title: In Vitro Mouse and Human Serum Stability of a Heterobivalent Dual-Target Probe That Has Strong Affinity to Gastrin-Releasing Peptide and Neuropeptide Y1 Receptors on Tumor Cells.
abstract: Receptor-targeting radiolabeled molecular probes with high affinity and specificity are useful in studying and monitoring biological processes and responses. Dual- or multiple-targeting probes, using radiolabeled metal chelates conjugated to peptides, have potential advantages over single-targeting probes as they can recognize multiple targets leading to better sensitivity for imaging and radiotherapy when target heterogeneity is present. Two natural hormone peptide receptors, gastrin-releasing peptide (GRP) and Y1, are specifically interesting as their expression is upregulated in most breast and prostate cancers. One of our goals has been to develop a dual-target probe that can bind both GRP and Y1 receptors. Consequently, a heterobivalent dual-target probe, t-BBN/BVD15-DO3A (where a GRP targeting ligand J-G-Abz4-QWAVGHLM-NH2and Y1 targeting ligand INP-K [ɛ-J-(α-DO3A-ɛ-DGa)-K] YRLRY-NH2were coupled), that recognizes both GRP and Y1 receptors was synthesized, purified, and characterized in the past. Competitive displacement cell binding assay studies with the probe demonstrated strong affinity (IC50values given in parentheses) for GRP receptors in T-47D cells (18 ± 0.7 nM) and for Y1 receptors in MCF7 cells (80 ± 11 nM). As a further evaluation of the heterobivalent dual-target probe t-BBN/BVD15-DO3A, the objective of this study was to determine its mouse and human serum stability at 37°C. The in vitro metabolic degradation of the dual-target probe in mouse and human serum was studied by using a153Gd-labeled t-BBN/BVD15-DO3A and a high-performance liquid chromatography/radioisotope detector analytical method. The half-life (t1/2) of degradation of the dual-target probe in mouse serum was calculated as 7 hours and only ∼20% degradation was seen after 6 hours incubation in human serum. The slow in vitro metabolic degradation of the dual-target probe can be compared with the degradation t1/2of the corresponding monomeric probes, BVD15-DO3A and AMBA: 15, and ∼40 minutes for BVD15-DO3A and 3.1 and 38.8 hours for AMBA in mouse and human serum, respectively. A possible pathway for in vitro metabolic degradation of the t-BBN/BVD15-DO3A in mouse serum is proposed based on the chromatographic retention times of the intact probe and its degradants.
authors.affiliation: Laboratory for Translational Research in Imaging Pharmaceuticals, The Wright Center of Innovation in Biomedical Imaging, Department of Radiology, The Ohio State University , Columbus, Ohio.
authors.forename: Arijit
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Laboratory for Translational Research in Imaging Pharmaceuticals, The Wright Center of Innovation in Biomedical Imaging, Department of Radiology, The Ohio State University , Columbus, Ohio.
authors.forename: Natarajan
authors.initials: N
authors.lastname: Raju
authors.affiliation: Laboratory for Translational Research in Imaging Pharmaceuticals, The Wright Center of Innovation in Biomedical Imaging, Department of Radiology, The Ohio State University , Columbus, Ohio.
authors.forename: Michael
authors.initials: M
authors.lastname: Tweedle
authors.affiliation: Laboratory for Translational Research in Imaging Pharmaceuticals, The Wright Center of Innovation in Biomedical Imaging, Department of Radiology, The Ohio State University , Columbus, Ohio.
authors.forename: Krishan
authors.initials: K
authors.lastname: Kumar
mesh_terms: D000345:Affinity Labels / Q000737:chemistry; D000818:Animals; D002614:Chelating Agents / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005682:Gadolinium / Q000737:chemistry; D019886:Gastrin-Releasing Peptide / Q000378:metabolism*; D006207:Half-Life; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D006801:Humans; D008024:Ligands; D061986:MCF-7 Cells; D051379:Mice; D015335:Molecular Probes / Q000737:chemistry*; D009478:Neuropeptide Y / Q000378:metabolism*; D011868:Radioisotopes; D018004:Receptors, Bombesin / Q000378:metabolism*; D017476:Receptors, Neuropeptide Y / Q000378:metabolism*; D044967:Serum / Q000737:chemistry
chemical_list: C520644:1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid; D000345:Affinity Labels; D002614:Chelating Agents; D006573:Heterocyclic Compounds, 1-Ring; D008024:Ligands; D015335:Molecular Probes; D009478:Neuropeptide Y; D011868:Radioisotopes; D018004:Receptors, Bombesin; D017476:Receptors, Neuropeptide Y; C097212:neuropeptide Y-Y1 receptor; D019886:Gastrin-Releasing Peptide; D005682:Gadolinium
keywords: GRP receptor; NPY receptor; dual-target probe; heterobivalent; human serum stability; mouse serum stability; radiolabeling; radiotracers