title: Fusion of Gaussia luciferase to an engineered anti-carcinoembryonic antigen (CEA) antibody for in vivo optical imaging.
abstract: The bioluminescent protein Gaussia luciferase (GLuc) was fused to an anti-carcinoembryonic antigen (CEA) antibody fragment, the diabody, for in vivo optical tumor imaging. A 15-amino acid N-terminal truncation (GLDelta15) resulted in a brighter protein. Fusions of the anti-CEA diabody to full-length GLuc and GLDelta15 retained high affinity for the antigen, emitted light, and exhibited excellent enzymatic stability. In vivo optical imaging of tumor-bearing mice demonstrated specific targeting of diabody-GLDelta15 to CEA-positive xenografts, with a tumor/background ratio of 3.8 +/- 0.4 at four hours after tail-vein injection, compared to antigen-negative tumors at 1.3 +/- 0.1 (p = 0.001). MicroPET imaging using (124)I-diabody-GLDelta15 demonstrated specific uptake in the CEA-positive tumor (2.6% ID [injected dose]/g) compared to the CEA-negative tumor (0.4% ID/g) at 21 hours. Although further optimization of this fusion protein may be needed to improve in vivo performance, the diabody-GLDelta15 is a promising optical imaging probe for tumor detection in vivo.
authors.affiliation: Crump Institute for Molecular Imaging, Department of Molecular & Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Katy M
authors.initials: KM
authors.lastname: Venisnik
authors.forename: Tove
authors.initials: T
authors.lastname: Olafsen
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000912:Antibodies, Neoplasm / Q000235:genetics; D001483:Base Sequence; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D045744:Cell Line, Tumor; D033342:Copepoda / Q000201:enzymology / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics; D007457:Iodine Radioisotopes; D008156:Luciferases / Q000235:genetics; D008163:Luminescent Measurements; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000175:diagnosis* / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D015202:Protein Engineering; D019275:Radiopharmaceuticals; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014183:Transplantation, Heterologous
chemical_list: D000912:Antibodies, Neoplasm; D002272:Carcinoembryonic Antigen; D017931:DNA Primers; D007128:Immunoglobulin Fragments; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D011993:Recombinant Fusion Proteins; D008156:Luciferases