Improving Delivery of Molecularly-Targeted Therapy to Invasive Glioma Cells

描述(申请人提供)：多形性胶质母细胞瘤(GBM)是一种全脑疾病。即使完全手术切除肿瘤半球，也不可避免地会导致复发，因此已被放弃。尽管如此，大多数使用小分子药物的临床试验都将疗效(包括临床结果和生物标记物)的测量集中在可以手术切除的实体肿瘤上。尽管越来越多的证据表明，GBM不可避免的复发和致命性是由于未能有效地靶向侵袭性胶质瘤细胞，但还是这样做了。脑瘤细胞过度表达保护性主动外排转运系统，包括P-糖蛋白(Pgp)和乳腺癌耐药蛋白(BCRP)。肿瘤核心的血脑屏障(BBB)是“漏水的”，允许全身给药，但胶质瘤细胞渗透到距离手术切除边缘几厘米远的正常脑结构中，那里的BBB完好无损，具有功能外流运输系统。分子靶向抗肿瘤药物，如酪氨酸激酶抑制剂(TKIs，如伊马替尼、厄洛替尼、达沙替尼)，其疗效受到到达实际靶点的顺序障碍的限制，包括宏观分布障碍(血脑屏障主动外排)和微观给药障碍(侵袭性胶质瘤细胞的主动外排)。因此，采用如下给药策略：(1)改善通过血脑屏障的选择性“分子靶向”化疗药物的递送；(2)改善侵袭性胶质瘤细胞内的药物蓄积，将显著提高分子靶向治疗的疗效。我们的中心假设是，侵袭性胶质瘤细胞可以通过在血脑屏障和侵袭性肿瘤细胞水平上特异性地抑制主动外排来靶向，从而提高分子靶向酪氨酸激酶抑制剂的疗效。我们提出了三个具体目标来检验这一假设。目的1将描述改善TKI在人和小鼠原代胶质瘤细胞系中的传递和疗效的策略。目的2将确定主动外排的影响，并优化克服外排的策略，在一种新的自发的侵袭性生长的小鼠脑胶质瘤模型中，对TKI疗效产生影响。目的3研究以Pgp和BCRP为靶点的新型前体药物抑制主动外排转运对原发人脑胶质瘤异种移植模型中TKIs疗效的影响。这些目标的完成将表明，血脑屏障、侵袭性胶质瘤细胞屏障或两者的主动外流转运是通过限制药物输送到侵袭性胶质瘤细胞来影响分子靶向治疗效果的重要机制。如果成功，这一信息应该很容易转化为临床试验，并最终改善胶质瘤和其他中枢神经系统肿瘤的治疗。

DESCRIPTION (provided by applicant): Glioblastoma multiforme (GBM) is a disease of the entire brain. Even complete surgical resection of the tumor-bearing hemisphere inevitably leads to recurrence and has been abandoned. Nonetheless, the majority of clinical trials employing small molecule drugs have focused their measurements of efficacy (both clinical outcome and biomarkers) on the bulk tumor mass that can be surgically removed. This is done in spite of mounting evidence that suggests the inevitable relapse and lethality of GBM is due to a failure to effectively target invasive glioma cells. Brain tumor cells overexpress protective active efflux transport systems, including p-glycoprotein (Pgp) and breast cancer resistance protein (BCRP). The blood-brain barrier (BBB) in the tumor core is "leaky", allowing systemic drug delivery, but glioma cells infiltrate normal brain structures centimeters away from the margin of surgical resection where the BBB is intact and has functional efflux transport systems. Molecularly- targeted anti-tumor agents such as tyrosine kinase inhibitors (TKIs, e.g., imatinib, erlotinib, dasatinib) have their efficacy limited by sequential barriers to delivery to the actual target, including barriers to macroscopic distribution (active efflux at the BBB) and barriers to microscopic delivery (active efflux from invasive glioma cell). Therefore, drug delivery strategies that (1) improve the delivery of selected "molecularly-targeted" chemotherapeutic agents through the BBB, and (2) improve the intracellular drug accumulation in invasive glioma cells, will significantly enhance the efficacy of molecularly-targeted therapy. Our central hypothesis is that invasive glioma cells can be targeted through specific inhibition of active efflux at the level of both the BBB and the invasive tumor cell leading to improved efficacy of molecularly-targeted tyrosine kinase inhibitors. We propose three specific aims to test this hypothesis. Aim 1 will characterize strategies to improve TKI delivery and efficacy in both human and mouse primary glioma cell lines. Aim 2 will determine the influence of active efflux, and optimize strategies to overcome efflux, on TKI efficacy in a novel spontaneous mouse model of glioma that grows invasively. Aim 3 will determine the influence of inhibiting active efflux transport using a novel prodrug targeting Pgp and BCRP on the efficacy of TKIs in a primary human glioma xenograft model that grows invasively relative to traditional xenografts. Completion of these aims will indicate if active efflux transport at the BBB, the invasive glioma cell barrier, or both is an important mechanism that can influence the efficacy of molecularly-targeted therapy by limiting drug delivery to the invasive glioma cell. If successful, this information should be readily translatable to clinical trials and lead to eventual improvement in the treatment of gliomas, and other tumors of the central nervous system.