Malignant transformation and chromosome analysis of γ-irradiated C3H/10T1/2 cells

This paper reports on the results of a study on malignant transformation in vitro of C3H/10T1/2 cells induced by 60Co γ-rays. The transformed foci were formed in cells cultured for more than six weeks after irradiation with 350 rads. Cells in a bottle without obvious transformed foci four weeks after irradiation were transferred to and seeded in fresh cultured bottles, and were kept under observation for another four weeks. The amount of transformed foci increased obviously after reseeding. It showed that the cells with potential malignant transformation might have been formed in four weeks after γ-ray irradiation. The transformed cells lost their sensitivity to post-confluence inhibition of cell division and prolonged their exponential growing period. In newborn mice inoculated with transformed cells together with injection of ATS, sarcomas were observed after two weeks. Therefore, the transformed cells possessed confirmable malignant property. By means of chromosome analysis metacentric chromosomes were oberved in 18% of malignant cells. It is probable that DNA damage of cells induced by irradiation might result in chromosome aberration and further development of transformed cells