CLOCK and neoplasm: Melatonin, produced in the pineal gland and mitochondria, participates in complicated intracellular signaling pathways with anti-ageing, antioxidant, chemopreventive, immunostimulatory, and tumor-inhibitory functions.248 SIRT1 modulation is associated with the activity of clock machinery and might resynchronize the dysfunctional cellular key clock circuits.249 Moreover, many environmental factors, like light exposure, lifestyle, and societal factors, can modify the circadian clock phase.