Cell surface expression of urokinase receptor in normal mammary epithelialcells and breast cancer cell lines

Background: The urokinase receptor (uPAR) is important in the process of ex tracellular matrix degradation occurring during cancer cell invasion and me tastasis. We wished to quantify uPAR on the surfaces of normal mammary epit helial cells (HMEC) and 6 well-known breast cancer cell lines using flow cy tometry. Materials and Methods: Cell surface uPAR was labelled with a monoc lonal antibody, and this was detected with a florescent-labelled second ant ibody and accurately measured using flow cytometry. The measured fluorescen t signals of the stained cells were interpolated with those of Quantum Simp ly Cellular bead standards to determine the number of uPAR sites per cell. Results: The breast cancer cell lines ranged from 13,700 to 50,800 uPAR sit es per cell, whilst HMEC cells had only 2,500 sites. Conclusions: This simp le and reliable method showed that the expression of cell surface uPAR is h igher in the breast cancer cell lines than in the normal mammary cells.