Normal human colonic epithelial cell line, CCD841, was purchased from American Type Culture Collection (ATCC, Manassas, VA, U.S.A.). The cell line was cultured in RPMI 1640 (Corning, Corning, NY, U.S.A.) supplemented with 10% FBS (Fisher Scientific, Pittsburgh, PA, U.S.A.) and 1% penicillin/streptomycin (Corning, Corning, NY, U.S.A.). Viral packaging cell line, HEK293FT, was purchased from ATTC (Manassas, VA, U.S.A.) and maintained in DMEM 4.5 g/L glucose, l-glutamine, sodium pyruvate (Corning, Corning, NY, U.S.A.) supplemented with 10% FBS and 1% penicillin/streptomycin. HEK293FT cells were used for transient transfection experiments where they were cultured for three passages in the presence and absence of excess iron in the form of ferric ammonium citrate (FAC) (Sigma, St. Louis, MO, U.S.A.) [26 (link)] and then used for ectopic expression of p53.