  HCT-116 (A) and HT-29 (B) cells were exposed to 5mM 3-MA or 5μM chloroquine (CQ) for 30 min and then treated with 2mM sodium butyrate (NaB) for 24 h. The percentage of apoptotic cells (annexinV+/PI-) was quantified by flow cytometry using an annexinV/PI assay and expressed as mean ± SD of three independent experiments. One-way ANOVA was used for statistical analysis to compare control cells and NaB treatments. *p<0.05, ** p<0.01 compared to control. (C.D.) Cells were treated as described above and the proteins were harvested for Western blot analysis. Expression of full-length and cleaved PARP in HCT-116 (C) or HT-29 (D) cells was compared to GAPDH, the loading control. The ratio of cleaved PARP to total PARP was calculated and the fold change in normalized PARP expression relative to cells treated with 2mM NaB is shown as the mean ± SD of three independent experiments. One-way ANOVA was used for statistical analysis. *P<0.05, ** p<0.01, compared to the 2mM NaB group.  