I3C shows effective anti-tumor properties in estrogen receptor α (ERα)-positive breast cancer cells through the ligand-activated aryl hydrocarbon receptor (AhR), which amplifies ERα signaling via ROS induction by the upregulation of cyclic-AMP-dependent transcription factor (ATF)-3 and downstream pro-apoptotic BH3-only proteins [145]. The gene discussed is AHR; the disease is breast cancer.