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Blood-brain barrier alterations in human brain tumors revealed by genome-wide transcriptomic profiling

ABSTRACT: Brain tumors, either primary or secondary, have limited therapeutic options despite advances in understanding tumor driving gene mutations and heterogeneity within tumor cells. The cellular and molecular composition of brain tumor stroma, an important modifier of tumor growth, has been less investigated and understood. Especially, studies focusing on brain tumor blood vessels are rare, yet, the brain endothelium and the blood-brain barrier (BBB) are the major obstacle for efficient drug delivery. In this study we have employed the RNA sequencing approach to get insights into transcriptional alterations of endothelial cells isolated from primary and secondary brain tumors. We used an immunoprecipitation approach to enrich for endothelial cells of normal brain, glioblastoma (GBM) and adenocarcinoma brain metastasis (BM). Analysis of the endothelial transcriptome showed that both the GBM and the BM vasculature showed deregulation of genes implicated in cell proliferation, angiogenesis, deposition of extracellular matrix (ECM), and deregulation of genes defining the BBB dysfunction module. We describe alterations in the BBB genes in the GBM and BM vasculature and identify proteins that could be exploited for developing drug delivery platforms into primary and secondary brain tumors. In addition, we identify deregulated expression of genes defining vessel-associated fibroblasts in the GBM tissue, highlighting that the cellular composition of the brain tumor stroma deserves further investigation.

ORGANISM(S): Homo sapiens

PROVIDER: GSE159851 | GEO | 2021/02/10

REPOSITORIES: GEO

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Project description:Genetic variation in the population has an influence on the manifestation of monogenic as well as multifactorial disorders, with the underlying genetic contribution dependent on several interacting variants. Common laboratory mouse strains used for modelling human disease lack the genetic variability of the human population. Therefore, outcomes of rodent studies show limited correlation with human disease. The functionality of brain vasculature is an important modifier of brain diseases. Importantly, the restrictive interface between blood and brain – the blood-brain barrier (BBB) serves as a major obstacle for CNS drug delivery. Using genetically diverse mouse strains, we aimed to investigate the phenotypic and transcriptomic variation of the intact BBB in different inbred mouse strains.We investigated the heterogeneity of brain vasculature in recently wild-derived mouse strains (CAST/EiJ, WSB/EiJ, PWK/PhJ) and long-inbred mouse strains (129S1/SvImJ, A/J, C57BL/6J, DBA/2J, NOD/ShiLtJ) using different phenotypic arms. We used immunohistochemistry and confocal laser microscopy followed by quantitative image analysis to determine vascular density and pericyte coverage in two brain regions – cortex and hippocampus. Using a low molecular weight fluorescence tracer, sodium fluorescein and spectrophotometry analysis, we assessed BBB permeability in young and aged mice of selected strains. For further phenotypic characterization of endothelial cells in inbred mouse strains, we performed bulk RNA sequencing of sorted endothelial cells isolated from cortex and hippocampus. We did not detect differences in cortical and hippocampal vessel density and pericyte coverage among all the investigated strains. The staining patterns of endothelial arteriovenous zonation markers were similar in different strains. BBB permeability to a small fluorescent tracer, sodium fluorescein, was also similar in different strains. Transcriptomic analysis of endothelial cells revealed that sex of the animal was a major determinant of gene expression differences. In addition, the expression level of several genes implicated in endothelial function and BBB biology differed between wild-derived and long-inbred mouse strains. Our analysis shows that although there were no major differences in parenchymal vascular morphology and BBB permeability between investigated mouse strains or sexes, transcriptomic differences of brain endothelial cells point to variation in gene expression of the intact BBB. These baseline variances might be confounding factors in pathological conditions that may lead to a differential functional outcome dependent on the sex or genetic polymorphism.

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Blood-brain barrier alterations in human brain tumors revealed by genome-wide transcriptomic profiling

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