HER-2/neu expression in gastric cancer cell lines. The expression of HER2/neu protein in all cancer cell lines were measured by fluorescence-activated cell sorting analysis. The HER2/neu expression in three gastric cancer cell lines (YBC-2, YBC-3 and NCI-N87) were 48% (weak ), 55% (medium) and 88% (strong), respectively. All groups of Isotype control were not more than 0.5% (data not showed). As the positive control, SK-BR-3 of HER2/neu expression is 89%. U-87 MG showed lower expression of HER2/neu (6%) as negetive control.