A polysaccharide from pomegranate peels induces the apoptosis of human osteosarcoma cells via the mitochondrial apoptotic pathway. 
Pomegranate (Punica granatum L.) peels, as one of the most valuable by-products of the food industry, has attracted much attention due to its wide range of bioactivities.  In this study, the potential anticancer effect of a polysaccharide from pomegranate peels (PPP) on human osteosarcoma cancer cells was investigated.  PPP was found to induce the arrest of G2/M phase, induce apoptosis, and inhibit the growth of U-2 osteosarcoma (OS) cells in a dose-dependent manner.  Moreover, Western blotting analysis showed that PPP triggered the mitochondrial apoptotic pathway, as indicated by an increase in Bax/Bcl-2 ratios, a loss of mitochondrial membrane potential, release of cytochrome c, activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase (PARP) in U-2 OS cells.  Our results indicate that PPP inhibits the proliferation of human osteosarcoma cancer cells by inducing apoptosis through the intrinsic mitochondrial pathway.