Monitoring translocations by M-FISH and three-color FISH painting techniques: a study of two radiotherapy patients

Chromosomal damage in occupationally exposed health professionals assessed by two cytogenetic methods

The study assessed occupationally induced chromosomal damage in hospital personnel at risk of exposure to antineoplastic drugs and/or low doses of ionizing radiation by two cytogenetic methods. Cultured peripheral blood lymphocytes of eighty-five hospital workers were examined twice over 2 to 3 years by classical chromosomal aberration analysis and fluorescence in situ hybridization. The comparison of the 1^st and the 2^nd sampling of hospital workers showed a significant increase in chromatid and chromosomal aberrations (all p < .05) examined by classical chromosomal aberration analysis, and in unstable aberrations (all p < .05) detected by fluorescence in situ hybridization. Both cytogenetic methods were able to detect an increase of unstable aberrations in the 2^nd sampling. The raised frequency of unstable cytogenetic parameters suggested higher recent exposure to genotoxic agents.

Pattern of chromosomal aberrations persisting over 30 years in a Chernobyl Nuclear Power Plant accident survivor: study using mFISH

The long-term in vivo cytogenetic effects of high-dose radiation exposure can be traced in accidentally irradiated persons, and particularly useful for developing strategies of monitoring and therapy of such patients, as well as for elucidating the fundamental aspects of hematopoiesis and radiobiology. Using 24-color fluorescent in situ hybridization (mFISH), we analysed the frequency and the spectrum of chromosomal aberrations (CA) in peripheral blood lymphocytes of the Chernobyl Nuclear Power Plant (NPP) accident victim 30, 31, 32 and 33 years after acute accidental exposure to high-dose gamma radiation of the whole body. Totally, 993 metaphase cells were analyzed (or 219, 272, 258, 244 cells each year), of which 297 were aberrant. Our study demonstrated a constant aberrant cell frequency at 28% in 2016-2018 years, while in 2019, a significant increase up to 35% occurred due to contribution of significantly elevated frequency of simple aberrations in the absence of evident recent genotoxic factors. Four clonal aberrations were detected, three of which persisted for more than one year at a frequency up to 2.5% of analyzed cells. The distribution of 731 breakpoints per individual chromosomes was nearly proportional to their physical length, excepting Chromosomes 13 and 20, which were significantly breakpoint-deficient compared to the genome median rate. Monitoring of the long-term effects on chromosomal instability caused by radiation exposure is important for understanding and predicting the long-term effects of ionizing radiation.

Effects of Valproic Acid on Radiation-Induced Chromosomal Aberrations in Human Lymphocytes

One of the most widely employed histone deacetylases inhibitors in the clinic is the valproic acid (VA), proving to have a good tolerance and low side effects on human health. VA induces changes in chromatin structure making DNA more susceptible to damage induction and influence DNA repair efficiency. VA is also proposed as a radiosensitizing agent. To know if VA is suitable to sensitize human lymphocytes γ-irradiation in vitro, different types of chromosomal aberrations in the lymphocytes, either in the absence or presence of VA, were analyzed. For this purpose, blood samples from four healthy donors were exposed to γ-rays at a dose of 1.5 Gy and then treated with two different doses of VA (0.35 or 0.70 mM). Unstable and stable chromosomal aberrations were analyzed by means of fluorescence in situ hybridization. Human lymphocytes treated with VA alone did not show any increase in the frequency of chromosomal aberrations. However, a moderate degree of sensitization was observed, through the increase of chromosomal aberrations, when 0.35 mM VA was employed after γ-irradiation, whereas 0.70 mM VA did not modify chromosomal aberration frequencies. The lower number of chromosomal aberrations obtained when VA was employed at higher dose after γ-irradiation, could be related to the induction of a cell cycle arrest, a fact that should be taken into consideration when VA is employed in combination with physical or chemical agents.

FISH-based analysis of 10- and 25-kV soft X-ray-induced DNA damage in 184A1 human mammary epithelial cells

Over the past years, several in vitro studies have been performed on DNA damage induced by soft X-rays, especially in the energy range below 50 keV. Radiation effects originating from such low-energy photons are relevant in the context of medical diagnostics, for example, mammography, or of accidental exposure to scattered radiation. The present study was initiated to investigate the X-ray energy-dependent induction of stable and unstable chromosomal aberrations in the human mammary epithelial cell line 184A1. Three colour fluorescence in situ hybridisation was applied to identify chromosomal damage in chromosomes 1, 8 and 17, induced by 10-kV or 25-kV soft X-rays as well as by 200-kV X-rays as a reference quality. The overall results confirm the X-ray energy dependencies published for human lymphocytes showing increasing chromosomal aberration frequencies and higher aberration complexity with decreasing X-ray energy and increasing dose. Comparing the obtained dose dependencies, ratios of 0.84 ± 0.09 and 1.22 ± 0.18 were revealed for stable translocations induced by 25- and 10-kV X-rays, respectively, using 200-kV X-rays as reference. Moreover, the analysis of the minimum number of breaks required to form the visible chromosomal damage resulted in similar ratios of 0.93 ± 0.07 for 25-kV X-rays and 1.25 ± 0.10 for 10-kV X-rays relative to 200-kV X-rays. In addition, non-DNA-proportional contributions of chromosomes 8 and 17 to the whole DNA damage and deviations from the expected 1:1 ratio of translocations and dicentrics were observed for cell line 184A1.