Differential Adhesiveness of Rhabdomyosarcoma-derived Cloned Metastatic Cell Lines to Vascular Endothelial Monolayers

A series of 11 cloned cell lines derived from a primary, nickel-induced rat rhabdomyosarcoma was evaluated for their metastatic capacity (number of lung colonies following i.v. injection) and attachment kinetics to confluent pig endothelial cell monolayers grown in vitro . The morphology of the adhering cells was also studied by optical and scanning electron microscopy. Cells from all lines tested began to attach to the endothelial monolayers within 15 min of incubation at 37°C, with 64% to 93% of the cells adhering after 2 h. Attachment rates at 30 min ranged from 29 to 48% for four lines classed as “weakly adhesive” (attachment, 50%). Four clones of five displaying low lung-colonizing capacities also showed low attachment rates to endothelial monolayers in vitro . All of six highly colonizing lines studied had high attachment rates. A degree of positive correlation was observed between the amount of cell surface fibronectin as evaluated by immunofluorescence and the early phase attachment rates (and lung-colonizing capabilities) of the different cloned cell lines. Early (15 min) attachment of tumor cells to isolated extracellular matrix preparations proceeded at higher rates than to endothelial monolayers, and previously detected differences between high- and low-colonizing clones were less evident with these matrix substrates. Our results suggest possible interrelationships between specific cell adhesion properties and the metastatic potential of blood-borne tumor cells.