S100A8 and gastroesophageal reflux disease: Gastric cancer, gastropanel, gastrin-17, cytotoxin associated gene A (CagA), vacuolating cytotoxin, duodenal ulcer promoting gene (dupA), malignancy, gastric ulcer, duodenal ulcer, PPI, antacids, rebamipide, reflux esophagitis, quadruple therapy, triple therapy