ERBB2 and gastric cancer: We compared the antitumor activity of trastuzumab, IFN-β-R27T, and trastuzumab-R27T using an in vitro proliferation assay with HER2-positive (NCI-N87, YCC-19, YCC-38, and SNU216; Figure 3A and Supplementary Figure S3A) and HER2-negative (KATOIII, Hs746T, MKN74, and MKN45; Figure 3B and Supplementary Figure S3B) gastric cancer cell lines and a normal gastric epithelial cell line (HFE145; Figure 3C).