Furthermore, the involvement of insulin in immune checkpoint regulation has been shown to enhance the expression of PD-L1 in pancreatic ductal adenocarcinoma cells via multiple signaling pathways, including increased expression of InsR-A in A818-6 cells and modification of the adaptor protein Gab1 in BxPc3 cells [47]. Here, GAB1 is linked to pancreatic ductal adenocarcinoma.