Traditional Chinese medicine formula Xiang Bei San suppresses the growth and metastasis of breast cancer by regulating macrophage polarization and tumor vascularization.

Breast cancer poses a severe global health threat, necessitating effective therapeutic strategies. Traditional Chinese medicine (TCM) has demonstrated promise in breast cancer treatment. Xiang Bei San (XBS), an empirical formula used in TCM for breast cancer treatment. Despite its frequent clinical application, the anti-breast cancer mechanisms of XBS remain elusive. The present work initially analyzed XBS chemical composition with high-resolution ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). For evaluating the in vivo anti-breast cancer effects of XBS, an orthotopic 4T1 cell mouse model of breast cancer was established. Administration of XBS significantly inhibited tumor growth, with tumor inhibition rates of 45.59%, 49.48%, and 60.89% observed for low, medium, and high-dose groups, separately. Notably, XBS treatment exerted no significant impact on mouse body weight and exhibited no apparent toxic or side impacts. Furthermore, morphological, H&E, and immunohistochemical staining confirmed XBS's suppression of lung metastasis. Mechanisms were explored through transcriptome sequencing, flow cytometry, immunofluorescence, and immunoblotting. Our findings suggested that XBS inhibited polarization of M2 macrophages while facilitating that of M1 macrophages. Additionally, it also upregulated TNF-α and IL-1β while inhibiting Arg-1 expression. Moreover, XBS facilitated T-cell infiltration and reduced the expression of CD31 and VEGF, thereby inhibiting tumor angiogenesis, and upregulated α-SMA expression to stabilize vascular structure. Collectively, XBS exerts inhibitory effects on breast cancer growth and metastasis through regulating macrophage polarization and tumor vascularization within the tumor microenvironment. Therefore, XBS represents a potential candidate drug for treating breast cancer.