Doherty’s study is the first to elucidate the link of cathepsin activity to PP2A in the context of COPD, although as highlighted by Janga & Hamm-Alvarez, this study highlights CTSS and PP2A regulation in smoking induced COPD, so further studies must be conducted in smoking independent COPD models to validate these results [160]. This evidence concerns the gene CTSS and chronic obstructive pulmonary disease.