The NFKBIE gene, which encodes the NF-κB inhibitor IκBε, is mutated in 3-7% of patients with chronic lymphocytic leukemia (CLL). The most recurrent alteration is a 4-bp frameshift deletion associated with NF-κB activation in leukemic B cells and poor clinical outcome. To study the functional consequences of NFKBIE gene inactivation, both in vitro and in vivo, we engineered CLL B cells and CLL-prone mice to stably down-regulate NFKBIE expression and investigated its role in controlling NF-κB activity and disease expansion. We found that IκBε loss leads to NF-κB pathway activation and promotes both migration and proliferation of CLL cells in a dose-dependent manner. Importantly, NFKBIE inactivation was sufficient to induce a more rapid expansion of the CLL clone in lymphoid organs and contributed to the development of an aggressive disease with a shortened survival in both xenografts and genetically modified mice. IκBε deficiency was associated with an alteration of the MAPK pathway, also confirmed by RNA-sequencing in NFKBIE-mutated patient samples, and resistance to the BTK inhibitor ibrutinib. In summary, our work underscores the multimodal relevance of the NF-κB pathway in CLL and paves the way to translate these findings into novel therapeutic options.

Centre for Research and Technology Hellas Thessaloniki Greece

Clinical Genetics and Genomics Karolinska University Hospital Stockholm Sweden

Department of Molecular Medicine and Surgery Karolinska Institutet Stockholm Sweden

Erasmus MC Rottherdam Netherlands

Institution Université Pierre et Marie Curie and Hôpital Pitié Salpêtrière Paris France

IRCSS Ospedale San Raffaele Milan Italy

Masaryk University Brno Czech Republic

Mayo Clinic Rochester USA

University Hospital Brno Brno Czech Republic

Vita Salute San Raffaele University Milan Italy

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