CASP9 and osteosarcoma: Low concentrations of the AMP MSP-4 were shown to induce the apoptosis of osteosarcoma MG63 cells through Fas/FasL- and a mitochondria-mediated pathway, which could be reversed by caspase-8 and caspase-9 inhibitors, suggesting that MSP-4 can be a potentially alternative drug for the treatment of human osteosarcoma [28].