Transforming growth factor-β (TGF-β) is a secreted multifunctional factor that plays a key role in intercellular communication. Perturbations of TGF-β signaling can lead to breast cancer. TGF-β elicits its effects on proliferation and differentiation via specific cell surface TGF-β type I and type II receptors (i.e., TβRI and TβRII) that contain an intrinsic serine/threonine kinase domain. Upon TGF-β-induced heteromeric complex formation, activated TβRI elicits intracellular signaling by phosphorylating SMAD2 and SMAD3. These activated SMADs form heteromeric complexes with SMAD4 to regulate specific target genes, including plasminogen activation inhibitor 1 (PAI-1, encoded by the SERPINE1 gene). The induction of epithelial-to-mesenchymal transition (EMT) allows epithelial cancer cells at the primary site or during colonization at distant sites to gain an invasive phenotype and drive tumor progression. TGF-β acts as a potent inducer of breast cancer invasion by driving EMT. Here, we describe systematic methods to investigate TGF-β signaling and EMT responses using premalignant human MCF10A-RAS (M2) cells and mouse NMuMG epithelial cells as examples. We describe methods to determine TGF-βinduced SMAD2 phosphorylation by Western blotting, SMAD3/SMAD4-dependent transcriptional activity using luciferase reporter activity and SERPINE1 target gene expression by quantitative real-time-polymerase chain reaction (qRT-PCR). In addition, methods are described to examine TGF-β-induced EMT by measuring changes in morphology, epithelial and mesenchymal marker expression, filamentous actin staining and immunofluorescence staining of E-cadherin. Two selective small molecule TGF-β receptor kinase inhibitors, GW788388 and SB431542, were used to block TGF-β-induced SMAD2 phosphorylation, target genes and changes in EMT marker expression. Moreover, we describe the transdifferentiation of mesenchymal breast Py2T murine epithelial tumor cells into adipocytes. Methods to examine TGF-

Ovo-like transcriptional repressor 1 (OVOL1) is a key mediator of epithelial lineage determination and mesenchymal–epithelial transition (MET). The cytokines transforming growth factor-β (TGF-β) and bone morphogenetic proteins (BMP) control the epithelial–mesenchymal plasticity (EMP) of cancer cells, but whether this occurs through interplay with OVOL1 is not known. Here, we show that OVOL1 is inversely correlated with the epithelial–mesenchymal transition (EMT) signature, and is an indicator of a favorable prognosis for breast cancer patients. OVOL1 suppresses EMT, migration, extravasation, and early metastatic events of breast cancer cells. Importantly, BMP strongly promotes the expression of OVOL1, which enhances BMP signaling in turn. This positive feedback loop is established through the inhibition of TGF-β receptor signaling by OVOL1. Mechanistically, OVOL1 interacts with and prevents the ubiquitination and degradation of SMAD family member 7 (SMAD7), which is a negative regulator of TGF-β type I receptor stability. Moreover, a small-molecule compound 6-formylindolo(3,2-b)carbazole (FICZ) was identified to activate OVOL1 expression and thereby antagonizing (at least in part) TGF-β-mediated EMT and migration in breast cancer cells. Our results uncover a novel mechanism by which OVOL1 attenuates TGF-β/SMAD signaling and maintains the epithelial identity of breast cancer cells.

Endothelial-to-mesenchymal transition (EndMT) plays an important role in embryonic development and disease progression. Yet, how different members of the transforming growth factor-β (TGF-β) family regulate EndMT is not well understood. In the current study, we report that TGF-β2, but not bone morphogenetic protein (BMP)9, triggers EndMT in murine endothelial MS-1 and 2H11 cells. TGF-β2 strongly upregulates the transcription factor SNAIL, and the depletion of Snail is sufficient to abrogate TGF-β2-triggered mesenchymal-like cell morphology acquisition and EndMT-related molecular changes. Although SLUG is not regulated by TGF-β2, knocking out Slug also partly inhibits TGF-β2-induced EndMT in 2H11 cells. Interestingly, in addition to SNAIL and SLUG, BMP9 stimulates inhibitor of DNA binding (ID) proteins. The suppression of Id1, Id2, or Id3 expression facilitated BMP9 in inducing EndMT and, in contrast, ectopic expression of ID1, ID2, or ID3 abrogated TGF-β2-mediated EndMT. Altogether, our results show that SNAIL is critical and indispensable for TGF-β2-mediated EndMT. Although SLUG is also involved in the EndMT process, it plays less of a crucial role in it. In contrast, ID proteins are essential for maintaining endothelial traits and repressing the function of SNAIL and SLUG during the EndMT process. These data suggest that the control over endothelial vs. mesenchymal cell states is determined, at least in part, by a balance between the expression of SNAIL/SLUG and ID proteins.

Epithelial‐mesenchymal transition (EMT) is pivotal in the initiation and development of cancer cell metastasis. We observed that the abundance of glycosphingolipids (GSLs), especially ganglioside subtypes, decreased significantly during TGF‐β‐induced EMT in NMuMG mouse mammary epithelial cells and A549 human lung adenocarcinoma cells. Transcriptional profiling showed that TGF‐β/SMAD response genes and EMT signatures were strongly enriched in NMuMG cells, along with depletion of UDP‐glucose ceramide glucosyltransferase (UGCG), the enzyme that catalyzes the initial step in GSL biosynthesis. Consistent with this finding, genetic or pharmacological inhibition of UGCG promoted TGF‐β signaling and TGF‐β‐induced EMT. UGCG inhibition promoted A549 cell migration, extravasation in the zebrafish xenograft model, and metastasis in mice. Mechanistically, GSLs inhibited TGF‐β signaling by promoting lipid raft localization of the TGF‐β type I receptor (TβRI) and by increasing TβRI ubiquitination and degradation. Importantly, we identified ST3GAL5‐synthesized a‐series gangliosides as the main GSL subtype involved in inhibition of TGF‐β signaling and TGF‐β‐induced EMT in A549 cells. Notably, ST3GAL5 is weakly expressed in lung cancer tissues compared to adjacent nonmalignant tissues, and its expression correlates with good prognosis.

Transforming growth factor-β (TGF-β) is a secreted multifunctional factor that plays a key role in intercellular communication. Perturbations of TGF-β signaling can lead to breast cancer. TGF-β elicits its effects on proliferation and differentiation via specific cell surface TGF-β type I and type II receptors (i.e., TβRI and TβRII) that contain an intrinsic serine/threonine kinase domain. Upon TGF-β-induced heteromeric complex formation, activated TβRI elicits intracellular signaling by phosphorylating SMAD2 and SMAD3. These activated SMADs form heteromeric complexes with SMAD4 to regulate specific target genes, including plasminogen activation inhibitor 1 (PAI-1, encoded by the SERPINE1 gene). The induction of epithelial-to-mesenchymal transition (EMT) allows epithelial cancer cells at the primary site or during colonization at distant sites to gain an invasive phenotype and drive tumor progression. TGF-β acts as a potent inducer of breast cancer invasion by driving EMT. Here, we describe systematic methods to investigate TGF-β signaling and EMT responses using premalignant human MCF10A-RAS (M2) cells and mouse NMuMG epithelial cells as examples. We describe methods to determine TGF-βinduced SMAD2 phosphorylation by Western blotting, SMAD3/SMAD4-dependent transcriptional activity using luciferase reporter activity and SERPINE1 target gene expression by quantitative real-time-polymerase chain reaction (qRT-PCR). In addition, methods are described to examine TGF-β-induced EMT by measuring changes in morphology, epithelial and mesenchymal marker expression, filamentous actin staining and immunofluorescence staining of E-cadherin. Two selective small molecule TGF-β receptor kinase inhibitors, GW788388 and SB431542, were used to block TGF-β-induced SMAD2 phosphorylation, target genes and changes in EMT marker expression. Moreover, we describe the transdifferentiation of mesenchymal breast Py2T murine epithelial tumor cells into adipocytes. Methods to examine TGF-

In response to specific external cues and the activation of certain transcription factors, endothelial cells can differentiate into a mesenchymal-like phenotype, a process that is termed endothelial to mesenchymal transition (EndMT). Emerging results have suggested that EndMT is causally linked to multiple human diseases, such as fibrosis and cancer. In addition, endothelial-derived mesenchymal cells may be applied in tissue regeneration procedures, as they can be further differentiated into various cell types (e.g., osteoblasts and chondrocytes). Thus, the selective manipulation of EndMT may have clinical potential. Like epithelial-mesenchymal transition (EMT),EndMT can be strongly induced by the secreted cytokine transforming growth factorbeta (TGF-β), which stimulates the expression of so-called EndMT transcription factors (EndMT-TFs), including Snail and Slug. These EndMT-TFs then up-and downregulate the levels of mesenchymal and endothelial proteins, respectively. Here, we describe methods to investigate TGF-β-induced EndMT in vitro, including a protocol to study the role of particular TFs in TGF-β-induced EndMT. Using these techniques, we provide evidence that TGF-β2 stimulates EndMT in murine pancreatic microvascular endothelial cells (MS-1 cells), and that the genetic depletion of Snail using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPRassociated protein 9 (Cas9)-mediated gene editing, abrogates this phenomenon. This approach may serve as a model to interrogate potential modulators of endothelial biology, and can be used to perform genetic or pharmacological screens in order to identify novel regulators of EndMT, with potential application in human disease.

No abstract

In response to specific external cues and the activation of certain transcription factors, endothelial cells can differentiate into a mesenchymal-like phenotype, a process that is termed endothelial to mesenchymal transition (EndMT). Emerging results have suggested that EndMT is causally linked to multiple human diseases, such as fibrosis and cancer. In addition, endothelial-derived mesenchymal cells may be applied in tissue regeneration procedures, as they can be further differentiated into various cell types (e.g., osteoblasts and chondrocytes). Thus, the selective manipulation of EndMT may have clinical potential. Like epithelial-mesenchymal transition (EMT), EndMT can be strongly induced by the secreted cytokine transforming growth factorbeta (TGF-β), which stimulates the expression of so-called EndMT transcription factors (EndMT-TFs), including Snail and Slug. These EndMT-TFs then up-and downregulate the levels of mesenchymal and endothelial proteins, respectively. Here, we describe methods to investigate TGF-β-induced EndMT in vitro, including a protocol to study the role of particular TFs in TGF-β-induced EndMT. Using these techniques, we provide evidence that TGF-β2 stimulates EndMT in murine pancreatic microvascular endothelial cells (MS-1 cells), and that the genetic depletion of Snail using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPRassociated protein 9 (Cas9)-mediated gene editing, abrogates this phenomenon. This approach may serve as a model to interrogate potential modulators of endothelial biology, and can be used to perform genetic or pharmacological screens in order to identify novel regulators of EndMT, with potential application in human disease.