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Objective:To evaluate the effects of curcumin on regulating the proliferation

cell cycle distribution

apoptosis and relevant mechanisms in keratinocyte cell lines.Methods:The human immortalized human keratinocyte lines（HaCaT cells） were treated with different doses of curcumin.The effects of curcumin on cell viability were measured by MTT assay

and the cell cycle distribution and apoptosis determined by flow cytometry.The mRNA expression changes of proliferating cell nuclear antigen（PCNA）

cyclin D1 and Bcl-x

L

were from real-time PCR analysis and the protein levels were detected by Western blotting.Results:Data obtained in the study showed that curcumin could cause significantly inhibitory effect on proliferation in HaCaT cells in a time- and dose-dependent manner.Cell arrest at G

1

/S phase and significant apoptosis were observed after being treated with curcumin for 24 h.In association with these

the expression of PCNA

cyclin D1 and Bcl-x

L

were decreased both at mRNA and protein levels for the same treatment.Conclusion:Curcumin can inhibit proliferation

induce cell arrest at G

1

/S phase and cause apoptosis in HaCaT cells.The decreased expression of PCNA

cyclin D1 and Bcl-x

L

induced by curcumin contributes to the above effects in vitro.