Urokinase-like plasminogen activator receptor expression on disseminated breast cancer cells

Disseminated tumor cells are detected frequently in bone marrow, peripheral blood, and cytokine-mobilized peripheral blood cell products of women undergoing high-dose therapy for breast cancer. Several attempts were made to purge autografts from contaminating cancer cells; however, the biological and clinical impact of these contaminations has not been clarified so far. Expression of distinct phenotypes is a surrogate marker for metastatic behavior of cancer cells. The expression of the urokinase-like plasminogen activator receptor seems to be a factor of high importance. It is not expressed by normal mammary tissue. Disseminated cancer cells from marrow, blood, and stem cell products have been investigated by double-stain technique for urokinase-like plasminogen activator receptor (uPA-R) expressing cytokeratin-positive cells. uPA-R+/CK+ cells could be found in all qualities of samples; however, significantly less in G-CSF-mobilized peripheral blood stem cells compared to samples of other provenance (p = 0.02). It can be concluded that epithelial cells of malignant phenotype occur in blood, marrow, and autografts of breast cancer patients. Populations of disseminated tumor cells are phenotypically heterogeneous. Reduced uPA-R expression on cancer cells from leukapheresis samples might suggest a less aggressive nature of these cells compared to disseminated cells found in bone marrow. Furthermore, the data suggest that the phenotype of tumor cell contamination in leukapheresis products differs significantly from those of disseminated cancer cells in bone marrow or blood.