IL15 and hepatocellular carcinoma: Cytokines were previously shown to be the positive regulators of HCC progression, including CXCL5, IFNG, CCL5, PLAU, PTN, CSF1, and HGF, and they were significantly up-regulated in tumors with higher PD-L1 or PD-L2 expression (43–49).There are also other cytokines inhibiting the progression of HCC, including IL15, IL18, and CD40LG.