ABSTRACT
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.
Subject(s)
B7 Antigens/metabolism , Brain Neoplasms/metabolism , Brain Neoplasms/pathology , Glioblastoma/metabolism , Glioblastoma/pathology , Animals , Heterografts , Humans , Lateral Ventricles/pathology , Mice , Neoplasm Recurrence, Local/metabolism , Neoplasm Recurrence, Local/pathology , Protein IsoformsABSTRACT
Glioblastoma (GBM) is the most frequent and aggressive primary tumor in the central nervous system. Previously, the secretion of CXCL12 in the brain subventricular zones has been shown to attract GBM cells and protect against irradiation. However, the exact molecular mechanism behind this radioprotection is still unknown. Here, we demonstrate that CXCL12 modulates the phosphorylation of MAP kinases and their regulator, the nuclear MAP kinase phosphatase 1 (MKP1). We further show that MKP1 is able to decrease GBM cell death and promote DNA repair after irradiation by regulating major apoptotic players, such as Jun-N-terminal kinase, and by stabilizing the DNA repair protein RAD51. Increases in MKP1 levels caused by different corticoid treatments should be reexamined for GBM patients, particularly during their radiotherapy sessions, in order to prevent or to delay the relapses of this tumor.
Subject(s)
Biomarkers, Tumor/metabolism , Brain Neoplasms/genetics , Chemokine CXCL12/metabolism , DNA Repair , DNA/metabolism , Dual Specificity Phosphatase 1/metabolism , Glioblastoma/genetics , Apoptosis , Biomarkers, Tumor/genetics , Brain Neoplasms/metabolism , Brain Neoplasms/pathology , Cell Proliferation , Chemokine CXCL12/genetics , DNA/genetics , DNA/radiation effects , Dual Specificity Phosphatase 1/genetics , Gene Expression Regulation, Neoplastic , Glioblastoma/metabolism , Glioblastoma/pathology , Humans , Phosphorylation , Prognosis , Signal Transduction , Survival Rate , Tumor Cells, CulturedABSTRACT
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.
Subject(s)
Disease Susceptibility , Glioma/etiology , Peptide Chain Initiation, Translational , Animals , Biomarkers , Biomarkers, Tumor , Gene Expression Regulation, Neoplastic , Glioma/drug therapy , Glioma/metabolism , Humans , Internal Ribosome Entry Sites , Molecular Targeted Therapy , Protein Biosynthesis , Signal TransductionABSTRACT
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.
Subject(s)
Aurora Kinase A/physiology , Brain Neoplasms/enzymology , Chemokine CXCL12/physiology , Glioblastoma/enzymology , Neoplasm Proteins/physiology , Animals , Brain Neoplasms/pathology , Cell Line, Tumor , Cell Movement/drug effects , Cell Survival , Chemokine CXCL12/pharmacology , Enzyme Activation , Glioblastoma/pathology , Heterografts , Humans , LIM Domain Proteins/biosynthesis , LIM Domain Proteins/genetics , Lateral Ventricles/pathology , MAP Kinase Signaling System , Mice , Neoplasm Invasiveness , Phosphorylation , Protein Processing, Post-Translational , Receptors, CXCR4/physiology , Signal TransductionABSTRACT
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.