Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
EJNMMI Res. 2012 Sep 7;2(1):46. doi: 10.1186/2191-219X-2-46.
We aimed to develop a mouse spontaneous liver metastasis model from an orthotopically implanted human colon cancer cell line stably expressing a human sodium/iodide symporter (NIS) reporter gene, which can be imaged with single-photon emission computed tomography (SPECT) using 99mTcO4-.
A recombinant plasmid containing a constitutively driven NIS gene (pcDNA3-NIS) was transfected into the human colon cancer cell line HCT116, and stable cell lines were established. The stable cells were subcutaneously injected into the nude mice. When the diameter reached 10 mm, the xenografts were excised, cut into small fragments, and orthotopically implanted into the cecal walls of another nude mice. 99mTcO4- SPECT/CT imaging was initiated 8 weeks later and repeated every 1 to 2 weeks.
The production and function of NIS protein was confirmed in vitro by Western blotting and 99mTcO4- uptake assay. On SPECT/CT imaging, focal 99mTcO4- uptake was detected in the liver. Necropsy revealed local growth of the orthotopic colon xenografts with extensive invasion, microscopic serosal metastasis, and metastatic foci in the corresponding hepatic regions showing focal 99mTcO4- uptake. Immunohistochemistry revealed high levels of NIS expression in cells forming liver tumor, indicating that the liver tumor cells originated from the orthotopic colon xenografts.
The present proof-of-concept study provided a rationale for employing a radionuclide reporter gene for the specific visualization of spontaneous liver metastasis in living mice. This unique animal model of clinically relevant and externally detectable liver metastasis will be a powerful tool for investigating tumor biology and developing novel therapies for cancer metastasis.
我们旨在建立一个可通过单光子发射计算机断层扫描（SPECT）使用 99mTcO4-显影的稳定表达人钠/碘同向转运体（NIS）报告基因的原位植入人结肠癌细胞系的小鼠自发性肝转移模型，该模型可用于研究。
将包含组成型驱动的 NIS 基因（pcDNA3-NIS）的重组质粒转染入人结肠癌细胞系 HCT116，并建立稳定细胞系。将稳定细胞系皮下注射入裸鼠。当直径达到 10mm 时，切除异种移植物，切成小块，原位植入另一只裸鼠的盲肠壁。8 周后开始进行 99mTcO4- SPECT/CT 成像，并每 1-2 周重复一次。
通过 Western blot 和 99mTcO4-摄取测定，在体外证实了 NIS 蛋白的产生和功能。在 SPECT/CT 成像上，肝脏检测到焦点 99mTcO4-摄取。尸检显示原位结肠异种移植物局部生长，广泛侵袭，显微镜下可见浆膜转移，相应肝区有转移灶，显示焦点 99mTcO4-摄取。免疫组化显示形成肝肿瘤的细胞中 NIS 表达水平较高，表明肝肿瘤细胞来源于原位结肠异种移植物。
本概念验证研究为使用放射性核素报告基因特异性可视化活体小鼠自发性肝转移提供了依据。这种具有临床相关性和可外部检测的肝转移的独特动物模型将成为研究肿瘤生物学和开发癌症转移新疗法的有力工具。
