CD274 and neoplasm: Tumor cells can activate PD-L1 expression via multiple oncogenic signaling pathways involving IFN-γ/JAK2/IFN37, PI3K38, ALK/STAT339, MEK/ERK/STAT1, MYD88/TRAF640 or exposure to inflammatory cytokines such as IFN-γ41 produced by infiltrating immune cells.