S100A4 and chronic obstructive pulmonary disease: The use of inhaled corticosteroids (ICSs), the standard treatment for severe COPD, for more than 6 months has been shown to reduce the number of S100A4 and MMP9-positive cells (S100A4 and MMP9 are EMT-related proteins) in the fragmented basal membrane region of COPD patients [9].