title: Uptake, penetration, and binding of monoclonal antibodies with increasing affinity in human osteosarcoma multicell spheroids.
abstract: BACKGROUND
  Multicell spheroids from the human osteosarcoma cell line, OHS, were incubated with increasing concentrations of the monoclonal antibodies TP-1, TP-3 and 9.2.27 having different affinities (Ka = 8.5 x 10(8) M-1, 3.4 x 10(9) M-1 and 1.4 x 10(11) M-1, respectively).
  
  
  METHODS
  Uptake and penetration of the fluorescein labelled antibodies were studied using confocal laser scanning fluorescence microscopy, and antibodies bound per cell were measured using flow cytometry.
  
  
  RESULTS
  The antibody with highest affinity, 9.2.27, bound to all available binding sites in one cell-layer before reaching the next, whereas TP-3 and TP-1 gradually bound to an increasing number of epitopes of all cells throughout the spheroids. The penetration rate and antibody uptake increased with increasing antibody concentration up to saturating concentrations. 9.2.27 required saturation concentrations to reach the center of the spheroids, whereas TP-1 and TP-3 penetrated the centre when concentrations below saturation were applied.
  
  
  CONCLUSIONS
  The antibodies might be useful in radioimmunotherapy of micrometastases.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: M H
authors.initials: MH
authors.lastname: Hjelstuen
authors.forename: K
authors.initials: K
authors.lastname: Rasch-Halvorsen
authors.forename: O
authors.initials: O
authors.lastname: Bruland
authors.forename: C
authors.initials: C
authors.lastname: De L Davies
mesh_terms: D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D000951:Antigens, Neoplasm / Q000378:metabolism; D001859:Bone Neoplasms / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D012516:Osteosarcoma / Q000276:immunology / Q000378:metabolism; D018874:Spheroids, Cellular / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm