Department of Oncology, University of Alberta, Edmonton, Canada T6G 1Z2.
Department of Surgery, University of Alberta, Edmonton, Canada T6G 2B7.
Mol Pharm. 2024 Sep 2;21(9):4648-4663. doi: 10.1021/acs.molpharmaceut.4c00549. Epub 2024 Aug 17.
Occult nodal spread and metastatic disease require longstanding imaging and biochemical assessments for thyroid cancer, a disease that has a propensity for diffuse, small-volume disease. We have developed a Cu-labeled platelet-derived growth factor receptor α (PDGFRA) antibody for immuno-PET of PDGFRA in metastatic papillary thyroid cancer (PTC). The present work describes the discovery of small cyclic PDGFRA-targeting peptides, their binding features, and radiolabeling with positron emitter gallium-68 (Ga) for characterization in thyroid cancer models. Phage-display technology with two separate libraries and seven different cell lines was used through three rounds of biopanning as well as flow cytometry and comparative analysis with recombinant protein to select specific peptide sequences. Phenotypic binding analysis was completed by using phosphorylation and cell migration assays. protein binding was analyzed with thermophoresis and flow cytometry using the fluorescent-labeled PDGFRA peptide. Peptide candidates were modified with the NOTA chelator for radiolabeling with Ga. cell uptake was studied in various thyroid cancer cell lines. studies of Ga-labeled peptides included metabolic stability and PET imaging. From the original library (10 compounds), five different peptide groups were identified based on biopanning experiments with and without the α subunit of PDGFR, leading to ∼50 peptides. Subsequent phenotypic screening revealed two core peptide sequences ( and ) that demonstrated significant changes in the level of PDGFRA phosphorylation and cell migration. Alanine scan sublibraries were created from these two lead peptide sequences, and peptides were radiolabeled using Ga-GaCl at pH 4.5, resulting in RCP > 95% within 34-40 min, including SPE purification. Cyclic peptide showed the strongest effects on cell migration, flow cytometry, and binding by visual interference color assay. Ga-labeled PDGFRA-targeting peptides showed elevated cell and tumor uptake in models of thyroid cancer, with being the lead candidate. However, metabolic stability was compromised for vs but without impacting tumor uptake or clearance profiles. First-generation radiolabeled cyclic peptides have been developed as novel radiotracers, particularly , for the molecular imaging of PDGFRA in thyroid cancer.
隐匿性淋巴结转移和转移性疾病需要对甲状腺癌进行长期的影像学和生化评估，甲状腺癌倾向于弥漫性、小体积疾病。我们开发了一种 Cu 标记的血小板衍生生长因子受体α（PDGFRA）抗体，用于免疫 PET 检测转移性甲状腺乳头状癌（PTC）中的 PDGFRA。本研究描述了小环 PDGFRA 靶向肽的发现、它们的结合特征以及用正电子发射体镓-68（Ga）进行放射性标记，用于在甲状腺癌模型中进行表征。使用两个独立的文库和七种不同的细胞系，通过三轮生物淘选以及流式细胞术和与重组蛋白的比较分析，选择特定的肽序列。通过磷酸化和细胞迁移测定完成表型结合分析。使用荧光标记的 PDGFRA 肽进行热泳动和流式细胞术分析蛋白质结合。用 NOTA 螯合剂修饰肽候选物，用 Ga 进行放射性标记。在各种甲状腺癌细胞系中研究了细胞摄取。Ga 标记肽的研究包括代谢稳定性和 PET 成像。从原始文库（10 个化合物）中，根据有无 PDGFRα 亚基的生物淘选实验，确定了五个不同的肽组，导致约 50 个肽。随后的表型筛选显示，两种核心肽序列（和）在 PDGFRA 磷酸化和细胞迁移水平上均发生显著变化。从这两个先导肽序列创建了丙氨酸扫描亚文库，并使用 Ga-GaCl 在 pH 4.5 下对肽进行放射性标记，导致在 34-40 分钟内 RCP ＞95％，包括 SPE 纯化。环状肽显示对细胞迁移、流式细胞术和视觉干扰颜色测定的结合具有最强的影响。Ga 标记的 PDGFRA 靶向肽在甲状腺癌模型中显示出升高的细胞和肿瘤摄取，其中是主要候选物。然而，与相比，代谢稳定性受到影响，但不影响肿瘤摄取或清除谱。第一代放射性标记的环状肽已被开发为新型放射性示踪剂，特别是，用于甲状腺癌中 PDGFRA 的分子成像。
