Treatment of HBE cells from COPD patients with Erlotinib, a known EGFR inhibitor, increased PP2A activity, downregulating CIP2A mRNA and protein, resulting in decreased ERK phosphorylation and expression of matrix metalloproteinase 1 (MMP1) and MMP9 compared to non-COPD subjects [28]. Here, MMP9 is linked to chronic obstructive pulmonary disease.