Using Cell-Penetrant Peptides to Target ATF5 in Mouse Glioma Models

描述（由申请人提供）：脑胶质瘤，明确多形性胶质母细胞瘤（GBM），是最无法治愈的癌症之一。这种肿瘤被认为是由脑神经干细胞和祖细胞转化为肿瘤而产生的。肿瘤干细胞被认为是化疗和手术切除后胶质瘤复发的原因。我们发现激活转录因子5 （ATF5）在神经干细胞/祖细胞中高度表达，包括癌症干细胞和GBMs。在体外和体内，通过显性阴性ATF5 （d/n-ATF5）或siRNA-ATF5阻断ATF5功能可促进胶质瘤细胞的凋亡，但对非肿瘤细胞没有作用。目前，我们合成了重组细胞渗透d/n-ATF5肽，该肽穿过血脑屏障，进入胶质瘤细胞，促进胶质瘤细胞快速死亡。我们研究的长期目标是通过使用不同的胶质母细胞瘤小鼠模型，进一步测试并确定细胞渗透d/n-ATF5在临床前对肿瘤消退或完全根除的表观治疗指数。我们的具体目标是：1)确定不损害正常组织的细胞渗透剂d/n-ATF5的最有效剂量计划；在小鼠胶质瘤/胶质母细胞瘤模型中，通过祖细胞从头转化和人GBM异种移植物产生脑瘤，测试其有效性；确定用肽治疗是否能长期根除胶质母细胞瘤；在初始治疗后肿瘤再次出现的情况下，是否可以通过应用d/n肽使其再次退化。2)明确d/n-ATF5介导胶质母细胞瘤细胞凋亡的相关分子机制途径。了解这些途径将启发肿瘤如何依赖ATF5存活，这在非转化细胞中没有观察到。机制途径的知识将有助于预测和规避脱靶效应，并将解释和促进避免对d/n-ATF5治疗的潜在肿瘤耐药。最后，随着对这些途径的认识，d/n- ATF5与其他目前使用的胶质母细胞瘤疗法的协同作用将得到更充分的解决。

DESCRIPTION (provided by applicant): Brain glioma tumors, unequivocally glioblastoma multiforme (GBM), are among the most incurable forms of cancer. Such tumors are thought to arise from brain neural stem cells and progenitors that have undergone transformation into neoplasias. Neoplastic stem cells are thought to contribute to the recurrence of the glioma after chemotherapy and surgical resection. We found that activating transcription factor 5 (ATF5) is highly expressed in neural stem/progenitor cells, including cancer stem cells and GBMs. Blocking ATF5 function by dominant negative ATF5 (d/n-ATF5) or siRNA-ATF5 promotes apoptosis of glioma tumor cells, but not of non- neoplastic cells, both in vitro and in vivo. Currently, we synthesize recombinant cell penetrant d/n-ATF5 peptide that crosses the blood brain barrier, and enters into glioma cells, promoting their rapid death. The long-term objectives of our study will be to further test, as well as determine the apparent therapeutic index, of cell penetrant d/n-ATF5 toward tumor regression or full eradication in a pre-clinical approach by using different glioblastoma mouse models. Our specific aims will be to 1) Define the most effective dosing schedule for delivery of the cell penetrant d/n-ATF5 that does not harm normal tissues; test efficacy in mouse glioma/glioblastoma models by creating brain tumors through de novo transformation of progenitors and by human GBM xenografts; determine whether treatment with the peptide can bring about long-term eradication of glioblastomas; and, in the case that tumors reappear after initial treatment, whether they can again be caused to regress by application of the d/n peptide. 2) To define the responsible molecular mechanistic pathways that mediate apoptotic actions of d/n-ATF5 in glioblastoma cells. To gain insight on these pathways will enlighten how neoplasm relies on ATF5 for survival that is not observed in non-transformed cells. Knowledge of the mechanistic routes will aid in predicting and circumventing off-target effects and will explain as well as promote avoidance of potential tumor resistance toward d/n-ATF5 therapy. Finally, synergy of d/n- ATF5 with other currently employed glioblastoma therapies will be more adequately addressed with awareness of such pathways.