TNFRSF9 and neoplasm: Other important co-receptors are OX40, 4-1BB, ICOS, GITR, and CD27, which are usually expressed upon T-cell activation to regulate different aspects of T cells, including proliferation, the effector functions, generation of T-cell memory, induction of specific T-cell lineages, and importantly, similar to CD28, can also impact anti-tumor responses [80].