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

描述（由申请人提供）：脑胶质瘤，明确的多形性胶质母细胞瘤（GBM），是最无法治愈的癌症形式之一。这种肿瘤被认为是由脑神经干细胞和祖细胞转化为肿瘤引起的。肿瘤干细胞被认为是导致化疗和手术切除后胶质瘤复发的原因。我们发现，转录激活因子5（ATF5）在神经干/祖细胞，包括肿瘤干细胞和GBM中高度表达。在体外和体内，通过显性负性ATF 5（d/n-ATF 5）或siRNA-ATF 5阻断ATF 5功能促进神经胶质瘤肿瘤细胞的凋亡，但不促进非肿瘤细胞的凋亡。目前，我们合成了重组细胞穿透剂d/n-ATF5肽，其穿过血脑屏障，进入胶质瘤细胞，促进其快速死亡。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剂d/n-ATF 5在临床前方法中对肿瘤消退或完全根除的表观治疗指数。我们的具体目标将是1）定义用于递送不损害正常组织的细胞渗透剂d/n-ATF 5的最有效的给药方案;通过经由祖细胞的从头转化和通过人GBM异种移植物产生脑肿瘤来测试小鼠神经胶质瘤/胶质母细胞瘤模型中的功效;确定用所述肽的治疗是否可以带来胶质母细胞瘤的长期根除;以及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肽使它们再次消退。2)确定介导d/n-ATF5在胶质母细胞瘤细胞中凋亡作用的分子机制途径。深入了解这些途径将启发肿瘤如何依赖于ATF 5生存，这在非转化细胞中没有观察到。对机制途径的了解将有助于预测和规避脱靶效应，并将解释和促进避免对d/n-ATF 5疗法的潜在肿瘤抗性。最后，d/n-ATF 5与其他目前采用的胶质母细胞瘤疗法的协同作用将随着对这些途径的认识而得到更充分的解决。

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.