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，它会消耗非必需的氨基酸天冬酰胺，是天冬酰胺的核心 急性淋巴细胞性白血病一线治疗的组成部分。然而，抗药性的发展 以天冬酰胺酶为基础的治疗是一种常见的问题，预后较差，其生物学基础 天冬酰胺酶的反应和耐药性还不是很清楚。利用全基因组的基因筛查，我们最近 研究发现，Wnt途径的激活使耐药白血病对天冬酰胺酶高度敏感。这一效果 发生于不同的急性白血病耐药亚型，包括T-ALL、亚二倍体B-ALL和急性 髓系白血病，但在正常造血祖细胞中不存在。天冬酰胺酶增敏作用不依赖于 Wnt信号中典型的β-连环蛋白分支。相反，这种效应是由Wnt依赖的稳定所介导的 蛋白(Wnt/Stop)，Wnt信号的一个未被研究的分支，它抑制依赖GSK3的蛋白 泛素化和蛋白酶体降解。抑制GSK3的α亚型就足以复制这一现象 效果。在体内，GSK3α选择性抑制和天冬酰胺酶的结合具有深刻的治疗活性 对抗患者来源的异种移植物，这些移植物对任何一种药物的单一治疗都完全抵抗。因此， 门冬酰胺酶耐药白血病通过依赖蛋白质降解而在这种酶治疗下存活下来，a 分解代谢的氨基酸来源，补充细胞内的天冬酰胺。这种适应性反应是 可被Wnt途径激活或选择性抑制Gsk3α所阻断。然而，分子决定因素 对GSK3α抑制和天冬酰胺酶结合的反应和抗性尚不清楚。这些 知识差距是合理应用这一强有力的联合疗法的主要障碍。 临床益处，这将通过调查以下具体目标来解决：1)定义分子 GSK3α抑制和天冬酰胺酶治疗指数的依据；2)研究为什么天冬酰胺酶 抗性完全依赖于Gsk3α，而其密切相关的Paralog Gsk3β对于调节 典型的Wnt/β-连环蛋白信号转导。这项提案的成功完成预计将揭示出重大见解 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 明白了。我们独特地准备将这些进步转化为高度创新和有效的治疗方法 在癌症治疗中最大化天冬酰胺酶治疗指数的策略。

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.