PET imaging of prostate cancer with 18F-Al-NODA-MATBBN

Design, Synthesis and Binding Affinity Evaluation of Cytochrome P450 1B1 Targeted Chelators

BACKGROUND

Cytochrome P450 1B1 (CYP1B1) is specifically expressed in a variety of tumors which makes it a promise imaging target of tumor.

OBJECTIVE

We aimed to design and synthesize CYP1B1 targeted chelators for the potential application in positron emission tomography (PET) imaging of tumor.

METHODS

1,4,7-triazacyclononane-1,4-diiacetic acid (NODA) was connected to the CYP1B1 selective inhibitor we developed before through polyethylene glycol (PEG) linkers with different lengths. The inhibitory activities of chelators 6a-c against CYP1 family were evaluated by 7-ethoxyresorufin o-deethylation (EROD) assay. The manual docking between the chelators and the CYP1B1 are conducted subsequently. To determine the binding affinities of 6a-c to CYP1B1 in cells, we further performed a competition study at the cell level.

RESULTS

Among three chelators, 6a with the shortest linker showed the best inhibitory activity against CYP1B1. In the following molecular simulation study, protein-inhibitor complex of 6a showed the nearest F-heme distance which is consistent with the results of enzymatic assay. Finally, the cell based competitive assay proved the binding affinity of 6a-c to CYP1B1 enzyme.

CONCLUSION

We designed and synthesized a series of chelators which can bind to CYP1B1 enzyme in cancer cells.To our knowledge, this work is the first attempt to construct CYP1B1 targeted chelators for radiolabeling and we hope it will prompt the application of CYP1B1 imaging in tumor detection.

Positron emission tomography imaging of a novel Anxa1-targeted peptide 18 F-Al-NODA-Bn-p-SCN-GGGRDN-IF7 in A431 cancer mouse models

Annexin 1 (Anxa1) is a highly specific surface marker of tumor vasculature in the lung and prostate solid tumors. The IF7 peptide was modified with a hydrophilic linker, GGGRDN, and coupled with a new bifunctional chelating agent NODA-Bn-p-SCN. The resulting peptides (NODA-Bn-p-SCN-GGGRDN-IF7) were successfully labeled with Al18 F. The targeting characteristics of the radiolabeled peptides were evaluated in the Anxa1 positive A431 tumor model. Micro-positron emission tomography (micro-PET) imaging revealed that the A431 tumors were clearly visualized (5.74 ± 1.13%ID/g, 3.92 ± 0.78%ID/g and 1.30 ± 0.43%ID/g at 0.5, 1, and 2 h post-injection, respectively). Anxa1 binding specificity was also demonstrated by reduced tumor uptake after co-injection with excessive unlabeled GGGRDN-IF7 peptide at 30, 60, and 120 min post-injection. 18 F-Al-NODA-Bn-p-SCN-GGGRDN-IF7 might be a potential PET imaging agent for detecting Anxa1 levels in cancers due to the favorable characteristics such as convenient synthesis, specific Anxa1 targeting, and good tumor uptakes.