FIGURE 7.

Nuclear morphology of Top1-deficient cells in response to TRAIL. Electron microcopy analysis of HCT116 cells transiently transfected with a duplex siRNA against Top1 (siRNA-Top1) (B) or a negative control sequence (siRNA-Ctrl) (A) before treatment with 0.1 μg/ml TRAIL for 2.5 h. A, TRAIL-treated siRNA-Ctrl cells show typical apoptotic features including cell shrinkage, highly condensed chromatin, numerous vesicles in the cytoplasm, and apoptotic bodies in the extracellular space. B, in TRAIL-treated siRNA-Top1 cells, chromatin is condensed mostly around the envelope of lobulated or fragmented nuclei and much less apoptotic bodies are observed. Condensed chromatin areas are in close contact with the inner nuclear envelope and are associated with nuclear envelope blebbing. The double arrows indicate inner and outer nuclear membranes. An asterisk indicates nuclear envelope blebbing in Top1-deficient TRAIL-treated cells. Nu, nucleus; Cy, cytoplasm.