Figure 3.

Age attenuates the anti-tumor efficacy of anti-OX40 antibody treatment. CT26 tumor cells were subcutaneously implanted on the flank of female BALB/c mice either at 6-8 weeks old (young) or at 60-72 weeks old (aged). The mice were treated with anti-OX40 antibody IP at 1 mg/kg 4 and 7 days after tumor cell implantation. (A) Kaplan-Meier curves showing time-to-welfare endpoint. 50-52 mice per group. (B) Fold change in the rate of tumor growth for each animal for both young and aged mice after anti-OX40 antibody treatment compared to untreated age-matched mice. 50-52 mice per group. (C) 15 days after implantation, tumors were analyzed by flow cytometry. Comparison of the proportion of Tregs in the tumor of young and aged mice after anti-OX40 antibody treatment compared to untreated mice. 5-8 mice per group. (D) Frequency of CD44^-CD62L^- effector (T_eff), CD44⁺CD62L^- effector memory (T_EM), CD44⁺CD62L⁺ central memory (T_CM) and CD44^-CD62L⁺ naïve cell subsets within the CD4⁺ T cell compartment in the tumor of both young and aged mice after anti-OX40 antibody treatment compared to untreated mice. 5-8 mice per group. (E) 53 days after initial tumor implantation, 11 young mice and 4 aged mice that achieved complete tumor clearance after treatment with anti-OX40 antibody were re-implanted with CT26 tumor cells on the opposite flank and monitored for tumor growth. 3 control young mice (untreated and not previously tumor-bearing) were implanted as controls (naïve). The results in panels A and B include data from 4 experiments, the results in panels (C, D) include data from 1 representative of 2 experiments. ***P < 0.001 and ****P < 0.0001.