Lats2 kinase potentiates Snail1 activity by promoting nuclear retention upon phosphorylation

Determination of In Vitro and In Vivo Effects of Taxifolin and Epirubicin on Epithelial-Mesenchymal Transition in Mouse Breast Cancer Cells

Background: One of the most significant characteristics of cancer is epithelial-mesenchymal transition and research on the relationship between phenolic compounds and anticancer medications and epithelial-mesenchymal transition is widespread. Methods: In order to investigate the potential effects of Taxifolin on enhancing the effectiveness of Epirubicin in treating breast cancer, specifically in 4T1 cells and an allograft BALB/c model, the effects of Taxifolin and Epirubicin, both individually and in combination, were examined. Cell viability assays and cytotoxicity assays in 4T1 cells were performed. In addition, 4T1 cells were implanted into female BALB/c mice to conduct in vivo studies and evaluate the therapeutic efficacy of Taxifolin and Epirubicin alone or in combination. Tumor volumes and histological analysis were also assessed in mice. To further understand the mechanisms involved, we examined the messenger RNA and protein levels of epithelial-mesenchymal transition-related genes, as well as active Caspase-3/7 levels, using quantitative real-time polymerase chain reaction, western blot, and enzyme-linked immunosorbent assays, respectively. Results: In vitro results demonstrated that the coadministration of Taxifolin and Epirubicin reduced cell viability and cytotoxicity in 4T1 cell lines. In vivo, coadministration of Taxifolin and Epirubicin suppressed tumor growth in BALB/c mice with 4T1 breast cancer cells. Additionally, this combination treatment significantly increased the levels of active caspase-3/7 and downregulated the messenger RNA and protein levels of N-cadherin, β-catenin, vimentin, snail, and slug, but upregulated the E-cadherin gene. It significantly decreased the messenger RNA levels of the Zeb1 and Zeb2 genes. Conclusion: The in vitro and in vivo results of our study indicate that the concurrent use of Epirubicin with Taxifolin has supportive effects on breast cancer treatment.

ERK3 Increases Snail Protein Stability by Inhibiting FBXO11-Mediated Snail Ubiquitination

Snail is a key regulator of the epithelial-mesenchymal transition (EMT), the key step in the tumorigenesis and metastasis of tumors. Although induction of Snail transcription precedes the induction of EMT, the post-translational regulation of Snail is also important in determining Snail protein levels, stability, and its ability to induce EMT. Several kinases are known to enhance the stability of the Snail protein by preventing its ubiquitination; however, the precise molecular mechanisms by which these kinases prevent Snail ubiquitination remain unclear. Here, we identified ERK3 as a novel kinase that interacts with Snail and enhances its protein stability. Although ERK3 could not directly phosphorylate Snail, Erk3 increased Snail protein stability by inhibiting the binding of FBXO11, an E3 ubiquitin ligase that can induce Snail ubiquitination and degradation, to Snail. Importantly, functional studies and analysis of clinical samples indicated the crucial role of ERK3 in the regulation of Snail protein stability in pancreatic cancer. Therefore, we conclude that ERK3 is a key regulator for enhancing Snail protein stability in pancreatic cancer cells by inhibiting the interaction between Snail and FBXO11.

Reciprocal positive regulation between BRD4 and YAP in GNAQ-mutant uveal melanoma cells confers sensitivity to BET inhibitors

Uveal melanoma (UM) is the most common intraocular cancer in adults. UMs are usually initiated by a mutation in GNAQ or GNA11 (encoding Gq or G11, respectively), unlike cutaneous melanomas (CMs), which usually carry a BRAF or NRAS mutation. Currently, there are no clinically effective targeted therapies for UM carrying Gq/11 mutations. Here, we identified a causal link between Gq activating mutations and hypersensitivity to bromodomain and extra-terminal (BET) inhibitors. BET inhibitors transcriptionally repress YAP via BRD4 regardless of Gq mutation status, independently of Hippo core components LATS1/2. In contrast, YAP/TAZ downregulation reduces BRD4 transcription exclusively in Gq-mutant cells and LATS1/2 double knockout cells, both of which are featured by constitutively active YAP/TAZ. The transcriptional interdependency between BRD4 and YAP identified in Gq-mutated cells is responsible for the preferential inhibitory effect of BET inhibitors on the growth and dissemination of Gq-mutated UM cells compared to BRAF-mutated CM cells in both culture cells and animal models. Our findings suggest BRD4 as a viable therapeutic target for Gq-driven UMs that are addicted to unrestrained YAP function.

The molecular mechanisms and therapeutic strategies of EMT in tumor progression and metastasis

Epithelial–mesenchymal transition (EMT) is an essential process in normal embryonic development and tissue regeneration. However, aberrant reactivation of EMT is associated with malignant properties of tumor cells during cancer progression and metastasis, including promoted migration and invasiveness, increased tumor stemness, and enhanced resistance to chemotherapy and immunotherapy. EMT is tightly regulated by a complex network which is orchestrated with several intrinsic and extrinsic factors, including multiple transcription factors, post-translational control, epigenetic modifications, and noncoding RNA-mediated regulation. In this review, we described the molecular mechanisms, signaling pathways, and the stages of tumorigenesis involved in the EMT process and discussed the dynamic non-binary process of EMT and its role in tumor metastasis. Finally, we summarized the challenges of chemotherapy and immunotherapy in EMT and proposed strategies for tumor therapy targeting EMT.

LATS kinases and SLUG regulate the transition to advanced stage in aggressive oral cancer cells

The epithelial-to-mesenchymal transition (EMT) is a critical process by which cancer cells acquire malignant features. However, the molecular mechanism and functional implications of EMT and the mesenchymal-to-epithelial transition (MET) in tumor progression remain elusive. In this study, we established two aggressive cancer cell lines from the human oral cancer cell line SAS, mesenchymal-like SAS-m4 and epithelial-like SAS-δ. SAS-δ is a revertant cell obtained by inducing MET in SAS-m4. SAS-δ, but not SAS-m4, exhibited abnormal cell growth, including piled-up overgrowth and invasive tumor formation in the tongues of nude mice, suggesting that SAS-δ represented more advanced cancer cells than the parental SAS cells. EMT-related transcriptional factor SLUG is phosphorylated at T208 and partly stabilized by the Hippo pathway kinases, LATS1 and LATS2. Depletion of SLUG promoted the invasive activity of SAS-δ by increasing the protein levels of LATS1/2 and the proportion of the phosphorylated form among total SLUG protein. Our results suggest that the LATS1/2-SLUG axis regulates the transition of SAS cells to the advanced stage via repeated switching between EMT and MET. Therefore, an anti-SLUG-pT208 antibody would be valuable not alone as a malignant tumor marker antibody but also as a prognostic tool for patients with malignant disease.

Transcriptional and post-transcriptional control of epithelial-mesenchymal plasticity: why so many regulators?

The dynamic transition between epithelial-like and mesenchymal-like cell states has been a focus for extensive investigation for decades, reflective of the importance of Epithelial-Mesenchymal Transition (EMT) through development, in the adult, and the contributing role EMT has to pathologies including metastasis and fibrosis. Not surprisingly, regulation of the complex genetic networks that underlie EMT have been attributed to multiple transcription factors and microRNAs. What is surprising, however, are the sheer number of different regulators (hundreds of transcription factors and microRNAs) for which critical roles have been described. This review seeks not to collate these studies, but to provide a perspective on the fundamental question of whether it is really feasible that so many regulators play important roles and if so, what does this tell us about EMT and more generally, the genetic machinery that controls complex biological processes.

An emergent Wnt5a/YAP/TAZ regulatory circuit and its possible role in cancer

Wnt5a is a ligand that plays several roles in development, homeostasis, and disease. A growing body of evidence indicates that Wnt5a is involved in cancer progression. Despite extensive research in this field, our knowledge about how Wnt5a is precisely involved in cancer is still incomplete. It is usually thought that certain combinations of Frizzled receptors and co-receptors might explain the observed effects of Wnt5a either as a tumor suppressor or by promoting migration and invasion. While accepting this 'receptor context' model, this review proposes that Wnt5a is integrated within a larger regulatory circuit involving β-catenin, YAP/TAZ, and LATS1/2. Remarkably, WNT5A and YAP1 are transcriptionally regulated by the Hippo and Wnt pathways, respectively, and might form a regulatory circuit acting through LATS kinases and secreted Wnt/β-catenin inhibitors, including Wnt5a itself. Therefore, understanding the precise role of Wnt5a and YAP in cancer requires a systems biology perspective.

Epigenetic Regulation and Post-Translational Modifications of SNAI1 in Cancer Metastasis

SNAI1, a zinc finger transcription factor, not only acts as the master regulator of epithelial-mesenchymal transition (EMT) but also functions as a driver of cancer progression, including cell invasion, survival, immune regulation, stem cell properties, and metabolic regulation. The regulation of SNAI1 occurs at the transcriptional, translational, and predominant post-translational levels including phosphorylation, acetylation, and ubiquitination. Here, we discuss the regulation and role of SNAI1 in cancer metastasis, with a particular emphasis on epigenetic regulation and post-translational modifications. Understanding how signaling networks integrate with SNAI1 in cancer progression will shed new light on the mechanism of tumor metastasis and help develop novel therapeutic strategies against cancer metastasis.

Snail enhances arginine synthesis by inhibiting ubiquitination-mediated degradation of ASS1

Snail is a dedicated transcriptional repressor and acts as a master inducer of EMT and metastasis, yet the underlying signaling cascades triggered by Snail still remain elusive. Here, we report that Snail promotes colorectal cancer (CRC) migration by preventing non-coding RNA LOC113230-mediated degradation of argininosuccinate synthase 1 (ASS1). LOC113230 is a novel Snail target gene, and Snail binds to the functional E-boxes within its proximal promoter to repress its expression in response to TGF-β induction. Ectopic expression of LOC113230 potently suppresses CRC cell growth, migration, and lung metastasis in xenograft experiments. Mechanistically, LOC113230 acts as a scaffold to facilitate recruiting LRPPRC and the TRAF2 E3 ubiquitin ligase to ASS1, resulting in enhanced ubiquitination and degradation of ASS1 and decreased arginine synthesis. Moreover, elevated ASS1 expression is essential for CRC growth and migration. Collectively, these findings suggest that TGF-β and Snail promote arginine synthesis via inhibiting LOC113230-mediated LRPPRC/TRAF2/ASS1 complex assembly and this complex can serve as potential target for the development of new therapeutic approaches to treat CRC.

STK39 promotes breast cancer invasion and metastasis by increasing SNAI1 activity upon phosphorylation

SNAI1 is widely regarded as a master driver of epithelial-mesenchymal transition (EMT) and associated with breast cancer progression and metastasis. This pro-malignant role is strongly linked to posttranslational modification, especially phosphorylation, which controls its protein levels and subcellular localization. While multiple kinases are implicated in regulation of SNAI1 stability, the precise mechanism by which SNAI1 is stabilized in tumors remains to be fully elucidated.

Methods: A series of in vitro and in vivo experiments were conducted to reveal the regulation of SNAI1 by Serine/Threonine Kinase 39 (STK39) and the role of STK39 in breast cancer metastasis.

Results: We identified STK39, a member of Stem 20-like serine/threonine kinase family, as a novel posttranslational regulator that enhances the stability of SNAI1. Inhibition of STK39 via knockdown or use of a specific inhibitor resulted in SNAI1 destabilization. Mechanistically, STK39 interacted with and phosphorylated SNAI1 at T203, which is critical for its nuclear retention. Functionally, STK39 inhibition markedly impaired the EMT phenotype and decreased tumor cell migration, invasion, and metastasis both in vitro and in vivo. These effects were rescued by ectopic SNAI1 expression. In addition, depletion of STK39 dramatically enhanced sensitivity to chemotherapeutic agents.

Conclusions: Our study demonstrated that STK39 is a key mediator of SNAI1 stability and is associated with the pro-metastatic cellular process, highlighting the STK39-SNAI1 signaling axis as promising therapeutic targets for treatments of metastatic breast cancer.

GTSE1 promotes SNAIL1 degradation by facilitating its nuclear export in hepatocellular carcin oma cells

Snail family transcriptional repressor 1 (SNAIL1) is a master inducer of the epithelial-to-mesenchymal transition (EMT) process, contributing to tumor metastasis and recurrence. Our previous study reported that G₂ and S phase-expressed-1 (GTSE1) served a role in regulating SNAIL1 expression in hepatocellular carcinoma (HCC). However, the underlying mechanism remains unknown. Therefore, the present study aimed to reveal the regulatory mechanism of GTSE1 on SNAIL1 expression using in vitro assays performed in HCC cell models. It was demonstrated that endogenous SNAIL1 expression was downregulated and upregulated by GTSE1 overexpression or small interfering RNA-mediated knockdown, respectively. Via cycloheximide chase experiments, it was identified that GTSE1 overexpression increased the protein turnover of SNAIL1, while knockdown of GTSE1 reduced its degradation rate. Furthermore, it was demonstrated that GTSE1 overexpression induced the cytoplasmic expression of SNAIL1 using immunofluorescence and subcellular fractionation methods. The nuclear export inhibitor leptomycin B was able to decrease the cytoplasmic retention of SNAIL1 caused by GTSE1 overexpression. In addition, TGF-βI treatment increased both the mRNA and protein expression levels of GTSE1, and decreased the protein expression level of SNAIL1 without affecting its mRNA transcription in Huh7 cells. It was also found that TGF-β signaling could upregulate the transcription of GTSE1 expression by transactivating the Smad binding elements in the GTSE1 promoter. Moreover, the TGF-βI-induced decrease in SNAIL1 protein expression was GTSE1-dependent in Huh7 cells. In conclusion, the current study provides a novel mechanism via which GTSE1 affects the stability of SNAIL1 by regulating its subcellular localization in HCC cells.

The Post-Translational Regulation of Epithelial-Mesenchymal Transition-Inducing Transcription Factors in Cancer Metastasis

Epithelial-mesenchymal transition (EMT) is generally observed in normal embryogenesis and wound healing. However, this process can occur in cancer cells and lead to metastasis. The contribution of EMT in both development and pathology has been studied widely. This transition requires the up- and down-regulation of specific proteins, both of which are regulated by EMT-inducing transcription factors (EMT-TFs), mainly represented by the families of Snail, Twist, and ZEB proteins. This review highlights the roles of key EMT-TFs and their post-translational regulation in cancer metastasis.

SCRT1 is a novel beta cell transcription factor with insulin regulatory properties

Here we show that scratch family transcriptional repressor 1 (SCRT1), a zinc finger transcriptional regulator, is a novel regulator of beta cell function. SCRT1 was found to be expressed in beta cells in rodent and human islets. In human islets, expression of SCRT1 correlated with insulin secretion capacity and the expression of the insulin (INS) gene. Furthermore, SCRT1 mRNA expression was lower in beta cells from T2D patients. siRNA-mediated Scrt1 silencing in INS-1832/13 cells, mouse- and human islets resulted in impaired glucose-stimulated insulin secretion and decreased expression of the insulin gene. This is most likely due to binding of SCRT1 to E-boxes of the Ins1 gene as shown with ChIP. Scrt1 silencing also reduced the expression of several key beta cell transcription factors. Moreover, Scrt1 mRNA expression was reduced by glucose and SCRT1 protein was found to translocate between the nucleus and the cytosol in a glucose-dependent fashion in INS-1832/13 cells as well as in a rodent model of T2D. SCRT1 was also regulated by a GSK3β-dependent SCRT1-serine phosphorylation. Taken together, SCRT1 is a novel beta cell transcription factor that regulates insulin secretion and is affected in T2D.

Snail-Family Proteins: Role in Carcinogenesis and Prospects for Antitumor Therapy

The review analyzes Snail family proteins, which are transcription factors involved in the regulation of the epithelial-mesenchymal transition (EMT) of tumor cells. We describe the structure of these proteins, their post-translational modification, and the mechanisms of Snail-dependent regulation of genes. The role of Snail proteins in carcinogenesis, invasion, and metastasis is analyzed. Furthermore, we focus on EMT signaling mechanisms involving Snail proteins. Next, we dissect Snail signaling in hypoxia, a condition that complicates anticancer treatment. Finally, we offer classes of chemical compounds capable of down-regulating the transcriptional activity of Snails. Given the important role of Snail proteins in cancer biology and the potential for pharmacological inhibition, Snail family proteins may be considered promising as therapeutic targets.

p90RSK-MAGI1 Module Controls Endothelial Permeability by Post-translational Modifications of MAGI1 and Hippo Pathway

Previously, we reported that post-translational modifications (PTMs) of MAGI1, including S741 phosphorylation and K931 de-SUMOylation, both of which are regulated by p90RSK activation, lead to endothelial cell (EC) activation. However, roles for p90RSK and MAGI1-PTMs in regulating EC permeability remain unclear despite MAGI1 being a junctional molecule. Here, we show that thrombin (Thb)-induced EC permeability, detected by the electric cell-substrate impedance sensing (ECIS) based system, was decreased by overexpression of dominant negative p90RSK or a MAGI1-S741A phosphorylation mutant, but was accelerated by overexpression of p90RSK, siRNA-mediated knockdown of magi1, or the MAGI1-K931R SUMOylation mutant. MAGI1 depletion also increased the mRNA and protein expression of the large tumor suppressor kinases 1 and 2 (LATS1/2), which inhibited YAP/TAZ activity and increased EC permeability. Because the endothelial barrier is a critical mediator of tumor hypoxia, we also evaluated the role of p90RSK activation in tumor vessel leakiness by using a relatively low dose of the p90RSK specific inhibitor, FMK-MEA. FMK-MEA significantly inhibited tumor vessel leakiness at a dose that does not affect morphology and growth of tumor vessels in vivo. These results provide novel insights into crucial roles for p90RSK-mediated MAGI1 PTMs and the Hippo pathway in EC permeability, as well as p90RSK activation in tumor vessel leakiness.

Epitranscriptomics and epiproteomics in cancer drug resistance: therapeutic implications

Drug resistance is a major hurdle in cancer treatment and a key cause of poor prognosis. Epitranscriptomics and epiproteomics are crucial in cell proliferation, migration, invasion, and epithelial–mesenchymal transition. In recent years, epitranscriptomic and epiproteomic modification has been investigated on their roles in overcoming drug resistance. In this review article, we summarized the recent progress in overcoming cancer drug resistance in three novel aspects: (i) mRNA modification, which includes alternative splicing, A-to-I modification and mRNA methylation; (ii) noncoding RNAs modification, which involves miRNAs, lncRNAs, and circRNAs; and (iii) posttranslational modification on molecules encompasses drug inactivation/efflux, drug target modifications, DNA damage repair, cell death resistance, EMT, and metastasis. In addition, we discussed the therapeutic implications of targeting some classical chemotherapeutic drugs such as cisplatin, 5-fluorouridine, and gefitinib via these modifications. Taken together, this review highlights the importance of epitranscriptomic and epiproteomic modification in cancer drug resistance and provides new insights on potential therapeutic targets to reverse cancer drug resistance.

Prediction and evaluation of deleterious and disease causing non-synonymous SNPs (nsSNPs) in human NF2 gene responsible for neurofibromatosis type 2 (NF2)

The majority of genetic variations in the human genome that lead to variety of different diseases are caused by non-synonymous single nucleotide polymorphisms (nsSNPs). Neurofibromatosis type 2 (NF2) is a deadly disease caused by nsSNPs in the NF2 gene that encodes for a protein called merlin. This study used various in silico methods, SIFT, Polyphen-2, PhD-SNP and MutPred, to investigate the pathogenic effect of 14 nsSNPs in the merlin FERM domain. The G197C and L234R mutations were found to be two deleterious and disease mutations associated with the mild and severe forms of NF2, respectively. Molecular dynamics (MD) simulations were conducted to understand the stability, structure and dynamics of these mutations. Both mutant structures experienced larger flexibility compared to the wildtype. The L234R mutant suffered from more prominent structural instability, which may help to explain why it is associated with the more severe form of NF2. The intramolecular hydrogen bonding in L234R mutation decreased from the wildtype, while intermolecular hydrogen bonding of L234R mutation with solvent greatly increased. The native contacts were also found to be important. Protein-protein docking revealed that L234R mutation decreased the binding complementarity and binding affinity of LATS2 to merlin, which may have an impact on merlin's ability to regulate the Hippo signaling pathway. The calculated binding affinity of the LATS2 to L234R mutant and wildtype merlin protein is found to be 21.73 and -11 kcal/mol, respectively. The binding affinity of the wildtype merlin agreed very well with the experimental value, -8 kcal/mol.Communicated by Ramaswamy H. Sarma.

HDAC8 promotes the dissemination of breast cancer cells via AKT/GSK-3β/Snail signals

The mechanistic action of histone deacetylase 8 (HDAC8) in cancer motility, including epithelial-mesenchymal transition (EMT), remains largely undefined. We found that the expression of HDAC8 was upregulated in breast cancer (BC) cells and tissues as compared to the controls. Further, BC tissues had the highest values of HDAC8 expression among 31 kinds of cancers. Cellular study indicated that HDAC8 can positively regulate the dissemination and EMT of BC cells. It increased the protein stability of Snail, an important regulator of EMT, by phosphorylation of its motif 2 in serine-rich regions. There are 21 factors that have been reported to regulate the protein stability of Snail. Among them, HDAC8 can decrease the expression of GSK-3β through increasing its Ser9-phosphorylation. Mass spectrum analysis indicated that HDAC8 interact with AKT1 to decrease its acetylation while increase its phosphorylation, which further increased Ser9-phosphorylation of GSK-3β. The C-terminal of AKT1 was responsible for the interaction between HDAC8 and AKT1. Further, Lys426 was the key residue for HDAC8-regulated deacetylation of AKT1. Moreover, HDAC8/Snail axis acted as adverse prognosis factors for in vivo progression and overall survival (OS) rate of BC patients. Collectively, we found that HDAC8 can trigger the dissemination of BC cells via AKT/GSK-3β/Snail signals, which imposed that inhibition of HDAC8 is a potential approach for BC treatment.

F-Box Proteins and Cancer

Controlled protein degradation is essential for the operation of a variety of cellular processes including cell division, growth, and differentiation. Identification of the relations between ubiquitin ligases and their substrates is key to understanding the molecular basis of cancer development and to the discovery of novel targets for cancer therapeutics. F-box proteins function as the substrate recognition subunits of S-phase kinase-associated protein 1 (SKP1)−Cullin1 (CUL1)−F-box protein (SCF) ubiquitin ligase complexes. Here, we summarize the roles of specific F-box proteins that have been shown to function as tumor promoters or suppressors. We also highlight proto-oncoproteins that are targeted for ubiquitylation by multiple F-box proteins, and discuss how these F-box proteins are deployed to regulate their cognate substrates in various situations.

Hybrid Epithelial/Mesenchymal State in Cancer Metastasis: Clinical Significance and Regulatory Mechanisms

Epithelial-mesenchymal transition (EMT) has been well recognized for its essential role in cancer progression as well as normal tissue development. In cancer cells, activation of EMT permits the cells to acquire migratory and invasive abilities and stem-like properties. However, simple categorization of cancer cells into epithelial and mesenchymal phenotypes misleads the understanding of the complicated metastatic process, and contradictory results from different studies also indicate the limitation of application of EMT theory in cancer metastasis. Nowadays, growing evidence suggests the existence of an intermediate status between epithelial and mesenchymal phenotypes, i.e., the "hybrid epithelial-mesenchymal (hybrid E/M)" state, provides a possible explanation for those conflicting results. Appearance of hybrid E/M phenotype offers a more plastic status for cancer cells to adapt the stressful environment for proceeding metastasis. In this article, we review the biological importance of the dynamic changes between the epithelial and the mesenchymal states. The regulatory mechanisms encompassing the translational, post-translational, and epigenetic control for this complex and plastic status are also discussed.

circRNA_0000140 suppresses oral squamous cell carcinoma growth and metastasis by targeting miR-31 to inhibit Hippo signaling pathway

Oral squamous cell carcinoma (OSCC) is one of the most common malignancies and has a poor prognosis. Circular RNA (circRNA) has been increasingly recognized as a crucial contributor to carcinogenesis. circRNA_0000140 has been aberrantly expressed in OSCC, but its role in tumor growth and metastasis remains largely unclear. Sanger sequencing, actinomycin D, and RNase R treatments were used to confirm head-to-tail junction sequences and the stability of circ_0000140. In vitro cell activities, including proliferation, migration, invasion, and apoptosis, were determined by colony formation, transwell, and flow cytometry assays. The expression levels of circ_0000140, Hippo signaling pathway, and serial epithelial–mesenchymal transition (EMT) markers were measured by quantitative real-time PCR, western blotting, immunofluorescence, and immunohistochemistry. Dual luciferase reporter assays and Argonaute 2-RNA immunoprecipitation assays were performed to explore the interplay among circ_0000140, miR-31, and LATS2. Subcutaneous tumor growth was observed in nude mice, in which in vivo metastasis was observed following tail vein injection of OSCC cells. circ_0000140 is derived from exons 7 to 10 of the KIAA0907 gene. It was down-regulated in OSCC tissues and cell lines, and correlated negatively with poor prognostic outcomes in OSCC patients. Gain-of-function experiments demonstrated that circ_0000140 enhancement suppressed cell proliferation, migration, and invasion, and facilitated cell apoptosis in vitro. In xenograft mouse models, overexpression of circ_0000140 was able to repress tumor growth and lung metastasis. Furthermore, mechanistic studies showed that circ_0000140 could bind with miR-31 and up-regulate its target gene LATS2, thus affecting OSCC cellular EMT. Our findings demonstrated the roles of circ_0000140 in OSCC tumorigenesis as well as in metastasis, and circ_0000140 exerts its tumor-suppressing effect through miR-31/LATS2 axis of Hippo signaling pathway in OSCC.

Epithelial-Mesenchymal Plasticity in Cancer Progression and Metastasis

Epithelial-to-mesenchymal transition (EMT) and its reversed process, mesenchymal-to-epithelial transition (MET), are fundamental processes in embryonic development and tissue repair but confer malignant properties to carcinoma cells, including invasive behavior, cancer stem cell activity, and greater resistance to chemotherapy and immunotherapy. Understanding the molecular and cellular basis of EMT provides fundamental insights into the etiology of cancer and may, in the long run, lead to new therapeutic strategies. Here, we discuss the regulatory mechanisms and pathological roles of epithelial-mesenchymal plasticity, with a focus on recent insights into the complexity and dynamics of this phenomenon in cancer.

Outcome in serous ovarian cancer is not associated with LATS expression

Background

Large tumor suppressor (LATS) proteins are putative tumor suppressors and poorly expressed associated with poor outcome in many cancers. A recent immunohistochemistry study showed that LATS protein expression correlated with poor outcome in serous ovarian cancer.

Materials and methods

We analyzed LATS expression in various ovarian cancer transcriptomic data sets and immunohistochemically assessed LATS protein expression in a Swiss ovarian tumor cohort. Results were compared to clinicopathological characteristics and outcome. We also compared LATS protein expression in serous ovarian cancer cell lines to their EMT status (Western blotting) and drug sensitivity (MTT assay).

Results

The analysis of 15 different transcriptomic data sets showed that LATS2 was associated with poorer outcome, while LATS1 was irrelevant (HR = 1.19 and HR = 1.00, respectively). The TCGA-RNASeqV2 data set showed that low LATS1 and LATS2 were associated with better survival in serous ovarian carcinoma. Despite heterogeneity among the different data sets, LATS expression is not an indicator of survival in serous ovarian cancer and LATS2 expression may even be tumorigenic. LATS expression was neither associated with survival nor with the stage and grade in the Swiss cohort. It was low in cystadenoma, intermediate in carcinoma, and high in borderline tumors and was higher in serous than mucinous ovarian carcinoma. LATS protein expression extent was comparable in epithelial-, intermediate-, and mesenchymal-type ovarian cancer cells and was not associated with drug sensitivity.

Conclusion

These results are largely incompatible with a tumor-suppressive function of LATS in ovarian cancer, and LATS protein level is also not an indicator for drug sensitivity and EMT status of ovarian cancer cells.

p38 Stabilizes Snail by Suppressing DYRK2-Mediated Phosphorylation That Is Required for GSK3β-βTrCP-Induced Snail Degradation

Snail is a key regulator of epithelial-mesenchymal transition (EMT), which is a major step in tumor metastasis. Although the induction of Snail transcription precedes EMT, posttranslational regulation, especially phosphorylation of Snail, is critical for determining Snail protein levels or stability, subcellular localization, and the ability to induce EMT. To date, several kinases are known that enhance the stability of Snail by preventing its ubiquitination; however, the molecular mechanism(s) underlying this are still unclear. Here, we identified p38 MAPK as a crucial posttranslational regulator that enhances the stability of Snail. p38 directly phosphorylated Snail at Ser107, and this effectively suppressed DYRK2-mediated Ser104 phosphorylation, which is critical for GSK3β-dependent Snail phosphorylation and βTrCP-mediated Snail ubiquitination and degradation. Importantly, functional studies and analysis of clinical samples established a crucial role for the p38-Snail axis in regulating ovarian cancer EMT and metastasis. These results indicate the potential therapeutic value of targeting the p38-Snail axis in ovarian cancer. SIGNIFICANCE: These findings identify p38 MAPK as a novel regulator of Snail protein stability and potential therapeutic target in ovarian cancer.

Roles of the Phosphorylation of Transcriptional Factors in Epithelial-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) is the first step in the development of the invasive and migratory properties of cancer metastasis. Since the transcriptional reprogramming of a number of genes occurs in EMT, the regulation of EMT transcription factors has been intensively investigated. EMT transcriptional factors are commonly classified by the direct or indirect repression of E-cadherin because one of hallmarks of EMT is the loss of E-cadherin. This facilitates the expression of genes for EMT, tumor invasion, and metastasis. The posttranslational modification of EMT transcriptional factors, such as Snail and Slug, directly regulates their functions, including their stability, nuclear localization, protein-protein interaction, and ubiquitination for the promotion or termination of EMT at the specific points. Here, we discuss how posttranslational modifications regulate gene expression in a dynamic and reversible manner by modifying upstream signaling pathways, focusing in particular on the posttranslational modifications of Snail, Slug, ZEB1, ZEB2, and TWIST1. This review demonstrates that EMT transcription factors regulate metastasis through their posttranslational modifications and that the flexibility and reversibility of EMT can be modified by phosphorylation.

Snail1: A Transcriptional Factor Controlled at Multiple Levels

Snail1 transcriptional factor plays a key role in the control of epithelial to mesenchymal transition and fibroblast activation. As a consequence, Snail1 expression and function is regulated at multiple levels from gene transcription to protein modifications, affecting its interaction with specific cofactors. In this review, we describe the different elements that control Snail1 expression and its activity both as transcriptional repressor or activator.

C-terminal domain small phosphatase-like 2 promotes epithelial-to-mesenchymal transition via Snail dephosphorylation and stabilization

The epithelial-to-mesenchymal transition (EMT) is a cellular reprogramming process converting epithelial cells into mesenchymal cell morphology. Snail is a critical regulator of EMT by both suppressing epithelial gene expression and promoting mesenchymal gene expression. Expression and activity of Snail are tightly controlled at transcriptional and post-translational levels. It has previously been reported that Snail undergoes phosphorylation and ubiquitin-dependent proteasome degradation. Here, we report nuclear phosphatase SCP4/CTDSPL2 acts as a novel Snail phosphatase. SCP4 physically interacts with and directly dephosphorylates Snail. SCP4-mediated dephosphorylation of Snail suppresses the ubiquitin-dependent proteasome degradation of Snail and consequently enhances TGFβ-induced EMT. The knockdown of SCP4 in MCF10A mammary epithelial cells leads to attenuated cell migration. Collectively, our finding demonstrates that SCP4 plays a critical role in EMT through Snail dephosphorylation and stabilization.

Nodal Promotes the Migration and Invasion of Bladder Cancer Cells via Regulation of Snail

Urinary bladder cancer is one of commonly diagnosed malignancies worldwide, especially in males. Understanding the mechanisms of advanced metastasis in bladder cell is important for therapy and drug development. Nodal, an important embryonic morphogen, has been reported to modulate tumorigenesis. We found that the expression of Nodal was upregulated in bladder cancer cells and tissues as compared to their corresponding controls. Knockdown of Nodal can suppress the migration, invasion, and epithelial-to-mesenchymal transition (EMT) of bladder cancer cells. Nodal can positively regulate the expression of Snail, one powerful EMT transcription factors, in bladder cancer cells. Overexpression of Snail can attenuate the si-Nodal suppressed cell migration and invasion. Nodal can increase the transcription and protein stability of Snail in bladder cancer cells. YY1, which can be activated by Nodal, is responsible for Nodal induced transcription of Snail. ATM, which can stabilize Snail by phosphorylation on Serine-100, was involved in Nodal upregulated protein stability of Snail. Collectively, our data showed that Nodal can trigger the malignancy of bladder cancer cells via increasing the transcription and protein stability of Snail. It indicated that Nodal might be a potential therapeutic target for bladder cancer treatment.

LATS1/2 kinases trigger self-renewal of cancer stem cells in aggressive oral cancer

Cancer stem cells (CSCs), which play important roles in tumor initiation and progression, are resistant to many types of therapies. However, the regulatory mechanisms underlying CSC-specific properties, including self-renewal, are poorly understood. Here, we found that LATS1/2, the core Hippo pathway-kinases, were highly expressed in the oral squamous cell carcinoma line SAS, which exhibits high capacity of CSCs, and that depletion of these kinases prevented SAS cells from forming spheres under serum-free conditions. Detailed examination of the expression and activation of LATS kinases and related proteins over a time course of sphere formation revealed that LATS1/2 were more highly expressed and markedly activated before initiation of self-renewal. Moreover, TAZ, SNAIL, CHK1/2, and Aurora-A were expressed in hierarchical, oscillating patterns during sphere formation, suggesting that the process consists of four sequential steps. Our results indicate that LATS1/2 trigger self-renewal of CSCs by regulating the Hippo pathway, the EMT, and cell division.

TGFβ-Activated USP27X Deubiquitinase Regulates Cell Migration and Chemoresistance via Stabilization of Snail1

In cancer cells, epithelial-to-mesenchymal transition (EMT) is controlled by Snail1, a transcriptional factor also required for the activation of cancer-associated fibroblasts (CAF). Snail1 is short-lived in normal epithelial cells as a consequence of its coordinated and continuous ubiquitination by several F-box-specific E3 ligases, but its degradation is prevented in cancer cells and in activated fibroblasts. Here, we performed an siRNA screen and identified USP27X as a deubiquitinase that increases Snail1 stability. Expression of USP27X in breast and pancreatic cancer cell lines and tumors positively correlated with Snail1 expression levels. Accordingly, downregulation of USP27X decreased Snail1 protein in several tumor cell lines. USP27X depletion impaired Snail1-dependent cell migration and invasion and metastasis formation and increased cellular sensitivity to cisplatin. USP27X was upregulated by TGFβ during EMT and was required for TGFβ-induced expression of Snail1 and other mesenchymal markers in epithelial cells and CAF. In agreement with this, depletion of USP27X prevented TGFβ-induced EMT and fibroblast activation. Collectively, these results indicate that USP27X is an essential protein controlling Snail1 expression and function and may serve as a target for inhibition of Snail1-dependent tumoral invasion and chemoresistance. SIGNIFICANCE: These findings show that inhibition of USP27X destabilizes Snail1 to impair EMT and renders tumor cells sensitive to chemotherapy, thus opening new strategies for the inhibition of Snail1 expression and its protumoral actions.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/1/33/F1.large.jpg.

Inhibition of tumor-microenvironment interaction and tumor invasion by small-molecule allosteric inhibitor of DDR2 extracellular domain

To effectively prevent cancer spread from primary tumor sites, new treatments need to target tumor cells, the cells and extracellular matrix within the tumor environment, and communicating pathways between these sites simultaneously. The collagen receptor discoidin domain receptor 2 (DDR2) has been implicated as such a target. Here, we describe the identification and characterization of a small molecule inhibitor of DDR2 that uniquely acts in an allosteric manner via the extracellular domain to selectively inhibit the action of DDR2 in tumor cells and tumor stromal cancer-associated fibroblasts. In experimental mouse models of breast cancer, WRG-28 inhibits DDR2 signaling and tumor cell invasion.

The action of the collagen binding receptor tyrosine kinase (RTK) discoidin domain receptor 2 (DDR2) in both tumor and tumor stromal cells has been established as critical for breast cancer metastasis. Small molecule inhibitors that target the extracellular domain of RTKs are rare, as they have classically been regarded as too small to block binding with large polypeptide ligands. Here, we report the identification and characterization of a selective, extracellularly acting small molecule inhibitor (WRG-28) of DDR2 that uniquely inhibits receptor–ligand interactions via allosteric modulation of the receptor. By targeting DDR2, WRG-28 inhibits tumor invasion and migration, as well as tumor-supporting roles of the stroma, and inhibits metastatic breast tumor cell colonization in the lungs. These findings represent an approach to inhibiting tumor–stromal interactions and support the development of allosteric inhibitors of DDR2, such as WRG-28, as a promising approach to antimetastasis treatment.

miR-363 confers taxane resistance in ovarian cancer by targeting the Hippo pathway member, LATS2

Ovarian cancer is the most aggressive female reproductive tract tumours. Taxane (paclitaxel; TX) is widely used for ovarian cancer treatment. However, ovarian cancers often acquire chemoresistance. MicroRNAs (miR) have been reported to mediate many tumours'chemoresistance. We investigated the role of miR-363 in the chemoresistance of the ovarian cancer cell line, KF, and its TX-resistant derivative (KF-TX) cells. QRT-PCR indicated that miR-363 was upregulated in KF-TX cells, and introduction of miR-363 into sensitive ovarian cancer cells confers TX-resistance and significantly inhibited the expression of the Hippo member, LATS2, as indicated by viability, clonogenic assay and expression analysis. Furthermore, we validated the role of LATS2 in TX-response by sh-based silencing, which also confers TX-resistance to the ovarian cancer cells. On the other hand, specific inhibitor against miR-363 restored the response to TX in the resistant cells. In addition, miR-363 was found to bind to the 3'-UTR of LATS2 mRNA, confirming that miR-363 directly targets LATS2 as indicated by dual luciferase assay. RT-PCR-based evaluation of miR-363 in a panel of human ovarian tumours revealed its upregulation in most of the tumour tissues identified as resistant while it was downregulated in most of the tissues identified as sensitive ones. Moreover, higher levels of miR-363 in human ovarian cancer specimens were significantly correlated with TX chemoresistance. Taken together, our study reveals the involvement of miR-363 in chemoresistance by targeting LATS2 in ovarian cancers, raising the possibility that combination therapy with a miR-363 inhibitor and TX may increase TX efficacy and reduce the chance of TX-resistance.

Heterozygosity of mitogen-activated protein kinase organizer 1 ameliorates diabetic nephropathy and suppresses epithelial-to-mesenchymal transition-like changes in db/db mice

Background

Progressive diabetic nephropathy (DN) is characterized by tubulointerstitial fibrosis that is caused by accumulation of extracellular matrix. Induced by several factors, matrix-producing myofibroblasts may to some extent originate from tubular cells by epithelial-to-mesenchymal transition (EMT). Although previous data document that activation of hypoxia-inducible factor (HIF) signalling can be renoprotective in acute kidney disease, this issue remains controversial in chronic kidney injury. Here, we studied whether DN and EMT-like changes are ameliorated in a mouse model of type 2 diabetes mellitus with increased stability and activity of the HIF.

Methods

We used db/db mice that were crossed with transgenic mice expressing reduced levels of mitogen-activated protein kinase organizer 1 (MORG1), a scaffold protein interacting with prolyl hydroxylase domain 3 (PHD3), because of deletion of one MORG1 allele.

Results

We found significantly reduced nephropathy in diabetic MORG1+/- heterozygous mice compared with the diabetic wild-types (db/dbXMORG1+/+). Furthermore, we demonstrated that EMT-like changes in the tubulointerstitium of diabetic wild-type MORG1+/+ mice are present, whereas diabetic mice with reduced expression of MORG1 showed significantly fewer EMT-like changes.

Conclusions

These findings reveal that a deletion of one MORG1 allele inhibits the development of DN in db/db mice. The data suggest that the diminished interstitial fibrosis in these mice is a likely consequence of suppressed EMT-like changes.

Genomewide binding of transcription factor Snail1 in triple-negative breast cancer cells

Transcriptional regulation mediated by the zinc finger protein Snail1 controls early embryogenesis. By binding to the epithelial tumor suppressor CDH1 gene, Snail1 initiates the epithelial–mesenchymal transition (EMT). The EMT generates stem‐like cells and promotes invasiveness during cancer progression. Accordingly, Snail1 mRNA and protein is abundantly expressed in triple‐negative breast cancers with enhanced metastatic potential and phenotypic signs of the EMT. Such high endogenous Snail1 protein levels permit quantitative chromatin immunoprecipitation‐sequencing (ChIP‐seq) analysis. Snail1 associated with 185 genes at cis regulatory regions in the Hs578T triple‐negative breast cancer cell model. These genes include morphogenetic regulators and signaling components that control polarized differentiation. Using the CRISPR/Cas9 system in Hs578T cells, a double deletion of 10 bp each was engineered into the first exon and into the second exon–intron junction of Snail1, suppressing Snail1 expression and causing misregulation of several hundred genes. Specific attention to regulators of chromatin organization provides a possible link to new phenotypes uncovered by the Snail1 loss‐of‐function mutation. On the other hand, genetic inactivation of Snail1 was not sufficient to establish a full epithelial transition to these tumor cells. Thus, Snail1 contributes to the malignant phenotype of breast cancer cells via diverse new mechanisms.

Epithelial Mesenchymal Transition in Embryonic Development, Tissue Repair and Cancer: A Comprehensive Overview

The epithelial mesenchymal transition (EMT) plays a central role in both normal physiological events (e.g., embryonic development) and abnormal pathological events (e.g., tumor formation and metastasis). The processes that occur in embryonic development are often reactivated under pathological conditions such as oncogenesis. Therefore, defining the regulatory networks (both gene and protein levels) involved in the EMT during embryonic development will be fundamental in understanding the regulatory networks involved in tumor development, as well as metastasis. There are many molecules, factors, mediators and signaling pathways that are involved in the EMT process. Although the EMT is a very old topic with numerous publications, recent new technologies and discoveries give this research area some new perspective and direction. It is now clear that these important processes are controlled by a network of transcriptional and translational regulators in addition to post-transcriptional and post-translational modifications that amplify the initial signals. In this review article, we will discuss some key concepts, historical findings, as well as some recent progresses in the EMT research field.

SPSB3 targets SNAIL for degradation in GSK-3β phosphorylation-dependent manner and regulates metastasis

Epithelial-mesenchymal transition (EMT) is a process during which normal epithelial cells acquire mesenchymal characteristics. EMT has a critical role in various human diseases especially in cancer. EMT facilitates tumor initiation and progression by mediating cancer cell stemness and motility. Zinc finger transcription factor SNAIL is one of the most important initiators of EMT. Therefore, it is of great significance to understand the regulating mechanism of SNAIL. In this study, we carried out a luciferase-based genome-wide screening using small interfering RNA library against ~200 of E3 ligases and ubiquitin-related genes and identified SOCS box protein SPSB3 as a novel E3 ligase component that targets SNAIL into polyubiquitination and degradation in response to GSK-3β phosphorylation of SNAIL. Functionally, we observed that SPSB3 overexpression greatly inhibits tumor metastasis by regulating SNAIL degradation both in vitro and in vivo. The expression of SPSB3 and SNAIL are negatively correlated in human esophageal squamous cell carcinoma tissues, and low SPSB3 expression indicates lymph node metastasis. Moreover, high SPSB3 expression indicates good survivals in various kinds of cancer. Collectively, these findings suggest that SPSB3-mediated SNAIL degradation has a vital role in regulating EMT and cancer progression.

Cancer-associated fibroblasts support vascular growth through mechanical force

The role of cancer-associated fibroblasts (CAFs) as regulators of tumor progression, specifically vascular growth, has only recently been described. CAFs are thought to be more mechanically active but how this trait may alter the tumor microenvironment is poorly understood. We hypothesized that enhanced mechanical activity of CAFs, as regulated by the Rho/ROCK pathway, contributes to increased blood vessel growth. Using a 3D in vitro tissue model of vasculogenesis, we observed increased vascularization in the presence of breast cancer CAFs compared to normal breast fibroblasts. Further studies indicated this phenomenon was not simply a result of enhanced soluble signaling factors, including vascular endothelial growth factor (VEGF), and that CAFs generated significantly larger deformations in 3D gels compared to normal fibroblasts. Inhibition of the mechanotransductive pathways abrogated the ability of CAFs to deform the matrix and suppressed vascularization. Finally, utilizing magnetic microbeads to mechanically stimulate mechanically-inhibited CAFs showed partial rescue of vascularization. Our studies demonstrate enhanced mechanical activity of CAFs may play a crucial and previously unappreciated role in the formation of tumor-associated vasculature which could possibly offer potential novel targets in future anti-cancer therapies.

Targeting epithelial-mesenchymal plasticity in cancer: clinical and preclinical advances in therapy and monitoring

The concept of epithelial-mesenchymal plasticity (EMP), which describes the dynamic flux within the spectrum of phenotypic states that invasive carcinoma cells may reside, is being increasingly recognised for its role in cancer progression and therapy resistance. The myriad of events that are able to induce EMP, as well as the more recently characterised control loops, results in dynamic transitions of cancerous epithelial cells to more mesenchymal-like phenotypes through an epithelial-mesenchymal transition (EMT), as well as the reverse transition from mesenchymal phenotypes to an epithelial one. The significance of EMP, in its ability to drive local invasion, generate cancer stem cells and facilitate metastasis by the dissemination of circulating tumour cells (CTCs), highlights its importance as a targetable programme to combat cancer morbidity and mortality. The focus of this review is to consolidate the existing knowledge on the strategies currently in development to combat cancer progression via inhibition of specific facets of EMP. The prevalence of relapse due to therapy resistance and metastatic propensity that EMP endows should be considered when designing therapy regimes, and such therapies should synergise with existing chemotherapeutics to benefit efficacy. To further improve upon EMP-targeted therapies, it is imperative to devise monitoring strategies to assess the impact of such treatments on EMP-related phenomenon such as CTC burden, chemosensitivity/-resistance and micrometastasis in patients.

Regulation of FBXO4-mediated ICAM-1 protein stability in metastatic breast cancer

Advanced or progressive cancers share common traits such as altered transcriptional modulation, genetic modification, and abnormal post-translational regulation. These processes influence protein stability and cellular activity. Intercellular adhesion molecule-1 (ICAM-1) is involved in the malignant progression of various human cancers, including breast, liver, renal, and pancreatic cancers, but protein stability has not been deal with in metastatic breast cancer. Additionally, the relevance of the stability maintenance of ICAM-1 protein remains obscure. Here, we identified a novel interaction of E3 ligase FBXO4 that is specifically presented to ICAM-1. To understand how FBXO4 modulates ICAM-1 stability, we investigated ICAM-1-overexpressing or knockdown metastatic/non-metastatic breast cancers. ICAM-1 was found to influence tumor progression and metastasis, whereas FBXO4 regulated aggressive tumorigenic conditions. These results demonstrate that FBXO4 is a major regulator of ICAM-1 stability and that alterations in the stability of ICAM-1 can influence therapeutic outcome in metastatic cancer.

JMJD1C Ensures Mouse Embryonic Stem Cell Self-Renewal and Somatic Cell Reprogramming through Controlling MicroRNA Expression

The roles of histone demethylases (HDMs) for the establishment and maintenance of pluripotency are incompletely characterized. Here, we show that JmjC-domain-containing protein 1c (JMJD1C), an H3K9 demethylase, is required for mouse embryonic stem cell (ESC) self-renewal. Depletion of Jmjd1c leads to the activation of ERK/MAPK signaling and epithelial-to-mesenchymal transition (EMT) to induce differentiation of ESCs. Inhibition of ERK/MAPK signaling rescues the differentiation phenotype caused by Jmjd1c depletion. Mechanistically, JMJD1C, with the help of pluripotency factor KLF4, maintains ESC identity at least in part by regulating the expression of the miR-200 family and miR-290/295 cluster to suppress the ERK/MAPK signaling and EMT. Additionally, we uncover that JMJD1C ensures efficient generation and maintenance of induced pluripotent stem cells, at least partially through controlling the expression of microRNAs. Collectively, we propose an integrated model of epigenetic and transcriptional control mediated by the H3K9 demethylase for ESC self-renewal and somatic cell reprogramming.

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JMJD1C is required for the maintenance of ESC identity

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Depletion of Jmjd1c leads to the activation of ERK/MAPK signaling and EMT

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JMJD1C interplays with KLF4 to activate the expression of miR-200 family

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JMJD1C ensures efficient induction of pluripotency partially via miR-200 family

The LATS1 and LATS2 tumor suppressors: beyond the Hippo pathway

Proper cellular functionality and homeostasis are maintained by the convergent integration of various signaling cascades, which enable cells to respond to internal and external changes. The Dbf2-related kinases LATS1 and LATS2 (LATS) have emerged as central regulators of cell fate, by modulating the functions of numerous oncogenic or tumor suppressive effectors, including the canonical Hippo effectors YAP/TAZ, the Aurora mitotic kinase family, estrogen signaling and the tumor suppressive transcription factor p53. While the basic functions of the LATS kinase module are strongly conserved over evolution, the genomic duplication event leading to the emergence of two closely related kinases in higher organisms has increased the complexity of this signaling network. Here, we review the LATS1 and LATS2 intrinsic features as well as their reported cellular activities, emphasizing unique characteristics of each kinase. While differential activities between the two paralogous kinases have been reported, many converge to similar pathways and outcomes. Interestingly, the regulatory networks controlling the mRNA expression pattern of LATS1 and LATS2 differ strongly, and may contribute to the differences in protein binding partners of each kinase and in the subcellular locations in which each kinase exerts its functions.

microRNA-605 promotes cell proliferation, migration and invasion in non-small cell lung cancer by directly targeting LATS2

Lung cancer is the most common cause of cancer- associated mortality for men and women worldwide. An increasing number of studies have reported that the abnormal expression of microRNAs contributes to the pathogenesis of the majority of human cancer types, including non-small cell lung cancer (NSCLC). The present study aimed to measure microRNA-650 (miR-650) expression in NSCLC and evaluate its function in NSCLC cells. Reverse transcription-quantitative polymerase chain reaction was used to determine miR-650 expression in NSCLC tissue samples and cell lines. Assays for cell proliferation, migration and invasion were performed to investigate the roles of miR-650 on NSCLC progression. Furthermore, the mechanisms underlying the effects of miR-650 on NSCLC cell growth and metastasis were determined. In the current study, miR-650 was demonstrated to be highly expressed in NSCLC tissue samples and cell lines. Inhibition of expression of miR-650 suppressed NSCLC cell proliferation, migration and invasion in vitro. Additionally, large tumor suppressor kinase 2 (LATS2) was identified as a direct target gene of miR-650 in NSCLC. LATS2 was revealed to be significantly downregulated in NSCLC tissues and was negatively correlated with miR-650 expression. Notably, LATS2 re-expression decreased NSCLC cell proliferation, migration and invasion; similar to the effects induced by miR-650 underexpression. In conclusion, the results of the current study suggest that miR-650 may serve as an oncogene by direct targeting LATS2 in NSCLC formation and progression.

Snail acetylation by histone acetyltransferase p300 in lung cancer

Background

Epithelial to mesenchymal transition (EMT) is a complex and dynamic molecular event in lung cancer metastasis that has not yet been thoroughly investigated. EMT transcriptional factors, such as Snail, play a central role in regulation of the EMT process. In this study, we sought to identify an association between p300 and Snail in lung cancer, as well as the engagement of p300 in Snail acetylation.

Methods

We transfected p300 small interfering RNA into lung cancer cells to detect Snail and E‐cadherin expression levels by real time‐PCR. Immunoprecipitation assay was conducted to determine Snail acetylation in vivo. Bacteria‐expressed Snail was purified to analyze Snail acetylation in vitro. We further mutated lysine 187 for identifying acetylated residue in Snail.

Results

Snail transcription in lung cancer cells was repressed by p300 knockdown. E‐cadherin expression was increased by transfection of p300 small interfering RNA in a dose‐dependent manner. Immunoprecipitation and Western blot assay with anti‐acetylated lysine antibody were used to confirm that Snail was acetylated by p300. A sequence coding snail gene was cloned into glutathione S‐transferase‐tagged vector and the fusion protein was purified using glutathione. We observed Snail acetylation in vitro by incubation of recombinant Snail and p300 histone acetyltransferase domain with acetyl coenzyme A. The reduced Snail acetylation level was related to lysine mutation at position 187 of Snail.

Conclusion

There was a correlation between Snail and p300 expressions in lung cancer. Moreover, p300 acetylates Snail both in vivo and in vitro, and K187 may be involved in this modification.

The clinical significance and biological function of large tumour suppressor 2 in hepatocellular carcinoma

OBJECTIVES

Present evidence has suggested that large tumour suppressor 2 (LATS2) is abnormally expressed in most human cancer. However, the clinical and prognostic value in hepatocellular carcinoma (HCC) is still unknown.

MATERIALS AND METHODS

Large tumour suppressor 2 mRNA and protein expression levels in HCC tissues and cell lines were detected by qRT-PCR, immunohistochemistry or Western blot. The correlation between LATS2 expression and clinicopathological factors was analysed through immunohistochemistry. The function of LATS2 on HCC cell growth and mobility was explored through MTT, colony formation, Transwell migration and invasion assays. The molecular mechanism of LATS2 was screened and confirmed by qRT-PCR and Western blot.

RESULTS AND CONCLUSION

In this study, LATS2 mRNA and protein expressions were decreased in HCC tissues and cell lines compared with normal hepatic tissues and hepatic cell line. Low LATS2 expression was oppositely corrected with tumour stage, vascular invasion and metastasis. The univariate and multivariate analyses suggested that low LATS2 expression was an independent poor prognostic factor for HCC patients. The in vitro experiments showed that LATS2 regulated HCC cells migration and invasion, but had no effect on HCC cells proliferation. Meanwhile, LATS2 modulated metastasis-associated genes expression including E-cadherin, vimentin, snail, slug, MMP2 and MMP9. In conclusion, LATS2 is a prognostic biomarker and a tumour metastasis suppressor in HCC.

EMT: 2016

The significant parallels between cell plasticity during embryonic development and carcinoma progression have helped us understand the importance of the epithelial-mesenchymal transition (EMT) in human disease. Our expanding knowledge of EMT has led to a clarification of the EMT program as a set of multiple and dynamic transitional states between the epithelial and mesenchymal phenotypes, as opposed to a process involving a single binary decision. EMT and its intermediate states have recently been identified as crucial drivers of organ fibrosis and tumor progression, although there is some need for caution when interpreting its contribution to metastatic colonization. Here, we discuss the current state-of-the-art and latest findings regarding the concept of cellular plasticity and heterogeneity in EMT. We raise some of the questions pending and identify the challenges faced in this fast-moving field.

The regulation of snail: on the ubiquitin edge

Metastasis accounts for a majority of cancer death. One key feature during metastasis is epithelial-mesenchymal transition (EMT), which is regulated by transcription factors such as Snail and Twist. In non-malignant cells, Snail has a short half-life and is degraded via ubiquitination, but its stability is increased in cancer cell. However, the mechanism by which Snail escapes ubiquitination and degradation remains unknown. Recently, we found that Dub3 is a deubiquinase of Snail. Most importantly, we determined that Dub3 responded to extracellular signals such as IL-6, and that the resultant signaling prevented Snail degradation, and promoted cancer growth, invasion, and migration. In this highlight, we present a concise picture of how the transcription factor Snail is regulated by ubiquitination in cancer cells, the role of Dub3 in this process, and its potential use as a treatment target.

Tackling Cancer Stem Cells via Inhibition of EMT Transcription Factors

Cancer stem cell (CSC) has become recognized for its role in both tumorigenesis and poor patient prognosis in recent years. Traditional therapeutics are unable to effectively eliminate this group of cells from the bulk population of cancer cells, allowing CSCs to persist posttreatment and thus propagate into secondary tumors. The therapeutic potential of eliminating CSCs, to decrease tumor relapse, has created a demand for identifying mechanisms that directly target and eliminate cancer stem cells. Molecular profiling has shown that cancer cells and tumors that exhibit the CSC phenotype also express genes associated with the epithelial-to-mesenchymal transition (EMT) feature. Ample evidence has demonstrated that upregulation of master transcription factors (TFs) accounting for the EMT process such as Snail/Slug and Twist can reprogram cancer cells from differentiated to stem-like status. Despite being appealing therapeutic targets for tackling CSCs, pharmacological approaches that directly target EMT-TFs remain impossible. In this review, we will summarize recent advances in the regulation of Snail/Slug and Twist at transcriptional, translational, and posttranslational levels and discuss the clinical implication and application for EMT blockade as a promising strategy for CSC targeting.

TIP60 inhibits metastasis by ablating DNMT1-SNAIL2-driven epithelial-mesenchymal transition program

HIV-Tat-interacting protein of 60 kDa (TIP60) is a lysine acetyltransferase and known to be downregulated in multiple cancers. Among various signalling pathways, TIP60 is implicated in regulating epithelial-mesenchymal transition (EMT). Here, we show that TIP60 expression abrogates cell migration and metastatic potential of breast cancer cells using in vitro and in vivo models. Mechanistically, we show that this is through its ability to destabilize DNMT1 and inhibit SNAIL2 function (SNAIL2-mediated EMT/cell migration). Depletion of TIP60 stabilizes DNMT1 and increases SNAIL2 levels, resulting in EMT. Recruitment of DNMT1 to the SNAIL2 targets in the absence of TIP60 increases DNA methylation on their promoter region and further represses the expression of epithelial markers. In pathophysiological scenario, we find TIP60 to be significantly downregulated in breast cancer patients with poor overall survival and disease-free survival prognoses. These data suggest that levels of TIP60 can be a prognostic marker of breast cancer progression and stabilization of TIP60 could be a promising strategy to treat cancers.

The Hippo pathway, p53 and cholesterol

ASBTRACT Increased rates of cholesterol and lipid synthesis have long been recognized as important aspects of the metabolic rewiring that occurs during cancerous transformation. Many genes encoding enzymes involved in cholesterol and fatty acid biogenesis are transcriptional targets of the sterol regulatory element-binding proteins (SREBPs). The SREBPs act as a hub for metabolic and proliferation-related signals; their activity is the focus of a tug-of-war between tumor suppressors, who generally inhibit SREBP function, and oncogenes, who often promote, and rely on, SREBP activity. The Hippo pathway plays a central role in coordinating cell proliferation and organ size, whereas p53 is a crucial tumor suppressor that maintains metabolic homeostasis and orchestrates cellular stress responses. Together, the Hippo and p53 signaling pathways cooperate on multiple levels to fine-tune SREPB activity and regulate cholesterol/lipid levels. Cholesterol biosynthesis inhibitors such as statins are appealing conceptually, but have yet to show an indisputable effect on cancer development. Fortunately, the complex regulation surrounding the Hippo-p53-SREBP network potentially provides a broad interface for additional novel cancer-targeting interventions.

PAR1 participates in the ability of multidrug resistance and tumorigenesis by controlling Hippo-YAP pathway

The Hippo pathway significantly correlates with organ size control and tumorigenesis. The activity of YAP/TAZ, a transducer of the Hippo pathway, is required to sustain self-renewal and tumor-initiation capacities in cancer stem cells (CSCs). But, upstream signals that control the mammalian Hippo pathway have not been well understood. Here, we reveal a connection between the Protease-activated receptor 1 (PAR1) signaling pathway and the Hippo-YAP pathway in gastric cancer stem-like cells. The selective PAR1 agonist TFLLR-NH₂ induces an increase in the fraction of side population cells which is enriched in CSCs, and promotes tumorigenesis, multi cancer drug resistance, cell morphological change, and cell invasion which are characteristics of CSCs. In addition, PAR1 activation inhibits the Hippo-YAP pathway kinase Lats via Rho GTPase. Lats kinase inhibition in turn results in increased nuclear localization of dephosphorylated YAP. Furthermore, PAR1 activation confers CSCs related traits via the Hippo-YAP pathway, and the Hippo-YAP pathway correlates with epithelial mesenchymal transition which is induced by PAR1 activation. Our research suggests that the PAR1 signaling deeply participates in the ability of multi drug resistance and tumorigenesis through interactions with the Hippo-YAP pathway signaling in gastric cancer stem-like cells. We presume that inhibited YAP is a new therapeutic target in the treatment human gastric cancer invasion and metastasis by dysregulated PAR1 or its agonists. The Hippo pathway significantly correlates with organ size control and tumorigenesis. The activity of YAP/TAZ, a transducer of the Hippo pathway, is required to sustain self-renewal and tumor-initiation capacities in cancer stem cells (CSCs). But, upstream signals that control the mammalian Hippo pathway have not been well understood. Here, we reveal a connection between the Protease-activated receptor 1 (PAR1) signaling pathway and the Hippo-YAP pathway in gastric cancer stem-like cells. The selective PAR1 agonist TFLLR-NH₂ induces an increase in the fraction of side population cells which is enriched in CSCs, and promotes tumorigenesis, multi cancer drug resistance, cell morphological change, and cell invasion which are characteristics of CSCs. In addition, PAR1 activation inhibits the Hippo-YAP pathway kinase Lats via Rho GTPase. Lats kinase inhibition in turn results in increased nuclear localization of Dephosphorylated YAP. Furthermore, PAR1 activation confers CSCs related traits via the Hippo-YAP pathway, and the Hippo-YAP pathway correlates with epithelial mesenchymal transition which is induced by PAR1 activation. Our research suggests that the PAR1 signaling deeply participates in the ability of multi drug resistance and tumorigenesis through interactions with the Hippo-YAP pathway signaling in gastric cancer stem-like cells. We presume that inhibited YAP is a new therapeutic target in the treatment human gastric cancer invasion and metastasis by dysregulated PAR1 or its agonists.