Since AHR protein levels are increased in human breast carcinoma cell lines compared with primary human mammary epithelial cells (11), and there is emerging interest in inhibiting AHR to treat cancer, we compared the ability of two AHR antagonists, BAY2416964 and GNF351, to inhibit AHR signaling in a PyMT mouse mammary cancer cell line. The gene discussed is AHR; the disease is cancer.