ABCG2 and cancer: Various proteins in the ABC superfamily are reported to be involved in the absorption, excretion, and distribution of drugs in normal cells (Szakács et al., 2008), however, in cancer cells (where these transporters are overexpressed), therapeutic agents administered are challenged by the efflux activity of these membrane-bound efflux pumps mainly ABC transporters like P-glycoprotein (P-gp) and Multidrug Resistance Protein 1(MRP1) since they serve as the first line of defense (Gottesman, Pastan & Ambudkar, 1996; Kool et al., 1997).