UTX Loss Alters Therapeutic Responses in KMT2A-rearranged Acute Myeloid Leukemia [ChIP-seq]

Acute myeloid leukemias (AML) patients bearing chromosomal rearrangements of KMT2A or MLL gene (KMT2A -r) have poor overall survival. Recently, compounds targeting the KMT2A fusion protein complex, such as DOT1L and Menin inhibitors, have shown promising pre-clinical efficacy. Yet, molecular regulators of the anti-tumor activities of these agents remain poorly studied. UTX is a histone H3K27 demethylase with recurrent loss-of-function mutations in human cancers including leukemia. UTX-null leukemia shows greater resistance to chemotherapy agents. However, the impact of UTX on drug resistance of KMT2A -r AML has not been explored. Through a epigenetic compound screen, we identified a unique role of UTX in the regulation of DOT1L and Menin therapies in KMT2A-r AML. Loss of UTX confers resistance to DOT1L and Menin inhibition in an MLL target gene-independent manner. Mechanistically, We show that UTX is required for activation of myeloid differentiation programs induced by DOT1L inhibition. We also revealed BCL2A1 as a target of UTX. Depletion of UTX increased vulnerability to BCL2 inhibitor venetoclax in vitro and in vivo, and combinational treatment of venetoclax could overcome the therapeutic resistance to DOT1L inhibition caused by UTX loss. Our study provides new insights into the role of UTX in therapeutic responses in KMT2A-r AML. Overall design: Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for UTX and H3K27ac in UTX wildtype and UTX knockout OCI-AML2 cells.

急性髓系白血病（Acute myeloid leukemias, AML）患者携带KMT2A或MLL基因染色体重排（KMT2A-r）时，总体生存期较差。近年来，靶向KMT2A融合蛋白复合物的化合物，如DOT1L与Menin抑制剂，已展现出颇具前景的临床前疗效，但此类药物抗肿瘤活性的分子调控机制仍有待深入研究。
UTX是一种组蛋白H3K27去甲基化酶，在包括白血病在内的多种人类癌症中存在频发的功能丧失性突变。UTX缺陷型白血病对化疗药物的耐药性更强，然而UTX对KMT2A-r AML耐药性的影响尚未被探究。
本研究通过表观遗传化合物筛选，揭示了UTX在调控KMT2A-r AML中DOT1L与Menin靶向治疗的独特作用：UTX缺失会以不依赖MLL靶基因的方式，使细胞对DOT1L和Menin抑制产生耐药性。机制层面，我们证实UTX是激活DOT1L抑制所诱导的髓系分化程序所必需的；同时鉴定出BCL2A1为UTX的靶基因。体外与体内实验均表明，UTX敲除会增加细胞对BCL2抑制剂维奈克拉（venetoclax）的敏感性，而联合使用维奈克拉可克服UTX缺失导致的DOT1L抑制耐药性。本研究为UTX在KMT2A-r AML治疗应答中的作用提供了全新的见解。
总体设计：对UTX野生型与UTX敲除的OCI-AML2细胞，开展UTX与H3K27ac的染色质免疫沉淀测序（Chromatin immunoprecipitation DNA-sequencing, ChIP-seq）分析。