(A) MKP-1, MKP-5, and MKP-3 mRNA levels were measured in U87MG dead kinase (DK) EGFRvIII cells expressing control shRNA or SPRY2-targeting shRNA (shRNA #1). (B) Whole cell lysates from U87MG DK or high (H) EGFRvIII cells expressing a control, MKP-1-targeting, or MKP-5-targeting shRNA were probed by western blot using antibodies against the indicated proteins, and blots were analyzed by densitometry. (C) The indicated cell lines were treated with DMSO or 10 µM gefitinib + 5 µM PHA665752 (G+P) for 48 hrs prior to flow cytometry analysis for ToPro3 permeability. Throughout the panels, data are represented as the average of three independent experiments ± s.e.m. Asterisks indicate p < 0.05, and “NS” indicates lack of statistical significance.