Genetic changes in Slovenian patients with gastric adenocarcinoma evaluated in terms of microsatellite DNA

[Update on gastric cancer. New molecular classifications]

Gastric cancer (GC) is an aggressive tumor, which is usually diagnosed at an advanced stage and shows high mortality rates. Several GC classifications have been published, based on features such as tumor location, endoscopic features or microscopic architecture. However, TNM stage remains the mainstay of GC management and treatment. In the last years, technical advances have allowed us to investigate the biological heterogeneity of GC and develop new molecular classifications. This knowledge may enhance current classifications, and has the potential to refine GC management and aid in the identification of new molecular targets. In this literature review we have summarized the main findings in epidemiology, screening, classification systems and treatment of GC, focusing on the molecular alterations and new molecular classifications published in the last years.

Gene expression profile analysis of ENO1 knockdown in gastric cancer cell line MGC-803

Gastric cancer (GC) is the third leading cause of cancer-associated mortality. In a previous study, we identified that α-enolase (ENO1) promoted cell migration in GC, but the underlying molecular mechanisms remain to be fully elucidated. In the present study, small interfering RNAs were identified to interfere with ENO1 expression. The cDNA expression profiling was performed using an Affymetrix mRNA array platform to identify genes that may be associated with ENO1 in human GC cell line MGC-803. The differentially expressed genes (DEGs) were identified using the reverse transcription-quantitative polymerase chain reaction, followed by a series of bioinformatic analyses. As a result, there were 448 DEGs, among which 183 (40.85%) were downregulated. The most significant functional terms for the DEGs were the nuclear lumen for cell components (P=2.83×10⁻⁴), transcription for biological processes (P=3.7×10⁻⁷) and transcription factor activity for molecular functions (P=1.16×10⁴). In total, six significant pathways were enriched, including the most common cancer-associated forkhead box O signaling pathway (P=0.0077), microRNAs in cancer (P=0.0183) and the cAMP signaling pathway (P=0.0415). Furthermore, a network analysis identified three hub genes (HUWE1, PPP1CB and HSPA4), which were all involved in tumor metastasis. Taken together, the DEGs, significant pathways and hub genes identified in the present study shed some light on the molecular mechanisms of ENO1 involved in the pathogenesis of GC.

Meta-analysis of microsatellite instability in relation to clinicopathological characteristics and overall survival in gastric cancer

BACKGROUND

Several associations between microsatellite instability (MSI) and other clinicopathological factors have been reported in gastric cancer, but the results have been ambiguous. This systematic review and meta-analysis investigated the relationship between MSI and overall survival and clinicopathological characteristics of patients with gastric cancer.

METHODS

A systematic literature search of the PubMed, Cochrane and Ovid databases until 31 January 2016 was performed in accordance with the PRISMA statement. The articles were screened independently according to PICO (population, intervention, comparator, outcome) eligibility criteria. All eligible articles were evaluated independently by two reviewers for risk of bias according to the Quality In Prognosis Study tool.

RESULTS

Overall, 48 studies with a total of 18 612 patients were included. MSI was found in 9·2 per cent of patients (1718 of 18 612), and was associated with female sex (odds ratio (OR) 1·57, 95 per cent c.i. 1·31 to 1·89; P < 0·001), older age (OR 1·58, 2·20 to 1·13; P < 0·001), intestinal Laurén histological type (OR 2·23, 1·94 to 2·57; P < 0·001), mid/lower gastric location (OR 0·38, 0·32 to 0·44; P < 0·001), lack of lymph node metastases (OR 0·70, 0·57 to 0·86, P < 0·001) and TNM stage I-II (OR 1·77, 1·47 to 2·13; P < 0·001). The pooled hazard ratio for overall survival of patients with MSI versus those with non-MSI gastric cancer from 21 studies was 0·69 (95 per cent c.i. 0·56 to 0·86; P < 0·001).

CONCLUSION

MSI in gastric cancer was associated with good overall survival, reflected in several favourable clinicopathological tumour characteristics.

EBV infection and MSI status significantly influence the clinical outcomes of gastric cancer patients

BACKGROUND

Epstein-Barr virus (EBV) and microsatellite instability (MSI) are associated with the carcinogenesis of many kinds of tumors, including gastric cancer (GC). However, the impact of EBV and MSI status on the prognosis of stage II and III GC is still unclear. The aim of this study was to find out the prognostic value of EBV and MSI status in a population of GC patients from Southern China.

METHODS

Patients were genotyped for EBV infection based on the detection of EBV DNA from the formalin-fixed paraffin-embedded (FFPE) specimens. Sequentially, MSI status was measured by direct sequencing. Clinical characteristics and overall survival (OS) were analyzed in 202 GC patients. Additionally, the association of EBV and MSI status with chemotherapy-based toxicity was analyzed in 324 GC patients.

RESULTS

The survival analysis revealed EBV+ patients had a poorer OS than EBV- patients (HR=1.75, 95% CI: 1.08-2.82, FDR p=0.04). This survival advantage for EBV- patients was also found in patients <60y (FDR p=0.04) and patient with stage III disease (FDR p=0.04).

CONCLUSIONS

EBV infection and MSI status are associated with overall survival of gastric cancer patients. However, traditional chemotherapy showed no difference on outcome of patients in EBV and MSI subgroups.

Gastric carcinoma in canines and humans, a review

Gastric carcinoma (GC) is the most common neoplasm in the stomach of dogs. Although incidence in the general population is reported to be low, breed-specific GC has a high incidence. Median age at presentation ranges from 8 to approximately 10 years. The disease is mostly located in the lesser curvature and antropyloric region of the stomach. Unfortunately, diagnosis is usually made when the disease is at an advanced stage and, therefore, prognosis is poor. Due to similarities in clinical presentation, diagnosis, histology and prognosis, canine GC may serve as a valuable model for human GC. Extensive pedigrees of canine gastric carcinoma cases could reveal insights for human gastric carcinoma. Putative species differences include the role of Helicobacter in pathogenesis, the wide array of genetic data and screening available for humans, and treatment protocols that are available for human GC.

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.

Molecular alterations in gastric cancer with special reference to the early-onset subtype

Currently, gastric cancer (GC) is one of the most frequently diagnosed neoplasms, with a global burden of 723000 deaths in 2012. It is the third leading cause of cancer-related death worldwide. There are numerous possible factors that stimulate the pro-carcinogenic activity of important genes. These factors include genetic susceptibility expressed in a single-nucleotide polymorphism, various acquired mutations (chromosomal instability, microsatellite instability, somatic gene mutations, epigenetic alterations) and environmental circumstances (e.g., Helicobcter pylori infection, EBV infection, diet, and smoking). Most of the aforementioned pathways overlap, and authors agree that a clear-cut pathway for GC may not exist. Thus, the categorization of carcinogenic events is complicated. Lately, it has been claimed that research on early-onset gastric carcinoma (EOGC) and hereditary GC may contribute towards unravelling some part of the mystery of the GC molecular pattern because young patients are less exposed to environmental carcinogens and because carcinogenesis in this setting may be more dependent on genetic factors. The comparison of various aspects that differ and coexist in EOGCs and conventional GCs might enable scientists to: distinguish which features in the pathway of gastric carcinogenesis are modifiable, discover specific GC markers and identify a specific target. This review provides a summary of the data published thus far concerning the molecular characteristics of GC and highlights the outstanding features of EOGC.

Molecular classification of gastric cancer

Gastric cancer (GC), a heterogeneous disease characterized by epidemiologic and histopathologic differences across countries, is a leading cause of cancer-related death. Treatment of GC patients is currently suboptimal due to patients being commonly treated in a uniform fashion irrespective of disease subtype. With the advent of next-generation sequencing and other genomic technologies, GCs are now being investigated in great detail at the molecular level. High-throughput technologies now allow a comprehensive study of genomic and epigenomic alterations associated with GC. Gene mutations, chromosomal aberrations, differential gene expression and epigenetic alterations are some of the genetic/epigenetic influences on GC pathogenesis. In addition, integrative analyses of molecular profiling data have led to the identification of key dysregulated pathways and importantly, the establishment of GC molecular classifiers. Recently, The Cancer Genome Atlas (TCGA) network proposed a four subtype classification scheme for GC based on the underlying tumor molecular biology of each subtype. This landmark study, together with other studies, has expanded our understanding on the characteristics of GC at the molecular level. Such knowledge may improve the medical management of GC in the future.

Genetics of gastric cancer

Gastric cancer remains highly prevalent and accounts for a notable proportion of global cancer mortality. This cancer is also associated with poor survival rates. Understanding the genetic basis of gastric cancer will offer insights into its pathogenesis, help identify new biomarkers and novel treatment targets, aid prognostication and could be central to developing individualized treatment strategies in the future. An inherited component contributes to <3% of gastric cancers; the majority of genetic changes associated with gastric cancer are acquired. Over the past few decades, advances in technology and high-throughput analysis have improved understanding of the molecular aspects of the pathogenesis of gastric cancer. These aspects are multifaceted and heterogeneous and represent a wide spectrum of several key genetic influences, such as chromosomal instability, microsatellite instability, changes in microRNA profile, somatic gene mutations or functional single nucleotide polymorphisms. These genetic aspects of the pathogenesis of gastric cancer will be addressed in this Review.

Is microsatellite instability a prognostic marker in gastric cancer? A systematic review with meta-analysis

BACKGROUND AND OBJECTIVE

The relationship between survival in gastric cancer patients and the status of microsatellite instability (MSI) has not yet been established. The purpose of this meta-analysis was to obtain integrated and more precise data for the value of MSI as a prognostic marker in gastric cancer.

METHODS

A comprehensive systematic review and meta-analysis were conducted using major electronic databases (PubMed, EMBASE, and the Cochrane Central) with keywords related to "microsatellite instability," "gastric cancer," and "prognosis."

RESULTS

Twenty-four studies with 5,438 participants (712 cases were MSI gastric cancer) were included for pooling risk estimates of MSI in gastric cancer. Seventeen studies reported overall survival. The pooled hazard ratio (HR) for overall survival of MSI vs. non-MSI was 0.72 (95%CI: 0.59-0.88, P = .001) in a random-effects model. In the sensitivity analysis, the result from the most recent study showed the most heterogeneity.

CONCLUSION

MSI gastric cancer was associated with good prognosis but there was heterogeneity in the recent studies. Changed epidemiology and effects of chemotherapy are potential causes of heterogeneity. Establishing a consensus for defining MSI in gastric cancer should be preferred for future studies.

Microsatellite instability is associated with a better prognosis for gastric cancer patients after curative surgery

BACKGROUND

Microsatellite instability (MSI) is one of the leading mechanisms for the carcinogenesis of gastric cancer. Its prognostic value is controversial.

METHODS

Between May 1988 and Oct 2003, a total of 214 gastric cancer patients undergoing curative surgery were enrolled, and their MSI statuses were classified as MSI-H (high) or MSI-L/S (low/stable). The clinicopathologic characteristics of MSI-H and MSI-L/S gastric cancers were compared.

RESULTS

The MSI-H tumors accounted for 11.7 % (n = 25) of the 214 total gastric cancers. Although not statistically significant, the MSI-H gastric cancers were more frequently located in the lower third of the stomach (64 % vs. 49.2 %) and were more often the intestinal type (72 % vs. 61.4 %) compared to the MSI-L/S gastric cancers. The MSI-H gastric cancers had a significantly better 5-year overall survival (OS) rate (68 % vs. 47.6 %, p = 0.030) and a trend of a better 3-year disease-free survival rate (71.8 % vs. 55.2 %, p = 0.076) compared to the MSI-L/S gastric cancers. A multivariate analysis revealed that pathologic TNM stage and MSI status were the independent prognostic factors for OS after curative surgery.

CONCLUSIONS

Compared to MSI-L/S tumors, MSI-H tumors are associated with a better OS rate for gastric cancer patients after R0 resection.

Molecular Pathology of Gastrointestinal Cancer

The purpose of this review is to discuss important molecular changes that aid decision making in patient management and play a role in emerging treatment strategies for gastrointestinal malignancies. Although screening and surveillance practices have had an impact on the natural history of some tumor types, gastric carcinoma is a major cause of morbidity and mortality in high prevalence regions and colorectal carcinoma is still the fourth leading cause of cancer related death in the United States.

Understanding the genetic basis of gastric cancer: recent advances

Two major gastric cancer histological subtypes are recognized with distinct morphology, epidemiology, pathogenesis and clinical behavior. Genetically, the intestinal and diffuse subtypes are also characterized by distinct germline susceptibility patterns and somatic aberrations. Helicobacter pylori is strongly associated with both Lauren's subtypes, although the underlying carcinogenic mechanisms are unique. Risk is modulated by strain-specific virulence factors, host responses and specific host-microbe interactions. Somatic aberrations in gastric cancer are driven by three major mechanisms, namely chromosomal instability, microsatellite instability and epigenetic alterations. These processes drive carcinogenesis in both Lauren's subtypes; however, the relative contribution of these processes and the specific genes aberrated differ. Moving beyond Lauren's subtypes, next-generation techniques have identified major genomic subtypes that have prognostic impact and exhibit distinct response patterns to standard cytotoxics.

Genetic aspects of gastric cancer instability

Unravelling the molecular mechanisms underlying gastric carcinogenesis is one of the major challenges in cancer genomics. Gastric cancer is a very complex and heterogeneous disease, and although much has been learned about the different genetic changes that eventually lead to its development, the detailed mechanisms still remain unclear. Malignant transformation of gastric cells is the consequence of a multistep process involving different genetic and epigenetic changes in numerous genes in combination with host genetic background and environmental factors. The majority of gastric adenocarcinomas are characterized by genetic instability, either microsatellite instability (MSI) or chromosomal instability (CIN). It is believed that chromosome destabilizations occur early in tumour progression. This review summarizes the most common genetic alterations leading to instability in sporadic gastric cancers and its consequences.

Analysis of genomic instability in adult-onset celiac disease patients by microsatellite instability and loss of heterozygosis

BACKGROUND AND AIMS

Malignant complications of celiac disease (CD) include carcinomas and lymphomas. The genetic basis behind cancer development in CD is not known, but acquisition of genetic abnormalities and genomic instability has been involved. The aim of this study was to explore molecular characteristics of genomic instability in CD patients by analyzing microsatellite instability (MSI) and loss of heterozygosis (LOH) with carefully selected microsatellites.

METHODS

We genotyped small bowel biopsies and peripheral blood samples from 20 untreated CD patients using five microsatellites related to MMR genes (panel A), and five repeats associated with tumor suppressor genes, chromosome instability, inflammation, and cancer (panel B).

RESULTS

Genomic instability was found in seven out of 20 (35%) cases at: D5S107, D18S58, GSTP, TP53 or DCC, being TP53 the most frequently affected (five out of seven cases; 71%). Microsatellite alterations were significantly found using panel B markers (P=0.04). No cases with high frequency of MSI and replication error phenotype were detected. Only one case displayed MSI-L alone. Three patients exhibited LOH and three other cases showed LOH with low level of MSI, being classified as having chromosome instability phenotype.

CONCLUSION

Two novel observations were found in this study: first, the finding that non-neoplastic cells from a group of untreated CD patients present genomic instability at nucleotide level; and second, the advantage to use carefully selected microsatellites to identify celiac patients with molecular instability. Our data support the existence of chromosome instability phenotype in CD, suggesting that stable and unstable patients are genomically distinct subtypes that may follow a different evolution.

Interaction of microsatellite instability and loss of heterozygosity in adenocarcinoma: multiple markers in adenocarcinoma: an introduction to 'Genetic changes in Slovenian patients with gastric adenocarcinoma evaluated in terms of microsatellite DNA'

Gastric cancer is the second most frequent cause of cancer death worldwide, yet the precise mechanisms underlying the different subtypes of gastric carcinogenesis are poorly understood. Improvements in the diagnosis and prognosis of gastric cancer over classical clinicopathologic findings such as TNM stage, age or macroscopic tumor type, now include novel techniques for superficial endoscopic examination, and new strategies for genetically analyzing biopsied specimens. The development of gastric adenocarcinomas, such as that of many tumor classes, represents the cumulative effects of several different types of mutations, and it is now recognized that both the loss of normal DNA repair, as well as the mutation, loss or inhibition of tumor suppressor genes contribute to the genetic instability leading to cancer. It might be logically anticipated that the combined burden of these two defects would synergize in carcinogenesis, but the extent to which such pathways cooperate in promoting cancer is still not yet well understood. Clearly, an enhanced appreciation of the mechanisms and interactions of these pathways would aid development of diagnosis and treatment options.