STUDY OF CHROMOSOME STABILITY OF HUMAN SOMATIC CELLS IN THE DEVELOPMENT OF THE SECONDARY RADIATION-INDUCED BYSTANDER EFFECT.

Objective: To establish the level of chromosomal instability in human peripheral blood lymphocytes during thedevelopment of secondary radiation-induced bystander effect.

Materials and methods: Human peripheral blood lymphocytes; culture of human non-small-cell lung cancer cell lineA549 (irradiated in vitro by 137Cs in a dose of 0.50 Gy/unirradiated). Cytogenetic analysis of uniformly colored chromosomes of human peripheral blood lymphocytes with determination of the frequency of all types of aberrations.

Results: The mean group frequency of chromosome aberrations (4.75 per 100 cells) in human peripheral blood lymphocytes co-cultivated with conditioned culture medium from bystander cells of human non-small cell lung cancercell lines A-549 exceeded the control (1.60 per 100 cells) (p < 0.001) due to an increase in the frequency of singlefragments from 1.20 to 3.95 per 100 cells (p < 0.001). The mean group frequency of chromosome aberrations andchromatid-type aberrations in human peripheral blood lymphocytes during the development of primary (5.80 and4.35 per 100 cells, respectively) and secondary (4.75 and 3.95 per 100 cells, respectively) radiation-induced bystander effect did not significantly differ from each other (p > 0.05).

Conclusions: Under the conditions of co-cultivation of human peripheral blood lymphocytes with conditioned culture medium from bystander cells of human non-small cell lung cancer A-549, a secondary radiation-induced bystander effect was registered, the cytogenetic manifestation of which was an increase in the level of chromosomalinstability due to the rise in the frequency of chromatid-type aberrations (single fragments). The levels of chromatid-type chromosome aberrations during the development of the primary and secondary radiation-inducedbystander effect did not differ significantly. The development of the secondary radiation-induced bystander effectdid not affect the induction of chromosomal-type aberrations.