Vitexicarpin Directly Targets RSK2 to Attenuate Migration and Invasion of Triple‐Negative Breast Cancer Through Modulating HIF‐1α/MMP‐9 Pathway

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with high metastatic potential and lacking effective treatment strategies. Vitexicarpin (VIT) has been reported to have excellent inhibitory effects on several types of cancer, including TNBC. However, its potential mechanisms on metastatic TNBC are not well understood. Herein, we found that VIT inhibited migration and invasion of TNBC through reducing MMP-9 expression in vitro and in vivo. Subsequently, RSK2 was identified as the potential target of VIT in TNBC by pull-down and MS analysis. Moreover, the further validations showed that VIT bound to Asp148 and Asp154 residues of NTKD, and Thr493 of CTKD, thereby inhibiting its phosphorylation and kinase activity. Mechanistically, we found that HIF-1α/MMP-9 was involved in VIT-mediated inhibition of migration and invasion of TNBC, and similar results were observed upon RSK2 knockdown or combined with VIT treatment, which demonstrated that VIT-mediated inhibition of HIF-1α/MMP-9 pathway was dependent on targeting RSK2. Finally, TNBC mouse xenograft models showed that VIT effectively inhibited TNBC metastasis and growth through regulating the RSK2/HIF-1α/MMP-9 axis in vivo. Taken together, our findings demonstrated that VIT downregulated the HIF-1α/MMP-9 pathway to suppress TNBC migration and invasion by directly targeting RSK2. These results suggested that VIT is a potential drug candidate for TNBC treatment.