In the nude mouse xenograft model of human GBM, in vivo validation further demonstrated that GDF15 overexpression increased M2 macrophage infiltration, whereas GDF15 knockdown reduced M2 macrophage accumulation in human GBM tissues (Fig. 6C-D, Supplementary Fig. 3E, I, J and K, O, P). Here, GDF15 is linked to glioblastoma.