Differential role of Snail1 and Snail2 zinc fingers in E-cadherin repression and epithelial to mesenchymal transition

Down-regulation of SIRT3 promotes ovarian carcinoma metastasis

Distant metastasis and local recurrence are still the major causes for failure of treatment in patients with ovarian carcinoma (OC), making it urgent to further elicit the molecular mechanisms of OC metastasis. Sirtuin-3 (SIRT3), a member of the NAD(+)-dependent Class III histone deacetylases, may function as different role depending on the cell-type and tumor-type. However, the function and mechanism of SIRT3 has been not explored in OC metastasis. Here, we found that SIRT3 was significantly down-regulated in the metastatic tissues and highly metastatic cell line of ovarian cancer. In addition, knockdown of SIRT3 enhanced the migration and invasion in vitro and the liver metastasis in vivo of ovarian cancer cell. By contrast, ectopic overexpression of SIRT3 dramatically suppressed cancer cell metastatic capability. Mechanistically, SIRT3 inhibits epithelial-to-mesenchymal transition (EMT) by down-regulating Twist in ovarian cancer cells. Furthermore, an interaction between SIRT3 and Twist was detected. In conclusion, our results demonstrated that SIRT3 plays a crucial suppressive role in the metastasis of ovarian cancer by down-regulating Twist, and that this novel SIRT3/Twist axis may be valuable to develop new strategies for treating OC patients with metastasis.

BMP4 Signaling Is Able to Induce an Epithelial-Mesenchymal Transition-Like Phenotype in Barrett's Esophagus and Esophageal Adenocarcinoma through Induction of SNAIL2

Background

Bone morphogenetic protein 4 (BMP4) signaling is involved in the development of Barrett’s esophagus (BE), a precursor of esophageal adenocarcinoma (EAC). In various cancers, BMP4 has been found to induce epithelial-mesenchymal transition (EMT) but its function in the development of EAC is currently unclear.

Aim

To investigate the expression of BMP4 and several members of the BMP4 pathway in EAC. Additionally, to determine the effect of BMP4 signaling in a human Barrett’s esophagus (BAR-T) and adenocarcinoma (OE33) cell line.

Methods

Expression of BMP4, its downstream target ID2 and members of the BMP4 pathway were determined by Q-RT-PCR, immunohistochemistry and Western blot analysis using biopsy samples from EAC patients. BAR-T and OE33 cells were incubated with BMP4 or the BMP4 antagonist, Noggin, and cell viability and migration assays were performed. In addition, expression of factors associated with EMT (SNAIL2, CDH1, CDH2 and Vimentin) was evaluated by Q-RT-PCR and Western blot analysis.

Results

Compared to squamous epithelium (SQ), BMP4 expression was significantly upregulated in EAC and BE. In addition, the expression of ID2 was significantly upregulated in EAC and BE compared to SQ. Western blot analysis confirmed our results, showing an upregulated expression of BMP4 and ID2 in both BE and EAC. In addition, more phosphorylation of SMAD1/5/8 was observed. BMP4 incubation inhibited cell viability, but induced cell migration in both BAR-T and OE33 cells. Upon BMP4 incubation, SNAIL2 expression was significantly upregulated in BAR-T and OE33 cells while CDH1 expression was significantly downregulated. These results were confirmed by Western blot analysis.

Conclusion

Our results indicate active BMP4 signaling in BE and EAC and suggest that this results in an invasive phenotype by inducing an EMT-like response through upregulation of SNAIL2 and subsequent downregulation of CDH1.

TALENs-directed knockout of the full-length transcription factor Nrf1α that represses malignant behaviour of human hepatocellular carcinoma (HepG2) cells

The full-length Nrf1α is processed into distinct isoforms, which together regulate genes essential for maintaining cellular homeostasis and organ integrity, and liver-specific loss of Nrf1 in mice results in spontaneous hepatoma. Herein, we report that the human constitutive Nrf1α, rather than smaller Nrf1β/γ, expression is attenuated or abolished in the case of low-differentiated high-metastatic hepatocellular carcinomas. Therefore, Nrf1α is of importance in the physio-pathological origin and development, but its specific pathobiological function(s) remains elusive. To address this, TALENs-directed knockout of Nrf1α, but not Nrf1β/γ, is created in the human hepatocellular carcinoma (HepG2) cells. The resulting Nrf1α^−/− cells are elongated, with slender spindle-shapes and enlarged gaps between cells observed under scanning electron microscope. When compared with wild-type controls, the invasive and migratory abilities of Nrf1α^−/− cells are increased significantly, along with the cell-cycle G2-M arrest and S-phase reduction, as accompanied by suppressed apoptosis. Despite a modest increase in the soft-agar colony formation of Nrf1α^−/− cells, its loss-of-function markedly promotes malgrowth of the subcutaneous carcinoma xenograft in nude mice with hepatic metastasis. Together with molecular expression results, we thus suppose requirement of Nrf1α (and major derivates) for gene regulatory mechanisms repressing cancer cell process (e.g. EMT) and malignant behaviour (e.g. migration).

E-cadherin regulators are differentially expressed in the epithelium and stroma of keratocystic odontogenic tumors

BACKGROUND

The epithelial-mesenchymal transition (EMT) is the process where cells lose their epithelial features and acquire properties of typical mesenchymal cells. The dissociation of tumor cells due to changes in cell-cell adhesion is one of the key principles of tumor invasion and EMT. Thus, the knowledge of the molecular features of EMT in keratocyst odontogenic tumor (KOT) can provide useful markers to aid in the diagnosis and prognosis and perhaps contribute to an alternative therapeutic approach as it shows an aggressive clinical behavior and high recurrence rates. This study aimed to evaluate the EMT in KOT by the immunoexpression of E-cadherin, N-cadherin, Snail, and Slug and comparing to radicular cysts and dental follicles.

METHODS

Thirty-two KOTs, 15 radicular cysts, and 08 dental follicles were used for immunohistochemistry, evaluating the extent, intensity, labeling pattern, cellular compartment in the epithelium and stroma, and the presence of inflammation.

RESULTS

E-cadherin was preserved in most cases of keratocystic odontogenic tumor. N-cadherin was increased in the tumor epithelium, a result that was positively correlated with the heterogeneous and nuclear immunoexpression of Slug in the epithelium; Slug also correlated with high Snail immunoexpression. N-cadherin was positively correlated with Slug in the stroma of keratocystic odontogenic tumors.

CONCLUSIONS

The high immunoexpression of Snail and nuclear Slug in keratocystic odontogenic tumors suggests these proteins as transcription factors without necessarily participating in 'cadherin switching'. However, the knowledge of their induction of the epithelial-mesenchymal transition in odontogenic tumors is still limited.

SPRY4 Intronic Transcript 1 Promotes Epithelial-Mesenchymal Transition Through Association with Snail1 in Osteosarcoma

Osteosarcoma is an aggressive tumor and the most common malignancy of the skeleton. Due to pulmonary metastasis, the 5-year survival rate is still unsatisfactory. It has been reported that SPRY4 intronic transcript 1 (SPRY4-IT1) promotes cell growth, invasion, and inhibits apoptosis in several cancers. However, the role of SPRY4-IT1 in osteosarcoma remains unclear. In the present study, we investigated the role of SPRY4-IT1 in osteosarcoma cells. Loss- and gain-of-function assays demonstrated that SPRY4-IT1 promoted cell proliferation, migration, and invasion in osteosarcoma. Moreover, SPRY4-IT1 induced epithelial-mesenchymal transition phenotype in osteosarcoma cells. Subsequent investigations revealed that SPRY4-IT1 promoted migration and invasion through association with Snail1 and regulating its stability. Based on these findings, the SPRY4-IT1/Snail1/E-cadherin pathway may play a crucial role in promoting osteosarcoma metastasis. Thus, SPRY4-IT1 may be a potential target for new therapies of osteosarcoma.

Grhl3 induces human epithelial tumor cell migration and invasion via downregulation of E-cadherin

Grainyhead genes are involved in wound healing and developmental neural tube closure. Metastasis is a multistep process during which cancer cells disseminate from the site of primary tumors and establish secondary tumors in distant organs. The adhesion protein E-cadherin plays an essential role in metastasis. In light of the high degree of similarity between the epithelial-mesenchymal transition (EMT) occurring in wound-healing processes and the EMT occurring during the acquisition of invasiveness in skin or breast cancer, we investigated the role of the Grainyhead genes in cancer invasion. Here, we show that there is an inverse relationship between Grainyhead-like 3 (Grhl3) and E-cadherin expression in some epithelial tumor cell lines. Overexpression of Grhl3 in the E-cadherin-positive epithelial tumor cell line, characterized by less invasiveness, generated a transcriptional blockage of the E-cadherin gene and promoted cell migration and cell invasion. Conversely, Grhl3 depletion inhibited cell migration and cell invasion and was associated with a gain of E-cadherin expression. To further explore the mechanism by which Grhl3 regulated E-cadherin expression, an E-cadherin promoter report analysis was performed and results showed that Grhl3 repressed E-cadherin gene expression by directly or indirectly binding to the E-boxes present in the proximal E-cadherin promoter. Taken together, our findings define a major role for Grhl3 in the induction of migration and invasion by the downregulation of E-cadherin in cancer cells.

BRAF and epithelial-mesenchymal transition in primary cutaneous melanoma: a role for Snail and E-cadherin?

In vitro studies in melanoma indicate that up-regulation of the transcriptional repressor Snail occurs with a concomitant decrease of its target E-cadherin, both hallmarks of epithelial-mesenchymal transition-an association not established in vivo. We sought to elucidate the relationship between BRAF, Snail, E-cadherin, and established histopathologic prognosticators in primary cutaneous melanoma. Archived annotated samples with a diagnosis of primary cutaneous melanoma were retrieved (n = 68 cases; 34 BRAF mutant and 34 BRAF wild type) and immunohistochemically stained for Snail and E-cadherin protein expression. A semiquantitative scoring system was used. Multivariate logistic analysis was used to control confounders of BRAF. Snail expression was significantly associated only with ulceration (42% versus 13%; P = .02). E-cadherin expression was present in 26% of BRAF mutant and 71% of BRAF wild-type cases (P = .0003). Loss of E-cadherin expression was associated with female sex (60% versus 34%; P = .05), BRAF mutation (74% versus 29%; P = .0003), thickness greater than or equal to 1 mm (68% versus 32%; P = .004), mitosis (63% versus 25%; P = .007), and ulceration (75% versus 44%; P = .05). BRAF mutation was associated with male sex (60% versus 30%; P = .02), Breslow thickness (P = .007), thickness greater than or equal to 1 mm (68% versus 29%; P = .002), and ulceration (75% versus 42%; P = .02). Snail expression did not correlate with loss of E-cadherin expression (47% versus 53%; P = .79). After controlling for potential confounding, BRAF mutation was associated with loss of E-cadherin (adjusted odds ratio, 8.332; 95% confidence interval, 2.257-30.757; P = .0015) and Breslow thickness greater than 1 mm (adjusted odds ratio, 7.360; 95% confidence interval, 1.534-35.318; P = .0126). Our findings, indicating that mutant BRAF represses E-cadherin expression, implicating a catalytic role for BRAF in epithelial-mesenchymal transition.

Roads to melanoma: Key pathways and emerging players in melanoma progression and oncogenic signaling

Melanoma has markedly increased worldwide during the past several decades in the Caucasian population and is responsible for 80% of skin cancer deaths. Considering that metastatic melanoma is almost completely resistant to most current therapies and is linked with a poor patient prognosis, it is crucial to further investigate potential molecular targets. Major cell-autonomous drivers in the pathogenesis of this disease include the classical MAPK (i.e., RAS-RAF-MEK-ERK), WNT, and PI3K signaling pathways. These pathways play a major role in defining the progression of melanoma, and some have been the subject of recent pharmacological strategies to treat this belligerent disease. This review describes the latest advances in the understanding of melanoma progression and the major molecular pathways involved. In addition, we discuss the roles of emerging molecular players that are involved in melanoma pathogenesis, including the functional role of the melanoma tumor antigen, p97/MFI2 (melanotransferrin).

The epithelial-mesenchymal transition in cancer: a potential critical topic for translational proteomic research

The epithelial-mesenchymal transition (EMT) is a morphogenetic process that results in a loss of epithelial characteristics and the acquisition of a mesenchymal phenotype. First described in embryogenesis, the EMT has been recently implicated in carcinogenesis and tumor progression. In addition, recent evidence has shown that stem-like cancer cells present the hallmarks of the EMT. Some of the molecular mechanisms related to the interrelationships between cancer pathophysiology and the EMT are well-defined. Nevertheless, the precise molecular mechanism by which epithelial cancer cells acquire the mesenchymal phenotype remains largely unknown. This review focuses on various proteomic strategies with the goal of better understanding the physiological and pathological mechanisms of the EMT process.

Targeting CD146 with a 64Cu-labeled antibody enables in vivo immunoPET imaging of high-grade gliomas

Given the highly heterogeneous character of brain malignancies and the associated implication for its proper diagnosis and treatment, finding biomarkers that better characterize this disease from a molecular standpoint is imperative. In this study, we evaluated CD146 as a potential molecular target for diagnosis and targeted therapy of glioblastoma multiforme (GBM), the most common and lethal brain malignancy. YY146, an anti-CD146 monoclonal antibody, was generated and radiolabeled for noninvasive positron-emission tomography (PET) imaging of orthotopic GBM models. (64)Cu-labeled YY146 preferentially accumulated in the tumors of mice bearing U87MG xenografts, which allowed the acquisition of high-contrast PET images of small tumor nodules (∼ 2 mm). Additionally, we found that tumor uptake correlated with the levels of CD146 expression in a highly specific manner. We also explored the potential therapeutic effects of YY146 on the cancer stem cell (CSC) and epithelial-to-mesenchymal (EMT) properties of U87MG cells, demonstrating that YY146 can mitigate those aggressive phenotypes. Using YY146 as the primary antibody, we performed histological studies of World Health Organization (WHO) grades I through IV primary gliomas. The positive correlation found between CD146-positive staining and high tumor grade (χ(2) = 9.028; P = 0.029) concurred with the GBM data available in The Cancer Genome Atlas (TCGA) and validated the clinical value of YY146. In addition, we demonstrate that YY146 can be used to detect CD146 in various cancer cell lines and human resected tumor tissues of multiple other tumor types (gastric, ovarian, liver, and lung), indicating a broad applicability of YY146 in solid tumors.

Down-regulation of prostate stem cell antigen (PSCA) by Slug promotes metastasis in nasopharyngeal carcinoma

Distant metastasis and local recurrence are still the major causes for failure of treatment in patients with nasopharyngeal carcinoma (NPC), making it urgent to further elicit the molecular mechanisms of NPC metastasis. Using a gene microarray including transcription factors and known markers for cancer stem cells, prostate stem cell antigen (PSCA) was found to be significantly down-regulated in metastatic NPC in lymph node, compared to its primary tumour, and in NPC cell lines with high metastatic ability compared to those with low metastatic ability. NPC patients with low PSCA expression had a consistently poor metastasis-free survival (p = 0.003). Knockdown and overexpression of PSCA respectively enhanced and impaired the migration and invasion in vitro and the lung metastasis in vivo of NPC cells. Mechanistically, the enhancement of NPC metastasis by knocking down PSCA probably involved epithelial-mesenchymal transition (EMT), by up-regulating N-cadherin and ZEB1/2 and by activating RhoA. The down-regulation of PSCA in NPC cells resulted directly from the binding of Slug to the PSCA promoter. PSCA may be a potential diagnostic marker and therapeutic target for patients with NPC.

Searching the Human Genome for Snail and Slug With DNA@Home

DNA@Home is a volunteer computing project that aims to use Gibbs Sampling for the identification and location of DNA control signals on full genome-scale datasets. A fault tolerant and asynchronous implementation of Gibbs sampling using the Berkeley Open Infrastructure for Network Computing (BOINC) was used to identify the location of binding sites of the SNAI1 (Snail) and SNAI2 (Slug) transcription factors across the human genome. Genes regulated by Slug but not Snail, and genes regulated by Snail but not Slug provided two datasets with known motifs. These datasets contained up to 994 DNA sequences which to our knowledge is largest scale use of Gibbs sampling for discovery of binding sites. 1000 parallel sampling walks were used to search for the presence of 1, 2 or 3 possible motifs using small, medium, and full size sets of these sequences. These runs were performed over a period of two months using over 1500 volunteered computing hosts and generated over 2.2 Terabytes of sampling data. High performance computing resources were used for post processing. This paper presents intra and inter walk analyses used to determine walk convergence. The results were validated against current biological knowledge of the Snail and Slug promoter regions and present avenues for further biological study.

SLUG: Critical regulator of epithelial cell identity in breast development and cancer

SLUG, a member of the SNAIL family of transcriptional repressors, is known to play a diverse number of roles in the cell, and its deregulation has been observed in a variety of cancers including breast. Here, we focus on SLUG's role as a master regulator of mammary epithelial cell (MEC) fate and lineage commitment in the normal mammary gland, and discuss how aberrant SLUG expression can influence breast tumor formation, phenotype, and progression. Specifically, we discuss SLUG's involvement in MEC differentiation, stemness, cellular plasticity, and the epithelial to mesenchymal transition (EMT), and highlight the complex connection between these programs during development and disease progression. Undoubtedly, delineating how molecular factors influence lineage identity and cell-state dynamics in the normal mammary gland will contribute to our understanding of breast tumor heterogeneity.

Endogenous Nodal promotes melanoma undergoing epithelial-mesenchymal transition via Snail and Slug in vitro and in vivo

Nodal, an important embryonic morphogen, has been reported to modulate tumorigenesis. Epithelial-mesenchymal transition (EMT) plays an important role in cancer metastasis. We have previously reported that recombinant Nodal treatment can promote melanoma undergoing EMT, but the effects of endogenous Nodal on EMT are still unknown. Here we generated both Nodal-overexpression and -knockdown stable cell lines to investigate the in vitro and in vivo characteristics of Nodal-induced EMT in murine melanoma cells. Nodal-overexpression cells displayed increased migration ability, accompanied by typical phenotype changes of EMT. In contrast, Nodal-knockdown stable cells repressed the EMT phenotype as well as reduced cell motility. Results of animal experiments confirmed that overexpression of Nodal can promote the metastasis of melanoma tumor in vivo. Mechanistically, we found that Nodal-induced expression of Snail and Slug involves its activation of ALK/Smads and PI3k/AKT pathways, which is an important process in the Nodal-induced EMT. However, we also found that the EMT phenotype was not completely inhibited by blocking the paracrine activity of Nodal in Nodal overexpression cell line suggesting the presence of additional mechanism(s) in the Nodal-induced EMT. This study provides a better understanding of Nodal function in melanoma, and suggests targeting Nodal as a potential strategy for melanoma therapey.

EBV-miR-BART7-3p promotes the EMT and metastasis of nasopharyngeal carcinoma cells by suppressing the tumor suppressor PTEN

The epithelial-mesenchymal transition (EMT) is crucial to cancer progression and metastasis. Although multiple cellular miRNAs have been identified to regulate the EMT and metastasis in cancers, the role of viral miRNAs in cancer progression remains largely unknown. Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy typically characterized by its early metastasis. In the present study, we have discovered the involvement of a viral miRNA, EBV-miR-BART7-3p, in the EMT and metastasis of NPC cells. Initially, we observed that EBV-miR-BART7-3p was highly expressed in NPC and positively correlated with lymph node metastasis and clinical stage of NPC. Subsequently, we demonstrated that EBV-miR-BART7-3p enhanced cell migration/invasion in vitro, cancer metastasis in vivo, and particularly the EMT characterized by loss of epithelial markers and gain of mesenchymal features in NPC cells. Furthermore, mechanistic studies disclosed that EBV-miR-BART7-3p targeted a major human tumor suppressor PTEN, modulating PI3K/Akt/GSK-3β signaling and eventually leading to the high expression and nuclear accumulation of Snail and β-catenin, which favor EMT. Knockdown of PTEN could phenocopy the effect of EBV-miR-BART7-3p, whereas re-expression of PTEN resulted in a phenotypic reversion. Moreover, these findings were supported by an observation of an EBV-positive cell model in which silencing of endogenous EBV-miR-BART7-3p partially attenuated cell migration/invasion and altered EMT protein expression pattern via reverting PI3K/Akt, Snail and β-catenin expression. Thus, this study suggests a novel mechanism by which EBV-miR-BART7-3p modulates the EMT and metastasis of NPC cells, and a clinical implication of EBV-miR-BART7-3p as a potential biomarker or therapeutic target.

Notch signaling and EMT in non-small cell lung cancer: biological significance and therapeutic application

Through epithelial-mesenchymal transition (EMT), cancer cells acquire enhanced ability of migration and invasion, stem cell like characteristics and therapeutic resistance. Notch signaling regulates cell-cell connection, cell polarity and motility during organ development. Recent studies demonstrate that Notch signaling plays an important role in lung cancer initiation and cross-talks with several transcriptional factors to enhance EMT, contributing to the progression of non-small cell lung cancer (NSCLC). Correspondingly, blocking of Notch signaling inhibits NSCLC migration and tumor growth by reversing EMT. Clinical trials have showed promising effect in some cancer patients received treatment with Notch1 inhibitor. This review attempts to provide an overview of the Notch signal in NSCLC: its biological significance and therapeutic application.

Myocardial ischemic preconditioning upregulated protein 1(Mipu1):zinc finger protein 667 - a multifunctional KRAB/C2H2 zinc finger protein

Myocardial ischemic preconditioning upregulated protein 1 (Mipu1) is a newly discovered upregulated gene produced in rats during the myocardial ischemic preconditioning process. Mipu1 cDNA contains a 1824-base pair open reading frame and encodes a 608 amino acid protein with an N-terminal Krüppel-associated box (KRAB) domain and classical zinc finger C2H2 motifs in the C-terminus. Mipu1 protein is located in the cell nucleus. Recent studies found that Mipu1 has a protective effect on the ischemia-reperfusion injury of heart, brain, and other organs. As a nuclear factor, Mipu1 may perform its protective function through directly transcribing and repressing the expression of proapoptotic genes to repress cell apoptosis. In addition, Mipu1 also plays an important role in regulating the gene expression of downstream inflammatory mediators by inhibiting the activation of activator protein-1 and serum response element.

Bioinformatic approaches to augment study of epithelial-to-mesenchymal transition in lung cancer

Bioinformatic approaches are intended to provide systems level insight into the complex biological processes that underlie serious diseases such as cancer. In this review we describe current bioinformatic resources, and illustrate how they have been used to study a clinically important example: epithelial-to-mesenchymal transition (EMT) in lung cancer. Lung cancer is the leading cause of cancer-related deaths and is often diagnosed at advanced stages, leading to limited therapeutic success. While EMT is essential during development and wound healing, pathological reactivation of this program by cancer cells contributes to metastasis and drug resistance, both major causes of death from lung cancer. Challenges of studying EMT include its transient nature, its molecular and phenotypic heterogeneity, and the complicated networks of rewired signaling cascades. Given the biology of lung cancer and the role of EMT, it is critical to better align the two in order to advance the impact of precision oncology. This task relies heavily on the application of bioinformatic resources. Besides summarizing recent work in this area, we use four EMT-associated genes, TGF-β (TGFB1), NEDD9/HEF1, β-catenin (CTNNB1) and E-cadherin (CDH1), as exemplars to demonstrate the current capacities and limitations of probing bioinformatic resources to inform hypothesis-driven studies with therapeutic goals.

Snail1 induced in breast cancer cells in 3D collagen I gel environment suppresses cortactin and impairs effective invadopodia formation

Although an in vitro 3D environment cannot completely mimic the in vivo tumor site, embedding tumor cells in a 3D extracellular matrix (ECM) allows for the study of cancer cell behaviors and the screening of anti-metastatic reagents with a more in vivo-like context. Here we explored the behaviors of MDA-MB-231 breast cancer cells embedded in 3D collagen I. Diverse tumor environmental conditions (including cell density, extracellular acidity, or hypoxia as mimics for a continuous tumor growth) reduced JNKs, enhanced TGFβ1/Smad signaling activity, induced Snail1, and reduced cortactin expression. The reduced JNKs activity blocked efficient formation of invadopodia labeled with actin, cortactin, or MT1-MMP. JNKs inactivation activated Smad2 and Smad4, which were required for Snail1 expression. Snail1 then repressed cortactin expression, causing reduced invadopodia formation and prominent localization of MT1-MMP at perinuclear regions. MDA-MB-231 cells thus exhibited less efficient collagen I degradation and invasion in 3D collagen I upon JNKs inhibition. These observations support a signaling network among JNKs, Smads, Snail1, and cortactin to regulate the invasion of MDA-MB-231 cells embedded in 3D collagen I, which may be targeted during screening of anti-invasion reagents.