Low serum level of pro-matrix metalloproteinase 2 correlates with aggressive behavior in breast carcinoma

Malignant tumors that are capable of invading surrounding structures and metastasizing possess certain capacities to cross tissue barriers. Matrix metalloproteinases (MMPs), especially gelatinases and their inhibitor molecules, are known to affect the extracellular matrix turnover, and the proteolytic imbalance due to the abnormal expression of these enzymes eventually leads to cancer progression. This has been well documented at the tissue level. In this study, the different forms of the circulating MMP-2 have been studied in the preoperative sera of 71 patients with breast carcinoma. A quantitative enzyme-linked immunosorbent assay was performed for total proMMP-2, proMMP-2-tissue inhibitor of metalloproteinase 2 (TIMP-2) complex, and free active MMP-2. It is shown here, for the first time, that the total proMMP-2 levels in the serum correlate inversely with node positivity, high stage of the disease, and high nuclear grade of the breast tumor. An association with the levels of lower free active MMP-2 and tumor recurrence is also demonstrated. Interestingly, the tumor tissue expression of MMP-2 had an inverse correlation with proMMP-2-TIMP-2 complex levels in the serum. In conclusion, the levels of the total proMMP-2 correlate inversely with tumor burden, whereas free active MMP-2 might be associated with survival. This could indicate that the prognostic value of the circulating forms of MMP-2 is not congruent with the prognostic information obtained from tissue expression. This is further supported by the inverse correlation of the proMMP-2-TIMP-2 complex and MMP-2 tissue expression in the tumor. Therefore, the different forms of circulating metalloproteinases need to be evaluated further to explore their full potential for clinical use.