FAS and neoplasm: Moreover, TNFRSF6 is essential for the process of cytotoxic T and NK cells killing tumor cells (Berke, 1995), whereas in its ligand, the expression of TNFSF6 in carcinoma cells could eliminate the infiltration of T cells and promote tumor proliferation and progression (Hahne et al., 1996; O'Connell et al., 1996).