| Autor: |
Pike, Susan, Wuest, Melinda, Lopez-Campistrous, Ana, Hu, Mi Yao, Derda, Ratmir, Wuest, Frank, McMullen, Todd |
| Zdroj: |
Molecular Pharmaceutics; September 2024, Vol. 21 Issue: 9 p4648-4663, 16p |
| Abstrakt: |
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 64Cu-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 (68Ga) for in vitro and in vivocharacterization 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. In vitroprotein 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 68Ga. In vitrocell uptake was studied in various thyroid cancer cell lines. In vivostudies of 68Ga-labeled peptides included metabolic stability and PET imaging. From the original library (1013compounds), 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 (CP16and CP18) 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 68Ga-GaCl3at pH 4.5, resulting in RCP > 95% within 34–40 min, including SPE purification. Cyclic peptide CP18.5showed the strongest effects on cell migration, flow cytometry, and binding by visual interference color assay. 68Ga-labeled PDGFRA-targeting peptides showed elevated cell and tumor uptake in models of thyroid cancer, with 68Ga-NOTA-CP18.5being the lead candidate. However, metabolic stability in vivowas compromised for 68Ga-NOTA-CP18.5vs 68Ga-NOTA-CP18but without impacting tumor uptake or clearance profiles. First-generation radiolabeled cyclic peptides have been developed as novel radiotracers, particularly 68Ga-NOTA-CP18.5, for the molecular imaging of PDGFRA in thyroid cancer. |
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