The results of our previous study revealed that transforming growth factor-β1 (TGFβ1) stimulated proliferation of the prostate cancer cell line, TSU-Pr1. This observation is unexpected, for TGFβ usually inhibits proliferation in prostate cancer cells. The present study examines possible mechanisms through which TGFβ1 induces this proliferation. We postulate that TGFβ1 action is mediated through an indirect mechanism by inducing the expression of platelet derived growth factor (PDGF), which, in turn, stimulates proliferation. The TGFβ1-induced proliferation can be abrogated by treatment with a PDGF-neutralizing antibody. Treatment with exogenous PDGF significantly increased TSU-Pr1 proliferation. Finally, treatment of TSU-Pr1 cells with TGFβ1 resulted in an increase in PDGF secretion. These results indicate that TGFβ1-induced proliferation in TSU-Pr1 cells is at least mediated through an increased secretion of PDGF.
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