Effect of hirudin treatment on growth of tumors in syngeneic mice. B16F10 cells (1 × 10⁶) or 4T1 cells (1 × 10⁵) were injected subcutaneously into C57BL/6 or BALB/C mice, respectively, in similar experiments as in Figure 1. (A) Hirudin (10 mg/kgm) was given 5 minutes before B16F10 implantation, as well as 5 consecutive days afterward (n = 4) or (B) 5 days followed by every other day for 10 days (n = 4). (C) Hirudin (10 mg/kg) was given 5 minutes before 4T1 implantation followed by 10 days or (D) 10 days followed by every other day for 10 treatments (n = 5). Bars indicate SEM.