Alterations of expression and regulation of transforming growth factor beta in human cancer prostate cell lines

TGF beta can promote and/or suppress prostate tumor growth through multiple and opposing actions. Alterations of its expression, secretion, regulation or of the sensitivity of target cells can lead to a favorable environment for tumor development. To gain a better insight in TGF beta function during cancer progression, we have used different cultured human prostate cells: preneoplastic PNT2 cells, the androgen-dependent LNCaP and the androgen-independent PC3 and DU145 prostate cancer cell lines. We have studied by specific ELISA assays in conditioned media (CM), the secretion of TGF beta 1 and TGF beta 2 in basal conditions and after hormonal treatment (DHT or E2) and the expression of TGF beta 1 mRNA by Northern blot. We have also compared the effect of fibroblast CM on TGF beta secretion by the different cell types. Compared to PNT2 cells, cancer cell lines secrete lower levels of active TGF beta which are not increased in the presence of fibroblast CM. LNCaP cells respond to androgen or estrogen treatment by a 10-fold increase of active TGF beta secretion while PC3 and DU145 are unresponsive. In conclusion, prostate cancer cell lines have lost part of their ability to secrete and activate TGF beta, and to regulate this secretion through stromal-epithelial interactions. Androgen-sensitive cancer cells may compensate this loss by hormonal regulation.