Aim: To investigate whether prostaglandin E2 (PGE2) can increase endogenous Nurr1 expression in a dopamine-synthesizing cell line (MN9D) with immature characteristics and to study whether tyrosine hydroxylase (TH) expression is up-regulated in response to Nurr1-overexpression, in order to investigate the role of Nurr1 during dopaninergic neurons development. Methods: MN9D cells were treated with 100 μg · L -1 PGE2 for 2 h to 6 h. The morphology changes of MN9D cells were observed under phase-contrast microscope. The expression of Nurrl and TH in MN9D cells was analyzed by using immunohistochemieal staining and Western blot analysis. Results: 1 The morphology of MN9D cells did not change significantly following PGE, treatment for 2 h, 4 h and 6h compared with that of MN9D cells left untreated. 2 Nurr1-positive staining in MN9D cells treated with PGE2 for 2 h, 4 h and 6 h was much stronger than that of untreated cells while the percent of TH-positive MN9D cells after PGE2 treatment for 2 h, 4 h and 6 h was similar to that of untreated. 3 The expression of Nurr1 protein in MN9D cells treatment with PGE2 for 6 h was significantly higher than that of untreated (P < 0.05), while the expression of TH protein in MN9D cells did not change significantly following NurrI up-regulation induced by PGE2. Conclusion: PGE2 up-regulates Nurr1 protein expression in MN9D cells within short time (2-6 h) but TH expression doesn't elevate significantly. Up-regulation of Nurrl expression alone may be insufficient for activating TH expression in MN9D cells, but rather requires specific cellular (or neuronal) environments or cofactors.