Although HER2-overexpressing gastric cancer cell lines thus far proved to addict to the self-activated PI3K/Akt pathway, it is still somewhat puzzling that gefitinib is a tyrosine kinase inhibitor specific for EGFR, yet exhibits a marked antitumour effect against HER2-, but not EGFR- overexpressing gastric cancer cells. This evidence concerns the gene ERBB2 and gastric cancer.