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导致复发，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其疗效（临床结果和生物标志物）的测量集中在可以通过手术切除的大块肿瘤上。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靶向侵袭性胶质瘤细胞而导致的。脑肿瘤细胞过度表达保护性主动外排运输系统，包括p糖蛋白（Pgp）和乳腺癌抵抗蛋白（BCRP）。肿瘤核心的血脑屏障（BBB）是“渗漏的”，允许全身药物递送，但胶质瘤细胞浸润到离手术切除边缘几厘米远的正常脑结构中，那里的血脑屏障是完整的，并具有功能性的外排运输系统。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）的疗效受到递送到实际靶点的顺序障碍的限制，包括宏观分布障碍（血脑屏障的主动外排）和微观递送障碍（侵袭性胶质瘤细胞的主动外排）。因此，(1)改善选定的“分子靶向”化疗药物通过血脑屏障的递送，(2)改善侵袭性胶质瘤细胞内药物蓄积的药物递送策略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抑制主动外排，从而提高分子靶向酪氨酸激酶抑制剂的疗效。我们提出三个具体目标来检验这一假设。目的1将描述改善TKI在人和小鼠原发性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，在一种新的侵袭性胶质瘤自发小鼠模型中对TKI疗效的影响。Aim 3将确定使用一种新的靶向Pgp和BCRP的前药抑制主动外排运输对TKIs在侵袭性生长的原发性人类胶质瘤异种移植模型中的疗效的影响。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排运输是否是通过限制药物向侵袭性胶质瘤细胞的递送来影响分子靶向治疗疗效的重要机制。如果成功，这些信息将很容易转化为临床试验，并最终改善神经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.