Fig. 3

High concentration glucose upregulates PD-L1 expression of pancreatic tumor cells by activating EGFR downstream pathways. A Western blotting analysis of EGFR downstream pathways including RAS-ERK, STAT3, PI3K-Akt signaling in PANC-1 and SW1990 cells 48 h after different sugar concentration (5.5 mM, 15 mM, 25 mM) medium culturing. B–D Western blotting analysis of EGFR downstream signaling and PD-L1 expression in PANC-1 and SW1990 cells following 24 h treatment with EGFR-IN-5 B or STAT3-IN-1 C or KRAS-IN-1 D in 25 mM sugar medium. E qPCR analysis of PD-L1 mRNA expression in PANC-1 and SW1990 cells following 24 h treatment with different inhibitors (EGFR-IN-5, STAT3-IN-1, KRAS-IN-1, PI3K-IN-1) in 25 mM sugar medium. F Western blotting analysis of PD-L1 expression in PANC-1 and SW1990 cells following 24 h treatment with STAT3-IN-1 or KRAS-IN-3 individually or combination of the two inhibitors in 25 mM sugar medium. G qPCR analysis of PD-L1 expression in PANC-1 and SW1990 cells following 24 h treatment with STAT3-IN-1 or KRAS-IN-3 individually or combination of the two inhibitors in 25 mM sugar medium. H qPCR analysis of PD-L1 mRNA stability in PANC-1 and SW1990 cells after the concomitant addition of actinomycin D (10 μg/ml) and STAT3-IN-1 or KRAS-IN-3 added at time = 0 h in 25 mM sugar medium. ns non-significant. The graphs show representative results from three independently repeated experiments. *p  < 0.05, **p  < 0.01, ***p  < 0.001