PTGER4 and non-small cell lung carcinoma: A549 NSCLC cells exposed to nicotine showed increased EP4 protein levels in a time- and dose-dependent manner with maximal increases noted at a concentration of 0.5 μM at 24h (Figure 2A, 1.307 ± 0.143 vs 1.009 ± 0.023, P < 0.01; Figure 2B 1.249 ± 0.198 vs 1.002 ± 0.015, P < 0.01).