eISSN: 1644-4124
ISSN: 1426-3912
Central European Journal of Immunology
Current issue Archive Manuscripts accepted About the journal Editorial board Abstracting and indexing Subscription Contact Instructions for authors Ethical standards and procedures
SCImago Journal & Country Rank

4/2007
vol. 32
 
Share:
Share:
more
 
 


Review paper
CD20 as a target for therapy

Magdalena Winiarska
,
Jacek Bil
,
Urszula Demkow
,
Maria Wąsik

(Centr Eur J Immunol 2007; 32 (4): 239-246)
Online publish date: 2007/12/10
Article file
- CD20.pdf  [0.16 MB]
Get citation
ENW
EndNote
BIB
JabRef, Mendeley
RIS
Papers, Reference Manager, RefWorks, Zotero
AMA
APA
Chicago
Harvard
MLA
Vancouver
 
 

Introduction


It is more than one hundred years ago that Paul Ehrlich invented the targeted therapy. His magic ball was supposed to target selectively every disease. Nowadays, this magic ball consists of therapeutics that inhibit many molecular pathways, such as monoclonal antibodies, small-molecule inhibitors, peptide mimetics and antisense oligonucleotides.
The monoclonal antibodies were introduced into the medicine quite a long time ago. At the beginning polyclonal anti-D antibodies were used to prevent the hemolytic disease of the newborns. In 1975 Georges Kohler and Cesar Milstein were the first to invent and describe the production of monoclonal antibodies. In 1984 they were awarded
a Nobel Prize for this groundbreaking invention. Since then, monoclonal antibodies were improved to be more efficient and less immunogenic. The production of chimeric and humanized antibodies has started. Nowadays, human antibodies (produced in transgenic mice or by means of phage peptide libraries) are undergoing clinical studies [1].
In 1980 for the first time the monoclonal antibody (Ab89) directed against lymphoma antigen was used to treat a patient [2]. In 1986 the FDA (Food and Drug Administration) registered first monoclonal antibody-muromonab (anti-CD3 antibody) to treat acute kidney rejection. However, the last decade is connected with a huge development, improvement and practical application of monoclonal antibodies in medicine. 21 monoclonal antibodies are registered at the moment and 10 of them are widely used in oncology. Others are used in many fields of medicine, such as transplantology, rheumatology, dermatology, ophtalmology.

CD20 antigen


The CD20 antigen is the surface molecule characteristic for precursors (pre-B lymphocytes) and mature B lymphocytes. CD20 is neither expressed on plasma cells [3], nor on hematopoietic stem cells and pro-B lymphocytes (figure 1). However, IFN-γ was reported to induce CD20 expression on plasma cell [4].

Because CD20 antigen is not expressed by either plasma cells or B-lymphoid stem cells, therapy with rituximab does not affect significantly immunoglobulin serum concentrations. Also, after a conventional regimen therapy with rituximab B lymphocyte count recovers in
9-12 months [5]. The CD20 expression on the surface of B lymphocytes increases with age [6].
Certain characetristics make the CD20 antigen an appealing target for monoclonal antibody (MAb) therapy. The CD20 antigen is one of the most stable lymphocyte antigen. It does not circulate in the plasma as a free protein that could competitively inhibit MAb binding to lymphoma cells, does not shed from the surface of CD20 positive cells after antibody binding [7] and does not seem to be internalized [8] or, subsequently, downregulated on antibody binding. It is also expressed on the surface of lymphocytes in the large number of copies (approximately 10000 molecules per cell). It was also reported that plasma from lymphoma-or leukemia-bearing patients did not block the CD20 – rituximab binding [9]. However, in some studies the decrease in CD20 expression after rituximab treatment of CLL patients was reported [10, 11]. To sum up, in the majority of in vivo and in vitro studies no internalization nor down-regulation in CD20 expression was detected [12].

CD20 structure


No CD20 ligand has been known so far. Therefeore, the exact CD20 functions remain largely unknown. Some data indicate that CD20 plays an important role in B lymphocytes signalling, growth and differentation [3]. It could also function as a Ca2+ membrane channel that sustains intracellular Ca2+ concentration and allows the activation of B cells. CD20 is a nonglycosylated phosphoprotein of 33, 35 and 37 kDa. The predicted CD20 structure consists of 4 membrane-spanning domains with both amino and carboxy termini located within the cytoplasm (hence, CD20 is also called MS4A1 – membrane spanning 4 domain subfamily A, member 1) [13].
CD20 has two extracellular loops. The smaller one (a segment of 7 aminoacids, between the first and second transmembrane regions) probably does not extent beyond the cellular membrane. This loop is identical in every member of MS4A family [13, 14]. The bigger loop, a segment of 43 aminoacids, between the third and fourth transmembrane regions has a disulfide bond [13, 14] (figure 2) and is recognized by the majority of anti-CD20 antibodies.
Phosphorylation and dephosphorylation of proteins is recognized as a major process of regulation of cellular functions and serves a prominent role in signal transduction. No tyrosine residues or recognized signaling motifs occur in any of the cytoplasmic regions of CD20 molecule, although there are number of consensus sites for serine and threonine phosphorylation.
It has been reported that CD20 relocalizes into lipid rafts upon binding with antibodies [15]. The association between CD20 and lipid rafts is dependent on cholesterol and on a short cytoplasmic sequence. Lipid rafts are membrane microdomains enriched in cholesterol and sphingolipids, that serve as platform for signal transduction, allowing the colocalization of different proteins. Thus, CD20 may exist as dimers and tetramers in complex with at least one additional protein component [3]. The CD20 protein has been reported to be closely associated with the transmembrane adapter protein p75/80 (also named C-terminal src kinase-binding protein Cbp), CD40 and major histocompatibility complex class II proteins (MHC II) [16]. CD20 antigen undergoes conformational changes during B lymphocytes diferentiation. At least two conformational isoforms of CD20 exist.
IL-4 and CD40 signaling both can influence the conformation of CD20 [17].
Some evidence indicates that various cytokines including IFN-α, GM-CSF, IL-4, TNF upregulate CD20 expression on lymphoma cells isolated from patients with CLL in vitro and probably in vivo [18]. However, the mechanism of
this up-regulation is unknown. Altgough, some of these cytokines may increase the therapeutic activity of rituximab and do not increase the CD20 expression [19, 20].

Anti-CD20 therapeutics


Rituximab was approved by FDA in 1997 for treating low-grade non-Hodgkin’s lymphoma. Beside rituximab there are two other anti-CD20 antibodies, approved by FDA. Also other therapeutics directed against CD20 are currently undergoing clinical studies. In Non-Hodkgin’s lymphomas murine monoclonal antibodies conjugated with radioisotopes are approved: ibritumomab (Zevalin) and tositumomab (Bexxar). Ibritumomab is an IgG1 murine antibody that recognizes the same epitope as rituximab. Ibritumomab is conjugated with metal chelator – tiuxetan that binds with radioactive yttrium (90Y). Tositumomab is an IgG2α murine antibody directly conjugated with radioactive iodine (131I). Both radioimmunoconjugates eradicate tumor cells by the antibody-mediated effects (CDC, ADCC) as well as by the cytotoxic activity of the radiation. Their main disadvantages are toxicity against the bone marrow and immunogenicity that results in HAMA (human anti-mouse antibodies) production. Ibritumomab and tositumomab are used to treat rituximab-resistant and refractory non-Hodgkin’s lymphomas.
Over recent years much of the effort has focused on decreasing immunogenicity of antibodies by creating humanized and human antibodies. Ocrelizumab is a humanized monoclonal antibody directed against CD20 antigen. It is currently undergoing phase II clinical studies in patients with non-Hodgkin’s lymphomas and rheumatoid arthritis.
Ofatumumab (2F2-HuMax-CD20) is a human anti-CD20 antibody generated in human Ig transgenic mice. It recognizes a unique epitope of CD20, which is located probably in both loops of CD20 antigen [21]. It is currently undergoing phase III studies in the treatment of non-Hodgkin’s lymphomas, chronic lymphocytic leukemia and rheumatoid arthritis. In
in vitro studies 2F2 antibody was shown to have high affnity for CD20 antigen as well as slow off-rates (after 3 hours dissociation rate of rituximab fluctuates around 70-80%, while that of 2F2 is only about 20-30%). CDC activity of 2F2 antibody (as well as other human antibodies) is unusually potent, also against rituximab – resistant lymphoma cells with low expression of CD20.
One-chain polypeptide directed against CD20 is also currently undergoing phase II studies in patients with rheumatoid arthritis. It belongs to the SMIP group of drugs (small modular immunopharmaceutical drugs). It strongly binds with CD20, activates ADCC, although has no CDC activity.
The other strategy to target lymphoma cells is to force the patient’s organism to produce anti-CD20 antibodies. In order to obtain this effect the small peptides (mimotopes) are created that mimic CD20 antigen. It is only hard to predict the results of such an autoagression.

Rituximab



Mechanisms of action


Rituximab is a chimeric human-mouse monoclonal antibody directed against CD20 molecule. The mechanism of its action in vivo is not entirely clear. However, rituximab is thought to induce complement-mediated cytotoxicity (CDC) or phagocytosis and antibody-dependent cellular cytotoxicity (ADCC). CDC is triggered by C1q component that binds to Fc portion of the antibody. ADCC is mediated by Fcγ receptors (FcγR) that are widely expressed on the surface of granulocytes, macrophages and NK lymphocytes.
Besides, rituximab binding may result in direct effects
on cell growth and viability by inducing apoptosis in the
absence of complepment and effector cells (figure 3). It was also showed that rituximab may sensitize tumor cells to cytotoxic therapies (doxorubicin, cisplatin, fludarabine, retinoids) and glycocorticosteroids (dexamethazone) [22, 23].
Some results suggest that rituximab also has a ’vaccinal’ effect. Several studies have indicated that maximal clinical and molecular responses to rituximab may occur after several months. It suggests that not only short-term cytolytic mechanisms (CDC, ADCC, apoptosis) are involved in the activity of rituximab. Rituximab-induced lysis of tumor cells may promote an uptake and presentation of lymphoma--derived peptide by dendritic cells. As a result an increase in number of specific cytotoxic T lymphocytes appears [24]. The specific antitumor reponse after therapy with monoclonal antibodies was demonstrated in murine experiments, although it is hard to demonstrate it in humans [25, 26].
Despite many in vitro studies still little is known about which mechanism is the most important for antitumor activity of rituximab in vivo.


Complement-dependent cytotoxicity


The complement system that consists of about 30 proteins may be activated by 3 different pathways – classical, lectin and alternative. The classical pathway requires the presence of immunoglobulins, while alternative pathway is activated spontaneously on every accessible cellular membrane. Collectins that bind unspecifically sugar groups on the microorganisms’ surface trigger lectin pathway.
The first step in the activation of the classical pathway is the binding of C1q component to conformationally changed Fc portion of IgG (except IgG4) or IgM immunoglobulin. As a result a proteolytic cascade is triggered that generates large amounts of C3b, the main effector molecule of the complement system. The final effect of complement activation is a generation of MAC (membrane attacking complex). MAC kills target cells by C9 polymerization, pore formation and disrupting the cellular membrane. Consequently, the water and ions infux leads to the cell swelling and necrosis. Microorganisms, virus-infected cells, tumor cells and erythrocytes are main targets for MAC. C3b component may also bind to complement receptors (CRs) expressed on many effector cells such as granulocytes, macrophages or NK-cells and induce cell-mediated lysis or phagocytosis (opsonization).
IgG1 and IgG3 are the most effective in inducing complement-dependent cytotoxicity. Rituximab was shown to induce CDC in many B-lymphoma cell lines, fresh
B-lymphoma cells and in in vivo studies with Macaque cynomolgus monkeys [28, 29, 30]. The increase in complement activation products during therapy with rituximab suggests that the process of complement activation is indeed involved in vivo [31]. However, it is only recently that experiments with C1q-deficient mice were performed and confirmed this hypothesis. Rituximab was uneffective in C1q-deficient mice inoculated with syngenic lymphoma cells transduced with human CD20 [32]. The similar effect was observed in SCID mice that had the complement cascade inhibited with cobra venom factor CVF [33].
Complement inhibitors are membrane proteins that protect cells from complement activation. Thus, the effectiveness of rituximab-induced CDC may also depend on the expression of complement inhibitors. Among them the most important are glycosylphosphatidylinositol (GPI) – anchored proteins: CD46, CD55, CD59. CD46 (membrane cofactor protein MCP) acts as a cofactor for the cleavage of C3b and C4b. CD55 (decay accelarating factor DAF) accelerates the decay of C3 and C5 convertases. CD59 prevents MAC deposition and pore formation.
While the positive correlation between CD20 expression level and rituximab – induced CDC has been found [34, 35], the relationship between complement inhibitors and the effectiveness of rituximab has not been established [29, 34, 36]. However, it was demonstrated in vitro that rituximab induces CDC that is related to the ratio of CD20 and complement inhibitors [35]. The in vitro functional block of CD59 and to some extent of CD55 and CD46 enhanced the ability of rituximab to induce CDC [37, 38]. In CLL patients, treated with rituximab for 8 weeks, an increase in CD59 expression in lymphoma cells was observed [39]. In CLL, resistant cells with low density of CD20 on the cell surface, along with high expression of CD59 persist and reexpand. This may explain the need for higher doses of rituximab to achieve clinically meaningful responses in patients with CLL.
Contrary to these studies analysis of tumor cells obtained from patients with follicular lymphoma showed no significant correlation between the expression of CD46, CD55 and CD59 and response to rituximab [36].
In lymphomas that are not characterized by large numbers of circulating malignant cells, such as follicular lymphoma, rituximab mainly reaches lymphoma cells outside the intravascular compartment and exerts its effects through ADCC. This observation is confirmed by experiments with SCID mice [40]. ADCC was a main mechanism of rituximab activity in mice implanted subcutaneously with Burkitt’s lymphoma [41], while in mice injected with lymphoma cells intravenously rituximab mainly exerted complement-related effects [32].


Antibody-dependent cellular cytotoxicity


Many effector cells, such as NK cells, monocytes and macrophages, play an important role in the mechanism
of cellular cytotoxicity. ADCC is an important effector mechanism in the eradication of intracellular pathogens and tumor cells. Tumor cells are mainly killed by lymphoid cells, poorly by phagocytic cells (macrophages, monocytes, granulocytes). IgG1 and IgG3, that bind to FcγRI (CD64) and FcγRIII (CD16), respectively, are the most effective
in inducing ADCC. Cross-linking of activating FcgR by
IgG-coated cells induces effector cells activation and phagocytosis, granule exocytosis and ADCC. Activating receptors such as FcγRIa, FcγRIIa, FcγRIIc i FcγRIIIa (CD16a) possess the ITAM sequences (immunoreceptor tyrosine-based activation motif) that are phosphorylated upon binding with IgG antibodies. FcγRIIb is the only one inhibitory Fc receptor that contains ITIM sequences (immunoreceptor tyrosine-based inhibitory motif). ADCC mediated through cross-linking of rituximab is considered
as a major antitumor mechanism of rituximab activity in vivo. This was supported by studies with FcγRI and RIIIa-deficient mice [41]. It was also shown that FcγRIIIa on macrophages are critical to the ability of rituximab to control subcutaneous B-cell lymphoma. The impairment of rituximab--induced ADCC was observed in a model with FcγR neutralizing antibody [42].
However, it seems that not only FcγR activating receptors play an important role in rituximab activity. FcγRIIb-deficient mice displayed a better response to antitumor activity of rituximab [41]. It was also shown that response to rituximab, especially ADCC, is associated with FcγRIIIa polymorphism. Human FCGR3A gene displays a polymorphism at 559 nucleotide that results in amino acid substitution at position 158 (with phenylalanine (F) or valine (V)). Patients with follicular lymphoma expressing the high-affinity 158V variant of the FCGR3A gene (homozygous 158 VV) had the best clinical and molecular responses to rituximab when compared with heterozygotes VF or homozygotes FF [43, 44, 45]. However, this correlation was not observed in patients with CLL [44]. It can not be excluded that also other Fcg receptors play a pivotal role in mediating the antitumor activity of rituximab. Rituximab-sensitized lymphoma cells in in vitro studies were shown to be phagocytised by macrophages with the help of FcγRIIa [35].
The interaction between the FcγR and Fc portion of rituximab is established as an important mechanism of antitumor rituximab activity. Some potential ways to increase it include the improvement by molecular engineering of affinity of rituximab for FcγRIIIa. It is widely known that glycosylation of IgG is necessary for its interaction with FcγR [46]. Hence, the modification of glycosylation such as addition of N-acetylglucosamine or removal of fucose could potentiate the monoclonal antibody-induced ADCC [47]. Also cytokines such as
IL-2, IL-12, IFN-γ, GM-CSF (granulocyte-macrophage colony-stimulating factor), G-CSF (granulocyte colony--stimulating factor) potentiate ADCC and phagocytosis by stimulation and expansion of NK cells and macrophages [48, 49, 50, 51]. IL-2 (in patients with non-Hodgkin’s lymphoma), IL-12 [52] or IFN-γ [53] were shown to potentiate the antitumor activity of rituximab.


Apoptosis


Binding of antibody with antigen may result in arrest
of cell growth (usually G0-G1 arrest) or in apoptosis.
Non-Hodgkin’s lymphomas are especially sensitive to
anti-idiotype antibodies directed against the surface immunoglobulins. There was a case of 64 years old man reported in advanced stage of lymphoma with long-term remission after the treatment with anti-idiotype antibodies.
Rituximab in many studies has been shown to induce apoptosis in certain B-cell lymphomas in vitro [54]. However, mechanism of its action remains still elusive. This effect is probably achieved through modulation of intracellular proteins resulting in increase of proapoptotic Bax and decrease of antiapoptotic Bcl-xL [55]. It has also been reported that rituximab-mediated activation of Src kinases (Fyn, Lyn, Lck) [56] results in phosphorylation of phospholipase C [57]. This activation leads to Ca2+ influx and caspase activation [58].
It has been also reported that rituximab stimulated CD20 translocation into lipid rafts [59]. Upon binding with rituximab CD20 complexes translocate into lipid rafts that are rich in cell signaling proteins, such as Src kinases. This leads to a higher concentration and cross-linking of CD20. Consequently, this translocation down-modulates the activity of Lyn kinase and thus leads to susceptibility to apoptosis. Lck and Fyn inhibitors, calcium chelators and caspase inhibitors were shown to attenuate the rituximab-induced apoptosis [58, 55]. Whereas CD20 hypercrosslinking was reported to increase Fas expression. It is not a general rule, although it is thought that CD20 cross-linking potentiates the apoptosis and in some cases it is essential to trigger apoptosis.
In one study caspase activation after treatment with rituximab was reported in patients with CLL, that support that rituximab-induced apoptosis may take place in vivo [60]. However, these results were not confirmed by other groups. In fact, even different cell lines vary in sensitivity to anti-CD20 – triggered apotosis in vitro. This sensitivity also depends on the type of antibody used [33].
However, in contrast with previously mentioned studies, it was also reported that CD20-induced apoptosis is associated with membrane changes (phosphoserine translocation), but not with DNA fragmentation and chromatin condensation. In addition, in that study apoptosis seemed to be caspase--independent, as not blocked by caspase inhibitors [61, 62].


Chemosensitizing effects


Chemotherapy is so far the most important and the most frequently used therapy of lymphomas. In many studies rituximab was shown to exert chemosensitizing effects.
It synergizes with alkylating agents (e.g. cyclophosphamide [63], chlorambucil [64], cisplatin [65]), antimetabolites (e.g. methotrexate [66], fludarabine [67], doxorubicin [63]), paclitaxel [68] or etoposide [69] in vitro. Moreover, rituximab also potentiates chemotherapy regimens such as CHOP (cyclophosphamid + doxorubicin + vincristine + prednisolone) [70, 71]. The mechanism of chemosensitization is probably connected with proapoptotic activity of rituximab and influence on intracellular proteins. Among them the most important are those implicated in regulation of cell death, such as Bcl-2, Bcl-xL, XIAP (X-linked inhibitor of apoptosis protein) and Mcl-1.
There is also another hypothesis, so far confirmed in in vitro studies. After CD20 binding rituximab leads through Src kinases to decrease in IL-10 transcription and secretion. IL-10 in B lymphocytes plays an important role of maintaning the viability of lymphocytes, even when stimulated with proapoptotic signals. IL-10 is essential for STAT3 consitutive expression, that in turn is responsible for expression of antiapoptotic Bcl-2 [72]. Hence, rituximab by decreasing Bcl-2 expression sensitizes lymphoma cells to chemotherapy. Moreover, rituximab was also reported to synergize with novel therapeutics such as anti-CD19 immunotoxin in the treatment of Burkitt’s lymphoma [73] or bortezomib in CLL treatment [74].


Rituximab in other diseases


Rituximab is widely used in the treatment of B-cell lymphoproliferative disorders. However, the accumulating data suggest that it may prove an optimal treatment in various diseases related to autoantibody production, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), dermatomyositis, idiopathic thrombocytopenia purpura, essential mixed cryoglobulinemia, hemolytic anemias. B lymphocytes appear to play a central role in the immunopathogenesis of autoimmune diseases. Rituximab was shown to be effective in RA [75], SLE [76, 77, 78] and hemolytic anemia [79, 80]. The effectiveness of rituximab in autoimmune disease is related not only to the decrease in the production of autoantibodies, but also to the inhibition of B lymphocyte-mediated antigen presentation [81].
In recent studies immunotherapy with anti-CD20 antibodies demonstrated also some eficacy in the treatment of posttransplant lymphoproliferative disorders (PTLD). PTLD are serious complication arising in solid organ transplant recipients. The incidence varies from 1-10%, depending on the type of organ transplanted, EBV infection and doses of immunosuppression [82]. Most patients develop CD20-positive malignancies. Rituximab was well tolerated by patients with PTLD when compared to standard chemotherapy [83]. Therefore rituximab appears to be beneficial as first-line therapy for PTLD.

References


1. von Mehren M, Adams GP, Weiner LM (2003): Monoclonal antibody therapy for cancer. Annu Rev Med 54: 343-369.
2. Nadler LM, Stashenko P, Hardy R et al. (1980): Serotherapy of a patient with a monoclonal antibody directed against a human lymphoma-associated antigen. Cancer Res 40: 3147-3154.
3. Tedder TF, Engel P (1994): CD20: a regulator of cell-cycle progression of B lymphocytes. Immunol Today 15: 450-454.
4. Treon SP, Pilarski LM, Belch AR et al. (2002): CD20-directed serotherapy in patients with multiple myeloma: biologic considerations and therapeutic applications. J Immunother (1997) 25: 72-81.
5. Leandro MJ, Cambridge G, Ehrenstein MR, Edwards JC (2006): Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis. Arthritis Rheum 54: 613-620.
6. Ginaldi L, De Martinis M, D’Ostilio A et al. (2001): Changes in the expression of surface receptors on lymphocyte subsets in the elderly: quantitative flow cytometric analysis. Am
J Hematol 67: 63-72.
7. Press OW, Howell-Clark J, Anderson S, Bernstein I (1994): Retention of B-cellspecific monoclonal antibodies by human lymphoma cells. Blood 83: 1390-1397.
8. Press OW, Appelbaum F, Ledbetter JA et al. (1987): Monoclonal antibody 1F5 (anti-CD20) serotherapy of human B cell lymphomas. Blood 69: 584-591.
9. Beum PV, Kennedy AD, Taylor RP (2004): Three new assays for rituximab based on its immunological activity or antigenic properties: analyses of sera and plasmas of RTX-treated patients with chronic lymphocytic leukemia and other B cell lymphomas. J Immunol Methods 289: 97-109.
10. Jilani I, O’Brien S, Manshuri T et al. (2003): Transient down-modulation of CD20 by rituximab in patients with chronic lymphocytic leukemia. Blood 102: 3514-3520.
11. Kennedy AD, Beum PV, Solga MD et al. (2004): Rituximab infusion promotes rapid complement depletion and acute CD20 loss in chronic lymphocytic leukemia. J Immunol 172: 3280-3288.
12. Cragg MS, Walshe CA, Ivanov AO, Glennie MJ (2005): The biology of CD20 and its potential as a target for mAb therapy. Curr Dir Autoimmun 8: 140-174.
13. Ishibashi K, Suzuki M, Sasaki S, Imai M (2001): Identification of a new multigene four-transmembrane family (MS4A) related to CD20, HTm4 and beta subunit of the high-affinity IgE receptor. Gene 264: 87-93.
14. Liang Y, Tedder TF (2001): Identification of a CD20-, FcepsilonRIbeta-, and HTm4-related gene family: sixteen new MS4A family members expressed in human and mouse. Genomics 72: 119-127.
15. Deans JP, Robbins SM, Polyak MJ, Savage JA (1998): Rapid redistribution of CD20 to a low density detergent-insoluble membrane compartment. J Biol Chem 273: 344-348.
16. Léveillé C, AL-Daccak R, Mourad W (1999): CD20 is physically and functionally coupled to MHC class II and CD40 on human B cell lines. Eur J Immunol 29: 65-74.
17. Dancescu M, Wu C, Rubio M et al. (1992): IL-4 induces conformational change of CD20 antigen via a protein kinase C-independent pathway. Antagonistic effect of anti-CD40 monoclonal antibody. J Immunol 148: 2411-2416.
18. Venugopal P, Sivaraman S, Huang XK et al. (2000): Effects of cytokines on CD20 antigen expression on tumor cells from patients with chronic lymphocytic leukemia. Leuk Res 24: 411-415.
19. Davis TA, Maloney DG, Grillo-López AJ et al. (2000): Combination immunotherapy of relapsed or refractory low-grade or follicular non-Hodgkin’s lymphoma with rituximab and interferon-alpha-2a. Clin Cancer Res 6: 2644-2652.
20. Rossi JF, Yang LZ, Quitett P et al. (2001): Rituximab and GM-CSF, an efective therapy for relapsed/refractory patients with low-grade B-cell lymphoma: correlation between response and dendritic cell subpopulation mobilized. Blood 98: 607a.
21. Teeling JL, Mackus WJ, Wiegman LJ et al. (2006): The biological activity of human CD20 monoclonal antibodies is linked to unique epitopes on CD20. J Immunol 177: 362-371.
22. Chow KU, Sommerlad WD, Boehrer S et al. (2002): Anti-CD20 antibody (IDEC-C2B8, rituximab) enhances efficacy of cytotoxic drugs on neoplastic lymphocytes in vitro: role of cytokines, complement, and caspases. Haematologica 87: 33-43.
23. Emmanouilides C, Jazirehi AR, Bonavida B (2002): Rituximab--mediated sensitization of B-non-Hodgkin’s lymphoma
(NHL) to cytotoxicity induced by paclitaxel, gemcitabine, and vinorelbine. Cancer Biother Radiopharm 17: 621-630.
24. Selenko N, Majdic O, Jäger U et al. (2002): Cross-priming of cytotoxic T cells promoted by apoptosis-inducing tumor cell reactive antibodies? J Clin Immunol 22: 124-130.
25. Rafiq K, Bergtold A, Clynes R (2002): Immune complex-
-mediated antigen presentation induces tumor immunity. J Clin Invest 110: 71-79.
26. Kalergis AM, Ravetch JV (2002): Inducing tumor immunity through the selective engagement of activating Fcgamma receptors on dendritic cells. J Exp Med 195: 1653-1659.
27. Olszewski AJ, Grossbard ML (2004): Empowering targeted therapy: lessons from rituximab. Sci STKE: pe30.
28. Reff ME, Carner K, Chambers KS et al. (1994): Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20. Blood 83: 435-445.
29. Flieger D, Renoth S, Beier I et al. (2000): Mechanism of cytotoxicity induced by chimeric mouse human monoclonal antibody IDEC-C2B8 in CD20-expressing lymphoma cell lines. Cell Immunol 204: 55-63.
30. Mathas S, Rickers A, Bommert K et al. (2000): Anti-CD20- and B-cell receptor-mediated apoptosis: evidence for shared intracellular signaling pathways. Cancer Res 60: 7170-7176.
31. van der Kolk LE, Grillo-López AJ, Baars JW et al. (2001): Complement activation plays a key role in the side-effects of rituximab treatment. Br J Haematol 115: 807-811.
32. Di Gaetano N, Cittera E, Nota R et al. (2003): Complement activation determines the therapeutic activity of rituximab in vivo. J Immunol 171: 1581-1587.
33. Cragg MS, Glennie MJ (2004): Antibody specificity controls in vivo effector mechanisms of anti-CD20 reagents. Blood 103: 2738-2743.
34. Golay J, Lazzari M, Facchinetti V et al. (2001): CD20 levels determine the in vitro susceptibility to rituximab and complement of B-cell chronic lymphocytic leukemia: further regulation by CD55 and CD59. Blood 98: 3383-3389.
35. Manches O, Lui G, Chaperot L et al. (2003): In vitro mechanisms of action of rituximab on primary non-Hodgkin lymphomas. Blood 101: 949-954.
36. Weng WK, Levy R (2001): Expression of complement inhibitors CD46, CD55, and CD59 on tumor cells does not predict clinical outcome after rituximab treatment in follicular non-Hodgkin lymphoma. Blood 98: 1352-1357.
37. Harjunpää A, Junnikkala S, Meri S (2000): Rituximab (anti-
-CD20) therapy of B-cell lymphomas: direct complement killing is superior to cellular effector mechanisms. Scand
J Immunol 51: 634-641.
38. Treon SP, Mitsiades C, Mitsiades N et al. (2001): Tumor Cell Expression of CD59 Is Associated With Resistance to CD20 Serotherapy in Patients With B-Cell Malignancies. J Immunother 24: 263-271.
39. Cragg MS, Morgan SM, Chan HT et al. (2003): Complement-mediated lysis by anti-CD20 mAb correlates with segregation into lipid rafts. Blood 101: 1045-1052.
40. Hernandez-Ilizaliturri FJ, Jupudy V, Ostberg J et al. (2003): Neutrophils contribute to the biological antitumor activity of rituximab in a non-Hodgkin’s lymphoma severe combined immunodeficiency mouse model. Clin Cancer Res 9: 5866-5873.
41. Clynes RA, Towers TL, Presta LG, Ravetch JV (2000): Inhibitory Fc receptors modulate in vivo cytoxicity against tumor targets. Nat Med 6: 443-446.
42. Funakoshi S, Longo DL, Murphy WJ (1996): Differential in vitro and in vivo antitumor effects mediated by anti-CD40 and anti-
-CD20 monoclonal antibodies against human B-cell lymphomas. J Immunother Emphasis Tumor Immunol 19: 93-101.
43. Koene HR, Kleijer M, Algra J et al. (1997): Fc gammaRIIIa--158V/F polymorphism influences the binding of IgG
by natural killer cell Fc gammaRIIIa, independently of the
Fc gammaRIIIa-48L/R/H phenotype. Blood 90: 1109-1114.
44. Cartron G, Dacheux L, Salles G et al. (2002): Therapeutic activity of humanized anti-CD20 monoclonal antibody and polymorphism in IgG Fc receptor FcgammaRIIIa gene. Blood 99: 754-758.
45. Weng WK, Levy R (2003): Two immunoglobulin G fragment C receptor polymorphisms independently predict response to rituximab in patients with follicular lymphoma. J Clin Oncol 21: 3940-3947.
46. Wright A, Morrison SL (1997): Effect of glycosylation on antibody function: implications for genetic engineering. Trends Biotechnol 15: 26-32.
47. Shinkawa T, Nakamura K, Yamane N et al. (2003): The absence of fucose but not the presence of galactose or bisecting N-acetylglucosamine of human IgG1 complex-type oligosaccharides shows the critical role of enhancing antibody-dependent cellular cytotoxicity. J Biol Chem 278: 3466-3473.
48. Wing EJ, Magee DM, Whiteside TL et al. (1989): Recombinant human granulocyte/macrophage colony-stimulating factor enhances monocyte cytotoxicity and secretion of tumor
necrosis factor alpha and interferon in cancer patients. Blood 73: 643-646.
49. Herberman RB, Ortaldo JR, Mantovani A et al. (1982): Effect of human recombinant interferon on cytotoxic activity of natural killer (NK) cells and monocytes. Cell Immunol
67: 160-167.
50. Phillips JH, Lanier LL (1986): Dissection of the lymphokine-
-activated killer phenomenon. Relative contribution of peripheral blood natural killer cells and T lymphocytes to cytolysis. J Exp Med 164: 814-825.
51. Trinchieri G (2003): Interleukin-12 and the regulation of innate resistance and adaptive immunity. Nat Rev Immunol 3: 133-146.
52. Ansell SM, Witzig TE, Kurtin PJ et al. (2002): Phase 1 study of interleukin-12 in combination with rituximab in patients with B-cell non-Hodgkin lymphoma. Blood 99: 67-74.
53. Sacchi S, Federico M, Vitolo U et al. (2001): Clinical activity and safety of combination immunotherapy with IFN-alpha 2a and Rituximab in patients with relapsed low grade non-Hodgkin’s lymphoma. Haematologica 86: 951-958.
54. Shan D, Ledbetter JA, Press OW (1998): Apoptosis of malignant human B cells by ligation of CD20 with monoclonal antibodies. Blood 91: 1644-1652.
55. Shan D, Ledbetter JA, Press OW (2000): Signaling events involved in anti-CD20-induced apoptosis of malignant human B cells. Cancer Immunol Immunother 48: 673-683.
56. Deans JP, Kalt L, Ledbetter JA et al. (1995): Association of 75/80-kDa phosphoproteins and the tyrosine kinases Lyn, Fyn, and Lck with the B cell molecule CD20. Evidence against involvement of the cytoplasmic regions of CD20. J Biol Chem 270: 22632-22638.
57. Deans JP, Schieven GL, Shu GL et al. (1993): Association
of tyrosine and serine kinases with the B cell surface antigen CD20. Induction via CD20 of tyrosine phosphorylation and activation of phospholipase C-gamma 1 and PLC phospholipase C-gamma 2. J Immunol 151: 4494-4504.
58. Hofmeister JK, Cooney D, Coggeshall KM (2000): Clustered CD20 induced apoptosis: src-family kinase, the proximal regulator of tyrosine phosphorylation, calcium influx, and caspase 3-dependent apoptosis. Blood Cells Mol Dis 26: 133-143.
59. Deans JP, Li H, Polyak MJ et al. (2002): CD 20-mediated apoptosis: signalling through lipid rafts. Immunology 107: 176-182.
60. Byrd JC, Kitada S, Flinn IW et al. (2002): The mechanism of tumor cell clearance by rituximab in vivo in patients with
B-cell chronic lymphocytic leukemia: evidence of caspase activation and apoptosis induction. Blood 99: 1038-1043.
61. Chan HT, Hughes D, French RR et al. (2003): CD20-induced lymphoma cell death is independent of both caspases and its redistribution into triton X-100 insoluble membrane rafts. Cancer Res 63: 5480-5489.
62. van der Kolk LE, Evers LM, Omene C et al. (2002): CD20-
-induced B cell death can bypass mitochondria and caspase activation. Leukemia 16: 1735-1744.
63. Wöhrer S, Troch M, Zwerina J et al. (2007): Influence of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone on serologic parameters and clinical course
in lymphoma patients with autoimmune diseases. Ann Oncol 18: 647-651.
64. Martinelli G, Laszlo D, Bertolini F et al. (2003): Chlorambucil in combination with induction and maintenance rituximab is feasible and active in indolent non-Hodgkin’s lymphoma.
Br J Haematol 123: 271-277.
65. Machover D, Delmas-Marsalet B, Misra SC et al. (2001): Dexamethasone, high-dose cytarabine, and oxaliplatin (DHAOx) as salvage treatment for patients with initially refractory or relapsed non-Hodgkin’s lymphoma. Ann Oncol 12: 1439-1443.
66. Romaguera JE, Fayad L, Rodriguez MA et al. (2005): High rate of durable remissions after treatment of newly diagnosed aggressive mantle-cell lymphoma with rituximab plus
hyper-CVAD alternating with rituximab plus high-dose methotrexate and cytarabine. J Clin Oncol 23: 7013-7023.
67. Tam CS, Wolf M, Prince HM et al. (2006): Fludarabine, cyclophosphamide, and rituximab for the treatment of patients with chronic lymphocytic leukemia or indolent non-Hodgkin lymphoma. Cancer 106: 2412-2420.
68. Jazirehi AR, Gan XH, De Vos S et al. (2003): Rituximab (anti--CD20) selectively modifies Bcl-xL and apoptosis protease activating factor-1 (Apaf-1) expression and sensitizes human non-Hodgkin’s lymphoma B cell lines to paclitaxel-induced apoptosis. Mol Cancer Ther 2: 1183-1193.
69. Gasparetto M, Gentry T, Sebti S et al. (2004): Identification of compounds that enhance the anti-lymphoma activity of rituximab using flow cytometric high-content screening.
J Immunol Methods 292: 59-71.
70. Zaja F, Tomadini V, Zaccaria A et al. (2006): CHOP-rituximab with pegylated liposomal doxorubicin for the treatment of elderly patients with diffuse large B-cell lymphoma. Leuk Lymphoma 47: 2174-2180.
71. Jermann M, Jost LM, Taverna Ch et al. (2004): Rituximab-
-EPOCH, an effective salvage therapy for relapsed, refractory or transformed B-cell lymphomas: results of a phase II study. Ann Oncol 15: 511-516.
72. Vega MI, Huerta-Yepaz S, Garban H et al. (2004): Rituximab inhibits p38 MAPK activity in 2F7 B NHL and decreases
IL-10 transcription: pivotal role of p38 MAPK in drug resistance. Oncogene 23: 3530-3540.
73. Flavell DJ, Warnes SL, Bryson CJ et al. (2006): The anti-CD20 antibody rituximab augments the immunospecific therapeutic effectiveness of an anti-CD19 immunotoxin directed against human B-cell lymphoma. Br J Haematol 134: 157-170.
74. Smolewski P, Duechler M, Linke A et al. (2006): Additive cytotoxic effect of bortezomib in combination with anti-CD20 or anti-CD52 monoclonal antibodies on chronic lymphocytic leukemia cells. Leuk Res 30: 1521-1529.
75. Leandro MJ, Edwards JC, Cambridge G (2002): Clinical outcome in 22 patients with rheumatoid arthritis treated with B lymphocyte depletion. Ann Rheum Dis 61: 883-888.
76. Leandro MJ, Edwards JC, Cambridge G et al. (2002): An open study of B lymphocyte depletion in systemic lupus erythematosus. Arthritis Rheum 46: 2673-2677.
77. Weide R, Heymanns J, Pandorf A, Köppler H (2003): Successful long-term treatment of systemic lupus erythematosus with rituximab maintenance therapy. Lupus 12: 779-782.
78. Looney RJ, Anolik J, Sanz I (2005): Treatment of SLE
with anti-CD20 monoclonal antibody. Curr Dir Autoimmun 8: 193-205.
79. Zecca M, Nobili B, Ramenghi U et al. (2003): Rituximab for the treatment of refractory autoimmune hemolytic anemia in children. Blood 101: 3857-3861.
80. Wakim M, Shah A, Arndt PA et al. (2004): Successful anti-
-CD20 monoclonal antibody treatment of severe autoimmune hemolytic anemia due to warm reactive IgM autoantibody
in a child with common variable immunodeficiency. Am
J Hematol 76: 152-155.
81. Eisenberg R, Looney RJ (2005): The therapeutic potential of anti-CD20 “what do B-cells do?”. Clin Immunol 117: 207-213.
82. Blaes AH, Peterson BA, Bartlett N et al. (2005): Rituximab therapy is effective for posttransplant lymphoproliferative disorders after solid organ transplantation: results of a phase II trial. Cancer 104: 1661-1667.
83. Oertel SH, Verschuuren E, Reinke P et al. (2005): Effect of anti-CD 20 antibody rituximab in patients with post-transplant lymphoproliferative disorder (PTLD). Am J Transplant 5: 2901-2906.
Copyright: © 2007 Polish Society of Experimental and Clinical Immunology This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) License (http://creativecommons.org/licenses/by-nc-sa/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material, provided the original work is properly cited and states its license.
Quick links
© 2019 Termedia Sp. z o.o. All rights reserved.
Developed by Bentus.
PayU - płatności internetowe