Arsenic Trioxide Activaed Pathways in APL

说明(申请人提供)：三氧化二砷(As2O3)是一种重金属衍生物，在体外和体内都具有强大的抗白血病特性。这种药物用于治疗急性早幼粒细胞白血病(APL)，但其抗白血病作用的确切机制尚不清楚。我们在APL细胞中发现了由三氧化二砷激活的一条新的信号通路，该通路涉及p38MAPK。我们的数据表明，该信号级联的激活对APL细胞的凋亡和细胞分化的诱导具有负调控作用。这项资助申请的总体目标是了解p38在APL细胞中负向调节As2O3反应的诱导机制。目的：明确As2O3激活APL细胞中p38MAPK的机制。将进行研究，以检查小GTP酶rac1和CDc42，以及Pak1激酶的作用，并确定直接磷酸化和激活p38的MKK(MKK)。具体目的B是确定下游效应机制，p38Map激酶通过这些机制控制依赖于As2O3的细胞凋亡。有人建议研究APL细胞中不同p38亚型的激活模式，并确定它们在产生As2O3反应中的作用。还将进行实验，以剖析p38途径的不同下游效应器在调节这些反应中的作用。具体目的是检测APL患者或其他亚型急性髓系白血病(AML)患者的原代白血病细胞中p38的激活情况，并确定这种激活是否与三氧化二砷的敏感性或抵抗力有关。总之，这些研究应该会促进我们对三氧化二砷对恶性肿瘤细胞产生影响的机制的全面理解。它们也可能为未来AS2O3和p38抑制剂组合治疗急性髓细胞白血病以及可能的其他形式的急性髓细胞白血病的临床翻译工作提供基础。

DESCRIPTION (provided by applicant): Arsenic trioxide (AS2O3) is a heavy metal derivative that has potent antileukemic properties in vitro and in vivo. This agent is used in the treatment of patients with acute promyelocytic leukemia (APL), but the precise mechanisms by which it induces its antileukemic effects are not known. We have identified a novel signaling pathway activated by arsenic trioxide in APL cells, involving the p38 Map kinase. Our data suggest that activation of this signaling cascade exhibits a negative regulatory role on the induction of apoptosis and cell differentiation of APL cells. The overall goal of this grant application is to understand the mechanisms by which p38 negatively regulates the induction of AS2O3-responses in APL cells. Specific aim A is to determine the mechanisms of activation of the p38 Map kinase by AS2O3 in APL cells. Studies will be performed to examine the roles of the small GTPases Rac1 and Cdc42, and the Pak1 kinase, and to identify the Map kinase kinase (Mkk) that directly phosphorylates and activates p38. Specific aim B is to identify the downstream effector mechanisms by which the p38 Map kinase controls AS2O3-dependent apoptosis. Studies are proposed to examine the patterns of activation of different p38-isoforms in APL cells and to determine their roles in the generation of AS2O3-responses. Experiments will be also performed to dissect the contributions of different downstream effectors of the p38 pathway in the regulation of such responses. Specific aim C is to examine the activation of p38 in primary leukemic blasts from APL patients or patients with other subtypes of acute myeloid leukemia (AML), and determine whether such activation correlates with sensitivity or resistance to the effects of arsenic trioxide. Altogether, these studies should advance our overall understanding of the mechanisms by which AS2O3 generates its effects on malignant cells. They may also provide the basis for future clinical-translational efforts of combinations of AS2O3 and p38 inhibitors for the treatment of APL, and possibly other forms of AML.