Although the specific pathogenesis of COPD is unclear, it is widely accepted that airway tissue remodeling results from disorder of the proteinase-antiproteinase balance and aberrant inflammation in the lung.[30] Among various proteinases, MMP-12 have been shown to play a predominant role in the occurrence and progression of COPD.[31,32] Elevated MMP12 may lead to imbalance of protease-antiprotease and degradation of lung extracellular Matrix, thereby increasing individual's susceptibility to COPD. This evidence concerns the gene MMP12 and chronic obstructive pulmonary disease.