Identification of Bruceine A as a novel HSP90AB1 inhibitor for suppressing hepatocellular carcinoma growth.

INTRODUCTION: Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality worldwide, with limited therapeutic options available. Natural compounds, such as Bruceine A (BRA), derived from Brucea javanica, have emerged as promising anticancer agents. However, the underlying mechanisms of action in HCC remain largely unexplored. OBJECTIVES: This study aims to identify the molecular target of BRA and elucidate its anticancer effects. METHODS: Patient-derived organoids (PDOs) and xenograft (PDX) models were employed to assess the anticancer activity of BRA. Chemical proteomics and binding assays, including MST, SPR, and CETSA, facilitated the identification of heat shock protein 90α family class B member 1 (HSP90AB1) as the primary target of BRA, with SER-108 identified as the critical binding site. HSP90AB1 knockdown further confirmed its pivotal role in BRA-mediated anti-HCC effects. Additionally, TMT-based proteomics was applied to investigate the downstream chaperones of HSP90AB1. RESULTS: BRA significantly suppressed HCC proliferation and induced apoptosis. Molecular analyses revealed HSP90AB1 as the key target, with SER-108 as the critical binding site. Proteomic analysis identified downstream HSP90AB1 partner proteins, including PIK3CG, EGFR, and KDM5C, as contributors to BRA's inhibitory effects on HCC progression. CONCLUSION: This study establishes HSP90AB1 as the primary target of BRA, which exerts its anti-HCC effects through modulation of downstream chaperones PIK3CG, EGFR, and KDM5C. These findings highlight the therapeutic potential of BRA in HCC and suggest that HSP90AB1 represents a promising target for future drug development.