Unraveling signalling cascades for the Snail family of transcription factors

Linking NLRP3 inflammasome and pulmonary fibrosis: mechanistic insights and promising therapeutic avenues

Pulmonary fibrosis is a devastating disorder distinguished by redundant inflammation and matrix accumulation in the lung interstitium. The early inflammatory cascade coupled with recurring tissue injury orchestrates a set of events marked by perturbed matrix hemostasis, deposition of matrix proteins, and remodeling in lung tissue. Numerous investigations have corroborated a direct correlation between the NLR family pyrin domain-containing 3 (NLRP3) activation and the development of pulmonary fibrosis. Dysregulated activation of NLRP3 within the pulmonary microenvironment exacerbates inflammation and may incite fibrogenic responses. Nevertheless, the precise mechanisms through which the NLRP3 inflammasome elicits pro-fibrogenic responses remain inadequately defined. Contemporary findings suggest that the pro-fibrotic consequences stemming from NLRP3 signaling primarily hinge on the action of interleukin-1β (IL-1β). IL-1β instigates IL-1 receptor signaling, potentiating the activity of transforming growth factor-beta (TGF-β). This signaling cascade, in turn, exerts influence over various transcription factors, including SNAIL, TWIST, and zinc finger E-box-binding homeobox 1 (ZEB 1/2), which collectively foster myofibroblast activation and consequent lung fibrosis. Here, we have connected the dots to illustrate how the NLRP3 inflammasome orchestrates a multitude of signaling events, including the activation of transcription factors that facilitate myofibroblast activation and subsequent lung remodeling. In addition, we have highlighted the prominent role played by various cells in the formation of myofibroblasts, the primary culprit in lung fibrosis. We also provided a concise overview of various compounds that hold the potential to impede NLRP3 inflammasome signaling, thus offering a promising avenue for the treatment of pulmonary fibrosis.

METFORMIN MITIGATES SEPSIS-ASSOCIATED PULMONARY FIBROSIS BY PROMOTING AMPK ACTIVATION AND INHIBITING HIF-1α-INDUCED AEROBIC GLYCOLYSIS

ABSTRACT

Recent research has revealed that aerobic glycolysis has a strong correlation with sepsis-associated pulmonary fibrosis (PF). However, at present, the mechanism and pathogenesis remain unclear. We aimed to test the hypothesis that the adenosine monophosphate-activated protein kinase (AMPK) activation and suppression of hypoxia-inducible factor 1α (HIF-1α)-induced aerobic glycolysis play a central role in septic pulmonary fibrogenesis. Cellular experiments demonstrated that lipopolysaccharide increased fibroblast activation through AMPK inactivation, HIF-1α induction, alongside an augmentation of aerobic glycolysis. By contrast, the effects were reversed by AMPK activation or HIF-1α inhibition. In addition, pretreatment with metformin, which is an AMPK activator, suppresses HIF-1α expression and alleviates PF associated with sepsis, which is caused by aerobic glycolysis, in mice. Hypoxia-inducible factor 1α knockdown demonstrated similar protective effects in vivo . Our research implies that targeting AMPK activation and HIF-1α-induced aerobic glycolysis with metformin might be a practical and useful therapeutic alternative for sepsis-associated PF.

Characterizing the SREB G protein-coupled receptor family in fish: Brain gene expression and genomic differences in upstream transcription factor binding sites

The SREB (Super-conserved Receptors Expressed in Brain) family of orphan G protein-coupled receptors is highly conserved in vertebrates and consists of three members: SREB1 (orphan designation GPR27), SREB2 (GPR85), and SREB3 (GPR173). SREBs are associated with processes ranging from neuronal plasticity to reproductive control. Relatively little is known about similarities across the entire family, or how mammalian gene expression patterns compare to non-mammalian vertebrates. In fish, this system may be particularly complex, as some species have gained a fourth member (SREB3B) while others have lost genes. To better understand the system, the present study aimed to: 1) use qPCR to characterize sreb and related gene expression patterns in the brains of three fish species with different systems, and 2) identify possible differences in transcriptional regulation among the receptors, using upstream transcription factor binding sites across 70 ray-finned fish genomes. Overall, regional patterns of sreb expression were abundant in forebrain-related areas. However, some species-specific patterns were detected, such as abundant expression of receptors in zebrafish (Danio rerio) hypothalamic-containing sections, and divergence between sreb3a and sreb3b in pufferfish (Dichotomyctere nigroviridis). In addition, a gene possibly related to the system (dkk3a) was spatially correlated with the receptors in all three species. Genomic regions upstream of sreb2 and sreb3b, but largely not sreb1 or sreb3a, contained many highly conserved transcription factor binding sites. These results provide novel information about expression differences and transcriptional regulation across fish that may inform future research to better understand these receptors.

Cancer metastasis: Molecular mechanisms and clinical perspectives

Metastatic progression combined with non-responsiveness towards systemic therapy often shapes the course of disease for cancer patients and commonly determines its lethal outcome. The complex molecular events that promote metastasis are a combination of both, the acquired pro-metastatic properties of cancer cells and a metastasis-permissive or -supportive tumor micro-environment (TME). Yet, dissemination is a challenging process for cancer cells that requires a series of events to enable cancer cell survival and growth. Metastatic cancer cells have to initially detach themselves from primary tumors, overcome the challenges of their intravasal journey and colonize distant sites that are suited for their metastases. The implicated obstacles including anoikis and immune surveillance, can be overcome by intricate intra- and extracellular signaling pathways, which we will summarize and discuss in this review. Further, emerging modulators of metastasis, like the immune-microenvironment, microbiome, sublethal cell death engagement, or the nervous system will be integrated into the existing working model of metastasis.

Expression of Snail and Twist compared with clinical and pathological parameters in patients with gastric cancer

INTRODUCTION

Epithelial-mesenchymal transition (EMT) is a process of change in the cellular phenotype from epithelial to mesenchymal morphology. The changes at the cellular level can explain the great heterogeneity and plasticity in the different histological subtypes of gastric carcinomas, which causes difficulties in therapy. In it, epithelial cells reduce intercellular adhesion, which is crucial in the process of invasion and metastasis of gastric carcinomas. Inhibition of cell adhesion molecules such as E-cadherin is known to be influenced by a number of transcription factors, such as Snail and Twist.

Prenatal stress induces changes in PAR2- and M3-dependent regulation of colon primitive cells

Prenatal stress is associated with a high risk of developing adult intestinal pathologies, such as irritable bowel syndrome, chronic inflammation, and cancer. Although epithelial stem cells and progenitors have been implicated in intestinal pathophysiology, how prenatal stress could impact their functions is still unknown. We have investigated the proliferative and differentiation capacities of primitive cells using epithelial crypts isolated from colons of adult male and female mice whose mothers have been stressed during late gestation. Our results show that stem cell/progenitor proliferation and differentiation in vitro are negatively impacted by prenatal stress in male progeny. This is promoted by a reinforcement of the negative proliferative/differentiation control by the protease-activated receptor 2 (PAR2) and the muscarinic receptor 3 (M3), two G protein-coupled receptors present in the crypt. Conversely, prenatal stress does not change in vitro proliferation of colon primitive cells in female progeny. Importantly, this maintenance is associated with a functional switch in the M3 negative control of colonoid growth, becoming proliferative after prenatal stress. In addition, the proliferative role of PAR2 specific to females is maintained under prenatal stress, even though PAR2-targeted stress signals Dusp6 and activated GSK3β are increased, reaching the levels of males. An epithelial serine protease could play a critical role in the activation of the survival kinase GSK3β in colonoids from prenatally stressed female progeny. Altogether, our results show that following prenatal stress, colon primitive cells cope with stress through sexually dimorphic mechanisms that could pave the way to dysregulated crypt regeneration and intestinal pathologies.NEW & NOTEWORTHY Primitive cells isolated from mouse colon following prenatal stress and exposed to additional stress conditions such as in vitro culture, present sexually dimorphic mechanisms based on PAR2- and M3-dependent regulation of proliferation and differentiation. Whereas prenatal stress reinforces the physiological negative control exerted by PAR2 and M3 in crypts from males, in females, it induces a switch in M3- and PAR2-dependent regulation leading to a resistant and proliferative phenotype of progenitor.

Vitamin D resistant genes - promising therapeutic targets of chronic diseases

Vitamin D is an essential vitamin indispensable for calcium and phosphate metabolism, and its deficiency has been implicated in several extra-skeletal pathologies, including cancer and chronic kidney disease. Synthesized endogenously in the layers of the skin by the action of UV-B radiation, the vitamin maintains the integrity of the bones, teeth, and muscles and is involved in cell proliferation, differentiation, and immunity. The deficiency of Vit-D is increasing at an alarming rate, with nearly 32% of children and adults being either deficient or having insufficient levels. This has been attributed to Vit-D resistant genes that cause a reduction in circulatory Vit-D levels through a set of signaling pathways. CYP24A1, SMRT, and SNAIL are three genes responsible for Vit-D resistance as their activity either lowers the circulatory levels of Vit-D or reduces its availability in target tissues. The hydroxylase CYP24A1 inactivates analogs and prohormonal and/or hormonal forms of calcitriol. Elevation of the expression of CYP24A1 is the major cause of exacerbation of several diseases. CYP24A1 is rate-limiting, and its induction has been correlated with increased prognosis of diseases, while loss of function mutations cause hypersensitivity to Vit-D. The silencing mediator of retinoic acid and thyroid hormone receptor (SMRT) and its corepressor are involved in the transcriptional repression of VDR-target genes. SNAIL1 (SNAIL), SNAIL2 (Slug), and SNAIL3 (Smuc) are involved in transcriptional repression and binding to histone deacetylases and methyltransferases in addition to recruiting polycomb repressive complexes to the target gene promoters. An inverse relationship between the levels of calcitriol and the epithelial-to-mesenchymal transition is reported. Studies have demonstrated a strong association between Vit-D deficiency and chronic diseases, including cardiovascular diseases, diabetes, cancers, autoimmune diseases, infectious diseases, etc. Vit-D resistant genes associated with the aforementioned chronic diseases could serve as potential therapeutic targets. This review focuses on the basic structures and mechanisms of the repression of Vit-D regulated genes and highlights the role of Vit-D resistant genes in chronic diseases.

Influence of sphingomyelin metabolism during epithelial-mesenchymal transition associated with aging in the renal papilla

The renal collecting ducts (CD) are formed by a fully differentiated epithelium, and their tissue organization and function require the presence of mature cell adhesion structures. In certain circumstances, the cells can undergo de-differentiation by a process called epithelial-mesenchymal transition (EMT), in which the cells lose their epithelial phenotype and acquire the characteristics of the mesenchymal cells, which includes loss of cell-cell adhesion. We have previously shown that in renal papillary CD cells, cell adhesion structures are located in sphingomyelin (SM)-enriched plasma membrane microdomains and the inhibition of SM synthase 1 activity induced CD cells to undergo an EMT process. In the present study, we evaluated the influence of SM metabolism during the EMT of the cells that form the CD of the renal papilla during aging. To this end, primary cultures of renal papillary CD cells from young, middle-, and aged-rats were performed. By combining biochemical and immunofluorescence studies, we found experimental evidence that CD cells undergo an increase in spontaneous and reversible EMT during aging and that at least one of the reasons for this phenomenon is the decrease in SM content due to the combination of decreased SM synthase activity and an increase in SM degradation mediated by neutral sphingomyelinase. Age is a risk factor for many diseases, among which renal fibrosis is included. Our findings highlight the importance of sphingolipids and particularly SM as a modulator of the fate of CD cells and probably contribute to the development of treatments to avoid or reverse renal fibrosis during aging.

3D genome organization in the epithelial-mesenchymal transition spectrum

Background

The plasticity along the epithelial-mesenchymal transition (EMT) spectrum has been shown to be regulated by various epigenetic repertoires. Emerging evidence of local chromatin conformation changes suggests that regulation of EMT may occur at a higher order of three-dimensional genome level.

Results

We perform Hi-C analysis and combine ChIP-seq data across cancer cell lines representing different EMT states. We demonstrate that the epithelial and mesenchymal genes are regulated distinctively. We find that EMT genes are regulated within their topologically associated domains (TADs), with only a subset of mesenchymal genes being influenced by A/B compartment switches, indicating topological remodeling is required in the transcriptional regulation of these genes. At the TAD level, epithelial and mesenchymal genes are associated with different regulatory trajectories. The epithelial gene-residing TADs are enriched with H3K27me3 marks in the mesenchymal-like states. The mesenchymal gene-residing TADs, which do not show enrichment of H3K27me3 in epithelial-like states, exhibit increased interaction frequencies with regulatory elements in the mesenchymal-like states.

Conclusions

We propose a novel workflow coupling immunofluorescence and dielectrophoresis to unravel EMT heterogeneity at single-cell resolution. The predicted three-dimensional structures of chromosome 10, harboring Vimentin, identify cell clusters of different states. Our results pioneer a novel avenue to decipher the complexities underlying the regulation of EMT and may infer the barriers of plasticity in the 3D genome context.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13059-022-02687-x.

A novel role of snail in regulating tuberin/AMPK pathways to promote renal fibrosis in the new mouse model of type II diabetes

Epithelial-mesenchymal transition (EMT) plays an important role in tissue fibrosis following chronic exposure to hyperglycemia. This study investigates the role of chronic diabetes in regulating tuberin/snail/AMPK to enhance EMT and increase renal fibrosis. A new mouse model of db/db/TSC2 ^+/- was generated by backcrossing db/db mice and TSC2 ^+/- mice. Wild type (WT), db/db, TSC2 ^+/- and dbdb/TSC2 ^+/- mice were sacrificed at ages 6 and 8 months old. Tuberin protein level was significantly decreased in kidneys from diabetic compared to WT mice at both ages. In addition, tuberin and E-cadherin protein levels were significantly decreased in dbdb/TSC2 ^+/- compared to TSC2 ^+/- and db/db mice. In contrast, p-PS6K, NFkB, snail, vimentin, fibronectin, and α-SMA protein levels were significantly increased in dbdb/TSC2 ^+/- compared to db/db and TSC2 ^+/- mice at ages 6 and 8 months. Both downregulation of AMPK by DN-AMPK and downregulation of tuberin by siRNA resulted in increased NFkB, snail, and fibronectin protein expression and decreased E-cadherin protein expression in mouse primary renal proximal tubular cells. Interestingly, downregulation of snail by siRNA increased tuberin expression via feedback through activation of AMPK and reversed the expression of epithelial proteins such as E-cadherin as well as mesenchymal proteins such as fibronectin, NF-KB, vimentin, and α-SMA in mouse primary renal proximal tubular cells isolated from kidneys of four mice genotypes. The data show that chronic diabetes significantly decreases tuberin expression and that provides strong evidence that tuberin is a major key protein involved in regulating EMT. These data also demonstrated a novel role for snail in regulating of AMPK/tuberin to enhance EMT and renal cell fibrosis in diabetes.

TNF-α augments CXCL10/CXCR3 axis activity to induce Epithelial-Mesenchymal Transition in colon cancer cell

Chronic inflammation-induced metastases have long been regarded as one of the significant obstacles in treating cancer. Tumor necrosis factor-α (TNF-α), a main inflammation mediator within tumor microenvironment, affects tumor development by inducing multiple chemokines to establish a complex network. Recent reports have revealed that CXCL10/CXCR3 axis affects cancer cells invasiveness and metastases, and Epithelial-mesenchymal transition (EMT) is the main reason for frequent proliferation and distant organ metastases of colon cancer (CC) cells, However, it is unclear whether TNF-α- mediated chronic inflammation can synergically enhance EMT-mediated CC metastasis through promoting chemokine expression. According to this study, TNF-α activated the PI3K/Akt and p38 MAPK parallel signal transduction pathways, then stimulate downstream NF-κB pathway p65 into the nucleus to activate CXCL10 transcription. CXCL10 enhanced the metastases of CC-cells by triggering small GTPases such as RhoA and cdc42. Furthermore, overexpression of CXCL10 significantly enhanced tumorigenicity and mobility of CC cells in vivo. We further clarified that CXCL10 activated the PI3K/Akt pathway through CXCR3, resulting in suppression of GSK-3β phosphorylation and leading to upregulation of Snail expression, thereby regulating EMT in CC cells. These outcomes lay the foundation for finding new targets to inhibit CC metastases.

Olig2 regulates p53-mediated apoptosis, migration and invasion of melanoma cells

Melanoma is a disease with a high recurrence rate and poor prognosis; therefore, the need for targeted therapeutics is steadily increasing. Oligodendrocyte transcription factor2 (Olig2) is a basic helix-loop-helix transcription factor that is expressed in the central nervous system during embryonic development. Olig2 is overexpressed in various malignant cell lines such as lung carcinoma, glioma and melanoma. Olig2 is known as a key transcription factor that promotes tumor growth in malignant glioma. However, the role of Olig2 in melanoma is not well characterized. We analyzed the role of Olig2 in apoptosis, migration, and invasion of melanoma cells. We confirmed that Olig2 was overexpressed in melanoma cells and tissues. Reduction of Olig2 increased apoptosis in melanoma cells by increasing p53 level and caspase-3/-7 enzyme activity. In addition, downregulation of Olig2 suppressed migration and invasion of melanoma cells by inhibiting EMT. Reduction of Olig2 inhibited expression of MMP-1 and the enzyme activity of MMP-2/-9 induced by TGF-β. Moreover, Olig2 was involved in the downstream stages of MEK/ERK and PI3K/AKT, which are major signaling pathways in metastatic progression of melanoma. In conclusion, this study demonstrated the crucial roles of Olig2 in apoptosis, migration, and invasion of melanoma and may help to further our understanding of the relationship between Olig2 and melanoma progression.

Impact of Selected Signaling Proteins on SNAIL 1 and SNAIL 2 Expression in Ovarian Cancer Cell Lines in Relation to Cells' Cisplatin Resistance and EMT Markers Level

It has been increasingly recognized that SNAIL1 and SNAIL2, as major EMT-inducers, might also be involved in drug resistance of cancer cells. We sought to determine a relation between SNAIL1/2, E-cadherin and N-cadherin expression, as well as ovarian cancer cells’ resistance to cisplatin and EMT markers’ level. Thus, four ovarian cancer cell lines, were used: A2780, A2780cis, SK-OV-3 and OVCAR-3. We assessed the impact of ERK1/2, AKT and STAT3 proteins (chosen by the profiling activity of over 40 signaling proteins) on SNAIL1/2 expression, along with E-cadherin and N-cadherin levels. We showed that expression of SNAIL1 and N-cadherin are the highest in cisplatin-resistant A2780cis and SK-OV-3 cells, while high SNAIL2 and E-cadherin levels were observed in cisplatin-sensitive A2780 cells. The highest E-cadherin level was noticed in OVCAR-3 cells. SNAIL1/2 expression was dependent on ERK1/2 activity in cisplatin-resistant and potentially invasive SK-OV-3 and OVCAR-3 cells. STAT-3 regulates expression of SNAIL1/2 and leads to the so-called “cadherin switch” in cancer cells, independently of their chemoresistance. In conclusion, SNAIL1, but not SNAIL2, seems to be involved in ovarian cancer cells’ cisplatin resistance. STAT3 is a universal factor determining the expression of SNAIL1/2 in ovarian cancer cells regardless of their chemoresitance or invasive capabilities.

The New Model of Snail Expression Regulation: The Role of MRTFs in Fast and Slow Endothelial-Mesenchymal Transition

Endothelial–mesenchymal transition (EndMT) is a crucial phenomenon in regulating the development of diseases, including cancer metastasis and fibrotic disorders. The primary regulators of disease development are zinc-finger transcription factors belonging to the Snail family. In this study, we characterized the myocardin-related transcription factor (MRTF)-dependent mechanisms of a human snail promoter regulation in TGF-β-stimulated human endothelial cells. Although in silico analysis revealed that the snail promoter’s regulatory fragment contains one GCCG and two SP1 motifs that could be occupied by MRTFs, the genetic study confirmed that MRTF binds only to SP1 sites to promote snail expression. The more accurate studies revealed that MRTF-A binds to both SP1 elements, whereas MRTF-B to only one (SP1near). Although we found that each MRTF alone is capable of inducing snail expression, the direct cooperation of these proteins is required to reinforce snail expression and promote the late stages of EndMT within 48 hours. Furthermore, genetic and biochemical analysis revealed that MRTF-B alone could induce the late stage of EndMT. However, it requires a prolonged time. Therefore, we concluded that MRTFs might cause EndMT in a fast- and slow-dependent manner. Based on MRTF-dependent Snail upregulation, we recognized that TGF-β1, as an MRTF-B regulator, is involved in slow EndMT induction, whereas TGF-β2, which altered both MRTF-A and MRTF-B expression, promotes a fast EndMT process.

Nodakenin alleviated obstructive nephropathy through blunting Snail1 induced fibrosis

Tubulointerstitial fibrosis plays an important role in end‐stage renal failure, and there are only limited therapeutic options available to preserve organ function. In the present study, we identified that nodakenin, a coumarin isolated from the roots of Angelicae gigas, functions effectively against unilateral ureteral obstruction (UUO)‐induced fibrosis via down‐regulating Snail1 expression. We established UUO‐induced renal fibrosis in mice and then administered with nodakenin orally ata a dose of 1 and 10 mg/kg. The in‐vivo results indicated that nodakenin protected obstructive nephropathy through its anti‐inflammatory and anti‐fibrotic properties. Nodakenin prevented the infiltration of inflammatory cells, alleviated the levels of pro‐inflammatory cytokines, reduced the polarization of macrophages and down‐regulating the aberrant deposition of extracellular matrix at the site of injury. Of note, nodakenin dramatically impeded Smad3, NF‐κB p65 phosphorylation and Snail1 expression. In line with in vivo studies, nodakenin suppressed the expression of Snail1, Smad3 phosphorylation and fibrogenesis in TGF‐β1‐treated renal epithelial cells in‐vitro. Furthermore, we found that the effect of nodaknin against fibrosis was reversed in Snail1 overexpressing cells, whereas nodakenin could not further reduce expression of fibrogenesis in Snail1 silenced cells, suggesting that nodaknein may function through a Snail1‐dependent manner. Collectively, this study reveal a critical role of nodakenin in the cure of renal fibrosis.

Long Noncoding RNA NEAT1 Regulates TGF-β2-Induced Epithelial-Mesenchymal Transition of Lens Epithelial Cells through the miR-34a/Snail1 and miR-204/Zeb1 Pathways

The aim of this study was to explore whether the long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1)/miR-34a/Snail1 and NEAT1/miR-204/Zeb1 pathways are involved in epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs). Primary human LECs (HLECs) were separated and cultured. Our results identified that TGF-β2 induces NEAT1 overexpression in a dose-dependent manner and a time-dependent manner. Additionally, TGF-β2 induced downregulation of E-cadherin and upregulation of fibronectin in primary HLECs through a NEAT1-dependent mechanism. Microarray analysis showed that NEAT1 overexpression inhibited the miR-34a and miR-204 levels in the LECs. The expression of miR-34a and miR-204 was decreased, and the levels of Snail1 and Zeb1 were elevated in human posterior capsule opacification- (PCO-) attached LECs and the LECs obtained from anterior subcapsular cataract (ASC) by quantitative RT-PCR (qRT-PCR). Mechanistic studies revealed that NEAT1 negatively regulates miR-34a or miR-204, and miR-34a or miR-204 directly targets Snail1 or Zeb1 by luciferase assay and RNA-binding protein immunoprecipitation assay, respectively. Overall, the NEAT1/miR-34a/Snail1 and NEAT1/miR-204/Zeb1 pathways are involved in TGF-β2-induced EMT of HLECs. In summary, TGF-β2 induces NEAT1 overexpression, which in turn suggests that NEAT1 acts as a ceRNA targeting Snail1 or Zeb1 by binding miR-34a or miR-204, and promotes the progression of EMT of LECs.

Combined Snail and E-cadherin Predicts Overall Survival of Cervical Carcinoma Patients: Comparison Among Various Epithelial-Mesenchymal Transition Proteins

Background

Activation of Snail and synergistic loss of E-cadherin are hallmark features of the epithelial-mesenchymal transition (EMT), which contributes to the metastasis phenotype of epithelial cancer cells. However, the prognostic impact of Snail and of its combination with E-cadherin and with other EMT prognostic markers has not yet been systematically studied in cervical carcinoma. This study aimed to explore the prognostic value of combined Snail and E-cadherin in patients with cervical carcinoma and compared it to the prognostic value of other EMT prognostic markers.

Methods

We retrospectively identified every initial diagnosis of cervical carcinoma among 203 patients treated at our hospital in China from January 2008 to March 2013. We examined the prognostic significance of Snail and other EMT protein markers, such as E-cadherin, Slug, ZEB1, Twist, Vimentin, and Survivin, by univariate and multivariate survival analyses.

Results

Multivariate analyses showed that Snail and E-cadherin were significant biomarkers for overall survival (OS) in cervical carcinoma patients (HR, hazard ratio = 1.744, P = 0.036 and HR = 1.738, P = 0.047; respectively). Moreover, a combined index including Snail and E-cadherin showed enhanced prognostic value compared to that of Snail or E-cadherin alone. The present data demonstrate that Snail shows a negative correlation with E-cadherin (P < 0.001). High Snail expression and low E-cadherin expression were also more common in high tumor stages (P = 0.044 and P = 0.036; respectively), and lymph node metastasis (both P < 0.001). Moreover, Snail was a superior prognosis factor compared to Slug, ZEB1, Twist, Vimentin, and Survivin in cervical carcinoma.

Conclusion

Based on our results, Snail and E-cadherin may be considered as independent prognosis markers, and the combination of Snail and E-cadherin might improve the OS prediction accuracy for patients with cervical carcinoma.

Interplay among SNAIL Transcription Factor, MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Regulation of Tumor Growth and Metastasis

SNAIL (SNAI1) is a zinc finger transcription factor that binds to E-box sequences and regulates the expression of genes. It usually acts as a gene repressor, but it may also activate the expression of genes. SNAIL plays a key role in the regulation of epithelial to mesenchymal transition, which is the main mechanism responsible for the progression and metastasis of epithelial tumors. Nevertheless, it also regulates different processes that are responsible for tumor growth, such as the activity of cancer stem cells, the control of cell metabolism, and the regulation of differentiation. Different proteins and microRNAs may regulate the SNAIL level, and SNAIL may be an important regulator of microRNA expression as well. The interplay among SNAIL, microRNAs, long non-coding RNAs, and circular RNAs is a key event in the regulation of tumor growth and metastasis. This review for the first time discusses different types of regulation between SNAIL and non-coding RNAs with a focus on feedback loops and the role of competitive RNA. Understanding these mechanisms may help develop novel therapeutic strategies against cancer based on microRNAs.

Anti-cancer effects of ethanol extract of Reynoutria japonica Houtt. radix in human hepatocellular carcinoma cells via inhibition of MAPK and PI3K/Akt signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Reynoutria japonica Houtt. has been used as a traditional medicine of cancer in East Asia for thousands of years. However, the mechanism of the anti-cancer effect of R. japonica has not been investigated at the molecular level. The regulation of intracellular signaling pathways by the extract of R. japonica radix needs to be evaluated for a deeper understanding and application of the anti-cancer effect of R. japonica radix.

AIM OF THE STUDY

The purpose of this study was to evaluate the inhibitory effects of the ethanol extracts of R. japonica radix (ERJR) on cancer metastasis and the regulation mechanism of metastasis by ERJR in human hepatocellular carcinomas.

MATERIALS AND METHODS

Suppression of cancer metastasis by ERJR in SK-Hep1 and Huh7 cells were investigated. Prior to experiments, the cytotoxic effect of ERJR was examined by cell viability assays. To evaluate the inhibitory effects of ERJR on cancer metastasis, wound-healing assays, invasion assays, zymography, and multicellular tumor spheroids (MCTS) assays were performed. Molecular mechanisms in the suppressive regulation of metastasis by ERJR were verified by measuring the expression levels of metastatic markers, and the phosphorylation and protein levels of cancer metastasis-related signaling pathways.

RESULTS

In all experiments, ERJR was used at a maximum concentration of 20 μg/ml, which did not show cytotoxicity in SK-Hep1 and Huh7 cells. We examined the inhibitory effects of ERJR on cancer metastasis. In wound-healing and invasion assays, ERJR treatment effectively suppressed the wound-recovery of Huh7 cells and inhibited the invasion ability of SK-Hep1 cells. Also, ERJR treatment significantly decreased the enzymatic activity of matrix metalloproteinase-2 and -9 in SK-Hep1 cells. ERJR suppressed the growth of MCTS in SK-Hep1 cells in a dose-dependent manner. These results indicated that ERJR effectively inhibited the invasive and proliferative ability of SK-Hep1 and Huh7 cells. Moreover, ERJR treatment reduced the expression levels of Snail1, Twist1, N-cadherin, and Vimentin, which are metastatic markers, by inhibiting the activation of protein kinase B and mitogen-activated protein kinases in SK-Hep1 cells.

CONCLUSIONS

These results verified the molecular mechanism of ERJR that has been used in traditional anti-cancer remedy and suggest that it can be developed as a promising therapy for cancer metastasis in the future.

Epidermal Growth Factor Potentiates Migration of MDA-MB 231 Breast Cancer Cells by Increasing NaV1.5 Channel Expression

INTRODUCTION

Breast cancer is one of the leading causes of death worldwide and is the result of dysregulation of various signaling pathways in mammary epithelial cells. The mortality rate in patients suffering from breast cancer is high because the tumor cells have a prominent invasive capacity towards the surrounding tissues. Previous studies carried out in tumor cell models show that voltage-gated ion channels may be important molecular actors that contribute to the migratory and invasive capacity of the tumor cells.

METHODS

In this study, by using an experimental strategy that combines cell and molecular biology assays with electrophysiological recording, we sought to determine whether the voltage-dependent sodium channel NaV1.5 regulates the migratory capacity of the human breast cancer cell line MDA-MB 231, when cells are maintained in the presence of epidermal growth factor (EGF), as an inductor of the epithelial-mesenchymal transition.

RESULTS

Our data show that EGF stimulates the migratory capacity of MDA-MB 231 cells, by regulating the functional expression of NaV1.5 channels. Consistent with this, the stimulatory actions of the growth factor were prevented by the use of tetrodotoxin, an Na+ channel selective blocker, as well as by resveratrol, an antioxidant that can also affect Na+ channel activity.

DISCUSSION

The understanding of molecular mechanisms, such as the EGF pathway in the progression of breast cancer is fundamental for the design of more effective therapeutic strategies for the disease.

Gene therapy and cell therapy for the management of radiation damages to healthy tissues: Rationale and early results

Nowadays, ionizing radiations have numerous applications, especially in medicine for diagnosis and therapy. Pharmacological radioprotection aims at increasing detoxification of free radicals. Radiomitigation aims at improving survival and proliferation of damaged cells. Both strategies are essential research area, as non-contained radiation can lead to harmful effects. Some advances allowing the comprehension of normal tissue injury mechanisms, and the discovery of related predictive biomarkers, have led to developing several highly promising radioprotector or radiomitigator drugs. Next to these drugs, a growing interest does exist for biotherapy in this field, including gene therapy and cell therapy through mesenchymal stem cells. In this review article, we provide an overview of the management of radiation damages to healthy tissues via gene or cell therapy in the context of radiotherapy. The early management aims at preventing the occurrence of these damages before exposure or just after exposure. The late management offers promises in the reversion of constituted late damages following irradiation.

SNAI1 recruits HDAC1 to suppress SNAI2 transcription during epithelial to mesenchymal transition

Aberrant activation of epithelial to mesenchymal transition (EMT) associated factors were highly correlated with increased mortality in cancer patients. SNAIL family of transcriptional repressors comprised of three members, each of which were essentially associated with gastrulation and neural crest formation. Among which, SNAI1 and SNAI2 were efficiently induced during EMT and their expressions were correlated with poor clinical outcome in patients with breast, colon and ovarian carcinoma. In an ovarian cancer cell lines panel, we identified that SNAI1 and SNAI2 expressions were mutually exclusive, where SNAI1 predominantly represses SNAI2 expression. Detailed analysis of SNAI2 promoter region revealed that SNAI1 binds to two E-box sequences that mediated transcriptional repression. Through epigenetic inhibitor treatments, we identified that inhibition of histone deacetylase (HDAC) activity in SNAI1 overexpressing cells partially rescued SNAI2 expression. Importantly, we demonstrated a significant deacetylation of histone H3 and significant enrichments of HDAC1 and HDAC2 corepressors in both E-box regions of SNAI2 promoter. Our results suggested that SNAI1 repression on SNAI2 expression was predominantly mediated through the recruitment of the histone deacetylation machinery. Utilization of HDAC inhibitors would require additional profiling of SNAI1 activity and combined targeting of SNAI1 and HDACs might render efficient cancer treatment.

Cirsiliol Suppressed Epithelial to Mesenchymal Transition in B16F10 Malignant Melanoma Cells through Alteration of the PI3K/Akt/NF-κB Signaling Pathway

Malignant melanoma is a highly aggressive form of skin cancer which has a propensity for metastasis. Epithelial mesenchymal transition (EMT) plays a primordial role in the progression of metastatic disease. Metastatic melanoma is resistant to conventional therapies. Hence, researchers have been exploring alternative approaches, including the utility of bioactive phytochemicals to manage metastatic disease. In the present study, we investigated the potential of cirsiliol, a flavonoid isolated from Centaurea jacea L., in modulating the aggressive behavior of B16F10 metastatic melanoma cells, including EMT, and associated molecular mechanisms of action. Cirsiliol was found to be effective in restraining the colony formation and migration of fibronectin-induced B16F10 metastatic melanoma cells. Cirsiliol inhibited the activity and expression of matrix metalloproteinase-9 (MMP-9). Cirsiliol also suppressed the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (also known as Akt)/nuclear factor-κB (NF-κB) signaling pathway which, in turn, caused upregulation of E-cadherin and downregulation of N-cadherin, Snail and Twist. Based on these results, cirsiliol may be considered a promising compound against EMT in the therapeutic management of malignant melanoma.

Signaling Pathways Induced by Leptin during Epithelial⁻Mesenchymal Transition in Breast Cancer

Leptin is an adipokine that is overexpressed in obese and overweight people. Interestingly, women with breast cancer present high levels of leptin and of its receptor ObR. Leptin plays an important role in breast cancer progression due to the biological processes it participates in, such as epithelial⁻mesenchymal transition (EMT). EMT consists of a series of orchestrated events in which cell⁻cell and cell⁻extracellular matrix interactions are altered and lead to the release of epithelial cells from the surrounding tissue. The cytoskeleton is also re-arranged, allowing the three-dimensional movement of epithelial cells into the extracellular matrix. This transition provides cells with the ability to migrate and invade adjacent or distal tissues, which is a classic feature of invasive or metastatic carcinoma cells. In recent years, the number of cases of breast cancer has increased, making this disease a public health problem worldwide and the leading cause of death due to cancer in women. In this review, we focus on recent advances that establish: (1) leptin as a risk factor for the development of breast cancer, and (2) leptin as an inducer of EMT, an event that promotes tumor progression.

PCP4/PEP19 promotes migration, invasion and adhesion in human breast cancer MCF-7 and T47D cells

Purkinje cell protein (PCP) 4/peptide (PEP) 19 is expressed in Purkinje cells where it has a calmodulin-binding, anti-apoptotic function. We recently demonstrated that PCP4/PEP19 is expressed and inhibit apoptosis in human breast cancer cell lines. In the present study we investigated the role of PCP4/PEP19 in cell morphology, adhesion, migration, and invasion in MCF-7 and T47D human breast cancer cell lines. Knockdown of PCP4/PEP19 reduced the formation of filopodia-like cytoplasmic structures and vinculin expression, and enhanced E-cadherin expression. Activities of migration, invasion, and cell adhesion were also decreased after the knockdown of PCP4/PEP19 in MCF-7 and T47D cells. These results suggested that PCP4/PEP19 promotes cancer cell adhesion, migration, and invasion and that PCP4/PEP19 may be a potential target for therapeutic agents in breast cancer treatment which act by inhibiting epithelial-mesenchymal transition and enhancing apoptotic cell death.

Differential expression profiles of conserved Snail transcription factors in the mouse testis

Snail transcription factors are key regulators of cellular transitions during embryonic development and tumorigenesis. The closely related SNAI1 and SNAI2 proteins induce epithelial-mesenchymal transitions (EMTs), acting predominantly as transcriptional repressors, while the functions of SNAI3 are unknown. An initial examination of Snai2-deficient mice provided evidence of deficient spermatogenesis. To address the hypothesis that Snail proteins are important for male fertility, this study provides the first comprehensive cellular expression profiles of all three mammalian Snail genes in the post-natal mouse testis. To evaluate Snail transcript expression profiles, droplet digital (dd) PCR and in situ hybridization were employed. Snai1, 2 and 3 transcripts are readily detected at 7, 14, 28 days post-partum (dpp) and 7 weeks (adult). Unique cellular expression was demonstrated for each by in situ hybridization and immunohistochemistry using Western blot-validated antibodies. SNAI1 and SNAI2 are in the nucleus of the most mature germ cell types at post-natal ages 10, 15 and 26. SNAI3 is only detected from 15 dpp onwards and is localized in the Sertoli cell cytoplasm. In the adult testis, Snai1 and Snai2 transcripts are detected in spermatogonia and spermatocytes, while Snai3 is in both germ and Sertoli cells. SNAI1 protein is evident in nuclei of spermatogonia, spermatocytes, round spermatids and elongated spermatids (Stages IX-XII). SNAI2 is present in the nuclei of spermatogonia and spermatocytes, with a faint signal detected in round spermatids. SNAI3 was detected only in Sertoli cell cytoplasm, as in juvenile testes. Additionally, colocalization of SNAI1 and SNAI2 with previously identified key binding partners, LSD1 and PRC2 complex components, provides strong evidence that these important functional interactions are conserved during spermatogenesis to control gene activity. These distinct expression profiles suggest that each Snail family member has unique functions during spermatogenesis.

Low-level overexpression of p53 promotes warfarin-induced calcification of porcine aortic valve interstitial cells by activating Slug gene transcription

The most frequently used oral anti-coagulant warfarin has been implicated in inducing calcification of aortic valve interstitial cells (AVICs), whereas the mechanism is not fully understood. The low-level activation of p53 is found to be involved in osteogenic transdifferentiation and calcification of AVICs. Whether p53 participates in warfarin-induced AVIC calcification remains unknown. In this study, we investigated the role of low-level p53 overexpression in warfarin-induced porcine AVIC (pAVIC) calcification. Immunostaining, quantitative PCR, and Western blotting revealed that p53 was expressed in human and pAVICs and that p53 expression was slightly increased in calcific human aortic valves compared with non-calcific valves. Terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling staining indicated that apoptosis slightly increased in calcific aortic valves than in non-calcific valves. Warfarin treatment led to a low-level increase of p53 mRNA and protein in both pAVICs and mouse aortic valves. Low-level overexpression of p53 in pAVICs via an adenovirus vector did not affect pAVIC apoptosis but promoted warfarin-induced calcium deposition and expression of osteogenic markers. shRNA-mediated p53 knockdown attenuated the pAVIC calcium deposition and osteogenic marker expression. Moreover, ChIP and luciferase assays showed that p53 was recruited to the slug promoter and activated slug expression in calcific pAVICs. Of note, overexpression of Slug increased osteogenic marker Runx2 expression, but not pAVIC calcium deposition, and Slug knockdown attenuated pAVIC calcification and p53-mediated pAVIC calcium deposition and expression of osteogenic markers. In conclusion, we found that p53 plays an important role in warfarin induced pAVIC calcification, and increased slug transcription by p53 is required for p53-mediated pAVIC calcification.

Zinc finger protein 668 suppresses non-small cell lung cancer invasion and migration by downregulating Snail and upregulating E-cadherin and zonula occludens-1

Zinc finger protein 668 (ZNF668) is a recently discovered protein and its expression levels, as well as its involvement in the invasion and metastasis of non-small cell lung cancer (NSCLC), are largely unknown. In the present study, immunohistochemical analysis demonstrated that ZNF668 protein expression was decreased in lung tumors (51/167, 30.5%) compared with adjacent normal lung tissues (43/62, 69.4%; P<0.001). Subsequent statistical analysis revealed that ZNF668 expression was negatively associated with increased tumor-node-metastasis stage (P=0.019) and lymph node metastasis (P=0.002). Following ZNF668 downregulation by transfection of a ZNF668-expressing plasmid or small interfering RNA, it was demonstrated that ZNF668 inhibited the invasion and migration of NSCLC cells. Furthermore, restoration of ZNF668 expression downregulated the expression of Snail and increased the protein levels of epithelial (E-)cadherin and zonula occludens-1 (ZO-1). The results of the present study suggest that ZNF668 is downregulated in human NSCLC. Furthermore, restoration of ZNF668 expression was demonstrated to decrease the expression of Snail and increase the expression of E-cadherin and ZO-1, suppressing the invasion and migration of NSCLC cells.

TGF-β induces M2-like macrophage polarization via SNAIL-mediated suppression of a pro-inflammatory phenotype

Tumor-associated macrophages (TAMs) are a major component of leukocytic infiltrate in tumors, which facilitates tumor progression and promotes inflammation. TGF-β promotes the differentiation of non-activated macrophages into a TAM-like (M2-like) phenotype; however, the underlying mechanisms are not clear. In this study, we found that TGF-β induces a M2-like phenotype characterized by up-regulation of the anti-inflammatory cytokine IL-10, and down-regulation of the pro-inflammatory cytokines TNF-α and IL-12. In human THP-1 macrophages, overexpression of SNAIL caused M2-like differentiation by inhibiting pro-inflammatory cytokine release and promoting the expression of M2-specific markers. By contrast, SNAIL knockdown promoted M1 polarization through up-regulation of pro-inflammatory cytokines and abolished TGF-β-mediated M2-polarization of THP-1 macrophages. The SMAD2/3 and PI3K/AKT signaling pathways were crucial for TGF-β-induced SNAIL overexpression in THP-1 cells. These findings suggest that TGF-β skews macrophage polarization towards a M2-like phenotype via SNAIL up-regulation, and blockade of TGF-β/SNAIL signaling restores the production of pro-inflammatory cytokines. This study provides new understanding of the role of SNAIL in M2 polarization of macrophages, and suggests a potential therapeutic target for antitumor immunity.

Snail collaborates with EGR-1 and SP-1 to directly activate transcription of MMP 9 and ZEB1

The Snail transcription factor plays as a master regulator of epithelial mesenchymal transition (EMT), one of the steps of tumor metastasis. Snail enhances expressions of a lot of mesenchymal genes including the matrix degradation enzyme matrix metalloproteinases 9 (MMP9) and the EMT transcription factor zinc finger E-box binding homeobox 1 (ZEB1), however, the underlying mechanisms are not clarified. Herein, we investigated how Snail upregulated transcription of ZEB1 and MMP9 induced by the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate (TPA) in hepatoma cell HepG2. According to deletion mapping and site directed mutagenesis analysis, the TPA-responsive elements on both MMP9 and ZEB1 promoters locate on a putative EGR1 and SP1 overlapping region coupled with an upstream proposed Snail binding motif TCACA. Consistently, chromatin immunoprecipitation (ChIP) assay showed TPA triggered binding of Snail, EGR1 and SP1 on MMP9 and ZEB1 promoters. Double ChIP further indicated TPA induced association of Snail with EGR1 and SP1 on both promoters. Also, electrophoresis mobility shift assay revealed TPA enhanced binding of Snail with a MMP9 promoter fragment. According to shRNA techniques, Snail was essential for gene expression of both ZEB1 and MMP9. In conclusion, Snail transactivates genes involved in tumor progression via direct binding to a specific promoter region.

Integrin linked kinase regulates syncytialization of BeWo trophoblast cells

During placental development, mononuclear villous cytotrophoblast cells differentiate and fuse with the overlying syncytiotrophoblast. This process requires the dissolution of E-cadherin (CDH1)-containing adherens junctions in cytotrophoblast. Integrin linked kinase (ILK) can downregulate CDH1 through poly (ADP-ribose) polymerase 1 (PARP1) and Snail-1 (SNAI1) during epithelial-mesenchymal transition. ILK is known to be expressed in cytotrophoblast; thus, the role of a potential ILK-PARP1-SNAI1 pathway in aiding trophoblast syncytialization via the downregulation of CDH1 was examined. The spatiotemporal expression of PARP1, SNAI1, and CDH1 were determined in first and early second trimester chorionic villi, term villi, and BeWo cells by immunofluorescence analysis. PARP1 and SNAI1 were highly detectable in villous cytotrophoblast nuclei of human chorionic villi and SNAI1 expression, in particular, also persisted in syncytiotrophoblast. In BeWo cells undergoing syncytialization, PARP1 and SNAI1 increasingly localized to cell nuclei in correlation with decreased CDH1 expression. Using luciferase reporter assays, it was determined that PARP1 and SNAI1 promoter activities were significantly higher in BeWo cells during syncytialization compared to the activities in proliferating cells. Overexpression of wild type or constitutively active ILK also resulted in significantly increased PARP1 and SNAI1 promoter activities while dominant negative ILK overexpression significantly reduced promoter activities. Lastly, siRNA-mediated depletion of ILK expression in BeWo cells undergoing syncytialization resulted in significantly reduced SNAI1 expression and a significant reduction in the incidence of syncytialization correlating with increased CDH1 expression. These results demonstrate that ILK aids trophoblast syncytialization via the downregulation of CDH1, perhaps through an ILK-PARP1-SNAI1 pathway.

TMEM17 depresses invasion and metastasis in lung cancer cells via ERK signaling pathway

Transmembrane protein 17(TMEM17) is a newly identified protein, its expression pattern and clinicopathological relevance is still unclear. In this study, western blot assay was performed in 20 paired lung cancer samples and found that TMEM17 protein levels were lower in lung cancer tissues than that in the corresponding normal lung tissues (p=0.010). Immunohistochemistry staining in 143 cases lung cancer specimens also showed that TMEM17 expression in lung cancer tissues were significantly lower than adjacent normal lung tissues (35.7% vs 63.2%, p<0.001). And negative TMEM17 expression was significantly associated with poor histological differentiation (p=0.027), advanced TNM stages (p=0.006), positive lymph node metastasis (p=0.002) and poor prognosis (p=0.002). After overexpressing TMEM17, levels of p-ERK and its downstream molecules, p-P90RSK and Snail, were down-regulated, while levels of Occludin and Zo-1 were up-regulated, which result in the inhibition of invasion and migration ability of lung cancer cells. The effects were reversed by the incorporation of specific ERK inhibitor PD98059. In conclusion, loss of TMEM17 correlates with the development of non-small cell lung cancer (NSCLC) and predicts adverse clinical outcome of NSCLC patients. The effect of TMEM17 on inhibiting invasion and migration may attribute to restoring Occludin and Zo-1 expression through inactivating ERK-P90RSK-Snail pathway.

Baicalein Inhibits Epithelial to Mesenchymal Transition via Downregulation of Cyr61 and LOXL-2 in MDA-MB231 Breast Cancer Cells

Epithelial-mesenchymal transition (EMT) is a critical step in the acquisition of the migratory and invasive capabilities associated with metastatic competence. Cysteine-rich protein 61 (CCN1/Cyr61) has been implicated as an important mediator in the proliferation and metastasis of breast cancer. Hence, Cyr61 and associated pathways are attractive targets for therapeutic interventions directed against the EMT. In the present study, we report that baicalein significantly inhibits the expression of Cyr61 and migration and invasion of MDA-MB231 human breast cancer cells. Exposure to baicalein led to increased E-cadherin expression, possibly due to the ubiquitination of Snail and Slug, which was mediated by the Cyr61/Akt/glycogen synthase kinase 3β (GSK3β) pathway. Further analysis revealed that baicalein inhibited the expression of lysyl oxidase like-2 (LOXL-2), which is a functional collaborator of Snail and Slug, and subsequently attenuated the direct interaction between LOXL-2 and Snail or Slug, thereby enhancing GSK3β-dependent Snail and Slug degradation. Our findings provide new insights into the antimetastatic mechanism of baicalein and may contribute to its beneficial use in breast cancer therapies.

Left-right axis asymmetry determining human Cryptic gene is transcriptionally repressed by Snail

BACKGROUND

Establishment of the left-right axis is important for positioning organs asymmetrically in the developing vertebrate-embryo. A number of factors like maternally deposited molecules have emerged essential in initiating the specification of the axis; the downstream events, however, are regulated by signal-transduction and gene-expression changes identifying which remains a crucial challenge. The EGF-CFC family member Cryptic, that functions as a co-receptor for some TGF-beta ligands, is developmentally expressed in higher mammals and mutations in the gene cause loss or change in left-right axis asymmetry. Despite the strong phenotype, no transcriptional-regulator of this gene is known till date.

RESULTS

Using promoter-analyses tools, we found strong evidence that the developmentally essential transcription factor Snail binds to the human Cryptic-promoter. We cloned the promoter-region of human Cryptic in a reporter gene and observed decreased Cryptic-promoter activation upon increasing Snail expression. Further, the expression of Cryptic is down-regulated upon exogenous Snail expression, validating the reporter assays and the previously identified role of Snail as a transcriptional repressor. Finally, we demonstrate using gel-shift assay that Snail in nuclear extract of PANC1 cells interacts with the promoter-construct bearing putative Snail binding sites and confirm this finding using chromatin immunoprecipitation assay.

CONCLUSIONS

Snail represses the expression of human Cryptic and therefore, might affect the signaling via Nodal that has previously been demonstrated to specify the left-right axis using the EGF-CFC co-receptors.

MicroRNA-544a Regulates Migration and Invasion in Colorectal Cancer Cells via Regulation of Homeobox A10

BACKGROUND/AIMS

MicroRNAs (miRNAs) are a group of small RNA molecules that post-transcriptionally regulate gene expression. Aberrant expression of miRNAs has been associated with tumorigenesis in various cancers. miR-544a is an understudied miRNA that has recently been implicated in regulating invasion in lung cancer. However, its role in regulating invasion and the underlying mechanism have not been investigated in colorectal cancer (CRC) cells.

METHODS

Microarray analysis was performed in metastatic colorectal tumor samples and their matched normal tissues to identify differentially expressed miRNAs. Quantitative real-time PCR was used to detect miR-544a levels in tumor samples and CRC cell lines with varying metastatic properties. miR-544a mimic or inhibitor was transfected into SW480 and HCT116 cells, respectively, followed by wound healing and invasion assays. Western Blot and luciferase assay were performed to investigate the direct target of miR-544a. Xenograft mouse models was used to examine in vivo function of miR-544a.

RESULTS

Our data showed that expression of miR-544a was significantly up-regulated in metastatic tumor samples and CRC cell lines. Inhibition of miR-544a reduced migration and invasion in HCT116 cells. Homeobox A10 (HOXA10) was the direct target of miR-544a which was required for the function of miR-544a in regulating invasiveness. miR-544a inhibitor and/or HOXA10 overexpression reduced lung metastases in HCT116 xenografts.

CONCLUSIONS

Our study demonstrates that miR-544a regulates invasive and metastatic properties of CRC cells by modulating HOXA10 expression level both in vitro and in vivo. miR-544a may represent a new therapeutic target for the intervention of metastatic colorectal cancer.

Cytosolic TMEM88 promotes triple-negative breast cancer by interacting with Dvl

TMEM88, a newly discovered protein localized on the cell membrane, inhibits canonical Wnt signaling. Immunohistochemic alanalysis of 139 breast cancers pecimens(64 triple-negative cancers and 75 non-triple-negative cancers) indicated that TMEM88 is expressed at significantly higher levels in breast cancer tissues (71.22%, 99/139) than in normal breast tissues (11.4%, 4/35; p < 0.001). The cytosolic and nuclear expression rates of TMEM88 were 57.81% and 9.37% in triple-negative and 52% and 33.33% (p = 0.5 and p = 0.001) in the non-triple-negative breast cancer tissues, respectively. Western blot analyses indicated that TMEM88 promoted Snail expression and inhibited Zo-1 and Occludin expression by interacting with dishevelled (Dvl) proteins, thereby stimulating invasion and metastasis in breast cancer. While cytosolic TMEM88 did not affect canonical Wnt signaling, cytosolic localization of this protein was positively correlated with both advanced TNM stage (p = 0.038 and p < 0.001) and lymph node metastasis (p = 0.01 and p = 0.002) in all and triple-negative specimens, respectively, and stimulated cell invasion by interacting with Dvls. Meanwhile, nuclear localization of TMEM88 was negatively correlated with lymph node metastasis (p = 0.046). Lastly, the increased prevalence of TMEM88 nuclear localization observed in non-triple-negative, compared to triple-negative tissues, suggests that the biological roles of TMEM88 differ depending on the subcellular localization.

Negative Regulatory Role of TWIST1 on SNAIL Gene Expression

Epithelial-mesenchymal transition (EMT) is crucial for specific morphogenetic movements during embryonic development as well as pathological processes of tumor cell invasion and metastasis. TWIST and SNAIL play vital roles in both developmental and pathological EMT. Our aim in this study was to investigate the functional correlation between TWIST1 and SNAIL in human ESCC cell line (KYSE-30). The packaging cell line GP293T was cotransfected with either control retroviral pruf-IRES-GFP plasmid or pruf-IRES-GFP-hTWIST1 and pGP plasmid. The KYSE-30 ESCC cells were transduced with produced viral particles and examined with inverted fluorescence microscope. DNA was extracted from transduced KYSE-30 cells and analyzed for copy number of integrated retroviral sequences in the target cell genome. The concentration of retroviral particles was determined by Real-time PCR. After RNA extraction and cDNA synthesis, the mRNA expression of TWIST1 and SNAIL was assessed by comparative real-time PCR amplification. Ectopic expression of TWIST1 in KYSE-30, dramatically reduces SNAIL expression. Retroviral transduction enforced TWIST1 overexpression in GFP-hTWIST1 nearly 9 folds in comparison with GFP control cells, and interestingly, this TWIST1 enforced expression caused a - 7 fold decrease of SNAIL mRNA expression in GFP-hTWIST1 compared to GFP control cells. Inverse correlation of TWIST1 and SNAIL mRNA levels may introduce novel molecular gene expression pathway controlling EMT process during ESCC aggressiveness and tumorigenesis. Consequently, these data extend the spectrum of biological activities of TWIST1 and propose that therapeutic repression of TWIST1 may be an effective strategy to inhibit cancer cell invasion and metastasis.

Coiled-coil domain-containing protein 8 inhibits the invasiveness and migration of non-small cell lung cancer cells

Lung cancer has always been the leading cause of death among patients with malignant tumors, and the majority of these patients die because of cancer cell invasion and metastasis. Previous studies have implicated coiled-coil domain-containing protein 8 (CCDC8) as a tumor suppressor in several types of cancer, such as breast and prostate cancers. However, the expression levels or functions of CCDC8 in lung cancer have not been elucidated. Here, we used immunohistochemical staining to measure CCDC8 expression in 147 samples from tumors and 30 samples from the adjacent normal lung tissues of patients with non-small cell lung cancer. CCDC8 was shown to be located predominantly in the cytoplasm and partially on the cell membrane, and its expression level was significantly lower in lung cancer samples than that in the adjacent normal lung tissues (P=.001). CCDC8 expression was closely related to tumor differentiation (P=.039), tumor-node-metastasis stage (P=.009), lymph node metastasis (P=.038), and prognosis (P=.043) of lung cancer. Transfection of A549 cells with CCDC8 significantly reduced cell invasion and migration (P<.05), whereas the invasiveness and migration capacity in CCDC8-knockdown A549 cells were significantly increased in comparison with the control cells (P<.05). Furthermore, we demonstrated that CCDC8 can downregulate the expression of Snail and upregulate the expression of E-cadherin by inhibiting p-P38 and p-IκBα. Collectively, CCDC8 may suppress the invasion and metastasis of lung cancer cells, and it may represent a promising therapeutic target for non-small cell lung cancer.

SNAIL gene inhibited by hypoxia-inducible factor 1α (HIF-1α) in epithelial ovarian cancer

The aim of this study was to investigate the relationship between HIF-1α and SNAIL gene expression in the epithelial ovarian cancer (EOC) cell line. EOC cells were treated with hypoxia, hypoxia combined with rapamycin, and control. The expression of HIF-1α and E-cad were assessed by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The gene expression of SNAIL was studied by RT-PCR and real-time PCR. RNA interference technology was used to determine the relationship between HIF-1α and SNAIL. The present study indicated that the HIF-1α protein was expressed and increased in EOC cell line. SNAIL mRNA was found to increase and E-cad expression decreased with the time of hypoxia prolonged. Hypoxia increased invasion abilities of EOC cell line, but compared with cells exposed to hypoxia, the change of invasive ability of cells with rapamycin had no effect. The expression of HIF-1α protein and SNAIL mRNA could be inhibited gradually by rapamycin. siRNA of HIF-1α could suppress the expression of SNAIL while siRNA of SNAIL had no influence on HIF-1α protein expression. HIF-1α may be the upstream of the SNAIL gene in EOC. Our data suggested that HIF-1α might be an upregulator of the SNAIL gene and HIF-1α-SNAIL-E-cad pathway may play an important role in EOC invasion and metastasis.

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).

Oroxylin A inhibits invasion and migration through suppressing ERK/GSK-3β signaling in snail-expressing non-small-cell lung cancer cells

Snail is closely linked to tumor invasion, metastasis, and recurrence and indicates prognosis of patients suffering from cancer. Overexpression of Snail increases motility and invasiveness of cancer cells, which has become target for anti-metastatic treatment. Oroxylin A, a natural compound extracted from Scutellaria radix, has been reported to inhibit invasion and migration in breast cancer. In this study, we investigated the anti-invasive effect of oroxylin A on lung cells and uncovered its underlying mechanism. The results suggested that oroxylin A could inhibit migration and invasion in Snail-expressing 95-D, and A549 cells whereas it had little effect on non-expressing GLC-82 cells. Furthermore, enhanced Snail expression after transfection of Snail vector in GLC-82 cells is decreased by oroxylin A. Snail can also induce epithelial-mesenchymal transition. We found oroxylin A could reverse TGFβ1-induced epithelial-mesenchymal transition by inhibiting Snail expression. As a result, oroxylin A up-regulated E-cadherin expression and down-regulated vimentin, MMP-9, and CD44v6 expression, which could lead to the inhibition of tumor migration and invasion. Mechanically, we demonstrated that oroxylin A suppressed activation of ERK instead of AKT pathway and then promoted activation of GSK-3β to reduce Snail protein content. Finally, we established transplanted, metastatic, and orthotopic models of A549 cells, and found that oroxylin A inhibited the growth and lung metastasis of A549 cells in vivo. Taken together, we proposed that oroxylin A might be a promising candidate targeting tumor metastasis. © 2016 Wiley Periodicals, Inc.

Omental adipose tissue fibrosis and insulin resistance in severe obesity

Background/Objectives:

The unresolved chronic inflammation of white adipose tissue (WAT) in obesity leads to interstitial deposition of fibrogenic proteins as reparative process. The contribution of omental adipose tissue (oWAT) fibrosis to obesity-related complications remains controversial. The aim of our study was to investigate whether oWAT fibrosis may be related to insulin resistance in severely obese population.

Subjects/Methods:

Forty obese subjects were studied by glucose clamp before undergoing bariatric surgery and thus stratified according to insulin resistance severity (M-value). From the first (Group B: n=13; M=1.9±0.7 mg kg⁻¹ min⁻¹) and the highest (Group A: n=14; M=4.5±1.4 mg kg⁻¹ min⁻¹) M-value tertiles, which were age-, waist- and body mass index-matched, oWAT samples were then obtained.

Gene expression of collagen type I, III and VI, interleukin-6, profibrotic mediators (transforming growth factor (TGF)-β1, activin A, connective tissue growth factor), hypoxia inducible factor-1α (HIF-1α) and macrophage (CD68, monocyte chemotactic protein (MCP)-1, CD86, CD206, CD150) markers were analyzed by quantitative reverse transcription PCR. Adipocyte size and total fibrosis were assessed by histomorphometry techniques.

Results:

Fibrosis at morphological level resulted significantly greater in Group B compared with Group A, although collagens gene expression did not differ. Notably, collagen VI messenger RNA significantly correlated with collagen I, collagen III, HIF-1α, TGF-β1, CD68, MCP-1 and CD86 transcription levels, supporting their relation with fibrosis development.

Conclusions:

In conclusion, we show for the first time that human oWAT fibrosis in severe obesity is consistent with a higher degree of insulin resistance measured by glucose clamp. Therefore, collagen deposition could represent a maladaptive mechanism contributing to obesity-related metabolic complications.

Transcriptional and translational mechanisms contribute to regulate the expression of Discs Large 1 protein during different biological processes

Human discs large (DLG1) has been demonstrated to be involved in cell polarity and maintenance of tissue architecture. However, the mechanisms controlling DLG1 expression are not fully understood. This is relevant as DLG1 is lost during the later stages of malignant progression. We initiated a series of studies to analyse the mechanisms regulating DLG1 expression. We have previously reported the identification of an alternative splicing event in the 5′ untranslated region (5′-UTR) of DLG1 mRNA that generates transcripts with two different 5′-UTR (short and large 5′-UTR variants). In this study, we further examined the impact of the DLG1 transcription and the role of the differential expression of the alternative 5′-UTRs on DLG1 protein levels. We analysed these mechanisms during cell processes like differentiation, cell cycle progression and cell-cell contact formation, where the importance of DLG1 activities was previously established. The data presented in this report suggest that the transcriptional regulation of DLG1 strongly contributes to DLG1 abundance and that differential expression of alternative 5′-UTRs with different translational properties, also cooperates, depending on the cell type and cell situation. This study provides new evidence for understanding the transcriptional regulation of DLG1 and the changes in DLG1 expression during different biological processes.

miR-153 inhibits epithelial-to-mesenchymal transition in hepatocellular carcinoma by targeting Snail

Epithelial-to-mesenchymal transition (EMT) has been implicated as a dynamic cellular process in embryonic development and invasion of human cancers. Snail1 is a critical convergence hub in EMT regulation which transcriptionally represses E-cadherin expression. Currently, published data indicate that upregulation of Snail is mainly due to transcriptional activation and regulation of protein stability and cellular location. However, whether there is an alternative regulatory mechanism remains unclear. Our study showed that the expression of miR-153 was noticeably downregulated in hepatocellular carcinoma (HCC) cell lines and tissues, compared with normal liver epithelial cells (NLCs) and matched adjacent normal HCC tissues. Ectopic expression of miR-153 inhibited the migration and invasion ability of HCC cells, while suppression of miR-153 rescued this inhibitory effect. In addition, upregulation of miR-153 in HCC cells resulted in a decrease in epithelial markers, E-cadherin and α-catenin, and an increase in mesenchymal markers, N-cadherin and vimentin, and vice versa. Moreover, we demonstrated that miR-153 downregulated Snail expression by directly targeting the 3'-untranslated region (3'UTR) of Snail. Taken together, our results suggest that miR-153 plays a critical role in suppressing EMT and HCC progression by direct suppression of Snail expression.

Ghrelin promotes renal cell carcinoma metastasis via Snail activation and is associated with poor prognosis

Ghrelin is an appetite-regulating molecule that promotes growth hormone (GH) release and food intake through growth hormone secretagogue receptor (GHS-R). Recently, high ghrelin levels have been detected in various types of human cancer. Ghrelin expression is observed in proximal and distal renal tubules, where renal cell carcinoma (RCC) arises. However, whether ghrelin is up-regulated and promotes renal cell carcinogenesis remains obscure. In this study, we observed that ghrelin was highly expressed in renal tumours, especially in metastatic RCC. In addition, high ghrelin levels correlated with poor outcome, lymph node and distant metastasis. The addition of ghrelin promoted the migration ability of RCC cell lines 786-0, ACHN and A-498. Furthermore, knockdown of ghrelin expression reduced in vitro migration and in vivo metastasis, suggesting a requirement for ghrelin accumulation in the microenvironment for RCC metastasis. Analysis of microarray signatures using Ingenuity Pathway Analysis (IPA) and MetaCore pointed to the potential regulation by ghrelin of Snail, a transcriptional repressor of E-cadherin. We further observed that Ghrelin increased the expression, nuclear translocation and promoter-binding activity of Snail. Snail silencing blocked the ghrelin-mediated effects on E-cadherin repression and cell migration. Snail-E-cadherin regulation was mediated by GHS-R-triggered Akt phosphorylation at Ser473 and Thr308. Pretreatment with PI3K inhibitors, LY294002 and wortmannin, as well as Akt siRNA, decreased ghrelin-induced Akt phosphorylation, Snail promoter binding activity and migration. Taken together, our findings indicate that ghrelin can activate Snail function via the GHS-R-PI3K-Akt axis, which may contribute to RCC metastasis. The microarray raw data were retrieved from the Cancer Genome Atlas (TCGA) [KIRC gene expression (IlluminaHiSeq) dataset].

Friend or foe: Endoplasmic reticulum protein 29 (ERp29) in epithelial cancer

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ERp29 regulates epithelial cell plasticity and the mesenchymal–epithelial transition.

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ERp29 shows a tumor suppressive function in primary tumor development.

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ERp29 is potentially associated with distant metastasis in cancer.

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ERp29 modulates cell survival against genotoxic stress.

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Thus, ERp29 displays dual functions as a “friend or foe” in epithelial cancer.

The endoplasmic reticulum (ER) protein 29 (ERp29) is a molecular chaperone that plays a critical role in protein secretion from the ER in eukaryotic cells. Recent studies have also shown that ERp29 plays a role in cancer. It has been demonstrated that ERp29 is inversely associated with primary tumor development and functions as a tumor suppressor by inducing cell growth arrest in breast cancer. However, ERp29 has also been reported to promote epithelial cell morphogenesis, cell survival against genotoxic stress and distant metastasis. In this review, we summarize the current understanding on the biological and pathological functions of ERp29 in cancer and discuss the pivotal aspects of ERp29 as “friend or foe” in epithelial cancer.