Arsenic trioxide induces apoptosis through a reactive oxygen species-dependent pathway and loss of mitochondrial membrane potential in HeLa cells

IC Park, PhD a, SH Woo, MSa, MJ Park, PhDa, HC Lee, MSa, SJ Lee, PhDb, YJ Chun, MSb, SH Lee, MDa, SI Hong, MDa, CH Rhee, MDa

aLaboratory of Cell Biology, bLaboratory of Radiation Effects, Korea Cancer Center Hospital, Seoul, Nowongu Korea Republic

AIM: Arsenic trioxide (As2O3) can induce clinical remission in patients with acute promyelocytic leukemia through induction of apoptosis. To investigate the potential therapeutic usage of As2O3 in cervical cancer and its possible mechanisms, human cervical cancer cell line HeLa was employed. Methods: The effects of As2O3 on viability of HeLa cells was investigated with cell growth assay, apoptosis was determined by flow cytometry and DNA fragmentation assay, and changes of the mitochodrial membrane potential and intracellular hydrogen peroxide concentration was measured by flow cytometry using specific fluorescent dye. Results: The cells underwent apoptosis in response to As2O3, accompanied by a decrease of mitochondrial membrane potential and caspase-3 activation. Overexpression of Bcl-2, however, prevented the dissipation of mitochondrial membrane potential, subsequently protecting the cells from As2O3-induced apoptosis. As2O3 increased cellular content of reactive oxygen species (ROS), especially hydrogen peroxide, and the antioxidant N-acetyl-L-cysteine completely suppressed As2O3-induced apoptosis. Furthermore, incubation of the cells with catalase resulted in significant suppression of As2O3-induced apoptosis. Conclusions: The above results indicate that the induction of HeLa cell apoptosis by As2O3 involved an early decrease in cellular mitochondrial membrane potential and increase in ROS content, predominantly hydrogen peroxide, followed by caspase-3 activation and DNA fragmentation.

KEY WORDS: Caspase, Cervical cancer, Hydrogen peroxide.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Apoptosis - Molecular Mechanisms.