LRP6 and breast cancer: To gain further insights into the underlying mechanism by which GRP94 promotes metastasis in breast cancer, we focused on the Wnt signaling pathway, considering that GRP94 is a crucial HSP localized in the ER and a critical chaperone for low-density lipoprotein receptor-related protein 6 (LRP6), a key co-receptor involved in Wnt signaling [24].