Effects of Brucine on the OPG/RANKL/RANK Signaling Pathway in MDA-MB-231 and MC3T3-E1 Cell Coculture System

The present study examined the effects of brucine on the OPG/RANKL/RANK signaling pathway for exploring the mechanism of brucine suppression of bone metastasis in breast cancer. MDA-MB-231 breast cancer cells and mouse osteoblast MC3T3-E1 cells were cocultured to mimic the breast cancer bone metastasis microenvironment in vitro. qRT-PCR and Western blotting were used to detect the expressions of OPG and RANKL at the mRNA and protein levels, respectively, in brucine-treated cultures and they were compared to those in untreated cultures. We aimed to understand the effect of brucine on the entire OPG/RANKL/RANK signaling pathway after analyzing these effects. Results showed that brucine treatment significantly increased both the OPG mRNA/RANKL mRNA expression ratio and the OPG protein/RANKL protein ratio in cocultures compared to those in untreated cocultures (P < 0.01). Brucine, therefore, plays a regulatory role in the OPG/RANKL/RANK signaling pathway, suggesting that it can indirectly control osteoclasts by regulating the expression and secretion of OPG and RANKL in osteoblast cells, thereby inhibiting the differentiation and bone resorption function of osteoclasts.