ERBB2 and breast cancer: Nine breast cancer and gastric cancer cell lines were divided into 4 groups, HER2-high (NCI-N87, SK-BR-3, and HCC1954), HER2-medium (JIMT-1), HER2-low (capan-1, AGS, MKN45, and SNU-16) and HER2-negative group (MDA-MB-468), according to the flow cytometry analysis (S2 Fig).