title: Cellular processing in the SW1222 cell line of mAb A33 directly and indirectly radiohalogenated.
abstract: Investigations into the cellular processing of radiolabeled monoclonal antibodies (mAbs) for their further use in radioimmunodiagnosis and cancer therapy are needed in order to understand the fate of internalized and catabolized mAbs. The anti-colorectal cancer mAb, A33, was labelled with 76Br and 125I using the direct Chloramine-T method, or by labelling N-succinimidyl para-(tri-methylstannyl) benzoate and its further conjugation to the mAb. The cellular processing of the four conjugates was investigated in SW1222 cells in vitro. Uptake of mAb was rapid, peaking after 14-16 h. Intracellular degradation was slow and the early loss of radioactivity was due to dissociation of cell-surface bound mAb. The indirect labelling resulted in stronger binding of the mAb as well as prolonged intracellular retention of the radiolabel. Direct and indirect halogen radiolabelling results in different cell-processing patterns of radiolabels, and radioactive catabolic products follow different routes of cellular excretion. The results of this cellular study indicate that indirect labelling is preferable to the direct Chloramine-T method.
authors.affiliation: Division of Radiology, Department of Oncology, Radiology and Clinical Immunology, Uppsala University, Uppsala, Sweden.
authors.forename: Johanna
authors.initials: J
authors.lastname: Höglund
authors.forename: Anna
authors.initials: A
authors.lastname: Orlova
authors.forename: Anders
authors.initials: A
authors.lastname: Sundin
authors.forename: Hans
authors.initials: H
authors.lastname: Lundqvist
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tolmachev
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D000912:Antibodies, Neoplasm / Q000737:chemistry; D001565:Benzoates / Q000494:pharmacology; D001967:Bromine Radioisotopes / Q000737:chemistry; D045744:Cell Line, Tumor; D002700:Chloramines / Q000494:pharmacology; D015179:Colorectal Neoplasms / Q000276:immunology* / Q000628:therapy*; D003470:Culture Media / Q000378:metabolism; D006219:Halogens / Q000737:chemistry; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry; D011485:Protein Binding; D016499:Radioimmunotherapy / Q000379:methods*; D013388:Succinimides / Q000494:pharmacology; D013997:Time Factors; D014105:Tosyl Compounds / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D001565:Benzoates; D001967:Bromine Radioisotopes; D002700:Chloramines; D003470:Culture Media; D006219:Halogens; D007457:Iodine Radioisotopes; C422194:N-succinimidyl 4-bromobenzoate; D013388:Succinimides; D014105:Tosyl Compounds; C016300:chloramine-T