Data from Efficacy of Affibody-Based Ultrasound Molecular Imaging of Vascular B7-H3 for Breast Cancer Detection

Abstract

<div>AbstractPurpose:<p>Human B7-H3 (hB7-H3) is a promising molecular imaging target differentially expressed on the neovasculature of breast cancer and has been validated for preclinical ultrasound (US) imaging with anti–B7-H3-antibody-functionalized microbubbles (MB). However, smaller ligands such as affibodies (ABY) are more suitable for the design of clinical-grade targeted MB.</p>Experimental Design:<p>Binding of ABY<sub>B7-H3</sub> was confirmed with soluble and cell-surface B7-H3 by flow cytometry. MB were functionalized with ABY<sub>B7-H3</sub> or anti–B7-H3-antibody (Ab<sub>B7-H3</sub>). Control and targeted MB were tested for binding to hB7-H3–expressing cells (MS1<sub>hB7-H3</sub>) under shear stress conditions. US imaging was performed with MB<sub>ABY-B7-H3</sub> in an orthotopic mouse model of human MDA-MB-231 coimplanted with MS1<sub>hB7-H3</sub> or control MS1<sub>WT</sub> cells and a transgenic mouse model of breast cancer development.</p>Results:<p>ABY<sub>B7-H3</sub> specifically binds to MS1<sub>hB7-H3</sub> and murine-B7-H3–expressing monocytes. MB<sub>ABY-B7-H3</sub> (8.5 ± 1.4 MB/cell) and MB<sub>Ab-B7-H3</sub> (9.8 ± 1.3 MB/cell) showed significantly higher (<i>P</i> < 0.0001) binding to the MS1<sub>hB7-H3</sub> cells compared with control MB<sub>Non-targeted</sub> (0.5 ± 0.1 MB/cell) under shear stress conditions. <i>In vivo</i>, MB<sub>ABY-B7-H3</sub> produced significantly higher (<i>P</i> < 0.04) imaging signal in orthotopic tumors coengrafted with MS1<sub>hB7-H3</sub> (8.4 ± 3.3 a.u.) compared with tumors with MS1<sub>WT</sub> cells (1.4 ± 1.0 a.u.). In the transgenic mouse tumors, MB<sub>ABY-B7-H3</sub> (9.6 ± 2.0 a.u.) produced higher (<i>P</i> < 0.0002) imaging signal compared with MB<sub>Non-targeted</sub> (1.3 ± 0.3 a.u.), whereas MB<sub>ABY-B7-H3</sub> signal in normal mammary glands and tumors with B7-H3 blocking significantly reduced (<i>P</i> < 0.02) imaging signal.</p>Conclusions:<p>MB<sub>ABY-B7-H3</sub> enhances B7-H3 molecular signal in breast tumors, improving cancer detection, while offering the advantages of a small size ligand and easier production for clinical imaging.</p></div>