MMP12 and chronic obstructive pulmonary disease: Conversely, the following proteins have been linked to a higher risk of COPD: KLC1, Plasminogen, MSP, Angiostatin, sTie-1, PILRA isoform FDF03-deltaTM, PILRA isoform FDF03-M14, Cathepsin H, MMP12, ASM, and COAA1.