Department of Diagnostic Radiology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
Department of Medicine, University of Louisville School of Medicine, Louisville, KY 40202, USA; James Graham Brown Cancer Center, University of Louisville School of Medicine, Louisville, KY 40202, USA.
Nucl Med Biol. 2014 Feb;41(2):179-85. doi: 10.1016/j.nucmedbio.2013.10.008. Epub 2013 Oct 29.
AS1411 is a 26-base guanine-rich oligonucleotide aptamer shown binding to surface nucleolin, a protein over-expressed in multiple cancer cells, thus AS1411 labeled with a PET isotope can be explored as a potential diagnostic imaging agent. Our objective was to perform preliminary biological characterization of (64)Cu-labeled AS1411 in vitro and in vivo.
Four chelators (DOTA, CB-TE2A, DOTA-Bn and NOTA-Bn) were selected to label AS1411 with Cu-64. 185kBq (5μCi) of each tracer was incubated in each well with H460 cells at 37°C for 1, 3, 6, 12, 24 and 48h, respectively (n=4). For microPET/CT imaging, 7.4MBq (200μCi) of AS1411 labeled with either (64)Cu-DOTA or (64)Cu-CB-TE2A was I.V. injected and multiple scans were obtained at 1, 3, 6 and 24h post injection. Afterward in vivo biodistribution studies were performed.
Percent uptake of (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was significantly higher than that of (64)Cu-DOTA-Bn-AS1411 and (64)Cu-NOTA-Bn-AS1411. About 90% of uptake for (64)Cu-DOTA-AS1411 and (64)Cu-CB-TE2A-AS1411 was internalized into cells within 3h and the internalization process was completed before 24h. Both tracers demonstrated reasonable in vivo stability and high binding affinity to the cells. MicroPET imaging with (64)Cu-CB-TE2A-AS1411 showed clear tumor uptake at both legs from 1 to 24h post injection, whereas both tumors were undetectable for up to 24h with (64)Cu-DOTA-AS1411. In addition, (64)Cu-CB-TE2A-AS1411 had faster in vivo pharmacokinetics than (64)Cu-DOTA-AS1411 with lower liver uptake and higher tumor to background contrast.
CB-TE2A is a preferred chelator with higher tumor-to-background ratio, lower liver uptake and faster clearance than DOTA. Aptamer imaging with (64)Cu-CB-TE2A-AS1411 may be feasible for detecting lung cancer, if an appropriate chelator can be identified and further validation can be performed with a known control oligonucleotide. It may also be used as a companion diagnostic imaging agent for AS1411 in the treatment of cancer.
AS1411 是一种 26 个碱基的富含鸟嘌呤的寡核苷酸适体，已被证明与表面核仁素结合，核仁素在多种癌细胞中过度表达，因此用 PET 同位素标记的 AS1411 可以作为一种有潜力的诊断成像剂进行探索。我们的目的是对体外和体内的（64）Cu 标记 AS1411 进行初步的生物学特征分析。
选择了四种螯合剂（DOTA、CB-TE2A、DOTA-Bn 和 NOTA-Bn）来标记 AS1411 与 Cu-64。每个示踪剂的 185kBq（5μCi）分别在 37°C 下与 H460 细胞孵育 1、3、6、12、24 和 48h（n=4）。对于 microPET/CT 成像，以静脉注射的方式注射了 7.4MBq（200μCi）的用（64）Cu-DOTA 或（64）Cu-CB-TE2A 标记的 AS1411，并在注射后 1、3、6 和 24h 进行多次扫描。之后进行了体内生物分布研究。
（64）Cu-DOTA-AS1411 和（64）Cu-CB-TE2A-AS1411 的摄取百分率明显高于（64）Cu-DOTA-Bn-AS1411 和（64）Cu-NOTA-Bn-AS1411。（64）Cu-DOTA-AS1411 和（64）Cu-CB-TE2A-AS1411 中约 90%的摄取在 3h 内被内化到细胞内，并且在 24h 之前完成了内化过程。两种示踪剂在体内均具有良好的稳定性和对细胞的高结合亲和力。用（64）Cu-CB-TE2A-AS1411 进行 microPET 成像，在注射后 1 至 24h 时，两条腿上的肿瘤摄取均清晰可见，而用（64）Cu-DOTA-AS1411 则在 24h 内无法检测到肿瘤。此外，（64）Cu-CB-TE2A-AS1411 的体内药代动力学比（64）Cu-DOTA-AS1411 更快，肝脏摄取更低，肿瘤与背景的对比度更高。
CB-TE2A 是一种更优的螯合剂，与 DOTA 相比，它具有更高的肿瘤与背景的比值、更低的肝脏摄取和更快的清除率。如果能够确定合适的螯合剂，并且可以用已知的对照寡核苷酸进行进一步验证，那么用（64）Cu-CB-TE2A-AS1411 进行适体成像可能有助于检测肺癌。它也可以作为 AS1411 治疗癌症的伴随诊断成像剂。
