ABCB1 and malignant colon neoplasm: The use of the human colon cancer derived Caco-2 cell line [5,6] and Madin Darby canine kidney cells with the MDR1 gene (MDCK-MDR1), the gene encoding for the efflux protein, P-glycoprotein (P-gp) [7,8], is widely established to predict in vivo absorption.