Radiosensitizing effects of melatonin on radiation induced chromosomal aberration in G2-lymphocytes of breast cancer patients

Background: radiotherapy is regarded as a standard treatment modality inbreast cancer (bc). radiation causes cellular damage both in cancer andnormal cells by inducing dna-damage and chromosomal aberrations (ca).different agents were used for ameliorating effects of radiation, mainlyantioxidants such as melatonin. melatonin shows oncostatic properties onhuman bc. the aim of this study was to evaluate the modulating effect ofmelatonin on radiation induced ca in cells irradiated at g2 phase of the cellcycle. materials and methods: g2 assay was applied on whole peripheralblood lymphocytes received from 10 bc patients and 5 normal controls. bloodculture was initiated in complete culture medium. four h prior to harvesting,cells were irradiated with 1gy gamma rays. pretreatment of samples withmelatonin was done 3 h before irradiation. after metaphase preparation andslide making, slides were stained in giemsa. hundred well spread metaphaseswere scored for the presence of chromatid type aberrations with amicroscope at a magnification of × 1000. result: results indicated a high andsignificant frequency of ca both in lymphocytes of normal and breast cancerpatient after irradiation; however, the frequency was much more inlymphocytes from bc patients. pretreatment of samples with melatonin ledto a considerable increase in the frequency of aberrations especially inlymphocytes of bc patient. conclusion: results showed that despite havingantioxidant property, melatonin led to enhanced frequency of radiationinduced ca in lymphocytes of bc patients.