Formosanin C induces autophagy-mediated apoptosis in multiple myeloma cells through the PI3K/AKT/mTOR signaling pathway

Objectives Multiple myeloma (MM) is an incurable plasma cell malignancy associated with poor survival. Novel therapeutic drugs are urgently needed to improve MM therapy and patient outcomes. This study aimed to investigate the effect of formosanin C (FC), a Chinese medicine monomer, on MM in vitro and disclose the underlying molecular mechanism.Methods The effect of FC on the viability, proliferation, apoptosis, and autophagy of MM cell lines (NCI-H929 and ARP1) was studied through CCK-8, colony formation, flow cytometry, GFP-LC3, and western blotting assays, respectively. A pharmacological approach and network pharmacology technology were implemented to explore the potential mechanisms of the action of FC on MM cells.Results FC efficiently suppressed the viability and colony-forming capacity, but promoted the number of autophagic vacuoles with GFP-LC3 localization and the percentage of apoptotic cells in MM cells. Additionally, FC significantly increased the levels of the autophagy-related proteins LC3-Ⅱ and Beclin 1, as well as the apoptosis-related proteins Bax and cleaved caspase-3, but blocked the expression of the proapoptotic protein Bcl-2 in the cells; these effects were reversed by an inhibitor of autophagy, 3-methyladenine. What's more, we found that the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway was involved in the FC-mediated inhibition of MM. Pharmacological inhibition of this pathway dramatically relieved FC-triggered excessive expression of autophagy-related proteins and rescued MM cells from FC-induced apoptosis.Conclusion Our findings indicate that FC exhibits an anti-MM effect by activating cell autophagy through the PI3K/AKT/mTOR signaling pathway.