Tagged and untagged TRAIL show different activity against tumor cells.

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is a novel cytotoxic ligand belonging to the TNF superfamily which is currently being developed as a cancer therapeutic drug. Here, we observed the different functions of recombinant TRAIL protein with a foreign protein label and non-labeled TRAIL. We used a prokaryotic expression system to prepare two different versions of the extracellular TRAIL 114-281aa protein: TRAIL-HS, a protein modified with 6xHis-Tag and S-Tag; and TRAIL-FT, which had no foreign protein. The proteins were purified using Ni-NTA chromatography (TRAIL-HS) and cation ion-exchange column chromatography (TRAIL-FT) and identified by SDS-PAGE and western blot analysis. We compared the abilities of the proteins to bind to death receptor 5 (DR5) by ELISA and to induce apoptosis in a normal liver cell line (Chang liver) and a human T-lymphocyte leukemia cell line (Jurkat) by MTT assay, GR staining and FACS. The results indicate that the biological functions of TRAIL-FT were superior to those of TRAIL-HS in binding and the induction of apoptosis, and may be useful to further the development and applications of TRAIL.