CD38 is a multifunctional transmembrane glycoprotein that serves as both an enzyme and receptor with critical roles in immune regulation and cellular signaling 1. As an enzyme, CD38 exhibits NADase and cyclase activities, consuming NAD+ and synthesizing second messengers like cyclic ADP-ribose (cADPR) and nicotinate-adenine dinucleotide phosphate (NAADP+) that mobilize intracellular calcium 21. CD38 is predominantly expressed on hematopoietic cells, including T cells, B cells, and plasma cells, where it regulates immune cell differentiation, activation, and effector functions 12. In T cells, CD38 affects calcium homeostasis by altering membrane lipid composition, leading to endoplasmic reticulum stress and suppressed IL-2 production 3. CD38 is highly and uniformly expressed on multiple myeloma cells, making it an important therapeutic target 45. Anti-CD38 monoclonal antibodies like daratumumab induce tumor cell death through multiple mechanisms including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and immunomodulatory effects 65. CD38 expression is regulated by post-translational modifications, including palmitoylation by ZDHHC9, which stabilizes protein expression and promotes cancer progression 7.