Epigenetic profiling of tumor infiltrating lymphocytes

Blocking T cell inhibitory signals, or “checkpoint blockade”, has provided unprecedented clinical results for therapy of cancer (1). Antibodies that block negative interactions between programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) allow activation of T cells that recognize tumor antigens and promote immune destruction of the tumor. To determine the activities of T cells of tumor infiltrating lymphocytes (TILs), and to determine which patients will most effectively respond to checkpoint blockade therapies, Schietinger and colleagues developed a novel inducible autochthonous tumor in AST × CreER T2 mice. In this system, they successfully analyzed TIL activity and chromatin remodeling during tumor development (2,3).