ABZ reduces PD-L1 and enhances CTL activity by downregulating UBQLN4. (A) Representative western blotting and quantitative analysis of UBQLN4 and PD-L1 protein levels in A375 and SK-MEL-28 cells treated with increasing concentrations of ABZ (0.625–1.25 µM) for 24 hours under IFN-γ exposure, each bar represents the mean±SD of three independent experiments, *p<0.05, **p<0.01, ***p<0.001. (B) Representative western blotting and quantitative analysis of PD-L1 protein levels in A375, which were stable transfected with sgRNAs (sgUBQLN4 #1, sgUBQLN4 #2 and control (NC)) and treated with increasing concentrations of ABZ (0.625-1.25 µM), each bar represent the mean±SD of three independent experiments, NSP >0.05, *p<0.05, **p<0.01, ***p<0.001. (C) Representative western blotting and quantitative analysis of PD-L1 protein levels in A375 and SK-MEL-28 cells, which were transfected with HA-UBQLN4 and empty vector and treated with increasing concentrations of ABZ (0.625–1.25 µM), each bar represents the mean±SD of three independent experiments, *p<0.05, **p<0.01, ***p<0.001. (D) A375 and SK-MEL-28 cells were transfected with HA-UBQLN4 and empty vector and cocultured with activated T cells for 24 hours with or without ABZ (0.625-1.25 µM) were subjected to crystal violet staining. The tumor cell to T cell ratio, 1:3. The quantitative analysis of A375 and SK-MEL-28 cells survive rate from three independent experiments and showed as means±SD, NSP >0.05, *p<0.05, **p<0.01, ***p<0.001. #p<0.05, ###p<0.001, vs the DMSO group. †††p<0.001 vs the ABZ (0.625 µM) group. SSSp <0.001 vs the ABZ (1.25 µM) group. NS∙Tp >0.05, #∙Tp <0.05, vs the DMSO +T group. †∙Tp <0.05, †††∙Tp <0.001 vs the ABZ (0.625 µM+T) group. SS∙Tp <0.001, SSS∙T p<0.001 vs the ABZ (1.25 µM+T) group. ABZ, albendazole; IFN-γ, interferon gamma.