TGF-β-Mediated Epithelial-Mesenchymal Transition and Cancer Metastasis

Histone deacetylase inhibitors dysregulate DNA repair proteins and antagonize metastasis-associated processes

Purpose

We set out to determine whether clinically tested epigenetic drugs against class I histone deacetylases (HDACs) affect hallmarks of the metastatic process.

Methods

We treated permanent and primary renal, lung, and breast cancer cells with the class I histone deacetylase inhibitors (HDACi) entinostat (MS-275) and valproic acid (VPA), the replicative stress inducer hydroxyurea (HU), the DNA-damaging agent cis-platinum (L-OHP), and the cytokine transforming growth factor-β (TGFβ). We used proteomics, quantitative PCR, immunoblot, single cell DNA damage assays, and flow cytometry to analyze cell fate after drug exposure.

Results

We show that HDACi interfere with DNA repair protein expression and trigger DNA damage and apoptosis alone and in combination with established chemotherapeutics. Furthermore, HDACi disrupt the balance of cell adhesion protein expression and abrogate TGFβ-induced cellular plasticity of transformed cells.

Conclusion

HDACi suppress the epithelial–mesenchymal transition (EMT) and compromise the DNA integrity of cancer cells. These data encourage further testing of HDACi against tumor cells.

Electronic supplementary material

The online version of this article (10.1007/s00432-019-03118-4) contains supplementary material, which is available to authorized users.

Apoptotic induction and anti-metastatic activity of eugenol encapsulated chitosan nanopolymer on rat glioma C6 cells via alleviating the MMP signaling pathway

Glioma is the prime cause of cancer allied mortality in adolescent people and it accounts about 80% of all malignant tumours. Eugenol is a major bioactive constituent present in the essential oils with numerous pharmacological benefits including nueroprotective activity. The major drawback of eugenol is its extreme volatile property and oxygen sensitivity therefore we increased the efficacy of drug; eugenol by encapsulating with chitosan polymer. Eugenol loaded chitosan polymer (EuCs) was characterized using FTIR, XRD, SEM, HR-TEM analysis and the encapsulation, drug release efficacy was assessed at in vitro condition. The induction of autophagy and anticancer efficacy of EuCs on glioma cells was evaluated with rat C6 glioma cells using MTT assay, acridine orange staining, immunocytochemical analysis of NFκβ protein expression and FLOW cytometric analysis. The anti-metastatic property of Eu-CS was assessed by immunoblotting and RT-PCR analysis of epithelial mesenchymal transition protein expression in EuCs treated rat C6 glioma cells. Our characterization analysis proves that EuCs possess essential physical and functional properties of copolymer to be utilized as a drug. Further the MTT analysis and AO staining confirms even in the presence of oncogenic inducer and autophagic inhibitors, EuCs exhibits apoptotic potency on rat C6 glioma cells. The result of immunocytochemical studies depicts the inhibition of NFκβ protein expression and flow cytometry studies confirm apoptosis induction by EuCs. The inhibition of metastasis by EuCs was proven by the decrease in epithelial mesenchymal transition protein expression in Eu-Cs treated rat C6 glioma cells. Over all our results authentically confirms eugenol loaded chitosan nanopolymer persuasively induces apoptosis and inhibits metastasis in rat C6 glioma cells.

On-Target Anti-TGF-β Therapies Are Not Succeeding in Clinical Cancer Treatments: What Are Remaining Challenges?

Metastasis is the leading cause of death for cancer patients. During cancer progression, the initial detachment of cells from the primary tumor and the later colonization of a secondary organ are characterized as limiting steps for metastasis. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are opposite dynamic multistep processes that enable these critical events in metastasis by altering the phenotype of cancer cells and improving their ability to migrate, invade and seed at distant organs. Among the molecular pathways that promote tumorigenesis in late-stage cancers, transforming growth factor-β (TGF-β) is described as an EMT master inducer by controlling different genes and proteins related to cytoskeleton assembly, cell-cell attachment and extracellular matrix remodeling. Still, despite the successful outcomes of different TGF-β pharmacological inhibitors in cell culture (in vitro) and animal models (in vivo), results in cancer clinical trials are poor or inconsistent at least, highlighting the existence of crucial components in human cancers that have not been properly explored. Here we review most recent findings to provide perspectives bridging the gap between on-target anti-TGF-β therapies in vitro and in pre-clinical models and the poor clinical outcomes in treating cancer patients. Specifically, we focus on (i) the dual roles of TGF-β signaling in cancer metastasis; (ii) dynamic signaling; (iii) functional differences of TGF-β free in solution vs. in exosomes; (iv) the regulatory effects of tumor microenvironment (TME) - particularly by cancer-associated fibroblasts - on TGF-β signaling pathway. Clearly identifying and establishing those missing links may provide strategies to revitalize and clinically improve the efficacy of TGF-β targeted therapies.

The role of extracellular matrix proteins in gastric cancer development via epithelial-mesenchymal transition

AIM

To acquire a deeper perception of EMT, we evaluated the expression of some candidate extra cellular matrix (ECM) proteins including THBS2, OSMR and CHI3L1 which were collected from RNA-seq bioinformatic analyses.

BACKGROUND

Gastric cancer (GC) is a major incident gastrointestinal cancer with a high rate of mortality. Metastasis is a challenging issue in gastric cancer treatment. Epithelial mesenchymal transition (EMT) of cancer cells is a complicated process controlled by different cells and molecular pathways regarded as an important step at the onset of metastasis.

METHODS

AGS gastric cancer cell line was cultured and treated by TGF-β. EMT induction was verified by measuring the expression of E-cadherin, Snail, β-catenin and Vimentin genes by real time PCR. Then, following our previous study, we evaluated the expression of THBS2, OSMR and CHI3L1 genes in EMT induced cells by real time PCR.

RESULTS

Downregulation of E-cadherin and upregulation of Snail, β-catenin and Vimentin genes were verified in AGS treated cells in comparison with none-treated cells (P-value = 0.0355, P-value = 0.007, P-value = 0.0059, P-value = 0.0206 respectively). Also, upregulation of THBS2, OSMR and CHI3L1 were validated in these cells after EMT induction (P-value = 0.0147, P-value = 0.05, P-value = 0.05 respectively).

CONCLUSION

Our morphological and molecular results validated EMT induction by TGF- β cytokine in AGS gastric cancer cell line. Furthermore, significant upregulation of candidate genes including THBS2, OSMR and CHI3L1 verified the role of these proteins in gastric cancer invasiveness. However, further studies are needed for the validation of prognostic value of these markers.

CSN6 promotes the cell migration of breast cancer cells by positively regulating Snail1 stability

Background: CSN6, a subunit of the highly conserved constitutive photomorphogenesis 9 (COP9) signalosome (CSN), has been reported to be implicated in tumor progression in various kinds of malignant tumors. However, the mechanism underlying CSN6 in the tumor development of breast cancer has not yet been fully elucidated. Methods: CSN6 staining in breast cancer tissues and paracancerous tissues was measured by tissue microarray (TMA) technology. The metastatic effect of CSN6 was measured by cell migration assay. Co-immunoprecipitation study was used to show the interaction between the protein CSN6 and Snail1. Ubiquitination assay was performed to validate whether ubiquitination is involved in the upregulation of Snail1 by CSN6. The impact of CSN6 on tumor metastasis in vivo was analyzed using xenotransplantation experiments in BALB/c mice. Results: Here, we demonstrated that CSN6 expression was dramatically increased in breast cancer tissues compared with paired adjacent cancerous tissues. CSN6 promoted the cell migration and wound healing abilities in breast cancer cell lines. Also we showed that CSN6 associates with Snail1 and enhances Snail1 protein level by inhibiting the ubiquitin-mediated degradation of Snail1. Thus, CSN6 is involved in positively regulating the stability of Snail1. We further proved that CSN6 protein level was positively correlated with the Snail1 expression in xenograft model. Conclusion: These findings provide new insight into applicability of using the CSN6-Snail1 axis as a potential therapeutic target in breast cancer.

Metabolic rewiring and redox alterations in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare malignancy of mesothelial cells with increasing incidence, and in many cases, dismal prognosis due to its aggressiveness and lack of effective therapies. Environmental and occupational exposure to asbestos is considered the main aetiological factor for MPM. Inhaled asbestos fibres accumulate in the lungs and induce the generation of reactive oxygen species (ROS) due to the presence of iron associated with the fibrous silicates and to the activation of macrophages and inflammation. Chronic inflammation and a ROS-enriched microenvironment can foster the malignant transformation of mesothelial cells. In addition, MPM cells have a highly glycolytic metabolic profile and are positive in 18F-FDG PET analysis. Loss-of-function mutations of BRCA-associated protein 1 (BAP1) are a major contributor to the metabolic rewiring of MPM cells. A subset of MPM tumours show loss of the methyladenosine phosphorylase (MTAP) locus, resulting in profound alterations in polyamine metabolism, ATP and methionine salvage pathways, as well as changes in epigenetic control of gene expression. This review provides an overview of the perturbations in metabolism and ROS homoeostasis of MPM cells and the role of these alterations in malignant transformation and tumour progression.

Epiregulin promotes trophoblast epithelial-mesenchymal transition through poFUT1 and O-fucosylation by poFUT1 on uPA

Objectives

The transformation of cytotrophoblasts into mesenchymal‐like extravillous trophoblasts is necessary for successful embryo implantation, and the inadequate transformation may cause abortion. Epiregulin, which is a new growth factor, plays important roles in the reproductive processes. The glycosylation of many proteins in reproduction processes is critical. Protein O‐fucosyltransferase 1 (poFUT1) is the key enzyme for the biosynthesis of O‐fucosylation on the specific glycoproteins. Urokinase‐type plasminogen activator (uPA) contains O‐fucosylated domain on Thr¹⁸. However, the functions of epiregulin and poFUT1 in the trophoblast epithelial–mesenchymal transition (EMT) process, the regulatory mechanism of epiregulin on poFUT1 and the resulting O‐fucosylated uPA remain unclear.

Materials and methods

We employed ELISA and Western blot to detect serum levels of epiregulin and poFUT1 from non‐pregnancy women, pregnancy women and abortion patients. Using two trophoblast cell lines and a mouse pregnancy model, we investigated the underlying mechanisms of epiregulin and poFUT1 in trophoblast EMT process.

Results

Serum levels of epiregulin and poFUT1 were higher in pregnant women compared with non‐pregnant women, and their levels were significantly decreased in abortion patients compared with pregnant women. The results showed that epiregulin upregulated poFUT1 expression and increased O‐fucosylation on uPA, which further activated the PI3K/Akt signalling pathway, facilitating EMT behaviour of trophoblast cells and embryo implantation in the mouse pregnant model.

Conclusions

Level of epiregulin and poFUT1 is lower in abortion patients than early pregnancy women. Epiregulin promotes trophoblast EMT through O‐fucosylation on uPA catalysed by poFUT1. Epiregulin and poFUT1 may be suggested as the potential diagnostic biomarkers and useful treatment targets for abortion.

SND1 facilitates the invasion and migration of cervical cancer cells by Smurf1-mediated degradation of FOXA2

Staphylococcal nuclease domain-containing protein 1 (SND1) is known to be involved in the progression of a variety of human cancers. However, the role of SND1 in cervical cancer remains unclear. Here, we found that the expression of SND1 in cervical cancer tissue was higher than that in normal cervical tissue. Importantly, high SND1 expression was closely associated with tumorigenic phenotype and shorter survival among cervical cancer patients. Functional assays demonstrated that SND1 knockdown inhibited the migration and invasion capabilities of cervical cancer cells in vitro. Additionally, a xenograft assay showed that silencing SND1 in cervical cancer cells suppressed lung metastasis in vivo. Further investigation revealed that knockdown of SND1 inhibited epithelial-to-mesenchymal transition (EMT) of cervical cancer cells by enhancing FOXA2 expression. Moreover, the pro-metastasis effect of SND1 in cervical cancer was at least in part dependent on FOXA2 inhibition. Mechanistically, we found that SND1-induced FOXA2 ubiquitination resulted in degradation, mediated by the E3 ligase enzyme Smurf1. In summary, SND1 plays a crucial role in cervical cancer metastasis, and we provide evidence that SND1 may serve as a prognostic and therapeutic target in cervical cancer.

Hyperglycemia promotes Snail-induced epithelial-mesenchymal transition of gastric cancer via activating ENO1 expression

Background

Gastric cancer (GC) is one of the most common gastrointestinal malignancies worldwide. Emerging evidence indicates that hyperglycemia promotes tumor progression, especially the processes of migration, invasion and epithelial-mesenchymal transition (EMT). However, the underlying mechanisms of GC remain unclear.

Method

Data from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases were used to detect the expression of glycolysis-related enzymes and EMT-related transcription factors. Small interfering RNA (siRNA) transfection was performed to decrease ENO1 expression. Immunohistochemistry (IHC), Western blot and qRT-PCR analyses were used to measure gene expression at the protein or mRNA level. CCK-8, wound-healing and Transwell assays were used to assess cell proliferation, migration and invasion.

Results

Among the glycolysis-related genes, ENO1 was the most significantly upregulated in GC, and its overexpression was correlated with poor prognosis. Hyperglycemia enhanced GC cell proliferation, migration and invasion. ENO1 expression was also upregulated with increasing glucose concentrations. Moreover, decreased ENO1 expression partially reversed the effect of high glucose on the GC malignant phenotype. Snail-induced EMT was promoted by hyperglycemia, and suppressed by ENO1 silencing. Moreover, ENO1 knockdown inhibited the activation of transforming growth factor β (TGF-β) signaling pathway in GC.

Conclusions

Our results indicated that hyperglycemia induced ENO1 expression to trigger Snail-induced EMT via the TGF-β/Smad signaling pathway in GC.

HTR-8/SVneo: A model for epithelial to mesenchymal transition in the human placenta

INTRODUCTION

The placenta is a transitory organ essential for proper fetal maturation and growth. Trophoblasts, the main cell type of the placenta, differentiate along the villous or extravillous pathways. The ability of villous cytotrophoblasts to undergo an epithelial-to-mesenchymal transition to form the invasive extravillous trophoblasts is vital for a successful pregnancy outcome. Many trophoblastic cell lines, including HTR-8/SVneo, have been widely used to investigate extravillous trophoblast biology and functions. We have previously reported that HTR-8/SVneo cell line contains a mixed populations of epithelial and mesenchymal cells. Uncovering the mechanisms underlying this heterogeneity is essential for the proper study of normal and pathological placental function.

METHODS

HTR-8/SVneo was subjected to monoclonal isolation, spheroid formation assay and cell sorting to isolate pure epithelial and mesenchymal populations. These fractions were maintained in culture and assessed for expression of epithelial and mesenchymal markers using quantitative real-time PCR and immunofluorescence. In addition, the implication of TGFβ in the EMT process was investigated using a selective inhibitor of TGF-βR1 (A83-01).

RESULTS

Passaging of the pure epithelial population maintained under normal culture condition resulted in a shift to a mesenchymal phenotype. This transition was reduced upon inhibiting TGF-βR1. Similarly, E-cadherin positive HTR-8/SVneo spheroids plated in 2D culture resulted in the emergence of streams of invading mesenchymal cells.

DISCUSSION

HTR-8/SVneo cell line is undergoing EMT under normal culture condition and TGFβ is a key mediator of this process. Our results raise the possibility of using HTR-8/SVneo cell line as a model to investigate EMT in extravillous trophoblast cells.

Transforming Growth Factor-β Signaling Pathway in Colorectal Cancer and Its Tumor Microenvironment

Transforming growth factor-beta (TGF-β) signaling is one of the important cellular pathways that play key roles for tissue maintenance. In particular, it is important in the context of inflammation and tumorigenesis by modulating cell growth, differentiation, apoptosis, and homeostasis. TGF-β receptor type 2 (TGFBR2) mutations affected by a mismatch repair deficiency causes colorectal cancers (CRCs) with microsatellite instability, which is, however, associated with relatively better survival rates. On the other hand, loss of SMAD4, a transcription factor in the TGF-β superfamily signaling, promotes tumor progression. Loss of heterozygosity on chromosome 18 can case SMAD4-deficient CRC, which results in poorer patients' survival. Such bidirectional phenomenon driven by TGF-β signaling insufficiency reflects the complexity of this signaling pathway in CRC. Moreover, recent understanding of CRC at the molecular level (consensus molecular subtype classification) provides deep insight into the important roles of TGF-β signaling in the tumor microenvironment. Here we focus on the TGF-β signaling in CRC and its interaction with the tumor microenvironment. We summarize the molecular mechanisms of CRC tumorigenesis and progression caused by disruption of TGF-β signaling by cancer epithelial cells and host stromal cells.

Transforming Growth Factor-β Signaling Pathway in Colorectal Cancer and Its Tumor Microenvironment

Transforming growth factor-beta (TGF-β) signaling is one of the important cellular pathways that play key roles for tissue maintenance. In particular, it is important in the context of inflammation and tumorigenesis by modulating cell growth, differentiation, apoptosis, and homeostasis. TGF-β receptor type 2 (TGFBR2) mutations affected by a mismatch repair deficiency causes colorectal cancers (CRCs) with microsatellite instability, which is, however, associated with relatively better survival rates. On the other hand, loss of SMAD4, a transcription factor in the TGF-β superfamily signaling, promotes tumor progression. Loss of heterozygosity on chromosome 18 can case SMAD4-deficient CRC, which results in poorer patients’ survival. Such bidirectional phenomenon driven by TGF-β signaling insufficiency reflects the complexity of this signaling pathway in CRC. Moreover, recent understanding of CRC at the molecular level (consensus molecular subtype classification) provides deep insight into the important roles of TGF-β signaling in the tumor microenvironment. Here we focus on the TGF-β signaling in CRC and its interaction with the tumor microenvironment. We summarize the molecular mechanisms of CRC tumorigenesis and progression caused by disruption of TGF-β signaling by cancer epithelial cells and host stromal cells.

DHPS-dependent hypusination of eIF5A1/2 is necessary for TGFβ/fibronectin-induced breast cancer metastasis and associates with prognostically unfavorable genomic alterations in TP53

Metastasis is the leading cause of mortality in patients with solid tumors. In this regard, we previously reported that Pseudopodium-Enriched Atypical Kinase One (PEAK1) is necessary for non-canonical Transforming Growth Factor β (TGFβ) signaling and TGFβ/fibronectin-induced metastasis. Here, we demonstrate that inhibition of DHPS-dependent eIF5A1/2 hypusination blocks PEAK1 and E-Cadherin expression, breast cancer cell viability and TGFβ/fibronectin-induced PEAK1-dependent breast cancer metastasis. Interestingly, TGFβ stimulation of high-grade metastatic breast cancer cells increases and sustains eIF5A1/2 hypusination. We used a suite of bioinformatics platforms to search biochemical/functional interactions and clinical databases for additional control points in eIF5A1/2 and PEAK1-Epithelial to Mesenchymal Transition (EPE) pathways. This effort revealed that interacting EPE genes were enriched for TP53 transcriptional targets and were commonly co-amplified in breast cancer patients harboring inactivating TP53 mutations. Taken together, these results suggest that combinatorial therapies targeting DHPS and protein activities elevated in TP53-mutant breast cancers may reduce systemic tumor burden and improve patient outcomes.

Epidermolysis Bullosa-Associated Squamous Cell Carcinoma: From Pathogenesis to Therapeutic Perspectives

Epidermolysis bullosa (EB) is a heterogeneous group of inherited skin disorders determined by mutations in genes encoding for structural components of the cutaneous basement membrane zone. Disease hallmarks are skin fragility and unremitting blistering. The most disabling EB (sub)types show defective wound healing, fibrosis and inflammation at lesional skin. These features expose patients to serious disease complications, including the development of cutaneous squamous cell carcinomas (SCCs). Almost all subjects affected with the severe recessive dystrophic EB (RDEB) subtype suffer from early and extremely aggressive SCCs (RDEB-SCC), which represent the first cause of death in these patients. The genetic determinants of RDEB-SCC do not exhaustively explain its unique behavior as compared to low-risk, ultraviolet-induced SCCs in the general population. On the other hand, a growing body of evidence points to the key role of tumor microenvironment in initiation, progression and spreading of RDEB-SCC, as well as of other, less-investigated, EB-related SCCs (EB-SCCs). Here, we discuss the recent advances in understanding the complex series of molecular events (i.e., fibrotic, inflammatory, and immune processes) contributing to SCC development in EB patients, cross-compare tumor features in the different EB subtypes and report the most promising therapeutic approaches to counteract or delay EB-SCCs.

Microcalcifications Drive Breast Cancer Occurrence and Development by Macrophage-Mediated Epithelial to Mesenchymal Transition

BACKGROUND

This study aims to investigate: (a) the putative association between the presence of microcalcifications and the expression of both epithelial-to-mesenchymal transition and bone biomarkers, (b) the role of microcalcifications in the breast osteoblast-like cells (BOLCs) formation, and (c) the association between microcalcification composition and breast cancer progression.

METHODS

We collected 174 biopsies on which we performed immunohistochemical and ultrastructural analysis. In vitro experiments were performed to demonstrate the relationship among microcalcification, BOLCs development, and breast cancer occurrence. Ex vivo investigations demonstrated the significant increase of breast osteoblast-like cells in breast lesions with microcalcifications with respect to those without microcalcifications.

RESULTS

In vitro data displayed that in the presence of calcium oxalate and activated monocytes, breast cancer cells undergo epithelial to mesenchymal transition. Also, in this condition, cells acquired an osteoblast phenotype, thus producing hydroxyapatite. To further confirm in vitro data, we studied 15 benign lesions with microcalcification from patients that developed a malignant condition in the same breast quadrant. Immunohistochemical analysis showed macrophages' polarization in benign lesions with calcium oxalate.

CONCLUSIONS

Altogether, our data shed new light about the role of microcalcifications in breast cancer occurrence and progression.

miR-190-5p in human diseases

miRNAs, a major class of small noncoding RNAs approximately 18-25 nucleotides in length, function by repressing the expression of target genes through binding to complementary sequences in the 3'-UTRs of target genes. Emerging evidence has highlighted their important roles in numerous diseases, including human cancers. Recently, miR-190 has been shown to be dysregulated in various types of human cancers that participates in cancer-related biological processes, including proliferation, apoptosis, metastasis, drug resistance, by regulating associated target genes, and to predict cancer diagnosis and prognosis. In this review, we summarized the roles of miR-190-5p in human diseases, especially in human cancers. Then we classified its target genes in tumorigenesis and progression, which might provide evidence for cancer diagnosis and prognosis, promising tools for cancer treatment, or leads for further investigation.

The Molecular Mechanism of Epithelial-Mesenchymal Transition for Breast Carcinogenesis

The transforming growth factor-β (TGF-β) signaling pathway plays multiple regulatory roles in the tumorigenesis and development of cancer. TGF-β can inhibit the growth and proliferation of epithelial cells and induce apoptosis, thereby playing a role in inhibiting breast cancer. Therefore, the loss of response in epithelial cells that leads to the inhibition of cell proliferation due to TGF-β is a landmark event in tumorigenesis. As tumors progress, TGF-β can promote tumor cell invasion, metastasis, and drug resistance. At present, the above-mentioned role of TGF-β is related to the interaction of multiple signaling pathways in the cell, which can attenuate or abolish the inhibition of proliferation and apoptosis-promoting effects of TGF-β and enhance its promotion of tumor progression. This article focuses on the molecular mechanisms through which TGF-β interacts with multiple intracellular signaling pathways in tumor progression and the effects of these interactions on tumorigenesis.

Links between Fibrogenesis and Cancer: Mechanistic and Therapeutic Challenges

Fibrosis is the end-stage of chronic inflammatory diseases and tissue damage resulting from a dysregulated wound-healing response [...].

Endothelial-to-Mesenchymal Transition (EndoMT): Roles in Tumorigenesis, Metastatic Extravasation and Therapy Resistance

Cancer cells evolve in a very complex tumor microenvironment, composed of several cell types, among which the endothelial cells are the major actors of the tumor angiogenesis. Today, these cells are also characterized for their plasticity, as endothelial cells have demonstrated their potential to modify their phenotype to differentiate into mesenchymal cells through the endothelial-to-mesenchymal transition (EndoMT). This cellular plasticity is mediated by various stimuli including transforming growth factor-β (TGF-β) and is modulated dependently of experimental conditions. Recently, emerging evidences have shown that EndoMT is involved in the development and dissemination of cancer and also in cancer cell to escape from therapeutic treatment. In this review, we summarize current updates on EndoMT and its main induction pathways. In addition, we discuss the role of EndoMT in tumorigenesis, metastasis, and its potential implication in cancer therapy resistance.

Transglutaminase 2 maintains a colorectal cancer stem phenotype by regulating epithelial-mesenchymal transition

Transglutaminase 2 (TG2), a multifunctional protein, is reported in regulating the cancer stem cell (CSC) phenotype in various cancers. Our previous work suggested the link between TG2 and Epithelial-Mesenchymal Transition (EMT) in colorectal cancer (CRC). Here we demonstrate the importance of TG2 in CSC development in human CRC cell lines HCT116 and SW620. CRC spheroid cells showed increased CSC characteristics over their monolayer cells with increased expression of CD44 and over expression of Oct3/4, Sox2 and Nanog. They also showed increased EMT and invasiveness, and enhanced expression of TG2. TG2 inhibition by its selective inhibitor 1-155 reduced both spheroid formation and invasive potential of the spheroid cells. β-catenin, a mediator of stem cell maintenance, was overexpressed in the spheroid cells and could be attenuated by TG2 inhibition. Spheroid cells possessed increased angiogenesis stimulating ability via overexpression of Vascular Endothelial Growth Factor (VEGF). Increased VEGF was present in the culture media from spheroid cells when compared to monolayer cultures which could be reduced by selective inhibition by 1-155. Stemness and malignancy in the colorectal spheroid cells was associated with increased TG2, EMT, β-catenin and VEGF. Here we demonstrate that inhibiting TG2 reduces both stemness and angiogenic stimulating activity in CRC.