ETS2 and Twist1 promote invasiveness of Helicobacter pylori-infected gastric cancer cells by inducing Siah2

Construction of gastric cancer prognostic signature based on the E26 transcription factor and the identification of novel oncogene ELK3

The aim of the present study was to investigate the function of 29 E26 (ETS) transcription factor families in gastric cancer (GC) and determine their association with prognosis. Our analysis of the expression of the ETS family revealed that 28 genes were dysregulated in GC, and that their expression was associated with multiple clinicopathological features (P<0.05). Based on the expression signature of the ETS family, consensus clustering was performed to generate two gastric cancer subtypes. These subtypes exhibited differences in overall survival (OS, P = 0.161), disease-free survival (DFS, P<0.05) and GC grade (P<0.01). Functional enrichment analysis of the target genes associated with the ETS family indicated that these genes primarily contribute to functions that facilitate tumor progression. A systematic statistical analysis was used to construct a prognostic model related to OS and DFS in association with the ETS family. This model demonstrated that the maximum area under the curve (AUC) values for predicting OS and DFS were 0.729 and 0.670, respectively, establishing ETS as an independent prognostic factor for GC Furthermore, a nomogram was created from the prognostic signature, and its predictive accuracy was confirmed by a calibration curve. Finally, the expression and prognostic significance of the six genes comprising the model were also examined. Among these, ELK3 was found to be significantly overexpressed in GC clinical samples. Subsequent in vitro and in vivo studies verified that ELK3 regulates GC proliferation and metastasis, highlighting its potential as a therapeutic target for gastric cancer.

Suppression of USP7 negatively regulates the stability of ETS proto-oncogene 2 protein

Ubiquitin-specific protease 7 (USP7) is one of the deubiquitinating enzymes (DUBs) that remove mono or polyubiquitin chains from target proteins. Depending on cancer types, USP7 has two opposing roles: oncogene or tumor suppressor. Moreover, it also known that USP7 functions in the cell cycle, apoptosis, DNA repair, chromatin remodeling, and epigenetic regulation through deubiquitination of several substrates including p53, mouse double minute 2 homolog (MDM2), Myc, and phosphatase and tensin homolog (PTEN). The [P/A/E]-X-X-S and K-X-X-X-K motifs of target proteins are necessary elements for the binding of USP7. In a previous study, we identified a novel substrate of USP7 through bioinformatics analysis using the binding motifs for USP7, and suggested that it can be an effective tool for finding new substrates for USP7. In the current study, gene ontology (GO) analysis revealed that putative target proteins having the [P/A/E]-X-X-S and K-X-X-K motifs are involved in transcriptional regulation. Moreover, through protein-protein interaction (PPI) analysis, we discovered that USP7 binds to the AVMS motif of ETS proto-oncogene 2 (ETS2) and deubiquitinates M1-, K11-, K27-, and K29-linked polyubiquitination of ETS2. Furthermore, we determined that suppression of USP7 decreases the protein stability of ETS2 and inhibits the transcriptional activity of ETS2 by disrupting the binding between the GGAA/T core motif and ETS2. Therefore, we propose that USP7 can be a novel target in cancers related to the dysregulation of ETS2.

Identifying novel regulators of placental development using time-series transcriptome data

The placenta serves as a connection between the mother and the fetus during pregnancy, providing the fetus with oxygen, nutrients, and growth hormones. However, the regulatory mechanisms and dynamic gene interaction networks underlying early placental development are understudied. Here, we generated RNA-sequencing data from mouse fetal placenta at embryonic days 7.5, 8.5, and 9.5 to identify genes with timepoint-specific expression, then inferred gene interaction networks to analyze highly connected network modules. We determined that timepoint-specific gene network modules were associated with distinct developmental processes, and with similar expression profiles to specific human placental cell populations. From each module, we identified hub genes and their direct neighboring genes, which were predicted to govern placental functions. We confirmed that four novel candidate regulators identified through our analyses regulate cell migration in the HTR-8/SVneo cell line. Overall, we predicted several novel regulators of placental development expressed in specific placental cell types using network analysis of bulk RNA-sequencing data. Our findings and analysis approaches will be valuable for future studies investigating the transcriptional landscape of early development.

Methods to Evaluate the Effects of HAT/KAT Inhibition on SIAH2-Driven Reactive Oxygen Species Generation in Helicobacter pylori-Infected Gastric Epithelial Cells

Helicobacter pylori infection is one of the leading factors that promotes, among other diseases, gastric cancer (GC). Infection of gastric epithelial cells (GECs) by H. pylori enhances the expression as well as acetylation of the E3 ubiquitin ligase SIAH2 which promotes GC progression. The histone acetyltransferase (HAT) activity of p300 catalyzes SIAH2 acetylation following H. pylori infection. Since reactive oxygen species (ROS) generation in H. pylori-infected GECs accelerates GC progression, acetylation-mediated SIAH2 regulation might be a crucial modifier of ROS generation in the infected GECs. Here, we describe a compendium of methods to evaluate the effects of HAT/lysine acetyl transferase (KAT) inhibitors (HAT/KATi) on SIAH2-mediated ROS regulation in H. pylori-infected GECs.

Siah2-GRP78 interaction regulates ROS and provides a proliferative advantage to Helicobacter pylori-infected gastric epithelial cancer cells

Helicobacter pylori-mediated gastric carcinogenesis involves upregulation of the E3 ubiquitin ligase Siah2 and its phosphorylation-mediated stabilization. This study elucidates a novel mechanism of oxidative stress regulation by phosphorylated Siah2 in H. pylori-infected gastric epithelial cancer cells (GECs). We identify that H. pylori-mediated Siah2 phosphorylation at the 6th serine residue (P-S6-Siah2) enhances proteasomal degradation of the 78-kDa glucose-regulated protein (GRP78) possessing antioxidant functions. S6 phosphorylation stabilizes Siah2 and P-S6-Siah2 potentiates H. pylori-mediated reactive oxygen species (ROS) generation. However, infected S6A phospho-null Siah2-expressing cells have decreased cellular GRP78 level as surprisingly these cells release GRP78 to a higher extent and accumulate significantly higher ROS than the wild type (WT) Siah2 construct-expressing cells. Ectopic expression of GRP78 prevents the loss of mitochondrial membrane potential and cellular ROS accumulation caused by H. pylori. H. pylori-induced mitochondrial damage and mitochondrial membrane potential loss are potentiated in Siah2-overexpressing cells but these effects are further enhanced in S6A-expressing cells. This study also confirms that while phosphorylation-mediated Siah2 stabilization optimally upregulates aggresome accumulation, it suppresses autophagosome formation, thus decreasing the dependency on the latter mechanism in regulating cellular protein abundance. Disruption of the phospho-Siah2-mediated aggresome formation impairs proliferation of infected GECs. Thus, Siah2 phosphorylation has diagnostic and therapeutic significance in H. pylori-mediated gastric cancer (GC).

The role of Siah2 in tumorigenesis and cancer therapy

Seven in absentia homolog 2 (Siah2), an RING E3 ubiquitin ligases, has been characterized to play the vital role in tumorigenesis and cancer progression. Numerous studies have determined that Siah2 promotes tumorigenesis in a variety of human malignancies such as prostate, lung, gastric, and liver cancers. However, several studies revealed that Siah2 exhibited tumor suppressor function by promoting the proteasome-mediated degradation of several oncoproteins, suggesting that Siah2 could exert its biological function according to different stages of tumor development. Moreover, Siah2 is subject to complex regulation, especially the phosphorylation of Siah2 by a variety of protein kinases to regulate its stability and activity. In this review, we describe the structure and regulation of Siah2 in human cancer. Moreover, we highlight the critical role of Siah2 in tumorigenesis. Furthermore, we note that the potential clinical applications of targeting Siah2 in cancer therapy.

Manifold role of ubiquitin in Helicobacter pylori infection and gastric cancer

Infection with H. pylori induces a strong host cellular response represented by induction of a set of molecular signaling pathways, expression of proinflammatory cytokines and changes in proliferation. Chronic infection and inflammation accompanied by secretory dysfunction can result in the development of gastric metaplasia and gastric cancer. Currently, it has been determined that the regulation of many cellular processes involves ubiquitinylation of molecular effectors. The binding of ubiquitin allows the substrate to undergo a change in function, to interact within multimolecular signaling complexes and/or to be degraded. Dysregulation of the ubiquitinylation machinery contributes to several pathologies, including cancer. It is not understood in detail how H. pylori impacts the ubiquitinylation of host substrate proteins. The aim of this review is to summarize the existing literature in this field, with an emphasis on the role of E3 ubiquitin ligases in host cell homeodynamics, gastric pathophysiology and gastric cancer.

Helicobacter pylori-induced gastric cancer is orchestrated by MRCKβ-mediated Siah2 phosphorylation

BACKGROUND

Helicobacter pylori-mediated gastric carcinogenesis is initiated by a plethora of signaling events in the infected gastric epithelial cells (GECs). The E3 ubiquitin ligase seven in absentia homolog 2 (Siah2) is induced in GECs in response to H. pylori infection. Posttranslational modifications of Siah2 orchestrate its function as well as stability. The aim of this study was to evaluate Siah2 phosphorylation status under the influence of H. pylori infection and its impact in gastric cancer progression.

METHODS

H. pylori-infected various GECs, gastric tissues from H. pylori-infected GC patients and H. felis-infected C57BL/6 mice were evaluated for Siah2 phosphorylation by western blotting or immunofluorescence microscopy. Coimmunoprecipitation assay followed by mass spectrometry were performed to identify the kinases interacting with Siah2. Phosphorylation sites of Siah2 were identified by using various plasmid constructs generated by site-directed mutagenesis. Proteasome inhibitor MG132 was used to investigate proteasome degradation events. The importance of Siah2 phosphorylation on tumorigenicity of infected cells were detected by using phosphorylation-null mutant and wild type Siah2 stably-transfected cells followed by clonogenicity assay, cell proliferation assay, anchorage-independent growth and transwell invasion assay.

RESULTS

Siah2 was phosphorylated in H. pylori-infected GECs as well as in metastatic GC tissues at residues serine⁶ (Ser⁶) and threonine²⁷⁹ (Thr²⁷⁹). Phosphorylation of Siah2 was mediated by MRCKβ, a Ser/Thr protein kinase. MRCKβ was consistently expressed in uninfected GECs and noncancer gastric tissues but its level decreased in infected GECs as well as in metastatic tissues which had enhanced Siah2 expression. Infected murine gastric tissues showed similar results. MRCKβ could phosphorylate Siah2 but itself got ubiquitinated from this interaction leading to the proteasomal degradation of MRCKβ and use of proteasomal inhibitor MG132 could rescue MRCKβ from Siah2-mediated degradation. Ser⁶ and Thr²⁷⁹ phosphorylated-Siah2 was more stable and tumorigenic than its non-phosphorylated counterpart as revealed by the proliferation, invasion, migration abilities and anchorage-independent growth of stable-transfected cells.

CONCLUSIONS

Increased level of Ser⁶ and Thr²⁷⁹-phosphorylated-Siah2 and downregulated MRCKβ were prominent histological characteristics of Helicobacter-infected gastric epithelium and metastatic human GC. MRCKβ-dependent Siah2 phosphorylation stabilized Siah2 which promoted anchorage-independent survival and proliferative potential of GECs. Phospho-null mutants of Siah2 (S6A and T279A) showed abated tumorigenicity.

HIF1α-dependent upregulation of ATAD2 promotes proliferation and migration of stomach cancer cells in response to hypoxia

Stomach cancer is a difficult-to-treat disease. Lack of detection markers and limited understanding of the disease mechanisms contribute to the aggressive nature of stomach cancer cells (SCCs). Recently, an ATPase, ATAD2 has been found to be highly expressed in stomach cancer contributing to increased malignancy. However, nothing is known about the mechanism of ATAD2 upregulation and its involvement in stomach carcinogenesis. Since hypoxic microenvironment plays a crucial role in the progression of solid tumors like stomach cancer; we have examined the regulation and function of ATAD2 expression in hypoxic SCCs. ATAD2 is induced in hypoxia-treated SCCs. Stomach adenocarcinoma and metastatic tissues with high HIF1α level also show enhanced ATAD2 expression. In the absence of hypoxia-inducible factor HIF1α, ATAD2 protein level is found to be less indicating towards a potential correlation between them. We identify the presence of HIF1α-binding site (HBS) and HIF1α ancillary site (HAS) in the ATAD2 promoter. Using both in vitro and in vivo binding studies, we confirm that HIF1α binds with the ATAD2 promoter in hypoxic condition. ATAD2 upregulation promotes proliferation and migration of SCCs exposed to hypoxia. Thus, we identify ATAD2 as a hypoxia-responsive and HIF1α-regulated gene and elucidate that upregulated expression of ATAD2 enhances tumor-promoting functions in hypoxic SCCs. Therefore, we propose ATAD2 as a promising therapeutic target for stomach cancer.

Establishment of novel long-term cultures from EpCAM positive and negative circulating tumour cells from patients with metastatic gastroesophageal cancer

Circulating tumour cell (CTC) enumeration and profiling has been established as a valuable clinical tool in many solid malignancies. A key challenge in CTC research is the limited number of cells available for study. Ex vivo CTC culture permits expansion of these rare cell populations for detailed characterisation, functional assays including drug sensitivity testing, and investigation of the pathobiology of metastases. We report for the first time the establishment and characterisation of two continuous CTC lines from patients with gastroesophageal cancer. The two cell lines (designated UWG01CTC and UWG02CTC) demonstrated rapid tumorigenic growth in immunodeficient mice and exhibit distinct genotypic and phenotypic profiles which are consistent with the tumours of origin. UWG02CTC exhibits an EpCAM+, cytokeratin+, CD44+ phenotype, while UWG01CTC, which was derived from a patient with metastatic neuroendocrine cancer, displays an EpCAM−, weak cytokeratin phenotype, with strong expression of neuroendocrine markers. Further, the two cell lines show distinct differences in drug and radiation sensitivity which match differential cancer-associated gene expression pathways. This is strong evidence implicating EpCAM negative CTCs in metastasis. These novel, well characterised, long-term CTC cell lines from gastroesophageal cancer will facilitate ongoing research into metastasis and the discovery of therapeutic targets.

Ets2 suppresses inflammatory cytokines through MAPK/NF-κB signaling and directly binds to the IL-6 promoter in macrophages

Proper activation of Toll-like receptor (TLR)-mediated signaling and production of proinflammatory cytokines are critical for the initiation of innate immunity, while the specific mechanism maintaining inflammatory homeostasis remains mostly unknown. Here, we show that Ets2 is upregulated following LPS and VSV stimulation. Ets2 knockdown or knockout leads to increased IL-6, TNF-α, and IFN-β production in macrophages. Consistently, Ets2-deficient mice show exacerbated inflammatory cytokine production and are more susceptible to CLP-induced sepsis. Mechanistically, Ets2 inhibits the LPS- and VSV-induced activation of ERK1/2, JNK, p38, and p65. Ets2 also binds to the promoter of IL-6 to inhibit transcription. Collectively, the results of the present study show the negative regulatory role of Ets2 in LPS- and VSV-induced inflammation through the suppression of MAPK/NF-κB signaling, direct binding to the IL-6 promoter and inhibition of transcription.

Immune Cell Signaling by Helicobacter pylori: Impact on Gastric Pathology

Helicobacter pylori represents a highly successful colonizer of the human stomach. Infections with this Gram-negative bacterium can persist lifelong, and although in the majority of cases colonization is asymptomatic, it can trigger pathologies ranging from chronic gastritis and peptic ulceration to gastric cancer. The interaction of the bacteria with the human host modulates immune responses in different ways to enable bacterial survival and persistence. H. pylori uses various pathogenicity-associated factors such as VacA, NapA, CGT, GGT, lipopolysaccharide, peptidoglycan, heptose 1,7-bisphosphate, ADP-heptose, cholesterol glucosides, urease and a type IV secretion system for controlling immune signaling and cellular functions. It appears that H. pylori manipulates multiple extracellular immune receptors such as integrin-β₂ (CD18), EGFR, CD74, CD300E, DC-SIGN, MINCLE, TRPM2, T-cell and Toll-like receptors as well as a number of intracellular receptors including NLRP3, NOD1, NOD2, TIFA and ALPK1. Consequently, downstream signaling pathways are hijacked, inducing tolerogenic dendritic cells, inhibiting effector T cell responses and changing the gastrointestinal microbiota. Here, we discuss in detail the interplay of bacterial factors with multiple immuno-regulatory cells and summarize the main immune evasion and persistence strategies employed by H. pylori.

Testin and filamin-C downregulation by acetylated Siah2 increases invasiveness of Helicobacter pylori-infected gastric cancer cells

Helicobacter pylori is the strongest known risk-factor for gastric cancer. However, its role in gastric cancer metastasis remains unclear. Previously we have reported that H. pylori promotes gastric cancer invasiveness by stabilizing the E3 ubiquitin ligase Siah2 which is mediated by Siah2 acetylation at Lys 139 (K¹³⁹) residue. Here we identify that cell adhesion-related proteins testin (TES) and filamin-C (FLN-C) interact with Siah2 and get proteasomally degraded. The efficiency of TES and FLN-C degradation is significantly potentiated by K¹³⁹-acetylated Siah2 (ac-K¹³⁹ Siah2) in infected gastric cancer cells (GCCs). ac-Siah2-mediated downregulation of TES and FLN-C disrupts filopodia structures but promotes lamellipodia formation and enhances invasiveness and migration of infected GCCs. Since H. felis-infected mice as well as human gastric cancer biopsy samples also show high level of ac-K¹³⁹ Siah2 and downregulated TES and FLN-C, we believe that acetylation of Siah2 is an important checkpoint that can be useful for therapeutic intervention.

Acetylation-mediated Siah2 stabilization enhances PHD3 degradation in Helicobacter pylori-infected gastric epithelial cancer cells

Gastric epithelial cells infected with Helicobacter pylori acquire highly invasive and metastatic characteristics. The seven in absentia homolog (Siah)2, an E3 ubiquitin ligase, is one of the major proteins that induces invasiveness of infected gastric epithelial cells. We find that p300-driven acetylation of Siah2 at lysine 139 residue stabilizes the molecule in infected cells, thereby substantially increasing its efficiency to degrade prolyl hydroxylase (PHD)3 in the gastric epithelium. This enhances the accumulation of an oncogenic transcription factor hypoxia-inducible factor 1α (Hif1α) in H. pylori-infected gastric cancer cells in normoxic condition and promotes invasiveness of infected cells. Increased acetylation of Siah2, Hif1α accumulation, and the absence of PHD3 in the infected human gastric metastatic cancer biopsy samples and in invasive murine gastric cancer tissues further confirm that the acetylated Siah2 (ac-Siah2)-Hif1α axis is crucial in promoting gastric cancer invasiveness. This study establishes the importance of a previously unrecognized function of ac-Siah2 in regulating invasiveness of H. pylori-infected gastric epithelial cells.-Kokate, S. B., Dixit, P., Das, L., Rath, S., Roy, A. D., Poirah, I., Chakraborty, D., Rout, N., Singh, S. P., Bhattacharyya, A. Acetylation-mediated Siah2 stabilization enhances PHD3 degradation in Helicobacter pylori-infected gastric epithelial cancer cells.

Ectopic expression of TWIST1 upregulates the stemness marker OCT4 in the esophageal squamous cell carcinoma cell line KYSE30

Background

The transcription factor TWIST1 plays an important role in the epithelial–mesenchymal transition (EMT) process and in the migration, invasion and metastasis of cancer cells. OCT4, which is a homeobox transcription factor, has an important role in the self-renewal potential of cancer cells. Our aim here is to elucidate impact of ectopic expression of TWIST1 on OCT4 gene expression in esophageal squamous cell carcinoma (ESCC).

Methods

The ESCC line was KYSE30. GP293T cells were transfected with purf-IRES-GFP and pGP plasmids to produce recombinant viral particles. A semi-confluent KYSE30 culture was transduced with the prepared retroviral particles. mRNA extraction and cDNA synthesis were performed from normal KYSE30 cells and those ectopically expressing TWIST1. Expressional analysis of TWIST1 and OCT4 were performed with relative comparative real-time PCR.

Results

Ectopic expression of TWIST1 in KYSE30 cells was related to its significant overexpression: nearly nine-fold higher in GFP-hTWIST1 KYSE-30 cells than in control GFP cells. This induced expression of TWIST1 caused significant upregulation of OCT4 in GFP-hTWIST1 KYSE-30 cells: nearly eight-fold higher. In silico analysis predicted the correlation of TWIST1 and OCT4 through ETS2.

Conclusions

Overexpressed TWIST1 can be correlated with upregulation of the cancer stem cell marker OCT4 and the protein may play critical regulatory role in OCT4 gene expression. Since OCT4 is involved in the self-renewal process, the results may suggest a new linkage between TWIST1 and OCT4 in the cell biology of ESCC, highlighting the probable role of TWIST1 in inducing self-renewal.

Seven in Absentia E3 Ubiquitin Ligases: Central Regulators of Neural Cell Fate and Neuronal Polarity

During neural development, neural precursors transition from a proliferative state within their germinal niches to a migratory state as they relocate to their final laminar positions. Transitions across these states are coupled with dynamic alterations in cellular polarity. This key feature can be seen throughout the developing vertebrate brain, in which neural stem cells give rise to multipolar or unpolarized transit-amplifying progenitors. These transit-amplifying progenitors then expand to give rise to mature neuronal lineages that become polarized as they initiate radial migration to their final laminar positions. The conventional understanding of the cellular polarity regulatory program has revolved around signaling cascades and transcriptional networks. In this review, we discuss recent discoveries concerning the role of the Siah2 ubiquitin ligase in initiating neuronal polarity during cerebellar development. Given the unique features of Siah ubiquitin ligases, we highlight some of the key substrates that play important roles in cellular polarity and propose a function for the Siah ubiquitin proteasome pathway in mediating a post-translational regulatory network to control the onset of polarization.

miR-320 inhibited ovarian cancer oncogenicity via targeting TWIST1 expression

Ovarian cancer is the most lethal gynecological cancer in most countries. Increasing studies have demonstrated that dysregulation of microRNAs (miRNAs) can contribute to cancer progression. In this study, we showed that miR-320 was underexpressed in ovarian cancer samples compared to their non-tumor tissues. The expression of Twist homolog 1 (TWIST1) in ovarian cancer tissues was upregulated compared with that in the non-tumorous tissues. We found that the expression of TWIST1 was inversely correlated with that of miR-320 in the ovarian cancer. Overexpression of miR-320 suppressed cell proliferation, cell cycle and invasion in ovarian cancer. We identified TWIST1 as a direct target gene of miR-320 in the ovarian cancer cell. Overexpression of TWIST1 promoted the ovarian cancer cell proliferation, cell cycle and invasion. Ectopic expression of TWIST1 restored the effects of miR-320 on cell proliferation, cell cycle and invasion. These findings revealed that miR-320 was a tumor suppressive gene that supressed cell prloferation, cycle and invasion through targeting TWIST1 in ovarian cancer.

EMP3 is induced by TWIST1/2 and regulates epithelial-to-mesenchymal transition of gastric cancer cells

In this study, we aimed to explore new downstream effectors of TWIST1/2 in inducing epithelial-to-mesenchymal transition in gastric cancer. Bioinformatic data mining was performed using data in The Cancer Genome Atlas Stomach Adenocarcinoma. Survival curves were generated using Kaplan-Meier plotter. Gastric cancer cell lines (AGS and SGC-7901) were used as in vitro cell model to investigate the regulative effect of TWIST1/2 on epithelial membrane protein 3 expression and the progression of epithelial-to-mesenchymal transition. Results showed that TWIST1 and TWIST2 are usually co-upregulated in patients with primary gastric cancer. High TWIST1 expression is associated with worse overall survival (hazard ratio = 1.26; 95% confidence interval = 1.06-1.49; p = 0.007) and also worse first progression-free survival (hazard ratio = 1.47; 95% confidence interval = 1.18-1.82; p < 0.0001). Similarly, high TWIST2 expression is associated with unfavorable overall survival (hazard ratio = 1.71; 95% confidence interval = 1.32-2.22; p < 0.0001) and progression-free survival (hazard ratio = 1.99; 95% confidence interval = 1.45-2.72; p < 0.0001). Epithelial membrane protein 3 is negatively correlated to CDH1 expression (Pearson's r = -0.46) but is positively correlated to VIM expression (Pearson's r = 0.83). Knockdown of epithelial membrane protein 3 significantly increased E-cadherin but significantly decreased Vimentin expression in AGS cells. Gastric cancer patients with metastasis have significantly higher epithelial membrane protein 3 expression than the cases without metastasis. In addition, high epithelial membrane protein 3 expression is associated with worse overall survival (hazard ratio = 2.59; 95% confidence interval = 2.06-3.26; p < 0.0001) and also worse progression-free survival (hazard ratio = 2.21; 95% confidence interval = 1.78-2.74; p < 0.0001). In conclusion, epithelial membrane protein 3 is a downstream effector of TWIST1/2 in inducing epithelial-to-mesenchymal transition in gastric cancer. Epithelial membrane protein 3 upregulation might be associated with gastric cancer metastasis and is a potential indicator of unfavorable overall survival and progression-free survival in gastric cancer patients.

Membrane-bound β-catenin degradation is enhanced by ETS2-mediated Siah1 induction in Helicobacter pylori-infected gastric cancer cells

β-catenin has two different cellular functions: intercellular adhesion and transcriptional activity. The E3 ubiquitin ligase Siah1 causes ubiquitin-mediated degradation of the cytosolic β-catenin and therefore, impairs nuclear translocation and oncogenic function of β-catenin. However, the effect of Siah1 on the cell membrane bound β-catenin has not been studied. In this study, we identified that the carcinogenic bacterium H. pylori increased ETS2 transcription factor-mediated Siah1 protein expression in gastric cancer cells (GCCs) MKN45, AGS and Kato III. Siah1 protein level was also noticeably higher in gastric adenocarcinoma biopsy samples as compared to non-cancerous gastric epithelia. Siah1 knockdown significantly decreased invasiveness and migration of H. pylori-infected GCCs. Although, Siah1 could not increase degradation of the cytosolic β-catenin and its nuclear translocation, it enhanced degradation of the membrane-bound β-catenin in the infected GCCs. This loss of membrane-bound pool of β-catenin was not associated with the proteasomal degradation of E-cadherin. Thus, this work delineated the role of Siah1 in increasing invasiveness of H. pylori-infected GCCs.

GPR155 Serves as a Predictive Biomarker for Hematogenous Metastasis in Patients with Gastric Cancer

The prognosis of patients with gastric cancer (GC) with hematogenous metastasis is dismal. Identification of biomarkers specific for hematogenous metastasis is required to develop personalized treatments that improve patients' outcomes. Global expression profiling of GC tissues with synchronous hepatic metastasis without metastasis to the peritoneal cavity or distant lymph nodes was conducted using next-generation sequencing and identified the G protein-coupled receptor 155 (GPR155) as a candidate biomarker. GPR155 transcription was suppressed in GC cell lines compared with a nontumorigenic cell line. DNA methylation of the GPR155 promoter region was not detected, albeit 20% of GC cell lines harbored copy number loss at GPR155 locus. The expression levels of GPR155 mRNA correlated inversely with those of TWIST1 and WNT5B. Inhibition of GPR155 expression increased the levels of p-ERK1/2 and p-STAT1, significantly increased cell proliferation, and increased the invasiveness of a GC cell lines. GPR155 mRNA levels in GC clinical samples correlated with hematogenous metastasis and recurrence. Multivariate analysis revealed that reduced expression of GPR155 mRNA was an independent predictive marker of hematogenous metastasis. GPR155 may represent a biomarker for diagnosing and predicting hematogenous metastasis of GC.

Modeling the Role of Lanthionine Synthetase C-Like 2 (LANCL2) in the Modulation of Immune Responses to Helicobacter pylori Infection

Immune responses to Helicobacter pylori are orchestrated through complex balances of host-bacterial interactions, including inflammatory and regulatory immune responses across scales that can lead to the development of the gastric disease or the promotion of beneficial systemic effects. While inflammation in response to the bacterium has been reasonably characterized, the regulatory pathways that contribute to preventing inflammatory events during H. pylori infection are incompletely understood. To aid in this effort, we have generated a computational model incorporating recent developments in the understanding of H. pylori-host interactions. Sensitivity analysis of this model reveals that a regulatory macrophage population is critical in maintaining high H. pylori colonization without the generation of an inflammatory response. To address how this myeloid cell subset arises, we developed a second model describing an intracellular signaling network for the differentiation of macrophages. Modeling studies predicted that LANCL2 is a central regulator of inflammatory and effector pathways and its activation promotes regulatory responses characterized by IL-10 production while suppressing effector responses. The predicted impairment of regulatory macrophage differentiation by the loss of LANCL2 was simulated based on multiscale linkages between the tissue-level gastric mucosa and the intracellular models. The simulated deletion of LANCL2 resulted in a greater clearance of H. pylori, but also greater IFNγ responses and damage to the epithelium. The model predictions were validated within a mouse model of H. pylori colonization in wild-type (WT), LANCL2 whole body KO and myeloid-specific LANCL2-/- (LANCL2^Myeloid) mice, which displayed similar decreases in H. pylori burden, CX3CR1+ IL-10-producing macrophages, and type 1 regulatory (Tr1) T cells. This study shows the importance of LANCL2 in the induction of regulatory responses in macrophages and T cells during H. pylori infection.