Natural killer T (NKT) cells are a subpopulation of T lymphocytes, which are considered tumor cell killers; they produce antitumor molecules, such as Fas ligand (FasL), IL-4, IFN-γ, IL-13, perforin, and granzyme, that also promote lysis of tumor cells [30, 31]. The gene discussed is IL4; the disease is neoplasm.