CASP9 and chronic obstructive pulmonary disease: Increasing number of data suggests that cysteine proteases; caspase-3, caspases-8 and caspase-9 play important roles in COPD (Muzio et al., 1998; Yasuda et al., 1998; Demedts et al., 2006; Abboud and Vimalanathan, 2008).