Context: Xiaoyaosan (XYS), a traditional Chinese medicine (TCM), has been widely used to relieve a variety of disorders caused by depression.
Objective: This study evaluates the effect of XYS against tumour metastasis in a chronic restraint stress mouse model.
Methods and materials: Forty C57BL/6J mice were randomly divided into four groups, including blank-control (BC), blank-stress (BS), XYS-control (XC) and XYS-stress (XS). BS and XS groups were exposed to immobilization stress for 2 h per day for 28 days commencing seven days before tumour cell injection. XC and XS groups were given a gavage of XYS (1516.67 mg/kg) before chronic immobilization stress. Mice were injected with HT-29 colon cancer cells in the spleen to produce liver metastasis. After 28 days of injecting with HT-29 cells, flow cytometry, western blot, PCR and immunohistochemical staining were performed to uncover the role of chronic restraint stress and XYS in the liver metastasis of colon cancer.
Results: Metastatic liver weight of mice in XS group (3.33 ± 0.18 g) was significantly lower than BS group (4.01 ± 0.27 g). Chronic restraint stress significantly increased CD11b+F4/80+ and CD11b+GrloLy6Chi cell infiltration. XYS treatment significantly decreased the CD11b+F4/80+ tumour-associated macrophage (TAM) population and CD11b+GrloLy6Chi myeloid-derived suppressor cell (MDSC). TGF-β, IL-6, MMP-9 and VEGF in spleen tumours significantly decreased in XYS group. XYS also reduced VEGF and CD31 in hepatic metastatic tissue, which were elevated by chronic restraint stress.
Conclusions: XYS may successfully inhibit chronic-stress-induced liver metastasis. Results suggest that XYS may have therapeutic value for colorectal cancer treatment.
Keywords: Colorectal cancer; psychological stress; tumour metastasis.