Down modulation of PDGFR activity affects cell growth and survival of GBM CSC. (A-C) Concurrent treatment with Crenolanib and AG1478 enhances apoptosis as monitored by Caspase-3 and PARP-1 cleavage, either in GBM c-CSC or p-CSC, except for p-CSC3. Instead, Crenolanib alone is less effective in inducing apoptosis either in c-CSC or p-CSC pools. High PDGFRα expression is a distinctive feature of p-CSC pools and its expression is de-repressed following AG1478 treatment clearly evident in case 1 and 2, while its expression is downmodulated following Crenolanib treatment in all cases reported. (D) Cell growth assay of shPDGFRα-p-CSC2 clones (cl.1 and 3) displays a significant reduction of cell proliferation with respect to control cells (pLKO.1). Data shown are representative of results obtained from experiments conducted two times. Western blots display downmodulation of PDGFRα in shPDGFRα-p-CSC2 clone 1 and 3, but not of PDGFRβ. (E) c-CSC2 and p-CSC2 starved for 2 days and undergoing PDGFAA stimulation, manifest early phosphorylation of Akt1 and Erk1/2 in p-CSC2 but not in c-CSC2. No effects were observed on STAT3 phosphorylation upon PDGFAA stimulation. Expression of Cyclin D1 protein serves as a control of cell starvation. ns denotes not specific bands.