MT-CO1 and osteosarcoma: In order to substantiate our observations, two cell lines with genetic alteration of COX, the human osteosarcoma cybrid cell line 143BΔCOX (mtDNA mutation leading to inactivation of subunit 1 of COX, COXI)12 and the murine fibroblasts COX10−/− (conditional inactivation of nDNA-encoded subunit 10 of COX, COX10)13 were employed to examine the role of COX dysfunction in susceptibility toward oxidative stress (Figure 1c).