RESUMO
The aim of the present study was to investigate and compare the effects of diferuloylmethane (curcumin) and diphenyldifluoroketone (EF-24) on cell growth and apoptosis induction in human osteogenic sarcoma cells. This was examined by MTT assay, nuclear DAPI staining, caspase-activation assay, flow cytometry analysis and immunoblotting in Saos2 human osteogenic sarcoma cells. Curcumin and EF-24 inhibited the growth of Saos2 cells in a dose-dependent manner. The apparent potency of EF-24 was more than 3-fold higher that of curcumin. Treatment with curcumin or EF-24 resulted in nuclear condensation and fragmentation in the cells. The caspase-3/-7 activities were detected in living cells treated with curcumin or EF-24. Flow cytometry showed that the rate of apoptosis was increased by curcumin and EF-24 compared to the control. Curcumin and EF-24 promoted the proteolytic cleavages of procaspase-3/-7/-8/-9 with increases in the amount of cleaved caspase-3/-7/-8/-9. The curcumin- or EF-24-induced apoptosis in the Saos2 cells was mediated by the expression of Fas and activation of caspase-8, caspase-3 and poly(ADP-ribose) polymerase. Immunoblotting revealed the Bid and Bcl-2 proteins to be downregulated, and truncated-Bid, Bax and p53 proteins to be upregulated by curcumin and EF-24. Curcumin and EF-24 increased the Bax/Bcl-2 ratio significantly. These results suggest that the curcumin and EF-24 inhibit cell proliferation and induce apoptotic cell death in Saos2 human osteogenic sarcoma cells via both the mitochondria-mediated intrinsic pathway and the death receptor-mediated extrinsic pathway, and may have potential properties for anti-osteosarcoma drug discovery.