SFRP2 and breast cancer: Further studies have revealed that in breast cancer cells, miR-218-5p directly targets two key inhibitors of the Wnt signaling pathway—Sclerostin (SOST) and secreted frizzled-related protein 2 (sFRP2)—thereby activating Wnt signaling, promoting osteoclast differentiation, and accelerating breast cancer bone metastasis (Taipaleenmäki et al., 2016).