细胞递送载体介导基因及金纳米棒精准协同放射治疗肿瘤的分子影像学研究

Gene and nanoparticles therapy is the most revolutionary medical technology, but targeted delivery is the key for tumor therapy. Bone marrow mesenchymal stem cells (BMSC) can target tumors by identifying tumor cytokines. Our previous study found that Egr1 promoter can drive sodium iodide symporter (NIS) gene expression and promote the uptake of 131I, forming a positive feedback. But not achieving the desired effect because of short retention time and rapid excretion of the isotopes. Gold nanoparticles (Au) are new radiosensitizers in cancer radiation therapy owing to its strong absorption and high efficiency in generating secondary electrons under X-ray or γ-ray irradiation. In this study, a stable BMSC-Egr1-NIS cell line containing gold nanorods will be constructed, which contains: 1) NIS gene, driven by Egr1 promoter; 2) gold nanorods (Au-Gd) containing MR contrast agent Gd. The BMSC-Egr1-NIS containing Au-Gd will be transplanted into the glioblastoma and pancreatic carcinoma-bearing nude mice and further be recruited to the tumor microenvironment. 131I will then be injected intravenously, leading to the NIS expression in BMSCs within the tumor by activation of the Egr1 promoter through β and γ rays. More expression of NIS protein in tumor tissue will result in more tumor-spefic uptake of 131I, forming a positive feedback. Noninvasive 124I and Gd dual-modal PET/MR hybrid imaging with small animal coil will be used to monitor the location of BMSC dynamically, meanwhile, 18F-FDG and 18F-FMISO will be used to assess the treatment response. If successful, this Au-Gd nanorods delivered by BMSC-Egr1-NIS will be highly useful radiosensitizers capable of enhancing 131I radiation therapy of tumors.

基因及纳米治疗是最具革命性的医疗技术，但其靶向递送是肿瘤治疗的关键。骨髓间充质干细胞(BMSC)可识别肿瘤细胞分泌的细胞因子，靶向肿瘤组织。我们前期研究发现，以辐射敏感启动子Egr1在BMSC中启动NIS基因表达促进131I摄取，形成正反馈，提高了肿瘤核素摄取，但因滞留时间短、排出快，未达预期疗效。金纳米棒(Au)为新型放射增敏剂，经X或γ射线照射后，产生强的光电吸收效应和二次电子，增强射线对肿瘤的杀伤力，降低肿瘤乏氧细胞对射线的抵抗。本项目拟在前期研究基础上，构建携带Au-Gd金纳米棒的 BMSC-Egr1-NIS细胞，并静脉注射靶向脑胶质瘤及胰腺癌。通过Gd和激活NIS摄取的124I，采用具有小动物线圈PET/MR进行实时双模态定位显像；探索131I及Au对肿瘤最佳协同疗效，并以18F-FDG及18F-FMISO PET/MR对疗效进行评估。建立实时在体双模态精准定位及疗效评估技术。

如何将基因安全、高效、靶向地导入到肿瘤是基因治疗的研究热点。细胞为递送载体，靶向递送治疗基因，不但能提高疗效，而且可降低对正常组织的毒副作用。骨髓间充质干细胞（BMSC），具有独特的优势，利用肿瘤细胞分泌的多种细胞因子，靶向肿瘤组织。金纳米团簇(AuNCS)由于其优异的组织相容性和独特的光学性能，在生物医学领域具有特殊的价值。其在X 或γ 射线照射后，产生强的光电吸收效应和二次电子，能增强射线对肿瘤的杀伤力，可作为新型的放射增敏剂。在本研究中，我们利用BMSCs作为“细胞炸弹”，携带并同时将Erg1-hNIS和AuNCS传递到肿瘤，以实现细胞和核素的双重靶向治疗功能。通过NIS 基因摄取的124I 在具有小动物线圈的PET/CT 进行双模态定位显像，达到了双重精准定位靶细胞同时进行显像和治疗的作用。进一步成功建立了仿生细胞膜聚合物囊泡，通过十六烷基三甲基溴氨（CTAB）的配位从AuNRs表面与吲哚菁绿（ICG）和多丙丙酮（PCL）段结合，实现在一个激发波长下协同光热/光动力治疗前列腺癌。这个结构表现出了良好的细胞摄取，高效的肿瘤内积累，光热转换效率高和优异的光漂白性能，有助于基于ICG的肿瘤荧光成像。使用相同波长的近红外光谱进行激发，AuNR/ICG囊泡治疗可降低皮肤光损伤副作用。雄激素非依赖性的PSMA表达谱阴性的进展性前列腺癌在近红外照射下，AuNR/ICG囊泡通过产生ROS和破坏肿瘤细胞质中溶酶体膜的完整性来促进肿瘤细胞凋亡。近红外辐射增强PTT/PDT的体内实验也证实了这一疗效。AuNR/ICG囊泡可作为一种抗PSMA阴性去势的很有前途的辅助治疗方法。

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