title: In vivo and in vitro studies on renal uptake of radiolabeled affibody molecules for imaging of HER2 expression in tumors.
abstract: Affibody molecules (6-7 kDa) are a new class of small robust three-helical scaffold proteins. Radiolabeled subnanomolar anti-HER2 affibody ZHER2:342 was developed for imaging of HER2 expression in tumors, and a clinical study has demonstrated that the (111)In- and (68)Ga-labeled affibody molecules can efficiently detect HER2 expressing metastases in breast cancer patients. However, a significant renal accumulation of radioactivity after systemic injection of a radiolabeled anti-HER2 affibody conjugate is observed. The aim of this study was to investigate the mechanism of renal reabsorption of anti-HER2 affibody at the molecular level. Renal accumulation of radiolabeled anti-HER2 affibody molecules was studied in a murine model and in vitro using opossum-derived proximal tubule (OK) cells. It was found that kidney reabsorption of affibody molecule was not driven by megalin/cubilin. Amino acids in the target-binding side of affibody molecule were involved in binding to OK cells. On OK cells, two types of receptors for anti-HER2 affibody molecule were found: KD1=0.8 nM, Bmax1=71,500 and KD2=9.2 nM, Bmax2=367,000. The results of the present study indicate that affibody molecule and other scaffold-based targeting proteins with a relatively low kidney uptake can be selected using in vitro studies with tubular kidney cells.
authors: Unit of Biomedical Radiation Sciences, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden .
authors: Mohamed
authors: M
authors: Altai
authors: Zohreh
authors: Z
authors: Varasteh
authors: Karl
authors: K
authors: Andersson
authors: Annemarie
authors: A
authors: Eek
authors: Otto
authors: O
authors: Boerman
authors: Anna
authors: A
authors: Orlova
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry / Q000493:pharmacokinetics; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics; D007205:Indium Radioisotopes / Q000737:chemistry; D007668:Kidney / Q000378:metabolism*; D008297:Male; D051379:Mice; D057054:Molecular Imaging / Q000379:methods; D009893:Opossums; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis* / Q000096:biosynthesis*; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics*; D013667:Technetium / Q000737:chemistry; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D006573:Heterocyclic Compounds, 1-Ring; D018796:Immunoconjugates; D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; D013667:Technetium; C533351:affibody (ZHER2-342)2; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid