Caspase-3 activation and induction of PARP cleavage by cyclic dipeptide cyclo(Phe-Pro) in HT-29 cells

Abstract

Background: Cyclo(Phe-Pro) has been shown to inhibit cancer cell growth and induce apoptosis in HT-29 colon cancer cells.

Materials and methods: The molecular mechanisms mediating cyclo(Phe-Pro)-induced apoptosis in HT-29 cells were investigated. Cells were treated with 5 mM or 10 mM cyclo(Phe-Pro) for varying times. Immunoblot analysis was used to detect poly(ADP-ribose)polymerase (PARP) cleavage. A fluorescence-based enzymatic assay was used to measure caspase-3 activity.

Results: Cyclo(Phe-Pro) (10 mM) induced time-dependent cleavage of PARP, detected as early as 8 hours post treatment. PARP cleavage was blocked by co-administration with the broad-range caspase inhibitor Z-VAD-FMK Cyclo(Phe-Pro) also induced a time-dependent increase (p < 0.01) in caspase-3 activity. This increase in activity was blocked in the presence of the caspase-3 inhibitor Ac-DEVD-CHO.

Conclusion: These results provide evidence that cyclo(Phe-Pro)-induced apoptosis in HT-29 cells is mediated by a caspase cascade. These findings warrant further investigation into the potential antitumour activity of cyclo(Phe-Pro) and its related cyclic dipeptide derivatives.