Transduced endothelial cells expressing high levels of tissue plasminogen activator have an unaltered phenotype in vitro

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Abstract
Elevated cellular plasminogen activator activity has been associated with significant alterations in the in vitro phenotype of both malignant cell lines and nonmalignant endothelial cells. To examine the role of elevated cellular plasminogen activator activity in the production of altered endothelial cell behavior, bovine coronary artery endothelial cells were transduced with a retroviral vector expressing large amounts of tissue plasminogen activator. Cells transduced with the tissue plasminogen activator vector were compared with both untransduced cells and cells transduced with a control vector in a series of in vitro assays of cellular attachment, proliferation, migration, and invasion. The morphology of the 2 transduced populations was unchanged. There was a small decrease (5–15%) in the horizontal migration rate of both transduced cell populations, as compared with that of untransduced cells. No significant differences were detected among the three cell populations in any of the other assays. We conclude that expression of high levels of tissue plasminogen activator does not specifically affect endothelial cell phenotype in vitro. These data lend support to the hypothesis that elevated plasminogen activator activity is necessary but not sufficient to produce alterations in endothelial cell behavior.