Abstract
3216
Introduction: The role of autophagy in cancer is controversial. Initially autophagy was thought to represent an alternative pathway for cell death. However, more recently it has been suggested to play a role in tumor survival. In this study we describe how the induction of autophagy by a novel isoflavone derivative, NV128, induce cell death in chemo-resistant ovarian cancer cells. Methods: Eight primary cultures and two established epithelial ovarian cancer (EOC) cell lines were treated with increasing concentrations of NV128 (0.1, 1, and 10 ug/ml) with or without the pan-caspase inhibitor, Z-VAD-FMK. Cell viability was determined after 24h using the Celltiter 96 assay. DNA fragmentation was analyzed by flow cytometry with Hoechst and Propidium iodide staining. Activity of caspases- 3/7, -8, and -9 was measured using Caspase-Glo assay. Autophagic markers LC3-II and Beclin-1 was determined by Western blot analysis. Results: NV128 treatment decreased cell viability in all tested EOC cells lines in a dose-dependent manner with IC50 between 1 and 5 ug/ml. Flow cytometry analysis revealed DNA fragmentation, with Hoechst and Propidium iodide double-positive cells increasing 2-4 fold after NV128 treatment. However, cell death was caspase independent as evidenced by the lack of caspases- 3/7, -8, and -9 activity and the inability of the caspase inhibitor, Z-VAD-FMK, to prevent cell death. Western blot analysis of autophagic markers showed early involvement of LC3-II and Beclin-1. Conclusion: We demonstrate that induction of autophagy by NV128 in chemo-resistant ovarian cancer cells is able to promote caspase- independent cell death. Our results suggest that the autophagic pathway can be an alternative target in EOC cells, especially those that are highly resistant to apoptosis.
Footnotes
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA
- American Association for Cancer Research