g2 chromosomal radiosensitivity and background frequency of sister chromatid exchanges of peripheral blood lymphocytes of breast cancer patients

background: chromosomal alterations play an important role in carcinogenesis. enhanced chromosomal radiosensitivity is shown for many cancer predisposition conditions including breast cancer. in this study chromosomal radiosensitivity and the frequency of background sister chromnatid exchanges (sce) in lymphocytes of normal individuals and breast cancer patients was compared. materials and methods: g2 assay was performed on peripheral blood lymphocytes obtained from 60 breast cancer patients and 50 normal control. blood culture was initiated and cells were irradiated with 1 gy gammarays 4 h prior to harvesting. after metaphase preparations and slide making, chromatid aberrations were scored. for sce studies, blood samples from 30 breast cancer patients and 30 normal control were studied. 24 hours after culture initiation, 5- bromodeoxy uridine (brdu) was added and cells were harvested 48 hours after addition of brdu. slides were stained in hoechst 33258 and exposed to uva source, then stained in giemsa. results: results indicated that the frequency of radiation induced chromatid breaks was significantly higher in breast cancer patients compared to normal control (p<0.01). from radiosensitivity point of view, 12% of normal control and 47% of breast cancer patients showed elevated chromatid radiosensitivity. frequency of background sce was significantly higher in lymphocytes of breast cancer patients compared to lymphocytes of control (p<0.05). conclusion: elevated chromosomal radiosensitivity and higher frequency of sce in lymphocytes of breast cancer patients might be indicative of genomic instability of these cells. increased radiosensitivity could also be due to defects in dna repair genes involved in breast cancer formation. iran. j. radiat. res., 2011 9(3): 167-174