Our recent studies have focused on ABCG2 (BCRP), first identified due to its overexpression in multidrug-resistant breast cancer cell lines and later found to be highly expressed in a variety of human cancers including acute myelogenous leukemia, acute lymphoblastic leukemia, breast and lung cancers (1), where its overexpression has been correlated with poor prognosis. This evidence concerns the gene ABCG2 and cancer.