The epithelial-mesenchymal transition (EMT) contributes to cancer metastasis. Two ZEB family members, ZEB1 and ZEB2(SIP1), inhibit transcription of the E-cadherin gene and induce EMT in vitro. However, their relevance to human cancer is insufficiently studied. Here, we performed a comparative study of SIP1 and ZEB1 proteins in cancer cell lines and in one form of human malignancy, carcinoma of the bladder. Whereas ZEB1 protein was expressed in all E-cadherin-negative carcinoma cell lines, being in part responsible for the high motility of bladder cancer cells, SIP1 was hardly ever detectable in carcinoma cells in culture. However, SIP1 represented an independent factor of poor prognosis (P ‫؍‬ 0.005) in a series of bladder cancer specimens obtained from patients treated with radiotherapy. In contrast, ZEB1 was rarely expressed in tumor tissues; and E-cadherin status did not correlate with the patients' survival. SIP1 protected cells from UV-and cisplatin-induced apoptosis in vitro but had no effect on the level of DNA damage. The anti-apoptotic effect of SIP1 was independent of either cell cycle arrest or loss of cell-cell adhesion and was associated with reduced phosphorylation of ATM/ATR targets in UV-treated cells. The prognostic value of SIP1 and its role in DNA damage response establish a link between genetic instability and metastasis and suggest a potential importance for this protein as a therapeutic target. In addition, we conclude that the nature of an EMT pathway rather than the deregulation of E-cadherin per se is critical for the progression of the disease and patients' survival. E pithelial mesenchymal transition (EMT) is a genetic program controlling cell migration during embryonic development and in wound healing (1, 2). Aberrant activation of EMT programs occurs in cells of epithelial tumors and contributes to the formation of cancer stem cells and metastasis (1-4). EMT is characterized by the loss of epithelial and the acquisition of mesenchymal features. EMT programs are controlled by several master regulators including TWIST, SNAIL (SNAI1 and SNAI2), and ZEB (ZEB1/␦EF1/TCF8 and SIP1/ZEB2) protein family members. These proteins act downstream in EMTinducing signal transduction pathways activated by growth factors, integrin engagement and hypoxia (1-3). Their expression is tightly regulated at the posttranscriptional level. Recent reports highlighted the importance of miR-200 microRNA family in the regulation of ZEB1 and SIP1 protein expression (5). ZEB proteins bind proximal E-boxes within the E-cadherin gene (cdh1) promoter and repress transcription by recruiting corepressor complexes (6). Likewise, they directly repress numerous genes encoding components of the epithelial junctional complex and cell polarity factors (7,8). The relevance of ZEB proteins to tumor progression has been studied in several forms of human cancer. Expression of ZEB1 correlated with the aggressive phenotype in various histological types of endometrial carcinoma and was detected in sarcomatous compartment of endometri...

No abstract

No abstract