STI571 and hydroxyurea.

Isobolograms of simultaneous exposure to STI571 and hydroxyurea (HU) 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; the SEMs were less than 25% and were omitted. In all 4 cell lines, all or most data points fell within the area of the envelope of additivity, suggesting additive effects.