DESCRIPTION (provided by applicant): Aggressive carcinomas are characterized by epithelial to mesenchymal transition (EMT). The hallmarks of EMT, loss of cell-cell interactions and an increase in cell motility, potentiate the exodus of cancer cells from the primary tumor site, increasing the likelihood of metastasis. In a number of epithelial cell lines continuous tumor growth factor beta 1 (TGF-beta1) signaling is necessary for initiating and maintaining EMT. Multiple TGF-beta1 induced transcriptional repressors (TITR) of E-cadherin have been implicated in EMT, including Snail, Slug, ZEB-1 and ZEB-2. We will test the hypothesis that a cell's commitment to EMT may be determined by positive and negative feedback loops involving the TITRs by using dominant negative versions of the TITRs, small interfering RNA (siRNA) directed towards the TITRs and overexpression of the individual TITRs in EpH4 cells. To firmly establish the role of these TITRs in EMT mediated metastasis, we will determine in vivo if the TITRs cause increased metastatic potential of EpH4 cells. Finally using a newly established genome wide screen based on siRNA we will identify shared downstream signaling factors of TGF-beta1 that control the expression of the TITRs, providing therapeutic targets for preventing metastasis.