SPARC and breast cancer: For example, it has been shown that secreted protein acid and rich in cysteine (SPARC), vascular cell adhesion molecule 1 (VCAM1), matrix metalloproteinase 2 (MMP2), and interleukin-13 receptor subunit α2 (IL-13Rα2) are involved in breast cancer lung metastasis [1], whereas interleukin-11 (IL-11) and connective tissue growth factor (CTGF) play a key role in breast cancer bone metastasis [3].