CD99 antigen (CD99) (CD99)

CD99 is a 32-kDa Type I transmembrane glycoprotein encoded by the MIC2 gene, primarily recognized for its high and consistent expression in Ewing sarcoma [UniProt: P14209]. It functions as a critical cell adhesion molecule, facilitating the transendothelial migration of leukocytes, a process essential for inflammatory responses [PubMed: 25631143]. In the context of oncology, CD99 is involved in maintaining the undifferentiated state of tumor cells and promoting cell survival and migration [PubMed: 23563498]. The extracellular domain of CD99 is the primary target for therapeutic intervention, as its engagement by specific monoclonal antibodies can trigger rapid, often caspase-independent, apoptosis in malignant cells [PubMed: 28453504]. Beyond Ewing sarcoma, CD99 has emerged as a promising target in hematologic malignancies such as acute myeloid leukemia (AML) and T-cell lymphoblastic lymphoma [PubMed: 30104341]. Experimental therapies including monoclonal antibodies (e.g., 12E7, O13) and CD99-specific CAR-T cells are currently under investigation for their ability to selectively eliminate CD99-positive cancer cells. However, the clinical application of CD99-targeted agents is complicated by the protein's expression on various normal tissues, including endothelial cells and hematopoietic stem cells, which poses risks for off-target toxicity [PubMed: 28453504]. Consequently, current research focuses on optimizing the therapeutic window to exploit CD99's role in disease while minimizing adverse effects on healthy physiology.

Other names

MIC2MIC2XMIC2YE2 antigen12E7 antigenT-cell surface glycoprotein E2HuLy-m6

Binding to the extracellular domain of CD99 triggers signal transduction pathways that lead to caspase-independent apoptosis in malignant cells and disrupts the interaction between leukocytes and endothelial cells during diapedesis.