A requirement for calcium in the caspase-independent killing of Burkitt lymphoma cell lines by Rituximab.
The therapeutic monoclonal antibody rituximab has previously been shown to kill B cells in a caspase-independent manner. The signalling pathways underpinning this novel death pathway are unknown. The present study showed that rituximab treatment of Burkitt lymphoma cell lines induced a slow rise in intracellular calcium ([Ca(2+)](i)). This rise was only witnessed in cell lines that were killed by antibody, suggesting a critical role for Ca(2+) in mediating rituximab-driven caspase-independent cell death. Inhibition of the two main intracellular store-located Ca(2+) channels, i.e. the ryanodine and inositol-1,4,5-triphosphate receptor channels by dantrolene and xestospongen-c respectively did not prevent the rise in Ca(2+) seen with rituximab or protect cells from subsequent death. In sharp contrast, inhibition of Ca(2+) entry via plasma membrane channels with (2-aminoethoxy) diphenylborate or SKF-96365 or complete chelation of extracellular Ca(2+) with ethyleneglycol bis (aminoethylether) tetra-acetate inhibited the rise in [Ca(2+)](i) and increased cell viability. Together, these data suggest that ligation of the CD20 receptor with rituximab allows a slow sustained influx of Ca(2+) from the external environment that under certain conditions can lead to cell death.
David Evans Medical Research Centre, Nottingham University Hospitals Trust, City Hospital Campus, Nottingham, UK. iandaniels25@hotmail.com
Ian
I
Daniels
Julie
J
Turzanski
Andrew P
AP
Haynes
D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002051:Burkitt Lymphoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D047028:Macrocyclic Compounds / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D000069283:Rituximab; D012433:Ryanodine / Q000378:metabolism
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D002121:Calcium Channel Blockers; D007093:Imidazoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047028:Macrocyclic Compounds; D010080:Oxazoles; C511704:xestospongin C; D012433:Ryanodine; D000069283:Rituximab; D020169:Caspases; D003620:Dantrolene; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium