Fig. 4.

In vivo studies comparing antitumor efficacy of Hf-based NPs. Tumor growth inhibition curves (a) and body weights (b) after RT treatment in the single CT26 tumor-bearing mice treated with PBS, HfO₂ (low and high doses), Hf₆-DBA, or Hf₁₂-DBA. Tumor growth curves of c primary tumors and d distant tumors of CT26 bilateral tumor-bearing mice treated with Hf₆-DBA (with or without anti-PD-L1 antibody), Hf₁₂-DBA (with or without anti-PD-L1 antibody), anti-PD-L1 antibody, or PBS with X-rays irradiation. e Tumor growth curves of CT26 tumor-bearing mice with T cell depletion and treated with Hf₁₂-DBA, anti-PD-L1 antibody, and X-ray irradiation. f Tumor growth curves after the tumor rechallenge with CT26 cells. Treatment began on day 7 after tumor inoculation when the tumor reached a volume of 100–150 mm³. X-ray irradiation was carried out on mice 12 h after the i.t. injection of PBS or NPs on 10 consecutive days at a dose of 1 Gy/fraction (120 kVp, 20 mA, 2 mm Cu filter). Antibody was given intraperitoneally every 3 days at a dose of 75 µg/mouse. Black, red, and green arrows refer to the times of PBS or nanoparticles injections, X-ray irradiation, and antibody administration, respectively. n = 6. P values for comparisons with controls by t test are indicated by three asterisks: ***P < 0.001. Central data points and error bars represent mean ± s.d. values, respectively. The Hf₁₂-DBA with anti-PD-L1 treatment group was repeated once