HDAC1 and Airway obstruction: Despite higher levels of HDAC1 mRNA in biopsies of patients with COPD, there was no significant correlation between the HDAC1 mRNA expression and the airway obstruction, as measured by the FEV1 (r = −0.13, p = 0.2185) and the FEV1/VC ratio (r = −0.20, p = 0.1118)(supporting information, Figure S2B).