CDX2 autoregulation in human intestinal metaplasia of the stomach: impact on the stability of the phenotype

The Killer's Web: Interconnection between Inflammation, Epigenetics and Nutrition in Cancer

Inflammation is a key contributor to both the initiation and progression of tumors, and it can be triggered by genetic instability within tumors, as well as by lifestyle and dietary factors. The inflammatory response plays a critical role in the genetic and epigenetic reprogramming of tumor cells, as well as in the cells that comprise the tumor microenvironment. Cells in the microenvironment acquire a phenotype that promotes immune evasion, progression, and metastasis. We will review the mechanisms and pathways involved in the interaction between tumors, inflammation, and nutrition, the limitations of current therapies, and discuss potential future therapeutic approaches.

Inference on autoregulation in gene expression with variance-to-mean ratio

Some genes can promote or repress their own expressions, which is called autoregulation. Although gene regulation is a central topic in biology, autoregulation is much less studied. In general, it is extremely difficult to determine the existence of autoregulation with direct biochemical approaches. Nevertheless, some papers have observed that certain types of autoregulations are linked to noise levels in gene expression. We generalize these results by two propositions on discrete-state continuous-time Markov chains. These two propositions form a simple but robust method to infer the existence of autoregulation from gene expression data. This method only needs to compare the mean and variance of the gene expression level. Compared to other methods for inferring autoregulation, our method only requires non-interventional one-time data, and does not need to estimate parameters. Besides, our method has few restrictions on the model. We apply this method to four groups of experimental data and find some genes that might have autoregulation. Some inferred autoregulations have been verified by experiments or other theoretical works.

Using Fano factors to determine certain types of gene autoregulation

The expression of one gene might be regulated by its corresponding protein, which is called autoregulation. Although gene regulation is a central topic in biology, autoregulation is much less studied. In general, it is extremely difficult to determine the existence of autoregulation with direct biochemical approaches. Nevertheless, some papers have observed that certain types of autoregulations are linked to noise levels in gene expression. We generalize these results by two propositions on discrete-state continuous-time Markov chains. These two propositions form a simple but robust method to infer the existence of autoregulation in certain scenarios from gene expression data. This method only depends on the Fano factor, namely the ratio of variance and mean of the gene expression level. Compared to other methods for inferring autoregulation, our method only requires non-interventional one-time data, and does not need to estimate parameters. Besides, our method has few restrictions on the model. We apply this method to four groups of experimental data and find some genes that might have autoregulation. Some inferred autoregulations have been verified by experiments or other theoretical works.

Epigenetics as a mediator of plasticity in cancer

The concept of an epigenetic landscape describing potential cellular fates arising from pluripotent cells, first advanced by Conrad Waddington, has evolved in light of experiments showing nondeterministic outcomes of regulatory processes and mathematical methods for quantifying stochasticity. In this Review, we discuss modern approaches to epigenetic and gene regulation landscapes and the associated ideas of entropy and attractor states, illustrating how their definitions are both more precise and relevant to understanding cancer etiology and the plasticity of cancerous states. We address the interplay between different types of regulatory landscapes and how their changes underlie cancer progression. We also consider the roles of cellular aging and intrinsic and extrinsic stimuli in modulating cellular states and how landscape alterations can be quantitatively mapped onto phenotypic outcomes and thereby used in therapy development.

TEAD4 regulates trophectoderm differentiation upstream of CDX2 in a GATA3-independent manner in the human preimplantation embryo

STUDY QUESTION

What is the role of transcriptional-enhanced associate (TEA) domain family member 4 (TEAD4) in trophectoderm (TE) differentiation during human embryo preimplantation development in comparison to mouse?

SUMMARY ANSWER

TEAD4 regulates TE lineage differentiation in the human preimplantation embryo acting upstream of caudal-type homeobox protein 2 (CDX2), but in contrast to the mouse in a GATA-binding protein 3 (GATA3)-independent manner.

WHAT IS KNOWN ALREADY

Tead4 is one of the earliest transcription factors expressed during mouse embryo preimplantation development and is required for the expression of TE-associated genes. Functional knock-out studies in mouse, inactivating Tead4 by site-specific recombination, have shown that Tead4-targeted embryos have compromised development and expression of the TE-specific Cdx2 and Gata3 is downregulated. Cdx2 and Gata3 act in parallel pathways downstream of Tead4 to induce successful TE differentiation. Downstream loss of Cdx2 expression, compromises TE differentiation and subsequent blastocoel formation and leads to the ectopic expression of inner cell mass (ICM) genes, including POU Class 5 homeobox 1 (Pou5f1) and SRY-box transcription factor (Sox2). Cdx2 is a more potent regulator of TE fate in mouse as loss of Cdx2 expression induces more severe phenotypes compared with loss of Gata3 expression. The role of TEAD4 and its downstream effectors during human preimplantation embryo development has not been investigated yet.

STUDY DESIGN, SIZE, DURATION

The clustered regularly interspaced short palindromic repeats-clustered regularly interspaced short palindromic repeats (CRISPR)-associated genes (CRISPR-Cas9) system was first introduced in pronuclei (PN)-stage mouse zygotes aiming to identify a guide RNA (gRNA), yielding high editing efficiency and effective disruption of the Tead4 locus. Three guides were tested (gRNA1-3), each time targeting a distinct region of Exon 2 of Tead4. The effects of targeting on developmental capacity were studied in Tead4-targeted embryos (n = 164-summarized data from gRNA1-3) and were compared with two control groups; sham-injected embryos (n = 26) and non-injected media-control embryos (n = 51). The editing efficiency was determined by next-generation sequencing (NGS). In total, n = 55 (summarized data from gRNA1-3) targeted mouse embryos were analysed by NGS. Immunofluorescence analysis to confirm successful targeting by gRNA1 was performed in Tead4-targeted embryos, and non-injected media-control embryos. The downregulation of secondary TE-associated markers Cdx2 and Gata3 was used as an indirect confirmation of successful Tead4-targeting (previously shown to be expressed downstream of Tead4). Additional groups of gRNA1 Tead4-targeted (n = 45) and media control (n = 36) embryos were cultured for an extended period of 8.5 days, to further assess the developmental capacity of the Tead4-targeted group to develop beyond implantation stages. Following the mouse investigation, human metaphase-II (MII) oocytes obtained by IVM were microinjected with gRNA-Cas9 during ICSI (n = 74) to target TEAD4 or used as media-control (n = 33). The editing efficiency was successfully assessed in n = 25 TEAD4-targeted human embryos. Finally, immunofluorescence analysis for TEAD4, CDX2, GATA3 and the ICM marker SOX2 was performed in TEAD4-targeted (n = 10) and non-injected media-control embryos (n = 29).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A ribonucleoprotein complex consisting of a gRNA-Cas9 mixture, designed to target Exon 2 of Tead4/TEAD4, was microinjected in mouse PN stage zygotes or human IVM MII oocytes along with sperm. Generated embryos were cultured in vitro for 4 days in mouse or 6.5 days in human. In mouse, an additional group of Tead4-targeted and media-control embryos was cultured in vitro for an extended period of 8.5 days. Embryonic development and morphology were assessed daily, during culture in vitro of mouse and human embryos and was followed by a detailed scoring at late blastocyst stage. Targeting efficiency following gRNA-Cas9 introduction was assessed via immunostaining and NGS analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

NGS analysis of the Tead4-targeted locus revealed very high editing efficiencies for all three guides, with 100% of the mouse embryos (55 out of 55) carrying genetic modifications resulting from CRISPR-Cas9 genome editing. More specifically, 65.22% (15 out 23) of the PN zygotes microinjected with gRNA1-Cas9, which exhibited the highest efficiency, carried exclusively mutated alleles. The developmental capacity of targeted embryos was significantly reduced (data from gRNA1), as 44.17% of the embryos arrested at the morula stage (2.5 days post coitum), coincident with the initiation of TE lineage differentiation, compared with 8.51% in control and 12.50% in sham control groups. High-quality blastocyst formation rates (Grade 3) were 8.97% in the gRNA1-targeted group, compared with 87.23% in the media-control and 87.50% in the sham group. Immunofluorescence analysis in targeted embryos confirmed downregulation of Tead4, Cdx2, and Gata3 expression, which resulted from successful targeting of the Tead4 locus. Tead4-targeted mouse embryos stained positive for the ICM markers Pou5f1 and Sox2, indicating that expression of ICM lineage markers is not affected. Tead4-targeted embryos were able to cavitate and form a blastocoel without being able to hatch. Extended embryo culture following zona pellucida removal, revealed that the targeted embryos can attach and form egg-cylinder-like structures in the absence of trophoblast giant cells. In human embryos, Exon 2 of TEAD4 was successfully targeted by CRISPR-Cas9 (n = 74). In total, 25 embryos from various developmental stages were analysed by NGS and 96.00% (24 out of 25) of the embryos carried genetic modifications because of gRNA-Cas9 editing. In the subgroup of the 24 edited embryos, 17 (70.83%) carried only mutant alleles and 11 out of these 17 (64.70%) carried exclusively frameshift mutations. Six out of 11 embryos reached the blastocyst stage. In contrast to mice, human-targeted embryos formed blastocysts at a rate (25.00%) that did not differ significantly from the control group (23.81%). However, blastocyst morphology and TE quality were significantly compromised following TEAD4-targeting, showing grade C TE scores, with TE containing very few cells. Immunofluorescence analysis of TEAD4-targeted embryos (n = 10) confirmed successful editing by the complete absence of TEAD4 and its downstream TE marker CDX2, but the embryos generated retained expression of GATA3, which is in contrast to what we have observed and has previously been reported in mouse. In this regard, our results indicate that GATA3 acts in parallel with TEAD4/CDX2 towards TE differentiation in human.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

CRISPR-Cas9 germline genome editing, in some cases, induces mosaic genotypes. These genotypes are a result of inefficient and delayed editing, and complicate the phenotypic analysis and developmental assessment of the injected embryos. We cannot exclude the possibility that the observed differences between mouse and human are the result of variable effects triggered by the culture conditions, which were however similar for both mouse and human embryos in this study. Furthermore, this study utilized human oocytes obtained by IVM, which may not fully recapitulate the developmental behaviour of in vivo matured oocytes.

WIDER IMPLICATIONS OF THE FINDINGS

Elucidation of the evolutionary conservation of molecular mechanisms that regulate the differentiation and formation of the trophoblast lineage can give us fundamental insights into early implantation failure, which accounts for ∼15% of human conceptions.

STUDY FUNDING/COMPETING INTEREST(S)

The research was funded by the FWO-Vlaanderen (Flemish fund for scientific research, Grant no. G051516N), and Hercules funding (FWO.HMZ.2016.00.02.01) and Ghent University (BOF.BAS.2018.0018.01). G.C. is supported by FWO-Vlaanderen (Flemish fund for scientific research, Grant no. 11L8822N). A.B. is supported by FWO-Vlaanderen (Flemish fund for scientific research, Grant no. 1298722 N). We further thank Ferring Pharmaceuticals (Aalst, Belgium) for their unrestricted educational grant. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Morphogen Signals Shaping the Gastric Glands in Health and Disease

The adult gastric mucosa is characterised by deep invaginations of the epithelium called glands. These tissue architectural elements are maintained with the contribution of morphogen signals. Morphogens are expressed in specific areas of the tissue, and their diffusion generates gradients in the microenvironment. Cells at different positions in the gland sense a specific combination of signals that instruct them to differentiate, proliferate, regenerate, or migrate. Differentiated cells perform specific functions involved in digestion, such as the production of protective mucus and the secretion of digestive enzymes or gastric acid. Biopsies from gastric precancerous conditions usually display tissue aberrations and change the shape of the glands. Alteration of the morphogen signalling microenvironment is likely to underlie those conditions. Furthermore, genes involved in morphogen signalling pathways are found to be frequently mutated in gastric cancer. We summarise the most recent findings regarding alterations of morphogen signalling during gastric carcinogenesis, and we highlight the new stem cell technologies that are improving our understanding of the regulation of human tissue shape.

Transcription factor-mediated intestinal metaplasia and the role of a shadow enhancer

Here, Singh et al. show extensive but selective recruitment of intestinal enhancers by CDX2 in gastric cells and that HNF4A-mediated ectopic CDX2 expression in the stomach occurs through a conserved shadow cis-element. These findings identify mechanisms for TF-driven intestinal metaplasia and a likely pathogenic TF hierarchy.

Barrett's esophagus (BE) and gastric intestinal metaplasia are related premalignant conditions in which areas of human stomach epithelium express mixed gastric and intestinal features. Intestinal transcription factors (TFs) are expressed in both conditions, with unclear causal roles and cis-regulatory mechanisms. Ectopic CDX2 reprogrammed isogenic mouse stomach organoid lines to a hybrid stomach–intestinal state transcriptionally similar to clinical metaplasia; squamous esophageal organoids resisted this CDX2-mediated effect. Reprogramming was associated with induced activity at thousands of previously inaccessible intestine-restricted enhancers, where CDX2 occupied DNA directly. HNF4A, a TF recently implicated in BE pathogenesis, induced weaker intestinalization by binding a novel shadow Cdx2 enhancer and hence activating Cdx2 expression. CRISPR/Cas9-mediated germline deletion of that cis-element demonstrated its requirement in Cdx2 induction and in the resulting activation of intestinal genes in stomach cells. dCas9-conjugated KRAB repression mapped this activity to the shadow enhancer's HNF4A binding site. Altogether, we show extensive but selective recruitment of intestinal enhancers by CDX2 in gastric cells and that HNF4A-mediated ectopic CDX2 expression in the stomach occurs through a conserved shadow cis-element. These findings identify mechanisms for TF-driven intestinal metaplasia and a likely pathogenic TF hierarchy.

Chromatin regulatory dynamics of early human small intestinal development using a directed differentiation model

The establishment of the small intestinal (SI) lineage during human embryogenesis ensures functional integrity of the intestine after birth. The chromatin dynamics that drive SI lineage formation and regional patterning in humans are essentially unknown. To fill this knowledge void, we apply a cutting-edge genomic technology to a state-of-the-art human model of early SI development. Specifically, we leverage chromatin run-on sequencing (ChRO-seq) to define the landscape of active promoters, enhancers and gene bodies across distinct stages of directed differentiation of human pluripotent stem cells into SI spheroids with regional specification. Through comprehensive ChRO-seq analysis we identify candidate stage-specific chromatin activity states, novel markers and enhancer hotspots during the directed differentiation. Moreover, we propose a detailed transcriptional network associated with SI lineage formation or regional patterning. Our ChRO-seq analyses uncover a previously undescribed pattern of enhancer activity and transcription at HOX gene loci underlying SI regional patterning. We also validated this unique HOX dynamics by the analysis of single cell RNA-seq data from human fetal SI. Overall, the results lead to a new proposed working model for the regulatory underpinnings of human SI development, thereby adding a novel dimension to the literature that has relied almost exclusively on non-human models.

Silencing LINC01021 inhibits gastric cancer through upregulation of KISS1 expression by blocking CDK2-dependent phosphorylation of CDX2

Gastric cancer remains one of the most dangerous cancers, bringing suffering and economic burden to people worldwide. Long noncoding RNAs (lncRNAs) exhibit great potentials for targeted therapy of various cancers. In this investigation, we tested mechanisms by which LINC01021 may regulate gastric cancer progression. We collected gastric cancer tissues and procured cell lines to explore the potential factors by which LINC01021 had effects on angiogenesis, invasion, and migration, by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), Transwell assay, and western blot analysis. Relationships among LINC01021, Caudal-type homeobox 2 (CDX2), and KISS1 were validated by dual-luciferase gene reporter, RNA pull-down, and RNA immunoprecipitation assays. Additionally, a murine model was developed to further explore the impact of LINC01021 on tumors in vivo. LINC01021 was upregulated in gastric cancer tissues and cells. LINC01021 regulated KISS1 through CDK2, which promoted phosphorylation and nuclear export in CDX2. Inhibition of LINC01021 suppressed the tumorigenesis of gastric cancer. Further, silencing LINC01021 exerted an inhibitory effect on cancer cell migration, invasion, and angiogenesis by promoting the binding between CDX2 and KISS1, while inhibiting that between CDK2 and CDX2. Taken altogether, high LINC01021 expression in gastric cancer promotes malignant cell migration and angiogenesis by downregulation of KISS1 through CDK2-mediated CDX2 phosphorylation.

Caudal type homeoboxes as a driving force in Helicobacter pylori infection-induced gastric intestinal metaplasia

(H. pylori), a common pathogenic bacterium in the stomach, has been demonstrated to be a major cause of gastric cancer (GC). The typical pathological evolution of H. pylori infection-induced GC involves development from gastric atrophy, via intestinal metaplasia (IM) and dysplasia, to intestinal-type GC. During this process, IM is considered to be an "irreversible point" that significantly increases the risk for GC. Therefore, the elucidation of the mechanism underlying IM is of great significance for the prevention and treatment of gastric mucosal carcinogenesis associated with H. pylori infection. Caudal type homeoboxes (CDXs) are transcription factors involved in intestinal differentiation establishment and the maintenance of normal intestinal mucosa and IM. H. pylori infection increases the expression of CDXs through epigenetic regulation, the nuclear factor-kappaB signaling pathway and its downstream proinflammatory factors, and the transforming growth factor-beta signaling pathway, leading to the progression from normal gastric mucosa to IM. However, the precise mechanisms of gastric intestinal metaplasia have not yet been fully elucidated. In this review, we focus on research progress revealing the functions of CDXs in H. pylori infection-induced IM, as well as the regulators modulating this process.

Deoxycholic acid-stimulated macrophage-derived exosomes promote intestinal metaplasia and suppress proliferation in human gastric epithelial cells

The crosstalk between macrophages and gastric epithelial cells has emerged as a player in chronic inflammation during intestinal metaplasia. However, the role of bile acid on this modulation remains to be studied. We hypothesized that deoxycholic acid-induced macrophages secreted exosomes to mediate intercellular communication and promoted intestinal metaplasia in human gastric epithelial cells (GES-1 cells). Macrophage-derived exosomes (M-Exos) and deoxycholic acid-induced macrophage-derived exosomes (D-Exos) were isolated by ultracentrifugation. EdU staining and CCK-8 assay were utilized to evaluate the effects of exosomes on the proliferation of GES-1 cells. Intestinal metaplasia was assessed by the expression of caudal-related homeobox transcription factor 2 (CDX2) at both mRNA and protein level. MicroRNA sequencing revealed the microRNA (miRNA) expression profiles of M-Exos and D-Exos. The role of a specific miRNA and mRNA was analyzed by using miRNA mimics, miRNA inhibitors and siRNAs. D-Exos promoted the expression of CDX2 and suppressed the proliferation of GES-1 cells, compared to M-Exos. The miRNA profiles and quantitative real-time PCR examination showed D-Exos enriched a higher level of hsa-miR-30a-5p than M-Exos. Overexpressed has-miR-30a-5p increased CDX2 expression and inhibited the proliferation in GES-1 cells via targeted Forkhead Box D1 (FOXD1), a potential regulatory factor in the process of intestinal metaplasia. D-Exos may promote intestinal metaplasia and suppress proliferation of GES-1 cells via hsa-miR-30a-5p targeting FOXD1, which may be involved in the action mechanism of bile acid on gastric mucosa.

A panel of intestinal differentiation markers (CDX2, GPA33, and LI-cadherin) identifies gastric cancer patients with favourable prognosis

BACKGROUND

Gastric cancer is the fifth most common cancer and the third cause of global cancer mortality. CDX2 is an intestinal differentiation marker with prognostic value in gastric cancer and transcriptionally regulates the expression of glycoprotein A33 (GPA33) and liver intestine cadherin (LI-cadherin).

METHODS

This study evaluated the clinical significance of the combined expression of CDX2 and its targets GPA33 and LI-cadherin in gastric cancer by fluorescence-based multiplex immunohistochemistry together with digital image analysis and chromogenic immunohistochemistry in 329 gastric cancer samples arranged in tissue microarrays. Additionally, publicly available RNA-seq expression data from 354 gastric cancer samples from the TCGA database were used to validate the immunohistochemistry results.

RESULTS

Expression of the three markers (CDX2, GPA33, and LI-cadherin) was strongly correlated, defining an intestinal differentiation panel. Low or negative protein expression of the intestinal differentiation panel identified patients with particularly poor overall survival, irrespective of the methodology used, and was validated in the independent series at the RNA-seq level.

CONCLUSIONS

Expression of the intestinal differentiation panel (CDX2, GPA33, and LI-cadherin) defines a set of biomarkers with a strong biological rationale and favourable impact for prognostication of gastric cancer patients.

The role of transcription factor caudal-related homeobox transcription factor 2 in colorectal cancer

Colorectal cancer (CRC) is one of the most malignant tumors in humans and causes mass mortality. In the age of precise medicine, more and more subtypes of CRC were classified. The caudal-related homeobox transcription factor 2 (CDX2) is an intestine-specific transcription factor which is implicated in differentiation, proliferation, cell-adhesion, and migration. The loss of CDX2 in immunohistochemical stain was reported to be a prognostic factor of colon cancer, but the clinical application remained controversial. Most of the CRCs expressed or over-expressed CDX2. Homeobox genes can display either an oncogenic or a tumor-suppressing activity. CDX2 regulates the developing intestinal epithelium and CRC by different pathways. The complex regulation of CDX2 and its complex targets cause the difficulties of application for CDX2 in the prediction of prognosis. However, CDX2 is a potential biomarker applied in the precise classification of CRC for personalized medicine. This review partially clarifies the role of CDX2 in CRC.

TGR5-HNF4α axis contributes to bile acid-induced gastric intestinal metaplasia markers expression

Intestinal metaplasia (IM) increases the risk of gastric cancer. Our previous results indicated that bile acids (BAs) reflux promotes gastric IM development through kruppel-like factor 4 (KLF4) and caudal-type homeobox 2 (CDX2) activation. However, the underlying mechanisms remain largely elusive. Herein, we verified that secondary BAs responsive G-protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5) was increased significantly in IM specimens. Moreover, TGR5 contributed to deoxycholic acid (DCA)-induced metaplastic phenotype through positively regulating KLF4 and CDX2 at transcriptional level. Then we employed PCR array and identified hepatocyte nuclear factor 4α (HNF4α) as a candidate mediator. Mechanically, DCA treatment could induce HNF4α expression through TGR5 and following ERK1/2 pathway activation. Furthermore, HNF4α mediated the effects of DCA treatment through directly regulating KLF4 and CDX2. Finally, high TGR5 levels were correlated with high HNF4α, KLF4, and CDX2 levels in IM tissues. These findings highlight the TGR5-ERK1/2-HNF4α axis during IM development in patients with BAs reflux, which may help to understand the mechanism underlying IM development and provide prospective strategies for IM treatment.

R-spondin1/Wnt-enhanced Ascl2 autoregulation controls the self-renewal of colorectal cancer progenitor cells

The Wnt signaling pathway controls stem cell identity in the intestinal epithelium and cancer stem cells (CSCs). The transcription factor Ascl2 (Wnt target gene) is fate decider of intestinal cryptic stem cells and colon cancer stem cells. It is unclear how Wnt signaling is translated into Ascl2 expression and keeping the self-renewal of CRC progenitor cells. We showed that the exogenous Ascl2 in colorectal cancer (CRC) cells activated the endogenous Ascl2 expression via a direct autoactivatory loop, including Ascl2 binding to its own promoter and further transcriptional activation. Higher Ascl2 expression in human CRC cancerous tissues led to greater enrichment in Ascl2 immunoprecipitated DNA within the Ascl2 promoter in the CRC cancerous sample than the peri-cancerous mucosa. Ascl2 binding to its own promoter and inducing further transcriptional activation of the Ascl2 gene was predominant in the CD133⁺CD44⁺ CRC population. R-spondin1/Wnt activated Ascl2 expression dose-dependently in the CD133⁺CD44⁺ CRC population, but not in the CD133^-CD44^- CRC population, which was caused by differences in Ascl2 autoregulation under R-spondin1/Wnt activation. R-spondin1/Wnt treatment in the CD133⁺CD44⁺ or CRC CD133^-CD44^- populations exerted a different pattern of stemness maintenance, which was defined by alterations of the mRNA levels of stemness-associated genes, the protein expression levels (Bmi1, C-myc, Oct-4 and Nanog) and tumorsphere formation. The results indicated that Ascl2 autoregulation formed a transcriptional switch that was enhanced by Wnt signaling in the CD133⁺CD44⁺ CRC population, thus conferring their self-renewal.

Activation of FXR promotes intestinal metaplasia of gastric cells via SHP-dependent upregulation of the expression of CDX2

Gastric intestinal metaplasia (IM) induced by bile acid is a precancerous lesion of gastric adenocarcinoma and is associated with the expression of caudal-related homeobox 2 (CDX2). In the present study, the role of farnesoid X receptor (FXR) on the regulation of CDX2 in gastric cells was investigated and the underlying molecular mechanisms were examined. Human gastric cell lines were treated with chenodeoxycholic acid (CDCA) or FXR agonist GW4064. Cells were treated with CDCA in the presence or absence of the FXR antagonist or FXR siRNA transfection. Next, cells were treated with CDCA in the presence or absence of SHP siRNA transfection and FXR, CDX2 and SHP mRNA and protein levels were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. A chromatin immunoprecipitation assay was performed to examine the relationship between FXR and SHP and the expressions of FXR and CDX2 in gastritis and IM tissues were detected using immunohistochemistry. The results revealed that CDCA was able to induce CDX2 expression, which could be blocked by inhibition or knockdown of FXR. Mechanistically, FXR directly induced the expression of small heterodimer partner (SHP). SHP knockdown significantly decreased CDCA-induced CDX2 expression. ChIP results indicated that FXR could directly bind SHP promoter and promote SHP expression. Finally, immunohistochemistry results demonstrated that the expression levels of CDX2 and FXR in human IM lesions were significantly higher, compared with those in gastritis lesions, and were positively correlated. Collectively, these results revealed that the activation of FXR and sequential direct transcriptional induction of SHP were involved in the expression of CDX2 induced by bile acid in gastric IM lesions.

hTERT promotes gastric intestinal metaplasia by upregulating CDX2 via NF-κB signaling pathway

Background

hTERT has been reported involved in the proliferation and metastasis of gastric cancer, but the role of hTERT in gastric intestinal metaplasia, a premalignant lesion of the gastric mucosa was unknown. The aim of the present study was to investigate the role of hTERT in GIM and the effect of hTERT on CDX2 expression in gastric cells.

Results

Experiments showed that expression of hTERT was significantly higher in GIM than in normal gastric mucosa. Moreover, hTERT increased the KLF4 level via NF-κB during GIM. Furthermore, KLF4 is involved in the up-regulation of CDX2 induced by hTERT, and hTERT can interact with p50, thereby increasing the level of CDX2.

Materials and Methods

Immunohistochemistry was used to detect the expression of hTERT in gastric intestinal metaplasia tissue. Then, effect of hTERT on the expression of CDX2 was detected by qRT-PCR, WB and dual luciferase experiment. The role of p65 and p50 in the regulation of CDX2 were further detected by WB, CO-IP and ChIP.

Conclusions

We may conclude that hTERT promotes GIM by up-regulating CDX2 via NF-κB signaling pathway.

Helicobacter pylori-induced gastric pathology: insights from in vivo and ex vivo models

Gastric colonization with Helicobacter pylori induces diverse human pathological conditions, including superficial gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma and its precursors. The treatment of these conditions often relies on the eradication of H. pylori, an intervention that is increasingly difficult to achieve and that does not prevent disease progression in some contexts. There is, therefore, a pressing need to develop new experimental models of H. pylori-associated gastric pathology to support novel drug development in this field. Here, we review the current status of in vivo and ex vivo models of gastric H. pylori colonization, and of Helicobacter-induced gastric pathology, focusing on models of gastric pathology induced by H. pylori, Helicobacter felis and Helicobacter suis in rodents and large animals. We also discuss the more recent development of gastric organoid cultures from murine and human gastric tissue, as well as from human pluripotent stem cells, and the outcomes of H. pylori infection in these systems.

HpSlyD inducing CDX2 and VIL1 expression mediated through TCTP protein may contribute to intestinal metaplasia in the stomach

Helicobacter pylori infection is the most important risk factor for gastric intestinal metaplasia (IM). Our previous study demonstrated that infection with H. pylori HpslyD-positive strains associated with IM. To further investigate the signalling pathway involved in HpSlyD-induced IM, CDX2 and VIL1 expressions were determined before and after HpSlyD application. TCTP was knocked down by siRNA or overexpressed by plasmid transfection. An HpSlyD binding protein was used to block HpSlyD's enzymatic activity. The expression of CDX2 and TCTP in gastric diseases was measured by immunohistochemistry. Our results showed HpSlyD induced CDX2 and VIL1 expressions. TCTP protein expression was markedly increased after application of HpSlyD and in an HpSlyD-expressing stable cell line. Downregulation of TCTP protein led to decreased HpSlyD-induced CDX2 and VIL1. Overexpression of TCTP protein improved the expression of CDX2 and VIL1. Co-application of HpSlyD and FK506 led to significant reductions in CDX2, VIL1, and TCTP expression. Immunohistochemistry demonstrated that CDX2 and TCTP expression was higher in HpslyD-positive specimens compared with HpslyD-negative ones. Expression of CDX2 was positively correlated with TCTP in HpslyD-positive cells. Our study is the first to show that HpSlyD induction of CDX2 and VIL1 expression mediated through TCTP may contribute to IM in the stomach.

Inhibition of CDH17 gene expression via RNA interference reduces proliferation and apoptosis of human MKN28 gastric cancer cells

Gastric cancer is the fourth most common type of cancer and the second cause of cancer-related mortalities worldwide despite the use of multimodal therapy. Cadherins are transmembrane glycoproteins that are involved in tumorigenesis. CDH17 has been found to be over-expressed in gastric cancer and its overexpression was associated with lymph node metastasis and tumor-node-metastasis stage of the patients, yet the exact role and molecular mechanism of CDH17 in gastric cancer have not been determined. Using a lentiviral system as a delivery mediator of RNA interference, we found that inhibition of CDH17 can lead to reduce proliferation and increase apoptosis of gastric cancer cell line MKN28 in vitro and significantly diminish their tumorigenicity in vivo. Our results of the present study suggest that CDH17 may be a promising candidate for the therapeutic targeting of gastric cancer.

CDX2 immunostaining in primary and metastatic germ cell tumours of the testis

Objective To evaluate the immunohistochemical staining pattern of caudal type homeobox 2 (CDX2) protein in germ cell tumours (GCTs) of the testis. Methods This study reassessed archival tissue samples collected from patients diagnosed with primary and metastatic testicular GCTs for CDX2 immunoreactivity using standard immunohistochemical techniques. Positive nuclear immunostaining was evaluated with regard to both the staining intensity and the extent of the staining. Results Tissue sections from primary and metastatic testicular GCTs ( n = 104), germ cell neoplasia in situ (GCNis) ( n = 5) and benign testicles ( n = 15) were analysed. The GCNis and benign testicular tissues showed no immunoreactivity for CDX2. Strong and diffuse staining of CDX2 was demonstrated only in the mature colonic epithelium of teratomas in both primary and metastatic GCTs. CDX2 positivity in other tumours (one pure yolk sac tumour, one yolk sac component of a mixed GCT and one pure seminoma) was infrequent, and was only weak and focal. Conclusions CDX2 immunostaining should be interpreted based on both the staining intensity and the extent of staining so as not to cause misdiagnosis. Teratomas with colonic-type epithelium should be considered in the differential diagnosis if a metastatic tumour with an unknown primary shows prominent CDX2 immunostaining.

CDX2 homeoprotein is involved in the regulation of ST6GalNAc-I gene in intestinal metaplasia

De novo expression of Sialyl-Tn (STn) antigen is one of the most common features of intestinal metaplasia (IM) and gastric carcinomas, and its biosynthesis has been mostly attributed to ST6GalNAc-I activity. However, the regulation of this glycosyltransferase expression is not elucidated. In IM lesions and in the intestine, CDX2 homeobox transcription factor is co-expressed with STn and ST6GalNAc-I. We therefore hypothesized that CDX2 might induce STn expression by positive regulation of ST6GalNAc-I. We showed that ST6GalNAc-I transcript levels and CDX2 have a coordinated expression upon Caco-2 in vitro differentiation, and overexpression of CDX2 in MKN45 gastric cells increases ST6GalNAc-I transcript levels. Nine putative CDX-binding sites in the ST6GalNAc-I-regulatory sequence were identified and analyzed by chromatin immunoprecipitation in Caco-2 cells and in IM. The results showed that CDX2 protein is recruited to all regions, being the most proximal sites preferentially occupied in vivo. Luciferase assays demonstrated that CDX2 is able to transactivate ST6GalNac-I-regulatory region. The induction was stronger for the regions mapped in the neighbourhood of ATG start codon and site-directed mutagenesis of these sites confirmed their importance. In conclusion, we show that CDX2 transcriptionally regulates ST6GalNAc-I gene expression, specifically in the preneoplastic IM lesion.

Intestinal Stem Cell Markers in the Intestinal Metaplasia of Stomach and Barrett's Esophagus

Gastric intestinal metaplasia (IM) is a highly prevalent preneoplastic lesion; however, the molecular mechanisms regulating its development remain unclear. We have previously shown that a population of cells expressing the intestinal stem cell (ISC) marker LGR5 increases remarkably in IM. In this study, we further investigated the molecular characteristics of these LGR5⁺ cells in IM by examining the expression profile of several ISC markers. Notably, we found that ISC markers—including OLFM4 and EPHB2—are positively associated with the CDX2 expression in non-tumorous gastric tissues. This finding was confirmed in stomach lesions with or without metaplasia, which demonstrated that OLFM4 and EPHB2 expression gradually increased with metaplastic progression. Moreover, RNA in situ hybridization revealed that LGR5⁺ cells coexpress several ISC markers and remained confined to the base of metaplastic glands, reminiscent to that of normal intestinal crypts, whereas those in normal antral glands expressed none of these markers. Furthermore, a large number of ISC marker-expressing cells were diffusely distributed in gastric adenomas, suggesting that these markers may facilitate gastric tumorigenesis. In addition, Barrett’s esophagus (BE)—which is histologically similar to intestinal metaplasia—exhibited a similar distribution of ISC markers, indicating the presence of a stem cell population with intestinal differentiation potential. In conclusion, we identified that LGR5⁺ cells in gastric IM and BE coexpress ISC markers, and exhibit the same expression profile as those found in normal intestinal crypts. Taken together, these results implicate an intestinal-like stem cell population in the pathogenesis of IM, and provide an important basis for understanding the development and maintenance of this disease.

Transcription factor AP-2γ induces early Cdx2 expression and represses HIPPO signaling to specify the trophectoderm lineage

Cell fate decisions are fundamental to the development of multicellular organisms. In mammals the first cell fate decision involves segregation of the pluripotent inner cell mass and the trophectoderm, a process regulated by cell polarity proteins, HIPPO signaling and lineage-specific transcription factors such as CDX2. However, the regulatory mechanisms that operate upstream to specify the trophectoderm lineage have not been established. Here we report that transcription factor AP-2γ (TFAP2C) functions as a novel upstream regulator of Cdx2 expression and position-dependent HIPPO signaling in mice. Loss- and gain-of-function studies and promoter analysis revealed that TFAP2C binding to an intronic enhancer is required for activation of Cdx2 expression during early development. During the 8-cell to morula transition TFAP2C potentiates cell polarity to suppress HIPPO signaling in the outside blastomeres. TFAP2C depletion triggered downregulation of PARD6B, loss of apical cell polarity, disorganization of F-actin, and activation of HIPPO signaling in the outside blastomeres. Rescue experiments using Pard6b mRNA restored cell polarity but only partially corrected position-dependent HIPPO signaling, suggesting that TFAP2C negatively regulates HIPPO signaling via multiple pathways. Several genes involved in regulation of the actin cytoskeleton (including Rock1, Rock2) were downregulated in TFAP2C-depleted embryos. Inhibition of ROCK1 and ROCK2 activity during the 8-cell to morula transition phenocopied TFAP2C knockdown, triggering a loss of position-dependent HIPPO signaling and decrease in Cdx2 expression. Altogether, these results demonstrate that TFAP2C facilitates trophectoderm lineage specification by functioning as a key regulator of Cdx2 transcription, cell polarity and position-dependent HIPPO signaling.

Effects of the hippo signaling pathway in human gastric cancer

BACKGROUND/AIM

The Hippo signaling pathway is a newly discovered and conserved signaling cascade, which regulates organ size control by governing cell proliferation and apoptosis. This study aimed to investigate its effects in human gastric cancer.

METHODS

Tumor tissues (n=60), adjacent non-tumor tissues (n=60) and normal tissues (n=60) were obtained from the same patients with primary gastric cancer (GC). In addition, 70 samples of chronic atrophic gastritis (CAG) tissues were obtained from patients with intestinal metaplasia (IM) by endoscopic biopsy. Hippo signaling molecules, including Mst1, Lats1, YAP1, TAZ, TEAD1, Oct4 and CDX2, were determined by quantitative polymerase chain reaction (qPCR). Protein expression of Mst1, Lats1, YAP1, TEAD1 and CDX2 was assessed by immunohistochemistry and Western blotting.

RESULTS

Mst1, Lats1 and Oct4 mRNA expression showed an increasing tendency from GC tissues to normal gastric tissues, while the mRNA expression of YAP1, TAZ and TEAD1 was up-regulated (all P<0.01). Mst1 and Lats1 protein expression presented a similar trend with their mRNA expression. In addition, YAP1 and TEAD1 protein expression in GC was significantly higher than in the other groups (all P<0.01). CDX2 mRNA and protein expression in the CAG group were higher than in the other groups (all P<0.01). In GC, mRNA expression of Mst1, Lats1, Oct4, YAP1, TAZ, TEAD1 and CDX2 had a close correlation with lymphatic metastasis and tumor TNM stage (all P<0.01). Furthermore, protein expression of Mst1, Lats1 ,YAP1, TAZ, TEAD1 and CDX2 had a close correlation between each other (P<0.05).

CONCLUSION

The Hippo signaling pathway is involved in the development, progression and metastasis of human gastric cancer. Therefore, manipulation of Hippo signaling molecules may be a potential therapeutic strategy for gastric cancer.

Differentiation reprogramming in gastric intestinal metaplasia and dysplasia: role of SOX2 and CDX2

AIMS

Intestinal metaplasia (IM), which results from de-novo expression of CDX2, and dysplasia are precursor lesions of gastric cancer that are associated with an increased risk for cancer development. There is much evidence suggesting a role for the transcription factor SOX2 in gastric differentiation. The aim of this study was to attempt to establish the relationship of SOX2 with CDX2 and with the differentiation reprogramming that characterizes gastric carcinogenesis, to assess their involvement in IM and dysplasia.

METHODS AND RESULTS

Characterization of gastric (SOX2, MUC5AC, and MUC6) and intestinal (CDX2 and MUC2) markers in normal gastric mucosa, in 55 foci of IM and in 26 foci of dysplasia, was performed by immunohistochemistry. SOX2 was expressed in the normal gastric mucosa, in the presumptive stem cell compartment, and was maintained in 7% of the complete (MUC5AC-negative) and 85% of the incomplete (MUC5AC-positive) IM subtypes. Twelve per cent of the dysplastic lesions expressed SOX2, and the association with MUC5AC was lost. CDX2 was present in all IMs and dysplastic lesions.

CONCLUSIONS

SOX2 is associated with gastric differentiation in incomplete IM and is lost in the progression to dysplasia, whereas CDX2 is acquired de novo in IM and maintained in dysplasia. This suggests that the balance between gastric and intestinal differentiation programmes impacts on the gastric carcinogenesis cascade progression.

Gli regulates MUC5AC transcription in human gastrointestinal cells

MUC5AC is a well-known gastric differentiation marker, which has been frequently used for the classification of stomach cancer. Immunohistochemistry revealed that expression of MUC5AC decreases accompanied with increased malignant property of gastric mucosa, which further suggests the importance of MUC5AC gene regulation. Alignment of the 5′-flanking regions of MUC5AC gene of 13 mammal species denoted high homology within 200 bp upstream of the coding region. Luciferase activities of the deletion constructs containing upstream 451 bp or shorter fragments demonstrated that 15 bp region between −111 and −125 bp plays a critical role on MUC5AC promoter activity in gastrointestinal cells. We found a putative Gli-binding site in this 15 bp sequence, and named this region a highly conserved region containing a Gli-binding site (HCR-Gli). Overexpression of Gli homologs (Gli1, Gli2, and Gli3) clearly enhanced MUC5AC promoter activity. Exogenous modulation of Gli1 and Gli2 also affected the endogenous MUC5AC gene expression in gastrointestinal cells. Chromatin immunoprecipitation assays demonstrated that Gli1 directly binds to HCR-Gli: Gli regulates MUC5AC transcription via direct protein-DNA interaction. Conversely, in the 30 human cancer cell lines and various normal tissues, expression patterns of MUC5AC and Gli did not coincide wholly: MUC5AC showed cell line-specific or tissue-specific expression whereas Gli mostly revealed ubiquitous expression. Luciferase promoter assays suggested that the far distal MUC5AC promoter region containing upstream 4010 bp seems to have several enhancer elements for gene transcription. In addition, treatments with DNA demethylation reagent and/or histone deacetylase inhibitor induced MUC5AC expression in several cell lines that were deficient in MUC5AC expression. These results indicated that Gli is necessary but not sufficient for MUC5AC expression: namely, the multiple regulatory mechanisms should work in the distal promoter region of MUC5AC gene.

A polymorphic enhancer near GREM1 influences bowel cancer risk through differential CDX2 and TCF7L2 binding

A rare germline duplication upstream of the bone morphogenetic protein antagonist GREM1 causes a Mendelian-dominant predisposition to colorectal cancer (CRC). The underlying disease mechanism is strong, ectopic GREM1 overexpression in the intestinal epithelium. Here, we confirm that a common GREM1 polymorphism, rs16969681, is also associated with CRC susceptibility, conferring ∼20% differential risk in the general population. We hypothesized the underlying cause to be moderate differences in GREM1 expression. We showed that rs16969681 lies in a region of active chromatin with allele- and tissue-specific enhancer activity. The CRC high-risk allele was associated with stronger gene expression, and higher Grem1 mRNA levels increased the intestinal tumor burden in Apc(Min) mice. The intestine-specific transcription factor CDX2 and Wnt effector TCF7L2 bound near rs16969681, with significantly higher affinity for the risk allele, and CDX2 overexpression in CDX2/GREM1-negative cells caused re-expression of GREM1. rs16969681 influences CRC risk through effects on Wnt-driven GREM1 expression in colorectal tumors.

Notch and hippo converge on Cdx2 to specify the trophectoderm lineage in the mouse blastocyst

The first lineage choice in mammalian embryogenesis is that between the trophectoderm, which gives rise to the trophoblast of the placenta, and the inner cell mass, from which is derived the embryo proper and the yolk sac. The establishment of these lineages is preceded by the inside-versus-outside positioning of cells in the early embryo and stochastic expression of key transcription factors, which is then resolved into lineage-restricted expression. The regulatory inputs that drive this restriction and how they relate to cell position are largely unknown. Here, we show an unsuspected role of Notch signaling in regulating trophectoderm-specific expression of Cdx2 in cooperation with TEAD4. Notch activity is restricted to outer cells and is able to influence positional allocation of blastomeres, mediating preferential localization to the trophectoderm. Our results show that multiple signaling inputs at preimplantation stages specify the first embryonic lineages.

Nuclear factor of activated T-cells 5 increases intestinal goblet cell differentiation through an mTOR/Notch signaling pathway

This study demonstrates a role for nuclear factor of activated T-cell 5 (NFAT5) in the regulation of mTOR signaling in intestinal cells, which suggests that NFAT5 participates in the regulation of intestinal homeostasis via suppression of the mTORC1/Notch signaling pathway.

The intestinal mucosa undergoes a continual process of proliferation, differentiation, and apoptosis that is regulated by multiple signaling pathways. Previously, we have shown that the nuclear factor of activated T-cells 5 (NFAT5) is involved in the regulation of intestinal enterocyte differentiation. Here we show that treatment with sodium chloride (NaCl), which activates NFAT5 signaling, increased mTORC1 repressor regulated in development and DNA damage response 1 (REDD1) protein expression and inhibited mTOR signaling; these alterations were attenuated by knockdown of NFAT5. Knockdown of NFAT5 activated mammalian target of rapamycin (mTOR) signaling and significantly inhibited REDD1 mRNA expression and protein expression. Consistently, overexpression of NFAT5 increased REDD1 expression. In addition, knockdown of REDD1 activated mTOR and Notch signaling, whereas treatment with mTOR inhibitor rapamycin repressed Notch signaling and increased the expression of the goblet cell differentiation marker mucin 2 (MUC2). Moreover, knockdown of NFAT5 activated Notch signaling and decreased MUC2 expression, while overexpression of NFAT5 inhibited Notch signaling and increased MUC2 expression. Our results demonstrate a role for NFAT5 in the regulation of mTOR signaling in intestinal cells. Importantly, these data suggest that NFAT5 participates in the regulation of intestinal homeostasis via the suppression of mTORC1/Notch signaling pathway.

CDX2 can be regulated through the signalling pathways activated by IL-6 in gastric cells

The inflammatory infiltrate of the gastric mucosa associated with Helicobacter pylori infection increases the presence of the pro-inflammatory cytokine IL-6 that activates both the SHP-2/ERK/MAPK and the JAK/STAT signalling pathways. Furthermore, the ectopic expression of CDX2 is detected in pre-neoplasic lesions associated with decreased levels of SOX2, and we found that in gastric adenocarcinomas their expression is inversely correlated. To determine the role of IL-6 in the regulation of CDX2, MKN45 that constitutively expresses p-STAT3, and NUGC-4 gastric cancer cell lines were treated with IL-6, which induced the CDX2 up-regulation and SOX2 down-regulation. ChIP assays determined that in IL-6-treated cells, c-JUN and p-STAT3 bound to CDX2 promoter in MKN45 cells whereas in NUGC-4 cells, p-STAT3 binds to and c-JUN releases from the CDX2 promoter. Specific inhibition of STAT3 and ERK1/2 phosphorylation through AG490 and U0126, respectively, and STAT3 down-regulation using shRNA verified that the SHP-2/ERK/MAPK pathway regulates the expression of CDX2 in basal conditions, and the CDX2 up-regulation by IL-6 is through the JAK/STAT pathway in NUGC-4 cells whereas in MKN45 cells both pathways contribute to the CDX2 up-regulation. In conclusion, the signalling pathways activated by IL-6 have a crucial role in the regulation of CDX2 that is a key factor in the process of gastric carcinogenesis, suggesting that the inflammatory infiltrate in the gastric mucosa is relevant in this process and a potential target for new therapeutic approaches.

Modified-chitosan/siRNA nanoparticles downregulate cellular CDX2 expression and cross the gastric mucus barrier

Development of effective non-viral vectors is of crucial importance in the implementation of RNA interference in clinical routine. The localized delivery of siRNAs to the gastrointestinal mucosa is highly desired but faces specific problems such as the stability in gastric acidity conditions and the presence of the mucus barrier. CDX2 is a transcription factor critical for intestinal differentiation being involved in the initiation and maintenance of gastrointestinal diseases. Specifically, it is the trigger of gastric intestinal metaplasia which is a precursor lesion of gastric cancer. Its expression is also altered in colorectal cancer, where it may constitute a lineage-survival oncogene. Our main objective was to develop a nanoparticle-delivery system of siRNA targeting CDX2 using modified chitosan as a vector. CDX2 expression was assessed in gastric carcinoma cell lines and nanoparticles behaviour in gastrointestinal mucus was tested in mouse explants. We show that imidazole-modified chitosan and trimethylchitosan/siRNA nanoparticles are able to downregulate CDX2 expression and overpass the gastric mucus layer but not colonic mucus. This system might constitute a potential therapeutic approach to treat CDX2-dependent gastric lesions.

Antral atrophy, intestinal metaplasia, and preneoplastic markers in Mexican children with Helicobacter pylori-positive and Helicobacter pylori-negative gastritis

Chronic inflammation and infection are major risk factors for gastric carcinogenesis in adults. As chronic gastritis is common in Mexican children, diagnosis of Helicobacter pylori and other causes of gastritis are critical for the identification of children who would benefit from closer surveillance. Antral biopsies from 82 Mexican children (mean age, 8.3 ± 4.8 years) with chronic gastritis (36 H pylori+, 46 H pylori-) were examined for gastritis activity, atrophy, intestinal metaplasia (IM), and immunohistochemical expression of gastric carcinogenesis biomarkers caudal type homeobox 2 (CDX2), ephrin type-B receptor 4 (EphB4), matrix metalloproteinase 3 (MMP3), macrophage migration inhibitory factor (MIF), p53, β-catenin, and E-cadherin. Atrophy was diagnosed in 7 (9%) of 82, and IM, in 5 (6%) of 82 by routine histology, whereas 6 additional children (7%) (3 H pylori+) exhibited aberrant CDX2 expression without IM. Significant positive correlations were seen between EphB4, MMP3, and MIF (P<.0001). Atrophy and follicular pathology were more frequent in H pylori+ biopsies (P<.0001), whereas IM and CDX2 expression showed no significant correlation with H pylori status. Antral biopsies demonstrating atrophy, IM, and/or aberrant CDX2 expression were seen in 21.95% (18/82) of the children, potentially identifying those who would benefit from closer surveillance and preventive dietary strategies. Biomarkers CDX2, EphB4, MMP3, and MIF may be useful in the workup of pediatric gastritis.

Involvement of CDX2 in the cross talk between TNF-α and Wnt signaling pathway in the colon cancer cell line Caco-2

Tumor necrosis factor-α (TNF-α) is highly upregulated in inflammation and reduces the expression of the intestinal transcription factor, Caudal-related homeobox transcription factor 2 (CDX2). Wnt/β-catenin signaling is critical for intestinal cell proliferation, but a decreased CDX2 expression has influence on the Wnt signaling-related genes and progression of colorectal cancer. Although several inflammatory signaling pathways, including TNF-α, have been reported to promote Wnt/β-catenin activity and development of cancer, the underlying molecular mechanisms remain unclear. The aim was to investigate the signaling pathways involved in the TNF-α-mediated downregulation of CDX2, and its influence on Wnt/β-catenin signaling components in colon cancer cells. The expression of TNF-α and CDX2 at the invasive front were evaluated by immunohistochemical staining and showed reduced CDX2-positive cells in tumor buddings in areas with TNF-α expression in the surrounding inflammatory cells. In vitro studies revealed that TNF-α treatment showed a dose-dependent decrease of CDX2 messenger RNA (mRNA) and protein expression in Caco-2 cells. Inhibition of nuclear factor-kappaB or p38 pathways showed that these are involved in the TNF-α-dependent downregulation of CDX2. Furthermore, TNF-α-mediated downregulation of CDX2 was found to significantly decrease the mRNA levels of adenomatous polyposis coli (APC), axis inhibition protein 2 (AXIN2) and glycogen synthase kinase-3 beta (GSK3β), whereas the mRNA levels of Wnt targets were significantly elevated in TNF-α-treated Caco-2 cells. These findings were associated with reduced binding of CDX2 to promoter or enhancer regions of APC, AXIN2 and GSK3β. In conclusion, it was found that TNF-α induces the expression of Wnt signaling components through a downregulation of the CDX2 expression that might have a tumor-promoting effect on colon cancer cells.

Reversal of multidrug resistance in gastric cancer cells by CDX2 downregulation

AIM: To explore the role of CDX2 in the multi-drug resistance (MDR) process of gastric cancer in vitro and in vivo.

METHODS: A cisplatin-resistant gastric cancer cell line with stable downregulation of CDX2 was established. mRNA and protein expression levels of CDX2, survivin, cyclin D1, and c-Myc were detected by western blotting and semi-quantitative reverse-transcriptase polymerase chain reaction (RT-PCR). The influence of downregulation of CDX2 on MDR was assessed by measuring IC50 of SGC7901/DDP cells to cisplatin, doxorubicin, and 5-fluorouracil, rate of doxorubicin efflux, apoptosis, and cell cycle progression detected by flow cytometry. In addition, we determined the in vivo effects of CDX2 small interfering RNA (siRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining.

RESULTS: CDX2 siRNA led to downregulation of endogenous CDX2 mRNA (0.31 ± 0.05 vs 1.10 ± 0.51, 0.31 ± 0.05 vs 1.05 ± 0.21, P = 0.003) and protein (0.12 ± 0.08 vs 0.51 ± 0.07, 0.12 ± 0.08 vs 0.55 ± 0.16, P = 2.57 × 10^-4) expression. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin (0.12 ± 0.05 vs 0.33 ± 0.08, 0.12 ± 0.05 vs 0.39 ± 0.15, P = 0.001), doxorubicin (0.52 ± 0.13 vs 4.11 ± 1.25, 0.52 ± 0.13 vs 4.05 ± 1.44, P = 2.81 × 10^-4), and 5-fluorouracil (0.82 ± 0.13 vs 2.81 ± 0.51, 0.82 ± 0.13 vs 3.28 ± 1.03, P = 1.71 × 10^-4). Flow cytometry confirmed that the percentage of apoptotic cells increased after CDX2 downregulation (32.15% ± 2.15% vs 17.63% ± 3.16%, 32.15% ± 2.15% vs 19.3% ± 2.25%, P = 1.73 × 10^-6). This notion was further supported by the observation that downregulation of CDX2 blocked entry into the S-phase of the cell cycle (31.53% ± 3.78% vs 65.05% ± 7.25%, 31.53% ± 3.78% vs 62.27% ± 5.02%, P = 7.55 × 10^-7). Furthermore, downregulation of CDX2 significantly increased intracellular accumulation of doxorubicin (0.21 ± 0.06 vs 0.41 ± 0.11, 0.21 ± 0.06 vs 0.40 ± 0.08, P = 0.003). In molecular studies, semiquantitative RT-PCR and western blotting revealed that CDX2 downregulation could inhibit expression of c-Myc, survivin and cyclin D1.

CONCLUSION: CDX2 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that CDX2 may represent a novel target for gastric cancer therapy.

Premalignant conditions of gastric cancer

Premalignant lesions of gastric cancer encompass a variety of conditions such as chronic gastritis, intestinal metaplasia and dysplasia, in which elevated risk of developing gastric cancer have been documented. Among them, intestinal metaplasia is frequently encountered in our daily endoscopic examination, yet its clinical significance is often underestimated despite of a number of reports demonstrating genetic and epigenetic alterations in the intestinal metaplastic mucosa. In this review, I will describe the molecular mechanisms of phenotypic changes from gastric mucosa to intestinal metaplasia based on our analysis of mouse model of intestinal metaplasia generated by ectopic expression of CDX2 in conjunction with the studies with human intestinal metaplasia.

Molecular subtyping of primary prostate cancer reveals specific and shared target genes of different ETS rearrangements

This work aimed to evaluate whether ETS transcription factors frequently involved in rearrangements in prostate carcinomas (PCa), namely ERG and ETV1, regulate specific or shared target genes. We performed differential expression analysis on nine normal prostate tissues and 50 PCa enriched for different ETS rearrangements using exon-level expression microarrays, followed by in vitro validation using cell line models. We found specific deregulation of 57 genes in ERG-positive PCa and 15 genes in ETV1-positive PCa, whereas deregulation of 27 genes was shared in both tumor subtypes. We further showed that the expression of seven tumor-associated ERG target genes (PLA1A, CACNA1D, ATP8A2, HLA-DMB, PDE3B, TDRD1, and TMBIM1) and two tumor-associated ETV1 target genes (FKBP10 and GLYATL2) was significantly affected by specific ETS silencing in VCaP and LNCaP cell line models, respectively, whereas the expression of three candidate ERG and ETV1 shared targets (GRPR, KCNH8, and TMEM45B) was significantly affected by silencing of either ETS. Interestingly, we demonstrate that the expression of TDRD1, the topmost overexpressed gene of our list of ERG-specific candidate targets, is inversely correlated with the methylation levels of a CpG island found at -66 bp of the transcription start site in PCa and that TDRD1 expression is regulated by direct binding of ERG to the CpG island in VCaP cells. We conclude that ETS transcription factors regulate specific and shared target genes and that TDRD1, FKBP10, and GRPR are promising therapeutic targets and can serve as diagnostic markers for molecular subtypes of PCa harboring specific fusion gene rearrangements.

H. pylori induces the expression of Hath1 in gastric epithelial cells via interleukin-8/STAT3 phosphorylation while suppressing Hes1

Chronic gastritis associated with Helicobacter pylori is a leading cause of gastric intestinal metaplasia (IM), which arises from abnormal cell differentiation of the epithelium in the gastric mucosa. However, the mechanisms involved in H. pylori-mediated IM remain elusive. The aim of our study was to explore the effects and the underlying mechanisms of H. pylori on the abnormal expression of Hath1 and Sox2 and to reveal its relationship to the development of gastric IM. We found that Hath1 and Sox2 were overexpressed in gastric IM tissue. Hath1 expression was up-regulated, whereas Sox2 expression, which was independent of the CagA virulence factor, was down-regulated in gastric epithelial cells and coincided with increased IL-6 and IL-8 levels in the culture media. Stimulation with H. pylori-related cytokine IL-8, but not IL-6 or IL-1β, was induced by Hath1 expression in the gastric epithelial cells. Although IL-8 and IL-6 levels correlated with STAT3 (signal transducer and activator of transcription) phosphorylation before and after H. pylori eradication in the gastric mucosa, only the blocking of IL-8-induced STAT3 activation using AG490 or STAT3-targeting RNA interference altered Hath1 expression. Additionally, we found that H. pylori down-regulated Hes1, which is a direct downstream target gene of Notch signaling and a repressor of Hath1 expression. These findings suggest that H. pylori induced inflammation up-regulate Hath1 expression via interleukin-8/STAT3 (IL-8) phosphorylation while suppressing Hes1, which provides a novel molecular connection between a H. pylori infection and intestinal metaplasia.

CDX2 regulation by the RNA-binding protein MEX3A: impact on intestinal differentiation and stemness

The homeobox transcription factor CDX2 plays a crucial role in intestinal cell fate specification, both during normal development and in tumorigenic processes involving intestinal reprogramming. The CDX2 regulatory network is intricate, but it has not yet been fully uncovered. Through genome-wide screening of a 3D culture system, the RNA-binding protein MEX3A was identified as putatively involved in CDX2 regulation; therefore, its biological relevance was addressed by setting up cell-based assays together with expression studies in murine intestine. We demonstrate here that MEX3A has a repressive function by controlling CDX2 levels in gastric and colorectal cellular models. This is dependent on the interaction with a specific binding determinant present in CDX2 mRNA 3'untranslated region. We have further determined that MEX3A impairs intestinal differentiation and cellular polarization, affects cell cycle progression and promotes increased expression of intestinal stem cell markers, namely LGR5, BMI1 and MSI1. Finally, we show that MEX3A is expressed in mouse intestine, supporting an in vivo context for interaction with CDX2 and modulation of stem cell properties. Therefore, we describe a novel CDX2 post-transcriptional regulatory mechanism, through the RNA-binding protein MEX3A, with a major impact in intestinal differentiation, polarity and stemness, likely contributing to intestinal homeostasis and carcinogenesis.

No association between the CDX2 G543C polymorphism and risk of gastric atrophy and cancer

Ectopic expression of CDX2 in the stomach is closely associated with chronic Helicobacter pylori (H. pylori) infection and intestinal metaplasia. Whether CDX2 has tumor suppression or tumorigenesis potential remains to be elucidated. In this study, we investigated the association between the CDX2 G543C polymorphism (silent mutation) and the risk for H. pylori-induced gastric atrophy and cancer as well as H. pylori infection, using 454 Japanese subjects undergoing a health checkup and 202 gastric cancer patients. The frequency of the minor allele was the same as previously reported in China, but different from that reported in England. CDX2 G543C was not associated with risk of H. pylori infection, gastric atrophy, or gastric cancer, although the point estimate for non-cardiac differentiated gastric cancer as compared to controls with gastric atrophy was 2.22 (95%CI=0.17-29.4). In conclusion, our results indicate that the CDX2 G543C polymorphism is unlikely to affect the H. pylori infection-gastric atrophy-gastric cancer sequence.

Potential downstream target genes of aberrant ETS transcription factors are differentially affected in Ewing's sarcoma and prostate carcinoma

FLI1 and ERG, the major ETS transcription factors involved in rearrangements in the Ewing's sarcoma family of tumors (ESFT) and in prostate carcinomas (PCa), respectively, belong to the same subfamily, having 98% sequence identity in the DNA binding domain. We therefore decided to investigate whether the aberrant transcription factors in both malignancies have some common downstream targets. We crossed a publicly available list of all putative EWSR1-FLI1 target genes in ESFT with our microarray expression data on 24 PCa and 6 non-malignant prostate tissues (NPT) and choose four genes among the top-most differentially expressed between PCa with (PCa ERG+) and without (PCa ETS-) ETS fusion genes (HIST1H4L, KCNN2, ECRG4 and LDOC1), as well as four well-validated direct targets of the EWSR1-FLI1 chimeric protein in ESFT (NR0B1, CAV1, IGFBP3 and TGFBR2). Using quantitative expression analysis in 16 ESFT and seven alveolar rhabdomyosarcomas (ARMS), we were able to validate the four genes previously described as direct targets of the EWSR1-FLI1 oncoprotein, showing overexpression of CAV1 and NR0B1 and underexpression of IGFBP3 and TGFBR2 in ESFT as compared to ARMS. Although none of these four genes showed significant expression differences between PCa ERG+ and PCa ETS-, CAV1, IGFBP3 and TGFBR2 were less expressed in PCa in an independent series of 56 PCa and 15 NPT, as also observed for ECRG4 and LDOC1, suggesting a role in prostate carcinogenesis in general. On the other hand, we demonstrate for the first time that both HIST1H4L and KCNN2 are significantly overexpressed in PCa ERG+ and that ERG binds to the promoter of these genes. Conversely, KCNN2 was found underexpressed in ESFT relative to ARMS, suggesting that the EWSR1-ETS oncoprotein may have the opposite effect of ERG rearrangements in PCa. We conclude that aberrant ETS transcription factors modulate target genes differently in ESFT and PCa.

Gastric intestinal metaplasia revisited: function and regulation of CDX2

Intestinal metaplasia of the stomach is a preneoplastic lesion that appears following Helicobacter pylori infection and confers increased risk for gastric cancer development. However, the molecular networks connecting infection to lesion formation and the cellular origin of this lesion remain largely unknown. A more comprehensive understanding of how intestinal metaplasia arises and is maintained will be a major breakthrough towards developing novel therapeutic interventions. Furthermore, after ascertaining the pivotal role of CDX2 in establishing and maintaining intestinal metaplasia, it becomes important to decipher the upstream molecular pathways leading to its ectopic expression. Here, we review the pathophysiology of intestinal metaplasia in the context of the molecular network involved in its establishment and maintenance, with emphasis on CDX2 function and regulation.

Barrett's esophagus and esophageal cancer: an overview

Although esophageal cancer (EC) is the eighth most common cancer in several European countries, it is one of deadliest worldwide. The most frequent predisposing factor implicated in its development is Barrett's esophagus (BE), an acquired metaplastic transformation of the esophageal lining cells from normal squamous epithelium into specialised or intestinal-like columnar epithelium. The major risk factor for BE is gastroesophageal reflux disease. Although BE is in itself a benign and often asymptomatic disorder, its clinical importance stems from the recognition that it represents the main precursor lesion for the development of esophageal adenocarcinoma (AC), a tumor that is rapidly increasing especially in developed countries and is associated with a low survival rate. This paper provides an overview of the epidemiology and natural history of BE as well as of the possible pathogenetic mechanisms underlying the development of BE and its progressive transition to AC. New diagnostic tests are described, recommendations for screening and surveillance are provided and surgical and ablative procedures to treat dysplastic lesions and early neoplasia are discussed. Claimed chemopreventive agents and biomarkers that in the near future may help identify people with a higher risk of EC are also considered.

siRNA targeting of Cdx2 inhibits growth of human gastric cancer MGC-803 cells

AIM: To investigate the effects of small interference RNA (siRNA) targeting of Cdx2 on human gastric cancer MGC-803 cells in vitro and in vivo.

METHODS: The recombinant pSilencer 4.1-Cdx2 siRNA plasmids were constructed and transfected into gastric cancer MGC-803 cells in vitro. The stable transfectants were selected. The effects of Cdx2 siRNA on growth, proliferation, cell cycle, apoptosis, migration and invasiveness of human gastric cancer MGC-803 cells were evaluated and the expression of phosphatase and tensin homolog (PTEN), caspase-9 and caspase-3 was observed in vitro by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting analysis. We also investigated the effect of Cdx2 siRNA on growth of MGC-803 cells in nude mice in vivo.

RESULTS: Cdx2 siRNA led to inhibition of endogenous Cdx2 mRNA and protein expression as determined by RT-PCR and Western blotting analysis. Cdx2 siRNA significantly inhibited cell growth and proliferation, blocked entry into the S-phase of the cell cycle, induced cell apoptosis, and reduced the motility and invasion of MGC-803 cells. Cdx2 siRNA also increased PTEN expression, and activated caspase-9 and caspase-3 in MGC-803 cells in vitro . In addition, siRNA targeting of Cdx2 inhibited the growth of MGC-803 cells and promoted tumor cell apoptosis in vivo in nude mice tumor models.

CONCLUSION: Cdx2 was involved in regulating pro-gression of human gastric cancer cells MGC-803. Manipulation of Cdx2 expression may be a potential therapeutic strategy for gastric cancer.

The Role of CDX2 in Intestinal Metaplasia Evaluated Using Immunohistochemistry

Background/Aims

Intestinal metaplasia (IM) has been regarded as a premalignant condition. This study evaluated the role of the transforming factor CDX2 according to the severity and type of IM.

Methods

This analysis was performed on 383 subjects with IM in the antrum and/or body, with diagnoses that were categorized as controls, dysplasias, and gastric cancers. The IM grades were classified into four groups as negative, mild, moderate or severe using the updated Sydney scoring system. The IM subtypes were categorized as type I, type II, and type III using high iron diamine and alcian blue (pH 2.5) staining. The CDX2 expression in the IM foci was evaluated using immunohistochemistry in specimens from the antrum and/or body.

Results

CDX2 expression increased according to IM severity (p=0.001) but was not associated with the IM subtype (p=0.881) in the antrum specimens. Similarly, CDX2 expression increased according to the IM grade (p=0.001) but was not associated with the IM subtype (p=0.755) in the body specimens. CDX2 expression was also increased according to baseline disease in the antrum, especially dysplastic and GC group (p=0.003), but not in the body (p=0.582). However, status of Helicobacter pylori infection was not associated with CDX2 expression in the antrum (p=0.692) and body (p=0.271).

Conclusions

These results show that CDX2 expression is associated with the IM grade regardless of the IM subtype and that it was more frequent in the dysplasia group. These results suggest that CDX2 expression might play an important role in the progression of IM in various environments that can affect neoplastic change.

The relationship among PDX1, CDX2, and mucin profiles in gastric carcinomas; correlations with clinicopathologic parameters

PURPOSE

Several studies performed on pancreatic-duodenal homeobox 1 (PDX1) have demonstrated a loss of expression and negative tumor modulator effect in gastric carcinoma. Relations between PDX1 and gastric metaplasia, differentiated type of gastric carcinoma, and the early stage of the disease have been exhibited in previous reports. The aim of this study was to examine expressions of PDX1, caudal type homeobox 2 (CDX2) and mucin (MUC) profiles to address the role of PDX1 in gastric carcinogenesis and its relationship with CDX2.

METHODS

Seventy gastrectomy specimens were analyzed immunohistochemically for PDX1, CDX2, MUC2, MUC5AC, and MUC6 expressions. The sum of cytoplasmic and nuclear PDX1 immunostaining and PDX1 positivity were assessed. All of the antibodies were examined for a correlation with tumor type, clinicopathologic parameters, and metaplasias. The relation of Ki-67 proliferation index with the expression profiles was also investigated.

RESULTS

Neither PDX1 (66/70) nor CDX2 (37/70) and the mucin profiles (MUC2:11/70, MUC5AC:48/70, MUC6:41/70) showed a significant difference between differentiated and undifferentiated types of gastric carcinoma and clinicopathologic parameters. The PDX1 expression frequency was 94.3%, with an average PDX1 score of 8.8 ± 4.2. PDX1 and CDX2 expression showed a significant difference (P = 0.026 and P = 0.002, respectively) among the phenotypic classification of gastric carcinomas. All of the gastric and intestinal mixed-phenotype gastric carcinomas (GI-type) showed both PDX1 and CDX2 immunopositivity. Except for the relation of PDX1 score with MUC6 expression, no significant difference was detected between PDX1 and CDX2, MUC2, and MUC5AC expressions. A relationship between CDX2 and MUC2 and also between MUC5AC and MUC6 was found statistically. The Ki-67 proliferation index revealed a significant positive correlation with PDX1, CDX2, and MUC2 positivity.

CONCLUSIONS

PDX1 expression revealed a higher positivity in gastric carcinomas than the previous studies and showed no relation with tumor type, clinicopathologic parameters, CDX2 expression, or mucin profiles. However, a significant relation of PDX1 and CDX2 expressions among phenotypic classification of gastric carcinomas reveals an idea about similar functions for PDX1 and CDX2 in the evolution of gastric carcinoma.

Gastric cancer: clinical aspects, epidemiology and molecular background

The validity and usefulness of the 7th edition of the UICC tumor node metastasis classification in the context of clinical management of gastric cancer are discussed. The most relevant new agent in gastric cancer therapy is trastuzumab for HER2-positive gastric carcinomas. This marks the success of continuous effort of translational research. Trastuzumab, initially applied in palliative settings, is currently being evaluated also in neoadjuvant treatment regimens. Several new meta-analyses support the carcinogenic effect of high salt intake and smoking in the context of Helicobacter pylori infection. Further data have become available on the efficacy of protective agents, acetyl salicylic acid/nonsteroidal anti-inflammatory drugs, and antioxidants. In search for a successful prevention strategy, the focus is on the identification of individuals at high risk who demand screening (testing) and surveillance. Serological assessment of gastric mucosal abnormalities with increased risk for gastric cancer development is extensively studied, and new data are presented from Asia as well as from Europe. New high-throughput techniques combined with bioinformatic vector analysis open the gate to the identification of new potential diagnostic and therapeutic targets. Furthermore, these approaches allow us to elucidate the interplay of bacterial virulence factors and the host's immune response as well as H. pylori-associated alterations of mucosal gene expression.