Targeting of Tyrosine Phosphatase SHP2 in Myeloproliferative Neoplasms

 描述(申请人提供)：骨髓增生性肿瘤(MPN)包括真性红细胞增多症(PV)、原发性血小板增多症(ET)和原发性骨髓纤维化(PMF)，是以髓系细胞过度生成为特征的慢性髓系恶性肿瘤。在大多数MPNS患者中发现了获得性JAK2V617F突变，该突变导致JAK2酪氨酸激酶的结构性激活。这导致了JAK2抑制剂的开发。Ruxolitinib是一种JAK1/JAK2抑制剂，已被批准用于治疗羟基脲抵抗的PV和晚期MF。鲁索利替尼治疗虽然可以减轻脾肿大和躯体症状，但不能完全缓解PV/MF患者。很明显，目前包括JAK2抑制剂在内的化疗不足以治愈MPN。因此，迫切需要开发针对MPN的新型靶向治疗方法。我们发现，在表达JAK2V617F的小鼠和人MPN细胞中，SHP2被结构性磷酸化/激活。Shp2是一种蛋白酪氨酸磷酸酶，在细胞信号转导中发挥积极作用。在初步研究中，我们观察到SHP2基因的敲除显著抑制了表达JAK2V617F的细胞的增殖。此外，SHP2基因的缺失抑制了JAK2V617F敲入小鼠PV和MF的发生。此外，一种新的SHP2抑制剂11a-1处理显著抑制JAK2V617F阳性的MPN细胞的生长。因此，我们推测SHP2可能在JAK2V617F诱导的造血转化/MPNS中起重要作用，并且SHP2的药理抑制作用可能对MPNS有效。为了检验我们的假设，我们提出了两个具体目标。在目标1中，我们将使用SHP2和条件性JAK2V617F敲入小鼠进一步确定SHP2在PV和MF的发生和维持中的作用。在目标2中，我们将确定一种新的SHP2抑制剂11a-1对培养和原代MPN细胞以及PV和MF动物模型的安全性和有效性。我们还将确定SHP2缺失或抑制对JAK2V617F诱导的信号转导的影响，并确定SHP2调节JAK2V617F诱导的转化/MPN的机制。我们提出的研究将首次证明SHP2在MPNS(PV和MF)的发生发展中起重要作用，利用小分子抑制剂11a-1靶向SHP2是治疗MPNS的一种新策略。此外，这些临床前研究的结果将为SHP2抑制剂11a-1治疗MPNS的I/II期临床试验提供支持数据。

 DESCRIPTION (provided by applicant): Myeloproliferative neoplasms (MPNs) including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) are chronic myeloid malignancies characterized by overproduction of myeloid lineage cells. An acquired JAK2V617F mutation, which results in constitutive activation of the JAK2 tyrosine kinase, has been found in a majority of patients with MPNs. This has led to the development of JAK2 inhibitors. Ruxolitinib, a JAK1/JAK2 inhibitor, has been approved for treatment of hydroxyurea-resistant PV and advanced MF. Although Ruxolitinib therapy can reduce splenomegaly and constitutional symptoms, it failed to produce complete remission in patients with PV/MF. It has become clear that current chemotherapies including JAK2 inhibitors are not sufficient to cure MPNs. So, there is a critical need to develop novel targeted therapies for MPNs. We have found that SHP2 is constitutively phosphorylated/activated in mouse and human MPN cells expressing JAK2V617F. SHP2 is a protein tyrosine phosphatase that plays a positive role in cell signaling. In preliminary studies, we have observed that knockdown of SHP2 significantly inhibits proliferation of cells expressing JAK2V617F. Moreover, deletion of SHP2 inhibits the development of PV and MF in JAK2V617F knock-in mice. Furthermore, treatment with a novel SHP2 inhibitor 11a-1 significantly inhibits the growth of JAK2V617F-positive MPN cells. So, we hypothesize that SHP2 may play important roles in hematopoietic transformation/MPNs induced by JAK2V617F, and pharmacologic inhibition of SHP2 might be efficacious against MPNs. To test our hypothesis, we have proposed two specific aims. In Aim 1, we will further define the role of SHP2 in the development and maintenance of PV and MF using floxed SHP2 and conditional JAK2V617F knock-in mice. In Aim 2, we will determine the safety and efficacy of a novel SHP2 inhibitor 11a-1 against cultured and primary MPN cells and animal models of PV and MF. We will also determine the effects of SHP2 deletion or inhibition on JAK2V617F-evoked signaling and define the mechanism by which SHP2 regulates JAK2V617F-induced transformation/MPNs. Our proposed studies will provide the first demonstration that SHP2 plays an important role in the development of MPNs (PV and MF) and targeting of SHP2 using small molecule inhibitor 11a-1 is a novel strategy in treating MPNs. Moreover, results from these pre-clinical studies will generate the supportive data for Phase I/II clinical trials of SHP2 inhibitor 11a-1 in the treatment of MPNs.