CD44 Antagonists in Targeted and Combinational Therapy for Glioblastoma

描述（申请人提供）：多形性胶质母细胞瘤（GBM）预后极差。因此，迫切需要鉴定靶向可能消除GBM细胞和/或使GBM对细胞毒性和靶向药物反应敏感的分子。CD44是透明质酸（HA）的主要细胞表面受体和癌症干细胞标志物，与癌症进展有关。然而，人们对其在GBM进展中的作用、对GBM细胞对化疗和靶向治疗的反应以及介导CD44促肿瘤作用的主要下游信号通路知之甚少。我们发现CD44在恶性胶质瘤中被上调，它的缺失阻断了GBM的生长，并使GBM细胞对体内细胞毒性药物敏感。我们首先证明了CD44拮抗剂在小鼠模型中显示出强大的抗gbm功效，并且CD44在哺乳动物Hippo信号通路上游发挥作用。此外，CD44通过减弱Hippo通路激酶MST1/2和Lats1/2的激活，促进GBM细胞对活性氧和细胞毒性剂诱导的应激和凋亡的抗性。我们还发现CD44增强了ErbB和c-Met受体酪氨酸激酶（RTKs）的生长信号。基于这些结果，我们假设CD44拮抗剂通过增强Hippo信号通路的激活和抑制ErbB/c-Met RTKs来源的生长信号来抑制GBM细胞的存活，从而抑制GBM的进展并使GBM对化疗和靶向治疗的反应变得敏感。我们进一步假设CD44是GBM治疗的主要靶点，其拮抗剂在GBM小鼠模型中单独使用和/或与化疗药物和erbB和c-Met RTKs的药理抑制剂联合使用时是有效的。提出了三个具体目标。目的1是建立CD44拮抗剂，各种可溶性CD44- fc融合蛋白，显示抗胶质瘤活性，使GBM对体内化疗和靶向治疗的反应增敏。目的2是建立CD44拮抗剂在体内的化学增敏作用是通过增强Hippo信号通路的激活来实现的。最后，目的3是确定hsCD44-Fc融合蛋白通过抑制erbB和c-Met rtk的活性来实现其抗胶质瘤作用，并使GBM对靶向治疗的反应增敏，至少部分增敏。拟议实验的结果将确定CD44作为GBM的主要治疗靶点，并在临床前GBM模型中证明新开发的CD44拮抗剂作为单药和/或与化疗和其他靶向治疗联合使用的有效治疗效果。这些结果可能会在未来为GBM患者带来更好的临床结果和更持久的临床获益。因此，该建议具有较高的生物学和临床相关性和意义，以及转化潜力。

DESCRIPTION (provided by applicant): The prognosis for glioblastoma multiforme (GBM) is extremely poor. Identification of molecules whose targeting may eliminate GBM cells and/or sensitize GBM responses to cytotoxic and targeted agents is therefore urgently needed. CD44 is a major cell surface receptor for hyaluronan (HA) and a cancer stem cell marker, and has been implicated in cancer progression. However, little is known about its contributions to GBM progression and to the responses of GBM cells to chemo- and targeted therapies and about the major downstream signaling pathway that mediates the pro-tumor effect of CD44. We show that CD44 is up regulated in malignant gliomas and that its depletion blocks GBM growth and sensitizes GBM cells to cytotoxic drugs in vivo. We first demonstrate that CD44 antagonists display potent anti-GBM efficacy in mouse models and that CD44 functions upstream of mammalian Hippo signaling pathway. Furthermore, CD44 promotes GBM cell resistance to reactive oxygen species- and cytotoxic agent-induced stress and apoptosis by attenuating activation of the Hippo pathway kinases MST1/2 and Lats1/2. We also show that CD44 enhances the growth signals derived from ErbB and c-Met receptor tyrosine kinases (RTKs). Based on these results, we hypothesize that CD44 antagonists inhibit GBM progression and sensitize GBM responses to chemo- and targeted therapies by inhibiting GBM cell survival through enhancing activation of the Hippo signaling pathway and inhibiting the growth signals derived from ErbB/c-Met RTKs. We further hypothesize that CD44 is a prime target for GBM therapy and its antagonists are efficacious when used as single agents and/or combination with chemotherapeutic agents and pharmacological inhibitors of erbB and c-Met RTKs in the GBM mouse models. Three specific aims are proposed. Aim 1 is to establish that CD44 antagonists, a variety of soluble CD44-Fc fusion proteins, display anti- glioma activity, sensitize GBM response to chemo- and targeted therapies in vivo. Aim 2 is to establish that the chemosensitizing effect of CD44 antagonists in vivo is achieved by enhancing activation of Hippo signaling pathway. Finally, aim 3 is to establish that hsCD44-Fc fusion proteins achieve their anti-glioma effect and sensitize GBM response to the targeted therapies, at least partially, through inhibiting activities of erbB and c-Met RTKs. The results from proposed experiments will establish CD44 as a prime therapeutic target for GBM and demonstrate potent therapeutic efficacies of the newly developed CD44 antagonists as single agents and/or in combinations with chemo- and other targeted therapies in preclinical GBM models. These results may lead to better clinical outcome and longer lasting clinical benefit for GBM patients in the future. Therefore, this proposal has high biological and clinical relevance and significance, and translational potential.