Extracellular matrix and androgen receptor expression associated with spontaneous transformation of rat prostate fibroblasts.

Spontaneous transformation in continuous culture of the androgen-sensitive rat prostate fibroblast cell line, NbF-1, resulted in an aggressively tumorigenic nonmetastatic phenotype that coincided with few gross chromosome abnormalities. This study identified transformation-associated alterations in extracellular matrix and androgen receptor expression in the NbF-1 cell line. Substantial levels of procollagens I, III, and IV and fibronectin mRNAs were detected in nontumorigenic NbF-1 cells. Laminin B1 and B2 mRNAs were also detectable, but at lower levels. Expression of all six extracellular matrix mRNAs was nonuniformly lower in tumorigenic NbF-1 cells. This decrease in expression was greatest for alpha 2 procollagen IV mRNA, which was reduced 17-fold. Proteoglycans and glycosaminoglycans synthesized by the NbF-1 cultures were also characterized. The NbF-1 cell line expressed chondroitin sulfate proteoglycans predominantly, and expression was reduced 5- to 10-fold in tumorigenic cultures. In contrast to the extensive alterations in the extracellular matrix, measurement of high-affinity androgen binding and androgen receptor mRNA levels showed substantial expression of androgen receptors in both NbF-1 cultures. Cultures of early and late passage NbF-1 cells demonstrated a mitogenic response to dihydrotestosterone. These data indicate (a) that alterations in expression of extracellular matrix components may represent early markers for tumorigenic transformation in prostatic mesenchymal cells and (b) that these changes can occur without disrupting androgen receptor expression and androgen sensitivity.