title: Biodistribution and preparation of technetium-99m-labeled D-D₃ monoclonal antibody against pro-gastrin-releasing peptide (₃₁₋₉₈) in mice.
abstract: BACKGROUND
  We previously reported that iodine-131((131)I)-labeled anti-pro-gastrin-releasing peptide (ProGRP(31-98)) monoclonal antibody D-D3 could selectively accumulate in the tumor sites of nude mice bearing small cell lung cancer (SCLC) xenografts. However, (131)I-D-D3 was cleared slowly from the body, and the best radioimmunoimaging time for SCLC was 72 - 96 hours after injection. The aims of this study were to radiolabel anti-ProGRP(31-98) D-D3 monoclonal antibody with technetium-99m ((99m)Tc) and to investigate the biodistribution of this antibody in healthy ICR mice.
  
  
  METHODS
  D-D3 was labeled with (99m)Tc via the 2-mercaptoethanol reduction method. (99m)Tc-D-D3 was purified by the gel column separation method. The labeling efficiency and radiochemical purity were measured by thin-layer chromatography. The immunological activity of (99m)Tc-D-D3 was determined with cell conjugation assays. (99m)Tc-D-D3 was injected into healthy ICR mice via a tail vein, and all the healthy ICR mice were sacrificed by cervical dislocation at a designated time. Then, the blood and major organs were removed and weighed, and counted in a gamma scintillation counter to determine the percentage of the injected dose per gram (%ID/g).
  
  
  RESULTS
  The labeling rate and the radiochemical purity of (99m)Tc-D-D3 were (73.87 ± 2.89)% and (94.13 ± 4.49)%, respectively. The immunobinding rates of (99m)Tc-D-D3 to the human small cell lung cancer NCI-H446 cell line and lung adenocarcinoma A549 cell line were (81.2 ± 2.37)% and (24.3 ± 1.46)%, respectively. The distribution data of normal ICR mice demonstrated that (99m)Tc-D-D3 was mainly distributed in the liver, kidney and lung, and less in the brain tissue and muscle.
  
  
  CONCLUSIONS
  (99m)Tc-D-D3 antibody not only had high radiochemical purity, but also had good stability both in vitro and in vivo, and maintained good immunological activity. (99m)Tc-D-D3 was metabolized mainly in the kidney and liver, and the blood radioactivity decreased rapidly. Thus, (99m)Tc-D-D3 is conducive to the radioimmunoimaging of SCLC.
authors.affiliation: Department of Ultrasound, Second Affiliated Hospital of Soochow University, Suzhou 215004, Jiangsu, China.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Hao
authors.forename: Zhi-Hui
authors.initials: ZH
authors.lastname: Hong
authors.forename: Yi-Zhen
authors.initials: YZ
authors.lastname: Shi
authors.forename: Zeng-Li
authors.initials: ZL
authors.lastname: Liu
authors.forename: Xiao-Lin
authors.initials: XL
authors.lastname: Zhou
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D005260:Female; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010446:Peptide Fragments / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D013667:Technetium / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D011994:Recombinant Proteins; C087079:pro-gastrin-releasing peptide (31-98); D013667:Technetium