COL1A1 and glioblastoma: COL1 was mainly secreted by cancer‐associated fibroblasts in various kinds of cancer.[20] TCGA data analysis also showed that the expression of COL1A1 was positively correlated with the markers of fibroblasts including FAP, PDGFRB, ACTA2, S100A4, and VIM in GBM tissues (Figure 2D–F; Figure S2C,D, Supporting Information).