To evaluated the effects of MACC1 on resistance to trastuzumab in GC cells, first, we tested the expression of HER2 and MACC1 protein levels (Additional file 1: Figure S1a) and the sensitivity to trastuzumab of MKN28, BGC823, SGC7901, MKN45, and NCI-N87 cell lines. Here, ERBB2 is linked to gastric cancer.