STI571 and methotrexate.

Isobolograms of simultaneous exposure to STI571 and methotrexate (MTX) in (A) KU812, (B) K-562, (C) TCC-S, and (D) TCC-Y cells. Data are presented as mean values of at least 3 independent experiments. In K562, and TCC-S cells, the SEMs were less than 20% and were omitted. In KU812 and TCC-Y cells, the SEMs were not less than 50%. In KU812, TCC-S, and TCC-Y cells, all or most data points fell in the areas of subadditivity and protection. The observed data were significantly larger than the predicted maximum values (P < .01, .02, and .02, respectively), suggesting antagonistic effects. The observed data were not significantly larger than the predicted maximum values in the K562 cells (P > .05), suggesting additive to antagonistic effects.