CD137 as a Biomarker for Tumor-Reactive T Cells: Finding Gold in the Desert

Although human cancer is often surrounded by immune cells, only a small number are tumor-reactive T cells that recognize the tumor antigens and are able to eliminate the cancer cells. Ye and colleagues now found that many of these tumor-reactive T cells are marked by expressing CD137, a T-cell costimulatory receptor. (C) 2013 AACR.