Vaccination with autologous endothelium inhibits angiogenesis and metastasis of colon cancer through autoimmunity

Anti-angiogenic properties of plaunotol

We have investigated a potential anti-angiogenic effect of plaunotol, an extract from the leaves of Plau-noi, in an angiogenesis model consisting of human umbilical vein endothelial cells (HUVECs). Plaunotol inhibited the proliferative activity of HUVECs in a dose-dependent manner. In addition, it caused a remarkable decrease of the ability of HUVECs to adhere and spread on gelatin and vitronectin, but not fibronectin. Tube-like formation in Matrigel was also inhibited in a dose-dependent way. These results strongly suggest the specific inhibition of integrin alphavbeta3 to be the main event of plaunotol-induced suppression of angiogenesis. The alphavbeta3 antagonists are known to be potent inhibitors of tumor angiogenesis and plaunotol, by causing the functional inhibition of alphavbeta3, should be considered a promising new anti-angiogenic drug.

A novel method for isolation of endothelial cells and macrophages from murine tumors based on Ac-LDL uptake and CD16 expression

Analysis of specific properties of tumor endothelium should be useful for development of novel antiangiogenic strategies. However, the isolation of pure endothelial cells from tumor tissues is still a fundamental problem. In this study, we have attempted to develop a reliable method for the isolation of endothelial cells from murine tumors. We found that the labeling with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-acetylated-low density lipoprotein (Dil-Ac-LDL), commonly used for this purpose, can result in the contamination of isolated endothelium by macrophages due to the overlapping staining patterns of these two distinct cell types. Therefore, we chose the CD16, which is expressed on macrophages but not endothelial cells, to better distinguish them when labeled with Dil-Ac-LDL. By using this method, we obtained pure populations of endothelial cells and macrophages from murine colorectal cancer tissues, showing characteristic morphological and functional properties of the either cell type. The endothelial cells were long spindle-shaped, spread on gelatin, formed tube-like structures on Matrigel and expressed MECA-32 but not CD68. In contrast, the macrophages were round-shaped, partially spread on gelatin, formed unorganized aggregates on Matrigel and expressed CD68 but not MECA-32. The additional analysis of normal and tumor tissues revealed a positive correlation between the relative numbers of tumor endothelial cells and macrophages, calculated as % total cells, as well as the respective relative number and tumor weight. The present method is hoped to be useful for the evaluation of tumor angiogenesis and antitumor immunity.