Urokinase receptor expression is upregulated by cell culture sparsity in breast cancer cell line BT-20

Background: The processes of tumour cell migration and invasion are enhance d by urokinase activity mediated by the urokinase receptor on the cell surf ace. Various factors affect the expression of the urokinase receptor, and a mongst them we have found evidence that cell culture dispersity strongly up regulates it in breast cancer cell line BT 20. Materials and methods: Flow cytometry was used to quantify urokinase enzyme and urokinase receptors on the surfaces of cells cultured at different levels of dispersity. Results: Increasing the cell culture sparsity caused more than a doubling in the lev el of expression of the cell surface urokinase receptor in this cell line. A marked increase in the level of cell surface receptor-bound urokinase cor responding to the increase in the receptor itself also occurred in sparse c ell cultures. Conclusions: The marked effect of culture sparsity on the uro kinase pathway may have important implications for the behavior of tumour c ells during the process of metastasis formation.