MMP9 and breast cancer: In vitro studies show that mechanically stimulated osteocytes reduced the transendothelial migration of breast cancer cells.68 Further, interactions between osteocytes and endothelial cells decrease the expression of matrix metalloproteinase 9 (MMP‐9), an enzyme known to facilitate the movement of metastatic cancer cells through the extracellular matrix.68 The disparity between these findings suggest that interactions between osteocytes and tumor cells are context and cancer specific.