Molecular analysis of gastric cancer identifies subtypes associated with distinct clinical outcomes

Potentially Curable Cancers of the Esophagus and Stomach

Gastric and gastroesophageal adenocarcinomas continue to be a major health burden globally and collectively represent the third leading cause of cancer death. Among patients with metastatic disease, most die of their cancer because of the limited number of modestly effective treatment regimens available today. The progress against these cancers has been slow compared with many other solid tumors despite many attempts. In-depth molecular profiling has also not been completed. Even when these cancers are localized, they impose considerable challenges for the patient, relatives, and treatment team alike. Localized gastric or gastroesophageal cancer is best managed with a multidisciplinary approach. This review focuses on the management of localized cancers by reviewing the current literature and explaining certain principles that help guide therapy for these patients. The future, however, will afford numerous opportunities, including exploitation of initial data from The Cancer Genome Atlas, to identify novel targets and drugs, harness the prowess of the immune system, and customize therapy for each patient.

FGFR2 in gastric cancer: protein overexpression predicts gene amplification and high H-index predicts poor survival

FGFR2 gene amplification, and resulting FGFR2 protein overexpression, is rare in gastric cancer patients, and development of an accurate and widely available method for mass screening to identify patients who may respond to treatment with fibroblast growth factor receptor (FGFR) inhibitors is important. We first screened 312 gastric cancer patients with known copy number variations by FGFR2b immunohistochemistry using FPR2-D, an isoform-specific antibody. Next, we performed immunohistochemistry on tissue microarrays from 1574 gastric cancer patients. Selected cases were analyzed for FGFR2 amplification by FISH. In addition, FGFR2b overexpression was studied in 88 matched primary and metastatic gastric cancers. In the first cohort, FGFR2b immunohistochemistry results correlated very well with those of copy number variation (r=0.79) and FISH (r=1.0). In total, FGFR2b overexpression was identified in 73 of 1974 gastric cancers (4%). The concordance between immunohistochemistry and FISH was extremely high; all 2+ and 3+ cases identified by immunohistochemistry were FGFR2 amplified. In the matched primary and metastatic gastric cancer pairs, the positivity and percentage of positive tumor cells were significantly higher in metastatic gastric cancers than in primary gastric cancers (8% vs 3% and 75% vs 47%, respectively; P<0.001). FGFR2b overexpression was significantly more frequent in gastric cancers with diffuse subtype (P=0.01) and higher N stage (P=0.006). FGFR2b overexpression with H-score ≥150 were independent prognostic factors for overall survival with hazard ratio of 1.836 (95% confidence interval, 1.034-3.261; P=0.038). FGFR2b positivity in immunohistochemistry was strongly correlated with FGFR2 amplification. Given the low frequency of FGFR2 amplification in gastric cancers, FGFRb2 immunohistochemistry is an accurate screening tool to detect FGFR2 amplification, and both primary and metastatic gastric cancer tissues should be tested to select gastric cancer patients for treatment with FGFR2 inhibitors.

SOX9 Elevation Acts with Canonical WNT Signaling to Drive Gastric Cancer Progression

Gastric cancer remains one of the leading causes of global cancer mortality due to therapy resistance, with Helicobacter pylori (H. pylori) infection being a major risk factor. In this study, we report the significance of an elevation of the stem cell regulator SOX9 in bacteria-infected human gastritis and cancer samples, paralleling increased levels of TNFα SOX9 elevation was more intense in specimens containing the pathogenically significant cagA+ strains of H. pylori Notably, we found that SOX9 was required for bacteria-induced gastric cancer cell proliferation, increased levels of β-catenin, and acquisition of stem cell-like properties. Analysis of three large clinical cohorts revealed elevated SOX9 levels in gastric cancer with advanced tumor stage and poor patient survival. Functionally, SOX9 silencing in gastric cancer cells enhanced apoptosis and senescence, concomitantly with a blockade to self-renewal and tumor-initiating capability. Paralleling these effects, we also found SOX9 to mediate cisplatin chemoresistance associated with reduced disease-free survival. Mechanistic interactions between SOX9 and β-catenin expression suggested the existence of a regulatory role for SOX9 targeting the WNT canonical pathway. Taken together, our findings establish the significance of SOX9 in gastric cancer pathobiology and heterogeneity, with implications for targeting WNT-SOX9 signaling as a rational therapeutic strategy. Cancer Res; 76(22); 6735-46. ©2016 AACR.

Gastric cancer adjuvant therapy

From a global perspective, gastric cancer is one of the most common and lethal forms of cancer. The incidence of gastric cancer is very high in East Asia and varies considerably in countries of the Western hemisphere. Even after curative resection, the relapse rates are high in stages II and III. Therefore, adjuvant treatment with chemotherapy has been studied with positive results, especially in East Asian populations. In the Western World, where many locally advanced and borderline resectable gastric cancers are diagnosed, perioperative chemotherapy has become a standard of care. Perioperative chemotherapy increases the chances for curative resection. The additional role of radiation therapy, either in the neoadjuvant or in the adjuvant setting, needs to be defined by studies with a quality assurance for all treatment modalities.

Immunological battlefield in gastric cancer and role of immunotherapies

Like the wars predating the First World War where human foot soldiers were deemed tools in the battlefield against an enemy, so too are the host immune cells of a patient battling a malignant gastric cancer. Indeed, the tumour microenvironment resembles a battlefield, where the patient’s immune cells are the defence against invading tumour cells. However, the relationship between different immune components of the host response to cancer is more complex than an “us against them” model. Components of the immune system inadvertently work against the interests of the host and become pro-tumourigenic while other components soldier on against the common enemy – the tumour cell.

Patient-derived cell models as preclinical tools for genome-directed targeted therapy

Background

In this study, we established patient-derived tumor cell (PDC) models using tissues collected from patients with metastatic cancer and assessed whether these models could be used as a tool for genome-based cancer treatment.

Methods

PDCs were isolated and cultured from malignant effusions including ascites and pleural fluid. Pathological examination, immunohistochemical analysis, and genomic profiling were performed to compare the histological and genomic features of primary tumors, PDCs. An exploratory gene expression profiling assay was performed to further characterize PDCs.

Results

From January 2012 to May 2013, 176 samples from patients with metastatic cancer were collected. PDC models were successfully established in 130 (73.6%) samples. The median time from specimen collection to passage 1 (P1) was 3 weeks (range, 0.5–4 weeks), while that from P1 to P2 was 2.5 weeks (range, 0.5–5 weeks). Sixteen paired samples of genomic alterations were highly concordant between each primary tumor and progeny PDCs, with an average variant allele frequency (VAF) correlation of 0.878. We compared genomic profiles of the primary tumor (P0), P1 cells, P2 cells, and patient-derived xenografts (PDXs) derived from P2 cells and found that three samples (P0, P1, and P2 cells) were highly correlated (0.99–1.00). Moreover, PDXs showed more than 100 variants, with correlations of only 0.6–0.8 for the other samples. Drug responses of PDCs were reflective of the clinical response to targeted agents in selected patient PDC lines.

Conclusion(s)

Our results provided evidence that our PDC model was a promising model for preclinical experiments and closely resembled the patient tumor genome and clinical response.

Mismatch Repair Deficiency and Response to Immune Checkpoint Blockade

: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers.

IMPLICATIONS FOR PRACTICE

Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.

Exploring the role of molecular biomarkers as a potential weapon against gastric cancer: A review of the literature

Gastric cancer (GC) is a global health problem and a major cause of cancer-related death with high recurrence rates ranging from 25% to 40% for GC patients staging II-IV. Unfortunately, while the majority of GC patients usually present with advanced tumor stage; there is still limited evidence-based therapeutic options. Current approach to GC management consists mainly of; endoscopy followed by, gastrectomy and chemotherapy or chemo-radiotherapy. Recent studies in GC have confirmed that it is a heterogeneous disease. Many molecular characterization studies have been performed in GC. Recent discoveries of the molecular pathways underlying the disease have opened the door to more personalized treatment and better predictable outcome. The identification of molecular markers is a useful tool for clinical managementin GC patients, assisting in diagnosis, evaluation of response to treatment and development of novel therapeutic modalities. While chemotherapeutic agents have certain physiological effects on the tumor cells, the prediction of the response is different from one type of tumor to the other. The specificity of molecular biomarkers is a principal feature driving their application in anticancer therapies. Here we are trying to focus on the role of molecular pathways of GC and well-established molecular markers that can guide the therapeutic management.

Mismatch Repair Deficiency and Response to Immune Checkpoint Blockade

: More than 1.6 million new cases of cancer will be diagnosed in the U.S. in 2016, resulting in more than 500,000 deaths. Although chemotherapy has been the mainstay of treatment in advanced cancers, immunotherapy development, particularly with PD-1 inhibitors, has changed the face of treatment for a number of tumor types. One example is the subset of tumors characterized by mismatch repair deficiency and microsatellite instability that are highly sensitive to PD-1 blockade. Hereditary forms of cancer have been noted for more than a century, but the molecular changes underlying mismatch repair-deficient tumors and subsequent microsatellite unstable tumors was not known until the early 1990s. In this review article, we discuss the history and pathophysiology of mismatch repair, the process of testing for mismatch repair deficiency and microsatellite instability, and the role of immunotherapy in this subset of cancers.

IMPLICATIONS FOR PRACTICE

Mismatch repair deficiency has contributed to our understanding of carcinogenesis for the past 2 decades and now identifies a subgroup of traditionally chemotherapy-insensitive solid tumors as sensitive to PD-1 blockade. This article seeks to educate oncologists regarding the nature of mismatch repair deficiency, its impact in multiple tumor types, and its implications for predicting the responsiveness of solid tumors to immune checkpoint blockade.

EGFR gene amplification is relatively common and associates with outcome in intestinal adenocarcinoma of the stomach, gastro-oesophageal junction and distal oesophagus

BACKGROUND

Approximately 50 % of gastric adenocarcinomas belong to a molecular subgroup characterised by chromosomal instability and a strong association with the intestinal histological subtype. This subgroup typically contains alterations in the receptor tyrosine kinase-RAS pathway, for example EGFR or HER2 gene amplifications leading to protein overexpression. In clinical practice, HER2 overexpressing metastatic gastric cancer is known to respond to treatment with anti-HER2 antibodies. By contrast, anti-EGFR antibodies have not been able to provide survival benefit in clinical trials, which, however, have not included patient selection based on the histological subtype or EGFR gene copy number analysis of the tumours. To examine the role of EGFR as a potential biomarker, we studied the prevalence, clinicopathological associations as well as prognostic role of EGFR and HER2 expression and gene amplification in intestinal adenocarcinomas of the stomach, gastro-oesophageal junction and distal oesophagus.

METHODS

Tissue samples from 220 patients were analysed with EGFR and HER2 immunohistochemistry. Those samples with moderate/strong staining intensity were further analysed with silver in situ hybridization to quantify gene copy numbers. The results were associated with clinical patient characteristics and survival.

RESULTS

Moderate/strong EGFR protein expression was found in 72/220 (32.7 %) and EGFR gene amplification in 31/220 (14.1 %) of the tumours, while moderate/strong HER2 protein expression was detected in 31/220 (14.1 %) and HER2 gene amplification in 29/220 (13.2 %) of the tumours. EGFR and HER2 genes were co-amplified in eight tumours (3.6 %). EGFR gene amplification was more common in tumours of distal oesophagus/gastro-oesophageal junction/cardia than in those of gastric corpus (p = 0.013). It was associated with shortened time to cancer recurrence (p = 0.026) and cancer specific survival (p = 0.033).

CONCLUSIONS

EGFR gene amplification is relatively common in intestinal adenocarcinomas and associates with decreased survival. It is rarely concurrent with HER2 gene amplification, suggesting that anti-EGFR therapies might be applicable to some patients not eligible for anti-HER2 treatment. Analogous to HER2 testing, determination of EGFR gene amplification status in concert with immunohistochemistry could improve the specificity of patient selection when investigating the possible benefits of anti-EGFR therapies in the treatment of gastric adenocarcinomas.

A protein and mRNA expression-based classification of gastric cancer

The overall survival of gastric carcinoma patients remains poor despite improved control over known risk factors and surveillance. This highlights the need for new classifications, driven towards identification of potential therapeutic targets. Using sophisticated molecular technologies and analysis, three groups recently provided genetic and epigenetic molecular classifications of gastric cancer (The Cancer Genome Atlas, 'Singapore-Duke' study, and Asian Cancer Research Group). Suggested by these classifications, here, we examined the expression of 14 biomarkers in a cohort of 146 gastric adenocarcinomas and performed unsupervised hierarchical clustering analysis using less expensive and widely available immunohistochemistry and in situ hybridization. Ultimately, we identified five groups of gastric cancers based on Epstein-Barr virus (EBV) positivity, microsatellite instability, aberrant E-cadherin, and p53 expression; the remaining cases constituted a group characterized by normal p53 expression. In addition, the five categories correspond to the reported molecular subgroups by virtue of clinicopathologic features. Furthermore, evaluation between these clusters and survival using the Cox proportional hazards model showed a trend for superior survival in the EBV and microsatellite-instable related adenocarcinomas. In conclusion, we offer as a proposal a simplified algorithm that is able to reproduce the recently proposed molecular subgroups of gastric adenocarcinoma, using immunohistochemical and in situ hybridization techniques.

How Can Gastric Cancer Molecular Profiling Guide Future Therapies?

Gastric cancer is the third greatest global cause of cancer-related deaths. Despite its high prevalence, only recently have comprehensive genomic surveys shed light on its molecular alterations. As surgery is the only curative treatment strategy and chemotherapy has shown limited efficacy, new treatments are urgently needed. Many molecular therapies for gastric cancer have entered clinical trials but-apart from Trastuzumab and Ramucirumab-all have failed. We analyze the current knowledge of the genetic 'landscape' of gastric cancers, elaborating on novel, preclinical approaches. We posit that this knowledge lays the basis for identifying bona fide molecular targets and developing solid therapeutic approaches, requiring accurate patient selection and taking advantage of preclinical models to assist clinical development of novel combination strategies.

Mouse models for gastric cancer: Matching models to biological questions

Gastric cancer is the third leading cause of cancer-related mortality worldwide. This is in part due to the asymptomatic nature of the disease, which often results in late-stage diagnosis, at which point there are limited treatment options. Even when treated successfully, gastric cancer patients have a high risk of tumor recurrence and acquired drug resistance. It is vital to gain a better understanding of the molecular mechanisms underlying gastric cancer pathogenesis to facilitate the design of new-targeted therapies that may improve patient survival. A number of chemically and genetically engineered mouse models of gastric cancer have provided significant insight into the contribution of genetic and environmental factors to disease onset and progression. This review outlines the strengths and limitations of current mouse models of gastric cancer and their relevance to the pre-clinical development of new therapeutics.

Increased RhoA Activity Predicts Worse Overall Survival in Patients Undergoing Surgical Resection for Lauren Diffuse-Type Gastric Adenocarcinoma

BACKGROUND

Several studies have reported a high rate of RHOA mutations in the Lauren diffuse-type gastric adenocarcinoma (GA) but not in intestinal-type GA. The aim of this study was to determine if RhoA activity is prognostic for overall survival (OS) in patients with resectable GA.

METHODS

Retrospective review was performed on a prospective database of GA patients who underwent potentially curative resection between 2003 and 2012 at a single institution. Tissue microarrays were constructed from surgical specimens and analyzed for phosphorylated RhoA, a marker of inactive RhoA signaling. OS was estimated by the Kaplan-Meier method, and multivariate analysis was performed by Cox proportional hazards regression modeling.

RESULTS

One hundred thirty-six patients with diffuse-type GA and 129 patients with intestinal-type GA were examined. Compared to intestinal-type GA, diffuse-type GA tumors were significantly associated with increased tumor size and advanced tumor, node, metastasis (TNM) classification system stage. In patients with diffuse-type GA, high RhoA activity was associated with significantly worse OS when compared to low RhoA activity (5-year OS 52.5 vs. 81.0 %, p = 0.017). This difference in OS was not observed in patients with intestinal-type GA (5-year OS 83.9 vs. 81.6 %, p = 0.766). On multivariate analysis of diffuse-type GA patients, high RhoA activity was an independent negative prognostic factor for OS (hazard ratio 2.38, 95 % confidence interval 1.07-5.28).

CONCLUSIONS

Increased RhoA activity is predictive of worse OS in patients with diffuse-type GA who undergo potentially curative surgical resection. Along with findings from genomic studies, these results suggest RhoA may be a novel therapeutic target in diffuse-type GA.

Molecular mechanisms of gastric cancer initiation and progression by Helicobacter pylori

PURPOSE OF REVIEW

Infection with the Gram-negative, microaerophilic pathogen Helicobacter pylori results in gastric cancer in a subset of infected individuals. As such, H. pylori is the only WHO classified bacterial class I carcinogen. Numerous studies have identified mechanisms by which H. pylori alters host cell signaling pathways to cause disease. The purpose of this review is to highlight recent studies that explore mechanisms associated with induction of gastric cancer.

RECENT FINDINGS

Over the last year and a half, new mechanisms contributing to the etiology of H. pylori-associated gastric cancer development have been discovered. In addition to utilizing the oncogenic CagA toxin to alter host cell signaling pathways, H. pylori also induces host DNA damage and alters DNA methylation to perturb downstream signaling. Furthermore, H. pylori activates numerous host cell pathways and proteins that result in epithelial-to-mesenchymal transition and induction of cell survival and proliferation.

SUMMARY

Mounting evidence suggests that H. pylori promotes gastric carcinogenesis using a multifactorial approach. Intriguingly, many of the targeted pathways and mechanisms show commonality with diverse forms of cancer.

Monoclonal antibodies for treating gastric cancer: promises and pitfalls

INTRODUCTION

Gastric cancer (GC) presents dismal prognosis when diagnosed at advanced stages, standard chemotherapy having shown little efficacy. Introduction of biotherapies interfering with novel targets and signaling pathways is currently an emerging strategy.

AREAS COVERED

Only two monoclonal antibodies (trastuzumab and ramucirumab) have been approved, mostly in association with cytotoxics. Conversely, testing other promising biotherapies (panitumumab, cetuximab, bevacizumab, rilotumumab) have yielded conflicting results, since encouraging early clinical trials have failed to be confirmed in larger phase-III studies. Empirical and underpowered strategies when designing combinational studies, lack of comprehensive knowledge of pharmacokinetics/pharmacodynamics (PK/PD) relationships, and underestimation of the large inter-patient variability in drug exposure levels with monoclonal antibodies, could explain the failures in developing biotherapies in gastric cancer. This review covers the achievements and limits of monoclonal antibodies in gastric cancer and proposes clues to overcome current failures.

EXPERT OPINION

Trastuzumab efficacy could be improved thanks to its combination with triplet chemotherapy or with another anti-HER2 agents or in continuation during second-line chemotherapy. Concerning ramucirumab, further studies are necessary to prove its interest in first line treatment of advanced GC, to use the optimal dose in each patient-given the large inter-patients variability, and to find predictive biomarkers of efficacy.

Clinical impact of tumour biology in the management of gastroesophageal cancer

The characterization of oesophageal and gastric cancer into subtypes based on genotype has evolved in the past decade. Insights into the molecular landscapes of gastroesophageal cancer provide a roadmap to assist the development of new drugs and their use in combinations, for patient stratification, and for trials of targeted therapies. Trastuzumab is the only approved treatment for gastroesophageal cancers that overexpress HER2. Acquired resistance usually limits the duration of response to this treatment, although a number of new agents directed against HER2 have the potential to overcome or prolong the time until resistance occurs. Beyond that, anti-VEGFR2 therapy with ramucirumab was the first biological treatment strategy to produce a survival benefit in an unselected population of patients with chemotherapy-refractory gastroesophageal cancer. Large initiatives are starting to address the role of biomarker-driven targeted therapy in the metastatic and in the perioperative setting for patients with this disease. Immunotherapy also holds promise, and our understanding of subsets of gastroesophageal cancer based on patterns of immune response continues to evolve. Efforts are underway to identify more relevant genomic subsets through genomic screening, functional studies, and molecular characterization. Herein, we provide an overview of the key developments in the treatment of gastroesophageal cancer, and discuss potential strategies to further optimize therapy by targeting disease subtypes.

Synergistic combination of DT-13 and topotecan inhibits human gastric cancer via myosin IIA-induced endocytosis of EGF receptor in vitro and in vivo

Combination therapy has a higher success rate for many cancers compared to mono-therapy. The treatment of Topotecan (TPT) on gastric cancer (GC) is limited by its toxicity and the potential drug resistance. We found that the combination of the saponin monomer 13 from the dwarf lilyturf tuber (DT-13), performing anti-metastasis and anti-angiogenesis effects, with TPT synergistically induced apoptotic cytotoxicity in GCs with high EGF receptor (EGFR) expression, which was dependent on DT-13-induced endocytosis of EGFR. With TPT, DT-13 promoted EGFR ubiquitin--mediated degradation through myosin IIA-induced and Src/ caveolin-1 (Cav-1)-induced endocytosis of EGFR; inhibited EGFR downstream signalling and then increased the pro-apoptotic effects. Moreover, the synergistic pro-apoptotic efficacy of DT-13 and TPT in GCs with high EGFR expression was eliminated by both the NM II inhibitor (-)-blebbistatin and MYH-9 shRNA. The combination therapy of DT-13 with TPT showed stronger anti-tumour effects in vivo compared with their individual effects. Moreover, the results of combination therapy revealed selective upregulation of pro-apoptotic activity in TUNEL assays and cleaved caspase-3 and NM IIA in immunohischemical analysis; while specific downregulation of p-extracellular regulated kinase 1/2 (p-ERK1/2), EGFR and Cav-1 in immunohischemical analysis. Collectively, these findings have significant clinical implications for patients with tumours harbouring high EGFR expression due to the possible high sensitivity of this regimen.

Emerging molecular classifications and therapeutic implications for gastric cancer

Gastric cancer (GC) is a highly aggressive and life-threatening malignancy. Even with radical surgical removal and front-line chemotherapy, more than half of GCs locally relapse and metastasize at a distant site. The dismal outcomes reflect the ineffectiveness of a one-size-fits-all approach for a highly heterogeneous disease with diverse etiological causes and complex molecular underpinnings. The recent comprehensive genomic and molecular profiling has led to our deepened understanding of GC. The emerging molecular classification schemes based on the genetic, epigenetic, and molecular signatures are providing great promise for the development of more effective therapeutic strategies in a more personalized and precise manner. To this end, the Cancer Genome Atlas (TCGA) research network conducted a comprehensive molecular evaluation of primary GCs and proposed a new molecular classification dividing GCs into four subtypes: Epstein-Barr virus-associated tumors, microsatellite unstable tumors, genomically stable tumors, and tumors with chromosomal instability. This review primarily focuses on the TCGA molecular classification of GCs and discusses the implications on novel targeted therapy strategies. We believe that these fundamental findings will support the future application of targeted therapies and will guide our efforts to develop more efficacious drugs to treat human GCs.

Novel biomarkers for the identification and targeted therapy of gastric cancer

Gastric cancer development follows the pathologic pattern such that chronic inflammation in the gastric mucosa progressively transforms normal mucosa into atrophy, intestinal metaplasia, adenoma/dysplasia and eventually invasive and metastatic tumors. The accumulation of multiple genetic and epigenetic alterations leads to the dysregulation of oncogenes and tumor suppressors, which was considered as the driver behind events during the tumorigenesis. Almost all gastric cancers are adenocarcinomas, which share considerable heterogeneity with distinct morphology, pathogenesis and clinical behavior. Therefore, identifying subtypes of gastric cancers with molecular and genetic features will be beneficial for the early identification and selection of new effective agents for targeted treatment. High-throughput sequencing techniques such as whole genomic, epigenome and transcriptome sequencing and proteomics platforms have identified major genomic characteristics that exhibit identification and prognostic impacts and distinct response patterns. In this article, the authors aim to summarize the information regarding the most promising molecules that may have clinical application as non-invasive biomarkers and therapy targets.

Genomic alterations and molecular subtypes of gastric cancers in Asians

Gastric cancer (GC) is a highly heterogenic disease, and it is the second leading cause of cancer death in the world. Common chemotherapies are not very effective for GC, which often presents as an advanced or metastatic disease at diagnosis. Treatment options are limited, and the prognosis for advanced GCs is poor. The landscape of genomic alterations in GCs has recently been characterized by several international cancer genome programs, including studies that focused exclusively on GCs in Asians. These studies identified major recurrent driver mutations and provided new insights into the mutational heterogeneity and genetic profiles of GCs. An analysis of gene expression data by the Asian Cancer Research Group (ACRG) further uncovered four distinct molecular subtypes with well-defined clinical features and their intersections with actionable genetic alterations to which targeted therapeutic agents are either already available or under clinical development. In this article, we review the ACRG GC project. We also discuss the implications of the genetic and molecular findings from various GC genomic studies with respect to developing more precise diagnoses and treatment approaches for GCs.

Oesophageal adenocarcinoma and gastric cancer: should we mind the gap?

Over recent decades we have witnessed a shift in the anatomical distribution of gastric cancer (GC), which increasingly originates from the proximal stomach near the junction with the oesophagus. In parallel, there has been a dramatic rise in the incidence of oesophageal adenocarcinoma (OAC) in the lower oesophagus, which is associated with antecedent Barrett oesophagus (BO). In this context, there has been uncertainty regarding the characterization of adenocarcinomas spanning the area from the lower oesophagus to the distal stomach. Most relevant to this discussion is the distinction, if any, between OAC and intestinal-type GC of the proximal stomach. It is therefore timely to review our current understanding of OAC and intestinal-type GC, integrating advances from cell-of-origin studies and comprehensive genomic alteration analyses, ultimately enabling better insight into the relationship between these two cancers.

Identifying Reproducible Molecular Biomarkers for Gastric Cancer Metastasis with the Aid of Recurrence Information

To precisely diagnose metastasis state is important for tailoring treatments for gastric cancer patients. However, the routinely employed radiological and pathologic tests for tumour metastasis have considerable high false negative rates, which may retard the identification of reproducible metastasis-related molecular biomarkers for gastric cancer. In this research, using three datasets, we firstly shwed that differentially expressed genes (DEGs) between metastatic tissue samples and non-metastatic tissue samples could hardly be reproducibly detected with a proper statistical control when the metastatic and non-metastatic samples were defined by TNM stage alone. Then, assuming that undetectable micrometastases are the prime cause for recurrence of early stage patients with curative resection, we reclassified all the “non-metastatic” samples as metastatic samples whenever the patients experienced tumour recurrence during follow-up after tumour resection. In this way, we were able to find distinct and reproducible DEGs between the reclassified metastatic and non-metastatic tissue samples and concordantly significant DNA methylation alterations distinguishing metastatic tissues and non-metastatic tissues of gastric cancer. Our analyses suggested that the follow-up recurrence information for patients should be employed in the research of tumour metastasis in order to decrease the confounding effects of false non-metastatic samples with undetected micrometastases.

Stratification of Digestive Cancers with Different Pathological Features and Survival Outcomes by MicroRNA Expression

MicroRNAs (miRNAs) are aberrantly expressed in virtually all cancer types, including digestive cancers. Herein, we aggregated and systematically analyzed miRNA expression profiles of 1765 tumor samples, including esophageal, gastric, liver, pancreatic, colon and rectal cancers, obtained through small RNA sequencing by The Cancer Genome Atlas. We found that digestive cancers of different tissue origins could be differentiated according to their miRNA expression profiles. In particular, esophageal squamous cell carcinoma and esophageal adenocarcinoma exhibited distinct miRNA expression patterns. Thirteen (e.g. miR-135b, miR-182) and sixteen (e.g. miR-139, miR-133a-1, miR-490) miRNAs were commonly upregulated and downregulated in more than four cancer types, respectively. Pertinent to pathological features, low miR-181d expression was associated with microsatellite instability in colon and gastric cancers whereas low miR-106a expression was associated with hepatitis B virus infection in hepatocellular carcinoma. Progression in colon cancer could also be predicted by low let-7f-2 and high miR-106a expression. Molecular subtypes with distinct prognostic outcomes independent of tumor-node-metastasis staging were identified in hepatocellular carcinoma and colon cancer. In total, 4 novel and 6 reported associations between specific miRNAs and patients’ survival were identified. Collectively, novel miRNA markers were identified to stratify digestive cancers with different pathological features and survival outcomes.

Inflammation in gastric cancer: Interplay of the COX-2/prostaglandin E2 and Toll-like receptor/MyD88 pathways

Cyclooxygenase‐2 (COX‐2) and its downstream product prostaglandin E₂ (PGE₂) play a key role in generation of the inflammatory microenvironment in tumor tissues. Gastric cancer is closely associated with Helicobacter pylori infection, which stimulates innate immune responses through Toll‐like receptors (TLRs), inducing COX‐2/PGE₂ pathway through nuclear factor‐κB activation. A pathway analysis of human gastric cancer shows that both the COX‐2 pathway and Wnt/β‐catenin signaling are significantly activated in tubular‐type gastric cancer, and basal levels of these pathways are also increased in other types of gastric cancer. Expression of interleukin‐11, chemokine (C‐X‐C motif) ligand 1 (CXCL1), CXCL2, and CXCL5, which play tumor‐promoting roles through a variety of mechanisms, is induced in a COX‐2/PGE₂ pathway‐dependent manner in both human and mouse gastric tumors. Moreover, the COX‐2/PGE₂ pathway plays an important role in the maintenance of stemness with expression of stem cell markers, including CD44, Prom1, and Sox9, which are induced in both gastritis and gastric tumors through a COX‐2/PGE₂‐dependent mechanism. In contrast, disruption of Myd88 results in suppression of the inflammatory microenvironment in gastric tumors even when the COX‐2/PGE₂ pathway is activated, indicating that the interplay of the COX‐2/PGE₂ and TLR/MyD88 pathways is needed for inflammatory response in tumor tissues. Furthermore, TLR2/MyD88 signaling plays a role in maintenance of stemness in normal stem cells as well as gastric tumor cells. Accordingly, these results suggest that targeting the COX‐2/PGE₂ pathway together with TLR/MyD88 signaling, which would suppress the inflammatory microenvironment and maintenance of stemness, could be an effective preventive or therapeutic strategy for gastric cancer.

Comprehensive molecular portrait using next generation sequencing of resected intestinal-type gastric cancer patients dichotomized according to prognosis

In this study, we evaluated whether the presence of genetic alterations detected by next generation sequencing may define outcome in a prognostically-selected and histology-restricted population of resected gastric cancer (RGC). Intestinal type RGC samples from 34 patients, including 21 best and 13 worst prognostic performers, were studied. Mutations in 50 cancer-associated genes were evaluated. A significant difference between good and poor prognosis was found according to clinico-pathologic factors. The most commonly mutated genes in the whole population were PIK3CA (29.4%), KRAS (26.5%), TP53 (26.5%) MET (8.8%), SMAD4 (8.8%) and STK11 (8.8%). Multiple gene mutations were found in 14/21 (67%) patients with good prognosis, and 3/13 (23%) in the poor prognosis group. A single gene alteration was found in 5/21 (24%) good and 6/13 (46%) poor prognosis patients. No mutation was found in 2/21 (9.5%) and 4/13 (31%) of these groups, respectively. In the overall series, ß-catenin expression was the highest (82.4%), followed by E-Cadherin (76.5%) and FHIT (52.9%). The good prognosis group was characterized by a high mutation rate and microsatellite instability. Our proof-of-principle study demonstrates the feasibility of a molecular profiling approach with the aim to identify potentially druggable pathways and drive the development of customized therapies for RGC.

Establishment and characterisation of patient-derived xenografts as paraclinical models for gastric cancer

The patient-derived xenograft (PDX) model is emerging as a promising translational platform to duplicate the characteristics of tumours. However, few studies have reported detailed histological and genomic analyses for model fidelity and for factors affecting successful model establishment of gastric cancer. Here, we generated PDX tumours surgically-derived from 62 gastric cancer patients. Fifteen PDX models were successfully established (24.2%, 15/62) and passaged to maintain tumours in immune-compromised mice. Diffuse type and low tumour cell percentage were negatively correlated with success rates (p = 0.005 and p = 0.025, respectively), while reducing ex vivo and overall procedure times were positively correlated with success rates (p = 0.003 and p = 0.01, respectively). The histology and genetic characteristics of PDX tumour models were stable over subsequent passages. Lymphoma transformation occurred in five cases (33.3%, 5/15), and all were in the NOG mouse, with none in the nude mouse. Together, the present study identified Lauren classification, tumour cell percentages, and ex vivo times along with overall procedure times, as key determinants for successful PDX engraftment. Furthermore, genetic and histological characteristics were highly consistent between primary and PDX tumours, which provide realistic paraclinical models, enabling personalised development of treatment options for gastric cancer.

Novel targets in the treatment of advanced gastric cancer: a perspective review

Gastric cancer is responsible for a high burden of disease globally. Although more extensive use of chemotherapy together with the recent introduction of the two targeted agents trastuzumab and ramucirumab have contributed to marginal outcome prolongation, overall survival for patients with advanced stage disease remains poor. Over the last decade, a number of novel agents have been examined in clinical trials with largely disappointing results. Potential explanations for this are the absence of molecularly selected trial populations or weak predictive biomarkers within the context of a highly heterogeneous disease. In the recently published gastric cancer The Cancer Genome Atlas (TCGA) project a new classification of four different tumour subtypes according to different molecular characteristics has been proposed. With some overlap, several relatively distinct and potentially targetable pathways have been identified for each subtype. In this perspective review we match recent trial results with the subtypes described in the gastric cancer TCGA aiming to highlight data regarding novel agents under evaluation and to discuss whether this publication might provide a framework for future drug development.

Translating gastric cancer genomics into targeted therapies

Gastric cancer is a common disease with limited treatment options and a poor prognosis. Many gastric cancers harbour potentially actionable targets, including over-expression and mutations in tyrosine kinase pathways. Agents have been developed against these targets with varying success- in particular, the use of trastuzumab in HER2-overexpressing gastric cancers has resulted in overall survival benefits. Gastric cancers also have high levels of somatic mutations, making them candidates for immunotherapy; early work in this field has been promising. Recent advances in whole genome and multi-platform sequencing have driven the development of molecular classification systems, which may in turn guide the selection of patients for targeted treatment. Moving forward, challenges will include the development of appropriate biomarkers to predict responses to targeted therapy, and the application of new molecular classifications into trial development and clinical practice.

NanoString expression profiling identifies candidate biomarkers of RAD001 response in metastatic gastric cancer

Background

Gene expression profiling has contributed greatly to cancer research. However, expression-driven biomarker discovery in metastatic gastric cancer (mGC) remains unclear. A gene expression profile predicting RAD001 response in refractory GC was explored in this study.

Methods

Total RNA isolated from 54 tumour specimens from patients with mGC, prior to RAD001 treatment, was analysed via the NanoString nCounter gene expression assay. This assay targeted 477 genes representing 10 different GC-related oncogenic signalling and molecular subtype-specific expression signatures. Gene expression profiles were correlated with patient clinicopathological variables.

Results

NanoString data confirmed similar gene expression profiles previously identified by microarray analysis. Signature I with 3 GC subtypes (mesenchymal, metabolic and proliferative) showed approximately 90% concordance where the mesenchymal and proliferative subtypes were significantly associated with signet ring cell carcinoma and the WHO classified tubular adenocarcinoma GC, respectively (p=0.042). Single-gene-level correlations with patient clinicopathological variables showed strong associations between FHL1 expression (mesenchymal subtype) and signet ring cell carcinoma, and NEK2, OIP5, PRC1, TPX2 expression (proliferative subtype) with tubular adenocarcinoma (adjusted p<0.05). Increased BRCA2 (p=0.040) and MMP9 (p=0.045) expression was significantly associated with RAD001 good response and longer progression-free survival outcome (BRCA2, p=0.012, HR 0.370 95% CI (0.171 to 0.800); MMP9, p=0.010, HR 0.359 95% CI (0.166 to 0.779)). In contrast, increased BTC (p=0.035) expression was significantly associated with RAD001 poor response and poor progression-free survival (p=0.031, HR 2.336 95% CI (1.079 to 5.059) by univariate Cox regression analysis.

Conclusions

Microarray results are highly reproducible with NanoString nCounter gene expression profiling. Additionally, BRCA2 and MMP9 expression are potential predictive biomarkers for good response in RAD001-treated mGC.

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.

New Biology to New Treatment of Helicobacter pylori-Induced Gastric Cancer

BACKGROUND

Helicobacter pylori is a bacterial carcinogen that is supposed to have the highest known level of risk for the development of gastric cancer, a disease that claims hundreds of thousands of lives per year. Approximately 89% of the global gastric cancer burden and 5.5% of malignancies worldwide are attributed to H. pylori-induced inflammation and injury. However, only a fraction of colonized persons ever develop neoplasia, and disease risk involves well-choreographed interactions between pathogen and host, which are dependent upon strain-specific bacterial factors, host genotypic traits, and/or environmental conditions.

KEY MESSAGES

One H. pylori strain-specific virulence determinant that augments the risk for gastric cancer is the cag pathogenicity island, a secretion system that injects the bacterial oncoprotein CagA into host cells. Host polymorphisms within genes that regulate immunity and oncogenesis also heighten the risk for gastric cancer, in conjunction with H. pylori strain-specific constituents. Further, conditions such as iron deficiency and high salt intake can influence H. pylori phenotypes that lower the threshold for disease.

CONCLUSIONS

Delineation of bacterial, host, and environmental mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer, but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Angiogenesis inhibitors in gastric and gastroesophageal junction cancer

Despite significant improvements in systemic chemotherapy during the past two decades, the prognosis of patients with advanced gastric and gastroesophageal junction adenocarcinoma remains poor. Because of molecular heterogeneity, it is essential to classify tumors based on the underlying oncogenic pathways and to develop targeted therapies acting on individual tumors. Unfortunately, although a number of molecular targets have been studied, very few of these agents can be used in a clinical setting. In this review, we summarize the available data on anti-angiogenic agents in advanced/metastatic gastric cancer.

Genomics Study of Gastric Cancer and Its Molecular Subtypes

Gastric cancer is a heterogeneous disease encompassing diverse morphological (intestinal versus diffuse) and molecular subtypes (MSI, EBV, TP53 mutation). Recent advances in genomic technology have led to an improved understanding of the driver gene mutational profile, gene expression, and epigenetic alterations that underlie each of the subgroups, with therapeutic implications in some of these alterations. There have been attempts to classify gastric cancers based on these genomic features, with an aim to improve prognostication and predict responsiveness to specific drug therapy. The eventual aims of these genomic studies are to develop deep biological insights into the carcinogenic pathway in each of these subtypes. Future large-scale drug screening strategies may then be able to link these genomic features to drug responsiveness, eventually leading to genome-guided personalized medicine with improved cure rates.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

Gastric Adenocarcinoma: An Update on Genomics, Immune System Modulations, and Targeted Therapy

Gastric adenocarcinoma (GAC) is a global health burden on all societies, and it was the third-leading cause of cancer-related mortality in 2012, causing 723,000 deaths worldwide. The prognosis of patients with metastatic GAC remains poor, with a median overall survival of less than 1 year in patients treated with currently available therapies. A limited number of therapeutic agents is currently available. Recent additions to the armamentarium include trastuzumab and ramucirumab, which have shown some survival advantage when added to cytotoxic(s). Genomic analyses have defined various genotypes of GACs. The novel genomic knowledge can lead to discovery of novel targets and novel therapeutic agents. In this update, we focus on the current genomic data, targeted therapies including immune system modulators, and expand on HER2/neu testing and the use of agents against this target. Several other facets of GAC and its therapy are not to be included in this review but have been discussed elsewhere.

Seom guidelines for the treatment of gastric cancer 2015

Gastric cancer is the fourth cause of death by cancer in Spain and a significant medical problem. Molecular biology results evidence that gastroesophageal junction tumors and gastric cancer should be considered as two independent entities with a different prognosis and treatment approach. Endoscopic resection in very early tumors is feasible. Neoadjuvant and adjuvant therapy in locally advanced resectable tumor increase overall survival and should be considered standard treatments. In stage IV tumors, platinum–fluoropyrimidine-based schedule, with trastuzumab in HER2-overexpressed tumors, is the first-line treatment. Different therapies in second line have demonstrated in randomized studies their clear benefit in survival improvement.

Molecular Dimensions of Gastric Cancer: Translational and Clinical Perspectives

Gastric cancer is a global health burden and has the highest incidence in East Asia. This disease is complex in nature because it arises from multiple interactions of genetic, local environmental, and host factors, resulting in biological heterogeneity. This genetic intricacy converges on molecular characteristics reflecting the pathophysiology, tumor biology, and clinical outcome. Therefore, understanding the molecular characteristics at a genomic level is pivotal to improving the clinical care of patients with gastric cancer. A recent landmark study, The Cancer Genome Atlas (TCGA) project, showed the molecular landscape of gastric cancer through a comprehensive molecular evaluation of 295 primary gastric cancers. The proposed molecular classification divided gastric cancer into four subtypes: Epstein-Barr virus–positive, microsatellite unstable, genomic stable, and chromosomal instability. This information will be taken into account in future clinical trials and will be translated into clinical therapeutic decisions. To fully realize the clinical benefit, many challenges must be overcome. Rapid growth of high-throughput biology and functional validation of molecular targets will further deepen our knowledge of molecular dimensions of this cancer, allowing for personalized precision medicine.

Incremental diagnostic utility of gastric distension FDG PET/CT

PURPOSE

To assess the diagnostic utility of gastric distension (GD) FDG PET/CT in both patients with known gastric malignancy and those not known to have gastric malignancy but with incidental focal FDG uptake in the stomach.

METHODS

This retrospective analysis included 88 patients who underwent FDG PET/CT following GD with hyoscine N-butylbromide (Buscopan®) and water ingestion as part of routine clinical evaluation between 2004 and 2014. FDG PET/CT scans before and after GD were reported blinded to the patient clinical details in 49 patients undergoing pretreatment staging of gastric malignancy and 39 patients who underwent GD following incidental suspicious gastric uptake. The PET findings were validated by a composite clinical standard.

RESULTS

In the 49 patients undergoing pretreatment staging of gastric malignancy, GD improved PET detection of the primary tumour (from 80 % to 90 %). PET evaluation of tumour extent was concordant with endoscopic/surgical reports in 31 % (interpreter 1) and 45 % (interpreter 2) using pre-GD images and 73 % and 76 % using GD images. Interobserver agreement also improved with GD (κ = 0.29 to 0.69). Metabolic and morphological quantitative analysis demonstrated a major impact of GD in normal gastric wall but no significant effect in tumour, except a minor increase in SUV related to a delayed acquisition time. The tumour to normal stomach SUVmax ratio increased from 3.8 ± 2.9 to 9.2 ± 8.6 (mean ± SD) with GD (p < 0.0001), facilitating detection and improved assessment of the primary tumour. In 25 (64 %) of the 39 patients with incidental suspicious gastric uptake, acquisition after GD correctly excluded a malignant process. In 10 (71 %) of the remaining 14 patients with persistent suspicious FDG uptake despite GD, malignancy was confirmed and in 3 (21 %) an active but benign pathology was diagnosed.

CONCLUSION

GD is a simple way to improve local staging with FDG PET in patients with gastric malignancy. In the setting of incidental suspicious gastric uptake, GD is also an effective tool for ruling out malignancy and leads to the avoidance of unnecessary endoscopy.

Genetics and Molecular Pathogenesis of Gastric Adenocarcinoma

Gastric cancer (GC) is globally the fifth most common cancer and third leading cause of cancer death. A complex disease arising from the interaction of environmental and host-associated factors, key contributors to GC's high mortality include its silent nature, late clinical presentation, and underlying biological and genetic heterogeneity. Achieving a detailed molecular understanding of the various genomic aberrations associated with GC will be critical to improving patient outcomes. The recent years has seen considerable progress in deciphering the genomic landscape of GC, identifying new molecular components such as ARID1A and RHOA, cellular pathways, and tissue populations associated with gastric malignancy and progression. The Cancer Genome Atlas (TCGA) project is a landmark in the molecular characterization of GC. Key challenges for the future will involve the translation of these molecular findings to clinical utility, by enabling novel strategies for early GC detection, and precision therapies for individual GC patients.

Micronutrients: A double-edged sword in microbial-induced gastric carcinogenesis

Epidemiologic studies throughout the world have uniformly demonstrated significant relationships between the intake of dietary micronutrients and gastric cancer risk. An exciting concept that has gained considerable traction recently is that micronutrients modulate gene expression within Helicobacter pylori, the strongest identified risk factor for gastric carcinogenesis. We present evidence here that essential micronutrients have a direct effect on H. pylori virulence, which subsequently affects interactions at the host-pathogen interface, thereby facilitating the development of premalignant and malignant lesions in the stomach. Further, these fundamental concepts provide a framework for understanding mechanisms driving the development of other malignancies that arise from foci of gastrointestinal inflammation.

Gene mutations in gastric cancer: a review of recent next-generation sequencing studies

Gastric cancer (GC) is one of the most common malignancies worldwide. Although some driver genes have been identified in GC, the molecular compositions of GC have not been fully understood. The development of next-generation sequencing (NGS) provides a high-throughput and systematic method to identify all genetic alterations in the cancer genome, especially in the field of mutation detection. NGS studies in GC have discovered some novel driver mutations. In this review, we focused on novel gene mutations discovered by NGS studies, along with some well-known driver genes in GC. We organized mutated genes from the perspective of related biological pathways. Mutations in genes relating to genome integrity (TP53, BRCA2), chromatin remodeling (ARID1A), cell adhesion (CDH1, FAT4, CTNNA1), cytoskeleton and cell motility (RHOA), Wnt pathway (CTNNB1, APC, RNF43), and RTK pathway (RTKs, RAS family, MAPK pathway, PIK pathway) are discussed. Efforts to establish a molecular classification based on NGS data which is valuable for future targeted therapy for GC are introduced. Comprehensive dissection of the molecular profile of GC cannot only unveil the molecular basis for GC but also identify genes of clinical utility, especially potential and specific therapeutic targets for GC.

Evolution of Gastric Cancer Treatment: From the Golden Age of Surgery to an Era of Precision Medicine

Gastric cancer imposes a global health burden. Although multimodal therapies have proven to benefit patients with advanced diseases after curative surgery, the prognosis of most advanced cancer patients still needs to be improved. Surgical extirpation is the mainstay of gastric cancer treatment. Indeed, without curative surgery, variations and combinations of chemotherapy and/or radiation cannot bring clinically meaningful success. Centered around D2 surgery, adjuvant and peri-operative multimodal therapies have improved survival in a certain group of gastric cancer patients. Moving toward a personalized cancer therapy era, molecular targeted strategies have been tested in clinical trials for gastric cancer. With some success and failures, we have learned valuable lessons regarding the biology of gastric cancer and the clinical relevance of biological therapies in addition to conventional treatments. Future treatment of gastric cancer will be shifted to molecularly tailored and genome information-based personalized therapy. Collaboration across disciplines and actively adopting emerging anti-cancer strategies, along with in-depth understanding of molecular and genetic underpinnings of tumor development and progression, are imperative to realizing personalized therapy for gastric cancer. Although many challenges remain to be overcome, we envision that the era of precision cancer medicine for gastric cancer has already arrived and anticipate that current knowledge and discoveries will be transformed into near-future clinical practice for managing gastric cancer patients.

Noncoding Genomics in Gastric Cancer and the Gastric Precancerous Cascade: Pathogenesis and Biomarkers

Gastric cancer is the fifth most common cancer and the third leading cause of cancer-related death, whose patterns vary among geographical regions and ethnicities. It is a multifactorial disease, and its development depends on infection by Helicobacter pylori (H. pylori) and Epstein-Barr virus (EBV), host genetic factors, and environmental factors. The heterogeneity of the disease has begun to be unraveled by a comprehensive mutational evaluation of primary tumors. The low-abundance of mutations suggests that other mechanisms participate in the evolution of the disease, such as those found through analyses of noncoding genomics. Noncoding genomics includes single nucleotide polymorphisms (SNPs), regulation of gene expression through DNA methylation of promoter sites, miRNAs, other noncoding RNAs in regulatory regions, and other topics. These processes and molecules ultimately control gene expression. Potential biomarkers are appearing from analyses of noncoding genomics. This review focuses on noncoding genomics and potential biomarkers in the context of gastric cancer and the gastric precancerous cascade.