Monitoring angiogenesis in human melanoma xenograft model using contrast-enhanced ultrasound imaging

The potential for noninvasive monitoring and quantification of tumor angiogenesis with contrast-enhanced ultrasound imaging has been investigated in a murine cancer model. Seventy athymic nude mice were implanted with the human melanoma cell line DB-1 but only 30 of these were available for the final study. The 30 mice were divided into three groups (10 mice/group), which were studied with contrast-enhanced ultrasound imaging 4, 5 or 6 weeks post-implantation. Power Doppler and pulse inversion harmonic imaging (PIHI) were performed (in real time and intermittently) with a Sonoline Elegra scanner (Siemens Medical Solutions, Issaquah, WA) following injection of Optison (dose: 0.4-0.6 ml/kg; GE Healthcare, Princeton, NJ). Ultrasound results were compared to immunohistochemical stains for endothelial cells (CD31), vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2). Linear regression analysis indicated statistically significant correlations between the percent area stained with VEGF and ultrasound measures of tumor neovascularity obtained with all three techniques (p < 0.01). Contrast-enhanced ultrasound imaging of tumor neovascularity appears to provide a noninvasive marker of angiogenesis corresponding to the expression of VEGF in the DB-1 model and may become a useful tool for monitoring clinical anti-angiogenic therapies.