Enhanced Drug Delivery to Metastatic Brain Tumors

描述（由申请人提供）：脑毛细血管内皮及其邻近细胞、周细胞和星形胶质细胞是血脑屏障（BBB）的结构和功能组分。供应脑肿瘤的微血管保留BBB的特征，形成血肿瘤屏障（BTB）。虽然药物的充分递送发生在全身性肿瘤中，但BTB限制了药物递送到转移性脑肿瘤。像赫赛汀这样的药物，在治疗脑外转移性肿瘤方面是有效的，但由于通过BTB的输送不足，在脑内的失败率很高。转移性脑肿瘤的发病率比原发性脑肿瘤高10倍。我们已经证明，钙敏感性钾（KCa）通道激动剂选择性地增加跨BTB的药物递送，并假设这种选择性BTB渗透性增加的生化机制。我们也有初步的数据表明，ATP敏感性钾（KATP）通道激动剂选择性增加BTB的渗透性独立的KCa通道。这些新的观察结果允许选择性地增加跨BTB的药物递送的药理学机制。该提议将（a）进一步理解KCa和KATP通道激活在增加BTB渗透性中的机制，和（B）优化通过基于钾通道的机制将有效浓度的药物递送至大鼠和人的转移性乳腺和肺肿瘤。我们的数据显示KCa通道激动剂在大鼠胶质瘤模型中选择性增加药物通过BTB的能力，初步证据表明BTB渗透性增加可能与胶质瘤细胞和肿瘤毛细血管内皮上KCa通道的过度表达有关。在这篇文章中，我们将研究5个具体目标。目标1：确定KCa和KATP通道是否在转移性脑肿瘤微血管和肿瘤细胞中过表达，以及表达增加是否与KCa和KATP激动剂诱导的渗透性增加相关。检测肿瘤细胞是否能诱导脑内皮细胞上KCa或KATP通道的过度表达。目标二：通过定量电子显微镜检测KATP通道激动剂诱导的BTB通透性增加的机制是否是由于内皮囊泡转运增加或紧密连接打开。检测囊泡形成的增加是否与内皮细胞和肿瘤细胞膜电位的变化相关。目标3：研究KCa和KATP通道激动剂是否增加治疗性单克隆抗体和化疗药物穿过BTB向裸鼠/小鼠转移性人乳腺癌和肺癌的递送。目标4：在携带转移性乳腺和肺肿瘤的裸大鼠/小鼠中，我们将研究使用KCa或KATP激动剂通过BTB增加药物递送是否导致肿瘤生长的抑制，以及存活率是否增加。目标5：KATP通道激动剂米诺地尔增加抗肿瘤药物向脑肿瘤患者的递送的能力将通过切除的肿瘤组织中的LC-MS-MS来确定。这项拨款是响应最近的脑肿瘤PRG建议在2001年，以支持研究，以改善药物通过血脑屏障，特别是转移性脑肿瘤。总体而言，这些研究将进一步描述KCa和KATP通道激活作为跨BTB选择性递送抗癌药物的机制的作用，并可能改善转移性脑肿瘤患者的疾病控制。

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.