MCF7 cells transfected with control siRNA or HEXIM1 siRNA were treated with vehicle (DMSO), HMBA (5 mM), or 4a1 (50 uM) for 8, 18 or 72 h. (A) Cells were processed for Western blot analyses of HEXIM1 or p21 expression or (B) stained with Nile Red to determine lipid vacoule formation (differentiation marker). MDA-MB-231 cells transfected with control or FLAG-tagged HEXIM1 expression vector or MDA-MB-468 cells transfected with control siRNA or HEXIM1 siRNA were treated with vehicle (DMSO), HMBA (5 mM), or 4a1 (50 uM) for 8, 18 or 72 h. (D) Cells were processed for Western blot analyses of HEXIM1 or p27 expression or (B) stained with Nile Red. All photographs of stained cells were taken at 40x magnification. The figures are representative of 3 experiments.