PDCD1 and neoplasm: Sorafenib reduced doxorubicin-induced PD-L1 upregulation, enhancing the anti-tumor-immune response by increasing interferon-γ-secreting CD8+ T lymphocytes.274 Moreover, the interaction between PD-1 on T cells and PD-L1 on tumor cells effectively “turns off” T cells, allowing the tumor to evade immune destruction.273,275 This mechanism is particularly insidious because it hijacks a natural regulatory process intended to prevent tissue damage and autoimmunity, thereby creating a shield that protects the tumor from immune-mediated elimination.