Purpose: Selective serotonin reuptake inhibitors (SSRIs) are widely used for the treatment of patients with depression. Approximately 60% of women with breast cancer suffer from depression. This study was performed to investigate the effect of SSRIs on cell viability of human breast cancer MCF-7 cells.

Methods: Cell viability, ROS generation, and Ca2+ increase were quantified using MTT, H2DCFDA, and Fluo-3 AM. Apoptotic signaling pathways were analyzed by immuno-blotting and -staining. Plasma and mitochondrial membrane potentials were determined by DiO PMP and JC-1 dyes, respectively. K+ channel activity was analyzed by whole-cell and single-channel recordings.

Results: Of the antidepressants tested in this study, paroxetine most reduced the viability of MCF-7 cells. Paroxetine (10 and 30 μM) treatment resulted in a significant increase in the number of apoptotic cells, an increase in Bax/Bcl-2 ratio, an activation of caspase-8, 9, and PARP, and a release of cytochrome c from mitochondria. In addition, paroxetine markedly increased ROS generation and intracellular Ca2+ levels. Moreover, paroxetine blocked K+ channels, such as large conductance Ca2+-activated K+ channel and TASK-3 channel, which are present in plasma membrane and mitochondria. The paroxetine-induced apoptosis was reduced by antioxidants, in particular NAC. Combination with SB202190 (a p38 MAPK inhibitor) prevented cells from undergoing apoptosis.

Conclusion: Our findings show that apoptotic effect of paroxetine is mediated by mitochondrial dysfunction and modulation of K+ channels in MCF-7 cells. We suggest that paroxetine could be an agent for anti-tumor therapy in breast cancer.

Citation Format: Kee R. Kang, Young-Woo Cho, Ji Hyun Ryu, Eun-Jin Kim, Jaehee Han, Dawon Kang. Paroxetine induces apoptosis in human breast cancer MCF-7 cells through mitochondrial dysfunction and modulation of K+ channels. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3519.