Effects of microenvironmental modulation on BH3 dependence in AML

摘要 急性髓系白血病(AML)以分化障碍和髓系前体细胞克隆性增殖为特征 最终导致正常造血失败的细胞。尽管有密集的研究努力，但很少有治疗作用 在过去的40年里取得了进步，绝大多数患者的死亡率仍然很高。 在治疗后五年内死于疾病。抗凋亡蛋白bc1-2的过度表达是 AML。一类新的小分子抑制剂，称为BH3模拟物，选择性靶向特定的bcl2家族 蛋白质。文奈德(VEN)是一种选择性bcl2抑制剂，最近被FDA批准与DNA联合使用 甲基转移酶抑制剂用于不适合接受标准化疗的老年AML患者，表现出有效 利率高达70%。尽管有这些显著的结果，原始和获得性VEN耐药仍然是一个令人担忧的问题。我们和 其他研究表明，VEN耐药主要是通过诱导另一个bcl2家族成员表达上调而发生的。 髓系白血病细胞分化蛋白(MCL-1)，抑制MCL-1可导致VEN耐药细胞发生凋亡。 然而，在对这些基础进行进一步分析后，我们观察到在对BH3模拟的反应中 不同原始移植AML PDX模型的造血室。BH3基因和AML原始PDX骨移植 使用骨髓单个核细胞的骨髓扩增研究准确地预测了患者对BH3的依赖，但 我们在外周血液中看到了相互矛盾的结果。尽管外周细胞通常具有相同的克隆性和 分化阶段与在骨髓中一样，我们的研究表明外周血AML原始细胞对MCL-1更敏感 抑制细胞系和患者来源的异种移植，而不考虑对骨髓BH3的依赖。因此，我们 假设AML的外周原始细胞比骨髓中的原始细胞对mcl1抑制更敏感。 建议使用动员剂将增加AML细胞对MCL-1抑制的敏感性，潜在地降低 达到疗效所需的MCL-1抑制剂剂量。我们将利用我们实验室的宝贵资源 通过以下目的来检验这一假说的专家：1.评估急性髓系白血病细胞的BH3依赖特征 从患者和PDX模型的骨髓和外周采集，以及2.确定动员的效用为 一种辅助疗法，以增强BH3模拟。这些研究将进一步阐明BCL-2家族与BCL-2家族 原始细胞和不同造血微环境中的蛋白质以及微环境的改变是否会影响 这段关系。此外，众所周知，骨髓利基提供了增殖和存活的优势，从而 在化疗耐药方面，CXCR4激动剂plerixafor已成功地与其他药物联合使用 AML作为一种动员剂，将细胞从骨髓释放到外周，延缓疾病复发。 重要的是，由于BH3模拟物并非没有毒性，这些研究将调查plerixafor在增强 对BH3模拟方案的反应或减少VEN和VEN实现反应所需的剂量 耐药的急性髓系白血病。

Abstract Acute Myeloid Leukemia (AML) is characterized by differentiation blockade and the clonal proliferation of myeloid precursor cells that culminates in the failure of normal hematopoiesis. Regardless of intensive research efforts, few therapeutic advancements have been made in past 40 years, and mortality remains high with the overwhelming majority of patients succumbing to disease within five years of treatment. Overexpression of anti-apoptotic protein, BCL-2, is one hallmark of AML. A new class of small molecule inhibitors, referred to as BH3 mimetics, selectively target specific BCL-2 family proteins. Venetoclax (VEN), a selective BCL-2 inhibitor, was recently approved by the FDA in combination with DNA methyltransferase inhibitors for use in elderly AML patients unfit to receive standard chemotherapy, exhibiting response rates up to 70%. Despite these remarkable results, primary and acquired VEN resistance remains a concern. We and others have shown that VEN resistance occurs mainly through the upregulation of another BCL-2 family member, induced myeloid leukemia cell differentiation protein (MCL-1), and that inhibition of MCL-1 leads to apoptosis in VEN resistant cells. However, upon further analyses of these underpinnings, we observed discordance in response to BH3 mimetics in the different hematopoietic compartments of primagraft AML PDX models. BH3 profiling and AML primagraft PDX bone marrow expansion studies using bone marrow mononuclear cells accurately predict patient specific BH3 dependency, but we have seen contradictory results in the peripheral blood. Although peripheral cells are often of the same clonality and differentiation stage as in the bone marrow, our studies indicate that peripheral AML blasts are more sensitive to MCL-1 inhibition in both cell line and patient derived xenografts, regardless of marrow BH3 dependency. Therefore, we hypothesize that peripheral blast cells in AML are more sensitive to MCL-1 inhibition than those in the bone marrow and propose that the use of mobilization agents will increase sensitivity of AML cells to MCL-1 inhibition, potentially reducing the dose of MCL-1 inhibitors needed to achieve response. We will leverage our laboratory’s invaluable resources and expertise to test this hypothesis with the following aims: 1. Assess the BH3 dependent characteristics of AML blasts harvested from the bone marrow and periphery of patients and PDX models and 2. Determine the utility of mobilization as an accessory therapy to enhance BH3 mimetics. These studies will further elucidate the relationship between BCL-2 family proteins in blast cells and different hematopoietic microenvironments and whether altering the microenvironment can affect this relationship. Further, as it is well known that the marrow niche provides proliferative and survival advantages that result in chemotherapy resistance, plerixafor, a CXCR4 agonist, has successfully been used in combination with other agents in AML as a mobilization agent to release cells from the bone marrow into the periphery and delay disease relapse. Importantly, as BH3 mimetics are not without toxicity, these studies will investigate the utility of plerixafor to enhance response to BH3 mimetic based regimens or reduce the dose needed to achieve response in both VEN naïve and VEN resistant AML.