Anti-mitochondrial therapy in human breast cancer multi-cellular spheroids

► Proliferative and quiescent breast cancer micro-regions depend on mitochondrial ATP. ► Anti-mitochondrial therapy at nanomolar doses arrests breast tumor spheroid growth. ► Glycolysis and chemotherapy inhibitors do not affect breast tumor spheroid growth. ► Anti-mitochondrial therapy does not modify energy metabolism of normal breast spheroids. ► Anti-mitochondrial drugs prevent, and revert, breast tumor spheroid growth.