Effects of silencing PLSCR1 expression by siRNA on ATRA/PMA-induced leukemic cell differentiation. U937 cells stably transfected with empty vector or P2/P5 siRNA-carrying vectors were treated without (c) or with 10^-6 M ATRA (r) or 100 nM PMA (p) for 3 days. (A) PLSCR1 was detected by Western blot with β-actin as loading control. (B) CD11b⁺ cells were measured by flow cytometry. In the histograms, each value represents the mean from triplicate samples with a variance of less than 15%. (C) Cells were collected onto slides by cytospin, stained by Wright staining, and observed under microscope (100×/1.30 oil). PMA-induced morphologic differentiation was also inhibited by P5 iRNA (data not shown). All experiments were repeated at least 3 times with similar results.