Amino Acid Transport and the Biology of Human Gliomas

描述（由申请人提供）：胶质瘤是最常见和致命的原发性脑肿瘤。对于许多患者来说，顽固性头痛和癫痫发作是早期症状。癫痫发作由肿瘤相关的“瘤周”脑引起，并且在低级别胶质瘤中特别常见，其中高达90%的患者存在自发性复发性癫痫发作或通常难以治疗的“瘤周癫痫”。在该资助的上一个资助周期中开发的中心假设假定癫痫发作是由神经胶质瘤故意释放谷氨酸到肿瘤周围的大脑中引起的，导致异常的神经元谷氨酸受体激活，并且随着时间的推移，谷氨酸导致肿瘤相关的大脑区域变得过度兴奋。假设谷氨酸作为胱氨酸摄取的强制性副产物通过系统xc-（SXC）胱氨酸-谷氨酸交换剂释放到肿瘤细胞中。此外，肿瘤可能会吸收邻近的星形胶质细胞或招募小胶质细胞释放谷氨酸。这两种细胞中谷氨酸的释放是否以及如何参与癫痫发作的机制是本研究的主要问题。这个问题将通过比较从具有高或低SXC表达、shRNA沉默或药理学抑制的人异种移植物产生的荷瘤小鼠的癫痫发作表型来解决。将通过EEG/视频监测记录癫痫发作发展的时间过程，预期SXC表达减少会延迟癫痫发作并降低癫痫发作严重程度。为了研究神经元超兴奋性的细胞变化，包括神经递质受体和转运蛋白表达和功能，将对已知癫痫发作状态的动物的急性脑切片进行生物药理学研究。这些结果将通过对来自300多名人类胶质瘤患者的活检和组织微阵列的生物化学和免疫组织化学分析来补充，以寻找参与谷氨酸释放，再摄取或催化的蛋白质的变化。如果谷氨酸在癫痫发作中的作用得到证实，那么两种FDA批准的抑制谷氨酸释放或谷氨酸受体的药物柳氮磺胺吡啶和他仑帕奈的可用性将允许快速转化为患者的临床治疗。以前的胶质瘤研究几乎完全集中在高级别胶质瘤上，因此本研究的一个新目标是更有效地管理低级别胶质瘤的瘤周癫痫发作，这是一个重大的临床挑战。

DESCRIPTION (provided by applicant): Glioma is the most common and deadly primary brain tumor. For many patients intractable headaches and epileptic seizures are early symptoms. Seizures arise from tumor associated "peritumoral" brain and are particularly common in low grade gliomas where up to 90% of patients present with spontaneous recurring seizures, or "peritumoral epilepsy" that is often refractory to treatment. The central hypothesis developed during the previous funding cycle of this grant posits that seizures are caused by the deliberate release of glutamate from gliomas into the peritumoral brain, causing abnormal neuronal glutamate receptor activation, and, over time, glutamate causes tumor associated brain regions to become hyperexcitable. It is hypothesized that glutamate is released as an obligatory by-product of cystine uptake into tumor cells via the system xc- (SXC) cystine-glutamate exchanger. In addition, the tumor may co-opt adjacent astrocytes or recruit microglial cells to release glutamate. Whether and how glutamate release from either of these cells is mechanistically involved in seizure initiation is the principle question of this proposal. This question will be addressed by comparing the seizure phenotype of tumor bearing mice generated from human xenografts with high or low SXC expression, shRNA silencing or pharmacological inhibition. The time-course of seizure development will be documented by EEG/video monitoring with the expectation that reduced SXC expression delays seizure onset and reduces seizure severity. To study cellular changes underlying the neuronal hyperexcitability, including neurotransmitter receptor and transporter expression and function, acute brain slices from animals with known seizure status will be studied biophysically. These results will be complemented by biochemical and immunohistochemical analysis of biopsies and tissue micro arrays from over 300 human glioma patients to search for changes in proteins involved in glutamate release, reuptake or catabolism. If a role for glutamate in seizure initiatio is confirmed, the availability of two FDA approved drugs, Sulfasalazine and Talampanel that inhibit either glutamate release or glutamate receptors should allow for a rapid translation towards clinical treatment of patients. Previous glioma research has almost exclusively focused on high grade gliomas and hence a novel objective of this study is a focus on a more effective management of peritumoral seizures in low grade gliomas, which present a significant clinical challenge.