Lyzed alterations of BarH-like 2 homeobox protein (BARHL2) in GC cell lines and tissues, as well as in DNA obtained from 128 gastric washes and 30 gastric juice-derived exosomes. GC cell lines were transfected with plasmids encodingBARHL2and subjected to proliferation, colony formation, and gene expression analyses. RESULTS: High levels ofBARHL2methylation were detected in three of seven GC cell lines; consistent with this, these cell lines expressed low levels ofBARHL2. Treatment of these cell lines with 5-aza-2′-deoxycytidine restoredBARHL2expression. Levels ofBARHL2methylation in 18 normal and 14 atrophic gastritis samples were low irrespective ofHelicobacter pyloriinfection. High levels ofBARHL2methylation were observed in gastric wash-derived DNA obtained from early GC patients before endoscopic resection (ER), but methylation was significantly lower after curative ER. Analysis using gastric juice-derived exoDNA samples revealed thatBARHL2methylation yielded an area under the curve of 0.923 with 90% sensitivity and 100% specificity with respect to discriminating GC patients from non-GC controls. BARHL2 nuclear immunoreactivity was found in all normal gastric epithelial cells and in cells from patients with gastritis and adenoma. In contrast, loss of BARHL2 expression was observed in the vast majority of the GC tissues. Finally, transfection ofBARHL2into MKN7 and MKN45 cell lines significantly inhibited their proliferation and ability to form colonies. CONCLUSIONS: Methylation analysis ofBARHL2using gastric wash-derived DNA and/or gastric juice-derived exoDNA could be useful for early detection of GC in clinical settings....

Deficient mismatch repair (dMMR) results in microsatellite instability (MSI), a pronounced mutator phenotype. High‐frequency MSI (MSI‐H)/dMMR is gaining increasing interest as a biomarker for advanced cancer patients to determine their eligibility for immune checkpoint inhibitors (ICIs). Various methods based on next‐generation sequencing (NGS) have been developed to assess the MSI status. Comprehensive genomic profiling (CGP) testing can precisely ascertain the MSI status as well as genomic alterations in a single NGS test. The MSI status can be also ascertained through the liquid biopsy‐based CGP assays. MSI‐H has thus been identified in various classes of tumors, resulting in a greater adoption of immunotherapy, which is hypothesized to be effective against malignancies that possess a substantial number of mutations and/or neoantigens. NGS‐based studies have also characterized MSI‐driven carcinogenesis, including significant rates of fusion kinases in colorectal cancers (CRCs) with MSI‐H that are targets for therapeutic kinase inhibitors, particularly in MLH1‐methylated CRCs with wild‐type KRAS/BRAF. NTRK fusion is linked to the colorectal serrated neoplasia pathway. Recent advances in investigations of MSI‐H malignancies have resulted in the development of novel diagnostic or therapeutic techniques, such as a synthetic lethal therapy that targets the Werner gene. DNA sensing in cancer cells is required for antitumor immunity induced by dMMR, opening up novel avenues and biomarkers for immunotherapy. Therefore, clinical relevance exists for analyses of MSI and MSI‐H‐associated genomic alterations in malignancy. In this article, we provide an update on MSI‐driven carcinogenesis, with an emphasis on unique landscapes of diagnostic and immunotherapeutic strategies.

Gastric cancer (GC) is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. There is an increasing understanding of the roles that genetic and epigenetic alterations play in GCs. Recent studies using next-generation sequencing (NGS) have revealed a number of potential cancer-driving genes in GC. Whole-exome sequencing of GC has identified recurrent somatic mutations in the chromatin remodeling gene ARID1A and alterations in the cell adhesion gene FAT4, a member of the cadherin gene family. Mutations in chromatin remodeling genes (ARID1A, MLL3 and MLL) have been found in 47% of GCs. Whole-genome sequencing and whole-transcriptome sequencing analyses have also discovered novel alterations in GC. Recent studies of cancer epigenetics have revealed widespread alterations in genes involved in the epigenetic machinery, such as DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs and microRNAs. Recent advances in molecular research on GC have resulted in the introduction of new diagnostic and therapeutic strategies into clinical settings. The anti-human epidermal growth receptor 2 (HER2) antibody trastuzumab has led to an era of personalized therapy in GC. In addition, ramucirumab, a monoclonal antibody targeting vascular endothelial growth factor receptor (VEGFR)-2, is the first biological treatment that showed survival benefits as a single-agent therapy in patients with advanced GC who progressed after first-line chemotherapy. Using NGS to systematically identify gene alterations in GC is a promising approach with remarkable potential for investigating the pathogenesis of GC and identifying novel therapeutic targets, as well as useful biomarkers. In this review, we will summarize the recent advances in the understanding of the molecular pathogenesis of GC, focusing on the potential use of these genetic and epigenetic alterations as diagnostic biomarkers and novel therapeutic targets.