Glioblastoma (GBM) is an incurable form of primary astrocytic brain tumor driven by glioma stem cell (GSC) compartment closely associated with the vascular niche. GSC phenotypes are heterogeneous and ...range from proneural to mesenchymal-like, the latter characterised by greater invasiveness. Here we document the secretory (angiocrine) role of endothelial cells and their derived extracellular vesicles (EVs) as drivers of proneural-to-mesenchymal reprogramming of GSCs. These changes involve activation of matrix metalloproteinases (MMPs) and NFκB, and inactivation of NOTCH, while altering responsiveness to chemotherapy and driving infiltrative growth in the brain. Our findings suggest that EV-mediated angiocrine interactions impact the nature of cellular stemness in GBM with implications for disease biology and therapy.
Capicua (Cic) is a transcriptional repressor mutated in the brain cancer oligodendroglioma. Despite its cancer link, little is known of Cic's function in the brain. We show that nuclear Cic ...expression is strongest in astrocytes and neurons but weaker in stem cells and oligodendroglial lineage cells. Using a new conditional Cic knockout mouse, we demonstrate that forebrain-specific Cic deletion increases proliferation and self-renewal of neural stem cells. Furthermore, Cic loss biases neural stem cells toward glial lineage selection, expanding the pool of oligodendrocyte precursor cells (OPCs). These proliferation and lineage effects are dependent on de-repression of Ets transcription factors. In patient-derived oligodendroglioma cells, CIC re-expression or ETV5 blockade decreases lineage bias, proliferation, self-renewal, and tumorigenicity. Our results identify Cic as an important regulator of cell fate in neurodevelopment and oligodendroglioma, and suggest that its loss contributes to oligodendroglioma by promoting proliferation and an OPC-like identity via Ets overactivity.
Non-coding RNA (ncRNA) species have emerged in as molecular fingerprints and regulators of brain tumor pathogenesis and progression. While changes in ncRNA levels have been traditionally regarded as ...cell intrinsic there is mounting evidence for their extracellular and paracrine function. One of the key mechanisms that enables ncRNA to exit from cells is their selective packaging into extracellular vesicles (EVs), and trafficking in the extracellular space and biofluids. Vesicular export processes reduce intracellular levels of specific ncRNA in EV donor cells while creating a pool of EV-associated ncRNA in the extracellular space and biofluids that enables their uptake by other recipient cells; both aspects have functional consequences. Cancer cells produce several EV subtypes (exosomes, ectosomes), which differ in their ncRNA composition, properties and function. Several RNA biotypes have been identified in the cargo of brain tumor EVs, of which microRNAs are the most studied, but other species (snRNA, YRNA, tRNA, and lncRNA) are often more abundant. Of particular interest is the link between transforming oncogenes and the biogenesis, cargo, uptake and function of tumor-derived EV, including EV content of oncogenic RNA. The ncRNA repertoire of EVs isolated from cerebrospinal fluid and serum is being developed as a liquid biopsy platform in brain tumors.
Cancer-associated thrombosis (CAT) results from the hemostatic system being dysregulated by the progression of cancer. Despite common clinical manifestations, the mechanisms of CAT may vary greatly ...because cancers develop along distinct biological trajectories that are imposed by the interaction between the tumor cell genome, the epigenome, the surrounding microenvironment, and the tissue of origin. The coagulome, or repertoire of coagulation effectors, expressed by stromal, inflammatory, and cancer cells at the tumor-vascular interface and systemically, reflects this biological variability. Complex landscapes of coagulant and non-coagulant cellular populations are revealed by single-cell RNA sequencing analyses conducted on unperturbed human cancer tissues. Additionally, through mediators of cell-cell interactions, soluble coagulants, and extracellular vesicles containing tissue factor, podoplanin, and other effectors, coagulomes are projected into the pericellular milieu and systemic circulation. As this complexity is currently outside of the clinical paradigm, one could argue that better CAT management could result from a more individualized analysis of coagulomes in cancer patients.
Targeting neovascularization in glioblastoma (GBM) is hampered by poor understanding of the underlying mechanisms and unclear linkages to tumour molecular landscapes. Here we report that different ...molecular subtypes of human glioma stem cells (GSC) trigger distinct endothelial responses involving either angiogenic or circumferential vascular growth (vasectasia). The latter process is selectively triggered by mesenchymal (but not proneural) GSCs and is mediated by a subset of extracellular vesicles (EVs) able to transfer EGFR/EGFRvIII transcript to endothelial cells. Inhibition of the expression and phosphorylation of EGFR in endothelial cells, either pharmacologically (Dacomitinib) or genetically (gene editing), abolishes their EV responses in vitro and disrupts vasectasia in vivo. Therapeutic inhibition of EGFR markedly extends anticancer effects of VEGF blockade in mice, coupled with abrogation of vasectasia and prolonged survival. Thus, vasectasia driven by intercellular transfer of oncogenic EGFR may represent a new therapeutic target in a subset of GBMs.
The
gene family has three members;
, which is a tumor suppressor gene, and
and
, which are proto-oncogenes. All three genes are known to be expressed in embryonic neural progenitors, and
regulates ...proliferation, neuronal differentiation and migration in the developing neocortex. Here we examined the functions of
and
in neocortical development. We first attempted, and were unable to generate, E12.5
double mutants, indicating that at least one
or
gene copy is required for embryonic survival. We therefore focused on single mutants, revealing a telencephalic patterning defect in E12.5
mutants and a proliferation/differentiation defect in
mutant neocortices. Specifically, the ventral pallium, a dorsal telencephalic territory, expands into the ventral telencephalon in
mutants. In contrast,
mutants develop normal regional territories, but neocortical progenitors proliferate less and instead produce more neurons. Finally, in gain-of-function studies, both
and
reduce neurogenesis and increase BrdU-uptake, indicative of enhanced proliferation, but while
effects on proliferation are more immediate,
effects are delayed. Taken together, we found that the
proto-oncogenes genes are essential regulators of neocortical development and although
and
functions are similar, they do not entirely overlap. This article has an associated First Person interview with the first author of the paper.
hamartoma tumour syndrome (PHTS) is a heterogeneous group of rare, autosomal dominant disorders associated with
germline mutations. PHTS patients routinely develop hamartomas, which are benign tissue ...overgrowths comprised of disorganized 'normal' cells. Efforts to generate PHTS animal models have been largely unsuccessful due to the early lethality of homozygous germline mutations in
, together with the lack of hamartoma formation in most conditional mutants generated to date. We report herein a novel PHTS mouse model that reproducibly forms hamartoma-like lesions in the central retina by postnatal day 21. Specifically, we generated a
conditional knockout (cKO) using a retinal-specific
driver that leads to a nearly complete deletion of
in the peripheral retina but produces a mosaic of 'wild-type' and
cKO cells centrally. Structural defects were only observed in the mosaic central retina, including in Müller glia and in the outer and inner limiting membranes, suggesting that defective mechanical integrity partly underlies the hamartoma-like pathology. Finally, we used this newly developed model to test whether rapamycin, an mTOR inhibitor that is currently the only PHTS therapy, can block hamartoma growth. When administered in the early postnatal period, prior to hamartoma formation, rapamycin reduces hamartoma size, but also induces new morphological abnormalities in the
cKO retinal periphery. In contrast, administration of rapamycin after hamartoma initiation fails to reduce lesion size. We have thus generated and used an animal model of retinal PHTS to show that, although current therapies can reduce hamartoma formation, they might also induce new retinal dysmorphologies.This article has an associated First Person interview with the first author of the paper.
Abstract
Endothelial secretome exerts a potent influence on the phenotype of cancer cells and immune microenvironment. Recently, we have reported that glioblastoma stem cells acquire a more ...aggressive mesenchymal state under influence of vascular endothelial cell derived extracellular vesicles (EVs). Since Rab27, GTPases involved in multiple aspects of EV (exosome) biogenesis, has been implicated in control of angiogenic pathways through regulation of VEGFR1 turnover and possibly other mechanisms, we interrogated the role of Rab27 in the function of normal and glioblastoma associated brain microvasculature. Using mice with disrupted Rab27a and Rab27b isoforms, we documented that these proteins control development and stability of the brain vasculature including pathological angiogenesis in glioblastoma. Thus, relative to wild-type C57bl/6 (WT) and double heterozygous Rab27a+/-;Rab27b+/- (dHET) mice, animals with Rab27a/b double knock-out (Rab27a/b-dKO) exhibit reduced microvascular density in brain cortices. When neoangiogensis was induced following orthotopic inoculation of mouse glioma cells (GL261), multiple morphological anomalies were observed in the tumour vasculature relative to tumours established in control mice. Moreover, vascular permeability of tumours in Rab27a/b-dKO mice markedly exceeded that of similar tumours in wild type or heterozygous controls resulting in augmented T-cell infiltration into the otherwise ‘cold’ brain tumor microenvironment. Our results suggest that key switches in the cellular secretome, such as Rab27a and Rab27b, may impact endothelial membrane dynamic and intercellular interactions capabilities, whereby they may play a critical role in ensuring the stability and sustained cellular barrier function of the vasculature during brain tumour progression. Therapeutic implications of these findings are being explored.
ABSTRACT
First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. ...Lata Adnani is first author on ‘Plag1 and Plagl2 have overlapping and distinct functions in telencephalic development’, published in BiO. Lata conducted the research described in this article while a PhD student in Dr Carol Schuurmans’ lab at University of Calgary, Canada. She is now a postdoctoral fellow in the lab of Dr Janusz Rak at McGill University Health Centre, Montreal, Canada, investigating neuroscience.
Abstract
Rab27 is a GTPase involved in the biogenesis of extracellular vesicles (EVs) and cellular secretion pathway. Among two Rab27 isoforms (a and b) Rab27a has been identified in regulating ...angiogenesis during development and wound healing via VEGFR1. Here, we show that Rab27 plays a role in the development and stability of the brain vasculature including pathological angiogenesis in glioblastoma.. Thus, relative to wild-type C57bl/6 (WT) and double heterozygous Rab27a+/-;Rab27b+/- (dHET) mice, animals with Rab27a/b double knock-out (Rab27a/b-dKO) exhibit reduced microvascular density in brain cortices. Additionally, we also observed a reduction in permeability of Evans Blue in the Rab27 dKO cortices relative to controls. When neoangiogensis was induced following orthotopic inoculation of mouse glioma cells (GL261), a similar reduction and morphological anomalies were observed in the tumour vasculature relative to tumours established in control mice. Moreover, vascular permeability of tumours in Rab27a/b-dKO mice markedly exceeded that of similar tumours in wild type or heterozygous controls. Our results suggest Rab27a and Rab27b may play a critical role in ensuring stability of the vasculature under physiological conditions and in glioma.
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