Multidrug resistance in acute myeloid leukemia (AML), non-small cell lung cancer (NSCLC), colon carcinoma and breast cancer were also reported to be strongly correlated with the overexpression of ABCG2 (Steinbach et al., 2002; van den Heuvel-Eibrink et al., 2002; Nakanishi and Ross, 2012). Here, ABCG2 is linked to breast cancer.