FACS was used to assess the surface expression of HER2 proteins in a series of human GC cell lines (GCCLs), including the N87, 7901, AGS, HGC27, MGC803, BGC823, and MKN45 cells, and in primary gastric cancer cells (PGCCs) obtained from two patients with GC. The gene discussed is ERBB2; the disease is gastric cancer.