RRM2 expression was significantly correlated with the immune-associated cells T cells in four cancer types, cytotoxic cells in four cancer types, B cells in two cancer types, CD8+T cells in three cancer types, Treg cells in four cancer types, dendritic cells in one cancer type, macrophages in three cancer types, NK cells in six cancer types, and neutrophils in three cancer types. This evidence concerns the gene CD8A and cancer.