Effects of the CID755673 analogs on cell proliferation in PC3 cells. A, The analogs caused potent arrest in cell proliferation. PC3 cells were plated in triplicate in 24-well plates. Cells were allowed to attach overnight. A cell count at day 1 was made, and then either vehicle (DMSO) or the indicated compound at 10 μM concentration was added. Cells were counted daily for a total of 6 days. Media and inhibitor were refreshed every 2 days. The mean cell number ± S.E. was plotted over time. The experiment was repeated twice and a representative graph is shown. Statistical significance versus Day 1 cell count was determined by unpaired t-test and is indicated. *, p < 0.05; **, p < 0.01; ***, p < 0.001. B, The analogs caused G2/M phase cell cycle arrest. PC3 cells were treated with either vehicle (DMSO), or 10 μM concentration of indicated compound for 48 hours. Cell cycle distribution was determined by flow cytometry after propidium iodide labeling of fixed cells. The experiment was repeated three times and a representative is shown for each compound.