Seyed Mohammad Amin Kormi - Department of Biology, Faculty of Sciences, University of Zabol, Zabol, Iran
Gholamreza Motalleb - Institution of Biotechnology, University of Zabol, Zabol, Iran
Mohammad Amin Kerachian - Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences (MUMS), Mashhad, Iran

With the modernity of the world today and disruption and changing of lifestyle of people andthe incidence of a phenomenon named insomnia, enough grounds has been provided fordevelopment of many common diseases like cancer; hence, one of the most controversialand newest discussions in cancer genetics is the issue of circadian rhythm and molecularclock and their influence on the cancer risk. While the modern lifestyle has affected ourcircadian habits, many of the molecular and metabolic processes are also influenced by itand it plays a significant role in the ground of cancer risk. When the immune system of thebody fails to effectively defend the body against the possible tumors, then cancer occurs.Changes in the levels of melatonin leads to some defects in the immune system. Also, theeffect of melatonin on the estrogen signaling pathways leads to the induction effects oftumorogenesis. Undoubtedly, changes in the melatonin levels and changes in the heart rateare the first significant changes of the circadian rhythm. Moreover, a decrease in melatonin isconsidered as one of the risk factors for development of the breast cancer in women. Manygenes related to the circadian, regulating of the rhythms of the biological clock of our body,play an important role in many molecular mechanisms in cancer, including apoptosis and cellcycle check-point. In this review article, we have tried to discuss the relationship between themolecular clock and the biological clock and cancer risk, especially breast cancer in womenby mentioning the molecular cause of time incidents in the human body, and, moreover,having recommendation to set up circadian habits as an important factor in preventing cancerdevelopment.

Biological Clock, Molecolar Clock, Cancer, Circadian, Immune System