To assess whether FAP+ pericyte‐like cells significantly contribute to the production of fibrillar ECM in GBM, we analyzed COLI and FN1 expression in these cells, in primary endothelial cells derived from freshly resected GBM tissues [27], as well as in glioma cells (U87, U251, GSCs), primary M2 macrophages, and human brain vascular pericytes (HBVP) (Figure 3A). Here, FN1 is linked to glioblastoma.