Genome-wide analysis of endogenously expressed ZEB2 binding sites reveals inverse correlations between ZEB2 and GalNAc-transferase GALNT3 in human tumors

Role of Post-Translational Modifications in Colorectal Cancer Metastasis

Colorectal cancer (CRC) is one of the most common malignant tumors of the digestive tract. CRC metastasis is a multi-step process with various factors involved, including genetic and epigenetic regulations, which turn out to be a serious threat to CRC patients. Post-translational modifications (PTMs) of proteins involve the addition of chemical groups, sugars, or proteins to specific residues, which fine-tunes a protein's stability, localization, or interactions to orchestrate complicated biological processes. An increasing number of recent studies suggest that dysregulation of PTMs, such as phosphorylation, ubiquitination, and glycosylation, play pivotal roles in the CRC metastasis cascade. Here, we summarized recent advances in the role of post-translational modifications in diverse aspects of CRC metastasis and its detailed molecular mechanisms. Moreover, advances in drugs targeting PTMs and their cooperation with other anti-cancer drugs, which might provide novel targets for CRC treatment and improve therapeutic efficacy, were also discussed.

Zeb2 DNA-Binding Sites in Neuroprogenitor Cells Reveal Autoregulation and Affirm Neurodevelopmental Defects, Including in Mowat-Wilson Syndrome

Functional perturbation and action mechanism studies have shown that the transcription factor Zeb2 controls cell fate decisions, differentiation, and/or maturation in multiple cell lineages in embryos and after birth. In cultured embryonic stem cells (ESCs), Zeb2’s mRNA/protein upregulation is necessary for the exit from primed pluripotency and for entering general and neural differentiation. We edited mouse ESCs to produce Flag-V5 epitope-tagged Zeb2 protein from one endogenous allele. Using chromatin immunoprecipitation coupled with sequencing (ChIP-seq), we mapped 2432 DNA-binding sites for this tagged Zeb2 in ESC-derived neuroprogenitor cells (NPCs). A new, major binding site maps promoter-proximal to Zeb2 itself. The homozygous deletion of this site demonstrates that autoregulation of Zeb2 is necessary to elicit the appropriate Zeb2-dependent effects in ESC-to-NPC differentiation. We have also cross-referenced all the mapped Zeb2 binding sites with previously obtained transcriptome data from Zeb2 perturbations in ESC-derived NPCs, GABAergic interneurons from the ventral forebrain of mouse embryos, and stem/progenitor cells from the post-natal ventricular-subventricular zone (V-SVZ) in mouse forebrain, respectively. Despite the different characteristics of each of these neurogenic systems, we found interesting target gene overlaps. In addition, our study also contributes to explaining developmental disorders, including Mowat-Wilson syndrome caused by ZEB2 deficiency, and also other monogenic syndromes.

Glycobiology of the Epithelial to Mesenchymal Transition

Glycosylation consists in the covalent, enzyme mediated, attachment of sugar chains to proteins and lipids. A large proportion of membrane and secreted proteins are indeed glycoproteins, while glycolipids are fundamental component of cell membranes. The biosynthesis of sugar chains is mediated by glycosyltransferases, whose level of expression represents a major factor of regulation of the glycosylation process. In cancer, glycosylation undergoes profound changes, which often contribute to invasion and metastasis. Epithelial to mesenchymal transition (EMT) is a key step in metastasis formation and is intimately associated with glycosylation changes. Numerous carbohydrate structures undergo up- or down-regulation during EMT and often regulate the process. In this review, we will discuss the relationship with EMT of the N-glycans, of the different types of O-glycans, including the classical mucin-type, O-GlcNAc, O-linked fucose, O-linked mannose and of glycolipids. Finally, we will discuss the role in EMT of galectins, a major class of mammalian galactoside-binding lectins. While the expression of specific carbohydrate structures can be used as a marker of EMT and of the propensity to migrate, the manipulation of the glycosylation machinery offers new perspectives for cancer treatment through inhibition of EMT.

ZEB2 Knock-down Induces Apoptosis in Human Myeloid Leukemia HL-60 Cells

INTRODUCTION

Acute myeloid leukemia (AML) is the most prevalent type of cancer in the adult hematopoietic system. Conventional therapies are associated with unfavorable side effects in individuals diagnosed with AML. These after-effects with partial remission reflect the urgent need for novel therapeutic approaches for inducing apoptosis, specifically in malignant cells, without affecting other cells. As a transcription factor (TF), ZEB2 (Zinc Finger E-Box Binding Homeobox 2) regulates the expression of specific genes in normal conditions. However, increased expression of ZEB2 is reported in various cancers, especially in AML, which is related to a higher degree of apoptosis inhibition of malignant cells. In this work, the role of ZEB2 in apoptosis inhibition is surveyed through ZEB2 specific knocking-down in human myeloid leukemia HL-60 cells.

MATERIALS AND METHODS

Transfection of HL-60 cells was conducted using ZEB2-siRNA at concentrations of 20, 40, 60, and 80 pmol within 24, 48, and 72 h. After determining the optimum dose and time, flow cytometry was used to measure the apoptosis rate. The MTT assay was also utilized to evaluate the cytotoxic impact of transfection on the cells. The expression of candidate genes was measured before and after transfection using qRT-PCR.

RESULTS

According to obtained results, suppression of ZEB2 expression through siRNA was associated with the induction of apoptosis, increased pro-apoptotic, and decreased anti-apoptotic gene expression. Transfection of ZEB2-siRNA was also associated with reduced cell proliferation and viability.

CONCLUSION

Our study results suggest that ZEB2 suppression in myeloid leukemia cells through apoptosis induction could be a proper therapeutic method.

Sp1-mediated up-regulation of lnc00152 promotes invasion and metastasis of retinoblastoma cells via the miR-30d/SOX9/ZEB2 pathway

PURPOSE

Previously, we found that long non-coding RNA (lncRNA) MEG3 may act as a tumour suppressor in retinoblastoma. Overall, however, little is known about the role of lncRNAs in retinoblastoma. Here, we aimed to determine the expression and clinical significance of lnc00152 in retinoblastoma.

METHODS

Lnc00152 and its downstream targets were selected using GEO datasets. The level of lnc00152 in primary patient samples was determined using RT-qPCR. Odds ratios of invasion and metastasis were calculated using logistic regression analysis. Recurrence-free survival was assessed using Cox regression analysis. Scratch wound healing, transwell and tumorigenesis assays were used to determine migration and invasion abilities of retinoblastoma cells in vitro and in vivo. Levels of EMT-related proteins were measured using Western blotting. Binding sites between lnc00152 and its targets were validated using dual-luciferase reporter and RNA pull-down assays. Lnc00152 activating transcription factors were determined using ChIP assays.

RESULTS

We found that Lnc00152 was significantly up-regulated in retinoblastoma tumour tissues, and was a risk factor for tumour invasion, metastasis and recurrence. Lnc00152 overexpressing retinoblastoma cells exhibited a tendency to transform into mesenchymal cells, with significantly increased migration and invasion capacities, significantly decreased E-cadherin expression levels, and significantly increased N-cadherin, SOX9 and ZEB2 expression levels. In addition, we found that lnc00152, which was activated by Sp1, could inhibit miR-30d as an endogenous miRNA 'sponge', thereby regulating the expression of SOX9 and ZEB2.

CONCLUSIONS

Our data indicate that Lnc00152 may be associated with retinoblastoma invasion, metastasis and prognosis. In addition, we conclude that Lnc00152, which can be activated by Sp1, can induce EMT via the miR-30d/SOX9/ZEB2 pathway and, by doing so, promote the invasion and metastasis of retinoblastoma cells.

Ser and Thr acceptor preferences of the GalNAc-Ts vary among isoenzymes to modulate mucin-type O-glycosylation

A family of polypeptide GalNAc-transferases (GalNAc-Ts) initiates mucin-type O-glycosylation, transferring GalNAc onto hydroxyl groups of Ser and Thr residues of target substrates. The 20 GalNAc-T isoenzymes in humans are classified into nine subfamilies according to sequence similarity. GalNAc-Ts select their sites of glycosylation based on weak and overlapping peptide sequence motifs, as well prior substrate O-GalNAc glycosylation at sites both remote (long-range) and neighboring (short-range) the acceptor. Together, these preferences vary among GalNAc-Ts imparting each isoenzyme with its own unique specificity. Studies on the first identified GalNAc-Ts showed Thr acceptors were preferred over Ser acceptors; however studies comparing Thr vs. Ser glycosylation across the GalNAc-T family are lacking. Using a series of identical random peptide substrates, with single Thr or Ser acceptor sites, we determined the rate differences (Thr/Ser rate ratio) between Thr and Ser substrate glycosylation for 12 isoenzymes (representing 7 GalNAc-T subfamilies). These Thr/Ser rate ratios varied across subfamilies, ranging from ~2 to ~18 (for GalNAc-T4/GalNAc-T12 and GalNAc-T3/GalNAc-T6, respectively), while nearly identical Thr/Ser rate ratios were observed for isoenzymes within subfamilies. Furthermore, the Thr/Ser rate ratios did not appreciably vary over a series of fixed sequence substrates of different relative activities, suggesting the ratio is a constant for each isoenzyme against single acceptor substrates. Finally, based on GalNAc-T structures, the different Thr/Ser rate ratios likely reflect differences in the strengths of the Thr acceptor methyl group binding to the active site pocket. With this work, another activity that further differentiates substrate specificity among the GalNAc-Ts has been identified.

Non-redundant functions of EMT transcription factors

Epithelial-mesenchymal transition (EMT) is a crucial embryonic programme that is executed by various EMT transcription factors (EMT-TFs) and is aberrantly activated in cancer and other diseases. However, the causal role of EMT and EMT-TFs in different disease processes, especially cancer and metastasis, continues to be debated. In this Review, we identify and describe specific, non-redundant functions of the different EMT-TFs and discuss the reasons that may underlie disputes about EMT in cancer.

FOXP3 and miR-155 cooperate to control the invasive potential of human breast cancer cells by down regulating ZEB2 independently of ZEB1

Control of oncogenes, including ZEB1 and ZEB2, is a major checkpoint for preventing cancer, and loss of this control contributes to many cancers, including breast cancer. Thus tumour suppressors, such as FOXP3, which is mutated or lost in many cancer tissues, play an important role in maintaining normal tissue homeostasis. Here we show for the first time that ZEB2 is selectively down regulated by FOXP3 and also by the FOXP3 induced microRNA, miR-155. Interestingly, neither FOXP3 nor miR-155 directly altered the expression of ZEB1. In breast cancer cells repression of ZEB2, independently of ZEB1, resulted in reduced expression of a mesenchymal marker, Vimentin and reduced invasion. However, there was no de-repression of E-cadherin and migration was enhanced. Small interfering RNAs targeting ZEB2 suggest that this was a direct effect of ZEB2 and not FOXP3/miR-155. In normal human mammary epithelial cells, depletion of endogenous FOXP3 resulted in de-repression of ZEB2, accompanied by upregulated expression of vimentin, increased E-cadherin expression and cell morphological changes. We suggest that FOXP3 may help maintain normal breast epithelial characteristics through regulation of ZEB2, and loss of FOXP3 in breast cancer cells results in deregulation of ZEB2.