title: Design, preparation, in vitro and in vivo evaluation of (99m)Tc-N2S2-Tat(49-57)-bombesin: a target-specific hybrid radiopharmaceutical.
abstract: The gastrin-releasing peptide receptor (GRP-r) is over-expressed in various human tumors. Recently, (99m)Tc-EDDA/HYNIC-Lys(3)-bombesin ((99m)Tc-BN) was reported as a radiopharmaceutical with specific cell GRP-r binding and images in breast cancer patients demonstrated distinct radioactivity accumulation in malignant tissue. The HIV Tat-derived peptide has been used to deliver a large variety of cargoes into cells. Therefore, a new hybrid radiopharmaceutical of type (99m)Tc-N(2)S(2)-Tat(49-57)-Lys(3)-bombesin ((99m)Tc-Tat-BN) would increase cell uptake. The aim of this research was to prepare and assess in vitro and in vivo uptake kinetics in cancer cells of (99m)Tc-Tat-BN and to compare its cellular internalization with that of (99m)Tc-BN. Structures of N(2)S(2)-Tat-BN and Tc(O)N(2)S(2)-Tat-BN were calculated by an MM procedure. (99m)Tc-Tat-BN was synthesized and stability studies carried out by HPLC and ITLC-SG analyses in serum and cysteine solutions. In vitro internalization was tested using human prostate cancer PC-3 cells and breast carcinoma cell lines MDA-MB231 and MCF7. Biodistribution was determined in PC-3 tumor-bearing nude mice. Results showed a minimum energy of 271 kcal/mol for N(2)S(2)-Tat-BN and 300 kcal/mol for Tc(O)N(2)S(2)-Tat-BN. (99m)Tc-Tat-BN radiochemical purity was >90%. In vitro studies demonstrated stability in serum and cysteine solutions, specific cell receptor binding and internalization in three cell lines was significantly higher than that of (99m)Tc-BN (p<0.05). The tumor-to-muscle radioactivity ratio was 8.5 for (99m)Tc-Tat-BN and 7 for (99m)Tc-BN. Therefore, this hybrid is potentially useful in breast and prostate cancer imaging.
authors.affiliation: Instituto Nacional de Investigaciones Nucleares, Mexico.
authors.forename: Clara L
authors.initials: CL
authors.lastname: Santos-Cuevas
authors.forename: Guillermina
authors.initials: G
authors.lastname: Ferro-Flores
authors.forename: Consuelo
authors.initials: C
authors.lastname: Arteaga de Murphy
authors.forename: Flor de M
authors.initials: Fde M
authors.lastname: Ramírez
authors.forename: Myrna A
authors.initials: MA
authors.lastname: Luna-Gutiérrez
authors.forename: Martha
authors.initials: M
authors.lastname: Pedraza-López
authors.forename: Rocío
authors.initials: R
authors.lastname: García-Becerra
authors.forename: David
authors.initials: D
authors.lastname: Ordaz-Rosado
mesh_terms: D000818:Animals; D001839:Bombesin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D001943:Breast Neoplasms / Q000175:diagnosis; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D016503:Drug Delivery Systems; D004355:Drug Stability; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D015609:Organotechnetium Compounds / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D011471:Prostatic Neoplasms / Q000175:diagnosis; D011485:Protein Binding; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D018004:Receptors, Bombesin / Q000378:metabolism; D013667:Technetium / Q000737:chemistry; D014018:Tissue Distribution
chemical_list: C542910:(99m)Tc-N(2)S(2)-Tat(49-57)-Lys(3)-bombesin; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D018004:Receptors, Bombesin; D013667:Technetium; D001839:Bombesin