It is second member of the ABC transporter G subfamily, which is known as breast cancer resistance protein (BCRP), and overexpression of ABCG2 in tumor cell lines in vitro has been shown to induce resistance to several anticancer drugs, including MTX (Wang et al., 2011).It is a transmembrane protein made up of 665 amino acids (Robey et al., 2009). The gene discussed is ABCG2; the disease is neoplasm.