Colon cancer cell death induced by bortezomib. Sub-confluent HCT116 and HCT116p53-/- cells were treated with and without bortezomib at different concentrations as shown for 24 hours. Cells were then collected and stained with PI, followed by flow cytometry analysis of DNA content profiles. A. The flow cytometry resultant data in histogram showed the striking difference in DNA content profiles between HCT116 cells and HCT116p53-/- cells. B. Histogram to compare the different percentage of cells in sub-G1 (dead cells) between HCT116 cells and HCT116p53-/- cells. The histogram in B is the mean ± SD derived from two independent determinations.