Understanding the genetic basis of gastric cancer: recent advances

Role of Helicobacter pylori in Gastric Carcinoma: A Review

Gastric cancer (GC) is one of the leading causes of cancer-related deaths globally. Gastritis caused by Helicobacter pylori (H. pylori) is a potent cause of gastrointestinal malignancies. The majority of all humans on the planet have H. pylori invasion in their stomachs, yet only a few diseased people develop GC. The human gastrointestinal system contains a broad population of microorganisms in addition to H. pylori. H. pylori heterogeneity has been studied because not all H. pylori diseases result in cancer. Individuals in the adult age group account for the bulk of gastric carcinoma cases. H. pylori has various strains, which is beneficial for its survival in host cell epithelium for a longer duration of time. Along with H. pylori, oral microbes have a major role in the pathogenicity of gastric carcinoma. The complex ecology of oral microbiota helps to defend against infections, preserve homeostasis, and regulate the immune system. In contrast, oral microbiota is involved in various mechanisms like anti-apoptotic activity, suppression of the immune system of the host, and initiation of chronic inflammation. These oral microbes are also responsible for the development of mutations. Interactions between the host immune system and bacteria promote the progression of cancer. For this review, various research articles were studied, and information was collected using databases like PubMed and Google Scholar. This review emphasizes on the role of H. pylori in gastric carcinoma, its pathogenesis, the role of various virulence factors and risk factors related to it, the role of oral microbiota in gastric carcinoma pathogenesis, diagnostic modalities, treatment options, and preventive measures for gastric carcinoma.

Profiles of alternative splicing events in the diagnosis and prognosis of Gastric Cancer

Background: Gastric cancer (GC) is a heterogeneous disease, and alternative splicing (AS) is a powerful universal transcriptional regulatory mechanism that contributes to the occurrence and development of cancer. However, the systematic analysis of AS events in GC is lacking; therefore, further studies are needed. Methods: Genome-wide analysis of AS events was performed using RNA-Seq data to evaluate the difference between GC and adjacent tissues at the AS level. Prognostic signatures based on differentially expressed alternative splicing (DEAS) events and a correlation network between DEAS and genes were built. Results: We identified 48,141 AS events, of which 2325 showed differential expression patterns. The parental genes before DEAS events play an essential role in regulating GC-related processes such as ribosome (FDR < 0.0001) and thermogenesis (FDR = 0.0002). There were 76 survival-associated DEAS cases. Stratifying patients according to the percent spliced in index value of six types of splicing patterns formed significant Kaplan-Meier curves in the overall survival analysis. A prognostic feature based on DEAS performed well for stratification in patients with GC. Conclusion: The present study will enrich our understanding regarding the distinction of GC and provide a generous amount of biomarkers and potential targets for the treatment of GC.

Design and optimize N-substituted EF24 as effective and low toxicity NF-κB inhibitor for lung cancer therapy via apoptosis-to-pyroptosis switch

As NF-κB signaling pathway is constitutively activated in lung cancer, targeting NF-κB has a potential for the treatment. EF24 has been proved to be a NF-κB inhibitor with good antitumor activity, while whose toxicity possibly became one of the obstacles to enter into clinical application. In order to find high efficiency and low toxicity NF-κB inhibitors, EF24 was modified and 13d was screened out. It was proved that 13d possessed an effective combination of inhibiting NF-κB pathway and showing lower cytotoxicity on normal cells as well as less toxicity in acute toxicity experiment compared with the lead compound of EF24. In addition, 13d was found to inhibit cell vitality, arrest cell cycle in G2/M phase, promote cell apoptosis, and suppress the xenograft tumor growth. Furthermore, 13d was elucidated to induce pyroptosis developing from apoptosis, which was associated with the inhibition of NF-κB. Taken together, it was suggested that 13d was a potent antitumor agent.

Molecular Diagnostics in Esophageal and Gastric Neoplasms: 2018 Update

Esophageal cancer (EC) is rapidly increasing in incidence in the United States. Genetic changes associated with the development of EC involve the p16, p53, and APC genes. Human epidermal growth factor 2 (HER-2) overexpression is seen in gastroesophageal junction carcinoma and a subset gastric carcinoma (GC). Interestingly, up to 50% cases of GC are related to Helicobacter pylori infection and up to 16% are related to EBV infection. Microsatellite instability is observed in up to 39% of GC and cell free nucleic acid analysis provides additional opportunities for diagnosis and prognosis of disease.

Concomitant modulation of PTEN and Livin in gastric cancer treatment

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Livin are important in the development of gastric cancer (GC). PTEN and Livin are involved in the regulation of tumor cell proliferation, migration and apoptosis. The modulation of PTEN or Livin has been investigated extensively in various cancer models. However, no studies have been performed to evaluate the combined effect of concurrently modulating these two genes on the development of GC. In the present study, the BGC823 human gastric carcinoma cell line was transfected with a dual gene modified vector (pCL-neo-PTEN-siLivin) in parallel with single gene modified vectors (pCL‑neo‑PTEN or pRNAT‑U6.1‑siLivin), and an empty control vector. Dual gene modulation (pCL‑neo‑PTEN‑siLivin) had a more marked effect on the inhibition of cell proliferation, induction of apoptosis, and reduction of cell penetration in Matrigel, compared with either single gene alone or empty vector transfection. In a xenograft nude mouse model, the inoculation of pCL‑neo‑PTEN‑siLivin‑transfected BGC823 cells led to a markedly reduced tumor burden, compared with that in all other inoculation groups. In conclusion, the overexpression of PTEN concomitant with Livin gene silencing was confirmed as a feasible and effective in vitro and in vivo gene modulation method, which may represent a potential therapeutic strategy for the treatment of GC.

Insulin-like growth factor binding protein-1 (IGFBP-1) upregulated by Helicobacter pylori and is associated with gastric cancer cells migration

Insulin-like growth factor binding protein-1 (IGFBP-1), a secreted protein, implicated of various cells in mediating the proliferation, migration, invasion, adhesion, survival and so on. In this study, we assessed the expression and release of IGFBP-1 from gastric cancer cells with H. pylori 26695 infection and the biological functions of IGFBP-1 in gastric cancer cells. The results showed that the expression and release of IGFBP-1 were increased in gastric cancer cells (MGC-803, BGC-823, SGC-7901) infected with H. pylori 26695. In addition, the upregulation of IGFBP-1 was dose-dependent in BGC-823 cells infected with H. pylori 26695 but not time-dependent. The upregulation of IGFBP-1 got to peak at 12h after H. pylori 26695 infection and then decreased over time. Subsequently, we measured its functions by silencing and overexpressing IGFBP1 which suggested that overexpression of IGFBP-1 could inhibit the migration of BGC-823 and SGC-7901 cells. However, knocking down the IGFBP-1 could increase the migration of BGC-823 and SGC-7901 cells. Functional findings illustrated that IGFBP-1 was implicated in H. pylori 26695-induced MMP-9 expression in BGC-823 cells. In addition, overexpressing IGFBP1 reduce the promoting effect of MMP-9 on the BGC-823 cells migration. In summary, we demonstrated that IGFBP-1 suppress the migration of BGC-823 cells and play a protective role in the process of H. pylori-induced gastric cancer.

Expression of Mismatch Repair Proteins in Early and Advanced Gastric Cancer in Poland

BACKGROUND Mutations in DNA of mismatch repair (MMR) genes result in failure to repair errors that occur during DNA replication in microsatellites, resulting in accumulation of frameshift mutations in these genes and leading to DNA mismatch replication errors and microsatellite instability. Gastric cancers (GCs) with high MSI (MSI-H) are a well-defined subset of carcinomas showing distinctive clinicopathological features. In this study we investigated the rate of MSI and the correlation between MSI status and clinicopathological features of GC. MATERIAL AND METHODS The study included 107 patients with GCs: 61 with advanced gastric cancers (AGC) and 46 with early gastric cancer (EGC). MSI deficiency in GCs was assessed by the immunohistochemical analysis of expression of MMR proteins - MLH1, MSH2, MSH6, and PMS2 - using formalin-fixed and paraffin-embedded tissue. RESULTS A total of 6 (5.6%) MSI-H were observed. The loss of MMR proteins expression was associated with the intestinal type of GC in Lauren classification, and tubular and papillary architecture in WHO classification. There was no statistically significant association between negative MMR expression and other selected clinical parameters: age, sex, tumor location, depth of invasion (EGC and AGC), lymph nodes status, presence of the ulceration, and lymphocytic infiltrate. CONCLUSIONS In the present era of personalized medicine, the histological type of GC and MMR proteins status in cancer cells are very important for the proper surveillance of patients with familial GC and sporadic GCs, as well as for selecting the proper follow-up and treatment. Larger collaborative studies are needed to verify the features of MSI-H GCs in Poland.

Alternative RNA splicing and gastric cancer

Alternative splicing (AS) linked to diseases, especially to tumors. Recently, more and more studies focused on the relationship between AS and gastric cancer (GC). This review surveyed the hot topic from four aspects: First, the common types of AS in cancer, including exon skipping, intron retention, mutually exclusive exon, alternative 5 ' or 3' splice site, alternative first or last exon and alternative 3' untranslated regions. Second, basic mechanisms of AS and its relationship with cancer. RNA splicing in eukaryotes follows the GT-AG rule by both cis-elements and trans-acting factors regulatory. Through RNA splicing, different proteins with different forms and functions can be produced and may be associated with carcinogenesis. Third, AS types of GC-related genes and their splicing variants. In this paper, we listed 10 common genes with AS and illustrated its possible molecular mechanisms owing to genetic variation (mutation and /or polymorphism). Fourth, the splicing variants of GC-associated genes and gastric carcinogenesis, invasion and metastasis. Many studies have found that the different splicing variants of the same gene are differentially expressed in GC and its precancerous diseases, suggesting AS has important implications in GC development. Taking together, this review highlighted the role of AS and splicing variants in the process of GC. We hope that this is not only beneficial to advances in the study field of GC, but also can provide valuable information to other similar tumor research.Although we already know some gene splicing and splicing variants play an important role in the development of GC, but many phenomena and mechanisms are still unknown. For example, how the tumor microenvironment and signal transduction pathway effect the forming and function of AS? Unfortunately, this review did not cover the contents because the current study is limited. It is no doubt that clarifying the phenomena and mechanisms of these unknown may help to reveal the relationship of AS with complex tumor genetic variation and the occurrence and development of tumors.

Ubiquitin-conjugating enzyme UbcH10 promotes gastric cancer growth and is a potential biomarker for gastric cancer

Gastric cancer is a fatal disease and the availability of early diagnostic methods is limited. There is an urgent need to identify effective targets for early diagnosis and therapeutics. UbcH10 is a ubiquitin-conjugating enzyme with high expression in various types of cancers. In the present study, several gastric tumor cell lines with high or low expression of UbcH10 were exploited to study the role of UbcH10 in gastric cancer. Knockdown of UbcH10 expression using siRNA in gastric cancer cell lines with high expression of UbcH10 resulted in reduced proliferation, increased cisplatin-induced apoptosis and reduced serum-induced ERK, Akt and p38 phosphorylation signaling. In agreement, overexpression of UbcH10 in gastric cancer cell lines with low expression of UbcH10 led to enhanced cell proliferation and resistance to cisplatin-induced apoptosis. Most importantly, IHC analyses showed that the UbcH10 protein was expressed at a high level in most patient gastric cancer tissues, but was absent in adjacent mesenchyme tissues. These data suggest that UbcH10 may promote gastric cancer growth and can serve as a biomarker for diagnosis or as a target for novel therapeutics in gastric cancer.

Helicobacter pylori in gastric carcinogenesis

Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently. This review focuses on multiple factors including microbial virulence factors, host genetic factors, and environmental factors, which can heighten the chance of occurrence of gastric adenocarcinoma due to H. pylori infection. Bacterial virulence factors are key components in controlling the immune response associated with the induction of carcinogenesis, and cagA and vacA are the most well-known pathogenic factors. Host genetic polymorphisms contribute to regulating the inflammatory response to H. pylori and will become increasingly important with advancing techniques. Environmental factors such as high salt and smoking may also play a role in gastric carcinogenesis. It is important to understand the virulence factors, host genetic factors, and environmental factors interacting in the multistep process of gastric carcinogenesis. To conclude, prevention via H. pylori eradication and controlling environmental factors such as diet, smoking, and alcohol is an important strategy to avoid H. pylori-associated gastric carcinogenesis.

Genetic variation and gastric cancer risk: a field synopsis and meta-analysis

BACKGROUND

Data on genetic susceptibility to sporadic gastric carcinoma have been published at a growing pace, but to date no comprehensive overview and quantitative summary has been available.

METHODS

We conducted a systematic review and meta-analysis of the evidence on the association between DNA variation and risk of developing stomach cancer. To assess result credibility, summary evidence was graded according to the Venice criteria and false positive report probability (FPRP) was calculated to further validate result noteworthiness. Meta-analysis was also conducted for subgroups, which were defined by ethnicity (Asian vs Caucasian), tumour histology (intestinal vs diffuse), tumour site (cardia vs non-cardia) and Helicobacter pylori infection status (positive vs negative).

RESULTS

Literature search identified 824 eligible studies comprising 2 530 706 subjects (cases: 261 386 (10.3%)) and investigating 2841 polymorphisms involving 952 distinct genes. Overall, we performed 456 primary and subgroup meta-analyses on 156 variants involving 101 genes. We identified 11 variants significantly associated with disease risk and assessed to have a high level of summary evidence: MUC1 rs2070803 at 1q22 (diffuse carcinoma subgroup), MTX1 rs2075570 at 1q22 (diffuse), PSCA rs2294008 at 8q24.2 (non-cardia), PRKAA1 rs13361707 5p13 (non-cardia), PLCE1 rs2274223 10q23 (cardia), TGFBR2 rs3087465 3p22 (Asian), PKLR rs3762272 1q22 (diffuse), PSCA rs2976392 (intestinal), GSTP1 rs1695 11q13 (Asian), CASP8 rs3834129 2q33 (mixed) and TNF rs1799724 6p21.3 (mixed), with the first nine variants characterised by a low FPRP. We also identified polymorphisms with lower quality significant associations (n=110).

CONCLUSIONS

We have identified several high-quality biomarkers of gastric cancer susceptibility. These data will form the backbone of an annually updated online resource that will be integral to the study of gastric carcinoma genetics and may inform future screening programmes.

Myeloid cell leukemia-1 promotes epithelial-mesenchymal transition of human gastric cancer cells

Epithelial-mesenchymal transition (EMT) is a critical process that occurs during cancer progression, and cancer stem cells have been shown to acquire the EMT phenotype. Myeloid cell leukemia-1 (Mcl-1) has been implicated in cancer progression and is overexpressed in a variety of human cancers. However, the interaction between Mcl-1 and EMT in human gastric cancer (GC) is unclear. We investigated the impact of Mcl-1 expression levels on EMT and the underlying signaling pathways in human GC cells. We used the human GC cell lines, AGS and SNU638, and small interfering RNAs (siRNAs) to evaluate the effects of Mcl-1 knockdown on cell adhesion, migration and invasion. Expression of Mcl-1 and other target genes was determined using reverse transcription-polymerase chain reaction assays and western blotting. The results revealed that expression levels of Mcl-1 mRNA and protein in the AGS and SNU638 cells were reduced following transfection with Mcl-1 siRNAs. Knockdown of Mcl-1 led to increased cellular adhesion to fibronectin and collagen. Expression levels of vimentin, MMP-2, MMP-9 and Snail protein were decreased following knockdown of Mcl-1. However, expression of E-cadherin was increased in the AGS cells following knockdown of Mcl-1. The expression of cancer stemness markers, such as CD44 and CD133, was not altered by knockdown of Mcl-1. Knockdown of Mcl-1 suppressed tumor cell migration and invasion in both human GC cell lines. Signaling cascades, including the β-catenin, MEK1/2, ERK1/2 and p38 pathways, were significantly blocked by knockdown of Mcl-1. Our results indicate that Mcl-1 expression induces EMT via β-catenin, MEK1/2 and MAPK signaling pathways, which subsequently stimulates the invasive and migratory capacity of human GC cells.

Molecular oncology testing in resource-limited settings

Cancer prevalence and mortality are high in developing nations, where resources for cancer control are inadequate. Nearly one-quarter of cancers in resource-limited nations are infection related, and molecular assays can capitalize on this relationship by detecting pertinent pathogen genomes and human gene variants to identify those at highest risk for progression to cancer, to classify lesions, to predict effective therapy, and to monitor tumor burden over time. Prime examples are human papillomavirus in cervical neoplasia, Helicobacter pylori and Epstein-Barr virus in gastric adenocarcinoma and lymphoma, and hepatitis B or C virus in hepatocellular cancer. Research is underway to engineer devices that overcome social, economic, and technical barriers limiting effective laboratory support. Additional challenges include an educated workforce, infrastructure for quality metrics and record keeping, and funds to sustain molecular test services. The combination of well-designed interfaces, novel and robust electrochemical technology, and telemedicine tools will promote adoption by frontline providers. Fast turnaround is crucial for surmounting loss to follow-up, although increased use of cell phones, even in rural areas, enhances options for patient education and engagement. Links to a broadband network facilitate consultation and centralized storage of medical data. Molecular technology shows promise to address gaps in health care through rapid, user-friendly, and cost-effective devices reflecting clinical priorities in resource-poor areas.

Molecular genetics of gastric adenocarcinoma in clinical practice

The molecular genetics of gastric carcinoma (GC) dictates their biology and clinical behavior. The two morphologically distinct types of gastric carcinoma by Lauren classification, i.e., intestinal and diffuse cell types, have a significant difference in clinical outcome. These two types of GC have different molecular pathogenetic pathways with unique genetic alterations. In addition to environmental and other etiologies, intestinal type GC is associated with Helicobacter pylori (H. pylori) infection and involves a multistep molecular pathway driving the normal epithelium to intestinal metaplasia, dysplasia, and malignant transformation by chromosomal and/or microsatellite instability (MSI), mutation of tumor suppressor genes, and loss of heterozygosity among others. Diffuse type shows no clear causal relationship with H. pylori infection, but is commonly associated with deficiency of cell-cell adhesion due to mutation of the E-cadherin gene (CDH1), and a manifestation of the hereditary gastric cancer syndrome. Thus, detection of CDH1 mutation or loss of expression of E-cadherin may aid in early diagnosis or screening of diffuse type GC. Detection of certain genetic markers, for example, MSI and matrix metalloproteinases, may provide prognostic information, particularly for intestinal type. The common genetic alterations may offer therapeutic targets for treatment of GC. Polymorphisms in Thymidylate synthase to metabolize 5-fluorouracil, glutathione S-transferase for degradation of Cisplatin, and amplification/overexpression of human epidermal growth factor receptor 2 targeted by monoclonal antibody Trastuzumab, are a few examples. P13K/Akt/mTOR pathway, c-Met pathways, epidermal growth factor receptor, insulin-like growth factor receptor, vascular endothelial growth factor receptor fibroblast growth factor receptor, and micro RNAs are several potential therapeutic biomarkers for GC under investigation.

A Golgi-specific protein PAQR3 is closely associated with the progression, metastasis and prognosis of human gastric cancers

BACKGROUND

The aim of this study is to determine whether PAQR3, a protein specifically localized in the Golgi apparatus, is associated with tumor progression, metastasis and survival of human patients with gastric cancer.

PATIENTS AND METHODS

PAQR3 expression status was investigated in a large panel of gastric cancer (n = 300) and their corresponding para-cancerous histological normal tissues (PCHNT) at both mRNA and protein levels. The correlation of PAQR3 expression levels with clinical features such as metastasis and prognosis was analyzed. The effect of PAQR3 on the growth and migration of gastric cancer cells was also determined.

RESULTS

PAQR3 was frequently down-regulated in gastric cancer samples compared with PCHNT at both mRNA and protein levels (both P < 0.0001). The expression level of PAQR3 was negatively correlated with Helicobacter pylori infection (P < 0.0001), tumor size (P < 0.0001), tumor stage (P < 0.0001), venous and lymphatic invasion (P < 0.0001), distant and nodal metastasis (P < 0.0001), and patient survival (P < 0.0001). Down-regulation of PAQR3 was highly correlated with increased epithelial-mesenchymal transition (EMT) in gastric cancer samples. In addition, PAQR3 overexpression was able to negatively modulate cell proliferation, migration and EMT of gastric cancer cells.

CONCLUSION

PAQR3 is markedly down-regulated in human gastric cancers. PAQR3 expression level is closely associated with the progression and metastasis of gastric cancers. PAQR3 is also a new genetic signature that can predict the prognosis of the patients with gastric cancer.

Recent advances and future trends in the targeted therapy of metastatic gastric cancer

The better understanding of the molecular mechanisms behind gastric cancer has led to the development of new therapeutic strategies that are likely to improve patient outcomes in the near future. Recently, targeting the HER2 and the VEGF pathways with trastuzumab and ramucirumab, respectively, have been found to improve survival, while directed therapies against a number of other pathways are under clinical evaluation. These include the hepatocyte growth factor and its receptor c-MET, the insulin-like growth factor 1, the fibroblast growth factor, the mammalian target of rapamycin (mTOR), the epidermal growth factor receptor, and other pathways, as well as relevant immunotherapeutic strategies. This article reviews recent advances and future trends of these concepts for gastric cancer and adenocarcinoma of the gastroesophageal junction.

Proteogenomic convergence for understanding cancer pathways and networks

During the past several decades, the understanding of cancer at the molecular level has been primarily focused on mechanisms on how signaling molecules transform homeostatically balanced cells into malignant ones within an individual pathway. However, it is becoming more apparent that pathways are dynamic and crosstalk at different control points of the signaling cascades, making the traditional linear signaling models inadequate to interpret complex biological systems. Recent technological advances in high throughput, deep sequencing for the human genomes and proteomic technologies to comprehensively characterize the human proteomes in conjunction with multiplexed targeted proteomic assays to measure panels of proteins involved in biologically relevant pathways have made significant progress in understanding cancer at the molecular level. It is undeniable that proteomic profiling of differentially expressed proteins under many perturbation conditions, or between normal and "diseased" states is important to capture a first glance at the overall proteomic landscape, which has been a main focus of proteomics research during the past 15-20 years. However, the research community is gradually shifting its heavy focus from that initial discovery step to protein target verification using multiplexed quantitative proteomic assays, capable of measuring changes in proteins and their interacting partners, isoforms, and post-translational modifications (PTMs) in response to stimuli in the context of signaling pathways and protein networks. With a critical link to genotypes (i.e., high throughput genomics and transcriptomics data), new and complementary information can be gleaned from multi-dimensional omics data to (1) assess the effect of genomic and transcriptomic aberrations on such complex molecular machinery in the context of cell signaling architectures associated with pathological diseases such as cancer (i.e., from genotype to proteotype to phenotype); and (2) target pathway- and network-driven changes and map the fluctuations of these functional units (proteins) responsible for cellular activities in response to perturbation in a spatiotemporal fashion to better understand cancer biology as a whole system.

Ethnic differences in gastric cancer genetic susceptibility: Allele flips of interleukin gene

Polymorphisms in promoter regions of inflammatory cytokines have been widely studied, and potentially functional polymorphisms have been discovered. Conflicting results from meta-analyses of interleukin (IL)-1B and IL-10 polymorphisms show differences in gastric cancer susceptibilities between Caucasian and Asian populations. In particular, we note the suggestion of an allele flip in IL-1B and IL-10 gene polymorphisms. In Asian populations, the IL-1B-1464G/-511C/-31T haplotype indicates risk for gastric cancer, while the opposite haplotype, IL-1B-1464C/-511T/-31C is the risk-related allele in Caucasians. Furthermore, while IL-10-1082G/-819C/-592C is associated with gastric cancer in Asians, IL-10-1082A/-819T/-592T is linked to gastric cancer risk in Caucasians. These seemingly contradictory results may be attributed to distinct carcinogenic mechanisms underlying the different gastric cancer subtypes. The allele flip observed in IL-10 and gastric cancer appears to reflect allelic heterogeneity, similar to that observed in IL-1B. In this review, we focus on the allele flip phenomenon observed between different ethnic groups in an effort to resolve certain controversial results from recent studies on interleukin polymorphism. In addition, we re-emphasize the importance of stratifying gastric cancer subtypes based on anatomical site and Lauren classification to prevent false associations arising through dilution of true ones.

Advances in molecular biomarkers for gastric cancer: miRNAs as emerging novel cancer markers

Carcinoma of the stomach is one of the most prevalent cancer types in the world. Although the incidence of gastric cancer is declining, the outcomes of gastric cancer patients remain dismal because of the lack of effective biomarkers to detect early gastric cancer. Modern biomedical research has explored many potential gastric cancer biomarker genes by utilising serum protein antigens, oncogenic genes or gene families through improving molecular biological technologies, such as microarray, RNA-Seq and the like. Recently, the small noncoding microRNAs (miRNAs) have been suggested to be critical regulators in the oncogenesis pathways and to serve as useful clinical biomarkers. This new class of biomarkers is emerging as a novel molecule for cancer diagnosis and prognosis, including gastric cancer. By translational suppression of target genes, miRNAs play a significant role in the gastric cancer cell physiology and tumour progression. There are potential implications of previously discovered gastric cancer molecular biomarkers and their expression modulations by respective miRNAs. Therefore, many miRNAs are found to play oncogenic roles or tumour-suppressing functions in human cancers. With the surprising stability of miRNAs in tissues, serum or other body fluids, miRNAs have emerged as a new type of cancer biomarker with immeasurable clinical potential.

Differential association of RANTES-403 and IL-1B-1464 polymorphisms on histological subtypes in male Korean patients with gastric cancer

The aims of this study were to elucidate the association between RANTES-403 and an increased risk of gastric cancer in Korean males and to investigate the gene-gene interaction between IL-1B and RANTES. In total, 218 male patients with gastric cancer (114 diffuse types, 97 intestinal types, and 7 mixed types) and 377 male controls were included. RANTES-403 was genotyped, and age-adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were estimated by logistic regression. A multifactor dimensionality reduction (MDR) test with three-way split interval validation confirmed by likelihood ratio and permutation analysis was carried out. A significant increase in the risk of gastric cancer for the intestinal-type group was observed for IL-1B-1464G carriers (OR = 2.535; 95% CI = 1.121-5.732; P = 0.02) as well as for those with IL-1B-1464 CG (OR = 2.342; 95% CI = 0.998-5.500; P = 0.05) or IL-1B-1464 GG (OR = 2.819; 95% CI = 1.170-6.793; P = 0.02). For the RANTES-403 genotype, there was no significant difference in the risk of gastric cancer between the overall gastric cancer and the control groups. When further stratified according to histological types, RANTES-403A carriers (OR = 1.743; 95% CI = 1.086-2.798; P = 0.021) or heterozygotes (OR = 1.791; 95% CI = 1.092-2.935; P = 0.021) showed increased risk for developing diffuse-type gastric cancer. MDR revealed a three-way locus-locus interaction between RANTES-403AA, IL-1B-1464GG, and IL-1B-511CT for diffuse-type gastric cancer in Korean males. We demonstrated that RANTES-403 was significantly associated with the risk of developing diffuse-type gastric cancer in men and found a possible gene-gene interaction between RANTES and IL-1B polymorphisms in gastric cancer carcinogenesis.

Up-regulation of CLDN1 in gastric cancer is correlated with reduced survival

Background

The genetic changes in gastric adenocarcinoma are extremely complex and reliable tumor markers have not yet been identified. There are also remarkable geographical differences in the distribution of this disease. Our aim was to identify the most differentially regulated genes in 20 gastric adenocarcinomas from a Norwegian selection, compared to matched normal mucosa, and we have related our findings to prognosis, survival and chronic Helicobacter pylori infection.

Methods

Biopsies from gastric adenocarcinomas and adjacent normal gastric mucosa were obtained from 20 patients immediately following surgical resection of the tumor. Whole genome, cDNA microarray analysis was performed on the RNA isolated from the sample pairs to compare the gene expression profiles between the tumor against matched mucosa. The samples were microscopically examined to classify gastritis. The presence of H. pylori was examined using microscopy and immunohistochemistry.

Results

130 genes showed differential regulation above a predefined cut-off level. Interleukin-8 (IL-8) and Claudin-1 (CLDN1) were the most consistently up-regulated genes in the tumors. Very high CLDN1 expression in the tumor was identified as an independent and significant predictor gene of reduced post-operative survival. There were distinctly different expression profiles between the tumor group and the control mucosa group, and the histological subsets of mixed type, diffuse type and intestinal type cancer demonstrated further sub-clustering. Up-regulated genes were mapped to cell-adhesion, collagen-related processes and angiogenesis, whereas normal intestinal functions such as digestion and excretion were associated with down-regulated genes. We relate the current findings to our previous study on the gene response of gastric epithelial cells to H. pylori infection.

Conclusions

CLDN1 was highly up-regulated in gastric cancer, and CLDN1 expression was independently associated with a poor post-operative prognosis, and may have important prognostic value. IL-8 and CLDN1 may represent central links between the gene response seen in acute H. pylori infection of gastric epithelial cells, and ultimately gastric cancer.

Molecular diagnostics in esophageal and gastric neoplasms

Esophageal carcinoma is the most rapidly increasing tumor in incidence in the United States. It has an established association with a precursor lesion (Barrett esophagus). Gastric carcinoma (GC) is the second leading cause of cancer death in the world. The prognosis for patients with advanced stage GC and esophageal carcinoma is poor. Human epidermal growth factor 2 (HER-2) overexpression is seen in gastroesophageal junction carcinoma and a subset of GC. HER-2 overexpressing tumors are eligible for HER-2 targeted therapies, which lead to a better survival in these patients.

Expression and prognostic significance of Livin in gastric cancer

Livin is one of the most important members of the inhibitor of apoptosis protein family. It is overexpressed in several types of tumors and may have prognostic significance. The present study investigated the biological role of Livin in the oncogenic behavior of gastric cancer cells, the expression of Livin in gastric cancer tissue and the relationship of its expression with various clinicopathological parameters and patient survival. Small interfering RNA blocked Livin gene expression in AGS and SNU638 human gastric cancer cell lines. The expression of Livin was investigated in gastric cancer tissues by RT-PCR, western blotting and immunohistochemistry. The associations with various clinicopathological parameters and survival were analyzed. Livin knockdown inhibited tumor cell migration, invasion and proliferation in AGS and SNU638 cells. Livin knockdown induced apoptosis by activating caspase-3, caspase-7 and PARP. Livin knockdown induced cell cycle arrest by a decrease in cyclin D1, cyclin-dependent kinase 4 and 6 and an increase in expression of p21 and p27. The ERK1/2 and JNK signaling pathways were inhibited by Livin knockdown. Livin expression was upregulated in gastric cancer tissues at the mRNA and protein levels. However, no significant correlation was found between Livin expression and various clinicopathological parameters including survival. In conclusion, Livin expression may be important in the alteration of invasive and oncogenic phenotypes of gastric cancer cells. The prognostic relevance of Livin remains unclear.

3,3'-Diindolylmethane suppresses the growth of gastric cancer cells via activation of the Hippo signaling pathway

Recent studies have revealed that 3,3-diindolylmethane (DIM) has antitumor effects in both in vivo and in vitro tumor models. However, the biological function of DIM in human gastric cancer cells is unknown. Genetic and biological studies have confirmed the importance of the novel Hippo tumor-suppressor pathway in regulating cell proliferation, apoptosis, organ size and tumorigenesis in mammals. Thus, the purpose of this study was to investigate the cytotoxic effects of DIM in human gastric cancer cells and to elucidate whether DIM induces cell death by activating the Hippo signaling pathway. Two human gastric cancer cell lines (SNU-1 and SNU-484) were used to investigate the DIM response. DIM significantly inhibited the proliferation of human gastric cancer cells in a dose-dependent manner. The percentage of G1 phase cells increased 24 h following DIM treatment. DIM reduced CDK2, CDK4, CDK6 and cyclin D1 protein levels, while increasing p53 protein levels. DIM induced the levels of cleaved poly(ADP-ribose) polymerase, cleaved-caspase-9, and diminished pro-caspase-3 protein production. In addition, DIM increased pLATS1, Mob1, pMob1, pYAP and Ras association domain family 1 (RASSF1) protein levels and reduced Yap protein production levels. DIM stimulated the binding of RASSF1 with the Mst1/2-LATS1-Mob1 complex, promoting an active Hippo signaling pathway and favoring YAP phosphorylation (pYAP) that inactivates cell proliferation. Furthermore, DIM inhibited the growth of human gastric tumors in a xenograft mouse model. These results indicate that DIM suppresses the growth of gastric cancer cells by activating the Hippo signaling pathway.

Expression of early growth response-1 in human gastric cancer and its relationship with tumor cell behaviors and prognosis

The early growth response-1 (Egr-1) is crucial in many cell regulatory processes related to the progression of human cancers. Its overexpression has been demonstrated in variable human cancers and may have prognostic significance. The aims of this current study were to evaluate whether Egr-1 affects invasive and oncogenic phenotypes of human gastric cancer cells, and to examine the relationships between its expression and various clinicopathological parameters, including survival in human gastric cancer patients. We investigated the biologic role of Egr-1 in tumor cell behavior by using a small interfering RNA in human gastric cancer cell lines, AGS and TMK1. The expression of Egr-1 by reverse transcription-polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry was investigated in human gastric cancer tissues. The knockdown of Egr-1 suppressed tumor cell migration and invasion in AGS and TMK1 cells. Egr-1 expression was significantly increased in human gastric cancer and metastatic lymph node tissues compared to the normal gastric mucosa and non-metastatic lymph node tissues. Positive expression of Egr-1 was significantly associated with tumor size, depth of invasion, lymph node metastasis, tumor stage and poor survival. These results indicate that Egr-1 is associated with human gastric cancer progression through the alteration of tumor cell behavior, such as migration and invasion. Egr-1 expression may help in predicting the clinical outcomes of human gastric cancer patients.

Associations of three common polymorphisms in CD95 and CD95L promoter regions with gastric cancer risk

There are many studies performed to assess the associations of CD95 A670G and G1377A polymorphisms with gastric cancer, and the association of CD95L T844C polymorphism with gastric cancer risk, but the data are remaining controversial. To get a comprehensive assessment of the association above, we performed a meta-analysis of published studies. PubMed, Embase, Web of Science, and Wanfang Medicine databases were searched for eligible studies. There were eight studies including 3,790 subjects on CD95 A670G polymorphism, eight studies including 4,563 subjects on CD95 G1377A polymorphism, and eight studies including 4,563 subjects on CD95L T844C polymorphism. Overall, CD95 G1377A polymorphism was associated with a significantly increased risk of gastric cancer (for AA versus GG: odds ratio (OR) = 1.24, 95 % confidence interval (95 % CI) = 1.02-1.52, P = 0.030; for AA versus GG + GA: OR = 1.27, 95 % CI = 1.05-1.53, P = 0.012). However, there were no associations of CD95 A670G and CD95L T844C polymorphisms with gastric cancer. Subgroup analysis by ethnicity found similar associations in Asians, but the associations in Caucasians were still unclear owing to the lack of relevant data. Therefore, the outcomes of this meta-analysis show that there is a significant association between CD95 G1377A polymorphism and risk of gastric cancer.