Previous studies have confirmed that trastuzumab inHER2-positive gastric cancer patients can modulate the tumor microenvironment (TME), via upregulating PD-1 and PD-L1 expression, expansion of tumor-specific CD4 and CD8 T cells, and enhancing the antitumor effects of immune checkpoint inhibitors (11, 12). This evidence concerns the gene CD8A and neoplasm.