HMDB inhibited proliferation of HeLa cells via inducing the G1 cell cycle arrest. (a) The chemical structure of HMDB; and (b) the effect of HMDB on cell viability of HeLa cells. Cells were treated with a variety of dosages of HMDB for 0–24 h or (c) with 40 µM HMDB for different time periods. Cell survival was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue exclusion assays, respectively. The protein levels of PCNA were determined by Western blotting; and (d) a histogram of the cell cycle distribution. HeLa cells were treated with 40 μM HMDB for 0, 6, 12, and 24 h. Cell distribution at G1, S and G2/M phase was determined using flow cytometry. All of the data resulted from repeating independent experiments three times and results are expressed as mean ± SE. Values were statistically significant (versus HMDB treatment) for * p < 0.05, ** p < 0.01, *** p < 0.001 as compared with the control group.