Cytotoxic lymphocytes (CTLs) are key immune cells that play a crucial role in antitumor immune responses through their ability to kill tumor cells by releasing perforin or granzymes which cause caspase-dependent apoptosis in tumor cells [125], employing the Fas/FasL death receptor system [126], or secreting IFN-γ and TNF-α [127]. The gene discussed is FAS; the disease is neoplasm.