Targeting the Novel PI5P4K Pathway to Induce Glioblastoma Senescence

描述（由申请人提供）：细胞衰老是一种肿瘤抑制机制。然而，多形性胶质母细胞瘤（GBM）是最恶性的原发性脑肿瘤，中位生存期约为一年，对衰老具有高度抗性。迫切需要使GBM对衰老敏感以改善患者结果的新治疗方式和药剂。PI 5 P4 K家族使磷脂酰肌醇5-磷酸（PI 5 P）磷酸化并将其转化为磷脂酰肌醇4，5-磷酸（PI[4，5]P2）以调节磷酸肌醇信号传导。在前期研究中，本实验室发现PI 5 P4 K β直接与鸟嘌呤核苷酸结合。我们的X射线结构分析表明，PI 5 P4 K β利用GTP作为首选的磷酸供体，而不是ATP。动力学分析还预测，生理GTP水平控制PI 5 P4 K β活性。重要的是，我们发现细胞GTP水平在抑制GBM衰老中起关键作用，并且PI 5 P4 K β敲低触发GBM细胞的衰老。我们已经确定了一种小的化合物，抑制PI 5 P4 K活性在体外和体内。PI 5 P4 K化学抑制剂的处理诱导GBM细胞的衰老。这些结果表明PI 5 P4 K β抑制剂可用于预防或治疗GBM。本研究的目的是确定一种新型的GTP依赖性激酶PI 5 P4 K β在调节GBM衰老中的意义，并确定在体外和体内抑制PI 5 P4 β是否可以诱导GBM衰老并降低其致瘤活性。为了验证这一假设，我们将使用体外细胞培养和胶质母细胞瘤的临床相关原位植入模型，通过shRNA介导的PI 5 P4 K β敲低和药理学抑制来确定PI 5 P4 K β在GBM细胞生长中的作用（目的1）。我们将使用生化和生物学分析来确定通过PI 5 P4 K β（Aim 2）检测GTP的机制。我们将通过表征PI 5 P4 K β下游效应子来确定PI 5 P4 K β如何调节衰老（目的3）。这些研究将揭示PI 5 P4 K β靶向诱导胶质母细胞瘤细胞衰老和生长停滞的新机制和机会。

DESCRIPTION (provided by applicant): Cellular senescence is a tumor suppressor mechanism. However glioblastoma multiforme (GBM), the most malignant primary brain tumor with a median survival of about one year, is highly resistant to senescence. There is a critical need for new therapeutic modalities and agents that sensitize GBM to senescence to improve patient outcome. A family of PI5P4K phosphorylates phosphatidylinositol 5-phosphate (PI5P) and converts it to phosphatidylinositol 4,5-phosphate (PI[4,5]P2) to regulate phosphoinositide signaling. In the preliminary studies, my laboratory found that PI5P4Kβ binds directly to guanine nucleotides. Our X-ray structural analyses show that PI5P4Kβ utilizes GTP as the preferred phospho-donor, as opposed to ATP. Kinetic analyses also predict that physiological GTP levels control the PI5P4Kβ activity. Importantly, we have found that cellular GTP levels play critical rol in suppressing GBM senescence and that PI5P4Kβ knockdown triggers senescence of GBM cells. We have identified a small chemical compound that inhibits PI5P4K activity in vitro and in vivo. The treatment of the PI5P4K chemical inhibitor induces senescence of GBM cells. These results indicate that inhibitors of PI5P4Kβ could be useful in preventing or treating GBM. The goal of this proposal is to determine the significance of a novel type of GTP-dependent kinase, PI5P4Kβ, in regulating GBM senescence, and to determine whether inhibition of PI5P4β could induce GBM senescence and reduce its tumorigenic activity in vitro and in vivo. To test the hypothesis, we will determine the role of PI5P4Kβ in GBM cell growth by shRNA-mediated PI5P4Kβ knockdown and pharmacological inhibition using in vitro cell culture and a clinically relevant orthotopic implantation model of glioblastoma (Aim 1). We will use biochemical and biological analyses to determine the mechanism of GTP detection by PI5P4Kβ (Aim 2). We will determine how PI5P4Kβ regulates senescence by characterizing PI5P4Kβ downstream effectors (Aim 3). Collectively, these studies will lead to reveal the novel mechanism and opportunity for inducing senescence and growth arrest of glioblastoma cells by targeting PI5P4Kβ.