Effects of ATRA on PLSCR1 expression in leukemic cell lines U937 and HL60. U937 and HL60 cells were treated with 10^-6 M ATRA for times indicated. CD11b⁺/CD14⁺ cells (A), semiquantitative RT-PCR for PLSCR1 mRNA (B), and Western blot for PLSCR1 with β-actin as loading control (C) were performed as detailed in “Materials and methods.”