Objective: To investigate the anti-osteolytic metastasis effects of Zuogui Wan for breast cancer. Method: Balb/C Nu mice were used to establish in vivo experimental bone metastasis models by left ventricle injection of human breast cancer MDA-MB-231 cells. The mice in the experiment was divided into three groups: blank group

Zuogui Wan groups (21

42 g·kg-1). The cytokeratin 19(CK19) in bone marrow were detected by nest PCR assay. The bone marrow-derived macrophages (BMMs) were in vitro isolated as osteoclast precurosors

and soluble receptor activator of nuclear factor-κB ligand(sRANKL) was exogenously added to simulate the activation of osteoclasts under tumor conditions

and then the effects of Zuogui Wan on activation of osteoclasts

Cathepsin K secretion levels and bone slices absorption were observed. Western blot assay was used to detect its effect on RANK expression levels in BMMs. Result: As compared with the blank group

Zuogui Wan(21

42 g·kg-1) exhibited significant inhibition on human CK19 expression levels in bone marrow tissues of animals with breast cancer bone metastasis (P<0.01). In vitro serum pharmacological studies showed that Zuogui Wan significantly inhibited RANKL-induced osteoclastogenesis in murine BMMs(P<0.05) and significantly inhibited the secretion of Cathepsin K in RANKL-induced osteoclasts (P<0.05). Bone slices experiment indicated that

the number and area of bone slices resorption pits in 10% Zuogui Wan group were significantly lower than those in normal group (P<0.05). Western blot assay indicated that medicated serum of Zuogui Wan could significantly inhibit the expression of RANK in RANKL-induced osteoclasts. Conclusion: Zuogui Wan have significant anti-osteolytic metastasis effects for breast cancer cells

and the mechanism may be associated with inhibiting RANKL/RANK activation.