Direct in vivo measurement of targeted binding in a human tumor xenograft.
Binding is crucial to the function of most biologically active molecules, but difficult to quantify directly in living tissue. To this end, fluorescence recovery after photobleaching was used to detect the immobilization of fluorescently labeled ligand caused by binding to receptors in vivo. Measurements of mAb affinity to target antigen within human tumor xenografts revealed a saturable binding isotherm, from which an in vivo carcinoembryonic antigen density of 0.56 nmol/g (5.0 x 10(5)/cell) and an association constant of Ka < or = 4 x 10(7) M(-1) were estimated. The present method can be adapted for in vivo studies of cell signaling, targeted drugs, gene therapy, and other processes involving receptor-ligand binding.
Berk
D A
DA
Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
Yuan
F
F
Leunig
M
M
Jain
R K
RK
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000954:Antigens, Surface / Q000378:metabolism*; D001665:Binding Sites; D002272:Carcinoembryonic Antigen / Q000276:immunology / Q000378:metabolism*; D003110:Colonic Neoplasms; D004058:Diffusion; D019793:Fluorescein; D005452:Fluoresceins / Q000378:metabolism; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011485:Protein Binding; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D002272:Carcinoembryonic Antigen; D005452:Fluoresceins; D005456:Fluorescent Dyes; C081679:monoclonal antibody ZCE 025; D019793:Fluorescein