Cinobufacini Injection Suppresses the Proliferation of Human Osteosarcoma Cells by Inhibiting PI3K/Akt Signaling Pathway

Background: Cinobufacini injection (CI), an aqueous extraction from the Cutis Bufonis, is broadly used in clinical treatment of cancer in China. However, the underlying molecular mechanisms of CI in treating osteosarcoma (OS) remain unclear. Aberrant activation of PI3K-AKT signaling pathway is the cause of many types of cancer, including OS. Therefore, we investigated the effect of CI on proliferation, apoptosis and cell cycle of OS cells and elucidated the molecular mechanism of CI in inhibiting OS cells. Methods: Cell proliferation of U2OS and MG63 cells after CI treatment was measured by CCK-8 assay, colony formation and morphological changes. Additionally, the cell cycle arrest and apoptosis induced by CI, were determined by FACS and Western blot analysis. The mechanisms of CI on OS were evaluated by RNA-seq and Western blot analysis. Results: We founf that CI reduced the proliferation of U2OS and MG63 cells in a dose- and time- dependent manner. Furthermore, CI induced the U2OS cells cycle arrest in G0/G1 phase, but the MG63 cells cycle arrest in G2/M phase. Consequently, CI triggered the apoptosis in both OS cells, with enhanced caspase-3 activity and decreased expression of Bcl-2/Bax. In addition, RNA-seq data indicated that PI3K-Akt signaling pathway played an essential role in CI treatment. Moreover PI3K and phosphorylation of AKT (p-AKT) were significantly down-regulated by CI in both OS cells. Conclusions: These results indicate that CI significantly inhibited the proliferation, induced the cell cycle arrest, as well as apoptosis in human OS cells, which is mediated by the inactivation of PI3K-Akt signaling pathway. These findings suggest that CI may have potential for the treatment of OS.