A requirement for calcium in the caspase-independent killing of Burkitt lymphoma cell lines by Rituximab

Br J Haematol. 2008 Jul;142(3):394-403. doi: 10.1111/j.1365-2141.2008.07193.x. Epub 2008 Jun 9.


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.

MeSH terms

  • Antibodies, Monoclonal / therapeutic use*
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20 / immunology
  • Antineoplastic Agents / therapeutic use*
  • B-Lymphocytes / drug effects
  • B-Lymphocytes / metabolism
  • B-Lymphocytes / pathology
  • Burkitt Lymphoma / drug therapy*
  • Burkitt Lymphoma / metabolism
  • Burkitt Lymphoma / pathology
  • Calcium / analysis
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Caspases / metabolism
  • Cell Death
  • Cell Line
  • Cell Membrane / metabolism
  • Dantrolene / pharmacology
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism
  • Flow Cytometry
  • Humans
  • Imidazoles / pharmacology
  • Inositol 1,4,5-Trisphosphate Receptors / metabolism
  • Macrocyclic Compounds / pharmacology
  • Oxazoles / pharmacology
  • Rituximab
  • Ryanodine / metabolism


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20
  • Antineoplastic Agents
  • Calcium Channel Blockers
  • Imidazoles
  • Inositol 1,4,5-Trisphosphate Receptors
  • Macrocyclic Compounds
  • Oxazoles
  • xestospongin C
  • Ryanodine
  • Rituximab
  • Caspases
  • Dantrolene
  • 1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
  • Calcium