2018 Volume 46 Issue 3 Pages 111-118
Gastric cancer (GC) is one of the most common malignancies and is the leading cause of cancer-related deaths worldwide. CagA, encoded by cytotoxin-associated gene A (CagA), is a major virulence factor of Helicobacter pylori, a gastric pathogen involved in the development of GC. We previously developed a method for DNA methylation analysis, and early detection of GC using gastric washes rather than highly acidic gastric juice. Extracellular vesicles known as exosomes present in the gastric juice may provide an alternative to gastric washes for the molecular detection of GC. We determined tumor-related alterations in the functional molecular contents within the exosomes, which were purified from the gastric juice of patients with GC, and whether the exosomes contained CagA. Using ultracentrifugation, we purified exosomes from the gastric juice of patients with GC and analyzed their expression levels of microRNA-34 (miR-34) by real-time PCR. Methylation levels of the miR-34b/c gene in exosomal DNA were analyzed by bisulfite pyrosequencing. The microvesicles were verified as exosomes by transmission electron microscopy and western blot analysis with the CD9 exosomal marker. Expression levels of miR-34 were lower in tumor-derived exosomes than in non-tumor-derived exosomes. Methylation levels of miR-34b/c were higher in tumor-derived exosomes than in non-tumor-derived exosomes. Concordant miR-34b/c methylation levels were observed between the exosomal and tissue nuclear DNA from patients with GC. CagA was detected in exosomes obtained from the gastric juice of CagA-positive H. pylori-infected patients with GC. These findings suggest the use of gastric juice-derived exosomes as a biomarker for GC in clinical settings in the future.
