a Protein levels of WSX1, FLAG, and PD-L1 analyzed by Western blotting. HCC cell lines SNU449 and SNU475 were transfected with plasmid DNA encoding WSX1-FLAG (449WSX1 and 475 WSX1) or with vector plasmids. b Effect of WSX1 overexpression on cell surface PD-L1 expression analyzed by flow cytometry. WSX1 overexpression reduced the proportion of PD-L1+ HCC cells in both SNU449 (n = 4 independent experiments, P < 0.0001) and SNU475 cells (P = 0.0002). c Immunoblotting analysis of protein levels of WSX1 and PD-L1 in SNU398 cells. CRISPR/Cas9 guiding RNAs against human WSX1 (crWSX1) were used for WSX1 knockdown, and nontargeting crRNAs were added as control (crCtrl). d WSX1 knockdown increased the proportion of PD-L1+ HCC cells in SNU398 cells (n = 4 independent experiments, P = 0.0028). e t-SNE map derived from CyTOF analysis of mouse hepatocytes obtained from the HCC mouse model in Fig. 2a. Cells were color coded by the intensity of the expression levels of PD-L1 and WSX1. f Difference in the proportions of PD-L1+ (n = 4 mice, P = 0.0012) and WSX1+ mouse hepatocytes (P = 0.0002) based on CyTOF analysis. Data shown are representative of 2 independent experiments. g Immunoblotting analysis of PD-L1 protein levels in mouse liver lysates (C1–C3 represent independent samples from “oncogene” group, T1–T3 are independent samples from “oncogene + WSX1” group). All images shown are representative of 3 independent experiments. Quantitative data are presented as mean ± SD and analyzed by two-sided Student t test. **P < 0.01, ***P < 0.001, ****P < 0.0001. The gating strategy for sorting PD-L1+ HCC cells is shown in Supplementary Fig. 8b. Source data are provided as a Source Data file.