An agonistic monoclonal antibody against DR5 induces ROS production, sustained JNK activation and Endo G release in Jurkat leukemia cells

We have previously reported that AD5-10, a novel agonistic monoclonal antibody against DRS, possessed a strong cytotoxic activity in various tumor cells, via induction of caspase-dependent and -independent signaling pathways. The present study further demonstrates that reactive oxygen species （ROS） were generated in abundance in Jurkat leukemia cells upon AD5-10 stimulation and that ROS accumulation subsequently evoked sustained activation of c-Jun N-terminal kinase （JNK）, loss of mitochondrial membrane potential, and release of endonuclease G （Endo G） from mitochondria into the cytosol. The reducing agent, N-acetylcysteine （NAC）, effectively inhibited the sustained activation of JNK, release of Endo G, and cell death in Jurkat cells treated by AD5-10. Moreover, a dominant-negative form of JNK （but not of p38） enhanced NF-κB activation, suppressed caspase-8 recruitment in death-inducing signaling complexes （DISCs）, and reduced adverse effects on mitochondria, thereby inhibiting AD5-10-induced cell death in Jnrkat leukemia cells. These data provide novel information on the DR5-mediated ceil death-signaling path- way and may shed new light on effective strategies for leukemia and solid tumor therapies.