US Imaging of Tumor Angiogenesis with Microbubbles Targeted to Vascular Endothelial Growth Factor Receptor Type 2 in Mice

Abstract

Purpose-To prospectively evaluate contrast material-enhanced ultrasonography (US) with microbubbles targeted to vascular endothelial growth factor receptor type 2 (VEGFR2) for imaging tumor angiogenesis in two murine tumor models. Materials and Methods-Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. A US contrast agent, consisting of encapsulated gaseous microbubbles, was developed specifically to bind to VEGFR2 (by using anti-VEGFR2 antibodies and biotin-streptavidin interaction) which is up-regulated on endothelial cells of tumor blood vessels. VEGFR2-targeted microbubbles (MB V), control microbubbles (MB C), and nonlabeled microbubbles (MB N) were tested for binding specificity on cells expressing VEGFR2 (mouse angiosarcoma SVR cells) and control cells (mouse skeletal myoblast C2C12 cells). Expression of mouse VEGFR2 in culture cells was tested with immunocytochemical and Western blot analysis. Contrast-enhanced US imaging with MB V and MB C was performed in 28 tumor-bearing nude mice (mouse angiosarcoma, n = 18; rat malignant glioma, n = 10). Differences were calculated by using analysis of variance. Results-In cell culture, adherence of MB V on SVR cells (2.1 microbubbles per SVR cell) was significantly higher than adherence of control microbubbles (0.01-0.10 microbubble per SVR cell; P < .001) and significantly more MB V attached to SVR cells than to C2C12 cells (0.15 microbubble per C2C12 cell; P < .001). In vivo, contrast-enhanced US imaging showed significantly higher average video intensity when using MB V compared with MB C for

Assessment of hepatic VX2 tumors with combined percutaneous transhepatic lymphosonography and contrast-enhanced ultrasonographic imaging

“…Ultrasound contrast agents containing encapsulated microbubbles are mainly used to increase the diagnostic imaging of tumors. McCarville et al [18] showed that gray-scale US measurements of microbubble contrast agent flow can be used to detect the functional consequences of antiangiogenic therapy for tumors and to assess angiogenesis inhibitors that act through different mechanisms [19][20][21][22][23] . Recently, lymphangiogenesis has become a new research frontier [10] .…”

Recent progress in nanomedicine: therapeutic, diagnostic and theranostic applications

“…low background in circulation), are optimal. VEGF-R2-targeted microbubbles (MB) are a clinically relevant example of this, and are currently in early-stage trials for prostate cancer staging and treatment monitoring using ultrasound imaging [47,48].…”

Molecular Imaging of Tumor Angiogenesis

“…In 2 murine tumor models, microbubbles conjugated to anti-VEGFR-2 monoclonal antibodies were used to image VEGFR-2 expression (Willmann, Paulmurugan et al 2008). The targeted microbubbles produced a significantly higher average signal intensity than control microbubbles, and the signal intensity was significantly lower when anti-VEGFR-2 antibodies (blocking antibodies) were used, demonstrating target specificity.…”