Enhanced Drug Delivery to Metastatic Brain Tumors

描述（申请人提供）：脑毛细血管内皮及其相邻细胞，周细胞和星形胶质细胞，是血脑屏障（BBB）的结构和功能组成部分。供应脑肿瘤的微血管保留血脑屏障的特征，形成血肿瘤屏障（BTB）。虽然全身性肿瘤可以得到充分的药物输送，但BTB限制了抗肿瘤药物对转移性脑肿瘤的输送。治疗脑外转移性肿瘤有效的药物，如赫赛汀（Herceptin），在脑内的失败率很高，因为无法通过BTB传递。转移性脑瘤的发病率是原发性脑瘤的十倍。我们已经证明，钙敏感的钾（KCa）通道激动剂选择性地增加BTB的药物传递，并假设了这种选择性BTB通透性增加的生化机制。我们也有初步的数据表明，atp敏感的钾（KATP）通道激动剂选择性地增加BTB的通透性，而不依赖于KCa通道。这些新的观察结果允许选择性地增加BTB的药物递送的药理学机制。该提案将(a)进一步了解KCa和KATP通道激活增加BTB通透性的机制，以及(b)通过基于钾通道的机制优化大鼠和人类转移性乳腺和肺部肿瘤有效浓度的药物递送。我们的数据表明，KCa通道激动剂能够选择性地增加大鼠胶质瘤模型中BTB的药物递送，初步证据表明BTB通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。在这项资助中，我们将研究5个具体目标。目的1：确定KCa和KATP通道在转移性脑肿瘤微血管和肿瘤细胞中是否过表达，以及表达增加是否与KCa和KATP激动剂诱导的通透性增加相关。检测肿瘤细胞是否能诱导脑内皮细胞过表达KCa或KATP通道。目的2：通过定量电镜检测KATP通道激动剂诱导BTB通透性增加的机制是由于内皮泡转运增加还是紧密连接打开。检测囊泡形成增加是否与内皮和肿瘤细胞膜电位变化相关。目的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通过BTB进入转移性人乳腺癌和肺癌裸鼠/小鼠。目的4：在携带转移性乳腺和肺肿瘤的裸鼠/小鼠中，我们将研究使用KCa或KATP激动剂增加BTB的药物递送是否会抑制肿瘤生长，以及是否会增加生存率。目的5：用LC-MS-MS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抗肿瘤药物递送的能力。这项拨款是对2001年脑肿瘤PRG建议的回应，该建议支持研究改善血脑屏障的药物输送，特别是转移性脑肿瘤。总的来说，这些研究将进一步描述KCa和KATP通道激活作为抗癌药物通过BTB选择性递送的机制的作用，并可能导致转移性脑肿瘤患者疾病控制的改善。

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.