In patients with colon cancer, we found that tumor-infiltrating CD8+ T cells, as well as CD8+ T cells in peripheral blood express CD73 but CD73 expression on CD28−CD8+ T cells, is significantly increased after cell infiltration into the tumor as compared to that on CD28+CD8+ T cells (Fig. 5c, d). This evidence concerns the gene CD28 and malignant colon neoplasm.