Serum levels of matrix metalloproteinase-9 predict lymph node metastasis in breast cancer patients

Matrix metalloproteinases (MMPs) are proteolytic enzymes that play important roles in cancer progression and metastasis. Although serum MMP expression is known to correlate with the primary lesion of breast cancer, there has yet to be a study regarding the correlation between serum MMP expression and metastatic lesions, particularly lymph nodes. The present study evaluated the correlation of serum and lymph node MMP expression with axillary node metastasis. The preoperative serum levels of MMP-2 and MMP-9 in 77 patients with breast cancer and in 10 patients with benign breast tumor were determined by ELISA and zymography. One hundred and twelve axillary lymph nodes were collected for zymography during breast cancer surgery. Significantly higher serum levels of MMP-2 and MMP-9 were found in breast cancer patients compared to patients with benign tumor. High serum levels of MMP-2 and MMP-9 were significantly associated with node metastasis. ELISA and zymography results for serum MMP-2 and MMP-9 correlated significantly, with a Pearson correlation coefficient (r) of 0.76 for MMP-2 (P=0.001) and 0.81 for MMP-9 (P=0.001). In terms of lymph node, total MMP-2, MMP-9 and MMP-9 activity were significantly higher in metastatic than in non-metastatic nodes. There was a correlation between serum and lymph node MMP-9 levels on zymographic measurements (r=0.34, P=0.011), but not in terms of MMP-2 levels. Serum MMP-9 levels may have a diagnostic value for predicting axillary node metastasis.