For instance, the AhR antagonist N,2-dimethyl-N-[1,2-dimethylindol-5-yl]quinazoline-4-amine (compound 12) inhibits proliferation in estrogen receptor (ER)-positive breast cancer cells by reducing the levels of cyclin-dependent protein kinase (CDC2) and cell division cycle 25c (CDC25c) and increasing that of cyclin B1 [31]. This evidence concerns the gene ESR1 and breast cancer.