Differential Action of Anti-CD20 Monoclonal Antibodies: Role in Induction of Cell Death

Purpose: To study and assess to the sensitivity of Burkitt’s lymphoma cells harboring differential levels of cell surface CD20 for anti-CD20 monoclonal Antibodies. Material and methods: Burkitt’s lymphoma cell line ‘Daudi’ was used during present study. Cells were exposed to single dose of γ-radiation (0.5 Gy) and thereafter incubated with rituximab (Rtx) or tositumomab (Tst) (0.5 μg/ ml concentration each). The changes in expression of RelA, Akt and Bax/Bcl-2 ratio was measured to assess sensitivity of cells in term of cell death. Results: During the present investigation, we found that cells incubated with anti-CD20 mAbs at +20 hrs post radiation exposure showed higher levels of cell death in term of Bax/Bcl-2 ratio. In addition, we also found the significant changes in expression of pro-survival signaling proteins such as RelA and Akt pathways. Moreover, we found that tositumomab is a potent inducer of apoptotic cell death. Conclusion: These findings suggested that the efficacy of anti-CD20 mAbs depends on the number of CD20 molecules expressed on cell surface and type of antibody used. It may provide new treatment options for selection of anti-CD20 mAbs even in aggressive B-cell lymphoma, which harbors low levels of CD20 or even resistant to current therapies in vivo.