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Bortezomib Sensitizes Non–Hodgkin's Lymphoma Cells to Apoptosis Induced by Antibodies to Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand (TRAIL) Receptors TRAIL-R1 and TRAIL-R2

Authors' Affiliation: Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania

Requests for reprints: Mitchell R. Smith, Lymphoma Service, Department of Medical Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111. Phone: 215-728-2674; Fax: 215-728-3639; E-mail: M_smith{at}fccc.edu.

Non–Hodgkin's lymphoma (NHL) is an increasingly common disease that, despite advances in antibody-targeted therapy, still requires novel therapeutic approaches. Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) activates a major nonmitochondrial pathway for tumor cell killing through binding to a receptor family, some activating and some decoy. Agonistic antibodies to the receptors TRAIL-R1 and TRAIL-R2 can mimic many of the effects of TRAIL. We are investigating the effects of such agonistic antibodies, mapatumumab directed at TRAIL-R1 and lexatumumab directed at TRAIL-R2, on NHL cell lines. These antibodies induce apoptosis through caspase-8 but also activate BID to involve the mitochondrial pathway and activate caspase-9. In addition, we find signaling through both the nuclear factor-B and c-Jun NH₂-terminal kinase pathways. Because the proteasome inhibitor bortezomib also affects these pathways, we have investigated the combination of TRAIL-R antibodies and bortezomib and show enhanced apoptosis and signaling as well as enhanced killing of NHL cells in a severe combined immunodeficient mouse/human NHL cell line xenograft system. The combination of bortezomib and TRAIL signaling warrants further investigation as a therapeutic regimen. Understanding the multiple intracellular pathways of TRAIL activation may lead to rationally designed therapeutic trials.