CD56 on immune and tumor cells: what is known and beyond?

Recent studies on cancer cells and the immune microenvironment have offered valuable insights into personalized diagnostics, targeted therapies, and individualized prognosis evaluation. A comprehensive understanding of new and existing biomarkers in both healthy and diseased conditions is essential for advancing these goals. CD56, also known as the neural cell adhesion molecule, is a well-established phenotypic marker of natural killer cells. It is also expressed by various immune cells under healthy conditions, such as T cells, dendritic cells, and monocytes. Despite its widespread expression, the functions of CD56 are still poorly understood. In patients with infectious, autoimmune, or malignant diseases, changes in the proportion, phenotype, and function of CD56+ immune cells have been observed. In patients with hematolymphoid disorders, malignant cells may exhibit aberrant CD56 expression, making it a valuable diagnostic and prognostic marker. CD56 also holds potential as a therapeutic target. In this review, we summarize the current understanding of CD56 expression and function across various immune cells in infectious, immune-related, and cancerous conditions. We also explore its diagnostic, prognostic, and therapeutic significance in hematological malignancies. This review aims to present a comprehensive overview of CD56 in hematolymphoid disorders, offering insights into how CD56 and its associated immune cells could inform future immunotherapeutic strategies.