CEACAM5 (carcinoembryonic antigen-related cell adhesion molecule 5) is a glycoprotein mediating cell-cell adhesion through homophilic and heterophilic interactions 1. It functions as a receptor for E. coli Dr adhesins and localizes to plasma membranes including basolateral and apical surfaces. CEACAM5 has limited normal tissue expression but is substantially overexpressed in epithelial carcinomas of the gastrointestinal tract, genitourinary and respiratory systems, and breast cancer 2. In cancer, CEACAM5 serves as both a prognostic biomarker and therapeutic target; it is elevated in gastric precancerous lesions (particularly incomplete intestinal metaplasia) and associated with dysplasia progression 3. CEACAM5 expression correlates with neuroendocrine prostate cancer and is regulated by epigenetic modifications including H3K27me3 4. Beyond cancer, CEACAM5 is emerging in non-malignant pathology: it exacerbates asthma by promoting ferroptosis and autophagy in airway epithelial cells via JAK/STAT6 pathway activation 5. Clinically, CEACAM5-targeting antibody-drug conjugates (SAR408701, M9140) show promise for treating CEACAM5-positive tumors with manageable safety profiles 26. CEACAM5 represents an approved emerging biomarker in non-small cell lung cancer management 7.