Inhibition of ERK1/2 and CREB phosphorylation by caspase-dependent mechanism enhances apoptosis in a fibrosarcoma cell line treated with butyrate.

We evaluated the role of MAPKs on apoptosis induced by butyrate in cells derived from a human fibrosarcoma (2C4). Culture of 2C4 cells in 5% of fetal bovine serum (FBS) induced ERK1/2 and CREB phosphorylation and delayed apoptosis induced by butyrate. Butyrate inhibited phosphorylation of ERK1/2 and CREB. Furthermore, the use of specific inhibitors PD98059 (MEK) and H89 (PKA), which block ERK1/2 and CREB phosphorylation, accelerated butyrate induced cell death in 2C4 cells. The butyrate effect was shown to be dependent on caspase activation, once caspase inhibitors restored phosphorylation of ERK1/2 and CREB in 2C4 cells. However, the proteolytic effect of caspases was not directly on ERK1/2 and CREB proteins. In conclusion, butyrate induced apoptosis in 2C4 cells is regulated by the levels of ERK1/2 and CREB phosphorylation in a caspase dependent mechanism.