A recent study by Vogel et al. sought to determine the impact of the overexpression of AhRR (a target gene of AhR and a repressor of AhR’s transcriptional activity) on the progression of two breast cancer mouse models [148]: syngeneic E0771 breast cancer cell transplantation [149] (ERα-, PR+, HER2+), and the polyoma middle T antigen (PyMT) transgenic mouse model. This evidence concerns the gene ESR1 and breast cancer.