CD274 and hepatocellular carcinoma: Furthermore, our study implicated that HERC2 induced PD-L1 expression by activating STAT3, which is consistent with a previous research that showed that STAT3 increases PD-L1 expression via direct interaction with the PD-L1 promoter [45]. Additionally, we employed a coculture system in which activated PBMCs from healthy donors were cocultured with HCC cells in vitro.