CLDN18 and gastric cancer: Additional biomarkers, such as Reg IV and claudin-18, have been reported to be more highly expressed in SRCC as compared to CAC, and both markers have been previously implicated to be involved in gastric cancer.[17] HATH1, MUC2, and SOX2, identified as the key genes involved in controlling mucin secretion in the gastrointestinal tract, have also been reported to be more highly expressed in SRCC, consistent with histologic findings of excess mucin buildup.[17–20]