CD274 and neoplasm: On the other hand, the PD-1/PD-L1 pathway is regulated by a variety of molecular pathways in tumorigenesis, including the PI3K/AKT, MAPK, JAK/STAT, WNT, NF-κB and Hedgehog (Hh) pathways [7], which can function as upstream mediators of the PD-1/PD-L1 axis in different tumor cells.