TNFRSF9 and neoplasm: In line with previous reports in which the therapeutic activity of TA99 against established B16 tumors was enhanced with antibody-cytokine fusion (TA99-TNF) [28], we showed that agonist antibodies to 4-1BB, a member of the TNFR family expressed on activated T and NK cells, synergized the anti-tumor effects of TA99.