Fig. 4

RAS signaling pathway enhance stability of PD-L1 mRNA by down-regulating PTRH1. A Dot plot depicting the correlation between the mRNA level of RBPs and PD-L1 in 178 PDAC samples from TCGA data. B Box plot depicting the differential level of PTRH1 mRNA between PDAC samples with wild KRAS (n = 65) and mutant KRAS (n = 113) from TCGA data. C Box plot depicting the differential level of PTRH1 mRNA between PDAC samples complicated with diabetes (n = 38) and those without diabetes (n = 108) from TCGA data. D Dot plot depicting the changes of the mRNA expression level of RBPs in tumor epithelial cells of PDAC samples complicated with diabetes (n = 10) compared to those without diabetes (n = 14) from single cell RNA-seq data (CRA001160). E–F Western blotting analysis E and Heatmap F of PTRH1 and PD-L1 expression in operative specimens of PDAC tissue (n = 16) and adjacent tissue (n = 16). G Box plot depicting the differential expression of PTRH1 and PD-L1 between PDAC samples complicated with diabetes (n = 7) and those without diabetes (n = 9). H Box plot depicting the differential expression of PTRH1 and PD-L1 between PDAC tissue (n = 16) and adjacent tissue (n = 16). I Box plot depicting the differential level of PTRH1 mRNA between PDAC samples (n = 39) and adjacent samples (n = 39) from public data (GSE15471). J Box plot depicting the differential level of PD-L1 mRNA between PDAC samples (n = 45) and adjacent samples (n = 45) from public data (GSE28735). K Correlation analysis of protein level of PTRH1 and PD-L1 in operative specimens (n = 32). L Western blotting analysis of PTRH1 and PD-L1 expression in PANC-1 and SW1990 cells following 24 h treatment with different inhibitors (STAT3-IN-1, KRAS-IN-1, PI3K-IN-1) in 25 mM sugar concentration medium. M qPCR analysis of mRNA level of PTRH1 in PANC-1 and SW1990 cells following 24 h treatment with KRAS-IN-1 in 25 mM sugar concentration medium. N Western blotting analysis of PD-L1 expression in PANC-1 and SW1990 cells with overexpression of PTRH1 following 24 h treatment with combination of STAT3-IN-1 and PI3K-IN-1 in 25 mM sugar concentration medium. O qPCR analysis of PD-L1 mRNA stability in PANC-1 (PTRH1 KD, NC, PTRH1 OE) and SW1990 cells (PTRH1 KD, NC, PTRH1 OE) after the addition of actinomycin D (10 μg/ml) in 15 mM or 25 mM sugar medium. PDAC pancreatic ductal adenocarcinoma, TCGA The Cancer Genome Atlas, RBP RNA binding protein, OE overexpression, KD knock down, NC negative control, ns non-significant. The graphs of Western blotting and qPCR show representative results from three independently repeated experiments. *p  < 0.05, **p  < 0.01, ***p  < 0.001