Following recruitment to the DISC, FLIP(L) forms a heterodimer with caspase-8 through both death effector domain (DED) and caspase-like domain (CLD). In addition, FLIP-L can also regulate TNF-R1 signaling via interaction with the DED of FADD. The regulatory function of FLIP(L) has been found to differ depending on its expression levels. c-FLIP was shown to inhibit death receptor (DR)-mediated apoptosis only when expressed at high levels, while low cell levels of FLIP(L) enhanced DR signaling to apoptosis (Boatright KM et al. 2004; Okano H et al. 2003; Yerbes R et al. 2011). The expression levels of c-FLIP proteins were shown to be regulated by NFkappaB signaling pathway (Micheau O et a. 2001; Kreuz S et al 2001).