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

携带MLL 1基因易位的Akute髓性白血病（AML）患者尽管采用了高剂量化疗和同种异体干细胞移植等积极治疗方法，但仍具有不良临床结局。致癌基因融合复合物驱动一组靶基因的转录激活，促进成人和儿童患者AML的发展和维持。通过该复合物的特定成员的遗传失活来破坏该复合物的功能，导致疾病进展的阻断，并最终在几种临床前动物模型中治愈AML。最近，波士顿Dana-Farber癌症研究所的Scott Armstrong教授小组已经建立了一种小分子药物VTP 50469，该药物可以破坏MLL融合癌基因与异常转录激活因子复合物的另一个关键成员MEN 1之间的蛋白质-蛋白质相互作用。VTP 50469具有口服生物利用度，在患者来源的异种移植物中产生了显著而持久的反应，并将于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MEN 1抑制剂的体外治疗，导致耐药细胞群能够在药物存在下增殖。这些细胞失去了对MEN 1的依赖性，这通过CRISPR-Cas9介导的敲除证实。 在拟议项目的过程中，我们的目标是在全球范围内表征VTP 50469耐药AML细胞系中基因表达和染色质状态的变化。随后，我们计划使用患者来源的异种移植小鼠模型在体内验证这些发现。此外，我们将使用全基因组CRISPR-Cas9筛选方法来识别MEN 1抑制剂耐药细胞中的特定遗传脆弱性，最终目的是识别可以促进消除耐药细胞克隆的药物靶标。继发性耐药性是一个主要的临床挑战，特别是在涉及小分子药物的靶向治疗方法中。来自Armstrong实验室的初步数据促进了一种假设，即医学界将不得不在VTP 50469和其他MEN 1靶向药物的临床管理中处理这个问题。通过拟议的项目，我们希望提供有关克服MEN 1抑制剂耐药性的潜在机制和潜在策略的初步见解。

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.