The brain microenvironment mediates resistance in luminal breast cancer to PI3K inhibition through HER3 activation

Although targeted therapies are often effective systemically, they fail to adequately control brain metastases. In preclinical models of breast cancer that faithfully recapitulate the disparate clinical responses in these microenvironments, we observed that brain metastases evade phosphatidylinositide 3-kinase (PI3K) inhibition despite drug accumulation in the brain lesions. In comparison to extracranial disease, we observed increased HER3 expression and phosphorylation in brain lesions. HER3 blockade overcame the resistance of HER2-amplified and/or PIK3CA-mutant breast cancer brain metastases to PI3K inhibitors, resulting in marked tumor growth delay and improvement in mouse survival. These data provide a mechanistic basis for therapeutic resistance in the brain microenvironment and identify translatable treatment strategies for HER2-amplified and/or PIK3CA-mutant breast cancer brain metastases

A Glial Signature and Wnt7 Signaling Regulate Glioma-Vascular Interactions and Tumor Microenvironment.

Gliomas comprise heterogeneous malignant glial and stromal cells. While blood vessel co-option is a potential mechanism to escape anti-angiogenic therapy, the relevance of glial phenotype in this process is unclear. We show that Olig2+ oligodendrocyte precursor-like glioma cells invade by single-cell vessel co-option and preserve the blood-brain barrier (BBB). Conversely, Olig2-negative glioma cells form dense perivascular collections and promote angiogenesis and BBB breakdown, leading to innate immune cell activation. Experimentally, Olig2 promotes Wnt7b expression, a finding that correlates in human glioma profiling. Targeted Wnt7a/7b deletion or pharmacologic Wnt inhibition blocks Olig2+ glioma single-cell vessel co-option and enhances responses to temozolomide. Finally, Olig2 and Wnt7 become upregulated after anti-VEGF treatment in preclinical models and patients. Thus, glial-encoded pathways regulate distinct glioma-vascular microenvironmental interactions

Next-generation in vivo optical imaging with short-wave infrared quantum dots

The short-wavelength infrared region (SWIR; 1000—2000 nm) provides several advantages over the visible and near-infrared regions for in vivo imaging. The general lack of autofluorescence, low light absorption by blood and tissue, and reduced scattering can render a mouse translucent when imaged in the SWIR region. Despite these advantages, the lack of a versatile emitter platform has prevented its general adoption by the biomedical research community. Here we introduce high-quality SWIR-emitting core/shell quantum dots (QDs) for the next generation of in vivo SWIR imaging. Our QDs exhibit a dramatically higher emission quantum yield (QY) than previously described SWIR probes, as well as a narrow and size-tunable emission that allows for multiplexing in the SWIR region. To demonstrate some of its capabilities, we used this imaging platform to measure the heartbeat and breathing rates in awake and unrestrained mice, as well as to quantify the metabolic turnover rates of lipoproteins in several organs simultaneously in real time in mice. Finally, we generate detailed three-dimensional quantitative flow maps of brain vasculature by intravital microscopy and visualize the differences between healthy tissue and a tumor in the brain. In conclusion, SWIR QDs enable biological optical imaging with an unprecedented combination of deep penetration, high spatial resolution, and fast acquisition speed

Dual targeting of Angiopoietin-2 and VEGF For Glioblastoma Therapy

Glioblastoma multiforme (GBM) is the most common primary brain malignancy in adults. With an incidence of 3 in 100,000 individuals it is a relatively rare but devastating condition, with five-year survival rates below 5%. The standard of care therapy for GBM consists of maximal safe resection of the tumor mass, followed by radio-chemotherapy with the DNA-alkylating agent Temozolomide (TMZ), and adjuvant TMZ therapy. The tumor blood vessel architecture in GBMs is abnormal, resulting in ineffective blood flow and ineffective delivery of chemotherapeutics. Vessel normalizing therapies aim to restore the architecture and function of tumor blood vessels through inhibition of angiogenic cytokines such as the vascular endothelial growth factor (VEGF). Therapeutic inhibition of the VEGF pathway in unselected populations of GBM patients, however, has failed to provide survival benefits. Résistance to anti- angiogenic monotherapy can be mediated by upregulation of alternative anti- angiogenic pathways such as Angiopoietin-2 (Ang-2). In tumors, Ang-2 can confer therapy résistance to classic anti-angiogenic therapy by protecting endothelial cells from therapeutic VEGF withdrawal. For my PhD work I tested the hypothesis that simultaneous inhibition of Ang-2 and VEGF can overcome résistance to anti-VEGF monotherapy. Using murine models of glioblastoma we compared the treatment effects of a VEGF antibody (B20) with a bispecific antibody targeting both Ang-2 and VEGF (A2V). We examined treatment effects on the tumor vasculature, immune cell populations, tumor growth, and survival in both the syngeneic GI261 and the patient-derived MGG8 tumor models. We found that in the GI261 model, which displays a highly abnormal tumor vasculature, A2V decreased vessel density, delayed tumor growth, and prolonged survival compared with B20. In the MGG8 model, which displays a low degree of vessel abnormality, A2V induced no significant changes in the tumor vasculature but still prolonged survival. In both the GI261 and MGG8 models A2V reprogrammed protumor M2 macrophages toward the antitumor M1 phenotype. These findings indicate that simultaneous inhibition of Ang-2 and VEGF may prolong survival in mice with GBM by reprogramming the tumor immune microenvironment and delaying tumor growth. -- Le glioblastome multiforme (GBM) est la néoplasie cérébrale primaire la plus fréquente chez l'adulte. Avec une incidence de 3 sur 100,000 individus le GBM est une maladie relativement rare, mais dévastatrice, avec une survie à 5 ans inférieure à 5%. La thérapie standard pour les GBM consiste en une résection maximale de la masse tumorale, suivie par une radio-chimiothérapie avec une molécule à action alkylante de la ADN, nommée Temozolomide (TMZ), et une chimiothérapie adjuvante avec TMZ. L'architecture des vaisseaux tumoraux dans les GBM est anormale, ce qui rend inefficace le flux sanguin est la délivrance de chimiothérapies. Les thérapies normalisatrices des vaisseaux ont pour but de restaurer l'architecture et la fonction des vaisseaux tumoraux en inhibant des cytokines angiogéniques comme le facteur de croissance vasculaire endothélial (VEGF). L'inhibition thérapeutique de la voie VEGF dans des populations non sélectives de patients souffrant des GBM n'a toutefois pas montré une amélioration de la survie. La résistance aux thérapies anti- angiogéniques peut être causée par une surexpression de facteurs de croissance angiogéniques comme l'angiopoietin-2 (Ang-2). Dans les tumeurs, l'expression de l'Ang-2 peut protéger les cellules endothéliales d'un sevrage thérapeutique de VEGF et de ce fait causer une résistance thérapeutique. Pour mon travail de PhD j'ai testé l'hypothèse qu'une inhibition simultanée de l'Ang-2 et VEGF peut surmonter la résistance thérapeutique à l'inhibition aux thérapies anti- VEGF. En utilisant des modèles murins du glioblastome nous avons comparé les effets d'un traitement avec un anticorps contre la VEGF (B20) avec ceux d'un anticorps bispécifique (A2V) qui neutralise l'Ang-2 et la VEGF au même titre. Nous avons comparé les effets de ces traitements sur les vaisseaux tumoraux, les populations immunitaires, la croissance tumorale et la survie dans le modèle syngénique GI261 et le modèle MGG8, dérivé d'un patient. Nous avons trouvé que dans le modèle GI261, qui présente des vaisseaux tumoraux hautement anormaux, A2V diminuait la densité vasculaire et la croissance tumorale et prolongeait la survie en comparaison avec B20. Dans le modèle MGG8, qui présente un bas dégré d'anomalies vasculaires, A2V n'induisait pas des changements significatifs dans les vaisseaux tumoraux, mais prolongeait quand même la survie. Nous avons trouvé que le traitement avec A2V cause une reprogrammation des macrophages associés à la tumeur d'un phénotype pro-tumoral (M2) à un phénotype anti-tumoral (M1). Ces données indiquent que l'inhibition simultanée d'Ang-2 et VEGF peut prolonger la survie de souris porteuses d'un GBM en reprogrammant l'environnement immunitaire tumoral et en ralentissant la croissance tumorale

Endothelial cell-derived GABA signaling modulates neuronal migration and postnatal behavior

The cerebral cortex is essential for integration and processing of information that is required for most behaviors. The exquisitely precise laminar organization of the cerebral cortex arises during embryonic development when neurons migrate successively from ventricular zones to coalesce into specific cortical layers. While radial glia act as guide rails for projection neuron migration, pre-formed vascular networks provide support and guidance cues for GABAergic interneuron migration. This study provides novel conceptual and mechanistic insights into this paradigm of vascular-neuronal interactions, revealing new mechanisms of GABA and its receptor-mediated signaling via embryonic forebrain endothelial cells. With the use of two new endothelial cell specific conditional mouse models of the GABA pathway (Gabrb3ΔTie2-Cre and VgatΔTie2-Cre), we show that partial or complete loss of GABA release from endothelial cells during embryogenesis results in vascular defects and impairs long-distance migration and positioning of cortical interneurons. The downstream effects of perturbed endothelial cell-derived GABA signaling are critical, leading to lasting changes to cortical circuits and persistent behavioral deficits. Furthermore, we illustrate new mechanisms of activation of GABA signaling in forebrain endothelial cells that promotes their migration, angiogenesis and acquisition of blood-brain barrier properties. Our findings uncover and elucidate a novel endothelial GABA signaling pathway in the CNS that is distinct from the classical neuronal GABA signaling pathway and shed new light on the etiology and pathophysiology of neuropsychiatric diseases, such as autism spectrum disorders, epilepsy, anxiety, depression and schizophrenia

Targeting Treg cells with GITR activation alleviates resistance to immunotherapy in murine glioblastomas

International audienceAbstract Immune checkpoint blockers (ICBs) have failed in all phase III glioblastoma (GBM) trials. Here, we show that regulatory T (Treg) cells play a key role in GBM resistance to ICBs in experimental gliomas. Targeting glucocorticoid-induced TNFR-related receptor (GITR) in Treg cells using an agonistic antibody (αGITR) promotes CD4 Treg cell differentiation into CD4 effector T cells, alleviates Treg cell-mediated suppression of anti-tumor immune response, and induces potent anti-tumor effector cells in GBM. The reprogrammed GBM-infiltrating Treg cells express genes associated with a Th1 response signature, produce IFNγ, and acquire cytotoxic activity against GBM tumor cells while losing their suppressive function. αGITR and αPD1 antibodies increase survival benefit in three experimental GBM models, with a fraction of cohorts exhibiting complete tumor eradication and immune memory upon tumor re-challenge. Moreover, αGITR and αPD1 synergize with the standard of care treatment for newly-diagnosed GBM, enhancing the cure rates in these GBM models

Solid Stress in Brain Tumours Causes Neuronal Loss and Neurological Dysfunction and Can Be Reversed by Lithium

The compression of brain tissue by a tumour mass is believed to be a major cause of the clinical symptoms seen in patients with brain cancer. However, the biological consequences of these physical stresses on brain tissue are unknown. Here, via imaging studies in patients and by using mouse models of human brain tumours, we show that a subgroup of primary and metastatic brain tumours, classified as nodular on the basis of their growth pattern, exert solid stress on the surrounding brain tissue, causing a decrease in local vascular perfusion as well as neuronal death and impaired function. We demonstrate a causal link between solid stress and neurological dysfunction by applying and removing cerebral compression, which respectively mimic the mechanics of tumour growth and of surgical resection. We also show that, in mice, treatment with lithium reduces solid-stress-induced neuronal death and improves motor coordination. Our findings indicate that brain-tumour-generated solid stress impairs neurological function in patients, and that lithium as a therapeutic intervention could counter these effects

Ang-2/VEGF bispecific antibody reprograms macrophages and resident microglia to anti-tumor phenotype and prolongs glioblastoma survival.

Inhibition of the vascular endothelial growth factor (VEGF) pathway has failed to improve overall survival of patients with glioblastoma (GBM). We previously showed that angiopoietin-2 (Ang-2) overexpression compromised the benefit from anti-VEGF therapy in a preclinical GBM model. Here we investigated whether dual Ang-2/VEGF inhibition could overcome resistance to anti-VEGF treatment. We treated mice bearing orthotopic syngeneic (Gl261) GBMs or human (MGG8) GBM xenografts with antibodies inhibiting VEGF (B20), or Ang-2/VEGF (CrossMab, A2V). We examined the effects of treatment on the tumor vasculature, immune cell populations, tumor growth, and survival in both the Gl261 and MGG8 tumor models. We found that in the Gl261 model, which displays a highly abnormal tumor vasculature, A2V decreased vessel density, delayed tumor growth, and prolonged survival compared with B20. In the MGG8 model, which displays a low degree of vessel abnormality, A2V induced no significant changes in the tumor vasculature but still prolonged survival. In both the Gl261 and MGG8 models A2V reprogrammed protumor M2 macrophages toward the antitumor M1 phenotype. Our findings indicate that A2V may prolong survival in mice with GBM by reprogramming the tumor immune microenvironment and delaying tumor growth