TNFRSF9 and pancreatic adenocarcinoma: In our current study, the expression of 12 immune checkpoint genes (CD40, TNFRSF4, CD86, LAIR1, TNFRSF14, HAVCR2, CD244, TMIGD2, TNFRSF9, KIR3DL1, TNFRSF8, and CD48) were downregulated in PAAD tissues compared with the normal group.