Figure 3. miR-155 expression is regulated by the JAK/STAT pathway. (A) Representative western blot showing siRNA-mediated knockdown of STAT3, STAT5A, STAT5B and STAT5A+B in malignant MyLa2059/MAC2A cells. (B) Relative quantification of miR-155 (top) and BIC (bottom) in malignant MyLa2059 (left) and MAC2A (right) cells as measured by qPCR and determined by the ddCt method. miR-155 expression was decreased by 40% after knockdown of STAT5A and STAT5B, but not STAT3 in both cell lines; nt, non-targeting control. p values were obtained from Student’s t-test. *Indicates a significance of p < 0.05. (C) Incubation with JAK3 inhibitor (JAK3i) CP-690550 (50 µM) decreased pY-STAT5 (top) and resulted in decreased miR-155 expression in malignant MyLa2059 cells. miR-155 expression was decreased by 60–80% when cells were treated with JAK3i for 24, 48 or 72 h. Control DMSO. (D) JAK3 inhibition with CP-690550 (0.1 and 50 µM, 24 h) in PBMCs from a patient with SS resulted in a decreased STAT5 phosphorylation (top) and a 50% inhibition of miR-155 expression.