In line with this, it has been reported previously that the activity of CFTR corrector compounds in cell lines used for heterologous expression are not predictive of their efficacy in primary airway epithelial cells of CF patients (Pedemonte et al., 2010), and that modulator response may be overestimated in recombinant cell expression systems (Sondo et al., 2011). The gene discussed is CFTR; the disease is cystic fibrosis.