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Fas receptor clustering and involvement of the death receptor pathway in rituximab-mediated apoptosis with concomitant sensitization of lymphoma B cells to Fas-induced apoptosis

Stel, A. J., ten Cate, B., Jacobs, S., Kok, J. W., Spierings, D. C. J., Dondorff, M., Helfrich, W., Kluin-Nelemans, H. C., de Leij, L. F. A. H., Withoff, S. & Kroesen, B. J., 15-Feb-2007, In : Journal of Immunology. 178, 4, p. 2287-2295 9 p.

Research output: Contribution to journalArticleAcademicpeer-review

Ab binding to CD20 has been shown to induce apoptosis in B cells. In this study, we demonstrate that rituximab sensitizes lymphoma B cells to Fas-induced apoptosis in a caspase-8-dependent manner. To elucidate the mechanism by which Rituximab affects Fas-mediated cell death, we investigated rituximab-induced signaling and apoptosis pathways. Rituximab-induced apoptosis involved the death receptor pathway and proceeded in a caspase-8-dependent manner. Ectopic overexpression of FLIP (the physiological inhibitor of the death receptor pathway) or application of zIETD-fmk (specific inhibitor of caspase-8, the initiator-caspase of the death receptor pathway) both specifically reduced rituximab-induced apoptosis in Ramos B cells. Blocking the death receptor ligands Fas ligand or TRAIL, using neutralizing Abs, did not inhibit apoptosis, implying that a direct death receptor/ligand interaction is not involved in CD20-mediated cell death. Instead, we hypothesized that rituximab-induced apoptosis involves membrane clustering of Fas molecules that leads to formation of the death-inducing signaling complex (DISC) and downstream activation of the death receptor pathway. Indeed, Fas coimmune precipitation experiments showed that, upon CD20-cross-linking, Fas-associated death domain protein (FADD) and caspase-8 were recruited into the DISC. Additionally, rituximab induced CD20 and Fas translocation to raft-like domains on the cell surface. Further analysis revealed that, upon stimulation with rituximab, Fas, caspase-8, and FADD were found in sucrose-gradient raft fractions together with CD20. In conclusion, in this study, we present evidence for the involvement of the death receptor pathway in rituximab-induced apoptosis of Ramos B cells with concomitant sensitization of these cells to Fas-mediated apoptosis via Fas multimerization and recruitment of caspase-8 and FADD to the DISC.

Original languageEnglish
Pages (from-to)2287-2295
Number of pages9
JournalJournal of Immunology
Volume178
Issue number4
Publication statusPublished - 15-Feb-2007

    Keywords

  • NON-HODGKINS-LYMPHOMA, INSOLUBLE MEMBRANE COMPARTMENT, SIGNALING PATHWAY, DOWN-REGULATION, LIPID RAFTS, TYROSINE PHOSPHORYLATION, ANTIBODY IDEC-C2B8, CASPASE ACTIVATION, CYTOTOXIC DRUGS, CALCIUM INFLUX

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