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）是胰腺癌的典型例子。 肿瘤是非常具有挑战性的治疗。治疗策略，可以绕过结缔组织增生“堡垒” 并进入缺氧微环境而不显著影响健康细胞将解决关键的 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（RT）的创新方法有着浓厚的兴趣。一种新的方法来增强 递送到肿瘤的辐射剂量是通过以下方式增加靶组织的辐射相互作用概率 递送高原子序数（Z）纳米颗粒（例如，金或氧化铪）与肿瘤细胞的结合。但由于 由于PDAC的旺盛结缔组织增生特征，即使是最小的纳米颗粒的扩散也受到以下限制： 致密的基质使得向癌细胞的递送极具挑战性。此外，最近的证据显示， 证实耗尽间质可能不是答案，因为间质抑制并限制癌细胞 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，我们解决了这个传递障碍，阻碍了有效的 放射增敏PDAC肿瘤采用最近报道的过程中，在原位金生物矿化， 哺乳动物癌细胞该策略将允许替换预合成的放射增敏金 纳米颗粒（GNP）与离子金原子，从而实现最小的可能大小的治疗剂- 单个离子原子。我们的假设是，小的金离子（i）将均匀地分布在整个肿瘤中，因为它们的 扩散不太可能受到基质的阻碍，（ii）将通过原位还原过程还原为GNP 在癌细胞特异性摄取后的生物矿化，和（iii）将放射增敏肿瘤，同时保留 邻近的正常组织这一假设是基于我们的初步数据表明， 细胞内合成的GNP在体外和体内对PDAC细胞的放射增敏作用。此外，本发明还提供了一种方法， 与最近的报道一致，正常胰腺细胞合成的GNP明显少于癌细胞 显示了在癌细胞中原位金生物矿化的效率高于非癌细胞。此外， 金盐类药物治疗类风湿关节炎的临床应用可以提供一个明确的途径， 临床翻译在这个项目中，我们设计了全面的机制研究，以评估和 优化原位生物矿化以实现PDAC的有效放射增敏。为此，我们将在以下领域开展研究： 三个协同目标：（1）确定细胞内合成的机制并优化条件 （2）评价体外和体内放射增敏效应的决定因素; (3)建立原位合成GNP放射增敏生物效应预测计算模型。 这些研究将为继续开发易于部署的放射增敏剂提供框架 胰腺癌的治疗策略可以扩展到其他不可切除的实体瘤。

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.