Butyrate mediates Caco-2 cell apoptosis via up-regulation of pro-apoptoticBAK and inducing caspase-3 mediated cleavage of poly-(ADP-ribose) polymerase (PARP)

Butyrate exerts potent anti-tumor effects by inhibiting cancer cell growth and inducing apoptosis, However, the molecular mechanisms mediating these e ffects remain largely unknown. Using the Caco-2 cell line, a well establish ed model of colon cancer cells, our data show that butyrate induced apoptos is (maximum 79%) is mediated via activation of the caspase-cascade. A key e vent was the proteolytic activation of caspase-3, triggering degradation of poly-(ADP-ribose) polymerase (PARP), Inactivation of caspase-3 with the te trapeptide zDEVD-FMK completely inhibited the apoptotic response to butyrat e, In parallel, butyrate potently upregulated the expression of the pro-apo ptotic protein bak, without changing Caco-2 cell bcl-2 expression. Butyrate -induced Caco-2 cell apoptosis was completely blocked by the addition of cy cloheximide, indicating the necessity of protein synthesis. However, when t his inhibitor was added at a time point where bak expression was already en hanced (12-16 h after butyrate stimulation), it failed to protect Caco-2 ce lls against apoptosis, Taken together, these data provide evidence that the molecular events involved in butyrate induced colon cancer cell apoptosis include the caspase-cascade and the mitochondrial bcl-pathway.