Snail Family Of Transcription Factors Research Articles

Escargot controls somatic stem cell maintenance through the attenuation of the insulin receptor pathway in Drosophila.

SummaryAdult stem cells coordinate intrinsic and extrinsic, local and systemic, cues to maintain the proper balance between self-renewal and differentiation. However, the precise mechanisms stem cells use to integrate these signals remain elusive. Here, we show that Escargot (Esg), a member of the Snail family of transcription factors, regulates the maintenance of somatic cyst stem cells (CySCs) in the Drosophila testis by attenuating the activity of the pro-differentiation insulin receptor (InR) pathway. Esg positively regulates the expression of an antagonist of insulin signaling, ImpL2, while also attenuating the expression of InR. Furthermore, Esg-mediated repression of the InR pathway is required to suppress CySC loss in response to starvation. Given the conservation of Snail-family transcription factors, characterizing the mechanisms by which Esg regulates cell-fate decisions during homeostasis and a decline in nutrient availability is likely to provide insight into the metabolic regulation of stem cell behavior in other tissues and organisms.

Slug regulates the Dll4-Notch-VEGFR2 axis to control endothelial cell activation and angiogenesis

Slug (SNAI2), a member of the well-conserved Snail family of transcription factors, has multiple developmental roles, including in epithelial-to-mesenchymal transition (EMT). Here, we show that Slug is critical for the pathological angiogenesis needed to sustain tumor growth, and transiently necessary for normal developmental angiogenesis. We find that Slug upregulation in angiogenic endothelial cells (EC) regulates an EMT-like suite of target genes, and suppresses Dll4-Notch signaling thereby promoting VEGFR2 expression. Both EC-specific Slug re-expression and reduced Notch signaling, either by γ-secretase inhibition or loss of Dll4, rescue retinal angiogenesis in SlugKO mice. Conversely, inhibition of VEGF signaling prevents excessive angiogenic sprouting of Slug overexpressing EC. Finally, endothelial Slug (but not Snail) is activated by the pro-angiogenic factor SDF1α via its canonical receptor CXCR4 and the MAP kinase ERK5. Altogether, our data support a critical role for Slug in determining the angiogenic response during development and disease.

Cardiac Snail family of transcription factors directs systemic lipid metabolism in Drosophila.

Maintenance of normal lipid homeostasis is crucial to heart function. On the other hand, the heart is now recognized to serve an important role in regulating systemic lipid metabolism; however, the molecular basis remains unclear. In this study, we identify the Drosophila Snail family of transcription factors (herein termed Sna TFs) as new mediators of the heart control of systemic lipid metabolism. Overexpression of Sna TF genes specifically in the heart promotes whole-body leanness whereas their knockdown in the heart promotes obesity. In addition, flies that are heterozygous for a snail deficiency chromosome also exhibit systemic obesity, and that cardiac-specific overexpression of Sna substantially reverses systemic obesity in these flies. We further show that genetically manipulating Sna TF levels in the fat body and intestine do not affect systemic lipid levels. Mechanistically, we find that flies bearing the overexpression or inhibition of Sna TFs in the postnatal heart only exhibit systemic lipid metabolic defects but not heart abnormalities. Cardiac-specific alterations of Sna TF levels also do not perturb cardiac morphology, viability, lipid metabolism or fly food intake. On the other hand, cardiac-specific manipulations of Sna TF levels alter lipogenesis and lipolysis gene expression, mitochondrial biogenesis and respiration, and lipid storage droplet 1 and 2 (Lsd-1 and Lsd-2) levels in the fat body. Together, our results reveal a novel and specific role of Sna TFs in the heart on systemic lipid homeostasis maintenance that is independent of cardiac development and function and involves the governance of triglyceride synthesis and breakdown, energy utilization, and lipid droplet dynamics in the fat body.

Abstract 1882: Molecular context dictates the effects of eribulin on key EMT regulators: Snail and Slug

Abstract Microtubule targeting agents (MTAs) are a mainstay in the treatment of breast cancer and a growing body of evidence demonstrates that they have non-mitotic effects that contribute to their anticancer actions. Even after decades of clinical use, there is much to be learned about the mechanisms of action these drugs, and differences among them, for optimal utility. MTAs rapidly alter microtubule dynamics, often within minutes, leading to significant changes in oncogenic cellular signaling. We evaluated the early effects of eribulin on key oncogenic signaling pathways following a 2 h incubation using clinically relevant concentrations and compared the effects to those initiated by other MTAs. These studies led to the identification of novel mechanisms by which MTAs disrupt oncogenic signaling and contribute to the reversal of epithelial to mesenchymal transition (EMT), including unanticipated differences among drugs. The TGF-β-mediated expression of the Snail transcription factor is a key driver pathway of EMT in breast cancer. The effects of eribulin and other MTAs on TGF-β-induced, Smad-dependent expression of Snail were evaluated. Our results show that eribulin and vinorelbine inhibit the ability of TGF-β to promote the transcriptional induction of Snail by impeding the nuclear transport of Smad2/3 proteins in 4 triple-negative breast cancer cell lines. The effects of microtubule destabilizers contrasted with those of paclitaxel, which had no effect on the expression of Snail. This study begins to explain how microtubule disruption might contribute to the eribulin-mediated EMT reversal. Slug is another member of the Snail family of transcription factors that plays a central role in breast cancer EMT. Although Snail and Slug are often grouped together due to functional similarities, it is now understood that they regulate non-overlapping sets of genes. In contrast to our findings with Snail, eribulin and vinorelbine, but not paclitaxel or ixabepilone, induced Slug over-expression in a subset of breast cancer cell lines. We have identified molecular contexts where eribulin and vinorelbine induced Slug expression, resulting in the identification of a potential biomarker for response to microtubule destabilization. This work highlights the multifaceted nature of MTA-mediated effects on EMT-associated signaling pathways in breast cancer cells. These studies are supported by Eisai Inc. Citation Format: Roma Kaul, April L. Risinger, Susan L. Mooberry. Molecular context dictates the effects of eribulin on key EMT regulators: Snail and Slug [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1882.

Abstract P5-08-06: Differential effects of eribulin on key transcription factors snail and slug

Abstract Microtubule targeting agents (MTAs) are a mainstay in the treatment of breast cancer and a growing body of evidence demonstrates that they have non-mitotic effects that contribute to their anticancer actions. Even after decades of clinical use, there is much to still be learned about the mechanisms of action these drugs, and differences among them, for optimal utility. MTAs rapidly alter microtubule dynamics, often within minutes, leading to significant changes in oncogenic cellular signaling. We evaluated the early effects of eribulin on key oncogenic signaling pathways following a 2 h incubation using clinically relevant concentrations and compared the effects to those initiated by other MTAs. These studies led to the identification of novel mechanisms by which MTAs disrupt oncogenic signaling and contribute to the reversal of epithelial to mesenchymal transition (EMT), including unanticipated differences among drugs. The TGF-β-mediated expression of the Snail transcription factor is a key driver pathway of EMT in breast cancer. The effects of eribulin and other MTAs on TGF-β-induced, Smad-dependent expression of Snail were evaluated. Our results show that eribulin and vinorelbine, but not paclitaxel or ixabepilone, inhibit the ability of TGF-β to promote the transcriptional induction of Snail by impeding the nuclear transport of Smad2/3 proteins in 4 triple-negative breast cancer cell lines. This study begins to explain how microtubule disruption might contribute to the eribulin-mediated EMT reversal observed in vitro, in vivo, and in patients. Slug is another member of the Snail family of transcription factors that plays a central role in breast cancer EMT. Although Snail and Slug are often grouped together due to functional similarities, it is becoming increasingly clear that Slug has an independent role in regulating stemness and cancer cell survival during partial EMT. In contrast to our findings with Snail, eribulin and vinorelbine, but not paclitaxel or ixabepilone, induced Slug expression independent of TGF-β stimulation in a subset of triple-negative breast cancer cell lines. Studies are ongoing to identify the molecular pathways and consequences of eribulin and vinorelbine-induced Slug induction, which might begin to identify biomarkers of patient response to different MTAs. This work highlights the multifaceted nature of MTA-mediated effects on EMT-associated signaling pathways in breast cancer cells and prompts a reevaluation of their differential efficacy in tumors with distinct molecular profiles. These studies are supported by Eisai Inc. Citation Format: Kaul R, Risinger AL, Mooberry SL. Differential effects of eribulin on key transcription factors snail and slug [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-08-06.

Effect of modulation of epithelial-mesenchymal transition regulators Snail1 and Snail2 on cancer cell radiosensitivity by targeting of the cell cycle, cell apoptosis and cell migration/invasion.

Cancer is one of the leading causes of cancer-associated mortality worldwide. Several strategies of treatment, including radiotherapy, have been developed and used to treat this disease. However, post-treatment metastasis and resistance to treatment are two major causes for the limited effectiveness of radiotherapy in cancer patients. Epithelial-mesenchymal transition (EMT) is regulated by SNAIL family transcription factors, including Snail1 and Snail2 (Slug), and serves important roles in progression and cancer resistance to treatment. Snail1 and Slug also have been shown to be implicated in cancer treatment resistance. For resolving the resistance to treatment problems, combining the modulation of gene expression with radiotherapy is a novel strategy to treat patients with cancer. The present review focuses on the effect of Snail1 and Slug on cancer radiosensitivity by targeting cell apoptosis, the cell cycle and cell migration/invasion.

Bone Marrow-Derived Mesenchymal Stem Cells Promoted Cutaneous Wound Healing by Regulating Keratinocyte Migration via β2-Adrenergic Receptor Signaling.

Mesenchymal stem cells (MSCs) play an important role in cutaneous wound healing; however, the functional mechanisms involved in the healing process are poorly understood. A series of studies indicate that keratinocytes that migrate into the wound bed rely on an epithelial-mesenchymal transition (EMT)-like process to initiate re-epithelialization. We therefore examined whether bone marrow-derived MSCs (BMSCs) could affect biological behavior and induce EMT-like characteristics in the human epidermal keratinocytes (HEKs) and in the immortalized human keratinocyte cell line HaCaT cells, and we investigated the signaling pathways of BMSC-mediated phenotypic changes. By assessing the expression of EMT-related markers including E-cadherin, α-SMA, and Snail family transcription factors by β2-adrenergic receptor (β2-AR) blockage using ICI-118,551, a β2-AR selective antagonist, or β2-AR small interfering RNA (siRNA), we showed an involvement of β2-AR signaling in the induction of EMT-like alterations in human keratinocytes in vitro. β2-AR signaling also affected collective and individual cell migration in human keratinocyte cell lines, which was attenuated by administration of ICI-118,551. Treating the cells with BMSC-conditioned media (BMSC-CM) not only recapitulated the effect of isoproterenol (ISO) on cell migration but also induced the expression of β2-AR and a panel of proteins associated with mesenchymal phenotype in HEKs and HaCaT cells. Similarly, a blockade of the β2-AR by either ICI-118,551 or β2-AR siRNAs reversed both responses of the epidermal keratinocyte cell lines relative to BMSC-CM exposure. These results were further verified in our vivo findings and indicated that the exogenous application of MSCs promoted cutaneous wound healing and endowed the keratinocytes surrounding the wound area with an increased migratory phenotype through activation of β2-AR signaling. Our findings suggest a biochemical mechanism underlying the function of MSCs in wound re-epithelization, which provides a reliable theoretical basis for the wide application of MSCs in the treatment of chronic wounds.

Snail Is a Critical Mediator of Invadosome Formation and Joint Degradation in Arthritis

Progressive cartilage destruction, mediated by invasive fibroblast-like synoviocytes, is a central feature in the pathogenesis of rheumatoid arthritis (RA). Members of the Snail family of transcription factors are required for cell migration and invasion, but their role in joint destruction remains unknown. Herein, we demonstrate that Snail is essential for the formation of extracellular matrix-degrading invadosomal structures by synovial cells from collagen-induced arthritis (CIA) rats and RA patients. Mechanistically, Snail induces extracellular matrix degradation in synovial cells by repressing PTEN, resulting in increased phosphorylation of platelet-derived growth factor receptor and activation of the phosphatidylinositol 3-kinase/AKT pathway. Of significance, Snail is overexpressed in synovial cells and tissues of CIA rats and RA patients, whereas knockdown of Snail in CIA joints prevents cartilage invasion and joint damage. Furthermore, Snail expression is associated with an epithelial-mesenchymal transition gene signature characteristic of transglutaminase 2/transforming growth factor-β activation. Transforming growth factor-β and transglutaminase 2 stimulate Snail-dependent invadosome formation in rat and human synoviocytes. Our results identify the Snail-PTEN platelet-derived growth factor receptor/phosphatidylinositol 3-kinase axis as a novel regulator of the prodestructive invadosome-forming phenotype of synovial cells. New therapies for RA target inflammation, and are only partly effective in preventing joint damage. Blocking Snail and/or its associated gene expression program may provide an additional tool to improve the efficacy of treatments to prevent joint destruction.

Targeted Inhibition of Snail Activity in Breast Cancer Cells by Using a Co(III) -Ebox Conjugate.

The transition from a non-invasive to an invasive phenotype is an essential step in tumor metastasis. The Snail family of transcription factors (TFs) is known to play a significant role in this transition. These TFs are zinc fingers that bind to the CAGGTG Ebox consensus sequence. Co(III) -Ebox is a cobalt(III) complex attached to an Ebox oligonucleotide that confers specificity towards Snail TFs. Co(III) -Ebox has been shown to inhibit Snail-mediated embryonic neural crest development in Xenopus laevis, but its efficacy in inhibiting Snail-induced cancer cell invasiveness has not been explored. Here, we describe the efficacy of Co(III) -Ebox in inhibiting the invasive aspects of heregulin-β1(HRG)-treated breast cancer cells. Co(III) -Ebox was found to inhibit the capacity of Snail to repress target genes after HRG induction. Snail inhibition by Co(III) -Ebox reduced the invasive propensity of cells in 2D and 3D, thereby demonstrating promise in inhibiting metastasis.

Abstract 1425: FBXO11 suppresses epithelial plasticity and proliferation by ubiquitinating the Snail family of transcription factors

Abstract Epithelial-to-mesenchymal transition (EMT) is central to embryonic development and carcinoma progression. The cell adhesion molecule E-cadherin critically maintains epithelial property and restricts epithelial cell proliferation and motility. The Snail family of transcription factors are core inducers of EMT in part through direct repression of E-cadherin transcription. The Snail factors are normally under tight control to safeguard epithelial identity and homeostasis. However, their physiological regulation remains largely elusive. In the present study, we show that the F-box protein FBXO11 binds to Snail in a phosphorylation-independent manner and targets it for ubiquitin-mediated proteasomal degradation. FBXO11 promotes the degradation of other Snail family members Slug and SCRT1 as well. Overexpression of FBXO11 in mesenchymal cells reduces Snail protein abundance and activates E-cadherin transcription. Conversely, depletion of endogenous FBXO11 in epithelial cancer cells causes Snail protein accumulation, EMT, and tumor invasion. Human cancer-derived FBXO11 missense mutants are impaired to degrade Snail. In human cancer, FBXO11 expression correlates with E-cadherin, and decreased expression of FBXO11 is robustly associated with adverse clinical outcomes. Inactivation of FBXO11 in mice results in neonatal lethality, increased Snail and Slug protein levels, decreased E-cadherin expression, and epidermal hyperplasia, which phenotypically resemble epidermis-specific transgenic overexpression of Snail or deletion of E-cadherin. These findings establish FBXO11 as a physiological ubiquitin ligase of Snails that is indispensable for suppressing epithelial hyperproliferation and plasticity during embryonic development and carcinoma progression. Note: This abstract was not presented at the meeting. Citation Format: Jianrong Lu, Yue Jin, Anitha K. Shenoy, Hao Chen, Huacheng Luo,Lizi Wu, Kamal A. Mohammed. FBXO11 suppresses epithelial plasticity and proliferation by ubiquitinating the Snail family of transcription factors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1425. doi:10.1158/1538-7445.AM2015-1425

575. Complete Removal of E-Cadherin from 4T-1 Murine Breast Cancer Cells Has No Effect on Metastasis

Currently accepted models for metastatic progression involve several steps. The first of these, local invasion of the primary tumor, requires detachment from the tumor mass and increased mobility. Epithelial to Mesenchymal Transition (EMT) is believed to play an important role in this increased mobility and consequent local invasion. Following local invasion, the tumor cells must intravasate and survive in the bloodstream prior to extravasation. Once the metastatic tumor cells have completed these steps, it is believed that the invading cells must undergo Mesenchymal to Epithelial Transition (MET), returning to their epithelial phenotype, in order to effectively establish metastasis. Importantly, E-cadherin expression positively correlates with the epithelial status of the cell. As part of the EMT mechanism, the change from E-cadherin to N-cadherin is driven by the ZEB and SNAIL family transcription factors. Loss of E-cadherin contributes to the increased cell motility associated with EMT by reducing the number of cell-cell contacts, allowing the cell to emerge from its local tissue environment. On the contrary, during MET, the re-expression of E-cadherin reestablishes cell connections.In order to test the requirement of MET during the final stages of metastasis, we used Cas9 to knock-out E-cadherin in the murine breast cancer cell line 4T1. As a result, the cells converted to a mesenchymal-like morphology. We hypothesized that the permanent disruption of the E-cadherin gene would prevent the cancer cells from undergoing MET thereby suppressing their ability to form metastasis. Surprisingly, upon implantation of the modified 4T1 cells, there was no difference in the appearance of metastasis as compared to the control. Both parental and E-cadherin knock-out 4T1 cells were able to form metastasis in the lung. These results demonstrate that E-cadherin is not necessary for the metastatic process in 4T1 cells. Further, the study suggests that MET may not be crucial during the final stages of metastasis. More detailed understanding of when MET is required, if at all, during metastatic progression will help to shape treatment strategies and continued research of metastatic disease.

FBXO11 promotes ubiquitination of the Snail family of transcription factors in cancer progression and epidermal development

The Snail family of transcription factors are core inducers of epithelial-to-mesenchymal transition (EMT). Here we show that the F-box protein FBXO11 recognizes and promotes ubiquitin-mediated degradation of multiple Snail family members including Scratch. The association between FBXO11 and Snai1 in vitro is independent of Snai1 phosphorylation. Overexpression of FBXO11 in mesenchymal cells reduces Snail protein abundance and cellular invasiveness. Conversely, depletion of endogenous FBXO11 in epithelial cancer cells causes Snail protein accumulation, EMT, and tumor invasion, as well as loss of estrogen receptor expression in breast cancer cells. Expression of FBXO11 is downregulated by EMT-inducing signals TGFβ and nickel. In human cancer, high FBXO11 levels correlate with expression of epithelial markers and favorable prognosis. The results suggest that FBXO11 sustains the epithelial state and inhibits cancer progression. Inactivation of FBXO11 in mice leads to neonatal lethality, epidermal thickening, and increased Snail protein levels in epidermis, validating that FBXO11 is a physiological ubiquitin ligase of Snail. Moreover, in C. elegans, the FBXO11 mutant phenotype is attributed to the Snail factors as it is suppressed by inactivation/depletion of Snail homologs. Collectively, these findings suggest that the FBXO11-Snail regulatory axis is evolutionarily conserved and critically governs carcinoma progression and mammalian epidermal development.

FBXL5 Inhibits Metastasis of Gastric Cancer Through Suppressing Snail1

Background/Aims: The Snail family of transcription factors controls epithelial to mesenchymal transition (EMT), a process associated with tumorigenesis originated from epithelial cells. Snail1 is a member from Snail family and upregulation of Snail1 has been detected in gastric cancer (GC), suggesting a potential role of Snail1 in GC metastasis. We have recently reported that FBXL5 regulates cortactin by inducing its ubiquitylation and subsequent proteasomal degradation, resulting in inhibition of metastasis of GC. However, a role of FBXL4 in regulation of other EMT-associated proteins is not unknown. Methods: The levels of FBXL5 and Snail1 as well as their relationship were determined in GC specimen. Co-immunoprecipitation (IP) was performed to detect the interaction between Snail1 and FBXL5 in GC cells. The effects on Snail1 by FBXL5 were examined by overexpression of depletion of FBXL5 in GC cells. The invasiveness of the FBXL5-modified GC cells was examined in both scratch wound healing assay and transwell matrix penetration assay. Results: FBXL5 also physiologically interacted with Snail1. FBXL5 inhibited Snail1 to suppress GC cell invasiveness. Conclusion: FBXL5 negatively regulates several EMT-enhancing factors. FBXL5 is an attractive novel target for inhibiting invasion and metastasis of GC cells.

Escargot maintains stemness and suppresses differentiation in Drosophila intestinal stem cells.

Snail family transcription factors are expressed in various stem cell types, but their function in maintaining stem cell identity is unclear. In the adult Drosophila midgut, the Snail homolog Esg is expressed in intestinal stem cells (ISCs) and their transient undifferentiated daughters, termed enteroblasts (EB). We demonstrate here that loss of esg in these progenitor cells causes their rapid differentiation into enterocytes (EC) or entero-endocrine cells (EE). Conversely, forced expression of Esg in intestinal progenitor cells blocks differentiation, locking ISCs in a stem cell state. Cell type-specific transcriptome analysis combined with Dam-ID binding studies identified Esg as a major repressor of differentiation genes in stem and progenitor cells. One critical target of Esg was found to be the POU-domain transcription factor, Pdm1, which is normally expressed specifically in differentiated ECs. Ectopic expression of Pdm1 in progenitor cells was sufficient to drive their differentiation into ECs. Hence, Esg is a critical stem cell determinant that maintains stemness by repressing differentiation-promoting factors, such as Pdm1.

Snail cooperates with Kras G12D in vivo to increase stem cell factor and enhance mast cell infiltration.

Pancreatic ductal adenocarcinoma (PDAC) is associated with a pronounced fibro-inflammatory stromal reaction that contributes to tumor progression. A critical step in invasion and metastasis is the epithelial-to-mesenchymal transition (EMT), which can be regulated by the Snail family of transcription factors. Overexpression of Snail (Snai1) and mutant Kras(G12D) in the pancreas of transgenic mice, using an elastase (EL) promoter, resulted in fibrosis. To identify how Snail modulates inflammation in the pancreas, we examined the effect of expressing Snail in EL-Kras(G12D) mice (Kras(G12D)/Snail) on mast cell infiltration, which has been linked to PDAC progression. Using this animal model system, it was demonstrated that there are increased numbers of mast cells in the pancreas of Kras(G12D)/Snail mice compared with control Kras(G12D) mice. In addition, it was revealed that human primary PDAC tumors with increased Snail expression are associated with increased mast cell infiltration, and that Snail expression in these clinical specimens positively correlated with the expression of stem cell factor (SCF/KITLG), a cytokine known to regulate mast cell migration. Concomitantly, SCF levels are increased in the Kras(G12D)/Snail mice than in control mice. Moreover, overexpression of Snail in PDAC cells increased SCF levels, and the media conditioned by Snail-expressing PDAC cells promoted mast cell migration. Finally, inhibition of SCF using a neutralizing antibody significantly attenuated Snail-induced migration of mast cells. Together, these results elucidate how the EMT regulator Snail contributes to inflammation associated with PDAC tumors.

Snail Cooperates with KrasG12D to Promote Pancreatic Fibrosis

Patients with pancreatic cancer, which is characterized by an extensive collagen-rich fibrotic reaction, often present with metastases. A critical step in cancer metastasis is epithelial-to-mesenchymal transition (EMT), which can be orchestrated by the Snail family of transcription factors. To understand the role of Snail (SNAI1) in pancreatic cancer development, we generated transgenic mice expressing Snail in the pancreas. Because chronic pancreatitis can contribute to pancreatic cancer development, Snail-expressing mice were treated with cerulein to induce pancreatitis. Although significant tissue injury was observed, a minimal difference in pancreatitis was seen between control and Snail-expressing mice. However, because Kras mutation is necessary for tumor development in mouse models of pancreatic cancer, we generated mice expressing both mutant Kras(G12D) and Snail (Kras(+)/Snail(+)). Compared with control mice (Kras(+)/Snai(-)), Kras(+)/Snail(+) mice developed acinar ectasia and more advanced acinar-to-ductal metaplasia. The Kras(+)/Snail(+) mice exhibited increased fibrosis, increased phosphorylated Smad2, increased TGF-β2 expression, and activation of pancreatic stellate cells. To further understand the mechanism by which Snail promoted fibrosis, we established an in vitro model to examine the effect of Snail expression in pancreatic cancer cells on stellate cell collagen production. Snail expression in pancreatic cancer cells increased TGF-β2 levels, and conditioned media from Snail-expressing pancreatic cancer cells increased collagen production by stellate cells. Additionally, inhibiting TGF-β signaling in stellate cells attenuated the conditioned media-induced collagen production by stellate cells. Together, these results suggest that Snail contributes to pancreatic tumor development by promoting fibrotic reaction through increased TGF-β signaling. Expression of the EMT regulator Snail in the context of mutant Kras provides new insight into pancreatic cancer progression.

Notch1 destabilizes the adherens junction complex through upregulation of the Snail family of E-cadherin repressors in non-small cell lung cancer

One of the critical steps driving cancer cell migration and metastasis is the repression of cell adhesion molecules resulting in loss of cell‑to-cell adhesion. Although interactions between Notch1 and components of the adherens junction complex have been suggested, little is known concerning the consequence of their interactions. In this study, we investigated the interaction between the Notch1 and the E‑cadherin/β‑catenin complex, its effect on the expression of adherens junction complex components and its influence on non-small cell lung cancer (NSCLC) cell proliferation. With progression of lung neoplastic lesions in LSL K-ras G12D mice, the expression of E‑cadherin was inhibited whereas that of Notch1 was increased with frequent nuclear localization, suggesting an inverse relationship between E‑cadherin and Notch1 expression with tumor progression. Transduction of the human Notch1 intracellular domain (N1ICD) into NSCLC cells inhibited expression of E‑cadherin and β‑catenin and induced changes in the localization of adherens junction molecules. The loss of E‑cadherin was mediated through upregulation of the Snail family of transcription factors, Snail and Slug. Experiments in which siRNA against E-cadherin was introduced into NSCLC cells revealed that N1ICD decreased the expression of β‑catenin in an E‑cadherin‑independent manner, leading to inhibition of markers of Wnt/β‑catenin signaling activation. Despite inhibition of Wnt/β‑catenin signaling in the N1ICD‑transduced cells, cells transduced with N1ICD showed no difference in cell cycle progression when compared with that of the control vector-transduced cells. In conclusion, Notch1 inhibited the expression of E‑cadherin through upregulation of the Snail family of transcriptional factors, resulting in inhibition of expression of β‑catenin and destabilization of adherens junctions.

Retraction Note: Slug enhances invasion ability of pancreatic cancer cells through upregulation of matrix metalloproteinase-9 and actin cytoskeleton remodeling

The authors of this article have requested its retraction from Laboratory Investigation because of their inability to reproduce key experiments. The authors of this article have requested its retraction from Laboratory Investigation because of their inability to reproduce key experiments. Retraction to:Laboratory Investigation (2011) 91, 426–438; doi:10.1038/labinvest.2010.201; published online 31 January 2011 The authors of this article have requested its retraction from Laboratory Investigation because of their inability to reproduce key experiments: Zhang K, Chen D, Jiao X, Zhang S, Liu X, Cao J, Wu L, Wang D. Slug enhances invasion ability of pancreatic cancer cells through upregulation of matrix metalloproteinase-9 and actin cytoskeleton remodeling. Lab Invest 2011;91:426–438. This paper reports that Slug transfection does not affect E-cadherin expression. However, upon repeating the experiment, we found Slug transfection significantly reduces the E-cadherin expression. Additionally, MMP-2 was upregulated in new experiments. The paper also reveals that intracellular F-actin and MMP-9 levels are increased and relocated to the tip of the extending pseudopodia from the perinuclear pool in Slug-transfected PANC-1 cells. However, upon repeating the experiment, it appeared that only F-actin, not MMP-9, was relocated to the tip of the extending pseudopodia. Therefore, the cellular localization of the MMP-2 cells needs further investigation. Furthermore, there were several minor errors in the paper:1.The primer sequence for E-cadherin should be 5′-GGAAGTCAGTTCAGACTCCAGCC-3′ and 5′-AGGCCTTTTGACTGTAATCACACC-3′; not 5′-TTCAGTTCCGAGGTCTACAC-30; antisense: 30-GTCTCTGTGGTGATGCCGGT-5, as was reported.2.The wrong reference was cited for the BB94 treatment. The correct concentration was 0.25 μmol/l, not 0.1 umol/l, as was written.3.Female C57BL/6 mice were at 4–6 weeks, not 6–8 weeks of age.4.All statistical analyses were performed using SPSS 7.0 software, not SPSS 13. The authors regret the impact that these inconsistencies and errors may have had on other researchers. Slug enhances invasion ability of pancreatic cancer cells through upregulation of matrix metalloproteinase-9 and actin cytoskeleton remodelingLaboratory InvestigationVol. 91Issue 3PreviewSlug, a member of the Snail family of transcription factors, has a crucial role in the regulation of epithelial-mesenchymal transition (EMT) by suppressing several epithelial markers and adhesion molecules, including E-cadherin. A recent study demonstrated that no relationship exists between Slug and E-cadherin in pancreatic cancer. Another study showed that in malignant mesothelioma effusions Slug was associated with matrix metalloproteinase (MMP) expression, but that there was no association with E-cadherin. Full-Text PDF Open Access

Actin isoforms and reorganization of adhesion junctions in epithelial-to-mesenchymal transition of cervical carcinoma cells

Malignant cell transformation requires changes in the ability of cells to migrate. The disruption of actin cytoskeleton and intercellular adhesions is an important component of the acquisition of invasive properties in epithelial malignancies. The invasive ability of carcinoma cells is associated with reduced expression of adhesion junction molecules and increased expression of mesenchymal markers, frequently referred to as epithelial-to-mesenchymal transition (EMT). Standard features of the EMT program in cancer cells include fibroblastic phenotype, downregulation of the epithelial marker E-cadherin, induction of Snail-family transcription factors, as well as expression of mesenchymal proteins. We compared the epithelial and mesenchymal marker profiles of nonmalignant HaCaT keratinocytes to the corresponding profiles of cervical carcinoma cell lines C-33A, SiHa, and CaSki. The characteristics of the EMT appeared to be more developed in SiHa and CaSki cervical cancer cells. Further activation of the EMT program in cancer cells was induced by epidermal growth factor. Decreased epithelial marker E-cadherin in CaSki cells was accompanied by increased mesenchymal markers N-cadherin and vimentin. Downregulated expression of E-cadherin in SiHa and CaSki cells was associated with increased expression of Snail transcription factor. Our goal was to study actin reorganization in the EMT process in cell cultures and in tissue. We found that β-cytoplasmic actin structures are disorganized in the cervical cancer cells. The expression of β-cytoplasmic actin was downregulated.

The Snail Family Member Worniu Is Continuously Required in Neuroblasts to Prevent Elav-Induced Premature Differentiation

Snail family transcription factors are best known for regulating epithelial-mesenchymal transition (EMT). The Drosophila Snail family member Worniu is specifically transcribed in neural progenitors (neuroblasts) throughout their lifespan, and worniu mutants show defects in neuroblast delamination (a form of EMT). However, the role of Worniu in neuroblasts beyond their formation is unknown. We performed RNA-seq on worniu mutant larval neuroblasts and observed reduced cell-cycle transcripts and increased neural differentiation transcripts. Consistent with these genomic data, worniu mutant neuroblasts showed a striking delay in prophase/metaphase transition by live imaging and increased levels of the conserved neuronal differentiation splicing factor Elav. Reducing Elav levels significantly suppressed the worniu mutant phenotype. We conclude that Worniu is continuously required in neuroblasts to maintain self-renewal by promoting cell-cycle progression and inhibiting premature differentiation.