The overexpression of the translocator protein (TSPO) has been amply reported for a variety of conditions, including neurodegenerative disorders, heart failure, and cancer. Thus, TSPO has been proposed as an excellent imaging biomarker, allowing, in this manner, to obtain an accurate diagnosis and to follow disease progression and therapy response. Accordingly, several radioligands have been developed to accomplish this purpose. In this work, we selected [¹⁸F]FEPPA, as one of the clinical established tracers, and assessed its in vitro performance in colorectal cancer. Moreover, we setup an improved radiosynthesis method and assessed the in vitro binding affinity of the nonradioactive ligand toward the human TSPO. Our results show an excellent to moderate affinity, in the subnanomolar and nanomolar range, as well as the suitability of [¹⁸F]FEPPA as an imaging agent for the TSPO in colorectal cancer.

中文翻译：

---

[ ¹⁸ F] FEPPA：改善结直肠癌的自动放射合成，结合亲和力和初步体外评估

大量报道了多种疾病（包括神经退行性疾病，心力衰竭和癌症）中易位蛋白（TSPO）的过表达。因此，已经提出将TSPO作为优异的成像生物标志物，从而以这种方式获得准确的诊断并跟踪疾病的进展和治疗反应。因此，已经开发了几种放射性配体来实现该目的。在这项工作中，我们选择了[ ¹⁸F] FEPPA，作为临床上建立的示踪剂之一，并评估了其在结直肠癌中的体外性能。此外，我们建立了一种改进的放射合成方法，并评估了非放射性配体对人TSPO的体外结合亲和力。我们的结果显示，在亚纳摩尔和纳摩尔范围内具有极好的中度亲和力，以及[ ¹⁸ F] FEPPA作为TSPO在大肠癌中的显像剂的适用性。