Overexpression of caspase-9 triggers its activation and apoptosis in vitro.

AIM: To investigate the consequences of increased expression of caspase-9: 1) whether the caspase-9 overexpression resulted in cell death through apoptosis, 2) whether apoptosis could be triggered in normal and tumor cells, and 3) what is the role of caspase-9 in the process.
METHODS: The caspase-9 fused to green fluorescent protein was expressed in primary cultures of anterior pituitary cells and of HeLa tumor cells. The expressed caspase-9 and the number of apoptotic and necrotic cells were determined using fluorescence microscopy.
RESULTS: Overexpression of caspase-9 resulted in cell death of primary pituitary cells and HeLa cells. More than 94% of the cells died of apoptosis, which was triggered by the activation of caspase-9, since the cell deaths were prevented in the presence of caspase-9 specific inhibitor. HeLa cells were about 50% more resistant to apoptosis than pituitary cells.
CONCLUSIONS: Caspase-9 overexpression and its activation leads to apoptosis. It occurs both in normal and tumor cells. Since the majority of cancer therapy treatments initiate apoptosis through the caspase-9 activation, the modulation of caspase-9 expression may be exploited in designing new ways to control apoptosis in neurodegenerative or malignant diseases.