CD274 and pancreatic ductal adenocarcinoma: Blockade of MAPK pathway through MEK1 and two inhibitors prevented the expression of PD-L1 in lung adenocarcinoma cells (Stutvoet et al., 2019), whereas inhibition of ERK could improve the anti-PD-L1 checkpoint blockade effect in preclinical pancreatic ductal adenocarcinoma (Henry et al., 2021).