Optimized immunohistochemistry in combination with image analysis: A reliable alternative to quantitative ELISA determination of uPA and PAI-1 for routine risk group discrimination in breast cancer

The determination of the invasion markers urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) has further improved the possibilities for individualized therapy of breast cancer. To date, quantitative measurement by ELISA, that needs large amounts of fresh, frozen material, is the only standardized procedure for diagnostic purposes. Therefore, the aim of this study was the establishment of a reliable alternative method based on immunohistochemistry (IHC) and image analysis requiring only small amounts of fixed tumor tissue. Protein expression of uPA and PAI-1 was analyzed in HOPE-fixed tumor samples using tissue microarrays (TMAs) and semiquantitative image analysis. The results of both methods were significantly correlated and risk assessment showed an overall concordance of 78% (83/107; high- and low-risk) and of 94% (74/79) regarding only high-risk patients. The data demonstrate that optimized IHC in combination with image analysis can provide adequate clinical significance compared to ELISA-derived determination of uPA and PAI-1.