ABCG2 and breast cancer: A modulation of MCF7 breast cancer cell phenotype was observed, with increased proliferation and colony formation (Pfoa, Bpa, Mtx, Bp-1), particularly at 15-day exposure and with expression of genes involved in cell survival, proliferation, differentiation, and chemoresistance (STAT3 and VEGFA [Bpa, Mtx, Bp-1], BRCA1 [Bp1], ESR2 [Pfoa, Bpa], ABCG2 [Pfoa]).