BACKGROUNDTo investigate the expressions of matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of metalloproteinase 1 (TIMP-1) and their correlation with metastasis and prognosis in human lung cancer.

METHODSImmunohistochemical S-P method was used to detect the expression of MMP-9 and TIMP-1 in 65 lung cancer tissues, 35 hyperplastic and dysplastic epithelium from patients with non-cancerous pulmonary diseases, and 30 normal epithelial tissues of the lung.

RESULTSThe positive expression rates of MMP-9 in normal tissue, hyperplastic or dysplastic epithelium, and lung cancer tissue were 16.7%(5/30), 42.9%(15/35) and 72.3%(47/65) respectively, whereas the positive rates of TIMP-1 expression in normal tissue, hyperplastic or dysplastic epithelium, and lung cancer tissue were 6.7%(2/30), 28.6%(10/35) and 50.8%(33/65) respectively. Significant differences of the expression rates of MMP-9 and TIMP-1 were found between lung cancer and normal groups, between lung cancer and hyperplasia groups, and between hyperplasia and normal groups (P < 0.05). Small cell carcinoma and adenocarcinoma had higher MMP-9 expression than squamous cell carcinoma (P < 0.025). Expression rate of MMP-9 had negative relation with cell differentiation of lung cancer (P < 0.05), and positive relation with TNM stage (P < 0.025). Between the survival time < 2 years group and ≥2 years groups, both the expressions of MMP-9 and TIMP-1 had significant difference (P < 0.05 ). The expression of MMP-9 was closely related to metastasis of lung cancer (P < 0.005), but the expression of TIMP-1 was not related to metastasis.

CONCLUSIONSOverexpression of MMP-9 may appear in precancerous lesion and at the early stage of lung cancer. Activation of MMP-9 gene may be an important factor for oncogenesis of the lung. MMP-9 and TIMP-1 may play important roles in lung cancer invasion and metastasis, their overexpression could act as a reference to evaluate metastasis and unfavourable prognosis of lung cancer.