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Updated: Jul 7, 2026
Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy
Published on: September 11, 2015
Imaging epidermal growth factor receptor expression in vivo: pharmacokinetic and biodistribution characterization of
Parmeswaran Diagaradjane1, Jacobo M Orenstein-Cardona, Norman E Colón-Casasnovas
1Department of Experimental Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
Purpose:
To develop and validate an optical imaging nanoprobe for the discrimination of epidermal growth factor (EGF) receptor (EGFR)-overexpressing tumors from surrounding normal tissues that also expresses EGFR.
Experimental Design:
Near-infrared (NIR) quantum dots (QD) were coupled to EGF using thiol-maleimide conjugation to create EGF-QD nanoprobes. In vitro binding affinity of these nanoprobes and unconjugated QDs was evaluated in a panel of cell lines, with and without anti-EGFR antibody pretreatment. Serial optical imaging of HCT116 xenograft tumors was done after systemic injection of QD and EGF-QD.
Results:
EGF-QD showed EGFR-specific binding in vitro. In vivo imaging showed three distinct phases, tumor influx ( approximately 3 min), clearance ( approximately 60 min), and accumulation (1-6 h), of EGF-QD nanoprobes. Both QD and EGF-QD showed comparable nonspecific rapid tumor influx and clearance followed by attainment of an apparent dynamic equilibrium at approximately 60 min. Subsequently (1-6 h), whereas QD concentration gradually decreased in tumors, EGF-QDs progressively accumulated in tumors. On delayed imaging at 24 h, tumor fluorescence decreased to near-baseline levels for both QD and EGF-QD. Ex vivo whole-organ fluorescence, tissue homogenate fluorescence, and confocal microscopic analyses confirmed tumor-specific accumulation of EGF-QD at 4 h. Immunofluorescence images showed diffuse colocalization of EGF-QD fluorescence within EGFR-expressing tumor parenchyma compared with patchy perivascular sequestration of QD.
Conclusion:
These results represent the first pharmacokinetic characterization of a robust EGFR imaging nanoprobe. The measurable contrast enhancement of tumors 4 h after systemic administration of EGF-QD and its subsequent normalization at 24 h imply that this nanoprobe may permit quantifiable and repetitive imaging of EGFR expression.
