ABCG2 and breast cancer: In addition, in the triple negative (basal-type) breast cancer cell line MDA-MB-231, which shows low expression of endogenous ABCG2, an inverse correlation between ENPP1 and miR-27b expression was observed (Supplementary Fig. 13c, d), although the cell surface localization of ABCG2 was not induced by knockdown of miR-27b (Supplementary Fig. 13e).