PDCD1 and hepatocellular carcinoma: LPS induces PD-1 and PD-L1 expression, significantly upregulating PD-L1 in HCC. LPS enhances METTL14, promoting m6A methylation of MIR155HG, which is stabilized by ELAVL1. MIR155HG acts as a ceRNA, regulating PD-L1 via the miR-223/STAT1 axis.