In addition, qRT–PCR (Fig. 1C, D) and western blotting (Fig. 1E–G) demonstrated that the expression of E2F-1 and ATM in DDP-resistant NPC cells (CNE2/DDP and HNE1/DDP) was much higher than that in these parental cells (all P < 0.05). The gene discussed is E2F1; the disease is nasopharyngeal carcinoma.