Figure 5

IFNγ augments PD-L1 promoter activity by binding to the putative IRF-1α sequence (−171 to −159) in EBV (+) GC cells. (A) Schematic representation of the promoter deletion constructs and nucleotide sequence of the PD-L1 promoter. The 456-bp sequence of the 5′-flanking region of PD-L1 is shown. The transcription start site is indicated by +1. Underlined sequences represent two putative IRF-1 binding sites (IRF-1α and -1β). Shaded sequences are deleted for the promoter constructs. (B,C) EBV (−) AGS and EBV (+) SNU-719 cell lines were transfected with the reporter constructs. After 4 h, cells were stimulated with 10 ng/mL IFNγ for an additional 24 h, luciferase activities were measured. The data are presented as mean ± SEM (n = 3). *P < 0.05 and **P < 0.001 compared to the same unstimulated cell line (Student’s t-test).