Evaluating the effect of Avastin on breast cancer angiogenesis using synchrotron radiation.

Background: The visualization of microvasculature is an essential step in understanding the mechanisms underlying early vessel disorders involved in breast cancer and for developing effective therapeutic strategies. However, generating detailed and reproducible data using immunohistochemistry analysis of breast cancer angiogenesis has been difficult.

Methods: To analyze the diversification of angiogenesis in the development of tumor growth and evaluate the anti-vascular effects of Avastin (bevacizumab), we used new X-ray microangiography and third-generation synchrotron radiation-based micro-computed tomography (SR micro-CT) technology. With these techniques, we were able to investigate the structures and density of microvessels in xenograft mouse models (n=24). Barium sulfate nanoparticles were injected into the left cardiac ventricle of the mice to allow the visualization of blood vessels.

Results: Three-dimensional structures of microvessels were displayed with a high spatial image resolution of 20-30 µm. The density of angiogenesis and the incidence of lung metastasis were significantly reduced in xenograft mouse models of breast cancer treated with Avastin compared with control groups. Also, the density of smaller vessels (diameter <50 µm) was significantly decreased in the Avastin-treated mice, while the density of larger vessels (diameter >100 µm) was not significantly changed.

Conclusions: Avastin inhibited tumor growth and lung metastasis by reducing microvessels. Additionally, synchrotron radiation (SR) techniques are useful as an additional tool for more precise quantification of angiogenesis.