TGF-β1 and TGF-β2 strongly enhance the secretion of plasminogen activator inhibitor-1 and matrix metalloproteinase-9 of the human prostate cancer cell line PC-3

Background: Recently it was demonstrated that transforming growth factor beta 2 (TGF-beta 2) is the predominant TGF-beta isoform in the human prostate. However, with the human prostatic cancer cells PC-3 mostly effects of TGF-beta 1 were investigated. This study aimed to analyze the effects of TGF-beta 2 on its own secretion, on the secretion of plasminogen activator inhibitor-1 (PAI-1), and the matrix metalloproteinases (MMP)-2 and MMP-9 in comparison to stimulations with TGF-beta 1. Materials and methods: PC-3 cells were cultured with and without TGF-beta 1 and TGF-beta 2 to analyze autostimulation and their effects on protein secretion. ELISAs for TGF beta 1, TGF-beta 2, TGF-beta 3, PAI-1, MMP-2 and MMP-9 were used to analyze protein levels in the supernatant. Cell proliferation was determined with a proliferation assay. Results: A dose-dependent and significant suppression of cell proliferation with TGF-beta 1 (p<0.05) and TGF-beta 2 (p<0.05) was observed. PC-3 cells secrete higher amounts of total TGF-beta 2 compared to total TGF-beta 1. Only for TGF-beta 2, we found the active isoform. In contrast, the secretion of TGF-beta 3 was not detectable. Additionally, we observed a strong and significant increase in the secretion of MMP-9 and PAI-1 after stimulations with TGF-beta 1 and TGF-beta 2, respectively. However, no protein levels of MMP-2 were detectable. Conclusion: Our experiments revealed that TGF-beta 2 is the predominant TGF-beta isoform in PC-3 cells. Furthermore, a strong effect of TGF-beta 1 and TGF-beta 2 on the secretion of MMP-9 and PAI-1 was found. Thus, PC-3 cells not only secrete TGF-beta 1 and TGF-beta 2 but also respond to stimulations with the TGF-beta isoforms. The interesting observation that only TGF-beta 2 is activated points to different mechanisms of proteolytic activation of the diverse TGF-beta isoforms. (C) 2009 Elsevier B.V. All rights reserved.