Mechanisms of RIOK2 function in glioblastoma

项目总结 胶质母细胞瘤(GBM)是最常见和最致命的原发恶性脑肿瘤，常表现为 激活受体酪氨酸激酶(RTK)和PI-3激酶-Akt(PI3K)信号通路的突变。 然而，到目前为止，直接抑制RTK和/或PI3K信号转导的药物在治疗GBM方面被证明无效。 我们的研究计划使用补充的实验模型系统，包括患者衍生的初级 果蝇基底膜干细胞培养和新的基底膜模型，以鉴定和询问遗传学 以及神经胶质肿瘤发生的细胞过程。使用我们的GBM模型系统，我们确定了RIOK2， 一种高度保守的非典型丝氨酸-苏氨酸激酶，我们的结果表明，在GBMS中，RIOK2成为 RTK-PI3K信号过表达促进肿瘤细胞增殖和存活，RIOK2 在依赖RTK-PI3K的GBM细胞中，基因敲除可抑制细胞增殖并诱导细胞凋亡。我们的初步数据 还表明，在果蝇和人类GBM模型中，对RIOK2催化活性的强烈抑制 抵消RTK-PI3K驱动的转换。相反，正常人RIOK2活性的丧失或抑制 或者果蝇的神经胶质祖细胞/干细胞不会导致细胞死亡，也不会显著影响细胞 扩散。因此，RTK-PI3K突变的肿瘤细胞，而不是正常的胶质细胞，依赖于RIOK2的活性 为了他们的成长和生存。根据我们的初步数据，我们假设RIOK2通过以下方式驱动GBM 磷酸化和激活RNA结合蛋白以促进致癌靶mRNAs的翻译， 并且RIOK2通过刺激转录因子RIOK2的翻译来促进GBM细胞的生长和存活 作为胶质瘤生成RTK和PI3K信号转导的结果而表达的致癌mRNAs。这 提案集中了两个目标，旨在1)确定RIOK2和RIOK2之间的相互作用机制 其相关的RNA结合蛋白，以及Aim 2)确定RIOK2活性是否专门促进 选择肿瘤细胞中的靶mRNAs。该项目可能揭示驱动肿瘤发生的新机制，以及 为开发潜在靶向治疗GBM的RIOK2抑制剂奠定基础。

PROJECT SUMMARY Glioblastomas (GBMs), the most common and deadly primary malignant brain tumors, frequently display mutations that activate receptor tyrosine kinases (RTKs) and the Pi-3 kinase-Akt (PI3K) signaling pathway. Yet, to date, drugs that directly inhibit RTK and/or PI3K signaling have proven ineffective in treatment of GBM. Our research program uses complementary experimental model systems, including patient-derived primary GBM stem cell cultures and novel GBM models in Drosophila melanogaster, to identify and interrogate genetic and cellular processes that underlie glial tumorigenesis. Using our GBM model systems, we identified RIOK2, a highly conserved atypical serine-threonine kinase, and our results revealed that, in GBMs, RIOK2 becomes overexpressed in response to RTK-PI3K signaling to drive tumor cell proliferation and survival, and that RIOK2 knockdown in RTK-PI3K dependent GBM cells inhibits proliferation and elicits apoptosis. Our preliminary data also indicate that, in both Drosophila and human GBM models, inhibition of RIOK2 catalytic activity strongly counteracts RTK-PI3K-driven transformation. In contrast, loss or inhibition of RIOK2 activity in normal human or Drosophila glial progenitor/stem cells does not elicit cell death and does not dramatically affect cell proliferation. Thus, RTK-PI3K mutant tumor cells, but not normal glial cells, are dependent on RIOK2 activity for their growth and survival. Based on our preliminary data, we hypothesize that RIOK2 drives GBM by phosphorylating and activating RNA-binding proteins to promote the translation of oncogenic target mRNAs, and that RIOK2 differentially promotes the growth and survival of GBM cells by stimulating the translation of oncogenic mRNAs that are expressed as a consequence of gliomagenic RTK and PI3K signaling. This proposal focuses two aims designed to Aim 1) Determine the mechanisms of interaction between RIOK2 and its associated RNA-binding proteins, and Aim 2) Determine if RIOK2 activity specifically promotes translation of select target mRNAs in tumor cells. This project may reveal new mechanisms that drive tumorigenesis, and establish a basis for developing RIOK2 inhibitors for potential targeted treatment for GBM.