P12.06.A PERICYTE-LIKE CELLS EXPRESSING FIBROBLAST ACTIVATION PROTEIN ARE MAIN PRODUCERS OF FIBRILLAR EXTRACELLULAR MATRIX IN GLIOBLASTOMA

Abstract

Abstract BACKGROUND Compared to the normal brain, glioblastomas (GBMs) contain higher amounts of extracellular matrix (ECM) composed of fibrillar proteins such as collagen I and fibronectin. These proteins are associated with glioma cell invasion and poor clinical outcome of GBM patients, but their origin remains unclear. The highest levels of fibrillar ECM can be found in perivascular niches, which are, among others, resided by fibroblast activation protein (FAP) expressing pericyte-like cells. The aim of this study was to determine the role of FAP+ pericyte-like cells in the production of fibrillar ECM proteins and their importance in glioma cell biology. MATERIAL AND METHODS FAP+ pericyte-like cells, glioma stem-like cells (GSCs) and primary endothelial cells were isolated from human GBMs. M2 macrophages were differentiated from monocytes isolated from healthy donors´ buffy coats. The expression of FAP, collagen I and fibronectin in GBM tissues and different cell types (FAP+ pericyte-like cells, glioma cell lines, GSCs, M2 macrophages) was analyzed by immunohistochemistry and ELISA. FAP+ pericyte-like cells and glioma cells were used to prepare extracellular matrices, which were analyzed using mass spectrometry. Solubilized ECM was used in a modified transwell migration assay. RESULTS Compared to the non-tumorous brain, high levels of collagen I and fibronectin were present in the vicinity of FAP+ pericyte-like cells in GBMs. The expression of collagen I and fibronectin was higher in GBMs with higher FAP expression. In vitro, FAP+ pericyte-like cells produced the largest amount of collagen I and fibronectin compared to other cell types and secreted these proteins extracellularly, resulting in production of 3D extracellular matrices rich in collagen I and fibronectin. Mass spectrometry revealed that the ECM produced by FAP+ pericyte-like cells strongly differs in composition compared to glioma cell ECM. The ECM produced by FAP+ pericyte-like cells enhanced migration of glioma stem-like cells. CONCLUSION FAP+ pericyte-like cells are the main producers of fibrillar ECM proteins such as collagen I and fibronectin in GBM tissue. By this means, their presence within the GBM microenvironment affect the migration of glioma stem-like cells. Funding: Supported by the National institute for cancer research (LX22NPO5102), Charles University Grant Agency (GAUK 1084120) and Centre for Tumour Ecology (CZ.02.1.01/0.0/0.0/16_019/0000785). EATRIS-CZ (LM2023053), Cooperatio Program, research area ,,Oncology and Haematology", and Ministry of Health of the Czech Republic (NV19 03 00501).