CHANGES OF CYCLIN D1-DEPENDENT REGULATION OF CELL CYCLE IN PERIPHERAL BLOOD LYMPHOCYTES OF CHORNOBYL CLEAN-UP WORKERS AT A REMOTE PERIOD AFTER RADIATION EXPOSURE

Objective. To study proliferative potential of peripheral blood lymphocytes of Chornobyl clean-up workers by level of expression of cyclin D1 and quantitative parameters of cell cycle at a remote period after radiation exposure. Materials and methods. The research subject was the peripheral blood lymphocytes (PB) of Chornobyl clean-up workers 30–33 years after radiation exposure. A total of 207 men were surveyed, 164 of them were clean-up workers exposed in the dose range 10.43–3623.31 mSv and 43 persons of the control group. Analysis of proliferation potential (cell cycle initiation) and cyclin D1 expression in PB lymphocytes were performed in vitro by a micro method of whole blood leukocytes culture with phytohemagglutinine-P (PHA). Sample preparation was performed by a standard immunofluorescent assay for intracellular proteins using the FITC labelled Mouse Anti-Human Cyclin D1 Antibody Set. Cell distribution by cell cycle phases studied by propidium iodide DNA staining and analysis on FACSCalibur laser flow cytometer in histogram mode with separation of G0/G1-, S- and G2/M-regions and Sub-G0/G1- region (apoptotic cells). Results and conclusions. An increase in the level of spontaneous сyclin D1 expression and disturbance of сyclin D1-dependent regulation of cell cycle of PB lymphocytes after mitogen activation were determined in a remote period after radiation exposure. An increase in the level of cyclin D1 expression was accompanied by increase in pool of cells in the S- and G2/M-phases of cell cycle which characterizes the high proliferative potential of PB lymphocytes. Mitogen-induced delay of cell cycle of lymphocytes in G1/S check point and reduction of S-phase was revealed. These changes are a manifestation of genomic instability caused by the effect of radiation and depend on the radiation dose. The results confirm the hypothesis about the significance of levels of cyclin D1 expression, as a criterion for manifestations of genome instability and risks of oncogenesis in a remote period after irradiation. Key words: cell cycle, cell proliferation, cyclin D1, genome instability, radiation exposure, Chornobyl clean-up workers.