MMP9 and breast cancer: TIMP2 is a naturally secreted and 21 kDa unglycosylated protein, which could inhibit the activity of MMPs through binding in a 1:1 stoichiometric ratio to MMPs, like MMP-2 and MMP-9.[11,12] Numerous researches showed that TIMP2 was involved in cell proliferation, apoptosis, angiogenesis, invasion, metastasis, and so on.[13,14] However, the exact roles and the patterns of expression of TIMP2 in breast cancer remained unclear.