The WDR5-H3K4me3 epigenetic axis regulates OPN expression to compensate PD-L1 function to promote pancreatic cancer immune escape [RNA-seq]

Two orthotopic pancreatic tumor mouse models were used for ChIP-Seq and RNA-Seq to identify genome-wide dysfunction of H3K4me3 and gene expression. Mouse pancreatic tumors have a genome-wide increase in H3K4me3 deposition as compared to normal pancreas. Osteopontin (OPN) and its receptor CD44 were identified being up-regulated in pancreatic tumors by their promoter H3K4me3 deposition. OPN protein is increased in both tumor cells and tumor-infiltrating immune cells in human pancreatic carcinoma and is inversely correlated with pancreatic cancer patient survival. OPN is primarily expressed in tumor cells and monocytic myeloid-derived suppressor cells (M-MDSCs), whereas PD-L1 is expressed in tumor cells, M-MDSCs, polymorphonuclear MDSCs (PMN-MDSCs) and tumor-associated macrophages. WDR5 is essential for H3K4me3-specific histone methyltransferase activity and OPN expression in tumor cells and MDSCs. Pharmacological inhibition of WDR5 significantly decreased OPN protein level, suppressed pancreatic tumor growth, and significantly increased efficacy of anti-PD-1 immunotherapy in suppression of pancreatic tumor growth in vivo. Overall design: Total RNA was isolated from normal C57BL/6 mouse pancreas, PANC02-H7, and UN-KC-6141 tumors from tumor-bearing mice. The RNA was used for RNA-Seq. The gene expression profiles between normal mouse pancreas and orthotopic pancreatic tumors were compared, and differentially expressed genes were identified.