ESR1 and breast cancer: (iii) Synthetic halogenated aromatic AhR ligands: Confirmation that the AhR is a target for developing anticancer drugs for treating breast cancer has been extensively investigated using different structural classes of AhR ligands and an array of breast cancer cell lines, including ER-positive (T47D, MCF-7 and ZR-75), ER-negative (MDA-MB-231, MDA-MB-468, MDA-MB-436, MDA-MB-157, MDA-MB435, BT26, CRL2335, BT20, BT549, BT479, HS5787, HCC38, mouse 4T1) and HER-2/ErbB2 positive (BT474, SKBR3 and MDA-MB-453) cells.