ABCC1 and cystic fibrosis: To examine the association between ABCC1 expression and lung function in CF, we analyzed the functional ABCC1 promoter polymorphism (rs504348), plasma-induced ABCC1 expression in PBMCs, and ABCC1 promoter methylation status among CF subjects with differing CFTR genotypes and then examined the correlation of these molecular measures with clinical status.