CD8A and neoplasm: Functionally, PSAP drives oncogenesis through multiple mechanisms: it enhances ERα signaling in breast cancer, promotes AR activity and cell survival in PCa, drives glioma stem cell growth via TLR4/NF-κB signaling in gliomas, facilitates invasion and EMT in glioblastoma via TGF-β1/Smad, supports proliferation in hepatocellular carcinoma via the circVAPA/miR-377-3p axis, and contributes to an immunosuppressive tumor microenvironment in PDAC by inhibiting CD8+ T-cell infiltration.