Tumor priming to promote nanoparticle gene delivery

描述(申请人提供)：基因载体传递不足一直是癌症基因治疗的一个主要限制因素。因此，成功地建立了一种促进基因载体传递的技术，特别是那些不太可能像病毒载体那样引起显著的、潜在的致命宿主毒性的非病毒载体，具有促进基因治疗的应用的潜力。我们实验室最近证实，大分子在实体肿瘤中渗透的主要决定因素是组织结构和组成，以及肿瘤细胞密度。我们进一步证明，通过使用紫杉醇和阿霉素等诱导细胞凋亡的药物(称为肿瘤启动)，可以破坏肿瘤结构和降低肿瘤细胞密度。这反过来会扩大间质空间，从而在三维肿瘤组织培养中和在动物体内移植的肿瘤中，大分子(在细胞凋亡发生后给药)对肿瘤的渗透更大、更均匀。我们将通过研究荧光标记的乳胶珠和脂质体在实体肿瘤中的传递和空间分布，来检验肿瘤启动增强纳米颗粒传递的假设。我们的初步结果表明，单一的紫杉醇治疗可以改善乳胶珠(直径100 nm)对实体肿瘤的输送。此外，还建议进行研究，以确定利用肿瘤启动方法提供最有利的递送增强的粒子特性，定义肿瘤结构变化的时间进程，并确定在具有不同灌流特性的肿瘤区域中启动的效果。研究将集中在脂质体上，因为这是有效的非病毒基因载体。需要这些数据来确定在肿瘤启动后提供基因治疗的机会窗口，并确定该技术的潜在效用和局限性。这些研究的成功完成将为非病毒基因载体和其他纳米粒子的传递提供一个新的范式，并为我们进一步研究粒子传递到肿瘤的机制提供背景信息。

DESCRIPTION (provided by applicant): Insufficient delivery of gene vectors has been a major limiting factor in gene therapy of cancer. Hence, successful establishment of a technology that promotes gene vector delivery, especially the nonviral vectors that are less likely to elicit significant, potentially fatal host toxicities as have been observed with viral vectors, has the potential of advancing the use of gene therapy. Our laboratory recently demonstrated that the major determinants of penetration of large molecules in solid tumors are tissue structure and composition, and tumor cell density. We further showed that disruption of tumor structure and reduction of tumor cell density can be accomplished by using drugs such as paclitaxel and doxorubicin that induce apoptosis (referred to as tumor priming). This, in turn, results in expanded interstitial space and consequently greater and more even tumor penetration of large molecules (administered after apoptosis has occurred), both in 3-dimensional tumor histocultures and in tumors implanted in animals. We will test the hypothesis that tumor priming enhances nanoparticle delivery, by studying the delivery and spatial distribution of fluorescence-labeled latex beads and liposomes in solid tumors. Our preliminary results indicate that a single paclitaxel treatment improved the delivery of latex beads (100 nm in diameter) to solid tumors. Further, studies are proposed to define the particle characteristics giving the most favorable enhancement of delivery with the tumor priming approach, define the time course of changes in the tumor architecture, and determine the effect of priming in tumor regions with different perfusion characteristics. Studies will focus on liposomes, as these are effective nonviral gene vectors. This data is needed to determine the window of opportunity for delivering gene therapy after tumor priming and to determine the potential utility and limitations of the technology. Successful completion of the proposed studies would provide a new paradigm for delivery of nonviral gene vectors and other nanoparticles, and provide the background information on which we can formulate further studies into the mechanism of particle delivery to tumors.