Inhibition of the LSD1 (KDM1A) demethylase reactivates the all-trans-retinoic acid differentiation pathway in acute myeloid leukemia [Illumina HumanHT-12 gene expression array]. Homo sapiens

All-trans-retinoic acid (ATRA) has been successfully used in therapy of acute promyelocytic leukemia (APL), a cytogenetically distinct subtype of acute myeloid leukemia (AML) but the response of non-APL AML cases to ATRA-based treatment has been poor. Here we show that, via epigenetic reprogramming, inhibitors of LSD1/KDM1 demethylase including tranylcypromine (TCP) unlocked the ATRA-driven therapeutic response in non-APL AML. LSD1 inhibition did not lead to an increase in genome-wide H3 lysine4 dimethylation (H3K4me2) but did increase H3K4me2 and expression of myeloid differentiation-associated genes. Importantly, treatment with ATRA plus TCP dramatically diminished engraftment of primary human AML cells in vivo in NOD.SCID mice, suggesting that ATRA in combination with TCP may target leukemia-initiating cells. Furthermore, initiation of ATRA plus TCP co-treatment 15 days post-engraftment of human AML cells in NOD.SCID gamma mice also revealed the ATRA plus TCP drug combination to have a potent anti-leukemic effect, which was superior to treatment with either drug alone. These data identify LSD1 as a therapeutic target and strongly suggest that it may contribute to AML pathogenesis by inhibiting the normal pro-differentiative function of ATRA, paving the way for novel combinatorial therapies of AML. Overall design: Overall, 30 specimens derived from HL-60 or TEX cell line were treated with drugs and hybridized to Illumina HumanHT-12 gene expression arrays.

全反式维甲酸（All-trans-retinoic acid, ATRA）已成功应用于急性早幼粒细胞白血病（acute promyelocytic leukemia, APL）的治疗——后者是一类具有独特细胞遗传学特征的急性髓系白血病（acute myeloid leukemia, AML）亚型，但非APL型AML患者对以ATRA为基础的治疗应答不佳。本研究表明，通过表观遗传重编程，LSD1/KDM1去甲基化酶抑制剂（包括反苯环丙胺（tranylcypromine, TCP)）可在非APL型AML中恢复ATRA驱动的治疗应答。LSD1抑制并未引发全基因组范围内组蛋白H3赖氨酸4二甲基化（H3 lysine4 dimethylation, H3K4me2）水平升高，却可提升髓系分化相关基因的H3K4me2修饰水平与表达量。值得注意的是，ATRA联合TCP治疗可显著降低NOD.SCID小鼠（NOD.SCID mice）体内原代人AML细胞的定植能力，提示ATRA与TCP联合疗法或可靶向白血病起始细胞。此外，在人AML细胞植入NOD.SCID伽马小鼠（NOD.SCID gamma mice）后的15天启动ATRA联合TCP治疗，同样证实该联合疗法具有强效的抗白血病作用，其效果优于任一单一药物治疗。上述数据确认LSD1可作为治疗靶点，并强烈提示LSD1或通过抑制ATRA正常的促分化功能参与AML的发病机制，为AML的新型联合治疗方案开辟了新路径。
整体实验设计：本研究共纳入30份来源于HL-60或TEX细胞系的标本，经药物处理后，采用Illumina HumanHT-12基因表达芯片进行杂交检测。