Also consistent with a previous report,26 we failed to increase the mtDNA copy number through the overexpression of TFAM in vitro (Supplementary Figure S7), and it has been speculated that overexpression of TFAM inhibits normal mtDNA replication, which offsets its effect on increasing mtDNA copy number.26 In this study, we found that decreasing the mtDNA copy number by shRNA-TFAM transfection made the tumor cells more sensitive to chemotherapeutics (Figure 2, Supplementary Figure S2). The gene discussed is TFAM; the disease is neoplasm.