CD226 and gastric cancer: The association between the percentages of CD226+CD8+IFN-γ+T cells/CD8+CD226+T cells, CD226+CD8+IFN-γ+T cells/CD8+CD226+T cells in the epithelial cell region, and CD226+CD8+IFN-γ+T cells/CD8+CD226+T cells in the stromal cell region in tumor and clinical features of GC patients.