CTSK and breast cancer: As concerns the present issue, the main positive effect of sulforaphane treatment is the enrolment of a new gene network, i.e., RUNX2, NF-κB1, and SOX9, which becomes downregulated, and in turn negatively affects the transcription and secretion of collagen type 1 α1 (COL1A1), a metastasis-promoting factor, MMP-9, and cathepsin K (CTSK), matrix-degrading factors involved in breast cancer metastasis.