Abstract
Sequential stages of B-cell development is stringently coordinated by transcription factors (TFs) network that include B-lineage commitment TFs (Ikaros, Runx1/Cbfb, E2A, and FOXO1), B-lineage maintenance TFs (EBF1and PAX5) and stage specific set of TFs (IRF4, IRF8, BCL6, BLIMP1). Deregulation of TFs expression and activity is often occurs in malignant B cells. The aim of this study was to evaluate TFs expression in chronic lymphocytic leukemia cells taking into consideration CD150cell surface expression. From other side we attempted to regulate TFs expression via CD150and CD180cell surface receptors. Studies were performed on normal peripheral blood B-cell subpopulations and chronic lymphocytic leukemia(CLL) cells isolated from peripheral blood of 67primary untreated patients with CLL. Evaluation of TFs expression was performed on mRNA level using qRT-PCR and on protein level by western blot analysis. Median of PAX5and EBF1mRNA expression was higher in cell surface CD150positive (csCD150+) compared to csCD150- CLL cases or normal CD19+ and CD19+CD5+ B-cell subsets. Differences in mRNA expression of IRF8, IRF4and BLIMP1between studied groups of CLL and normal B cells were not revealed. All CLL cases were characterized by downregulated expression of PU.1and BCL6mRNAs in comparison to normal B cells. At the same time elevated SPIB mRNA expression level was restricted to CLL cells. Protein expression of IRF4, IRF8 and BCL6was uniformly distributed between csCD150- and csCD150+ CLL cases. PU.1protein and CD20that is direct PU.1target gene positively correlated with CD150cell surface expression on CLL cells. Ligation of CD150and CD180alone or in combination upregulated IRF8and PU.1while downregulated the IRF4mRNA expression. Signaling via CD150or CD180alone elevated the level of BCL6mRNA. Strong downregulation of IRF4mRNA was observed after CD150, CD180or CD150 andCD180 coligation on CLL cells. We found that in CLL cells CD150is a negative regulator of SPIB while CD180is involved in upregulation of EBF1expression level. Moreover, CD180ligation on CLL cells caused increase of CD150mRNA level that is a one of the EBF1 target genes. Analysis of TFs expression profile revealed upregulated SPIB mRNA level and downregulated PU.1 inCLL cells. CD150and CD180receptors may modulate transcriptional program in CLL cells by regulating the TFs expression levels.
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