The data revealed increased amount of CD8 and PD1 double-positive cells in mammary tumor tissues implanted by HP cells with elevated expression of Smyd3, but this increase was suppressed in tumor tissues with the expressions of sgSmyd3 or OE-Smyd3/sgShcbp1 (Fig. 6m, n) and PD1 expression level in the spleen of mice implanted with OE-Smyd3 cells were increased but were largely suppressed in mice implanted with sgSmyd3 or OE-Smyd3/sgShcbp1 cells (Fig. 6o). This evidence concerns the gene CD8A and breast cancer.