TNFRSF9 and neoplasm: Beneficial therapeutic effects have been demonstrated in mice with established tumors [14,15] by engaging CD137 (a.k.a. 4-1BB), using agonist antibodies, dimeric RNA aptamers or tumor cells expressing a surface-attached anti-CD137 single chain antibody [15,16], and the preclinical data have led to clinical trials with humanized mAbs directed against CD137 [17].