In vitro Invasion of Endothelial Cell Monolayer by Rat Ascites Hepatoma Cells

To study the tissue preference of invasion, we developed an assay system for the invasion of endothelial cells as a modification of the previously established assay of tumor cell invasion of meso‐thelial cells. Rat ascites hepatoma cells (AH 130) that had been seeded on a monolayer of cultured endothelial cells penetrated and formed tumor cell colonies under the monolayer. The penetration was time‐dependent and the number of penetrated tumor cells and colonies was proportional to the number of tumor cells seeded. Comparison of the in vitro tumor cell invasion of endothelial cell monolayer with that of cultured mesothelial cell layer showed that a clone from the tumor cells (CI‐30) which was highly penetrative into the mesothelial cell layer had only a limited ability to penetrate the endothelial cell layer.