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. This evidence concerns the gene ERBB2 and cancer.