Transforming Growth Factor-β1 Induces Tissue Inhibitor of Metalloproteinase-1 Expression via Activation of Extracellular Signal-Regulated Kinase and Sp1 in Human Fibrosarcoma Cells

Abstract

The net balance of matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases (TIMP) system has been known to be a key factor in tumor cell invasion. In the present study, we investigated the molecular mechanisms of anti-invasive and antimigrative activity of transforming growth factor (TGF)-β1 on HT1080 human fibrosarcoma cells. In in vitro Matrigel invasion and Transwell migration assays, TGF-β1 dose-dependently inhibited the invasion and migration of HT1080 cells, respectively. Gelatin zymography, Western blot, and real-time PCR analysis showed that TGF-β1 enhanced the expression and secretion of MMP-2, TIMP-1, and, to a lesser degree, MMP-9 but not membrane type 1-MMP and TIMP-2. The addition of recombinant TIMP-1 protein reduced the Matrigel invasion and Transwell migration of HT1080 cells, similar to TGF-β1. Because augmentation of TIMP-1 might be the major factor for the anti-invasive and antimigrative activity of TGF-β1, we investigated possible molecular mechanisms responsible for the expression of TIMP-1 induced by TGF-β1. Treatment of HT1080 cells with TGF-β1 rapidly phosphorylated three mitogen-activated protein kinases [MAPK; extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and c-Jun NH₂-terminal kinase] and Akt. Among these kinases, the inhibition of only ERK1/2 pathway by PD98059, a specific inhibitor of MAPK/ERK kinase(MEK)-1, and transfection of dominant-negative MEK 1 effectively blocked the TIMP-1 induction by TGF-β1. Mithramycin, a specific inhibitor of Sp1 transcription factor, but not curcumin, an inhibitor of activator protein-1, and transfection of Sp1 small interfering RNA significantly inhibited the TGF-β1-induced expression of TIMP-1. In addition, electrophoretic mobility shift assay showed that TGF-β1 up-regulated Sp1 DNA-binding activity, and PD98059 and mithramycin effectively inhibited these events. Finally, pretreatment of HT1080 cells with PD98059 and mithramycin, but not curcumin, restored the invasive activity of these cells. Taken together, these data suggest that TGF-β1 modulates the net balance of the MMPs/TIMPs the systems in HT1080 cells for anti-invasion and antimigration by augmenting TIMP-1 through ERK1/2 pathway and Sp1 transcription factor. (Mol Cancer Res 2006;4(3):209–20)