PDGFD and neoplasm: Nevertheless, ERK activation by PDGFRβ signaling pathway cannot compensate the loss of HIF1α-PDGFD-PDGFRα-AKT network for GBM tumor growth because knockout of either HIF1A or PDGFD or PDGFRA in U251 cells eradicated the tumor growth (Fig. 2G, H and Fig. 4G, H).