Defining and targeting asparaginase resistance mechanisms in high-risk acute leukemias

摘要 天冬酰胺酶是一种抗白血病的酶，它可以消耗非必需氨基酸天冬酰胺， 急性淋巴细胞白血病一线治疗的组成部分。然而，抵抗力的发展 天冬酰胺酶为基础的治疗是一个常见的问题，预后不良，和生物学基础 天冬酰胺酶反应和抗性还不清楚。利用全基因组遗传筛选，我们最近 发现Wnt通路的激活使耐药白血病对天冬酰胺酶高度敏感。这种效果 发生在急性白血病的不同治疗耐药亚型中，包括T-ALL、亚二倍体B-ALL和急性 骨髓性白血病，但不是在正常的造血祖细胞。门冬酰胺酶致敏不依赖于 Wnt信号传导的典型β-连环蛋白分支。相反，这种作用是由Wnt依赖性稳定化介导的。 蛋白质（Wnt/STOP），Wnt信号传导的一个未充分研究的分支，抑制GSK 3依赖性蛋白 泛素化和蛋白酶体降解。抑制GSK3的α亚型足以表型化这一点。 效果在体内，GSK 3 α选择性抑制和天冬酰胺酶的组合具有深刻的治疗活性 针对患者来源的异种移植物，这些异种移植物对任一药剂的单一疗法完全耐受。因此，在本发明中， 天冬酰胺酶耐药白血病依靠蛋白质降解而存活， 氨基酸的分解代谢来源，补充细胞内天冬酰胺库。这种适应性反应是 通过Wnt途径激活或通过选择性抑制GSK 3 α阻断。然而，分子决定因素 对GSK 3 α抑制剂和天冬酰胺酶的组合的应答和抗性尚不清楚。这些 知识差距是合理应用这种有效的治疗组合的主要障碍， 临床益处，这将通过研究以下具体目的来解决：1）定义分子生物学， GSK3 α抑制和天冬酰胺酶治疗指数的基础，以及2）研究天冬酰胺酶为什么 耐药性仅依赖于GSK 3 α，而与其密切相关的副作用GSK 3 β对于调节耐药性是多余的。 经典Wnt/β-catenin信号传导。成功完成这一提案有望揭示重大见解 研究细胞对氨基酸饥饿的反应及其与Wnt信号的相互作用。这些过程 是后生动物生物学的基础，但它们的分子调控和治疗利用仍然很差 明白我们正准备将这些进展转化为高度创新和有效的治疗方法。 最大化天冬酰胺酶在癌症治疗中的治疗指数的策略。

ABSTRACT Asparaginase, an antileukemic enzyme that depletes the nonessential amino acid asparagine, is a core component of front-line therapy for acute lymphoblastic leukemias. However, the development of resistance to asparaginase-based therapy is a common problem with a poor prognosis, and the biology underlying asparaginase response and resistance is not well understood. Using a genome-wide genetic screen, we recently found that Wnt pathway activation profoundly sensitizes drug-resistant leukemias to asparaginase. This effect occurs in distinct treatment-resistant subtypes of acute leukemia, including T-ALL, hypodiploid B-ALL, and acute myeloid leukemia, but not in normal hematopoietic progenitors. Asparaginase sensitization is independent of the canonical β-catenin branch of Wnt signaling. Instead, this effect is mediated by Wnt-dependent stabilization of proteins (Wnt/STOP), an understudied branch of Wnt signaling that inhibits GSK3-dependent protein ubiquitination and proteasomal degradation. Inhibiting the alpha isoform of GSK3 is sufficient to phenocopy this effect. In vivo, the combination of GSK3α-selective inhibition and asparaginase has profound therapeutic activity against patient-derived xenografts that are completely resistant to monotherapy with either agent. Thus, asparaginase-resistant leukemias survive treatment with this enzyme by relying on protein degradation, a catabolic source of amino acids, to replenish the pool of intracellular asparagine. This adaptive response is blocked by Wnt pathway activation, or by selective inhibition of GSK3α. However, the molecular determinants of response and resistance to the combination of GSK3α inhibition and asparaginase are unknown. These knowledge gaps are major obstacles to the rational application of this potent therapeutic combination for maximal clinical benefit, which will be addressed by investigating the following Specific Aims: 1) Define the molecular basis for the therapeutic index of GSK3α inhibition and asparaginase, and 2) Investigate why asparaginase resistance is solely dependent on GSK3α, when its closely related paralog GSK3β is redundant for regulation of canonical Wnt/β-catenin signaling. Successful completion of this proposal is expected to reveal major insights into the cellular response to amino acid starvation and its interaction with Wnt signaling. These processes are fundamental to metazoan biology, yet their molecular regulation and therapeutic exploitation remain poorly understood. We are uniquely poised to translate these advances into highly innovative and effective therapeutic strategies to maximize the therapeutic index of asparaginase in cancer therapy.