Radiosensitivity and Repair Kinetics of Gamma Irradiated Leukocytes from Healthy Individuals and Prostate Cancer Patients as Measured by the Alkaline Comet Assay
Trauma Monthly: 10 (3); 153-165 Article Type: Research Article
F. Radiosensitivity and Repair Kinetics of Gamma Irradiated Leukocytes from Healthy Individuals and Prostate Cancer Patients as Measured by the Alkaline Comet Assay,
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Objective: In this study the radiation sensitivity and repair kinetics in peripheral leukocytes obtained from prostate cancer patients and healthy volunteers, were compared using the alkaline comet assay (single-cell alkaline gel electrophoresis). Materials and Methods: Blood samples obtained from 30 prostate cancer patients and 32 healthy volunteers were assayed in vitro without radiation and immediately after exposure with 1 Gy gamma rays from a 60Co source at a dose rate of 277.48 ± 11.51 cGy/min. To study the repair kinetics of radiation induced DNA damages, blood samples from 5 prostate cancer patients and 5 healthy volunteers were irradiated with 4 Gy gamma rays and assayed immediately after various time intervals, with alkaline version of the comet assay. The comets were analyzed by visual classification and the level of DNA damage was measured in controls and prostate cancer patients using standard comet classification. Results: The levels of baseline DNA damage were 1.4-fold higher in prostate cancer cases than in controls. The radio-induced damage showed that the two groups had a similar response when analyzed immediately after irradiation. But in repair experiments, while the healthy donors presented a considerable reduction of damage after 3 h, the patients had a higher residual damage even 24 h after exposure. The repair capacity of blood leukocytes from the patients was slower than that of leukocytes from healthy donors. Conclusion: Results indicate that leukocytes from the prostate cancer patients presented an initial radio sensitivity similar to that of healthy subjects but a deficient repair mechanism in cancer patients caused higher baseline DNA damage and also presence of unrepaired DNA damages after 24 hours. Thus prostate cancer patients may be more vulnerable to the genotoxic effects of ionizing radiation due to deficiency in DNA damage repair mechanisms .
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