RESUMO
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.
Assuntos
Caspases/metabolismo , Dipeptídeos/farmacologia , Peptídeos Cíclicos/farmacologia , Poli(ADP-Ribose) Polimerases/metabolismo , Clorometilcetonas de Aminoácidos/farmacologia , Células CACO-2 , Caspase 3 , Inibidores de Caspase , Caspases/biossíntese , Inibidores de Cisteína Proteinase/farmacologia , Dipeptídeos/toxicidade , Ativação Enzimática/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Células HT29 , Humanos , Peptídeos Cíclicos/toxicidadeRESUMO
BACKGROUND: An increasing number of cyclic dipeptides (CDPs), particularly those containing proline, have been shown to exhibit important biological activity. MATERIALS AND METHODS: We investigated the potential of seven proline-based CDPs to inhibit cancer cell growth in HT-29, HeLa and MCF-7 cell lines. We also tested whether any of the CDPs were able to induce apoptosis in HT-29 cells. RESULTS: The SRB assay showed that only cyclo(Phe-Pro) (10 mM) exhibited more than 50% growth inhibition (p<0.01). The MTT assay was used to demonstrate a dose-dependent (0.008-10 mM) growth inhibition by cyclo(Phe-Pro). Hoechst 33342 staining showed that 5 mM cyclo(Phe-Pro) induced chromatin condensation in 18.3+/-2.8% (p<0.01) of HT-29 cells after 72 hours. Furthermore, annexin V binding revealed phosphatidylserine externalisation in cyclo(Phe-Pro)-treated HT-29 cells. CONCLUSION: Our findings demonstrate that cyclo(Phe-Pro) inhibits the growth of HT-29, MCF-7 and HeLa cells and induces apoptosis in HT-29 colon cancer cells, suggesting a potential antitumour activity.
