Decreased expression of gastrokine 1 and the trefoil factor interacting protein TFIZ1/GKN2 in gastric cancer: influence of tumor histology and relationship to prognosis

Ubiquitination of ADRα1d/SerpinA1 complex stimulates hypoxia to induce gastric tumorigenesis with a combination of Helicobacter pylori and chronic stress through IL-1α

BACKGROUND

Helicobacter pylori (H. pylori) has been recognized as the class I carcinogen of gastric cancer and several studies have demonstrated that chronic stress may accelerate gastric cancer progression. However, the evidence is not sufficient.

METHODS

Here, we developed a mouse model that combined H. pylori infection with chronic stress. Gastric inflammation promotes gastric tumor development progression. To evaluate the number of pro-inflammatory cells through observing the numbers of activated macrophages and neutrophils in mice gastric tumors compared with untreated mice or only treated with one factor. ADRα1d /SerpinA1 expression and localization were assessed under stress conditions and H. pylori infection, and evaluated by analyzing IL-1α, CD8, platelet, and RBC status using α- or β- blockers against gastritis to prevent gastric cancer.

RESULTS

Further mechanism study showed that stress hormones increase the number of CD8⁺ lymphocytes by activating ADRβ2 receptors, leading to IL-1α secretion and tumorigenicity. Gastric carcinogenesis also involves gastric muscle contraction mediated through ADRα1d/Serpina1 interaction. Specifically, we showed that the ADRα1d/SerpinA1 complex increases glucose uptake and the development of hypoxia conditions. These responses promote platelet aggregation and muscle contraction. In turn, gastric cancer cells increase lactate production and promote gastric cell proliferation through Muc-13 and IL-1α stimulation.

CONCLUSION

H. pylori infection in combination with chronic stress can lead to gastric cancer, and the synergistic effects of cytokine production (i.e. IL-1α), T lymphocyte dysfunction contributes to gastric carcinogenesis which will offer treatment opportunities for stress-associated gastric cancer and provide new strategies for the prevention and treatment of gastric cancer in clinics.

Genetic and molecular biology of gastric cancer among Iranian patients: an update

Background

There is a declining trend of gastric cancer (GC) incidence in the world during recent years that is related to the development of novel diagnostic methods. However, there is still a high ratio of GC mortality among the Iranian population that can be associated with late diagnosis. Despite various reports about the novel diagnostic markers, there is not any general and standard diagnostic panel marker for Iranian GC patients. Therefore, it is required to determine an efficient and general panel of molecular markers for early detection.

Main body of the abstract

In the present review, we summarized all of the reported markers until now among Iranian GC patients to pave the way for the determination of a population-based diagnostic panel of markers. In this regard, we categorized these markers in different groups based on their involved processes to know which molecular process is more frequent during the GC progression among Iranians.

Conclusion

We observed that the non-coding RNAs are the main factors involved in GC tumorigenesis in this population.

Research progress on exosomal proteins as diagnostic markers of gastric cancer (review article)

Gastric cancer (GC) is one of the most common types of tumors and the most common cause of cancer mortality worldwide. The diagnosis of GC is critical to its prevention and treatment. Available tumor markers are the crucial step for GC diagnosis. Recent studies have shown that proteins in exosomes are potential diagnostic and prognostic markers for GC. Exosomes, secreted by cells, are cup-shaped with a diameter of 30–150 nm under the electron microscope. They are also surrounded by lipid bilayers and are widely found in various body fluids. Exosomes contain proteins, lipids and nucleic acid. The examination of exosomal proteins has the advantages of quickness, easy sampling, and low pain and cost, as compared with the routine inspection method of GC, which may lead to marked developments in GC diagnosis. This article summarized the exosomal proteins with a diagnostic and prognostic potential in GC, as well as exosomal proteins involved in GC progression.

Low-level gastrokine 2 promoted progress of NSCLC and as a potential biomarker

Background

Gastrokine 2 (GKN2) is significantly downregulated in non‐small cell lung cancer (NSCLC) tissues than in normal tissues (NT), as assessed by mRNA microassay; however, the mechanism and clinical value of GKN2 is unknown in NSCLC.

Methods

A total of 60 NSCLC samples and corresponding NT samples were prospectively collected GKN2 expression in NSCLC tissues was estimated. Also, the expression level of GKN2 promoter methylation and correlation with clinical data in NSCLC patients from public databases were analyzed. Cytology experiments were also carried out.

Results

The GKN2 mRNA and protein expression level in NSCLC was significantly lower than that in the NT, and the GKN2 expression level in large tumors NSCLC was significantly lower than that in the small tumor group. Public data showed that expression of GKN2 in LUAD with P53 mutation group was lower than that of the P53 non‐mutation group, and GKN2 promoter methylation level of LUAD was significantly higher than its NT and close to age and clinical stage. Cell migration, invasion, and proliferation ability of GKN2 overexpressed were lower in A549 and PC9 groups than those in GKN2 overexpressed A549 and PC9 negative control groups, while the percentage of apoptotic cells increased in the GKN2 overexpressed A549 and PC9 groups. The DNMT3B mRNA expression levels were higher in PC9 and A549 cells than BEAS‐2B cells.

Conclusion

The overexpression of GKN2 significantly inhibited cell proliferation, migration, and invasion and promoted apoptosis. Low‐level GKN2 promoted the progression of NSCLC via DNMT3B and is expected to be a biomarker for NSCLC.

Gastric tumorigenesis induced by combining Helicobacter pylori infection and chronic alcohol through IL-10 inhibition

Helicobacter pylori (H. pylori) infection and alcohol intake are independent risk factors in gastric carcinogenesis; however, until now, the combined effect of H. pylori infection and alcohol consumption and the specific mechanism is still problematic. Here, we developed a series of mouse models that progress from chronic gastritis to gastric cancer, induced by infecting H. pylori combined with chronic alcohol consumption and then determining the molecular mechanism of the progression by flow cytometry, Western blotting, qPCR, Mito Traker assay in the gastric cancer and T-cell lines. Interleukin-10 (IL-10) knockout mice was used to determine whether IL-10 deficiency directly contribute to H. pylori and alcohol induced gastric tumorigenesis. Alcohol consumption, together with H. pylori infection, causes gastric cancer; IL-10 downregulation and mitochondrial metabolic dysfunction in CD8 + cells are also involved. IL-10 knockout accelerates tumor development in mice with either H. pylori infection or alcohol induced gastric cancer or both. IL-10 inhibits glucose uptake and glycolysis and promotes oxidative phosphorylation with lactate inhibition. Consequently, in the absence of IL-10 signaling, CD8 + cells accumulate damaged mitochondria in a mouse model of gastric cancer induced with the combination of alcohol plus H. pylori infection, and this results in mitochondrial dysfunction and production of IL-1β. IL-1β promotes H. pylori infection and reduces NKX6.3 gene expression, resulting in increased cancer cell survival and proliferation. Gastric cancer can be induced by combination of Helicobacter pylori infection and chronic alcohol consumption through IL-10 inhibition induced CD8 + cells dysfunction and NKX6.3 suppression.

Immunoexpression of Trefoil Factor 1 in Non-Neoplastic and Neoplastic Canine Gastric Tissues

Simple Summary

Gastric carcinoma (GC) is the second leading cause of death in humans and the most frequent malignancy in the stomach of dogs. As in humans, the prognosis of canine gastric cancer is generally poor owing to the advanced stage at the time of diagnosis, resulting in limited treatment options. In dogs, the molecular mechanisms involved in the growth and progression of gastric cancer remain largely unknown. Trefoil factor 1 (TFF1) protein is a mucin-associated secretory molecule that plays an important role in the maintenance and protection of epithelial surface integrity. Some human studies showed that TFF1 can protect mucosa against damage and suppress carcinogenesis, while other studies showed that TFF1 can restrict cell adhesion, promote tumor cell invasion, and block necrosis of tumor cells. In human gastric cancer, TFF1 has been found to decrease, and it has been proposed that it might act as a tumor suppressor factor. The present study was carried out to investigate whether there is a relationship between TFF1 and canine gastric carcinogenesis. We found an association between reduced expression of TFF1 and the development and progression of gastric cancer in dogs. The pathological and behavioral similarities between spontaneous canine GC and human counterparts make it logical to assume that dogs may be a useful model for human gastric cancer.

Abstract

TFF1 expression is markedly reduced in human GCs, suggesting that TFF1 is a tumor suppressor for human gastric cancer. The present study evaluated the expression and distribution pattern of TFF1 in paraffin-embedded canine gastric tissue samples, including normal mucosa (n = 3), polyps (n = 8), carcinomas (n = 31) and their adjacent non-neoplastic mucosa (n = 30), neoplastic emboli (n = 14), and metastatic lesions (n = 9), by immunohistochemistry (IHC). All normal gastric tissues expressed TFF1 in the superficial foveolar epithelium and mucopeptic cells of the neck region. Most gastric polyps (GPs) displayed immunoreactivity for TFF1 in >75% of the epithelial component. In GCs, the expression of TFF1 was found reduced in 74.2% of the cases. The level of TFF1 expression had a decreased tendency from normal gastric mucosa to GPs and GCs (p < 0.05). No significant differences in the expression of TFF1 were found in GCs, according to age, sex, histological type based on World Health Organization (WHO) and Lauren classification, tumor location, depth of tumor invasion, presence of neoplastic emboli or metastatic lesions. The median survival time of GC patients with preserved and reduced TFF1 immunoexpression were 30 and 12 days, respectively. Kaplan–Meier analysis revealed no significant survival differences between the two groups (p > 0.05). These findings suggest that TFF1 protein may play a role in canine gastric carcinogenesis, and further studies are necessary to define its usefulness as a prognostic indicator in canine gastric carcinoma.

Gastrokine 2 Regulates the Antitumor Effect of JAK2/STAT3 Pathway in Gastric Cancer

GKN2 (gastrokine 2) mainly plays a regulatory role in gastric mucosal defense and cell protection mechanisms, and its role in gastric cancer has not been thoroughly elucidated. Immunohistochemistry was used to detect GKN2 and TFF1 expressions in 90 gastric cancer tissues, 48 neoplastic resection margins, and 22 normal gastric mucosa epithelia. It showed that the downregulation of GKN2 and TFF1 expressions in gastric cancer tissues was significantly different from that in adjacent normal gastric tissues and distal gastric mucosal tissues. Nevertheless, correlation analysis showed that GKN2 expression in gastric cancer tissues was independent of TFF1 expression. After overexpression of GKN2 was constructed in human gastric cancer cell line MKN28 with the Ad-GFP-GKN2 transfected, cell viability was measured by CCK-8 assay, and migration and invasion ability were analyzed by transwell migration assay and transwell invasion assay. It indicated that overexpression of GKN2 significantly reduced the viability of MKN28 and SGC7901 cells. Overexpression of GKN2 could also inhibit the migration and invasion ability in MKN28 and SGC7901 cells. In addition, upregulation of GKN2 can inactivate the JAK2/STAT3 pathway. Our data suggest that GKN2 and TFF1 play the antitumor role in gastric carcinoma, and TFF1 may not interact or cooperate with GKN2. GKN2 overexpression can inhibit the growth and metastasis by downregulating the JAK2/STAT3 pathway in gastric cancer cells.

Gastrokine-1, an anti-amyloidogenic protein secreted by the stomach, regulates diet-induced obesity

Obesity and its sequelae have a major impact on human health. The stomach contributes to obesity in ways that extend beyond its role in digestion, including through effects on the microbiome. Gastrokine-1 (GKN1) is an anti-amyloidogenic protein abundantly and specifically secreted into the stomach lumen. We examined whether GKN1 plays a role in the development of obesity and regulation of the gut microbiome. Gkn1-/- mice were resistant to diet-induced obesity and hepatic steatosis (high fat diet (HFD) fat mass (g) = 10.4 ± 3.0 (WT) versus 2.9 ± 2.3 (Gkn1-/-) p < 0.005; HFD liver mass (g) = 1.3 ± 0.11 (WT) versus 1.1 ± 0.07 (Gkn1-/-) p < 0.05). Gkn1-/- mice also exhibited increased expression of the lipid-regulating hormone ANGPTL4 in the small bowel. The microbiome of Gkn1-/- mice exhibited reduced populations of microbes implicated in obesity, namely Firmicutes of the class Erysipelotrichia. Altered metabolism consistent with use of fat as an energy source was evident in Gkn1-/- mice during the sleep period. GKN1 may contribute to the effects of the stomach on the microbiome and obesity. Inhibition of GKN1 may be a means to prevent obesity.

Prognostic Value of Gastrokine-2 (GKN2) and Its Correlation with Tumor-Infiltrating Immune Cells in Lung Cancer and Gastric Cancers

Background

GKN2, as a secretory protein, is involved in the inflammation and immune modulation, and its aberrant expression is closely related to tumorigenesis. However, integrated studies on the value of GKN2 as a promising clinical biomarker and immunotherapy target in multiple tumors are still rare.

Methodology

Multiple online databases, including ONCOMINE, SEGreg, UALCAN, GEPIA, K-M Plotter, cBioPortal, MethSurv, CellMarker, and Timer, were applied to assess the clinical significance of GKN2 and its correlation with tumor-infiltrating immune cells in differentially expressed cancers.

Results

Several databases confirmed that GKN2 was significantly down-regulated in lung and gastric cancers compared that in normal samples. GKN2 was altered in 3%, 5%, and 4% of the LUAD, LUSC, and STAD samples, respectively. Hyper-methylation of GKN2 was found in LUAD and LUSC samples. For the clinical values of GKN2, we found that the low transcription level of GKN2 was associated with worse OS in lung cancer, and inferior FP and PPS in gastric cancer, and the relationships between GKN2 expression and clinical variables regarding OS/FP/PPS in lung and gastric cancers were assessed. Moreover, the prognostic value of the DNA methylation patterns of GKN2 in LUAD, LUSC, and STAD was identified. Furthermore, GKN2 expression was found to be significantly correlated with the infiltrating multiple tumor immune cells, and statistically significant differences in the correlation between GKN2 expression and multiple markers of neutrophils and macrophage polarization were observed in LUAD, LUSC, and STAD.

Conclusion

The study revealed the prognosis and risk factors for deterioration in patients with low expression of GKN2. GKN2 may be used as a valuable prognostic biomarker and therapeutic target in lung and gastric cancers.

Helicobacter pylori Virulence Factor Cytotoxin-Associated Gene A (CagA)-Mediated Gastric Pathogenicity

Helicobacter pylori causes persistent infection in the gastric epithelium of more than half of the world’s population, leading to the development of severe complications such as peptic ulcer diseases, gastric cancer, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Several virulence factors, including cytotoxin-associated gene A (CagA), which is translocated into the gastric epithelium via the type 4 secretory system (T4SS), have been indicated to play a vital role in disease development. Although infection with strains harboring the East Asian type of CagA possessing the EPIYA-A, -B, and -D sequences has been found to potentiate cell proliferation and disease pathogenicity, the exact mechanism of CagA involvement in disease severity still remains to be elucidated. Therefore, we discuss the possible role of CagA in gastric pathogenicity.

Trefoil factor 1 and gastrokine 2 inhibit Helicobacter pylori-induced proliferation and inflammation in gastric cardia and distal carcinogenesis

Helicobacter pylori (H. pylori) infection has been associated with non-cardia adenocarcinoma in the stomach, while its role in gastric cardia adenocarcinoma (GCA) remains controversial. In addition, the association between H. pylori and the protective factors trefoil factor 1 (TFF1) and gastrokine 2 (GKN2) in gastroesophageal adenocarcinomas has not been fully investigated. Therefore, the mRNA and protein expression levels of TFF1 and GKN2 in GCA and distal gastric adenocarcinoma (DGA) were analyzed using quantitative PCR (qPCR) and immunohistochemistry, and the association with H. pylori infection was investigated. In addition, the effects of TFF1 and GKN2 overexpression on H. pylori-induced cells were investigated using western blot and reverse transcription-qPCR analysis. The comparative analysis of 16S rRNA-positive mRNA expression between GCA and DGA showed no statistically significant difference. However, the rate of the H. pylori vacuolating toxin A (VacA) genotype was significantly higher in GCA (49.2%) compared with that in DGA (26.9%; P<0.05). H. pylori infection downregulated the mRNA and protein expression levels of TFF1 and GKN2 in gastric tumor tissues, and the mRNA expression level of TFF1 and GKN2 was also markedly decreased in vitro. Furthermore, the cell proliferation varied in H. pylori total protein treatment group with the different doses. Notably, treatment with 20 µg/ml H. pylori total protein for 24 h resulted in the highest cellular proliferation rate. In addition, TFF1 and GKN2 overexpression inversely inhibited H. pylori-induced cell proliferation and upregulated NF-κB, tumor necrosis factor-α, IL-1β, IL-2, IL-4 and IL-6. The results of the present study indicate that H. pylori, particularly the VacA+ strain, plays an important role in GCA pathogenesis in high-risk areas of China, while TFF1/GKN2 inhibits H. pylori-induced cell proliferation and inflammation in GCA and DGA.

Women with chronic follicular gastritis positive for Helicobacter pylori express lower levels of GKN1

In women, serum levels of CTSB, GKN2, LIPF, LIPFG, AZGP1, TOP2A and PGA4 are proposed as predictive markers of gastric cancer. It is unknown whether GKN1 expression varies with the sex of patients with chronic gastritis or gastric cancer. We studied 36 patients with histopathological diagnosis of chronic gastritis from the state of Guerrero, Mexico. PCR was performed for H. pylori detection and GKN1 expression was determined by RT-qPCR and western blot. GKN1 mRNA expression was significantly lower in patients with chronic follicular gastritis than in those with chronic chemical gastritis (p = 0.00071). The mRNA and protein level of expression of GKN1 were significantly lower in women with chronic follicular gastritis than in men with the same condition (p = 0.0279 and p = 0.0014, respectively); the lowest levels of GKN1 were detected in women with H. pylori-positive follicular gastritis (p = 0.0175 and p = 0.0111, respectively). Through a bioinformatic analysis, estrogen response elements were identified in the GKN1 promoter.

Induction and Prevention of Gastric Cancer with Combined Helicobacter Pylori and Capsaicin Administration and DFMO Treatment, Respectively

Gastric cancer risk evolves over time due to environmental, dietary, and lifestyle changes, including Helicobacter pylori (H. pylori) infection and consumption of hot peppers (i.e., capsaicin). H. pylori infection promotes gastric mucosal injury in the early phase of capsaicin exposure. This relationship suggests a need to investigate the mechanism of how both H. pylori infection and capsaicin contribute to gastric inflammation and lead to gastric cancer. C57-Balb/c mice were infected with the H. pylori (SS1) strain and then fed capsaicin (0.05% or 0.2 g/kg/day) or not. Consequently, tumor size and phenotype were analyzed to determine the molecular mechanism driving the shift from gastritis to stomach cancer. Moreover, we used 2-difluoromethylornithine (DFMO) in mice to prevent gastric tumorigenesis by reducing inflammation and promoting recovery of disease-free stasis. This study provides evidence showing that a combination of H. pylori infection and capsaicin consumption leads to gastric carcinogenesis mediated through interleukin-6 (IL-6) stimulation with an incidence rate of 50%. The anti-inflammatory role of DFMO highlights the injurious effect of inflammation in gastric cancer development and the need to reduce gastric inflammation for cancer prevention by inhibiting IL-6. Accordingly, preventive measures such as reduced capsaicin consumption, H. pylori clearance, and DFMO treatment may lessen gastric cancer incidence.

Poly(1-vinylimidazole) polyplexes as novel therapeutic gene carriers for lung cancer therapy

The present work explores the ability of poly(1-vinylimidazole) (PVI) to complex small interfering RNA (siRNA) silencing vascular endothelial growth factor (VEGF) and the in vitro efficiency of the formed complexes in A549 lung cancer cells. The polyplex formed was found to exhibit 66% complexation efficiency. The complexation was confirmed by gel retardation assays, FTIR and thermal analysis. The blank PVI polymer was not toxic to cells. The polyplex was found to exhibit excellent internalization and escaped the endosome effectively. The polyplex was more effective than free siRNA in silencing VEGF in lung cancer cells. The silencing of VEGF was quantified using Western blot and was also reflected in the depletion of HIF-1α levels in the cells treated with the polyplex. VEGF silencing by the polyplex was found to augment the cytotoxic effects of the chemotherapeutic agent 5-fluorouracil. Microarray analysis of the mRNA isolated from cells treated with free siRNA and the polyplex reveal that the VEGF silencing by the polyplex also altered the expression levels of several other genes that have been connected to the proliferation and invasion of lung cancer cells. These results indicate that the PVI complexes can be an effective agent to counter lung cancer.

Helicobacter pylori inhibits GKN1 expression via the CagA/p-ERK/AUF1 pathway

BACKGROUND

Recent studies have shown that gastrokine 1 (GKN1), an important tumor suppressor gene, is downregulated in Helicobacter pylori (H. pylori) infected gastric mucosa and gastric cancer. However, the underlying mechanism is poorly understood. Herein, we investigated the potential mechanism of H. pylori-induced GKN1 downregulation.

MATERIALS AND METHODS

GKN1 and AU-rich element RNA-binding factor 1 (AUF1) expressions were assessed by quantitative real-time PCR, Western blot, or immunohistochemistry in H. pylori-infected tissues and H. pylori co-cultured cell lines. The regulation of AUF1 on GKN1 was determined by RNA pulldown assay, RNA immunoprecipitation, mRNA turnover, and luciferase activity assays. The involvement of phosphorylated extra-cellular signal-regulated kinase (p-ERK) or CagA in H. pylori-induced AUF1 expression was verified using p-ERK inhibitor or CagA knockout H. pylori. In addition, the cell proliferation and migration capacities of AUF1-knockdown cells were investigated.

RESULTS

GKN1 expression progressively decreased from H. pylori-infected gastritis to gastric cancer tissues. H. pylori co-culture also induced significant GKN1 reduction in GES-1 and BGC-823 cells. Besides, the mRNA level of GKN1 and AUF1 in human gastric mucosa showed negative correlation significantly. AUF1 knockdown resulted in upregulation of GKN1 expression and promoted GKN1 mRNA decay by binding the 3' untranslated region of GKN1 mRNA H. pylori-induced AUF1 expression was associated with p-ERK activation and CagA. Furthermore, knockdown of AUF1 significantly inhibited cell viability, migration ability, and arrested fewer cells in S-phase.

CONCLUSION

Our data demonstrated that H. pylori infection downregulated GKN1 expression via the CagA/p-ERK/AUF1 pathway. AUF1 promoted gastric cancer at least partly through downregulating GKN1, which presented a novel potential target for the treatment of gastric cancer.

Multiscale network analysis reveals molecular mechanisms and key regulators of the tumor microenvironment in gastric cancer

Gastric cancer (GC) is the third leading cause of cancer deaths and the fourth most prevalent malignancy worldwide. The high incidence and mortality rates of gastric cancer result from multiple factors such as ineffective screening, diagnosis, and limited treatment options. In our study, we sought to systematically identify predictive molecular networks and key regulators to elucidate complex interacting signaling pathways in GC. We performed an integrative network analysis of the transcriptomic data in The Cancer Genome Atlas (TCGA) gastric cancer cohort and then comprehensively characterized the predictive subnetworks and key regulators by the matched genetic and epigenetic data. We identified 221 gene subnetworks (modules) in GC. The most prognostic subnetworks captured multiple aspects of the tumor microenvironment in GC involving interactions among stromal, epithelial and immune cells. We revealed the genetic and epigenetic underpinnings of those subnetworks and their key transcriptional regulators. We computationally predicted and experimentally validated specific mechanisms of anticancer effects of GKN2 in gastric cancer proliferation and invasion in vitro. The network models and the key regulators of the tumor microenvironment in GC identified here pave a way for developing novel therapeutic strategies for GC.

What's new?

Gene signatures have been identified for diagnosis and classification of gastric cancer (GC) as well as prediction of therapeutic response. However, key molecular mechanisms underlying prognosis remain to be revealed. Our study systematically identifies and characterizes predictive molecular networks and key regulators. The most prognostic subnetworks capture multiple aspects of the tumor microenvironment in GC involving interactions among stromal, epithelial, and immune cells. The authors computationally predicted and experimentally validated specific mechanisms of anti‐cancer effects of GKN2 in GC proliferation and invasion in vitro. These network models and key regulators pave the way for developing novel therapeutic strategies for GC.

GKN1 expression in gastric cancer cells is negatively regulated by miR-544a

Gastrokine1 (GKN1), important for maintaining the physiological function of the gastric mucosa, is highly expressed in the stomach of healthy individuals but is down-regulated or absent in gastric tumor tissues and derived cell lines. The mechanisms underlying GKN1 gene inactivation are still unknown. We previously showed that GKN1 downregulation in gastric tumors is likely associated with an epigenetic transcriptional complex that negatively regulates GKN1 expression. In addition, TSA-mediated inhibition of HDACs leads to GKN1 restoration at the transcriptional level, but no at the translational level. These findings led to hypothesize the activation of a second regulatory mechanism microRNAs-mediated, thus resulting in translational repression and gene silencing. Bioinformatic analyses performed with 5 different algorithms highlighted that 4 miRNAs contained a seed sequence for the 3'UTR of GKN1 mRNA. Among these, only two miRNAs, hsa-miR-544a and miR-1245b-3p directly target the GKN1-3'UTR as evaluated by luciferase reporter assays. TaqMan miRNA assay performed on gastric cancer cell lines after TSA treatment showed a stronger increase of miR-544a expression than that of miR-1245b-3p. Finally, co-transfection of AGS cells with GKN1-3'UTR and premiR-544a showed compared to controls, a strong reduction of GKN1 expression both at translational and transcriptional levels. The up-regulation of miR-544a could be crucially involved in the GKN1 translational repression, thus suggesting its potential role as a biomarker and therapeutic target in GC patients. These findings indicate that epigenetic mechanisms leading to the inactivation of GKN1 play a key role in the multi-step process of gastric carcinogenesis and would provide an essential starting point for the development of new therapeutic strategies based on epigenetic targets for alternatives gene.

Regulation of GKN1 expression in gastric carcinogenesis: A problem to resolve (Review)

Gastrokine 1 (GKN1) is a protein expressed on the surface mucosa cells of the gastric antrum and fundus, which contributes to maintaining gastric homeostasis, inhibits inflammation and is a tumor suppressor. The expression of GKN1 decreases in mucosa that are either inflamed or infected by Helicobacter pylori, and is absent in gastric cancer. The measurement of circulating GKN1 concentration, the protein itself, or the mRNA in gastric tissue may be of use for the early diagnosis of cancer. The mechanisms that modulate the deregulation or silencing of GKN1 expression have not been completely described. The modification of histones, methylation of the GKN1 promoter, or proteasomal degradation of the protein have been detected in some patients; however, these mechanisms do not completely explain the absence of GKN1 or the reduction in GKN1 levels. Only NKX6.3 transcription factor has been shown to be a positive modulator of GKN1 transcription, although others also have an affinity with sequences in the promoter of this gene. While microRNAs (miRNAs) are able to directly or indirectly regulate the expression of genes at the post‑transcriptional level, the involvement of miRNAs in the regulation of GKN1 has not been reported. The present review analyzes the information reported on the determination of GKN1 expression and the regulation of its expression at the transcriptional, post‑transcriptional and post‑translational levels; it proposes an integrated model that incorporates the regulation of GKN1 expression via transcription factors and miRNAs in H. pylori infection.

SCFFBXW7/GSK3β-Mediated GFI1 Degradation Suppresses Proliferation of Gastric Cancer Cells

Gastric cancer is the third leading cause of cancer-related death worldwide. The regulatory mechanisms underlying gastric cancer cell proliferation are largely unclear. Here, we show that the transcription factor GFI1 is associated with advanced clinical gastric cancer progression and promoted gastric cancer cell proliferation partially through inhibition of gastrokine-2 (GKN2) transcription. GFI1 was a degrading substrate of FBXW7, whose loss was observed in gastric cancer. Mechanistically, GSK3β-mediated GFI1 S94/S98 phosphorylation triggered its interaction with FBXW7, resulting in SCFFBXW7-mediated ubiquitination and degradation. A nondegradable GFI1 S94A/S98A mutant was more potent in driving gastric cancer cell proliferation and tumorigenesis than wild-type GFI1. Overall, this study reveals the oncogenic role of GFI1 in gastric cancer and provides mechanistic insights into the tumor suppressor function of FBXW7. SIGNIFICANCE: These findings demonstrate the oncogenic role of the transcription factor GFI1 and the tumor suppressive function of FBXW7 in gastric cancer.

Dysbindin promotes progression of pancreatic ductal adenocarcinoma via direct activation of PI3K

Pancreatic ductal adenocarcinoma (PDAC) represents a biggest challenge in clinic oncology due to its invasiveness and lack of targeted therapeutics. Our recent study showed that schizophrenia susceptibility factor dysbindin exhibited significant higher level in serum of PDAC patients. However, the functional relevance of dysbindin in PDAC is still unclear. Here, we show that dysbindin promotes tumor growth both in vitro and in vivo by accelerating the G1/S phase transition in cell cycle via PI3K/AKT signaling pathway. Mechanistically, dysbindin interacts with PI3K and stimulates the kinase activity of PI3K. Moreover, overexpression of dysbindin in PDAC is correlated with clinicopathological characteristics significantly, such as histological differentiation (P = 0.011) and tumor size (P = 0.007). Kaplan-Meier survival curves show that patients with high dysbindin expression exhibit poorer overall survival, compared to those with low dysbindin expression (P < 0.001). Multivariate analysis reveals that dysbindin is an independent prognostic factor for pancreatic ductal adenocarcinoma (P = 0.001). Thus, our findings reveal that dysbindin is a novel PI3K activator and promotes PDAC progression via stimulation of PI3K/AKT. Dysbindin therefore represents a potential target for prognosis and therapy of PDAC.

The role and diagnostic potential of gastrokine 1 in gastric cancer

Introduction

Gene for gastrokine 1 (GKN1) was identified as one of the most significant in gastric cancer and indicated as a potential therapeutic target.

Aim

The aim was a review of literature reports concerning the role and diagnostic potential of GKN1 in gastric cancer.

Materials and methods

PubMED database was searched for sources using the following keywords: gastrokine 1/GKN1/AMP-18 and gastric cancer, Helicobacter pylori, aspirin, nonsteroidal anti-inflammatory drugs. Preference was given to the sources which were published within the past 10 years.

Conclusion

GKN1 is a stomach-specific protein, and its role consists of maintaining mucosal integrity as well as the replenishment of the surface lumen epithelial cells layer. The evaluation of GKN1 expression seems to be a useful indicator of the presence of neoplastic or inflammatory lesions in the gastric mucosa. GKN1 expression is decreased in gastric tumor tissues and derived cell lines and its upregulation in cell lines of gastric cancer induces cells apoptosis. The mechanism by which GKN1 is inactivated in gastric cancer cells is still not fully understood. The future diagnostic capabilities of gastric cancer concern the assessment of serum GKN1 concentration by means of ELISA method. Serum GKN1 concentration is not related to patients’ sex. Moreover, the measurement of GKN1 concentration is possible only after the incubation of samples at 70°C for 10 minutes. Nevertheless, the aspect of quantitative serum GKN1 evaluation is new in the context of available literature and requires further studies.

Evaluation of GKN1 and GKN2 gene expression as a biomarker of gastric cancer

AIM

The aim of this study was to investigate the expression of GKN1 and GKN2 genes as probable biomarkers for gastric cancer.

BACKGROUND

Gastric cancer is a multifactorial process characterized by the uncontrolled growth and dissemination of abnormal cells. Survival rates of gastric cancer tend to be poor, a plausible explanation is a combination of a late-stage diagnosis and limited access to treatment. In this regard, finding relevant and measurable biomarkers is urgently needed.

METHODS

27 samples of gastric cancer tissues were enrolled into this study, according to their pathological responses. The alteration of genes expression were evaluated by Real-Time PCR technique.

RESULTS

Our findings showed the significant reduction of Gastrokin-1 and Gastrokine-2 genes expression in the cancerous specimens in comparison with the normal tissues. (P = 0.008 and P = 0.004 respectively).

CONCLUSION

Our findings showed the significant reduction of Gastrokin-1 and Gastrokine-2 genes expression in the cancerous specimens in comparison with the normal tissues. (P = 0.008 and P = 0.004 respectively).

Global transcriptome‑wide analysis of the function of GDDR in acute gastric lesions

Acute gastric lesions induced by stress are frequent occurrences in medical establishments. The gastric dramatic downrelated gene (GDDR) is a secreted protein, which is abundantly expressed in normal gastric epithelia and is significantly decreased in gastric cancer. In our previous study, it was found that GDDR aggravated stress-induced acute gastric lesions. However, the role of GDDR in acute gastric lesions remains to be fully elucidated. In the present study, RNA sequencing was performed in order to examine the gene expression profile regulated by GDDR in acute gastric lesions. The dataset comprised four stomach samples from wild-type (WT) mice and four stomach samples from GDDR-knockout mice. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to analyze the differentially-expressed genes (DEGs). Weighted correlation network analysis was used to identify clusters of highly correlated genes. Cytoscape was used to construct a protein-protein interaction network (PPI) of the DEGs. Based on the GO analysis, the upregulated DEGs were distinctly enriched in muscle contraction and response to wounding; and the downregulated DEGs were significantly enriched in the regulation of nitrogen compound metabolic process and regulation of RNA metabolic process. The results of the KEGG pathway analysis showed that the upregulated DEGs were enriched in ECM-receptor interaction and the signaling pathway of cGMP-PKG, and the downregulated DEGs were enriched in the renin-angiotensin system and glycerolipid metabolism. The co-expression network revealed a group of genes, which were associated with increased wound healing in the WT mice. Significant pathways were identified through the PPI network, including negative regulation of the signaling pathway of glucocorticoid receptor, regulation of cellular stress response, and regulation of hormone secretion. In conclusion, the present study improves current understanding of the molecular mechanism underlying acute gastric lesions and may assist in the treatment of gastric lesions.

Heterodimeric interaction between GKN2 and TFF1 entails synergistic antiproliferative and pro-apoptotic effects on gastric cancer cells

BACKGROUND

GKN2 and TFF1 form a heterodimer that is only generated in the mucus-secreting cells of the normal stomach. The formation of this heterodimer is frequently disrupted in gastric cancer. However, the precise roles of GKN2 alone and in the heterodimer with TFF1 as well as the contributions of GKN2 and the heterodimer to gastric carcinogenesis are poorly understood.

METHODS

Cell viability, proliferation, and apoptosis were analyzed in AGS, MKN1, MKN28, and MKN45 gastric cancer cells transfected with GKN2 and/or TFF1 using MTT, BrdU incorporation, and apoptosis assays, respectively. In addition, cell viability was examined in HFE-145 non-neoplastic gastric epithelial cells after GKN2 and/or TFF1 silencing. Furthermore, the cell cycle and the expression of cell cycle and apoptosis related proteins were assessed. The interaction between GKN2 and TFF1 was confirmed by co-immunoprecipitation. Immunohistochemistry was employed to explore TFF1 expression in 169 gastric cancer tissues.

RESULTS

Co-transfection with GKN2 and TFF1 significantly inhibited cell viability and proliferation by inducing G1/S cell cycle arrest and suppressing positive cell cycle regulators. Simultaneous knockdown of GKN2 and TFF1 in HFE-145 cells resulted in markedly increased cell viability. Moreover, the interaction of GKN2 and TFF1 promoted cell death by enhancing caspase-3/7 activity and upregulating pro-apoptotic proteins. At the mRNA level, GKN2 and TFF1 were found to be positively correlated in non-tumor and tumor samples. Immunohistochemistry revealed loss of TFF1 expression in 128 (75.73%) of 169 gastric cancers. There was a borderline-significant association between GKN2 and TFF1 protein expression in gastric cancers (P = 0.0598).

CONCLUSION

Collectively, our data demonstrated that the interaction between GKN2 and TFF1 can have synergistic antiproliferative and pro-apoptotic effects on gastric cancer.

GKN2 increases apoptosis, reduces the proliferation and invasion ability of gastric cancer cells through down-regulating the JAK/STAT signaling pathway

OBJECTIVES

To investigate the effect of gastric motility protein 2 (GKN2) on the proliferation, apoptosis and invasion of gastric cancer cell and on the JAK/signal transducer and activator of transcription 3 (STAT3) signaling pathway.

METHODS

Expression of GKN2 was qualified using Western blot analysis in four gastric cancer cell lines and immortalized human gastric mucosal epithelial cell line GES-1. The cells were then transfected with pcDNA3.1-GKN2 and control vector using Lipofectamine^tm2000 and assayed for viability, apoptosis, cell cycle changes, invasion ability as well as expression of cell cycle protein D1 (Cylin D1), Bcl-2, Bax, matrix metalloproteinase 2 (MMP2), MMP9, JAK2 and p-STAT3.

RESULTS

Western blot analyses showed that the expression of GKN2 was significantly lower in 4 gastric cancer cell lines (BGC-823, SGC-7901, AGS and MKN-45) than in GES-1. Of them, SGC-7901 had the lowest expression. The line was chosen for subsequent transfection experiments. Compared with control (transfection with empty vector), pcDNA3.1-GKN2-transfected cells had significantly more GKN2 protein and mRNA, decreased cell viability, increased apoptosis, more cells arrested at G1 phase and reduced invasiveness. Expression analyses showed that expression of Cyclin D1, Bcl-2, MMP2, MMP9, JAK2 and STAT3 was significantly down-regulated, while Bax was significantly up-regulated.

CONCLUSION

Over-expression of GKN2 can increase apoptosis, reduce proliferation and invasion ability of gastric cancer cells as a result of down-regulated JAK2/STAT3 signaling pathway.

Gastrointestinal Factor GDDR Attenuates Epithelial-Mesenchymal Transition in Gastric Cancer via Inhibiting AKT Signal

BACKGROUND

The gastric dramatic down-related gene (GDDR) is an abundantly expressed secretory protein in normal gastric epithelia, while its expression is distinctly decreased in gastric cancer. However, the role of GDDR in gastric cancer remains poorly understood.

AIMS

This study aims to detect the expression and clinical significance of GDDR in gastric cancer and investigate its effects on epithelial-mesenchymal transition.

METHODS

The expression of GDDR in gastric cancer was examined by immunohistochemistry, immunoblotting, and Western blotting. The relationships between GDDR expression and clinicopathological factors were evaluated. The effects of GDDR on epithelial-mesenchymal transition of gastric cancer cells were investigated in vitro.

RESULTS

GDDR was absent in gastric cancer tissue or dramatically downregulated in gastric cancer cell lines. Loss of GDDR expression in gastric cancer was strongly correlated with clinicopathological factors, such as tumor differentiation (p = 0.037), T stage (p < 0.001), lymph node metastasis (p = 0.008) and TNM stage (p < 0.001). Patients with decreased GDDR expression presented shortened overall survival (p = 0.033). Functional studies demonstrated that GDDR elevation augmented cell-cell adhesion and suppressed cell motility, concomitant with increased expression of E-cadherin and decreased expression of β-catenin and vimentin. Conversely, GDDR depletion increased cell motility, concomitant with decreased expression of E-cadherin and increased expression of β-catenin and vimentin. Moreover, GDDR had an inhibitory effect on PI3K/Akt signaling pathway.

CONCLUSIONS

Our findings suggested that GDDR expression was significantly associated with the progression of gastric cancer and GDDR may function as a tumor suppressor via inhibiting the epithelial-mesenchymal transition.

A Novel Peptide for Simultaneously Enhanced Treatment of Head and Neck Cancer and Mitigation of Oral Mucositis

We have characterized a novel 21 amino acid-peptide derived from Antrum Mucosal Protein (AMP)-18 that mediates growth promotion of cultured normal epithelial cells and mitigates radiation-induced oral mucositis in animal models, while suppressing in vitro function of cancer cells. The objective of this study was to evaluate these dual potential therapeutic effects of AMP peptide in a clinically relevant animal model of head and neck cancer (HNC) by simultaneously assessing its effect on tumor growth and radiation-induced oral mucositis in an orthotopic model of HNC. Bioluminescent SCC-25 HNC cells were injected into the anterior tongue and tumors that formed were then subjected to focal radiation treatment. Tumor size was assessed using an in vivo imaging system, and the extent of oral mucositis was compared between animals treated with AMP peptide or vehicle (controls). Synergism between AMP peptide and radiation therapy was suggested by the finding that tumors in the AMP peptide/radiation therapy cohort demonstrated inhibited growth vs. radiation therapy-only treated tumors, while AMP peptide-treatment delayed the onset and reduced the severity of radiation therapy-induced oral mucositis. A differential effect on apoptosis appears to be one mechanism by which AMP-18 can stimulate growth and repair of injured mucosal epithelial cells while inhibiting proliferation of HNC cells. RNA microarray analysis identified pathways that are differentially targeted by AMP-18 in HNC vs. nontransformed cells. These observations confirm the notion that normal cells and tumor cells may respond differently to common biological stimuli, and that leveraging this finding in the case of AMP-18 may provide a clinically relevant opportunity.

Loss of gastrokine-2 drives premalignant gastric inflammation and tumor progression

Chronic mucosal inflammation is associated with a greater risk of gastric cancer (GC) and, therefore, requires tight control by suppressive counter mechanisms. Gastrokine-2 (GKN2) belongs to a family of secreted proteins expressed within normal gastric mucosal cells. GKN2 expression is frequently lost during GC progression, suggesting an inhibitory role; however, a causal link remains unsubstantiated. Here, we developed Gkn2 knockout and transgenic overexpressing mice to investigate the functional impact of GKN2 loss in GC pathogenesis. In mouse models of GC, decreased GKN2 expression correlated with gastric pathology that paralleled human GC progression. At baseline, Gkn2 knockout mice exhibited defective gastric epithelial differentiation but not malignant progression. Conversely, Gkn2 knockout in the IL-11/STAT3-dependent gp130F/F GC model caused tumorigenesis of the proximal stomach. Additionally, gastric immunopathology was accelerated in Helicobacter pylori-infected Gkn2 knockout mice and was associated with augmented T helper cell type 1 (Th1) but not Th17 immunity. Heightened Th1 responses in Gkn2 knockout mice were linked to deregulated mucosal innate immunity and impaired myeloid-derived suppressor cell activation. Finally, transgenic overexpression of human gastrokines (GKNs) attenuated gastric tumor growth in gp130F/F mice. Together, these results reveal an antiinflammatory role for GKN2, provide in vivo evidence that links GKN2 loss to GC pathogenesis, and suggest GKN restoration as a strategy to restrain GC progression.

A possible role of GDDR in the development of Helicobacter pylori-associated gastric cancer

Helicobacter pylori (H. pylori) infection plays an important part in the development of gastric carcinoma. GDDR has been confirmed as a tumor suppressor gene in gastric tumorigenesis. However, the underlying mechanism of GDDR in H. pylori-induced carcinogenesis is not well known. The aim of this study is to investigate the clinicopathological significance and possible molecular mechanism of GDDR in gastric cancer associated with H. pylori. Western blot, real-time quantitative PCR (qRT-PCR), and immunohistochemistry were used to detect the expression level of GDDR with or without H. pylori infection. The function and possible related molecular mechanisms of GDDR were further explored in vitro and in vivo. The variability of GDDR expression appeared in the early stage of gastric carcinogenesis with positive H. pylori infection status. GDDR might inhibit the progression of normal gastric epithelial cells to cancer cells by suppressing NF-kappaB signaling pathway, which in turn could be regulated by H. pylori infection. Our results suggested, for the first time, that the gradual change in GDDR expression might not only be directly related to H. pylori infection but also be an early molecular event in the development of gastric carcinoma.

Mining for novel tumor suppressor genes using a shortest path approach

Cancer, being among the most serious diseases, causes many deaths every year. Many investigators have devoted themselves to designing effective treatments for this disease. Cancer always involves abnormal cell growth with the potential to invade or spread to other parts of the body. In contrast, tumor suppressor genes (TSGs) act as guardians to prevent a disordered cell cycle and genomic instability in normal cells. Studies on TSGs can assist in the design of effective treatments against cancer. In this study, we propose a computational method to discover potential TSGs. Based on the known TSGs, a number of candidate genes were selected by applying the shortest path approach in a weighted graph that was constructed using protein-protein interaction network. The analysis of selected genes shows that some of them are new TSGs recently reported in the literature, while others may be novel TSGs.

Trefoil factors: Gastrointestinal-specific proteins associated with gastric cancer

Trefoil factor family (TFF), composed of TFF1, TFF2, and TFF3, is a cluster of secreted peptides characterized by trefoil domain (s) and C-terminal dimerization domain. TFF1, a gastric tumor suppressor, is a single trefoil peptide originally detected in breast cancer cell lines but expressed mainly in the stomach; TFF2, a candidate of gastric cancer suppressor with two trefoil domains, is abundant in the stomach and duodenal Brunner's glands; and TFF3 is another single trefoil peptide expressed throughout the intestine which can promote the development of gastric carcinoma. According to multiple studies, TFFs play a regulatory function in the mammals' digestive system, namely in mucosal protection and epithelial cell reconstruction, tumor suppression or promotion, signal transduction and the regulation of proliferation and apoptosis. Action mechanisms of TFFs remain unresolved, but the recent demonstration of a GKN (gastrokine) 2-TFF1 heterodimer implicates structural and functional interplay with gastrokines. This review aims to encapsulate the structural and biological characteristics of TFF.

Identification of genes and long non-coding RNAs associated with the pathogenesis of gastric cancer

Gastric cancer is a lethal disease characterized by high diffusivity and mortality. To examine the mechanisms involved in gastric cancer, we analyzed the microarray of GSE41476. GSE41476 was downloaded from the Gene Expression Omnibus and included 3 primary cell culture samples from gastric cancer tissues, 3 gastric cancer cell lines and 2 normal tissue samples. Long non-coding RNAs (lncRNAs) and differentially expressed genes (DEGs) were screened by Cuffdiff software. Functions of the DEGs were predicted by functional and pathway enrichment analyses. The interaction relationships of the proteins encoded by DEGs that were obtained from the STRING database and protein‑protein interaction (PPI) network were visualized using Cytoscape. Modules analysis of PPI network was performed using CFinder. Moreover, lncRNA analysis was performed. A total of 86 lncRNAs, and 1,088 up- and 1,537 downregulated transcriptions were screened. For DEGs in module A of the PPI network for upregulated genes, the enriched pathways included ECM-receptor interaction and focal adhesion, both of which involved COL and ITG genes. The COL genes interacted with the ITG genes (e.g., COL1A1‑ITGA5 and COL1A2‑ITGB1). For DEGs in module B of the PPI network for downregulated genes, the enriched pathways for DEGs included the T‑cell receptor signaling pathway, which involved PIK3CG and PIK3R5. PIK3CG had an interaction relationship with PIK3R5. In addition, IL7 was co-expressed with TCONS-00068220. In summary, the results showed that COL and ITG genes, PIK3CG, PIK3R5, IL7 and lncRNA TCONS‑00068220 may play a role in gastric cancer.

Trefoil factor 3 as a novel biomarker to distinguish between adenocarcinoma and squamous cell carcinoma

In carcinoma, such as of the lung, the histological subtype is important to select an appropriate therapeutic strategy for patients. However, carcinomas with poor differentiation cannot always be distinguished on the basis of morphology alone nor on clinical findings. Hence, delineation of poorly differentiated adenocarcinoma and squamous cell carcinoma, the 2 most common epithelial-origin carcinomas, is pivotal for selection of optimum therapy. Herein, we explored the potential utility of trefoil factor 3 (TFF3) as a biomarker for primary lung adenocarcinoma and extrapulmonary adenocarcinomas derived from different organs. We observed that 90.9% of lung adenocarcinomas were TFF3-positive, whereas no expression of TFF3 was observed in squamous cell carcinomas. The subtype of lung carcinoma was confirmed by four established biomarkers, cytokeratin 7 and thyroid transcription factor 1 for adenocarcinoma and P63 and cytokeratin 5/6 for squamous cell carcinoma. Furthermore, expression of TFF3 mRNA was observed by quantitative PCR in all of 11 human lung adenocarcinoma cell lines and highly correlated with markers of the adenocarcinomatous lineage. In contrast, little or no expression of TFF3 was observed in 4 lung squamous cell carcinoma cell lines. By use of forced expression, or siRNA-mediated depletion of TFF3, we determined that TFF3 appeared to maintain rather than promote glandular differentiation of lung carcinoma cells. In addition, TFF3 expression was also determined in adenocarcinomas from colorectum, stomach, cervix, esophagus, and larynx. Among all these extrapulmonary carcinomas, 93.7% of adenocarcinomas exhibited TFF3 positivity, whereas only 2.9% of squamous cell carcinomas were TFF3-positive. Totally, 92.9% of both pulmonary and extrapulmonary adenocarcinomas exhibited TFF3 positivity, whereas only 1.5% of squamous cell carcinomas were TFF3-positive. In conclusion, TFF3 is preferentially expressed in adenocarcinoma and may function as an additional biomarker for distinguishing adenocarcinoma from squamous cell carcinoma.

Ectopic expression of gastrokine 1 in gastric cancer cells up-regulates tight and adherens junction proteins network

Gastrokine 1 (GKN1) is a stomach-specific protein important in the replenishment of the surface lumen epithelial cell layer and in maintaining mucosal integrity. A role in cell proliferation and differentiation has also been hypothesized. Despite these findings, the function(s) as well as the cellular localization of GKN1 in the cellular machinery are currently not clarified. The investigation of subcellular localization of GKN1 in gastric cancer cells can provide insights into its potential cellular roles. Subcellular fractions of gastric cancer cells (AGS) transfected with full-length GKN1 (flGKN1) or incubated with recombinant GKN1 (rGKN1) lacking the first 20 amino acids at N-terminal were analyzed by Western blot and confocal microscopy and compared with those from normal gastric tissue. Wild type GKN1 (wtGKN1) and flGKN1 were revealed in the cytoplasm and in the membrane fractions of gastric cells, whereas rGKN1 was revealed in the cytoplasmic fractions, but a high amount was detected in the membrane pellet of the AGS lysate. The cellular distribution of GKN1 was also confirmed by confocal microscopy. The purified protein was also used to highlight its possible association with actin through confocal microscopy, pelleting assay, and size-exclusion chromatography. GKN1 co-localizes with actin in normal gastric tissue, but no direct interaction was observed between the two proteins in vitro. Most likely, GKN1 indirectly participates in actin stabilization since its overexpression in gastric cancer cells strongly increases the expression of tight and adherens junction proteins.

Increased expression of protease-activated receptor 4 and Trefoil factor 2 in human colorectal cancer

Protease-activated receptor 4 (PAR4), a member of G-protein coupled receptors family, was recently reported to exhibit decreased expression in gastric cancer and esophageal squamous cancer, yet increased expression during the progression of prostate cancer. Trefoil factor 2 (TFF2), a small peptide constitutively expressed in the gastric mucosa, plays a protective role in restitution of gastric mucosa. Altered TFF2 expression was also related to the development of gastrointestinal cancer. TFF2 has been verified to promote cell migration via PAR4, but the roles of PAR4 and TFF2 in the progress of colorectal cancer are still unknown. In this study, the expression level of PAR4 and TFF2 in colorectal cancer tissues was measured using real-time PCR (n = 38), western blotting (n=38) and tissue microarrays (n = 66). The mRNA and protein expression levels of PAR4 and TFF2 were remarkably increased in colorectal cancer compared with matched noncancerous tissues, especially in positive lymph node and poorly differentiated cancers. The colorectal carcinoma cell LoVo showed an increased response to TFF2 as assessed by cell invasion upon PAR4 expression. However, after intervention of PAR4 expression, PAR4 positive colorectal carcinoma cell HT-29 was less responsive to TFF2 in cell invasion. Genomic bisulfite sequencing showed the hypomethylation of PAR4 promoter in colorectal cancer tissues and the hypermethylation in the normal mucosa that suggested the low methylation of promoter was correlated to the increased PAR4 expression. Taken together, the results demonstrated that the up-regulated expression of PAR4 and TFF2 frequently occurs in colorectal cancer tissues, and that overexpression of PAR4 may be resulted from promoter hypomethylation. While TFF2 promotes invasion activity of LoVo cells overexpressing PAR4, and this effect was significantly decreased when PAR4 was knockdowned in HT-29 cells. Our findings will be helpful in further investigations into the functions and molecular mechanisms of Proteinase-activated receptors (PARs) and Trefoil factor factors (TFFs) during the progression of colorectal cancer.

Effects of gastrokine‑2 expression on gastric cancer cell apoptosis by activation of extrinsic apoptotic pathways

Gastrokine‑2 is a putative gastric cancer‑specific tumor suppressor gene, the loss of which is known to be involved in the development and progression of gastric cancer, and restoration of gastrokine‑2 expression inhibits growth of gastric cancer cells in vitro. However, the underlying mechanism of these effects requires elucidation. In the present study, expression patterns of gastrokine‑2 protein were examined in gastric cancer tissues and cell lines. Expression of gastrokine‑2 was restored in gastric cancer cells in order to assess its effect on cell viability, apoptosis and gene expression. A total of 76 gastric cancer tissues with corresponding normal mucosae samples, and two gastric cancer cell lines (SGC‑7901 and AGS) were subjected to western blot analysis of gastrokine‑2 expression. SGC‑7901 cells were transiently transfected with gastrokine‑2 cDNA and then treated with anti‑CD95 and/or anti‑Fas antibodies prior to analysis of cell viability, apoptosis and gene expression levels. Expression of gastrokine‑2 protein was reduced or absent in gastric cancer tissues and gastric cancer cell lines. Following restoration of gastrokine‑2 expression, the protein expression level of Fas was significantly increased, but no marked change was observed in the levels of bcl‑2 and Bax proteins. Expression of gastrokine‑2 protein reduced gastric cancer cell viability and induced apoptosis. Activity of caspase‑3 and caspase‑8 was increased, but caspase‑9 activity remained unchanged in the SGC‑7901 cells. Reduction or knockout of gastrokine‑2 protein expression may contribute to gastric cancer development or progression, as the current study demonstrated that restoration of gastrokine‑2 expression induces apoptosis of gastric cancer cells through the extrinsic apoptosis pathway.

Decreased expression of gastrokine 1 in gastric mucosa of gastric cancer patients

AIM: To investigate the expression of gastrokine 1 (GKN1) in normal gastric mucosa, precancerous lesions and gastric cancer tissues, and to analyse its correlations with tumour site and pathological pattern.

METHODS: Thirty gastric cancer patients (12 cases of diffuse type and 18 cases of intestinal type), 13 atrophic gastritis patients and 15 healthy volunteers with almost normal gastric mucosa (superficial gastritis) were enrolled in this study. Helicobacter pylori (H. pylori) infection was examined in all subjects. All gastric mucosa biopsy specimens were obtained. Cancer-adjacent specimens were taken from corresponding gastric cancer patients. Immunohistochemistry and real-time PCR were performed to determine the expressions of the GKN1 protein and mRNA, respectively.

RESULTS: H. pylori infection had no significant association with age, gender, tumour site or pathological pattern in all subjects. Compared with the superficial gastritis and atrophic gastritis groups, the expression of GKN1 protein (P = 0.011) and mRNA (P < 0.001) in gastric cancer was significantly decreased. The GKN1 mRNA level in diffuse type gastric cancer was significantly lower than in intestinal type gastric cancer (0.296 ± 0.076 vs 0.525 ± 0.164, P < 0.001).

CONCLUSION: Compared with almost normal gastric mucosa, GKN1 expression in the gastric mucosa of gastric cancer patients is decreased; this is associated with progression and prognosis of gastric cancer.

RNA-Seq accurately identifies cancer biomarker signatures to distinguish tissue of origin

Metastatic cancer of unknown primary (CUP) accounts for up to 5% of all new cancer cases, with a 5-year survival rate of only 10%. Accurate identification of tissue of origin would allow for directed, personalized therapies to improve clinical outcomes. Our objective was to use transcriptome sequencing (RNA-Seq) to identify lineage-specific biomarker signatures for the cancer types that most commonly metastasize as CUP (colorectum, kidney, liver, lung, ovary, pancreas, prostate, and stomach). RNA-Seq data of 17,471 transcripts from a total of 3,244 cancer samples across 26 different tissue types were compiled from in-house sequencing data and publically available International Cancer Genome Consortium and The Cancer Genome Atlas datasets. Robust cancer biomarker signatures were extracted using a 10-fold cross-validation method of log transformation, quantile normalization, transcript ranking by area under the receiver operating characteristic curve, and stepwise logistic regression. The entire algorithm was then repeated with a new set of randomly generated training and test sets, yielding highly concordant biomarker signatures. External validation of the cancer-specific signatures yielded high sensitivity (92.0% ± 3.15%; mean ± standard deviation) and specificity (97.7% ± 2.99%) for each cancer biomarker signature. The overall performance of this RNA-Seq biomarker-generating algorithm yielded an accuracy of 90.5%. In conclusion, we demonstrate a computational model for producing highly sensitive and specific cancer biomarker signatures from RNA-Seq data, generating signatures for the top eight cancer types responsible for CUP to accurately identify tumor origin.

The role of gastrokine 1 in gastric cancer

Homeostatic imbalance between cell proliferation and death in gastric mucosal epithelia may lead to gastritis and gastric cancer. Despite abundant gastrokine 1 (GKN1) expression in the normal stomach, the loss of GKN1 expression is frequently detected in gastric mucosa infected with Helicobacter pylori, as well as in intestinal metaplasia and gastric cancer tissues, suggesting that GKN1 plays an important role in gastric mucosal defense, and the gene functions as a gastric tumor suppressor. In the stomach, GKN1 is involved in gastric mucosal inflammation by regulating cytokine production, the nuclear factor-κB signaling pathway, and cyclooxygenase-2 expression. GKN1 also inhibits the carcinogenic potential of H. pylori protein CagA by binding to it, and up-regulates antioxidant enzymes. In addition, GKN1 reduces cell viability, proliferation, and colony formation by inhibiting cell cycle progression and epigenetic modification by down-regulating the expression levels of DNMT1 and EZH2, and DNMT1 activity, and inducing apoptosis through the death receptor-dependent pathway. Furthermore, GKN1 also inhibits gastric cancer cell invasion and metastasis via coordinated regulation of epithelial mesenchymal transition-related protein expression, reactive oxygen species production, and PI3K/Akt signaling pathway activation. Although the modes of action of GKN1 have not been clearly described, recent limited evidence suggests that GKN1 acts as a gastric-specific tumor suppressor. This review aims to discuss, comment, and summarize the recent progress in the understanding of the role of GKN1 in gastric cancer development and progression.

GKN2 contributes to the homeostasis of gastric mucosa by inhibiting GKN1 activity

Gastrokine 1 (GKN1) plays an important role in maintaining gastric mucosa integrity. Here, we investigated whether gastrokine 2 (GKN2) contributes to the homeostasis of gastric epithelial cells by regulating GKN1 activity. We analyzed cell viability, proliferation, and death in AGS cells transfected with GKN1, GKN2, GKN1 plus GKN2 using MTT, BrdU incorporation, and apoptosis assays, respectively. In addition, the expression levels of the cell cycle- and apoptosis-related proteins, miR-185, DNMT1, and EZH2 were determined. We also compared the expression of GKN1, GKN2, and CagA in 50 non-neoplastic gastric mucosae and measured GKN2 expression in 169 gastric cancers by immunohistochemistry. GKN2 inhibited anti-proliferative and pro-apoptotic activities, miR-185 induction, and anti-epigenetic modifications of GKN1. There was a positive correlation between GKN1 and GKN2 expression (P = 0.0074), and the expression of GKN1, but not GKN2, was significantly lower in Helicobacter pylori CagA-positive gastric mucosa (P = 0.0013). Interestingly, ectopic GKN1 expression in AGS cells increased GKN2 mRNA and protein expression in a time-dependent manner (P = 0.01). Loss of GKN2 expression was detected in 126 (74.6%) of 169 gastric cancers by immunohistochemical staining and was closely associated with GKN1 expression and differentiation of gastric cancer cells (P = 0.0002 and P = 0.0114, respectively). Overall, our data demonstrate that in the presence of GKN2, GKN1 loses its ability to decrease cell proliferation, induce apoptosis, and inhibit epigenetic alterations in gastric cancer cells. Thus, we conclude that GKN2 may contribute to the homeostasis of gastric epithelial cells by inhibiting GKN1 activity.

Promoter hypermethylation and downregulation of trefoil factor 2 in human gastric cancer

Trefoil factor 2 (TFF2) plays a protective role in gastric mucosa and may be involved in the progression of gastric cancer, but the detailed functions and underlying molecular mechanisms are not clear. The present study used a combination of clinical observations and molecular methods to investigate the correlation between abnormal expression of TFF2 and gastric cancer progression. TFF2 expression was evaluated by reverse transcription polymerase chain reaction (RT-PCR), quantitative PCR (qPCR), and western blot and immunohistochemistry analyses. TFF2 methylation levels were analyzed by genomic bisulfite sequencing method. The results showed that TFF2 mRNA and protein expression were decreased in gastric cancer tissues compared with the matched non-cancerous mucosa, and the decreased level was associated with the differentiation and invasion of gastric cancer. Moreover, the average TFF2 methylation level of CpG sites in the promoter region was 70.4% in three gastric cancer tissues, while the level in associated non-neoplastic tissues was 41.0%. Furthermore, the promoter hypermethylation of TFF2 was also found in gastric cancer cell lines, AGS and N87, and gene expression was significantly increased following treatment with a demethylating agent, 5-Aza-2′-deoxycytidine. In conclusion, TFF2 expression was markedly decreased in gastric cancer and promoter hypermethylation was found to regulate the downregulation of TFF2. TFF2 has been suggested as a tumor suppressor in gastric carcinogenesis and metastasis.

Down-regulation of protease-activated receptor 4 in lung adenocarcinoma is associated with a more aggressive phenotype

The role of protease-activated receptors (PARs) in lung tumors is controversial. Although PAR4 is preferentially expressed in human lung tissues, its possible significance in lung cancer has not been defined. The studies reported herein used a combination of clinical observations and molecular methods. Surgically resected lung adenocarcinomas and associated adjacent normal lung tissues were collected and BEAS-2B and NCI-H157 cell lines were grown in tissue culture. PAR4 expression was evaluated by RT-PCR, RT-qPCR, Western blotting and immunohistochemistry analysis. The results showed that PAR4 mRNA expression was generally decreased in lung adenocarcinoma tissues as compared with matched noncancerous tissues (67.7%) and was associated with poor differentiation (p=0.017) and metastasis (p=0.04). Western blotting and immunohistochemical analysis also showed that PAR4 protein levels were mostly decreased in lung adenocarcinoma tissues (61.3%), and were also associated with poor differentiation (p=0.035) and clinical stage (p=0.027). Moreover, PAR4 expression was decreased in NCI-H157 cells as compared with BEAS-2B cells. In conclusion, PAR4 expression is significantly decreased in lung adenocarcinoma, and down-regulation of PAR4 is associated with a more clinically aggressive phenotype. PAR4 may acts as a tumor suppressor in lung adenocarcinoma.

EBNA1 binding and epigenetic regulation of gastrokine tumor suppressor genes in gastric carcinoma cells

BACKGROUND

Epstein-Barr Virus (EBV) latently infects ~10% of gastric carcinomas (GC). Epstein-Barr Nuclear Antigen 1 (EBNA1) is expressed in EBV-associated GC, and can bind host DNA, where it may impact cellular gene regulation. Here, we show that EBNA1 binds directly to DNA upstream of the divergently transcribed GC-specific tumor suppressor genes gastrokine 1 (GKN1) and gastrokine 2 (GKN2).

METHODS

We use ChIP-Seq, ChIP-qPCR, and EMSA to demonstrate that EBNA1 binds directly to the GKN1 and GKN2 promoter locus. We generate AGS-EBV, and AGS-EBNA1 cell lines to study the effects of EBNA1 on GKN1 and GKN2 mRNA expression with or without 5' azacytidine treatment.

RESULTS

We show that gastrokine genes are transcriptionally silenced by DNA methylation. We also show that latent EBV infection further reduces GKN1 and GKN2 expression in AGS gastric carcinoma cells, and that siRNA depletion of EBNA1 partially alleviates this repression. However, ectopic expression of EBNA1 slightly increased GKN1 and GKN2 basal mRNA levels, but reduced their responsiveness to demethylating agent.

CONCLUSIONS

These findings demonstrate that EBNA1 binds to the divergent promoter of the GKN1 and GKN2 genes in GC cells, and suggest that EBNA1 contributes to the complex transcriptional and epigenetic deregulation of the GKN1 and GKN2 tumor suppressor genes in EBV positive GC.

Exploring the proteomic landscape of a gastric cancer biopsy with the shotgun imaging analyzer

Accessing localized proteomic profiles has emerged as a fundamental strategy to understand the biology of diseases, as recently demonstrated, for example, in the context of determining cancer resection margins with improved precision. Here, we analyze a gastric cancer biopsy sectioned into 10 parts, each one subjected to MudPIT analysis. We introduce a software tool, named Shotgun Imaging Analyzer and inspired in MALDI imaging, to enable the overlaying of a protein's expression heat map on a tissue picture. The software is tightly integrated with the NeXtProt database, so it enables the browsing of identified proteins according to chromosomes, quickly listing human proteins never identified by mass spectrometry (i.e., the so-called missing proteins), and the automatic search for proteins that are more expressed over a specific region of interest on the biopsy, all of which constitute goals that are clearly well-aligned with those of the C-HPP. Our software has been able to highlight an intense expression of proteins previously known to be correlated with cancers (e.g., glutathione S-transferase Mu 3), and in particular, we draw attention to Gastrokine-2, a "missing protein" identified in this work of which we were able to clearly delineate the tumoral region from the "healthy" with our approach. Data are available via ProteomeXchange with identifier PXD000584.

The tumor suppressor gastrokine-1 is expressed in placenta and contributes to the regulation of trophoblast migration

INTRODUCTION

Gastrokine-1 (GKN1) is a secreted auto-/paracrine protein, described to be expressed in the gastric mucosa. In gastric cancers GKN1 expression is commonly down-regulated. While current research focusses on the exploration of tumor-suppressive properties of GKN1 with regard to its potential clinical use in the treatment of gastroenterologic tumor disease, nothing is known about GKN1 expression and function in other organ systems. We investigated GKN1 expression in placental tissue and cells.

MATERIALS AND METHODS

GKN1 was localized using immunohistochemistry in first and third trimester placental tissue, hydatidiform moles and various gestational trophoblastic neoplasias. We determined the expression of GKN1 in immunomagnetic bead-separated term placental cells and in choriocarcinoma cell lines. The role of GKN1 for JEG-3 migration was studied using live cell imaging. E-cadherin, MMP-2 and -9, TIMP-1 and -2, as well as urokinase (uPA) expression levels were determined.

RESULTS

GKN1 is expressed in healthy third trimester placentas. Its expression is specifically limited to the extravillous trophoblast (EVT). GKN1 expression is significantly reduced in choriocarcinoma cell lines and gestational trophoblastic neoplasias. GKN1 attenuates the migration of JEG-3 choriocarcinoma cells in vitro, possibly via AKT-mediated induction of E-cadherin. GKN1 treatment reduced MMP-9 expression in JEG-3.

DISCUSSION

Besides its role in gastric physiology our results clearly indicate regulatory functions of GKN1 in the EVT at the feto-maternal interface during pregnancy. Based on our findings in the JEG-3 choriocarcinoma cell line, an auto-/paracrine role of GKN1 for EVT motility and villous anchorage at the basal plate is conceivable. Thus, the tumor suppressor GKN1 is expressed in placental EVT and might contribute to the regulation of EVT migration/invasion.