ABCB1 and adenocarcinoma: Both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) require evaluation of drug candidates for P-gp interaction potential, including transport, inhibition, and related drug-drug interactions.29 Widely utilized for this purpose are cell lines like Caco-2 (human-derived immortalized adenocarcinoma) and MDCK-MDR1 (canine-derived derived cell-line transfected with human P-gp).30,31 These are valuable tools for assessing the P-gp substrate activity of pharmaceuticals and drug candidates.