ERBB2 and gastric cancer: The growth of HER2-overexpressing cell lines (GLM-1, GLM-2, GLM-4 and NCI-N87) in vitro was markedly inhibited by gefitinib with IC50 of 0.028, 0.32, 0.078 and 0.091 μM, whereas most of the HER2 low-expressing gastric cancer cell lines (GCIY, MKN-28, MKN-45, MKN-74) were resistant to gefitinib with IC50 more than 10 μM (Figure 2A), indicating a correlation between degree of HER2 expression and gefitinib sensitivity in gastric cancer cell lines.