IMPROVED TUMOR CELL KILLING BY TRAIL REQUIRES SELECTIVE AND HIGH AFFINITY RECEPTOR ACTIVATION

Apoptosis can be activated by tumor necrosis factor-related apoptosis-inducing ligand(TRAIL) in a wide range of tumor cells, but not in non-transformed cells.TRAIL interaction with receptors DR4 or DR5 induces apoptosis, whereas DcR1,DcR2 and osteoprotegerin are decoy receptors for TRAIL. TRAIL variants (singlemutant, D269H, and double mutant D296H/E195R) engineered to selectively activateDR5 but not DR4 enhanced pro-caspase-8 processing and apoptosis in tumorcells, compared to wild-type TRAIL. D269H/E195R showed a 17 fold faster kineticsof receptor activation than wild-type TRAIL. The robust receptor activation wasnot due to altered 3D ligand structures or aggregation but to high affinity and selectivitytowards DR5, which prevented ligand-induced receptor heteromerization andneutralization by decoys. These findings have important implications for the designof anticancer therapeutic agents and cytokine engineering