WT1 Induction of MAP Kinase Phosphatase 3 Represents a Novel Mechanism of Growth Suppression

摘要

In its role as a tumor suppressor, WT1 transactivates several genes which are regulators of cell growth and differentiation pathways. For instance, WT1 induces the expression of the cell cycle regulator p21, the growth regulating glycoprotein amphiregulin, the proapoptotic gene Bak and the Ras/MAPKinase inhibitor, sprouty1. Here we show that WT1 transactivates another important negative regulator of the Ras/MAPKinase pathway, MKP3. In a WT1-inducible cell line that exhibits decreased cell growth and increased apoptosis upon expression of WT1, microarray analysis showed that MKP3 is the most highly induced gene. This was confirmed by real time PCR where MKP3 and other members of the FGF8 syn expression group which includes sprouty1 and the ets family of transcription factors were induced rapidly following WT1 expression. WT1 induction was associated with a block in the phosphorylation of ERK in response to EGF stimulation, an effect mediated by MKP3. In the presence of a dominant negative MKP3, WT1 could no longer block phosphorylation of ERK. Lastly when MKP3 expression is down regulated by shRNA, WT1 is less able to block Ras mediated transformation of 3T3 cells.