Vegh, A. G. | bioRxiv Science

bioRxiv2026

Extracellular vesicles from triple negative breast cancer cells disrupt the blood-brain barrier via miR-146a-5p- and TGF-β1-mediated downregulation of endothelial Paqr5

Brain metastases are a common and often fatal complication of certain cancer types, such as triple-negative breast cancer. However, the molecular pathways driving brain metastasis formation, including the migration of cancer cells from the bloodstream to the brain parenchyma across the blood-brain barrier, are not yet fully defined. Therefore, using highly relevant mouse and human model systems, the mechanisms by which triple-negative breast cancer cells and their released extracellular vesicles modulate the blood-brain barrier-forming endothelium to increase its permissiveness to tumour cell entry into the brain are investigated. It is observed that extracellular vesicles derived from tumour cells are taken up by cerebral endothelial cells, where they induce miR-146a-5p- and TGF-{beta}1-mediated downregulation of PAQR5/mPR{gamma}, a membrane progesterone receptor. This, in turn, leads to disruption of interendothelial tight junctions, particularly through repression of claudin-5 expression, a critical protein for maintaining barrier function. Altogether this identifies a novel mechanism by which triple-negative breast cancer-derived extracellular vesicles compromise blood-brain barrier integrity, thereby facilitating transendothelial migration of cancer cells and promoting brain metastasis development. Moreover, this study is the first to highlight the role of membrane progesterone receptors in regulating the blood-brain barrier. Table of contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/701753v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@113c0a8org.highwire.dtl.DTLVardef@1cd5625org.highwire.dtl.DTLVardef@1d2b3c2org.highwire.dtl.DTLVardef@178a97_HPS_FORMAT_FIGEXP M_FIG Extracellular vesicles from triple-negative breast cancer cells induce miR-146a-5p- and TGF-1-mediated downregulation of PAQR5/mPR{gamma}, a membrane progesterone receptor, in blood-brain barrier-forming endothelial cells. This results in disruption of interendothelial tight junctions, thereby promoting enhanced migration of cancer cells into the brain. This mechanism highlights the role of membrane progesterone receptors in regulating the blood-brain barrier. C_FIG

cancer biology↗

bioRxiv2025

Endothelial tight junctions and cell-matrix adhesions reciprocally control blood-brain barrier integrity

Brain endothelial cells (ECs) rely on mechanical cues to provide a physical barrier that protects the brain. Yet how ECs integrate forces to establish and maintain the blood-brain barrier (BBB) remains poorly understood. Here, we show that the two main endothelial force-bearing systems, tight junctions and cell-matrix adhesions, reciprocally control BBB integrity. Using a combination of super-resolution imaging and biophysical techniques, we reveal increasing mechanical loads on cell-cell junctions vs. cell-matrix adhesions in human stem cell-derived ECs during BBB maturation. This force redistribution is enabled by cytoskeletal remodeling, a compacted pattern of the tight junction protein claudin-5, and the emergence of specialised perinuclear cell-matrix adhesions. Mechanistically, we find an inverse relationship between claudin-5 levels and the expression of key cell-matrix adhesion proteins zyxin and vinculin in vitro and in mice. Finally, we demonstrate that this mechanobiological signature associated with BBB maturation is reversed upon BBB dysfunction after seizures in mice and in human patients with temporal lobe epilepsy. Collectively, our findings establish a novel interplay between mechanoresponsive elements in brain ECs, with implications for BBB stabilisation therapy in epilepsy.

neuroscience↗