Fig. 4

Histone H3 acetylation in the PD-L1 promoter is increased and mediated by the c-Jun/HDAC3 axis. Cells were chromatin immunoprecipitated for acetylated histone H3 or IgG, and the DNA pull-down samples were then quantified by qRT-PCR. a The fold enrichment of histone H3 acetylation in the PD-L1 promoter DNA fragments (− 1178 bp to − 1117 bp, − 455 bp to − 356 bp, and − 105 bp to − 32 bp from PD-L1 exon 1) was detected and compared in the drug-resistant and parental cancer cells. b Parental cancer cells and drug-resistant cancer cells were collected, and HDAC3 expression was detected by western blotting. A549/CDDP, MCF-7/ADR, and HepG2/ADR cells were transfected with HDAC3 expression vector (HDAC3) or control vector (pReceiver), then the fold enrichment in histone H3 acetylation in the PD-L1 promoter was detected by ChIP assays (c, upper), HDAC3 expression was confirmed by western blotting (c, lower), and PD-L1 protein expression was detected by western blotting (d). e Drug-resistant cancer cells were transfected with c-Jun-targeting siRNAs for 48 h, and HDAC3 and PD-L1 expression was detected by western blotting. Drug-resistant cancer cells were transfected with c-Jun-targeting siRNAs or c-Jun expression plasmids for 24 h, then the fold enrichment in histone H3 acetylation in the PD-L1 promoter was detected by ChIP analysis (f and g, upper), and c-Jun expression was confirmed by western blotting (f and g, lower). ^*P ≤ 0.05, ^**P ≤ 0.01, ^***P ≤ 0.001