Matrix metalloproteinases(MMP) are essential enzymes for tumor invasion and metastasis. Among the MMP family, elevated MMP-9 and stromelysin-3(STR-3) expression have been reported to be poor prognostic factors in lung cancer patients. To evaluate the possibility of a molecular diagnosis of lung cancer using peripheral blood, the mRNA expression level of MMP-9 and STR-3 was measured using a reverse transcriptase-polymerase chain reaction(RT-PCR) in patients with lung cancer.

Ninety six patients(44 patients with lung cancer, 19 pulmonary infection, and 33 control) were included. To detect MMP-9 and STR-3 mRNA expression, RT-PCR was performed in peripheral blood mononuclear cells. ELISA was also used to measure the serum level of MMP-9.

MMP-9 was expressed more frequently in patients with a pulmonary infection(18/19, 94.7%) compared to lung cancer patients(26/44, 59.1%) or the controls (23/33, 69.7%) (p=0.018). On the other hand, STR-3 expression was observed more frequently in patients with lung cancer(37/44, 84.1%) compared to the lung infection patients(8/19, 42.1%) or control(20/33, 60.6%) (p=0.003). Among the lung cancer patients, MMP-9 was expressed more frequently when a tumor invaded the lymph nodes(17/24, 70.8%) compared to when a tumor did not(3/13, 23.1%) (p=0.005). The MMP-9 and STR-3 expression levels had no relationship with age, sex, tumor size, distant metastasis, or tumor histology. The serum MMP-9 concentration was not higher in lung cancer patients compared to patients with a pulmonary infection or the control subjects.

STR-3 may be used as a diagnostic marker in the peripheral blood of lung cancer patients using RT-PCR. Further studies to evaluate the clinical significance of elevated STR-3 expression in lung cancer patients is recommended.