Endogenous APOBEC3B Overexpression Constitutively Generates DNA Substitutions and Deletions in Myeloma Cells
Endogenous APOBEC3B Overexpression Constitutively Generates DNA Substitutions and Deletions in Myeloma Cells
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DOI：
10.1038/s41598-019-43575-y
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发表时间：
2019-05-09
影响因子：
4.6
通讯作者：
Takaori-Kondo, Akifumi
中科院分区：
文献类型：
--
作者：
Yamazaki, Hiroyuki;Shirakawa, Kotaro;Takaori-Kondo, Akifumi
载脂蛋白B mrna编辑酶催化多肽样（APOBEC） DNA胞嘧啶脱氨酶已成为各种癌症中潜在的基因组突变体。多发性骨髓瘤在病程中积累APOBEC特征突变；然而，APOBEC特征获取的机制及其后果仍然难以捉摸。在本研究中，我们研究了APOBEC3B （A3B）活性在多发性骨髓瘤中的意义和临床影响。在APOBECs中，只有高表达的A3B与骨髓瘤患者的不良预后相关，与其他已知的不良预后因素无关。定量PCR结果显示，cd138阳性的原发性骨髓瘤细胞和骨髓瘤细胞系具有显著高的A3B表达水平。有趣的是，慢病毒A3B敲低阻止了外源DNA中缺失和功能丧失突变的产生，而在对照细胞中，这些突变随着时间的推移而积累。A3B敲低也降低了γ - h2ax病灶的基础水平，表明A3B促进骨髓瘤细胞的组成性DNA双链断裂。重要的是，在shrna转导的对照细胞中，我们观察到在骨髓瘤中存在多种外源基因突变和几种内源基因突变的克隆，包括TP53。综上所述，研究结果表明，A3B使肿瘤基因组发生结构性突变，超出了DNA修复系统的保护，这可能导致骨髓瘤的克隆进化和基因组不稳定。
Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) DNA cytosine deaminases have emerged as potential genomic mutators in various cancers. Multiple myeloma accumulates APOBEC signature mutations as it progresses; however, the mechanisms underlying APOBEC signature acquisition and its consequences remain elusive. In this study, we examined the significance and clinical impact of APOBEC3B (A3B) activity in multiple myeloma. Among APOBECs, only highly expressed A3B was associated with poor prognosis in myeloma patients, independent of other known poor prognostic factors. Quantitative PCR revealed that CD138-positive primary myeloma cells and myeloma cell lines exhibited remarkably high A3B expression levels. Interestingly, lentiviral A3B knockdown prevented the generation of deletion and loss-of-function mutations in exogenous DNA, whereas in control cells, these mutations accumulated with time. A3B knockdown also decreased the basal levels of gamma-H2AX foci, suggesting that A3B promotes constitutive DNA double-strand breaks in myeloma cells. Importantly, among control shRNA-transduced cells, we observed the generation of clones that harboured diverse mutations in exogenous genes and several endogenous genes frequently mutated in myeloma, including TP53. Taken together, the results suggest that A3B constitutively mutates the tumour genome beyond the protection of the DNA repair system, which may lead to clonal evolution and genomic instability in myeloma.