Effect of anti-CD137 mAb in the stimulation of Tms to prevent tumor outgrowth in the OT-1 adoptive transfer model. (A) A schematic of the treatment of a melanoma mouse model with Tms and anti-CD137 mAb. In vitro–activated OT-1 TCR-transgenic T cells were transferred into mice for the development of Tms. (B) Effect of anti-CD137 mAb in preventing B16-OVA tumor challenge. One month after transfer of activated OT-1 T cells, mice were treated with anti-CD137 mAb and subsequently challenged with B16-OVA tumor cells subcutaneously. The sizes of tumors were measured individually and recorded as the mean tumor diameter regularly. Results are 1 representative of 4 independent experiments. Each point is the mean ± SD of tumor diameters in a group of 5 mice. (C) Effect of anti-CD137 mAb in the prevention of metastases of B16-OVA tumor. One month after transfer of activated OT-1 T cells, mice were treated with anti-CD137 mAb and subsequently challenged with B16-OVA tumor cells intravenously. The survival of mice was monitored daily up to 100 days. Results are 1 representative of 3 independent experiments. ***Significantly different from control mAb (rat Ig) treatment group, P < .001. (D-E) Effect of anti-CD137 mAb fails to prevent tumor challenge after transfer of naive OT-1 cells. The procedure is the same as in panel A, but naive instead of activated OT-1 T cells were transferred. Tumor growth (D) and survival (E) of the mice were monitored as described in panels B-C. Results are 1 representative of 2 independent experiments.