Spred2 inhibits TGF-beta 1-induced urokinase type plasminogen activator expression, cell motility and epithelial mesenchymal transition

Abstract

TGF-beta 1 is a potent inductor of malignance in cancer cells. TGF-beta 1 stimulates the expression of extracellular matrix degrading proteases, cell migration and it is also involved in the epithelial-mesenchymal transition (EMT). In the present work, we analyzed the role of Spred2 in the urokinase-type plasminogen activator (uPA) stimulation, EMT and cell migration by TGF-beta 1. We found that both the expression of mRNA and the protein level of Spred2 were lower in transformed keratinocytes PDV compared with immortalized keratinocytes MCA-3D. The transient ectopic expression of Spred2 in PDV cells inhibited the TGF-beta 1-transactivated SRE-Luc reporter which is related with the ERK1,2 signal. The stable ectopic expression of Spred2 in PDV cells (SP cells) led to the loss of ERK 1,2 activation by TGF-beta 1, although Smad2 activation was not affected, and the knockdown of Spred2 enhanced the activation of ERK1,2 signal by TGF-beta 1. The increment of uPA expression induced by TGF-beta 1 was suppressed in SP cells. In contrast, the stimulus on PAI-1 expression was not affected and comparable to parental PDV cells. SP cells under TGF-beta 1 treatment were unable to display the EMT, since the overexpression of Spred2 abolished the TGF-beta 1-induced disruption of the E-cadherin cell to cell interactions, reorganization of the actin cytoskeleton and upregulation of the mesenchymal marker vimentin. Finally, SP cells could not respond to the TGF-beta 1 stimulus on cell migration. Taken together, the data in the present study suggests that Spred2 is a regulator of TGF-beta 1-induced malignance in transformed keratinocytes.