ESR1 and breast cancer: In the T47D ER+ breast cancer cell line ectopic expression of either EGFR or HER2 rendered endogenous HER3 more sensitive to downregulation by the DDA NSC624205 (Figure 2E), and EGFR overexpression sensitizes EGFR, HER2, and HER3 to RBF3-mediated downregulation (Figure 2G).