An Integrative Morphomolecular Classification System of Gastric Carcinoma With Distinct Clinical Outcomes

The prognostic and immunomodulatory role of the MMR system in patients with stomach adenocarcinoma

The mismatch repair (MMR) system plays a crucial role in the maintenance of DNA replication fidelity and genomic stability. The clinical value of the MMR molecular marker as an immunotherapy for advanced solid tumors has been documented. However, this therapy is not effective in some patients. This study aimed to develop an MMR-related molecular prognostic model for identifying appropriate populations of stomach adenocarcinoma (STAD) for better treatment outcome. The MMR genes expression data were downloaded from TCGA and CCLE databases. The expression of four MMR genes, construction of a prognostic risk model, and assessment of immune infiltration in STAD were performed using Xiantao online tool. GEPIA2 was used to explore the association of MMR genes expression with clinical stage and overall survival. The frequency and prognostic value of MMR genes in STAD were conducted on the cBioPortal. The MLH1 co-expression network was established based on the LinkedOmics database. This study found that the expression of MSH2, MSH6 and PMS2 was up-regulated in STAD tissues. Moreover, differential MMR genetic expression levels were not significantly correlated with the clinical stages of STAD. Besides, no significant difference in PFS or OS was observed in STAD patients with or without MMR genetic alteration. Moreover, MLH1 and MSH2 were used to establish a prognostic risk model. The immune infiltration levels of most immune cells were upregulated in the high-risk group with elevated expression of PDCD1 and low TMB score. Finally, we found that MLH1 was an independent predictor of STAD prognosis among the four MMR genes. An MMR-related prognostic model for STAD was constructed based on genes. This model provides a new therapeutic concept for the diagnosis and treatment of STAD.

Molecular characterization and biomarker discovery in gastric cancer progression through transcriptome meta-analysis

Gastric cancer (GC) is a leading cause of cancer-related deaths globally. It is a multifactorial, molecularly heterogeneous disease whose carcinogenic patterns are not yet well established, requiring the development of new tools for better understanding and identifying gastric carcinogenesis. From this point of view, this study aims to compare transcriptome profiles from The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) and a human-merged dataset to identify potential biomarkers and therapeutic targets. Principal component analysis (PCA) revealed shared and distinct gene expression patterns between datasets. Differential expression analysis identified key genes with altered expression across non-malignant and malignant samples. Six genes, including SERPINE1 and CLDN9, were significantly associated with patient survival. The findings underscore the molecular diversity of GC and highlight novel biomarkers for early diagnosis and therapeutic strategies. Further validation in clinical specimens is necessary.

NTRK gene alterations were enriched in hepatoid or enteroblastic differentiation type of gastric cancer

Aims Currently, the clinicopathological characteristics of gastric cancer (GC) with oncogenic NTRK alterations are not well known. Although NTRK fusion has been identified as prevalent in DNA mismatch repair protein deficient (dMMR) colorectal cancer (CRC), the relationship between NTRK alterations and dMMR protein expression in GC has not been previously explored.

METHODS

Our study comprised 51 cases of EBV(Epstein-barr virus)-associated gastric carcinomas, 94 cases of dMMR GC, 90 cases of gastric adenocarcinoma with hepatoid or enteroblastic differentiation (GAHED) and 256 cases of conventional GC. Furthermore, to investigate the connection between NTRK fusion and dMMR proteins, we collected dMMR tumours of various types, including 21 cases of duodenal adenocarcinomas, 46 endometrioid carcinomas and 82 CRCs. NTRK fusion and amplification were screened in GC and various types of dMMR tumours using fluorescence in situ hybridisation (FISH), while cases positive for FISH translocation underwent next-generation sequencing testing.

RESULTS

Our findings revealed the existence of two cases each of NTRK fusions and NTRK amplifications, which were all enriched in case of GAHED. Additionally, following an analysis of several types of cancers, we discovered that NTRK gene alterations were only present in dMMR CRC.

CONCLUSIONS

Our results indicate that NTRK gene alterations are not enriched in GC with dMMR but are specifically enriched in cases of GAHED.

Integrated analysis of transcriptome and epigenome reveals ENSR00000272060 as a potential biomarker in gastric cancer

Background: Enhancer RNAs (eRNAs) are involved in gene expression regulation. Although functional roles of eRNAs in the pathophysiology of neoplasms have been reported, their involvement in gastric cancer (GC) is less known. Materials & methods: A network-based integrative approach was utilized for analyzing transcriptome and epigenome alterations in GC, and an eRNA was selected for experimental validation. Survival analysis and clinicopathological associations were also performed. Results: A hub eRNA, ENSR00000272060, showed significantly increased expression in tumor versus nontumor tissues, as well as an association with clinicopathological features. A seven-gene prognostic model was also constructed. Conclusion: The constructed network provides a comprehensive understanding of the underlying processes implicated in the progression of GC, along with a starting point from which to derive potential diagnostic/prognostic biomarkers.

Molecular profile of gastric adenocarcinoma, relevant epidemiological factors - Systematic review and meta-analysis relating sex with Epstein-Barr virus and unstable microsatellites subtypes

INTRODUCTION

Gastric epithelial tumors exhibit morphological heterogeneity, diverse biological behaviors, and different oncopathological pathways. The Cancer Genome Atlas (TCGA) proposed a molecular classification of gastric adenocarcinomas based on genetic and molecular findings, which shows particular characteristics of diagnosis, prognosis, and indirectly, therapeutic alternatives. Within this classification, Epstein-Barr virus-positive (EBV+) and high microsatellite instability (MSI-H) subtypes stand out as subtypes that present a less aggressive biological behavior and a highly mutilated phenotype. This study conducted a systematic review with an emphasis on epidemiological and prognostic factors based on the molecular classification proposed by TCGA.

METHODS

A broad, comprehensive, and reproducible search with methodological rigor was conducted for study selection using the ROBINS-I and GRADEpro protocols and appropriate combinations of keywords.

RESULTS

A total of 25 studies were selected: six with a complete classification similar to TCGA and 19 with a distinction between MSI-H and EBV+. The application of meta-analysis calculations reinforces the prevalence of positive Epstein-Barr adenocarcinomas in males and high microsatellite instability in females, with a high level of certainty of evidence and low risk of bias in the analyzed studies due to the rigorous methods used.

CONCLUSION

The molecular classification proposed by TCGA shows limited dissemination, with MSI-H and EBV+ subtypes being the most researched, probably due to the benefit of the association with immunotherapies. However, the subclassification cannot be restricted to less than a quarter of the cases, and improvements in this aspect are urgent for the construction of knowledge on this important topic of global health.

Chromosomal Instability in Gastric Cancer: Role in Tumor Development, Progression, and Therapy

According to the Cancer Genome Atlas (TCGA), gastric cancers are classified into four molecular subtypes: Epstein-Barr virus-positive (EBV+), tumors with microsatellite instability (MSI), tumors with chromosomal instability (CIN), and genomically stable (GS) tumors. However, the gastric cancer (GC) with chromosomal instability remains insufficiently described and does not have effective markers for molecular and histological verification and diagnosis. The CIN subtype of GC is characterized by chromosomal instability, which is manifested by an increased frequency of aneuploidies and/or structural chromosomal rearrangements in tumor cells. Structural rearrangements in the CIN subtype of GC are not accidental and are commonly detected in chromosomal loci, being abnormal because of specific structural organization. The causes of CIN are still being discussed; however, according to recent data, aberrations in the TP53 gene may cause CIN development or worsen its phenotype. Clinically, patients with the CIN subtype of GC demonstrate poor survival, but receive the maximum benefit from adjuvant chemotherapy. In the review, we consider the molecular mechanisms and possible causes of chromosomal instability in GC, the common rearrangements of chromosomal loci and their impact on the development and clinical course of the disease, as well as the driver genes, their functions, and perspectives on their targeting in the CIN subtype of GC.

Estimating the Global Burden of Epstein-Barr Virus-Associated Gastric Cancer: A Systematic Review and Meta-Analysis

BACKGROUND & AIMS

Evidence suggests that a fraction of new gastric cancer cases may be etiologically associated with Epstein-Barr virus (EBV), a known carcinogenic agent. We aimed to systematically explore the proportion of EBV-positive gastric cancer.

METHODS

We did a systematic review (PROSPERO CRD42020164473) from January 1990 to August 2021. For each country and geographical region with available data, pooled prevalence and corresponding 95% confidence intervals (CIs) of EBV in gastric tumors were calculated for 3 subtypes of gastric adenocarcinoma (conventional adenocarcinoma, lymphoepithelioma-like gastric carcinoma, and remnant/stump carcinoma). For conventional adenocarcinoma, prevalence ratios (PRs) were presented for sex, Lauren's classification, gastric cancer stage, and anatomical location of the stomach.

RESULTS

In 220 eligible studies including over 68,000 cases of conventional gastric adenocarcinoma, EBV prevalence in tumor cells was 7.5% (95% CI, 6.9%-8.1%) and was higher in men compared with women (PR, 2.1; 95% CI, 1.9-2.4), in diffuse type compared with intestinal type (PR, 1.3; 95% CI, 1.1-1.5), and in the proximal region compared with the distal region (PR, 2.5; 95% CI, 2.0-3.1). There was no difference in EBV prevalence by gastric cancer stage. EBV prevalence was 75.9% (95% CI, 62.8%-85.5%) among lymphoepithelioma-like gastric carcinoma and 26.3% (95% CI, 22.2%-32.0%) among remnant or stump carcinoma.

CONCLUSIONS

Assuming a causal association between EBV and gastric cancer, our findings, when applied to the GLOBOCAN 2020 gastric cancer incidence, suggest that primary prevention such as the development of an effective EBV vaccine might prevent 81,000 EBV-associated gastric cancer cases worldwide annually.

Clinicopathological analysis of a type of "low grade" poorly cohesive gastric adenocarcinoma not otherwise specified with a good prognosis

Poorly cohesive carcinoma not otherwise specified (PCGCA-NOS) is regarded in the most recent WHO classification as a high-grade malignancy; however, some cases may be associated with a relatively good prognosis. We have studied a series of 115 cases of PCGCA-NOS and were able to identify low-grade features in 14 cases based on three morphological manifestations. Immunohistochemical staining, EBER in situ hybridization, Feulgen staining and flow cytometry were employed. Among the 115 cases of PCGAC-NOS, 14 cases met the criteria of "low grade", accounting for 12.2 %. The "low grade" cases exhibited more shallow invasion and less lymph node metastasis (both P < 0.05); showed less frequent expression of MUC5AC, E-cadherin and p53 (all P < 0.05). Moreover, "low grade" PCGAC-NOS had a lower proliferative index(P < 0.001). We also found that the DNA content was lower in the "low grade" group, and aneuploidy was not detected in the "low grade" group, which was sharply different from the control group (50 %). Last, "low grade" PCGAC-NOS had a more favorable prognosis. A small subset of PCGAC-NOS cases have a low grade nature, and the clinicopathological features, immunophenotypes, and cytogenetics of these "low grade" cases differ from those of traditional PCGAC-NOS.

Further prognostic stratification of intestinal type of gastric adenocarcinoma by CDX2 expression pattern

Gastric cancer is one of the most deadly malignancies worldwide. It is routinely divided into 2 common histologic subtypes by the Lauren classification, intestinal type and diffuse type. In recent years, the intestinal type of gastric cancer has been found to represent a heterogeneous disease with divergent prognosis. Our objective was to investigate the CDX2/CK7 immunohistochemical pattern and its role in further stratifying this type of gastric cancer. Gastrectomy cases with a diagnosis of the intestinal type of gastric adenocarcinoma from a single large institution between 2008 and 2022 were collected. Forty-four cases with available blocks and enough tumor tissue were included in this study. Four different immunohistochemical patterns were identified: CDX2+/CK7+ (40.9%), CDX2-/CK7+ (34.1%), CDX2+/CK7- (18.2%), and CDX2-/CK7- (6.8%). Compared to CDX2-negative cases, CDX2-positive ones are more likely to present better prognostic histopathological features including early stage, less perineural and lymphovascular invasion, and lower nodal metastasis. In addition, CDX2 expression was associated with specific molecular features like HER2 overexpression and genetic alterations of receptor tyrosine kinase (TRK) genes including EGFR, ERBB2, ERBB3, DDR2, and MET. In conclusion, according to the CDX2 expression pattern, the intestinal type of gastric cancer could be further divided into 2 subgroups, which have different histopathological and molecular features and different prognosis.

Targeting the complexity of ERBB2 biology in gastroesophageal carcinoma

ERBB2 is the most prominent therapeutic target in gastroesophageal adenocarcinoma (GEA). For two decades, trastuzumab was the only treatment available for GEA overexpressing ERBB2. Several drugs showing evidence of efficacy over or in complement to trastuzumab in breast cancer failed to show clinical benefit in GEA. This resistance to anti-ERBB2 therapy is peculiarly recurrent in GEA and is mostly due to tumor heterogeneity with the existence of low expressing ERBB2 tumor clones and loss of ERBB2 over time. The development of new ERBB2 testing strategies and the use of antibody-drug conjugates having a bystander effect are providing new tools to fight heterogeneity in ERBB2-positive GEA. Co-amplifications of tyrosine kinase receptors, alterations in mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K) signaling pathways and in proteins controlling cell cycle are well known to contribute resistance to anti-ERBB2 therapy, and they can be targeted by dual therapy. Recently described, NF1 mutations are responsible for Ras phosphorylation and activation and can also be targeted by MEK/ERK inhibition along with anti-ERBB2 therapy. Multiple lines of evidence suggest that immune mechanisms involving antibody-dependent cell-mediated cytotoxicity are preponderant over intracellular signaling in anti-ERBB2 therapy action. A better comprehension of these mechanisms could leverage immune action of anti-ERBB2 therapy and elucidate efficacy of combinations associating immunotherapy and anti-ERBB2 therapy, as suggested by the recent intermediate positive results of the KEYNOTE-811 trial.

Increasing frequency of gene copy number aberrations is associated with immunosuppression and predicts poor prognosis in gastric adenocarcinoma

BACKGROUND

Patients with Epstein-Barr virus-positive gastric cancers or those with microsatellite instability appear to have a favourable prognosis. However, the prognostic value of the chromosomal status (chromosome-stable (CS) versus chromosomal instable (CIN)) remains unclear in gastric cancer.

METHODS

Gene copy number aberrations (CNAs) were determined in 16 CIN-associated genes in a retrospective study including test and validation cohorts of patients with gastric cancer. Patients were stratified into CS (no CNA), CINlow (1-2 CNAs) or CINhigh (3 or more CNAs). The relationship between chromosomal status, clinicopathological variables, and overall survival (OS) was analysed. The relationship between chromosomal status, p53 expression, and tumour infiltrating immune cells was also assessed and validated externally.

RESULTS

The test and validation cohorts included 206 and 748 patients, respectively. CINlow and CINhigh were seen in 35.0 and 15.0 per cent of patients, respectively, in the test cohort, and 48.5 and 20.7 per cent in the validation cohort. Patients with CINhigh gastric cancer had the poorest OS in the test and validation cohorts. In multivariable analysis, CINlow, CINhigh and pTNM stage III-IV (P < 0.001) were independently associated with poor OS. CIN was associated with high p53 expression and low immune cell infiltration.

CONCLUSION

CIN may be a potential new prognostic biomarker independent of pTNM stage in gastric cancer. Patients with gastric cancer demonstrating CIN appear to be immunosuppressed, which might represent one of the underlying mechanisms explaining the poor survival and may help guide future therapeutic decisions.

The seen and the unseen: Molecular classification and image based-analysis of gastrointestinal cancers

Gastrointestinal cancers account for 22.5% of cancer related deaths worldwide and represent circa 20% of all cancers. In the last decades, we have witnessed a shift from histology-based to molecular-based classifications using genomic, epigenomic, and transcriptomic data. The molecular based classification revealed new prognostic markers and may aid the therapy selection. Because of the high-costs to perform a molecular classification, in recent years immunohistochemistry-based surrogate classification were developed which permit the stratification of patients, and in parallel multiple groups developed hematoxylin and eosin whole slide image analysis for sub-classifying these entities. Hence, we are witnessing a return to an image-based classification with the purpose to infer hidden information from routine histology images that would permit to detect the patients that respond to specific therapies and would be able to predict their outcome. In this review paper, we will discuss the current histological, molecular, and immunohistochemical classifications of the most common gastrointestinal cancers, gastric adenocarcinoma, and colorectal adenocarcinoma, and will present key aspects for developing a new artificial intelligence aided image-based classification of these malignancies.

Histological and mutational profile of diffuse gastric cancer: current knowledge and future challenges

Gastric cancer (GC) pathogenesis is complex and heterogeneous, reflecting morphological, molecular and genetic diversity. Diffuse gastric cancer (DGC) and intestinal gastric cancer (IGC) are the major histological types. GC may be sporadic or hereditary; sporadic GC is related to environmental and genetic low-risk factors and hereditary GC is caused by inherited high-risk mutations, so far identified only for the diffuse histotype. DGC phenotypic heterogeneity challenges the current understanding of molecular mechanisms underlying carcinogenesis. The definition of a DGC-specific mutational profile remains controversial, possibly reflecting the heterogeneity of DGC-related histological subtypes [signet-ring cell carcinoma (SRCC) and poorly cohesive carcinoma not otherwise specified (PCC-NOS)]. Indeed, DGC and DGC-related subtypes may present specific mutational profiles underlying the particularly aggressive behaviour and dismal prognosis of DGC vs IGC and PCC-NOS vs SRCC. In this systematic review, we revised the histological presentations, molecular classifications and approved therapies for gastric cancer, with a focus on DGC. We then analysed results from the most relevant studies, reporting mutational analysis data specifying mutational frequencies, and their relationship with DGC and IGC histological types, and with specific DGC subtypes (SRCC and PCC-NOS). We aimed at identifying histology-associated mutational profiles with an emphasis in DGC and its subtypes (DGC vs IGC; sporadic vs hereditary DGC; and SRCC vs PCC-NOS). We further used these mutational profiles to identify the most commonly affected molecular pathways and biological functions, and explored the clinical trials directed specifically to patients with DGC. This systematic analysis is expected to expose a DGC-specific molecular profile and shed light into potential targets for therapeutic intervention, which are currently missing.

Aberrant expression of SFRP1, SFRP3, DVL2 and DVL3 Wnt signaling pathway components in diffuse gastric carcinoma

Diffuse gastric carcinoma (DGC) is characterized by poorly cohesive cells, highly invasive growth patterns, poor prognosis and resistance to the majority of available systemic therapeutic strategies. It has been previously reported that the Wnt/β-catenin signaling pathway serves a prominent role in the tumorigenesis of gastric carcinoma. However, the mechanism underlying the dysregulation of this pathway in DGC has not been fully elucidated. Therefore, the present study aimed to investigate the expression profiles of Wnt antagonists, secreted frizzled-related protein 1 (SFRP1) and secreted frizzled-related protein 3 (SFRP3), and dishevelled protein family members, dishevelled segment polarity protein 2 (DVL2) and dishevelled segment polarity protein 3 (DVL3), in DGC tissues. The association between the expression levels of these factors and the clinicopathological parameters of the patients was determined. Protein and mRNA expression levels in 62 DGC tumor tissues and 62 normal gastric mucosal tissues obtained from patients with non-malignant disease were measured using immunohistochemical and reverse transcription-quantitative PCR (RT-qPCR) analysis. Significantly lower protein expression levels of SFRP1 (P<0.001) and SFRP3 (P<0.001), but significantly higher protein expression levels of DVL2 (P<0.001) and DVL3 (P<0.001) were observed in DGC tissues compared with in control tissues by immunohistochemistry. In addition, significantly lower expression levels of SFRP1 (P<0.05) and higher expression levels of DVL3 (P<0.05) were found in in DGC tissues compared with those in normal gastric mucosal tissues using RT-qPCR. According to correlation analysis between the SFRP1, SFRP3, DVL2 and DVL3 protein expression levels and the clinicopathological characteristics of patients with DGC, a statistically significant correlation was found between the SFRP3 volume density and T stage (r=0.304; P=0.017) and between the SFRP3 volume density and clinical stage (r=0.336; P=0.008). In conclusion, the findings of the present study suggested that the Wnt signaling pathway components SFRP1, SFRP3, DVL2 and DVL3 may be aberrantly expressed in DGC tissues, implicating their possible role in the development of this malignant disease. The present data also revealed a positive relationship between SFRP3 protein expression and the clinical and T stage of DGC.

MicroRNA and Other Non-Coding RNAs in Epstein-Barr Virus-Associated Cancers

EBV is a direct causative agent in around 1.5% of all cancers. The oncogenic properties of EBV are related to its ability to activate processes needed for cellular proliferation, survival, migration, and immune evasion. The EBV latency program is required for the immortalization of infected B cells and involves the expression of non-coding RNAs (ncRNAs), including viral microRNAs. These ncRNAs have different functions that contribute to virus persistence in the asymptomatic host and to the development of EBV-associated cancers. In this review, we discuss the function and potential clinical utility of EBV microRNAs and other ncRNAs in EBV-associated malignancies. This review is not intended to be comprehensive, but rather to provide examples of the importance of ncRNAs.

Analysis of clinicopathological and molecular features of crawling-type gastric adenocarcinoma

BACKGROUND

Crawling-type adenocarcinoma (CRA) is an important gastric cancer (GC) subtype that exhibits a specific histological pattern and has characteristic clinicopathological findings. Despite its characteristic histology, little is known about the molecular characteristics of CRA.

METHODS

We examined 177 GC cases, including 51 cases of CRA and 126 cases having conventional differentiated adenocarcinomas (CDAs). Results for immunohistochemistry (mucin phenotype; Muc5AC, Muc6, Muc2 and CD10, CDX-2, MLH-1, p53 and β-catenin), mutation analysis (TP53, KRAS and BRAF), microsatellite instability (BAT25, BAT26, D2S123, D5S346 and D17S250), DNA methylation status by a two-panel method (RUNX3, MINT31, LOX, NEUROG1, ELMO1 and THBD), MLH-1 promoter methylation, and allelic imbalance (AI; 1p, 3p, 4p, 5q, 8p, 9p, 13q, TP53, 18q and 22q) were examined.

RESULTS

CRAs were more likely to occur in the middle third of the stomach, in younger patients and to be macroscopically depressed. Nuclear accumulation of β-catenin and loss of MLH-1 expression were less frequent among CRA cases compared to CDA cases. At a molecular level, CRA is often characterized by the deletion mutation c.529_546 (18-base pair deletion at codon 177-182 in exon 5) in the TP53 gene (10 cases). Although the low methylation epigenotype was significantly more frequent for CRAs compared to CDAs, multiple AIs were more often seen in CRAs relative to CDAs.

CONCLUSIONS

The results demonstrated that TP53 mutations, particularly c.529_546del, and multiple AIs are closely associated with CRA carcinogenesis. Our results suggest that CRA is an independent entity of GC in terms of clinicopathologic and molecular findings.

Disparate and Alarming Impact of Gastrointestinal Cancers in Young Adult Patients

BACKGROUND

The rise in the incidence of gastric cancer (GC) and colorectal cancer (CRC) in young adults (YA) remains unexplained. We aim to identify differences in these malignancies between YA and older patients.

PATIENTS AND METHODS

We retrospectively analyzed the California Cancer Registry for all GC and CRC cases from 2000 to 2012. Pearson's Chi square analysis and stepwise regression model with backward elimination were used to analyze differences in demographic, clinical, and histopathologic features, and log-rank test to compare survival between young (≤ 40 years) and older adults (41-90 years) with GC or CRC, separately.

RESULTS

We analyzed 19,368 cases of GC and 117,415 cases of CRC. YA accounted for 4.6% of GC (n = 883) and 2.8% of CRC (n = 3273) patients. Compared with older patients, YA were more likely to be Hispanic (P < 0.0001) and have poorly differentiated (P < 0.0001), higher histologic grade (P < 0.0001), and signet ring features (P < 0.0001). Synchronous peritoneal metastases were more common in YA patients (32.1% vs. 14.1% GC, 8.8% vs. 5.4% CRC, P < 0.0001). The 5-year overall survival (OS) of YA with CRC or GC was longer than that of older patients with the same stage of malignancy; except YA with stage I GC, who demonstrated poor OS and disease-specific survival (DSS) (65.1% and 67.9%, respectively) which were significantly worse than those of adults aged 41-49 years (70.7% and 76.2%, respectively) and 50-64 years (69.1% and 78.1%, respectively).

CONCLUSIONS

YA with GC or CRC have distinctly worse clinical and histopathologic features compared with older patients and are disproportionately of Hispanic ethnicity. These results contribute to improving understanding of younger versus older GI cancer patients.