MMP9 and lung cancer: For instance, MMP-9 serum level was found to be increased by ~1.6 folds (P<0.05) in lung cancer patients compared to healthy donors but in comparison with COPD patients, there was insignificant change in the serum levels of MMP-9 and MMP-2, however, it is reported that a selective inhibitor of MMP-9 and -12 decreases the inflammatory process correlated with exposure to cigarette smoke in COPD patients (28,29).