자가조립된 육합체 트레일(TRAIL) 단백질의 항암 효능 개선

Abstract

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine that causes cell apoptosis, i.e., cell death, upon specific binding to the death receptor highly expressed on the surface of tumor cells but minimally on normal cells. Therefore, TRAIL has a potential as a targeted anticancer agent. However, its functionally active form, homo-trimer, is non-covalently associated and susceptible to decomposition. Nevertheless, attempts are being made to maintain the trimeric conformation and further improve its efficacy by developing TRAIL oligomers which stimulate superclustering of the death receptors and, as a result, amplify apoptotic signaling pathways. As a novel strategy to develop a potent TRAIL therapeutics, I herein presented a hexameric TRAIL built upon association between two single-chain TRAILs (3TRs) each of which was genetically fused to one of heterodimeric coiled-coil domains originating from a part of human transcription regulator complex. Each recombinant chimera separately expressed from E. coli could self-assemble into the hexameric TRAIL upon simple mixing in vitro. Microscale thermophoresis was used to measure the strength of self-assembly and the affinity of the hexameric TRAIL for the death receptor, resulting in 379 nM and 163 nM, respectively. Notably, the hexameric TRAIL exhibited anticancer efficacy stronger than a native TRAIL both in TRAIL-insensitive U87-luc cells in vitro and HCT116-luc xenografted mice in vivo. These results demonstrated that, as compared to trimeric TRAIL, hexameric TRAIL can trigger greater death receptor oligomerization, which considerably amplifies cell apoptotic signals and therefore improves efficacy of anti-tumor therapy.