For example, the hepatocellular carcinoma (HCC) microenvironment is devoid of interleukin (IL) 15 and 21, which are essential for the proper functioning of T-cells, therefore human GPC3-CAR T cells co-expressing IL-15 and IL-21 were very efficient in the treatment of HCC in preclinical models [51]. This evidence concerns the gene IL21 and hepatocellular carcinoma.