TUMOR UPTAKE OF GA67 BY PHOTODEGRADED NIFEDIPINE

Ga-67是否通过转铁蛋白（Tf依赖性或非依赖性方法）在肿瘤中积累多年来一直是一个有争议的话题。我们的初步数据表明，大多数正常组织和器官的Ga积累需要Tf和转铁蛋白受体（TfR）的存在下，但在许多情况下，肿瘤的Ga摄取可能是一个Tf独立的过程。 此外，我们已经证明，通过多种操作可以显着增加体外肿瘤细胞对镓的非转铁蛋白依赖性吸收，其中最有效的是将细胞与预先暴露的钙通道阻滞剂硝苯地平一起孵育。荧光或紫外线。在这项资助申请中，我们将探索光降解硝苯地平（PDN）介导Ga-67摄取的机制和效用。 我们将确定硝苯地平的光降解产物负责Ga-67摄取的行动。 本文对硝苯地平的紫外光和荧光光照射产物进行了色谱分离。 我们将通过HPLC，NMR，气相色谱-质谱，紫外和荧光光谱来表征它们的物理性质。 我们将评估最丰富的分离株介导细胞中Ga-67摄取的活性。 对于那些证明在促进吸收方面最丰富和最活跃的衍生物，我们将比较和定义它们在延长暴露于光的条件下和在储存中遇到的各种条件下促进Ga-67吸收的稳定性和持续活性。 最活跃，丰富和稳定的衍生物，我们建议定义PDN促进Ga-67摄取的机制。 基于PDN活性的其他报道和我们自己的观察，我们将关注PDN可能介导Ga-67摄取的4种最可能的方式：（1）通过钙通道;（2）通过激活Ca 2+介导的钙通道;（3）通过一氧化氮产生的作用;或（4）通过与受体介导的功能相关的作用。 我们还将确定PDN是否具有其他生物学或生理学特性，这些特性可能会扩大其实用性或使其临床应用复杂化。 将评估PDN的毒性。 将确定这些试剂对Ga-67在小鼠正常组织中的分布的影响，以及这些试剂是否允许以较低的活性进行早期成像。 将评价硝苯地平和PDN对作为培养细胞的外植体在小鼠中生长的各种类型的肿瘤对Ga-67的摄取的影响。 这将使我们能够评估PDN是否在所有组织中介导Ga-67的摄取，或者仅在癌症中介导Ga-67的摄取。 通过比较不同类型肿瘤中的摄取量，我们可以评估PDN在增强肿瘤中Ga-67摄取方面的广泛适用性。 即使对Ga-67摄取的刺激作用证明不是肿瘤特异性的，而是在所有组织中发现的，PDN仍然可以证明在缩短从Ga-67注射到成像所需的时间方面是有用的，并且可以允许以较低剂量的放射性核素获得诊断图像。

Whether Ga-67 accumulates in tumors by transferrin (Tf-dependent or independent methods has been a topic of controversy for years. Our preliminary data suggests that accumulation of Ga by most normal tissues and organs requires the presence of Tf and the transferric receptor (TfR), but that Ga uptake by tumors may be, in many cases, a Tf-independent process. Further, we have demonstrated that the Tf-independent uptake of gallium by tumor cells in-vitro can be increased significantly by a number of manipulations, the most powerful of which is incubation of the cells with nifedipine, a calcium channel blocker, that has been pre-exposed to either fluorescent or UV light. In this grant application, we will explore the mechanism and utility of photo-degraded nifedipine (PDN) in mediating Ga-67 uptake. We will determine which of the photodegradation products of nifedipine are responsible for the action on Ga-67 uptake. We will isolate the products of UV and fluorescent photo-irradiation of nifedpine chromatographically. We will characterize their physical properties by HPLC, NMR, gas chromatography-mass spectroscopy, and UV and fluorescence spectroscopy. We will assess the activity of the most abundant isolates on mediating uptake of Ga-67 in cells. For those derivatives that prove most abundant and active in promoting uptake, we will compare and define their stabilty and continued activity in promoting Ga-67 uptake under conditions of extended exposure to light and to a variety of conditions encountered in storage. With the most active, abundant and stable derivatives, we propose to define the mechanism by which PDN promotes Ga-67 uptake. Based on other reports of PDN activities, and our own observations, we will focus on the 4 most-likely ways that PDN may mediate Ga-67 uptake: (1) by means of a calcium channel; (2) by activating of a Ca2+-mediated calcium channel; (3) by an effect of nitric oxide production; or (4) by an effect related to a receptor-mediated function. We will also determine whether PDN has other biological or physiological properties that might expand their utility or complicate their clinical use. The toxicity of PDN will be assessed. The effect of these agents on the distribution of Ga-67 in normal tissues in mice will be determined, and whether the agents allow earlier imaging with less activity. The effect of nifedipine and PDN on the uptake of Ga-67 by a variety of types of tumors grown as explants of cultured cells in mice will be evaluated. This will enable us to assess whether PDN mediates uptake of Ga-67 in all tissues, or only in cancer. By comparing the magnitude of uptake in tumors of varying types, we can assess how broadly applicable PDN may be for enhancing uptake of Ga-67 in tumors. Even if the stimulatory effect on Ga-67 uptake proves not specific to tumors, but is found in all tissues, PDN may nonetheless prove useful in shortening the time required from injection of Ga-67 to imaging, and may allow diagnostic images to be obtained at a lower dose of the radionuclide.