HEPACAM2 (hepatocyte cell adhesion molecule 2) is an immunoglobulin superfamily member with dual roles in cell cycle regulation and cancer pathobiology. Structurally, HEPACAM2 localizes primarily to the plasma membrane and is involved in cell adhesion processes 1. In normal physiology, HEPACAM2 expression progressively decreases from normal colorectal mucosa through adenoma to carcinoma stages 2, suggesting tumor-suppressive properties during early neoplastic transformation. However, in specific malignancies, HEPACAM2 exhibits oncogenic functions. In small cell lung cancer (SCLC), HEPACAM2 is highly and specifically expressed, correlating inversely with progression-free and overall survival 3. HEPACAM2 promotes SCLC growth through ASCL1 and MYC signaling and is secreted extracellularly, making it a potential diagnostic biomarker 3. In colorectal cancer specifically, reduced HEPACAM2 expression correlates with worse prognosis and serves as an independent prognostic factor 4. Conversely, in ulcerative colitis, HEPACAM2 downregulation represents a disease biomarker 56. Additionally, HEPACAM2 expression increases following smoking cessation in human leukocytes, linking it to immune response modulation 7. These findings indicate cancer-type-dependent functions: tumor-promoting in SCLC but protective in CRC, suggesting context-dependent regulatory mechanisms.