Defining the role of beta2-integrin signaling for regulating cell survival, proliferation and apoptosis in acute myeloid leukemia

急性髓性白血病（AML）细胞接收来自骨髓微环境的致癌信号。这些信号触发AML细胞增殖并保护AML细胞免受治疗干预，但这一现象的分子基础尚不清楚。通过在体外研究AML细胞中脾酪氨酸激酶（Syk）功能的分子性质，我们发现，在AML细胞/骨髓基质相互作用的背景下，包括Mac-1在内的β 2整合素通过激活Syk和转录因子STAT3和STAT5参与致癌信号传导。β -整合素是白细胞限制性粘附受体，可将细胞锚定在细胞外基质（ECM）或邻近细胞。跨膜受体广泛表达于髓系和增殖性造血干细胞中。此外，AML细胞中Mac-1的表达与预后不良相关，尽管其潜在的分子机制尚不清楚。除了介导细胞粘附外，已知β -整合素还调节免疫细胞中的复杂信号网络，从而控制包括增殖和分化在内的多种细胞功能。β -整合素信号转导的机制是复杂的，因为它们涉及细胞骨架变化，GTPase-，磷酸肌肽-和酪氨酸激酶信号转导。因此，我们的假设是，包括Mac-1在内的β -整合素可能在体内通过激活致癌信号级联反应参与骨髓生态位，作为AML细胞生长和存活的促进因子。本研究计划的目的是进一步表征β -整合素在AML发病和进展阶段的作用。为了实现这一目标，我们提出：1.)利用小鼠逆转录病毒移植模型确定β -整合素在AML中的体内作用；2.)通过（磷酸化）蛋白质组学技术揭示AML细胞中β -整合素/ mac -1依赖的信号网络；3.)表征基质介导对AML细胞行为的影响。通过提出的实验方法，我们将阐明整合素信号的分子特性及其在保护性骨髓微环境存在下对AML细胞的影响。为了进一步改进细胞毒性和靶向AML治疗，需要更好地了解通过细胞间相互作用介导的致瘤作用。

Acute myeloid leukemia (AML) cells receive oncogenic signals from the bone marrow microenvironment. These signals trigger AML cell proliferation and protect AML cells from therapeutic interventions, but the molecular basis of this phenomenon is yet poorly understood. By investigating the molecular nature of spleen tyrosine kinase (Syk) function in AML cells in vitro, we discovered that beta2-integrins including Mac-1 are involved in oncogenic signaling by activating Syk and the transcription factors STAT3 and STAT5 in the context of AML cell/bone marrow stroma interactions. Beta2-integrins are leukocyte-restricted adhesion receptors that anchor cells to the extracellular matrix (ECM) or adjacent cells. The transmembrane receptors are widely expressed in the myeloid lineage as well as proliferating hematopoietic stem cells. Moreover, Mac-1 expression in AML cells correlates with a poor prognosis, albeit the underlying molecular mechanism is not understood to date. Apart from mediating cellular adhesion, beta2-integrins are known to regulate complex signaling networks in immune cells and thereby control diverse cellular functions including proliferation and differentiation. The mechanisms involved in beta2-integrin signal transduction are complex as they implicate cytoskeletal changes, GTPase-, phosphoinositide- and tyrosine kinase signaling. Hence, our hypothesis is that beta2-integrins including Mac-1 might function as promoters of AML cell growth and survival also in vivo by activating oncogenic signaling cascades upon their engagement in the bone marrow niche. The object of the present research proposal is to further characterize the role of beta2-integrins in the onset and progression phases of AML. To address this aim, we propose 1.) to define the in vivo role of beta2-integrins in AML using murine retroviral transplantation models, 2.) to uncover the beta2-integrin/Mac-1-dependent signaling networks in AML cells by (phospho)proteomic techniques and 3.) to characterize the stroma-mediated effects on AML cell behavior. By the proposed experimental approach, we will elucidate the molecular properties of integrin signaling and their impact on AML cells in the presence of a protective bone marrow microenvironment. A better understanding of the oncogenic effects mediated through intercellular interactions is needed for the further improvement of cytotoxic and targeted AML therapies.