CD105, also known as endoglin, is a type I transmembrane glycoprotein predominantly expressed on endothelial cells and serves as an accessory receptor for the transforming growth factor-beta (TGF-尾) superfamily. It plays a crucial role in angiogenesis, making it a key factor in tumor growth, survival, and metastasis. Structurally, CD105 is a homodimeric protein with a large extracellular domain, a hydrophobic transmembrane region, and a short cytoplasmic tail. Its expression is upregulated in proliferating endothelial cells, especially in tumor vessels, inflamed tissues, and during embryogenesis. Mutations in the CD105 gene are associated with hereditary hemorrhagic telangiectasia (HHT), a disorder characterized by abnormal blood vessel formation. Due to its involvement in angiogenesis, CD105 has emerged as a potential therapeutic target for cancer treatment.