PTGER4 and neoplasm: In breast cancer patients, expression of the EP4 receptor correlated with enhanced lymphatic invasion (Pan et al., 2008), and the EP4 antagonists, AH23848 and ONO AE3-208, attenuated lung metastasis of these tumor cells in mice, while ONO-AE2-227 prevented their osteolytic activity in vitro (Ohshiba et al., 2003; Ma et al., 2006).