Characterization of pro- and anti-apoptotic Bcl-2 proteins regulating hematopoiesis and leukemogenesis in the context of RAS hyperactivation

Bcl-2蛋白家族的促凋亡和抗凋亡成员及其平衡调节对于造血系统的产生、维持和功能至关重要。虽然在小鼠造血系统中有合理的定义，但Bcl-2蛋白在人类造血中的许多作用仍不完全清楚。因此，在目前的资助期间，我们正在研究Bcl-2蛋白如何有助于人类造血系统的正常运作。我们专注于促生存Bcl-2蛋白，以确定在稳态条件下和压力下保持人类造血干细胞和祖细胞存活所需的蛋白质或蛋白质组合。通过这样做，我们的目标是定义干细胞存活和血液形成的“最低要求”。在后续项目中，我们将研究Bcl-2蛋白的组成和调控在恶性转化过程中的变化。作为肿瘤发生多步骤过程的模型系统，我们将使用具有组成性激活的RAS信号传导的细胞。造血细胞中组成性激活的RAS信号传导（例如，由于NRAS、KRAS、PTPN 11、NF 1或CBL突变）可导致造血作用明显不受影响（即努南综合征患者）或导致多克隆和一过性骨髓增生，如努南综合征患者亚组中所见。然而，它也可以导致青少年骨髓单核细胞白血病（JMML），一种高度侵袭性的髓性儿童白血病。使用来自努南综合征（+/-骨髓增生）或JMML患者的细胞，以及相应的小鼠模型，我们建议表征Bcl-2蛋白在RAS驱动的白血病转化的不同阶段是否以及如何失调，并评估在哪些疾病阶段使用BH 3模拟物治疗患者可能是有益的。我们推测，Bcl-2蛋白失调的变化在疾病进展过程中，这些变化有助于骨髓增生和JMML的发病机制。我们预计，这些结果将在一定程度上从努南综合征，骨髓增生和JMML转移到更复杂的癌症类型，也是由RAS激活驱动。

Pro- and anti-apoptotic members of the Bcl-2 protein family and their balanced regulation are of crucial importance for generation, maintenance and function of the hematopoietic system. Although reasonably well defined in the mouse hematopoietic system, the many roles of Bcl-2 proteins in human hematopoiesis are still incompletely understood. In the current funding period, we are therefore investigating how Bcl-2 proteins contribute to proper functioning of the human hematopoietic system. We are focusing on pro-survival Bcl-2 proteins to identify the protein or protein combinations that are required to keep human hematopoietic stem and progenitor cells alive, both under steady state conditions and when put under stress. By doing so, we aim at defining the "minimal requirements" for stem cell survival and blood formation. In the follow-up project, we will investigate how composition and regulation of Bcl-2 proteins do change during malignant transformation. As a model system for the multistep process of tumorigenesis, we will use cells with constitutively activated RAS signaling. Constitutively activated RAS signaling (e.g. due to mutations in NRAS, KRAS, PTPN11, NF1 or CBL) in hematopoietic cells can either result in an apparently unaffected hematopoiesis (i.e. in patients with Noonan syndrome) or in polyclonal and transient myeloproliferation, as seen in a subset of Noonan syndrome patients. It can, however, also result in juvenile myelomonocytic leukemia (JMML), a highly aggressive myeloid childhood leukemia. Using cells derived from patients with Noonan syndrome (+/- myeloproliferation) or JMML, as well as corresponding mouse models, we propose to characterize if and how Bcl-2 proteins are deregulated in different stages of RAS-driven leukemic transformation and evaluate, in which disease stages it could be beneficial to treat patients with BH3-mimetics. We hypothesize that the profile of Bcl-2 protein deregulation changes during disease progression and that these changes contribute to the pathogenesis of myeloproliferation and JMML. We expect that these results will be transferable to some extent from Noonan syndrome, myeloproliferation and JMML to more complex types of cancer that are also driven by RAS activation.