SIRT1 and osteosarcoma: Consistent with this finding, the in vitro wound-healing assay revealed that primary osteosarcoma cells expressing higher levels of the SIRT1 protein (MDOS-16, MDOS-26, MDOS-14 and MDOS-27) exerted stronger wound-closure capability than those of low SIRT1-expressing cells (MDOS-22, MDOS-19 and MDOS-21) (Figure 4A and 4B).