BACKGROUND

Triple-negative breast cancer (TNBC) is characterized by its rapid progression and aggressive nature, with limited effective therapeutic interventions currently available. Cyclovirobuxine D (CVB-D), a natural alkaloid extracted from the traditional Chinese herb Buxus sinica, is renowned for its cardioprotective and anti-ischemic effects, demonstrating notable anti-cancer properties. Nevertheless, the anti-tumor effects of CVB-D on TNBC remain unverified.

PURPOSE

This study seeks to investigate the effects of CVB-D on TNBC and to uncover the underlying mechanisms.

STUDY DESIGN

Network pharmacology, SPR, DSF, and cell-based functional assays were conducted on TNBC cells to assess the impact of CVB-D. Findings were further corroborated using xenograft mouse models.

METHODS

Cell Counting Kit-8, 5-Ethynyl-2'-deoxyuridine, transwell assays, flow cytometry, wound healing assays, immunofluorescence, and immunoblotting were employed to evaluate CVB-D's influence on TNBC cell lines. SPR, DSF and molecular docking techniques were utilized to assess the binding affinity of CVB-D to Yes-associated protein (YAP). The interaction between CVB-D and autophagy/mitophagy was further analyzed through plasmid transient transfection, JC-1 assay, TUNEL assay, and the use of autophagy inhibitors. The anti-TNBC mechanism of CVB-D was elucidated by overexpressing YAP in MDA-MB-231 cells. Additionally, the in vivo efficacy and safety of CVB-D were assessed in a xenograft mouse model.

RESULTS

In vitro analyses revealed that CVB-D effectively suppressed G1 phase arrest and inhibited TNBC cell proliferation. Moreover, CVB-D induced mitochondrial-dependent apoptosis and reduced cell migration by antagonizing epithelial-mesenchymal transition. Mechanistically, CVB-D exerted its anti-cancer effects by directly binding to YAP, thereby inhibiting the nuclear translocation of YAP/TAZ and suppressing the transcription of downstream oncogenic target genes. Furthermore, CVB-D triggered excessive mitophagy by activating the FOXO3a/PINK1-Parkin axis, promoting apoptosis and leading to mitochondrial dysfunction in TNBC cells. Elevated YAP expression counteracted the effects of CVB-D on TNBC, including the suppression of mitophagy-related protein expression induced by CVB-D, suggesting that YAP modulates mitophagy through the FOXO3a/PINK1-Parkin axis. The anti-tumor efficacy of CVB-D and its underlying mechanisms were further substantiated using a subcutaneous xenograft model.

CONCLUSIONS

This study is the first to demonstrate that CVB-D can directly bind to the YAP target, proposing a novel therapeutic strategy for TNBC. CVB-D may serve both as a YAP/TAZ inhibitor and as an activator of the FOXO3a/PINK1-Parkin axis, leading to excessive mitophagy.