Figure 6: Schematic representation summarizing the proposed role of melatonin in cancer stem cells. Our hypothesis
ascribes an anti-tumor effect for melatonin only in differentiated cancer cells with an active oxidative metabolism, triggering a type of
mitochondrial-mediated cell death which is likely to be characterized by an arrest at S-phase, reduction of the mitochondrial electron
transport chain (ETC), generation of reactive oxygen species, BCL-2 down-regulation and AIF release. Thus, the treatment with melatonin
and the stimulation of mitochondrial metabolism constitute promising strategies against resistant cancer stem cells.