Metastasis can involve repeated cycles of epithelial-to-mesenchymal transition (EMT) and its reverse mesenchymal-to-epithelial transition. Cells can also undergo partial transitions to attain a hybrid epithelial/mesenchymal (E/M) phenotype that allows the migration of adhering cells to form a cluster of circulating tumour cells. These clusters can be apoptosis-resistant and possess an increased metastatic propensity as compared to the cells that undergo a complete EMT (mesenchymal cells). Hence, identifying the key players that can regulate the formation and maintenance of such clusters may inform anti-metastasis strategies. Here, we devise a mechanism-based theoretical model that links cell–cell communication via Notch-Delta-Jagged signalling with the regulation of EMT. We demonstrate that while both Notch-Delta and Notch-Jagged signalling can induce EMT in a population of cells, only Jagged-dominated Notch signalling, but not Delta-dominated signalling, can lead to the formation of clusters containing hybrid E/M cells. Our results offer possible mechanistic insights into the role of Jagged in tumour progression, and offer a framework to investigate the effects of other microenvironmental signals during metastasis.

Cancer is a complex disease and progresses within a dynamically evolving extracellular matrix that controls virtually every aspect of the tumour and tumour-associated cells. Interactions with the extracellular microenvironment are predominately mediated by a family of cell-surface transmembrane receptors called integrins. Integrin–matrix engagement leads to the formation of adhesion plaques, consisting of signalling and adaptor proteins, at the plasma membrane that link the extracellular matrix to the regulation of the cell cytoskeleton. In this review, we will highlight exciting data that identify new roles for integrins and integrin-dependent signalling in cancer away from the plasma membrane, discuss the implications of integrin-dependent regulation of Met and ErbB2 growth factor receptors and highlight the role of specific integrins in different stages of cancer development including maintenance of cancer stem cells.

The promising clinical effects of mesenchymal stromal/ stem cells (MSCs) rely especially on paracrine and nonimmunogenic mechanisms. Delivery routes are essential for the efficacy of cell therapy and systemic delivery by infusion is the obvious goal for many forms of MSC therapy. Lung adhesion of MSCs might, however, be a major obstacle yet to overcome. Current knowledge does not allow us to make sound conclusions whether MSC lung entrapment is harmful or beneficial, and thus we wanted to explore MSC lung adhesion in greater detail. We found a striking difference in the lung clearance rate of systemically infused MSCs derived from two different clinical sources, namely bone marrow (BM-MSCs) and umbilical cord blood (UCB-MSCs). The BM-MSCs and UCB-MSCs used in this study differed in cell size, but our results also indicated other mechanisms behind the lung adherence. A detailed analysis of the cell surface profiles revealed differences in the expression of relevant adhesion molecules. The UCB-MSCs had higher expression levels of a4 integrin (CD49d, VLA-4), a6 integrin (CD49f, VLA-6), and the hepatocyte growth factor receptor (c-Met) and a higher general fucosylation level. Strikingly, the level of CD49d and CD49f expression could be functionally linked with the lung clearance rate. Additionally, we saw a possible link between MSC lung adherence and higher fibronectin expression and we show that the expression of fibronectin increases with MSC culture confluence. Future studies should aim at developing methods of transiently modifying the cell surface structures in order to improve the delivery of therapeutic cells.

Human mesenchymal stem cells (hMSCs) are multipotent cells that have aroused great expectations in regenerative medicine. They are assumed to originate from hypoxic stem cell niches, especially in the bone marrow. This suggests that O 2 is of importance in their regulation. In order to characterize regulation of the oxygen sensing pathway in these cells, we studied hMSCs isolated from three origins, adult and pediatric bone marrow and umbilical cord blood (UCB). Surprisingly, pediatric bone marrow and UCB MSCs showed normoxic stabilization of hypoxiainducible factor-1a (HIF-1a) that is normally degraded completely by HIF prolyl 4-hydroxylases in the presence of oxygen. This was due to a high expression level of HIF1a mRNA rather than inappropriate post-translational degradation of HIF-1a protein. HIF-1a mRNA was also induced in normoxic adult bone marrow MSCs, but 40% less than in the pediatric cells, and this was apparently not enough to stabilize the protein. The high normoxic HIF expression in all the hMSCs studied was accompanied by increased expression of a large number of glycolytic HIF target genes and increased glycolysis. Osteogenic differentiation of bone marrow-derived hMSCs reduced HIF-1a mRNA and protein expression and the expression of glycolytic mRNAs, resulting in decreased glycolysis and induction of oxidative metabolism. Induced mitochondrial biogenesis, changes in mitochondrial morphology and size indicative of increased oxidative phosphorylation, and induction of extracellular matrix synthesis were observed following osteogenic differentiation. Altogether, these data suggest that HIF-1a is a general regulator controlling the metabolic fate and multipotency of the hMSCs. STEM CELLS

The human epidermal growth factor receptor 2 (HER2) is an oncogene targeted by several kinase inhibitors and therapeutic antibodies. While the endosomal trafficking of many other receptor tyrosine kinases is known to regulate their oncogenic signalling, the prevailing view on HER2 is that this receptor is predominantly retained on the cell surface. Here, we find that sortilin-related receptor 1 (SORLA; SORL1 ) co-precipitates with HER2 in cancer cells and regulates HER2 subcellular distribution by promoting recycling of the endosomal receptor back to the plasma membrane. SORLA protein levels in cancer cell lines and bladder cancers correlates with HER2 levels. Depletion of SORLA triggers HER2 targeting to late endosomal/lysosomal compartments and impairs HER2-driven signalling and in vivo tumour growth. SORLA silencing also disrupts normal lysosome function and sensitizes anti-HER2 therapy sensitive and resistant cancer cells to lysosome-targeting cationic amphiphilic drugs. These findings reveal potentially important SORLA-dependent endosomal trafficking-linked vulnerabilities in HER2-driven cancers.

The hESC lines derived in the same laboratory varied considerably in their potential to differentiate into beating cardiomyocytes. None of the expression markers could clearly predict cardiac differentiation potential, although the expression of early cardiomyogenic genes was upregulated in the best cardiac line. The proper cardiomyocyte characteristics and pharmacological response indicate that these cells could be used as a model for human cardiomyocytes in pharmacological and toxicological analyses when investigating new heart medications or cardiac side-effects.

Background Triple-negative breast cancers (TNBCs), which lack receptors for estrogen, progesterone, and amplification of epidermal growth factor receptor 2, are highly aggressive. Consequently, patients diagnosed with TNBCs have reduced overall and disease-free survival rates compared to patients with other subtypes of breast cancer. TNBCs are characterized by the presence of cancer cells with mesenchymal properties, indicating that the epithelial to mesenchymal transition (EMT) plays a major role in the progression of this disease. The EMT program has also been implicated in chemoresistance, tumor recurrence, and induction of cancer stem cell (CSC) properties. Currently, there are no targeted therapies for TNBC, and hence, it is critical to identify the novel targets to treat TNBC. Methods A library of compounds was screened for their ability to inhibit EMT in cells with mesenchymal phenotype as assessed using the previously described Z-cad reporters. Of the several drugs tested, GSK3β inhibitors were identified as EMT inhibitors. The effects of GSK3β inhibitors on the properties of TNBC cells with a mesenchymal phenotype were assessed using qRT-PCR, flow cytometry, western blot, mammosphere, and migration and cell viability assays. Publicly available datasets also were analyzed to examine if the expression of GSK3β correlates with the overall survival of breast cancer patients. Results We identified a GSK3β inhibitor, BIO, in a drug screen as one of the most potent inhibitors of EMT. BIO and two other GSK3β inhibitors, TWS119 and LiCl, also decreased the expression of mesenchymal markers in several different cell lines with a mesenchymal phenotype. Further, inhibition of GSK3β reduced EMT-related migratory properties of cells with mesenchymal properties. To determine if GSK3β inhibitors target mesenchymal-like cells by affecting the CSC population, we employed mammosphere assays and profiled the stem cell-related cell surface marker CD44+/24− in cells after exposure to GSK3β inhibitors. We found that GSK3β inhibitors indeed decreased the CSC properties of cell types with mesenchymal properties. We treated cells with epithelial and mesenchymal properties with GSK3β inhibitors and found that GSK3β inhibitors selectively kill cells with mesenchymal attributes while sparing cells with epithelial properties. We analyzed patient data to identify genes predictive of poor clinical outcome that could serve as novel therapeutic targets for TNBC. The Wnt signaling pathway is critical to EMT, but among the various factors known to be involved in Wnt signaling, only the higher expression of GSK3β correlated with poorer overall patient survival. Conclusions Taken together, our data demonstrate that GSK3β is a potential target for TNBCs and suggest that GSK3β inhibitors could serve as selective inhibitors of EMT and CSC properties for the treatment of a subset of aggressive TNBC. GSK3β inhibitors should be tested for use i...

Expression of the transcription factor FOXC2 is induced and necessary for successful epithelial-mesenchymal transition, a developmental program that when activated in cancer endows cells with metastatic potential and the properties of stem cells. As such, identifying agents that inhibit the growth of FOXC2-transformed cells represents an attractive approach to inhibit chemotherapy resistance and metastatic dissemination. From a high throughput synthetic lethal screen, we identified a small molecule, FiVe1, which selectively and irreversibly inhibits the growth of mesenchymally transformed breast cancer cells and soft tissue sarcomas of diverse histological subtypes. FiVe1 targets the intermediate filament and mesenchymal marker vimentin (VIM) in a mode which promotes VIM disorganization and phosphorylation during metaphase, ultimately leading to mitotic catastrophe, multinucleation, and the loss of stemness. These findings illustrate a previously undescribed mechanism for interrupting faithful mitotic progression and may ultimately inform the design of therapies for a broad range of mesenchymal cancers.vimentin | epithelial-to-mesenchymal transition | cancer stem cell | mitosis | drug discovery F or many tumor types, resistance to conventional chemotherapy and subsequent tumor relapse have been attributed to the presence of a slower cycling, drug-resistant population of cells termed cancer stem cells (CSCs) or tumor initiating cells. We and others have demonstrated that activation of a latent embryonic program, called the epithelial-mesenchymal transition (EMT), endows epithelial-derived cancer cells with the properties of stem cells as well as migratory and metastatic potential (1). Cells undergoing EMT exhibit the loss of epithelial cell-cell contacts (e.g., E-cadherin), the induction of matrix degrading proteases (e.g., matrix metalloproteinases), and the acquisition of motility-inducing intermediate filaments [e.g., vimentin (VIM)], features which promote metastatic progression by allowing dissemination from the local tumor niche (2). A number of transcription factors (e.g., Snail, Twist, ZEB1) and microenvironment-derived extracellular signaling molecules (e.g., TGF-β1) are capable of inducing the EMT transcriptional program. Among these factors, we have demonstrated that the transcription factor Forkhead Box C2 (FOXC2) is a central regulator of EMT in breast cancer (3, 4). FOXC2 expression is both up-regulated and required for the induction of CSC properties by the classical EMT-inducing factors Twist, Snail, and TGF-β1 (4