KIT D816V-induced expression of OSM is STAT5-dependent. A:KIT D816V+ HMC-1 cells were incubated with piceatannol (160 μmol/L), PD98059 (50 μmol/L), or LY294002 (20 μmol/L) for 16 hours. Cells were then harvested, and expression of OSM was determined by real-time PCR. Results represent the mean ± SD of three independent experiments. *P < 0.05. B:KIT D816V+ HMC-1 cells (4 × 106 cells/mL) were incubated with piceatannol at concentrations of 10, 40, or 160 μmol/L for 24 hours. Supernatants were then harvested, and the amount of secreted OSM was determined by ELISA. Results represent the mean ± SD of three independent experiments. *P < 0.05. C: Ton.Kit.D816V cells kept with IL-3 were cultured in the absence (Control) or presence (Doxy) of doxycycline (1 μg/mL). Cells cultured with doxycycline were treated with piceatannol (10 μmol/L) for 16 hours. Expression of OSM was then determined by real-time PCR. Results represent the mean ± SD of three independent experiments. *P < 0.05. D:KIT D816V+ HMC-1 cells were lentivirally transduced with a random sequence siRNA (rdm-siRNA) or an siRNA targeting STAT5 (Stat5-siRNA). At 24 hours after infection, transduced cells were selected with puromycin (2 μg/mL) for 48 hours. Cells were then harvested, and expression of STAT5 was determined by immunoblotting. Actin served as a loading control. E:KIT D816V+ HMC-1 cells were transduced with a random sequence siRNA (Rdm-siRNA) or an siRNA targeting STAT5 (Stat5-siRNA) and selected as described above. Expression of OSM was determined by real-time PCR. Results represent the mean ± SD of three independent experiments. *P < 0.05. F: Ton.Kit.D816V cells kept in the presence of IL-3 were transduced with a random sequence siRNA (Rdm-siRNA) or an siRNA targeting STAT5 (Stat5-siRNA) and were selected as described above. At 2 days after infection, cells were split and cultured in the absence [control (Co)] or presence (Doxy) of doxycycline for 16 hours. Expression of OSM was then determined by real-time PCR. Results represent the mean ± SD of three independent experiments. *P < 0.05.