ESR1 and breast cancer: We investigated ERα and MGMT expression in breast cancer cells - ER positive cells: MCF7 (MGMT +), T-47-D (MGMT +), ZR-75-1 (MGMT +); ER negative cells: ZR-75-30 (ER weakly positive and MGMT weakly positive), HCC 1428 (ER weakly positive and MGMT weakly positive), MDA MB 468 (ER negative and MGMT positive).