ESR2 and cancer: To this aim, EGFR- and ErbB2-positive cancer cells, including breast (SK-BR-3 and MDA-MB-453), prostate (LNCaP), and gastric (NCI-N87) cancer cell lines [51,52,53,54], were treated with a combination of Erb-hcAb and CL4 at increasing concentrations to test whether the inhibitors affect cell viability more efficiently than when they are used as single agents.