Expression Of Activated Notch1 Research Articles

HOXB3 promotes trophoblast cell proliferation, invasion, and migration to alleviate preeclampsia via mediating the Notch/Wnt/β-catenin pathway

Preeclampsia (PE) harms a significant number of pregnant women and fetuses. However, because of its complex pathological mechanisms, there is no cure except for delivery. This study identified the impact and mechanisms of action of HOXB3 in PE. The behaviors of HTR-8/SVneo cells were analyzed using a cell counting kit-8, EdU, and transwell assays. The interaction between HOXB3 and Notch1 was assessed using a luciferase reporter and chromatin immunoprecipitation assays. Expression was measured by quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence assays. Additionally, the function of HOXB3 was evaluated in an established rat model of PE. We found that HOXB3 was upregulated in PE. HOXB3 overexpression facilitated trophoblast cell proliferation, migration, and invasion. HOXB3 transcriptionally regulated Notch1 by binding to its promoter. Notch1 knockdown abrogated the functions of HOXB3 and the-catenin pathway in trophoblasts. Suppression of the Wnt/β-catenin pathway abrogated the effects of HOXB3. Additionally, HOXB3 alleviated the symptoms in PE rats. In conclusion, HOXB3 transcriptionally activated Notch1 expression and the-catenin pathway, promoting trophoblast cell proliferation, invasion, and migration, thereby alleviating PE progression. This study provides a novel approach for PE therapy.

Maturity State and MCL-1 Dependence Predetermines Response to NOTCH1 Inhibition in T-ALL

Introduction:Acute T cell lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic malignancy in children and young adults that frequently becomes treatment-refractory and relapses. The Notch1 pathway is a key oncogenic driver in T-ALL and is aberrantly activated in more than 50% of the cases. Despite promising pre-clinical data using gamma secretase inhibitors such as DBZ to target NOTCH1, resistance is rapidly occurring in vivo. As molecular heterogeneity has been linked to treatment escape, we focused our study on defining transcriptional cell states driving resistance to NOTCH inhibition and understanding their relation to mitochondrial priming.Methods:5 primary T-ALLs harboring NOTCH activating mutations were engrafted in NSG (NOD-scidIL2Rgnull) mice. Upon reaching ~ 10% of human CD45+ positive leukemic blasts in the peripheral blood, randomized groups of 8 mice per primary T-ALL were treated with DBZ (Dipenzazepine; 10 μM/kg every other day through tail vein) or vehicle (VEH). 3 mice per group were sacrificed after one week of treatment to assess short-term effect of DBZ, while the remaining 5 mice were weekly monitored for disease progression, leukemic blasts were collected from lymphoid organs and overall survival was determined.Full-length transcriptome analysis of 3188 blasts present in the blood of 20 sensitive and 22 refractory mice was performed by Smart-Seq2. Based on scRNA features, ‘scVelo’ and ‘CytoTRACE’ were used to identify developmental potential and differentiation trajectories. Cell fate and transcriptional regulatory networks were defined and reconstructed using ‘SCENIC’.Assessment of mitochondrial priming as measured by BH3 profiling was used to identify anti-apoptotic vulnerabilities present in these PDX models.Results:Upon DBZ, short or long-term disease control was observed in two strains, while rapid resistance occurred in three strains, thus establishing two sensitive and three refractories to NOTCH inhibition PDX models. Immunohistochemical analysis showed decreased expression of active NOTCH1 in spleen biopsies of all strains, validating the efficacy of DBZ and suggesting a mechanism of resistance independent of ICN1.Single cell transcriptional profiling showed enrichment of immature hematopoietic signatures and co-expression of lymphoid and myeloid progenitor programs in refractory models. Interestingly, pre-existing cells harboring refractory-like transcriptional circuits within the untreated sensitive population were identified. Upon treatment, despite increased differentiation in all models, lineage promiscuity was maintained in refractory strains, suggesting that cellular plasticity mediates treatment escape.Next, we characterized cell states driving treatment refraction. RNA velocity projections identified two distinct immature states differing in cell cycle and oncogenic signaling. Clustering of untreated, sensitive leukemic cells in immature state imply that aberrant lineage commitment can predict response to NOTCH inhibition in vivo. These observations were further confirmed by differentiation state analysis, where prior to treatment, high developmental potential was correlated to treatment escape. Surprisingly, in addition to early lineage differentiation drivers such as BCL11A, state-specific regulons analysis associated immature states with BCLAF1 a transcriptional regulator of apoptosis.We postulated that these transcriptional circuits lead to differential apoptotic priming, therefore the dependence on individual anti-apoptotic proteins was evaluated. Mitochondrial priming at baseline revealed BCL-2 dependence in sensitive strains whereas MCL1-dependence was observed in refractory ones. Upon DBZ treatment, while dependency profiles in refractory strains remained unchanged, a functional switch from BCL-2 to MCL1-dependency occurred in sensitive models.Conclusion:Our results suggest that response to NOTCH inhibition is predetermined by cell maturity states and their associated transcriptional circuits responsible for differential sensitivity to apoptotic priming via BCL2 and MCL1. These data suggest that combining BH3 and lineage commitment profiling may predict drug responses in vivo. Moreover, our findings highlight the importance of targeting co-existing cell states to overcome transcriptional heterogeneity as a driver of treatment escape. DisclosuresLetai: Zentalis Pharmaceuticals: Other: equity holding member of the scientific advisory board; Dialectic Therapeutics: Other: equity holding member of the scientific advisory board; Flash Therapeutics: Other: equity holding member of the scientific advisory board. Weinstock: Daiichi Sankyo: Consultancy, Research Funding; Verastem: Research Funding; Abcuro: Research Funding; Bantam: Consultancy; ASELL: Consultancy; SecuraBio: Consultancy; AstraZeneca: Consultancy; Travera: Other: Founder/Equity; Ajax: Other: Founder/Equity.

Abstract P3-03-11: Notch inhibition promotes triple negative breast cancer growth

Abstract Notch1 and Transforming Growth Factor-beta (TGF-β) signaling pathways in cancer have a paradoxical roles as they were shown to have both tumor suppressive and tumor promoting activities. The interaction between these two signaling pathways in cancer progression was addressed in a systematic way. In these studies, we utilized primary human mammary epithelial cells (HMEC) and various triple negative breast cancer (TNBC) cells and examined the molecular cross-talk between TGF-β and Notch signaling pathways using biochemical, molecular and cell biology techniques. First, we noticed lower expression of Notch1 in most of the TNBC cells compared to normal cells. Second, most of these TNBC cells overexpressed TMEPAI (transmembrane prostate androgen induced) protein, which was shown to switch TGF-β from a tumor suppressor to a tumor promoter role in breast cancer. Surprisingly, treatment of TNBC cells with Notch inhibitors increased their growth rate both in the absence or presence of TGF-β. Moreover, Notch inhibition relieved the growth suppression by TGF-β in normal cells. Both normal and TNBC cells showed increased growth in the presence of Notch inhibitors with decreased TGF-β signaling activity. Normal cells that express very low levels of TMEPAI both at mRNA and protein levels, overexpressed TMEPAI protein in the presence of various Notch inhibitors, suggesting that Notch negatively regulates TMEPAI expression. Correspondingly, knockdown of TMEPAI in TNBC cell lines showed increased expression of Notch1 and Jagged 1 suggesting a negative regulation of Notch1 by TMEPAI. Consistent with these observations, TMEPAI, a known binding partner of E3 ligases, causes increased turnover of Notch1 protein. In fact, over expression of active Notch1 in MDA-MB-231 cells inhibited tumor cell growth both in vitro and in vivo. Our results clearly suggest that a crosstalk exists between TGF-β and Notch1 signaling through TMEPAI. Therefore, our studies clearly indicate that use of Notch inhibitors is contraindicated in triple negative breast cancer patients. Citation Format: Pothana Saikumar, Prajjal K Singha, Manjeri A Venkatachalam. Notch inhibition promotes triple negative breast cancer growth [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-03-11.

Abstract 1172: Expression of notch1, numb, and musashi1 in non-small cell lung cancer

Abstract Background: Deregulation of Notch pathway is associated with carcinogenesis, and Notch signaling is identified as tumor activator in non-small cell lung cancer(NSCLC). The function of Musashi1 has been found to activate Notch signaling through the translational repression of Numb, which represses an intracellular Notch signaling. In NSCLC, the association between Numb or Musashi1 expression and clinicopathological factors or prognosis has remained unclear. In this study, we evaluated the expression of Notch1, Numb, and Musashi1 in NSCLC. Methods: A total of 135 surgically resected NSCLCs were immunohistochemically assessed for Notch1, Numb, and Musashi1 expression. Only cytoplasm and nuclear staining was considered in the evaluation of activated Notch1 expression. The immunoscores were determined, and then its correlation with either the clinicopathological variables or the survival outcomes was analyzed. Results: Immunohistochemical reactivity for Numb, and Musashi1 was detected in the cytoplasm and nuclear of the tumor cells. Notch1 expression was associated with several clinicopathological factors, including pathological histology (p = 0.002), and differentiation of tumor (p = 0.024). Numb expression was also associated with several clinicopathological factors, including sex (p = 0.037), smoking habit (p = 0.033), pathological histology (p = 0.002), and differentiation of tumor (p = 0.015). No correlations were noted between Musashi1 expression and any of the variables. Analysis of cellular biological expression demonstrated a link between low Numb expression and high Notch expression. Multivariate Cox regression analysis showed that positive Numb expression was an independent favorable prognostic factor. Conclusions: We demonstrate that Numb expression was associated with better prognosis in NSCLC. Numb might have the function as tumor suppressor in NSCLC. Citation Format: Hajime Kikuchi, Jun Sakakibara-Konishi, Yasuyuki Ikezawa, Taichi Takashina, Hidenori Mizugaki, Eiki Kikuchi, Junko Kikuchi, Naofumi Shinagawa, Satoshi Oizumi, Yasuhiro Hida, Kichizo Kaga, Ichiro Kinoshita, Hirotoshi Dosaka-Akita, Masaharu Nishimura. Expression of notch1, numb, and musashi1 in non-small cell lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1172.

Abstract 17361: Loss of Notch1 in the Secondary Heart Field Exacerbates Ascending Aortic Aneurysm and Causes Aortic Rupture in Marfan Syndrome Mice (Best of Basic Science Abstract)

Ascending aortic aneurysm (AscAA) is a life-threatening disease that affects approximately 3.5 in 100,000 people per year, but the mechanisms of AscAA remain poorly understood. We previously reported that NOTCH1 mutations are associated with familial bicuspid aortic valve (BAV), and a subset of these individuals displayed BAV aortopathy. NOTCH1 is expressed in multiple cell lineages that contribute to the aorta, and we found dysregulation of activated NOTCH1 expression in aneurysmal tissue from Marfan syndrome and BAV patients in comparison to control tissue. To investigate the role of NOTCH1 in AscAA, Notch1 haploinsufficiency was introduced into the Marfan syndrome mouse ( Fbn1 C1039G/+ ), a well-described model of AscAA. Serial echocardiographic, gross and histological characterization of the Notch1 deficient Marfan syndrome mice ( Notch1 +/- ;Fbn C1039G/+ ) demonstrated an exacerbated AscAA phenotype when compared to Fbn1 C1039G/+ mice. The compound mutant mice had increased aortic root diameter by three months of age (diameter: Notch1 +/- ;Fbn C1039G/+ = 2.11±0.11mm and Fbn1 C1039G/+ = 1.86±0.05mm, p<0.05) as well as a higher rate of dilation from 1-5 months of age (rate: Notch1 +/- ;Fbn C1039G/+ =0.24±0.06mm/month and Fbn1 C1039G/+ =0.09±0.03mm/month, p<0.05). Notch1 +/- and wildtype littermate mice had normal aortic diameters. Furthermore, a small subset (4/66) of the compound mutant mice succumbed to ascending aortic rupture, which was not observed in the Fbn1 C1039G/+ mice (0/63). Although endothelial Notch1 is critical for cardiovascular development, mice with heterozygous loss of Notch1 in endothelial cells that harbor the Fbn1 C1039G mutation ( Notch1 flox/+ ;Tie2-Cre +/- ;Fbn1 C1039G/+ ) did not recapitulate the phenotype of the Notch1 +/- ;Fbn C1039G/+ mice. Surprisingly, the phenotype was recapitulated with heterozygous loss of Notch1 in the lineage of secondary heart field cells ( Notch1 flox/+ ;Mef2C-AHF-Cre +/- ;Fbn1 C1039G/+ ) but not smooth muscle myosin heavy chain-expressing cells ( Notch1 flox/+ ;Myh11-Cre +/- ;Fbn1 C1039G/+ ). Our findings support a novel role for Notch1 in the non-endothelial secondary heart field and suggest that this loss of Notch1 alters a developmental process that contributes to AscAA.

Activated Notch1 expression is associated with angiogenesis in cutaneous melanoma.

An early event in melanocytic tumor growth is the upregulation of Notch signaling. When an active form of Notch1 is overexpressed in primary human melanocytes, it increases cell growth, survival and invasive properties, promoting melanoma progression. Recent evidence suggested that tumor initiation and growth are driven by a subset of tumor-initiating cells termed cancer stem cells. Notch1 plays a predominant role in the maintenance of melanoblasts, including melanocyte stem cells, by preventing initiation of apoptosis. Moreover, the importance of Notch1 in the regulation of tumor angiogenesis is supported by growing evidence in various cancers. Nestin has been widely used as a marker for melanocyte stem cells as well as an angiogenic marker to evaluate neovascularity of endothelial cells in tumors. To gain an insight into the impact of Notch1 activation on the maintenance of melanocyte stem cells and angiogenesis in melanoma, the expression levels of activated Notch1 and nestin were analyzed by immunohistochemistry in 114 primary cutaneous melanomas and 35 lymph node metastases. Activated Notch1 and nestin expression was also evaluated in four dysplastic melanocytic nevi. This study provides evidence that activated Notch1 is overexpressed in cutaneous melanoma, in tumor cells as well as in microvessel endothelium, and that it can promote tumor angiogenesis. Indeed, the overexpression of activated Notch1 in both tumor and vascular endothelial cells was significantly associated with microvascular density in melanoma samples. Thus, activated Notch1 inhibitors may provide a therapeutic strategy in the treatment of melanoma by blocking tumor-associated vascularization.

Prostate tumor OVerexpressed-1 (PTOV1) down-regulates HES1 and HEY1 notch targets genes and promotes prostate cancer progression

BackgroundPTOV1 is an adaptor protein with functions in diverse processes, including gene transcription and protein translation, whose overexpression is associated with a higher proliferation index and tumor grade in prostate cancer (PC) and other neoplasms. Here we report its interaction with the Notch pathway and its involvement in PC progression.MethodsStable PTOV1 knockdown or overexpression were performed by lentiviral transduction. Protein interactions were analyzed by co-immunoprecipitation, pull-down and/or immunofluorescence. Endogenous gene expression was analyzed by real time RT-PCR and/or Western blotting. Exogenous promoter activities were studied by luciferase assays. Gene promoter interactions were analyzed by chromatin immunoprecipitation assays (ChIP). In vivo studies were performed in the Drosophila melanogaster wing, the SCID-Beige mouse model, and human prostate cancer tissues and metastasis. The Excel package was used for statistical analysis.ResultsKnockdown of PTOV1 in prostate epithelial cells and HaCaT skin keratinocytes caused the upregulation, and overexpression of PTOV1 the downregulation, of the Notch target genes HEY1 and HES1, suggesting that PTOV1 counteracts Notch signaling. Under conditions of inactive Notch signaling, endogenous PTOV1 associated with the HEY1 and HES1 promoters, together with components of the Notch repressor complex. Conversely, expression of active Notch1 provoked the dismissal of PTOV1 from these promoters. The antagonist role of PTOV1 on Notch activity was corroborated in the Drosophila melanogaster wing, where human PTOV1 exacerbated Notch deletion mutant phenotypes and suppressed the effects of constitutively active Notch. PTOV1 was required for optimal in vitro invasiveness and anchorage-independent growth of PC-3 cells, activities counteracted by Notch, and for their efficient growth and metastatic spread in vivo. In prostate tumors, the overexpression of PTOV1 was associated with decreased expression of HEY1 and HES1, and this correlation was significant in metastatic lesions.ConclusionsHigh levels of the adaptor protein PTOV1 counteract the transcriptional activity of Notch. Our evidences link the pro-oncogenic and pro-metastatic effects of PTOV1 in prostate cancer to its inhibitory activity on Notch signaling and are supportive of a tumor suppressor role of Notch in prostate cancer progression.

ADAM17 regulates self-renewal and differentiation of U87 glioblastoma stem cells

Glioblastoma stem cells (GSCs) play an important role in the progression and recurrence of malignant glioblastoma because of their potential for self-renewal, multilineage differentiation and tumor initiation. A disintegrin and metalloproteinase 17 (ADAM17) is responsible for the proteolytic cleavage of Notch within its extracellular domain leading to the activation of Notch signaling, which is involved in the formation and maintenance of GSCs. Here, we show that glioma cells expressing the stem cell marker CD133 coexpress higher levels of ADAM17 than matched CD133-glioma cells. Knockdown of the ADAM17 gene in U87 GSCs down-regulated the expression of CD133, inhibited secondary neurosphere formation and induced multi-lineage differentiation. Furthermore, knockdown of ADAM17 inhibited Hes1 and Hes5 and activated Notch1 expression, which may explain the ADAM17 shRNA-induced suppression of self-renewal and differentiation of U87 GSCs. Our results suggest that ADAM17 may maintain the stemness of GSCs by promoting their self-renewal and inhibiting their differentiation via Notch signaling.

IKKα Activation of NOTCH Links Tumorigenesis via FOXA2 Suppression

Proinflammatory cytokine TNFα plays critical roles in promoting malignant cell proliferation, angiogenesis, and tumor metastasis in many cancers. However, the mechanism of TNFα-mediated tumor development remains unclear. Here, we show that IKKα, an important downstream kinase of TNFα, interacts with and phosphorylates FOXA2 at S107/S111, thereby suppressing FOXA2 transactivation activity and leading to decreased NUMB expression, and further activates the downstream NOTCH pathway and promotes cell proliferation and tumorigenesis. Moreover, we found that levels of IKKα, pFOXA2 (S107/111), and activated NOTCH1 were significantly higher in hepatocellular carcinoma tumors than in normal liver tissues and that pFOXA2 (S107/111) expression was positively correlated with IKKα and activated NOTCH1 expression in tumor tissues. Therefore, dysregulation of NUMB-mediated suppression of NOTCH1 by TNFα/IKKα-associated FOXA2 inhibition likely contributes to inflammation-mediated cancer pathogenesis. Here, we report a TNFα/IKKα/FOXA2/NUMB/NOTCH1 pathway that is critical for inflammation-mediated tumorigenesis and may provide a target for clinical intervention in human cancer.

PD08-01: JNK2 Regulates Mammary Lineage Differentiation in Tumors and Normal Glands through Notch1 and p53.

Abstract The classification of patient tumors by clinical subtype has gained wide acceptance due to the implications for prognosis and treatment. However, recent studies have cast doubt on previously advocated normal mammary origins of these subtypes. Thus, the link between the normal mammary gland and mammary tumors is more complex than expected. C-Jun N-Terminal Kinase-2 (JNK2) is a protein that is involved in numerous developmental processes and our previous work has shown it to be important for DNA damage response in mammary tumors. In attempt to gain insight into the link between mammary development and tumorigenesis, we compared normal mammary glands of JNK2 knockout (jnk2ko) mice to jnk2ko mammary tumors expressing or lacking wildtype p53 (p53ko). These studies showed that jnk2ko glands possess 35% fewer basal cells (p=0.0078) with a corresponding increase in luminal epithelial cell populations (p=0.100). This luminal response is corroborated by in vitro 3D assays of primary mammary epithelial cells (MECs) where luminal cell differentiation is normalized by inhibition of Notch signaling. Expression notch-1, a well-known regulator of MEC differentiation, is increased jnk2ko mammary glands. Increased expression of the Notch-1 target gene, hes-1, was also seen (p=0.005). Histology revealed that increased expression of active Notch-1 is localized to the mammary stem cell niche, the terminal end bud. Similar to the normal gland, jnk2ko mammary tumors possessing wildtype p53 exhibit decreased proportions of basal cells (p=0.0002) and increased proportions of luminal cells (p=0.0411) relative to wildtype. Jnk2ko cell lines derived from these tumors show decreased expression of notch-1 (p=0.0018) and hes-1 (p=0.0602) following introduction of JNK2. Luciferase assays comparing activity of the notch-1 promoter to a notch-1 promoter with mutated p53 response elements revealed a dependence of increased notch-1 promoter activity in jnk2ko cells on the p53 response element. P53ko tumor cells, by contrast, do not exhibit alterations in notch-1 promoter activity in the absence of p53 response elements, regardless of JNK2 status. QPCR showed that loss of JNK2 in normal mammary glands and tumors causes increased p53 expression—thus providing a potential mechanism. In support that Notch upregulation in the absence of JNK2 is dependent upon p53, normal glands lacking p53 show no differences in lineage differentiation. P53ko tumors also show no differences in basal lineage differentiation, however, increases in luminal differentiation are maintained in the absence of JNK2. Consistent with increased luminal differentiation, jnk2ko caused decreased expression of markers involved in the epithelial to mesenchymal transition phenotype. This data suggests that JNK2 is important not only for lineage differentiation in normal mammary glands, but in mammary tumors and that the effect is dependent on both Notch1 and p53. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD08-01.

Abstract 4362: RBM3 overexpression promotes cancer stem cell expansion through activation of Notch-1 signaling

Abstract Cancers are heterogeneous population of cells, a minor portion of which exhibit stem-like characteristics. Recent evidence suggests that these Cancer Stem Cells (CSCs) are responsible for tumor behavior. Recently, we reported that RNA binding protein RBM3 is overexpressed in various tumors of epithelial origin and downregulating its expression results in inhibition of tumor growth. Moreover, RBM3 affects the proliferation of CD34+ hematopoietic stem cell. Overexpression of RBM3 induces NIH-3T3 cells to transform and grow in an anchorage independent manner, and form tumors in athymic nude mice suggesting RBM3 is a proto-oncogene. Given these observations, we sought to determine whether RBM3 expression affects CSCs in solid tumors and its function in tumor initiation and/or metastasis. We have recently demonstrated that Doublecortin like Kinase-I (DCAMKL-1/DCLK1), a microtubule-associated kinase is a marker of quiescent intestinal stem cells. Immunohistochemical analyses of the NIH3T3-RBM3 tumors demonstrated an increase in the number of DCLK-1+ stem cells. Using fluorescence-activated cell sorting, we were able to isolate these DCLK-1+ stem cells from the bulk of the tumor and grow them in tissue culture dishes. We have named these cells as RNA binding protein-Induced Cancer Stem Cells (RICSCs). We next determined the stemness of the DCLK-1+ RICSCs. For this, we performed serial dilutions of the RICSCs starting at 10,000 cells and injected them into the flanks of nude mice. Even when 500 cells were injected, a primary tumor was observed at about 10 weeks; the histological analysis of the tissues revealing metastatic lesions in the lung, liver, bone and spleen. Recent studies with mammary and neuroectodermal tumors have suggested that inappropriate Notch activation promotes self-renewal and transformation of progenitor cells. We observed that there was a significant upregulation of activated Notch-1 expression in the NIH-3T3-RBM3 RICSCs. Inhibition of Notch-1 with a specific inhibitor, DAPT resulted in the arrest of RICSC-mediated tumor growth in nude mice. These data demonstrate that Notch signaling is essential for self-renewal in stem cells thereby affecting tumor growth. Taken together, these data imply that overexpression of RBM3 results in increased dedifferentiation into cancer stem cells that have an aggressive metastatic phenotype. These CSCs have great potentials for aiding in our understanding of oncogenesis and metastatic cascades. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4362. doi:10.1158/1538-7445.AM2011-4362

Epithelial Notch signaling regulates interstitial fibrosis development in the kidneys of mice and humans

Chronic kidney disease is a leading cause of death in the United States. Tubulointerstitial fibrosis (TIF) is considered the final common pathway leading to end-stage renal disease (ESRD). Here, we used pharmacologic, genetic, in vivo, and in vitro experiments to show that activation of the Notch pathway in tubular epithelial cells (TECs) in patients and in mouse models of TIF plays a role in TIF development. Expression of Notch in renal TECs was found to be both necessary and sufficient for TIF development. Genetic deletion of the Notch pathway in TECs reduced renal fibrosis. Consistent with this, TEC-specific expression of active Notch1 caused rapid development of TIF. Pharmacologic inhibition of Notch activation using a γ-secretase inhibitor ameliorated TIF. In summary, our experiments establish that epithelial injury and Notch signaling play key roles in fibrosis development and indicate that Notch blockade may be a therapeutic strategy to reduce fibrosis and ESRD development.

Endothelial Notch signaling is upregulated in human brain arteriovenous malformations and a mouse model of the disease

Brain arteriovenous malformations (BAVMs) can cause lethal hemorrhagic stroke and have no effective treatment. The cellular and molecular basis for this disease is largely unknown. We have previously shown that expression of constitutively-active Notch4 receptor in the endothelium elicits and maintains the hallmarks of BAVM in mice, thus establishing a mouse model of the disease. Our work suggested that Notch pathway could be a critical molecular mediator of BAVM pathogenesis. Here, we investigated the hypothesis that upregulated Notch activation contributes to the pathogenesis of human BAVM. We examined the expression of the canonical Notch downstream target Hes1 in the endothelium of human BAVMs by immunofluorescence, and showed increased levels relative to either autopsy or surgical biopsy controls. We then analyzed receptor activity using an antibody to the activated form of the Notch1 receptor, and found increased levels of activity. These findings suggest that Notch activation may promote the development and even maintenance of BAVM. We also detected increases in Hes1 and activated Notch1 expression in our mouse model of BAVM induced by constitutively active Notch4, demonstrating molecular similarity between the mouse model and the human disease. Our work suggests that activation of Notch signaling is an important molecular candidate in BAVM pathogenesis and further validates that our animal model provides a platform to study the progression as well as the regression of the disease.

Expression of active Notch1 in avian coronary development

Notch1 is an important regulator of intercellular interactions in cardiovascular development. We show that the nuclear-localized, cleaved and active form of Notch1, the Notch1 intracellular domain (N1ICD), appeared in mesothelial cells of the pro-epicardium during epicardial formation at looped heart stages. N1ICD was also present in mesothelial cells and mesenchymal cells specifically within the epicardium at sulcus regions. N1ICD-positive endothelial cells were detected within the nascent vessel plexus at the atrioventricular junction and within the compact myocardium (Hamburger and Hamilton stage [HH] 25-HH30). The endothelial cells expressing N1ICD were surrounded by N1ICD-positive smooth muscle cells after coronary orifice formation (HH32-HH35), while N1ICD expression was absent in the mesenchymal and mesothelial cells surrounding mature coronary vessels. We propose that differential activation of the hypoxia/HIF1-VEGF-Notch pathway may play a role in epicardial cell interactions that promote epicardial epithelial/mesenchymal transition and coronary progenitor cell differentiation during epicardial development and coronary vasculogenesis in particularly hypoxic sulcus regions.

Activated Notch pathway proteins and FoxG1 are co‐expressed in Medulloblastoma: correlation with phenotype

Notch pathway activation has been implicated in the negative regulation of neural differentiation in the developing central nervous sytem. Hes 1 and Hes 5 are downstream effectors of the Notch pathway. FoxG1 forms a transcriptional repressor complex with Hes1 and was recently reported as dysregulated in all histologic types of medulloblastoma. We examined 64 medulloblastomas by IHC for nuclear expression of activated Notch‐1, Hes1, and Hes5. Activated Notch‐1, Hes1, and Hes5 expression were detected in all histologic subtypes. Using Spearman correlation (SC) analysis, there was a positive correlation between the expression of activated Notch1 and Hes1 (SC coeff 0.36, p=0.0035) and Hes 5 (SC coeff 0.433, p<0.001). Expression of FoxG1 and Notch1 also showed a weak, but significant positive correlation (SC coeff 0.273, p=0.028).Activated Notch1 expression was higher in the anaplastic subtype (ANOVA on Ranks, Dunn's test, H=12.968, p=0.002). Co‐expression of FoxG1 and Notch pathway effectors is consistent with a putative combined role of FoxG1 and activated Notch pathway in the maintenance of an undiferentiated state in medulloblastoma. In view of the reported association of myc amplification with anaplastic progression and the known Notch‐Wnt signaling pathway crosstalk, the significance of our demonstration of a correlation between Notch1 expression and the anaplastic phenotype remains to be explored.

Notch Agonists: Emerging as a Feasible Therapeutic Approach in AML.

Introduction: The Notch pathway regulates critical cell-fate decisions affecting the growth and development of human hematopoietic cells. Although Notch1 is a known T cell oncogene, we have discovered that Notch signaling behaves as a tumor suppressor in acute myeloblastic leukemia (AML) inducing growth arrest and apoptosis in both cell lines and patient samples. To characterize the mechanism of this effect we have evaluated the influence of the Notch pathway on key effectors of differentiation, cell cycle, and apoptosis in human AML.Results: Notch signaling induces rapid growth arrest and apoptosis in a panel of human AML cell lines representing a range of AML FAB subtypes (M2–M6). Specifically, activated Notch1 expression caused a 70–95% reduction in AML cells compared to controls (p<0.001) (Figure 1). Notch-mediated growth arrest occurred in 24–48 hours with cells accumulating in G0/G1. Apoptosis was demonstrated by a 3.8-fold increase in AnnexinV binding (p<0.004) and a 3-fold upregulation of caspase 3 activity (p=0.0002) within 24 hours. The caspase 3 activity was abolished by the caspase 8 inhibitor IETD (p<0.0001) suggesting a potential role for the extrinsic death pathway.We also found that all four Notch receptors (1–4) are capable of inducing this effect, as is the Notch target gene HES1, suggesting a generalized Notch tumor suppressor effect in AML. Furthermore, Notch signaling through HES1 modulates the expression of key regulators of myeloid differentiation and cell cycle progression including downregulation of CEBPα 2.5-fold (p<0.02) and upregulation of p21WAF1 6-fold (p<0.004) suggesting potential mechanisms.As a novel therapeutic approach, we synthesized Notch agonists which effectively induce Notch signaling with a >18-fold increase in HES1 expression (p<.0001). Exposure of human AML cell lines and primary patient AML samples to this Notch agonist for 24 hours led to a 3 to 9-fold increase in apoptosis (p<0.017) compared to controls (Figure 2).Conclusions: We report here that Notch signaling is a novel tumor suppressor pathway in human AML. We demonstrate how Notch agonists can be used to induce growth arrest and apoptosis in human AML cell lines and patient AML samples. As a regulator of cell fate, proliferation and differentiation, Notch effectively disrupts multiple pathways in AML. We propose that Notch agonists represent a novel and feasible therapeutic approach in AML. Pre-clinical evaluation is underway. [Display omitted] [Display omitted]