c-IAP1 redistribution in human leukemia cell lines undergoing TPA-induced differentiation. U937 (A-B) and THP1 (C-D) cells were treated for indicated times with 20 nM TPA to induce a macrophage-like differentiation. (A,C) Western blot analysis of indicated proteins in whole-cell, cytoplasmic, and nuclear extracts. HSC70 was used as a loading control. (B,D) Fluorescence microscopy analysis of c-IAP1 (green), as observed using an anti-c-IAP1 mAb (Pharmingen). Nuclei, labeled with Hoechst 33342, are stained in blue. Magnification × 300.