ATF6 and liposarcoma: Nelfinavir, a HIV protease inhibitor, induces ER stress and caspase-dependent apoptosis and increases SREBP-1 protein half-life by blocking intracellular trafficking of SREBP-1 and activating transcription factor 6 (ATF6) from site-2 protease (S2P) inhibition in liposarcoma cells and xenograft mouse models (141).