CD274 and neoplasm: PD-L1 can be directly regulated by intracellular signaling pathways, mainly deregulated in many tumor types (RAS/RAF/MEK, PI3K/AKT/mTOR, JAK, and STAT) or by the IFN-Υ signaling, as a consequence of IFN-Υ release by immune cells in the tumor microenvironment.