Fluoxetine Simultaneously Induces Both Apoptosis and Autophagy in Human Gastric Adenocarcinoma Cells
Wah Wah Po1, Wynn Thein1, Phyu Phyu Khin1, Tin Myo Khing1, Khin Wah Wah Han1, Chan Hee Park1,2 and Uy Dong Sohn1,*
1Laboratory of Signalling and Pharmacological Activity, Department of Pharmacology, College of Pharmacy, Chung-Ang University, Seoul 06974, 2Center for Metareceptome Research, College of Pharmacy, Chung-Ang University, Seoul 06974, Republic of Korea
*E-mail: udsohn@cau.ac.kr
Tel: +82-2-820-5614, Fax: +82-2-826-8752
Received: June 24, 2019; Revised: August 1, 2019; Accepted: August 12, 2019; Published online: September 16, 2019.
© The Korean Society of Applied Pharmacology. All rights reserved.

Fluoxetine is used widely as an antidepressant for the treatment of cancer-related depression, but has been reported to also have anti-cancer activity. In this study, we investigated the cytotoxicity of fluoxetine to human gastric adenocarcinoma cells; as shown by the MTT assay, fluoxetine induced cell death. Subsequently, cells were treated with 10 or 20 µM fluoxetine for 24 h and analyzed. Apoptosis was confirmed by the increased number of early apoptotic cells, shown by Annexin V- propidium iodide staining. Nuclear condensation was visualized by DAPI staining. A significant increase in the expression of cleaved PARP was observed by western blotting. The pan-caspase inhibitor Z-VAD-FMK was used to detect the extent of caspase-dependent cell death. The induction of autophagy was determined by the formation of acidic vesicular organelles (AVOs), which was visualized by acridine orange staining, and the increased expression of autophagy markers, such as LC3B, Beclin 1, and p62/SQSTM 1, observed by western blotting. The expression of upstream proteins, such as p-Akt and p-mTOR, were decreased. Autophagic degradation was evaluated by using bafilomycin, an inhibitor of late-stage autophagy. Bafilomycin did not significantly enhance LC3B expression induced by fluoxetine, which suggested autophagic degradation was impaired. In addition, the co-administration of the autophagy inhibitor 3-methyladenine and fluoxetine significantly increased fluoxetine-induced apoptosis, with decreased p-Akt and markedly increased death receptor 4 and 5 expression. Our results suggested that fluoxetine simultaneously induced both protective autophagy and apoptosis and that the inhibition of autophagy enhanced fluoxetine-induced apoptosis through increased death receptor expression.
Keywords: Fluoxetine, Autophagy, Apoptosis, Gastric adenocarcinoma

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