Death receptor 4 is preferentially recruited to lipid rafts in chronic lymphocytic leukemia cells contributing to tumor necrosis related apoptosis inducing ligand-induced synergistic apoptotic responses

Tumor necrosis related apoptosis inducing ligand receptor 1 (TRAIL-R1, death receptor 4 [DR4]) and TRAIL-R2 (DR5) have been proposed as targets for cancer therapy, but which death receptor to target for chemotherapy in chronic lymphocytic leukemia (CLL) is uncertain. Herein, we discovered that Burkitt lymphoma B cell line, BJAB, CLL-like cell line, I-83, and pre-acute lymphocytic leukemia B cell line, NALM-6, underwent apoptosis following TRAIL, whereas a CLL-like cell line, JMV-3, and primary CLL cells failed to undergo apoptosis. In TRAIL resistant CLL cells, only activation of DR4 provided an increase in fludarabine induced apoptosis. This was mediated in part by the localization of DR4 but not DR5 in lipid rafts following TRAIL and fludarabine treatment. This preference for DR4 activation leading to increased fludarabine induced apoptosis was also observed following SAHA, PS-341, and chlorambucil treatment in primary CLL cells. Thus, CLL cells selectively activate DR4 partially mediated through its localization to lipid rafts leading to apoptosis when combined with chemotherapeutic drugs.