Identifying Mechanisms of Resistance to Pharmacological Inhibition of the MLL-MENIN Interaction in Acute Myeloid Leukemia.

尽管采用了积极的治疗方法，如大剂量化疗和同种异体干细胞移植，但携带mll1基因易位的急性髓性白血病（AML）患者的临床结果仍然不利。致癌基因融合复合体驱动一组靶基因的转录激活，促进成人和儿童AML患者的发展和维持。在一些临床前动物模型中，通过基因失活该复合体的特定成员来破坏该复合体的功能，导致疾病进展受阻，并最终治愈AML。最近，波士顿丹娜-法伯癌症研究所的Scott Armstrong教授小组已经建立了一种小分子药物VTP50469，它可以破坏mll融合癌基因和MEN1之间的蛋白质-蛋白质相互作用，MEN1是异常转录激活子复合体的另一个关键成员。VTP50469是口服生物利用的，在患者来源的异种移植物中产生了显著和持久的反应，将于2019年夏季在美国进入早期临床试验。然而，Armstrong教授实验室的初步实验表明，白血病细胞能够适应体外men1抑制剂的治疗，导致耐药细胞群能够在药物存在的情况下增殖。通过CRISPR-Cas9介导的敲除证实，这些细胞失去了对MEN1的依赖性。在拟议的项目过程中，我们的目标是在全球范围内表征VTP50469耐药AML细胞系中基因表达和染色质状态的变化。随后，我们计划在体内使用患者来源的异种移植小鼠模型验证这些发现。此外，我们将使用全基因组CRISPR-Cas9筛选方法来鉴定men1抑制剂耐药细胞中的特定遗传脆弱性，最终目的是鉴定可以促进消除耐药细胞克隆的药物靶点。继发性耐药是主要的临床挑战，特别是在涉及小分子药物的靶向治疗方法中。阿姆斯特朗实验室的初步数据支持这样的假设，即医学界在临床管理VTP50469和其他针对men1的药物时将不得不处理这一问题。在这个项目中，我们希望首次深入了解men1抑制剂耐药的潜在机制和潜在策略。

Patients with Akute Myeloid Leukemia (AML) harboring translocations involving the MLL1-gene have adverse clinical outcomes despite aggressive treatment approaches like high-dose chemotherapy and allogenic stem cell transplantation. The oncogenic gene-fusion complex is driving transcriptional activation of a set of target genes that promote development and maintenance of AML in both adult and pediatric patients. Disrupting the function of this complex by genetic inactivation of specific members of this complex led to a block in disease progression and ultimately to a cure of AML in several preclinical animal models. Recently, the group of Prof. Scott Armstrong at Dana-Farber Cancer Institute in Boston has established a small-molecule drug, VTP50469, that disrupts the protein-protein interaction between the MLL-fusion oncogenes and MEN1, another crucial member of the aberrant transcriptional activator complex. VTP50469 is orally bioavailable and led to dramatic and long lasting responses in patient-derived Xenografts and will enter early-phase clinical trials in Summer 2019 in the United States. Nevertheless, preliminary experiments from Prof. Armstrong’s laboratory showed, that leukemia cells are able to adapt to treatment with the MEN1-Inhibitor in vitro leading to a resistant cell population that is able to proliferate despite presence of the drug. These cells lost their dependency on MEN1 as confirmed by CRISPR-Cas9 mediated knockout. During the course of the proposed project we aim to characterize changes in gene-expression and chromatin-state in VTP50469 resistant AML cell lines on a global scale. Subsequently, we plan to validate those findings in vivo using patient derived xenograft mouse-models. Furthermore, we will use a genome-wide CRISPR-Cas9 screening approach to identify specific genetic vulnerabilities in the MEN1-inhibitor resistant cells with the ultimate aim of identifying drug targets that could facilitate elimination of the resistant cell clone. Secondary drug resistance is a major clinical challenge particularly in targeted therapy approaches involving small molecule drugs. The preliminary data from the Armstrong-Laboratory promote the hypothesis that the medical community will have to deal with this issue in clinical management of VTP50469 and other MEN1-targeting drugs. With the proposed project we hope to provide first insights into the underlying mechanisms and potential strategies to overcome MEN1-inhibitor resistance.