Abstract: ObjectiveTo examine the influence of low level,long-term arsenite exposure on cell cycle,cyclin D1 and p21 of human keratinocyte(HaCat)cells. MethodsHaCat cells were exposed to arsenic(0,0.05,0.1 μmol/L)for 15 weeks;then 10 000 cells were measured to detect cell cycle and protein expression levels of cyclin D1 and p21 were detected by western blot assay. ResultsCompared with those of the control,the number of cells in G₀/G₁ phase increased significantly,while the number of cells in S phase decreased markedly.The protein expression levels of cyclin D1 of 0.05 and 0.1 μmol/L group were 152.40±8.17% and 145.59±2.89%,respectively,which were significantly higher than that of the control(99.99±1.13%);the protein expression levels of p21 of 0.05 and 0.1 μmol/L groups were 64.06±1.62% and 39.57±1.82%,respectively,which were markedly lower than that of the control with dose-effect relationship(P<0.05). ConclusionLow level,long-term arsenite exposure could induce aberrant cell cycle and increased expression of cyclin D1 protein but decreased expression of p21 protein in HaCat cells.