Interactions of tumor cells with vascular endothelial cell monolayers: a model for metastatic invasion.

The interactions of tumorigenic and nontumorigenic human and rodent cells with vascular endothelial cells and their underlying extracellular matrix were studied in culture. The abilities of various cells to attach to endothelial monolayers and cause morphologic changes, such as rupture of endothelial-endothelial cell interactions leading to retraction of endothelial cells and exposure of extracellular matrix, as well as their propensities to invade and underlap retracted endothelial monolayers and continue migration were assessed by time-lapse and phase-contrast microscopy as well as scanning and transmission electron microscopy. In general, highly malignant or highly invasive cells in vivo were capable of attachment, invasion, and migration under endothelial cells in vitro. This system may be useful for elucidating mechanisms of tumor cell arrest and extravasation.