Department of Medical Imaging at College of Medicine, University of Arizona, Tucson, AZ , USA.
Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX, USA.
Mol Imaging Biol. 2023 Feb;25(1):133-143. doi: 10.1007/s11307-021-01684-z. Epub 2021 Nov 29.
Previous studies indicate that Tc- and fluorescent-labeled c[Cys-Thr-Pro-Ser-Pro-Phe-Ser-His-Cys]OH (TCP-1) peptides were able to detect colorectal cancer (CRC) and tumor-associated vasculature. This study was designed to characterize the targeting properties of PEGylated and non-PEGylated TCP-1 peptides for CRC imaging.
Cell uptake of cyanine 7 (Cy7)-labeled TCP-1 probes (Cy7-PEG-TCP-1 and Cy7-TCP-1) was investigated in three CRC cell lines (human, HCT116 and HT29; mouse, CT26). Xenograft and orthotopic CRC tumor models with HCT116 and CT26 cells were used to characterize biodistribution and CRC tumor-targeting properties of TCP-1 fluorescence and radioligand with and without PEGylation, [Tc]Tc-HYNIC-PEG-TCP-1 vs. [Tc]Tc-HYNIC-TCP-1.
Fluorescence images showed that TCP-1 probes were distributed in the cytoplasm and nucleus of CRC cells. When CT26 cells were treated with unlabeled TCP-1 peptide prior to the cell incubation with Cy7-PEG-TCP-1, cell fluorescent signals were significantly reduced relative to the cells without blockade. Relative to Cy7-TCP-1, superior brilliance and visibility of fluorescence was observed in the tumor with Cy7-PEG-TCP-1 and maintained up to 18 h post-injection. [Tc]Tc-HYNIC-PEG-TCP-1 images in xenograft and orthotopic CRC models demonstrated that TCP-1 PEGylation preserved tumor-targeting capability of TCP-1, but its distribution (%ID/g) in the liver and intestine was higher than that of [Tc]Tc-HYNIC-TCP-1 (1.51 ± 0.29 vs 0.53 ± 0.12, P < 0.01). Better tumor visualization by [Tc]Tc-HYNIC-TCP-1 was observed in the orthotopic CRC model due to lower intestinal radioactivity.
TCP-1-based probes undergo endocytosis and localize in the cytoplasm and nucleus of human and mouse CRC cells. Tumor detectability of fluorescent TCP-1 peptide with a PEG spacer is promising due to its enhanced tumor binding affinity and rapid clearance kinetics from nontumor tissues. Non-PEGylated [Tc]Tc-HYNIC-TCP-1 exhibits lower nonspecific accumulation in the liver and gastrointestinal tract and might have better capability for detecting CRC lesions in clinical sites. TCP-1 may represent an innovative targeting molecule for detecting CRC noninvasively.
先前的研究表明，Tc 和荧光标记的 c[Cys-Thr-Pro-Ser-Pro-Phe-Ser-His-Cys]OH（TCP-1）肽能够检测结直肠癌（CRC）和肿瘤相关血管。本研究旨在研究聚乙二醇化和非聚乙二醇化 TCP-1 肽对 CRC 成像的靶向特性。
在三种 CRC 细胞系（人 HCT116 和 HT29；鼠 CT26）中研究了 Cy7 标记的 TCP-1 探针（Cy7-PEG-TCP-1 和 Cy7-TCP-1）的细胞摄取。使用携带 HCT116 和 CT26 细胞的异种移植和原位 CRC 肿瘤模型，研究 TCP-1 荧光和放射性配体的生物分布和 CRC 肿瘤靶向特性，包括聚乙二醇化和非聚乙二醇化的 [Tc]Tc-HYNIC-PEG-TCP-1 与 [Tc]Tc-HYNIC-TCP-1。
荧光图像显示，TCP-1 探针分布在 CRC 细胞的细胞质和细胞核中。当 CT26 细胞在用未标记的 TCP-1 肽处理后再用 Cy7-PEG-TCP-1 孵育时，与未经阻断的细胞相比，细胞荧光信号显著降低。与 Cy7-TCP-1 相比，在肿瘤中观察到 Cy7-PEG-TCP-1 的荧光亮度和可视性更高，并且在注射后 18 小时内仍保持。在异种移植和原位 CRC 模型中，[Tc]Tc-HYNIC-PEG-TCP-1 图像表明 TCP-1 聚乙二醇化保留了 TCP-1 的肿瘤靶向能力，但它在肝脏和肠道中的分布（%ID/g）高于 [Tc]Tc-HYNIC-TCP-1（1.51±0.29 与 0.53±0.12，P<0.01）。由于肠道放射性较低，在原位 CRC 模型中观察到 [Tc]Tc-HYNIC-TCP-1 对肿瘤的更好可视化。
基于 TCP-1 的探针通过内吞作用进入细胞，并定位于人源和鼠源 CRC 细胞的细胞质和细胞核中。由于 TCP-1 肽与聚乙二醇间隔物结合的亲和力增强，以及从非肿瘤组织中快速清除动力学，带有聚乙二醇间隔物的荧光 TCP-1 肽具有良好的肿瘤检测潜力。非聚乙二醇化的 [Tc]Tc-HYNIC-TCP-1 在肝脏和胃肠道中的非特异性积聚较低，可能具有更好的检测临床部位 CRC 病变的能力。TCP-1 可能代表一种用于非侵入性检测 CRC 的创新靶向分子。
