Fig. 1

IFN-g-induced PD-L1 protein expression is associated with new PDL1 mRNA transcription in 32 cultured human tumors. a. Constitutive expression of cell surface PD-L1 protein by select tumor lines, detected by flow cytometry. RCCs expressed significantly more PD-L1 than MELs (p = 0.0041). Kruskal-Wallis test (Dunn’s multiple comparisons test), 2-sided p-value. ΔMFI, mean fluorescence of specific staining – isotype staining. Cell lines with ∆MFI ≥ 5, indicated by horizontal dotted line, were considered to be PD-L1 positive. b. Representative examples of IFN-g-induced (left panel) or IFN-g-enhanced (right panel) PD-L1 protein expression. Cultured tumor cells (1102mel, melanoma; 2192R, RCC) were treated with IFN-g 250 U/ml for 48 h, then cell surface PD-L1 protein was detected by flow cytometry. Histograms from two representative cell lines with or without constitutive PD-L1 expression are shown. c. IFN-g significantly increased PD-L1 protein expression on all types of tumor cells tested. Wilcoxon matched-pairs signed rank test, 2-sided p-value. d. IFN-g-induced PD-L1 protein expression is significantly associated with new PDL1 mRNA transcription. Thirty-two cultured tumor lines were treated with IFN-g 250 U/ml. PD-L1 mRNA and cell surface protein expression were detected by qRT-PCR and flow cytometry after 14 h and 48 h, respectively. Fold changes in PD-L1 protein (ΔMFI) and mRNA (ΔCt) were calculated, compared to pretreatment values. Spearman correlation r value, 2-sided p-value. A, C and D, data combined from 3 separate experiments