Role of the ischemic stress sensor IRE1α in the glioblastoma growth

Les glioblastomes (GBMs) sont les tumeurs cérébrales primaires les plus courantes chez l’adulte avec un pronostic fatal dans les douze mois suivant le diagnostic. De nouvelles avancées dans la connaissance de la pathologie moléculaire des GBMs et de leurs régulateurs clés sont indispensables à l’émergence de nouvelles pistes thérapeutiques. Inositol Requiring Enzyme 1 α (IRE1α) est une protéine résidente du réticulum endoplasmique (RE) agissant en tant que détecteur proximal de l’Unfolded Protein Response (UPR) en conditions physiologiques ou pathologiques. IRE1α est une enzyme bivalente possédant une activité Ser/Thr kinase et endoribonucléasique (RNase). Récemment, des mutations ponctuelles dans le gène ERN1/IRE1α ont été détectées dans les cancers chez l’homme, (en particulier dans les GBMs), et IRE1α a été proposé comme un régulateur majeur de la progression tumorale parmi les protéines kinases. Dans ce travail, nous avons montré que le blocage des deux activités Set/thr kinase et RNase dans les cellules U87-MG réprime fortement l’angiogenèse tumorale, la perfusion des vaisseaux et l’expression de facteurs pro-angiogéniques dans des modèles tumoraux de xénogreffes. Ce changement phénotypique est accompagné d’une réponse dite« d’échappement » des cellules tumorales. Celles-ci envahissent le tissu cérébral sain par migration de long des vaisseaux (mécanismes appelé co-option vasculaire). De plus, ce phénotype a été montré comme étant fonctionnellement associé au processus de transition mésenchymateuse. Par mutagenèse dirigée, nous avons montré qu’IRE1α module les processus d’angiogenèse et d’invasion par ces deux domaines catalytiques : l’activité Ser/Thr kinase d’IRE1α est essentielle pour l’angiogenèse alors que le domaine RNase d’IRE1α contrôle le phénotype invasif et co-opté. IRE1α est ainsi identifié comme un régulateur clé de la croissance du glioblastome, agissant au carrefour de signalisations majeures dans le contrôle de l’adaptation de la cellule tumorale à son micro-environnement.Glioblastomas (GBMs) are the most common primary brain tumors in humans and remain essentially incurable. New advances in the knowledge of GBM molecular pathology and their key regulators are crucial to identify new putative ways for GBM therapy. Inositol Requiring Enzyme 1 α (IRE1α) is a transmembrane Endoplasmic Reticulum (ER)-resident protein acting as proximal sensor of the Unfolded Protein Response (UPR) in both physiological and pathological situations. IRE1α is a bivalent enzyme, displaying Ser/Thr kinase and endoribonuclease (RNase) activities in its cytosolic side. Recently, single mutations in IRE1α gene were detected in human cancers, including GBM, and IRE1α was proposed as a major contributor to tumor progression among protein kinases. In this work, we have shown that blockade of both IRE1α Ser/Thr kinase and RNase activities in U87-MG cells highly repressed tumor angiogenesis, blood perfusion and the expression of pro-angiogenic factors in human xenograft tumor models. This phenotypic change is adversely associated to the so-called "evasive response" of tumors cells. The cells began to migrate along pre-existing brain capillaries and invade healthy tissue (a process named blood vessel co-option). Moreover, this phenotype was shown to be functionally linked to the mesenchymal differentiation process. By using site-directed mutagenesis, we demonstrated that IRE1α protein modulates both angiogenesis and invasive processes through its two catalytic domains: IRE1α Ser/Thr kinase domain was essential for IRE1-mediated angiogenesis, whereas IRE1's RNase domain drove the invasive, co-opted phenotype. IRE1α is therefore identified as a key regulator of glioma progression, acting at the crossroads of major signaling networks in the control of tumor cell adaptation to its microenvironment

Role of the ischemic stress sensor IRE1α in the glioblastoma growth

Les glioblastomes (GBMs) sont les tumeurs cérébrales primaires les plus courantes chez l’adulte avec un pronostic fatal dans les douze mois suivant le diagnostic. De nouvelles avancées dans la connaissance de la pathologie moléculaire des GBMs et de leurs régulateurs clés sont indispensables à l’émergence de nouvelles pistes thérapeutiques. Inositol Requiring Enzyme 1 α (IRE1α) est une protéine résidente du réticulum endoplasmique (RE) agissant en tant que détecteur proximal de l’Unfolded Protein Response (UPR) en conditions physiologiques ou pathologiques. IRE1α est une enzyme bivalente possédant une activité Ser/Thr kinase et endoribonucléasique (RNase). Récemment, des mutations ponctuelles dans le gène ERN1/IRE1α ont été détectées dans les cancers chez l’homme, (en particulier dans les GBMs), et IRE1α a été proposé comme un régulateur majeur de la progression tumorale parmi les protéines kinases. Dans ce travail, nous avons montré que le blocage des deux activités Set/thr kinase et RNase dans les cellules U87-MG réprime fortement l’angiogenèse tumorale, la perfusion des vaisseaux et l’expression de facteurs pro-angiogéniques dans des modèles tumoraux de xénogreffes. Ce changement phénotypique est accompagné d’une réponse dite« d’échappement » des cellules tumorales. Celles-ci envahissent le tissu cérébral sain par migration de long des vaisseaux (mécanismes appelé co-option vasculaire). De plus, ce phénotype a été montré comme étant fonctionnellement associé au processus de transition mésenchymateuse. Par mutagenèse dirigée, nous avons montré qu’IRE1α module les processus d’angiogenèse et d’invasion par ces deux domaines catalytiques : l’activité Ser/Thr kinase d’IRE1α est essentielle pour l’angiogenèse alors que le domaine RNase d’IRE1α contrôle le phénotype invasif et co-opté. IRE1α est ainsi identifié comme un régulateur clé de la croissance du glioblastome, agissant au carrefour de signalisations majeures dans le contrôle de l’adaptation de la cellule tumorale à son micro-environnement.Glioblastomas (GBMs) are the most common primary brain tumors in humans and remain essentially incurable. New advances in the knowledge of GBM molecular pathology and their key regulators are crucial to identify new putative ways for GBM therapy. Inositol Requiring Enzyme 1 α (IRE1α) is a transmembrane Endoplasmic Reticulum (ER)-resident protein acting as proximal sensor of the Unfolded Protein Response (UPR) in both physiological and pathological situations. IRE1α is a bivalent enzyme, displaying Ser/Thr kinase and endoribonuclease (RNase) activities in its cytosolic side. Recently, single mutations in IRE1α gene were detected in human cancers, including GBM, and IRE1α was proposed as a major contributor to tumor progression among protein kinases. In this work, we have shown that blockade of both IRE1α Ser/Thr kinase and RNase activities in U87-MG cells highly repressed tumor angiogenesis, blood perfusion and the expression of pro-angiogenic factors in human xenograft tumor models. This phenotypic change is adversely associated to the so-called "evasive response" of tumors cells. The cells began to migrate along pre-existing brain capillaries and invade healthy tissue (a process named blood vessel co-option). Moreover, this phenotype was shown to be functionally linked to the mesenchymal differentiation process. By using site-directed mutagenesis, we demonstrated that IRE1α protein modulates both angiogenesis and invasive processes through its two catalytic domains: IRE1α Ser/Thr kinase domain was essential for IRE1-mediated angiogenesis, whereas IRE1's RNase domain drove the invasive, co-opted phenotype. IRE1α is therefore identified as a key regulator of glioma progression, acting at the crossroads of major signaling networks in the control of tumor cell adaptation to its microenvironment

Rôle du capteur de stress ischémique IRE1a dans la croissance du glioblastome

Les glioblastomes (GBMs) sont les tumeurs cérébrales primaires les plus courantes chez l adulte avec un pronostic fatal dans les douze mois suivant le diagnostic. De nouvelles avancées dans la connaissance de la pathologie moléculaire des GBMs et de leurs régulateurs clés sont indispensables à l émergence de nouvelles pistes thérapeutiques. Inositol Requiring Enzyme 1 a (IRE1a) est une protéine résidente du réticulum endoplasmique (RE) agissant en tant que détecteur proximal de l Unfolded Protein Response (UPR) en conditions physiologiques ou pathologiques. IRE1a est une enzyme bivalente possédant une activité Ser/Thr kinase et endoribonucléasique (RNase). Récemment, des mutations ponctuelles dans le gène ERN1/IRE1a ont été détectées dans les cancers chez l homme, (en particulier dans les GBMs), et IRE1a a été proposé comme un régulateur majeur de la progression tumorale parmi les protéines kinases. Dans ce travail, nous avons montré que le blocage des deux activités Set/thr kinase et RNase dans les cellules U87-MG réprime fortement l angiogenèse tumorale, la perfusion des vaisseaux et l expression de facteurs pro-angiogéniques dans des modèles tumoraux de xénogreffes. Ce changement phénotypique est accompagné d une réponse dite d échappement des cellules tumorales. Celles-ci envahissent le tissu cérébral sain par migration de long des vaisseaux (mécanismes appelé co-option vasculaire). De plus, ce phénotype a été montré comme étant fonctionnellement associé au processus de transition mésenchymateuse. Par mutagenèse dirigée, nous avons montré qu IRE1a module les processus d angiogenèse et d invasion par ces deux domaines catalytiques : l activité Ser/Thr kinase d IRE1a est essentielle pour l angiogenèse alors que le domaine RNase d IRE1a contrôle le phénotype invasif et co-opté. IRE1a est ainsi identifié comme un régulateur clé de la croissance du glioblastome, agissant au carrefour de signalisations majeures dans le contrôle de l adaptation de la cellule tumorale à son micro-environnement.Glioblastomas (GBMs) are the most common primary brain tumors in humans and remain essentially incurable. New advances in the knowledge of GBM molecular pathology and their key regulators are crucial to identify new putative ways for GBM therapy. Inositol Requiring Enzyme 1 a (IRE1a) is a transmembrane Endoplasmic Reticulum (ER)-resident protein acting as proximal sensor of the Unfolded Protein Response (UPR) in both physiological and pathological situations. IRE1a is a bivalent enzyme, displaying Ser/Thr kinase and endoribonuclease (RNase) activities in its cytosolic side. Recently, single mutations in IRE1a gene were detected in human cancers, including GBM, and IRE1a was proposed as a major contributor to tumor progression among protein kinases. In this work, we have shown that blockade of both IRE1a Ser/Thr kinase and RNase activities in U87-MG cells highly repressed tumor angiogenesis, blood perfusion and the expression of pro-angiogenic factors in human xenograft tumor models. This phenotypic change is adversely associated to the so-called "evasive response" of tumors cells. The cells began to migrate along pre-existing brain capillaries and invade healthy tissue (a process named blood vessel co-option). Moreover, this phenotype was shown to be functionally linked to the mesenchymal differentiation process. By using site-directed mutagenesis, we demonstrated that IRE1a protein modulates both angiogenesis and invasive processes through its two catalytic domains: IRE1a Ser/Thr kinase domain was essential for IRE1-mediated angiogenesis, whereas IRE1's RNase domain drove the invasive, co-opted phenotype. IRE1a is therefore identified as a key regulator of glioma progression, acting at the crossroads of major signaling networks in the control of tumor cell adaptation to its microenvironment.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Combined antiangiogenic and anti–PD-L1 therapy stimulates tumor immunity through HEV formation

Inhibitors of VEGF (vascular endothelial growth factor)/VEGFR2 (vascular endothelial growth factor receptor 2) are commonly used in the clinic, but their beneficial effects are only observed in a subset of patients and limited by induction of diverse relapse mechanisms. We describe the up-regulation of an adaptive immunosuppressive pathway during antiangiogenic therapy, by which PD-L1 (programmed cell death ligand 1), the ligand of the negative immune checkpoint regulator PD-1 (programmed cell death protein 1), is enhanced by interferon-γ-expressing T cells in distinct intratumoral cell types in refractory pancreatic, breast, and brain tumor mouse models. Successful treatment with a combination of anti-VEGFR2 and anti-PD-L1 antibodies induced high endothelial venules (HEVs) in PyMT (polyoma middle T oncoprotein) breast cancer and RT2-PNET (Rip1-Tag2 pancreatic neuroendocrine tumors), but not in glioblastoma (GBM). These HEVs promoted lymphocyte infiltration and activity through activation of lymphotoxin β receptor (LTβR) signaling. Further activation of LTβR signaling in tumor vessels using an agonistic antibody enhanced HEV formation, immunity, and subsequent apoptosis and necrosis in pancreatic and mammary tumors. Finally, LTβR agonists induced HEVs in recalcitrant GBM, enhanced cytotoxic T cell (CTL) activity, and thereby sensitized tumors to antiangiogenic/anti-PD-L1 therapy. Together, our preclinical studies provide evidence that anti-PD-L1 therapy can sensitize tumors to antiangiogenic therapy and prolong its efficacy, and conversely, antiangiogenic therapy can improve anti-PD-L1 treatment specifically when it generates intratumoral HEVs that facilitate enhanced CTL infiltration, activity, and tumor cell destruction

Glioblastoma invasion and cooption depend on IRE1α endoribonuclease activity

International audienceIRE1α is an endoplasmic reticulum (ER)-resident transmembrane signaling protein and a cellular stress sensor. The protein harbors a cytosolic dual kinase/endoribonuclease activity required for adaptive responses to micro-environmental changes. In an orthotopic xenograft model of human glioma, invalidation of IRE1α RNase or/and kinase activities generated tumors with remarkably distinct phenotypes. Contrasting with the extensive angiogenesis observed in tumors derived from control cells, the double kinase/RNase invalidation reprogrammed mesenchymal differentiation of cancer cells and produced avascular and infiltrative glioblastomas with blood vessel co-option. In comparison, selective invalidation of IRE1α RNase did not compromise tumor angiogenesis but still elicited invasive features and vessel co-option. In vitro, IRE1α RNase deficient cells were also endowed with a higher ability to migrate. Constitutive activation of both enzymes led to wild-type-like lesions. The presence of IRE1α, but not its RNase activity, is therefore required for glioblastoma neovascularization, whereas invasion results only from RNase inhibition. In this model, two key mechanisms of tumor progression and cancer cell survival are functionally linked to IRE1

Vascular targeting of LIGHT normalizes blood vessels in primary brain cancer and induces intratumoural high endothelial venules

High-grade brain cancer such as glioblastoma (GBM) remains an incurable disease. A common feature of GBM is the angiogenic vasculature, which can be targeted with selected peptides for payload delivery. We assessed the ability of micelle-tagged, vascular homing peptides RGR, CGKRK and NGR to specifically bind to blood vessels in syngeneic orthotopic GBM models. By using the peptide CGKRK to deliver the tumour necrosis factor (TNF) superfamily member LIGHT (also known as TNF superfamily member 14; TNFSF14) to angiogenic tumour vessels, we have generated a reagent that normalizes the brain cancer vasculature by inducing pericyte contractility and re-establishing endothelial barrier integrity. LIGHT-mediated vascular remodelling also activates endothelia and induces intratumoural high endothelial venules (HEVs), which are specialized blood vessels for lymphocyte infiltration. Combining CGKRK-LIGHT with anti-vascular endothelial growth factor and checkpoint blockade amplified HEV frequency and T-cell accumulation in GBM, which is often sparsely infiltrated by immune effector cells, and reduced tumour burden. Furthermore, CGKRK and RGR peptides strongly bound to blood vessels in freshly resected human GBM, demonstrating shared peptide-binding activities in mouse and human primary brain tumour vessels. Thus, peptide-mediated LIGHT targeting is a highly translatable approach in primary brain cancer to reduce vascular leakiness and enhance immunotherapy. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd

Vascular targeting of LIGHT normalizes blood vessels in primary brain cancer and induces intratumoural high endothelial venules

High-grade brain cancer such as glioblastoma (GBM) remains an incurable disease. A common feature of GBM is the angiogenic vasculature, which can be targeted with selected peptides for payload delivery. We assessed the ability of micelle-tagged, vascular homing peptides RGR, CGKRK and NGR to specifically bind to blood vessels in syngeneic orthotopic GBM models. By using the peptide CGKRK to deliver the tumour necrosis factor (TNF) superfamily member LIGHT (also known as TNF superfamily member 14; TNFSF14) to angiogenic tumour vessels, we have generated a reagent that normalizes the brain cancer vasculature by inducing pericyte contractility and re-establishing endothelial barrier integrity. LIGHT-mediated vascular remodelling also activates endothelia and induces intratumoural high endothelial venules (HEVs), which are specialized blood vessels for lymphocyte infiltration. Combining CGKRK-LIGHT with anti-vascular endothelial growth factor and checkpoint blockade amplified HEV frequency and T-cell accumulation in GBM, which is often sparsely infiltrated by immune effector cells, and reduced tumour burden. Furthermore, CGKRK and RGR peptides strongly bound to blood vessels in freshly resected human GBM, demonstrating shared peptide-binding activities in mouse and human primary brain tumour vessels. Thus, peptide-mediated LIGHT targeting is a highly translatable approach in primary brain cancer to reduce vascular leakiness and enhance immunotherapy. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.status: publishe

High epiregulin expression in human U87 glioma cells relies on IRE1α and promotes autocrine growth through EGF receptor.

International audienceBACKGROUND: Epidermal growth factor (EGF) receptors contribute to the development of malignant glioma. Here we considered the possible implication of the EGFR ligand epiregulin (EREG) in glioma development in relation to the activity of the unfolded protein response (UPR) sensor IRE1α. We also examined EREG status in several glioblastoma cell lines and in malignant glioma. METHODS: Expression and biological properties of EREG were analyzed in human glioma cells in vitro and in human tumor xenografts with regard to the presence of ErbB proteins and to the blockade of IRE1α. Inactivation of IRE1α was achieved by using either the dominant-negative strategy or siRNA-mediated knockdown. RESULTS: EREG was secreted in high amounts by U87 cells, which also expressed its cognate EGF receptor (ErbB1). A stimulatory autocrine loop mediated by EREG was evidenced by the decrease in cell proliferation using specific blocking antibodies directed against either ErbB1 (cetuximab) or EREG itself. In comparison, anti-ErbB2 antibodies (trastuzumab) had no significant effect. Inhibition of IRE1α dramatically reduced EREG expression both in cell culture and in human xenograft tumor models. The high-expression rate of EREG in U87 cells was therefore linked to IRE1α, although being modestly affected by chemical inducers of the endoplasmic reticulum stress. In addition, IRE1-mediated production of EREG did not depend on IRE1 RNase domain, as neither the selective dominant-negative invalidation of the RNase activity (IRE1 kinase active) nor the siRNA-mediated knockdown of XBP1 had significant effect on EREG expression. Finally, chemical inhibition of c-Jun N-terminal kinases (JNK) using the SP600125 compound reduced the ability of cells to express EREG, demonstrating a link between the growth factor production and JNK activation under the dependence of IRE1α. CONCLUSION: EREG may contribute to glioma progression under the control of IRE1α, as exemplified here by the autocrine proliferation loop mediated in U87 cells by the growth factor through ErbB1

Lgr6 is a stem cell marker in mouse skin squamous cell carcinoma.

The G-protein-coupled receptors LGR4, LGR5 and LGR6 are Wnt signaling mediators, but their functions in squamous cell carcinoma (SCC) are unclear. Using lineage tracing in Lgr5-EGFP-CreERT2/Rosa26-Tomato and Lgr6-EGFP-CreERT2/Rosa26-Tomato reporter mice, we demonstrate that Lgr6, but not Lgr5, acts as an epithelial stem cell marker in SCCs in vivo. We identify, by single-molecule in situ hybridization and cell sorting, rare cells positive for Lgr6 expression in immortalized keratinocytes and show that their frequency increases in advanced SCCs. Lgr6 expression is enriched in cells with stem cell characteristics, and Lgr6 downregulation in vivo causes increased epidermal proliferation with expanded lineage tracing from epidermal stem cells positive for Lgr6 expression. Surprisingly, mice with germline knockout of Lgr6 are predisposed to SCC development, through a mechanism that includes compensatory upregulation of Lgr5. These data provide a model for human patients with germline loss-of-function mutations in Wnt pathway genes, including RSPO1 or LGR4, who show increased susceptibility to squamous tumor development

Discoidin Domain Receptor 2 orchestrates melanoma resistance combining phenotype switching and proliferation

International audienceCombined therapy with anti-BRAF plus anti-MEK is currently used as first-line treatment of patients with metastatic melanomas harboring the somatic BRAF V600E mutation. However, the main issue with targeted therapy is the acquisition of tumor cell resistance. In a majority of resistant melanoma cells, the resistant process consists in epithelial-to-mesenchymal transition (EMT). This process called phenotype switching makes melanoma cells more invasive. Its signature is characterized by MITF low, AXL high, and actin cytoskeleton reorganization through RhoA activation. In parallel of this phenotype switching phase, the resistant cells exhibit an anarchic cell proliferation due to hyper-activation of the MAP kinase pathway. We show that a majority of human melanoma overexpress discoidin domain receptor 2 (DDR2) after treatment. The same result was found in resistant cell lines presenting phenotype switching compared to the corresponding sensitive cell lines. We demonstrate that DDR2 inhibition induces a decrease in AXL expression and reduces stress fiber formation in resistant melanoma cell lines. In this phenotype switching context, we report that DDR2 control cell and tumor proliferation through the MAP kinase pathway in resistant cells in vitro and in vivo. Therefore, inhibition of DDR2 could be a new and promising strategy for countering this resistance mechanism