Altered expression of extracellular matrix and proteinases in Noble rat prostate gland after long-term treatment with sex steroids

BACKGROUND: Interactions between the epithelial cells and stromal tissues, which include the epithelial basement membrane, extracellular matrix, inducible factors, and various cell types, are believed to play a significant role in prostate gland carcinogenesis. Remodeling of extracellular matrix and degradation of basement membrane are the prerequisites for tumor cell invasion, and these changes are correlated with the expression of various proteinases. METHODS: The present study examined the alterations of epithelial basement membrane, extracellular matrix, and proteinase activities in the Noble rat prostate gland after long-term treatments with androgen and estrogen (T+DES or T+E(2) for 4-12 months) by histochemistry, immunohistochemistry, electron microscopy, and gelatin-gel zymography. RESULTS: After hormonal treatments, defects of epithelial basement membranes, such as focal disruption, diffuse staining and multilayering, were observed by histochemistry and immunohistochemistry in the dysplastic and neoplastic lesions induced in the lateral (LP) and ventral prostates (VP) but not in dorsal prostate (DP). An increase in the amount of extracellular matrix components, including hyaluronan (HA), chondroitin sulfate proteoglycan (CSPG) and tenascin, in the stroma of hormone-treated LP and VP was revealed by histochemistry and immunohistochemistry. Positive immunolabeling of matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9) was detected in the fibromuscular layer surrounding the adenoma and adenocarcinoma induced in LP and VP after treatments with steroids for over 9-12 months. Zymography also detected an increase in activities of proteinases of apparent MW 120, 90, 86 and 68 kDa in the hormone-treated LP and VP, and these proteinases were characterized as metalloproteinases. In addition, two serine proteinases of MW 100 and 30 kDa were identified as being overexpressed in the hormone-treated LP and VP. Compared to LP and VP, there was no significant change in the proteinase activities in the hormone-treated DP. CONCLUSIONS: The present study demonstrated that the epithelial basement membrane and stromal extracellular matrix were altered in dysplastic and neoplastic Noble rat prostates. Since HA and CSPG (or their complexes) are highly anionic molecules, their increased accumulation in the altered prostatic stroma would tend to hydrate this tissue. This would create an environment more favorable for tumor growth and invasion. These morphological changes were also correlated with the concurrent increase in gelatinolytic proteinase activities induced in these prostates. The results suggest that the remodeling of the stromal tissue might play a role in the early stage of prostate carcinogenesis as shown in the Noble rat model.