MMP-9 is a zinc-dependent endopeptidase that is involved in the proteolytic degradation of the extracellular matrix and plays an important role in cancer migration, invasion, and metastasis. The aim of this study was to evaluate the potential of MMP-tracers [18F]BR420 and [18F]BR351 for MMP-9 imaging in a colorectal cancer xenograft model. [18F]BR420 and [18F]BR351 were synthesized using an automated synthesis module. For [18F]BR420, a novel and improved radiosynthesis was developed. Plasma stability and MMP-9-targeting capacity of both radiotracers was compared in the Colo205 colorectal cancer model. MMP-9 and MMP-2 expression levels in the tumors were evaluated by immunohistochemistry and in situ zymography. μPET imaging as well as ex vivo biodistribution revealed a higher tumor uptake for [18F]BR420 (3.15% ± 0.03% ID/g vs 0.94% ± 0.18% ID/g for [18F]BR351 at 2 hours pi) but slower blood clearance compared with [18F]BR351. [18F]BR351 was quickly metabolized in plasma with 20.28% ± 5.41% of intact tracer remaining at 15 minutes postinjection (PI). By contrast, [18F]BR420 displayed a higher metabolic stability with >86% intact tracer remaining at 2 hours PI. Immunohistochemistry revealed the presence of MMP-9 and MMP-2 in the tumor tissue, which was confirmed by in situ zymography. However, an autoradiography analysis of tracer distribution in the tumors did not correlate with MMP-9 expression. [18F]BR420 displayed a higher tumor uptake and higher stability compared with [18F]BR351 but a low tumor-to-blood ratio and discrepancy between tracer distribution and MMP-9 immunohistochemistry. Therefore, both tracers will not be usefulness for MMP-9 imaging in colorectal cancer.
MMP-9是一种
锌依赖性肽链内切酶,参与细胞外基质的蛋白
水解降解,在癌症迁移、侵袭和转移中发挥重要作用。本研究的目的是评估 MMP 示踪剂 [18F]BR420 和 [18F]BR351 在结直肠癌异种移植模型中用于 MMP-9 成像的潜力。 [18F]BR420和[18F]BR351使用自动合成模块合成。对于[18F]BR420,开发了一种新颖且改进的放射合成。在 Colo205 结直肠癌模型中比较了两种放射性示踪剂的血浆稳定性和 MMP-9 靶向能力。通过免疫组织
化学和原位酶谱法评估肿瘤中 MMP-9 和 MMP-2 的表达
水平。 μPET 成像以及离体
生物分布显示,[18F]BR420 的肿瘤摄取较高(注射后 2 小时,[18F]BR420 为 3.15% ± 0.03% ID/g,而 [18F]BR351 为 0.94% ± 0.18% ID/g),但血液清除速度较慢与[18F]BR351相比。 [18F]BR351 在血浆中快速代谢,注射后 15 分钟 (
PI) 残留有 20.28% ± 5.41% 的完整示踪剂。相比之下,[18F]BR420 显示出更高的代谢稳定性,在 2 小时
PI 时仍保留 >86% 的完整示踪剂。免疫组织
化学显示肿瘤组织中存在 MMP-9 和 MMP-2,并通过原位酶谱法证实。然而,肿瘤中示踪剂分布的放射自显影分析与 MMP-9 表达无关。与 [18F]BR351 相比,[18F]BR420 显示出更高的肿瘤摄取和更高的稳定性,但肿瘤与血液的比率较低,并且示踪剂分布与 MMP-9 免疫组织
化学之间存在差异。因此,这两种示踪剂都不适用于结直肠癌的 MMP-9 成像。