Improving Delivery of Molecularly-Targeted Therapy to Invasive Glioma Cells

描述（由申请人提供）：多形性胶质母细胞瘤（GBM）是一种全脑疾病。即使是完整的手术切除肿瘤承载半球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块上。尽管越来越多的证据表明GBM的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转运系统，包括P-糖蛋白（Pgp）和乳腺癌耐药蛋白（BCRP）。肿瘤核心中的血脑屏障（BBB）是“渗漏的”，允许全身性药物递送，但胶质瘤细胞浸润离手术切除边缘几厘米远的正常脑结构，其中BBB是完整的并且具有功能性外排转运系统。分子靶向的抗肿瘤剂如酪氨酸激酶抑制剂（TKI，例如，伊马替尼、厄洛替尼、达沙替尼）的功效受到递送至实际靶标的连续障碍的限制，包括宏观分布的障碍（BBB处的主动外排）和微观递送的障碍（来自侵袭性神经胶质瘤细胞的主动外排）。因此，药物递送策略（1）改善所选“分子靶向”化疗剂通过BBB的递送，和（2）改善侵袭性神经胶质瘤细胞中的细胞内药物积累，将显著增强分子靶向治疗的功效。我们的中心假设是，侵袭性胶质瘤细胞可以通过特异性抑制BBB和侵袭性肿瘤细胞水平的主动外排来靶向，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递送和功效的策略。目的2将确定主动外排的影响，并优化策略，以克服外排，对TKI的疗效在一个新的自发性小鼠胶质瘤模型，生长侵袭性。目的3将确定在相对于传统异种移植物侵袭性生长的原发性人胶质瘤异种移植物模型中，使用靶向Pgp和BCRP的新型前药抑制主动外排转运对TKI疗效的影响。这些目标的完成将表明在BBB、侵袭性胶质瘤细胞屏障或两者处的主动外排转运是否是可以通过限制药物递送至侵袭性胶质瘤细胞来影响分子靶向治疗的功效的重要机制。如果成功的话，这些信息应该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.