The CDK4/6-UCHL5-BRD4 axis confers resistance to BET inhibitors in MLL-rearranged leukemia cells by suppressing BRD4 protein degradation
The CDK4/6-UCHL5-BRD4 axis confers resistance to BET inhibitors in MLL-rearranged leukemia cells by suppressing BRD4 protein degradation
复制标题
DOI：
10.1016/j.bbrc.2021.12.063
复制
发表时间：
2021-12-24
影响因子：
3.1
通讯作者：
Ashihara, Eishi
中科院分区：
文献类型：
--
作者：
Amari, Keigo;Sasagawa, Satoru;Ashihara, Eishi
在急性白血病中，混合谱系白血病重排（MLL-r）白血病与预后不良相关。溴结构域和末端外抑制剂（BETi）是用于治疗血液恶性肿瘤的有前景的药剂;然而，对BETi的潜在敏感性的机制和预测敏感性的生物标志物尚未阐明。在这里，我们建立了OTX 015耐药性MLL-r细胞系（OTX 015-R细胞），并使用它们来探索BETi耐药性MLL-r白血病的治疗靶点。OTX 015-R细胞对各种BETi表现出耐药性，相对于亲代细胞，OTX 015-R细胞中含溴结构域蛋白4（BRD 4）和BRD 4调节分子（例如c-MYC和B细胞/CLL淋巴瘤-2（BCL-2））的水平显着增加;然而，BRD 4 mRNA转录水平并未升高。这些结果表明，BRD 4蛋白的过表达，通过抑制BRD 4降解，可能有助于BETi抗性。OTX 015-R细胞中泛素羧基末端水解酶同工酶L5（UCHL 5）的表达明显增加。此外，UCHL 5抑制剂b-AP 15和UCHL 5敲低通过降解BRD 4具有抗肿瘤作用。此外，在用b-AP 15预处理的OTX 015-R细胞中，对OTX 015的敏感性部分恢复。此外，细胞周期蛋白依赖性激酶4/6（CDK 4/6）抑制降低UCHL 5的表达，抑制OTX 015-R细胞增殖，并诱导凋亡。这些结果表明CDK 4/6-UCHL 5-BRD 4轴通过抑制BRD 4降解来赋予对BETi的抗性。我们认为该通路是BRD 4过表达的BETi耐药MLL-r白血病的潜在新治疗靶点。(c)2021年由Elsevier Inc.出版
Among acute leukemias, mixed-lineage leukemia-rearranged (MLL-r) leukemia is associated with poor prognosis. Bromodomain and extra-terminal inhibitors (BETi) are promising agents for treatment of hematological malignancies; however, the mechanisms underlying sensitivity to BETi and biomarkers to predict sensitivity are yet to be clarified. Here, we established OTX015-resistant MLL-r cell lines (OTX015-R cells) and used them to explore therapeutic targets in BETi-resistant MLL-r leukemia. OTX015-R cells exhibited resistance to various BETi, and levels of bromodomain-containing protein 4 (BRD4) and BRD4-regulated molecules, such as c-MYC and B-cell/CLL lymphoma-2 (BCL-2), were remarkably increased in OTX015-R cells relative to those in the parental cells; however, BRD4 mRNA transcript levels were not elevated. These results suggest that overexpression of BRD4 protein, through suppression of BRD4 degradation, may contribute to BETi-resistance. Notably, expression of ubiquitin carboxyl-terminal hy-drolase isozyme L5 (UCHL5) was increased in OTX015-R cells. Further, a UCHL5 inhibitor, b-AP15, and UCHL5 knockdown had antitumor effects by degrading BRD4. In addition, sensitivity to OTX015 was partially recovered in OTX015-R cells pretreated with b-AP15. Furthermore, cyclin-dependent kinase 4/6 (CDK4/6) inhibition decreased UCHL5 expression, suppressed OTX015-R cell proliferation, and induced apoptosis. These results indicate that the CDK4/6-UCHL5-BRD4 axis confers resistance to BETi by sup -pressing BRD4 degradation. We propose that this pathway is a potential novel therapeutic target in BETi-resistant MLL-r leukemia with BRD4 overexpression. (c) 2021 Published by Elsevier Inc.