Abstract: Objective To investigate the effects of leflunomide(A77 1726) on the proliferation and apoptosis of human keratinocytes. Methods Proliferating cell nuclear antigen (PCNA) of HaCaT cells was analyzed with crystal violet staining and immunohistochemistry. The moiphological change was assessed with hematoxylin and eosin staining. The changes of cell cycle and apoptosis rate were measured by flow cytometry. Result Epidermal proliferation was inhibited by leflunomide, at concentration 5 μmol/L or more, which was begun after 24 hrs and manifested by PCNA positive cell decreasing. With the increasing of time or dosage, the anti-proliferation effect of leflunomide was significant. Meanwhile, the PCNA positive cell decreased respectively. There was no PCNA positive cell while the drug concentration achieved 200 μmol/L. Therefore, leflunomide significantly inhibited the proliferation of HaCaT cells in a dose-dependent and time-dependent manner. The morphological change and cell cycle change was found but no change of apoptosis rate was measured. Conclusion Leflunmide can inhibit the proliferation of HaCaT cell, without the effect on its apoptosis.

Key words: Keratinocytes, Leflunomide, Apotosis, Proliferating cell nucler antigen