| Metastasis is the final step in solid tumour progression and is the most common cause of death in cancer patients. Metastasis is a multi-step process:invasion of tumour cells into the adjacent tissues, entry of tumour cells in the systemic circulation (intravasation), survival in circulation, extravasation to distant organs, and finally growth of cancer cells to produce secondary tumours. At present the mechanism of metastasis has not yet fully understood.Apoptosis signaling is regulated and executed by specialized proteins that often carry protein-protein interaction domains. One of these domains is the Death effector domain (DED) that is predominantly found in components of the death receptor-induced signaling complex, which forms at the members of the death receptor family following their ligation. DED-containing proteins comprise Fas-associated death domain protein (FADD), Caspase-8and death effector domain containing DNA binding (DEDD), and the like. DEDD plays an important role in CD95-mediated apoptosis through activating caspase3or caspase6as a scaffold protein. Recently, the study found that DEDD can suppress the activity of Cdkl/cyclin B1complexes and keep S6K1activity, suggesting that DEDD participate in cell cycle and inhibit cell mitosis. We recently discovered that DEDD Negative regulate the TGF-bl signaling pathway by interact with smads.However, t is unclear whether DEDD involves in tumour growth, invasion and metastasis, and the pathophysiological functions of DEDD have not been fully clarified.In this study, we show that DEDD expression is negatively correlated with poor prognosis in breast cancer and colon cancer. Immunoblot analysis of DEDD levels show that DEDD expression is negatively correlated with aggressive tumour phenotypes in breast cancer cell lines and other tissue original cancer cell lines (liver, colon, pancreas, prostate).RNA-interference-mediated knockdown of DEDD in non-aggressive (MCF7) cells lead to acquire aggressive-tumour phenotypes.In vitro and in vivo experiments show that interference DEDD in MCF7cell, which greatly increase the activity of growth,migration,invasion and metastasis.Conversely, overexpressed DEDD in highly aggressive (MDA-MB-231) cancer cells reverse the activity of growth, migration, invasion and metastasis in vitro and in vivo.Epithelial-mesenchymal transition (EMT) is a mainly process in tumour invasion and metastasis. Western blot and confocal results show that knockdown DEDD in MCF7could promote EMT, significantly reduce the expression of epithelial markers(E-cadherin,β-cantenin), simultaneously,induce the expression of mesenchymal markers(Vimentin,α-SMA); Conversely,Overexpressed DEDD in MDA-MB-231could reverse the process of EMT,upregulate the expression of E-cadherin and β-cantenin,and downregulate the expression of Vimentin and a-SMA. Western blot results show that EMT transcriptional factors, such as Snail, Twist, Slug, were induced in MCF7-DEDDshRNA;Conversely,the expression of thers factors are decreased in231-DEDD cells compared with231-vector cells. Protein degradation assay show that DEDD could induce the degradation of Snail and Twist.Snail and LC3is showed co-location by confocal, this indicate that Snail also could be degraded by autophagy-lysosome degradation pathway.Co-IP assay show that DEDD could interact with PI3K Ⅲ/Beclinl complex.Knockdown DEDD could induce the degradation of PI3K Ⅲ. Transient transfection of PI3K Ⅲ or Beclin1in MCF7DEDD shRNA cells could decrease the expression of Snail and Twist. Conclusion:Our findings suggest that DEDD expression level negatively correlation with poor prognosis in breast and colon cancer. DEDD is a novel inhibitor in tumor growth, migration, invasion and metastasis. DEDD impede the invasion and metastasis by reverse EMT process in breast cancer.DEDD could interact with PI3K Ⅲ/Beclin1complex, this then induce the autophagy-lysosome degradation of snail, and reverse EMT process. |
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