Biological effects of melatonin on telomere length in breast cancer: a review article

There has been increasing interest in studying the effects of dietary factors on telomere length. The telomere is a noncoding DNA sequence including "TTAGGG" at the ends of chromosomes of vertebrates. The stability of telomere length is an important factor as a survival signal for cells and cancer prevention. Telomerase is a multi-subunit DNA polymerase that plays a crucial role in maintaining the telomere length, which is critical for the age-related pathogenesis of breast neoplasm. Some regulatory factors interfere with telomerase activity and therefore promote breast tumorigenesis. High telomerase activity and restoring telomere lengths are determined as key factors in progressing tumors to advanced stages of malignancies, which are highly estrogen-dependent in breast carcinogenesis. Melatonin is a hormone-like substance secreted by the pineal gland and has been reported to downregulate telomerase. It may therefore control telomere length in cancer cells. Certain malignancy-related biological pathways have recently been linked to telomere length, and this review provides new insights regarding the effects of melatonin on telomere length by reviewing the anticarcinogenic mechanisms underlying melatonin in relation to telomerase activity in breast carcinogenesis. Experimental insights presenting the effects of melatonin alone or in combination with drugs on enhancing therapeutic protocols were also reviewed, which could assist our understanding of this hormone-like substance and telomeres as prognostic and therapeutic biomarkers in breast cancer.