Discovery of Bufalin as a Molecular Glue Degrader of NCAPG to Inhibit the Proliferation of Hepatoma Cells

Inhibiting the malignant proliferation is crucial for managing the cancer progression. NCAPG (Non-SMC condensin I complex subunit G) is a main component in cell proliferation, which is highly expressed in liver tumors and negatively correlated with the overall survival of hepatocellular carcinoma (HCC) patients. In this study, we identified bufalin as a molecular glue for the first time that specifically degraded NCAPG by coupling it to cathepsin V (CTSV). Distinguished from traditional PROTACs, bufalin served as a molecular glue with the distinct advantages of a smaller molecular weight and superior bioavailability. This degradation inhibited the proliferation of HCC cells by inducing G2/M phase cell cycle arrest at low doses (20-40 nM), but did not trigger the apoptosis signaling. Using co-immunoprecipitation and confocal microscopy, we confirmed the interaction between CTSV and NCAPG by bufalin. Knockdown of CTSV or NCAPG attenuated the anti-proliferation effects of bufalin in HCC cells. Cell cycle analysis also showed significantly reduced G2/M arrest in knockdown cells. The downstream proliferation regulators Cyclin D1 and CDK1 were also regulated by bufalin in a CTSV/NCAPG-dependent manner. Our study not only identified the CTSV-NCAPG complex as a novel therapeutic target but also discovered a potential molecular glue, bufalin, which exerts anti-proliferation effects through cell cycle regulation. These findings highlight the potential clinical translational value of bufalin as a promising, bioavailable therapeutic agent for the targeted treatment of liver cancer.