Figure 1. Co-administration of gefitinib (GF) and cisplatin (DDP) result in an antagonistic effect.

Cells were treated with the indicated concentrations of gefitinib and cisplatin for 24 hours, and the inhibitory ratio of combination groups for PC9 cells (A) was measured by CCK-8. CDI values were measured in PC9 cells (B) and A549 cells (C). CDI < 0.95, CDI > 1.05 and between 0.95 and 1.05 represent synergism, antagonism and additive effects, respectively. Data are presented as the mean ± SD of at least three independent experiments.