IGF-1R blockade reinstates the IFN-γ/STAT1 apoptotic pathway. Flow cytometric analysis of (A) Fas and (B) FasL surface expression on ST4-E (i-ii), ST4-WT (iii-iv), and ST4-DN (v-vi) cultured for 24 hours in complete medium with or without IFN-γ. Expression of Fas or FasL (gray histograms) and the background of mouse IgG1 negative control (open histograms) are shown for 1 representative experiment out of 3 independently performed. Boxed results show the percentage of positive cells and the mean specific fluorescence. (C) ST4-E (○), ST4-WT (□), and ST4-DN (▪) cells were cultured in complete medium with different doses of IFN-γ. After 72 hours, cells were harvested, stained with trypan blue and counted. (D) ST4-E (i), ST4-WT (ii), and ST4-DN (iii) cells were cultured in the presence of complete medium (▴), IFN-γ (▵), a blocking anti-Fas mAb (1 μg/mL) (▾), and IFN-γ plus blocking anti-Fas mAb (▿), and the kinetics of their growth was evaluated. (E) ST4-E (i), ST4-WT (ii), and ST4-DN (iii) cells were cultured in complete medium in the presence (gray histogram) or absence (open histogram) of IFN-γ. After 48 hours, cells were recovered, stained with PE-conjugated annexin-V, and analyzed by flow cytometry. All experiments were performed independently at least 3 times.