title: Investigation of the Biological Impact of Charge Distribution on a NTR1-Targeted Peptide.
abstract: The neurotensin receptor 1 (NTR1) has been shown to be a promising target, due to its increased level of expression relative to normal tissue, for pancreatic and colon cancers. This has prompted the development of a variety of NTR1-targeted radiopharmaceuticals, based on the neurotensin (NT) peptide, for diagnostic and radiotherapeutic applications. A major obstacle for the clinical translation of NTR1-targeted radiotherapeutics would likely be nephrotoxicity due to the high levels of kidney retention. It is well-known that for many peptide-based agents, renal uptake is influenced by the overall molecular charge. Herein, we investigated the effect of charge distribution on receptor binding and kidney retention. Using the [(N-α-Me)Arg8,Dmt11,Tle12]NT(6-13) targeting vector, three peptides (177Lu-K2,177Lu-K4, and177Lu-K6), with the Lys moved closer (K6) or further away (K2) from the pharmacophore, were synthesized. In vitro competitive binding, internalization and efflux, and confocal microscopy studies were conducted using the NTR1-positive HT-29, human colon cancer cell line. The177/natLu-K6 demonstrated the highest binding affinity (21.8 ± 1.2 nM) and the highest level of internalization (4.06% ± 0.20% of the total added amount). In vivo biodistribution, autoradiography, and metabolic studies of177Lu-radiolabeled K2, K4, and K6 were examined using CF-1 mice.177Lu-K4 and177Lu-K6 gave the highest levels of in vivo uptake in NTR1-positive tissues, whereas177Lu-K2 yielded nearly 2-fold higher renal uptake relative to the other radioconjugates. In conclusion, the position of the Lys (positively charged amino acid) influences the receptor binding, internalization, in vivo NTR1-targeting efficacy, and kidney retention profile of the radioconjugates. In addition, we have found that hydrophobicity likely play a role in the unique biodistribution profiles of these agents.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, ‡Center for Drug Delivery and Nanomedicine, §Department of Biochemistry and Molecular Biology, College of Medicine, and ∥Eppley Cancer Center, University of Nebraska Medical Center , Omaha, Nebraska 985830, United States.
authors.forename: Yinnong
authors.initials: Y
authors.lastname: Jia
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, ‡Center for Drug Delivery and Nanomedicine, §Department of Biochemistry and Molecular Biology, College of Medicine, and ∥Eppley Cancer Center, University of Nebraska Medical Center , Omaha, Nebraska 985830, United States.
authors.forename: Wenting
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, ‡Center for Drug Delivery and Nanomedicine, §Department of Biochemistry and Molecular Biology, College of Medicine, and ∥Eppley Cancer Center, University of Nebraska Medical Center , Omaha, Nebraska 985830, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Fan
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, ‡Center for Drug Delivery and Nanomedicine, §Department of Biochemistry and Molecular Biology, College of Medicine, and ∥Eppley Cancer Center, University of Nebraska Medical Center , Omaha, Nebraska 985830, United States.
authors.forename: Susan
authors.initials: S
authors.lastname: Brusnahan
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, ‡Center for Drug Delivery and Nanomedicine, §Department of Biochemistry and Molecular Biology, College of Medicine, and ∥Eppley Cancer Center, University of Nebraska Medical Center , Omaha, Nebraska 985830, United States.
authors.forename: Jered
authors.initials: J
authors.lastname: Garrison
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D019073:HT29 Cells; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D051379:Mice; D009496:Neurotensin / Q000737:chemistry* / Q000378:metabolism* / Q000493:pharmacokinetics; D018028:Receptors, Neurotensin / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D018028:Receptors, Neurotensin; D009496:Neurotensin; D008239:Lysine