Mechanism for ginsenoside Rh2-induced apoptosis of triple-negative breast cancer MDA-MB-231 cells

Abstract

Objective: The authors aimed to explore the apoptosis of triple-negative breast cancer (TNBC) MDA-MB-231 cells induced by gin- senoside Rh2 and the underlying mechanism. Materials and Methods: Changes in the viability of MDA-MB-231 cells after treatment with 20 (S)-Rh2 and 20 (R)-Rh2 for 48 hours were detected by MTT assay. Changes in the morphology of cell nuclei were observed by DAPI staining. The expressions of caspase-3, caspase-9, cytochrome c, Smac, Bak, and Bax related to the mitochondrial pathway were detected by Western blotting. Results: 20 (S)-Rh2 inhibited the proliferation of MDA-MB-231 cells, but 20 (R)-Rh2 failed to do so. After treatment with 20(S)-Rh2 for two hours under visible light, they shrank and had incomplete morphology, whereas the mor- phology of control group hardly changed. Under UV light, the nuclei stained with DAPI were blue. After treatment with 20 (S)-Rh2 for one hour, the nuclei shrank and ruptured, and nearly 90% ruptured at two hours. In contrast, the nuclei of PBS control group remained intact. The activity of caspase-9 in MDA-MB-231 cells treated with 7.5 μg/mL 20 (S)-Rh2 was increased at 30 minutes, and gradually increased over extended time. Under identical conditions, the activity of caspase-9 in control group did not change significantly. Cy- tochrome c and Smac were released from mitochondria to the cytoplasm at one hour after treatment with 7.5 μg/mL 20 (S)-Rh2. How- ever, such release was not detected in the control group. Bax was translocated after 30 minutes of treatment with 7.5 μg/mL 20 (S)-Rh2, which then gradually accumulated in mitochondria over time and peaked at two hours. The Bax expression in the entire cell lysate re- mained unchanged. The translocation of Bax was not detected in control group. Conclusion: 20 (S)-Rh2 evidently inhibited the prolif- eration of TNBC cell line MDA-MB-231. It killed the cells by inducing apoptosis, probably by activating the mitochondrial pathway.