PGP and malignant colon neoplasm: Two adherent cancer cells (HCT 116, wild type colon cancer cells and HCT 116 p53 − / − , p53 knocked out colon cancer cells) and two other cancer cells in suspension (CEM/CCRF, T-lymphoblastic leukemia and CEM/ADR5000, T-lymphoblastic leukemia over-expressing P-gp) have been routinely cultured in our laboratory for various research works.