ABCC1 and asthma: Further studies are necessary to explore the link between serum cAMP levels with (a) bronchodilator or treatment responses by asthma severity; (b) ABCC1 expression and activity in health and disease, including specific cell types of origin; and, (c) whether these physiological outcomes and clinical phenotypes are affected by variations in ABCC1 genotypes in a large cohort of patients with and without asthma.