Since CAFs promote TGFβ signaling [34, 35] and TGFβ contributes to immunosuppression in GBM [36] and the maintenance of GBM stem cells [37, 38], we used double staining of FAP and TGF-β1, and found that a fraction of FAP+ cells (~ 17%) were co-labeled with TGF-β1 in GBM (Additional file 1: Fig. S3d). Here, FAP is linked to glioblastoma.