PAI-1 (plasminogen activator inhibitor-1) and its target protein uPA (urokinase plasminogen activator) are biomarkers used to manage therapy of cancer patients. High PAI-1 and uPA levels measured by ELISA in tumor biopsies are clinically-proven biomarkers of an invasive, metastatic phenotype in breast cancer. Prognostic biomarkers such as PAI-1 and uPA help to select the best treatment modality for each patient. PAI-1 and uPA are under study as biomarkers in other forms of cancer including oral cancer. Objectives: Determine whether PAI-1 levels are correlated with uPA levels in cultures of fibroblasts and three adenocarcinoma clonal cell lines that differ in metastatic potential in vivo. Methods: Secreted PAI-1 and uPA were measured by ELISA in serum-free conditioned media. Results: PAI-1 levels were not significantly different in media from normal mammary fibroblasts, non-metastatic MTC cells, or low metastatic potential MTLn2 cells (17±9, 5±2, 20±9 ng/mg protein), but PAI-1 was lower in media from highly-metastatic MTLn3 cells (0.9±0.4 ng/mg). In contrast, uPA levels were not significantly different in media from MTC and MTLn2 cells (22±7 and 10±4 ng/mg), but uPA was much higher in media from MTLn3 cells (193±38 ng/mg). uPA was not detected in fibroblast media. Conclusions: PAI-1 and uPA did not increase together in conditioned media from cultured adenocarcinoma cells, in contrast to results reported for tumor tissue. Instead, PAI-1 was lowest and uPA was highest in media from highly metastatic cells. The results suggest that the high levels of PAI-1 found in tumor tissue may be produced by stromal cells, including fibroblasts, endothelial cells, and inflammatory cells, rather than by cancer cells.
Supported by the UTHSC Dental Alumni Endowment Fund.
Keywords: Diagnosis, Enzymes, Neoplasia and Pathology