Fig. 2

HT-29 cell death and colony formation potential by HDACis ± HY-PDT. a Cell death (PI+) was measured after a sequential treatment starting with the HDACis Saha, Tsa, Vpa, and NaPB (for 24 h) followed by activation with hypericin (for 24 or 48 h, as indicated). b Colony formation ability was measured after a sequential treatment starting with HDACis (for 24 h) followed by activation with hypericin (for 48 h) and subsequent seeding in tissue culture plates (for 10 days). Samples treated with drug-free vehicle solvents (<0.1% DMSO) were used as the reference control. The results are expressed as percentage of control and represent the average ± SD of a four and b three independent experiments each done in singlets. Data was analyzed using one-way ANOVA with Tukey post hoc test. All conditions were compared to the reference control (*p < 0.05, **p < 0.01, ***p < 0.001), and the combined treatments were compared to HY-PDT alone (ǂp < 0.05, ǂǂp < 0.01, ǂǂǂp < 0.001) and to correspondingly equal concentrations of HDACis alone (▲p < 0.05, ▲▲p < 0.01, ▲▲▲p < 0.001)