PARP1 and osteosarcoma: CH-5, a synthetic structural analog of curcumin 4,4'-[(2-Oxo-1,3-cyclohexanediylidene)-di(E)methylylidene] dibenzonitrile, is more potent than curcumin in decreasing cell viability in human osteosarcoma U2OS, MG-63, and Saos-2 cells, and induces apoptosis through increases in caspase 3/7, cleaved PARP-1, and the p53/Sp1 axis in U2OS cells 160.