Isolation and Properties of Tumor‐derived Endothelial Cells from Rat KMT‐17 Fibrosarcoma

Rat KMT‐17 fibrosarcoma‐derived endothelial cells were isolated by Percoll gradient centrifugation with an attaching‐speed separation technique, and their properties in culture were examined. The primary cultured tumor‐derived endothelial cells (TEC) showed angiotensin‐converting enzyme activity, positivity for Factor VIII‐related antigen staining, and typical capillary‐like formation on Matrigel. The primary cultured TEC monolayer showed greater permeability than normal tissuederived endothelial cell (aorta, vena cava and epididymal fat capillary) monolayers on FITC‐dextran diffusion (molecular weight 70,000). Leukocyte adhesion to TEC was reduced compared to that to fat‐derived capillary endothelial cells. These characteristics resembled those of tumor vascular endothelium, and were observed both in the primary and first‐passage cell cultures, but not in the fourth‐passage cell cultures. Our findings indicate that primary or subcultured TEC are applicable for studies of the physiological characteristics of tumor endothelial cells.