Background: Serotonin is an important mediator of variety of physiological processess including fibrogenesis,steatosis,cell proliferation. It functions as a neurotransmitter and vasoconstrictor. In this study we explained the influence of physical exercise which induces serotonin in modulating liver cancer and its functions as a neurotransmitter that inhibits the growth of tumors in a concentration dependent. Hence they are less likely to develop liver cancer through an intrinsic apoptotic signaling pathway through three genes ( Bcl-xl, Bcl-2, p53).