Detection of lethal prostate cancer with macromolecule-based, EGFL-7 targeted MR imaging approach

 描述（由申请人提供）：成像方法对医学产生了变革性影响，允许在临床表现之前检测疾病，并促进诊断、预后以及疾病进展和治疗成功的纵向随访。磁共振成像（MRI）提供高空间分辨率和软组织对比度，而不会使患者暴露于电离辐射。然而，在患病和健康组织产生相似信号强度的区域，诊断可能很困难。我们提出了大分子对比度增强剂，其针对分子签名并提供大的磁共振造影Gd（DOTA）剂的有效载荷。我们将在前列腺癌的背景下评价拟议的MRI造影剂。在前列腺癌的早期诊断和过度治疗的可能性之间的平衡仍然是一个临床困境。为了区分侵袭性和惰性疾病，我们提出了一种靶向表皮生长因子样7（EGFL 7）的微创分子成像方法。这是一种促血管生成因子，其表达仅限于主动重塑血管内皮，并与不良预后相关。我们已经分离出以高选择性和亲和力（KD 7.2 nM）结合EGFL 7（HMYFLLGH）的肽配体。对于有效的MRI，载体需要提供足够的造影剂有效载荷;我们已经开发了一种超分子MRI造影剂，其携带螯合钆（Gd（DOTA））的大有效载荷，其T1弛豫率约为35，000 mM-1 s-1。这比小分子试剂高四个数量级，允许在亚微摩尔剂量的Gd（DOTA）下体内分子特征的可视化。该造影剂是使用由烟草花叶病毒（TMV）形成的中空蛋白质纳米管自组装而成，显示出优异的血液和组织生物相容性，包括快速组织清除以避免长期毒性。纳米管的细长形状使其能够逃避单核吞噬细胞系统（MPS）并增强分子靶向。基于这些令人兴奋的结果，我们建议开发这项技术作为前列腺癌分层的诊断工具。为了实现这一长期目标，该提案提出优化造影剂的形状和表面化学，以实现血管生成特征的高灵敏度和空间分辨率。自下而上的自组装协议将用于生产各种长度的纳米管，并将应用包括隐身和伪装在内的表面涂层，以避免免疫清除并增强分子靶向。将在前列腺癌动物模型中评价探针。将通过荧光成像和组织学验证MRI结果。我们假设，大分子MRI探针将超过当代的小分子，肽为基础的代理商增加灵敏度至少三个数量级。这将通过提供更大的有效载荷和优化分子靶向（表面化学和载体形状）来实现。这项技术可以在MR成像方法中产生广泛的影响，有助于恶性肿瘤的诊断和预后。

 DESCRIPTION (provided by applicant): Imaging approaches have made a transformative impact in medicine, allowing the detection of disease before clinical manifestation, and facilitating diagnosis, prognosis, and the longitudinal follow-up of disease progression and treatment success. Magnetic resonance imaging (MRI) provides high spatial resolution and soft tissue contrast without exposing the patient to ionizing radiation. However, diagnosis can be difficult in areas where diseased and healthy tissues produce similar signal intensities. We propose macromolecular contrast-enhancement agents that are targeted to molecular signatures and that deliver a large payload of magnetic resonance contrast Gd(DOTA) agents. We will evaluate the proposed MRI contrast agents in the setting of prostate cancer. The balance between early diagnosis and the potential for overtreatment in prostate cancer remains a clinical dilemma. To distinguish between aggressive and indolent disease, we propose a minimally-invasive molecular imaging approach targeting epidermal growth factor-like 7 (EGFL7). This is a pro-angiogenic factor whose expression is restricted to actively-remodeling vascular endothelium and correlates with poor prognosis. We have isolated peptide ligands that bind EGFL7 (HMYFLLGH) with high selectively and affinity (KD 7.2 nM). For effective MRI, carriers are required to deliver a sufficient payload of contrast enhancement agents; we have developed a supramolecular MRI contrast agent carrying large payloads of chelated gadolinium (Gd(DOTA)) which exhibits a T1 relaxivity of ~35,000 mM-1 s-1. This is four orders of magnitude higher than small-molecule agents, allowing the visualization of molecular signatures in vivo at sub-micromolar doses of Gd(DOTA). The contrast agent is self-assembled using hollow protein nanotubes formed by tobacco mosaic virus (TMV), which shows excellent blood and tissue biocompatibility, including rapid tissue clearance to avoid long-term toxicity. The elongated shape of the nanotube allows it to evade the mononuclear phagocyte system (MPS) and enhances molecular targeting. Building on these exciting results, we propose to develop this technology as a diagnostic tool for prostate cancer stratification. Toward this long-term goal, thi proposal sets out to optimize the shape and surface chemistry of the contrast agent to achieve high sensitivity and spatial resolution of the angiogenic signatures. A bottom-up self-assembly protocol will be used to produce nanotubes of various length and surface coatings including stealth and camouflage will be applied to avoid immune clearance and enhance molecular targeting. The probes will be evaluated in animal models of prostate cancer. MRI results will be validated by fluorescence imaging and histology. We hypothesize that the macromolecular MRI probe will outperform contemporary small-molecule, peptide-based agents by increasing sensitivity by at least three orders of magnitude. This will be achieved by delivering larger payloads and by optimized molecular targeting (surface chemistry and carrier shape). This technology could make a broad impact in MR imaging approaches aiding diagnosis and prognosis across malignancies.