Cell Adhesion Molecule CD99 in Cancer Immunotherapy

The CD99 antigen is a transmembrane protein expressed in a broad variety of tissues, particularly in hematopoietic cells, thymus, endothelial cells, etc. It participates in several crucial biological processes, including cell adhesion, migration, death, differentiation, and inflammation. CD99 has shown oncogenic or tumor suppressor roles in different types of cancer. Therefore, it has been used as a biomarker and therapeutic target for several types of cancer. Moreover, it has also been reported to be involved in several critical immune processes, such as T cell activation and differentiation, dendritic cell differentiation, and so on. Hence, CD99 may have potential values in cancer immunotherapy. Anti-CD99 antibodies have shown therapeutic effects on certain types of cancer, especially on Ewing sarcoma and T cell acute lymphoblastic leukemia (ALL). This review summarizes the recent progress of CD99 in cancer research and targeting therapies, especially in cancer immunotherapy, which may help researchers understand the crucial roles of CD99 in cancer development and design new therapeutic strategies.