Targeting Tumorigenic Pathways in Glioblastoma with Oncolytic HSV

描述(申请人提供)：胶质母细胞瘤，最恶性的原发脑瘤，对所有形式的治疗仍然很难治疗，几乎都是致命的。 中位生存期约15个月。最近，分离的胶质母细胞瘤干细胞(GSCs)被认为在肿瘤逃避治疗的能力中起着重要作用。此外，我们发现它们产生的脑瘤保留了患者肿瘤的许多特征，因此它们为测试新的治疗方法提供了一个具有代表性的肿瘤模型，这是现有的细胞系所不具备的。我们和其他人已经开发出溶瘤单纯疱疹病毒(OHSV)载体，这种载体可以选择性地在癌细胞中复制并杀死癌细胞，而不会损害周围的正常组织或导致疾病。OHSV疗法的安全性已经在胶质母细胞瘤的临床试验中得到证实；然而，疗效仍然是坊间传闻，需要改进。在胶质母细胞瘤的临床试验中，OHSV载体包含？34.5基因的缺失，这使得它们在GSCs中是不允许的。因此，我们开发了一种新的针对US3缺失的OHSV，MG18L，这是这些研究的重点。US3基因是一种丝氨酸-苏氨酸激酶，能抑制细胞凋亡并磷酸化TSC2诱导翻译。我们假设MG18L在癌细胞中选择性地复制，因为它不能促进正常细胞的翻译或抑制病毒诱导的细胞凋亡，但GSCs中的异常通路使它们具有渗透性。为了降低病毒在大脑中的致病性，MG18L还在病毒核糖核苷酸还原酶基因中发生突变，该基因以病毒复制为目标来分裂癌细胞。US3缺失的HSV的另一个特征是PI3K/Akt通路的激活，这在大多数胶质母细胞瘤中是基因改变的。因此，我们假设MG18L将与PI3K/Akt途径的小分子抑制剂协同作用，其中许多目前正在进行临床试验，并杀死GSCs和肿瘤。我们最近发现，OHSV感染GSCs靶向ATM途径，并抑制同源重组(HR)DNA修复。HR缺陷的癌细胞可以用多聚腺苷二磷酸核糖聚合酶(PARP)抑制剂合成致死。因此，我们假设用MG18L处理GSCs将使它们对PARP抑制剂敏感，从而诱导合成的致死效应。这两种联合策略应该会极大地提高胶质母细胞瘤的治疗水平，并克服耐药性。我们预计，拟议研究中展示的治疗方法将可移植到临床。我们的长期目标是开发安全有效的OHSV载体用于临床，并阐明将提高疗效的联合策略。

DESCRIPTION (provided by applicant): Glioblastoma, the most malignant primary brain tumor, has remained largely refractory to all forms of therapy, and is almost uniformly lethal with a median survival of approximately 15 months. Recently isolated glioblastoma stem cells (GSCs) are thought to be important in the tumor's ability to evade therapy. In addition, we found that the brain tumors they generate retain many of the features of the patient tumors, so they provide a representative tumor model for testing new therapies, something that established cell lines do not. We, and others have developed oncolytic herpes simplex virus (oHSV) vectors that selectively replicate in and kill cancer cells, without harming the surrounding normal tissue or causing disease. The safety of oHSV therapy has been demonstrated in clinical trials for glioblastoma; however efficacy remains anecdotal and needs improvement. The oHSV vectors in clinical trial for glioblastoma contain deletions of the ?34.5 gene, which renders them non-permissive in GSCs. Therefore, we developed a new oHSV, MG18L, deleted for Us3 that is the focus of these studies. The Us3 gene is a serine-threonine kinase that inhibits apoptosis and phosphorylates TSC2 inducing translation. We hypothesize that MG18L selectively replicates in cancer cells because it is unable to promote translation or inhibit virus-induced apoptosis in normal cells, but dysregulated pathways in GSCs makes them permisive. To reduce virus pathogenicity in the brain, MG18L also is mutated in the viral ribonucleotide reductase gene, which targets virus replication to dividing cancer cells. Another feature of Us3-deleted HSV is activation of the PI3K/Akt pathway, genetically altered in the majority of glioblastomas. Therefore, we hypothesize that MG18L will synergize with small molecule inhibitors of the PI3K/Akt pathway, many of which are currently in clinical trial, and kill GSCs and tumors. We recently found that oHSV infection of GSCs targets the ATM pathway and inhibits homologous recombination (HR) DNA repair. Cancer cells deficient in HR are synthetic lethal with poly(ADP-ribose) polymerase (PARP) inhibitors. Thus, we hypothesize that treating GSCs with MG18L will sensitize them to PARP inhibitors inducing a synthetic lethal-like effect. Both of these combination strategies should greatly improve the treatment of glioblastoma and overcome drug resistance. We anticipate that therapies demonstrated in the proposed studies will be translatable to the clinic. Our long-term goal is to develop oHSV vectors that are safe and effective for clinical use and to elucidate combination strategies that will enhance efficacy.