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Malignant progression in cancer requires populations of tumor-initiating cells (TICs) endowed with unlimited self renewal, survival under stress, and establishment of distant metastases. Additionally, the acquisition of invasive properties driven by epithelial-mesenchymal transition (EMT) is critical for the evolution of neoplastic cells into fully metastatic populations. Here, we characterize 2 human cellular models derived from prostate and bladder cancer cell lines to better understand the relationship between TIC and EMT programs in local invasiveness and distant metastasis. The model tumor subpopulations that expressed a strong epithelial gene program were enriched in highly metastatic TICs, while a second subpopulation with stable mesenchymal traits was impoverished in TICs. Constitutive overexpression of the transcription factor Snai1 in the epithelial/TIC-enriched populations engaged a mesenchymal gene program and suppressed their self renewal and metastatic phenotypes. Conversely, knockdown of EMT factors in the mesenchymal-like prostate cancer cell subpopulation caused a gain in epithelial features and properties of TICs. Both tumor cell subpopulations cooperated so that the nonmetastatic mesenchymal-like prostate cancer subpopulation enhanced the in vitro invasiveness of the metastatic epithelial subpopulation and, in vivo, promoted the escape of the latter from primary implantation sites and accelerated their metastatic colonization. Our models provide new insights into how dynamic interactions among epithelial, self-renewal, and mesenchymal gene programs determine the plasticity of epithelial TICs., Introduction There is a wealth of evidence that the acquisition of aggressive traits of cancer, or malignant progression, can be determined both by the occurrence of genetic mutations and by [...]

Author(s): Hector G Palmer [1, 8]; Maria Jesus Larriba [1, 8]; Jose Miguel Garcia [2]; Paloma Ordonez-Moran [1]; Cristina Pena [2]; Sandra Peiro [3]; Isabel Puig [3]; Rufo Rodriguez [4]; [...]

The initiation and the regulation of the Zeb2 or Sip1 expression during the process of snail-1 induced epithelial-mesenchymal transition (EMT) are discussed. The activation of the Zeb2 expression is shown to be highly dependent on the presence of a natural antisense transcript (NAT) in the pathway.

The [Beta]-catenin signaling pathway is designated in nearly all colon cancers. Nonhypercalcemic vitamin D3 (1[Alpha], 25-dehydroxyvitamin [D.sub.3]) analogues are candidate drugs to treat this neoplasia. We show that these compounds promote the differentiation of human colon carcinoma SW480 cells expressing vitamin D receptors (VDRs)(SW480-ADH) but not that of a malignant subline (SW480-R) or metastasic derivative (SW620) cells lacking VDR. 1[Alpha], 25[(OH).sub.2][D.sub.3] induced the expression of E-cadherin and other adhesion proteins (occludin, Zonula occludens [ZO]-1, ZO-2, vinculin) and promoted the translocation of [Beta]-catenin, plakoglobin, and ZO-1 from the nucleus to the plasma membrane. Ligand-activated VDR competed with T cell transcription factor (TCF)-4 for [Beta]-catenin binding. Accordingly, 1[Alpha], 25([OH.sub.2])[D.sub.3] repressed [Beta]-catenin-TCF-4 transcriptional activity. Moreover, VDR activity was enhanced by ectopic [Beta]-catenin and reduced by TCF-4. Also, 1[Alpha], 25[(OH).sub.2][D.sub.3] inhibited expression of [Beta]-catenin-TCF-4-responsive genes, c-myc, peroxisome proliferator-activated receptor [Delta], Tcf-1, and CD44, whereas it induced expression of ZO-1. Our results show that 1[Alpha], 25[(OH).sub.2][D.sub.3] induces E-cadherin and modulates [Beta]-catenin-TCF-4 target genes in a manner opposite to that of [Beta]-catenin, promoting the differentiation of colon carcinoma cells.

TWIST1 is a transcription factor that belongs to the family of basic helix-loop-helix proteins involved in epithelial-tomesenchymal transition and invasion processes. The TWIST1 protein possesses oncogenic, drug-resistant, angiogenic and invasive properties, and has been related with several human tumors and other pathologies. Colorectal cancer is one of the tumors in which TWIST1 is over-expressed, but its involvement in the clinical outcome of the disease is still unclear. We tested, by RT-PCR, the expression levels of TWIST1 in normal and tumor paired-sample tissues from a series of 151 colorectal cancer patients, in order to investigate its prognostic value as a tumor marker. TWIST1 expression was restricted to tumor tissues (86.1%) and correlated with lymph node metastasis (LNM). Adjusted analysis showed that the expression levels of TWIST1 correlated with overall survival (OS) and disease-free survival (DFS). Importantly, TWIST1 expression levels predicted OS specifically at stages I and II. Moreover, patients with stage II tumors and high TWIST1 levels showed even shorter survival than patients with stage III tumors. These results suggest that TWIST1 expression levels could be a tumor indicator in stage II patients and help select patients at greater risk of poor prognosis who might benefit from adjuvant chemotherapy. [ABSTRACT FROM AUTHOR]

A correction to the article "Wnt controls the transcriptional activity of Kaiso through CK1ε-dependent phosphorylation of p120-catenin" in the July 2011 issue is presented.

Epithelial-mesenchymal transition (EMT) is a morphogenetic process characterized by the acquisition of mesenchymal properties linked with an invasive phenotype and metastasis of tumor cells. NK group 2, member D (NKG2D) is an NK cell-activating receptor crucially involved in cancer immunosurveillance. In this study, we show that induction of EMT by TGF-β stimulation of human keratinocytes, by glycogen synthase kinase-3β inhibition in several epithelial tumor cell lines, and by Snail1 overexpression in colorectal cancer cells strongly upregulated the expression of NKG2D ligands (NKG2DLs), MHC class I chain-related molecules A and B (MICA/B) and ULBP1-3. Overexpression of Snaill and inhibition of glycogen synthase kinase-3β in colorectal tumor cells markedly induced the activity of Sp1 transcription factor, which plays a key role in the upregulation of NKG2DL expression during EMT. The stimulation of MICA/B expression by TGF-p treatment was independent of Sp1, but it involved posttranslational mechanisms mediated by mammalian target of rapamycin pathway. Accordingly, with the increased expression of NKG2DLs, triggering of EMT rendered cancer cells more susceptible to NKG2D-mediated killing by NK cells. In agreement, MICA/B were expressed in vivo in well-differentiated colorectal tumors with retained epithelial characteristics, whereas no expression of MICA/B was detected in poorly differentiated and invasive colorectal tumors that have lost epithelial characteristics. This decrease of MICA/B expression was associated with a dramatic increase of NKG2D+-tumor infiltrating lymphocytes. Overall, our findings indicate that EMT is a relevant checkpoint in the control of tumor progression through NKG2D-mediated immune responses. [ABSTRACT FROM AUTHOR]

The transcription factor SNAIL1 is a master regulator of epithelial to mesenchymal transition. SNAIL1 is a very unstable protein, and its levels are regulated by the E3 ubiquitin ligase β-TrCP1 that interacts with SNAIL1 upon its phosphorylation by GSK-3β. Here we show that SNAIL! polyubiquitylation and degradation may occur in conditions precluding SNAIL1 phosphorylation by GSK-3β, suggesting that additional E3 ligases participate in the control of SNAIL1 protein stability. In particular, we demonstrate that the F-box E3 ubiquitin ligase FBX114 interacts with SNAIL 1 and promotes its ubiquitylation and proteasome degradation independently of phosphorylation by GSK-3β. In vivo, inhibition of FBXI14 using short hairpin RNA stabilizes both ectopically expressed and endogenous SNAIL1. Moreover, the expression of FBXI14 is potently down-regulated during hypoxia, a condition that increases the levels of SNAIL! protein but not SNAIL1 mRNA. FBX14 mRNA is decreased in tumors with a high expression of two proteins up-regulated in hypoxia, carbonic anhydrase 9 and TWIST 1. In addition, Twist1 small interfering RNA prevents hypoxia-induced Fbxl14 down-regulation and SNAIL1 stabilization in NMuMG cells. Altogether, these results demonstrate the existence of an alternative mechanism controlling SNAIL1 protein levels relevant for the induction of SNAIL1 during hypoxia. [ABSTRACT FROM AUTHOR]

Epithelial-mesenchymal transition (EMT) is essential for organogenesis and is triggered during carcinoma progression to an invasive state. Transforming growth factor-beta (TGF-beta) cooperates with signalling pathways, such as Ras and Wnt, to induce EMT, but the molecular mechanisms are not clear. Here, we report that SMAD3 and SMAD4 interact and form a complex with SNAIL1, a transcriptional repressor and promoter of EMT. The SNAIL1-SMAD3/4 complex was targeted to the gene promoters of CAR, a tight-junction protein, and E-cadherin during TGF-beta-driven EMT in breast epithelial cells. SNAIL1 and SMAD3/4 acted as co-repressors of CAR, occludin, claudin-3 and E-cadherin promoters in transfected cells. Conversely, co-silencing of SNAIL1 and SMAD4 by siRNA inhibited repression of CAR and occludin during EMT. Moreover, loss of CAR and E-cadherin correlated with nuclear co-expression of SNAIL1 and SMAD3/4 in a mouse model of breast carcinoma and at the invasive fronts of human breast cancer. We propose that activation of a SNAIL1-SMAD3/4 transcriptional complex represents a mechanism of gene repression during EMT.

Despite considerable efforts to improve early detection and advances in chemotherapy, metastatic relapses remain a major challenge in the management of ovarian cancer. The endothelin A receptor (ET(A)R)/endothelin-1 (ET-1) axis has been shown to have a significant role in ovarian carcinoma by promoting tumorigenesis. Here we show that the ET-1/ET(A)R autocrine pathway drives epithelial-to-mesenchymal transition (EMT) in ovarian tumor cells by inducing a fibroblastoid and invasive phenotype, down-regulation of E-cadherin, increased levels of beta-catenin, Snail, and other mesenchymal markers, and suppression of E-cadherin promoter activity. Activation of ET(A)R by ET-1 triggers an integrin-linked kinase (ILK)-mediated signaling pathway leading to glycogen synthase kinase-3beta (GSK-3beta) inhibition, Snail and beta-catenin stabilization, and regulation of transcriptional programs that control EMT. Transfection of dominant negative ILK or exposure to an ILK inhibitor suppresses the ET-1-induced phosphorylation of GSK-3beta as well as Snail and beta-catenin protein stability, activity, and invasiveness, indicating that ET-1/ET(A)R-induced EMT-promoting effects depend on ILK. ET(A)R blockade by specific antagonists or reduction by ET(A)R RNA interference reverses EMT and cell invasion by inhibiting autocrine signaling pathways. In ovarian carcinoma xenografts, ABT-627, a specific ET(A)R antagonist, suppresses EMT determinants and tumor growth. In human ovarian cancers, ET(A)R expression is associated with E-cadherin down-regulation, N-cadherin expression, and tumor grade. Collectively, these findings provide evidence of a critical role for the ET-1/ET(A)R axis during distinct steps of ovarian carcinoma progression and identify novel targets of therapeutic intervention.