title: Rituximab antiproliferative effect in B-lymphoma cells is associated with acid-sphingomyelinase activation in raft microdomains.
abstract: Rituximab is a chimeric human immunoglobulin G1 (IgG1) anti-CD20 monoclonal antibody with significant activity against CD20+ malignant B cells. Rituximab is currently used with success in the treatment of B-cell-derived lymphoid neoplasias either alone or in combination with chemotherapy. However, the predominant mechanism by which rituximab exerts its antitumor properties in vivo remains unknown. In the present study, we demonstrate that in Daudi and RL B-lymphoma cells, rituximab (without cross-linking) used at the saturating dose of 10 microg/mL induced moderate accumulation in G1 phase, growth inhibition, and significant loss in clonogenic potential. However, in these cells, rituximab induced no apoptosis. Furthermore, we observed that treatment with rituximab resulted in a rapid and transient increase in acid-sphingomyelinase (A-SMase) activity and concomitant cellular ceramide (CER) generation in raft microdomains. We also observed that rituximab-treated cells externalized both A-SMase and CER that colocalized with the CD20 receptor. Finally, we present evidence that rituximab-induced growth inhibition may be mediated through a CER-triggered signaling pathway, leading to the induction of cell cycle-dependent kinase inhibitors such as p27Kip1 through a mitogen-activated protein kinase (MAPK)-dependent mechanism.
authors.affiliation: INSERM U563, CPTP, CHU Purpan, Pavillon Lefebvre, 31024 Toulouse Cedex, France. christinebezombes@yahoo.com
authors.forename: Christine
authors.initials: C
authors.lastname: Bezombes
authors.forename: Solène
authors.initials: S
authors.lastname: Grazide
authors.forename: Céline
authors.initials: C
authors.lastname: Garret
authors.forename: Claire
authors.initials: C
authors.lastname: Fabre
authors.forename: Anne
authors.initials: A
authors.lastname: Quillet-Mary
authors.forename: Sabina
authors.initials: S
authors.lastname: Müller
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jaffrézou
authors.forename: Guy
authors.initials: G
authors.lastname: Laurent
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation; D016193:G1 Phase; D006801:Humans; D016393:Lymphoma, B-Cell / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D021962:Membrane Microdomains / Q000201:enzymology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D000069283:Rituximab; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D002518:Ceramides; D000069283:Rituximab; D020928:Mitogen-Activated Protein Kinases; C112980:acid sphingomyelinase-1; D013108:Sphingomyelin Phosphodiesterase