Enhanced Drug Delivery to Metastatic Brain Tumors

描述(申请人提供)：脑毛细血管内皮细胞及其邻近细胞，周细胞和星形胶质细胞，是血脑屏障(BBB)的结构和功能组件。供应脑肿瘤的微血管保留了血脑屏障的特征，形成了血-肿瘤屏障(BTB)。虽然对全身肿瘤有足够的药物输送，但BTB限制了抗肿瘤药物对转移性脑瘤的输送。赫赛汀等药物对治疗脑外转移肿瘤有效，但由于BTB给药不足，其在大脑内的失败率很高。转移性脑瘤的发病率是原发脑瘤的10倍。我们已经证明了钙敏感钾(KCA)通道激动剂选择性地增加了跨BTB的药物输送，并推测了这种选择性BTB通透性增加的生化机制。我们也有初步数据表明，ATP敏感性钾(KATP)通道激动剂选择性地增加BTB通透性，而不依赖KCA通道。这些新颖的观察结果为选择性增加跨BTB的药物输送提供了一种药理学机制。这一建议将(A)进一步了解KCA和KATP通道激活在增加BTB通透性中的机制，以及(B)通过基于钾通道的机制优化有效浓度的药物输送到大鼠和人类的转移性乳腺和肺肿瘤。我们的数据表明，KCA通道激动剂能够选择性地增加大鼠脑胶质瘤模型中BTB的药物转运，初步证据表明，BTB通透性的增加可能与KCA通道在胶质瘤细胞和肿瘤毛细血管内皮细胞上的过度表达有关。在这笔赠款中，我们将调查5个具体目标。目的：探讨KCA和KATP通道在脑转移瘤微血管和肿瘤细胞中的过度表达及其与KCA和KATP激动剂诱导的通透性增加之间的关系。检测肿瘤细胞是否可诱导脑血管内皮细胞KCA或KATP通道过度表达。目的：用定量电子显微镜检测KATP通道激动剂诱导BTB通透性增加的机制是否与内皮细胞囊泡转运增加或紧密连接开放有关。以检验囊泡形成增加是否与内皮细胞和肿瘤细胞膜电位的变化有关。目的：研究KCA和KATP通道激动剂是否能增加治疗性单抗和化疗药物跨BTB向裸鼠转移性人乳腺癌和肺癌的转运。目的：在荷有转移性乳腺癌和肺癌的裸鼠模型上，我们将研究使用KCA或KATP激动剂增加跨BTB的药物释放是否会抑制肿瘤的生长，以及是否会增加存活率。目的：用LC-MS-MS法在切除的肿瘤组织中测定KATP通道激动剂米诺地尔增加脑肿瘤患者体内抗肿瘤药物转运的能力。这笔赠款是对2001年脑肿瘤研究小组建议的回应，该建议旨在支持研究，以改善跨血脑屏障的药物输送，特别是对转移性脑瘤的药物输送。总体而言，这些研究将进一步阐明KCA和KATP通道激活作为一种通过BTB选择性输送抗癌药物的机制的作用，并有可能改善转移性脑瘤患者的疾病控制。

DESCRIPTION (provided by applicant): Brain capillary endothelium and its contiguous cells, pericytes and astrocytes, are the structural and functional components of the blood-brain barrier (BBB). Microvessels supplying brain tumors retain characteristics of the BBB, forming a blood-tumor barrier (BTB). While adequate delivery of drugs occurs to systemic tumors, the BTB limits delivery of antineoplastic agents to metastatic brain tumors. Drugs such as Herceptin, which is effective in treating metastatic tumors outside the brain have a high failure rate within the brain due to inadequate delivery across the BTB. The incidence of metastatic brain tumors is ten-fold higher than primary brain tumors. We have demonstrated that calcium-sensitive potassium (KCa) channel agonists selectively increase drug delivery across the BTB, and have postulated the biochemical mechanisms of this selective BTB permeability increase. We also have preliminary data suggesting that ATP-sensitive potassium (KATP) channel agonists selectively increase BTB permeability independent of KCa channels. These novel observations allow for a pharmacological mechanism for selectively increasing drug delivery across the BTB. This proposal will (a) further understand the mechanisms of KCa, and KATP channel activation in increasing BTB permeability and (b) optimize delivery of effective concentrations of drugs to metastatic breast and lung tumors in rats and humans via potassium channel-based mechanisms. We build on our data showing the ability of KCa channel agonists to selectively increase drug delivery across the BTB in rat glioma models and preliminary evidence suggesting that the BTB permeability increase may relate to over expression of KCa channels on glioma cells and tumor capillary endothelium. In this grant we will investigate 5 specific aims. Aim 1: To determine whether KCa and KATP channels are over expressed in metastatic brain tumor microvessels and tumor cells and whether increased expression correlates with increased permeability induced by KCa and KATP agonists. To test whether tumor cells can induce over expression of KCa or KATP channels on brain endothelial cells. Aim 2: To test by quantitative electron microscopy whether the mechanism of KATP channel agonist-induced BTB permeability increase is due to increased endothelial vesicular transport or opening of tight junctions. To test whether increased vesicle formation is correlated with changes in endothelial and tumor cell membrane potential. Aim 3: To investigate whether KCa and KATP channel agonists increase delivery of therapeutic monoclonal antibodies and chemotherapeutic drugs across the BTB into metastatic human breast and lung cancer in nude rats/mice. Aim 4: In nude rats/mice harboring metastatic breast and lung tumors we will investigate whether increased drug delivery across the BTB using KCa or KATP agonists results in inhibition of tumor growth, and whether survival is increased. Aim 5: The ability of a KATP channel agonist, minoxidil, to increase delivery of an anti-tumor drug to patients with brain tumors will be determined by LC-MS-MS in resected tumor tissues. This grant is responsive to the recent Brain Tumor PRG recommendation in 2001 to support studies to improve delivery of drugs across the BBB, particularly for metastatic brain tumors. Overall, these studies will further delineate the role of KCa and KATP channel activation as a mechanism for selective delivery of anti-cancer agents across the BTB and could potentially result in improved control of disease in patients with metastatic brain tumors.