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. © the japanese pharmacological society.