Figure 4

TRAIL inhibited P-gp expression and DNA-PKcs/Akt/GSK-3β signaling pathway and up-regulation of death receptors and down-regulation of c-FLIP in MDR cells. (A) Cell lysates obtained from CEM or CEM/VLB₁₀₀ cells treated with indicated dose of TRAIL for 24 h were subjected to western blot analysis to monitor levels of P-glycoprotein (P-gp), DNA-PKcs, pAkt (Ser473), tAkt, pGSK3β (Ser 9), GSK-3α and -3β, Mcl-1. (B) CEM/VLB₁₀₀ cells treated with TRAIL (10 ng/ml) for 24 h were incubated on ice in the presence of DR4- and DR5-specific antibodies (1:500), and subsequently labeled with FITC-conjugated secondary antibody (1:1000). The fluorescence intensity was analyzed with flow cytometry. The thin line indicates that the cells only incubated with Goat IgG2a that was used as a control isotype antibody; the thick line indicates the specific labeling (left). The cells treated with or without TRAIL, and changed mRNA level of c-FLIP_L/S was determined by RT-PCR analysis (right).