The fate of radiation induced giant-nucleated cells of human skin fibroblasts

Radiation-induced giant-nucleated cells (GCs) have been observed to occur within survivors of irradiated cancerous and within healthy cells, both in vivo and in vitro. The expression of such morphological alterations is associated with genomic instability. This study was designed to investigate the fate of GCs induced in a normal human fibroblast cell line (AG1522) after exposure to 0.2, 1 or 2 Gy of X-ray or proton irradiation. The total of 79 individual AG1522 GCs present at 7, 14 or 21 days after each dose point were analysed from fluorescence microscopy images captured over approximately 120 h. The GCs were identified at the beginning of the observation period for each time point post-irradiation and the area of the cell nucleus was measured (μm2) using a cell-recognition MATLAB code. The results demonstrate that the majority of GCs had undergone a prolonged mitotic arrest, which might be an indication of the survival strategy. The live cell microscopy confirms that a giant-nucleated cell formed 14 days after exposure to 0.2 Gy of proton irradiation was divided into two asymmetrical normal-sized cells. These results suggest that a small fraction of GCs can proliferate and form progeny. Some of GCs had disappeared from the microscopy fields. The rate of their loss was decreased as the dose increased but there remains the potential for them to have progeny that could continue to proliferate, ultimately contributing to development of cancer risk. This important method to access delayed effects in normal tissues could act as a potential radioprotective assay for a dose-limiting parameter when applying radiotherapy. These results might have important implications in evaluating risk estimates for patients during radiation therapy treatment.