Improvement of Rituximab Efficiency in Chronic Lymphocytic Leukemia by CpG‐Mediated Upregulation of CD20 Expression Independently of PU.1

Abstract

Lipopolysaccharide (LPS), CpG-containing phosphothioate oligonucleotides (CpG) and various cytokines impact chronic lymphocytic leukemia (CLL) B cells. For example, they influence cell cycle entry, expression of co-receptors, and CD20. Rituximab (RTX), for which CD20 molecule is the target, proved to be less efficient in CLL than in lymphoma. This is accounted for by a lower CD20 level in the former than in the latter B lymphocytes. CD20 transcription is mediated by four transcription factors, of which only purine-rich box-1 (PU.1) is reduced in CLL. We thus examined the effects of LPS, CpG, tumor necrosis factor-alpha, interferon-alpha, interleukin (IL)-3, IL-4, IL-21, granulocyte macrophage-colony stimulating factor (CSF), and granulocyte-CSF on the transcription of PU.1, and the subsequent expression of CD20. It appeared that CpG was unique in that it raised the membrane expression of CD20 on malignant B cells, owing to a PU.1 independent increase in its gene transcription. Moreover, RTX-induced complement-mediated lysis was also ameliorated. Thus, CpG accelerates the transcription of CD20 independently of PU.1, and thereby improves the efficacy of RTX in CLL.

Development of a Murine model to dissect the CpG-oligonucleotide-enhancement of the killing of human B Cells by rituximab

“…Firstly, as described in CLL [27], we confirmed that CpG impact the first wave of effector cells by up-regulating the membrane expression of CD20 target molecules of Daudi human B cells (Fig. 1B left), and by inducing them into apoptosis through TLR9 with no effect on the density (Fig.…”

TLR9 Ligand Induces the Generation of CD20+ Plasmablasts and Plasma Cells from CD27+ Memory B-Cells

“…MM cells have been shown to express TLR9 and to respond to CpG ODN by increased proliferation and survival (Bohnhorst et al, 2006; Jego et al, 2006). In chronic lymphoid leukemia, a CD20+ neoplasm, CpG ODN was shown to increase the level of CD20 expression after 24–48 h (Mankaï et al, 2009). To assess whether CpG ODN could induce or increase CD20 expression in myeloma cells, eight TLR9+CD20− HMCLs, BCN, JIM3, MDN, NCI-H929, RPMI8226, SBN, U266 and XG6, and one TLR9+CD20+ HMCL, Karpas 620, were cultured for 2 days with 5 μg/ml CpG ODN 2006.…”

“…In malignant and normal B-cells, CpG ODN increase CD20 expression at both protein and mRNA levels but the mechanism(s) are not known (Jahrsdörfer et al, 2001; Mankaï et al, 2009). The effect of CpG ODN is more difficult to analyze in our study because cells differentiate and loose their CD20 phenotype during this process.…”

Prenyltransferases Regulate CD20 Protein Levels and Influence Anti-CD20 Monoclonal Antibody-mediated Activation of Complement-dependent Cytotoxicity

“…Transcriptional up-regulation of CD20 dependent on ERK phosphorylation was reported by Wojciechowski et al (30) in lymphoma and primary CLL cells treated with bryostatin-1. An increase in CD20 transcription was also shown to be triggered by CpG independently of PU.1 transcription factor in CLL cells (31). Epigenetic therapy also was reported to restore CD20 mRNA expression, a phenomenon observed in CD20-negative cells (15).…”