以外泌体为载体靶向肿瘤干细胞的多模态显像研究

Cancer stem cells are the main causes of tumor recurrence. Precise tracing and targeted therapy of cancer stem cells have become a hot field of current research. We have successfully applied 131I-CD133 mAb in tracing and preliminary treatment of colorectal cancer stem cells. However, every single imaging modality has its own limitations. Multimodality imaging technology can achieve complementary advantages and has become a new research direction. As a new type of natural nano-carrier with the advantages of strong passive targeting ability and low immunogenicity, exosome is becoming a potential carrier for the construction of multimodality imaging probes. In this project, we propose to construct a molecular probe with exosome as carrier, which is surface-modified with CD133 mAb as target-guiding molecules, loaded with super-small superparamagnetic nanoparticles, and labeled with positron nuclides 68Ga using pretargeting technology. In vivo and in vitro experiments will be conducted to investigate the probability of its application in PET/MR multimodal imaging for cancer stem cells. Furthermore, this project will provide theoretical and experimental basis for the construction of integrated theranostic probe based on exosomes for cancer stem cells.

肿瘤干细胞是导致肿瘤复发的主要原因，精准示踪及靶向治疗肿瘤干细胞已成为当前研究的热点，本课题组前期也成功应用131I-CD133 mAb进行了结直肠癌干细胞的示踪和初步治疗研究。但单模态显像技术有其局限性，多模态显像技术可以获取优势互补的生物学信息，因而正成为新的研究重点。外泌体作为一种新型天然纳米载体，具有被动靶向能力强、免疫原性低等优点，是多模态显像分子探针构建的潜在优质载体。本项目拟构建以外泌体为载体、表面修饰CD133 mAb靶向引导分子、包载超小超顺磁氧化铁纳米粒子的多模态分子探针，并应用预定位策略标记正电子核素68Ga。通过体内和体外实验，探索其用于PET/MR多模态显像靶向示踪肿瘤干细胞的可行性，进而可为下一步构建以外泌体为载体的诊疗一体化探针进行肿瘤干细胞靶向治疗奠定基础。

结直肠癌是最常见的胃肠道恶性肿瘤之一，我国结直肠癌发病率居恶性肿瘤第二位，死亡率居第五位。目前，手术是唯一可能治愈结直肠癌的方法，但大多数患者确诊时已处于中晚期，失去早期手术治疗的机会。因此，建立有效的结直肠癌早期诊断方法及精准的个体化治疗已成为研究热点，也是提高结肠癌预后的有效方法。纳米技术为结直肠癌早期精准诊疗提供了新思路。外泌体作为一种天然纳米载体，具备靶向能力强、表面易修饰、携载能力强等优势，是结直肠癌治疗的理想载体。本项目依托前期工作基础，逐步深入开展了以下5个研究：①脂质插入修饰外泌体用于结肠癌的SPECT/NIRF多模态成像；②预定位策略构建外泌体探针用于PET/CT/NIRF多模态影像引导结肠癌手术治疗；③外泌体诊疗探针在结肠癌的多模态成像及联合治疗；④羊奶外泌体诊疗探针用于多模态影像引导结肠癌的光热治疗；⑤以外泌体为载体靶向肿瘤干细胞的多模态显像；⑥以肿瘤来源外泌体为载体在荷瘤鼠模型中的PET/MR多模态显像研究。据此，我们探索了不同来源外泌体的优缺点（肿瘤来源外泌体具备优越的靶向性，脂肪干细胞源性外泌体具备高安生物全性，羊奶来源外泌体具备高产量、抗炎等特性），建立了外泌体修饰核素或荧光素的新方法（脂质插入和预定位策略），证实了外泌体的携载能力强（同时负载ALA与阿霉素），并将合成的外泌体探针应用于结肠癌模型的多种精准诊疗方式（影像引导手术，影像引导化学光动力联合治疗，影像引导光热治疗）。项目相关成果已发表JCR1区SCI论文5篇，其中10分以上的2篇；项目组成员参与国际核医学顶级会议（SNMMI年会）交流6场次。总之，本项目为结直肠癌的精准诊疗提供了一些新方法、新思路，具有一定的临床价值和转化前景。