Induction of apoptosis in colon cancer cells by GPR109A ligands. A, The normal colon cell line CCD841 was transfected with vector or human GPR109A cDNA, and then treated with or without nicotinate (1 mM) or butyrate (1 mM) for 48h. Cells were then used for analysis of apoptosis by FACS. B, The colon cancer cell line KM12L4 was transfected with vector or human GPR109A cDNA, and then treated with or without nicotinate (1 mM) or butyrate (1 mM) for 48h. Cells were then used for analysis of apoptosis by FACS. C, The cell lysates from the experiments described in A and B were used to monitor caspase activation by Western blot using antibodies specific for cleaved fragments of caspases.