CTLA4 and pancreatic adenocarcinoma: A more definitive study has also shown that circ-UBAP2 and has-miR-494 may regulate the expression of CXCR4 and ZEB1, which are positively correlated with the expression of CTLA-4 and PD-1, and thus affect the levels of M2 macrophages, depleted T cells, and T regulatory cells (Tregs) in PAAD tissues (59), suggesting that circ-UBAP2 and has-miR-494 may regulate immune checkpoints through CXCR4 and ZEB1 factors, which in turn inhibit antigen presentation by PCs and promote immune escape.