Figure 3. Inhibition of PLK1 activity with DMTC prevents the proliferation of human pancreatic cancer cells. (A) EPP85 cells were treated with varying concentrations of DMTC for 72 h, and the percentage of cell proliferation was measured by SRB-based in vitro cell proliferation assay. The drug concentration needed for 50% inhibition of cell proliferation (IC₅₀) is shown at the upper side. (B) Phase contrast images of EPP85 cells treated with 20 nM DMTC or equal volume of the DMSO control for 0, 24, 48 or 72 h. (C) EPP85 cells were treated for 72 h with 20 nM DMTC, 50 nM DMTC or DMSO as the control. After 2 weeks of culture, the colonies were shown with crystal violet staining. (D) Experiments were performed as in (C), and the number of colonies in each well was then quantified. Values, averages of three independent experiments; bars, SD; **p < 0.01.