Importantly, ST6GAL1 knockout (K.O.)ErbB2-addicted GC cells displayed a reduced ErbB2 degradation rate, and enhanced sensitivity to trastuzumab-induced cytotoxicity, supported by a decreased ability to sustain ErbB2 and epidermal growth factor receptor (EGFR) intracytoplasmic phosphorylation, and increased stabilization of ErbB dimeric compositions at the cell membrane. This evidence concerns the gene ST6GAL1 and gastric cancer.