STI571 abrogates FL-mediated antitumor effects. Twice the minimal tumorigenic dose of RMA-S (A) or MCA102 (B) cells was inoculated into the abdominal flank of C57BL/6 mice at day 0. From day –4 to day +5, FL (10 μg/mouse) or phosphate-buffered saline (PBS) only (200 μL) was injected intraperitoneally. From day +1 to day +5, STI571 (150 mg/kg per gavage) or H₂0 (200 μL) was administered twice a day by oral feeding. Tumor size was monitored with a caliper twice a week, and the product of largest perpendicular diameters is reported for individual time points as mean ± SEM. *Significantly lower than PBS plus H₂0, PBS plus STI571, and FL plus STI571; P < .05. Each experiment was performed 3 times with similar results and involved 5 to 7 animals per group. A representative experiment is depicted.