Gamma-secretase Research Articles

Long non-coding RNA HOTAIR induces GLI2 expression through Notch signalling in systemic sclerosis dermal fibroblasts

ObjectivesSystemic sclerosis (SSc) is characterised by tissue fibrosis of the major organs of the body including the skin, lungs and heart. We have previously reported that the lncRNA HOTAIR plays a central role in the activation of SSc myofibroblasts, the key cellular elements of fibrosis. HOTAIR induces fibroblast activation through H3K27me3-mediated activation of the Notch signalling pathway. Here we aimed to identify the signalling events downstream of Notch that drive SSc myofibroblast activation.MethodsPatient fibroblasts were obtained from full-thickness forearm skin biopsies of 3 adult patients with SSc of recent onset. The lncRNA HOTAIR was expressed in healthy dermal fibroblasts by lentiviral transduction. Hedgehog signalling pathway was inhibited with GANT61 and GLI2 siRNA. Gamma secretase inhibitors RO4929097 and DAPT were used to block Notch signalling. GSK126 was used to inhibit Enhancer of Zeste 2 (EZH2).ResultsOverexpression of HOTAIR in dermal fibroblasts induced the expression of the Hedgehog pathway transcription factor GLI2. This is mediated by activation of Notch signalling following epigenetic downregulation of miRNA-34a expression. Inhibition of H3K27 methylation and Notch signalling reduced expression of GLI2 in HOTAIR-expressing fibroblasts as well as in SSc dermal fibroblasts. Importantly, the inhibition of GLI2 function using GANT61 or siRNA mitigates the pro-fibrotic phenotype induced by HOTAIR.ConclusionsOur data indicates that GLI2 expression is stably upregulated in SSc myofibroblasts through HOTAIR and that GLI2 mediates the expression of pro-fibrotic markers downstream of Notch.

In Vitro Evaluation of Notch Inhibition to Enhance Efficacy of Radiation Therapy in Melanoma

PurposeThe scope of radiation therapy is limited in melanoma. Using in vitro melanoma models, we investigated a Notch signaling inhibitor as a radiosensitizer to explore its potential to improve the efficacy of radiation therapy to widen the clinical application of radiation therapy in melanoma. Methods and MaterialsMelanoma cell lines A375, SKMEL28, and G361 were grown using standard tissue culture methods. Radiation was delivered with a clinical x-ray unit, and a gamma secretase inhibitor RO4929097 was used to inhibit Notch signaling. Cell viability signal was used to calculate Loewe’s combination index to assess the interaction between radiation and RO4929097 and also the effect of scheduling of radiation and RO4929097 on synergy. Clonogenic assays were used to assess the clonogenic potential. An in vitro 3-dimensional culture model, γ-H2AX, and notch intracellular domain assays were used to interrogate potential underlying biological mechanisms of this approach. Scratch and transwell migration assays were used to assess cell migration. ResultsA375 and SKMEL28 cell lines showed consistent synergy for most single radiation doses examined, with a tendency for better synergy with the radiation-first schedule (irradiation performed 24 hours before RO4929097 exposure). Clonogenic assays showed dose-dependent reduction in colony numbers. Both radiation and RO4929097 reduced the size of melanospheres grown in 3-dimensional culture in vitro, where RO4929097 demonstrated a significant effect on the size of A375 and SKMEL28 melanospheres, indicating potential modulation of stem cell phenotype. Radiation induced γ-H2AX foci signal levels were reduced after exposure to RO4929097 with a tendency toward reduction in notch intracellular domain levels for all 3 cell lines. RO4929097 impaired both de novo and radiation-enhanced cell migration. ConclusionsWe demonstrate Notch signaling inhibition with RO4929097 as a promising strategy to potentially improve the efficacy of radiation therapy in melanoma. This strategy warrants further validation in vivo.

TAMI-11. IMPACT OF oHSV ACTIVATED NOTCH SIGNALING IN TUMOR MICROENVIRONMENT, AND ITS IMPACT ON ANTI-TUMOR IMMUNITY

Abstract NOTCH signaling is a method of cell-cell communication where membrane bound NOTCH ligands on signal-sending cells can bind to and initiate cleavage of the NOTCH receptor, releasing NICD which can initiate signal transduction in adjacent “signal-receiving” cells. We have recently shown that oHSV treatment of GBM cells induces NICD cleavage and NOTCH activation in adjacent uninfected glioma cells. RNA sequencing of GBM cells post-infection also uncovered Gene Ontology NOTCH signaling pathway to be significantly upregulated. This activation was induced by viral miRNA-H16, which represses FIH-1 expression. FIH-1 was found to be a negative regulator of Mib1, a ubiquitin ligase, which activates NOTCH ligand-mediated activation of adjacent signal-receiving cells bearing the NOTCH receptor (Otani et al Clin. Can. Res. 2020). Here we have investigated the impact of oHSV-induced NOTCH signaling on the tumor microenvironment. Treatment of brain tumors in immune competent mice with oHSV and NOTCH blocking gamma secretase inhibitor (GSI) induced an anti-tumor memory immune response. Long term survivors in mice treated with the combination also completely rejected subsequent tumor re-challenge in the other hemisphere. UMAP of flow cytometry of tumor-bearing hemispheres and functional analysis of isolated cellular fractions from treated mice showed a significant influx of MDSC cells after oHSV treatment that was rescued in mice treated with oHSV and GSI. Ongoing mechanistic studies are uncovering a significant induction of NOTCH in tumor associated macrophages that aids in recruitment of MDSC cells. Overall these studies have uncovered a significant impact of oHSV therapy on GBM tumor microenvironment and presents opportunities for combination therapies that can help improve therapeutic benefit and anti-tumor immunity.

Cancer Stem Cells as a new promising approach of efficient oncological treatment - the review of literature

Introduction and purpose:For many years a lot of research projects have been conducted with the aim to discover special cells, which are responsible for a neoplasm development. One of the theories concerns cancer stem cells (CSCs). This theory presumes the existence of original, undifferentiated cancer cells. These cells are capable of transform to all types of cells in neoplasm mass. The purpose of this study was to review the currently available data about the theory of CSCs and especially potential usage of this theory in oncological treatment. Pubmed and Scopus databases from the last 10 years were searched for phrase “cancer stem cells”. A brief description of the state of knowledge: Impaired signalling pathways lead to an occurrence of CSCs which may contribute to the development of neoplasm eventually. It is proved, that gamma secretase inhibitors impede Notch signalling pathway, which leads to a decrease of tumour markers expression and consequently decline in vivo tumour growth. It is believed that epigenetic mechanisms, including DNA methylation, histones alteration and RNA orientation are pivotal regulators of CSCs. It was shown, that histone deacetylases (HDAC) modulate refractoriness on chemotherapy in haematological tumours. It is also evidenced that peculiar designed microRNA directly inhibit CD44 which suppresses prostatic cancer stem cells and its metastases. CSCs have high expression of programmed death-ligand 1 (PD-L1) including breast and colon cancer, which proclaims in favour of immunotherapy aimed on CSCs. Conclusions:Constantly growing knowledge about CSCs biology is creating new opportunities of detection, isolation and design of the therapies aimed on CSCs.

919MO ACCURACY a phase II trial of AL101, a selective gamma secretase inhibitor, in subjects with recurrent/metastatic (R/M) adenoid cystic carcinoma (ACC) harboring Notch activating mutations (Notchmut)

919MO ACCURACY a phase II trial of AL101, a selective gamma secretase inhibitor, in subjects with recurrent/metastatic (R/M) adenoid cystic carcinoma (ACC) harboring Notch activating mutations (Notchmut)

Rapid Ex-Vivo Ciliogenesis and Dose-Dependent Effect of Notch Inhibition on Ciliogenesis of Respiratory Epithelia.

Background: Cilia are actin based cellular protrusions conserved from algae to complex multicellular organisms like Homo sapiens. Respiratory motile cilia line epithelial cells of the tracheobronchial tree, beat in a synchronous, metachronal wave, moving inhaled pollutants and pathogens cephalad. Their role in both congenital disorders like primary ciliary dyskinesia (PCD) to acquired disorders like chronic obstructive pulmonary disease (COPD) continues to evolve. In this current body of work we outline a protocol optimized to reciliate human nasal epithelial cells and mouse tracheal cells in vitro. Using this protocol, we knocked down known cilia genes, as well as use a small molecule inhibitor of Notch, N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl Ester (DAPT), to assess the effect of these on ciliogenesis in order to show the validity of our protocol. Methods: Tracheas were harvested from wild-type, adult C57B6 mice, pronase digested and sloughed off epithelial cells grown to confluence in stationary culture on rat-tail collagen coated wells. Upon reaching confluence, collagen was digested and cells placed suspension culture protocol to reciliate the cells. Using this suspension culture protocol, we employed siRNA gene knockdown to assay gene functions required for airway ciliogenesis. Knock down of Dynein axonemal heavy chain 5 (Dnah5), a ciliary structural protein, was confirmed using immunostaining. Mouse tracheal cells were treated in suspension with varying doses of DAPT, an inhibitor of Notch, with the purpose of evaluating its effect and dose response on ciliogenesis. The optimum dose was then used on reciliating human nasal epithelial cells. Results: siRNA knockdown of Foxj1 prevented ciliation, consistent with its role as a master regulator of motile cilia. Knockdown of Dnai1 and Dnah5 resulted in immotile cilia, and Cand1 knockdown, a centrosome protein known to regulate centrosome amplification, inhibited airway ciliogenesis. Dnah5 knockdown was confirmed with significantly decreased immunostaining of cilia for this protein. Inhibiting Notch signaling by inhibiting gamma secretase with DAPT enhanced the percentage of ciliation, and resulted in longer cilia that beat with higher frequency in both mouse and human airway epithelia. Conclusions: Modifying existing reciliation protocols to suit both human nasal epithelial and mouse tracheal tissue, we have shown that knockdown of known cilia-related genes have the expected effects. Additionally, we have demonstrated the optimal dosage for significantly improving reciliation of airway epithelia using DAPT. Given that cilia length and function are significantly compromised in COPD, these findings open up interesting avenues for further exploration.

Abstract 4557: BCMA-CD3 bispecific antibody PF-06863135: Preclinical rationale for therapeutic combinations

Abstract BCMA-CD3 bispecific antibody PF-06863135 is currently under evaluation in an ongoing Phase 1 clinical trial in relapsed/refractory (RR) multiple myeloma (MM) patients (NCT03269136). We showed previously that BCMA-CD3 bispecific has potent single agent activity in RR MM human bone marrow aspirates in vitro and in preclinical models of human myeloma (Panowski et al, MCT 2019). Herein we used in vitro assays, ex vivo MM patient 3D cultures, and in vivo efficacy models to study therapeutic combinations of PF-06863135 with immune checkpoint inhibitors, immunomodulatory drugs (IMiD), and gamma secretase inhibitors (GSI). Upregulation of immune checkpoints, such as programmed cell death protein-1 (PD-1) or programmed death ligand 1 (PD-L1) has been demonstrated downstream of response to CD3 bispecifics. While PF-06863135 is effective as a single agent in ex vivo 3D primary MM cultures (EC50 0.2 nM), PD-L1 was upregulated on myeloma cells. We combined PF-06863135 with anti-PD-1 in subcutaneous and orthotopic myeloma models MM.1S and MM.1S-PD-L1 in NSG mice engrafted with human T cells. PF-06863135 demonstrated single agent anti-tumor activity in the MM.1S models; however, in the MM.1S-PD-L1 model, PF-06863135 activity was blunted. When given in combination with an anti-PD-1 blocking antibody, the full thrust of the single agent anti-tumor activity of PF-06863135 was restored. Dysfunctional, senescent like T cells may emerge downstream of T cell immunotherapies. IMiDs, such as lenalidomide, are a standard of care therapy in MM and result in immunomodulatory effects on T cells leading us to hypothesize PF-06863135 mediated tumor growth inhibition could be enhanced by combining with lenalidomide. When PF-06863135 and lenalidomide were given in combination in the human T cell engrafted established orthotopic MM.1S and MOLP8 models, an even greater anti-tumor activity was observed as compared to either agent alone. These studies suggest that PF-06863135 activity can be augmented by combinations with immunomodulatory agents such as anti-PD-1 or lenalidomide. BCMA is shed from the surface of myeloma cells by gamma secretases, not only reducing cell surface target density but contributing to a soluble sink. When treated with GSI in vitro, myeloma cell surface BCMA expression increased concurrent with reduction in soluble/shed BCMA across a panel of myeloma and lymphoma cell lines expressing a range of BCMA. In cytotoxic T lymphocyte co-culture assays, the activity of PF-06863135 was potentiated by combining with GSI. Studies of the combination of PF-06863135 and GSI are ongoing in preclinical in vivo models of myeloma. Taken together, our preclinical studies provide insights into mechanisms of action and resistance for PF-06863135, which has potential for profound single agent activity that can be enhanced with therapeutic combinations. Citation Format: Katarzyna Karwacz, Andrea T. Hooper, Chao-Pei Betty Chang, Heike Krupka, Jeffrey Chou, Viola Lam, Ivana Djuretic, Javier Chaparro-Riggers, Puja Sapra. BCMA-CD3 bispecific antibody PF-06863135: Preclinical rationale for therapeutic combinations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4557.

Abstract LB-047: CHMP5 dependency is a therapeutic vulnerability of T cell acute lymphoblastic leukemia

Abstract T-cell acute lymphoblastic leukemia (T-ALL) is a very aggressive hematologic malignancy that results from the transformation of immature T-cell progenitors. Aberrant cell growth and proliferation is sustained by strong oncogenic drivers, notably NOTCH1 and MYC, whose activation is present in more than half of all T-ALL cases. However, although it is known that post-translational modifications, such as ubiquitination by the E3-ligase FBXW7, regulate NOTCH1 and MYC protein stability and activity, regulatory proteins involved in their stability remain unestablished. The Charged multivesicular body protein 5 (CHMP5), an accessory protein of the ESCRT (endosomal sorting complex required for transport) pathway, has been shown to regulate the stability of client proteins in thymocytes through the recruitment of de-ubiquitinating enzymes. Here, we report that CHMP5 protein is not only highly expressed in T-ALL cells, but also promotes the stability of transactivating intracellular NOTCH1 (ICN1) and MYC. We found that depletion of CHMP5 significantly reduced the abundance of ICN1 and MYC, and the transcription of their target genes in vitro, as well as suppressed the development of T-ALL in vivo in a murine model of NOTCH1 driven T-ALL. Additionally, loss of CHMP5 restored T-ALL cell susceptibility to chemotherapeutic agents, including glucocorticoids and gamma secretase inhibitors, resistance to which contributes to disease relapse in patients. We further reveal CHMP5 as an adaptor protein required to orchestrate T-ALL client protein deubiquitination and stability. Altogether, our data suggest that CHMP5 is a non-oncogenic dependency of T-ALL and its depletion may be an effective therapeutic strategy for T-ALL. Citation Format: Katharine Umphred-Wilson, Stanley Adoro. CHMP5 dependency is a therapeutic vulnerability of T cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-047.

Abstract 5630: Anti-BCMA bispecific tool therapy against Vk*MYC multiple myeloma is enhanced by IMiDs

Abstract BCMA is an ideal target antigen for myeloma immunotherapy as it is specifically expressed by plasma cells and T cell-engaging, BCMA-bispecific antibodies show potent tumor killing activity in human multiple myeloma (MM). However, a lack of longevity, potential immunotoxicity, and efficacy in high tumor burden situations are limitations to effective clinical utility. In order to optimize this therapeutic approach, we performed in vitro and in vivo assessments of a BCMA bispecific tool using the Vk*MYC immunocompetent mouse model of MM. Analysis at gene and protein level revealed variable levels of BCMA in Vk*MYC tumors, mirroring the heterogeneity of BCMA observed in human MM. In addition, we found that treatment with a gamma secretase inhibitor enhanced BCMA expression in Vk*MYC MM cells, similar to observations from patients. Having found the Vk*MYC model as a suitable model for BCMA targeted therapy, we treated Vk*MYC de novo and transplant mice with the BCMA targeting tool and established that the treatment was safe and efficacious (significant reduction in M-spike levels compared to control antibody). However, the response was transient and modest activity was noted in high tumor burden setting, likely because of poor T cell infiltration. Therefore, we hypothesized that combining BCMA therapy with agents capable of debulking the tumors would prolong and deepen therapeutic benefits and thus selected IMiDs for their anti-tumor and immunomodulatory properties. Because mice are resistant to therapy with IMiDs, we generated a humanized transgenic mouse strain with robust human CRBN expression and crossed it with the Vk*MYC mouse to obtain a novel immunocompetent, IMiD-responsive model, Vk*MYChCRBN. When combined with the IMiD pomalidomide (POM), bispecific-directed T cell control of MM was enhanced relative to bispecific alone. M-spike levels in two different transplantable models were reduced regardless of tumor burden. In addition, POM increased T cell effector activation, proliferation, and cytokine production. We also monitored transient weight loss unique to the bispecific-POM combination. Following this promising combinatorial result in vivo, we studied the relative roles of POM on target vs. effector cells by an in vitro killing assay using Vk*MYC tumor and splenocytes with or without expression of CRBN. Separately from the direct tumoricidal effects of POM on the tumor, we observed T cell-intrinsic effects of POM on the enhancement of BCMA-bispecific directed tumor lysis that correlated with T cell activation and proliferation. In summary, POM potentiated BCMA-CD3 bispecific directed T cell cytolysis of MM in the Vk*MYChCRBN animal model by enhancing effector cell activation, proliferation, cytokine production and directly reducing tumor burden. These results support ongoing preclinical studies of the benefits of combining standard of care therapy with potent T cell immunotherapy for MM. Citation Format: Erin W. Meermeier, Meaghen E. Sharik, Seth J. Welsh, Caleb K. Stein, Victoria M. Garbitt, Sochilt Brown, Kennedi T. Todd, Marco Bergsagel, P. Leif Bergsagel, Marta Chesi. Anti-BCMA bispecific tool therapy against Vk*MYC multiple myeloma is enhanced by IMiDs [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5630.

Gamma secretase inhibition impairs HCMV replication by reduction of immediate early gene expression at the transcriptional level

Due to diverse pathogenic potentials, there is a growing need for anti-HCMV agents. In this study, we show that treatment with DAPT, a γ-secretase inhibitor (GSI), impairs HCMV replication as assessed by a progeny assay based on immunostaining. This effect is not limited to DAPT because other GSIs with different structures and distinct mechanisms of action also exhibit a similar level of inhibitory effects on HCMV viral production, indicating that γ-secretase activity is required for efficient HCMV replication. Western blot and qPCR analyses reveal that DAPT does not interfere with the viral entry process, but reduces expression of the immediate early protein IE1 at the transcriptional level. Furthermore, we exclude the possible involvement of Notch signaling pathway during HCMV replication by showing that expression of the dominant-negative form of MAML1, which disrupts the transactivational ability of Notch intracellular domain (NICD), does not reduce viral particle formation, and that NICD cannot rescue the DAPT-treated outcomes. Taken together, these findings indicate that γ-secretase activity plays an important role in a key step of the HCMV life cycle and γ-secretase inhibition could potentially be used as a novel preventive and therapeutic strategy against HCMV infection and HCMV-related diseases.

Decreased Deposition of Beta-Amyloid 1-38 and Increased Deposition of Beta-Amyloid 1-42 in Brain Tissue of Presenilin-1 E280A Familial Alzheimer's Disease Patients.

Familial Alzheimer’s Disease (FAD) caused by Presenilin-1 (PS1) mutations is characterized by early onset, cognitive impairment, and dementia. Impaired gamma secretase function favors production of longer beta-amyloid species in PS1 FAD. The PS1 E280A mutation is the largest FAD kindred under study. Here, we studied beta-amyloid deposits in PS1 E280A FAD brains in comparison to sporadic Alzheimer’s disease (SAD). We analyzed cortices and cerebellum from 10 FAD and 10 SAD brains using immunohistochemistry to determine total beta-amyloid, hyperphosphorylated tau (pTau), and specific beta-amyloid peptides 1-38, 1-40, 1-42, and 1-43. Additionally, we studied beta-amyloid subspecies by ELISA, and vessel pathology was detected with beta-amyloid 1-42 and truncated pyroglutamylated beta-amyloid antibodies. There were no significant differences in total beta-amyloid signal between SAD and FAD. Beta-amyloid 1-38 and 1-43 loads were increased, and 1-42 loads were decreased in frontal cortices of SAD when compared to FAD. Beta-amyloid species assessment by ELISA resembled our findings by immunohistochemical analysis. Differences in beta-amyloid 1-38 and 1-42 levels between SAD and FAD were evidenced by using beta-amyloid length-specific antibodies, reflecting a gamma secretase-dependent shift in beta-amyloid processing in FAD cases. The use of beta-amyloid length-specific antibodies for postmortem assessment of beta-amyloid pathology can differentiate between SAD and PS1 FAD cases and it can be useful for identification of SAD cases potentially affected with gamma secretase dysfunction.

Canonical Notch signaling is required for bone morphogenetic protein-mediated human osteoblast differentiation.

Osteoblast differentiation of bone marrow-derived human mesenchymal stem cells (hMSC) can be induced by stimulation with canonical Notch ligand, Jagged1, or bone morphogenetic proteins (BMPs). However, it remains elusive how these two pathways lead to the same phenotypic outcome. Since Runx2 is regarded as a master regulator of osteoblastic differentiation, we targeted Runx2 with siRNA in hMSC. This abrogated both Jagged1 and BMP2 mediated osteoblastic differentiation, confirming the fundamental role for Runx2. However, while BMP stimulation increased Runx2 and downstream Osterix protein expression, Jagged1 treatment failed to upregulate either, suggesting that canonical Notch signals require basal Runx2 expression. To fully understand the transcriptomic profile of differentiating osteoblasts, RNA sequencing was performed in cells stimulated with BMP2 or Jagged1. There was common upregulation of ALPL and extracellular matrix genes, such as ACAN, HAS3, MCAM, and OLFML2B. Intriguingly, genes encoding components of Notch signaling (JAG1, HEY2, and HES4) were among the top 10 genes upregulated by both stimuli. Indeed, ALPL expression occurred concurrently with Notch activation and inhibiting Notch activity for up to 24 hours after BMP administration with DAPT (a gamma secretase inhibitor) completely abrogated hMSC osteoblastogenesis. Concordantly, RBPJ (recombination signal binding protein for immunoglobulin kappa J region, a critical downstream modulator of Notch signals) binding could be demonstrated within the ALPL and SP7 promoters. As such, siRNA-mediated ablation of RBPJ decreased BMP-mediated osteoblastogenesis. Finally, systemic Notch inhibition using diabenzazepine (DBZ) reduced BMP2-induced calvarial bone healing in mice supporting the critical regulatory role of Notch signaling in BMP-induced osteoblastogenesis.

Top Notch Targeting Strategies in Cancer: A Detailed Overview of Recent Insights and Current Perspectives.

Evolutionarily conserved Notch plays a critical role in embryonic development and cellular self-renewal. It has both tumour suppressor and oncogenic activity, the latter of which is widely described. Notch-activating mutations are associated with haematological malignancies and several solid tumours including breast, lung and adenoid cystic carcinoma. Moreover, upregulation of Notch receptors and ligands and aberrant Notch signalling is frequently observed in cancer. It is involved in cancer hallmarks including proliferation, survival, migration, angiogenesis, cancer stem cell renewal, metastasis and drug resistance. It is a key component of cell-to-cell interactions between cancer cells and cells of the tumour microenvironment, such as endothelial cells, immune cells and fibroblasts. Notch displays diverse crosstalk with many other oncogenic signalling pathways, and may drive acquired resistance to targeted therapies as well as resistance to standard chemo/radiation therapy. The past 10 years have seen the emergence of different classes of drugs therapeutically targeting Notch including receptor/ligand antibodies, gamma secretase inhibitors (GSI) and most recently, the development of Notch transcription complex inhibitors. It is an exciting time for Notch research with over 70 cancer clinical trials registered and the first-ever Phase III trial of a Notch GSI, nirogacestat, currently at the recruitment stage.

Leptin and Notch Signaling Cooperate in Sustaining Glioblastoma Multiforme Progression.

Glioblastoma multiforme (GBM) is the most malignant form of glioma, which represents one of the commonly occurring tumors of the central nervous system. Despite the continuous development of new clinical therapies against this malignancy, it still remains a deadly disease with very poor prognosis. Here, we demonstrated the existence of a biologically active interaction between leptin and Notch signaling pathways that sustains GBM development and progression. We found that the expression of leptin and its receptors was significantly higher in human glioblastoma cells, U-87 MG and T98G, than in a normal human glial cell line, SVG p12, and that activation of leptin signaling induced growth and motility in GBM cells. Interestingly, flow cytometry and real-time RT-PCR assays revealed that GBM cells, grown as neurospheres, displayed stem cell-like properties (CD133+) along with an enhanced expression of leptin receptors. Leptin treatment significantly increased the neurosphere forming efficiency, self-renewal capacity, and mRNA expression levels of the stemness markers CD133, Nestin, SOX2, and GFAP. Mechanistically, we evidenced a leptin-mediated upregulation of Notch 1 receptor and the activation of its downstream effectors and target molecules. Leptin-induced effects on U-87 MG and T98G cells were abrogated by the selective leptin antagonist, the peptide LDFI (Leu-Asp-Phe-Ile), as well as by the specific Notch signaling inhibitor, GSI (Gamma Secretase Inhibitor) and in the presence of a dominant-negative of mastermind-like-1. Overall, these findings demonstrate, for the first time, a functional interaction between leptin and Notch signaling in GBM, highlighting leptin/Notch crosstalk as a potential novel therapeutic target for GBM treatment.

Oncolytic HSV-Infected Glioma Cells Activate NOTCH in Adjacent Tumor Cells Sensitizing Tumors to Gamma Secretase Inhibition.

To examine the effect of oncolytic herpes simplex virus (oHSV) on NOTCH signaling in central nervous system tumors. Bioluminescence imaging, reverse phase protein array proteomics, fluorescence microscopy, reporter assays, and molecular biology approaches were used to evaluate NOTCH signaling. Orthotopic glioma-mouse models were utilized to evaluate effects in vivo. We have identified that herpes simplex virus-1 (HSV-1; oncolytic and wild-type)-infected glioma cells induce NOTCH signaling, from inside of infected cells into adjacent tumor cells (inside out signaling). This was canonical NOTCH signaling, which resulted in activation of RBPJ-dependent transcriptional activity that could be rescued with dnMAML. High-throughput screening of HSV-1-encoded cDNA and miRNA libraries further uncovered that HSV-1 miR-H16 induced NOTCH signaling. We further identified that factor inhibiting HIF-1 (FIH-1) is a direct target of miR-H16, and that FIH-1 downregulation by virus encoded miR-H16 induces NOTCH activity. FIH-1 binding to Mib1 has been reported, but this is the first report that shows FIH-1 sequester Mib1 to suppress NOTCH activation. We observed that FIH-1 degradation induced NOTCH ligand ubiquitination and NOTCH activity. REMBRANDT and The Cancer Genome Atlas data analysis also uncovered a significant negative regulation between FIH-1 and NOTCH. Furthermore, combination of oHSV with NOTCH-blocking gamma secretase inhibitor (GSI) had a therapeutic advantage in two different intracranial glioma models treated with oncolytic HSV, without affecting safety profile of the virus in vivo. To our knowledge this is the first report to identify impact of HSV-1 on NOTCH signaling and highlights the significance of combining oHSV and GSI for glioblastoma therapy.

Discovery of RO7185876, a Highly Potent γ-Secretase Modulator (GSM) as a Potential Treatment for Alzheimer's Disease.

γ-Secretase (GS) is a key target for the potential treatment of Alzheimer's disease. While inhibiting GS led to serious side effects, its modulation holds a lot of potential to deliver a safe treatment. Herein, we report the discovery of a potent and selective gamma secretase modulator (GSM) (S)-3 (RO7185876), belonging to a novel chemical class, the triazolo-azepines. This compound demonstrates an excellent in vitro and in vivo DMPK profile. Furthermore, based on its in vivo efficacy in a pharmacodynamic mouse model and the outcome of the dose range finding (DRF) toxicological studies in two species, this compound was selected to undergo entry in human enabling studies (e.g., GLP toxicology and scale up activities).

The Alzheimer Disease-Causing Presenilin-1 L435F Mutation Causes Increased Production of Soluble Aβ43 Species in Patient-Derived iPSC-Neurons, Closely Mimicking Matched Patient Brain Tissue

Familial Alzheimer disease-causing mutations in Presenilin 1 (PSEN1) are generally thought to shift the processing of APP toward longer, more amyloidogenic Aβ fragments. However, certain PSEN1 mutations cause severe reduction in gamma secretase function when expressed in the homozygous state, thus challenging the amyloid hypothesis. We sought to evaluate the effects of one such mutation, PSEN1 L435F, in more physiologic conditions and genetic contexts by using human induced pluripotent stem cell (iPSC)-derived neurons from an individual with familial AD (fAD) linked to the PSEN1 L435F mutation, and compared the biochemical phenotype of the iPS-derived neurons with brain tissue obtained at autopsy from the same patient. Our results demonstrate that in the endogenous heterozygous state, the PSEN1 L435F mutation causes a large increase in soluble Aβ43 but does not change the overall levels of soluble Aβ40 or Aβ42 when compared with control iPSC-neurons. Increased pathologically phosphorylated tau species were also observed in PSEN1-mutant iPSC-neurons. Concordant changes in Aβ species were present in autopsy brain tissue from the same patient. Finally, the feasibility of using Aβ43 immunohistochemistry of brain tissue to identify fAD cases was evaluated in a limited autopsy case series with the finding that strong Aβ43 staining occurred only in fAD cases.

Effects of Prostacyclin Signaling on Alzheimer’s Disease Associated Pathologies

Alzheimer’s disease (AD) is an incurable neurodegenerative disorder that is the most common cause of dementia in aged populations. A substantial amount of data demonstrates that chronic neuroinflammation can accelerate neurodegenerative pathologies, while epidemiological and experimental evidence suggests that use of anti‐inflammatory agents may be neuroprotective. In AD, chronic neuroinflammation results in the upregulation of cyclooxygenase and increased production of prostaglandin H2, a precursor for many vasoactive prostanoids. While is well‐established that many prostaglandins can modulate the progression of neurodegenerative disorders, little is known about the role of prostacyclin (PGI2) in the brain. We have conducted studies to assess the effect of elevated prostacyclin biosynthesis in a mouse model of AD. Upregulated prostacyclin expression significantly worsened cognitive abnormalities, accelerated amyloid pathology, and damaged the neurovasculature. PGI2 overexpression selectively increased soluble amyloid‐β 42 production, total amyloid accumulation, and burden. PGI2 altered microvessel length and branching, and PGI2 expression in combination with amyloid was more detrimental than amyloid expression alone. In vitro studies demonstrated that increased prostacyclin signaling inhibited microvessel formation and selectively altered gamma secretase subunit expression. Our findings demonstrate that chronic prostacyclin expression plays a novel and unexpected role that hastens the development of the AD phenotype.

Reader response: INTREPAD: A randomized trial of naproxen to slow progress of presymptomatic Alzheimer disease.

I read with interest the Null Hypothesis article by Meyer et al.1 In 2001, Weggen et al.2 suggested that flurbiprofen and ibuprofen had an effect on gamma secretase not shared by other cyclooxygenase inhibitors. This finding, along with several other failed studies of anti-inflammatory mechanisms in Alzheimer disease (AD), suggests that the widely replicated epidemiologic findings of nonsteroidal anti-inflammatory drug (NSAID) benefit for decreasing AD risk could be related to the effect on gamma-secretase, not inflammation. A flurbiprofen study failed to show a benefit for patients with AD,3 but a considerable number of studies suggest that the NSAID-related benefit requires years of treatment before dementia develops, which the study by Meyer et al.1 was appropriately targeting. However, the question remains as to whether ibuprofen is the drug to test, not naproxen.

Long non-coding RNA HOTAIR drives EZH2-dependent myofibroblast activation in systemic sclerosis through miRNA 34a-dependent activation of NOTCH

BackgroundSystemic sclerosis (SSc) is characterised by autoimmune activation, tissue and vascular fibrosis in the skin and internal organs. Tissue fibrosis is driven by myofibroblasts, that are known to maintain their...