Interferon-α enhances sensitivity of human osteosarcoma U2OS cells to doxorubicin by p53-dependent apoptosis

Aim: To determine whether interferon-alpha (IFN alpha) can enhance doxorubicin sensitivity in osteosarcoma cells and its molecular mechanism. Methods: Cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was studied using Flow cytometry analysis, Hoechst33258 staining, DNA fragmentation assay, as well as the activation of caspase-3 and poly (ADP-ribose) polymerase. Protein expression was detected by Western blotting. The dependence of p53 was determined using p53-siRNA transfection. Results: IFN alpha increased doxorubicin-induced cytotoxicity to a much greater degree through apoptosis in human osteosarcoma p53-wild U2OS cells, but not p53-mutant MG63 cells. IFN alpha markedly upregulated p53, Bax, Mdm2, and p21, downregulated Bcl-2, and activated caspase-3 and PARP cleavage in response to doxorubicin in U2OS cells. Moreover, the siRNA-mediated silencing of p53 significantly reduced the IFN alpha/doxorubicin combination-induced cytotoxic-ity and PARP cleavage. Conclusion: IFN alpha enhances the sensitivity of human osteosarcoma U2OS cells to doxorubicin by p53-dependent apoptosis. The proper combination with IFN alpha and conventional chemotherapeutic agents may be a rational strategy for improving the treatment of osteosarcoma with functional p53.