In situ cancer cell specific biomineralization to overcome nanoparticle delivery barriers and sensitize pancreatic cancer to radiotherapy

抽象的。胰腺导管腺癌(胰腺癌，PDAC)是顽固不化的典型例子。 这种肿瘤的治疗极具挑战性。可以绕过促结缔组织增生症的治疗策略 在不显著影响健康细胞的情况下获得低氧微环境将解决关键的 PDAC生理学提出的问题。局部治疗是PDAC治疗的关键组成部分， 人们对加强放射治疗的创新方法有着浓厚的兴趣。一种新的方法来增强 提供给肿瘤的辐射剂量是通过以下方式增加目标组织的辐射相互作用概率 向肿瘤细胞输送高原子序数(Z)纳米颗粒(例如，金或氧化汞)。然而，由于 PDAC旺盛的促结缔组织增生特性，即使是最小的纳米颗粒的扩散也受到以下限制 致密的间质使向癌细胞的传递具有极大的挑战性。此外，最近的证据表明 证实了耗尽间质可能不是答案，因为间质抑制和限制了癌细胞 而不是促进癌细胞的生长。我们认为，理想的战略是 穿透基质而不破坏它。在这里，我们解决了阻碍有效交付的交付障碍 采用最近报道的原位金生物矿化过程对PDAC肿瘤进行放射增敏 哺乳动物癌细胞。这一战略将允许替代预合成的放射增敏黄金 带有离子金原子的纳米颗粒(GNPs)，从而实现了治疗剂的最小尺寸-a 单离子原子。我们的假设是，小金离子(I)将均匀分布在整个肿瘤中，因为它们的 扩散不太可能受到基质的阻碍，(Ii)将通过原位过程还原为GNPs 癌细胞特定摄取后的生物矿化，以及(Iii)将使肿瘤放射增敏，同时节省 邻近的正常组织。这一假设是基于我们的初步数据证明了一个强大的 体外和体内细胞内合成的GNPs对PDAC细胞的放射增敏作用。此外, 正常胰腺细胞合成的GNPs明显少于癌细胞，这与最近的报道一致 显示与非癌症细胞相比，癌症细胞中原位金的生物矿化效率更高。此外，还有悠久的历史 以金盐为基础的药物在治疗类风湿性关节炎的临床应用可以提供一条明确的道路 临床翻译。在这个项目中，我们设计了全面的机械研究来评估和 优化原位生物矿化以实现PDAC的高效放射增敏。为此，我们将在以下方面进行研究 三个协同作用的目标：(1)确定细胞内合成的机制和优化条件 (2)评估体外和体内放射增敏效果的决定因素；以及 (3)建立原位合成GNPs放射增敏的预测生物效应计算模型。 这些研究将为继续开发易于部署的放射增敏提供框架 胰腺癌的策略，可以扩大到其他无法切除的实体肿瘤。

Abstract. Pancreatic ductal adenocarcinoma (pancreatic cancer, PDAC) is the classic example of a recalcitrant tumor that is extremely challenging to treat. Therapeutic strategies which can bypass the desmoplasia `fortress' and access hypoxic microenvironments without significantly affecting healthy cells would address the critical issues presented by PDAC physiology. Localized therapies are a critical component of PDAC treatment and there is strong interest in innovative ways to intensify radiation therapy (RT). A novel approach to enhancing the radiation dose delivered to tumors is to increase the radiation-interaction probability of the target tissues by delivering high atomic number (Z) nanoparticles (e.g., gold or hafnium oxide) to tumor cells. However, due to the exuberant desmoplasia characteristic of PDAC, the diffusion of even the smallest nanoparticles is limited by the dense stroma making delivery to cancer cells exceedingly challenging. Furthermore, recent evidence confirms that depleting the stroma may not be the answer since the stroma restrains and confines cancer cells to within the pancreas rather than promotes the growth of cancer cells. We contend that the ideal strategy is to penetrate the stroma without destroying it. Here we address this delivery barrier standing in the way of effective radiosensitization of PDAC tumors by employing a recently reported process of in situ gold biomineralization by mammalian cancer cells. This strategy will allow replacement of pre-synthetized radiosensitizing gold nanoparticles (GNPs) with ionic gold atoms thus achieving the smallest possible size of a therapeutic agent – a single ionic atom. Our hypothesis is that small gold ions (i) will uniformly distribute throughout the tumor as their diffusion is not likely to be impeded by the stroma, (ii) will be reduced to GNPs via the process of in situ biomineralization after specific uptake by cancer cells, and (iii) will radiosensitize the tumor while sparing adjacent normal tissue. This hypothesis is based on our preliminary data demonstrating a strong radiosensitization effect in PDAC cells by the intracellularly synthetized GNPs both in vitro and in vivo. In addition, normal pancreatic cells synthesized significantly fewer GNPs than cancer cells, consistent with recent reports showing higher efficiency of in situ gold biomineralization in cancer vs. non-cancer cells. Further, a long history of the clinical use of gold-salt based drugs in treatment of rheumatoid arthritis can provide a clear path towards clinical translation. In this project we have devised comprehensive mechanistic studies to evaluate and to optimize in situ biomineralization for efficient radiosensitization of PDAC. To this end we will carry out studies in three synergistic Aims: (1) to determine the mechanism of and to optimize conditions for intracellular synthesis of GNPs by PDAC cells; (2) to evaluate the determinants of radiosensitization efficacy in vitro and in vivo; and (3) to develop a predictive biological effect computational model of radiosensitization by in situ synthetized GNPs. These studies will provide the framework for continued development of a readily deployable radiosensitization strategy for pancreatic cancer that can be extended to other unresectable solid tumors.