Cold and alpha-conjugated anti-CD20 induce different in vitro apoptosis responses in B-chronic lymphocytic leukemia and splenic lymphoma with villous lymphocytes


Katia Vandenbulcke1, Fritz Offner2, Guido Slegers1, Filip De Vos3, Virginie de Gelder4, Annick Willems2, Simona Martin5, Roger Molinet5, Christos Apostolidis5, Tuomo K Nikula5, Willem Janssens5, Ann Jansenns2, Hubert Thierens4, Rudi A. Dierckx3, and Jan Philippe2. (1) Department of Radiopharmacy, University of Gent, Gent, Belgium, (2) Department of Hematology, University of Gent, Gent, Belgium, (3) Department of Nuclear Medicine, Gent University Hospital, Gent, Belgium, (4) Department of Radiation Physics, University of Gent, Gent, Belgium, (5) Nuclear Chemistry, European Commission, JRC, Institute for Transuranium Elements, B.O.Box 2340, 76125 Karlsruhe, Germany
Radiotherapy, fludarabine, anti-CD20 antibody and glucocorticoids can kill malignant lymphocytes in B-CLL and SLVL. To evaluate the relation of the number of CD20 molecules per cell and effect of radioconjugated and cold anti-CD20 antibodies we compared CD20 expression in B-CLL and SLVL and related this to apoptosis in response to 6 different cytotoxic treatments. Peripheral blood lymphocytes were isolated. Cells were treated in vitro with (1) 213Bi-anti-CD20, (2) external 60Co gamma irradiated, (3) fludarabine, (4) methylprednisolone, (5) cold anti-CD20 and human serum as a complement source or (6) cold anti-CD20 + gamma-radiation were intra individually compared with non treated cells. Apoptosis was evaluated by flow cytometry using Annexin V and 7-AAD. In conclusion no differences were observed between CLL and SLVL in apoptosis induced by fludarabine, gamma radiation and prednisolone. Both cold and radioconjugated antiCD20 induced more apoptosis in SLVL than in B-CLL, due to the much higher expression of CD20 molecules on SLVL cells. Cold anti-CD20 plus gamma radiation induced less apoptosis than 213Bi conjugated anti-CD20 in CLL (p<0.01) but not in SLVL.