Apoptosis in Hep2 cells treated with etoposide and colchicine.

When malignant cells undergo apoptosis, they exhibit many distinct patterns of behavior, with blebbing being one of the most spectacular and mysterious features. Despite huge advancements in our understanding of cell death, the mechanisms of apoptosis associated blebbing have not been elucidated. In order to verify the putative involvement of actin and tubulin in this process, Hep2 cells were treated with a combination of etoposide (10 microg/ml) and colchicine (0.2 microg/ml) for 24 h. Blebbing was analyzed using immunofluorescence staining of actin and tubulin, and the course of apoptosis was followed by time-lapse videomicroscopy, immunofluorescence detection of caspase-3 and cytokeratin fragment 18. The results indicate that microfilaments (actin) and not microtubules (tubulin) are involved in blebbing of Hep2 cells. Furthermore, despite the different mechanisms by which both chemicals act, their combined effects are not additive, but rather eliminate each other.