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

描述(由申请人提供)：脑胶质瘤，明确地说是多形性胶质母细胞瘤(GBM)，是最无法治愈的癌症之一。这类肿瘤被认为是从经历了转化为肿瘤的脑神经干细胞和前体细胞产生的。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/祖细胞中高表达，包括肿瘤干细胞和基底膜。无论在体内外，用显性负性ATF5(d/n-ATF5)或siRNA-ATF5阻断ATF5功能可促进胶质瘤细胞的凋亡，但不能促进非肿瘤细胞的凋亡。目前，我们合成的重组细胞穿透性d/n-ATF5多肽可以穿过血脑屏障，进入神经胶质瘤细胞，促进其快速死亡。我们研究的长期目标将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剂d/n-ATF5在临床前方法中对肿瘤消退或完全根除的明显治疗指数。我们的具体目标将是：1)确定不损害正常组织的细胞穿透剂d/n-ATF5的最有效给药方案；测试通过祖细胞从头转化和人GBM异种移植建立的小鼠脑胶质瘤/胶质母细胞瘤模型的疗效；确定多肽治疗是否可以实现胶质母细胞瘤的长期根除；以及，在肿瘤在最初治疗后再次出现的情况下，是否可以再次应用d/n多肽使其退化。2)明确介导d/n-ATF5诱导胶质母细胞瘤细胞凋亡的分子机制。对这些途径的深入了解将揭示肿瘤如何依赖ATF5生存，而这在未转化的细胞中没有观察到。对机制途径的了解将有助于预测和规避非靶点效应，并将解释和促进避免肿瘤对d/n-ATF5治疗的潜在耐药性。最后，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在意识到这些途径的情况下得到更充分的解决。

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.