VEGFR2-Targeted Contrast-Enhanced Ultrasound to Distinguish between Two Anti-Angiogenic Treatments

Abstract

The aim of this study was to evaluate the capacity of BR55, an ultrasound contrast agent specifically targeting vascular endothelial growth factor receptor 2 (VEGFR2), to distinguish the specific anti-VEGFR2 therapy effect of sunitinib from other anti-angiogenic effects of a therapy (imatinib) that does not directly inhibit VEGFR2. Sunitinib, imatinib and placebo were administered daily for 11 d (264 h) to 45 BalbC mice bearing ectopic CT26 murine colorectal carcinomas. During the course of therapy, B-mode ultrasound, contrast-enhanced ultrasound and VEGFR2-targeted contrast-enhanced ultrasound were performed to assess tumor morphology, vascularization and VEGFR2 expression, respectively. The angiogenic effects on these three aspects were characterized using tumor volume, contrast-enhanced area and differential targeted enhancement. Necrosis, microvasculature and expression of VEGFR2 were also determined by histology and immunostaining. B-Mode imaging revealed that tumor growth was significantly decreased in sunitinib-treated mice at day 11 (p < 0.05), whereas imatinib did not affect growth. Functional evaluation revealed that the contrast-enhanced area decreased significantly (p < 0.02) and by similar amounts under both anti-angiogenic treatments by day 8 (192 h): -23% for imatinib and -21% for sunitinib. No significant decrease was observed in the placebo group. Targeted contrast-enhanced imaging revealed lower differential targeted enhancement, that is, lower levels of VEGFR2 expression, in sunitinib-treated mice relative to placebo-treated mice from 24 h (p < 0.05) and relative to both placebo- and imatinib-treated mice from 48 h (p < 0.05). Histologic assessment of tumors after the final imaging indicated that necrotic area was significantly higher for the sunitinib group (21%) than for the placebo (8%, p < 0.001) and imatinib (11%, p < 0.05) groups. VEGFR2-targeted ultrasound was able to sensitively differentiate the anti-VEGFR2 effect from the reduced area of tumor with functional flow produced by both anti-angiogenic agents. BR55 molecular imaging was, thus, able both to detect early therapeutic response to sunitinib in CT26 tumors as soon as 24 h after the beginning of the treatment and to provide early discrimination (48 h) between tumor response during anti-angiogenic therapy targeting VEGFR2 expression and response during anti-angiogenic therapy not directly acting on this receptor.

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 Zocco et al who applied CEUS with untargeted microbubbles to investigate patients with advanced hepatocellular carcinoma under sorafenib therapy in a clinical study, assessing parameters of microcirculation including AUC and observed a significant decrease of AUC following 15 days of sorafenib therapy, associated with a longer survival and with a significant correlation to progression free survival [33]. Differing from our study, Zocco et al applied a non-targeted intravascular ultrasound contrast agent, which, however, resembles BR55 in bubble size and kinetics providing similar measures of tumor microcirculation and a similar wash-in-phase of the MB uptake as non-targeted agents with intravascular kinetics and distribution to the same tumor regions [13,34,35]. …”

Tbx1 and Foxi3 genetically interact in the third pharyngeal pouch endoderm required for thymus and parathyroid development

“…The PA develops from E8.5-E10.5, in which PA3 forms by E9.5. Tbx1 is expressed in the PE at E8.5 and E9.5 (Payen et al, 2015;Zhang et al, 2005;Zhang et al, 2006). We used RNAscope in situ hybridization on coronal sections from embryos to determine if there is overlap between Foxi3 and Tbx1 mRNA expression in wild type embryos at E9.5 ( Figure 3A-3L).…”

3-D Longitudinal Imaging of Tumor Angiogenesis in Mice in Vivo Using Ultrafast Doppler Tomography

“…A particularly interesting technique is photoacoustic imaging due to the penetration depth of the ultrasound and optical absorption contrasts (Yao and Wang 2014). A non-exhaustive but representative panel of current techniques applied for in vivo tumor imaging is given in Table 1. In this imaging landscape, assessment of tumor angiogenesis via ultrasound is currently contingent on the use of contrast agent (Payen et al 2015) or very high frequencies (40 to 100MHz) (Ferrara et al 2000) because conventional ultrasound Doppler techniques suffer from a lack of sensitivity and from the impossibility to extract very slow blood flow (below 10 mm.s -1 ). The recently introduced Ultrafast Doppler technique (Bercoff et al 2011) can resolve both issues by increasing the sensitivity to blood motion detection by a factor 50 (Macé et al 2013) compared to conventional techniques and by enabling new paradigms for discrimination between tissue and blood signal using spatiotemporal information (Demené et al 2015).…”