Moreover, these EBV-bearing cells in lymphoma tissues were shown to be of B-cell lineage, by the combinated analysis of immunostaining with CD20 and ISH with EBER1.
This is the first identified case of loss of CD20 expression in a lymphoma that has relapsed after rituximab therapy, although several other cases have since been identified.
MHC class I-negative lymphoma cells (Daudi) were labelled with a biotinylated mAb specific for a cell surface protein (anti-CD20) then linked to soluble biotinylated HLA-A2/gag complexes using an avidin bridge.
Additional immunostaining, which demonstrated positivity for CD20 and kappa light chain, as well as detection of the monoclonal rearrangement of the immunoglobulin heavy chain gene, helped to establish the diagnosis of lymphoma and to rule out an initially favored diagnosis of poorly differentiated carcinoma.
The lymphoma cell was positive for CD20 and T cell lineage markers such as cytoplasmic CD3, CD4, and CD5 and had a monoclonal rearrangement of the T cell receptor (TCR) gamma chain gene.
We have set up a new in vivo model in nonimmunodeficient mice by stable transduction of the human CD20 cDNA in the murine lymphoma line EL4.Animals injected i.v. with the EL4-CD20(+) lymphoma cells died within 30 days with evident liver, spleen, and bone marrow involvement, confirmed by immunohistochemistry and PCR analysis.
We and others have previously reported that immunoglobulin G Fc receptor (FcgammaR) polymorphisms predict the clinical response of lymphoma patients to passive anti-CD20 antibody infusions.
We have established a CD20- lymphoma cell line, RRBL1, from a diffuse large B-cell lymphoma with CD20- transformation from CD20+ follicular lymphoma after treatment with rituximab.
Importantly, in contrast to parental NK-92, CD20-specific NK cells efficiently lysed CD20 expressing but otherwise NK-resistant established and primary lymphoma and leukemia cells, demonstrating that this strategy can overcome NK-cell resistance and might be suitable for the development of effective cell-based therapeutics for the treatment of B-cell malignancies.
The recombinant antibodies were detected in the milk of transgenic mice with the highest expression level up to 17 microg/mul and could specifically bind the CD20 surface antigens on human B-lymphoma cells.
The anti-CD20 monoclonal antibody rituximab has been less successful in treating chronic lymphocytic leukemia (CLL) than lymphoma, possibly due to the lower density of CD20 on B lymphocytes from CLL patients than on those from lymphoma patients.
Treatment of patients with relapsed or refractory low grade follicular B-NHL lymphoma with rituximab (chimeric anti-CD20 mAb) has resulted in approximately 50% response rate.
Fusion proteins had reduced IFNalpha activity in vitro compared with native IFNalpha, but CD20 targeting permitted efficient antiproliferative and proapoptotic effects against an aggressive rituximab-insensitive human CD20(+) murine lymphoma (38C13-huCD20) and a human B-cell lymphoma (Daudi).
Combination treatment with 4-1BBL/anti-CD20 fusion protein and anti-CD3/anti-CD20 diabody led to significantly increased T-cell cytotoxicity to human B-lymphoma cells in vitro and drastically more potent tumor inhibitory activity in vivo in xenografted B-cell lymphoma in severe combined immunodeficiency disease mice.
The study showed that lymphoma xenografts could be targeted in the presence of endogenous biotin when anti-CD20 fusion proteins containing SAv mutants (scFv(4)-SAv-S45A or scFv(4)-SAv-Y43A) were employed in combination with CA 2 and [(111)In]4b.
Measles virus (MV)-PNP H(blind)antiCD20 is a CD20-targeted and prodrug convertase-armed MV that temporarily controls growth of lymphoma xenografts in severe combined immunodeficiency (SCID) mice in combination with fludarabine phosphate (fludarabine).