CD8A and neoplasm: Another study indicates that under hypoxic conditions, circPRDM4 facilitates the recruitment of hypoxia-inducible factor-1α (HIF-1α) to the promoter of CD274, thereby inhibiting the infiltration of CD8 T cells in the tumor microenvironment and promoting the immune evasion of hepatocellular carcinoma cells [119] (Fig. 3).