Biological effect of targeting proNGF in GBM cells. GBM cell growth was studied in a panel of GBM cell lines with methylated MGMT gene promoter (A) and unmethylated MGMT gene promoter (B) as well as human astrocytes (HA, served as a control cell line) treated with blocking antibodies against proNGF (anti-proNGF, 600 ng/mL), TMZ (50 μM) and anti-proNGF + TMZ for 72 h. Data shown are the mean ± SD of three independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001, Student’s t-test or ANOVA. proNGF: precursor for nerve growth factor, TMZ: Temozolomide. Black bars: PBS (vehicle control for anti-proNGF) + DMSO (vehicle control for TMZ); blue bars: anti-proNGF + DMSO (vehicle control for TMZ); purple bars: TMZ + PBS (vehicle control for anti-proNGF); orange bars: anti-proNGF + TMZ.