UPA and PAI-1 analysis from fixed tissues - new perspectives for a known set of predictive markers

The urokinase-type plasminogen activator (uPA) and its main inhibitor PAI-1 play key roles in tumor-associated processes such as the degradation of the extracellular matrix (ECM), tissue remodeling, cell adhesion and migration. Elevated expression of both molecules is known to correlate with negative outcomes in node negative breast cancer. To date, these molecules are the only prognostic markers to have reached the highest level of evidence (LOE I) in multi-centered clinical trials for prognosis of node negative breast cancer. Unfortunately, the clinical utility of these molecules as markers is limited by the use of enzyme-linked immunoassay (ELISA) tests for their detection. The ELISA relies on the use of fresh or frozen tissue, which are rarely available in routine clinical settings. In this review article, we provide an overview of the clinical relevance of uPA and PAI-1 and present alternative methods for their detection. Common uPA and PAI-1 detection methods discussed in literature include RT-PCR-based assays and classical immunohistochemistry approaches. In recent years, attempts have been made to isolate and analyze proteins of formalin fixed, paraffin embedded (FFPE) tissues. These new methods are of special interest because up to now neither RT-PCR nor immunohistochemistry are recommended for the detection of uPA and PAI-1. Here, we present an approach for the analysis of uPA and PAI-1 directly from FFPE tissues that may eventually overcome the limitations of current assays and make the use of both markers widely available for routine prognosis and therapy decisions for breast cancer patients.