基于全反式维甲酸(ATRA)的急性早幼粒细胞白血病(APL)的分化治疗是精准医学最有效的临床实例之一,也是靶向癌蛋白降解的第一个实例。ATRA在APL的成功,然而,仍有待转化为非APL急性髓系白血病(AML)。我们之前证明了异常的组蛋白修饰,包括组蛋白H3赖氨酸4(H3K4)和赖氨酸27(H3K27)甲基化,与这种缺乏反应相关,并且使用H3K4脱甲基酶LSD1/KDM1A的小分子抑制剂的表观遗传疗法可以重新编程AML细胞以响应ATRA。EZH2/KMT6A甲基转移酶作为Polycomb抑制复合物2的酶成分,通过影响自我更新和分化之间的平衡,在正常造血中起关键作用。EZH2的典型功能是H3K27的甲基化,尽管最近已经描述了重要的非典型作用。EZH2突变或表达失调已在AML的发病机制和治疗反应中得到了决定性的证明。从而使其成为一个有吸引力的治疗靶点。在这项研究中,因此,我们研究了抑制EZH2是否也可能改善非APLAML细胞对ATRA治疗的应答.我们专注于GSK-343,一种含吡啶酮的S-腺苷-L-甲硫氨酸辅因子竞争性EZH2抑制剂,代表其类别,和HKMTI-1-005,一种针对EZH2和密切相关的G9A/GLPH3K9甲基转移酶的底物竞争性双重抑制剂。我们发现,尽管GSK-343在消除H3K27三甲基化方面具有功效,但HKMTI-1-005表型治疗可降低EZH2,并且在诱导分化方面比GSK-343更有效。此外,转录组学分析显示,与用GSK-343处理相反,HKMTI-1-005在有和没有ATRA的情况下上调分化途径基因的表达,同时下调与造血干细胞表型相关的基因。这些结果指出了EZH2的非规范作用,这得到了EZH2与骨髓分化的主要调节因子相关的发现的支持。RARα,以ATRA依赖性方式被HKMTI-1-005增强,可能在转录激活过程中的共调节复合物交换中发挥作用。总之,我们的结果强烈表明,在ATRA中加入HKMTI-1-005是一种新的AML治疗方法,值得进一步研究.
All-trans-retinoic acid (ATRA)-based differentiation therapy of acute promyelocytic leukemia (APL) represents one of the most clinically effective examples of precision medicine and the first example of targeted oncoprotein degradation. The success of ATRA in APL, however, remains to be translated to non-APL acute myeloid leukemia (AML). We previously showed that aberrant histone modifications, including histone H3 lysine 4 (H3K4) and lysine 27 (H3K27) methylation, were associated with this lack of response and that epigenetic therapy with small molecule inhibitors of the H3K4 demethylase LSD1/KDM1A could reprogram AML cells to respond to ATRA. Serving as the enzymatic component of Polycomb Repressive Complex 2, EZH2/KMT6A methyltransferase plays a critical role in normal hematopoiesis by affecting the balance between self-renewal and differentiation. The canonical function of EZH2 is methylation of H3K27, although important non-canonical roles have recently been described. EZH2 mutation or deregulated expression has been conclusively demonstrated in the pathogenesis of AML and response to treatment, thus making it an attractive therapeutic target. In this study, we therefore investigated whether inhibition of EZH2 might also improve the response of non-APL AML cells to ATRA-based therapy. We focused on GSK-343, a pyridone-containing S-adenosyl-L-methionine cofactor-competitive EZH2 inhibitor that is representative of its class, and HKMTI-1-005, a substrate-competitive dual inhibitor targeting EZH2 and the closely related G9A/GLP H3K9 methyltransferases. We found that treatment with HKMTI-1-005 phenocopied EZH2 knockdown and was more effective in inducing differentiation than GSK-343, despite the efficacy of GSK-343 in terms of abolishing H3K27 trimethylation. Furthermore, transcriptomic analysis revealed that in contrast to treatment with GSK-343, HKMTI-1-005 upregulated the expression of differentiation pathway genes with and without ATRA, while downregulating genes associated with a hematopoietic stem cell phenotype. These results pointed to a non-canonical role for EZH2, which was supported by the finding that EZH2 associates with the master regulator of myeloid differentiation, RARα, in an ATRA-dependent manner that was enhanced by HKMTI-1-005, possibly playing a role in co-regulator complex exchange during transcriptional activation. In summary, our results strongly suggest that addition of HKMTI-1-005 to ATRA is a new therapeutic approach against AML that warrants further investigation.