FAS and neoplasm: Tumor-infiltrating cytotoxic CD8+ T cells, in particular, are capable of mediating directly the death of tumor cells via the release of cytokines (IFNγ, TNF), cytotoxic factors (perforin, granzymes) or the engagement of ligand-receptor interactions from the TNF family (TRAIL-TRAIL-R, FasL-Fas, TNF-TNF-R) [7,8].