The role of stromal-epithelial interaction in normal and malignant growth.

Stromal-epithelial interaction has a fundamental role in determining normal prostate development. Aberrant interaction between stroma and epithelium in the prostate is thought to contribute to neoplastic progression. Using a cell-cell interaction model, we observed that an inductive fibroblast cell line derived from fetal urogenital sinuses can confer growth responsiveness to androgen in both prostate and non-prostate epithelial cells in vivo. This concept was applied to test whether inductive stromal cells from bone or prostate alter cancer growth and metastasis. We observed that when a non-tumorigenic stromal cell line derived from a human osteosarcoma interacted with a non-tumorigenic androgen dependent prostate cancer cell line (LNCaP) in vivo, there was a marked alteration of both genotypes and phenotypes of the subsequently derived LNCaP sublines. One such subline, C4-2, acquired androgen independence as well as osseous-metastatic potential. These results support the concept that "genomic adaptation" is the most likely mechanism to explain the phenomenon of prostate cancer cell lines being permanently altered as a result of stromal-epithelial interaction in vivo. The establishment and further refinement of this cell-cell interaction model will allow us to define the roles of growth factors, growth factor receptors and extracellular matrices in prostate carcinogenesis. This approach could lead to the development of new therapeutic modalities that influence the rate of human prostate cancer progression.