Fig. 5.
Involvement of STAT3 in IL-6-induced production of IL-10. a STAT3 and ERK phosphorylation after stimulation of CM005 melanoma cells with IL-6. The CM005 cells were harvested after 16 h in the absence or presence of 10% FBS and then stimulated with 2 ng/mol of rhIL-6 for 24 h. Phosphorylation of STAT3 (Y705) and subsequent production of IL-10 after IL-6 stimulation were more dominant in CM005 cells cultured in serum-free medium. ERK1/2 was spontaneously phosphorylated without IL-6 stimulation. b Kinetics of IL-6-induced IL-10 production and its association with STAT3 and ERK activation. CM005 cells were stimulated with rhIL-6 (2 ng/ml) for 30 min, 1 h, 3 h, 5 h, and 24 h. The IL-10 levels in supernatant were analyzed by ELISA. Intensities of phosphorylated STAT3 (STAT3Y705) and ERK1/2 bands were compared to those of GAPDH control by the Western blot. *P < 0.05. c Blocking of STAT 3 by siRNA and subsequent decrease in IL-6-induced IL-10 production. After a 2-day knockdown with siRNA fragments of control (Ctl) and STAT3, quiescent CM005 cells were stimulated with 2 ng/ml of IL-6 for 24 h. The STAT3 transcription was decreased by STAT3 siRNA and IL-10 production after IL-6 stimulation was also decreased. **P < 0.01