CD99

An overview of the CD99 protein and its significance in medical science.

CD99, also known as MIC2, is a transmembrane protein encoded by the MIC2 gene in humans. It is a cell surface glycoprotein that plays a crucial role in various cellular processes, including cell adhesion, apoptosis, and immune response. CD99 is of particular interest in the field of oncology due to its involvement in the pathogenesis of certain cancers, such as Ewing's sarcoma.

Structure and Function

CD99 is a 32 kDa protein that is expressed on the surface of many cell types, including T cells, B cells, and endothelial cells. It is characterized by its small size and its presence in the plasma membrane. The protein is involved in the regulation of cell-cell interactions and is known to facilitate the transendothelial migration of leukocytes.

The CD99 protein is composed of an extracellular domain, a single transmembrane domain, and a short cytoplasmic tail. The extracellular domain is responsible for mediating homophilic interactions, which are critical for its role in cell adhesion.

Role in Disease

CD99 is highly expressed in Ewing's sarcoma, a type of bone cancer that primarily affects children and adolescents. The overexpression of CD99 in Ewing's sarcoma cells is used as a diagnostic marker and is associated with the aggressive nature of the tumor. Research has shown that targeting CD99 can induce apoptosis in Ewing's sarcoma cells, making it a potential therapeutic target.

In addition to its role in cancer, CD99 is involved in the regulation of the immune system. It has been implicated in the modulation of T cell activation and the inflammatory response.

Clinical Significance

The expression of CD99 is used as a diagnostic marker in immunohistochemistry for the identification of Ewing's sarcoma and other small round blue cell tumors. Its presence can help differentiate these tumors from other types of cancer.

Research into CD99 is ongoing, with studies focusing on its potential as a therapeutic target. Inhibitors of CD99 are being investigated for their ability to induce cell death in cancer cells, offering a promising avenue for the development of new cancer treatments.

Also see

• Ewing's sarcoma
• Cell adhesion molecules
• Transmembrane proteins
• Apoptosis
• Immune response