P287] Investigation of radiation induced mitotic arrest in irradiated cells

Abstract

Purpose Investigation of mitotic arrest in cells irradiated to radiotherapeutic doses. Methods Chinese hamster ovary (CHO) cell line was used as an irradiation object. CHO cells were irradiated to the doses from the range (0–10 Gy) in linear accelerator Varian ClinacDMX using 6 MeV photons. Clonogenic cell assay was used to assess radiation induced effects in irradiated cells. Cell colonies were manually counted using ImageJ software plug-in Colony Counter. Colony residence area was assessed using ImageJ software plug-in Analyze Particles, which enabled analysis of the scanned image of Petri dish with cells detecting separate cell colonies and calculating the average area of colonies within the dish. In parallel COMET assay was used for the assessment of radiation induced DNA damages in cells. Results It was found, that the statistically significant decrease of formed cell colony’s area with the increasing irradiation dose (known as mitotic arrest process in affected cells) was stopped when the dose of 6 Gy was applied, indicating almost the same low level of mitotic activity at higher doses. It was suggested that the irradiated cells may have maximal mitotic arrest time which is irradiation dose independent at the doses ⩾6 Gy, thus indicating the existence of the cell specific dose threshold at which maximal delayed mitosis effect with initiation of ∼30% of DNA damage on surviving cell fraction is present. There was no dose threshold effect observed evaluating cell viability and radiation induced DNA damages. Conclusions Investigation results based hypothesis regarding possible existence of time dependent threshold dose for maximal delayed mitosis effect in irradiated cells was raised and discussed indicating that the application of dose threshold based irradiation model can contribute to the improvement of fractionated radiotherapy treatment efficiency. A need for more detailed investigations for verification of these findings was also indicated.