Figure 1.

Treatment with plinabulin leads to tumor shrinkage and intratumoral accumulation of M1-like TAMs in vivo. (A) Mice bearing MC38 tumors (50–100 mm³) were left untreated or treated with plinabulin (7 mg/kg) administered peri-tumoral on days 0, 1, 2, 4, 7, 9, 11 post-treatment start (first dose administered 18 days post-MC38 cell innoculation). (B) Tumor volume (left) and percentage of live CD45⁻ cells out of total cells (i.e., tumor cells, right) 7 days post-plinabulin treatment start in plinabulin-treated or control mice. (C) Kaplan-Meier survival to humane endpoint curve of plinabulin-treated vs. control mice (log-rank test p-value is shown). (D) Mice bearing MC38 tumors (50–100 mm³) were left untreated or treated with plinabulin (7.5 mg/kg) administered intra-peritoneal twice a day on days 0, 2, 4, post-treatment start (first dose administered 18 days post-MC38 cell innoculation). Tumors were collected for flow cytometry analyses on day 7 post-treatment start. (E) Percentage of intratumoral CD4⁺ (left) and CD8⁺ (right) T cells out of total live CD45⁺ CD3⁺ cells in plinabulin-treated and untreated MC38 tumors. (F) Percentage of intratumoral Tregs in plinabulin treated and untreated MC38 tumors. (G) Percentage of IFNγ⁺CD4⁺ and IFNγ⁺ CD8⁺ cells after ex vivo anti-CD3 and anti-CD28 mAb re-stimulation of tumor infiltrating immune cells from plinabulin-treated or untreated MC38 tumors. (H) Kaplan-Meier survival curve of plinabulin-treated vs. untreated mice at the experiment endpoint in wild type C57BL/6 (WT) or T- and B-cell deficient C57BL/6 RAG^−/− mice. (I) Frequency of CD11b⁺ CD11c⁺ positive DCs (of all CD45⁺ cells, left) and F4/80⁺ Ly6C⁻ Ly6G⁻ TAMs (of CD11b⁺ population, right) in MC38-tumor bearing mice treated or untreated with plinabulin. (J) M1/M2 ratio (defined as the ratio between CD80⁺ and CD206⁺ TAMs) in plinabulin-treated MC38-tumor bearing mice and in untreated animals. Statistical significance was determined by Kolmogorov-Smirnov t-test (B,E–G,I,J) or log-rank Mantel-Cox test (C,H). ns, not significant; *p < 0.05; **p < 0.01. Error bars show SD. Data are derived from two independent experiments with 4–6 animals in each group. Each symbol represents an animal.