Bufalin inhibits glioblastoma growth by promoting proteasomal degradation of the Na+/K+-ATPase α1 subunit

Abstract

Chansu is a traditional Chinese medicine that is generally recognized as a specific inhibitor of Na+/K+-ATPase. Bufalin, an active component of Chansu, is an endogenous steroid hormone with great potential as a cancer treatment. However, the mechanism by which it exerts its antitumor activity requires further research. Currently, the α1 subunit of Na+/K+-ATPase (ATP1A1) is known to exert important roles in tumorigenesis, and the precise mechanisms underlying the effect of Bufalin on the Na+/K+-ATPase α1 subunit was therefore investigated in this study to determine its role in glioblastoma treatments. The effect of ATP1A1 on the sensitivity of glioblastoma cells to Bufalin was investigated using MTT assays, RT-PCR and siRNA. Western blot was also used to explore the important roles of the ubiquitin-proteasome pathway in the Bufalin-mediated inhibition of ATP1A1. Xenografted mice were used to examine the anti-tumor activity of Bufalin in vivo. LC–MS/MS analysis was performed to determine the ability of Bufalin to traverse the blood-brain barrier (BBB). The results indicated that Bufalin inhibited the expression of ATP1A1 in glioblastoma by promoting the activation of proteasomes and the subsequent protein degradation of ATP1A1, while Bufalin had no effect on ATP1A1 protein synthesis. Bufalin also inhibited the expression of ATP1A1 in xenografted mice and significantly suppressed tumor growth. These data should contribute to future basic and clinical investigations of Bufalin. In conclusion, Bufalin significantly inhibited the expression of ATP1A1 in glioblastoma cells by activating the ubiquitin-proteasome signaling pathway. Bufalin may therefore have the potential to be an effective anti-glioma drug for human glioblastoma in the future.