Bcl-2 inhibitor with a marked activity in CLL, but emerging patterns of resistance are being described. We hypothesize that intrinsic features of CLL cells may contribute to drive mechanisms of resistance to venetoclax. We analyzed the expression of Interferon Regulatory Factor 4 (IRF4), Notch2, and Mcl-1 in a cohort of CLL patients. We evaluated CLL cell viability after genetic and pharmaceutical modulation of Notch2 expression in patients harboring trisomy 12. We tested venetoclax in trisomy 12 CLL cells either silenced or not for Notch2 expression or in combination with an inhibitor of Mcl-1, AMG-176. Trisomy 12 CLL cells were characterized by low expression of IRF4 associated with high levels of Notch2 and Mcl-1. Notch2 and Mcl-1 expression determined protection of CLL cells from spontaneous and drug-induced apoptosis. Considering the involvement of Mcl-1 in venetoclax resistance, our data demonstrated a contribution of high levels of Notch2 and Mcl-1 in a reduced response to venetoclax in CLL cells carrying trisomy 12. Furthermore, reduction of Mcl-1 expression by silencing Notch2 or by treatment with AMG-176 was able to restore the response of CLL cells to venetoclax. The expression of Notch2 identifies a subset of CLL patients, mainly harboring trisomy 12, characterized by high levels of Mcl-1. This biological mechanism may compromise an effective response to venetoclax.

Could Candida Overgrowth Be Involved in the Pathophysiology of Autism?

The purpose of this review is to summarize the current acquiredknowledge of Candida overgrowth in the intestine as a possible etiology of autism spectrum disorder (ASD). The influence of Candida sp. on the immune system, brain, and behavior of children with ASD isdescribed. The benefits of interventions such as a carbohydrates-exclusion diet, probiotic supplementation, antifungal agents, fecal microbiota transplantation (FMT), and microbiota transfer therapy (MTT) will be also discussed. Our literature query showed that the results of most studies do not fully support the hypothesis that Candida overgrowth is correlated with gastrointestinal (GI) problems and contributes to autism behavioral symptoms occurrence. On the one hand, it was reported that the modulation of microbiota composition in the gut may decrease Candida overgrowth, help reduce GI problems and autism symptoms. On the other hand, studies on humans suggesting the beneficial effects of a sugar-free diet, probiotic supplementation, FMT and MTT treatment in ASD are limited and inconclusive. Due to the increasing prevalence of ASD, studies on the etiology of this disorder are extremely needed and valuable. However, to elucidate the possible involvement of Candida in the pathophysiology of ASD, more reliable and well-designed research is certainly required.

NOTCH signaling in the pathogenesis of splenic marginal zone lymphoma-opportunities for therapy

NOTCH signaling is a highly conserved pathway mediated by four receptors (NOTCH 1-4) playing critical functions in proliferation, differentiation, and cell death. Under physiologic circumstances, NOTCH2 is a key regulator in marginal zone differentiation and development. Over the last decade, growing data demonstrated frequent NOTCH2 mutations in splenic marginal zone lymphoma (SMZL) underscoring its critical role in the pathogenesis of this disease. Moreover, NOTCH2 specificity across studies supports the rationale to assess its value as a diagnosis biomarker in a disease without pathognomonic features. These data make NOTCH signaling an appealing target for drug discovery in SMZL; however, prior efforts attempting to manipulate this pathway failed to demonstrate meaningful clinical benefit, or their safety profile prevented further development. In this review, we discuss the current knowledge of NOTCH implications in the pathogenesis and as a potential druggable target in SMZL.

Notch Signaling in the Bone Marrow Lymphopoietic Niche

Lifelong mammalian hematopoiesis requires continuous generation of mature blood cells that originate from Hematopoietic Stem and Progenitor Cells (HSPCs) situated in the post-natal Bone Marrow (BM). The BM microenvironment is inherently complex and extensive studies have been devoted to identifying the niche that maintains HSPC homeostasis and supports hematopoietic potential. The Notch signaling pathway is required for the emergence of the definitive Hematopoietic Stem Cell (HSC) during embryonic development, but its role in BM HSC homeostasis is convoluted. Recent work has begun to explore novel roles for the Notch signaling pathway in downstream progenitor populations. In this review, we will focus an important role for Notch signaling in the establishment of a T cell primed sub-population of Common Lymphoid Progenitors (CLPs). Given that its activation mechanism relies primarily on cell-to-cell contact, Notch signaling is an ideal means to investigate and define a novel BM lymphopoietic niche. We will discuss how new genetic model systems indicate a pre-thymic, BM-specific role for Notch activation in early T cell development and what this means to the paradigm of lymphoid lineage commitment. Lastly, we will examine how leukemic T-cell acute lymphoblastic leukemia (T-ALL) blasts take advantage of Notch and downstream lymphoid signals in the pathological BM niche.

Anticancer Potential of Compounds from the Brazilian Blue Amazon

"Blue Amazon" is used to designate the Brazilian Economic Exclusive Zone, which covers an area comparable in size to that of its green counterpart. Indeed, Brazil flaunts a coastline spanning 8000 km through tropical and temperate regions and hosting part of the organisms accredited for the country's megadiversity status. Still, biodiversity may be expressed at different scales of organization; besides species inventory, genetic characteristics of living beings and metabolic expression of their genes meet some of these other layers. These metabolites produced by terrestrial creatures traditionally and lately added to by those from marine organisms are recognized for their pharmaceutical value, since over 50% of small molecule-based medicines are related to natural products. Nonetheless, Brazil gives a modest contribution to the field of pharmacology and even less when considering marine pharmacology, which still lacks comprehensive in-depth assessments toward the bioactivity of marine compounds so far. Therefore, this review examined the last 40 years of Brazilian natural products research, focusing on molecules that evidenced anticancer potential-which represents ~ 15% of marine natural products isolated from Brazilian species. This review discusses the most promising compounds isolated from sponges, cnidarians, ascidians, and microbes in terms of their molecular targets and mechanisms of action. Wrapping up, the review delivers an outlook on the challenges that stand against developing groundbreaking natural products research in Brazil and on a means of surpassing these matters.

Role of Notch Receptors in Hematologic Malignancies

Notch receptors are single-pass transmembrane proteins that play a critical role in cell fate decisions and have been implicated in the regulation of many developmental processes. The human Notch family comprises of four receptors (Notch 1 to 4) and five ligands. Their signaling can regulate extremely basic cellular processes such as differentiation, proliferation and death. Notch is also involved in hematopoiesis and angiogenesis, and increasing evidence suggests that these genes are involved and frequently deregulated in several human malignancies, contributing to cell autonomous activities that may be either oncogenic or tumor suppressive. It was recently proposed that Notch signaling could play an active role in promoting and sustaining a broad spectrum of lymphoid malignancies as well as mutations in Notch family members that are present in several disorders of T- and B-cells, which could be responsible for altering the related signaling. Therefore, different Notch pathway molecules could be considered as potential therapeutic targets for hematological cancers. In this review, we will summarize and discuss compelling evidence pointing to Notch receptors as pleiotropic regulators of hematologic malignancies biology, first describing the physiological role of their signaling in T- and B-cell development and homeostasis, in order to fully understand the pathological alterations reported.

A brief overview of clinical significance of novel Notch2 regulators

The Notch pathway is an essential signaling system allowing neighboring cells to communicate and accomplish their proper developmental role in physiological condition. Nevertheless, there are many controversies conferring its function in pathological condition, particularly in cancer. It has been discovered that epigenetic regulation, posttranslational modifications, gene overexpression, and mutations may lead to the dysregulation of the Notch pathway. Additionally, Notch-mediated signaling can support tumor-suppressing mechanisms in certain types of cancer or may have oncogenic functions in others. Notch2 is one of the receptors commonly expressed in a variety of cancer cells, including gastric, hematological, and lung cancer. Moreover, it can be dysregulated in other diseases. In efforts to explain the role of Notch2 in the pathogenesis of cancer, recent studies indicated an association between this receptor and dysregulation of miRNAs, tumor-associated stromal cell, and modulation in tumor cells. Consequently, Notch2 function in the carcinogenesis process is unquestionable, whereas information according to the effect of its inhibition in tumor is still obscure. Hence, the aim of our study was to evaluate the current state of knowledge conferring Notch2 inhibition, with a particular focus on its role in cancer.

Targeting Nuclear NOTCH2 by Gliotoxin Recovers a Tumor-Suppressor NOTCH3 Activity in CLL

NOTCH signaling represents a promising therapeutic target in chronic lymphocytic leukemia (CLL). We compared the anti-neoplastic effects of the nuclear NOTCH2 inhibitor gliotoxin and the pan-NOTCH γ-secretase inhibitor RO4929097 in primary CLL cells with special emphasis on the individual roles of the different NOTCH receptors. Gliotoxin rapidly induced apoptosis in all CLL cases tested, whereas RO4929097 exerted a variable and delayed effect on CLL cell viability. Gliotoxin-induced apoptosis was associated with inhibition of the NOTCH2/FCER2 (CD23) axis together with concomitant upregulation of the NOTCH3/NR4A1 axis. In contrast, RO4929097 downregulated the NOTCH3/NR4A1 axis and counteracted the spontaneous and gliotoxin-induced apoptosis. On the cell surface, NOTCH3 and CD23 expression were mutually exclusive, suggesting that downregulation of NOTCH2 signaling is a prerequisite for NOTCH3 expression in CLL cells. ATAC-seq confirmed that gliotoxin targeted the canonical NOTCH signaling, as indicated by the loss of chromatin accessibility at the potential NOTCH/CSL site containing the gene regulatory elements. This was accompanied by a gain in accessibility at the NR4A1, NFκB, and ATF3 motifs close to the genes involved in B-cell activation, differentiation, and apoptosis. In summary, these data show that gliotoxin recovers a non-canonical tumor-suppressing NOTCH3 activity, indicating that nuclear NOTCH2 inhibitors might be beneficial compared to pan-NOTCH inhibitors in the treatment of CLL.

The cellular and molecular toxicity of sporidesmin

The fungal metabolite sporidesmin is responsible for the hepatogenous photosensitising disease facial eczema in livestock. Toxicity is due to a sulfur-bridged epidithiodioxopiperazine ring that has wide biological reactivity. The ways in which the toxin causes hepatobiliary and other tissue damage have not been established. Hypotheses include direct interaction with cellular thiols including protein cysteine residues or production of reactive oxygen species resulting in oxidative stress. Comparison with the cellular effects of the structurally related compound gliotoxin suggests additional mechanisms including interaction with cell adhesion complexes and possible downstream consequences for regulated necrosis as a response to tissue injury. Revision of hypotheses of how sporidesmin affects cells has the potential to generate new strategies for control of facial eczema including through identification of proteins and genes that are associated with resistance to the disease.

Interaction of a Novel Zn2Cys6 Transcription Factor DcGliZ with Promoters in the Gliotoxin Biosynthetic Gene Cluster of the Deep-Sea-Derived Fungus Dichotomomyces cejpii

Gliotoxin is an important epipolythiodioxopiperazine, which was biosynthesized by the gli gene cluster in Aspergillus genus. However, the regulatory mechanism of gliotoxin biosynthesis remains unclear. In this study, a novel Zn2Cys6 transcription factor DcGliZ that is responsible for the regulation of gliotoxin biosynthesis from the deep-sea-derived fungus Dichotomomyces cejpii was identified. DcGliZ was expressed in Escherichia coli and effectively purified from inclusion bodies by refolding. Using electrophoretic mobility shift assay, we demonstrated that purified DcGliZ can bind to gliG, gliM, and gliN promoter regions in the gli cluster. Furthermore, the binding kinetics and affinity of DcGliZ protein with different promoters were measured by surface plasmon resonance assays, and the results demonstrated the significant interaction of DcGliZ with the gliG, gliM, and gliN promoters. These new findings would lay the foundation for the elucidation of future gliotoxin biosynthetic regulation mechanisms in D. cejpii.

Dysbiotic microbiota in autistic children and their mothers: persistence of fungal and bacterial wall-deficient L-form variants in blood

Based on our hypothesis for existing microbiota of wall-deficient variants (L-forms) in human blood, we created an innovative methodology, which allowed for the development of L-form populations from blood of all investigated people. In contrast to healthy controls, blood L-forms from autistic children and their mothers converted under appropriate conditions of cultivation into detectable opportunistic bacteria and fungi, а process demonstrated by light and transmission electron microscopy. It can be distinguished into two types of states – “eubiotic” blood microbiota in healthy individuals, and “dysbiotic” in autistic children and their mothers. Remarkably, the unifying finding for autistic children and their mothers was the presence in blood of wall-free variants from life-cycle of filamentous fungi. Increased specific IgG, IgM and IgA, together with typical mold growth were a decisive argument for proven presence of Aspergillus fumigatus in almost all of the autistic children. As it was demonstrated in our previous study, filterable L-forms can be transmitted by vertical pathway from mother to child before birth. Thus, it can be suggested that autistic children may be born already colonized with fungi, while a “silent aspergillosis” could contribute or even be a leading cause for neurodevelopmental disorders in the early childhood.

Gliotoxin Enhances Autophagic Cell Death via the DAPK1-TAp63 Signaling Pathway in Paclitaxel-Resistant Ovarian Cancer Cells

Death-associated protein kinase 1 (DAPK1) expression induced by diverse death stimuli mediates apoptotic activity in various cancers, including ovarian cancer. In addition, mutual interaction between the tumor suppressor p53 and DAPK1 influences survival and death in several cancer cell lines. However, the exact role and connection of DAPK1 and p53 family proteins (p53, p63, and p73) in drug-resistant ovarian cancer cells have not been studied previously. In this study, we investigated whether DAPK1 induction by gliotoxin derived from marine fungus regulates the level of transcriptionally active p63 (TAp63) to promote apoptosis in an autophagy-dependent manner. Pre-exposure of paclitaxel-resistant ovarian cancer cells to gliotoxin inhibited the expression of multidrug resistant-associated proteins (MDR1 and MRP1-3), disrupted the mitochondrial membrane potential, and induced caspase-dependent apoptosis through autophagy induction after subsequent treatment with paclitaxel. Gene silencing of DAPK1 prevented TAp63-mediated downregulation of MDR1 and MRP1-3 and autophagic cell death after sequential treatment with gliotoxin and then paclitaxel. However, pretreatment with 3-methyladenine (3-MA), an autophagy inhibitor, had no effect on the levels of DAPK1 and TAp63 or on the inhibition of MDR1 and MRP1-3. These results suggest that DAPK1-mediated TAp63 upregulation is one of the critical pathways that induce apoptosis in chemoresistant cancer cells.

Integrated genetic, epigenetic, and gene set enrichment analyses identify NOTCH as a potential mediator for PTSD risk after trauma: Results from two independent African cohorts

The risk of developing posttraumatic stress disorder (PTSD) increases with the number of traumatic event types experienced (trauma load) in interaction with other psychobiological risk factors. The NOTCH (neurogenic locus notch homolog proteins) signaling pathway, consisting of four different trans‐membrane receptor proteins (NOTCH1–4), constitutes an evolutionarily well‐conserved intercellular communication pathway (involved, e.g., in cell–cell interaction, inflammatory signaling, and learning processes). Its association with fear memory consolidation makes it an interesting candidate for PTSD research. We tested for significant associations of common genetic variants of NOTCH1–4 (investigated by microarray) and genomic methylation of saliva‐derived DNA with lifetime PTSD risk in independent cohorts from Northern Uganda (N₁ = 924) and Rwanda (N₂ = 371), and investigated whether NOTCH‐related gene sets were enriched for associations with lifetime PTSD risk. We found associations of lifetime PTSD risk with single nucleotide polymorphism (SNP) rs2074621 (NOTCH3) (p_uncorrected = 0.04) in both cohorts, and with methylation of CpG site cg17519949 (NOTCH3) (p_uncorrected = 0.05) in Rwandans. Yet, none of the (epi‐)genetic associations survived multiple testing correction. Gene set enrichment analyses revealed enrichment for associations of two NOTCH pathways with lifetime PTSD risk in Ugandans: NOTCH binding (p_corrected = 0.003) and NOTCH receptor processing (p_corrected = 0.01). The environmental factor trauma load was significant in all analyses (all p < 0.001). Our integrated methodological approach suggests NOTCH as a possible mediator of PTSD risk after trauma. The results require replication, and the precise underlying pathophysiological mechanisms should be illuminated in future studies.

Integrating genetic, epigenetic, and gene set enrichment analyses, while accounting for the environmental factor traumatic load, we identified stress‐ and memory‐associated neurogenic locus notch homolog protein (NOTCH) genes and related gene sets as potential risk mediators for the development of posttraumatic stress disorder (PTSD) after trauma. Thus, our results strengthen the presumed role of memory‐ and inflammation‐associated genes in PTSD development, and revealed a promising target for future treatment studies. Furthermore, we demonstrated the importance of traumatic load in PTSD etiology, and of an integrated approach in order to obtain a more comprehensive understanding of the functionality of PTSD‐associated markers.

Reactive oxygen species in haematopoiesis: leukaemic cells take a walk on the wild side

Oxidative stress is related to ageing and degenerative diseases, including cancer. However, a moderate amount of reactive oxygen species (ROS) is required for the regulation of cellular signalling and gene expression. A low level of ROS is important for maintaining quiescence and the differentiation potential of haematopoietic stem cells (HSCs), whereas the level of ROS increases during haematopoietic differentiation; thus, suggesting the importance of redox signalling in haematopoiesis. Here, we will analyse the importance of ROS for haematopoiesis and include evidence showing that cells from leukaemia patients live under oxidative stress. The potential sources of ROS will be described. Finally, the level of oxidative stress in leukaemic cells can also be harnessed for therapeutic purposes. In this regard, the reliance of front-line anti-leukaemia chemotherapeutics on increased levels of ROS for their mechanism of action, as well as the active search for novel compounds that modulate the redox state of leukaemic cells, will be analysed.

Effects of the Combination of Gliotoxin and Adriamycin on the Adriamycin-Resistant Non-Small-Cell Lung Cancer A549 Cell Line

Acquired drug resistance constitutes an enormous hurdle in cancer treatment, and the search for effective compounds against resistant cancer is still advancing. Marine organisms are a promising natural resource for the discovery and development of anticancer agents. In this study, we examined whether gliotoxin (GTX), a secondary metabolite isolated from marine-derived Aspergillus fumigatus, inhibits the growth of adriamycin (ADR)-resistant non-small-cell lung cancer (NSCLC) cell lines A549/ADR. We investigated the effects of GTX on A549/ADR cell viability with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the induction of apoptosis in A549/ADR cells treated with GTX via fluorescence-activated cell sorting analysis, Hoechst staining, annexin V/propidium iodide staining, tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining, and western blotting. We found that GTX induced apoptosis in A549/ADR cells through the mitochondria-dependent pathway by disrupting mitochondrial membrane potential and activating p53, thereby increasing the expression levels of p21, p53 upregulated modulator of apoptosis (PUMA), Bax, cleaved poly (ADP-ribose) polymerase (PARP), and cleaved caspase-9. More importantly, we discovered that GTX works in conjunction with ADR to exert combinational effects on A549/ADR cells. In conclusion, our results suggest that GTX may have promising effects on ADR-resistant NSCLC cells by inducing mitochondria-dependent apoptosis and through the combined effects of sequential treatment with ADR.

Reduced-gliotoxin induces ROS-mediated anoikis in human colorectal cancer cells

Reduced-gliotoxin is a small molecule derived from the secondary metabolites of marine fungi; compared to other gliotoxin analogues, it exhibits potent anticancer effects. However, the molecular basis of the death of colorectal cancer (CRC) cells induced by reduced-gliotoxin is unclear. Thus, the aim of this study was to investigate the potency of reduced-gliotoxin against CRC cells and to elucidate the underlying mechanisms. Cell morphology, flow cytometric analysis and western bolt analysis were performed to examine the functions and mechanisms of cell death induced by reduced-gliotoxin. Our findings demonstrated that reduced-gliotoxin triggered rapid cell detachment and induced anoikis in CRC cells. Mechanistically, our data indicated that the anoikis induced by reduced-gliotoxin was associated with the disruption of integrin-associated cell detachment and multiple signaling pathways. Furthermore, reduced-gliotoxin induced the excessive production of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP), resulting in the activation of both endogenous and exogenous apoptotic pathways and eventually, in the apoptosis of CRC cells. The blockage of ROS generation with N-acetylcysteine (NAC) attenuated the anoikis induced by reduced-gliotoxin. Taken together, these results suggest that reduced-gliotoxin may prove to be a potential candidate in the treatment of CRC.

The Notch-3 receptor: A molecular switch to tumorigenesis?

The Notch pathway is a highly conserved pathway increasingly implicated with the progression of human cancers. Of the four existing receptors associated with the pathway, the deregulation in the expression of the Notch-3 receptor is associated with more aggressive disease and poor prognosis. Selective targeting of this receptor has the potential to enhance current anti-cancer treatments. Molecular profiling strategies are increasingly incorporated into clinical decision making. This review aims to evaluate the clinical potential of Notch-3 within this new era of personalised medicine.

Gliotoxin Targets Nuclear NOTCH2 in Human Solid Tumor Derived Cell Lines In Vitro and Inhibits Melanoma Growth in Xenograft Mouse Model

Deregulation of NOTCH2 signaling is implicated in a wide variety of human neoplasias. The current concept of targeting NOTCH is based on using gamma secretase inhibitors (GSI) to regulate the release of the active NOTCH intracellular domain. However, the clinical outcome of GSI remains unsatisfactory. Therefore we analyzed human solid tumor derived cell lines for their nuclear NOTCH activity and evaluated the therapeutic potential of the NOTCH2 transactivation inhibitor gliotoxin in comparison to the representative GSI DAPT. Electrophoretic mobility shift assays (EMSA) were used as a surrogate method for the detection of NOTCH/CSL transcription factor complexes. The effect of gliotoxin on cell viability and its clinical relevance was evaluated in vitro and in a melanoma xenograft mouse model. Cell lines derived from melanoma (518A2), hepatocellular carcinoma (SNU398, HCC-3, Hep3B), and pancreas carcinoma (PANC1) express high amounts of nuclear NOTCH2. Gliotoxin efficiently induced apoptosis in these cell lines whereas the GSI DAPT was ineffective. The specificity of gliotoxin was demonstrated in the well differentiated nuclear NOTCH negative cell line Huh7, which was resistant to gliotoxin treatment in vitro. In xenotransplanted 518A2 melanomas, a single day dosing schedule of gliotoxin was well tolerated without any study limiting side effects. Gliotoxin significantly reduced the tumor volume in early (83 mm³ vs. 115 mm³, p = 0.008) as well as in late stage (218 mm³ vs. 576 mm³, p = 0.005) tumor models. In conclusion, NOTCH2 appears to be a key target of gliotoxin in human neoplasias and gliotoxin deserves further evaluation as a potential therapeutic agent in cancer management.

Gliotoxin Inhibits Proliferation and Induces Apoptosis in Colorectal Cancer Cells

The discovery of new bioactive compounds from marine natural sources is very important in pharmacological research. Here we developed a Wnt responsive luciferase reporter assay to screen small molecule inhibitors of cancer associated constitutive Wnt signaling pathway. We identified that gliotoxin (GTX) and some of its analogues, the secondary metabolites from marine fungus Neosartorya pseufofischeri, acted as inhibitors of the Wnt signaling pathway. In addition, we found that GTX downregulated the β-catenin levels in colorectal cancer cells with inactivating mutations of adenomatous polyposis coli (APC) or activating mutations of β-catenin. Furthermore, we demonstrated that GTX induced growth inhibition and apoptosis in multiple colorectal cancer cell lines with mutations of the Wnt signaling pathway. Together, we illustrated a practical approach to identify small-molecule inhibitors of the Wnt signaling pathway and our study indicated that GTX has therapeutic potential for the prevention or treatment of Wnt dependent cancers and other Wnt related diseases.

Cross talk between EBV and telomerase: the role of TERT and NOTCH2 in the switch of latent/lytic cycle of the virus

Epstein–Barr virus (EBV)-associated malignancies, as well as lymphoblastoid cell lines (LCLs), obtained in vitro by EBV infection of B cells, express latent viral proteins and maintain their ability to grow indefinitely through inappropriate activation of telomere-specific reverse transcriptase (TERT), the catalytic component of telomerase. Our previous studies demonstrated that high levels of TERT expression in LCLs prevent the activation of EBV lytic cycle, which is instead triggered by TERT silencing. As lytic infection promotes the death of EBV-positive tumor cells, understanding the mechanism(s) by which TERT affects the latent/lytic status of EBV may be important for setting new therapeutic strategies. BATF, a transcription factor activated by NOTCH2, the major NOTCH family member in B cells, negatively affects the expression of BZLF1, the master regulator of viral lytic cycle. We therefore analyzed the interplay between TERT, NOTCH and BATF in LCLs and found that high levels of endogenous TERT are associated with high NOTCH2 and BATF expression levels. In addition, ectopic expression of TERT in LCLs with low levels of endogenous telomerase was associated with upregulation of NOTCH2 and BATF at both mRNA and protein levels. By contrast, infection of LCLs with retroviral vectors expressing functional NOTCH2 did not alter TERT transcript levels. Luciferase reporter assays, demonstrated that TERT significantly activated NOTCH2 promoter in a dose-dependent manner. We also found that NF-κB pathway is involved in TERT-induced NOTCH2 activation. Lastly, pharmacologic inhibition of NOTCH signaling triggers the EBV lytic cycle, leading to the death of EBV-infected cells. Overall, these results indicate that TERT contributes to preserve EBV latency in B cells mainly through the NOTCH2/BAFT pathway, and suggest that NOTCH2 inhibition may represent an appealing therapeutic strategy against EBV-associated malignancies.

The emerging roles of Notch signaling in leukemia and stem cells

The Notch signaling pathway plays a critical role in maintaining the balance between cell proliferation, differentiation and apoptosis, and is a highly conserved signaling pathway that regulates normal development in a context- and dose-dependent manner. Dysregulation of Notch signaling has been suggested to be key events in a variety of hematological malignancies. Notch1 signaling appears to be the central oncogenic trigger in T cell acute lymphoblastic leukemia (T-ALL), in which the majority of human malignancies have acquired mutations that lead to constitutive activation of Notch1 signaling. However, emerging evidence unexpectedly demonstrates that Notch signaling can function as a potent tumor suppressor in other forms of leukemia. This minireview will summarize recent advances related to the roles of activated Notch signaling in human lymphocytic leukemia, myeloid leukemia, stem cells and stromal microenvironment, and we will discuss the perspectives of Notch signaling as a potential therapeutic target as well.