In Vivo Molecular Imaging of the Efficacy of Aminopeptidase N (APN/CD13) Receptor Inhibitor Treatment on Experimental Tumors Using ⁶⁸Ga‐NODAGA‐c(NGR) Peptide

Abstract

Introduction. The aminopeptidase N (APN/CD13) receptor plays an important role in the neoangiogenic process and metastatic tumor cell invasion. Clinical and preclinical studies reported that bestatin and actinonin are cytotoxic to APN/CD13-positive tumors and metastases due to their APN/CD13-specific inhibitor properties. Our previous studies have already shown that 68Ga-labeled NGR peptides bind specifically to APN/CD13 expressing tumor cells. The APN/CD13 specificity of 68Ga-NGR radiopharmaceuticals enables the following of the efficacy of antiangiogenic therapy with APN/CD13-specific inhibitors using positron emission tomography (PET). The aim of this in vivo study was to assess the antitumor effect of bestatin and actinonin treatment in subcutaneous transplanted HT1080 and B16-F10 tumor-bearing animal models using 68Ga-NODAGA-c(NGR). Materials and Methods. Three days after the inoculation of HT1080 and B16-F10 cells, mice were treated with intraperitoneal injection of bestatin (15 mg/kg) or actinonin (5 mg/kg) for 7 days. On the 5th and 10th day, in vivo PET scans and ex vivo biodistribution studies were performed 90 min after intravenous injection of 5.5 ± 0.2 MBq 68Ga-NODAGA-c(NGR). Results. Control-untreated HT1080 and B16-F10 tumors were clearly visualized by the APN/CD13-specific 68Ga-NODAGA-c(NGR) radiopharmaceutical. The western blot analysis also confirmed the strong APN/CD13 positivity in the investigated tumors. We found significantly ( p ≤ 0.05 ) lower radiopharmaceutical uptake after bestatin treatment and higher radiotracer accumulation in the actinonin-treated HT1080 tumors. In contrast, significantly lower ( p ≤ 0.01 ) 68Ga-NODAGA-c(NGR) accumulation was observed in both bestatin- and actinonin-treated B16-F10 melanoma tumors compared to the untreated-control tumors. Bestatin inhibited tumor growth and 68Ga-NODAGA-c(NGR) uptake in both tumor models. Conclusion. The bestatin treatment is suitable for suppressing the neoangiogenic process and APN/CD13 expression of experimental HT1080 and B16-F10 tumors; furthermore, 68Ga-NODAGA-c(NGR) is an applicable radiotracer for the in vivo monitoring of the efficacy of the APN/CD13 inhibition-based anticancer therapies.

Advances in Radionuclides and Radiolabelled Peptides for Cancer Therapeutics

“…Five days after injecting bestatin and actinonin, the PET scans showed that bestatin- and actinonin-treated B16-F10 tumours exhibited significantly low radiopharmaceutical uptake and accumulation. This means that the CD13 inhibitor may be suitable for suppressing the neoangiogenic process [ 154 ]. A comparative study of monomeric 68 Ga-NODAGA-NGR and dimeric 68 Ga-NODAGA-NH 2 was published by Ina Israel and colleagues in 2021.…”

Synthesis of 68Ga-Labeled cNGR-Based Glycopeptides and In Vivo Evaluation by PET Imaging

“…Previous studies already reported that B16-F10 melanoma tumors showed strong positivity for APN/CD13 and galectin-3 receptors [23,32,33]. For the determination of receptor targeting potential and biodistribution of the [ 68 Ga]-11, [ 68 Ga]-3, [ 68 Ga]-9, and [ 68 Ga]-10 radiotracers in vivo PET imaging studies and ex vivo tissue distribution studies were performed using B16-F10 melanoma tumor-bearing mice.…”

Chlorin e6 Phospholipid Delivery System Featuring APN/CD13 Targeting Peptides: Cell Death Pathways, Cell Localization, In Vivo Biodistribution

“…Studies have reported that APN/CD13 is overexpressed in endothelial cells of the tumor vascular network and in some solid tumors (melanoma, prostate carcinoma, lung cancer, pancreatic adenocarcinoma, ovarian cancer, breast cancer, colon cancer, etc.). Because of the increased expression, APN/CD13 can be regarded not only as an important clinical marker in some inflammatory diseases and malignancies, but also as a suitable target for antitumor and anti-inflammatory therapy [ 15 ]. The accessible location of the target (i.e., the tumor vascular network) and the high specificity of the ligand make NGR a suitable candidate for active targeting of macromolecule or nanoparticle systems in vivo.…”