Sphingosine-1-Phosphate and Interleukin-1 Independently Regulate Plasminogen Activator Inhibitor-1 and Urokinase-Type Plasminogen Activator Receptor Expression in Glioblastoma Cells: Implications for Invasiveness

Abstract

Glioblastoma multiforme is an invasive primary brain tumor, which evades the current standard treatments. The invasion of glioblastoma cells into healthy brain tissue partly depends on the proteolytic and nonproteolytic activities of the plasminogen activator system proteins, including the urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI-1), and a receptor for uPA (uPAR). Here we show that sphingosine-1-phosphate (S1P) and the inflammatory mediator interleukin-1 (IL-1) increase the mRNA and protein expression of PAI-1 and uPAR and enhance the invasion of U373 glioblastoma cells. Although IL-1 enhanced the expression of sphingosine kinase 1 (SphK1), the enzyme that produces S1P, down-regulation of SphK1 had no effect on the IL-1 -induced uPAR or PAI-1 mRNA expression, suggesting that these actions of IL-1 are independent of S1P production. Indeed, the S1P-induced mRNA expression of uPAR and PAI-1 was blocked by the S1P 2 receptor antagonist JTE013 and by the down-regulation of S1P 2 using siRNA. Accordingly, the inhibition of mitogen-activated protein kinase/extracellular signal -regulated kinase kinase 1/2 and Rho-kinase, two downstream signaling cascades activated by S1P 2 , blocked the activation of PAI-1 and uPAR mRNA expression by S1P. More importantly, the attachment of glioblastoma cells was inhibited by the addition of exogenous PAI-1 or siRNA to uPAR, whereas the invasion of glioblastoma cells induced by S1P or IL-1 correlated with their ability to enhance the expression of PAI-1 and uPAR. Collectively, these results indicate that S1P and IL-1 activate distinct pathways leading to the mRNA and protein expression of PAI-1 and uPAR, which are important for glioblastoma invasiveness.

HDL3, but not HDL2, stimulates plasminogen activator inhibitor-1 release from adipocytes: the role of sphingosine-1-phosphate

“…This inhibition of migration via S1P 2 was mediated by G 12/13 -dependent Rac inactivation and Rho-dependent PTEN (phosphatase and Tensin homolog inhibitory) pathway. The stimulation of glioblastoma cells with S1P increased PAI-1 expression via S1P 2 receptor-mediated by activation of ERK1/2 and Rho pathways ( 13 ). We have confi rmed and extended these observations and now report that HDL3 and S1P stimulate the release of PAI-1 from 3T3 adipocytes via the S1P 2 receptor ( Fig.…”

“…Results from in vitro studies have shown that insulin and isolated lipoproteins, especially tri glyceride-rich lipoproteins, stimulate PAI-1 production by cultured endothelial cells and hepatocytes ( 11,12 ). Of particular relevance to the present study, sphingosine-1-phosphate (S1P) has been shown to increase the mRNA and protein expression of PAI-1 in glioblastoma cells ( 13 ). S1P is a lysophospholipid that is emerging as key signaling molecule involved in the regulation of a variety of cellular functions, including cell growth and differentiation, proliferation, apoptotic cell death, and infl ammation (14)(15)(16)(17)(18)(19).…”

Export of sphingosine-1-phosphate and cancer progression

“…S1P can induce in vitro lymphatic endothelial cell (LEC) tube formation via activation of S1PR1 ( 77,89 ). Moreover, Ang2-induced in vitro lymphangiogenesis was suppressed by a SphK1-specifi c pharmacological inhibitor ( 90,91 ), suggesting cross talk between Ang2 and S1P signaling pathways ( 37 ). Interestingly, LEC-specifi c deletion of SphK1 in the SphK2 knockout mouse, i.e., total knockout of S1P production specifi cally in LECs, inhibited lymphatic vessel maturation, indicating that SphKs and S1P in LECs are required for proper development of lymphatic vessels ( 92 ).…”

Regulation of cancer cell migration and invasion by sphingosine-1-phosphate

“…Similarly, in glioblastoma cells, we and others have shown that S1P regulates a number of proteases that may be important for invasion and metastasis. Thus, S1P induces expression of uPA and its receptor, as well as plasminogen activator inhibitor, which leads to increased uPA activity [50,51] . Furthermore, neutralizing antibodies to uPA blocked S1P-receptor-induced invasion of glioblastoma cells in an in vitro spheroid invasion assay [51] .…”

“…Furthermore, neutralizing antibodies to uPA blocked S1P-receptor-induced invasion of glioblastoma cells in an in vitro spheroid invasion assay [51] . Upregulation of the uPA system appears to be mediated by S1P1 and S1P2 receptors [50,51] . Thus, although S1P2 is generally anti-migratory, it may contribute to invasion of glioma cells.…”