The Assessment of Targeted Ultrasound Contrast Agents in Prostate Cancer in Nude Mice

Background: The targeted ultrasound contrast agents by attaching anti-VEGF or anti-CD34 to the shell of perfluorocarbon-filled microbubbles (MBs) in prostate cancer in mice were developed, validated and compared. Methods: Single- and dual-targeted US imaging agents were prepared, with attaching anti-VEGF or anti-CD34 to the shell of perfluorocarbon-filled microbubbles, and being validated using fluorescence immunoassay in vitro. In vivo imaging signals of contrast material-enhanced ultrasound were quantified in 25 nude mice bearing 22RV1 tumors (human prostate cancer). Results: Under both of the electron microscope and the light microscope, the targeted microbubbles were round in shape, even in distribution and size, and without any aggregation. Under the fluorescence microscope, the cytoplasm of endothelial cells with targeted microbubbles, appeared as yellow-green color. Targeted ultrasound contrast agents had targeting ability and immune activity in vitro. In vivo, the contrast enhanced ultrasound imaging showed significantly higher average video intensity (ROI Area) with using anti-VEGF (MBv) (mean, 17.562 +/- 7.758), CD34 (MBc) (mean, 18.263 +/- 6.564) and MBb (mean, 17.785 +/- 7.975), compared with routine microbubbles (mean, 15.022 +/- 5.998) for prostate tumors (P < 0.001). There were no statistical differences between different adherent microbubbles groups (P > 0.05). Results of immunohistochemical analysis confirmed VEGF and CD34 expression on vascular endothelial cells of prostate tumor. Conclusions: Single-or Dual-targeted contrast-enhanced ultrasound, directed at both VEGF and CD34, were improved in vivo visualization of tumor angiogenesis in a human prostate cancer xenograft tumor model in mice, showing a noninvasive contrast-enhanced ultrasound imaging technique for the functional imaging of tumor neovascularization.