TNFRSF9 and neoplasm: Pioneering work from Byoung Kwon, who discovered 4-1BB (1, 2); Lieping Chen, Robert Mittler, and Ignacio Melero with the first stimulatory antibodies to 4-1BB (3); and the latter together with Tania Watts with over-expression of 4-1BBL (4, 5), established the concept that agonist targeting of 4-1BB can promote responses of T cells and NK cells that are favorable for protecting against tumor growth.