Cytotoxic granule disruption is a late event in chemotherapy-induced apoptosis in natural killer YT cells

Cytotoxic lymphocytes such as Natural Killer (NK) cells can result in leukemias and lymphomas with aggressive clinical course. The cytoplasmic granules of NK cells contain molecules that cause apoptosis of their target cells. In this study, we examined changes of the cytotoxic granules of the Natural Killer cell line YT during Etoposide-induced apoptosis. Etoposide treatment resulted in an early upregulation of Fas and cytoplasmic release of mitochondrial cytochrome c. The cytotoxic granules remain intact in the early stages of apoptosis induction with no significant cytoplasmic release of granzyme B, which is one of the components of the cytotoxic granules. These results suggest that disruption of the cytotoxic granules is not involved in the induction stage of Etoposide-induced apoptosis in the NK cell line YT.