NSC-741909-induced MKP1 and MKP7 clustering, and ROS production in sensitive cell lines. (A, B), Clustering of MKP1 (A) and MKP7 (B). H460 cells were treated with 1 μM NSC-741909 for the indicated time periods. MKP1 and MKP7 were detected by immunohistochemical staining. (C) and (D) ROS induction in H460 and H157 cells after treatment with 1 μM NSC-741909 for the indicated time periods (C), or with different concentrations of NSC-741909 (0.01 - 1 μM) for 6 h (D). Cells were stained with 2', 7'-dichlorofluorescein diacetate and the fluorescent cell population was counted by flow cytometry. Cells treated with solvent alone (dimethylsulfoxide, DMSO) were used as controls, and their mean fluorescence intensity was set at 1. Each data point represents the mean ± SD of three independent experiments. *p < 0.05, **p < 0.01, compared with cells treated with DMSO alone.