(A) HL-60, (B) THP-1 leukemia cells, and (C) monocytes isolated from whole blood taken from anonymous donors were treated with butyrate for 24 hours. Cell viability was determined using trypan blue exclusion assay. n = 6, 5, and 9 respectively. (D) Cells were untreated or treated with 5 or 10 mM butyrate for 24 hours and subjected to colorimetric caspase-3 assay. n = 6, 5, and 5 respectively. (E) HL-60 and (F) THP-1 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).