Figure 3. STAT3 activation is the major downstream effector for IL-6-mediated maintenance of stemness.

A. SkBr3/Lap#6 and SkBr3/Lap#9 cells were transfected with si-control or si-IL6. Four days later, cells lysates were harvested and the expressions of several IL-6 downstream effectors were examined by western blot with indicated antibodies. B. SkBr3 and SkBr3/Lap#6 cells were treated with 1 μM lapatinib for 24 hrs. Cell lysates were collected and the expressions of phosphorylated STAT3 tyrosine 705 and STAT3 were examined by western blot. C. SkBr3/Lap#6 and SkBr3/Lap#9 cells were transfected with si-control or si-STAT3. Two days later, cells were trypsinized and 4 × 10⁴ cells were cultured in ultra-low attachment plates with spheroid-inducing medium, followed by the observation of spheroid formation under microscope. Gene silencing of STAT3 was examined by western blot. D. SkBr3/Lap#6 cells were transfected with si-control or si-STAT3. Two days later, cells were trypsinized and 4 × 10⁴ cells were cultured in ultra-low attachment plates with spheroid-inducing medium for 7 days. Then, 2 × 10⁶ spheroids were collected and subjected to an ALDH activity assay. Protein expression of STAT3 was examined by western blot. Statistical analysis was performed by Student's t test. **, p<0.01 as compared to control group.