Abstract
It is widely accepted that basement membrane (BM) components are synthesized by epithelial cells and that production of BM-degrading proteases by cancer cells is necessary for invasive growth. In this study we used nucleic acid in situ hybridization (ISH) to investigate the presence of mRNAs for 72 KD and 92 KD Type IV collagenase, alpha 1 (IV) chain of Type IV collagen, and laminin B1 chain in 20 breast carcinomas of various histological types. The mRNA signals for 72 KD Type IV collagenase, Type IV collagen, and laminin were much more abundant in stromal fibroblasts and endothelial cells than in carcinoma cells. The signal for 92 KD Type IV collagenase mRNA was strong in carcinoma cells and considerably weaker in stromal fibroblasts and endothelial cells. Labeling for 72 KD and 92 KD Type IV collagenase mRNA was also found in benign fibroadenomas and for 92 KD Type IV collagenase in non-neoplastic ducts and acini. The results indicate that stromal cells have a more important role in the synthesis and degradation of BMs in breast carcinomas than previously thought and that production of these enzymes is not restricted to malignancy.