Several studies had demonstrated that depletion of mtDNA induces prostate colorectal and osteosarcoma cancer progression.[19–21] Similarly, we found that mtDNA content was remarkably reduced after NDUFB9 knockdown in MDA-MB-231 cells; and was accompanied by more traits that are associated with tumor progression, compared to the control cells (Fig 4C). The gene discussed is NDUFB9; the disease is neoplasm.