Value of ultrasound-targeted vascular endothelial growth factor receptor-2 in non-invasive monitoring of anti-angiogenic response in nude mice with subcutaneous xenograft model

Abstract

Objective: To investigate the value of contrast-enhanced ultrasound targeting vascular endothelial growth factor receptor-2 (VEGFR-2) in non-invasive monitoring of anti-angiogenesis response in subcutaneous transplantation tumor model of hepatocellular carcinoma in nude mice. Methods: Sixteen nude mice were randomly divided into control group and bevacizumab treatment group (treatment group). Two weeks later, the model of subcutaneous transplanted tumor was established. The mice in the treatment group were intratumorally injected with 0.2 mg bevacizumab, while the control group was given the same amount of saline, three times a week for 2 weeks. Ultrasound microbubbles targeting VEGFR-2 were prepared by biotin avidin method. Ultrasound examinations were performed before treatment, 7 days and 14 days after treatment, and the time intensity curve (TIC) was drawn to quantitatively analyze the differences of parameters with treatment time. The expression of CD31 in tumor tissues was detected by immunohistochemistry. Results: After 14 days of treatment, the volume of tumor tissue in the treatment group and the control group were (0.247±0.019) mm(3) and (0.307±0.031) mm(3,) respectively, the difference was statistically significant (P<0.01). After 7 days of treatment, the rise slope (K(1)), time to peak (TTP) and peak intensity (PI) of TIC curve in the treatment group were 3.77±0.62, (3.82±0.21) s and (24.35±3.34) dB, respectively, which were significantly different from 2.93±0.31, (4.47±0.50) s and (30.10±2.35) dB in the control group, respectively (P<0.05). Immunohistochemistry showed that the PI of contrast enhanced ultrasound was positively correlated with microvessel density (r(2)=0.898, P=0.017). Conclusions: The therapeutic effect of bevacizumab on tumor angiogenesis evaluated by contrast-enhanced ultrasound targeting VEGFR-2 is related to the differences of parameters such as K(1), TTP and PI of TIC index. Contrast enhanced ultrasound targeting VEGFR-2 is of great value in non-invasive monitoring of subcutaneous transplanted tumor model of hepatocellular carcinoma in nude mice.