Figure 4. Modulation of cell signaling pathways controls etoposide and sildenafil lethality. (A) DAOY cells were treated with drugs for 24 h before isolation, SDS PAGE, and determination of the phosphorylation and total expression of the indicated proteins. (B and C) DAOY cells were transfected with empty vector plasmid (CMV) or plasmids to express: an activated form of mTOR (ca-mTOR), an activated form of p70S6K (ca-p70), an activated form of MEK1 (caMEK1), and an activated form of AKT (caAKT). Thirty-six hours after transfection cells were treated with drugs and viability determined by trypan blue exclusion (n = 3, ± SEM) ^#P < 0.05 less than corresponding value in CMV control. (D) DAOY cells were treated with vehicle or the JNK inhibitory peptide (JNK-IP, 10 μM). Thirty minutes later cells were treated with drugs and viability determined by trypan blue exclusion (n = 3, ± SEM) ^#P < 0.05 less than corresponding value in vehicle control.