To rule out potential artifacts caused by antibody aggregation, we further purified the monomer of SMET2.1Fc by using size-exclusion chromatography (Figure 2C, right panel) and then tested it with a small panel of human cancer cell lines expressing various levels of HER2 (breast cancer cell lines MCF7, SKBR3, and BT474, gastric cancer cell line NCI-N87, and ovarian cancer cell line SKOV3). The gene discussed is ERBB2; the disease is breast cancer.