Eduard Batlle

The transcription factor snail is a repressor of E-cadherin gene expression in epithelial tumour cells.

The adhesion protein E-cadherin plays a central part in the process of epithelial morphogenesis. Expression of this protein is downregulated during the acquisition of metastatic potential at late stages of epithelial tumour progression. There is evidence for a transcriptional blockage of E-cadherin gene expression in this process. Here we show that the transcription factor Snail, which is expressed by fibroblasts and some E-cadherin-negative epithelial tumour cell lines, binds to three E-boxes present in the human E-cadherin promoter and represses transcription of E-cadherin. Inhibition of Snail function in epithelial cancer cell lines lacking E-cadherin protein restores the expression of the E-cadherin gene.

The β-catenin/TCF-4 complex imposes a crypt progenitor phenotype on colorectal cancer cells

The transactivation of TCF target genes induced by Wnt pathway mutations constitutes the primary transforming event in colorectal cancer (CRC). We show that disruption of β-catenin/TCF-4 activity in CRC cells induces a rapid G1 arrest and blocks a genetic program that is physiologically active in the proliferative compartment of colon crypts. Coincidently, an intestinal differentiation program is induced. The TCF-4 target gene c-MYC plays a central role in this switch by direct repression of the p21CIP1/WAF1 promoter. Following disruption of β-catenin/TCF-4 activity, the decreased expression of c-MYC releases p21CIP1/WAF1 transcription, which in turn mediates G1 arrest and differentiation. Thus, the β-catenin/TCF-4 complex constitutes the master switch that controls proliferation versus differentiation in healthy and malignant intestinal epithelial cells.

β-Catenin and TCF Mediate Cell Positioning in the Intestinal Epithelium by Controlling the Expression of EphB/EphrinB

In the small intestine, the progeny of stem cells migrate in precise patterns. Absorptive, enteroendocrine, and goblet cells migrate toward the villus while Paneth cells occupy the bottom of the crypts. We show here that beta-catenin and TCF inversely control the expression of the EphB2/EphB3 receptors and their ligand ephrin-B1 in colorectal cancer and along the crypt-villus axis. Disruption of EphB2 and EphB3 genes reveals that their gene products restrict cell intermingling and allocate cell populations within the intestinal epithelium. In EphB2/EphB3 null mice, the proliferative and differentiated populations intermingle. In adult EphB3(-/-) mice, Paneth cells do not follow their downward migratory path, but scatter along crypt and villus. We conclude that in the intestinal epithelium beta-catenin and TCF couple proliferation and differentiation to the sorting of cell populations through the EphB/ephrin-B system.

The intestinal stem cell signature identifies colorectal cancer stem cells and predicts disease relapse

A frequent complication in colorectal cancer (CRC) is regeneration of the tumor after therapy. Here, we report that a gene signature specific for adult intestinal stem cells (ISCs) predicts disease relapse in CRC patients. ISCs are marked by high expression of the EphB2 receptor, which becomes gradually silenced as cells differentiate. Using EphB2 and the ISC marker Lgr5, we have FACS-purified and profiled mouse ISCs, crypt proliferative progenitors, and late transient amplifying cells to define a gene program specific for normal ISCs. Furthermore, we discovered that ISC-specific genes identify a stem-like cell population positioned at the bottom of tumor structures reminiscent of crypts. EphB2 sorted ISC-like tumor cells display robust tumor-initiating capacity in immunodeficient mice as well as long-term self-renewal potential. Taken together, our data suggest that the ISC program defines a cancer stem cell niche within colorectal tumors and plays a central role in CRC relapse.

Complete Polarization of Single Intestinal Epithelial Cells upon Activation of LKB1 by STRAD

The LKB1 gene encodes a serine/threonine kinase that is mutated in the Peutz-Jeghers cancer syndrome. LKB1 is homologous to the Par-4 polarity genes in C. elegans and D. melanogaster. We have previously reported the identification and characterization of an LKB1-specific adaptor protein, STRAD, which activates LKB1 and translocates it from nucleus to cytoplasm. We have now constructed intestinal epithelial cell lines in which inducible STRAD activates LKB1. Upon LKB1 activation, single cells rapidly remodel their actin cytoskeleton to form an apical brush border. The junctional proteins ZO-1 and p120 redistribute in a dotted circle peripheral to the brush border, in the absence of cell-cell contacts. Apical and basolateral markers sort to their respective membrane domains. We conclude that LKB1 can induce complete polarity in intestinal epithelial cells. In contrast to current thinking on polarization of simple epithelia, these cells can fully polarize in the absence of junctional cell-cell contacts.

Snail induction of epithelial to mesenchymal transition in tumor cells is accompanied by MUC1 repression and ZEB1 expression

E-cadherin protein plays a key role in the establishment and maintenance of adherent junctions. Recent evidence implicates the transcription factor Snail in the blockage of E-cadherin expression in fibroblasts and some epithelial tumor cells through direct binding to three E-boxes in the E-cadherin promoter. Transfection of Snail into epithelial cells leads to a more fibroblastic phenotype. Cells expressing Snail presented a scattered flattened phenotype with low intercellular contacts. Other epithelial markers like Cytokeratin 18 or MUC1 were also repressed. The effects of Snail on MUC1 transcription were mediated by two E-boxes present in the proximal promoter. Snail also induced expression of the mesenchymal markers fibronectin and LEF1 and the transcription repressor ZEB1. ZEB1 and Snail had a similar pattern of expression in epithelial cell lines, and both were induced by overexpression of ILK1, a kinase that causes the loss of E-cadherin and the acquisition of a fibroblastic phenotype. Snail overexpression in several cell lines raised ZEB1 RNA levels and increased the activity of ZEB1 promoter. ZEB1 could also repress E-cadherin and MUC1 promoters but less strongly than Snail. However, since ZEB1 expression persisted after Snail was down-regulated, ZEB1 may regulate epithelial genes in several tumor cell lines.

Dependency of Colorectal Cancer on a TGF-β-Driven Program in Stromal Cells for Metastasis Initiation

A large proportion of colorectal cancers (CRCs) display mutational inactivation of the TGF-β pathway, yet, paradoxically, they are characterized by elevated TGF-β production. Here, we unveil a prometastatic program induced by TGF-β in the microenvironment that associates with a high risk of CRC relapse upon treatment. The activity of TGF-β on stromal cells increases the efficiency of organ colonization by CRC cells, whereas mice treated with a pharmacological inhibitor of TGFBR1 are resilient to metastasis formation. Secretion of IL11 by TGF-β-stimulated cancer-associated fibroblasts (CAFs) triggers GP130/STAT3 signaling in tumor cells. This crosstalk confers a survival advantage to metastatic cells. The dependency on the TGF-β stromal program for metastasis initiation could be exploited to improve the diagnosis and treatment of CRC.

Isolation and in vitro expansion of human colonic stem cells.

Here we describe the isolation of stem cells of the human colonic epithelium. Differential cell surface abundance of ephrin type-B receptor 2 (EPHB2) allows the purification of different cell types from human colon mucosa biopsies. The highest EPHB2 surface levels correspond to epithelial colonic cells with the longest telomeres and elevated expression of intestinal stem cell (ISC) marker genes. Moreover, using culturing conditions that recreate the ISC niche, a substantial proportion of EPHB2-high cells can be expanded in vitro as an undifferentiated and multipotent population.

EphB receptor activity suppresses colorectal cancer progression

Most sporadic colorectal cancers are initiated by activating Wnt pathway mutations, characterized by the stabilization of β-catenin and constitutive transcription by the β-catenin/T cell factor-4 (Tcf-4) complex. EphB guidance receptors are Tcf4 target genes that control intestinal epithelial architecture through repulsive interactions with Ephrin-B ligands. Here we show that, although Wnt signalling remains constitutively active, most human colorectal cancers lose expression of EphB at the adenoma–carcinoma transition. Loss of EphB expression strongly correlates with degree of malignancy. Furthermore, reduction of EphB activity accelerates tumorigenesis in the colon and rectum of ApcMin/+ mice, and results in the formation of aggressive adenocarcinomas. Our data demonstrate that loss of EphB expression represents a critical step in colorectal cancer progression.

Stromal gene expression defines poor-prognosis subtypes in colorectal cancer

Recent molecular classifications of colorectal cancer (CRC) based on global gene expression profiles have defined subtypes displaying resistance to therapy and poor prognosis. Upon evaluation of these classification systems, we discovered that their predictive power arises from genes expressed by stromal cells rather than epithelial tumor cells. Bioinformatic and immunohistochemical analyses identify stromal markers that associate robustly with disease relapse across the various classifications. Functional studies indicate that cancer-associated fibroblasts (CAFs) increase the frequency of tumor-initiating cells, an effect that is dramatically enhanced by transforming growth factor (TGF)-β signaling. Likewise, we find that all poor-prognosis CRC subtypes share a gene program induced by TGF-β in tumor stromal cells. Using patient-derived tumor organoids and xenografts, we show that the use of TGF-β signaling inhibitors to block the cross-talk between cancer cells and the microenvironment halts disease progression.