Squamous Cell Carcinoma Xenografts: Use of VEGFR2-targeted Microbubbles for Combined Functional and Molecular US to Monitor Antiangiogenic Therapy Effects

Abstract

Purpose-To assess the ability of vascular endothelial growth factor receptor type 2 (VEGFR2)-targeted and nontargeted ultrasonography (US) to depict antiangiogenic therapy effects and to investigate whether first-pass kinetics obtained with VEGFR2-targeted microbubbles provide independent data about tumor vascularization. Materials and Methods-Governmental approval was obtained for animal experiments.Vascularization in response to anti-vascular endothelial growth factor receptor or vehicle-control treatment (n=10/group) in HaCaT-ras A-5RT3 xenografts was longitudinally assessed in mice by means of first-pass kinetics of nontargeted microbubbles (BR1, BR38; Bracco, Geneva, Switzerland) and VEGFR2-targeted microbubbles (BR55; Bracco) before and 4, 7, and 14 days after therapy. VEGFR2 expression was determined 8 minutes after BR55 injection with destruction-replenishment analysis. US data were validated by immunohistochemistry. Significant differences were evaluated with the Mann-Whitney test.Results-First-pass analysis with BR1, BR38, and BR55 showed similar tendencies toward decreasing vascularization, with a stronger decrease in tumors treated with anti-VEGF antibody. Immunohistochemistry confirmed the lower microvessel density and VEGFR2-positive area fraction in tumors treated with anti-VEGF antibody. Europe PMC Funders GroupConclusion-Antiangiogenic therapy effects were detected earlier and more distinctly with VEGFR2-targeted US than with functional US. First-pass analyses with BR55, BR38, and BR1 revealed similar results, with a decrease in vascularization during therapy. Functional data showed that BR55 is not strongly affected by early binding of the microbubbles to VEGFR2. Thus, functional and molecular imaging of angiogenesis can be performed with BR55 within one examination.

Contrast-Enhanced Ultrasound with VEGFR2-Targeted Microbubbles for Monitoring Regorafenib Therapy Effects in Experimental Colorectal Adenocarcinomas in Rats with DCE-MRI and Immunohistochemical Validation

“…This is in accordance with Baetke et al, who showed in their study with heterotopic squamous cell carcinoma xenografts in nude mice under anti-VEGF antibody therapy 8 minutes after BR55 MB injection a significant lower amount of specifically bound BR55 MB in treated tumors compared to the control group on day 4, day 7 and day 14 [21]. Corresponding to our results, Pysz et al reported a significant difference of targeted imaging signal using CEUS and BR55 already 24h after initiation of anti-VEGF-antibody therapy in human colon cancer xenografts in mice, which remained significantly lower in treated than in untreated animals during 5 days of observation [10].…”

“…Multiparametric CEUS with targeted microbubbles (MB) can characterize morphological, functional and molecular parameters of tumor pathophysiology from its earliest stages [9–16]. Preclinical and clinical studies demonstrated the feasibility of functional and molecular CEUS imaging with VEGFR2 (vascular endothelial growth factor receptor 2) targeted MB in monitoring therapy response to anti-angiogenic treatment in different tumor entities [11,17–21], as VEGF is one of the most potent growth factors of endothelial cells and a main regulator of angiogenesis [22–24]. Following intravenous injection, in a first early phase tumor perfusion can be quantitatively evaluated by the assessment of various parameters of tissue microcirculation.…”

“…Following intravenous injection, in a first early phase tumor perfusion can be quantitatively evaluated by the assessment of various parameters of tissue microcirculation. In a second, late phase, targeted MB bound to tumor vascular endothelial cells, overexpressing VEGFR2 as molecular markers of angiogenesis, allow for the non-invasive visualization of VEGF receptor 2 expression in vivo [13,21]. Thereby CEUS with BR55 may be able to provide combined functional and molecular imaging biomarkers for the non-invasive assessment of tumor angiogenesis and therapy response of the investigated colon cancer xenografts under regorafenib therapy.…”

Early prediction of tumor response to bevacizumab treatment in murine colon cancer models using three-dimensional dynamic contrast-enhanced ultrasound imaging

“…Over the past decade, DCE-US has been increasingly investigated in preclinical [24,26,27] and clinical [28,29] studies to depict therapy induced changes in tumor perfusion. However, a major drawback of conventional DCE-US to date is its limitation to 2D, which results in limited perfusion assessments to a single 2D plane, and results in longitudinal sampling errors.…”

Intra-Animal Comparison between Three-dimensional Molecularly Targeted US and Three-dimensional Dynamic Contrast-enhanced US for Early Antiangiogenic Treatment Assessment in Colon Cancer

“…With the introduction of intravenous microbubble US contrast agents, functional imaging of tumor perfusion, also called dynamic contrast material–enhanced ( DCE ) US, has become clinically available (3). However, DCE US with current two-dimensional imaging capabilities is suboptimal because it fails to demonstrate the spatial heterogeneity of tumor perfusion, and it is challenging to position the two-dimensional US transducer at the exact same location for longitudinal assessment of tumor response (4–8). This limitation has been addressed by the introduction of three-dimensional (3D) DCE US techniques (9–11).…”