Aberrant methylation of PCDH10 and RASSF1A genes in blood samples for non-invasive diagnosis and prognostic assessment of gastric cancer

Liquid biopsy in gastric cancer: A snapshot of the current state of the art

Circulating tumor DNA (ctDNA) is nowadays considered a robust source to search for druggable tumoral genetic alterations, and in some specific settings liquid biopsy (LB) is already part of the diagnostics scenario and it has successfully implemented in the everyday practice. Three strengths make LB an extraordinary tool: i) to represent the complex molecular mosaicism that characterizes spatially heterogeneous malignancies; ii) to monitor in real-time the tumoral molecular landscape (i.e. to depict the longitudinal/temporal tumor evolution); iii) to ensure molecular profiling even in those cases in which tissue sampling is not feasible or not adequate. This review provides a snapshot of the current state of the art concerning ctDNA assay utility in gastric cancer (GC), testing its robustness as marker and seeking to understand the reasons for the delay in its application in clinical practice.

A dual-gene panel of two fragments of methylated IRF4 and one of ZEB2 in plasma cell-free DNA for gastric cancer detection

Early detection is crucial for increasing the survival rate of gastric cancer (GC). We aimed to identify a methylated cell-free DNA (cfDNA) marker panel for detecting GC. The differentially methylated CpGs (DMCs) were selected from datasets of The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The selected DMCs were validated and further selected in tissue samples (40 gastric cancer and 36 healthy white blood cell samples) and in a quarter sample volume of plasma samples (37 gastric cancer, 12 benign gastric disease, and 43 healthy individuals). The marker combination selected was then evaluated in a normal sample volume of plasma samples (35 gastric cancer, 39 control diseases, and 40 healthy individuals) using real-time methylation-specific PCR (MSP). The analysis of the results compared methods based on 2-ΔΔCt values and Ct values. In the results, 30 DMCs were selected through bioinformatics methods, and then 5 were selected for biological validation. The marker combination of two fragments of IRF4 (IRF4-1 and IRF4-2) and one of ZEB2 was selected due to its good performance. The Ct-based method was selected for its good results and practical advantages. The assay, IRF4-1 and IRF4-2 in one fluorescence channel and ZEB2 in another, obtained 74.3% sensitivity for the GC group at any stage, at 92.4% specificity. In conclusion, the panel of IRF4 and ZEB2 in plasma cfDNA demonstrates good diagnostic performance and application potential in clinical settings.

Identification of FGG as a Biomarker in Early Gastric Cancer via Tissue Proteomics and Clinical Verification

Early and accurate diagnosis of gastric cancer (GC) is essential for reducing mortality and improving patient well-being. However, methods for the early diagnosis of GC are still lacking. In this study, by isobaric tagging for relative and absolute quantitation (iTRAQ), we identified 336 proteins that overlapped among the upregulated differentially expressed proteins (DEPs) in early gastric cancer (EGC) versus progressive gastric cancer (PGC), upregulated DEPs in EGC versus nongastric cancer (NGC), and nonsignificant proteins in EGC versus NGC. These DEPs were involved primarily in the neutrophil-related immune response. Network analysis of proteins and pathways revealed that fibrinogen α (FGA), β (FGB), and γ (FGG) are candidates for distinguishing EGC. Furthermore, parallel reaction monitoring (PRM), immunohistochemistry (IHC), and Western blot (WB) assays of clinical samples confirmed that, compared with that in PGC and NGC, only FGG was uniquely and significantly upregulated in the gastric mucosa of EGC. Our results demonstrated that FGG in the gastric mucosa could be a novel biomarker to diagnose EGC patients via endoscopy.

Epigenetic reprogramming in gastrointestinal cancer: biology and translational perspectives

Gastrointestinal tumors, the second leading cause of human mortality, are characterized by their association with inflammation. Currently, progress in the early diagnosis and effective treatment of gastrointestinal tumors is limited. Recent whole-genome analyses have underscored their profound heterogeneity and extensive genetic and epigenetic reprogramming. Epigenetic reprogramming pertains to dynamic and hereditable alterations in epigenetic patterns, devoid of concurrent modifications in the underlying DNA sequence. Common epigenetic modifications encompass DNA methylation, histone modifications, noncoding RNA, RNA modifications, and chromatin remodeling. These modifications possess the potential to invoke or suppress a multitude of genes associated with cancer, thereby governing the establishment of chromatin configurations characterized by diverse levels of accessibility. This intricate interplay assumes a pivotal and indispensable role in governing the commencement and advancement of gastrointestinal cancer. This article focuses on the impact of epigenetic reprogramming in the initiation and progression of gastric cancer, esophageal cancer, and colorectal cancer, as well as other uncommon gastrointestinal tumors. We elucidate the epigenetic landscape of gastrointestinal tumors, encompassing DNA methylation, histone modifications, chromatin remodeling, and their interrelationships. Besides, this review summarizes the potential diagnostic, therapeutic, and prognostic targets in epigenetic reprogramming, with the aim of assisting clinical treatment strategies.

Research on the signaling pathway and the related mechanism of traditional Chinese medicine intervention in chronic gastritis of the "inflammation-cancer transformation"

Objective: The aim of this study is to uncover the traditional Chinese medicine (TCM) treatments for chronic gastritis and their potential targets and pathways involved in the "inflammation-cancer" conversion in four stages. These findings can provide further support for future research into TCM and its active components. Materials and methods: The literature search encompassed PubMed, Web of Science, Google Scholar, CNKI, WanFang, and VIP, employing keywords such as "chronic gastritis", "gastric cancer", "traditional Chinese medicine", "medicinal herb", "Chinese herb", and "natural plant". Results: Herbal remedies may regulate the signaling pathways linked to the advancement of chronic gastritis. Under the multi-target and multi-pathway independent or combined reaction, the inflammatory microenvironment may be enhanced, leading to repair of damaged gastric mucosal cells, buffering the progress of mucosal atrophic degeneration via the decrease of inflammatory factor expression, inhibition of oxidative stress-induced damage, facilitation of microvascular neovascularization in the gastric mucosa and regulation of the processes of gastric mucosal cell differentiation and proliferation. Simultaneously, the decreased expression of inflammatory factors may impact the expression of associated oncogenes and regulate the malignant proliferation of cells, thereby achieving the treatment and prevention objectives of gastric cancer through the reduction of cell metastasis and apoptosis. Conclusion: Chinese medicine formulations and individual drugs can be utilised at various stages of the "inflammation-cancer" progression of chronic gastritis to prevent and treat gastric cancer in a multi-level, multi-targeted, and multi-directional fashion. This can provide guidance for the accurate application of medicines during different stages of "inflammation-cancer" transformation. New insights into the mechanism of inflammation-cancer transformation and the development of novel drugs for chronic gastritis can be gained through an extensive investigation of TCM treatment in this condition.

Global progress and future prospects of early gastric cancer screening

Gastric cancer is a prevalent malignancy that poses a serious threat to global health. Despite advances in medical technologies, screening methods, and public awareness, gastric cancer remains a significant cause of morbidity and mortality worldwide. Early gastric cancer frequently does not present with characteristic symptoms, while advanced stage disease is characterized by a dismal prognosis. As such, early screening in gastric cancer is of great importance. In recent years, advances have been made globally in both clinical and basic research for the screening of early gastric cancer. The current predominant screening methods for early gastric cancer include imaging screening, endoscopic screening and serum biomarker screening. Imaging screening encompasses upper gastrointestinal barium meal, multidimensional spiral computed tomography (MDCT), Magnetic resonance imaging (MRI), and ultrasonography. Endoscopic screening methods include white light endoscopy, chromoendoscopy, computed virtual chromoendoscopy, and other endoscopic techniques like endocytoscopy, confocal laser endomicroscopy, optical coherence tomography and so on. Biomarkers screening involves the assessment of conventional biomarkers such as CEA, CA19-9 and CA72-4 as well as more emerging biomarkers such as peptides (PG, G-17, GCAA, TAAs and others), DNA (cfDNA, DNA methylation, MSI), noncoding RNA (miRNA, lncRNA, circRNA, and tsRNA) and others. Each screening method has its strengths and limitations. This article systematically summarizes worldwide progress and future development of early gastric cancer screening methods to provide new perspectives and approaches for early diagnostic and treatment advancements in gastric cancer worldwide.

Cell-free Nucleic Acid as Promising Diagnostic Biomarkers for Gastric Cancer: a Systematic Review

Background: Gastric cancer (GC) is a common malignancy with early detection being crucial for survival. Liquid biopsy analysis using cell-free nucleic acid is a preferred method for detection. Hence, we conducted a systematic review to assess the diagnostic efficacy of cell-free nucleic acid markers for GC. Methods: We searched PubMed and ISI Web of Science databases for articles that conformed to our inclusion and exclusion criteria from 2012 to 2022. The following information was abstracted: first author, year of publication, country/region, age, male proportion, tumor stage for cases, specimen type, measurement method, targeted markers and diagnostic related indicators (including sensitivity, specificity, AUC, P-value). Results: Fifty-eight studies examined cell-free RNAs (cfRNAs) with a total of 62 individual circulating markers and 7 panels in serum or plasma, while 21 studies evaluated cell-free DNAs (cfDNAs) with 29 individual circulating markers and 7 panels. For individual cfRNAs, the median (range) sensitivity and specificity were 80% (21% - 98%) and 80% (54% - 99%), respectively. The median (range) sensitivity and specificity for cfRNA panels were 86% (83% - 90%) and 75% (60% - 98%), respectively. In comparison, the median (range) sensitivity and specificity reported for individual cfDNAs were 50% (18% - 96%) and 93% (57% - 100%), respectively, while cfDNA panels had a median (range) sensitivity and specificity of 85% (41% - 92%) and 73.5% (38% - 90%), respectively. The meta results indicate that cfRNA markers exhibit high sensitivity (80%) and low specificity (80%) for detecting GC, while cfDNA markers have lower sensitivity (59%) but higher specificity (92%). Conclusions: This review has demonstrated that cell-free nucleic acids have the potential to serve as useful diagnostic markers for GC. Given that both cfRNA and cfDNA markers have shown promising diagnostic performance for GC, the combination of the two may potentially enhance diagnostic efficiency.

DNA methylation drives a new path in gastric cancer early detection: Current impact and prospects

Gastric cancer (GC) is one of the most common and deadly cancers worldwide. Early detection offers the best chance for curative treatment and reducing its mortality. However, the optimal population-based early screening for GC remains unmet. Aberrant DNA methylation occurs in the early stage of GC, exhibiting cancer-specific genetic and epigenetic changes, and can be detected in the media such as blood, gastric juice, and feces, constituting a valuable biomarker for cancer early detection. Furthermore, DNA methylation is a stable epigenetic alteration, and many innovative methods have been developed to quantify it rapidly and accurately. Nonetheless, large-scale clinical validation of DNA methylation serving as tumor biomarkers is still lacking, precluding their implementation in clinical practice. In conclusion, after a critical analysis of the recent existing literature, we summarized the evolving roles of DNA methylation during GC occurrence, expounded the newly discovered noninvasive DNA methylation biomarkers for early detection of GC, and discussed its challenges and prospects in clinical applications.

Clinical applications and perspectives of circulating tumor DNA in gastric cancer

Gastric cancer remains a leading cause of cancer-related death worldwide, largely due to inadequate screening methods, late diagnosis, and limited treatment options. Liquid biopsy has emerged as a promising non-invasive approach for cancer screening and prognosis by detecting circulating tumor components like circulating tumor DNA (ctDNA) in the blood. Numerous gastric cancer-specific ctDNA biomarkers have now been identified. CtDNA analysis provides insight into genetic and epigenetic alterations in tumors, holding promise for predicting treatment response and prognosis in gastric cancer patients. This review summarizes current research on ctDNA biology and detection technologies, while highlighting clinical applications of ctDNA for gastric cancer diagnosis, prognosis, and guiding treatment decisions. Current challenges and future perspectives for ctDNA analysis are also discussed.

Landscape of Innovative Methods for Early Diagnosis of Gastric Cancer: A Systematic Review

From a global perspective, gastric cancer (GC) persists as a significant healthcare issue. In the Western world, the majority of cases are discovered at late stages, when the treatment is generally unsuccessful. There are no organized screening programs outside of Asia (Japan and Republic of Korea). Traditional diagnosis techniques (such as upper endoscopy), conventional tumor markers (CEA, CA19-9, and CA72-4), radiographic imaging, and CT scanning all have drawbacks. The gold standard for the earliest detection of cancer and related premalignant lesions is still endoscopy with a proper biopsy follow-up. Since there are currently no clinically approved biomarkers for the early diagnosis of GC, the identification of non-invasive biomarkers is expected to help improve the prognosis and survival rate of these patients. The search for new screening biomarkers is currently underway. These include genetic biomarkers, such as circulating tumor cells, microRNAs, and exosomes, as well as metabolic biomarkers obtained from biofluids. Meanwhile, cutting-edge high-resolution endoscopic technologies are demonstrating promising outcomes in the visual diagnosis of mucosal lesions with the aid of linked color imaging and machine learning models. Following the PRISMA guidelines, this study examined the articles in databases such as PubMed, resulting in 167 included articles. This review discusses the currently available and emerging methods for diagnosing GC early on, as well as new developments in the endoscopic detection of early lesions of the stomach.

Utilizing circulating tumour DNA as a prognostic predictor of gastric cancer: a meta-analysis

Background: Circulating tumour DNA (ctDNA) has demonstrated robust diagnostic accuracy in several digestive cancers. However, the prognostic role of ctCDNA in gastric cancer (GC) is still controversial. This systematic review and meta-analysis aimed to evaluate the prognostic value of ctDNA in GC.Methods: PubMed, Web of Science and Cochrane databases were searched to identify studies reporting the use of ctDNA to predict GC outcome and all relevant studies published until November 2022 were enrolled for our analysis. Data were extracted by two authors independently and statistic analysis was conducted by R program with 'meta' and 'metafor' packages.Results: A total of 34 qualified articles with 5091 subjects were incorporated into our meta-analysis. The corresponding Hazard ratio (HR) of overall survival (OS), disease-free survival (DFS) and progression-free survival (PFS) were 2.74 (95% CI:2.24-3.35), 3.13 (95% CI:2.08-4.72) and 3.04 (95% CI:2.46-3.76), respectively, in GC patients.Conclusion: Blood-based ctDNA assay would be a potential novel biomarker for GC evaluation and prediction.Simple Summary: This is the integrated meta-analysis on the association of circulating tumour DNA (ctDNA) and prognosis of gastric cancer (GC) with an increasing number of studies exploring the prognostic value of GC in the last few years, which depicted that the detection of ctDNA could be a promising predictor in GC patients.

The role of Pcdh10 in neurological disease and cancer

BACKGROUND

Protocadherin 10 (PCDH 10), a member of the superfamily of protocadherins, is a Ca2+-dependent homophilic cell-cell adhesion molecule expressed on the surface of cell membranes. Protocadherin 10 plays a critical role in the central nervous system including in cell adhesion, formation and maintenance of neural circuits and synapses, regulation of actin assembly, cognitive function and tumor suppression. Additionally, Pcdh10 can serve as a non-invasive diagnostic and prognostic indicator for various cancers.

METHODS

This paper collects and reviews relevant literature in Pubmed.

CONCLUSION

This review describes the latest research understanding the role of Pcdh10 in neurological disease and human cancer, highlighting the importance of scrutinizing its properties for the development of targeted therapies and identifying a need for further research to explore Pcdh10 functions in other pathways, cell types and human pathologies.

An overview of DNA methylation markers for early detection of gastric cancer: current status, challenges, and prospects

Background: Gastric cancer (GC) is one of the most common malignancies, with a low 5-year survival rate. However, if diagnosed at an early stage, it can be cured by endoscopic treatment and has a good prognosis. While gastrointestinal X-ray and upper endoscopy are used as national GC screening methods in some GC high-risk countries, such as Japan and Korea, their radiation exposure, invasiveness, and high cost suggest that they are not the optimal tools for early detection of GC in many countries. Therefore, a cost-effective, and highly accurate method for GC early detection is urgently needed in clinical settings. DNA methylation plays a key role in cancer progression and metastasis and has been demonstrated as a promising marker for cancer early detection. Aims and methods: This review provides a comprehensive overview of the current status of DNA methylation markers associated with GC, the assays developed for GC early detection, challenges in methylation marker discovery and application, and the future prospects of utilizing methylation markers for early detection of GC. Through our analysis, we found that the currently reported DNA methylation markers related to GC are mainly in the early discovery stage. Most of them have only been evaluated in tissue samples. The majority of non-invasive assays developed based on blood lack standardized sampling protocols, pre-analytical procedures, and multicenter validation, and they exhibit insufficient sensitivity for early-stage GC detection. Meanwhile, the reported GC DNA methylation markers are generally considered pan-cancer markers. Conclusion: Therefore, future endeavors should focus on identifying additional methylation markers specific to GC and establishing non-invasive diagnostic assays that rely on these markers. These assays should undergo multicenter, large-scale prospective validation in diverse populations.

Epigenetic signatures in gastric cancer: current knowledge and future perspectives

INTRODUCTION

Gastric cancer (GC) is the fifth most common malignancy in the world and accounts for 7.7% of all cancer-related deaths. Early diagnosis of GC is critical in terms of prognosis, and aberrations at the molecular level, especially epigenetic alterations, manifest much earlier than histological findings. In recent years, there has been a great deal of research on the epigenomic profile of GC, and epigenetic alterations seem to play a more important role than genetic factors. With the introduction of epigenetic drugs into clinical use in the last decade, the importance of the epigenetic background of GC has increased considerably.

AREAS COVERED

In this review, we summarize the role of methylation changes, histone modifications, and non-coding RNAs in the pathogenesis of GC and how these signatures can be used as diagnostic and therapeutic targets in clinical management.

EXPERT OPINION

Epigenetic alterations take place before most genetic aberrations observed in GC and may have an initiating role in the pathogenesis of GC. They can be used as biomarkers in risk calculation, early diagnosis, and evaluation of prognosis of GC, as well as treatment targets.

Liquid biopsy in gastric cancer: predictive and prognostic biomarkers

Gastric cancer (GC) is a high-incidence cancer worldwide. Most patients are diagnosed at an advanced stage, by which time they have limited treatment options and poor prognosis. Early diagnosis and precise treatment are important. In the past few years, emerging research has been conducted on the use of non-invasive liquid biopsy, with its advantages of minimal invasiveness and repeated sampling, to monitor tumor occurrence and recurrence in real time and to evaluate prognosis and treatment response. Many studies have demonstrated the potential of liquid biopsy in GC, and the detection of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), circulating free DNA (cfDNA), and exosomes has achieved gratifying results. In this review, we summarize evolving technologies for and information regarding liquid biopsy, the most recently discovered GC liquid biopsy biomarkers, and ongoing clinical trials and discuss the challenges and application prospects of liquid biopsy in GC.

Biomarkers of gastric cancer: current advancement

Gastric cancer (GC) is one of the most prevalent malignant types worldwide, especially in East Asia. Due to its frequently advanced stage at diagnosis, the mortality from GC is high and the prognosis is still unsatisfactory. Thus, early detection using effective screening approaches is vital to decrease the morbidity and mortality of GC. Interestingly, biomarkers can be used for diagnosis, prediction of sensitivity to treatment, and prognosis in GC. The potential biomarkers detectable in liquid biopsies such as circulating tumor cells (CTCs), long non-coding RNAs (lncRNAs), cell-free DNA (cfDNA), microRNAs, and exosomes reveal numerous information regarding the early prediction and the outcomes for GC patients. Additionally, using the novel serum biomarkers has opened up new opportunities for diagnosing and monitoring patients with GC. This review mainly summarizes the novel progress and approaches in GC biomarkers, which could be potentially used for early diagnosis and therapy monitoring. Meanwhile, we also discussed the advantages, disadvantages, and future perspectives of GC biomarkers.

The relationship between P16INK4A and TP53 promoter methylation and the risk and prognosis in patients with oesophageal cancer in Thailand

DNA methylation can regulate the expression of tumour suppressor genes P16 and TP53, environmental factors, which are both important factors related to an increased risk and prognosis of oesophageal cancer (EC). However, the association between these two genes methylation status, as well as the effects of gene-environment interactions, EC risk remains unclear. A Hospital-based case-control study data were collected from 105 new EC cases and 108 controls. Promoter methylation status was investigated for P16 and TP53 genes using methylation-specific polymerase (MSP) chain reaction methods with SYBR green. Logistic and Cox regression models were used to analyse the association of P16 and TP53 promotor methylation status with EC risk and prognosis, respectively. Our results suggest P16, TP53 methylation significantly increased the risk of EC (OR = 5.24, 95% CI: 2.57-10.66, P < 0.001; OR = 3.38, 95% CI: 1.17-6.67, P < 0.001, respectively). In addition, P16 and TP53 promoter methylation status and the combined effects between environmental factors and its methylations in tissue were correlated with the EC risk and prognosis of EC patients. As a new biomarker, the methylation of P16 and TP53 can serve as a potential predictive biomarker of EC.

Correlation between RASSF1A Methylation in Cell-Free DNA and the Prognosis of Cancer Patients: A Systematic Review and Meta-Analysis

Background

Although the effects of methylation of the Ras association domain-containing protein 1 isoform A (RASSF1A) gene in cell-free DNA on the outcomes of patients with different types of cancer have been reported, the results are inconsistent.

Objective

: To explore the relationships between RASSF1A methylation in cell-free DNA and the outcomes of cancer patients.

Methods

The PubMed, Embase, and Web of Science databases were searched for papers related to this topic on December 8, 2021. The retrieved articles were screened by two independent researchers, following which the methodological quality of the selected studies was evaluated using the Newcastle-Ottawa Scale. Additionally, hazard ratios were calculated, and publication bias of the studies was determined using Egger's test.

Results

Nine relevant publications involving a combined total of 1254 patients with different types of cancer were included in this study. The combined results of the random effects models yielded a hazard ratio of 1.73 (95% confidence interval: 1.31, 2.29; P < 0.001), which suggested there was a significant association between RASSF1A methylation and overall survival, and patients with an RASSF1A methylation status had a significantly increased risk of total death. Moreover, the Egger test result suggested there was no significant publication bias among the included studies.

Conclusions

The methylation of RASSF1A in cell-free DNA in cancer patients was observably associated with an increased risk of poor overall survival.

DNA Methylation: An Important Biomarker and Therapeutic Target for Gastric Cancer

Gastric cancer (GC) is a very common malignancy with a poor prognosis, and its occurrence and development are closely related to epigenetic modifications. Methylation of DNA before or during gastric cancer is an interesting research topic. This article reviews the studies on DNA methylation related to the cause, diagnosis, treatment, and prognosis of gastric cancer and aims to find cancer biomarkers to solve major human health problems.

Gastric cancer: An epigenetic view

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

Circular RNA PCDH10 regulates the tumorigenesis of pancreatic cancer through the miR-338-3p/hTERT axis

Protocadherin-10 (PCDH10) was previously identified as a pancreatic cancer (PC) suppressor by reducing telomerase activity through binding with human telomerase reverse transcriptase (hTERT). However, we did not observe any effects of PCDH10 on hTERT mRNA or protein expression. Our research found that the PCDH10 gene could be transcribed into linear mRNA or circular RNA, and FUS could bind to the introns flanking the circularized exons, inducing the PCDH10 linear mRNA to shift to circPCDH10 in PC cells. Knockdown of circPCDH10 significantly inhibited PC progression. Mechanistically, circPCDH10 acted as a sponge of miR-338-3p, which could negatively regulate hTERT expression in PC cells. The inhibitory effects of circPCDH10 knockdown on PC cells could be notably reversed by miR-338-3p inhibition and ectopic expression of hTERT. Overall, we propose that the increased FUS expression in PC cells made circPCDH10 the preferred product of the PCDH10 gene, and circPCDH10 might promote PC progression through upregulation of hTERT expression by targeting miR-338-3p.

Circulating tumor DNA detection and its application status in gastric cancer: a narrative review

Circulating tumor DNA (ctDNA) is the small genomic fragment released by tumor cells into the circulating system, which carries the gene variation features, such as mutation, insertion, deletion, rearrangement, copy number variation (CNV) and methylation, rendering it an important biomarker. It can be used not only to diagnose certain types of solid tumors, but also to monitor the therapeutic response and explore the minimal residual disease (MRD) and resistant mutation of targeted therapy. Therefore, ctDNA detection may become the preferred non-invasive tumor screening method. For patients who cannot receive further gene detection due to insufficient or restricted sample collection with the defined pathological diagnosis, ctDNA detection can be carried out to determine the gene mutation type, with no need for repeated sampling. Gastric cancer (GC) is a malignancy with extremely high morbidity and mortality, and its genesis and development are the consequence of interactions of multiple factors, including environment, diet, heredity, helicobacter pylori infection, chronic inflammatory infiltration, and precancerous lesion. As the research on GC moves forward, the existing research mainly focuses on genetic and epigenetic changes, including DNA methylation, histone modification, non-coding RNA changes, gene mutation, gene heterozygosity loss and microsatellite instability. This paper aimed to summarize the contents of ctDNA detection, its application status in GC and clinical significance.

Cell-free DNA as a liquid biopsy for early detection of gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors with poor prognosis worldwide, mainly due to the lack of suitable modalities for population-based screening and early detection of this disease. Therefore, novel and less invasive tests with improved clinical utility are urgently required. The remarkable advances in genomics and proteomics, along with emerging new technologies for highly sensitive detection of genetic alterations, have shown the potential to map the genomic makeup of a tumor in liquid biopsies, in order to assist with early detection and clinical management. The present review summarize the current status in the identification and development of cell-free DNA (cfDNA)-based biomarkers in GC, and also discusses their potential utility and the technical challenges in developing practical cfDNA-based liquid biopsy for early detection of GC.

Epigenetic Mechanisms in Gastric Cancer: Potential New Therapeutic Opportunities

Gastric cancer (GC) is one of the deadliest malignancies worldwide. Complex disease heterogeneity, late diagnosis, and suboptimal therapies result in the poor prognosis of patients. Besides genetic alterations and environmental factors, it has been demonstrated that alterations of the epigenetic machinery guide cancer onset and progression, representing a hallmark of gastric malignancies. Moreover, epigenetic mechanisms undergo an intricate crosstalk, and distinct epigenomic profiles can be shaped under different microenvironmental contexts. In this scenario, targeting epigenetic mechanisms could be an interesting therapeutic strategy to overcome gastric cancer heterogeneity, and the efforts conducted to date are delivering promising results. In this review, we summarize the key epigenetic events involved in gastric cancer development. We conclude with a discussion of new promising epigenetic strategies for gastric cancer treatment.

Quantitation Analysis of PCDH10 Methylation in Adolescent Idiopathic Scoliosis Using Pyrosequencing Study

STUDY DESIGN

A retrospective and comparative study.

OBJECTIVE

To evaluate the difference of DNA methylation in protocadherin10 (PCDH10) genes between adolescent idiopathic scoliosis (AIS) and normal controls, and to assess the association between DNA methylation and the etiology of AIS.

SUMMARY OF BACKGROUND DATA

The PCDH10 gene showed abnormal expression in AIS. However, the mechanism was still unclear. DNA methylation was an important epigenetic mechanism at the interface between genetics and environmental phenotype, seeming to be a suitable epigenetic mark for the abnormal expression of PCDH10 in AIS.

METHODS

There were 50 AIS patients and 50 healthy controls included in the study. The peripheral blood sample of each participant was taken. The pyrosequencing assay was used to assess the methylation status of PCDH10 promoter and real time PCR (RT-PCR) was used to detect the PCDH10 gene expression. The comparison analysis was performed using independent t test and 2-tailed Pearson coefficients was calculated for the correlation analysis.

RESULTS

The average methylation level was 4.32 ± 0.73 in AIS patients and 3.14 ± 0.97 in healthy controls (P < 0.001). The PCDH10 gene expression was 0.23 ± 0.04 in AIS patients and 0.36 ± 0.08 in normal controls (P < 0.0001). Statistically significant linear correlation was found between PCDH10 gene methylation level and Cobb angle of major curve (P < 0.001). Besides, a significant negative correlation between PCDH10 methylation and PCDH10 gene expression was found (P < 0.001).

CONCLUSION

AIS patients were associated with high DNA methylation level and low gene expression of PCDH10 gene rather than normal controls. The high methylation level indicated high Cobb angle of major curves in AIS. The abnormal DNA methylation may widely exist and serve as a potential mechanism for AIS.

LEVEL OF EVIDENCE

3.

RASSF1A: A promising target for the diagnosis and treatment of cancer

The Ras association domain family 1 isoform A (RASSF1A), a tumor suppressor, regulates several tumor-related signaling pathways and interferes with diverse cellular processes. RASSF1A is frequently demonstrated to be inactivated by hypermethylation in numerous types of solid cancers. It is also associated with lymph node metastasis, vascular invasion, and chemo-resistance. Therefore, reactivation of RASSF1A may be a viable strategy to block tumor progress and reverse drug resistance. In this review, we have summarized the clinical value of RASSF1A for screening, staging, and therapeutic management of human malignancies. We also highlighted the potential mechanism of RASSF1A in chemo-resistance, which may help identify novel drugs in the future.

Methylation Analysis of P16, RASSF1A, RPRM, and RUNX3 in Circulating Cell-Free DNA for Detection of Gastric Cancer: A Validation Study

BACKGROUND

Most of Gastric Cancer (GC) patients are diagnosed at an advanced stage with poor prognosis. Hypermethylations of several tumor suppressor genes in cell-free DNA of GC patients have been previously reported. In this study, an attempt was made to investigate the methylation status of P16, RASSF1A, RPRM, and RUNX3 and their potentials for early diagnosis of GC.

METHODS

Methylation status of the four tumor suppressor genes in 96 plasma samples from histopathologically confirmed gastric adenocarcinoma patients (Stage I-IV) and 88 healthy controls was determined using methylation-specific PCR method. Receiver operating characteristic curve analysis was performed and Area Under the Curve (AUC) was calculated. Two tailed p<0.05 were considered statistically significant.

RESULTS

Methylated P16, RASSF1A, RPRM, and RUNX3 were significantly higher in the GC patients (41.7, 33.3, 66.7, and 58.3%) compared to the controls (15.9, 0.0, 6.8, and 4.5%), respectively (p<0.001). Stratification of patients showed that RPRM (AUC: 0.70, Sensitivity: 0.47, Specificity: 0.93, and p<0.001) and RUNX3 (AUC: 0.77, Sensitivity: 0.59, Specificity: 0.95, and p<0.001) had the highest performances in detection of early-stage (I+II) GC. The combined methylation of RPRM and RUNX3 in detection of early-stage GC had a higher AUC of 0.88 (SE=0.042; 95% CI:0.793-0.957; p<0.001), higher sensitivity of 0.82 and reduced specificity of 0.89.

CONCLUSION

Methylation analysis of RPRM and RUNX3 in circulating cell free-DNA of plasma could be suggested as a potential biomarker for detection of GC in early-stages.

Association Between Liquid Biopsy and Prognosis of Gastric Cancer Patients: A Systematic Review and Meta-Analysis

Background: Reports regarding liquid biopsy and gastric cancer (GC) have emerged rapidly in recent decades, yet their prognostic value still remains controversial. This study was aimed to assess the impact of liquid biopsy, including circulating tumor cells (CTCs) and cell-free nucleic acids, on GC patients' prognosis.

Methods: PubMed, Medline, EMBASE, and ClinicalTrial.gov databases were searched for studies that report GC patient survival data stratified by CTC/circulating tumor DNA (ctDNA)/circulating miRNAs' status. The hazard ratios (HRs) and their 95% confidence intervals (CIs) for patients' overall survival (OS) and disease-free survival (DFS)/progression-free survival (PFS) were recorded or calculated depending on circulating target status.

Results: We initially identified 4,221 studies, from which 43 were eligible for further analysis, comprising 3,814 GC patients. Pooled analyses showed that detection of certain CTCs, ctDNA, and circulating miRNA was associated with poorer OS (CTCs: HR = 1.84, 95%CI 1.50–2.26, p < 0.001; ctDNA: HR = 1.78, 95%CI 1.36–2.34, p < 0.001; circulating miRNA: HR = 1.74, 95%CI 1.13–2.69, p < 0.001) and DFS/PFS (CTCs: HR = 3.39, 95%CI 2.21–5.20, p < 0.001; ctDNA: HR = 2.38, 95%CI 1.31–4.32, p = 0.004; circulating miRNA: HR = 3.30, 95%CI 2.39–4.55, p < 0.001) of GC patients, regardless of disease stage and time point at which sample is taken (at baseline or post-treatment).

Conclusions: The presence of CTCs and/or cellular components identifies a group of GC with poorer prognosis. Among circulating markers, CTCs demonstrated a stronger and more stable predictive value for late-stage disease and among Mongolian populations with GC. Less data are available for ctDNA and miRNA; however, their presence may also reflect aggressive biology and warrants further prospective study.

Down-regulated of PCDH10 predicts poor prognosis in hepatocellular carcinoma patients

Protocadherin10 (PCDH10), a member of the nonclustered protocadherin family, functions as a tumor suppressor in many cancers. The aim of this study was to evaluate the expression level and prognostic value of PCDH10 in hepatocellular carcinoma (HCC) patients.Quantitative real-time polymerase chain reaction was used to analyze the expression level of PCDH10 in HCC tissues and adjacent nontumor tissues. The association of PCDH10 expression with clinicopathological features of patients was evaluated by chi-squared test. Overall survival was estimated using the Kaplan-Meier method. Besides, the patient prognosis was also evaluated by Cox regression analysis.PCDH10 expression was significantly lower in HCC tissues than that in adjacent nontumor tissues (P = .000). Kaplan-Meier curves showed that patients with lower PCDH10 expression had a worse overall survival. Moreover, PCDH10 expression level was associated tumor size (P = .005), tumor node metastasis stage (P = .002), smoking status (P = .000), and drinking status (P = .005). Multivariate analysis showed that the expression of PCDH10 (P = .000; hazard ratio = 4.784; 95% confidence interval: 2.550-8.977) was an independently associated with poor overall survival rates, as well as smoking status and drinking status.Our findings indicated that the decreased expression of PCDH10 was closely associated with poor prognosis of HCC patients. It might be considered as a valuable biomarker for HCC.

Aberrant promoter methylation of PCDH10 as a potential diagnostic and prognostic biomarker for patients with breast cancer

Protocadherin-10 (PCDH10) is a tumor suppressor gene. Its expression level is downregulated by promoter methylation in certain types of human tumors. The aim of the present study was to examine the expression level and promoter methylation status of PCDH10 in breast cancer cells and to evaluate the association of PCDH10 methylation and tumor progression and prognosis. MethyLight was used to detect the methylation status of PCDH10 in breast cancer tissues and healthy breast tissues. Reverse transcription-quantitative polymerase chain reaction was used to assess the mRNA expression level of PCDH10, as well as to evaluate the association between PCDH10 methylation and clinicopathological features, along with patients' overall survival (OS). PCDH10 5'-C-phosphate-G-3' (CpG) methylated sites were identified in tumor tissues and matched healthy tissues (n=392). Tumor tissues and matched healthy tissues exhibited identifiable PCR results, with PCDH10 gene promoter methylation identified in ductal carcinoma in situ (66%), invasive ductal carcinoma (82%), invasive ductal carcinoma with lymph node metastasis (85.32%) and hereditary breast cancer tissues (72.37%). PCDH10 mRNA expression was significantly decreased in breast cancer tissues compared with healthy breast tissues (P=0.032). PCDH10 methylation was associated with tumor size (P=0.004), but not associated with other clinical factors. Survival analysis revealed that the patients exhibiting methylated-PCDH10 had significantly poorer OS times than patients exhibiting unmethylated-PCDH10 (P<0.0001). Receiver operating characteristic analysis indicated a sensitivity of 75%, a specificity of 62.5%, and an area under the curve of 0.682 for PCDH10. Additionally, the results of the present study indicated that PCDH10 methylation status may be a useful diagnostic and prognostic evaluation biomarker for breast cancer. The results suggested that PCDH10 methylation is a common occurrence in primary breast cancer and is associated with poor survival rates among patients with breast cancer.

The Use of Circulating Tumor DNA for Prognosis of Gastrointestinal Cancers

Gastrointestinal cancers, including oesophageal, gastric and colorectal cancers (CRC) have high rates of disease recurrence despite curative resection. There are a number of recent studies that have investigated the use of circulating tumor DNA (ctDNA) for prognostic value in these cancers. We reviewed studies that had been published prior to March 2018 that assessed the prognostic values of ctDNA in patients with oesophageal and gastric cancers, gastrointestinal stromal tumors (GIST) and CRC. We identified 63 eligible clinical studies that focussed on recurrence and survival. Studies assessed investigated various ctDNA biomarkers in patients with different stages of cancer undergoing surgical resection, chemotherapy and no treatment. For oesophageal squamous cell carcinoma and oesophageal adenocarcinoma, methylation of certain genes such as APC and DAPK have been highlighted as promising biomarkers for prognostication, but these studies are limited and more comprehensive research is needed. Studies focusing on gastric cancer patients showed that methylation of ctDNA in SOX17 and APC were independently associated with poor survival. Two studies demonstrated an association between ctDNA and recurrence and survival in GIST patients, but more studies are needed for this type of gastrointestinal cancer. A large proportion of the literature was on CRC which identified both somatic mutations and DNA methylation biomarkers to determine prognosis. ctDNA biomarkers that identified somatic mutations were more effective if they were personalized based on mutations found in the primary tumor tissue, but ctDNA methylation studies identified various biomarkers that predicted increased risk of recurrence, poor disease free survival and overall survival. While the use of non-invasive ctDNA biomarkers for prognosis is promising, larger studies are needed to validate the clinical utility for optimizing treatment and surveillance strategies to reduce mortality from gastrointestinal cancers.

DNA methylation contributes to silencing the expression of linc00086 in gastric cancer

Previous evidence has revealed that long non-coding RNAs serve important functions in numerous types of cancer when dysregulated, including in gastric cancer (GC). In the present study, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis was used to detect the expression of small integral membrane protein 10 like 2A (linc00086) in GC tissues and non-cancerous tissues, and the expression of linc00086 in GC cell lines was analyzed. A RT-qPCR assay was used to assess linc00086 expression levels in GC cell lines following treatment with 5-Aza-2'-deoxycytidine (5-aza-dC), which is a DNA methyltransferase inhibitor. Small interfering RNA was used to silence the expression of methyl-CpG binding protein 2 (MeCP2), and then the expression of linc00086 was detected. Linc00086 expression was revealed to be downregulated in GC tissues and GC cell lines. Furthermore, it was revealed that 5-aza-dC induced linc00086 expression in SGC-7901 and MKN45 cells, and analysis of CpG methylation by bisulfite sequencing-polymerase chain reaction demonstrated that DNA methylation may regulate the expression of linc00086. MeCP2 is involved in gene regulation by binding to methylated promoters, and it was revealed that the knockdown of the expression of MeCP2 resulted in a higher expression of linc00086. The present study revealed that DNA methylation regulate the expression of linc00086 in human GC cell lines.

Diagnostic and prognostic value of circulating tumor DNA in gastric cancer: a meta-analysis

BACKGROUND

Circulating tumor DNA (ctDNA) has offered a minimally invasive approach for detection and measurement of gastric cancer (GC). However, its diagnostic and prognostic value in gastric cancer still remains unclear.

RESULTS

A total of 16 studies comprising 1193 GC patients met our inclusion criteria. The pooled sensitivity and specificity were 0.62 (95% confidence intervals (CI) 0.59-0.65) and 0.95 (95% CI 0.93-0.96), respectively. The AUSROC (area under SROC) curve was 0.94 (95% CI 0.89-0.98). The results showed that the presence of certain ctDNA markers was associated with larger tumor size (OR: 0.26, 95% CI 0.11-0.61, p = 0.002), TNM stage (I + II/III + IV, OR: 0.11, 95% CI 0.07-0.17, p = 0.000), as well as H. pylori infection. (H.p negative/H.p positive, OR: 0.57, 95% CI 0.36-0.91, p = 0.018). Moreover, there was also a significant association between the presence of ctDNA and worse overall survival (HR 1.77, 95% CI 1.38-2.28, p < 0.001), as well as disease-free survival (HR 4.36, 95% CI 3.08-6.16, p < 0.001).

MATERIALS AND METHODS

Pubmed, Embase, Cochrane Library and Web of Science databases were searched for relating literature published up until November 30, 2016. Diagnostic accuracy variables were pooled by the Meta-Disc software. Engauge Digitizer and Stata software were applied for prognostic data extraction and analysis.

CONCLUSIONS

Our meta-analysis indicates the detection of certain ctDNA targets is significantly associated with poor prognosis of GC patients, with high specificity and relatively moderate sensitivity.

The role of TFPI2 hypermethylation in the detection of gastric and colorectal cancer

Gastrointestinal cancer is a prevalent disease with high morbidity and mortality. Tissue factor pathway inhibitor 2 (TFPI2) gene could protect the extracellular matrix of cancer cells from degradation and tumor invasion. The goal of our study was to estimate the diagnostic value of TFPI2 hypermethylation in gastric cancer (GC) and colorectal cancer (CRC). TFPI2 methylation was measured by quantitative methylation-specific polymerase chain reaction (qMSP) method in 114 GC and 80 CRC tissues and their paired non-tumor tissues. Our results showed that TFPI2 methylation was significantly higher in tumor tissues (GC: 29.940% vs. 12.785%, P < 0.001; CRC: 26.930% vs. 5.420%, P < 0.001). The methylation level of TFPI2 in colorectal tumor tissues was significantly higher than that in colorectal normal tissues (26.930% versus 0.002%, P < 0.00001). In GC, TFPI2 hypermethylation yielded an area under the curve (AUC) of 0.762 (95% CI: 0.696–0.828) with a sensitivity of 68% and a specificity of 83%. In CRC, TFPI2 hypermethylation yielded an AUC of 0.759 (95% CI: 0.685–0.834) with a sensitivity of 61% and a specificity of 84%. Similarly, TCGA data also supported TFPI2 hypermethylation was a promising diagnostic marker for GC and CRC. Moreover, the dual-luciferase reporter assay showed TFPI2 fragment could upregulate gene expression (fold change = 5, P = 0.005). Data mining further indicated that TFPI2 expression in CRC cell lines was significantly increased after 5’-AZA-deoxycytidine treatment (fold change > 1.37). In conclusion, TFPI2 hypermethylation might be a promising diagnostic biomarker for GC and CRC.

Promoter methylation of tumor-related genes as a potential biomarker using blood samples for gastric cancer detection

Gene promoter methylation has been reported in gastric cancer (GC). However, the potential applications of blood-based gene promoter methylation as a noninvasive biomarker for GC detection remain to be evaluated. Hence, we performed this analysis to determine whether promoter methylation of 11 tumor-related genes could become a promising biomarker in blood samples in GC. We found that the cyclin-dependent kinase inhibitor 2A (p16), E-cadherin (CDH1), runt-related transcription factor 3 (RUNX3), human mutL homolog 1 (MLH1), RAS association domain family protein 1A (RASSF1A), cyclin-dependent kinase inhibitor 2B (p15), adenomatous polyposis coli (APC), Glutathione S-transferase P1 (GSTP1), TP53 dependent G2 arrest mediator candidate (Reprimo), and O6-methylguanine-DNAmethyl-transferase (MGMT) promoter methylation was notably higher in blood samples of patients with GC compared with non-tumor controls. While death-associated protein kinase (DAPK) promoter methylation was not correlated with GC. Further analyses demonstrated that RUNX3, RASSF1A and Reprimo promoter methylation had a good diagnostic capacity in blood samples of GC versus non-tumor controls (RUNX3: sensitivity = 63.2% and specificity = 97.5%, RASSF1A: sensitivity = 61.5% and specificity = 96.3%, Reprimo: sensitivity = 82.0% and specificity = 89.0%). Our findings indicate that promoter methylation of the RUNX3, RASSF1A and Reprimo genes could be powerful and potential noninvasive biomarkers for the detection and diagnosis of GC in blood samples in clinical practices, especially Reprimo gene. Further well-designed (multi-center) and prospective clinical studies with large populations are needed to confirm these findings in the future.

How to stomach an epigenetic insult: the gastric cancer epigenome

Gastric cancer is a deadly malignancy afflicting close to a million people worldwide. Patient survival is poor and largely due to late diagnosis and suboptimal therapies. Disease heterogeneity is a substantial obstacle, underscoring the need for precision treatment strategies. Studies have identified different subgroups of gastric cancer displaying not just genetic, but also distinct epigenetic hallmarks. Accumulating evidence suggests that epigenetic abnormalities in gastric cancer are not mere bystander events, but rather promote carcinogenesis through active mechanisms. Epigenetic aberrations, induced by pathogens such as Helicobacter pylori, are an early component of gastric carcinogenesis, probably preceding genetic abnormalities. This Review summarizes our current understanding of the gastric cancer epigenome, highlighting key advances in recent years in both tumours and pre-malignant lesions, made possible through targeted and genome-wide technologies. We focus on studies related to DNA methylation and histone modifications, linking these findings to potential therapeutic opportunities. Lessons learned from the gastric cancer epigenome might also prove relevant for other gastrointestinal cancers.

Status of Epstein-Barr Virus Coinfection with Helicobacter pylori in Gastric Cancer

Epstein-Barr virus is a ubiquitous human herpesvirus whose primary infection causes mononucleosis, Burkett's lymphoma, nasopharyngeal carcinoma, autoimmune diseases, and gastric cancer (GC). The persistent infection causes malignancies in lymph and epithelial cells. Helicobacter pylori causes gastritis in human with chronic inflammation. This chronic inflammation is thought to be the cause of genomic instability. About 45%-word population have a probability of having both pathogens, namely, H. pylori and EBV. Approximately 180 per hundred thousand population is developing GC along with many gastric abnormalities. This makes GC the third leading cause of cancer-related death worldwide. Although lots of research are carried out individually for EBV and H. pylori, still there are very few reports available on coinfection of both pathogens. Recent studies suggested that EBV and H. pylori coinfection increases the occurrence of GC as well as the early age of GC detection comparing to individual infection. The aim of this review is to present status on coinfection of both pathogens and their association with GC.