The expression of B7-H3 isoforms in newly diagnosed glioblastoma and recurrence and their functional role.

Short survival of glioblastoma (GBM) patients is due to systematic tumor recurrence. Our laboratory identified a GBM cell subpopulation able to leave the tumor mass (TM) and invade the subventricular zone (SVZ-GBM cells). SVZ-GBM cells escape treatment and appear to contribute to GBM recurrence. This study aims to identify proteins specifically expressed by SVZ-GBM cells and to define their role(s) in GBM aggressiveness and recurrence. The proteome was compared between GBM cells located in the initial TM and SVZ-GBM cells using mass spectrometry. Among differentially expressed proteins, we confirmed B7-H3 by western blot (WB) and quantitative RT-PCR. B7-H3 expression was compared by immunohistochemistry and WB (including expression of its isoforms) between human GBM (N = 14) and non-cancerous brain tissue (N = 8), as well as newly diagnosed GBM and patient-matched recurrences (N = 11). Finally, the expression of B7-H3 was modulated with short hairpin RNA and/or over-expression vectors to determine its functional role in GBM using in vitro assays and a xenograft mouse model of GBM. B7-H3 was a marker for SVZ-GBM cells. It was also increased in human GBM pericytes, myeloid cells and neoplastic cells. B7-H3 inhibition in GBM cells reduced their tumorigenicity. Out of the two B7-H3 isoforms, only 2IgB7-H3 was detected in non-cancerous brain tissue, whereas 4IgB7-H3 was specific for GBM. 2IgB7-H3 expression was higher in GBM recurrences and increased resistance to temozolomide-mediated apoptosis. To conclude, 4IgB7-H3 is an interesting candidate for GBM targeted therapies, while 2IgB7-H3 could be involved in recurrence through resistance to chemotherapy

CXCL12-loaded poly(lactic-co-glycolic) acid microspheres for the chemotactic recruitment of glioblastoma stem cells

INTRODUCTION Glioblastoma (GBM) stem cells (GSC) have been found to specifically migrate in response to a gradient of CXCL12 in a CXCR4-dependent manner1. This enables the escape of GSCs from the tumor mass, potentially evading treatment and initiating metastases. We seek to take advantage of this mechanism for GBM therapy. By encapsulating CXCL12 in poly(lactic-co-glycolic) acid (PLGA) microspheres, we aim to create a polymeric platform capable of recruiting and directing migratory GSCs, thereby influencing GBM progression and metastasis formation. METHODS Human CXCL12 was initially complexated with heparin and poloxamine (Tetronic 1107)2. Resulting nanocomplexes were encapsulated in PLGA via emulsion solvent evaporation/extraction to form microspheres. Microspheres were characterized for morphology, encapsulation efficiency, and in vitro release characteristics. To verify promigratory activity, media preconditioned with blank and CXCL12-loaded microspheres were evaluated for chemotactic activity on U87MG GBM cells using a transwell migration assay. RESULTS AND DISCUSSION CXCL12-heparin nanocomplexes were successfully encapsulated in PLGA microspheres with diameter of 81.9±58.3 µm. The formulation had low initial burst release in vitro at 40% of the payload over a period of up to 90 days. Furthermore, media preconditioned with CXCL12-loaded microspheres for 1 to 8 weeks displayed promigratory activity towards GSCs. The number of migrating cells were 1.8- to 2.8-fold higher as compared to media preconditioned with blank microspheres. Treatment with AMD3100, a CXCR4 antagonist, abrogated this promigratory effect, indicating CXCR4 involvement. CONCLUSION The obtained results point to the potential of CXCL12-loaded microspheres for long-term recruitment of GSCs. These chemotactic microspheres, in combination with conventional and/or novel therapies, present a promising strategy for tackling GBM and its recurrence.Using CXCL12 to target and selectively kill Glioblastoma initiating-cells in order to prevent glioblastoma relapse

Relevance of Translation Initiation in Diffuse Glioma Biology and its Therapeutic Potential

Cancer cells are continually exposed to environmental stressors forcing them to adapt their protein production to survive. The translational machinery can be recruited by malignant cells to synthesize proteins required to promote their survival, even in times of high physiological and pathological stress. This phenomenon has been described in several cancers including in gliomas. Abnormal regulation of translation has encouraged the development of new therapeutics targeting the protein synthesis pathway. This approach could be meaningful for glioma given the fact that the median survival following diagnosis of the highest grade of glioma remains short despite current therapy. The identification of new targets for the development of novel therapeutics is therefore needed in order to improve this devastating overall survival rate. This review discusses current literature on translation in gliomas with a focus on the initiation step covering both the cap-dependent and cap-independent modes of initiation. The different translation initiation protagonists will be described in normal conditions and then in gliomas. In addition, their gene expression in gliomas will systematically be examined using two freely available datasets. Finally, we will discuss different pathways regulating translation initiation and current drugs targeting the translational machinery and their potential for the treatment of gliomas

The functional diversity of Aurora kinases: a comprehensive review

Aurora kinases are serine/threonine kinases essential for the onset and progression of mitosis. Aurora members share a similar protein structure and kinase activity, but exhibit distinct cellular and subcellular localization. AurA favors the G2/M transition by promoting centrosome maturation and mitotic spindle assembly. AurB and AurC are chromosome-passenger complex proteins, crucial for chromosome binding to kinetochores and segregation of chromosomes. Cellular distribution of AurB is ubiquitous, while AurC expression is mainly restricted to meiotically-active germ cells. In human tumors, all Aurora kinase members play oncogenic roles related to their mitotic activity and promote cancer cell survival and proliferation. Furthermore, AurA plays tumor-promoting roles unrelated to mitosis, including tumor stemness, epithelial-to-mesenchymal transition and invasion. In this review, we aim to understand the functional interplay of Aurora kinases in various types of human cells, including tumor cells. The understanding of the functional diversity of Aurora kinases could help to evaluate their relevance as potential therapeutic targets in cancer

Le role radioprotecteur de MKP1 dans les cellules de Glioblastome

In patients with glioblastoma multiform (GBM), recurrenceis the rule despite continuous advances in surgery, radio-and chemotherapy. Within these most frequent primary brain tumors, glioblastoma stem cells or initiating cells (GIC) have recently been described and were shown to be involved in these recurrences. Our lab recently demonstrated that GIC, once injected into the striatum of immunodeficient nude mice, exhibit a tropism for the subventricular zones (SVZ), one of the adult neurogenic niches bringing them an appropriate molecular and cellular environment to growth. After irradiation of these mice, we still discovered cells inside the SVZ. We then questionned the role of the CXCL12/CXCR4 pathway in radioprotection phenotype. After demonstrating that CXCL12 could play a radioprotectiverole, we wanted to know by which mechanism it happens. Knowing that MKP1, the major regulator of the MAP kinase pathway, shown a higher phosphorylation profile after CXXL12 stimulation, and that this protein is involve in many cancers and that its role in glioblamstoma remain unclear, we wanted to know could have a radioprotectiverole link or not to the CXCL12/CXCR4 signalling pathwayThe possible role of MKP1 in GBM radioresistanc

Relevance of Translation Initiation in Diffuse Glioma Biology and its Therapeutic Potential.

Cancer cells are continually exposed to environmental stressors forcing them to adapt their protein production to survive. The translational machinery can be recruited by malignant cells to synthesize proteins required to promote their survival, even in times of high physiological and pathological stress. This phenomenon has been described in several cancers including in gliomas. Abnormal regulation of translation has encouraged the development of new therapeutics targeting the protein synthesis pathway. This approach could be meaningful for glioma given the fact that the median survival following diagnosis of the highest grade of glioma remains short despite current therapy. The identification of new targets for the development of novel therapeutics is therefore needed in order to improve this devastating overall survival rate. This review discusses current literature on translation in gliomas with a focus on the initiation step covering both the cap-dependent and cap-independent modes of initiation. The different translation initiation protagonists will be described in normal conditions and then in gliomas. In addition, their gene expression in gliomas will systematically be examined using two freely available datasets. Finally, we will discuss different pathways regulating translation initiation and current drugs targeting the translational machinery and their potential for the treatment of gliomas

Caractérisation moléculaire et fonctionnelle des cellules de glioblastome issues de la masse tumorale ou de la zone sous-ventriculaire

Life expectancy after diagnosis of glioblastoma (GBM) remains poor even with the best available treatment. This catastrophic survival is the direct consequence of systematic tumour recurrence. It has previously been demonstrated that the subventricular zone (SVZ, a neurogenic niche of the adult central nervous system) attracts and harbours GBM cells, expressing stem cell biomarkers that act like glioblastoma-initiating cells. These cells hosted in the SVZ may be responsible for tumour recurrence. To better understand the difference between cells from the tumour mass (TM) and those migrating to the SVZ, this project will focus on two axes. First, a proteomic and transcriptomic approach will be used to identify one or more biomarkers that might help to establish if recurrences originate from the TM or the SVZ. The second aim of the project is to compare these two populations of cells from a functional point of view. Some functional differences have already been observed: cells derived from SVZ form more spheroids than those derived from TM (1). U87MG cells from SVZ also form tumours more easily in mice compared to cells derived from the TM (2). However, preliminary results in chemo- and radioresistance assays on the cultured cells (U87MG) do not show significant differences between the two populations. Therefore, it might be the SVZ environment that plays a key role in therapeutic resistance, rather than intrinsic biological differences of cells from the TM versus the SVZ.GBM cells from the tumour mass versus the subventricular zone: molecular and functional characterisatio

Aurora A plays a dual role in migration and survival of human glioblastoma cells according to the CXCL12 concentration

Primary glioblastoma is the most frequent human brain tumor in adults and is generally fatal due to tumor recurrence. We previously demonstrated that glioblastoma-initiating cells invade the subventricular zones and promote their radio-resistance in response to the local release of the CXCL12 chemokine. In this work, we show that the mitotic Aurora A kinase (AurA) is activated through the CXCL12–CXCR4 pathway in an ERK1/2-dependent manner. Moreover, the CXCL12–ERK1/ 2 signaling induces the expression of Ajuba, the main cofactor of AurA, which allows the auto-phosphorylation of AurA. We show that AurA contributes to glioblastoma cell survival, radio-resistance, self-renewal, and proliferation regardless of the exogenous stimulation with CXCL12. On the other hand, AurA triggers the CXCL12-mediated migration of glioblastoma cells in vitro as well as the invasion of the subventricular zone in xenograft experiments. Moreover, AurA regulates cytoskeletal proteins (i.e., Actin and Vimentin) and favors the pro-migratory activity of the Rho-GTPase CDC42 in response to CXCL12. Altogether, these results show that AurA, a well-known kinase of the mitotic machinery, may play alternative roles in human glioblastoma according to the CXCL12 concentration