Due of this, over-expression of MMP-12 seems to be a result of an increased influx of macrophages, but on the other hand, it was shown that a functional variant in the MMP-12 promoter (a substitution A-to-G at position − 82; rs2276109) affects the enzyme expression level and COPD susceptibility. This evidence concerns the gene MMP12 and chronic obstructive pulmonary disease.