Fig. 4. Polyamine inhibition promotes multiple different therapies for GBM.

(A) Mice were implanted with 7.5 × 10⁴ CT-2A, pretreated with DFMO, and analyzed for PD-L1 MFI expression. (B) TAMCs were generated in vitro in the context of DFMO or DFMO + putrescine, and PD-L1 expression was analyzed after 7 days of differentiation. (C) The same DFMO schema was used in combination with anti–PD-L1 treatment (or treated with monoclonal antibody alone), and animal survival was measured. (D) Seven days after tumor implantation, mice were treated with anti–PD-1 (every 3 days, 10 mg/kg) or combination therapy, and survival was analyzed. (E) Seven days after tumor implantation, mice were treated with DFMO, 3 × 3-Gy irradiation (IR), or combination. (F and G) GL-261 (2 × 10⁵) overexpressing OVA were implanted intracranially into mice that were then treated with PD-L1, DFMO, or combinatorial treatment. Brains were harvested and stained for tetramer positivity. (A and B) Data are n = 3 per group representative of two independent experiments. Survival curves were performed n = 8 (C) and n = 10 (D and E) mice per group. Five male and five female mice per group were analyzed in (D) and (E); n = 4 per gender in (C), all age-matched at 6 to 8 weeks of age. (F and G) n = 5 per group were analyzed. Significance in (C) to (E) was calculated using log-rank analysis followed by Bonferroni correction. Significance in (A) and (B) and (F) and (G) was calculated by one-way analysis of variance (ANOVA), followed with a Tukey’s post hoc test: *P < 0.05, **P < 0.01, and ***P < 0.001.