High microsatellite instability predicts good prognosis in intestinal-type gastric cancers

Heterogeneity and Adjuvant Therapeutic Approaches in MSI-H/dMMR Resectable Gastric Cancer: Emerging Trends in Immunotherapy

Gastric cancer (GC) remains one of the world's most common and fatal malignant tumors. With a refined understanding of molecular typing in recent years, microsatellite instability (MSI) has become a major molecular typing approach for gastric cancer. MSI is well recognized for its important role during the immunotherapy of advanced GC. However, its value remains unclear in resectable gastric cancer. The reported incidence of microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) in resectable gastric cancer varies widely, with no consensus reached on the value of postoperative adjuvant therapy in patients with MSI-H/dMMR resectable GC. It has been established that MSI-H/dMMR tumor cells can elicit an endogenous immune antitumor response and ubiquitously express immune checkpoint ligands such as PD-1 or PD-L1. On the basis of these considerations, MSI-H/dMMR resectable GCs are responsive to adjuvant immunotherapy, although limited research has hitherto been conducted. In this review, we comprehensively describe the differences in geographic distribution and pathological stages in patients with MSI-H/dMMR with resectable gastric cancer and explore the value of adjuvant chemotherapy and immunotherapy on MSI-H/dMMR to provide a foothold for the individualized treatment of this patient population.

Prognostic Significance of ARID1A Expression Patterns Varies with Molecular Subtype in Advanced Gastric Cancer

Background/Aims

AT-rich interactive domain 1A (ARID1A) is frequently mutated in gastric cancer (GC), especially Epstein-Barr virus (EBV)-associated and microsatellite instability high GC. The loss of ARID1A expression has been reported as a poor prognostic marker in GC. However, the relationships between ARID1A alteration and EBV-associated and microsatellite instability high GC, which are known to have a favorable prognosis, has hampered proper evaluation of the prognostic significance of ARID1A expression in GC. We aimed to analyze the true prognostic significance of ARID1A expression by correcting confounding variables.

Methods

We evaluated the ARID1A expression in a large series (n=1,032) of advanced GC and analyzed the relationships between expression pattern and variable parameters, including clinicopathologic factors, key molecular features such as EBV-positivity, mismatch repair protein deficiency, and expression of p53 and several receptor tyrosine kinases including human epidermal growth factor receptor 2, epidermal growth factor receptor, and mesenchymal-epithelial transition factor. Survival analysis of the molecular subtypes was done according to the ARID1A expression patterns.

Results

Loss of ARID1A expression was found in 52.5% (53/101) of mutL homolog 1 (MLH1)-deficient and 35.8% (24/67) of EBV-positive GCs, compared with only 9.6% (82/864) of the MLH1-proficient and EBV-negative group (p<0.001). The loss of ARID1A expression was associated only with MLH1 deficiency and EBV positivity. On survival analysis, the loss of ARID1A expression was associated with worse prognosis only in MLH1-proficient and EBV-negative GC. Multivariate analysis revealed that both loss of ARID1A and decreased ARID1A expression were independent worse prognostic factors in patients with advanced GC.

Conclusions

Only in MLH1-proficient and EBV-negative GC, the loss of ARID1A expression is related to poorer prognosis.

PD-L1: Biological mechanism, function, and immunotherapy in gastric cancer

Gastric cancer (GC) is one of the main causes of cancer incidence rate and mortality worldwide. As the main breakthrough direction, the application of immune checkpoint inhibitors makes patients with GC have better prognosis, where PD-L1/PD-1 inhibitors in immunotherapy have good anti-tumor immune efficacy. Further understanding of the regulatory mechanism of PD-L1 in GC may bring substantial progress to the immunotherapy. In this review, we provide information on the endogenous and exogenous regulatory mechanisms of PD-L1 and its biological functions combined with current clinical trials of PD-L1/PD-1 inhibitors in GC. The malignant biological phenotypes caused by PD-L1 and the corresponding clinical combined treatment scheme have been reported. Identifying the biomarkers of the potential efficacy of immunotherapy and specifying the clinical immunotherapy scheme in combination with molecular characteristics of patients may maximize clinical benefits and better prognosis.

The Impact of Mismatch Repair Status on Prognosis of Patients With Gastric Cancer: A Multicenter Analysis

BACKGROUND

The clinical role of deficient DNA mismatch repair (dMMR)/microsatellite instability-high (MSI-H) in gastric cancer (GC) is still controversial. We aimed to analyze the relationship between dMMR/MSI-H and clinicopathological features along with survival.

METHODS

Patients who were diagnosed with GC at the three big cancer centers in China from 2015 to 2020 were evaluated retrospectively. MMR/MSI status was assessed using immunohistochemistry/PCR. Clinical and pathological data were collected from the medical record system.

RESULTS

A total of 196 patients with dMMR/MSI-H status were enrolled for analysis. The prevalence of MSI-H/dMMR in GC was 6.6%. Another 694 proficient MMR (pMMR) GC patients were enrolled for comparison. Compared with pMMR patients, dMMR/MSI-H patients were associated with older age, female predominance, distal location in the stomach, earlier TNM stage, intestinal subtype, better differentiation, and more negative HER2 status. The median overall survival (OS) of the dMMR/MSI-H group was better than that of the pMMR/microsatellite stability (MSS) group (not reached vs. 53.9 months, p = 0.014). Adjuvant chemotherapy had no impact in both disease-free survival (DFS) and OS of dMMR/MSI-H patients (p = 0.135 and 0.818, respectively). dMMR/MSI-H patients had poorer response and progression-free survival (PFS) of first-line chemotherapy, though they were statistically significant (p = 0.361 and 0.124, respectively).

CONCLUSIONS

dMMR/MSI-H GC patients have specific clinicopathological characteristics and better prognosis than pMMR patients.

Hyperprogressive Disease After Combined Anti-PD-L1 and Anti-CTLA-4 Immunotherapy for MSI-H/dMMR Gastric Cancer: A Case Report

Immune checkpoint inhibitors (ICI) have been developed in gastric adenocarcinomas and approved in first-line metastatic setting (in combination with chemotherapy) as well as in pretreated patients. Microsatellite instability-high (MSI-H) tumors are predicted to derive high benefit from ICI but data in gastric locations are limited. Here, we describe the case of a 68-year old patient with stage IV MSI-H gastric adenocarcinoma, referred to our center to receive immunotherapy after failure of standard of care (surgery with perioperative platin-based chemotherapy and paclitaxel plus ramucirumab at disease progression). The patient received one injection of durvalumab and tremelimumab and was hospitalized eighteen days after because of occlusive syndrome. The CT scan showed hyperprogression of the lymph nodes and hepatic lesions, compressing the gastric stump. He died few days later. Molecular analyses did not explain this outcome. To our knowledge, this is one of the first reported cases of hyperprogressive disease after combined ICI for a patient with MSI-H tumor. We review the potential causes and discuss the emerging literature regarding predictive factors of hyperprogression in the particular subset of MSI-H patients. If some data were available in retrospective studies, validation of strong predictive factors is needed to avoid such dramatic evolutions.

Immunohistochemical Analysis of Mismatch Repair Gene Proteins in Early Gastric Cancer Based on Microsatellite Status

BACKGROUND

Microsatellite instability (MSI) is a major pathway involved in gastric carcinogenesis and is observed in 10-20% of early gastric cancers (EGCs). Early detection of EGCs with an MSI-high phenotype would be useful for elucidating the mechanisms of gastric carcinogenesis and improving outcomes in patients with GC.

OBJECTIVE

We explored the usefulness of immunohistochemical expression of mismatch repair (MMR) proteins, including MLH1, PMS2, MSH2, and MSH6 in EGC.

METHODS

We examined the expression of 4 MMR proteins using immunohistochemistry in 119 patients with EGC based on MS status, as determined by polymerase chain reaction-microsatellite analysis. In addition, methylation of the MLH1 gene was quantified by pyrosequencing.

RESULTS

EGCs were classified into 46 MSI-high phenotypes and 73 microsatellite stable (MSS) phenotypes. Although loss of MLH1 expression was associated with loss of PMS2 expression in the MSI-high phenotype, discordant cases of loss of expression between MLH1 and PMS2 were found (MLH1 [-]/PMS2 [+], 3 cases). Loss of MLH1/PMS2 expression was observed in 2 of 73 MSS phenotypes. Loss of MSH2/MSH6 expression was found in 4 of 46 MSI-high phenotypes, whereas loss of MSH2/MSH6 expression was not detected in the MSS phenotype. In addition, loss of MLH1 expression was correlated with methylation of MLH1. However, there were discordant cases in which loss of MLH1 expression was not accompanied by methylation of MLH1.

CONCLUSION

Although immunostaining of MMR proteins could help predict MSI in EGCs, immunostaining did not have the same value as genetic testing for determination of MSI.

Microsatellite Instability Analysis in Gastric Carcinomas of Moroccan Patients

Aim: To investigate correlations between microsatellite instability (MSI) and the phenotype, clinicopathological features, and overall survival (OS) in Moroccan gastric cancer (GC) patients. We evaluated the mutation frequency of 22 MSI-target genes in MSI-positive tumors. Materials and Methods: MSI evaluation were performed for 97 gastric tumors by multiplex polymerase chain reaction (PCR) using a panel of five quasimonomorphic mononucleotide repeat markers (NR27, NR21, NR24, BAT25, and BAT26). The mutation profiles of 22 MSI-target genes were assessed by multiplex PCR and genotyping. Kaplan-Meier curves, the log-rank test, and the Cox proportional hazard regression model were used to conduct survival analyses. Results: Microsatellite stable (MSS) status was observed in 77/97 (79.4%) gastric cancer samples, MSI-Low in 7 (7.2%) samples, and MSI-High (MSI-H) in 13 (13.4%) cases. The MSI-H phenotype was significantly associated with older age (p = 0.004), tumor location (p < 0.001), and intestinal-type of Lauren classification (p < 0.001). Among the 22 MSI target genes analyzed, the most frequently altered genes were HSP110 (84.6%), EGFR (30.8%), BRCA2 (23.1%), MRE11 (23.1%), and MSH3 (23.1%). Multivariate analysis revealed the MSS phenotype (Hazard ratio, 0.23; 95% confidence interval, 0.7-7.4; p = 0.014) as an independent indicator of poor prognosis in our population. Conclusions: This study is the first analysis of MSI in Moroccan GC patients. MSI-H GCs have distinct clinicopathological features and an improved OS. We have identified candidate target genes altered in MSI-positive tumors with potential clinical implications. These findings can guide immunotherapy designed for Moroccan GC patients.

Are Borrmann's Types of Advanced Gastric Cancer Distinct Clinicopathological and Molecular Entities? A Western Study

Most studies on the clinicopathological impact of Borrmann classification for gastric cancer (GC) have been performed in Asian patients with type IV tumors, and immunohistochemical features of Borrmann types have scarcely been analyzed. We assessed the clinicopathological, molecular features and prognostic value of Borrmann types in all patients with advanced GC resected in a Western institution (n = 260). We observed a significant relationship between Borrmann types and age, systemic symptoms, tumor size, Laurén subtype, presence of signet-ring cells, infiltrative growth, high grade, tumor necrosis, HERCEPTEST positivity, microsatellite instability (MSI) and molecular subtypes. Polypoid GC showed systemic symptoms, intestinal-type histology, low grade, expansive growth and HERCEPTEST positivity. Fungating GC occurred in symptomatic older patients. It presented intestinal-type histology, infiltrative growth and necrosis. Ulcerated GC showed smaller size, intestinal-type histology, high grade and infiltrative growth. Most polypoid and ulcerated tumors were stable-p53-not overexpressed or microsatellite unstable. Flat lesions were high-grade diffuse tumors with no MSI, and occurred in younger and less symptomatic patients. No association was found between Borrmann classification and prognosis. According to our results, Borrmann types may represent distinct clinicopathological and biological entities. Further research should be conducted to confirm the role of Borrmann classification in the stratification of patients with advanced GC.

Amplification of the human epidermal growth factor receptor 2 (HER2) gene is associated with a microsatellite stable status in Chinese gastric cancer patients

BACKGROUND

Gastric cancer (GC) is one of the most common cancers worldwide. However, little is known about the combination of HER2 amplification and microsatellite instability (MSI) status in GC. This study aimed to analyze the correlation of HER2 amplification with microsatellite instability (MSI) status, clinical characteristics, and the tumor mutational burden (TMB) of patients.

METHODS

A total of 192 gastric cancer (GC) patients were enrolled in this cohort. To analyze genomic alterations (GAs), deep sequencing was performed on 450 target cancer genes. TMB was measured by an in-house algorithm. MSI status was inferred based on the MANTIS (Microsatellite Analysis for Normal-Tumor InStability) score.

RESULTS

The most frequently amplified genes in the GC patients included cyclin E1 (CCNE1), human epidermal growth factor receptor 2 (HER2), fibroblast growth factor receptor 2 (FGFR2), cyclin D1 (CCND1), fibroblast growth factor 19 (FGF19), fibroblast growth factor 3 (FGF3), and fibroblast growth factor 4 (FGF4). The frequency of HER2 amplification was 9.38% (18/192). HER2 amplification was higher in females than in males (14.52% vs. 6.92%, respectively, P=0.091), however, MSI was higher in males compared to females (7.69% vs. 4.84%, respectively, P=0.46). HER2 amplification was higher in metastatic loci compared to primary lesions (23.08% vs. 8.38%, respectively, P=0.079) and was lower in patients with high TMB (TMB-H) compared to those with low TMB (TMB-L) (4.0% vs. 11.35%, respectively, P=0.12). While the frequency of MSI in metastatic foci was higher than that in primary lesions (15.38% vs. 6.15%, respectively, P=0.48), MSI status was highly associated with TMB-H (20% vs. 0%, respectively, P=3.66×10-7). Furthermore, HER2 amplification was negatively correlated with MSI status in Chinese GC patients.

CONCLUSIONS

HER2 amplification was negatively correlated with TMB-H and MSI status, and MSI status was significantly associated with TMB-H in Chinese GC patients. These data suggested that HER2 amplification might be a negative indicator for GC immunotherapy.

Prognostic impact of microsatellite instability in gastric cancer

Gastric cancer is a common and deadly cancer. Several factors are associated with its prognosis; however, controversy exists about the role of microsatellite instability (MSI). We aimed to determine the 5-year overall survival (OS) of MSI in gastric adenocarcinoma. A cross-sectional study was carried out on gastric adenocarcinoma in clinical stages I to III treated with D2 gastrectomy between 2010-2013. MSI was demonstrated by immunohistochemistry. We performed a survival analysis comparing cases with and without MSI. From 102 cases, 9.8% showed MSI. The median age was 63 years (range 33-91 years), and 57.8% were men. The more prevalent site of occurrence was the antrum (46.1%), 78.5% of the cases presented in stage III, 47.1% were of the diffuse type, 45.1% were of an intestinal type, and 7.8% were mixed. MSI cases were associated with lower clinical stages (stages I-II) and with better 5-year OS (100 vs. 47 months, p = 0.017). In a multivariate analysis, MSI was independently associated with better survival (HR = 0.209, 95% CI: 0.046-0.945, p = 0.042). MSI gastric cancers presented in early clinical stages and had favourable prognosis compared with non-MSI cancers.

Diagnosis of Lynch Syndrome and Strategies to Distinguish Lynch-Related Tumors from Sporadic MSI/dMMR Tumors

Simple Summary

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific, as most of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Therefore, the identification of MSI/dMMR requires additional diagnostic tools to identify LS. In this review, we address the hallmarks of LS and present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with current strategies, which should be taken into account in order to improve the diagnosis of LS.

Abstract

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific to it, as approximately 80% of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Methods leading to the diagnosis of LS have considerably evolved in recent years and so have tumoral tests for LS screening and for the discrimination of LS-related to MSI-sporadic tumors. In this review, we address the hallmarks of LS, including the clinical, histopathological, and molecular features. We present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with the current strategies, which should be taken into account to improve the diagnosis of LS and avoid inappropriate clinical management.

Protein expression-based classification of gastric cancer by immunohistochemistry of tissue microarray

Recently, the Cancer Genome Atlas and Asian Cancer Research Group propose two new classifications system of gastric cancer by using multi-platforms of molecular analyses. However, these highly complicated and cost technologies have not yet been translated into full clinical utility. In addition, the clinicians are expected to gain more guidance of treatment for different molecular subtypes. In this study, we developed a panel of gastric cancer patients in population from Southern China using commercially accessible TMA and immunohistochemical technology. A cohort of 259 GC patients was classified into 4 subtypes on the basis of expression of mismatch repair proteins (PMS2, MLH1, MSH2, and MSH6), E-cadherin and p21 protein. We observed that the subtypes presented distinct prognosis. dMMR-like subtype was associated with the best prognosis, and E-cadherin-a subtype was associated with the worst prognosis. Patients with p21-High and p21-Ligh subtypes had intermediate overall survival. In multivariate analysis, the dMMR-like subtype remained an independent prediction power for overall survival in the model. We described a molecular classification of gastric cancers using clinically applicable assay. The biological relevance of the four subtypes was illustrated by significant differences in prognosis. Our molecular classification provided an effective and inexpensive screening tool for improving prognostic models. Nevertheless, our study should be considered preliminary and carries a limited predictive value as a single-center retrospective study.

Retrospective analysis for the efficacy and safety of nivolumab in advanced gastric cancer patients according to ascites burden

BACKGROUND

Nivolumab is a standard later-line therapy for advanced gastric cancer (AGC). However, few reports exist about its efficacy and safety in patients with massive ascites.

METHODS

We retrospectively collected clinical data from 72 AGC patients who received nivolumab administration at least once from Oct 2017 to Feb 2019 and studied their clinical outcomes dividing into two groups: 50 patients with no or localized ascites in the pelvic cavity or liver surface (LAB: low ascites burden) and 22 patients with massive ascites (HAB: high ascites burden).

RESULTS

Median overall survival (OS) was 5.3 months (95% CI 3.4-7.3) in the LAB group and 2.5 months (95% CI 0.0-5.0) in the HAB group. Multivariate Cox regression analysis for OS revealed blood neutrophil-to-lymphocyte ratio (hazard ratio 0.40, 95% CI 0.20-0.83, p = 0.013) as an independent prognostic factor. Response rates in the patients with measurable lesions were 16% (7/43) and 8% (1/12) in the LAB and HAB groups, respectively. Ascites decreased or disappeared in 6 HAB patients (27%) and these responders had a prolonged OS of median 9.7 months (95% CI 3.6-15.8). The median time to ascites response was 1.3 months (95% CI 0.8-1.9). These responders have lower neutrophil-to-lymphocyte ratios than 5.0 at the start of nivolumab. Immune-related adverse events occurred in 23% of HAB and 18% of LAB patients.

CONCLUSIONS

Nivolumab could improve massive ascites and confer survival benefit for some AGC patients. Considering a similar incidence of immune-related adverse events, it would be a recommended treatment option for AGC with massive ascites.

Immunotherapy in gastroesophageal cancers: Current state and future directions

While gastroesophageal (GE) cancers are one of the most common cancers worldwide, unfortunately, the mortality remains high. Commonly used treatment options include surgical resection, chemotherapy, radiotherapy, and molecular targeted therapy, which improve survival only minimally; thus, affirming the dire need for exploring alternative strategies to improve patient outcomes. Immunotherapy, which has revolutionized the world of oncology, has somewhat lagged behind in GE malignancies. Tumor-associated microenvironment and regulatory T cells, alongside cell cycle checkpoints, have been proposed by various studies as the mediators of carcinogenesis in GE cancers. Thus, inhibition of each of these could serve as a possible target of treatment. While the approval of pembrolizumab has provided some hope, it is not enough to override the dismal prognosis that this disease confers. Herein, we discuss the prospects of immunotherapy in this variety of cancer.

Finding the hot spot: identifying immune sensitive gastrointestinal tumors

Although researchers have been trying to harness the immune system for over 100 years, the advent of immune checkpoint blockers (ICB) marks an era of significant clinical outcomes in various metastatic solid tumors, characterized by complete and durable responses. ICBs are monoclonal antibodies that target either of a pair of transmembrane molecules in tumors or T-cells involved in immune evasion. Currently 2 ICBs targeting the checkpoint program death 1 (PD-1), nivolumab and pembrolizumab, and one cytotoxic lymphocyte antigen-4 (CTLA-4) inhibitor (ipilimumab) are approved in gastrointestinal malignancies. We review herein the current evidence on predictive biomarkers for ICB response in gastrointestinal tumors. A review of literature based on the National Cancer Institute list of FDA-approved drugs for neoplasms and FDA-approved therapies at the FDA website was performed. An initial literature review was based on the American Association for Clinical Research meeting 2019, the American Society of Clinical Oncology meeting 2019 and the European Society of Medical Oncology 2019 proceedings. A systematic search of PubMed was performed involving MeSH browser terms such as biomarkers, immunotherapy, gastrointestinal diseases and neoplasms. When appropriate, American and British terms were used in the search. The most relevant predictor of response to ICBs is microsatellite instability (MSI) and the data is strongest for colorectal cancer. At least 3 prospective trials show evidence of PD-L1 as a predictive biomarker for ICB response in gastroesophageal malignancies. At least one prospective trial has described tumor mutational burden high (TMB-H), independent of MSI, as predictive of response in anal and biliary tract carcinomas. DNA Polymerase Epsilon (POLE) or delta (POL-D) mutations have been implicated in a subset of MSS colorectal cancer with TMB-H but this biomarker requires prospective validation. There is evolving data based on retrospective observations that gene alterations predicting acquired resistance and hyper-progression. Ongoing clinical research is assessing the role of the human microbiome and RNA-editing complex mutations as predictive biomarkers of response to ICBs. MSI has the strongest predictive power among current biomarkers for ICB response in gastrointestinal cancers. Data continue to accumulate from ongoing clinical trials and new biomarkers are emerging from pre-clinical studies, suggesting that drug combinations targeting pathways complimentary to the PD-1/PD-L1 axis inhibition will define a robust field of clinical research.

Mismatch Repair System Genomic Scars in Gastroesophageal Cancers: Biology and Clinical Testing

Alterations in the mismatch repair (MMR) system result in genomic instability, neoantigen production, and immune response in cancer. There is evidence that gastroesophageal tumors with MMR deficiency may be susceptible to immune-checkpoint inhibitors treatment, especially in those presenting at advanced-stage disease. Although a number of biomarkers have been developed in histology-agnostic settings to assess MMR status, there is evidence that a tumor-specific testing approach would improve the selection of patients for immunotherapy. However, no testing methods have been developed specifically for gastroesophageal cancers so far. Here, we discuss the state of the art, current advances, and future perspectives of MMR-related biomarkers’ biologic and clinical role in gastroesophageal cancers.

Cost-Effectiveness Analysis of Biomarker-Guided Treatment for Metastatic Gastric Cancer in the Second-Line Setting

BACKGROUND

The 5-year survival rate of patients with metastatic gastric cancer (GC) is only 5%. However, trials have demonstrated promising antitumor activity for targeted therapies/immunotherapies among chemorefractory metastatic GC patients. Pembrolizumab has shown particular efficacy among patients with programmed death ligand-1 (PD-L1) expression and high microsatellite instability (MSI-H). The aim of this study was to assess the effectiveness and cost-effectiveness of biomarker-guided second-line GC treatment.

METHODS

We constructed a Markov decision-analytic model using clinical trial data. Our model compared pembrolizumab monotherapy and ramucirumab/paclitaxel combination therapy for all patients and pembrolizumab for patients based on MSI status or PD-L1 expression. Paclitaxel monotherapy and best supportive care for all patients were additional comparators. Costs of drugs, treatment administration, follow-up, and management of adverse events were estimated from a US payer perspective. The primary outcomes were quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) with a willingness-to-pay threshold of $100,000/QALY over 60 months. Secondary outcomes were unadjusted life years (survival) and costs. Deterministic and probabilistic sensitivity analyses were performed to evaluate model uncertainty.

RESULTS

The most effective strategy was pembrolizumab for MSI-H patients and ramucirumab/paclitaxel for all other patients, adding 3.8 months or 2.0 quality-adjusted months compared to paclitaxel. However, this strategy resulted in a prohibitively high ICER of $1,074,620/QALY. The only cost-effective strategy was paclitaxel monotherapy for all patients, with an ICER of $53,705/QALY.

CONCLUSION

Biomarker-based treatments with targeted therapies/immunotherapies for second-line metastatic GC patients substantially improve unadjusted and quality-adjusted survival but are not cost-effective at current drug prices.

The promising role of monoclonal antibodies for gastric cancer treatment

Gastric cancer (GC) is the second leading cause of cancer-related death world-wide. Despite improvements in prevention, early detection and various therapeutic options, the prognosis is still poor. GC is often diagnosed at an advanced stage with survivals less than 1 year. Chemotherapy as the mainstay of treatment in advanced stage is not of notable advantages, underlining the need for novel more effective therapeutic options. Based on current knowledge of molecular and cellular mechanisms, a number of novel biologic approaches such as monoclonal antibodies have been recently introduced for cancer treatment that mainly affect the immune system or target signaling pathways playing role in cancer and metastasis development. In this review, various monoclonal antibodies for GC therapy were explained.

Identification of Subtype-Specific Three-Gene Signature for Prognostic Prediction in Diffuse Type Gastric Cancer

Gastric cancer (GC), with high heterogeneity, can be mainly classified into intestinal type and diffuse type according to the Lauren classification system. Although a number of differences were reported between these two types, no study on the Lauren subtype-specific multi-gene signature for evaluation of GC prognosis has been conducted, and the molecular mechanism underlying its poor prognosis has still remained elusive. Therefore, this study aimed to explore subtype-specific multi-gene signature for prognostic prediction in different subtypes of Lauren classification. With combination of the least absolute shrinkage and selection operator (LASSO) algorithm and the Akaike information criterion (AIC), the 3-gene subtype-specific prognostic signature was successfully established in diffuse type GC using GSE62254 dataset. Following the calculation of risk score (RS) based on 3-gene signature, the nomogram models were established to predict 1-, 3-, and 5-year overall survival in diffuse type GC. Moreover, the prognostic predictive nomogram model of diffuse type GC was also proved to be effective for validation of GSE1549 dataset and by a Gene Expression Omnibus (GEO)-based meta-analysis. In the analysis of the correlation between RS and clinical-pathological characteristics, RS and two genes of the 3-gene signature (EMCN and COL4A5) were found to be positively correlated with peritoneal metastasis. Furthermore, EMCN and COL4A5, rather than CCL11, were proved to be able to enhance the adhesion ability of MKN45 and NUGC4 cells to peritoneal mesothelial cell line HMR-SV5. Eventually, it was proved that COL4A5 promoted peritoneal metastasis by activating Wnt signaling pathway, whereas the upregulation of integrin family genes mediated by FAK-AKT/ERK/STAT3 signaling pathway activation is involved in peritoneal metastasis promotion function of EMCN. Taken together, our study identified the subtype-specific 3-gene signature in diffuse type GC, which could effectively predict the patients' OS and might explain the molecular mechanisms in presence of its poor prognosis.

Mismatch Repair Status of Gastric Cancer and Its Association with the Local and Systemic Immune Response

BACKGROUND

Microsatellite instability (MSI)-high (MSI-H) colorectal cancer is known to be associated with increased tumor-infiltrating lymphocytes (TILs), elevated host systemic immune response, and a favorable prognosis. In gastric cancer, however, MSI status has rarely been evaluated in the context of TILs and systemic immune response.

MATERIALS AND METHODS

We evaluated data for 345 patients with gastric cancer who underwent gastrectomy with MSI typing. The numbers of TILs were counted after immunohistochemical staining with anti-CD3, CD4, CD8, forkhead box P3 (Foxp3), and granzyme B to quantify the subsets of TILs. To evaluate the systemic immune response, the differential white blood cell count and prognostic nutritional index (PNI) were obtained.

RESULTS

Of the 345 patients, 57 demonstrated MSI-H tumors and 288 demonstrated non-MSI-H tumors. MSI-H tumors carried significantly higher densities of CD8+ T cells, Foxp3+ T cells, and granzyme B+ T cells and a higher ratio of Foxp3/CD4 and granzyme B/CD8. The prognostic impact of TILs differed between patients with MSI-H tumors and those with non-MSI-H tumors. The TIL subsets were not found to be significant prognostic factors for recurrence-free survival (RFS) or overall survival (OS) in the MSI-H tumor group. In the non-MSI-H tumor group, multivariate analysis showed that stage, PNI, and CD4+ T cells were independent prognostic factors for RFS, and stage, PNI, and the Foxp3/CD4 ratio were independent prognostic factors for OS.

CONCLUSIONS

The association between systemic/local immune response and prognosis differed according to MSI status. Different tumor characteristics and prognoses according to MSI status could be associated with the immunogenicity caused by microsatellite instability and subsequent host immune response.

IMPLICATIONS FOR PRACTICE

This study demonstrates that the density of each subset of tumor-infiltrating lymphocytes (TILs) differed between microsatellite instability (MSI)-high and non-MSI-high tumors. Moreover, the prognostic effect of the preoperative systemic immune response status and TILs differed between the MSI-high (MSI-H) and non-MSI-H tumor groups. The present study may help to identify the mechanisms of cancer progression and develop treatment strategies for MSI-high gastric cancer.

Microsatellite Instability and Altered Expressions of MLH1 and MSH2 in Gastric Cancer

Introduction: Microsatellite instability (MSI) is a hallmark of defective DNA mismatch repair (MMR) of genes especially MLH1 and MSH2. It is frequently involved in the carcinogenesis of various tumours including gastric cancer (GC). However, MSI in GCs have not been reported in Malaysia before. Objective: This study was conducted to determine the microsatellite instability (MSI) status in gastric cancer by microsatellite analysis, sequencing, its association with MLH1 and MSH2 protein expression and H.pylori infection by immunohistochemistry. Method: A total of 60 gastric cancer cases were retrieved. DNA was extracted from paired normal and tumour tissues while MLH1 and MSH2 protein expression as well as H. pylori status were determined by IHC staining. For microsatellite analysis, polymerase chain reaction (PCR) was performed for paired tissue samples using a panel of five microsatellite markers. MSI-positive results were subjected for DNA sequencing to assess mutations in the MLH1 and MSH2 genes. Results: Microsatellite analysis identified ten MSI positive cases (16.7%), out of which only six cases (10.3%) showed absence of MLH1 (n=3) or MSH2 (n=3) protein expression by IHC. The most frequent microsatellite marker in MSI positive cases was BAT26 (90%). Nine of ten MSI positive cases were intestinal type with one diffuse and all were located distally. H. pylori infection was detected in 13 of 60 cases (21.7%) including in three MSI positive cases. All these results however were not statistically significant. Our sequencing data displayed novel mutations. However these data were not statistically correlated with expression levels of MLH1 and MSH2 proteins by IHC. This may be due to small sample size to detect small or moderately sized effects. Conclusion: The frequency of MSI in this study was comparable with published results. Determination of affected MMR genes by more than two antibodies may increase the sensitivity of IHC to that of MSI analysis.

Deficiency of mismatch repair genes is less frequently observed in signet ring cell compared with non-signet ring cell gastric cancer

Signet ring cell (SRC) gastric cancer at advanced stage has poor prognosis. While a recent study reported nearly one-third of SRC cases contain tumors with deficient mismatch repair (MMR) genes, other studies in SRC have been inconclusive. To re-analyze the results, we performed immunohistochemical staining of MLH1, MSH2, MSH6 and PMS2 proteins in 38 SRC gastric tumors compared with 109 non-SRC (NSRC) tumors from 94 patients. In contrast to the previous study, all SRC gastric tumors normally expressed MMR proteins, whereas 22 of 109 of NSRC (20%) showed deficient MMR proteins. To reinforce our results, we referred to the Cancer Genome Atlas (TCGA) genomic database and found that only 6 (6%) of 99 samples with diffuse gastric tumors showed deficient MMR, whereas 64 (21%) of 304 in intestinal gastric tumors showed deficient MMR. Our results as well as the TCGA database indicated that MMR genes are infrequently inactivated in SRC gastric cancer. These findings indicate that SRC patients may not be the best candidates for immuno-oncology therapy.

From Tumor Immunology to Immunotherapy in Gastric and Esophageal Cancer

Esophageal and gastric cancers represent tumors with poor prognosis. Unfortunately, radiotherapy, chemotherapy, and targeted therapy have made only limited progress in recent years in improving the generally disappointing outcome. Immunotherapy with checkpoint inhibitors is a novel treatment approach that quickly entered clinical practice in malignant melanoma and renal cell cancer, but the role in esophageal and gastric cancer is still poorly defined. The principal prognostic/predictive biomarkers for immunotherapy efficacy currently considered are PD-L1 expression along with defects in mismatch repair genes resulting in microsatellite instability (MSI-H) phenotype. The new molecular classification of gastric cancer also takes these factors into consideration. Available reports regarding PD-1, PD-L1, PD-L2 expression and MSI status in gastric and esophageal cancer are reviewed to summarize the clinical prognostic and predictive role together with potential clinical implications. The most important recently published clinical trials evaluating checkpoint inhibitor efficacy in these tumors are also summarized.

Current status of immunotherapy and immune biomarkers in gastro-esophageal cancers

Gastroesophageal (GE) cancers continue to be a significant cause of mortality globally. Despite therapeutic advances in oncology, the prognosis of advanced GE cancer remains exceedingly poor. Immunotherapy has caused a major paradigm shift in the field of oncology. Not all patients benefit from these agents and several studies are trying to identify predictive and prognostic biomarkers to better inform and guide treatment decisions. The potential role of immunotherapy in GE cancers is emerging. These cancer types are molecularly and immunologically heterogeneous, and this heterogeneity influences the tumor microenvironment posing a significant challenge to studying biomarkers of response to immunotherapy. Here in this article, we discuss the need for new therapeutic approaches in GE cancers, review the emerging data on the activity of checkpoint inhibitors and the role of biomarkers in this setting.

The Role of Microsatellite Instability in Positive Margin Gastric Cancer Patients

PURPOSE

A positive resection margin (RM+) is acknowledged as a poor prognostic factor after gastrectomy. Microsatellite instability (MSI-H) gastric cancer has been identified as a subgroup of gastric cancer that may be associated with an improved prognosis. The aim of the study was an analysis of MSI status on patients with margin involvement after gastrectomy and examination of the association between MSI, margin status, and survival outcomes.

METHODS

From a large prospectively annotated surgical database we collected clinicopathological and survival data on patients who had undergone a potentially curative resection for gastric cancer. MSI status was assessed using a standard 5-marker quasi-monomorphic mononucleotide repeat panel. Patients who were R+ and either microsatellite stable (MSS) or MSI-H were identified and clinicopathological characteristics and disease specific survival was compared.

RESULTS

Three hundred and eighty-six patients were identified; 102 (26.4%) cancers were MSI-H. The proportion of R+ resections was not significantly different in MSS and MSI-H groups. For MSS patients 3-, 5-, and 10-year disease-specific survival rates were 9.1%, 0%, and 0%, respectively; for patients with MSI-H R+ tumors these were 38.5%, 30.8%, and 15.4%, respectively. In Cox analysis MSI-H, female gender, and T ≥3 were significantly associated with survival.

CONCLUSIONS

Patients with MSI-H gastric cancer may have long-term survival despite R+ margin status. The molecular division of gastric cancer may be an important step in identifying possible tailored surgical treatments corresponding to clinical and pathological factors.

Hypermutation and microsatellite instability in gastrointestinal cancers

Recent progress in cancer genome analysis using next-generation sequencing has revealed a high mutation burden in some tumors. The particularly high rate of somatic mutation in these tumors correlates with the generation of neo-antigens capable of eliciting an immune response. Identification of hypermutated tumors is therefore clinically valuable for selecting patients suitable for immunotherapy treatment. There are several known causes of hypermutation in tumors, such as ultraviolet light in melanoma, tobacco smoke in lung cancer, and excessive APOBEC (apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like) activity in breast and gastric cancer. In gastrointestinal cancers, one of the leading causes of hypermutation is a defect in DNA mismatch repair, which results in microsatellite instability (MSI). This review will focus on the frequency, characteristics and genomic signature of hypermutated gastrointestinal cancers with MSI. Detection of tumor hypermutation in cancer is expected to not only predict the clinical benefit of immune checkpoint inhibitor treatment, but also to provide better surgical strategies for the patients with hypermutated tumors. Thus, in an era of precision medicine, identification of hypermutation and MSI will play an important role directing surgical and chemotherapeutic treatment.

Exome sequencing characterizes the somatic mutation spectrum of early serrated lesions in a patient with serrated polyposis syndrome (SPS)

Background

Serrated or Hyperplastic Polyposis Syndrome (SPS, HPS) is a yet poorly defined colorectal cancer (CRC) predisposition characterised by the occurrence of multiple and/or large serrated polyps throughout the colon. A serrated polyp-CRC sequence (serrated pathway) of CRC formation has been postulated, however, to date only few molecular signatures of serrated neoplasia (BRAF, KRAS, RNF43 mutations, CpG Island Methylation, MSI) have been described in a subset of SPS patients and neither the etiology of the syndrome nor the distinct genetic alterations during tumorigenesis have been identified.

Methods

To identify somatic point mutations in potential novel candidate genes of SPS-associated lesions and the involved pathways we performed exome sequencing of eleven early serrated polyps obtained from a 41 year-old female patient with clinically confirmed SPS. For data filtering and analysis, standard pipelines were used. Somatic mutations were identified by comparison with leukocyte DNA and were validated by Sanger sequencing.

Results

The BRAF p.V600E or KRAS p.G12D mutation was identified in six polyps (~50%) and not found in polyps from the distal colon. In addition, we found seven unique rare somatic alterations of seven different genes in four serrated tumours, all of which are missense variants. The variant in ABI3BP and CATSPERB are predicted to be deleterious. No established cancer gene or candidate genes related to serrated tumorigenesis were affected.

Conclusions

Somatic mutations seem to be rare events in early hyperplastic and serrated lesions of SPS patients. Neither frequently affected genes nor enrichment of specific pathways were observed. Thus, other alterations such as non-coding variants or epigenetic changes might be the major driving force of tumour progression in SPS.

Electronic supplementary material

The online version of this article (10.1186/s13053-017-0082-9) contains supplementary material, which is available to authorized users.

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.

Programmed cell death-ligand 1 expression predicts survival in patients with gastric carcinoma with microsatellite instability

Programmed death-ligand 1 (PD-L1) is expressed in a subgroup of gastric cancers that may benefit from immunotherapy. Microsatellite instability-high (MSI-H) is a potential predictive factor for response to immunotherapy targeting the PD-1 or its ligand PD-L1. The relationship between PD-L1 expression and MSI-H status remains poorly understood. In this study, we investigated PD-L1 expression in patients with MSI-H gastric cancer. We analyzed PD-L1 expression in 78 MSI-H gastric cancer tissue samples using immunohistochemistry. PD-L1 expression was classified as expression on tumor cells or on immune cells. We observed PD-L1 expression in 48 gastric cancer samples (61.5%), consisting of 7 (9.0%) cases with tumor PD-L1 expression and 47 (60.3%) cases with immune cell PD-L1 expression. Immune cell PD-L1 expression was frequently associated with intestinal type cancer by the Lauren classification (p = 0.015), with a lower risk of lymph node metastasis (p = 0.027) and lower tumor stages (p = 0.029) compared to MSI-H gastric cancers without PD-L1 expression. Moreover, immune cell PD-L1 expression was an independent favorable prognostic factor for overall survival (versus PD-L1 negative; hazard ratio, 3.451; 95% confidence interval, 1.172–12.745; p = 0.025). In MSI-H gastric cancer, PD-L1 expression was observed to be independently associated with a longer survival.

Deletion in HSP110 T17: correlation with wild-type HSP110 expression and prognostic significance in microsatellite-unstable advanced gastric cancers

Deletion of the HSP110 T₁₇ mononucleotide repeat has recently been identified as a prognostic marker that is correlated with wild-type HSP110 (HSP110wt) expression in microsatellite instability-high (MSI-H) colorectal cancers. The aim of this study was to assess the correlation between deletion of the HSP110 T₁₇ repeat and expression of HSP110wt using DNA testing and immunohistochemistry and to determine the prognostic implications of HSP110 T₁₇ deletion in MSI-H advanced gastric cancers (GCs). The status of HSP110wt expression was evaluated by immunohistochemistry using an HSP110wt-specific antibody in 142 MSI-H advanced GCs. The size of the HSP110 T₁₇ repeat deletion was analyzed in 96 MSI-H advanced GCs; deletions were divided into small (0-2base pairs) and large deletions (3-5base pairs). Low and high expressions of HSP110wt were detected in 38 (26.8%) and 104 (73.2%) of the 142 cases, respectively. The HSP110 T₁₇ deletion was observed in 45 (46.9%) of the 96 MSI-H GC samples. Tumors with high expression of HSP110wt showed a tendency to have small or no deletion of HSP110 T₁₇. In Kaplan-Meier survival analysis, tumors with a large HSP110 T₁₇ deletion were associated with favorable overall survival and disease-free survival compared with those with small/no deletion of HSP110 T₁₇. However, HSP110 T₁₇ deletion size was not an independent prognostic factor in multivariate analysis. In summary, deletion of the HSP110 T₁₇ repeat was frequently observed in MSI-H GCs, and HSP110 T₁₇ deletion size was inversely correlated with HSP110wt expression status. Large HSP110 T₁₇ was not a prognostic indicator in MSI-H GCs.

Clinicopathologic Characteristics of Microsatellite Instable Gastric Carcinomas Revisited: Urgent Need for Standardization

Microsatellite instable gastric cancer (MSI-GC) is a specific molecular subtype of GC. We studied the phenotypes, genotypes, and clinicopathologic characteristics of MSI-GC in a white GC cohort and compared our findings with an extended literature review. The study cohort consisted of 482 patients. Specimens were available from 452 cases and were used for immunostaining (MLH1, PMS2, MSH2, MSH6) and molecular biological analyses (BAT-25, BAT-26, NR-21, NR-24, NR-27; Epstein-Barr virus in situ hybridization). Thirty-four (7.5%) GCs were MSI. Loss of MLH1 and/or PMS2 was found in 30 (88%) MSI-GC, 3 (9%) showed loss of MSH2 and/or MSH6. One (3%) MSI-GC was identified only by molecular biological testing. A single case was heterogeneous and contained microsatellite-stable and instable tumor areas. Twenty-one (62%) MSI-GCs showed unusual histologic features. MSI-GC was not found in diffuse-type or Epstein-Barr virus-positive GC. MSI-GC was significantly more prevalent in elderly patients, distal stomach, and was associated with a significantly lower number of lymph node metastases and a significantly better overall and tumor-specific survival. MSI-GC constitutes a small but relevant subgroup of GC with distinct clinicopathologic characteristics. Our literature review illustrates the shortcomings of missing standardized testing algorithms with prevalences of MSI-GC ranging from 0% to 44.5%. Future studies should test the hypothesis that patients with MSI-GCs may not need adjuvant/perioperative chemotherapy. However, this will require a standardized, quality-controlled diagnostic algorithm of MSI for GC.

Comparison between mononucleotide and dinucleotide marker panels in gastric cancer with loss of hMLH1 or hMSH2 expression

BACKGROUND

DNA mismatch repair deficiency is an important molecular mechanism of genetic instability in gastric cancer, and a high instability at microsatellites is associated with favorable prognosis. We compared mononucleotide and dinucleotide microsatellite instability (MSI) marker panels in 56 paired gastric tumor and normal samples.

METHODS

The mononucleotide marker panel (mono panel) consisted of 8 markers: BAT25, BAT26, BAT40, BAT-RII, NR21, NR22, NR24 and NR27. The dinucleotide marker panel (di panel) contained D2S123, D5S346, D17S250, D17S261, D17S520, D18S34 and D18S58. The NCI panel was used as reference panel.

RESULTS

Among 13 gastric tumors showing no hMLH1 or hMSH2 expression, 8 MSI-H (high) and 5 MSI-L (low) were identified. The analytical sensitivities of the NCI, mono and di panels to detect unstable MSI were 61.5% (8/13), 76.9% (10/13) and 84.6% (11/13), respectively. The size change of allele shift was statistically greater in the mono panel than in the di panel (p = 0.02 by Mann-Whitney U-test). The BAT40 (69.2%, 9/13) and D18S34 (76.9%, 10/13) markers showed high sensitivity for determination of MSI status.

CONCLUSIONS

To improve the detection rate of MSI in gastric cancer with loss of hMLH1 or hMSH2 expression, the kind of MSI marker may need to be considered more, instead of the repetitive type of marker. Thus, an MSI panel designed with a combination of both BAT40 and D18S34 is suggested for providing more accurate and sensitive MSI analysis in gastric cancer.

Combined prognostic effect of PD-L1 expression and immunoscore in microsatellite-unstable advanced gastric cancers

Background

The aim of this study was to evaluate how programmed death-ligand-1 (PD-L1) expression is linked to the immunoscore in the context of the tumor microenvironment and to assess the differential prognostic value of PD-L1 expression according to the immunoscore in 153 patients with microsatellite instability-high (MSI-H) advanced gastric cancer (GC).

Results

We found that T-PD-L1 (+) and I-PD-L1 (+) were significantly associated with a high immunoscore. The integrated PD-L1 expression of tumor and immune cells was not significantly correlated with the overall survival (OS) of patients. However, a combined survival analysis of PD-L1 expression and immunoscore revealed four distinct subgroups with a statistically significant difference in OS. That is, the PD-L1 (+)/immunoscoreLow group showed the worst and the PD-L1 (+)/immunoscoreHigh group showed the best prognosis. Furthermore, a multivariate analysis revealed that the combined status of PD-L1 expression and immunoscore was an independent and significant prognostic factor for OS in patients with MSI-H GC.

Materials and Methods

The immunoscore was quantified by the number of high-density areas of CD3+ and CD8+ tumor infiltrating lymphocytes both in the tumor regions and compartments (i.e., epithelial and stromal compartments of the tumor center and the invasive front), the scores of which range from I0 to I8. By using immunohistochemistry, the expression of PD-L1 was also analyzed in tumor cells (T-PD-L1) and immune cells (I-PD-L1) using four different cut-off values (1%, 5%, 10% and 50%).

Conclusions

Our study revealed that PD-L1 expression is associated with the corresponding immunoscore and that the immunoscore can be a relevant marker for the determination of the prognostic role of PD-L1 expression in MSI-H GCs.

Helicobacter pylori-Mediated Genetic Instability and Gastric Carcinogenesis

Helicobacter pylori infection is the most important cause of human gastric cancer worldwide. Gastric cancer develops over a long time after H. pylori infection via stepwise accumulation of genetic alterations and positive selection of cells with growth advantages. H. pylori itself and the resultant chronic inflammation lead to the emergence of genetic alterations in gastric epithelial cells via increased susceptibility of these cells to DNA damage. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) in inflammatory and gastric epithelial cells, as well as the expression of cytidine deaminase in gastric epithelial cells, may link H. pylori-related inflammation and DNA damage. Recent comprehensive analyses of gastric cancer genomes provide clues for the possible molecular mechanisms of gastric carcinogenesis. In this chapter, we describe how genetic alterations emerge during gastric carcinogenesis related to H. pylori infection.

Distribution of somatic mutations of cancer-related genes according to microsatellite instability status in Korean gastric cancer

In studies of the molecular basis of gastric cancer (GC), microsatellite instability (MSI) is one of the key factors. Somatic mutations found in GC are expected to contribute to MSI-high (H) tumorigenesis. We estimated somatic mutation distribution according to MSI status in 52 matched pair GC samples using the Ion Torrent Ion S5 XL with the AmpliSeq Cancer Hotspot panel.Seventy-five (9.8%) somatic variants consisting of 34 hotspot mutations and 41 other likely pathogenic variants were identified in 34 GC samples. The TP53 mutations was most common (35%, 26/75), followed by EGFR (8%, 6/75), HNF1A (8%, 6/75), PIK3CA (8%, 6/75), and ERBB2 (5%, 4/75). To determine MSI status, 52 matched pair samples were estimated using 15 MSI markers. Thirty-nine MS stable (S), 5 MSI-low (L), and 8 MSI-H were classified. GCs with MSI-H tended to have more variants significantly compared with GCs with MS stable (MSS) and MSI-L (standardized J-T statistic  =  3.161 for number of variants; P  =  .002). The mean number of all variants and hotspot mutations per tumor samples only in GCs with MSI-H were 3.9 (range, 1-6) and 1.1 (range, 0-3), respectively. Whereas, the mean number of all variants and hotspot mutations per tumor samples only in GCs with MSS/MSI-L were 1 (0-5)/0.8 (0-1) and 0.5 (0-3)/0.8 (0-1), respectively.In conclusion, GC with MSI-H harbored more mutations in genes that act as a tumor suppressor or oncogene compared to GC with MSS/MSI-L. This finding suggests that the accumulation of MSIs contributes to the genetic diversity and complexities of GC. In addition, targeted NGS approach allows for detection of common and also rare clinically actionable mutations and profiles of comutations in multiple patients simultaneously. Because GC shows distinctive patterns related to ethnics, further studies pertaining to different racial/ethnic groups or cancer types may reinforce our investigations.

Clinical course and outcome of patients with high-level microsatellite instability cancers in a real-life setting: a retrospective analysis

BACKGROUND

The prognostic and predictive significance of the high-level microsatellite instability (MSI-H) phenotype in various malignancies is unclear. We describe the characteristics, clinical course, and outcomes of patients with MSI-H malignancies treated in a real-life hospital setting.

PATIENTS AND METHODS

A retrospective analysis of MSI-H cancer patient files was conducted. We analyzed the genetic data, clinical characteristics, and oncological treatments, including chemotherapy and surgical interventions.

RESULTS

Clinical data of 73 MSI-H cancer patients were available. Mean age at diagnosis of first malignancy was 52.3 years. Eight patients (11%) had more than four malignancies each. Most patients (76%) had colorectal cancer (CRC). Seventeen patients (23%) had only extracolonic malignancies. Eighteen women (36%) had gynecological malignancy. Nine women (18%) had breast cancer. Mean follow-up was 8.5 years. Five-year overall survival and disease-free survival of all MSI-H cancer patients from first malignancy were 86% and 74.6%, respectively. Five-year overall survival rates of stage 2, 3, and 4 MSI-H CRC patients were 89.5%, 58.4%, and 22.9%, respectively.

CONCLUSION

Although the overall prognosis of MSI-H cancer patients is favorable, this advantage may not be maintained in advanced MSI-H CRC patients.

Influence of microRNAs and Long Non-Coding RNAs in Cancer Chemoresistance

Innate and acquired chemoresistance exhibited by most tumours exposed to conventional chemotherapeutic agents account for the majority of relapse cases in cancer patients. Such chemoresistance phenotypes are of a multi-factorial nature from multiple key molecular players. The discovery of the RNA interference pathway in 1998 and the widespread gene regulatory influences exerted by microRNAs (miRNAs) and other non-coding RNAs have certainly expanded the level of intricacy present for the development of any single physiological phenotype, including cancer chemoresistance. This review article focuses on the latest research efforts in identifying and validating specific key molecular players from the two main families of non-coding RNAs, namely miRNAs and long non-coding RNAs (lncRNAs), having direct or indirect influences in the development of cancer drug resistance properties and how such knowledge can be utilised for novel theranostics in oncology.

Molecular key to understand the gastric cancer biology in elderly patients-The role of microsatellite instability

BACKGROUND AND OBJECTIVES

Microsatellite instability (MSI) in gastric cancer (GC) is associated with older age. We present the clinicopathological results of younger and older patients with MSI GC.

METHODS

We analyzed 472 patients with GC. MSI analysis was done on fresh frozen tissue using five quasimonomorphic mononucleotide repeats: NR-21, NR-24, NR-27, BAT-25, and BAR-26. Clinical and pathological analysis was performed for different age groups.

RESULTS

We observed better survival in elderly MSI GC patients compared to younger patients. The percentage of MSI GC increases gradually with increasing age, accounting for 48% of patients over the age of 85 years. A difference in survival was seen between MSI and MSS groups of patients older than 65 years, while no statistical difference was seen for younger groups. Multivariate analysis revealed that MSI status has a significant prognostic factor in patients aged over 70 years (MSS vs. MSI; HR 1.82, P = 0.013).

CONCLUSION

MSI is an important prognostic factor above all in elderly GC patients. It is associated with favorable prognosis and may help in planning different approaches to treatment in this subgroup. J. Surg. Oncol. 2017;115:344-350. © 2016 Wiley Periodicals, Inc.

Epstein-Barr virus positivity, not mismatch repair-deficiency, is a favorable risk factor for lymph node metastasis in submucosa-invasive early gastric cancer

BACKGROUND

Epstein-Barr virus (EBV)-associated gastric cancer (GC) and microsatellite-instability-high GC are associated with a low prevalence of regional lymph node metastasis (LNM). To evaluate the feasibility of endoscopic treatment of EBV-associated and/or microsatellite-instability-high early GC (EGC), we analyzed the risk factors for LNM using a large series (n = 756) of submucosa-invasive (SM) EGC.

METHODS

EBV-encoded RNA in situ hybridization (EBER ISH) and immunohistochemistry for four mismatch repair (MMR) proteins (MLH1, PMS2, MSH2, and MSH6) were performed. The clinicopathologic features and results of EBER ISH and immunohistochemistry were compared according to the LNM status.

RESULTS

Among the cases, 146 EGCs (19.3 %) showed LNM. EBV negativity, larger tumor size (greater than 2 cm), deeper level of submucosal invasion, submucosal invasion depth greater than 500 µm, presence of ulceration, and presence of lymphovascular invasion (LVI) were associated with LNM. However, the MMR deficiency was not correlated with LNM. On multivariate regression analysis, larger tumor size (greater than 2 cm; odds ratio 1.6, p = 0.030), deeper level of submucosal invasion (odds ratio 2.9, p = 0.001), LVI (odds ratio 7.4, p < 0.001), and EBV negativity (p = 0.020) were independent risk factors for LNM in SM EGCs.

CONCLUSIONS

EBV positivity was a favorable risk factor for LNM in SM EGC. However, MMR deficiency was not associated with the status of LNM. Thus, we suggest that examination with EBER ISH could be considered for endoscopic resected specimens, especially in cases of SM EGC showing no LVI and clear resection margins.

The promise of PD-1 inhibitors in gastro-esophageal cancers: microsatellite instability vs. PD-L1

Preliminary clinical studies of anti-programmed cell death-1 (anti-PD-1) therapy in gastro-esophageal cancers have suggested promising single-agent activity. In patients who received prior treatment for advanced disease, pembrolizumab has been associated with a response rate of 20% in programmed cell death-1 ligand 1 (PD-L1)-positive tumors, and nivolumab with a response rate of 12% in unselected tumors. Both agents yielded a median duration of response lasting ~6-7 months. PD-L1 expression and microsatellite instability (MSI) have emerged as potential predictive markers for PD-1/PD-L1 blockade. PD-L1 expression in tumor cells and in immune cells within the tumor microenvironment has been detected in 14-24% and ~35% of patients with gastro-esophageal cancer, respectively. PD-L1 tumor cell expression appears to be more common in Epstein-Barr virus (EBV)-positive gastric cancers (GCs) and has been associated with an increased density of tumor-infiltrating lymphocytes (TIL). To date, data are too sparse to determine whether PD-L1 expression predicts efficacy of anti-PD-1 therapy in gastro-esophageal cancer, but data from other tumor types have not been consistent regarding its predictive value. MSI occurs in 10-20% of gastro-esophageal cancers and arises from deficient mismatch repair (MMR). MSI is highly correlated with non-synonymous mutation burden, as well as a dense accumulation of TILs. MSI has been associated with improved response to anti-PD-1 therapy in gastrointestinal cancers. Multiple studies are ongoing which examine therapeutic blockade of the PD-1/PD-L1 axis in unselected patients with gastro-esophageal cancer, as well as patients whose tumors express PD-L1 or exhibit MSI. These studies will clarify their activity in this disease and potentially can determine whether identify a strong predictive biomarker can be identified. Checkpoint inhibition is also being studied in combination with curative-intent chemo (radio) therapy and surgery.

Immunotherapy for Gastroesophageal Cancer

Survival for patients with advanced oesophageal and stomach cancer is poor; together these cancers are responsible for more than a million deaths per year globally. As chemotherapy and targeted therapies such as trastuzumab and ramucirumab result in modest improvements in survival but not long-term cure for such patients, development of alternative treatment approaches is warranted. Novel immunotherapy drugs such as checkpoint inhibitors have been paradigm changing in melanoma, non-small cell lung cancer and urothelial cancers. In this review, we assess the early evidence for efficacy of immunotherapy in patients with gastroesophageal cancer in addition to considering biomarkers associated with response to these treatments. Early results of Anti- Programmed Cell Death Protein-1 (anti-PD-1), anti-PD-L1 and anti-Cytotoxic T-lymphocyte assosciated protein-4 (anti-CTLA4) trials are examined, and we conclude with a discussion on the future direction for immunotherapy for gastroesophageal cancer patients.

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.

Challenge and thought on treatment of diffuse gastric cancer

Diffuse gastric cancer, which has a high degree of malignancy and is metastasis-prone, is a pathological type of Lauren classification. The incidence of diffuse gastric cancer shows an increasing trend in China, and it greatly threatens the human health. There have been many studies on diffuse gastric cancer, and its treatment and prognosis have been improved to some extent. In this paper, we systematically describe diffuse gastric cancer with regard to its epidemiology, diagnosis, biological behavior, and factors affecting the treatment and prognosis, and discuss problems and disputes in current diagnosis and treatment, with an aim to provide convenience for the further research and help for clinical work.

Usefulness of Immunohistochemistry for Microsatellite Instability Screening in Gastric Cancer

BACKGROUND/AIMS

The usefulness of immunohistochemistry to screen for the microsatellite instability (MSI) phenotype in gastric cancer remains unclear. Moreover, the prognostic value of MSI phenotypes in gastric cancer has been debated.

METHODS

The clinicopathologic parameters and survival outcomes of 203 MSI-high (MSI-H) and 261 microsatellite-stable (MSS) advanced gastric cancers (AGCs) were compared. Next, we compared the immunohistochemistry results for hMLH1 and hMSH2 with those of a polymerase chain reaction (PCR)-based method. Kaplan-Meier curves and a Cox proportional hazard regression model were used to conduct survival analyses.

RESULTS

The MSI-H AGCs were correlated with older age (p<0.001), female gender (p=0.018), distal location (p<0.001), larger size (p=0.016), and intestinal type (p<0.001). Multivariate analysis revealed that the MSI-H phenotype was an independent favorable factor that was related to overall survival in patients with AGC (p<0.001). Compared with the PCR-based analysis, immunohistochemistry exhibited high sensitivity (91.1%) and specificity (98.5%) in the detection of MSI phenotypes.

CONCLUSIONS

MSI-H gastric cancers have distinct clinicopathologic features and better prognoses, which suggests the necessity of MSI analysis in gastric cancer. Immunohistochemistry can be a useful and reliable screening method in the assessment of MSI status in gastric cancer.

Lauren classification and individualized chemotherapy in gastric cancer

Gastric cancer is one of the most common malignancies worldwide. During the last 50 years, the histological classification of gastric carcinoma has been largely based on Lauren's criteria, in which gastric cancer is classified into two major histological subtypes, namely intestinal type and diffuse type adenocarcinoma. This classification was introduced in 1965, and remains currently widely accepted and employed, since it constitutes a simple and robust classification approach. The two histological subtypes of gastric cancer proposed by the Lauren classification exhibit a number of distinct clinical and molecular characteristics, including histogenesis, cell differentiation, epidemiology, etiology, carcinogenesis, biological behaviors and prognosis. Gastric cancer exhibits varied sensitivity to chemotherapy drugs and significant heterogeneity; therefore, the disease may be a target for individualized therapy. The Lauren classification may provide the basis for individualized treatment for advanced gastric cancer, which is increasingly gaining attention in the scientific field. However, few studies have investigated individualized treatment that is guided by pathological classification. The aim of the current review is to analyze the two major histological subtypes of gastric cancer, as proposed by the Lauren classification, and to discuss the implications of this for personalized chemotherapy.

Molecular Pathogenesis of Helicobacter pylori-Related Gastric Cancer

Helicobacter pylori infection plays a crucial role in gastric carcinogenesis. H pylori exerts oncogenic effects on gastric mucosa through complex interaction between bacterial virulence factors and host inflammatory responses. On the other hand, gastric cancer develops via stepwise accumulation of genetic and epigenetic alterations in H pylori-infected gastric mucosa. Recent comprehensive analyses of gastric cancer genomes indicate a multistep process of genetic alterations as well as possible molecular mechanisms of gastric carcinogenesis. Both genetic processes of gastric cancer development and molecular oncogenic pathways related to H pylori infection are important to completely understand the pathogenesis of H pylori-related gastric cancer.

Microsatellite instability and survival in gastric cancer: A systematic review and meta-analysis

Microsatellite instability (MSI) is associated with the prognosis in several cancers and is used for determination of the chemotherapy regimen in stage II colon cancer in the National Comprehensive Cancer Network guideline. However, the association between MSI and the prognosis of gastric cancer remains unclear. PubMed database was searched until January 2014 using MeSH terms and key words to identify the studies evaluating MSI and prognosis of gastric cancer and the references were manually searched. The main outcome was the overall survival rate and the subordinate outcome was the association between high-frequency MSI (MSI-H) and clinicopathological characteristics. Eight studies met the inclusion criteria and the majority of data were collected retrospectively. There were 1,976 patients, 431 of which were MSI-H patients, with a range of 11.68-33.82%. Four studies used the National Cancer Institute panel to define MSI-H, the other four had microsatellite markers ranging 2-11. Significant associations were found in three studies and the overall summary estimate was hazard ratio, 0.63 (95% confidence interval, 0.52-0.77), with no evidence of inter-study heterogeneity (I²=0.0%). MSI-H patients were identified to have a tendency to have less lymph node (LN) metastasis, superficial tumor invasion and to be intestinal type. In conclusion, MSI-H gastric cancers have an improved prognosis, accompanied with reduced risk of LN metastasis, tumor invasion and mortality.

Prognostic value of telomere function in gastric cancers with and without microsatellite instability

OBJECTIVE

To identify molecular markers that may be useful in the selection of gastric cancer patients with different prognoses, we investigated telomere function in gastric cancers with and without microsatellite instability (MSI).

MATERIALS AND METHODS

We analyzed 83 gastric cancers and its paired-normal tissues to investigate MSI and telomere function. MSI was established using five polymorphic human repeat DNA markers. Telomere function was evaluated by determining telomerase activity, telomere length, and telomere-repeat factors 1 and 2 (TRF1 and TRF2) expression.

RESULTS

Patients with high microsatellite instability (MSI-H) gastric cancers showed a significantly better prognosis than those affected by microsatellite stable or low microsatellite instability (MSS/MSI-L) tumors (P = 0.03). The lowest expression levels of TRF1 and TRF2 were associated with MSI-H gastric cancers (P = 0.008 and 0.006, respectively). Moreover, a clear trend toward a worse prognosis was found in the group of patients who had tumors with the shortest telomeres (P = 0.01). Cox multivariate analysis showed that MSI emerged as a protective prognostic factor; MSS/MSI-L tumors conferred a significantly poor prognosis in patients (relative risk = 4.862-fold greater than the MSI-H group) (P = 0.033). Telomere length of gastric tumors less than 2.86 kbp was a factor that led to a poor prognosis (relative risk = 4.420, with respect to tumors showing telomere length ≥ 2.86 kbp) (P = 0.002).

CONCLUSION

We propose telomere status as a potential molecular marker with usefulness in the establishment of the prognosis of gastric cancers both for the mutator phenotype and for the suppressor pathway.

Clinical implications of microsatellite instability in T1 colorectal cancer

PURPOSE

The estimation of regional lymph node metastasis (LNM) risk in T1 colorectal cancer is based on histologic examination and imaging of the primary tumor. High-frequency microsatellite instability (MSI-H) is likely to decrease the possibility of metastasis to either regional lymph nodes or distant organs in colorectal cancers. This study evaluated the clinical implications of MSI in T1 colorectal cancer with emphasis on the usefulness of MSI as a predictive factor for regional LNM.

MATERIALS AND METHODS

A total of 133 patients who underwent radical resection for T1 colorectal cancer were included. Genomic DNA was extracted from normal and tumor tissues and amplified by polymerase chain reaction (PCR). Five microsatellite markers, BAT-25, BAT-26, D2S123, D5S346, and D17S250, were used. MSI and clinicopathological parameters were evaluated as potential predictors of LNM using univariate and multivariate analyses.

RESULTS

Among 133 T1 colorectal cancer patients, MSI-H, low-frequency microsatellite instability (MSI-L), and microsatellite stable (MSS) colorectal cancers accounted for 7.5%, 6%, and 86.5%, respectively. MSI-H tumors showed a female predominance, a proximal location and more retrieved lymph nodes. Twenty-two patients (16.5%) had regional LNM. Lymphovascular invasion and depth of invasion were significantly associated with LNM. There was no LNM in 10 MSI-H patients; however, MSI status was not significantly correlated with LNM. Disease-free survival did not differ between patients with MSI-H and those with MSI-L/MSS.

CONCLUSION

MSI status could serve as a negative predictive factor in estimating LNM in T1 colorectal cancer, given that LNM was not detected in MSI-H patients. However, validation of our result in a different cohort is necessary.