Therapeutic Exploitation of Mutant BRAF for Astrocytoma

突变 BRAF 对星形细胞瘤的治疗利用

• 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
• 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

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）：儿童低级别星形细胞瘤（LGA）是一个重大的临床挑战。虽然化疗加放疗的5年无进展生存率约为68%，但显著的发病率与残留肿瘤的存在和当前治疗相关，包括神经内分泌-认知缺陷、视觉缺陷、血管病变和继发性肿瘤。此外，转移的可能性和恶性转化为高级别星形细胞瘤进一步有助于预后不良。最近的数据显示BRAF在~23%的LGA和60%的黄色星形细胞瘤中突变。我们已经建立了两个仅有的儿童LGA模型作为小鼠中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，因此提供了开发替代的、较少衰弱的治愈性疗法的独特模型。BT-40异种移植物对于突变的BRAF（V600 E）是杂合的，而BT-35异种移植物具有野生型BRAF。BT-40肿瘤对MEK抑制剂AZD 6244非常敏感，而BT-35肿瘤无反应，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。对AZD 6244的耐药性的特征在于MEK依赖性基因签名的增加、IL-6转录和分泌的增强以及STAT 3信号传导的激活。对AZD 6244的耐药性是不稳定的，因为在未经治疗的小鼠中传代的肿瘤恢复到药物敏感性，并且与IL-6和STAT 3活化降低相关。此外，两种BRAF（V600 E）突变型星形胶质细胞系对AZD 6244具有内在抗性，可诱导STAT 3激活，因为MEK受到抑制。STAT 3活化在抗性中的作用将在目标1中研究。对于BT-40肿瘤，对AZD 6244的敏感性的特征在于完全抑制TORC 1信号传导，这表明突变体BRAF控制PI 3 K/TORC 1信号传导轴。Akt和STAT 3信号在MEK调节TORC 1中的作用，以及同时抑制MEK和STAT 3以防止耐药性的发展或逆转对AZD 6244的耐药性，将在目的2中进行研究。我们计划在治疗上利用突变BRAF对TORC 1信号的控制。在BT-40异种移植物中，MEK抑制导致TORC 1下游的DNA修复蛋白FANCD 2的快速和完全丧失，从而潜在地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AZD 6244的组合将防止AZD 6244抗性细胞的出现的概念，因为需要突变BRAF来维持与暴露于顺铂或依托泊苷的细胞中的存活相关的Akt信号传导。我们将建立突变BRAF LGA的其他模型，并确定BT-40异种移植物的结果是否普遍适用。这些数据将成为快速翻译新型非遗传毒性和更传统的治疗方法的基础，与目前的治疗方法相比，这些治疗方法对复发性或手术不可切除的LGA儿童既有效又不那么虚弱。