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Real-time Cytotoxicity Assays in Human Whole Blood
Published on: November 7, 2014
Surface levels of CD20 determine anti-CD20 antibodies mediated cell death in vitro
Vijay Singh1, Damodar Gupta1, Rajesh Arora1
1Division of Radiation Biosciences, Institute of Nuclear Medicine & Allied Sciences, Brig SK Mazumdar Marg, Timarpur, Delhi, India.
Background:
The sensitivity of human Burkitt's lymphoma cells to rituximab (Rtx) and tositumomab (Tst) was assessed on cells expressing different levels of CD20 on surface. Cells that harbor low CD20 levels may resists against therapeutics response to CD20-specific antibodies. We postulated that, radiation-induced modulation of CD20 surface levels may play a crucial and central role in determining the relative efficacy of rituximab and tositumomab in treating Burkitt's lymphoma disease. Here, we examined the γ-radiation-induced CD20 expression in the Burkitt lymphoma cell line 'Daudi' and the relation of differential levels of CD20 with anti-CD20 mAbs mediated cell death.
Methodology:
In this study we examined kinetics of CD20 expression following sub lethal doses ofγ-radiation to Daudi cells and thereafter anti-CD20 mAbs (rituximab and tositumomab) were added in cell suspensions. The correlation of kinetics of CD20 expression and cells treated with anti-CD20 mAbs/or corresponding isotype Abs with special reference to changes in mitochondrial membrane potential and reactive oxygen species generation was also examined. Further, we also investigated the efficacy of anti-CD20 mAbs and possible induction of cell death in relation to levels of CD20 cell surface expression.
Conclusion:
This report provides evidence that CD20 expression can be induced by exposure of cells to γ-radiation. In addition, these findings demonstrated that the efficacy of anti-CD20 mAbs is dependent on the surface levels of CD20. Based on these findings, we hypothesized (i) irradiation just prior to immunotherapy may provide new treatment options even in aggressive B cell tumors, which are resistant to current therapies in vivo (ii) The efficacy of induction of apoptosis varies with type of monoclonal antibodies in vitro.
Insights
Gamma radiation can increase CD20 expression on Burkitt lymphoma cells, enhancing their sensitivity to rituximab and tositumomab therapies. This suggests pre-treatment irradiation may improve outcomes for B cell tumors resistant to current treatments.
Area of Science:
- Oncology
- Immunology
- Radiation Biology
Background:
- Burkitt's lymphoma cells exhibit variable sensitivity to CD20-specific antibodies like rituximab and tositumomab.
- Low surface CD20 levels on cancer cells can lead to resistance against antibody-based therapies.
- The role of radiation in modulating CD20 expression and its impact on therapeutic efficacy remains an area of investigation.
Purpose of the Study:
- To investigate the effect of gamma radiation on CD20 surface expression in the Daudi Burkitt lymphoma cell line.
- To determine the relationship between radiation-induced CD20 levels and the efficacy of anti-CD20 monoclonal antibodies (mAbs).
- To explore the potential of combining radiation with anti-CD20 immunotherapy for B cell malignancies.
Main Methods:
- Daudi cells were exposed to sub-lethal doses of gamma radiation.
- Kinetics of CD20 expression were analyzed post-irradiation.
- Cells were treated with rituximab or tositumomab, and cell death, mitochondrial membrane potential, and reactive oxygen species generation were assessed.
- The correlation between CD20 expression levels and mAb-mediated cell death was examined.
Main Results:
- Gamma radiation exposure was found to induce CD20 expression on Daudi cells.
- The efficacy of anti-CD20 mAbs (rituximab and tositumomab) in inducing cell death was directly dependent on the surface CD20 levels.
- Differential efficacy of apoptosis induction was observed between the tested monoclonal antibodies in vitro.
Conclusions:
- CD20 expression on Burkitt lymphoma cells can be upregulated by gamma radiation.
- The effectiveness of anti-CD20 antibody therapy is contingent upon the level of CD20 surface expression.
- Pre-treatment irradiation prior to immunotherapy presents a potential novel therapeutic strategy for aggressive, therapy-resistant B cell tumors.
