ABCG2 and breast cancer: Resistant CEM/ADR5000 and sensitive CCRF-CEM leukemia cells;MDA-MB-231-pcDNA3 breast cancer cells and its resistant subline MDA-MB-231-BCRP clone 23 cells;Colon cancer HCT116 (p53+/+) cells and their t clone HCT116 (p53−/−)Glioblastoma U87MG cells and resistant subline U87MG.ΔEGFR cells;Hepatic carcinoma (HepG2)