Description:
<jats:title>Abstract</jats:title>
<jats:p>Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) and its agonistic antibodies, which are currently in early clinical trials for treating various malignancies, induce apoptosis through triggering of either TRAIL-R1 or TRAIL-R2. Based on studies using agonistic monoclonal antibodies, we recently proposed that primary chronic lymphocytic leukemic cells seem to signal apoptosis primarily through TRAIL-R1. We have now synthesized mutant forms of TRAIL specific for TRAIL-R1 or TRAIL-R2. The selectivity of these mutants to induce apoptosis in cell lines is due to selective binding to their cognate receptors resulting in apoptosis via formation of a death-inducing signaling complex. Using these mutants, we now unequivocally show that primary cells from patients with chronic lymphocytic leukemia and mantle cell lymphoma signal to apoptosis almost exclusively through TRAIL-R1. Thus, no significant therapeutic benefit can be anticipated from treating such patients with agents currently in clinical trials that signal predominantly through TRAIL-R2, such as HGS-ETR2 or Apo2L/TRAIL. Our study highlights the necessity to determine whether primary cells from a particular tumor signal via TRAIL-R1 or TRAIL-R2. Such information will provide a rational approach to optimize TRAIL therapy. (Cancer Res 2005; 65(24): 11265-70)</jats:p>