Implications of Dll4-Notch signaling activation in primary glioblastoma multiforme

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Cancer-associated fibroblasts-induced remodeling of tumor immune microenvironment via Jagged1 in glioma

Tumor immunosuppression are prominent characteristics of brain glioma. Current standard modality including surgical resection and chemoradiotherapy do not significantly improve clinical outcomes. Cancer-associated fibroblasts (CAFs) that regard as important stromal cells in tumor microenvironment have been confirmed to play crucial roles in tumor development. However, the effects of CAFs on tumor immunosuppression in glioma are not well expounded. In this study, we report that CAFs contributes to the formation of glioma immunosuppressive microenvironment. Specifically, we found that glioma-derived Jagged1 enhanced the proliferation and PD-L1 expression of CAFs in vitro. Importantly, we discovered that Notch1, c-Myc and PD-L1 expression were significantly increased in high Jagged1-expressing gliomas, moreover, we further confirmed that Notch1 and PD-L1 expression located on the CAFs in glioma tissues. We also found that glioma-derived Jagged1 promotes the increase of tumor-infiltrating macrophages, M2 macrophages and Foxp3 Treg cells, as well as no significance of M1 macrophages and CD8+ T cells, indicating potential immunosuppression. This study opens up novel therapeutic strategies reversing CAF immunosuppression for gliomas.

Delta- like ligand 4- expressing macrophages and human diseases: Insights into pathophysiology and therapeutic opportunities

Macrophages are key players in the immune response and have been implicated in various human diseases, including atherosclerosis, cancer, and chronic inflammatory disorders. While numerous studies have delved into the nuances of macrophage behavior in these conditions, there remains a gap in understanding the specific role of Delta-like ligand 4 (Dll4)-expressing macrophages and their overarching implications across these diseases. Among the plethora of factors expressed by macrophages, Dll4 has emerged as a molecule of particular interest. Recent studies have highlighted its unique role in modulating macrophage functions and its potential implications in various diseases. This review seeks to consolidate existing knowledge, address this gap, and present a comprehensive overview of Dll4-expressing macrophages in the context of these disorders and highlight their potential as therapeutic targets. We examined the involvement of Dll4-expressing macrophages in multiple human diseases such as atherosclerosis, cancer and chronic inflammatory diseases, emphasizing their influence on disease progression. We also discussed the challenges, limitations, and emerging research areas in targeting Dll4-expressing macrophages and provide an outlook on potential therapeutic strategies for the treatment of these diseases. By addressing the previously existing research gap, we've provided a roadmap that brings together fragmented insights, paving the way for more holistic research and potentially more effective therapeutic strategies centered on Dll4-expressing macrophages.

Development and validation of an immune infiltration/tumor proliferation-related Notch3 nomogram for predicting survival in patients with primary glioblastoma

Background: Notch receptors (Notch 1/2/3/4), the critical effectors of the Notch pathway, participate in the tumorigenesis and progression of many malignancies. However, the clinical roles of Notch receptors in primary glioblastoma (GBM) have not been fully elucidated. Methods: The genetic alteration-related prognostic values of Notch receptors were determined in the GBM dataset from The Cancer Genome Atlas (TCGA). Two GBM datasets from TCGA and Chinese Glioma Genome Atlas (CGGA) were used to explore the differential expression between Notch receptors and IDH mutation status, and GBM subtypes. The biological functions of Notch Receptors were explored by Gene Ontology and KEGG analysis. The expression and prognostic significance of Notch receptors were determined in the TCGA and CGGA datasets and further validated in a clinical GBM cohort by immunostaining. A Notch3-based nomogram/predictive risk model was constructed in the TCGA dataset and validated in the CGGA dataset. The model performance was evaluated by receiver operating curves, calibration curves, and decision curve analyses. The Notch3-related phenotypes were analyzed via CancerSEA and TIMER. The proliferative role of Notch3 in GBM was validated in U251/U87 glioma cells by Western blot and immunostaining. Results: Notch receptors with genetic alterations were associated with poor survival of GBM patients. Notch receptors were all upregulated in GBM of TCGA and CGGA databases and closely related to the regulation of transcription, protein-lysine N-methyltransferase activity, lysine N-methyltransferase activity, and focal adhesion. Notch receptors were associated with Classical, Mesenchymal, and Proneural subtypes. Notch1 and Notch3 were closely correlated with IDH mutation status and G-CIMP subtype. Notch receptors displayed the differential expression at the protein level and Notch3 showed a prognostic significance in a clinical GBM cohort. Notch3 presented an independent prognostic role for primary GBM (IDH1 mutant/wildtype). A Notch3-based predictive risk model presented favorable accuracy, reliability, and net benefits for predicting the survival of GBM patients (IDH1 mutant/wildtype and IDH1 wildtype). Notch3 was closely related to immune infiltration (macrophages, CD4⁺ T cells, and dendritic cells) and tumor proliferation. Conclusion: Notch3-based nomogram served as a practical tool for anticipating the survival of GBM patients, which was related to immune-cell infiltration and tumor proliferation.

Notch signaling, hypoxia, and cancer

Notch signaling is involved in cell fate determination and deregulated in human solid tumors. Hypoxia is an important feature in many solid tumors, which activates hypoxia-induced factors (HIFs) and their downstream targets to promote tumorigenesis and cancer development. Recently, HIFs have been shown to trigger the Notch signaling pathway in a variety of organisms and tissues. In this review, we focus on the pro- and anti-tumorigenic functions of Notch signaling and discuss the crosstalk between Notch signaling and cellular hypoxic response in cancer pathogenesis, including epithelia-mesenchymal transition, angiogenesis, and the maintenance of cancer stem cells. The pharmacological strategies targeting Notch signaling and hypoxia in cancer are also discussed in this review.

Current Opportunities for Targeting Dysregulated Neurodevelopmental Signaling Pathways in Glioblastoma

Glioblastoma (GBM) is the most common and highly lethal type of brain tumor, with poor survival despite advances in understanding its complexity. After current standard therapeutic treatment, including tumor resection, radiotherapy and concomitant chemotherapy with temozolomide, the median overall survival of patients with this type of tumor is less than 15 months. Thus, there is an urgent need for new insights into GBM molecular characteristics and progress in targeted therapy in order to improve clinical outcomes. The literature data revealed that a number of different signaling pathways are dysregulated in GBM. In this review, we intended to summarize and discuss current literature data and therapeutic modalities focused on targeting dysregulated signaling pathways in GBM. A better understanding of opportunities for targeting signaling pathways that influences malignant behavior of GBM cells might open the way for the development of novel GBM-targeted therapies.

Monocentric evaluation of Ki-67 labeling index in combination with a modified RPA score as a prognostic factor for survival in IDH-wildtype glioblastoma patients treated with radiochemotherapy

Purpose

The prognosis for glioblastoma patients remains dismal despite intensive research on better treatment options. Molecular and immunohistochemical markers are increasingly being investigated as understanding of their role in disease progression grows. O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation has been shown to have prognostic and therapeutic relevance for glioblastoma patients. Other markers implicated in tumor formation and/or malignancy are p53, Alpha thalassemia/mental retardation syndrome X-linked (ATRX), Epidermal Growth Factor Receptor splice variant III (EGFRvIII), and Ki-67, with loss of nuclear ATRX expression and lower Ki-67 index being associated with prolonged survival. For p53 and EGFRvIII the data are contradictory. Our aim was to investigate the markers mentioned above regarding progression-free (PFS) and overall survival (OS) to evaluate their viability as independent prognostic markers for our patient collective.

Methods

In this retrospective study, we collected data on patients undergoing radiotherapy due to isocitrate dehydrogenase (IDH) wildtype glioblastoma at a single university hospital between 2014 and 2020.

Results

Our findings confirm Ki-67 labeling index ≤ 20% as an independent prognostic factor for prolonged PFS as well as MGMT promoter methylation for both prolonged PFS and OS, in consideration of age and Eastern Cooperative Oncology Group (ECOG) status, chemotherapy treatment, and total radiation dose for PFS as well as additionally sex, resection status, and receipt of treatment for progression or recurrence for OS. Additionally, Ki-67 labeling index ≤ 20% showed a significant correlation with prolonged OS in univariate analysis. Modification of the recursive partitioning analysis (RPA) score to include Ki-67 labeling index resulted in a classification with the possible ability to distinguish long-term-survivors from patients with unfavorable prognosis.

Conclusion

MGMT promoter methylation and Ki-67 labeling index were independent predictors of survival in our collective. We see further studies pooling patient collectives to reach larger patient numbers concerning Ki-67 labeling index as being warranted.

Supplementary Information

The online version of this article (10.1007/s00066-022-01959-6) contains supplementary material, which is available to authorized users.

Tracing the origins of glioblastoma by investigating the role of gliogenic and related neurogenic genes/signaling pathways in GBM development: a systematic review

Background

Glioblastoma is one of the most aggressive tumors. The etiology and the factors determining its onset are not yet entirely known. This study investigates the origins of GBM, and for this purpose, it focuses primarily on developmental gliogenic processes. It also focuses on the impact of the related neurogenic developmental processes in glioblastoma oncogenesis. It also addresses why glial cells are at more risk of tumor development compared to neurons.

Methods

Databases including PubMed, MEDLINE, and Google Scholar were searched for published articles without any date restrictions, involving glioblastoma, gliogenesis, neurogenesis, stemness, neural stem cells, gliogenic signaling and pathways, neurogenic signaling and pathways, and astrocytogenic genes.

Results

The origin of GBM is dependent on dysregulation in multiple genes and pathways that accumulatively converge the cells towards oncogenesis. There are multiple layers of steps in glioblastoma oncogenesis including the failure of cell fate-specific genes to keep the cells differentiated in their specific cell types such as p300, BMP, HOPX, and NRSF/REST. There are genes and signaling pathways that are involved in differentiation and also contribute to GBM such as FGFR3, JAK-STAT, and hey1. The genes that contribute to differentiation processes but also contribute to stemness in GBM include notch, Sox9, Sox4, c-myc gene overrides p300, and then GFAP, leading to upregulation of nestin, SHH, NF-κB, and others. GBM mutations pathologically impact the cell circuitry such as the interaction between Sox2 and JAK-STAT pathway, resulting in GBM development and progression.

Conclusion

Glioblastoma originates when the gene expression of key gliogenic genes and signaling pathways become dysregulated. This study identifies key gliogenic genes having the ability to control oncogenesis in glioblastoma cells, including p300, BMP, PAX6, HOPX, NRSF/REST, LIF, and TGF beta. It also identifies key neurogenic genes having the ability to control oncogenesis including PAX6, neurogenins including Ngn1, NeuroD1, NeuroD4, Numb, NKX6-1 Ebf, Myt1, and ASCL1. This study also postulates how aging contributes to the onset of glioblastoma by dysregulating the gene expression of NF-κB, REST/NRSF, ERK, AKT, EGFR, and others.

Characterization of Temozolomide Resistance Using a Novel Acquired Resistance Model in Glioblastoma Cell Lines

Simple Summary

Temozolomide (TMZ) is the first-line drug for chemotherapy of GBM, the most aggressive and incurable brain tumor. Acquired chemoresistance is a hallmark that causes the poor prognosis of GBM. Therefore, understanding the underlying mechanisms by using a proper model becomes emergent. Previous models usually take weeks/months and are often not fully representative of characteristics of TMZ resistance. We established an acute acquired TMZ resistance model using GBM cell lines with different genomic backgrounds. In response to TMZ, the resistant cells showed less susceptibility and sustained regrowth, high clonogenicity, reduced DNA damage accompanied by attenuated MMR, shortened G2/M arrest, uncontrolled DNA replication, and evasion of apoptosis. Moreover, these TMZ resistant cells presented stem cell properties that are critical for chemoresistance. Thus, our model recapitulates all key features of TMZ resistance and is believed to be a promising model to study the underlying mechanisms and define therapeutics for GBM in the future.

Abstract

Temozolomide (TMZ) is the first line of standard therapy in glioblastoma (GBM). However, relapse occurs due to TMZ resistance. We attempted to establish an acquired TMZ resistance model that recapitulates the TMZ resistance phenotype and the relevant gene signature. Two GBM cell lines received two cycles of TMZ (150 µM) treatment for 72 h each. Regrown cells (RG2) were defined as TMZ resistant cells. MTT assay revealed significantly less susceptibility and sustained growth of RG2 compared with parental cells after TMZ challenge. TMZ-induced DNA damage significantly decreased in 53BP1-foci reporter transduced-RG2 cells compared with parental cells, associated with downregulation of MSH2 and MSH6. Flow cytometry revealed reduced G2/M arrest, increased EdU incorporation and suppressed apoptosis in RG2 cells after TMZ treatment. Colony formation and neurosphere assay demonstrated enhanced clonogenicity and neurosphere formation capacity in RG2 cells, accompanied by upregulation of stem markers. Collectively, we established an acute TMZ resistance model that recapitulated key features of TMZ resistance involving impaired mismatch repair, redistribution of cell cycle phases, increased DNA replication, reduced apoptosis and enhanced self-renewal. Therefore, this model may serve as a promising research tool for studying mechanisms of TMZ resistance and for defining therapeutic approaches to GBM in the future.

Contradictory Effect of Notch1 and Notch2 on Phosphatase and Tensin Homolog and its Influence on Glioblastoma Angiogenesis

Many genes induce angiogenesis in tumors, and among them, Notch family genes have received particular attention due to their extensive network of connections with other genes active in this function. Suppression of angiogenic signaling has been studied in various cancers, confirming Notch's fundamental and extensive role. According to studies, four Notch genes work independently with many genes such as vascular endothelial growth factor, phosphatase and tensin homolog, Phosphoinositide 3-kinase/Akt, and matrix metalloproteinases, and so many other genes, as well as proteins (such as hypoxia-inducible factor-1 alpha) significantly affect tumor angiogenesis. Notch1 regular activity in a healthy person causes angiogenesis in body tissues, controlled by normal Notch2 activity. However, in many cases of glioblastoma, whether on patients or tumor xenografts or in vivo models, a mutation in one of these two essential genes or at least one of the genes and proteins that affected by them can cause better angiogenesis in hypoxic conditions and lead to become an invasive tumor. In this review, we examined the contrasting activity of Notch1 and Notch2 and the signaling cascade that each generates in the angiogenesis of glioblastoma, the most invasive cancer of the central nervous system.

POFUT1 acts as a tumor promoter in glioblastoma by enhancing the activation of Notch signaling

Dysregulation of protein O-fucosyl transferase 1 (POFUT1) contributes to the occurrence and progression of multiple cancers. However, whether POFUT1 has a relationship with the pathogenesis of glioblastoma (GBM) is unknown. This work was aimed at evaluating the detailed relevance of POFUT1 in GBM. Here, we demonstrated high levels of POFUT1 in GBM tissue and elucidated that GBM patients with high levels of POFUT1 had a shorter survival rate than those with low levels of POFUT1. POFUT1 knockdown in GBM cells markedly downregulated the ability to proliferate and invade, while overexpression of POFUT1 potentiated the proliferative and invasive ability of GBM cells. Further mechanistic studies indicated that silencing POFUT1 prohibited the activation of Notch signaling, leading to a reduction in the expression of HES1 and HEY1. On the contrary, overexpression of POFUT1 enhanced the activation of Notch signaling. Notably, inhibition of Notch signaling markedly reversed POFUT1-overexpression-induced tumor promotion effects in GBM cells. In addition, POFUT1 silencing markedly repressed the potential of GBM cells to form tumors in vivo. In conclusion, the data of this work indicates that POFUT1 serves a tumor promotion role in GBM by enhancing the activation of Notch signaling. This study underlines the potential role of the POFUT1/Notch axis in GBM progression and proposes POFUT1 as a promising anticancer target for GBM.

Epigenetics of glioblastoma multiforme: From molecular mechanisms to therapeutic approaches

Glioblastoma multiforme (GBM) is the most common form of brain cancer and one of the most aggressive cancers found in humans. Most of the signs and symptoms of GBM can be mild and slowly aggravated, although other symptoms might demonstrate it as an acute ailment. However, the precise mechanisms of the development of GBM remain unknown. Due to the improvement of molecular pathology, current researches have reported that glioma progression is strongly connected with different types of epigenetic phenomena, such as histone modifications, DNA methylation, chromatin remodeling, and aberrant microRNA. Furthermore, the genes and the proteins that control these alterations have become novel targets for treating glioma because of the reversibility of epigenetic modifications. In some cases, gene mutations including P16, TP53, and EGFR, have been observed in GBM. In contrast, monosomies, including removals of chromosome 10, particularly q23 and q25-26, are considered the standard markers for determining the development and aggressiveness of GBM. Recently, amid the epigenetic therapies, histone deacetylase inhibitors (HDACIs) and DNA methyltransferase inhibitors have been used for treating tumors, either single or combined. Specifically, HDACIs are served as a good choice and deliver a novel pathway to treat GBM. In this review, we focus on the epigenetics of GBM and the consequence of its mutations. We also highlight various treatment approaches, namely gene editing, epigenetic drugs, and microRNAs to combat GBM.

TRPM7 Induces Tumorigenesis and Stemness Through Notch Activation in Glioma

We have reported that transient receptor potential melastatin-related 7 (TRPM7) regulates glioma stem cells (GSC) growth and proliferation through Notch, STAT3-ALDH1, and CD133 signaling pathways. In this study, we determined the major contributor(s) to TRPM7 mediated glioma stemness by further deciphering each individual Notch signaling. We first determined whether TRPM7 is an oncotarget in glioblastoma multiforme (GBM) using the Oncomine database. Next, we determined whether TRPM7 silencing by siRNA TRPM7 (siTRPM7) induces cell growth arrest or apoptosis to reduce glioma cell proliferation using cell cycle analysis and annexin V staining assay. We then examined the correlations between the expression of TRPM7 and Notch signaling activity as well as the expression of GSC markers CD133 and ALDH1 in GBM by downregulating TRPM7 through siTRPM7 or upregulating TRPM7 through overexpression of human TRPM7 (M7-wt). To distinguish the different function of channel and kinase domain of TRPM7, we further determined how the α-kinase-dead mutants of TRPM7 (α-kinase domain deleted/M7-DK and K1648R point mutation/M7-KR) affect Notch activities and CD133 and ALDH1 expression. Lastly, we determined the changes in TRPM7-mediated regulation of glioma cell growth/proliferation, cell cycle, and apoptosis by targeting Notch1. The Oncomine data revealed a significant increase in TRPM7 mRNA expression in anaplastic astrocytoma, diffuse astrocytoma, and GBM patients compared to that in normal brain tissues. TRPM7 silencing reduced glioma cell growth by inhibiting cell entry into S and G2/M phases and promoting cell apoptosis. TRPM7 expression in GBM cells was found to be positively correlated with Notch1 signaling activity and CD133 and ALDH1 expression; briefly, downregulation of TRPM7 by siTRPM7 decreased Notch1 signaling whereas upregulation of TRPM7 increased Notch1 signaling. Interestingly, kinase-inactive mutants (M7-DK and M7-KR) resulted in reduced activation of Notch1 signaling and decreased expression of CD133 and ALDH1 compared to that of wtTRPM7. Finally, targeting Notch1 effectively suppressed TRPM7-induced growth and proliferation of glioma cells through cell G1/S arrest and apoptotic induction. TRPM7 is responsible for sustained Notch1 signaling activation, enhanced expression of GSC markers CD133 and ALDH1, and regulation of glioma stemness, which contributes to malignant glioma cell growth and invasion.

The predominant expression of cancer stem cell marker ALDH1A3 in tumor infiltrative area is associated with shorter overall survival of human glioblastoma

Background

ALDH1A3 is a cancer stem cell marker in neoplasms including glioblastoma (GBM). However, the comprehensive role of ALDH1A3 in GBM remains unclear. This study attempted to investigate the expression of ALDH1A3 in human GBM tissues and its association with clinical parameters.

Methods

Thirty primary GBM and 9 control were enrolled in this study. ALDH1A3 mRNA and protein expression levels were detected by RT²-PCR and western blot, respectively. Immunohistochemistry and immunofluorescence staining were performed to evaluate the regional and cellular expression manner of ALDH1A3. The association of ALDH1A3 expression with multiple clinical parameters was analyzed.

Results

ALDH1A3 protein level, but not mRNA level, in a subgroup of GBM was significantly higher than that in the control group. ALDH1A3 immunoreactivity was detected heterogeneously in individual GBMs. Fifteen of 30 cases showed a positive of ALDH1A3 immunoreactivity which was predominantly observed in the tumor infiltrative area (TI). Double immunofluorescence staining revealed a co-localization of ALDH1A3 with GFAP in glial-shaped cells and in tumor cells. ALDH1A3 immunoreactivity was often merged with CD44, but not with CD68. Moreover, ALDH1A3 expression was positively associated with the tumor edema grade and inversely with overall survival (OS) (median OS: 16 months vs 10 months), but with neither MGMT promoter methylation status nor Ki67 index in GBM. An upregulation of ALDH1A3 was accompanied by a reduced expression of STAT3β and p-STAT3β.

Conclusions

Inter- and intra-tumoral heterogeneous expression of ALDH1A3 was exhibited in GBMs. A high immunoreactivity of ALDH1A3 in tumor infiltrative area was associated with shorter OS, especially in patients with MGMT promoter methylation. Our findings propose ALDH1A3 not only as a predictive biomarker but also as a potential target for personalized therapy of GBM.

The Role of DLLs in Cancer: A Novel Therapeutic Target

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

Therapeutic Targeting of the Notch Pathway in Glioblastoma Multiforme

BACKGROUND

Glioblastoma (GBM) is the most common and deadly form of brain tumor. After standard treatment of resection, radiotherapy, and chemotherapy, the 5-year survival is <5%. In recent years, research has uncovered several potential targets within the Notch signaling pathway, which may lead to improved patient outcomes.

METHODS

A literature search was performed for articles containing the terms "Glioblastoma" and "Receptors, Notch" between 2003 and July 2015. Of the 62 articles retrieved, 46 met our criteria and were included in our review. Nine articles were identified from other sources and were subsequently included, leaving 55 articles reviewed.

RESULTS

Of the 55 articles reviewed, 47 used established human GBM cell lines. Seventeen articles used human GBM surgical samples. Forty-five of 48 articles that assessed Notch activity showed increased expression in GBM cell lines. Targeting the Notch pathway was carried out through Notch knockdown and overexpression and targeting δ-like ligand, Jagged, γ-secretase, ADAM10, ADAM17, and Mastermindlike protein 1. Arsenic trioxide, microRNAs, and several other compounds were shown to have an effect on the Notch pathway in GBM. Notch activity in GBM was also shown to be associated with hypoxia and certain cancer-related molecular pathways such as PI3K/AKT/mTOR and ERK/MAPK. Most articles concluded that Notch activity amplifies malignant characteristics in GBM and targeting this pathway can bring about amelioration of these effects.

CONCLUSIONS

Recent literature suggests targeting the Notch pathway has great potential for future therapies for GBM.

Role of Notch Signaling Pathway in Glioblastoma Pathogenesis

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

Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in glioblastoma

PURPOSE

Glioblastoma (GBM) is one of the most aggressive and incurable primary brain tumors. Identification of novel therapeutic targets is an urgent priority. Programmed cell death 10 (PDCD10), a ubiquitously expressed apoptotic protein, has shown a dual function in different types of cancers and in chemo-resistance. Recently, we reported that PDCD10 was downregulated in human GBM. The aim of this study was to explore the function of PDCD10 in GBM cells.

METHODS

PDCD10 was knocked down in three GBM cell lines (U87, T98g and LN229) by lentiviral-mediated shRNA transduction. U87 and T98g transduced cells were used for phenotype study and LN229 and T98g cells were used for apoptosis study. The role of PDCD10 in apoptosis and chemo-resistance was investigated after treatment with staurosporine and temozolomide. A GBM xenograft mouse model was used to confirm the function of PDCD10 in vivo. A protein array was performed in PDCD10-knockdown and control GBM cells.

RESULTS

Knockdown of PDCD10 in GBM cells promoted cell proliferation, adhesion, migration, invasion, and inhibited apoptosis and caspase-3 activation. PDCD10-knockdown accelerated tumor growth and increased tumor mass by 2.1-fold and led to a chemo-resistance of mice treated with temozolomide. Immunostaining revealed extensive Ki67-positive cells and less activation of caspase-3 in PDCD10-knockdown tumors. The protein array demonstrated an increased release of multiple growth factors from PDCD10-knockdown GBM cells.

CONCLUSIONS

Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in GBM, suggesting PDCD10 as a potential target for GBM therapy.

Molecular mechanism of Notch signaling with special emphasis on microRNAs: Implications for glioma

Glioma is the most aggressive primary brain tumor and is notorious for resistance to chemoradiotherapy. Although its associated mechanisms are still not completely understood, Notch signaling, an evolutionarily conserved pathway, appears to be the key processes involved. Nevertheless, its mechanisms are sophisticated, due to a variety of targets and signal pathways, especially microRNA. MicroRNAs, which are small noncoding regulatory RNA molecules, have been proposed as one of the key mechanisms in glioma pathogenesis. Among the known glioma associated microRNA, microRNA-129, microRNA-34 family, and microRNA-326 have been shown to influence the progress of glioma through Notch signaling. Evidence also indicates that recurrence is due to development or persistence of the glioma stem-like cells and active angiogenesis, which are tightly regulated by a variety of factors, including Notch signaling. In this review, we summarize the recent progress regarding the functional roles of Notch signaling in glioma, including Notch ligand, microRNA, intracellular crosstalk, glioma stem-like cells and active angiogenesis and explore their clinical implications as diagnostic or prognostic biomarkers and molecular therapeutic targets for glioma.

PVT1 regulates the malignant behaviors of human glioma cells by targeting miR-190a-5p and miR-488-3p

The long non-coding RNA (lncRNA) PVT1 is reported to be involved in tumorigenesis and the progression of many malignancies. However, the function of PVT1 in gliomas remains unclarified. The present study demonstrated the expression level of PVT1 using qRT-PCR. The role of PVT1 in the regulation of biological behaviors of glioma cells was investigated using CCK-8 assay, Transwell assay and flow cytometry. The possible molecular mechanisms were also elucidated. In our results, PVT1 was up-regulated in glioma specimens and cell lines. Knockdown of PVT1 impaired the malignant behaviors of glioma cells via the suppression of proliferation, migration and invasion, as well as through promotion of apoptosis. Furthermore, PVT1 was identified to affect the glioma cells via binding to miR-190a-5p and miR-488-3p, which were down-regulated and played tumor suppressor roles in glioma cells. Up-regulated miR-190a-5p or miR-488-3p partially rescued the suppressive effect induced by PVT1 knockdown. Myocyte enhancer factor 2C (MEF2C) was a direct downstream target of miR-190a-5p and miR-488-3p, which was proved to be an oncogene and involved in the PVT1 knockdown induced regulation of biological behaviors of glioma cells. Over-expression of MEF2C up-regulated JAGGED1 by increasing the promoter activity of JAGGED1. PVT1 knockdown combined with miR-190a-5p and miR-488-3p over-expression contributed to the smallest tumor volume and the longest survivals in nude mice. In conclusion, PVT1-miR-190a-5p/miR-488-3p-MEF2C-JAGGED1 axis is involved in proliferation and progression of glioma. Thus, PVT1 may become a novel target in glioma therapy.

Notch signaling: its roles and therapeutic potential in hematological malignancies

Notch is a highly conserved signaling system that allows neighboring cells to communicate, thereby controlling their differentiation, proliferation and apoptosis, with the outcome of its activation being highly dependent on signal strength and cell type. As such, there is growing evidence that disturbances in physiological Notch signaling contribute to cancer development and growth through various mechanisms. Notch was first reported to contribute to tumorigenesis in the early 90s, through identification of the involvement of the Notch1 gene in the chromosomal translocation t(7;9)(q34;q34.3), found in a small subset of T-cell acute lymphoblastic leukemia. Since then, Notch mutations and aberrant Notch signaling have been reported in numerous other precursor and mature hematological malignancies, of both myeloid and lymphoid origin, as well as many epithelial tumor types. Of note, Notch has been reported to have both oncogenic and tumor suppressor roles, dependent on the cancer cell type. In this review, we will first give a general description of the Notch signaling pathway, and its physiologic role in hematopoiesis. Next, we will review the role of aberrant Notch signaling in several hematological malignancies. Finally, we will discuss current and potential future therapeutic approaches targeting this pathway.

The two novel DLL4-targeting antibody-drug conjugates MvM03 and MGD03 show potent anti-tumour activity in breast cancer xenograft models

The anti-human Delta-like 4 (DLL4) monoclonal antibody MMGZ01 has a high affinity to hrDLL4 and arrests the DLL4-mediated human umbilical vein endothelial cell (HUVEC) phenotype, promotes immature vessels, and effectively reduces breast cancer cell growth in vivo. To develop a much more effective therapy, we conjugated MMGZ01 with two small-molecule cytotoxic agents, i.e., monomethyl auristatin E (MMAE) and doxorubicin (DOX), with different linkers to generate antibody-drug conjugates (ADCs), i.e., MMGZ01-vc-MMAE (named MvM03) and MMGZ01-GMBS-DOX (named MGD03), that are more potent therapeutic agents than naked antibody therapeutic agents. The produced anti-DLL4 ADCs can be effectively directed against DLL4 and internalized. Then, the release of MMAE or DOX into the cytosol can induce G2/M or G0/G1 phase growth arrest and cell death through the induction of apoptosis. In vitro, MvM03 was highly potent and selective against DLL4 cell lines. The anti-DLL4 ADCs, particularly MvM03, showed more potent anti-tumour activity than Docetaxel, which is an inhibitor of the depolymerisation of microtubules, in two xenograft breast cancer tumour models. Our findings indicate that anti-DLL4 ADCs have promising potential as an effective therapy for breast cancer.

The interference of Notch1 target Hes1 affects cell growth, differentiation and invasiveness of glioblastoma stem cells through modulation of multiple oncogenic targets

The invasive and lethal nature of Glioblastoma multiforme (GBM) necessitates the continuous identification of molecular targets and search of efficacious therapies to inhibit GBM growth. The GBM resistance to chemotherapy and radiation it is attributed to the existence of a rare fraction of cancer stem cells (CSC) that we have identified within the tumor core and in peritumor tissue of GBM. Since Notch1 pathway is a potential therapeutic target in brain cancer, earlier we highlighted that pharmacological inhibition of Notch1 signalling by γ-secretase inhibitor-X (GSI-X), reduced cell growth of some c-CSC than to their respective p-CSC, but produced negligible effects on cell cycle distribution, apoptosis and cell invasion. In the current study, we assessed the effects of Hes1-targeted shRNA, a Notch1 gene target, specifically on GBM CSC refractory to GSI-X. Depletion of Hes1 protein induces major changes in cell morphology, cell growth rate and in the invasive ability of shHes1-CSC in response to growth factor EGF. shHes1-CSC show a decrease of the stemness marker Nestin concurrently to a marked increase of neuronal marker MAP2 compared to pLKO.1-CSC. Those effects correlated with repression of EGFR protein and modulation of Stat3 phosphorylation at Y705 and S727 residues. In the last decade Stat3 has gained attention as therapeutic target in cancer but there is not yet any approved Stat3-based glioma therapy. Herein, we report that exposure to a Stat3/5 inhibitor, induced apoptosis either in shHes1-CSC or control cells. Taken together, Hes1 seems to be a favorable target but not sufficient itself to target GBM efficaciously, therefore a possible pharmacological intervention should provide for the use of anti-Stat3/5 drugs either alone or in combination regimen.

Remodeling the blood-brain barrier microenvironment by natural products for brain tumor therapy

Brain tumor incidence shows an upward trend in recent years; brain tumors account for 5% of adult tumors, while in children, this figure has increased to 70%. Moreover, 20%-30% of malignant tumors will eventually metastasize into the brain. Both benign and malignant tumors can cause an increase in intracranial pressure and brain tissue compression, leading to central nervous system (CNS) damage which endangers the patients' lives. Despite the many approaches to treating brain tumors and the progress that has been made, only modest gains in survival time of brain tumor patients have been achieved. At present, chemotherapy is the treatment of choice for many cancers, but the special structure of the blood-brain barrier (BBB) limits most chemotherapeutic agents from passing through the BBB and penetrating into tumors in the brain. The BBB microenvironment contains numerous cell types, including endothelial cells, astrocytes, peripheral cells and microglia, and extracellular matrix (ECM). Many chemical components of natural products are reported to regulate the BBB microenvironment near brain tumors and assist in their treatment. This review focuses on the composition and function of the BBB microenvironment under both physiological and pathological conditions, and the current research progress in regulating the BBB microenvironment by natural products to promote the treatment of brain tumors.

EphB4 forward signalling mediates angiogenesis caused by CCM3/PDCD10-ablation

CCM3, also named as PDCD10, is a ubiquitous protein expressed in nearly all tissues and in various types of cells. It is essential for vascular development and post-natal vessel maturation. Loss-of-function mutation of CCM3 predisposes for the familial form of cerebral cavernous malformation (CCM). We have previously shown that knock-down of CCM3 stimulated endothelial angiogenesis via impairing DLL4-Notch signalling; moreover, loss of endothelial CCM3 stimulated tumour angiogenesis and promoted tumour growth. The present study was designed to further elucidate the inside signalling pathway involved in CCM3-ablation-mediated angiogenesis. Here we report for the first time that silencing endothelial CCM3 led to a significant up-regulation of EphB4 mRNA and protein expression and to an increased kinase activity of EphB4, concomitantly accompanied by an activation of Erk1/2, which was reversed by treatment with the specific EphB4 kinase inhibitor NVP-BHG712 (NVP), indicating that silencing CCM3 activates EphB4 kinase forward signalling. Furthermore, treatment with NVP rescued the hyper-angiogenic phenotype induced by knock-down of endothelial CCM3 in vitro and in vivo. Additional study demonstrated that the activation of EphB4 forward signalling in endothelial cells under basal condition and after CCM3-silence was modulated by DLL4/Notch signalling, relying EphB4 at downstream of DLL4/Notch signalling. We conclude that angiogenesis induced by CCM3-silence is mediated by the activation of EphB4 forward signalling. The identified endothelial signalling pathway of CCM3-DLL4/Notch-EphB4-Erk1/2 may provide an insight into mechanism of CCM3-ablation-mediated angiogenesis and could potentially contribute to novel therapeutic concepts for disrupting aberrant angiogenesis in CCM and in hyper-vascularized tumours.

Integration of RNA-Seq and RPPA data for survival time prediction in cancer patients

Integration of several types of patient data in a computational framework can accelerate the identification of more reliable biomarkers, especially for prognostic purposes. This study aims to identify biomarkers that can successfully predict the potential survival time of a cancer patient by integrating the transcriptomic (RNA-Seq), proteomic (RPPA), and protein-protein interaction (PPI) data. The proposed method -RPBioNet- employs a random walk-based algorithm that works on a PPI network to identify a limited number of protein biomarkers. Later, the method uses gene expression measurements of the selected biomarkers to train a classifier for the survival time prediction of patients. RPBioNet was applied to classify kidney renal clear cell carcinoma (KIRC), glioblastoma multiforme (GBM), and lung squamous cell carcinoma (LUSC) patients based on their survival time classes (long- or short-term). The RPBioNet method correctly identified the survival time classes of patients with between 66% and 78% average accuracy for three data sets. RPBioNet operates with only 20 to 50 biomarkers and can achieve on average 6% higher accuracy compared to the closest alternative method, which uses only RNA-Seq data in the biomarker selection. Further analysis of the most predictive biomarkers highlighted genes that are common for both cancer types, as they may be driver proteins responsible for cancer progression. The novelty of this study is the integration of a PPI network with mRNA and protein expression data to identify more accurate prognostic biomarkers that can be used for clinical purposes in the future.

Notch: an interactive player in neurogenesis and disease

Notch signaling is evolutionarily conserved from Drosophila to human. It plays critical roles in neural stem cell maintenance and neurogenesis in the embryonic brain as well as in the adult brain. Notch functions greatly depend on careful regulation and cross-talk with other regulatory mechanisms. Deregulation of Notch signaling is involved in many neurodegenerative diseases and brain disorders. Here, we summarize the fundamental role of Notch in neuronal development and specification and discuss how epigenetic regulation and pathway cross-talk contribute to Notch function. In addition, we cover aberrant alterations of Notch signaling in the diseased brain. The aim of this review is to provide an insight into how Notch signaling works in different contexts to control neurogenesis and its potential effects in diagnoses and therapies of neurodegeneration, brain tumors and disorders.

Endosulfan inhibits proliferation through the Notch signaling pathway in human umbilical vein endothelial cells

Our previous research showed that endosulfan triggers the extrinsic coagulation pathway by damaging endothelial cells and causes hypercoagulation of blood. To identify the mechanism of endosulfan-impaired endothelial cells, we treated human umbilical vein endothelial cells (HUVECs) with different concentrations of endosulfan, with and without an inhibitor for Notch, N-[N-(3, 5-difluorophenacetyl)-1-alanyl]S-Phenylglycinet-butylester (DAPT, 20 μM), or a reactive oxygen species (ROS) scavenger, N-Acetyl-l-cysteine (NAC, 3 mM), for 24 h. The results showed that endosulfan could inhibit cell viability/proliferation by increasing the release of lactate dehydrogenase (LDH), arresting the cell cycle in both S and G2/M phases, and inducing apoptosis in HUVECs. We also found that endosulfan can damage microfilaments, microtubules, and nuclei; arrest mitosis; remarkably increase the expressions of Dll4, Notch1, Cleaved-Notch1, Jagged1, Notch4, Hes1, and p21; and significantly induce ROS and malondialdehyde production in HUVECs. The presence of DAPT antagonized the above changes of cycle arrest, proliferation inhibition, and expressions of Dll4, Notch1, Cleaved-Notch1, Hes1, and p21 caused by endosulfan; however, NAC could attenuate LDH release; ROS and malondialdehyde production; apoptosis; and the expression levels of Dll4, Notch1, Cleaved-Notch1, Notch4, and Hes1 induced by endosulfan. These results demonstrated that endosulfan inhibited proliferation through the Notch signaling pathway as a result of oxidative stress. In addition, endosulfan can damage the cytoskeleton and block mitosis, which may add another layer of toxic effects on endothelial cells.

Expression of angiopoietins in central nervous system hemangioblastomas is associated with cyst formation

PURPOSE

This study aimed to determine the expression of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and endothelial tyrosine kinase receptor (Tie-2) in central nervous system (CNS) hemangioblastomas (HBs) and explore the correlation with peritumoral cyst formation.

METHOD

A total of 22 paraffin-embedded specimens derived from 11 cyst-associated and 11 solid solitary CNS HBs were collected for streptavidin-peroxidase immunohistochemical staining. The expression levels of Ang-1, Ang-2 and Tie-2 in cystic and solid HBs were estimated and compared according to the integrated optical density (IOD) of staining in the sections. To further confirm the differential expression of Ang-1 and Ang-2 between cystic and solid HBs, an additional 9 frozen specimens from 5 cyst-associated and 4 solid solitary HBs were collected for Western blot analysis. Clinical histories and radiological records of the patients were reviewed retrospectively.

RESULTS

Compared to normal cerebellum tissue, Ang-1, Ang-2 and Tie-2 were prominently overexpressed in both the stromal cells and endothelial cells of CNS HBs. The expression of Ang-2 and the ratio of Ang-2/Ang-1 in the cystic group were significantly higher than those in the solid group. The intensity of Ang-2 expression in the cystic group was negatively correlated with age. There was no correlation between the expression level of the proteins and sex, tumor location, tumor volume or cyst volume.

CONCLUSIONS

Ang/Tie signaling is upregulated in HBs and is likely associated with the process of intense vascularization and cyst formation. Higher Ang-2 levels and a higher Ang-2/Ang-1 ratio may contribute to cyst formation by increasing the vascular permeability. The decrease in Ang-2 expression with advanced age in cystic-associated HBs may be associated with the reduced growth rate of peritumoral cysts among elderly patients. Ang-2 shows great potential as an effective therapeutic target of symptomatic CNS HBs associated with cysts.

Study of angiogenic signaling pathways in hemangioblastoma

Hemangioblastoma (HB) is mainly located in the brain and the spinal cord. The tumor is composed of two major components, namely neoplastic stromal cells and abundant microvessels. Thus, hyper-vascularization is the hallmark of this tumor. Despite the identification of germline and/or epigenetic mutations of Von Hippel Lindau (VHL) gene as an important pathogenic mechanism of HB, little is known about the molecular signaling involved in this highly vascularized tumor. The present study investigated the key players of multiple angiogenic signaling pathways including VEGF/VEGFR2, EphB4/EphrinB2, SDF1α/CXCR4 and Notch/Dll4 pathways in surgical specimens of 22 HB. The expression of key angiogenic factors was detected by RT² -PCR and Western blot. Immunofluorescent staining revealed the cellular localization of these proteins. We demonstrated a massive upregulation of mRNA levels of VEGF and VEGFR2, CXCR4 and SDF1α, EphB4 and EphrinB2, as well as the main components of Dll4-Notch signaling in HB. An increase in the protein expression of VEGF, CXCR4 and the core-components of Dll4-Notch signaling was associated with an activation of Akt and Erk1/2 and accompanied by an elevated expression of PCNA. Immuofluorescent staining revealed the expression of VEGF and CXCR4 in endothelial cells as well as in tumor cells. Dll4 protein was predominantly found in tumor cells, whereas EphB4 immunoreactivity was exclusively detected in endothelial cells. We conclude that multiple key angiogenic pathways were activated in HB, which may synergistically contribute to the abundant vascularization in this tumor. Identification of these aberrant pathways provides potential targets for a possible future application of anti-angiogenic therapy for this tumor, particularly when a total surgical resection becomes difficult due to the localization or multiplicity of the tumor.

Activation of multiple angiogenic signaling pathways in hemangiopericytoma

Hemangiopericytoma (HPC) is a highly vascularized mesenchymal tumor. Local recurrence and distant metastasis are common features of HPC. Considering the remarkable hyper-vasculature phenotype of HPC, we assumed that dysregulated angiogenic signaling pathways were involved in HPC. The key components of angiogenic signaling pathways including VEGF-VEGF-R2, EphrinB2-EphB4 and DLL4-Notch were examined by real-time RT-PCR, Western blotting and immunostaining in 17 surgical specimens of HPC patients and in 6 controls. A significant upregulation of VEGF and VEGF-R2 associated with elevated levels of p-Akt and proliferating cell nuclear antigen (PCNA) was detected in HPC. Moreover, a dramatic increase in the mRNA and protein expression of EphB4 and its downstream factor p-Erk1/2 was found in HPC. A massive activation of core-components of DLL4-Notch signaling was detected in HPC. Double-immunofluorescent staining confirmed the expression of these upregulated key factors in the endothelial cells of tumor vessels. The present study identified the activation of multiple and crucial angiogenic signaling pathways, which could function individually and/or synergistically to stimulate angiogenesis in HPC and eventually contribute to tumor growth and progression. Our findings emphasize the importance to target multiple angiogenic signaling pathways when an anti-angiogenic therapy is considered for this highly vascularized tumor.

MMGZ01, an anti-DLL4 monoclonal antibody, promotes nonfunctional vessels and inhibits breast tumor growth

Increasing evidence suggests that DLL4 (Delta-like 4)-Notch signaling plays a critical role in cell fate determination and differentiation in tissues. Blocking DLL4-Notch signaling results in inhibition of tumor growth, which is associated with increased nonfunctional vessels and poor perfusion in the tumor. We successfully generated a human DLL4 monoclonal antibody MMGZ01 that binds specifically to DLL4 to disrupt the interaction between DLL4 and Notch1. MMGZ01 showed high affinity to DLL4 to inhibit the DLL4-mediated human umbilical vein endothelial cell (HUVEC) phenotype. Furthermore, MMGZ01 stimulated HUVEC vessel sprouting and tubule formation in vitro. In addition, MMGZ01 had a pronounced effect in promoting immature vessels and reduced breast cancer cell growth in vivo. Finally, MMGZ01 treatment inhibited the proliferation of breast cancer cells, induced tumor cell apoptosis, suppressed mammosphere formation, decreased CD44(+)/CD24(-) cell population, and reduced epithelial mesenchymal transition (EMT). These findings suggest that antagonism of the DLL4-Notch signaling pathway might provide a potential therapeutic approach for breast cancer treatment.

A Tumor Suppressor Function for Notch Signaling in Forebrain Tumor Subtypes

In the brain, Notch signaling maintains normal neural stem cells, but also brain cancer stem cells, indicating an oncogenic role. Here, we identify an unexpected tumor suppressor function for Notch in forebrain tumor subtypes. Genetic inactivation of RBP-Jκ, a key Notch mediator, or Notch1 and Notch2 receptors accelerates PDGF-driven glioma growth in mice. Conversely, genetic activation of the Notch pathway reduces glioma growth and increases survival. In humans, high Notch activity strongly correlates with distinct glioma subtypes, increased patient survival, and lower tumor grade. Additionally, simultaneous inactivation of RBP-Jκ and p53 induces primitive neuroectodermal-like tumors in mice. Hence, Notch signaling cooperates with p53 to restrict cell proliferation and tumor growth in mouse models of human brain tumors.

Downregulation of programmed cell death 10 is associated with tumor cell proliferation, hyperangiogenesis and peritumoral edema in human glioblastoma

Background

Neovascularization and peritumoral edema are hallmarks of glioblastoma (GBM). Programmed cell death 10 (PDCD10) plays a pivotal role in regulating apoptosis, neoangiogenesis and vessel permeability and is implicated in certain tumor signaling pathways. However, little is known about PDCD10 in GBM. We aimed to investigate the expression pattern of PDCD10 and to identify the association of its expression with some molecular and clinical parameters in human GBM.

Methods

mRNA and protein expression of PDCD10 were examined respectively by real-time RT-PCR and Western blotting in GBM (n = 27), astrocytoma grade II (n = 13) and control (n = 11). The protein level of p-Akt and GFAP was detected by Western blot. Double-imunofluorecent staining was performed to reveal the cellular expression profile of PDCD10. Brain edema and microvascular density (MVD) were respectively analyzed based on pre-operative MRI and after laminin immnostaining. MGMT promoter methylation was detected by methylation specific PCR.

Results

mRNA and protein levels of PDCD10 were significantly downregulated in GBM, concomitantly accompanied by the activation of Akt. PDCD10 immunoreactivity was absent in proliferating tumor cells, endothelial cells and GFAP-positive cells, but exclusively present in the hypoxic pseudopalisading cells which underwent apoptosis. Moreover, loss of PDCD10 was associated with a higher MVD and a more severe peritumoral edema but not with MGMT promoter methylation in GBM.

Conclusion

We report for the first time that PDCD10 expression is downregulated in GBM, which is associated with the activation of Akt signaling protein. PDCD10 is potentially implicated in tumor proliferation and apoptosis, hyperangiogenesis and peritumoral edema in GBM.

Recent advance in molecular angiogenesis in glioblastoma: the challenge and hope for anti-angiogenic therapy

Glioblastoma (GBM) is the most highly malignant brain tumor in the human central nerve system. In this paper, we review new and significant molecular findings on angiogenesis and possible resistance mechanisms. Expression of a number of genes and regulators has been shown to be upregulated in GBM microvessel cells, such as interleukin-8, signal transducer and activator of transcription 3, Tax-interacting protein-1, hypoxia induced factor-1 and anterior gradient protein 2. The regulator factors that may strongly promote angiogenesis by promoting endothelial cell metastasis, changing the microenvironment, enhancing the ability of resistance to anti-angiogenic therapy, and that inhibit angiogenesis are reviewed. Based on the current knowledge, several potential targets and strategies are proposed for better therapeutic outcomes, such as its mRNA interference of DII4-Notch signaling pathway and depletion of b1 integrin expression. We also discuss possible mechanisms underlying the resistance to anti-angiogenesis and future directions and challenges in developing new targeted therapy for GBM.

Epigenetic pathways and glioblastoma treatment: insights from signaling cascades

There is an urgent need to identify novel therapies for glioblastoma (GBM) as most therapies are ineffective. A first step in this process is to identify and validate targets for therapeutic intervention. Epigenetic modulators have emerged as attractive drug targets in several cancers including GBM. These epigenetic regulators affect gene expression without changing the DNA sequence. Recent studies suggest that epigenetic regulators interact with drivers of GBM cell and stem-like cell proliferation. These drivers include components of the Notch, Hedgehog, and Wingless (WNT) pathways. We highlight recent studies connecting epigenetic and signaling pathways in GBM. We also review systems and big data approaches for identifying patient specific therapies in GBM. Collectively, these studies will identify drug combinations that may be effective in GBM and other cancers.

The mRNA related ceRNA-ceRNA landscape and significance across 20 major cancer types

Cross-talk between competitive endogenous RNAs (ceRNAs) through shared miRNAs represents a novel layer of gene regulation that plays important roles in the physiology and development of cancers. However, a global view of their system-level properties across various types of cancers is still unknown. Here, we constructed the mRNA related ceRNA–ceRNA interaction landscape across 20 cancer types by systematically analyzing molecular profiles of 5203 tumors and miRNA regulations. Our study highlights the conserved features shared by pan-cancer and higher similarity within similar origin cell type. Moreover, a core ceRNA network was identified. Function analysis identified a common theme of cancer hallmarks, however they exhibit phenotype-specific connectivity patterns. Besides, we found a marked rewiring in the ceRNA program between various cancers, and further revealed conserved and rewired network ceRNA hubs in each cancer, which were tensely competitive interactions to constitute conserved and cancer-specific modules. By providing mechanistic linkage between known cancer miRNAs, their mediated ceRNA–ceRNA interactions, and the associations with known cancer hallmarks, the inferred cancer ceRNA–ceRNA interaction landscape will serve as a powerful public resource for further biological discoveries of tumorigenesis.

Loss of endothelial programmed cell death 10 activates glioblastoma cells and promotes tumor growth

BACKGROUND

Neo-angiogenesis is a hallmark of glioblastoma (GBM) and is sustained by autocrine and paracrine interactions between neoplastic and nonneoplastic cells. Programmed cell death 10 (PDCD10) is ubiquitously expressed in nearly all tissues and plays crucial roles in regulating angiogenesis and apoptosis. We recently discovered the absence of PDCD10 expression in the tumor vessels of GBM patients. This raised the hypothesis that loss of endothelial PDCD10 affected GBM cell phenotyping and tumor progression.

METHODS

Endothelial PDCD10 was silenced by siRNA and lentiviral shRNA. The tumor cell phenotype was studied in direct and indirect co-culture of endothelial cells (ECs) with U87 or LN229. Angiogenic protein array was performed in the media of PDCD10-silenced ECs. Tumor angiogenesis and tumor growth were investigated in a human GBM xenograft mouse model.

RESULTS

Endothelial silence of PDCD10 significantly stimulated tumor cell proliferation, migration, adhesion, and invasion and inhibited apoptosis in co-cultures. Stable knockdown of endothelial PDCD10 increased microvessel density and the formation of a functional vascular network, leading to a 4-fold larger tumor mass in mice. Intriguingly, endothelial deletion of PDCD10 increased (≥2-fold) the release of 20 of 55 tested proangiogenic factors including VEGF, which in turn activated Erk1/2 and Akt in GBM cells.

CONCLUSIONS

For the first time, we provide evidence that loss of endothelial PDCD10 activates GBM cells and promotes tumor growth, most likely via a paracrine mechanism. PDCD10 shows a tumor-suppressor-like function in the cross talk between ECs and tumor cells and is potentially implicated in GBM progression.

Correlation of high delta-like ligand 4 expression with peritumoral brain edema and its prediction of poor prognosis in patients with primary high-grade gliomas

OBJECT

Peritumoral brain edema (PTBE) is a common phenomenon associated with high-grade gliomas (HGGs). In this study, the authors investigated the expression of Notch delta-like ligand 4 (DLL4) and its correlation with PTBE and prognosis in patients with an HGG.

METHODS

Tumors from 99 patients with HGG were analyzed for DLL4 expression using immunohistochemistry. PTBE on preoperative MR images and the relationship between PTBE and DLL4 expression were evaluated. The effect of DLL4 on patient prognosis was assessed by using Kaplan-Meier survival and Cox proportional hazard models.

RESULTS

Immunohistochemistry results revealed that the expression of DLL4 was distributed primarily within the cytoplasm of tumor vascular endothelial cells and seldom detected in tumor cells. DLL4 expression was correlated positively with the degree of edema (r = 0.845 and p < 0.001, Spearman's test). In addition, DLL4 was an independent predictor of prognosis in patients with HGGs (p = 0.001).

CONCLUSIONS

DLL4 expression was correlated positively with the degree of PTBE and was an independent unfavorable prognostic indicator in patients with HGG.

Novel paracrine modulation of Notch-DLL4 signaling by fibulin-3 promotes angiogenesis in high-grade gliomas

High-grade gliomas are characterized by exuberant vascularization, diffuse invasion, and significant chemoresistance, resulting in a recurrent phenotype that makes them impossible to eradicate in the long term. Targeting protumoral signals in the glioma microenvironment could have significant impact against tumor cells and the supporting niche that facilitates their growth. Fibulin-3 is a protein secreted by glioma cells, but absent in normal brain, that promotes tumor invasion and survival. We show here that fibulin-3 is a paracrine activator of Notch signaling in endothelial cells and promotes glioma angiogenesis. Fibulin-3 overexpression increased tumor VEGF levels, microvascular density, and vessel permeability, whereas fibulin-3 knockdown reduced vessel density in xenograft models of glioma. Fibulin-3 localization in human glioblastomas showed dense fiber-like condensations around tumor blood vessels, which were absent in normal brain, suggesting a remarkable association of this protein with tumor endothelium. At the cellular level, fibulin-3 enhanced endothelial cell motility and association to glioma cells, reduced endothelial cell sprouting, and increased formation of endothelial tubules in a VEGF-independent and Notch-dependent manner. Fibulin-3 increased ADAM10/17 activity in endothelial cells by inhibiting the metalloprotease inhibitor TIMP3; this resulted in increased Notch cleavage and increased expression of DLL4 independently of VEGF signaling. Inhibition of ADAM10/17 or knockdown of DLL4 reduced the proangiogenic effects of fibulin-3 in culture. Taken together, these results reveal a novel, proangiogenic role of fibulin-3 in gliomas, highlighting the relevance of this protein as an important molecular target in the tumor microenvironment.

High delta-like ligand 4 (DLL4) is correlated with peritumoral brain edema and predicts poor prognosis in primary glioblastoma

Delta-like ligand 4 (DLL4), 1 of the 5 known Notch ligands, is involved in a variety of tumor initiation and progression, particularly in the process of tumor angiogenesis. However, the clinical and prognostic significance of DLL4 in glioblastoma have not been fully elucidated.Tumor tissues from 69 glioblastoma patients were analyzed using immunohistochemistry for DLL4 expression. Peritumoral brain edema (PTBE) on preoperative magnetic resonance imaging of these patients and the relationship with DLL4 expression were evaluated. The effect on prognosis was assessed by using the Kaplan-Meier survival and the Cox proportional hazard model.The results showed that elevated DLL4 expression was primarily distributed in the cytoplasm of tumor vascular endothelial cells and rarely detected in tumor cells. Univariate analysis indicated significant correlation of high DLL4 expression with shorter time to progression (TTP) (P < 0.001) and overall survival (OS) (P < 0.001) in glioblastoma. Multivariate analysis confirmed high DLL4 expression as an unfavorable prognostic indicator for TTP (P < 0.001) and OS (P < 0.001), independent of age, gender, symptom duration, resection degree, and PTBE. Importantly, the study also found that DLL4 expression was positively related with PTBE (Spearman's test: r = 0.845, P < 0.001). A multiple linear regression model was constructed to confirm that the positive index of DLL4 was associated with an increase in maximum extent of PTBE (P < 0.001).It is thus concluded that DLL4 is correlated with PTBE and may be useful for predicting prognosis in glioblastoma.

The functional Aquaporin 1 -783G/C-polymorphism is associated with survival in patients with glioblastoma multiforme

BACKGROUND

Despite a dismal prognosis, variability exists regarding the survival-time in patients with glioblastoma-multiforme (GBM), which may be explained by genetic variation. A possible candidate-gene for such variation is Aquaporin-1 (AQP1), since Aquaporin-1-expression influences the pathogenesis and outcome of various malignancies. Functional genetic variants in the promoter of AQP1, modifying Aquaporin-1-expression, could be associated with altered survival in patients with GBM.

METHODS

We sequenced the human AQP1-promoter to detect novel sequence variants, which might impact on Aquaporin-1-expression and tested the hypothesis, that functional single nucleotide polymorphisms are associated with different survival-times of patients suffering from GBM.

RESULTS

Sequencing the AQP1-promoter revealed a novel -783G/C-polymorphism. Reporter-assays showed that substitution of G for C was associated both with increased transcriptional-activation of the AQP1-promoter by serum and with increased AQP1 mRNA expression. Finally, we assessed in a cohort of 155 Caucasian patients with GBM whether the functional single-nucleotide-783G/C-polymorphism is associated with survival-time. Cox-regression analyses revealed the AQP1 -783G/C genotype status as an independent prognostic-factor when jointly considering other predictors of survival. Homozygous CC subjects had a significantly worse outcome compared to GC/GG genotypes (hazard ratio: 3.09; 95% CI, 1.43-6.65; P = 0.004).

CONCLUSIONS

Our findings suggest the novel AQP1 polymorphism as a survival prognosticator in patients suffering from GBM that could help to identify a subgroup of patients at high risk for death. Further studies are necessary to reveal the exact molecular mechanisms.

ASYMMETRIC CELL DIVISION: IMPLICATIONS FOR GLIOMA DEVELOPMENT AND TREATMENT

Glioma is a heterogeneous disease process with differential histology and treatment response. It was previously thought that the histological features of glial tumors indicated their cell of origin. However, the discovery of continuous neuro-gliogenesis in the normal adult brain and the identification of brain tumor stem cells within glioma have led to the hypothesis that these brain tumors originate from multipotent neural stem or progenitor cells, which primarily divide asymmetrically during the postnatal period. Asymmetric cell division allows these cell types to concurrently self-renew whilst also producing cells for the differentiation pathway. It has recently been shown that increased symmetrical cell division, favoring the self-renewal pathway, leads to oligodendroglioma formation from oligodendrocyte progenitor cells. In contrast, there is some evidence that asymmetric cell division maintenance in tumor stem-like cells within astrocytoma may lead to acquisition of treatment resistance. Therefore cell division mode in normal brain stem and progenitor cells may play a role in setting tumorigenic potential and the type of tumor formed. Moreover, heterogeneous tumor cell populations and their respective cell division mode may confer differential sensitivity to therapy. This review aims to shed light on the controllers of cell division mode which may be therapeutically targeted to prevent glioma formation and improve treatment response.