Gamabufotalin induces a negative feedback loop connecting ATP1A3 expression and the AQP4 pathway to promote temozolomide sensitivity in glioblastoma cells by targeting the amino acid Thr794.

OBJECTIVES: Temozolomide (TMZ) is one of the most commonly used clinical drugs for glioblastoma (GBM) treatment, but its drug sensitivity needs to be improved. Gamabufotalin (CS-6), the primary component of the traditional Chinese medicine "ChanSu," was shown to have strong anti-cancer activity. However, more efforts should be directed towards reducing its toxicity or effective treatment doses. METHODS: Target fishing experiment, Western blotting, PCR, confocal immunofluorescence and molecular cloning techniques were performed to search for possible downstream signalling pathways. In addition, GBM xenografts were used to further determine the potential molecular mechanisms of the synergistic effects of CS-6 and TMZ in vivo. RESULTS: Mechanistic research revealed a negative feedback loop between ATP1A3 and AQP4 through which CS-6 inhibited GBM growth and mediated the synergistic treatment effect of CS-6 and TMZ. In addition, by mutating potential amino acid residues of ATP1A3, which were predicted by modelling and docking to interact with CS-6, we demonstrated that abrogating hydrogen bonding of the amino acid Thr794 interferes with the activation of ATP1A3 by CS-6 and that the Thr794Ala mutation directly affects the synergistic treatment efficacy of CS-6 and TMZ. CONCLUSIONS: As the main potential target of CS-6, ATP1A3 activation critically depends on the hydrogen bonding of Thr794 with CS-6. The combination of CS-6 and TMZ could significantly reduce the therapeutic doses and promote the anti-cancer efficacy of CS-6/TMZ monotherapy.

The sodium pump α1 subunit regulates bufalin sensitivity of human glioblastoma cells through the p53 signaling pathway.

Bufalin is the primary component of the traditional Chinese medicine "Chan Su," which has been widely used for cancer treatment at oncology clinics in certain countries. Evidence suggests that this compound possesses potent antitumor activities, although the exact molecular mechanism(s) require further elucidation. Therefore, this study aimed to further clarify the in vitro and in vivo antiglioma effects of bufalin and the molecular mechanism underlying the regulation of drug sensitivity. The anticancer effects of bufalin were determined by colony formation assays, apoptosis assays, and cellular redox state tests of glioma cells. Confocal microscopy was performed to determine the expression changes of the DNA damage biomarker γ-H2AX and the nuclear translocation of p53 in glioma cells. Western blotting and RT-PCR were used to detect the protein and gene expression levels, respectively. Here, we report that bufalin induced glioblastoma cell apoptosis and oxidative stress and triggered DNA damage. The critical roles of the sodium pump α1 subunit (ATP1A1) in mediating the XPO1-targeted anticancer effect of bufalin in human glioma were further confirmed. Mechanistic studies confirmed the important roles of Src and p53 signaling in mediating bufalin-induced apoptosis. Importantly, bufalin also inhibited the growth of glioma xenografts. In conclusion, our study indicated that therapies targeting the ATP1A1 and p53 signaling-mediated mitochondrial apoptotic pathways regulated by bufalin might be potential treatments for human glioma, and these findings will provide molecular bases for developing bufalin into a drug candidate for the treatment of malignant glioma.

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

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.