BIOM-40. BLOOD AND NASAL BIOMARKERS OF BRAIN MICROENVIRONMENT BLOOD–BRAIN BARRIER PERMEABILITY: CLINICAL AND APPLIED CONCEPTS

Abstract The limiting step to treating glioblastoma (GBM) patients is the close blood-brain barrier (BBB) which protects the brain making it an inaccessible compartment. Although multiple studies have highlighted the presence of circulating tumour cells (CTCs) in glioblastoma multiforme (GBM) patients their relationship with brain microenvironment and BBB permeability was not explored in depth. We studied the development of GBM by transferring tumour cells into the mouse brain and also in a subcutaneous location to verify how the different microenvironment affected the release of circulating tumour and endothelial cells. Glioblastoma U3T3MG IDHwt secondary cell line was transfected to track circulating tumour cells released. Moreover, both U3T3 cells and short-time-expanded CTCs1 from GBM patients were used for intracranial xenografts and patient-derived xenografts (PDX). The in vivo models demonstrated the correspondence between BBB permeability with the release of CTCs and the increment of endothelial progenitor cells in GBM HIFpos >20% compared to subcutaneous xenografts releasing CTCs in GBM HIFpos< 20%. These data were confirmed in HIFpos tissue biopsy of GBM-IDHwt patients with CTCs >30 cells/ml. Both in PDXs and in the GBM patient demonstrated that the release of CTCs was intermittent, related to BBB opening induced by HIF-dependent cytokines release (IL8, TNFa)2. In parallel, the analysis of structural Glial fibrillary acidic protein (GFAP)3, on nasal secretion and interstitial fluid, collected in surgical treated GBM patients, demonstrated that the recognition of the two GFAP isoforms (p150 and p50 kDa) were the result of inflammatory microenvironment enriched for proteases induced by IL8, TNFa. Overall data indicate at least two different ways of monitoring the BBB and the brain microenvironment, one distal (blood) and one proximal (nasal secretion) useful to perform precision treatments in patients with GBM. REFERENCES 1) Malara, N. et al. Mol Cancer 23, 32 (2024). doi.org/10.1186/s12943-024-01951-x2) Coluccio ML. et al Cancers (2020) doi: 10.3390/cancers12061362.3) Malara, N. et al Front. Oncol.(2021) doi.org/10.3389/fonc.2021.737730