Assessment of the clinical significance of antigenic and functional levels of α1-proteinase inhibitor (α1-Pi) in infiltrating ductal breast carcinomas.

To determine the clinical significance of α1-proteinase inhibitor (α1-Pi) in infiltrating ductal breast carcinoma patients.Serum levels of α1-Pi, tryptic specific inhibitory capacity and α1-Pi circulating immune complexes were determined using radial immunodiffusion, BAPNA assays and ELISA, respectively. 2-DE-MS and immunohistochemistry were performed to examine α1-Pi protein expression.A decreased serum level of α1-Pi was found among breast cancer patients in comparison to controls. In addition, we found a significantly decreased mean level of α1-Pi in the node metastatic group when compared to node negative patients. However, the functional activity of the inhibitor did not decrease proportionately. Through 2-DE analyses, a differential expression of α1-Pi isoforms according to tumor stage and node metastatic development was found.Both α1-Pi levels and specific activity could be a source of complementary clinical information and may provide useful information for a better understanding of the mechanisms of metastasis.