title: Quantitative in vivo immunohistochemistry of epidermal growth factor receptor using a receptor concentration imaging approach.
abstract: As receptor-targeted therapeutics become increasingly used in clinical oncology, the ability to quantify protein expression and pharmacokinetics in vivo is imperative to ensure successful individualized treatment plans. Current standards for receptor analysis are performed on extracted tissues. These measurements are static and often physiologically irrelevant; therefore, only a partial picture of available receptors for drug targeting in vivo is provided. Until recently, in vivo measurements were limited by the inability to separate delivery, binding, and retention effects, but this can be circumvented by a dual-tracer approach for referencing the detected signal. We hypothesized that in vivo receptor concentration imaging (RCI) would be superior to ex vivo immunohistochemistry (IHC). Using multiple xenograft tumor models with varying EGFR expression, we determined the EGFR concentration in each model using a novel targeted agent (anti-EGFR affibody-IRDye800CW conjugate) along with a simultaneously delivered reference agent (control affibody-IRDye680RD conjugate). The RCI-calculated in vivo receptor concentration was strongly correlated with ex vivo pathologist-scored IHC and computer-quantified ex vivo immunofluorescence. In contrast, no correlation was observed with ex vivo Western blot analysis or in vitro flow-cytometry assays. Overall, our results argue that in vivo RCI provides a robust measure of receptor expression equivalent to ex vivo immunostaining, with implications for use in noninvasive monitoring of therapy or therapeutic guidance during surgery.
authors.affiliation: Department of Surgery, Geisel School of Medicine at Dartmouth College, Lebanon, New Hampshire. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire. Kimberley.S.Samkoe@Dartmouth.edu.
authors.forename: Kimberley S
authors.initials: KS
authors.lastname: Samkoe
authors.affiliation: Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, Illinois.
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Tichauer
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Gunn
authors.affiliation: Department of Pathology, Geisel School of Medicine at Dartmouth College, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Wells
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Tayyaba
authors.initials: T
authors.lastname: Hasan
authors.affiliation: Department of Surgery, Geisel School of Medicine at Dartmouth College, Lebanon, New Hampshire. Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Pogue
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D066246:ErbB Receptors / Q000096:biosynthesis* / Q000302:isolation & purification; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D064593:Heterografts; D006801:Humans; D051379:Mice; D057054:Molecular Imaging / Q000379:methods*; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology / Q000628:therapy
chemical_list: D066246:ErbB Receptors