L-ARGININE AVAILABILITY REGULATES PROLIFERATION OF MALIGNANT T-CELLS

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 T细胞恶性肿瘤预后很差，尤其是在成人患者中。因此，迫切需要新的治疗方法来提高患者的反应和存活率。我们先前已经证明，实体瘤中炎性细胞产生的精氨酸酶1通过消耗L-精氨酸和阻断特定的途径来阻止正常T细胞的增殖。有趣的是，在T细胞白血病患者中没有发现精氨酸酶1的产生。因此，我们测试了精氨酸酶1是否也会抑制T细胞白血病的增殖。我们的初步结果表明，恶性T细胞需要高浓度的L-精氨酸(L-精氨酸)来维持其高增殖率。在体外，精氨酸酶I耗尽L-精氨酸可阻断恶性T细胞的增殖，并通过抑制细胞周期蛋白D3的表达将恶性T细胞阻滞在细胞周期的G0-G1期。我们还确定了这一过程中涉及的一些分子机制。细胞周期蛋白D3蛋白表达的降低是由转录后机制引起的，包括细胞周期蛋白D3mRNA稳定性降低和细胞周期蛋白D3翻译受阻。细胞周期蛋白D3m RNA半衰期的丧失是由细胞周期蛋白D3m RNA的3‘-非翻译区序列介导的，并与体外低结合的核糖核酸结合蛋白Hur有关。此外，在没有L-精氨酸的情况下，细胞周期蛋白D3的翻译减少与氨基酸饥饿感受器GCN2激酶的激活有关。这些结果支持精氨酸酶I饥饿L-精氨酸通过阻断包括细胞周期蛋白D3表达在内的特定途径来阻断恶性T细胞增殖的假说。因此，精氨酸酶I可用于治疗T细胞淋巴增生性疾病，如T-ALL。在这项研究中，我们建议确定L-Arg缺失损害恶性T细胞增殖的分子机制，并确定注射精氨酸酶I或L-Arg饥饿引发的靶向通路是否可用于T细胞白血病的新治疗。初步的小鼠模型结果表明，注射聚乙二醇化精氨酸酶I(PEG-Arg I)可以延长T-ALL肿瘤小鼠的存活时间。从这一努力中获得的信息可能会导致开发一种新的和重要的治疗方法，以补充现有的T细胞淋巴增生性疾病的治疗方法，如T-ALL。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. T cell malignancies have a poor prognosis, especially in adult patients. Therefore new therapies that result in increased response and survival of the patients are urgently needed. We previously demonstrated that Arginase 1 produced by inflammatory cells in solid tumors, arrests the proliferation of normal T cells by depleting L-Arginine and blocking specific pathways. Interestingly, Arginase 1 production is not found in patients with T cell leukemias. We therefore tested whether Arginase 1 would also inhibit T cell leukemia proliferation. Our preliminary results show that malignant T cells require high concentrations L-Arginine (L-Arg) to sustain their high rate of proliferation. In vitro depletion of L-Arg by Arginase I blocks malignant T cell proliferation, and arrests malignant T cells in the G0-G1 phase of the cell cycle by impairing the expression of cyclin D3. We also identified some of the molecular mechanisms involved in this process. The decrease in cyclin D3 protein expression was caused by post-transcriptional mechanisms including a decreased cyclin D3 mRNA stability and an arrest in cyclin D3 translation. The loss of cyclin D3 mRNA half-life induced by the absence of L-Arg was mediated by sequences within the 3'-untranslated region (3'-UTR) of the cyclin D3 mRNA and associated with a low in vitro binding of the RNA-binding protein HuR. Furthermore, the decreased translation of cyclin D3 in the absence of L-Arg correlated with the activation of the amino acid starvation sensor GCN2 kinase. These results support the hypothesis that L-Arg starvation by arginase I blocks malignant T cell proliferation by blocking specific pathways including the expression of cyclin D3. Arginase I can therefore be used in the treatment of T cell lympho-proliferative disorders such as T-ALL. In this study, we propose to identify the molecular mechanisms by which L-Arg depletion impairs malignant T cell proliferation and determine if L-Arg depletion by the injection of Arginase I, or targeting pathways triggered by L-Arg starvation, can be used as a new treatment in T cell leukemias. The initial murine model results demonstrate that the injection of pegylated arginase I (peg-Arg I) prolongs survival in mice bearing T-ALL tumors. Information garnered from this effort may lead to the development of a novel and important therapeutic approach to complement existing therapies for T cell lympho-proliferative disorders such as T-ALL.