CD137 expression in tumor vessel walls - High correlation with malignant tumors

CD137 (ILA4-1BB), a member of the tumor necrosis factor receptor family, an d its ligand are expressed on activated T lymphocytes and on antigen-presen ting cells, respectively. Via bidirectional signal transduction, this recep tor-ligand system regulates the activation, proliferation, and survival of T and B lymphocytes and monocytes. We used immunohistochemical studies on h uman tissue samples to determine in vivo CD137 expression in nonimmune tiss ue samples. Strong CD137 expression was found in blood vessel walls, on the endothelial layer; and on the vascular smooth muscle cells. But in 32 heal thy tissue samples examined, none contained CD137-positive vessels. Also, i n benign tumors (2/14) and in inflammatory tissues (2/9) only a minority ha d CD137-expressing vessels. However malignant tumors had a significantly en hanced frequency of CD137-expressing blood vessels (11/34).