Blockade of CTLA-4 in vivo with mAb led to enhanced regression of C1498/B7-1 myeloid leukemia.

C57BL/6 mice were injected intraperitoneally with PBS (A) or anti–CTLA-4 mAb (B, C) before subcutaneous injections of 1 × 10⁶ tumor cells (C1498/B7-1 in A and B and C1498 in C). Tumor growth was monitored over time, and mice that did not die directly because of tumor growth were killed when the tumor mass became greater than 250 mm². Each circle represents an individual mouse. Black bars represent median tumor size at each time point. *Mice that died and were censored from the data. As a group, the anti–CTLA-4 mAb-treated mice (B) had significantly smaller tumors than mice in the control groups (A, C) at every time point (P ≤ .05, Kruskal-Wallis analysis of variance). Tumor growth plots represent the combined results of 2 separate experiments.