Effects of different exposure schedules of gefitinib and docetaxel on cell proliferation.

<p>Cells were treated with three different sequences of gefitinib and docetaxel (D→G; G→D; D+G). The drug doses were combined using constant ratios of IC50 values (0.125, 0.25, 0.5, 1, 2 and 4 times of IC50). (<b>A, B</b>) The inhibition rate was determined by MTT assay. *<i>P</i><0.05, D→G versus G→D; #<i>P</i><0.05 D→G versus D+G. The D→G sequence produced the most potent inhibitory effect. (<b>C, D</b>) The combination index (CI) was calculated using CompuSyn software. Only the D→G sequence showed synergistic effect. (D–G) docetaxel followed by gefitinib; (G–D) gefitinib followed by docetaxel; (D+G) docetaxel and gefitinib administered concurrently. <i>Bars</i>: ± SD, n = 3.