CD99 molecule (CD99)

CD99 molecule (CD99) is a 32 kDa heavily O-glycosylated single-chain transmembrane glycoprotein encoded by the MIC2 gene, located in the pseudoautosomal regions of X and Y chromosomes.[1][2][3][5] It is broadly expressed, especially on hematopoietic cells (notably thymocytes and T cells), vascular endothelium, and various tumor cells. CD99 modulates cell adhesion, migration (especially leukocyte transendothelial migration), immune regulation, and cell death, acting both as a functional receptor and a diagnostic marker. In cancer, particularly Ewing sarcoma and certain leukemias, high CD99 expression is leveraged for immunohistochemical diagnosis and is under investigation as a therapeutic target, as antibody engagement can induce non-apoptotic cancer cell death. CD99 plays roles in T-cell maturation, immune synapse formation, actin cytoskeletal organization, and inflammation, and can act contextually as either a tumor suppressor or oncogene, depending on cellular environment.[1][2][3][4][5]

Other names

HBA71MIC2MIC2XMIC2YMSK5XCD99 antigenE2 antigenMIC2 (monoclonal antibody 12E7)T-cell surface glycoprotein E2antigen identified by monoclonal 12E7Y homologantigen identified by monoclonal antibodies 12E7, F21 and O13cell surface antigen 12E7cell surface antigen HBA-71cell surface antigen O13surface antigen MIC2CD99[1][3][5]

Direct engagement of CD99 by monoclonal antibodies induces non-apoptotic cell death in tumor cells (caspase-independent pathway, sometimes via methuosis-like vacuolization); modulates cell adhesion signaling, triggers immune cell migration by facilitating transendothelial migration, can induce apoptosis in select cell types, influences actin cytoskeleton dynamics[1][2][4]