BIRC3 is monoallelically deleted in up to 80% of chronic lymphocytic leukemia (CLL) cases harboring del(11q). In addition, truncating mutations in the remaining allele of this gene can lead to BIRC3 biallelic inactivation, which has been shown to be a marker for reduced survival in CLL. Nevertheless, the biological mechanisms by which these lesions could contribute to del(11q) CLL pathogenesis and progression are partially unexplored. We implemented the CRISPR/Cas9-editing system to generate isogenic CLL cell lines harboring del(11q) and/or BIRC3 mutations, modeling monoallelic and biallelic BIRC3 loss. Our results reveal that monoallelic BIRC3 deletion in del(11q) cells promotes non-canonical NF-κB signaling activation via RelB-p52 nuclear translocation, being these effects allelic dose-dependent and therefore further enhanced in del(11q) cells with biallelic BIRC3 loss. Moreover, we demonstrate ex vivo in primary cells that del(11q) cases including BIRC3 within their deleted region show evidence of non-canonical NF-κB activation which correlates with high BCL2 levels and enhanced sensitivity to venetoclax. Furthermore, our results show that BIRC3 mutations in del(11q) cells promote clonal advantage in vitro and accelerate leukemic progression in an in vivo xenograft model. Altogether, this work highlights the biological bases underlying disease progression of del(11q) CLL patients harboring BIRC3 deletion and mutation.

BIRC3在多达 80% 的慢性淋巴细胞白血病 (CLL) 病例中被单等位基因缺失，其中包含 del(11q)。此外，该基因剩余等位基因的截短突变可导致BIRC3 双等位基因失活，这已被证明是 CLL 存活率降低的标志。然而，这些病变可能导致 del(11q) CLL 发病机制和进展的生物学机制部分尚未探索。我们实施了 CRISPR/Cas9 编辑系统以生成带有 del(11q) 和/或BIRC3突变的同基因 CLL 细胞系，模拟单等位基因和双等位基因BIRC3丢失。我们的结果表明单等位基因BIRC3del(11q) 细胞中的缺失通过 RelB-p52 核易位促进非经典 NF-κB 信号激活，这些效应具有等位基因剂量依赖性，因此在双等位基因BIRC3缺失的 del(11q) 细胞中进一步增强。此外，我们在原代细胞中证明了在其缺失区域内包括BIRC3的 del(11q) 病例显示出非典型 NF-κB 激活的证据，这与高 BCL2 水平和对维奈托克的敏感性增强相关。此外，我们的结果表明， del(11q) 细胞中的BIRC3突变在体外促进了克隆优势，并在体内异种移植模型中加速了白血病进展。总而言之，这项工作强调了 del(11q) CLL 患者疾病进展的生物学基础BIRC3缺失和突变。