Snail1: A Transcriptional Factor Controlled at Multiple Levels

Bio-Pathological Functions of Posttranslational Modifications of Histological Biomarkers in Breast Cancer

Proteins are the most common types of biomarkers used in breast cancer (BC) theranostics and management. By definition, a biomarker must be a relevant, objective, stable, and quantifiable biomolecule or other parameter, but proteins are known to exhibit the most variate and profound structural and functional variation. Thus, the proteome is highly dynamic and permanently reshaped and readapted, according to changing microenvironments, to maintain the local cell and tissue homeostasis. It is known that protein posttranslational modifications (PTMs) can affect all aspects of protein function. In this review, we focused our analysis on the different types of PTMs of histological biomarkers in BC. Thus, we analyzed the most common PTMs, including phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, palmitoylation, myristoylation, and glycosylation/sialylation/fucosylation of transcription factors, proliferation marker Ki-67, plasma membrane proteins, and histone modifications. Most of these PTMs occur in the presence of cellular stress. We emphasized that these PTMs interfere with these biomarkers maintenance, turnover and lifespan, nuclear or subcellular localization, structure and function, stabilization or inactivation, initiation or silencing of genomic and non-genomic pathways, including transcriptional activities or signaling pathways, mitosis, proteostasis, cell-cell and cell-extracellular matrix (ECM) interactions, membrane trafficking, and PPIs. Moreover, PTMs of these biomarkers orchestrate all hallmark pathways that are dysregulated in BC, playing both pro- and/or antitumoral and context-specific roles in DNA damage, repair and genomic stability, inactivation/activation of tumor-suppressor genes and oncogenes, phenotypic plasticity, epigenetic regulation of gene expression and non-mutational reprogramming, proliferative signaling, endocytosis, cell death, dysregulated TME, invasion and metastasis, including epithelial-mesenchymal/mesenchymal-epithelial transition (EMT/MET), and resistance to therapy or reversal of multidrug therapy resistance. PTMs occur in the nucleus but also at the plasma membrane and cytoplasmic level and induce biomarker translocation with opposite effects. Analysis of protein PTMs allows for the discovery and validation of new biomarkers in BC, mainly for early diagnosis, like extracellular vesicle glycosylation, which may be considered as a potential source of circulating cancer biomarkers.

P4HA3 promotes head and neck squamous cell carcinoma progression via the WNT/β-catenin signaling pathway

Here, we explored the role of Prolyl 4-Hydroxylase Subunit Alpha 3 (P4HA3), the most recently identified member of the prolyl-4-hydroxylase (P4H) family, in head and neck squamous cell carcinoma (HNSCC) progression. P4HA3 is upregulated during cancer progression; however, its specific role in HNSCC progression remains elusive. Thus, this study aimed to elucidate the regulatory function of P4HA3 in HNSCC development and progression and to describe the underlying mechanisms. Initially, we analyzed the correlation between the expression of P4HA3 and the WNT pathway genes and clinicopathologic features in HNSCC based on microarray data from The Cancer Genome Atlas (TCGA). Next, we used Gene Oncology (GO) functional data to describe several potentially associated pathways in HNSCC. Then, we knocked down P4HA3 in SCC15 and SCC25 cells, two classic HNSCC cell lines, and assessed the resulting changes using RT-qPCR. Furthermore, we used Western blot to evaluate the regulatory role of P4HA3 in the epithelial-to-mesenchymal transition (EMT) and the WNT/β-catenin signaling pathway. To explore the effect of P4HA3 knockdown on tumor progression, in vivo experiments were conducted using a murine model. Immunohistochemistry assays were then employed to identify proteins associated with EMT and the WNT/β-catenin signaling pathway in tumor tissues. Upregulated P4HA3 in HNSCC patient tumor tissues was positively correlated with poor prognosis. Notably, P4HA3 knockdown significantly inhibited the proliferative and invasive abilities of HNSCC. The levels of genes and proteins associated with EMT and the WNT/β-catenin signaling pathway were also markedly reduced by P4HA3 knockdown. Importantly, the in vivo experiments demonstrated that P4HA3 can promote subcutaneous tumorigenesis in nude mice and knockdown of P4HA3 induce a significant ihibitation of EMT and WNT/β-catenin pathway detected by immunohistochemistry assay in tumor tissues. In summary, we demonstrated that P4HA3 is a promising diagnostic and therapeutic biomarker for HNSCC. As an oncogene, P4HA3 increases HNSCC proliferation by inducing the EMT and activating the WNT/β-catenin signaling pathway.

Effect of atractylenolide III on zearalenone-induced Snail1-mediated epithelial-mesenchymal transition in porcine intestinal epithelium

BACKGROUND

The intestinal epithelium performs essential physiological functions, such as nutrient absorption, and acts as a barrier to prevent the entry of harmful substances. Mycotoxins are prevalent contaminants found in animal feed that exert harmful effects on the health of livestock. Zearalenone (ZEA) is produced by the Fusarium genus and induces gastrointestinal dysfunction and disrupts the health and immune system of animals. Here, we evaluated the molecular mechanisms that regulate the effects of ZEA on the porcine intestinal epithelium.

RESULTS

Treatment of IPEC-J2 cells with ZEA decreased the expression of E-cadherin and increased the expression of Snai1 and Vimentin, which induced Snail1-mediated epithelial-to-mesenchymal transition (EMT). In addition, ZEA induces Snail-mediated EMT through the activation of TGF-β signaling. The treatment of IPEC-J2 cells with atractylenolide III, which were exposed to ZEA, alleviated EMT.

CONCLUSIONS

Our findings provide insights into the molecular mechanisms of ZEA toxicity in porcine intestinal epithelial cells and ways to mitigate it.

Snail transcription factors - Characteristics, regulation and molecular targets relevant in vital cellular activities of ovarian cancer cells

Snail transcription factors play essential roles in embryonic development and participate in many physiological processes. However, these genes have been implicated in the development and progression of various types of cancer. In epithelial ovarian cancer, high expression of these transcription factors is usually associated with the acquisition of a more aggressive phenotype and thus, considered to be a poor prognostic factor. Numerous molecular signals create a complex network of signaling pathways regulating the expression and stability of Snails, which in turn control genes involved in vital cellular functions of ovarian cancer cells, such as invasion, survival, proliferation and chemoresistance.

Role of STAT3 in cancer cell epithelial‑mesenchymal transition (Review)

Since its discovery, the role of the transcription factor, signal transducer and activator of transcription 3 (STAT3), in both normal physiology and the pathology of numerous diseases, including cancer, has been extensively studied. STAT3 is aberrantly activated in different types of cancer, fulfilling a critical role in cancer progression. The biological process, epithelial‑mesenchymal transition (EMT), is indispensable for embryonic morphogenesis. During the development of cancer, EMT is hijacked to confer motility, tumor cell stemness, drug resistance and adaptation to changes in the microenvironment. The aim of the present review was to outline recent advances in knowledge of the role of STAT3 in EMT, which may contribute to the understanding of the function of STAT3 in EMT in various types of cancer. Delineating the underlying mechanisms associated with the STAT3‑EMT signaling axis may generate novel diagnostic and therapeutic options for cancer treatment.

KDM4C represses liver fibrosis by regulating H3K9me3 methylation of ALKBH5 and m6A methylation of snail1 mRNA

OBJECTIVE

We aimed to disclose the molecular mechanism of snail1 in liver fibrosis.

METHODS

Carbon tetrachloride (CCl4) was used to induce a liver fibrosis model in mice whereby serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were evaluated, and liver pathological alternations were assessed. Rat hepatic stellate cells (HSC-T6) were irritated with transforming growth factor (TGF)-β1, followed by assessment of cell viability and migration. The levels of snail1, ALKBH5, and lysine specific demethylase 4C (KDM4C) were quantified by immunohistochemistry, western blot, or reverse transcription-quantitative polymerase chain reaction, in addition to α-smooth muscle actin (SMA), anti-collagen type I α1 (COL1A1), vimentin, and E-cadherin. Photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation and RNA stability were evaluated to determine the relationship between ALKBH5 and snail1. Changes in KDM4C-bound ALKBH5 promoter and enrichment of histone H3 lysine 9 trimethylation (H3K9me3) at the ALKBH5 promoter were determined using chromatin immunoprecipitation.

RESULTS

In fibrosis mice, snail1 was upregulated while ALKBH5 and KDM4C were downregulated. KDM4C overexpression reduced serum ALT and AST levels, liver injury, and α-SMA, COL1A1 and VIMENTIN expressions but increased E-cadherin expression. However, the aforementioned trends were reversed by concurrent overexpression of snail1. In HSC-T6 cells exposed to TGF-β1, ALKBH5 overexpression weakened cell viability and migration, downregulated α-SMA, COL1A1 and VIMENTIN, upregulated E-CADHERIN, and decreased m6A modification of snail1 and its mRNA stability. KDM4C increased ALKBH5 expression by lowering H3K9me3 level, but inhibited HSC-T6 cell activation by regulating the ALKBH5/snail1 axis.

CONCLUSION

KDM4C decreases H3K9me3 methylation to upregulate ALKBH5 and subsequently inhibits snail1, ultimately impeding liver fibrosis.

MARCH2, a Novel Oncogene-regulated SNAIL E3 Ligase, Suppresses Triple-negative Breast Cancer Metastases

Epithelial-mesenchymal transition (EMT) in cancer promotes metastasis and chemotherapy resistance. A subset of triple-negative breast cancer (TNBC) exhibits a mesenchymal gene signature that is associated with poor patient outcomes. We previously identified PTK6 tyrosine kinase as an oncogenic driver of EMT in a subset of TNBC. PTK6 induces EMT by stabilizing SNAIL, a key EMT-initiating transcriptional factor. Inhibition of PTK6 activity reverses mesenchymal features of TNBC cells and suppresses their metastases by promoting SNAIL degradation via a novel mechanism. In the current study, we identify membrane-associated RING-CH2 (MARCH2) as a novel PTK6-regulated E3 ligase that promotes the ubiquitination and degradation of SNAIL protein. The MARCH2 RING domain is critical for SNAIL ubiquitination and subsequent degradation. PTK6 inhibition promotes the interaction of MARCH2 with SNAIL. Overexpression of MARCH2 exhibits tumor suppressive properties and phenocopies the effects of SNAIL downregulation and PTK6 inhibition in TNBC cells, such as inhibition of migration, anoikis resistance, and metastasis. Consistent with this, higher levels of MARCH2 expression in breast and other cancers are associated with better prognosis. We have identified MARCH2 as a novel SNAIL E3 ligase that regulates EMT and metastases of mesenchymal TNBC.

SIGNIFICANCE

EMT is a process directly linked to drug resistance and metastasis of cancer cells. We identified MARCH2 as a novel regulator of SNAIL, a key EMT driver, that promotes SNAIL ubiquitination and degradation in TNBC cells. MARCH2 is oncogene regulated and inhibits growth and metastasis of TNBC. These insights could contribute to novel strategies to therapeutically target TNBC.

Dual role of Snail1 as transcriptional repressor and activator

Snail1 transcriptional factor plays a key role in the control of epithelial to mesenchymal transition, a process that remodels tumor cells increasing their invasion and chemo-resistance as well as reprograms their metabolism and provides stemness properties. During this transition, Snail1 acts as a transcriptional repressor and, as growing evidences have demonstrated, also as a direct activator of mesenchymal genes. In this review, I describe the different proteins that interact with Snail1 and are responsible for these two different functions on gene expression; I focus on the transcriptional factors that associate to Snail1 in their target promoters, both activated and repressed. I also present working models for Snail1 action both as repressor and activator and raise some issues that still need to be investigated.

Formation of an invasion-permissive matrix requires TGFβ/SNAIL1-regulated alternative splicing of fibronectin

BACKGROUND

As in most solid cancers, the emergence of cells with oncogenic mutations in the mammary epithelium alters the tissue homeostasis. Some soluble factors, such as TGFβ, potently modify the behavior of healthy stromal cells. A subpopulation of cancer-associated fibroblasts expressing a TGFβ target, the SNAIL1 transcription factor, display myofibroblastic abilities that rearrange the stromal architecture. Breast tumors with the presence of SNAIL1 in the stromal compartment, and with aligned extracellular fiber, are associated with poor survival prognoses.

METHODS

We used deep RNA sequencing and biochemical techniques to study alternative splicing and human tumor databases to test for associations (correlation t-test) between SNAIL1 and fibronectin isoforms. Three-dimensional extracellular matrices generated from fibroblasts were used to study the mechanical properties and actions of the extracellular matrices on tumor cell and fibroblast behaviors. A metastatic mouse model of breast cancer was used to test the action of fibronectin isoforms on lung metastasis.

RESULTS

In silico studies showed that SNAIL1 correlates with the expression of the extra domain A (EDA)-containing (EDA+) fibronectin in advanced human breast cancer and other types of epithelial cancers. In TGFβ-activated fibroblasts, alternative splicing of fibronectin as well as of 500 other genes was modified by eliminating SNAIL1. Biochemical analyses demonstrated that SNAIL1 favors the inclusion of the EDA exon by modulating the activity of the SRSF1 splicing factor. Similar to Snai1 knockout fibroblasts, EDA- fibronectin fibroblasts produce an extracellular matrix  that does not sustain TGFβ-induced fiber organization, rigidity, fibroblast activation, or tumor cell invasion. The presence of EDA+ fibronectin changes the action of metalloproteinases on fibronectin fibers. Critically, in an mouse orthotopic breast cancer model, the absence of the fibronectin EDA domain completely prevents lung metastasis.

CONCLUSIONS

Our results support the requirement of EDA+ fibronectin in the generation of a metastasis permissive stromal architecture in breast cancers and its molecular control by SNAIL1. From a pharmacological point of view, specifically blocking EDA+ fibronectin deposition could be included in studies to reduce the formation of a pro-metastatic environment.

The role of flavonoids in the regulation of epithelial-mesenchymal transition in cancer: A review on targeting signaling pathways and metastasis

One of the hallmarks of cancer is metastasis, a process that entails the spread of cancer cells to distant regions in the body, culminating in tumor formation in secondary organs. Importantly, the proinflammatory environment surrounding cancer cells further contributes to cancer cell transformation and extracellular matrix destruction. During metastasis, front-rear polarity and emergence of migratory and invasive features are manifestations of epithelial-mesenchymal transition (EMT). A variety of transcription factors (TFs) are implicated in the execution of EMT, the most prominent belonging to the Snail Family Transcriptional Repressor (SNAI) and Zinc Finger E-Box Binding Homeobox (ZEB) families of TFs. These TFs are regulated by interaction with specific microRNAs (miRNAs), as miR34 and miR200. Among the several secondary metabolites produced in plants, flavonoids constitute a major group of bioactive molecules, with several described effects including antioxidant, antiinflammatory, antidiabetic, antiobesogenic, and anticancer effects. This review scrutinizes the modulatory role of flavonoids on the activity of SNAI/ZEB TFs and on their regulatory miRNAs, miR-34, and miR-200. The modulatory role of flavonoids can attenuate mesenchymal features and stimulate epithelial features, thereby inhibiting and reversing EMT. Moreover, this modulation is concomitant with the attenuation of signaling pathways involved in diverse processes as cell proliferation, cell growth, cell cycle progression, apoptosis inhibition, morphogenesis, cell fate, cell migration, cell polarity, and wound healing. The antimetastatic potential of these versatile compounds is emerging and represents an opportunity for the synthesis of more specific and potent agents.

OTUD4 regulates metastasis and chemoresistance in melanoma by stabilizing Snail1

Melanoma is the most aggressive form of skin cancer with rapidly increased incidence worldwide especially in the Caucasian population. Surgical excision represents the curative treatment choice in patients with early-stage disease. However, the therapeutic outcomes in patients with metastatic melanoma remains unsatisfactory. Thus, understanding molecular mechanisms contributing to metastasis and chemoresistance is critical for new improved therapies of melanoma. Snail1, an important epithelial-mesenchymal transition transcription factors (EMT-TFs), is critical to induce the EMT process, thereby contributing to cancer metastasis. However, the involvement of Snail1 in melanoma metastasis remains elusive and the underlying mechanism to regulate Snail1 in melanoma needs to be further investigated. Here, we identified OTUD4 as a novel deubiquitinase of Snail1 in melanoma. Moreover, the depletion of OTUD4 in melanoma cells markedly inhibited Snail1 stability and Snail1-driven malignant phenotypes both in vitro and in vivo. Overall, our study establishes OTUD4 as a novel therapeutic target in metastasis and chemoresistance of melanoma by stabilizing Snail1 and provides a rationale for potential therapeutic strategies of melanoma.

USP36 stabilizes nucleolar Snail1 to promote ribosome biogenesis and cancer cell survival upon ribotoxic stress

Tumor growth requires elevated ribosome biogenesis. Targeting ribosomes is an important strategy for cancer therapy. The ribosome inhibitor, homoharringtonine (HHT), is used for the clinical treatment of leukemia, yet it is ineffective for the treatment of solid tumors, the reasons for which remain unclear. Here we show that Snail1, a key factor in the regulation of epithelial-to-mesenchymal transition, plays a pivotal role in cellular surveillance response upon ribotoxic stress. Mechanistically, ribotoxic stress activates the JNK-USP36 signaling to stabilize Snail1 in the nucleolus, which facilitates ribosome biogenesis and tumor cell survival. Furthermore, we show that HHT activates the JNK-USP36-Snail1 axis in solid tumor cells, but not in leukemia cells, resulting in solid tumor cell resistance to HHT. Importantly, a combination of HHT with the inhibition of the JNK-USP36-Snail1 axis synergistically inhibits solid tumor growth. Together, this study provides a rationale for targeting the JNK-USP36-Snail1 axis in ribosome inhibition-based solid tumor therapy.

Methanolic Extracts of D. viscosa Specifically Affect the Cytoskeleton and Exert an Antiproliferative Effect on Human Colorectal Cancer Cell Lines, According to Their Proliferation Rate

Numerous studies have reported the pharmacological effects exhibited by Dittrichia viscosa, (D. viscosa) including antioxidant, cytotoxic, antiproliferative, and anticancer properties. In our research, our primary objective was to validate a prescreening methodology aimed at identifying the fraction that demonstrates the most potent antiproliferative and anticancer effects. Specifically, we investigated the impact of various extract fractions on the cytoskeleton using a screening method involving transgenic plants. Tumors are inherently heterogeneous, and the components of the cytoskeleton, particularly tubulin, are considered a strategic target for antitumor agents. To take heterogeneity into account, we used different lines of colorectal cancer, specifically one of the most common cancers regardless of gender. In patients with metastasis, the effectiveness of chemotherapy has been limited by severe side effects and by the development of resistance. Additional therapies and antiproliferative molecules are therefore needed. In our study, we used colon-like cell lines characterized by the expression of gastrointestinal differentiation markers (such as the HT-29 cell line) and undifferentiated cell lines showing the positive regulation of epithelial-mesenchymal transition and TGFβ signatures (such as the DLD-1, SW480, and SW620 cell lines). We showed that all three of the D. viscosa extract fractions have an antiproliferative effect but the pre-screening on transgenic plants anticipated that the methanolic fraction may be the most promising, targeting the cytoskeleton specifically and possibly resulting in fewer side effects. Here, we show that the preliminary use of screening in transgenic plants expressing subcellular markers can significantly reduce costs and focus the advanced characterization only on the most promising therapeutic molecules.

Role of pelitinib in the regulation of migration and invasion of hepatocellular carcinoma cells via inhibition of Twist1

BACKGROUND

Overexpression of Twist1, one of the epithelial-mesenchymal transition-transcription factors (EMT-TFs), is associated with hepatocellular carcinoma (HCC) metastasis. Pelitinib is known to be an irreversible epidermal growth factor receptor tyrosine kinase inhibitor that is used in clinical trials for colorectal and lung cancers, but the role of pelitinib in cancer metastasis has not been studied. This study aimed to investigate the anti-migration and anti-invasion activities of pelitinib in HCC cell lines.

METHODS

Using three HCC cell lines (Huh7, Hep3B, and SNU449 cells), the effects of pelitinib on cell cytotoxicity, invasion, and migration were determined by cell viability, wound healing, transwell invasion, and spheroid invasion assays. The activities of MMP-2 and -9 were examined through gelatin zymography. Through immunoblotting analyses, the expression levels of EMT-TFs (Snail1, Twist1, and ZEB1) and EMT-related signaling pathways such as mitogen-activated protein kinases (MAPKs) and Akt signaling pathways were measured. The activity and expression levels of target genes were analyzed by reporter assay, RT-PCR, quantitative RT-PCR, and immunoblotting analysis. Statistical analysis was performed using one-way ANOVA with Dunnett's Multiple comparison tests in Prism 3.0 to assess differences between experimental conditions.

RESULTS

In this study, pelitinib treatment significantly inhibited wound closure in various HCC cell lines, including Huh7, Hep3B, and SNU449. Additionally, pelitinib was found to inhibit multicellular cancer spheroid invasion and metalloprotease activities in Huh7 cells. Further investigation revealed that pelitinib treatment inhibited the migration and invasion of Huh7 cells by inducing Twist1 degradation through the inhibition of MAPK and Akt signaling pathways. We also confirmed that the inhibition of cell motility by Twist1 siRNA was similar to that observed in pelitinib-treated group. Furthermore, pelitinib treatment regulated the expression of target genes associated with EMT, as demonstrated by the upregulation of E-cadherin and downregulation of N-cadherin.

CONCLUSION

Based on our novel finding of pelitinib from the perspective of EMT, pelitinib has the ability to inhibit EMT activity of HCC cells via inhibition of Twist1, and this may be the potential mechanism of pelitinib on the suppression of migration and invasion of HCC cells. Therefore, pelitinib could be developed as a potential anti-cancer drug for HCC.

Role of epithelial-mesenchymal transition factor SNAI1 and its targets in ovarian cancer aggressiveness

Ovarian cancer remains the most lethal gynecologic malignancy in the USA. For over twenty years, epithelial-mesenchymal transition (EMT) has been characterized extensively in development and disease. The dysregulation of this process in cancer has been identified as a mechanism by which epithelial tumors become more aggressive, allowing them to survive and invade distant tissues. This occurs in part due to the increased expression of the EMT transcription factor, SNAI1 (Snail). In the case of epithelial ovarian cancer, Snail has been shown to contribute to cancer invasion, stemness, chemoresistance, and metabolic changes. Thus, in this review, we focus on summarizing current findings on the role of EMT (specifically, factors downstream of Snail) in determining ovarian cancer aggressiveness.

GATA zinc finger protein p66β promotes breast cancer cell migration by acting as a co-activator of Snail

The transcriptional repressor Snail induces EMT during embryonic development and tumor metastasis. Growing evidence indicates that Snail functions as a trans-activator to induce gene expression; however, the underlying mechanism remains elusive. Here, we report that Snail cooperates with GATA zinc finger protein p66β to transactivate genes in breast cancer cells. Biologically, depletion of p66β reduces cell migration and lung metastasis in BALB/c mice. Mechanistically, Snail interacts with p66β and cooperatively induces gene transcription. Notably, a group of genes induced by Snail harbor conserved G-rich cis-elements (5'-GGGAGG-3', designated as G-box) in their proximal promoter regions. Snail directly binds to G-box via its zinc fingers and transactivates the G-box-containing promoters. p66β enhances Snail binding affinity to G-box, whereas depletion of p66β results in a decreased binding affinity of Snail to the endogenous promoters and concomitantly reduces the transcription of Snail-induced genes. Taken together, these data demonstrated that p66β is critical for Snail-mediated cell migration by acting as a co-activator of Snail to induce genes containing G-box elements in the promoters.

Noncanonical Wnt signaling promotes colon tumor growth, chemoresistance and tumor fibroblast activation

Colon tumors of the mesenchymal subtype have the lowest overall survival. Snail1 is essential for the acquisition of this phenotype, characterized by increased tumor stemness and invasion, and high resistance to chemotherapy. Here, we find that Snail1 expression in colon tumor cells is dependent on an autocrine noncanonical Wnt pathway. Accordingly, depletion of Ror2, the co-receptor for noncanonical Wnts such as Wnt5a, potently decreases Snail1 expression. Wnt5a, Ror2, and Snail1 participate in a self-stimulatory feedback loop since Wnt5a increases its own synthesis in a Ror2- and Snail1-dependent fashion. This Wnt5a/Ror2/Snail1 axis controls tumor invasion, chemoresistance, and formation of tumor spheres. It also stimulates TGFβ synthesis; consequently, tumor cells expressing Snail1 are more efficient in activating cancer-associated fibroblasts than the corresponding controls. Ror2 downmodulation or inhibition of the Wnt5a pathway decreases Snail1 expression in primary colon tumor cells and their ability to form tumors and liver metastases. Finally, the expression of SNAI1, ROR2, and WNT5A correlates in human colon and other tumors. These results identify inhibition of the noncanonical Wnt pathway as a putative colon tumor therapy.

USP22 aggravated diabetic renal tubulointerstitial fibrosis progression through deubiquitinating and stabilizing Snail1

Renal tubulointerstitial fibrosis (TIF) is one of the main pathological changes induced by diabetic kidney disease (DKD), and epithelial-to-mesenchymal transition (EMT) induced by high glucose (HG) can promote TIF. Our previous study has shown that ubiquitin-specific protease 22 (USP22) could affect the process of DKD by deubiquitinating and stabilizing Sirt1 in glomerular mesangial cells. However, whether USP22 could regulate EMT occurrence in renal tubular epithelial cells and further aggravate the pathological process of TIF in DKD remains to be elucidated. In this study, we found that USP22 expression was upregulated in kidney tissues of db/db mice and HG-treated NRK-52E cells. In vitro, USP22 overexpression promoted the EMT process of NRK-52E cells stimulated by HG and further increased the levels of extracellular matrix (ECM) components such as fibronectin, Collagen I, and Collagen Ⅳ. Meanwhile, USP22 deficiency exhibited the opposite effects. Mechanism studies showed that USP22, depending on its deubiquitinase activity, deubiquitinated and stabilized the EMT transcriptional factor Snail1. In vivo experiment showed that interfering with USP22 could improve the renal pathological damages and renal function of the db/db spontaneous diabetic mice by decreasing Snail1 expression, which could inhibit EMT occurrence, and reduce the production of ECM components. These results suggested that USP22 could accelerate renal EMT and promote the pathological progression of diabetic TIF by deubiquitinating Snail1, providing an experimental basis for using USP22 as a potential target for DKD.

LINC01013 Is a Determinant of Fibroblast Activation and Encodes a Novel Fibroblast-Activating Micropeptide

Myocardial fibrosis confers an almost threefold mortality risk in heart disease. There are no prognostic therapies and novel therapeutic targets are needed. Many thousands of unannotated small open reading frames (smORFs) have been identified across the genome with potential to produce micropeptides (< 100 amino acids). We sought to investigate the role of smORFs in myocardial fibroblast activation.Analysis of human cardiac atrial fibroblasts (HCFs) stimulated with profibrotic TGFβ1 using RNA sequencing (RNA-Seq) and ribosome profiling (Ribo-Seq) identified long intergenic non-coding RNA LINC01013 as TGFβ1 responsive and containing an actively translated smORF. Knockdown of LINC01013 using siRNA reduced expression of profibrotic markers at baseline and blunted their response to TGFβ1. In contrast, overexpression of a codon-optimised smORF invoked a profibrotic response comparable to that seen with TGFβ1 treatment, whilst FLAG-tagged peptide associated with the mitochondria.Together, these data support a novel LINC01013 smORF micropeptide-mediated mechanism of fibroblast activation. TGFβ1 stimulation of atrial fibroblasts induces expression of LINC01013, whose knockdown reduces fibroblast activation. Overexpression of a smORF contained within LINC01013 localises to mitochondria and activates fibroblasts.

Knockdown of lncRNA-ASLNC12002 alleviates epithelial-mesenchymal transition of type II alveolar epithelial cells in sepsis-induced acute respiratory distress syndrome

Patients with sepsis-induced acute respiratory distress syndrome (ARDS) have higher mortality and poor prognosis than pneumonia-induced ARDS. Pulmonary fibrosis is an irreversible accumulation of connective tissue in the interstitium of the lung and closely associated with the epithelial-mesenchymal transition (EMT) of type II alveolar epithelial cells (AECIIs). Therefore, it is undoubtedly worth studying whether the EMT of AECIIs in sepsis-induced ARDS patients is different from that in patients with pneumonia-induced ARDS in the regulatory mechanism. Here, we will report for the first time that an lncRNA-ASLNC12002 is highly expressed in AECIIs of patients with sepsis-induced pneumonia and promotes EMT in AECIIs. The research results showed that the expression of ASLNC12002 in AECIIs derived from patients with sepsis-induced ARDS is significantly higher than that in normal people and pneumonia-induced ARDS patients. Mechanism research showed that ASLNC12002 can cause the inactivation of the anti-EMT pathway NR2F2/miR128-3p/Snail1 by acting as the sponge of miR128-3p. Functional experiments showed that targeted silencing of ASLNC12002 could effectively inhibit EMT progression in AECIIs of patients with sepsis-induced pneumonia by restoring NR2F2/miR128-3p/Snail1 pathway. In a word, our study shows for the first time that the inactivation of NR2F2/miR128-3p/Snail1 pathway caused by the enhanced expression of ASLNC12002 is the direct reason why AECIIs in sepsis-induced ARDS patients are prone to get EMT progress. ASLNC12002 has the potential to become a biological target for the prevention and treatment of pulmonary fibrosis in patients with sepsis-induced ARDS. At the same time, the expectation that ASLNC12002 and its related products may be used as clinical markers for the evaluation of early pulmonary fibrosis in ARDS patients should not be ignored.

Enzymatic lysine oxidation as a posttranslational modification

Oxidoreductases catalyze oxidation-reduction reactions and comprise a very large and diverse group of enzymes, which can be subclassified depending on the catalytic mechanisms of the enzymes. One of the most prominent oxidative modifications in proteins is carbonylation, which involves the formation of aldehyde and keto groups in the side chain of lysines. This modification can alter the local macromolecular structure of proteins, thereby regulating their function, stability, and/or localization, as well as the nature of any protein-protein and/or protein-nucleic acid interactions. In this review, we focus on copper-dependent amine oxidases, which catalyze oxidative deamination of amines to aldehydes. In particular, we discuss oxidation reactions that involve lysine residues and that are regulated by members of the lysyl oxidase (LOX) family of proteins. We summarize what is known about the newly identified substrates and how this posttranslational modification regulates protein function in different contexts.

Human Cytomegalovirus Induces Vitamin-D Resistance In Vitro by Dysregulating the Transcriptional Repressor Snail

Vitamin-D supplementation is considered to play a beneficial role against multiple viruses due to its immune-regulating and direct antimicrobial effects. In contrast, the human cytomegalovirus (HCMV) has shown to be resistant to treatment with vitamin D in vitro by downregulation of the vitamin-D receptor. In this study, we aimed to elucidate the mechanism and possible biological consequences of vitamin-D resistance during HCMV infection. Mechanistically, HCMV induced vitamin-D resistance by downregulating the vitamin-D receptor (VDR) within hours of lytic infection. We found that the VDR was inhibited at the promoter level, and treatment with histone deacetylase inhibitors could restore VDR expression. VDR downregulation highly correlated with the upregulation of the transcriptional repressor Snail1, a mechanism likely contributing to the epigenetic inactivation of the VDR promoter, since siRNA-mediated knockdown of Snail partly restored levels of VDR expression. Finally, we found that direct addition of the vitamin-D-inducible antimicrobial peptide LL-37 strongly and significantly reduced viral titers in infected fibroblasts, highlighting VDR biological relevance and the potential of vitamin-D-inducible peptides for the antiviral treatment of vitamin-D deficient patients.

SNAI1-expressing fibroblasts and derived-extracellular matrix as mediators of drug resistance in colorectal cancer patients

Resistance to antitumor treatments is one of the most important problems faced by clinicians in the management of colorectal cancer (CRC) patients. Cancer-Associated Fibroblasts (CAFs) are the main producers and remodelers of the extracellular matrix (ECM), which is directly involved in drug resistance mechanisms. Primary Normal Fibroblasts (NFs) and CAFs and cell lines (fibroblasts and tumor cells), were used to generate ECM and to identify its role in the oxaliplatin and cetuximab chemoresistance processes of CRC cells mediated by SNAI1-expressing fibroblasts. Matrices generated by Snai1 KO MEFs (Knockout Mouse Embryonic Fibroblasts) confer less resistance on oxaliplatin and cetuximab than wild-type MEF-derived matrices. Similarly, matrices derived from CAFs cause greater survival of colorectal cancer cells than NF-derived matrices, in a similar way to Snai1 expression levels. In addition, Snail1 expression in fibroblasts regulates drug resistance and metabolism gene expression in tumor cells mediated by ECM. Finally, a series of 531 patients (TCGA) with CRC was used to assess the role of SNAI1 expression in patients' prognosis indicating an association between tumor SNAI1 expression and overall survival in colon cancer patients but not in rectal cancer patients. SNAI1 expression in CRC cancer patients, together with in vitro experimentation, suggests the possible use of SNAI1 expression in tumor-associated fibroblasts as a predictive biomarker of response to oxaliplatin and cetuximab treatments in patients with CRC.

Analysis of the Effect of SNAI Family in Breast Cancer and Immune Cell

SNAI family members are transcriptional repressors that induce epithelial-mesenchymal transition during biological development. SNAIs both have tumor-promoting and tumor-inhibiting effect. There are key regulatory effects on tumor onset and development, and patient prognosis in infiltrations of immune cell and tumor microenvironmental changes. However, the relationships between SNAIs and immune cell infiltration remain unclear. We comprehensively analyzed the roles of SNAIs in cancer. We used Oncomine and TCGA data to analyze pan-cancer SNAI transcript levels. By analyzing UALCAN data, we found correlations between SNAI transcript levels and breast cancer patient characteristics. Kaplan–Meier plotter analysis revealed that SNAI1 and SNAI2 have a bad prognosis, whereas SNAI3 is the opposite. Analysis using the cBio Cancer Genomics Portal revealed alterations in SNAIs in breast cancer subtypes. Gene Ontology analysis and gene set enrichment analysis were used to analyze differentially expressed genes related to SNAI proteins in breast cancer. We used TIMER to analyze the effects of SNAI transcript levels, mutations, methylation levels, and gene copy number in the infiltration of immune cell. Further, we found the relationships between immune cell infiltration, SNAI expression levels, and patient outcomes. To explore how SNAI proteins affect immune cell, we further studied the correlations between immunomodulator expression, chemokine expression, and SNAI expression. The results showed that SNAI protein levels were correlated with the expression of several immunomodulators and chemokines. Through analysis of PharmacoDB data, we identified antitumor drugs related to SNAI family members and analyzed their IC50 effects on various breast cancer cell lines. In summary, our study revealed that SNAI family members regulate different immune cells infiltrations by gene copy number, mutation, methylation, and expression level. SNAI3 and SNIA1/2 have opposite regulatory effects. They all play a key role in tumor development and immune cell infiltration, and can provide a potential target for drug therapy.

Two distinct males absent on the first (MOF)-containing histone acetyltransferases are involved in the epithelial-mesenchymal transition in different ways in human cells

Human males absent on the first (MOF), a histone acetyltransferase (HAT), forms male-specific lethal (MSL) and non-specific lethal (NSL), two multiprotein HATs, in cells. MSL was originally discovered in dosage compensation study in Drosophila that can specifically acetylate H4K16, while NSL can simultaneously catalyze the H4 at K5, K8, and K16 sites. However, comparative studies of the two HATs in regulating specific biological functions are rarely reported. Here, we present evidence to argue that MSL and NSL function in different ways in the epithelial-to-mesenchymal transition (EMT) process. At first, CRISPR/Cas9-mediated MSL1 (a key subunit of the MSL)-knockout (KO) and NSL3 (a key subunit of the NSL)-KO cells seem to prefer to grow in clusters. Interestingly, the former promotes cell survival and clonal formation, while the latter has the opposite effect on it. Cell staining revealed that MSL1-KO leads to multipolarized spindles, while NSL3-KO causes more lumen-like cells. Furthermore, in Transwell experiments, silencing of MSL1 promotes cell invasion in 293 T, MCF-7, and MDA-MB-231 cells. In contrast, the inhibitory effects on cell invasion are observed in the same NSL3-silenced cells. Consistent with this, mesenchymal biomarkers, like N-cadherin, vimentin, and snail, are negatively correlated with the expression level of MSL1; however, a positive relationship between these proteins and NSL3 in cells has been found. Further studies have clarified that MSL1, but not NSL3, can specifically bind to the E-box-containing Snail promoter region and thereby negatively regulate Snail transactivation. Also, silencing of MSL1 promotes the lung metastasis of B16F10 melanoma cells in mice. Finally, ChIP-Seq analysis indicated that the NSL may be mainly involved in phosphoinositide-mediated signaling pathways. Taken together, the MOF-containing MSL and NSL HATs may regulate the EMT process in different ways in order to respond to different stimuli.

Acupuncture and Moxibustion Inhibited Intestinal Epithelial-Mesenchymal Transition in Patients with Crohn's Disease Induced by TGF- β 1/Smad3/Snail Pathway: A Clinical Trial Study

OBJECTIVE

To explore whether acupuncture combined with moxibustion could inhibit epithelialmesenchymal transition in Crohn's disease by affecting the transforming growth factor β 1 (TGF- β 1)/Smad3/Snail pathway.

METHODS

Sixty-three patients with Crohn's disease were randomly divided into an observation group (31 cases) receiving moxibustion at 43 °C combined with acupuncture, and a control group (32 cases) receiving moxibustion at 37 °C combined with sham acupuncture using a random number table. Patients were treated for 12 weeks. Crohn's Disease Activity Index (CDAI) was used to evaluate disease activity. Hematoxylin-eosin staining and transmission electron microscopy were utilized to observe the morphological and ultrastructural changes. Immunohistochemistry was used to detect the expression of transforming growth factor β 1 (TGF-β 1), T β R1, T β R2, Smad3, Snail, E-cadherin and fibronectin in intestinal mucosal tissues.

RESULTS

The decrease of the CDAI score, morphological and ultrastructural changes were more significant in observation group. The expression levels of TGF- β 1, Tβ R2, Smad3, and Snail in the observation group were significantly lower than those before the treatment (P<0.05 or P<0.01). After treatment, the expression levels of TGF-β 1, TβR2, and Snail in the observation group were significantly lower than those in the control group (all P<0.05); compared with the control group, the expression of fibronectin in the observation group was significantly decreased, and the expression of E-cadherin was significantly increased (all P<0.05).

CONCLUSIONS

Moxibustion at 43 °C combined with acupuncture may suppress TGF-β 1/Smad3/Snail pathway-mediated epithelial-mesenchymal transition of intestinal epithelial cells in Crohn's disease patients by inhibiting the expression levels of TGF-β 1, Tβ R2, Smad3, and Snail. (Registration No. ChiCTR-IIR-16007751).

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.

Regulation of FGF-2, FGF-18 and Transcription Factor Activity by Perlecan in the Maturational Development of Transitional Rudiment and Growth Plate Cartilages and in the Maintenance of Permanent Cartilage Homeostasis

The aim of this study was to highlight the roles of perlecan in the regulation of the development of the rudiment developmental cartilages and growth plate cartilages, and also to show how perlecan maintains permanent articular cartilage homeostasis. Cartilage rudiments are transient developmental templates containing chondroprogenitor cells that undergo proliferation, matrix deposition, and hypertrophic differentiation. Growth plate cartilage also undergoes similar changes leading to endochondral bone formation, whereas permanent cartilage is maintained as an articular structure and does not undergo maturational changes. Pericellular and extracellular perlecan-HS chains interact with growth factors, morphogens, structural matrix glycoproteins, proteases, and inhibitors to promote matrix stabilization and cellular proliferation, ECM remodelling, and tissue expansion. Perlecan has mechanotransductive roles in cartilage that modulate chondrocyte responses in weight-bearing environments. Nuclear perlecan may modulate chromatin structure and transcription factor access to DNA and gene regulation. Snail-1, a mesenchymal marker and transcription factor, signals through FGFR-3 to promote chondrogenesis and maintain Acan and type II collagen levels in articular cartilage, but prevents further tissue expansion. Pre-hypertrophic growth plate chondrocytes also express high Snail-1 levels, leading to cessation of Acan and CoI2A1 synthesis and appearance of type X collagen. Perlecan differentially regulates FGF-2 and FGF-18 to maintain articular cartilage homeostasis, rudiment and growth plate cartilage growth, and maturational changes including mineralization, contributing to skeletal growth.

Triptonide effectively inhibits triple-negative breast cancer metastasis through concurrent degradation of Twist1 and Notch1 oncoproteins

Background

Triple-negative breast cancer (TNBC) is highly metastatic and lethal. Due to a lack of druggable targets for this disease, there are no effective therapies in the clinic.

Methods

We used TNBC cells and xenografted mice as models to explore triptonide-mediated inhibition of TNBC metastasis and tumor growth. Colony formation assay was used to quantify the tumorigenesis of TNBC cells. Wound-healing and cell trans-well assays were utilized to measure cell migration and invasion. Tube formation assay was applied to access tumor cell-mediated vasculogenic mimicry. Western blot, quantitative-PCR, immunofluorescence imaging, and immunohistochemical staining were used to measure the expression levels of various tumorigenic genes in TNBC cells.

Results

Here, we showed that triptonide, a small molecule from the traditional Chinese medicinal herb Tripterygium wilfordii Hook F, potently inhibited TNBC cell migration, invasion, and vasculogenic mimicry, and effectively suppressed TNBC tumor growth and lung metastasis in xenografted mice with no observable toxicity. Molecular mechanistic studies revealed that triptonide strongly triggered the degradation of master epithelial-mesenchymal transition (EMT)-inducing protein Twist1 through the lysosomal system and reduced Notch1 expression and NF-κB phosphorylation, which consequently diminished the expression of pro-metastatic and angiogenic genes N-cadherin, VE-cadherin, and vascular endothelial cell growth factor receptor 2 (VEGFR2).

Conclusions

Triptonide effectively suppressed TNBC cell tumorigenesis, vasculogenic mimicry, and strongly inhibited the metastasis of TNBC via degradation of Twist1 and Notch1 oncoproteins, downregulation of metastatic and angiogenic gene expression, and reduction of NF-κB signaling pathway. Our findings provide a new strategy for treating highly lethal TNBC and offer a potential new drug candidate for combatting this aggressive disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01488-7.

The implication of IL-6 in the invasiveness and chemoresistance of ovarian cancer cells. Systematic review of its potential role as a biomarker in ovarian cancer patients

Interleukin 6 (IL-6) is a pleiotropic cytokine that is strongly implicated in the development and progression of ovarian cancer. The most recognized actions of IL-6 in ovarian cancer (OC) cells are the induction of cell proliferation and inhibition of cell apoptosis. Equally important is its ability to enhance the migratory and invasive potential of OC cells. Moreover, the increased expression and secretion of this cytokine positively correlates with OC cell chemoresistance. Elevated concentrations of IL-6 are observed in the serum and ascites of ovarian cancer patients. Thus, its level is discussed in the literature as a potential biomarker that can help to discriminate malignant and nonmalignant ovarian tumors and allow for the prediction of the chemotherapy response. The importance of IL-6 in ovarian cancer is proved by the fact that this cytokine is a potential target to anti-cancer therapy. This review is divided into two parts. The first summarizes the general biological activity of IL-6, and overviews its impact on OC cells, as well as discusses the current proposition of IL-6 inclusion in combination of anti-OC therapy. The second part is a systematic review of IL-6 as a possible biomarker in ovarian cancer patients.

Alveolar Regeneration in COVID-19 Patients: A Network Perspective

A viral infection involves entry and replication of viral nucleic acid in a host organism, subsequently leading to biochemical and structural alterations in the host cell. In the case of SARS-CoV-2 viral infection, over-activation of the host immune system may lead to lung damage. Albeit the regeneration and fibrotic repair processes being the two protective host responses, prolonged injury may lead to excessive fibrosis, a pathological state that can result in lung collapse. In this review, we discuss regeneration and fibrosis processes in response to SARS-CoV-2 and provide our viewpoint on the triggering of alveolar regeneration in coronavirus disease 2019 (COVID-19) patients.

Anti-inflammation treatment for protection of hepatocytes and amelioration of hepatic fibrosis in rats

Chronic inflammation is considered as an important pathophysiologic mechanism of hepatic cirrhosis, which induces hepatocyte injury and activates hepatic stellate cells (HSCs), thus resulting in hepatic fibrosis. Previous studies have reported that cyclooxygenase-2 (COX-2) inhibitor can effectively treat liver fibrosis, while somatostatin (SST) analogues inhibit the activation of HSCs. The present study aimed to investigate the effects of a COX-2 inhibitor, celecoxib, combined with a SST analogue, octreotide, for protection of hepatocytes and prevention of fibrosis in a rat model of hepatic fibrosis. Therefore, a hepatic fibrosis rat model was established following peritoneal injection of thioacetamide (TAA), and the rats were then treated with a combination of celecoxib and octreotide (TAA + C). Immunohistochemistry and western blotting assays were used to assess the expression levels of proteins associated with inflammation, epithelial-mesenchymal transition (EMT), proliferation, apoptosis and autophagy. H&E staining, transmission electron microscopy and scanning electron microscopy were used to evaluate the destruction of hepatocytes. Masson's Trichrome and Sirius Red were used to measure the degree of liver fibrosis. The results demonstrated that, compared with those of the control group, the degree of liver fibrosis and the expression of the intrahepatic inflammation factors were aggravated in the TAA group. Furthermore, the apoptosis rate, EMT and autophagy of hepatocytes were also increased in the TAA group. However, treatment with TAA + C restored the aforementioned increased levels compared with the TAA group. In conclusion, treatment of rats with the combination of celecoxib and octreotide could attenuate the progress of hepatic fibrosis via protection of hepatocytes by reducing apoptosis, EMT and autophagy in hepatocytes.

The EMT transcription factor Snai1 maintains myocardial wall integrity by repressing intermediate filament gene expression

The transcription factor Snai1, a well-known regulator of epithelial-to-mesenchymal transition, has been implicated in early cardiac morphogenesis as well as in cardiac valve formation. However, a role for Snai1 in regulating other aspects of cardiac morphogenesis has not been reported. Using genetic, transcriptomic, and chimeric analyses in zebrafish, we find that Snai1b is required in cardiomyocytes for myocardial wall integrity. Loss of snai1b increases the frequency of cardiomyocyte extrusion away from the cardiac lumen. Extruding cardiomyocytes exhibit increased actomyosin contractility basally as revealed by enrichment of p-myosin and α-catenin epitope α-18, as well as disrupted intercellular junctions. Transcriptomic analysis of wild-type and snai1b mutant hearts revealed the dysregulation of intermediate filament genes, including desmin b (desmb) upregulation. Cardiomyocyte-specific desmb overexpression caused increased cardiomyocyte extrusion, recapitulating the snai1b mutant phenotype. Altogether, these results indicate that Snai1 maintains the integrity of the myocardial epithelium, at least in part by repressing desmb expression.

The Role of Snail-1 in Thyroid Cancer-What We Know So Far

Thyroid carcinomas, despite the usually indolent behaviour and relatively good overall prognosis, show a high tendency to gain invasive phenotype and metastasise in some cases. However, due to a relatively slow progression, the exact mechanisms governing the metastatic process of thyroid carcinomas, including the epithelial-to-mesenchymal transition (EMT), are poorly described. One of the best-known regulators of cancer invasiveness is Snail-1-a zinc-finger transcription factor that plays a key role as an EMT inducer. More and more attention is being paid to the role of Snail with regard to thyroid cancer development. Apart from the obvious implications in the EMT process, Snail-1 plays an important role in the regulation of chemoresistance of the thyroid cells and cancer stem cell (CSC) formation, and it also interacts with miRNA specific to the thyroid gland. The aim of this review was to summarise the knowledge on Snail-1, especially in the context of thyroid oncogenesis.

LncRNA PVT1 Regulates High Glucose-Induced Viability, Oxidative Stress, Fibrosis, and Inflammation in Diabetic Nephropathy via miR-325-3p/Snail1 Axis

BACKGROUND

Diabetic nephropathy (DN), as a complication of diabetes, is a leading cause of mortality in diabetic patients. It has been reported that lncRNA PVT1 (PVT1) could accelerate the progression of DN by promoting ECM accumulation and increasing the expression of fibronectin 1 (FN1). However, the underlying mechanism of PVT1 on DN remains unknown.

METHODS

To study the effect of PVT1 on DN, mice were injected 50 mg/kg STZ to build the DN models. Mesangial cells (MCs) were induced by high glucose as in vitro model of DN. The expression level of PVT1, miR-325-3 and Snail1 was assessed by qRT-PCR and Western blot. Luciferase reporter assay, RNA pull-down and RIP were used to explore the interaction among PVT1, miR-325-3 and Snail1.

RESULTS

In in vivo and in vitro DN models, the expression of PVT1 was upregulated. High glucose (HG) induced cell viability, oxidative stress, fibrosis and inflammation in MCs, which were reversed in the PVT1-KD MCs. The level of miR-325-3p was also increased in in vivo and in vitro experiments. Additionally, PVT1 can directly bind to miR-325-3p. Finally, Snail1 was a direct target of miR-325-3p.

CONCLUSION

PVT1 inhibits viability, oxidative stress, fibrosis, and inflammation in DN via miR-325-3p/Snail1 axis.

TGFβ promotes widespread enhancer chromatin opening and operates on genomic regulatory domains

The Transforming Growth Factor-β (TGFβ) signaling pathway controls transcription by regulating enhancer activity. How TGFβ-regulated enhancers are selected and what chromatin changes are associated with TGFβ-dependent enhancers regulation are still unclear. Here we report that TGFβ treatment triggers fast and widespread increase in chromatin accessibility in about 80% of the enhancers of normal mouse mammary epithelial-gland cells, irrespective of whether they are activated, repressed or not regulated by TGFβ. This enhancer opening depends on both the canonical and non-canonical TGFβ pathways. Most TGFβ-regulated genes are located around enhancers regulated in the same way, often creating domains of several co-regulated genes that we term TGFβ regulatory domains (TRD). CRISPR-mediated inactivation of enhancers within TRDs impairs TGFβ-dependent regulation of all co-regulated genes, demonstrating that enhancer targeting is more promiscuous than previously anticipated. The area of TRD influence is restricted by topologically associating domains (TADs) borders, causing a bias towards co-regulation within TADs.

Metastatic behavior analyses of tetraspanin TM4SF5-expressing spheres in three-dimensional (3D) cell culture environment

Cancer metastasis involves diverse cellular functions via bidirectional communications between intracellular and extracellular spaces. To achieve development of the anti-metastatic drugs, one needs to consider the efficacy and mode of action (MOA) of the drug candidates to block the metastatic potentials of cancerous cells. Rather than under two-dimensional environment, investigation of the metastatic potentials under three-dimensional environment would be much pharmaceutically beneficent, since it can mimic the in vivo tumor lesions in cancer patients, leading to allowance of drug candidates analyzed in the 3D culture systems to lower failure rates during the anti-metastatic drug development. Here we have reviewed on the analyses of metastatic potentials of certain cancer models in 3D culture systems surrounded with extracellular matrix proteins, which could be supported by TM4SF5- and/or EMT-mediated actions. We particularly focused the initial events of the cancer metastasis, such as invasive outgrowth and dissemination from the cancer cell masses, spheroids, embedded in the 3D gel culture systems. This review summarizes the significance of tetraspanin TM4SF5 and Snail1 that are related to EMT in the metastatic potentials explored in the 3D gel systems.

MicroRNA-138-5p targets the NFIB-Snail1 axis to inhibit colorectal cancer cell migration and chemoresistance

Background

Colorectal cancer ranks among the most lethal diseases worldwide. Although much progress has been made in research and treatment of colorectal cancer in recent years, the underlying mechanisms related to migration of the cancer cells and the reason for chemoresistance still remain unclear. In this research, we explored the underlying effect of miR-138-5p in colorectal cancer.

Methods

We used qRT-PCR to investigate the expression of miR-138-5p, Snail1, NFIB in colorectal cancer cells. Lentiviral vectors containing miR-138-5p mimics and inhibitors were constructed and transfected cells. Wound healing assay was applied to illustrate interferences on cell migration. Fluorouracial, doxorubicin, cisplat in were used to detect chemotherapy resistance. In order to identify target genes, bioinformatic methods were applied. Snail1 and NFIB protein expression in stable cell lines was detected using Western blot. Double luciferase and CHIP experiment were used to verify binding sites. We used rescue experiments to further explore the interactions among Snail1, NFIB and miR-138-5p.

Results

The expression of miR-138-5p in colorectal cancer cells was low. miR-138-5p inhibited cell migration in colorectal cancer, and could negatively regulate chemotherapy resistance. miR-138-5p targeted NFIB, and regulated Snail1 expression, which mediated colorectal cancer cell migration and chemotherapy resistance.

Conclusions

Our research indicates that miR-138-5p could be a crucial modulator controlling colorectal cancer cell migration and chemoresistance, by acting upon the NFIB-Snail1 axis. miR-138-5p has an emerging prospect to be exploited as a new target for colorectal cancer.

The SNAIL1 promoter contains G-quadruplex structures regulating its gene expression and DNA replication

SNAIL1 is a key regulator of epithelial-mesenchymal transition (EMT) and its expression is associated with tumor progression and poor clinical prognosis of cancer patients. Compared to the studies of SNAIL1 stability and its transcriptional regulation, very limited knowledge is available regarding effective approaches to directly target SNAIL1. In this study, we revealed the potential regulation of SNAIL1 gene expression by G-quadruplex structures in its promoter. We first revealed that the negative strand of the SNAIL1 promoter contained a multi-G-tract region with high potential of forming G-quadruplex structures. In circular dichroism studies, the oligonucleotide based on this region showed characteristic molar ellipticity at specific wavelengths of G-quadruplex structures. We also utilized native polyacrylamide gel electrophoresis, gel-shift assays, immunofluorescent staining, dimethyl sulfate footprinting and chromatin immunoprecipitation studies to verify the G-quadruplex structures formed by the oligonucleotide. In reporter assays, disruption of G-quadruplex potential increased SNAIL1 promoter-mediated transcription, suggesting that G-quadruplexes played a negative role in SNAIL1 expression. In a DNA synthesis study, we detected G-quadruplex-mediated retardation in the SNAIL1 promoter replication. Consistently, we discovered that the G-quadruplex region of the SNAIL1 promoter is highly enriched for mutations, implicating the clinical relevance of G-quadruplexes to the altered SNAIL1 expression in cancer cells.

STIM1 is a metabolic checkpoint regulating the invasion and metastasis of hepatocellular carcinoma

Background: Cancer cells undergoing invasion and metastasis possess a phenotype with attenuated glycolysis, but enhanced fatty acid oxidation (FAO). Calcium (Ca²⁺)-mediated signaling pathways are implicated in tumor metastasis and metabolism regulation. Stromal-interaction molecule 1 (STIM1) triggered store-operated Ca²⁺ entry (SOCE) is the major route of Ca²⁺ influx for non-excitable cells including hepatocellular carcinoma (HCC) cells. However, whether and how STIM1 regulates the invasion and metastasis of HCC via metabolic reprogramming is unclear.

Methods: The expressions of STIM1 and Snail1 in the HCC tissues and cells were measured by immunohistochemistry, Western-blotting and quantitative PCR. STIM1 knockout-HCC cells were generated by CRISPR-Cas9, and gene-overexpression was mediated via lentivirus transfection. Besides, the invasive and metastatic activities of HCC cells were assessed by transwell assay, anoikis rate in vitro and lung metastasis in vivo. Seahorse energy analysis and micro-array were used to evaluate the glucose and lipid metabolism.

Results: STIM1 was down-regulated in metastatic HCC cells rather than in proliferating HCC cells, and low STIM1 levels were associated with poor outcome of HCC patients. During tumor growth, STIM1 stabilized Snail1 protein by activating the CaMKII/AKT/GSK-3β pathway. Subsequently, the upregulated Snail1 suppressed STIM1/SOCE during metastasis. STIM1 restoration significantly diminished anoikis-resistance and metastasis induced by Snail1. Mechanistically, the downregulated STIM1 shifted the anabolic/catabolic balance, i.e., from aerobic glycolysis towards AMPK-activated fatty acid oxidation (FAO), which contributed to Snail1-driven metastasis and anoikis-resistance.

Conclusions: Our data provide the molecular basis that STIM1 orchestrates invasion and metastasis via reprogramming HCC metabolism.

HNF-1a promotes pancreatic cancer growth and apoptosis resistance via its target gene PKLR

Pancreatic ductal adenocarcinoma is one of the deadliest malignant tumors, and many genes play important roles in its development. The hepatocyte nuclear factor-1a (HNF-1a) gene encodes HNF-1a, which is a transcriptional activator. HNF-1a regulates the tissue-specific expression of multiple genes, especially in pancreatic islet cells and in the liver. However, the role of the HNF-1a gene in the development of pancreatic cancer is still unclear. Here, we used immunohistochemical staining and real-time PCR to analyze HNF-1a expression in pancreatic cancer tissue. Stable cell lines with HNF-1a knockdown or overexpression were established to analyze the role of HNF-1a in pancreatic cancer cell proliferation and apoptosis by colony formation assay and flow cytometry. We also analyzed the L-type pyruvate kinase (PKLR) promoter sequence to identify the regulatory effect of HNF-1a on PKLR transcription and confirmed the HNF-1a binding site in the PKLR promoter via a chromatin immunoprecipitation assay. HNF-1a was found to be overexpressed in pancreatic cancer and promoted proliferation while inhibiting apoptosis in pancreatic cancer cells. PKLR was identified as the downstream target gene of HNF-1a and binding of HNF-1a at two sites in PKLR (-1931/-1926 and -966/-961) regulated PKLR transcription. In conclusion, HNF-1a is overexpressed in pancreatic cancer, and the transcription factor HNF-1a can promote pancreatic cancer growth and apoptosis resistance via its target gene PKLR.

Epigenetic Silencing of Ubiquitin Specific Protease 4 by Snail1 Contributes to Macrophage-Dependent Inflammation and Therapeutic Resistance in Lung Cancer

There is a positive feedback loop driving tumorigenesis and tumor growth through coordinated regulation of epigenetics, inflammation, and stemness. Nevertheless, the molecular mechanism linking these processes is not well understood. In this study, we analyzed the correlation of de-ubiquitinases (DUBs) expression with survival data from the OncoLnc database. Among the DUBs analyzed, ubiquitin specific protease 4 (USP4) had the lowest negative Cox coefficient. Low expression of USP4 was associated with poor survival among lung cancer patients and was inversely correlated with expression of stemness and inflammation markers. Expression of USP4 were reduced at more advanced stages of lung cancer. Mechanistically, expression of USP4 was downregulated in snail1-overexpressing and stemness-enriched lung cancer cells. Snail1 was induced in lung cancer cells by interaction with macrophages, and epigenetically suppressed USP4 expression by promoter methylation. Stable knockdown of USP4 in lung cancer cells enhanced inflammatory responses, stemness properties, chemotherapy resistance, and the expression of molecules allowing escape from immunosurveillance. Further, mice injected with USP4 knockdown lung cancer cells demonstrated enhanced tumorigenesis and tumor growth. These results reveal that the Snail1-mediated suppression of USP4 is a potential mechanism to orchestrate epigenetic regulation, inflammation and stemness for macrophage-promoted tumor progression.

The role of DUBs in the post-translational control of cell migration

Cell migration is a multifactorial/multistep process that requires the concerted action of growth and transcriptional factors, motor proteins, extracellular matrix remodeling and proteases. In this review, we focus on the role of transcription factors modulating Epithelial-to-Mesenchymal Transition (EMT-TFs), a fundamental process supporting both physiological and pathological cell migration. These EMT-TFs (Snail1/2, Twist1/2 and Zeb1/2) are labile proteins which should be stabilized to initiate EMT and provide full migratory and invasive properties. We present here a family of enzymes, the deubiquitinases (DUBs) which have a crucial role in counteracting polyubiquitination and proteasomal degradation of EMT-TFs after their induction by TGFβ, inflammatory cytokines and hypoxia. We also describe the DUBs promoting the stabilization of Smads, TGFβ receptors and other key proteins involved in transduction pathways controlling EMT.