Abstract
The blood-brain barrier (BBB) is a highly selective barrier that strictly controls the passage of substances and cells into the brain, protecting it from potential harm while preserving homeostasis. It is composed of specialised endothelial cells (ECs), along with surrounding cells, such as pericytes and astrocytes. In glioblastoma (GBM), the most prevalent primary malignant brain tumour in adults, the BBB is heterogeneously dysfunctional. In the tumour microenvironment, regions enriched with glioblastoma stem cells (GSCs) are protected by an intact BBB. However, the influence of GSCs on BBB function remains largely unexplored. In this study, the impact of patient-derived GSC (PD GSC) secretomes on human brain capillary ECs has been investigated in vitro. Results showed that secretomes decrease the BBB permeability, leading to an increase of transendothelial electrical resistance and of tight junction protein claudin-5 (CLDN5) levels. Moreover, the receptor for advanced glycation endproducts (RAGE), which is involved in cancer and chemotherapy resistance, modulates CLDN5 expression by activating the pERK/ERK signaling pathway and influences junctional organization. These findings suggest a functional pathway through which PD GSC secretomes can modulate BBB permeability, potentially impacting therapeutic efficacy.