Proteomic characterization of extracellular matrix (ECM) produced by human fibroblast activation protein (FAP)-positive pericyte-like cells and glioma cells

Fibroblast activation protein (FAP) is upregulated in most cancers and represents an emerging theranostic target in oncology. In glioblastoma (GBM), FAP is predominantly expressed in mesenchymal pericyte-like cells, which contribute to GBM progression by promoting angiogenesis and glioma cell proliferation by soluble mediators. In this work, we show another possible mechanism by which these cells contribute to gliomagenesis. We observed that FAP+ pericyte-like cells residing in the perivascular niche in GBM are associated with elevated levels of the fibrillar extracellular matrix (ECM) proteins collagen I and fibronectin. Using sequential window acquisition of all theoretical mass spectra (SWATH-MS) analysis, we confirmed that the highest levels of collagen I and fibronectin are produced by FAP+ pericyte-like cells. In addition, we observed different expression pattern of basal membrane proteins between FAP+ pericyte-like cells and glioma cells.