PD-L1 blockade had no significant effect on the expression level of VEGFR1 on the surface of GBM-educated macrophages (Fig. 4B), but significantly promoted the expression level of sVEGFR1 mRNA (Fig. 4C), suggesting that PD-L1 blockade may regulate its secretion by affecting the de novo synthesis of sVEGFR1. Here, FLT1 is linked to glioblastoma.