Figure 2: AP sites increased in NSCLC cells after treatment with pemetrexed (Alimta®) in a dose-dependent manner. By using ARP assay, the formation of AP sites in NSCLC cells was measured. Cells were treated with pemetrexed (200 µM, 400 µM), pemetrexed (200 µM, 400 µM) plus MX (6 mM), pemetrexed (200 µM, 400 µM) plus FEX (6 mM) for 24 h. Co-treatment by pemetrexed with MX or FEX reduced the amount of AP sites detected by ARP-essays under the same conditions, suggesting that FEX, just as MX, competed with ARP in binding to AP sites induced by pemetrexed.