MMP9 and chronic obstructive pulmonary disease: The serum level of these biomarkers (CRP, IL-6, TNFα, MMP-9, PARC, VEGF) have been associated with some of the clinical features of the disease [8], [9] and have been proposed to be related to the systemic consequences of the disease [10], its progression [11] and the association between COPD with cardiovascular disease [12] and lung cancer [13].