IL21 and neoplasm: Research shows that Gpc3 CAR-T cells coexpressing IL-15 and IL-21 enriched poorly differentiated T cells pools, exhibited the strongest peak amplification and persistence in vivo, and mediated increased tumor control and survival in hepatocellular carcinoma (HCC) tumor-bearing mice compared to cytokines alone or controls (69).The above studies show that the expression of IL-7, IL-15 and IL-21 can promote the expansion of memory CD8+ cells and improve their antitumor activity.