Mechanisms of Chemo/Radioresistance in Human Gliomas

描述(申请人提供)：恶性胶质瘤是人类癌症中最难治愈的肿瘤之一，尽管进行了积极的手术、放射治疗、化疗和新的靶向分子疗法的出现。这种对当前治疗方法的无反应在很大程度上源于恶性胶质瘤细胞对广泛的细胞毒剂的先天抵抗力。在我们最初的资助期间，我们确定了转录前和转录后的机制，SF/HGF是一种由人类恶性胶质瘤过度表达的多功能生长因子，通过它可以保护胶质瘤细胞免受遗传毒性药物的影响。我们发现，在体内靶向SF/HGF可以诱导胶质瘤细胞死亡，使胶质瘤对放射治疗增敏，并显著延长携带SF/HGF表达脑瘤的动物的生存时间。这些令人兴奋的发现为新启动和计划中的临床试验测试多形性胶质母细胞瘤的SF/HGF：C-Met途径抑制剂提供了生物学基础。这一雄心勃勃的合作研究计划的持续目标是确定胶质瘤抵抗细胞毒性的生化和分子机制，并进一步开发新的和潜在的可翻译策略来克服对死亡诱导剂的耐药性。死亡受体激动剂(TRAIL，FASL)具有选择性杀伤肿瘤细胞的能力，是一种很有前途的抗肿瘤药物。我们已经确定了使胶质瘤细胞对死亡受体激动剂增敏的新策略(例如，山奈霉素诱导的核毒应激)。在目标1中，我们将确定遗传毒性和核毒性应激诱导DISC(死亡启动信号复合体)形成和caspase-8激活的机制。在目标2中，我们将确定SF/HGF和其他受体酪氨酸激酶通路保护胶质瘤细胞免受死亡受体激动剂攻击的机制。与激酶相反，人们对磷酸酶如何参与致癌信号级联反应知之甚少。我们发现两个含有SH2的肌醇-5-磷酸酶(SHIP1和SHIP2)调节胶质瘤细胞对化疗药物的敏感性。在目标3中，我们将确定这些脂质磷酸酶调节胶质瘤细胞死亡的机制。在AIM#4中，我们将应用AIMS#1-3的新的死亡调节策略来增强临床前体内胶质瘤模型对细胞毒治疗(死亡受体激动剂、化疗和放射治疗)的抗肿瘤反应。这些实验的成功完成将揭示促进胶质瘤细胞死亡的新机制，并提供支持其治疗适用性的临床前证据。公共卫生相关性：多形性胶质母细胞瘤是成人中最常见和最具侵袭性的脑肿瘤，平均预期寿命约为14个月，确诊后两年内存活的患者不到30%。对积极治疗的这些令人沮丧的反应是由于胶质瘤细胞对当前的细胞毒治疗的先天抵抗力。这项研究计划将确定克服胶质瘤细胞对细胞毒剂耐药性的分子/生化方法，并测试它们在体内的治疗适用性。

DESCRIPTION (provided by applicant): Malignant glioma ranks among the least curable of human cancer despite aggressive surgery, radiation therapy, chemotherapy, and the emergence of new targeted molecular therapeutics. This unresponsiveness to current therapeutics stems to a great degree from the innate resistance of malignant glioma cells to a broad range of cytotoxic agents. During our initial funding period, we identified pre- and post-transcriptional mechanisms by which SF/HGF, a multifunctional growth factor overexpressed by human malignant gliomas, protects glioma cells against genotoxic agents. We showed that targeting SF/HGF in vivo induces glioma cell death, sensitizes glioma to radiation therapy, and markedly prolongs the survival of animals bearing SF/HGF- expressing brain tumors. These exciting discoveries contributed to the biological rationale for newly activated and planned clinical trials testing SF/HGF:c-Met pathway inhibitors in glioblastoma multiforme. The continued goals of this ambitious and collaborative research program are to identify biochemical and molecular mechanisms of glioma resistance to cytotoxicity and to further develop novel and potentially translatable strategies for overcoming resistance to death-inducing agents. Death receptor agonists (TRAIL, FASL) are promising anti-tumor agents by virtue of their ability to selectively kill tumor cells. We have identified novel strategies (e.g. anisomycin-induce ribotoxic stress) for sensitizing glioma cells to death receptor agonists. In Aim #1 we will determine the mechanisms by which genotoxic and ribotoxic stresses induce DISC (death- initiating signaling complex) formation and caspase-8 activation. In Aim #2 we will determine mechanisms by which SF/HGF and other receptor tyrosine kinase pathways protect glioma cells against death receptor agonists. In contrast to kinases, little is known of how phosphatases contribute to oncogenic signaling cascades. We found that two SH2-containing inositol-5-phosphatases (SHIP1 and SHIP2) regulate glioma cell sensitivity to chemotherapeutics. In Aim #3 we will determine the mechanisms by which these lipid phosphatases modulate glioma cell death. In Aim #4 we will apply the novel death modulating strategies of Aims #1-3 to enhance anti-tumor responses to cytotoxic therapeutics (death receptor agonists, chemotherapy, and radiation therapy) in pre-clinical in vivo glioma models. The successful completion of these experiments will reveal novel mechanisms for enhancing glioma cell death and provide pre-clinical evidence supporting their therapeutic applicability. PUBLIC HEALTH RELEVANCE: Glioblastoma multiforme, the most common and aggressive brain tumor in adults, has a median life expectancy of ~ 14 mo and fewer that 30% of patients are alive 2 years after diagnosis. These dismal responses to aggressive therapy are due to the innate resistance of glioma cells to current cytotoxic treatments. This research plan will identify molecular/biochemical approaches for overcoming glioma cell resistance to cytotoxic agents and test their therapeutic applicability in vivo.