CTSK and breast cancer: Using a clinically relevant humanized mouse model of BC bone metastasis, altered expression of IL-1β, IL-1R1, S100A4, cathepsin K (CTSK), secreted phosphoprotein 1 (SPP1), and receptor activator of NF-κB (RANK) in BC cells as they progress from primary tumor to bone metastasis was demonstrated, and these molecules can be used to predict future bone recurrence in BC patients [112].