FASLG and neoplasm: Indeed, they express co-stimulatory molecules (e.g., CD40, CD80 and CD86), produce antibodies and cytokines, function as APC, initiate T-cell priming, promote T-cell expansion and memory differentiation [52,53,54] and directly kill tumor cells through FasL–Fas interaction [55] and the secretion of cytotoxic granules (e.g., granzyme B) [51].