This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lee, D. J. Articles by Fleischer, A. C. PubMed PubMed Citation Articles by Lee, D. J. Articles by Fleischer, A. C.

Relationship Between Retention of a Vascular Endothelial Growth Factor Receptor 2 (VEGFR2)-Targeted Ultrasonographic Contrast Agent and the Level of VEGFR2 Expression in an In Vivo Breast Cancer Model

Harvard Medical School, Boston, Massachusetts USA (D.J.L.); Departments of Radiology and Radiological Sciences (A.L., A.C.F.) and Radiation Oncology (J.H., D.E.H.), Vanderbilt University Medical Center, Nashville, Tennessee USA; Vanderbilt University Institute of Imaging Science, Nashville, Tennessee USA (A.L., D.E.H.); and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee (D.E.H.).

Address correspondence to Arthur C. Fleischer, MD, Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave S, CCC-1121 MCN, Nashville, TN 37232 USA. E-mail: arthur.fleischer{at}vanderbilt.edu

Objective. The aim of this study was to characterize the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent (UCA) and VEGFR2 expression in tumor vasculature of breast cancer. Methods. 67NR breast cancer tumors implanted in mice were evaluated in vivo with both VEGFR2-targeted and nontargeted UCAs, and a high-frequency ultrasound system. A bolus of the UCA was injected and allowed to circulate for 4 minutes to allow binding of targeted microbubbles. After that, 2 sets of images before and after a high-power ultrasonic destruction sequence were acquired. The average video intensity of predestruction and postdestruction images was measured and used as a relative measure of retention of the UCA in the tumor. Levels of VEGFR2 expression and tumor vascular density were quantified by immunohistochemical staining and compared with retention of the VEGFR2-targeted UCA. Results. Retention of VEGFR2-targeted microbubbles in tumors was significantly higher than retention of nontargeted microbubbles (mean ± SD, 47.75 ± 9.85 versus 18.5 ± 5.46 dB; P < .001). Retention of the VEGFR2-targeted UCA was found to correlate with the level of VEGFR2 expression in the studied tumors (r² = 0.41). In contrast, retention of the nontargeted UCA was not correlated with the level of VEGFR2 expression (r² = 0.08). Furthermore, retention of the VEGFR2-targeted UCA was not correlated with the level of tumor vascularity. Conclusions. The magnitude of the molecular ultrasonographic signal from a VEGFR2-targeted UCA retained by tissue correlates with VEGFR2 expression. These results validate the use of molecular ultrasonography for in vivo detection and quantification of VEGFR2 expression in this breast cancer model.

Key Words: contrast agent • microbubbles • molecular expression • targeted contrast agent • ultrasonography • vascular endothelial growth factor receptor 2

Abbreviations: CD31, platelet/endothelial cell adhesion molecule 1 • IgG, immunoglobulin G • PBS, phosphate-buffered saline • TBST, Tris-buffered saline–Tween 20 • UCA, ultrasonographic contrast agent • VEGF, vascular endothelial growth factor • VEGFR, vascular endothelial growth factor receptor