Fig. 5: PRMT3 enhances PD-L1 expression through lactate-mediated histone lactylation.

A, B PD-L1 mRNA levels were measured in Huh7 and Hepa1-6 cells with the indicated treatments. Hepatoma cells were infected with Lenti-PRMT3 or Lenti-Ctrl and then treated with JX06 (200 nM) or DMSO. * P < 0.05, ** P < 0.01. C PD-L1 mRNA and protein levels were detected in Huh7 xenografts derived from nude mice with JX06 treatment. n = 5 in each group. *P < 0.05. D PD-L1 expression in Huh7 cells was detected by RT-PCR after 24 hours of lactate stimulation at indicated concentrations. *P < 0.05, **P < 0.01. E PD-L1, pan-Kla, and H3K18la protein levels were detected by immunoblotting in Huh7 cells with lactate stimulation (left) or with PRMT3 overexpression (right). F Protein levels of PD-L1 and H3K18la were detected in Huh7 and Hepa1-6 cells with the indicated treatments. Briefly, Huh7 or Hepa1-6 cells pre-infected with lenti-PRMT3 or a control lentivirus (Ctrl) were seeded into 6-well plates at a concentration of 4 × 10⁵ cells per well for overnight culture. Then, these cells were treated with DMSO or JX06 (200 nM) for 24 hours to analyze protein levels by immunoblot. G Schematic diagram showing the primer site of the PD-L1 promoter for chromatin immunoprecipitation assay (upper). Huh7 cells were treated with indicated lactate concentration for 24 hours and subsequently subject to a chromatin immunoprecipitation assay with H3K18la antibody. ChIP assay revealed that lactate increased H3K18la occupancy at the PD-L1 promoter. Immunoblot analysis confirmed the immunoprecipitation of H3K18la. *P < 0.05, **P < 0.01, ***P < 0.001. H Enrichment of H3K18la at the PD-L1 promoter was detected in Huh7 cells with PRMT3 overexpression. *P < 0.05, **P < 0.01. The data are presented as mean ± SD, and the statistical tests were all two-tailed.