Correlation between matrix metalloproteinase-9 and vascular endothelial growth factor expression in lung adenocarcinoma

The aim of this study was to investigate the correlation between the expression of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) and clinicopathological features of lung adenocarcinoma. The expression of MMP-9 and VEGF was evaluated by immunohistochemistry of 30 samples from lung adenocarcinoma patients and 12 paratumoral (normal) tissue samples. In addition, the change in VEGF or MMP-9 expression after MMP-9 or VEGF blockade, respectively, was measured using western blot in lung adenocarcinoma A549 cells. High expression of MMP-9 was found in 63.3% of adenocarcinoma tissues versus 16.7% in normal tissues (P < 0.05). High expression of VEGF was found in 70% of adenocarcinoma tissues versus 25% in normal tissues (P < 0.05). A positive correlation was identified between MMP-9 and VEGF expression (correlation coefficient = 0.7094, P < 0.001), and their mutual overexpression was associated with clinical staging and lymph node status (P < 0.05). In addition, an decrease in VEGF protein expression was observed after MMP-9 blockade by an MMP-9-specific monoclonal antibody. Similarly, a decrease in MMP-9 protein expression was found after VEGF blockade by a VEGF-specific monoclonal antibody. In conclusion, VEGF and MMP-9 are overexpressed in lung adenocarcinoma tissues, and they have a synergistic effect on the invasion and metastasis of adenocarcinoma.