Pharmacodynamic changes to DNA damage checkpoint and cell cycle proteins in HT29 colon cancer cells by V158411 in combination with camptothecin. A. HT29 cells were treated with 0 to 400 nM camptothecin (CPT) in the presence of DMSO or 400 nM V158411 for 24 hours. B. HT29 cells were treated with 100 nM camptothecin plus DMSO or 400 nM V158411 for 1 to 24 hours. UT, untreated control. C. HT29 cells were treated with 200 nM camptothecin for 0 to 24 hours followed by 400 nM V158411 (+) or DMSO (−) for a further 24 hours. Protein expression was characterized by immunoblotting.