Cyclovirobuxine D induces autophagy-associated cell death via the Akt/mTOR pathway in MCF-7 human breast cancer cells

Autophagy is a highly regulated and multi-step biological process that serves to remove damaged cytoplasmic components and organelles. It has been suggested that the activation of Autophagy may be a promising therapeutic strategy for Cancer treatment by triggering cell death. In this study, we reported that cyclovirobuxine D (CVB-D), an alkaloid component in a traditional Chinese herb, could induce Autophagy in the MCF-7 human breast Cancer cell line. CVB-D inhibited the viability of MCF-7 cells in a concentration- and time-dependent manner. Activation of Autophagy was characterized by transmission electron microscopy, monodansylcadaverine staining, and expression of Autophagy marker microtubule-associated protein 1 LIGHT chain 3 (LC3). After CVB-D treatment, a clear accumulation of autophagosomes was observed accompanied with elevated LC3 fluorescent puncta. Western blot analysis revealed that CVB-D significantly promoted the conversion from LC3-I to LC3-II and the expression of autophagy-related protein 5 (ATG5), which are both essential for autophagosome formation. On the other hand, CVB-D-induced Autophagy and decrease in cell viability could be blocked by 3-methyladenine, a well-established Autophagy Inhibitor. Moreover, CVB-D attenuated the phosphorylation of Akt and mTOR, two pivotal suppressors in Autophagy pathways. These findings shed new LIGHT on the pharmacological actions and mechanism of CVB-D and may support the potential utility of Autophagy inducers in Cancer treatment.