Role of Notch signaling pathway in gastric cancer pathogenesis

Helicobacter pylori-activated fibroblasts as a silent partner in gastric cancer development

The discovery of Helicobacter pylori (Hp) infection of gastric mucosa leading to active chronic gastritis, gastroduodenal ulcers, and MALT lymphoma laid the groundwork for understanding of the general relationship between chronic infection, inflammation, and cancer. Nevertheless, this sequence of events is still far from full understanding with new players and mediators being constantly identified. Originally, the Hp virulence factors affecting mainly gastric epithelium were proposed to contribute considerably to gastric inflammation, ulceration, and cancer. Furthermore, it has been shown that Hp possesses the ability to penetrate the mucus layer and directly interact with stroma components including fibroblasts and myofibroblasts. These cells, which are the source of biophysical and biochemical signals providing the proper balance between cell proliferation and differentiation within gastric epithelial stem cell compartment, when exposed to Hp, can convert into cancer-associated fibroblast (CAF) phenotype. The crosstalk between fibroblasts and myofibroblasts with gastric epithelial cells including stem/progenitor cell niche involves several pathways mediated by non-coding RNAs, Wnt, BMP, TGF-β, and Notch signaling ligands. The current review concentrates on the consequences of Hp-induced increase in gastric fibroblast and myofibroblast number, and their activation towards CAFs with the emphasis to the altered communication between mesenchymal and epithelial cell compartment, which may lead to inflammation, epithelial stem cell overproliferation, disturbed differentiation, and gradual gastric cancer development. Thus, Hp-activated fibroblasts may constitute the target for anti-cancer treatment and, importantly, for the pharmacotherapies diminishing their activation particularly at the early stages of Hp infection.

Comprehensive bioinformatic analysis of mind bomb 1 gene in stomach adenocarcinoma

BACKGROUND

The carcinogenesis of stomach adenocarcinoma (STAD) involves many different molecules and multiple pathways, including the NOTCH signaling pathway. As a key factor that functions as a critical link in the NOTCH pathway, mind bomb 1 (MIB1) is upregulated in various tumors and has been reported to promote cell metastasis and invasion. However, studies on the role of MIB1 in STAD are limited. Here, we evaluated the prognostic value of MIB1 in STAD and its association with immune infiltration and copy number variation.

AIM

To elucidate the relationship between MIB1 gene and gastric cancer (GC) and provide a new idea for the treatment of GC.

METHODS

We identified mutations in the MIB1 gene by searching the cBioPortal database and then analyzed their relationship with the overall survival rate and disease-free survival rate using the Kaplan-Meier method. The Cancer Genome Atlas (TCGA) database provided transcript levels for MIB1 in STADs and normal tissues. As a method of distinguishing the STAD tissues from adjacent normal tissues, a receiver operating characteristic (ROC) curve was generated. Kaplan-Meier plotter was used to determine the effect of MIB1 expression on survival. Based on the LinkedOmics database, we were able to identify the coexpressed genes of the MIB1 gene, the top 50 positively correlated genes, and the top 50 negatively correlated genes. STRING was used to construct protein-protein interaction networks related to the MIB1 gene. An analysis of functional enrichment was carried out using the R package “Cluster Profiler”. The relationships between mRNA expression of MIB1 and immune infiltrates were assessed by Tumor IMmune Estimation Resource (TIMER) and the “GSVA package” in R.

RESULTS

According to the cBioPortal database, the MIB1 mutation rate in 287 patients in the TCGA dataset was approximately 6%. Kaplan-Meier survival analysis showed that patients with STAD in the mutated group had a worse prognosis than those in the unmutated group (P = 0.0156). There was a significant upregulation of MIB1 expression in STAD tissues compared to adjacent normal tissues. A high T stage was associated with increased MIB1 mRNA expression. The ROC curve analysis revealed 59.4% sensitivity and 85.6% specificity of MIB1 for differentiating STAD tissues from adjacent normal tissues at a truncation level of 2.248. Kaplan-Meier plotter indicated that patients with higher MIB1 levels had a worse prognosis than those with lower levels (26.4 mo vs 56.2 mo, P = 0.0330). A correlation analysis demonstrated an association between immune infiltrates and MIB1 mRNA expression.

CONCLUSION

Upregulation of MIB1 expression is significantly associated with poor survival rate and immune infiltration in gastric adenocarcinoma. MIB1 may be a biomarker for the poor prognosis of STAD patients and a potential immunotherapeutic target.

Signaling pathways of oxidative stress response: the potential therapeutic targets in gastric cancer

Gastric cancer is one of the top causes of cancer-related death globally. Although novel treatment strategies have been developed, attempts to eradicate gastric cancer have been proven insufficient. Oxidative stress is continually produced and continually present in the human body. Increasing evidences show that oxidative stress contributes significantly to the development of gastric cancer, either through initiation, promotion, and progression of cancer cells or causing cell death. As a result, the purpose of this article is to review the role of oxidative stress response and the subsequent signaling pathways as well as potential oxidative stress-related therapeutic targets in gastric cancer. Understanding the pathophysiology of gastric cancer and developing new therapies for gastric cancer depends on more researches focusing on the potential contributors to oxidative stress and gastric carcinogenesis.

Tumor Microenvironment, Clinical Features, and Advances in Therapy for Bone Metastasis in Gastric Cancer

Gastric cancer (GC) is one of the most malignant neoplasms worldwide, accounting for about 770,000 deaths in 2020. The incidence of gastric cancer bone metastasis (GC-BM) is low, about 0.9–13.4%, and GC patients develop GC-BM because of a suitable bone microenvironment. Osteoblasts, osteoclasts, and tumor cells interact with each other, secreting cytokines such as PTHrP, RANK-L, IL-6, and other growth factors that disrupt the normal bone balance and promote tumor growth. The functions and numbers of immune cells in the bone microenvironment are continuously inhibited, resulting in bone balance disorder due to the cytokines released from destroyed bone and growing tumor cells. Patients with GC-BM are generally younger than 65 years old and they often present with a later stage of the disease, as well as more aggressive tumors. They usually have shorter overall survival (OS) because of the occurrence of skeletal-related events (SREs) and undetected bone destruction due to the untimely bone inspection. Current treatments of GC-BM focus mainly on gastric cancer and SRE-related treatment. This article reviews the clinical features, possible molecular pathogeneses, and the most commonly used diagnostic methods and treatments of bone metastasis in gastric cancer.

Understanding the Complex Milieu of Epithelial-Mesenchymal Transition in Cancer Metastasis: New Insight Into the Roles of Transcription Factors

Epithelial-mesenchymal transition (EMT) is a physiological program during which polarised, immobile epithelial cells lose connection with their neighbours and are converted to migratory mesenchymal phenotype. Mechanistically, EMT occurs via a series of genetic and cellular events leading to the repression of epithelial-associated markers and upregulation of mesenchymal-associated markers. EMT is very crucial for many biological processes such as embryogenesis and ontogenesis during human development, and again it plays a significant role in wound healing during a programmed replacement of the damaged tissues. However, this process is often hijacked in pathological conditions such as tumour metastasis, which constitutes the most significant drawback in the fight against cancer, accounting for about 90% of cancer-associated mortality globally. Worse still, metastatic tumours are not only challenging to treat with the available conventional radiotherapy and surgical interventions but also resistant to several cytotoxic agents during treatment, owing to their anatomically diffuse localisation in the body system. As the quest to find an effective method of addressing metastasis in cancer intervention heightens, understanding the molecular interplay involving the signalling pathways, downstream effectors, and their interactions with the EMT would be an important requisite while the challenges of metastasis continue to punctuate. Unfortunately, the molecular underpinnings that govern this process remain to be completely illuminated. However, it is becoming increasingly clear that EMT, which initiates every episode of metastasis, significantly requires some master regulators called EMT transcription factors (EMT-TFs). Thus, this review critically examines the roles of TFs as drivers of molecular rewiring that lead to tumour initiation, progression, EMT, metastasis, and colonisation. In addition, it discusses the interaction of various signalling molecules and effector proteins with these factors. It also provides insight into promising therapeutic targets that may inhibit the metastatic process to overcome the limitation of “undruggable” cancer targets in therapeutic design and upturn the current spate of drug resistance. More so, it extends the discussion from the basic understanding of the EMT binary switch model, and ultimately unveiling the E/M cellular plasticity along a phenotypic spectrum via multiple trans-differentiations. It wraps up on how this knowledge update shapes the diagnostic and clinical approaches that may demand a potential shift in investigative paradigm using novel technologies such as single-cell analyses to improve overall patient survival.

The role of Notch ligand, Delta-like ligand 4 (DLL4), in cancer angiogenesis—implications for therapy

Background

It is generally accepted that angiogenesis is a complex and tightly regulated process characterized by the growth of blood vessels from existing vasculature. Activation of the Notch signalling pathway affects multiple aspects of vascular development. One of the components of the Notch signalling pathway, Delta-like ligand 4 (DLL4), has recently appeared as a critical regulator of tumour angiogenesis and thus as a promising therapeutic target.

Methods

This review article includes available data from peer-reviewed publications associated with the role of DLL4 in cancer angiogenesis. Searches were performed in PubMed, EMBASE, Google Scholar and Web of Science using the terms “tumour angiogenesis”, “DLL4”, “Notch signalling” and “anti-cancer therapy”.

Results

The survival curves of cancer patients revealed that the patients with high DLL4 expression levels had significantly shorter survival times than the patients with low DLL4 expression. Moreover, a positive correlation was also identified between DLL4 and VEGF receptorsʼ expression levels. It seems that inhibition of DLL4 may exert potent growth inhibitory effects on some tumours resistant to anti-VEGF therapies. A great number of blocking agents of DLL4/Notch signalling including anti-DLL4 antibodies, DNA vaccination, Notch antibodies and gamma-secretase inhibitors have been studied in preclinical tumour models.

Conclusion

DLL4 seems to be a promising target in anti-cancer therapy. Nevertheless, the careful evaluation of adverse effects on normal physiological processes in relation to therapeutic doses of anti-DLL4 drugs will be significant for advancement of DLL4 blocking agents in clinical oncology.

The clinical significance of Notch1 immunoexpression in Caucasian patients with colorectal adenocarcinoma

Introduction

Colorectal cancer (CRC) is traditionally regarded as the most commonly diagnosed gastrointestinal malignant disease. Nevertheless, despite advances in diagnosis and novel therapeutic options, the clinical outcomes of patients are still not satisfactory.

Aim

To investigate the clinicopathological and prognostic roles of Notch1 expression, the immunohistochemical investigation was performed in samples of CRC tumour tissues, adjacent non-pathological mucosa, and metastatic foci in regional lymph nodes in Caucasian patients.

Material and methods

Paraffin-embedded adenocarcinoma samples were assessed immunohistochemically for Notch1 protein and scored according to the percentage of cells with a positive reaction combined with staining intensity. Connections between Notch1 immunoexpression and clinicopathological factors including the 5-year overall survival (OS) were evaluated.

Results

The level of the Notch1 immunohistochemical reactivity was correlated with the grade of the histological differentiation, size of the primary tumour, regional lymph node involvement, and perineural invasion (all p < 0.001). Kaplan-Meier survival analysis showed that the survival time for patients with a low expression of Notch1 was significantly longer than that for patients with moderate or strong level of Notch1 immunoreactivity (p < 0.001).

Conclusions

The enhanced level of Notch1 immunoexpression was significantly associated with malignancy-related clinicopathological factors and reduced the 5-year overall survival in CRC patients.

The Relevance of Transcription Factors in Gastric and Colorectal Cancer Stem Cells Identification and Eradication

Gastric and colorectal cancers have a high incidence and mortality worldwide. The presence of cancer stem cells (CSCs) within the tumor mass has been indicated as the main reason for tumor relapse, metastasis and therapy resistance, leading to poor overall survival. Thus, the elimination of CSCs became a crucial goal for cancer treatment. The identification of these cells has been performed by using cell-surface markers, a reliable approach, however it lacks specificity and usually differs among tumor type and in some cases even within the same type. In theory, the ideal CSC markers are those that are required to maintain their stemness features. The knowledge that CSCs exhibit characteristics comparable to normal stem cells that could be associated with the expression of similar transcription factors (TFs) including SOX2, OCT4, NANOG, KLF4 and c-Myc, and signaling pathways such as the Wnt/β-catenin, Hedgehog (Hh), Notch and PI3K/AKT/mTOR directed the attention to the use of these similarities to identify and target CSCs in different tumor types. Several studies have demonstrated that the abnormal expression of some TFs and the dysregulation of signaling pathways are associated with tumorigenesis and CSC phenotype. The disclosure of common and appropriate biomarkers for CSCs will provide an incredible tool for cancer prognosis and treatment. Therefore, this review aims to gather the new insights in gastric and colorectal CSC identification specially by using TFs as biomarkers and divulge promising drugs that have been found and tested for targeting these cells.

MicroRNA-140-5p inhibits cell proliferation, migration and promotes cell apoptosis in gastric cancer through the negative regulation of THY1-mediated Notch signaling

Studies have highlighted the importance of microRNAs (miRs) in the development of various cancers, including gastric cancer (GC), a commonly occurring malignancy, accompanied by high recurrence and metastasis rate. The aim of the current study was to investigate the role of miR-140-5p in GC. Microarray expression profiles were initially employed to screen the differentially expressed gene related to GC, and the miR regulating the gene was predicted accordingly. The data obtained indicated that thymus cell antigen 1 (THY1) was differentially expressed in GC and confirmed to be a target gene of miR-140-5p. Poorly expressed miR-140-5p and highly expressed THY1 were observed in the GC tissues. SGC-7901 cells were treated with miR-140-5p mimic/inhibitor, siRNA against THY1 and siRNA against Notch1 in order to determine their regulatory roles in GC cell activities. The relationship of miR-140-5p, THY1 and the Notch signaling pathway was subsequently identified. Moreover, cell proliferation, migration, invasion and apoptosis were determined using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), wound-healing, transwell assay and flow cytometry, respectively. The overexpression of miR-140-5p and silencing of THY1 resulted in a diminished expression of the Notch signaling pathway-related proteins, as well as inhibited proliferation, migration and invasion of GC cells, enhanced expression of pro-apoptotic proteins in addition to elevated apoptosis rate. Taken together, the present study suggests that miR-140-5p directly targets and negatively regulates THY1 expression and inhibits activation of the Notch signaling pathway, whereby the up-regulation of miR-140-5p inhibits development of GC, highlighting the promise of miR-140-5p as a potential target for GC treatment.

ADAM17 promotes lymph node metastasis in gastric cancer via activation of the Notch and Wnt signaling pathways

Disintegrin and metalloproteinase domain-containing proteins (ADAMs) have been implicated in cell adhesion, signaling and migration. The aim of the present study was to identify key members of the ADAM protein family associated with the metastasis of gastric cancer and to evaluate their clinical significance. A total of 193 patients with gastric cancer and positive lymph node metastasis were enrolled. Key members of the ADAM family associated with lymph node metastasis were identified. The correlations between survival times and the clinicopathological features of patients were investigated. Furthermore, ADAM17 expression in gastric cancer cells with different metastatic potentials was determined. ADAM17 was overexpressed in BGC-823 cells and suppressed in SGC-7901 cells to further investigate its effects on cell viability and migration. The key pathways associated with ADAM17 were identified by gene set enrichment analysis (GSEA). It was found that ADAM9 and ADAM17 were significantly upregulated in gastric cancer and positive metastatic lymph node tissues. Further, there was a strong correlation between the survival times of patients and ADAM17 expression. ADAM17 was upregulated in gastric cancer cells with high metastatic potential. The viability of BGC-823 cells significantly increased following ADAM17 overexpression, whereas the viability and migration of SGC-7901 cells decreased following ADAM17 suppression. GSEA and western blot analysis revealed a positive correlation between the Notch and Wnt signaling pathways with ADAM17 expression. In conclusion, the increased expression of ADAM17 promoted the progression of gastric cancer, potentially via Notch and/or Wnt signaling pathway activation, and ADAM17 may serve as a useful prognostic marker.

Concurrent Treatment with Anti-DLL4 Enhances Antitumor and Proapoptotic Efficacy of a γ-Secretase Inhibitor in Gastric Cancer

The Notch signaling pathway has been identified as a therapeutic target for cancers. γ-Secretase inhibitors (GSIs) have been progressively recognized as potential anticancer drugs. The present study aimed to investigate the effects of anti-delta like legend 4 (anti-DLL4) treatment on the anticancer efficacy of GSIs in gastric cancer. SGC-7901-GFP human gastric cancer cells were tested for DLL4 expression by rosette formation test and immunofluorescence, and then were treated with anti-DLL4 antibody N-[N-(3,5-difluorophenacetyl)-L-ananyl]-S-phenylglycine t-butyl ester (DAPT, a type of GSI), or a combination of anti-DLL4 antibody and DAPT. The effects of in vitro treatments on cell apoptosis, cell cycle, and cell invasion were analyzed. For in vivo study, an orthotopic mouse model of gastric cancer was established with green fluorescence expressing SGC-7901. Ultrasound targeted microbubble destruction was used to treat tumor-bearing mice with anti-DLL4 antibody conjugated microbubbles, DAPT, and a combination of the two. Real-time fluorescence imaging was performed to assess tumor cell inhibition in each group. Following in vivo treatments, apoptosis of tumor cells and the expression of apoptosis-related genes BAX, Bcl-2, and P53 were detected by TUNEL and immunohistochemical staining. In vivo combined treatment of anti-DLL4 and DAPT led to a higher rate of cell apoptosis and greater inhibition of cell invasion than that observed with DAPT treatment alone. DAPT and anti-DLL4 combination therapy resulted in decreased cell distribution at G1 phase and increased cell distribution at S phase, compared to the untreated control group (P < .01). In vivo combined therapy with anti-DLL4 and DAPT significantly increased tumor growth inhibition and tumor cell apoptosis when compared to DAPT therapy alone (P < .05). In addition, combined treatment significantly increased expression of BAX and P53 and reduced Bcl-2 expression (P < .05). Conversely, treatment with DAPT alone only increased expression of BAX and P53 (P < .05), suggesting that the reduction of Bcl-2 expression may play an important role in the synergetic antitumor and proapoptosis effects of the combined treatment. Concurrent treatment with anti-DLL4 enhances the antitumor and proapoptotic efficacy of the γ-secretase inhibitor in gastric cancer both in vitro and in vivo.

Combination treatment of all-trans retinoic acid (ATRA) and γ-secretase inhibitor (DAPT) cause growth inhibition and apoptosis induction in the human gastric cancer cell line

Current medication for gastric cancer patients has a low success rate with resistance and side effects. According to recent studies, γ-secretase inhibitors is used as therapeutic drugs in cancer. Moreover, all-trans retinoic acid (ATRA) is a natural compound proposed for the treatment/chemo-prevention of cancers. The aim of this study was to explore the effects of ATRA in combination with N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT) as γ-secretase inhibitor on viability and apoptosis of the AGS and MKN-45 derived from human gastric cancer. AGS and MKN-45 gastric cancer cell lines were treated with different concentrations of ATRA or DAPT alone or ATRA plus DAPT. The viability, death detection and apoptosis of cells was examined by MTT assay and Ethidium bromide/acridine orange staining. The distribution of cells in different phases of cell cycle was also evaluated through flow cytometry analyses. In addition, caspase 3/7 activity and the expression of caspase-3 and bcl-2 were examined. DAPT and ATRA alone decreased gastric cancer cells viability in a concentration dependent manner. The combination of DAPT and ATRA exhibited significant synergistic inhibitory effects. The greater percentage of cells were accumulated in G0/G1 phase of cell cycle in combination treatment. The combination of DAPT and ATRA effectively increased the proportion of apoptotic cells and the level of caspase 3/7 activities compared to single treatment. Moreover, augmented caspase-3 up-regulation and bcl-2 down-regulation were found following combined application of DAPT and ATRA. The combination of DAPT and ATRA led to more reduction in viability and apoptosis in respect to DAPT or ATRA alone in the investigated cell lines.

Crosstalk between the Notch signaling pathway and non-coding RNAs in gastrointestinal cancers

The Notch signaling pathway is one of the main signaling pathways that mediates direct contact between cells, and is essential for normal development. It regulates various cellular processes, including cell proliferation, apoptosis, migration, invasion, angiogenesis and metastasis. It additionally serves an important function in tumor progression. Non-coding RNAs mainly include small microRNAs, long non-coding RNAs and circular RNAs. At present, a large body of literature supports the biological significance of non-coding RNAs in tumor progression. It is also becoming increasingly evident that cross-talk exists between Notch signaling and non-coding RNAs. The present review summarizes the current knowledge of Notch-mediated gastrointestinal cancer cell processes, and the effect of the crosstalk between the three major types of non-coding RNAs and the Notch signaling pathway on the fate of gastrointestinal cancer cells.

[The cellular and molecular mechanisms of angiogenesis regulation in the brain]

This review presents the data on cellular and molecular mechanisms of angiogenesis regulation linked to the vascular epithelium. According to current conceptions, activated endothelial cells and their predecessors (progenitor cells) are involved in the regulation of angiogenesis. These cells synthesize angiogenic molecules differing by the chemical structure and mechanism of biological effect and allowing a direct or indirect control over each stage of angiogenesis. Both the excess and insufficient angiogenesis can lead to fast and irreversible changes in nervous tissue under certain conditions. For this reason, the balance in the system of molecular stimulators and inhibitors of angiogenesis is especially important for brain function. Without adequate reperfusion of an affected brain area the post-stroke neuroreparation, which can be provided with timely stimulation of angiogenesis, is unattainable and the intensification of this process in tumors, on the contrary, has adverse consequences. Growth of a tumor and its metastatic spread are substantially associated with an increase in the level of tumor tissue vascularization, and blocking angiogenesis is often the only productive way to limit the growth of a tumor. However our knowledge of mechanisms of angiogenesis regulation in the brain on the cellular and molecular level in physiological and pathological conditions is still insufficient, and, therefore, the influence of angiogenic factors on tissue targets do not always cause the expected effects.

Notch and its oncogenic activity in human malignancies

BACKGROUND

Increasing evidence has demonstrated that Notch signaling is deregulated in human hematological malignancies and solid tumors. This signaling has a protumorigenic effect but may also act as a tumor suppressor. How induction of a single pathway gives rise to the opposite effects in different cell types is still unknown.

METHODS

This review article includes available data from peer-reviewed publications associated with the role of Notch signaling during cancer pathogenesis.

RESULTS

Numerous reports have indicated that alterations in Notch signaling and its oncogenic activity were originally associated with the pathogenesis of T‑cell acute lymphoblastic leukemia/lymphoma (T-ALL), an aggressive hematologic tumor affecting children and adolescents. The possibility that Notch could play a significant role in human breast cancer development comes from studies on mouse mammary tumor virus-induced cancer. Numerous findings over the past several years have indicated that alterations in Notch signaling are also responsible for ovarian cancer development. Mention should also be made of the connection between expression of Notch 3 and increased resistance to chemotherapy, which remains a major obstacle to successful treatment. Notch as an oncogenic factor is also involved in the development of colon cancer, lung carcinoma and Kaposi's sarcoma.

CONCLUSION

Notch is a binary cell fate determinant and its overexpression has been described as oncogenic in a wide array of human malignancies. This finding led to interest in therapeutically targeting this pathway, especially by the use of gamma-secretase inhibitors (GSIs) blocking the cleavage of Notch receptors at the cell membrane by the inhibition of Notch intracellular domain (NICD) releasing. Preclinical cancer models have revealed that GSIs suppress the growth of cancers such as pancreatic, breast and lung cancer.

The role of Notch signaling in gastric carcinoma: molecular pathogenesis and novel therapeutic targets

Notch signaling, an evolutionarily conserved signaling cascade system, is involved in promoting the progression of different types of cancers. Within the past decades, the Notch signaling pathway has increasingly been shown to have a primary role in deciding the fate of cancer cells and cancer stem cells in the stomach. Most components of Notch signaling are strongly expressed at different levels in gastric carcinoma tissue samples and are associated with a considerable number of clinical parameters. Moreover, crosstalk signaling between the Notch pathway and the Wnt, Ras, and NF-κB pathways promotes the process of gastric carcinogenesis. Consequently, this increases proliferation and prevents apoptosis in gastric cancer cells, and it contributes to the induction of angiogenesis and accelerates the progression of the epithelial-to-mesenchymal transition. Although the Notch signaling pathway presents novel therapeutic targets for cancer therapeutic intervention, there is still a dearth of in-depth understanding of the molecular mechanisms of Notch signaling in gastric carcinoma. In this review, we summarize the landscape of the Notch signaling pathway and recent findings on Notch signaling in gastric cancer. Furthermore, advanced studies and clinical treatments targeting the Notch signaling pathway arediscussed.

Notch signalling pathway as an oncogenic factor involved in cancer development

Notch signalling is an evolutionarily conserved signalling pathway, which plays a significant role in a wide array of cellular processes including proliferation, differentiation, and apoptosis. Nevertheless, it must be noted that Notch is a binary cell fate determinant, and its overexpression has been described as oncogenic in a broad range of human malignancies. This finding led to interest in therapeutically targeting this pathway especially by the use of GSIs, which block the cleavage of Notch at the cell membrane and inhibit release of the transcriptionally active NotchIC subunit. Preclinical cancer models have clearly demonstrated that GSIs suppress the growth of such malignancies as pancreatic, breast, and lung cancer; however, GSI treatment in vivo is associated with side effects, especially those within the gastrointestinal tract. Although intensive studies are associated with the role of γ-secretase in pathological states, it should be pointed out that this complex impacts on proteolytic cleavages of around 55 membrane proteins. Therefore, it is clear that GSIs are highly non-specific and additional drugs must be designed, which will more specifically target components of the Notch signalling.

Clinical significance of NOTCH1 intracellular cytoplasmic domain translocation into the nucleus in gastric cancer

Recent studies have shown constitutive activation of the Notch signaling pathway in various types of malignancies. However, it remains unclear whether this signaling pathway is activated in gastric cancer. In the present study, the aim was to investigate the role of Notch signaling in gastric cancer by investigating the subcellular localization of Notch-associated proteins in tissue samples from gastric cancer patients. Samples were obtained from 115 gastric cancer patients who had undergone surgery at the Department of Gastroenterological Surgery, Nagoya City University Graduate School of Medical Science without pre-operative chemotherapy or radiation. Subsequently the correlation between translocation of NOTCH1 intracellular cytoplasmic domain (NICD) into the nucleus (as measured by immunostaining) and survival in gastric cancer patients after surgery was investigated. The results were analyzed in reference to the patients' clinicopathological characteristics and the effects of these results on patient prognosis were determined. Significant correlations were observed between NICD nuclear localization and clinicopathological characteristics, such as tumor status (T factor), lymph node status (N factor), pathological stage and differentiation status. No significant correlations were observed between NICD nuclear localization and age, gender, tumor location, vein invasion or lymphatic invasion. Patients with >30% of cancer cell nuclei positively stained for NICD (as revealed by immunostaining) were associated with a significantly shorter survival following surgery than patients with <30% NICD-positive cancer cell nuclei (log-rank test, P=0.0194). Univariate analysis revealed that among the clinicopathological factors examined, T factor [risk rate (RR)=10.870; P=0.0016], N factor (RR=41.667; P=0.0003), lymphatic invasion (RR=13.158; P=0.0125), vein invasion (RR=25.000; P= 0.0019) and translocation of NICD to the nucleus (RR=3.937; P=0.0312) were all identified to be statistically significant prognostic factors. However, multivariate analysis revealed that translocation of NICD to the nucleus was not independently associated with an unfavourable prognosis in patients with gastric cancer. The present results suggest that NOTCH1 acts as an oncogene in gastric cancer. It is hypothesized that translocation of NICD into the nucleus may be used as a therapeutic target in gastric cancer.

Molecular classification of gastric cancer: Towards a pathway-driven targeted therapy

Gastric cancer (GC) is the third leading cause of cancer mortality worldwide. Although surgical resection is a potentially curative approach for localized cases of GC, most cases of GC are diagnosed in an advanced, non-curable stage and the response to traditional chemotherapy is limited. Fortunately, recent advances in our understanding of the molecular mechanisms that mediate GC hold great promise for the development of more effective treatment strategies. In this review, an overview of the morphological classification, current treatment approaches, and molecular alterations that have been characterized for GC are provided. In particular, the most recent molecular classification of GC and alterations identified in relevant signaling pathways, including ErbB, VEGF, PI3K/AKT/mTOR, and HGF/MET signaling pathways, are described, as well as inhibitors of these pathways. An overview of the completed and active clinical trials related to these signaling pathways are also summarized. Finally, insights regarding emerging stem cell pathways are described, and may provide additional novel markers for the development of therapeutic agents against GC. The development of more effective agents and the identification of biomarkers that can be used for the diagnosis, prognosis, and individualized therapy for GC patients, have the potential to improve the efficacy, safety, and cost-effectiveness for GC treatments.

New Concepts in Cancer Biomarkers: Circulating miRNAs in Liquid Biopsies

The effective and efficient management of cancer patients relies upon early diagnosis and/or the monitoring of treatment, something that is often difficult to achieve using standard tissue biopsy techniques. Biological fluids such as blood hold great possibilities as a source of non-invasive cancer biomarkers that can act as surrogate markers to biopsy-based sampling. The non-invasive nature of these “liquid biopsies” ultimately means that cancer detection may be earlier and that the ability to monitor disease progression and/or treatment response represents a paradigm shift in the treatment of cancer patients. Below, we review one of the most promising classes of circulating cancer biomarkers: microRNAs (miRNAs). In particular, we will consider their history, the controversy surrounding their origin and biology, and, most importantly, the hurdles that remain to be overcome if they are really to become part of future clinical practice.

Gastric cancer stem cells: evidence, potential markers, and clinical implications

Gastric cancer is a significant global health problem. It is the fifth most common cancer and third leading cause of cancer-related death worldwide (Torre et al. in CA Cancer J Clin 65(2):87-108, 2015). Despite advances in treatment, overall prognosis remains poor, due to tumour relapse and metastasis. There is an urgent need for novel therapeutic approaches to improve clinical outcomes in gastric cancer. The cancer stem cell (CSC) model has been proposed to explain the high rate of relapse and subsequent resistance of cancer to current systemic treatments (Vermeulen et al. in Lancet Oncol 13(2):e83-e89, 2012). CSCs have been identified in many solid malignancies, including gastric cancer, and have significant clinical implications, as targeting the CSC population may be essential in preventing the recurrence and spread of a tumour (Dewi et al. in J Gastroenterol 46(10):1145-1157, 2011). This review seeks to summarise the current evidence for CSC in gastric cancer, with an emphasis on candidate CSC markers, clinical implications, and potential therapeutic approaches.

Circulating tumour cells predict survival in gastric cancer patients: a meta-analysis

AIM OF THE STUDY

The prognostic value of the detection of circulating tumour cells (CTCs) in gastric cancer has been studied intensely in recent years. However, the application of different technologies led to inconsistent results between the studies. Here, we performed a meta-analysis of published studies to summarise the evidence.

MATERIAL AND METHODS

Medline and ISI Web of Knowledge were searched up to March 2013 using "circulating tumor cells" and "gastric cancer" as search terms. Hazard ratio (HR) with 95% confidence intervals (CIs) for prognostic outcomes and clinical characteristics were extracted from each study. Pooled hazard ratios (HR) and odds ratios (OR) were calculated using random or fixed-effects models.

RESULTS

Twelve studies enrolling 774 patients were included. The combined HR estimate for overall survival (OS), disease-free survival (DFS), and progression-free survival (PFS) were 1.41 (95% CI: 1.28-1.62), 2.99 (95% CI: 2.01-4.45) and 1.64 (95% CI: 1.02-2.62), respectively. Subgroup analysis concerning detection methods and sampling time showed that results of RT-PCR for the OS group and RT-PCR for the DFS group suggest a prognostic significance of CTC detection (pooled HR [95% CI]: 1.45 [1.28-1.65], I(2) = 38%, p = 0.13; 2.99 [2.01-4.45], I(2) = 0%, p = 0.32). In addition, results of the baseline CTC detection group also indicated a significant prognostic value to predict OS and DFS (pooled HR [95% CI]: 1.47 [1.19-1.82], I(2) = 38%, p = 0.14; 2.99 [2.01-4.45], I(2) = 0%, p = 0.32). We simultaneously found that the detection of CTCs correlated with pathological stage (pooled OR [95% CI]: 2.95 [1.65-5.28], I(2) = 56%, p = 0.03), lymph node status (pooled OR [95% CI]: 2.26 [1.50-3.41], I(2) = 37%, p = 0.09), the depth of invasion (pooled OR [95% CI]: 3.21 [1.38-7.43], I(2) = 72%, p = 0.002), and distant metastasis (pooled OR [95% CI]: 2.68 [1.25-5.73], I(2) = 43%, p = 0.15).

CONCLUSIONS

Detection of CTCs is associated with poorer prognosis in gastric cancer patients.

Notch2 signaling contributes to cell growth, invasion, and migration in salivary adenoid cystic carcinoma

Many studies have explored whether the Notch signaling pathway has a tumor-suppressive or an oncogenic role in various tumors; however, the role of the Notch signaling pathway in salivary adenoid cystic carcinoma (SACC) is still unknown. In this study, we attempt to define the role of Notch2 signaling in cell growth, invasion, and migration in SACC. We compared Notch2 expression in clinical SACC samples with that of normal samples by using immunohistochemical staining. Then, we down-regulated Notch2 expression to observe the effect of Notch2 on proliferation, invasion, migration, and the expression of known target genes of Notch signal pathway. According to our results, Notch2 expression was higher in SACC tissues compared with normal tissues. Knockdown of Notch2 inhibited cell proliferation, invasion, and migration in vitro and down-regulated the expression of HEY2 and CCND1. The results of this study suggest that Notch2 has an essential role in the cell growth, invasion, and migration of SACC. Notch2 may therefore be a potential target gene for the treatment of SACC by interfering with cell growth and metastasis.

Gastric tumor-initiating CD44+ cells and epithelial-mesenchymal transition are inhibited by γ-secretase inhibitor DAPT

It has been proposed that the Notch signaling pathway may serve a pivotal role in cellular differentiation, proliferation and apoptosis. However, the function of Notch signaling in gastric cancer stem cells (GCSCs) is largely unknown. The present study aimed to delineate the role of the Notch1 pathway in GCSCs and during epithelial-mesenchymal transition (EMT). Flow cytometry was used to isolate CD44⁺ cells from the human gastric cancer cell line, MKN45. CD44⁺ cells displayed the characteristics of CSCs and exhibited higher Notch1 expression compared with CD44^- cells. To investigate the role of the Notch1 pathway in GCSCs, CD44⁺ cells were treated with the γ-secretase inhibitor DAPT. DAPT treatment inhibited the expression of the Notch1 downstream target Hes1 and EMT markers, suppressed the properties of CSCs and impaired the invasion and proliferation capabilities of CD44⁺ cells. In addition, intraperitoneal treatment with DAPT effectively inhibited the growth of CD44⁺ cell xenograft tumors. The present study indicated that CD44⁺ GCSCs possess the characteristics of CSCs and that the Notch1 pathway serves a critical role in the maintenance of CSCs and EMT.

NOTCH3 gene polymorphism is associated with the prognosis of gliomas in Chinese patients

Recent studies show that NOTCH3 is involved in the glioma development and it is also a prognostic factor for glioma patients. However, the gene polymorphism of NOTCH3 in gliomas prognosis remains unknown.A total of 266 patients were enrolled into this study. The NOTCH3 gene polymorphism at 3 loci, including C>T polymorphism at nucleotide 381, C>A polymorphism at 474 and G>A polymorphism at 684 were determined. All patients received the surgical treatment and/or chemotherapy and/or radiotherapy.We found that the 684G>A polymorphism affects the tumor NOTCH3 expression level and is closely associated with a higher tumor grade, poorer tumor differentiation, and karnofsky performance score in these glioma patients. More importantly, the 684G>A polymorphism is significantly associated with the prognosis of these patients regardless of their treatment manner.Our study indicates that the NOTCH3 gene 684G>A polymorphism may be used as a prognosis marker for gliomas.

The aberrant overexpression of vimentin is linked to a more aggressive status in tumours of the gastrointestinal tract

Vimentin is an intermediate filament protein normally expressed in cells of mesenchymal origin, e.g. myofibroblasts, chondrocytes, macrophages, and endothelial cells. The expression of vimentin, which has been thought of as the main mesenchymal marker, is also detected in tumour tissue. In tumours of the gastrointestinal tract vimentin expression is usually correlated with advanced stage of tumour, lymph node metastasis, and patient survival.

Delta-like ligand 4 (Dll4) predicts the prognosis of clear cell renal cell carcinoma, and anti-Dll4 suppresses tumor growth in vivo

The Delta-like ligand 4 (Dll4) and Notch signaling pathway plays a key role in embryonic vascular development and tumor growth. In this study, we measured the expression of Dll4 in clear cell renal cell carcinoma (ccRCC) and explored the correlation between Dll4 and ccRCC. We used sh-Dll4 treatment in a nude mouse model to observe the effect that inhibition of the Dll4/Notch pathway had on angiogenesis and vasculogenesis. We found up-regulation of Dll4 to be closely correlated with distant metastasis and worse overall survival. Cox regression analysis showed that Dll4 might be a prognostic marker of ccRCC. Blockade of Dll4/Notch signaling inhibited tumor growth in the mouse model via anti-angiogenesis and anti-vasculogenesis effects. We concluded that Dll4 might be a novel therapeutic target for the treatment of ccRCC.

Gastric cancer cell growth and epithelial-mesenchymal transition are inhibited by γ-secretase inhibitor DAPT

The Notch signaling pathway may be important in the development and progression of several malignancies. However, the functions of Notch signaling in epithelial-mesenchymal transition (EMT) remain largely unknown. The aim of the present study was to delineate Notch1 expression in gastric cancer (GC) and its function in GC EMT. Using quantitative polymerase chain reaction and western blot analysis, the expression of Notch1 was found to increase in GC cell lines compared with the normal gastric mucosa cell line. In addition, Notch1 expression was found to be downregulated in the non-metastatic-derived GC cell line compared with the metastatic-derived cell line. Furthermore, Notch1 expression was significantly increased in the tumor tissues compared with the adjacent normal mucosa tissues, as well as in patients with metastases than in patients without metastases. To explore the role of the Notch1 signaling pathway in EMT, the GC cell lines, AGS and MKN45, were treated with γ-secretase inhibitor DAPT. Using MTT, Transwell and clonality assays, DAPT was found to inhibit the expression of the Notch1 downstream target, Hes1, and impair the ability of the GC cell lines to migrate, invade and proliferate. The protein levels of the mesenchymal markers, vimentin, neural cadherin and Snail, were decreased; however, the expression of the epithelial marker, epithelial cadherin, was increased in the GC cell lines treated with DAPT. These results indicated that the Notch1 signaling pathway may be important in the development and progression of GC. In conclusion, DAPT inhibits the Notch1 signaling pathway, as well as the growth, invasion, metastasis and EMT of GC cells.