ATM and nasopharyngeal carcinoma: In addition, the expression of drug resistance-related genes, including ATP binding cassette transporter-2 (ABCA2) and ABCA5, was also detected (Fig. 3C), and consequently, inhibition of E2F-1 reduced the expression of ABCA2 and ABCA5 in DDP-resistant NPC cells, while ATM overexpression showed the opposite changes, which could be further reversed by downregulation of E2F-1 (all P < 0.05).