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Basal NF-κB inhibition impacts BCR responsiveness in CLL
EBF1 was significantly downregulated in patients with CLL compared to conventional B cells.41 It was suggested that the low expression of EBF1 might result in reduced levels of B-cell signaling and might contribute to an aner- gic phenotype of CLL cells.41 Our results showing a lower level of EBF1 transcripts in unresponsive cases would sup- port this theory. Future studies are required to elucidate the importance of EBF1 in CLL pathogenesis.
In summary, our results indicate that responsive CLL cases, irrespective of IGHV SHM status, have a more activat- ed phenotype and reduced basal expression of several regu- latory molecules of the canonical NF-kB pathway including those associated with NF-kB inhibition. Upon α-IgM stimu- lation these responsive cases showed upregulation of NF-kB, including NF-kB inhibitors, whereas transcriptional levels of NF-kB signaling pathway components remained unaltered in unresponsive cases. Our findings suggest that enhanced basal NF-kB inhibition may be strongly associated with a lower capacity of CLL cells to respond to BCR stimulation and the survival of anergic CLL cells.
Acknowledgments
The authors would like to thank: Prof. Andre Uitterlinden, Mila Jahmai, Pascal Arp and Joost Verlouw (HuGeF laboratory, Dept. of Internal Medicine, Erasmus MC) for RNA-sequencing our samples and for the alignment and annotation of the raw data; Prof. Hassan Jumaa and Marcus Dühren-von Minden (Dept. of Molecular Immunology, Biology III, Faculty of Biology, Albert-Ludwigs University, Freiburgny) for helping with the TKO experiments which were performed in their department; Odilia Corneth (Dept. of Pulmonary Diseases, Erasmus MC) for her help in optimizing the Phosphoflow experiments; Larry Mansouri (Dept. of Immunology, Genetics and Pathology, Uppsala University) for sharing information regarding the pro- tocol used for NFKBIE sequencing; and Jorn Assmann (Dept. of Immunology, Erasmus MC) for technical assistance.
AFM was awarded with an EMBO Short Term Fellowship, a Dutch Society for Immunology (NVVI) grant, and an Erasmus Trust Fund grant. This work was financially supported by an unrestricted research grant from F. Hoffmann-La Roche (Basel, Switzerland) to AWL.
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