CD8A and cancer: The link between RRM2 and immune cell infiltration was investigated in this study, we observed a positive correlation between Treg infiltration levels and RRM2 in BRCA, KIRC, LIHC, PCPG, PRAD, and THCA, indicating that RRM2 contributes to Tregs exerting an inhibitory role in aiding malignant tumor cells in evading attack by cytotoxic CD8+ T cells (Shu et al., 2019; Liu, Workman & Vignali, 2016).