The increased expression of proteolytic systems is one of the characteristics of transformed and malignant cells and their evaluations in whole
tumor homogenates were considered as possible diagnostic and/or prognostic factors. Abnormal intracellular distribution, increased activities and secretion of
cysteine proteinases (CPs)
cathepsin B (Cat B) and L (Cat L), were associated with
tumor progression. In the present study of matched pairs of
breast carcinoma and normal breast tissue, the activities of Cat B and Cat L in
breast carcinoma homogenates were found to be 20 and 50 fold higher, respectively, than in normal tissues. In contrast, a decrease in total inhibitory activity of
cysteine proteinase inhibitors (CPIs) was observed but an average ratio between
tumor and normal tissues was only 0.75. One of the CPIs,
stefin A, was also determined immunochemically. The activities of CPs and CPIs were compared to the increased levels of
cathepsin D (Cat D) activities in individual patients, but no statistically significant correlations were found. We correlated CPs and CPIs with morphological and receptor data as well as the axillary
lymph node metastases. There was no statistical correlation of CP and CPIs with the number of
lymph node metastases. However, highly elevated levels of Cat B and Cat L and lowered
CPI activities in
tumor cytosols were often associated with poorly differentiated
carcinomas and those with negative ER and PR values. We conclude that
cysteine-dependent proteolysis may play an important role in
breast tumors.