Therapeutic Exploitation of Mutant BRAF for Astrocytoma

突变 BRAF 对星形细胞瘤的治疗利用

基本信息

批准号：
8584135
负责人：
PETER J HOUGHTON
金额：
$ 31.9万
依托单位：
RESEARCH INST NATIONWIDE CHILDREN'S HOSP
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-07-01 至 2018-04-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8584135
关键词：
Adult Astrocytoma BRAF gene Biological CDKN2A gene Cell Line Cells Cephalic Characteristics Child Childhood Childhood Astrocytic Tumor Childhood Solid Neoplasm Cisplatin Clinical Clinical Trials Cognitive deficits Cytotoxic agent DNA Damage DNA repair protein Data Dependence Development Disease Dose Drug Kinetics Drug resistance Etoposide Event Family member Genes Genetic Transcription Genomics Glioma Growth Factor Receptors Immune Induced Mutation Interleukin-6 Ionizing radiation JAK2 gene Juvenile Pilocytic Astrocytomas Lead MAP Kinase Gene MEK inhibition MEKs Malignant - descriptor Malignant Childhood Neoplasm Malignant Neoplasms Modeling Molecular Profiling Morbidity - disease rate Mus Mutate Mutation Neoplasm Metastasis Neurosecretory Systems Oncogenes Outcome PIK3CA gene PTEN gene Pathway interactions Patients Pediatric Brain Tumor Consortium Pediatric Neoplasm Pharmaceutical Preparations Pharmacotherapy Phase Physiological Population Progression-Free Survivals Radiation Toxicity Radiation therapy Radio Rare Diseases Recurrence Refractory Regulation Reporting Residual Tumors Resistance Resistance development Role STAT3 gene STK11 gene Signal Pathway Signal Transduction Survival Rate Testing Therapeutic Translations Vascular Diseases Visual Xenograft procedure base chemotherapy clinical application conventional therapy drug sensitivity effective therapy fusion gene gain of function gain of function mutation in vivo inhibitor/antagonist killings mutant neoplastic cell novel outcome forecast prevent public health relevance research clinical testing resistance mechanism subcutaneous therapeutic target tumor tumor xenograft

项目摘要

DESCRIPTION (provided by applicant): Low-grade astrocytomas (LGA) of childhood present a significant clinical challenge. While 5-year progression-free survival rate for chemotherapy plus radiotherapy is ~ 68%, significant morbidity is associated with the presence of residual tumor and the current therapy that includes neuroendocrine- cognitive deficits, visual deficits, vasculopathy and secondary tumors. Moreover, the metastatic potential and malignant transformation to a high-grade astrocytoma further contributes to the poor prognosis. Recent data show that BRAF is mutated in ~23% of LGA's, and 60% of xanthoastrocytomas. We have established two of the only childhood LGA models as direct patient- xenografts in mice. These tumors retain expression profiles and genomic alterations characteristic of the original patient's tumor, thus present unique models to develop alternative, less debilitating, curative therapy. BT-40 xenografts are heterozygous for mutated BRAF (V600E) whereas BT-35 xenografts have wild type BRAF. BT-40 tumors are exquisitely sensitive to the MEK inhibitor AZD6244, whereas BT-35 tumors are unresponsive, typical of other childhood tumor xenografts with wild type BRAF. Resistance to AZD6244 is characterized by an increase in the MEK-dependent gene signature, enhanced IL-6 transcription and secretion, and activation of STAT3 signaling. Resistance to AZD6244 is unstable, as tumors passaged in untreated mice revert to drug sensitivity, and correlates with decreased IL-6 and STAT3 activation. Further, two BRAF (V600E) mutant astrocytic cell lines intrinsically resistant to AZD6244 induce STAT3 activation as MEK is inhibited. The role of STAT3 activation in resistance will be studied in Aim 1. For BT-40 tumors sensitivity to AZD6244 is characterized by complete inhibition of TORC1 signaling, suggesting that mutant BRAF controls the PI3K/TORC1 signaling axis. The role of Akt and STAT3 signaling in MEK regulation of TORC1, and the simultaneous inhibition of MEK and STAT3 to prevent development of resistance, or reverse resistance to AZD6244, will be studied in Aim 2. We plan to exploit the control of mutant BRAF over TORC1 signaling therapeutically. In BT-40 xenografts, MEK inhibition leads to rapid and complete loss of the DNA repair protein FANCD2, downstream of TORC1, thus potentially selectively sensitizing tumor cells to cisplatin, etoposide and ionizing radiation. Further, we will test the concept that combination of cisplatin o etoposide with AZD6244 will prevent the emergence of AZD6244 resistant cells, as mutant BRAF is required to maintain Akt signaling associated with survival in cells exposed to cisplatin or etoposide. We will establish additional models of mutant BRAF LGA's, and determine whether results from BT-40 xenografts are generally applicable. These data will form the basis for rapid translation of novel non-genotoxic and also more conventional therapies that are both effective and less debilitating compared to current therapeutic approaches, for children with recurrent or surgically non-resectable LGA.

描述（由申请人提供）：儿童低度星形细胞瘤（LGA）提出了重大的临床挑战。虽然化疗加放疗的 5 年无进展生存率约为 68%，但显着的发病率与残留肿瘤的存在以及当前的治疗（包括神经内分泌认知缺陷、视力缺陷、血管病变和继发性肿瘤）有关。此外，高级别星形细胞瘤的转移潜力和恶变进一步导致预后不良。最近的数据显示，约 23% 的 LGA 和 60% 的黄色星形细胞瘤中 BRAF 发生突变。我们已经建立了两个唯一的儿童 LGA 模型作为小鼠的直接患者异种移植物。这些肿瘤保留了原始患者肿瘤的表达谱和基因组改变特征，因此提供了独特的模型来开发替代的、不那么衰弱的治疗疗法。 BT-40 异种移植物是突变 BRAF (V600E) 的杂合子，而 BT-35 异种移植物具有野生型 BRAF。 BT-40 肿瘤对 MEK 抑制剂 AZD6244 极其敏感，而 BT-35 肿瘤则无反应，这是其他具有野生型 BRAF 的儿童肿瘤异种移植物的典型特征。 AZD6244 抗性的特点是 MEK 依赖性基因特征增加、IL-6 转录和分泌增强以及 STAT3 信号传导激活。对 AZD6244 的耐药性不稳定，因为在未经治疗的小鼠中传代的肿瘤会恢复药物敏感性，并且与 IL-6 和 STAT3 激活降低相关。此外，两种对 AZD6244 具有内在抗性的 BRAF (V600E) 突变星形胶质细胞系会在 MEK 受到抑制时诱导 STAT3 激活。 STAT3 激活在耐药中的作用将在目标 1 中进行研究。对于 BT-40 肿瘤，对 AZD6244 敏感的特点是完全抑制 TORC1 信号传导，表明突变体 BRAF 控制 PI3K/TORC1 信号传导轴。目标 2 将研究 Akt 和 STAT3 信号在 TORC1 的 MEK 调节中的作用，以及同时抑制 MEK 和 STAT3 以防止耐药性的发展或逆转对 AZD6244 的耐药性。我们计划利用突变体 BRAF 对 AZD6244 的控制。 TORC1 信号传导治疗。在 BT-40 异种移植物中，MEK 抑制导致 TORC1 下游的 DNA 修复蛋白 FANCD2 快速完全丧失，从而可能选择性地使肿瘤细胞对顺铂、依托泊苷和电离辐射敏感。此外，我们将测试顺铂或依托泊苷与 AZD6244 组合将阻止 AZD6244 耐药细胞出现的概念，因为需要突变体 BRAF 来维持与暴露于顺铂或依托泊苷的细胞存活相关的 Akt 信号传导。我们将建立突变 BRAF LGA 的其他模型，并确定 BT-40 异种移植的结果是否普遍适用。这些数据将为快速转化新型非基因毒性疗法以及更传统的疗法奠定基础，对于患有复发性或手术不可切除的 LGA 的儿童，与目前的治疗方法相比，这些疗法既有效又不易使人衰弱。