AffymetrixHuman Gene 2.0 ST Array

Gene expression in glioblastoma cells from patients before treatment. The cells were inhibited or not for FGFR1. Glioblastoma are known to be aggressive and therapy-resistant tumors, due to the presence of glioblastoma stem cells (GSC) inside this heterogeneous tumor. We investigate here the involvement of FGFR1 in glioblastoma stem-like cells (GSLC) radioresistance mechanisms. We first demonstrated that the survival after irradiation was significantly diminished in FGFR1-silenced (FGFR1-) GSLC compared to control GSLC. The transcriptome analysis of GSLCs FGFR1(-) showed that FOX family members are differentially regulated by FGFR1 inhibition, particularly with an upregulation of FOXN3 and a downregulation of FOXM1. GSLC survival after irradiation was significantly increased after FOXN3 silencing and decreased after FOXM1 inhibition, showing opposite effects of FGFR1/FOX family members on cell response to ionizing radiation. Silencing FGFR1 or FOXM1 downregulated genes involved in mesenchymal transition such as GLI2, TWIST1, and ZEB1 in GSC. It also dramatically reduced GSLC migration, strongly suggesting that FGFR1/FOXM1 pathway which regulates GSLC radioresistance. Databases analysis confirmed that the combined expression of FGFR1/FOXM1/MELK/GLI2/ZEB1/TWIST1 is significantly associated with patients overall survival after chemo-radiotherapy treatment. All these results, associated with our previous conduced ones with differentiated cells, clearly established that FGFR1-FOXM1 dependent GSC radioresistance pathway is a central actor of GBM treatment resistance and a key target to inhibit in the aim to increase the sensitivity of GBM to the radiotherapy. Cells were transfected with different small interfering RNAs (siRNA): an aleatory sequence, SiScramble siRNA and siRNAs specific for FGFR1 (QIAGEN, SI02224677, Courtaboeuf, France). Total RNAs were isolated either from Neurospheres 48h post-transfection and hybridized on Affymetrix microarrays.