IFNG and neoplasm: Cytokine-induced killer (CIK) cells are major histocompatibility complex (MHC)-unrestricted anti-tumor effector CD3 + T lymphocytes that are easily generated by ex vivo expansion of peripheral blood mononuclear cells (PBMCs) with anti-CD3 antibodies, interleukin-2 (IL-2), and interferon-gamma (IFN-γ) [7, 8].