KDR and glioblastoma: Similarly, siRNA-mediated knockdown of PDGFR-α and PDGFR-β significantly attenuated FSP-1 expression and increased VEGFR-2 expression (Fig. 5b) and inhibited cell proliferation (Fig. 5c), suggesting a requisite role of autocrined PDGF/PDGFR for maintenance of mesenchymalization, VEGFR-2 down-expression, and hyper-proliferation in GBM ECs.