Analysis of the microvascular morphology and hemodynamics of breast cancer in mice using SPring-8 synchrotron radiation microangiography

Tumor vasculature is characterized by morphological and functional abnormalities. However, analysis of the dynamics in blood flow is still challenging because of limited spatial and temporal resolution. Synchrotron radiation (SR) microangiography above the K-edge of the iodine contrast agent can provide high-contrast imaging of microvessels in time orders of milliseconds. In this study, mice bearing the human breast cancer cell lines MDAMB231 and NOTCH4 overexpression in MDAMB231 (MDAMB231^NOTCH4+) and normal mice were assessed using SR microangiography. NOTCH is transmembrane protein that has crucial roles for vasculogenesis, angiogenesis and tumorigenesis, and NOTCH4 is considered to be a cause of high-flow arteriovenous shunting. A subgroup of mice received intravenous eribulin treatment, which is known to improve intratumor core circulation (MDAMB231-eribulin). Microvessel branches from approximately 200μm to less than 20μm in diameter were observed within the same visual field. The mean transition time (MTT) was measured as a dynamic parameter and quantitative analysis was performed. MTT in MDAMB231 was longer than that in normal tissue, and MDAMB231^NOTCH4+ showed shorter MTT [5.0 ± 1.4s, 3.6 ± 1.0s and 3.6 ± 1.1s (mean ± standard deviation), respectively]. After treatment, average MTT was correlated to tumor volume (r = 0.999) in MDAMB231-eribulin, while in contrast there was no correlation in MDAMB231 (r = -0.026). These changes in MTT profile are considered to be driven by the modulation of intratumoral circulation dynamics. These results demonstrate that a SR microangiography approach enables quantitative analysis of morphological and dynamic characteristics of tumor vasculature in vivo. Further studies will reveal new findings concerning vessel function in tumors.Synchrotron-radiation-based microvascular hemodynamic analysis was established in this study. Tumor vasculature analysis using this method showed unique characteristics of tumor blood flow in vivo.