CD8A and neoplasm: For sustainable anti-tumor response, generation of memory T cells is also important and CD137, CD30 or OX40 stimulation are known to provide survival signals or induce memory on T cells, while a deficiency of CD137 ligand (CD137L) or OX40 ligand (OX40L) results in a decrease of CD8+ memory T cells in bone marrow [25,26,27].