CLDN4 and gastric neoplasm: This analysis led to the selection of five potential candidate biomarkers based on their reported overexpression in gastric tumors and their membrane localization: carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) [24,25,26], polymeric immunoglobulin receptor (PIGR) [27,28], epithelial cell adhesion molecule (EpCAM) [26,29], olfactomedin4 (OLFM4) [30,31,32], and Claudin4 (CLDN4) [26,33,34].