Figure 1.

Agonistic anti-CD137 mAb exhibits antitumor activity and induces severe liver injury. Three groups of C57BL/six mice (n = 5 per group) were subcutaneously injected with 5 × 10⁵ MC38 tumor cells at day 0, and then treated with 100 µg 2A, RatIg or PBS for four times on days 8, 11, 14 and 18. (A) The tumor volumes in the three groups were monitored over time. Representative data from three independent experiments are shown. **p < 0.01. (B) Tumor and liver sections were stained for CD8⁺ on day 21 after tumor inoculation. (C) Serum ALT levels in RatIg, 2A, and PBS-treated mice are shown. **p < 0.01. (D) The liver sections were further stained for Gr-1 and F4/80 and (E) the numbers of Gr-1⁺ cells and F4/80⁺ cells in the livers per HPF (×200) are shown. **p < 0.01. (F) Consecutive liver sections were stained with H&E and Sirius Red. Scale bar, 50 μm. (G) One group of C57BL/6 mice without tumors was also treated with 2A four times as a control. Serum ALT levels in 2A-treated mice with or without tumors are shown. ns, not significant.