(A) U937 cells were treated with butyrate (NaB) or H2O for 24 hours. Cell viability was determined using trypan blue exclusion assay. n = 5. (B) Cells were untreated or treated with butyrate or H2O vehicle for 24 hours. After harvesting, total cell lysates were analyzed for caspase-3 by western blot analysis. (C) Cells were untreated or treated with 5 or 10 mM of butyrate or H2O vehicle for 6, 12, or 24 hours. Cell lysate proteins underwent western blot analysis for caspase-3. Arrows indicate the cleaved caspase-3 fragments at 17 and 19 kDa. (D) U937 cells were untreated or treated with 5 or 10 mM butyrate or H2O for 24 hours. A colorimetric caspase-3 assay was used to analyze caspase activity. n = 7. (E) Cells were treated with butyrate (5 mM) and Annexin V fluorescence was measured by flow cytometry. n = 7. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 when compared to the untreated (0, UT).